The 16th International Conference on Accelerator Mass Spectrometry

Name: The 16th International Conference on Accelerator Mass Spectrometry
Start: 2024-10-20T00:00:00+08:00
End: 2024-10-26T23:40:00+08:00
Location: No location set

20 Oct 2024, 00:00 → 26 Oct 2024, 23:40 Asia/Shanghai

GRAND BALLROOM (宴会厅), 2nd Floor

GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China

Hongtao Shen (Guangxi Normal University) , shan Jiang (China institute of Atomic Energy) , Xiaolin Hou, Weijian Zhou (Institute of Earth Environment, Chinese Academy of Sciences)

Description

Overview

The 16th International Conference on Accelerator Mass Spectrometry, co-hosted by Guangxi Normal University (GNU), China Institute of Atomic Energy (CIAE), and Institute of Earth Environment ，Chinese Academy of Sciences (IEECAS), will be held at Guangxi Normal University, Guilin, China, from October 20 to 26th 2024. All Topics on AMS and its applications are welcome to be presented at the conference. We hope all of you come and enjoy the conference with exciting lectures and the stunning landscape in Guilin.

The Early Registration Deadline has been extended to July 15, 2024.

Preliminary AMS-16 Conference Programme:

Registration and Icebreaker: 20 October.
Conference presentations：21-25 October.
Post-Conference Tour: 26 October.

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Contact

ams@gxnu.edu.cn

+86 13207735516

Sunday, 20 October
- Registration in the lobby of the Conference Hotel: GULIN BRAVO HOTEL, Address: No.14, Ronghunan Road, Xiangshan District, Guilin Lobby of the Conference Hotel
  
  Lobby of the Conference Hotel
  
  GULIN BRAVO HOTEL
  
  Convener: Mrs MO Qiaoli (Guangxi Normal University)
- CONFERENC ICEBREAKER: Hotel Restaurant Restaurant，Ground floor
  
  Restaurant，Ground floor
  
  GULIN BRAVO HOTEL
Monday, 21 October
- Registration in the lobby of the conference Hotel Lobby of the Conference Hotel
  
  Lobby of the Conference Hotel
  
  Chairperson: Prof. Shen, Hongtao
- Welcome; Opening remarks GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Convener: Prof. Hongtao Shen (Guangxi Normal University)
  - 1
    
    Welcome Speech by Mayor of Guilin CITY
  - 2
    
    Welcome Speech by Prof. Song,Shuxiang（President of GXNU）
  - 3
    
    Welcome Speech by Prof. Zhou,Weijian. (Institute of Earth Environment, Chinese Academy of Sciences)
  - 4
    
    Welcome Speech by Prof. Jiang,Shan. (China institute of Atomic Energy)
  - 5
    
    Group Photo
- Plenary GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Convener: Prof. Shan jiang (中国原子能科学研究院)
  - 6
    
    Novel Concepts For Multipurpose AMS Systems
    
    Conventional low-energy AMS has seen major progress in measurement efficiency via optimized beam stripping in the accelerator but also in measurement selectivity via improved suppression of molecular and atomic isobars after the accelerator. This led to a separation of systems specialized either on measurements of radiocarbon or on determination of a broader spectrum of radionuclides ranging from $^{10}$Be to the actinides. Both, the specialization and the general process of optimization and reduction of size and complexity have opened the field to a wide range of users and operators of AMS systems outside traditional accelerator laboratories. However, it has made it more complicated to incorporate new equipment. The recent developments of gas reaction cells and ion-laser interaction for isobar suppression promise to substantially enhance the measurement capabilities of compact systems.
    In this presentation, I will highlight common features and differences of state-of-the-art AMS systems and what this implies for the design of future multipurpose AMS systems. In the evolution of the AMS technique we will probably see a larger variety of specialized ion sources and injection lines in addition to the standard Middleton type Cs sputter ion source. I will specifically focus on examples from experiments at the ion-laser-interaction mass spectrometer ILIAMS at the VERA (Vienna Environmental Research Accelerator) facility. This technique allows measuring $^{36}$Cl or $^{26}$Al from extraction of AlO$^{–}$ and non-classical AMS radionuclides such as $^{135}$Cs. I will also discuss the new AMS system HAMSTER (Helmholtz Accelerator Mass Spectrometer Tracing Environmental Radionuclides; Wallner et al., this conference) at HZDR as an example of a new multipurpose AMS system holding several injection beamlines including an ion-laser interaction and a secondary ion mass spectrometer (SIMS).
    
    Speaker: Johannes Lachner (HZDR)
- 10:30
  
  Coffee break Lobby, 2nd Floor
  
  Lobby, 2nd Floor
- Applications in Atmospheric and Environmental C-14 GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  Applications involving modern C-14 in tracing environmental processes including greenhouse gases, soil processes, biodegradation, and groundwater.
  
  Convener: Prof. Jocelyn Turnbull (GNS Science)
  - 7
    
    Radiocarbon tracing deep carbon emissions from the Tibetan Plateau
    
    The Tibetan Plateau plays an important role in the global carbon cycle. Despite its significance, the mechanisms, sources and fluxes of CO2 emissions from this region remain poorly understood. This study employs radiocarbon to trace the origins of CO2 released in the southern Tibetan Plateau. Combining 14C and other geochemical proxies (chemical compositions, 3He/4He, δ13C, etc.) from soil gases, hydrothermal gases, hydrothermal waters and travertines, we aim to quantify the contribution of deep carbon to contemporary CO2 emissions.
    In this study, radiocarbon has been measured for dissolved inorganic carbon (DIC) in hydrothermal waters from representative rifts and strike-slip faults in the Tibetan Plateau and adjacent regions. The Δ14CDIC data vary from –220‰ to –1000‰, falling in the mixing trend between 14C-depleted end-members (i.e., deep carbon of mantle and metamorphic origins and carbonate minerals) and modern biological carbon components.
    Our findings reveal remarkable interaction between the deep and shallow carbon and a substantial release of deep carbon from deep faults in the Tibetan Plateau. By enhancing our understanding of deep CO2 release from the Tibetan Plateau, this study contributes to more accurate carbon cycle models and informs climate change mitigation efforts on both regional and global scales.
    
    Speaker: Prof. Sheng Xu
    
    Abstract (Sheng Xu).docx
  - 8
    
    Advanced 14C dating on organic carbon with distinct bond strengths for terrestrial carbon cycling dynamics
    
    Advanced 14C dating on organic carbon with distinct bond strengths for terrestrial carbon cycling dynamics
    Hong Wang1, Xiaofei Gao1, Peng Cheng2, Yi Yang1, Jia Cao1, Dongxue Li3, Peixian Shu2, Guodong Ming4, Yingna Liu1, Keli Zhang1, Baoshan Cui3, Yongming Han2, Xuefeng Lu2, Hua Du2, Feng Xian2, Sanyuan Zhu5, Yanmin Sun5, Tianhe Liu1, Lin liu1, Xiaolei Zhao1, Weijian Zhou2, Zhisheng An2
    
    1Faculty of Geography, Beijing Normal University, Beijing 100875, China
    2State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061, China.
    3School of Environment, State Key Joint Laboratory of Environmental Simulation and Pollution Control, Beijing Normal University, Beijing 100875, China
    4CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
    5State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640 Guangdong, China.
    
    Abstract
    Protective and selective preservation of OC are two carbon sequestration mechanisms that are hypothesized and quantified only by conceptual models. However, evidence of protective preservation is reported only in occlusion and pore spaces and selective preservation is mainly observed in fluvial sediments. Here, we use a specially-designed pyrolysis-combustion device to extract pyrolysis labile and recalcitrant molecules via O2-free thermal decomposition and pyrolysis inert molecules via pure-O2 combustion of the graphitic-like residue on a given sample for AMS 14C dating to quantify OC cycling dynamics. These OC fractions with measurable bond strengths from wide range of terrestrial sediments including lacustrine, mollisol, Yellow River wetland, loess, karst mountain rock vanish in China and previous daylight-free caves and engineered/managed soils in the U.S.A. and Japan show instant and hysteretic protection and elsewhere selection and in-situ dissipative mechanisms. The instant protection indicates that low energy OC molecules could yield older than or identical to 14C dates of high energy molecules. The hysteretic protection and dissipative selection dynamics that occur in high OC production environments provide a potential to improve accuracy of sediment chronology. The elsewhere selection-to-redistribution mechanism always predates the redistribution events with unpredictable 14C dates-depth trajectories.
    
    Speaker: Hong Wang (Beijing Normal University)
  - 9
    
    The sources and the range of renewable content in biofuels: implications to the precision and accuracy of certification
    
    The need for alternative sources of fuel has motivated the search for production routes based on renewable materials that may equal the fossil options in efficiency and which are economically viable. For the fuel industry to adapt to this reality, it is necessary to size up the investment in new production plants and in the development of new technologies. Regulatory bodies are supposed to guide this process, defining parameters for the products and means for certification, especially during the transition period we have been living, in which mixtures of fossil and renewable fuels are the possible options to be marketed. In such context, it is important to review and evaluate aspects such as the different sources of biofuel, from an economical point of view, and the viability of aiming for large biofraction contents in different types of fuels. Brazil is a very relevant country in the use of cleaner energy because, as recently pointed out by Montoya et al. (2021), among several other authors, Brazilian energy matrix is three times cleaner than the global average, with renewable energy representing about 50% of the total energy in the country. Realistic biofraction values for the current fuel industry are in the average order of 10% bio, maximum 20%. Oliveira and Coelho (2017), for example, mention the difficulties that the Brazilian biodiesel program has had to reach viable 15%. Although the ASTM 6866 regulates the certification of renewable fractions in fuels and that Accelerator Mass Spectrometry is recognized by the scientific community as the gold standard for such measurements, there remains reluctance within the productivity sector to implement the 14C AMS technique for such purpose. This is due, on one hand to of the high costs of the method, and on the other hand to the lack of full understanding of the radiocarbon technique. Due to variations in 14C concentration in the atmosphere during the unknown year of the crops and a wide range of delta 13C in the unknown sources, for the sake of accuracy the ASTM 6866 standard foresee 3 percentage absolute uncertainty in the bio fraction determination. From the regulatory bodies' point of view, it is necessary to keep in mind the real purpose of encouraging the use of renewable sources, contributing to the environment effectively and responsibly. For example, a 2% biofuel can theoretically be introduced in a market situation in which 5%bio is proposed, considering the large error margin suggested by the ASTM standard. As shown by Norton and Devlin (2006) there is an important implication in the analysis of samples formed by different carbon sources related to the correction for mass fractionation. This is in particular relevant for carbon sources having large differences in terms of isotopic composition. Despite the importance of considering the significant variability of the biofraction results when there is no information about the origin of the analyzed compound, in the interests of accuracy, studying particular cases that represent the context of the biofuels market can be extremely useful. Considering the great demand for certification of partially biogenic products, it is possible to use alternative standards to different scenarios to ensure greater precision.
    
    Montoya et al. 2021 https://doi.org/10.1016/j.jclepro.2021.127700
    Norton and Devlin 2006 https://doi.org/10.1016/j.biortech.2005.08.017
    Oliveira and Coelho 2017 https://doi.org/10.1016/j.rser.2016.10.060
    
    Speaker: Prof. Kita Macario (LAC-UFF (Radiocarbon Laboratory of the Fluminense Federal University), Physics Institute)
  - 10
    
    Applications of ¹⁴C tracing the deep carbon in the Changbaishan volcanic area
    
    Volcanic activities are known to release a substantial amount of deep carbon to the Earth’s surface, thereby influencing the global carbon cycle on geological timescales. Volcanic activities release CO₂ to the atmosphere not only from the crater, but also from the flank and base of the volcanoes in the form of soil emissions, hot springs, vents, and deep carbon in dissolved state. Carbon isotopes have been widely used to trace deep carbon and processes due to eigenvalue differences among carbon sources. ¹⁴C is more insensitive to CO₂ degassing than ¹³C, so it is less affected by the process and can provide accurate information on carbon sources. Changbaishan volcano is one of the largest active volcanos with the greatest potential for catastrophic eruption in east Asia, which has abundant hydrothermal resources, such as the Julong and Jinjiang hot springs. The deep carbon flux and corresponding climatic and environmental effects need to be clarified in the Changbaishan volcanic area.
    We investigated the carbon isotope compositions (δ¹³C and Δ¹⁴C) of hot springs, rivers, groundwater, soil gas, and plants. The results showed that the carbon isotope compositions of different study subjects had been affected by volcanic degassing, for example, The Δ¹⁴C values for riverine and groundwater dissolved inorganic carbon (DIC) are −832‰ to 22‰ and −676‰ to 1‰, respectively. The flux of deep carbon in the dissolved state is 0.33×10⁴ t C yr⁻¹. The minimum flux of deep CO₂ outgassing (i.e. deep carbon release in the gaseous state) from the air-water interface is 1.24×10⁴ t C yr⁻¹. The Changbaishan volcanic area exists as a net carbon source under the control of volcanic degassing and silicate weathering based on existing and this study. In addition, we measured the DIC isotopic compositions of the Erdaobai River in one year, which drains the Changbaishan volcanic area. The isotopic mixing model of ¹⁴C showed that hydrothermal DIC accounted for 40.8±3.7% of the DIC budget and deep carbon exists as a stable carbon source. This study highlights the superiority of ¹⁴C as a tracer in investigating carbon cycling and the impact of deep carbon degassing on the carbon cycle in the volcanic area, which is significant for understanding the global CO₂ balance and climate change.
    
    Speaker: Linan Wang (天津大学)
    
    Abstract.docx
- New and Advanced AMS Techniques GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  New techniques or innovations in AMS measurement and instrumentation.
  
  Convener: Hans-Arno Synal (Ionpuls AG)
  - 11
    
    The Physical problems that exist on AMS
    
    Shan Jiang1,2, Hongtao Shen3
    1, China Institute of Atomic Energy
    2，Qixian Nuclear Science and Technology Limi.Comp.
    3，Guangxi Normal University
    Since the invention of AMS, many scientific and technological problems in the natural sciences have been solved. However, there are still many problems that cannot be solved so far, such as (1) the measurement of inert gases; (2) higher or lower abundance isotopes, such as 10-16-10-18 or 10-8-10-11; (3) On-line measurements, such as CO2 on-line measurement; (4) Simultaneous measurement of high-precision stable isotopes, such as 16O, 17O, 18O; (5) Measurement of impurity content in ultra-pure materials (ppt-ppq range of semiconductor materials), etc. In order to achieve the measurement of the above problems, it is necessary to recognize the physical problems that exist in the AMS. This report will analyze these physical problems in detail, such as those on tandem accelerators, ion sources, and injectors, in order to develop new AMS instrument technologies.
    
    Speaker: Shan jiang (中国原子能科学研究院)
  - 12
    
    ALIS: The new infrastructure for low-energy isobar suppression at CologneAMS
    
    The integration of a unique low-energy isobar suppression unit, the Anion Laser Isobar Separator (ALIS), marks a significant extension to the CologneAMS infrastructure. After the successful test of the advanced gas-filled radio frequency quadrupole (RFQ) ion cooler at the Vienna test bench, we present insights from first benchmark tests conducted at ALIS.
    
    ALIS consists of three major sections. 1) Anion beam formation and mass selection, 2) Anion cooling and isobar suppression and 3) ion-beam transport to the 6 MV AMS system.
    The first section uses a 134 sample MC-SNICS NEC ion source followed by a 90°-bending magnet. This allows to superimpose the ion beam with a high-power laser beam, that is required for isobar photo detachment. Analyzing slits are installed at the focal point of the magnet for mass selection, thereafter an einzel lens is used to focus the anions into the ion cooler. A pneumatic actuated beam attenuator is installed in between the ion source and the magnet for the attenuation of intense stable isotope beams.
    The second section uses an advanced gas-filled radio-frequency quadrupole (RFQ) ion cooler with an elliptical deceleration electrode and hybrid RFQ-electrodes for ion confining and guiding.
    The third section is designed to transport the anions to the existing beam line of the 6 MV AMS system and to match the ion-optical requirements. Consequently, the laser beam is separated from the ion beam, using a double focussing electrostatic analyzer (ESA) with an 8 mm hole in the outer spherical electrode. Because of the resulting field inhomogeneities induced by the hole, we have designed an additional spherical electrode that is able to correct for this effect.
    In conclusion, we will report on the detailed design and status of ALIS and on the characterization of the system. Therefore, we present for example the anion extraction efficiency measurement for SrF$_3^-$ and AlO$^-$, the total transmission measurement and the field homogeneity measurements of the ESA.
    This project received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 824096.
    
    Speaker: Markus Schiffer (University of Cologne, Institute for Nuclear Physics, Germany)
  - 13
    
    AMS of $^{36}$Cl at the ETH Zurich 6 MV Tandem – the classical way
    
    Classical AMS measurements of $^{36}$Cl require high ion energies to enable isobar separation of $^{36}$S by nuclear separation techniques exploiting the different stopping power of S vs. Cl. The 6 MV Tandem accelerator at ETH Zurich was one of the first AMS systems being able to measure $^{36}$Cl already several decades ago [Synal et al. NIM B 29 (1987) 146] and has been heavily used for $^{36}$Cl measurements since then. A unique component of the AMS system was the Cs gun ion source, producing low $^{36}$S background and very low cross talk. However, the overall efficiency of this setup was limited because only a fraction of the sample material was consumed during the measurement. Thus, for samples with low counting statistics (small samples or low ratios) the performance was not optimal, which motivated an upgrade.
    Recently we rebuilt the low-energy side of the 6 MV Tandem accelerator with a new MICADAS-type ion source and an achromatic injector. After stripping in thin 2 µg/cm2 carbon foils at a terminal voltage of around 6 MV we achieve high ion energies of ~45 MeV (7+ charge state), which is sufficient for isobar separation in a multi-anode gas ionization detector after additional $^{36}$S-suppression by a 180° gas-filled magnet (GFM). The GFM is in use since 2008 and is described in a contribution in the proceedings of the AMS-14 conference [Vockenhuber et al. NIM B 455 (2019) 190]. High overall efficiency is reached because of high transmission though the accelerator (>20\%) and through the GFM (up to 70\%) while still measuring blank ratios in the 10$^{-15}$ range and below.
    We present here the upgraded AMS system and discuss background and performance for $^{36}$Cl AMS measurements at the ETH Zurich 6 MV Tandem accelerator.
    
    Speaker: Christof Vockenhuber (ETH Zurich)
  - 14
    
    Laser Spectroscopy: A Potential Solution for Versatile Radiocarbon Applications
    
    Radiocarbon has presented its importance in versatile applications, ranging from dating ancient (in e.g. Quaternary study and archaeology) or modern (in e.g. forensic science) samples, tracing metabolic pathways in human bodies, to determination of bio-/fossil- components (in fuel, fabric, or even emissions of green-house gases and particulate pollution) for environmental considerations. The development of analytical techniques are driven by and meanwhile further inspire these brilliant ideas. Radiation counting dominated in the first 30 years and accelerator mass spectroscopy (AMS) took over since 1970s. Laser spectroscopy on radiocarbon measurements keeps challenging its detection limit (parts-per-quadrillion level in the nature atmosphere) and finally achieved success in 2010, a technique called Saturated-absorption CAvity Ring-down spectroscopy (SCAR) was invented. Through a decade of improvement, SCAR has been commercialized at ppqSense company, with performances are quite close to AMS but costs are much less. Laser spectroscopy offers new opportunities for applications where AMS is too expensive/complicated, or Liquid scintillation counting is inappropriate for sample consumption or time resolution reasons. We are preparing to construct the first laser spectroscopy laboratory for radiocarbon analysis in China and will discuss feasibility and pros-and-cons of the technique in different applications.
    
    Speaker: Prof. Zuguang Guan (Zhejiang Normal University)
    
    SCAR_APL_AMS16_ZG.docx
- 12:10
  
  Lunch Restaurant，Ground floor
  
  Restaurant，Ground floor
- Applications in Atmospheric and Environmental C-14 GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  Applications involving modern C-14 in tracing environmental processes including greenhouse gases, soil processes, biodegradation, and groundwater.
  
  Convener: Sheng Xu (Tianjin University)
  - 15
    
    Fossil fuel CO2 tracing by atmospheric 14CO2 measurements in China
    
    As a large carbon emitter, how much of the increased atmospheric CO2 derived from fossil fuel emissions is not only an important scientific question, but also important to assess the current policies of carbon peak and carbon neutrality in China. Because of the complete depletion in fossil fuels, radiocarbon (14C) is regarded as an independent and objective tool to evaluate fossil fuel CO2 (CO2ff) emissions. In this presentation, we will show the progresses of tracing CO2ff emissions by atmospheric 14CO2 measurements in China, including the background 14CO2 measurements, spatial-temporal distribution of CO2ff in Chinese cities, and the contributions from different sources, etc.
    
    Speaker: Prof. Zhenchuan Niu (Institute of Earth Environment, Chinese Academy of Sciences)
  - 16
    
    Palaeoenvironmental variations of the past 3000 years in Russian Altai: insights from 14C and 210Pb/137Cs dating and elemental records of Lake Kolyvanskoe
    
    The 20 AMS 14C dates on a 96-cm long core (22-Al-02A) from Kolyvanskoe Lake in the Altai Krai, exhibit nuclear bomb 14C influence in the upper 13 cm part. However, the bomb 14C curve may have changed its shape owing to old carbon influence (OCI). An age-depth model (with selected 14C ages having less OCI) has been established for the past 3000 years by using the Bayesian statistical Bacon model approach. However, the Bacon model cannot provide good age estimation with the nuclear bomb 14C influenced age and often smoothed out rapid sedimentation changes. Therefore, 210Pb/137Cs dating results are used for the chronology of the upper 13 cm part. A sedimentary hiatus seems to have existed during the Little Ice Age (1850-1550 CE) perhaps owing to the frozen condition under cold climate. Elemental concentrations in 0.5N HCl leach fractions as well as organic C, N and C/N provide detailed climate and environmental changes in nine periods: I (1180~930 BC): high productivity and lower surface runoff; II (930~510 BC): lower productivity and surface runoff indicating a sudden cooler period; III (510~170 BC): increased surface runoff and organic activity owing to high moisture content; IV (170 BC~ 900 CE): reduced surface input reflecting prolonged frozen conditions; V (900~1160 CE): elevated detritus and organic productivity indicating wet and warm conditions, hence representing medieval warm period (MWP); VI (1160~1270 CE): reduced land input and organic productivity reflecting cold conditions; VII (1270~1460 CE): elevated surface runoff and organic productivity possibly because of sudden wet period; VIII (1460~1950 CE): abrupt sedimentation hiatus possibly because of cold conditions led to freeze the top surface of the lake during little ice age (LIA) period; IV (1950 CE ~ Present): high organic yield and terrestrial input, elevated organic content and heavy metal input showing human impact.
    
    Speakers: Dr Hong-Chun Li (National Taiwan University) , Dr SATABDI MISRA (Department of Geoscience, National Taiwan University)
    
    Abstract _AMS 16 CONFERENCE 2024.pdf
  - 17
    
    Analysis of 14C radioactivity in seawater of Beibu Gulf, Guangxi, China, using GXNU-AMS
    
    Analysis of 14C radioactivity in seawater of Beibu Gulf, Guangxi, China, using GXNU-AMS
    
    After the Fukushima nuclear accident in Japan, the safety management of nuclear power has been emphasized by various countries, while the radioactivity levels in the environment surrounding nuclear power plants have also received public attention. Studies have shown that the persistence of nuclear wastewater containing long half-life radiocarbon (also known as 14C) in the sea can affect marine ecosystems and ultimately harm human health through the hydrosphere-biosphere circulation, which highlights the importance of monitoring and assessing 14C in the marine environment. However, monitoring of fluctuations in 14C levels in the marine environment around nuclear power plants in China remains unpublished. Here, we used GXUN-AMS to evaluate 14C/12C ratios in seawater samples from several stations in the offshore waters of Beibu Gulf, Guangxi (108.1-109.1E), and to assess radioactivity in seawater.
    
    It was found that one station showed a high value of PMC (Percent Modern Carbon). More specifically, the PMC at this station was 183.0 ± 1.0. Subsequently, several other stations showed subtle fluctuations, i.e., PMCs between 89 and 101. By investigating and exploring the station with the highest PMC, we found that the perturbed level of 14C activity at this station may be affected by the combination of the nearby nuclear power plant and the winter currents in the Beibu Gulf. In summary, we do not find any abnormality in the 14C activity level in the offshore waters of Beibu Gulf, Guangxi, China, due to the discharge of nuclear wastewater from Japan.
    
    Speaker: He Ouyang
  - 18
    
    14C dating in forensics: the CMP (Committee on Missing Persons) project for the identification of missing persons
    
    Since few years the Centre of Applied Physics Dating and Diagnostics (CEDAD) at the University of Salento is collaborating with the Committee on Missing Persons in Cyprus (CMP) for the analysis of the human skeleton remains of around two thousand persons who went missing during the inter-communal fighting of 1963-64 and the events of 1974.
    The aim of the CMP, supported by the United Nations, is to locate and identify the remains of the missing and return them back to their relatives. Unfortunately, the identification process is often made complicated by the generally poor preservation status of the remains and the complex burial conditions, relatively large post-mortem intervals, and the lack of context information or associated artefacts and personal belongings.
    It is then often very important to assess a first compatibility of the recovered skeleton remains with the expected time range. This is the reason why radiocarbon dating is one of the steps of the well-established identification protocol set-up by CMP together with the anthropological and genetic analysis of the skeletal remains and the comparison between the physical evidence with the available witness information. The aim of the 14C analysis is first to assess whether the analysed sample is relevant to the CMP mandate or not, and then give a contribution to the identification of the person in terms, for instance, of birth year.
    We review the use of 14C dating for the analysis of around 197 bone samples so far analysed highlighting the potentialities, as well as the strategies developed to address possible issues such as dietary-induced offset in the measured age or the need to develop a proper model of carbon turnover in the analysed tissues.
    The importance of 14C dating is then shown by discussing some cases of both relevant and not relevant context to the CMP mandate.
    
    Speaker: Gianluca Quarta (University of Salento)
- New and Advanced AMS Techniques GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  New techniques or innovations in AMS measurement and instrumentation.
  
  Convener: Ming He (中国原子能科学研究院)
  - 19
    $^{10}$Be measurements at 220 kV terminal voltage
    
    The compact 0.3MV MILEA AMS facility was developed at ETH Zurich in collaboration with Ionplus AG, Switzerland, as an optimized low energy AMS system for the analysis of a series of long-lived radioisotopes such as $^{10}$Be, $^{14}$C, $^{26}$Al, $^{41}$Ca, $^{129}$I and actinides. The MILEA facility is equipped with a vacuum insulated accelerator that is powered by a commercial solid state power supply (Heinzinger GmbH, Germany) and deploys a Helium gas stripper. On the low energy side, a magnet - electro static analyzer (ESA) pair provides an achromatic injection of a negative ion beam into the accelerator. A quadrupole triplet located subsequent to the accelerator allows for an optimal beam transport on the high energy side for different positive charge states q ∈ {1, 2, 3, 4, 5}.
    
    $^{10}$Be is measured at ETH Zurich routinely on the MILEA facility at a terminal voltage of 220 kV since 2019. Despite the relatively low terminal voltage a high beam transmission through the accelerator of over 40% for the 2+ charge state is achieved. This is possible due to an unexpected increase of the Be$^{2+}$ charge state yield to 43% at low stripping energies (< 250 keV), while the yield of B$^{2+}$ is limited to about 20%. This results in a first Boron suppression directly by the charge exchange process. Further suppression of the isobar is achieved by a degrader foil technique that takes advantage of the higher stopping power of Boron compared to Beryllium. After passing a 75 nm silicon nitride foil, $^{10}$B can be blocked after an ESA with a movable aperture. Angular and energy straggling that are introduced by the degrader foil limit the beam transport on the high energy side to 25%. Hence, the total transport efficiency (from the ion-source to the detector) equates to around 10%. Final ion identification is performed in a two anode $\Delta$E-E$_{R}$ gas ionization chamber (GIC). The excellent separation provided by the GIC-detector allows for the selection of $^{10}$Be with no significant additional losses. This setup achieves a normalized $^{10}$Be / $^{9}$Be blank value below 2$\times10^{-15}$ that is sufficient for common applications.
    
    On the low energy side, the negative molecular BeO beam is selected for injection due to the higher extraction currents (of typically 6-10 $\mu$A) compared to atomic Be anions. However, the choice of injecting molecules into the stripper gas introduces an additional angular and energy spread to the beam. This is caused during the break-up process in the stripper gas when both former molecular constituents happen to be positively charged and consequentially repulse each other by coulomb force (coulomb explosion). This effect has a significant influence on the beam profile on the high energy side of the accelerator and required the degrader foil to be wider than expected to provide for sufficient spatial acceptance.
    
    Finally, a dilution series of $^{10}$Be standard solutions (Nishiizumi, 2022) is used to demonstrate the precision, stability and linearity of the system. Further, a new ETH Zurich in-house standard solution was prepared and calibrated that better represents the expected $^{10}$Be / $^{9}$Be ratios of typical user samples.
    
    References
    
    Nishiizumi K. (2022). Preparation of new $^{10}$Be and $^{26}$Al AMS standard reference materials. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 530: 43–47.
    
    Speaker: Dr Philip Gautschi (ETH Zurich, Laboratory of Ion Beam Physics)
  - 20
    
    Progress of Positive Ion Mass Spectrometry Based on 2.45 GHz Electron Cyclotron Resonance Ion Source
    
    Radiocarbon measurement technology has significant applications in archaeology, earth science, environmental science, biomedicine and so on, especially in radioactive dating, climate change, nuclear analysis, pharmacokinetics. The traditional 14C accelerator mass spectrometer (14C-AMS) based on tandem is much expensive and complex to maintain and operation. It is urgent to develop a new type carbon ion mass spectrometer. 14C Positive Ion Mass Spectrometry (14C-PIMS), that based on positive and negative ion conversion (C2+-C-), will be a low cost, compact equipment, which can be a potential new method. Recently, 14C -PIMS studies on C2+ producing and C2+-C- charge exchanging have been carried out at Peking University (PKU). Based on a 2.45 GHz ECR ion source, a desired C2+ beam was obtained. Simultaneously, a 6% C2+ to C- charge exchanging efficiency was achieved. Next step, attention will be paid on the development of specialized, miniaturized, maneuverable, automated 14C -PIMS equipment based on 2.45 GHz ECR ion source (PKU-PIMS).
    
    Speakers: Bujian Cui, Li Kai (Peking University) , Guo Zhiyu (Peking University)
  - 21
    
    Further Development of Manganese-53 AMS Nuclear Science Laboratory at the University of Notre Dame
    
    $^{53}$Mn is a rare, radioactive isotope with a half-life of 3.74 million years which has astrophysical applications as an early solar system chronometer and as a test of nucleosynthesis models of supernovae and asymptotic giant branch (AGB) stars. In addition, $^{53}$Mn has geological applications in determining the exposure and burial age of ferromanganese minerals. To fully exploit the capabilities of $^{53}$Mn as a chronometer, a sensitivity to the $^{53}$Mn/$^{55}$Mn ratio of 1 $\times$ 10$^{-13}$ is necessary. Due to this low ratio, and interference from the naturally abundant $^{53}$Cr isobar, Accelerator Mass Spectrometry (AMS) is the only technique sensitive enough to make these isotopic ratio measurements. However, 3 $\times$ 10$^{-13}$ is the detection limit among active facilities$^1$. At the University of Notre Dame’s Nuclear Science Laboratory (NSL), work is ongoing to develop $^{53}$Mn AMS capability using a 10 MV FN tandem accelerator and a Browne–Buechner Spectrograph operated as a gas-filled magnet. During previous experiments, meteoric samples with $^{53}$Mn/$^{55}$Mn ratios between 10$^{-10}$ and 10$^{-8}$ were measured. This presentation discusses the results of varying the experimental parameters on the detection limit.
    This work is supported by the National Science Foundation Grant No. NSF PHY-2310059.
    
    1) Wallner, A., Fifield, L. K., Froehlich, M. B., Koll, D., Leckenby, G., Martschini, M., Pavetich, S., Tims, S. G., Schumann, D., & Slavkovská, Z. (2023). Accelerator mass spectrometry with ANU’s 14 million Volt Accelerator. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 534, 48–53. https://doi.org/10.1016/j.nimb.2022.10.021
    
    Speaker: Griffin Mulcahy (University of Notre Dame)
  - 22
    
    Concept for a Cesium-Free Negative Ion Source based on Microwave Heating of a Low Work Function Granular Material
    
    The negative ion source most commonly used in AMS systems is the cesium sputter type. Cesium is hazardous, making its handling not easy. Recently, the spread of compact AMS systems with acceleration voltages of 500 kV or less has been progressing. For the widespread adoption of AMS systems, it is desirable for the ion source to not only be highly efficient but also cesium-free from the perspectives of safety and maintenance. We propose a concept for a high efficiency cesium-free negative ion source based on microwave heating of granular low work function materials.
    
    The proposed negative ion source features a structure where the plasma region and the negative ion generation region are adjacent within a microwave cavity. The negative ion generation region contains a mixture of low-temperature plasma and low work function material in granular form heated by a microwave. Typical low work function materials have a certain level of conductivity, making it difficult to directly heat their bulk state (e.g., plate, rod, and etc.) with the microwave. However, when the material is in a granular state, the aggregate of those granules can be volumetrically heated by microwaves. Sample gas that enters the plasma region becomes ionized and excited. The excited atoms and molecules then enter the negative ion generation region, coming into contact with the heated surface of the low work function material, transforming into negative ions that are ultimately drawn out by an electric field. This negative ion source concept is expected to offer the following advantages: (i) Since the low work function material is in granular state, the contact area with excited atoms and molecules is more than ten times larger compared to conventional cesium-free ion sources using low work function materials. (ii) Since the plasma region and the negative ion generation region are clearly separated, loss of negative ions due to electron impact can be reduced. (iii) In the plasma region, interfering isobars such as $^{13}$CH in $^{14}$C measurements can be dissociated to some extent.
    
    Currently, the assembly of the test bench is nearly complete. Future work will involve progressing with the proof-of-concept testing.
    
    Speaker: Dr Akihiro Matsubara (PESCO Co., Ltd)
- 14:50
  
  Coffee break Lobby , 2nd Floor
  
  Lobby , 2nd Floor
- Applications in Atmospheric and Environmental C-14 GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  Applications involving modern C-14 in tracing environmental processes including greenhouse gases, soil processes, biodegradation, and groundwater.
  
  Convener: Prof. Zhenchuan Niu (Institute of Earth Environment, Chinese Academy of Sciences)
  - 23
    
    CarbonWatch-Urban: Application of atmospheric radiocarbon measurements to evaluate and monitor urban carbon dioxide emissions
    
    Urban areas are responsible for the vast majority of fossil fuel carbon dioxide emissions, thus mitigation actions are often taken at the city level. Detailed information about urban emissions and offsetting potential is needed to guide mitigation actions and to evaluate the efficacy of these actions. CarbonWatch-Urban is a multi-tiered approach to provide fine-scale carbon dioxide emissions and sink information for all of New Zealand’s urban areas.
    
    First, we have established a high resolution (street segments and buildings, hourly) bottom-up inventory of New Zealand's fossil fuel carbon dioxide emissions and optimised the UrbanVPRM land surface model to estimate the biogenic carbon dioxide budget for our towns and cities. To evaluate and improve these detailed emission maps, we use atmospheric observations of carbon dioxide, carbon monoxide and radiocarbon in carbon dioxide. The radiocarbon measurements allow us to quantitatively separate urban CO2 fluxes into fossil fuel and biogenic components. The ratio of carbon monoxide to fossil fuel carbon dioxide allows us to evaluate the proportions of fossil fuel carbon dioxide from traffic versus other sectors. The ratio of fossil fuel to biogenic carbon dioxide derived from radiocarbon measurements allows us to evaluate the biogenic carbon dioxide fluxes, which are particularly poorly constrained by the current generation of models. This methodology utilises campaign-style flask measurements, which provides less detail than more comprehensive in situ observing systems, but can be applied across a wide range of towns and cities without requiring expensive and complex infrastructure.
    
    Speaker: Jocelyn Turnbull (GNS Science)
  - 24
    
    Numerical simulation of evolution of dissolved inorganic carbon chemical and isotopic compositions (13C and 14C) in carbonate-bearing areas
    
    Investigating the dissolved inorganic carbon (DIC) processes and associated chemical and isotopic (13C and 14C) evolutions is critical for deciphering its implications on climate change and groundwater quality. Growing number of 13C and 14C measurements of DIC in recent years,however, it is still unclear about the DIC evolution. In this study, we synthesize and deduce the isotopic fractionation and chemical equilibrium theory to understand DIC evolution under different scenarios. We summarize and model the DIC chemical and isotopic compositions in carbonate-rich areas, including:
    (1) Carbonate weathering under close and open system
    (2) Transition from open to close system
    (3) DIC-carbonate exchange in close system
    (4) Sulfuric acid-driven weathering
    (5) The impacts of climate on carbonate weathering
    (6) The effects of CO2 outgassing
    With this work, we summarize the interactions between soil CO2, DIC and carbonates, and understand how the DIC chemical and isotopic compositions evolve.
    
    Speaker: Dr Jun Zhong (Tianjin University)
  - 25
    
    Inter-comparison between 81Kr- and 14C-dating of groundwater
    
    81Kr is a cosmogenic isotope with a half-life of 229 ka. Due to its chemical inertness, it has a uniform distribution in the atmosphere and a simple transport behavior in the environment, avoiding some complexities in 14C dating. Therefore, 81Kr is an ideal tracer in the earth sciences.
    
    Limited by the precision of 81Kr analysis, there is a dating gap between 14C and 81Kr. Recently, we have achieved high precision 81Kr-dating method, reaching 1% analytical uncertainty of relative abundance for groundwater samples between 10 ka and 230 ka. This improvement now allows for direct comparison between 14C and 81Kr, enabling multi-tracer approaches in groundwater research.
    
    We have applied our high precision ATTA method to groundwater samples from the North China Plain, and compared it with 14C measurements (AMS). Our results not only verify the reliability of high precision 81Kr-dating method, but also open the opportunity to go beyond piston flow model in groundwater research.
    
    Speaker: Mr Hao Li (University of Science and Technology of China)
- Small C-14 Sample Techniques and Applications GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Discussions will focus on milligram to microgram C fractions of natural and anthropogenic biomarkers, compound specific samples and aerosol fractions. Improvements on analytical separations to better isolate C fractions for subsequent AMS analyses, accuracy and precision validation (including blank assessment and background corrections) and/or applications of smaller targets in a wide variety of research areas are welcome.
  
  Convener: Xiaomei Xu (University of California, Irvine)
  - 26
    
    Measurement of ultra-small CO2 samples with an EA-IRMS-AMS system at CologneAMS
    
    In the CRC1211 project "Evolution at the Dry Limit", precise dating analysis of soil samples from the Atacama Desert is essential. These soil samples result in ultra small CO$_2$ samples and have a carbon content of 2-20μg. At CologneAMS ultra-small samples are measured as CO$_2$ with, an elemental analyzer (EA), an isotope ratio mass spectrometer (IRMS) and the 6MV AMS system, by the use of a gas injection system (GIS). This EA-IRMS-AMS setup enables fully automated, online analysis of $^{14}$C/$^{12}$C ratios and provides accurate and precise 𝛿$^{13}$C values.
    The measurement process begins with oxidization of the samples to CO$_2$ gas in the EA. After this, the 𝛿$^{13}$C values are measured with the IRMS with only 10 percent of the gas while the remainder is transferred to the GIS, from which it is transferred to the AMS. For standard AMS measurements the initial two minutes of data are typically disregarded, due to the instability of the ion source output. Such a practice would significantly reduce data availability for ultra-small samples with carbon content below 10 μg. Typical measurement times range from 1-10 minutes. To still enable longer measurement times and reduce the loss of sample material during the ion source output stabilization, the sample is diluted by the addition of blank gas. Dilution takes place within the GIS syringe, where a precise amount of blank gas is introduced to the sample, thereby giving time for the ion source output to stabilize and to extend the measuring time.
    Additonally our investigation also focused on enhancing fractionation correction in 14C data evaluation. By simultaneously measuring 𝛿$^{13}$C values with AMS and IRMS, we found that they agree with each other within their respective errors. While the 𝛿$^{13}$C AMS values scatter multiple orders higher than the 𝛿$^{13}$C IRMS values we concluded that the 𝛿$^{13}$C IRMS values could be used for a better fractionation correction of AMS measurements.
    This contribution will give an overview of the first ultra-small samples measured with the EA-IRMS-AMS system.
    
    Speaker: Martina Gwozdz (University of Cologne)
  - 27
    
    FLEXIBLE SAMPLE PREPARATION WITH THE μGRAPHILINE SYSTEM
    
    The μGRAPHILINE, introduced in 2024, offers a new, fully automatic graphitization process, enabling rapid, reliable, and precise graphitization using the zinc reduction method for radiocarbon dating. While the majority of radiocarbon samples include bone, wood, charcoal, plant remains, carbonates, and sediments (Dee et al. 2020), there are niche areas of other samples that can be dated with this method.
    
    In this work, we present results of atypical samples, such as leather, liquid components of everyday organic products, and much more, which were combusted and graphitized with the μGRAPHILINE system and measured using the MICADAS spectrometer for AMS measurements (Synal et al. 2007; Wacker et al. 2010).
    
    Speaker: Dr Konrad Tudyka (1. Institute of Physics – Centre for Science and Education, Division of Geochronology and Environmental Isotopes, Silesian University of Technology, 2. miDose Solutions)
  - 28
    
    Assessment of radiocarbon measurement of dissolved organic carbon for small samples by MICADAS
    
    Radiocarbon (14C) composition of dissolved organic carbon (DOC) provides critical constraints on its sources, transformation and cycles. UV-irradiation is considered as an effective approach to oxidize the fresh/salty DOC to CO2 of samples with typical low concentration for high precision radiocarbon measurements. However, the challenge of this method is the complete oxidation of sufficient DOC with low procedural blanks. An UV-oxidation system at the Ocean University of China (OUC) can process 12 DOC samples simultaneously with high oxidation efficiency (>95%) and high reproducibility, and a mini carbon dating system (MICADAS) at the OUC Radiocarbon Accelerator Mass Spectrometer Center is suitable for radiocarbon measurements. Thus, to evaluate the radiocarbon measurement performance for small DOC samples by MICADAS, we applied two CO2 collection approaches on a vacuum line after UV-oxidation for fresh and salty samples (KI trap vs. No KI trap), two reference standards, oxalic acid II (OX-II, modern) and glycine (Gly, dead), and a series of natural DOC samples from the Pearl River-Estuary-northern South China Sea continuum with different salinities. Our results showed that the procedural blanks of UV-oxidation and generated CO2 collection of these two approaches were not very different, i.e. 1.65±0.50 µgC with F14C = 0.485±0.145 and 1.70±0.51 µgC with F14C = 0.412±0.124 for procedural blank, respectively. The procedural blank of small DOC samples was comparable with that of regular size DOC samples (< 2µgC), and the F14C values of field DOC samples were also in line with previous studies. Therefore, UV-oxidation method combined MICADAS measurement provided powerful tool to generate high throughput data to understand compositional, spatial and temporal variabilities of DOC.
    
    Speaker: Wenjing Fu
  - 29
    
    Examining Small-Scale Variation: Combining High-Precision Measurements with Statistical Approaches for 14C Dating and Analysis
    
    Advancements in high-precision AMS radiocarbon ($^{14}$C) measurements coupled with sophisticated statistical techniques offer a powerful approach to uncovering and utilizing annual features in the $^{14}$C record. In recent years, signatures of rapid increases in cosmogenic $^{14}$C have been successfully used as tools for achieving exact-year dating, with the aid of Classical statistical methods. Therefore, the prospect of utilizing even smaller-scale features may extend how often this goal is achievable. However, our analysis of two proposed events in the early second millennium CE highlights how important it is to acknowledge the complexity inherent in small-scale $^{14}$C increases, particularly when attempting to push the boundaries of their detection. The smaller their amplitude, the greater the uncertainty around their true presence and occurrence frequency. Hence, careful interpretation remains crucial for accurate detection and utilization. Furthermore, using a simulation approach, we investigated whether such annual rises are the only way to improve on the precision of calibrated date ranges. We observe that the routine integration of Classical chi-squared tests in the calibration process enhances the precision of $^{14}$C dating even without the aid of any dramatic features. Remarkably, in select cases, this approach is capable of achieving annual dating or, more commonly, returning estimates within 4 years of the true date at 95% probability.
    
    Speaker: Mr Andrea Scifo (Centre for Isotope Research, University of Groningen, Groningen, The Netherlands)
- Poster Session A: （The poster dimensions should be 120 cm in height and 80 cm in width.) Lobby and Hallway , 2nd Floor (( Poster session A should be set up in the morning.))
  
  Lobby and Hallway , 2nd Floor
  
  ( Poster session A should be set up in the morning.)
  
  Poster Session A
  - 30
    
    A gauge for the amount and condition of the cesium in the reservoir of the cesium sputter source
    
    The most common ion source of AMS instruments, the cesium sputter source (Middleton 1983), demands a substantial share of the regular maintenance work and causes a considerable number of operation interruptions. One reason is the difficulty of obtaining meaningful diagnostic measurements under the rough conditions inside. In addition to the high temperature and the strong electric fields, the hot cesium vapor degrades and shortcuts insulators and blinds viewports. Too much cesium in the source can look like too little, and an oversupply will shorten service life or cause immediate failure.
    Cesium is also prone to oxidation by atmosphere or moisture entering the vacuum system. Oxidized cesium does not vaporize, and additionally can form thin crusts on cesium metal, which block its evaporation. An ion source yielding low currents without obvious reason is a frequently observed phenomenon, which is usually targeted by trial and error, including risky procedures like "cesium cracking".
    We have developed a device which allows us to diagnose one possible cause, the depletion or degradation of the cesium in the reservoir of the source. The cylindrical body of the reservoir, machined of a single piece of stainless steel, folds in at the bottom where a ferrite rod is inserted. The cesium metal forms a ring around this insertion, and acts as the secondary winding of an electrical transformer. The conductivity of this ring determines the impedance of the outside primary coil. The method is indicative for both exhausted or oxidized cesium.
    Our prototype measures the impedance using an active rectifier at a fixed frequency. The electronics are only connected for a measurement when the ion source is off during changes of the sample magazine. The device has been in use now for several years at the VERA facility. We will present the method development and discuss the performance and limitations. We think that such diagnostics will be useful for other facilities also and share the engineering sources under the CERN-OHL-P license.
    
    R. Middleton, A versatile high intensity negative ion source, Nucl. Instrum. Methods Phys. Res. 214, 139–150 (1983).
    
    Speaker: Dr Peter Steier (University of Vienna, Faculty of Physics)
  - 31
    
    A method for preparing carbon 14 samples for AMS measurements without silver addition to remove sulfur
    
    Graphite target preparation is one of the key steps in accelerator mass spectrometry (AMS) radiocarbon chronology measurement, so it is crucial to make the graphitisation process simple and efficient. In traditional methods, desulphurisation of samples containing sulphur is essential, as sulphur can affect the yield of graphitisation, and usually requires the addition of silver to form Ag2S to remove the sulphur. However, this step increases the complexity and cost of the experiment. In contrast, the 14C sampling system set up in the AMS laboratory at Guangxi Normal University simplifies the tedious step of sulphur removal during graphite preparation.
    The sampling system allows CO2 to be separated from other gases (H2O, NO2, SO2, etc.) by means of a double cooling trap without additional sulphur removal. It uses the different condensation points of the different gases to purify and collect the carbon dioxide gas, facilitating further graphitisation. The graphitisation of a large number of carbon samples has demonstrated the reliability of this sampling system. Measurements of the prepared graphite samples were carried out using the GXNU-AMS and the results showed that the silverless combustion process not only reduces the cost of the experiment, but also reduces carbon contamination and provides accurate and reliable data for 14C analysis.
    
    Speaker: Xinya Huang (Guangxi Normal University)
  - 32
    
    A sample preparation method for extracting plutonium from soil samples for AMS measurement
    
    Plutonium (Pu) is recognized as an essential environmental indicator isotope. The purpose of this investigation is to devise a protocol for extracting plutonium from soil samples, aimed at Accelerator Mass Spectrometry (AMS) analysis. The procedure initiates with the purification and ashing of samples, followed by the integration of the standard reference material 242Pu before proceeding to acid dissolution. Subsequent to the matrix element reduction via Fe(OH)3 co-precipitation, NaNO2 is administered to stabilize the oxidation state of plutonium at Pu(IV). Further purification and separation of plutonium are achieved through TEVA resin application. The resultant eluate is then dried, re-acidified, and subjected to another round of Fe(OH)3 co-precipitation. The final precipitate is calcined to yield an iron oxide matrix embedding PuO, which is then mixed with niobium powder and pressed into the cathodes for AMS measurement.
    
    Speaker: Lingrong Du (Guangxi Normal University)
  - 33
    
    Atmospheric Methane 14C Analysis at the HEKAL AMS Facility
    
    The most powerful anthropogenically influenced greenhouse gas after carbon dioxide is methane. Its atmospheric mixing ratio is much lower than of CO2, but the global warming potential of CH4 is more than eighty times higher, on a 20-year timescale (IPCC, 2021). The atmospheric amount of CH4 has been growing rapidly since 2007, and the reasons are unclear. Several types of sources can contribute to this increase, but there is no scientific consensus on the contributions of the possible sources. Recently the global atmospheric 13C/12C (d13C) ratio in CH4 is decreasing, but d13C measurements of CH4 alone still cannot provide sufficient information about emission sources.
    
    That is why atmospheric CH4 studies are frequently coupled with 14C isotope measurements. Measurements of radiocarbon (14C) in methane (CH4) may provide a method for identifying regional CH4 emissions from fossil versus biogenic sources because adding 14C-free fossil carbon reduces the 14C/C ratio (Δ14CH4) in atmospheric CH4 much more than biogenic carbon does.
    
    In collaboration with the IMAU group at UU we have set up a new system for ambient air methane sample preparation for 14C analyses. Our aim was to reduce the necessary sample size below 30 dm3, to make sampling and transport easier. As methane amount in ambient air is about 200 times less (around 2 ppm) in ambient air than CO2, it is very important to eliminate the CO2 content. For this purpose, we have modified a bit the CH4 extraction line at IMAU Lab, to fit for 20-30 dm3 air samples, instead of the 1000-2000 dm3 size, which they normally use for stable and clumped isotope analyses of atmospheric CH4. After several cryogenic focusing steps, the air sample is rather enriched in CH4, and finally a gas chromatograph is used for complete separation from CO2 and CO. The cleaned CH4 gas samples were then transported and combusted in sealed tubes at HEKAL laboratory, and the cleaned CO2 gas product was measured by our LEA type AMS system in our Lab using its gas ion source interface (0.005-0.050 mg C). In this study we present the sample recovery, the preparation blank level, and the analytical uncertainty connected to the whole, complex sample preparation and 14C analyses method. A few examples will also be presented where real atmospheric samples (from elevated sources, city, and background regions) were measured.
    
    Project number C2295145 has been implemented with the support provided by the Ministry of Culture and Innovation of Hungary from the National Research, Development and Innovation Fund, financed under KDP-2023 funding scheme. The research at Isotoptech – Atomki AMS Laboratory was supported by the European Union and the State of Hungary, co-financed by the European Regional Development Fund in the project of GINOP-2.3.4–15-2020–00007 “INTERACT”. Fund and supported by the PARIS project (Grant Agreement No. 820846), which is funded by the European Commission through the Horizon Europe research programme.
    
    Speaker: Balázs Áron Baráth (1, 2, 3)
  - 34
    
    Cosmogenic nuclide dating (using 10Be-26Al in quartz and meteoric 10Be) from West Mediterranean archaeological-paleontological sites in Orce, southern Spain, and Guefaït, eastern Morocco
    
    In this paper we apply cosmogenic nuclide dating to the selected key archaeological sites in the western Mediterranean region (southern Spain and Morocco), to provide better chronological constrains to sites where previous geochronological data were scarce, scattered or unresolved. Our knowledge on the early hominin dispersal out of Africa, e.g., timing, causes, pathways, remain incomplete. Situated in the continental edges, the western Mediterranean region, both European and African sides, hosts numerous key archaeological-paleontological sites. Here, we focus on two areas: Orce, near Granada, in southern Spain and Guefaït in eastern Morocco. Orce, situated in the Guadix-Baza basin, one of the largest Neogene-Quaternary paleolakes in Europe, the area hosts several key archaeological-paleontological sites such as Barranco León and Fuente Nueva-3. Magnetostratigraphy revealed that the lake sequences extend from late Pliocene to early Pleistocene, which are in general agreement with biochronology based on mammal fossils. Early effort on absolute dating, e.g., ESR based on quartz, remained difficult in largely calcareous environment, though apparent Early Pleistocene ages obtained from a few archaeological layers in the area are largely consistent with age interval expected from magnetostratigraphy (~1.1-1.8 Ma, i.e., between Jaramillo and Olduvai subchrons). The second site, Guefaït-4 is a paleontological site in Aïn Beni Mathar-Guefaït Basin in east Morocco, an intermontane depression filled with Neogene-Quaternary sediments, where formation and evolution history of the basin has been little known. Recent paleomagnetic study in a relatively well-exposed stratigraphic sections in northern part of the basin, proposed that lower part of sediment sequences, below the paleontological unit, is either near the top of Gauss chron (i.e., >2.6 Ma) or the top of Olduvai subchron (~1.8 Ma). While mammal-fossil biostratigraphy favours the former interpretation, ESR dating (Ti centre) on sediment quartz obtained Early Pleistocene age (~1.6-1.8 Ma), leaving possibility in both interpretations. In this study, we apply 10Be-26Al burial dating, and also meteoric 10Be dating where applicable, in the selected sites in Orce, southern Spain, and Guefaït, eastern Morocco in an attempt to refine chronologies. Analytical feasibility and difficulty applying cosmogenic 10Be-26Al method on quartz to, in general, carbonate-rich environment are discussed, as well as validity of assumptions associated with these approaches via comparison with independent geochronological data (e.g., magnetostratigraphy, ESR).
    
    Speaker: Dr Toshiyuki Fujioka (CENIEH)
  - 35
    
    Development of Li molecular removal method that interferes with 14C measurement using laser
    
    Mass of Li molecule (Li2) is same to 14C, so 14C measurement is frequently interfered by it in using two plus ion of 14C after gas striping of AMS. Removal of Li molecule (Li2) is important in our AMS which use two plus ion of 14C. AMS generate negative ions of carbon (12C-, 13C-, 14C-) and Li2- in a source, which have binding energies of electron of 1.262eV, 982.35nm(14C-) and 0.42eV, 2.952nm (Li2-). Therefore, if laser of energy (1.166eV, 1064nm) between binding energies of electron in 14C and Li2- is incident on negative ions of 14C- and Li2-, one electron of Li2- can be detached but that of 14C- can’t be detached. Laser was equipped near injector magnet and is incident on negative ions (12C-, 13C-, 14C- and Li2-) on direction of Tandem accelerator after injector magnet. What the number of Li2 were decrease and what those of 14C were not changed were checked in E-ΔE spectrum of ionization chamber detector.
    
    Speaker: Junghun Park (KIGAM)
    
    laser_AMS16_abstract.docx
  - 36
    
    Developments towards ion cooler assisted AMS measurements of 90Sr at CologneAMS
    
    Strontium-90 (T$_{1/2}$ = 28.90 a) is among the most prominent fission products produced with high yield in the nuclear fuel cycle and nuclear weapons tests. It is very mobile in the environment and due to its chemical similarities to calcium it easily accumulates in bones and teeth following ingestion or inhalation. However, $^{90}$Sr is not only of environmental interest for its radiotoxicity, but also as a potential tracer.
    
    Decay counting is the state-of-the-art method for $^{90}$Sr. However, as $^{90}$Sr is a pure low-energy β$^–$-emitter, it is typically measured through the detection of its daughter nuclide $^{90}$Y in secular equilibrium, which is time-consuming as well as requiring thorough chemical separation. The main challenge for the detection by mass spectrometry is the interference of isobars, i.e., $^{90}$Zr and $^{90}$Y. Hence, the practical detection limit (LoD) of mass spectrometric methods, e.g., ICP-MS, RIMS, conventional AMS, is either above or close to the radiometric LoD of 3 mBq [1].
    
    The Ion-Laser InterAction Mass Spectrometry (ILIAMS) system at the Vienna Environmental Research Accelerator (VERA) is capable of near complete isobar suppression via element-selective laser photodetachment in a gas-filled radiofrequency (RFQ) ion cooler [2]. The technique exploits differences in detachment energies between the isotope of interest and isobars, thus, neutralizing the isobars while leaving the isotope of interest unaffected. Chemical reactions with a buffer gas can cause additional suppression. In the case of $^{90}$Sr, a suppression of ZrF$_3^–$ vs. SrF$_3^–$ of >10$^5$ can be achieved by admixing 3% of O$_2$ to the He buffer gas. With the ILIAMS system a LoD of <0.1 mBq for $^{90}$Sr has been achieved by AMS [2].
    
    In a collaboration between the University of Cologne and the University of Vienna, a new advanced ion cooler has been developed and built [3]. Performance tests of the new ion cooler have been conducted at a dedicated test bench in Vienna. Currently, around 30% of transmission through the ion cooler has been achieved. Ion residence time measurements have been performed to show that the new hybrid guiding electrode structure of the ion cooler is working as intended. Finally, a fast and simple chemical preparation for large sample sizes is under investigation. This new ion cooler will be part of the Anion Laser Isobar Separator (ALIS), a new low-energy isobar suppression system at the 6 MV accelerator of CologneAMS. Its suitability for high sample throughput for $^{90}$Sr will be tested and optimized.
    
    Ackn.: This project received funding by the RADIATE project under the Grant Agreement 824096 from the EU Research and Innovation programme HORIZON 2020.
    
    [1] W. Bu et al., Spectrochim. Acta Part B, 119, (2016), 65.
    [2] M. Martschini et al., Radiocarbon, 64 (2022), 555.
    [3] M. Schiffer et al., Nucl. Instr. Meth. B 528 (2022) 27.
    
    Speaker: Oscar Marchhart
    
    AMS-16_Marchhart.pdf
  - 37
    
    Icebound Stardust: Tracing the Local Interstellar Cloud by Supernova-produced $^{60}$Fe in Antarctica
    
    The solar neighborhood lies within the Local Bubble, a low-density region of space formed by stellar explosions [1]. The Local Interstellar Cloud (LIC) with the solar system inside is embedded in this cavity. Assuming the LIC contains remnants from supernovae events, the solar system may accumulate traces of long-lived supernova-produced radionuclides as it traverses the LIC. The radionuclide $^{60}$Fe with a half-life of 2.6 Myr [2] serves as an ideal indicator for supernova activity because it is predominantly produced inside of massive stars and ejected by supernovae.
    
    Previous research yielded evidence for enhanced levels of interstellar $^{60}$Fe in million-year-old deep-sea samples [3] and a recent influx into Antarctic snow [4]. In this project, we investigate the deposition of live $^{60}$Fe in the still unexplored time interval of 50-80 kyr before present when the solar system was not yet within the LIC [5]. A 300 kg sample from an Antarctic ice core (EPICA EDML) is utilized to explore the origins of the recent influx and its relation to the trajectory of the solar environment through the LIC.
    
    Investigating the ultra-low deposition rate of individual $^{60}$Fe atoms per cm$^{2}$ per year necessitates the use of the highly sensitive method of accelerator mass spectrometry. Moreover, the ice core sample is characterized by the analysis of the cosmogenic radionuclides $^{10}$Be and $^{26}$Al through the ratio $^{26}$Al/$^{10}$Be. The interplanetary radionuclides $^{41}$Ca and $^{53}$Mn serve to clearly distinguish the interstellar from the interplanetary $^{60}$Fe contributions [6]. The measurements of the cosmogenic radionuclides $^{10}$Be, $^{26}$Al, and $^{41}$Ca are carried out at HZDR's 6MV facility DREAMS, while HIAF at ANU is the only facility in the world equipped to detect $^{53}$Mn and $^{60}$Fe with its 14UD pelletron tandem accelerator. We report on the processing of 300 kg of Antarctic ice and the results of this project.
    
    [1] Berghoefer et al., A\&A, 390 (1): 299–306 (2002)
    
    [2] Rugel et al., PRL, 103, 072502 (2009)
    
    [3] Wallner et al., Nature, 532(7597): 69–72 (2016)
    
    [4] Koll et al., PRL, 103, 072701 (2019)
    
    [5] Frisch et al., ASTRA, 2, 53-61 (2006)
    
    [6] Koll et al., EPJ Web Conf., 260, 11022 (2022)
    
    Speakers: Annabel Rolofs (Helmholtz-Zentrum Dresden-Rossendorf & University of Bonn) , Dominik Koll (The Australian National University & TU Dresden & Helmholtz-Zentrum Dresden-Rossendorf)
  - 38
    
    Inspiration and reflection of 14C analysis with TJUAMS
    
    AMS, as an ultra-sensitive method, is increasingly used in the determination of 14C for studies on wide variety of fields. As a multi-nuclide 14C extended AMS system, TJUAMS has been operating at Tianjin University for seven years. The sample throughput of measured 14C has exceeded 6000. During the long-term 14C-AMS measurements and data processing, some new discoveries and ideas, such as the effect of strong or weak ion beam current on the experimental results, the suitability of using the machine δ13C value correction, and the problems faced in the measurement by small samples of graphite solid, are worth exploring and discussing. In this contribution, the relevant experimental tests, ideas and proposals will be presented in detail.
    
    Speaker: 克君董 (天津大学)
  - 39
    
    Laser Photo Detachment for Sr-90 Detection
    
    The rare radioisotope Sr-90 is one of the most important products of thermal neutron fission. On one hand, the Sr-90 yield from fission is relatively large;on the other hand, 90Sr is known for its bone-seeking radiotoxicity and the risk of causing bone cancer. Currently, researches related to 90Sr are facing the challenge of measuring the concentration of Sr-90 environmental samples, which could be as low as 90Sr/88Sr≈10-14.
    Based on this challenge, we're now trying to apply laser photo-detachment on the measurement of Sr-90 at Micro Analysis Laboratory Tandem accelerator, The University of Tokyo (MALT), contents of this report will be focused on the experiments and simulations of LPD on a test bench.
    
    Speaker: Lezhi Wang (MALT, The Universiry of Tokyo, Japan)
  - 40
    
    Low background In-situ 10Be AMS analysis using improved Be extraction method
    
    Surface exposure dating, which calculates the exposure age of rocks based on the accumulation of in-situ cosmogenic nuclides on the ground surface, is a very useful technique for directly dating the age of exposed rocks. Surface exposure dating has many advantages, but the required high-precision measurement is not easy. This is mainly due to the extremely low abundance of cosmogenic nuclides. The production of in-situ cosmogenic nuclides is proportional to the cosmic ray flux that reaches the ground surface. Cosmic ray penetration to earth’s surface is shielded by the atmosphere and the earth's magnetic field. Therefore, the generation rate of cosmogenic nuclides is lower at low altitudes and low-middle latitudes, where the shielding effect of the atmosphere and earth's magnetic field is high. Therefore, this method is widely applied to high latitude polar regions, such as Antarctica, where the production rate is comparatively higher and to high altitudes in the middle and low latitude regions. However, this method has the advantage of being able to directly measure the age at which rocks were exposed on the ground surface, and is also applied to low-middle latitude areas and low elevation areas near coastlines. Analysis of such samples requires low background beryllium-10 (10Be) measurements.
    Ion chromatography using a cation exchange resin has been used for extraction of Be from rock samples for accelerator mass spectrometry. However, with this method, the extraction position of the target Be may be shifted depending on the content of impurity ions contained in the sample, or the impurity ions remain after the ion exchange column experiment and adversely affect the subsequent Be purification. In this study, it was possible to obtain high-purity Be by adding the chelating resin solid phase extraction method using DIPEX (R) extractant to the separation and purification process of Be. By adding this extraction process, the residual amount of boron in the pretreatment process was reduced by more than 90%, and the analysis of ultra-low concentration 10Be became possible. This is expected to make it easier to apply surface exposure dating to low altitude areas in low and middle latitudes such as Japan.
    
    Speaker: Yosuke Miyairi (AORI,Univ.Tokyo)
  - 41
    
    New evidence of AMS 14C/13C for rock desertification in the rock vanish organics in the SW China
    
    Human activity-induced soil erosion and rock desertification in southern China's karst areas is a severe problem for the local economy and stability of ecosystem. However, it is challenge to quantitatively link the human activity-induced soil erosion to the local rock desertification by traditional geochemistry methods. In this study, we explored pyrolysis-combustion technology to partition rock varnish organics on exposed rock surface due to soil erosion into pyrolysis labile-recalcitrant and pyrolysis inert organic molecules for accelerator mass spectrometry (AMS) 14C dating analysis to investigate their relationship in Zhenfeng karst region in the Guizhou Province. This study focuses on the high-precision AMS 14C dating and 13C analyses for better understanding the evolutionary history of rock desertification in this region. The conceptual model posits that soil erosion increases rock exposure, facilitating varnish formation that is a thin layer of hard organic membrane on exposed rock surfaces. It could be a novel research material because it captures landscape evolutionary events. The results of AMS 14C dates and 13C values of pyrolysis labile and pyrolysis inert organic carbon molecular groups show that human activities virtually impact on soil erosion, karst geomorphology evolution, and the local desertification. This study provides valuable database through novel technology to explicitly examine the long-debated research problems in the rock desertification field in world karst geographic areas.
    
    Speaker: 佳曹 (北京师范大学)
  - 42
    
    Radiocarbon-based source apportioning of organic carbon aerosols over Mt. Tai, China : A case study from the 2006 sampling campaign
    
    In order to better characterize carbonaceous components in atmospheric aerosols and to assess the contributions of biomass sources in the carbonaceous aerosols in the regions where heavily influenced by field burning of agricultural wastes, we collected carbonaceous aerosols at the summit of Mt. Tai (1534 m above sea level) on a daytime and nighttime basis during a summertime campaign (May–June 2006) and analyzed radiocarbon and 13C of bulk-phase organic aerosols to determine the relative contribution of biomass and fossil sources. Mt. Tai is heavily influenced by field burning of agricultural wastes such as wheat straws in the North China Plain during the harvest season in early summer (Fu et al., 2008). Thus, it is an ideal site to characterize the air quality influenced by the heavy biomass burning for this purpose. In this study, we present radiocarbon and 13C data of carbonaceous aerosols at Mt Tai and discuss the source apportionment using the Markov Chain Monte Carlo-driven Bayesian modeling.
    Reference;
    Fu et al., Organic molecular compositions and temporal variations of summertime mountain aerosols over Mt. Tai, North China Plain, Journal of Geophysical Research, 113, D19107, doi:10.1029/2008JD009900.
    
    Speaker: Prof. Liu Shan (Hubei University)
    
    Fu Mt.Tai.pdf
    
    Liushan, AMS-16 OC_kk.docx
  - 43
    
    Restoration of the cooling water quality of a stand-alone accelerator facility
    
    Cooling water is an essential part of the infrastructure of all but the smallest AMS instruments, and of particle accelerators in general. While facilities situated on larger scientific campuses often can rely on good quality water from a central supply, many instruments, including VERA at the University of Vienna, are situated on sites where a stand-alone provision is necessary. Because it is considered part of the infrastructure, little support is provided by the accelerator manufacturers.
    VERA, established in 1995, operated smoothly for the first 14 years without paying much attention to water quality. Then, first blockages of magnet coils were observed. While removal by rinsing with commercial descaler liquids was successful initially, problems became more severe over time, culminating in the unrecoverable blockage of a quadrupole coil with magnetite. A major effort became necessary.
    Cooling systems of particle accelerators are a combination of materials like steel, aluminum, copper, and plastics. Directly cooled magnet coils apply voltages to the water. Oxygen and CO2 diffuse through plastic tubing. This evokes all kinds of degrading chemical reactions, dissolving copper and iron, and depositing carbonates, magnetite, and elementary copper. Information on these processes and possible remedies is mainly found in literature on nuclear reactors and stator coils of power generators. Specific information on particle accelerators and literature on the best practice for cooling water is scarce (Spencer 2014). Pure water, with pH about 8, conductivity below 1 µS/cm, and dissolved oxygen below 10 ppm seems advisable.
    We achieved this goal by replacing all plastic tubing with several hundred meters of diffusion tight multi-layer composite pipes, and EVOH where electrical insulation was necessary. A mixed-bed demineralization cartridge was mounted to remove any newly dissolved ions, and before addition of new water dissolved oxygen is stripped in a self-built nitrogen bubbler. As the complete removal of all accumulated magnetite in the steel tubing seemed impossible, filter frits were mounted before the individual components. Conductivity, pH, and oxygen content are regularly controlled with handheld instruments. The modifications took a lot of work, but minor financial efforts. Problems seem to have diminished since then.
    The best method for clearing magnet coils seems to be rinsing with circulating EDTA solution. The solution can be introduced even into completely blocked coils with the help of a suction flask. Deposits of particulates are efficiently knocked out with packets of water pushed through at high speed with pressurized air.
    We will present a summary of the relevant literature and describe the methods used at VERA.
    C. M. Spencer, Improving the Reliability of Particle Accelerator Magnets: Learning From Our Failures in IEEE Transactions on Applied Superconductivity 24/3, p 1 (2014) doi: 10.1109/TASC.2013.2280923.
    
    Speaker: Peter Steier (University of Vienna)
  - 44
    
    Technical design of a new facility: positive ion source mass spectrometry
    
    The positive ion source mass spectrometry is currently undergoing extensive research and development, being regarded as a more compact and cost-effective alternative to conventional tandem accelerator mass spectrometers. However, its elimination of the accelerator design presents challenges in overcoming the instability of low-energy carbon ion beams extracted by the Electron Cyclotron Resonance (ECR) ion source of gaseous samples, as well as the beam losses post-passing through the charge exchange cell. Particularly sensitive to changes in gas density within the charge exchange cell as the beam energy decreases. In this paper, the comprehensive design of low energy carbon ion beam is investigated deeply. In the optimization process, TraceWin, TOSCA and LISE++ are used to complete the task. LISE++ software, in particular, facilitates simulation calculations of complex interactions between ion beams and medium. Additionally, comprehensive testing of the device's bending magnet components has been conducted, with final results demonstrating strong concordance between magnetic field measurements and the physical design model. Presently, all components of the device have been fabricated, and equipment installation is forthcoming. Subsequent analysis of beam measurements will be carried out and compared with calculated models. The objective of this comparative analysis is to ascertain the final designing scheme, with a paramount focus on achieving efficiency and reliability in the entire system.
    
    Keywords PIMS·Beam dynamics·LISE++·TOSCA
    
    Speaker: wangxuan li (Shanghai Institute of Applied Physics, Chinese Academy of Sciences)
    
    Technical design of a new facility positive ion source mass spectrometry.docx
  - 45
    
    TESTING AND ASSESSMENT OF HIGH-PRECISION AND HIGH-ACCURACY AMS-RADIOCARBON MEASUREMENTS AT NANJING UNIVERSITY, CHINA
    
    In 2018, an Ionplus 200 kV MIni-CArbon DAting System (MICADAS) Accelerator Mass Spectrometer (AMS) was installed at the Laboratory of AMS Dating and the Environment, Nanjing University (NJU-AMS Laboratory), China. The NJU-AMS Laboratory is largely devoted to research on radiocarbon dating and 14C analysis in fields of earth, environmental and archaeological sciences. The laboratory has successfully employed various pretreatment methods, including routine pretreatment of tree rings, buried wood and subfossil wood, seeds, charcoal, pollen concentrates, organic matter, and shells. In this study, operational status of the NJU-AMS is presented, and results of radiocarbon measurements made on different sample types are reported. Measurements on international standards, references of known age, and blank samples demonstrate that the NJU-AMS runs stably and has good reproducibility on measurement of single samples. The facility is capable of measuring 14C in samples with the precision and accuracy that meet the requirements for investigating annual 14C changes, history-prehistory age dating, and Late Quaternary stratigraphic chronology research.
    
    Speaker: Dr Hongyan Zhang (Nanjing University)
  - 46
    
    Using 14C to trace the temporal variation and spatial distribution of fossil fuel CO2 in Guilin and its influencing factors
    
    In the context of today's global warming, China has proposed the carbon emission reduction target of carbon peaking and carbon neutrality, while the increase in atmospheric carbon dioxide concentration is mainly caused by man-made fossil fuel emissions. Radiocarbon isotope (14C) is the most effective tracers of fossil fuel CO2 (CO2ff). In this study, 5-liter air bags and PQ200 instrument were used to collect atmospheric and PM2.5 samples on the roof of the experimental building of Guangxi Normal University for a continuous year from 2023 to 2024. The leaves of sticktight (an annual plant) were sampled at 23 sites in Guilin in November 2023. A compact single-stage accelerator mass spectrometer (GXNU-AMS) was used to analyze the △14C content of these three types of samples in order to track the temporal variation and spatial distribution of CO2ff in Guilin and discuss its influencing factors. It can provide a scientific basis for local governments to implement effective carbon emission reduction measures.
    
    Speaker: Xinyi Han (Guangxi Normal University)
  - 47
    210Po, AMS 14C, 230Th/U dating and stable C/O isotope records of two stalagmites from South Ural, Russia
    
    210Po, AMS 14C, 230Th/U dating and stable C/O isotope records of two stalagmites from South Ural, Russia
    
    Hao-Ting Chiu1, Hong-Chun Li1,*, Tzu-Tsen Shen1, Dilyara Kuzina2, Satabdi Misra1, Horng-Sheng Mii 3, Lisheng Wang4, Zhibang Ma4
    
    Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan, ROC (hcli1960@ntu.edu.tw)
    
    Institute of Geology and Petroleum Technologies, Kazan (Volga Region) Federal University, Kazan 420008, Russia (di.kuzina@gmail.com)
    
    Department of Earth Sciences, National Taiwan Normal University, Taipei 11677, Taiwan, ROC (t44006@ntnu.edu.tw)
    
    Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029, China (wangls@mail.iggcas.ac.cn)
    
    Two stalagmites from Ikenskaya Cave and Oktyabrskaya Cave respectively were collected from south Ural Mountains in Russia in 2022. IKEN-1 from Ikenskaya Cave (54o43’1’’ N, 57o18’25’’ E) is 11.5 cm long and OTAR-1 from (54°10'09.7"N, 56°50'56.5"E) is 20.1 cm long. 210Pb (vis 210Po) dating indicates that IKEN-1 stopped growth before 200 years, whereas OTAR-1 continuously grew to the present. The 230Th/U dating results with large uncertainties and reversed age sequences due to low 238U but high 232Th contents. With high-resolution 14C dating, a total of 17 14C ages in IKEN-1 show stratigraphic order from 61535 Cal yr BP in the surface (1.25 mm) to 3515135 Cal yr BP (105 mm) at the bottom. Three available 230Th/U ages of IKEN-1 are similar to the 14C ages from the same samples, indicating negligible dead carbon influence (DCI) on the 14C ages. Based on the 17 14C ages, the chronology of IKEN-1 has been established by Bacon model. A total of 1155 samples from IKEN-1 have been measured for 18O and 13C, which allow us to reconstruct high-resolution paleoclimatic variations in the studying area during 590~3640 Cal yr BP. The 19 14C ages in OTAR-1 are generally in stratigraphic order from 85075 Cal yr BP in the surface (1.25 mm) to 6640135 Cal yr BP (195 mm) at the bottom, showing that the DCI on the 14C ages is relatively constant. As 210Po dating shows that the surface of this stalagmite is modern, the DCI on the 14C ages in OTAR-1 exists. The Three available 230Th/U ages of OTAR-1 are about 1000 years than the 14C ages from the same samples. We use the average of five 14C ages in the upper 6.25 mm as the DCI age which is 922 years. Subtracting this DCI age of 922 years from each 14C ages, the corrected 14C ages contain the least DCI. Using those corrected 14C ages, the chronology of OTAR-1 has been established by Bacon model. The dating results not only agree with the available 230Th/U ages, but also exhibit a growth hiatus between 200 and 1500 Cal yr BP. A total of 2009 subsamples from OTAR-1 are measuring 18O and 13C, which will provide paleoclimate records since 5590 Cal yr BP.
    
    Keywords: Stalagmite, South Ural Mountain, AMS 14C dating, 210Po and 230Th/U dating, stable isotope records
    
    Speaker: Mr Hao-Ting Chiu
  - 48
    
    Advances in Optical Detection of Radiocarbon Dioxide
    
    Radiocarbon detection and analysis is of great importance due its applications in dating and tracer for earth science, archaeology, forensic science, environmental evaluation, material analysis, metabolism, pharmacology and so on. Besides the well-known accelerator mass spectrometry (AMS) and liquid scintillation counting (LSC), optical technologies such as linear absorption spectroscopy, optical feedback linear cavity enhanced absorption spectroscopy (CEAS), two-color cavity ring-down spectroscopy (CRDS) and saturated-absorption CRDS have been proposed and developed for the detection of radiocarbon dioxide. In this report, we review the advances in optical detection of radiocarbon dioxide.
    
    Speaker: Prof. 达如陈 (浙江师范大学)
    
    Advances in Optical Detection of Radiocarbon Dioxide-ZJNU-Daru Chen.docx
  - 49
    
    AMS sample preparation method for Cl in soil
    
    Cl is a ubiquitous element in the environment. 36Cl ,half-life is 3.01x105a. The dating range can be up to 3.01x106a (10 times half-life), which covers the whole Quaternary period, has a unique advantage for the determination of Quaternary stratigraphy and Quaternary age. In recent years, with the continuous development of gas pedal mass spectrometry (AMS) technology, 36Cl has been measured with high sensitivity, which makes 36Cl dating technique more effective. With the development of accelerator mass spectrometry (AMS) , 36Cl can be measured with high sensitivity, which makes 36Cl dating technology promising. In this paper, we introduce the current status and difficulties in the study of 36Cl measurement by AMS. This paper introduces the current research status and research difficulties in the measurement of 36Cl using AMS, for the extraction of 36Cl in soil, and establishes a method for the preparation of 36Cl-AMS samples in the AMS laboratory of Guangxi Normal University (GXNU).The AMS samples were measured by the University of Tsukuba, Japan. Based on the obtained experimental data, the distribution of chlorine in soil at different depths in the Haihe River Basin was analyzed.
    
    Speaker: Guofeng Zhang (College of Physics and Technology, Guangxi Normal University, Guilin, Guangxi 541004, China)
  - 50
    
    Atmospheric CO2 and 14CO2 observations at the northern foot of the Qinling Mountains in China: temporal characteristics and source quantification
    
    A two-year (March 2021 to February 2023) continuous atmospheric CO2 and a one-year regular atmospheric 14CO2 measurement records were measured at the northern foot of the Qinling Mountains in Xi’an, China, aiming to study the temporal characteristics of atmospheric CO2 and the contributions from the sources of fossil fuel CO2 (CO2ff) and biological CO2 (CO2bio) fluxes. The two-year mean CO2 mole fraction was 442.2 ± 16.3 ppm, with a yearly increase of 4.7 ppm (i.e., 1.1%) during the two-year observations. Seasonal CO2 mole fractions were the highest in winter (452.1 ± 17.7 ppm) and the lowest in summer (433.5 ± 13.3 ppm), with the monthly CO2 levels peaking in January and troughing in June. Diurnal CO2 levels peaked at dawn (05:00–07:00) in spring, summer and autumn, and at 10:00 in winter. 14C analysis revealed that the excess CO2 (CO2ex, atmospheric CO2 minus background CO2) at this site was mainly from CO2ff emissions (67.0 ± 26.8%), and CO2ff mole fractions were the highest in winter (20.6 ± 17.7 ppm). Local CO enhancement above the background mole fraction (ΔCO) was significantly (r=0.74, p < 0.05) positively correlated with CO2ff in a one-year measurement, and ΔCO:CO2ff showed a ratio of 23 ± 6 ppb/ppm during summer and winter sampling days, much lower than previous measurements and suggesting an improvement in combustion efficiency over the last decade. CO2bio mole fractions also peaked in winter (14.2 ± 9.6 ppm), apparently due to biomass combustion and the lower and more stable wintertime atmospheric boundary layer. The negative CO2bio values in summer indicated that terrestrial vegetation of the Qinling Mountains had the potential to uptake atmospheric CO2 during the corresponding sampling days. This site is most sensitive to local emissions from Xi’an and to short distance transportation from the southern Qinling Mountains through the valleys. Conducting measurements of atmospheric CO2 and Δ14CO2 in the geographically and ecologically crucial area of the Qinling Mountains and quantifying the sources of CO2 can help to improve the accuracy of the inverse carbon emission data, assess the regional carbon emissions, and formulate the carbon emission reduction measures.
    
    Speaker: Wanyu Liu (Beijing Normal University)
  - 51
    
    Charge exchange cross-section for C-He collision at 70-220 keV
    
    Using helium as the stripping medium has become a dominant trend in 14C-AMS miniaturization. In order to explore how to utilize lower-energy beam for 14C analysis, more experimental data on low-energy C-He collisions are needed. In this work, the charge state yield versus target thickness after C- and helium collisions at 70-220 keV was investigated using the GXNU-AMS system, and the charge state yields and charge exchange cross-section data in C-He collision in 70-220 keV are obtained. The results show that the charge state yield of C+ increases significantly with decreasing incident carbon ion energy. The charge state yield of C+ increases from 50.4% to 74.8% when the incident energy of C- decreases from 220 keV to 70 keV. The equilibrium state yields of C2+, C3+, and C4+ show the opposite trend to C+. Compared with the cross-section σ_1,i_(i = -1, 0, 2, 3), the cross-section σ_i,1_(i = -1, 0, 2, 3) is relatively large and tends to increase with decreasing energy. These data can provide theoretical support for low-energy AMS construction below 100 keV.
    
    Speaker: Guofeng Zhang (College of Physics and Technology, Guangxi Normal University, Guilin, Guangxi 541004, China)
  - 52
    
    Creation of a database of the textile materials excavated from Egyptian monuments in the Kyoto University Museum
    
    This report presents the radiocarbon dating results obtained for these Egyptian materials from the Kyoto University Museum, including Coptic textiles, mummy cloth and sandals. It also reports on the material database, the Kyoto University Research Information Repository, which includes radiocarbon dates and material analyses.
    The Coptic Textile Collection of Egyptian Archaeological Materials at the Kyoto University Museum, with 28 items, is not large compared to other prominent collections. However, the Egyptian archaeological materials in the Kyoto University Museum were transferred and donated to the University by Dr Kosaku Hamada, the first professor of the Department of Archaeology at Kyoto University, after he left to study with Dr Petrie in England. The materials were selected because they cover a wide range of characteristics of the entire Coptic period. In addition, through interdisciplinary and cross-disciplinary efforts, we have recently discovered that the collection contains a variety of dated materials, including the world's oldest shell-purple dyed Coptic textiles and Byzantine rack-dyed materials from the end of the Coptic period, and have identified a wide range of textile production periods, regions and techniques.
    By providing radiocarbon dates, the collection is not only a globally valuable one, rich in variations of Coptic textile production dates, regions and methods, but also has the advantage of being the world's reference material for discussing the chronology of Coptic textile weaving.
    
    Speaker: Misao YOKOYAMA (Kyoto University)
    
    AMS16thmeeting_MisaoYokoyama_Japan.docx
  - 53
    
    Development of a chemical separation strategy for r-process derived radionuclides from terrestrial and lunar geological archives
    
    The understanding of the formation of the elements has been an intriguing topic within the last decades. It is now proven that the heaviest naturally occurring elements, the actinides, are produced in the astrophysical r-process. However, the exact site of this process is still under debate. Recently, the amount of interstellar $^{244}$Pu (T$_{1/2}$ = 81.3 Myr) in various geological archives like deep-sea ferromanganese crusts and sediments has been investigated by applying highly sensitive accelerator mass spectrometry (AMS) measurements.[1,2] Correlation of the influx of $^{244}$Pu with $^{60}$Fe (T$_{1/2}$ = 2.6 Myr), which is produced by the s-process in massive stars and ejected into the interstellar medium by supernovae, could point to supernovae as the origin of the r-process in the universe. To further prove this hypothesis, recent investigations focus on the determination of other long-lived radionuclides which are also produced in the r-process, e.g. $^{247}$Cm (T$_{1/2}$ = 15.6 Myr) and $^{182}$Hf (T$_{1/2}$ = 8.9 Myr). However, the separation of the expected ultra-trace amounts of these nuclides (a few 100 atoms per gram) from huge amounts of matrix and interfering elements represents a major analytical challenge. Thus, this contribution aims to probe existing chemical treatment strategies for the determination of minute amounts of actinides and Hf from various geological archives. The separation method is based on anion exchange for Pu separation and extraction chromatography for Cm and Hf, respectively.[3,4] The yield of the different elements is monitored by a combination of AMS, γ-counting and ICP-MS measurements. The effective separation strategy of different actinides and Hf from major matrix elements allows for processing multi-gram amounts of different geological samples. This is a prerequisite for the detection of live interstellar $^{244}$Pu, $^{247}$Cm and $^{182}$Hf in terrestrial and lunar geological archives. Furthermore, this method can be adapted for the analysis of other environmental samples regarding their content and isotopic ratio of anthropogenically produced Pu, Am and Cm which holds potential for nuclear safeguards and nuclear forensics studies.
    
    Acknowledgments
    Ulf Linnemann from Senckenberg Museum Dresden is gratefully acknowledged for providing deep-sea nodules for chemistry tests. The Central Radionuclide Laboratory of TU Dresden is acknowledged for using their laboratories, gamma counters and $^{241}$Am stock solution.
    
    Speaker: Sebastian Fichter (Helmholtz-Zentrum Dresden-Rossendorf)
  - 54
    
    Distribution of Beryllium-10 in top soils from the Tibetan Plateau and its climatic implications
    
    The Qinghai-Tibet Plateau is simultaneously influenced by the westerlies and the Asian monsoon, and the variations in monsoon moisture have significant impacts on the entire Qinghai-Tibet Plateau and Asian climate system. Among the interesting tracers of atmospheric circulation, the Be-10 isotope deposited in soils can be a potential one. The dominant atmospheric production, relatively long tropospheric residence time (a few weeks) and adsorption to aerosols make the isotope an excellent tracer of airmass circulation. The fallout of the isotope on the Earth’s surface is mainly linked to wet (precipitation) deposition and consequently, the isotope can also provide information on moisture sources. Once in the soil, the isotope has a relatively stable chemistry and is incorporated or adsorbed onto soil particles without extensive alteration. These properties, together with relatively long half-life (1.39 Myr), make Be-10 a valuable tracer for the reconstruction of past climate changes on long and short-time scales. In our study, we use soil samples from a depth of 0~30 cm taken in the southeastern Qinghai-Tibet Plateau, including 5 profiles of layered soil samples. The sampled soils were extracted from plain areas that are unaffected by human activity, to avoid extensive effects of soil erosion and mixing of the surface layer. The chemical extraction of Be-10 from sediment samples includes the stepwise precipitation and separation of other sediment components through pH adjustments, and the measurements were performed at the ETH AMS facility. We have combined our new Be-10 data with about 60 surface soil samples covering the majority of China. The results indicate that the concentrations of Be-10 in the surface soil of the Qinghai-Tibet Plateau range from 0.40 to 8.36×108 atoms/g, around an average of 2.37×108 atoms/g, while those from the northwestern and eastern parts of China vary between 0.56-3.62×108 atoms/g and 0.12-10.42×108 atoms/g, with averages of 1.50×108 atoms/g and 3.56×108 atoms/g, respectively. The samples are distributed in non-permafrost regions and changes in soil texture and mineralogy were not significantly affecting the Be-10 distribution. The general higher Be-10 concentration in the soils of the Qinghai-Tibet Plateau compared to those from the northwestern parts and at a lower level than those from the eastern parts of China reflects the medium precipitation amount received by Tibet. For the samples from the Tibet, the Be-10 concentrations are positively correlated with the mean annual rainfall over the past decades (ranging from 50 to 1300 mm/y) after excluding a maximum value (R2 = 0.34, p = 0.01). This is consistent with our previous findings, which showed a significant positive correlation between Be-10 in soil and annual precipitation in areas with rainfall less than 1200 mm/y. The results suggest that Be-10 in this region is mainly derived from wet deposition, and the amount of Be-10 retained in soil reflects information about precipitation changes. In addition, integrating a global Be-10 deposition model, the retention time of Be-10 in soils from this region has been calculated to be several hundred to three thousand years (the late Holocene), indicating the spatial distribution characteristics of precipitation patterns in the southeastern Qinghai-Tibet Plateau during the period. It was also found that the data from the profile-layered samples collected in this study show little vertical variation in the distribution of Be-10 at different depths of surface soil (0.3% to 20.6%, with an average of 6.5%). The uniformity of the Be-10 distribution proves relatively stable precipitation patterns in the study area over the past several hundred years or even longer periods and indicates that the soils are relatively old and have not been severely affected by erosion. The Be-10 data from soils of the Qinghai-Tibet Plateau will be coupled to atmospheric transport and depositional models to further expand the data base and also include more information from remote regions like the Tibet Plateau that will promote our understanding of historical climate changes in this region.
    
    Speaker: Peng Chen (Hohai University)
  - 55
    
    Formation age and state of soil organic carbon in the wetlands of northern Tibet
    
    Wetlands are the largest carbon storage in the tundra zone of the Tibetan Plateau (amsl >4500 m), and the stored carbon is highly vulnerable to global warming. We selected two major wetland types in northern Tibet, lacustrine wetland (NC) and intermountain wetlands (NB), and took one soil profile each for soil organic carbon (SOC) content and carbon isotopes (δ13C & 14C) analysis. The results showed that the deepest thickness of the soil was 60 cm and 65 cm, respectively, and the oldest soil organic matter was formed at about 3200 yr BP. The content of soil organic carbon was as high as 8% - 20% in the layer above 50 cm, and was higher than 2% in the layer below 50 cm. The δ13C values of soil organic carbon in the lacustrine wetland varied from -24.0‰ to -27.0‰, and those in the mountainous wetland varied from -22.0‰ to -25.0‰. Both of them showed that the δ13C values of soil organic carbon near the bottom were more negative, and the change occurred significantly at a depth of about 45 cm, with a corresponding 14C age of 2.0 ka BP. In conclusion, it is likely that the soil organic matter in the wetlands of northern Tibet was generally formed since the middle-late Holocene about 3.2 ka. They were preserved with high soil organic carbon content and no obvious decomposition feature of organic carbon δ13C. Changes in the content and δ13C values of the soil organic matter around 2.0 ka BP was probably related to the shift of climate and environment at that time.
    
    Speaker: PING DING (State Key Laboratory of Isotope Geochemistry , Guangzhou Institute of Geochemistry, Chinese Academy of Sciences)
  - 56
    
    Performance Assessment of Graphitization Process at AGE-3 for 14C-AMS Analysis in IHEG
    
    Abstract: To overcome the disadvantages of manual purification system during AMS-14C measurement, including inefficiency, unstable quality of graphite, and interference from modern carbon. CAGS-IHEG (Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences) introduced AGE-3 to improve the performance of small carbon graphite, leading to the rapid production of high-quality carbon samples. By changing the reaction temperature and H2/CO2 ratio, the optimum conditions for prompt graphitization reaction have been determined. Corrections for isotopic fractionation and increased modern C background are made by measuring samples in relation to standards of similar mass and a blank sample. In comparison to a manual purification system, AGE-3 results in improvements in parameter visualization and the precise synthesis of graphite. The enhanced technique for graphitization was specifically developed to achieve optimal beam currents of 14C in IHEG 1 MV AMS measurement, aiming to address issues related to inefficiency and impurities in the processing of soil and sediment samples.
    
    Speaker: 佳眉王 (中国地质科学院水文地质环境地质研究所)
  - 57
    
    Pushing the limits of $^{26}$Al at MILEA
    
    Competitive AMS measurements of $^{26}$Al are possible at low ion energies. Selecting Al$^-$ as a negative ion for the tandem accelerator has the benefit of the complete suppression of the interfering isobar $^{26}$Mg. However, because of the notoriously low yield of Al$^-$ from a Cs sputter ion source, we have to pull out all the stops to improve the overall efficiency, in particular the ionization yield at the ion source, the transmission through the accelerator and the detection efficiency. Here we describe the preformence of Al$^-$ measurements on the 300 kV MILEA multi-isotope AMS system and discuss the critical components and their optimization.
    Mixing the Al$_2$O$_3$ sample material with a carefully selected metal powder in an optimal mixing ratio can result in a high practical over all. We investigated several commonly used metal powders in different mixing ratios and found that, for our ion source, the optimal mixing ratio is 1:1 Al$_2$O$_3$ with Cu (by weight). With this mixing ratio, an ionization yield of 0.08% was achieved after 4 h of sputtering.
    At low energies and by using He stripping the highest transmission can be achieved by selecting the 2+ charge state(Al$^{2+}$) on the HE side. We investigated the transmission and deduced stripping yields for Al over the energy range accessible at MILEA (~100-330 keV). Highest transmission close to 60% was found at around 250 keV for the 2+ charge sate. However, even at much lower energies of 140 keV transmission values for 2+ charge state of ~50% are found, indicating that $^{26}$Al measurements are possible at very low energies with only slightly reduced yield.
    Selecting the 2+ charge state for $^{26}$Al, however, has the drawback that the mass/charge ambiguity of $^{13}$C$^+$ has to be suppressed. At low ion energies this can be solved using a passive absorber cell in front of the gas ionization detector, because at energies below ~500 keV/u the range of $^{13}$C is significantly shorter than $^{26}$Al, partly increased by anomalies in the stopping cross section. By optimizing the absorber geometry we can detect most of the $^{26}$Al despite the low residual ion energy and measure the nominal ratio to ~88%.
    In practice, most geological samples are not limited by the amount of sample material, but by low $^{26}$Al/$^{27}$Al ratios. With long measurement times we can still achieve high overall efficienies of a few 0.01% resulting in statistical errors comparable to $^{10}$Be. Currently, however, cross-talk at the ion source seems to be the ultimate limit for the background and a carefull assesment of this contribution is needed to fully exploit the high efficiency measurements at the low concentration limit.
    
    Speaker: Christof Vockenhuber (ETH Zurich, Laboratory of Ion Beam Physics)
  - 58
    
    Radiocarbon Dating of an Alpine Plant Leaf Found in Permafrost on the Daisetsu Mountains, Hokkaido, Japan
    
    The age of a small plant leaf frozen in ground ice at a depth of 8.3 meters in a borehole on the summit area of Mt. Goshiki in the Daisetsu Mountains, Hokkaido, Japan, was determined using radiocarbon dating. The calibrated age of the leaf (using OxCal v. 4.4.4) was 288±26 (40.0%) or 182±39 (48.2%) calendar years BP, placing it within the last Little Ice Age in Japan. This age indicates the last aggradation of mountain permafrost on the Daisetsu Mountains. The current summit area of the Daisetsu Mountains was formed approximately 5,000 years ago, and permafrost is sporadically distributed under the current mean annual air temperature of about -3°C. The leaf was found within ground ice that filled an oblique crack approximately 10 mm wide in the sample core. The dated leaf was identified as a member of the Ericaceae family, which is commonly found on the current ground surface around the sampled borehole.This finding suggests that the leaf infiltrated with liquid water down to 8.3 meters through a crack extending from the ground surface about 300 years ago. It also implies that the ground, consisting of volcanic ash and pumice, was dry and unsaturated by water or ice at the time the current ground ice in the summit area of Mt. Goshiki was formed. The permafrost must have thawed to at least 8.3 meters, likely due to volcanic activity related to the last eruption of Mt. Asahi, the highest peak of the Daisetsu Mountains, located about 5 km west of Mt. Goshiki.
    
    Speakers: Go Iwahana (International Arctic Research Center, University of Alaska Fairbanks) , Masao Uchida (NIES-TERRA AMS facility, National Institute for Environmental Studies)
  - 59
    
    Rapid UV-Oxidation setup at ETH for AMS radiocarbon analysis of dissolved organic carbon in marine and freshwater samples
    
    Dissolved organic carbon (DOC) is a major, yet little understood component of the global carbon cycle. Although radiocarbon analysis of DOC provides valuable information on the origin and age of this pool, the number of measurements, particularly in marine systems, is limited by the complexity and low efficiency of existing methods. These methods generally use UV irradiation to oxidize the organic carbon, and then perform 14C analyses on the resulting CO2. Disadvantages of most currently applied UVox methods include being limited to the processing of only one sample at a time, the large sample volumes required, and relatively high processing blanks. Here, we present a compact UV-Oxidation system, where up to 12 water samples can be oxidized simultaneously in separate quartz reactors arranged around a single UV lamp. This simple setup uses helium instead of vacuum to speed up the extraction of the CO2 formed after oxidation. Key improvements of the new UVox setup include: 1) Reduced required sample volumes (30- 60 ml instead of 1L), as samples are measured for 14C with the Micadas gas ion source, 2) High UV oxidation efficiency for standards (96%), 3) No KI trap needed, 4) Decreased processing time with the possibility of oxidizing up to 12 samples in 4-6 h, 5) And the possibility of combining CO2 from different reactors to one trap, enabling the measurement of samples with very low DOC concentrations. We determined a low background of 2.3 ± 0.6 µgC with F14C= 0.27±0.05 on fossil and modern standards dissolved in pre-irradiated Milli-Q water. We will present the reproducibility of the line and first measurements on DOC samples from Swiss lakes and the Sargasso Sea.
    
    Speaker: Dr Negar Haghipour (1Geological Institute, Department of Earth Sciences, ETH Zurich, 8092 Zurich, Switzerland 2 Laboratory for Ion Beam Physics, ETH Zürich, Switzerland)
  - 60
    
    Simple gas ionization chamber design for low-energy ion measurements
    
    Simple gas ionization chamber design for low-energy ion measurements
    
    Shulin Shi 1, Hongtao Shen 1、2* , Junsen Tang 1, Li Wang 1, Guofeng Zhang 1, Dingxing Chen 1, Linjie Qi 1, Yun He1、2,Ning Wang1、2, Qingzhang Zhao3, Ming He3, Shan Jiang3
    1. College of Physics and Technology, Guangxi Normal University, Guilin Guangxi 541004, China
    2．Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology, Guilin, Guangxi, 541004, China
    3. China Institute of Atomic Energy, Beijing 102413, China
    
    *Correspondence to: shenht@gxnu.edu.cn
    
    Abstract:
    A simple single anode gas ionization chamber (GIC) design for low-energy ions was developed for a compact accelerator mass spectrometer at Guangxi Normal University (GXNU-AMS) , China. This detector comprises a 50-nm silicon nitride window, an anode, a Frisch grid, and a cathode. To determine the optimal measurement conditions and to characterize the detector performance at low energy, test experiments were performed with a 239Pu/241Am α source and 3H and 14C ions at the energies of ~180 keV. The results prove that this GIC can be used for measuring ions at low energy and meets the requirements for low-energy ion measurements at GXNU-AMS.
    Keywords: GIC; low energy; AMS
    
    Speaker: Mr Shu lin Shi
    
    AMS16 abstract..docx
  - 61
    
    Source apportionment of carbonaceous aerosol in Canada’s oil sand region
    
    Oil sands (also tar sands) are a type of unconventional petroleum deposit from which bitumen is mined by surface mining or in-situ extraction to produce heavy oil. A globally significant soil sand region (producing 3.3 M barrels per day in 2022), is located in the Athabasca River basin of Alberta, Canada. The environmental impacts of oil sand mining, specifically air pollution, are not well understood. This is in part because mining activities are taking place in the boreal forest region where rapid climate change is leading to changes in vegetation productivity and composition and increasing the risk of wildfires.
    Here, we report the concentration and sources of total carbon (TC) and elemental carbon (EC) in fine airborne carbonaceous aerosol (PM2.5) in Canada’s oil sand region. A total of 36 24-hr quartz filter samples were collected with high‐volume samplers at the Wood Buffalo Environmental Association’s Bertha Ganter – Fort Mckay station in Fort McMurray between February and October 2017. Ancillary continuous measurements at the station included meteorological conditions, PM2.5, SO2, NOx, and ozone. Air mass contributions to the station were analyzed using NOAA’s Hysplit backward trajectory model. Bulk filter samples were analyzed for their total carbon and nitrogen content and stable isotope composition and radiocarbon content with EA-IRMS and AMS. EC was isolated on a modified Sunset OC/EC analyzer with the Swiss_4S protocol, converted to graphite using a small-sample closed-tube zinc-reduction method, and analyzed with AMS.
    Preliminary analyses show that bulk aerosol ranged in composition from pristine to 6 ug C m-3 (good AQI) and 0.5 ug N m-3, with C/N-ratio of 19 to 54. δ13C values were typical for emissions from C3-biomass (-23 to 27 ‰), with δ15N values ranging from 5 to 14 ‰. Analyses of radiocarbon in TC show significant contributions of fossil sources to the TC burden (10-80%) that are significantly greater than reported for other parts of the Arctic. Together, our data will enhance our understanding of the sources and seasonal dynamics of air pollution in Canada’s oil sands region.
    
    Speaker: Ms Lurui Niu (University of California, Irvine)
  - 62
    
    Source apportionment of sedimentary PAHs in Sakudrada Moat of Imperial Palace, Tokyo using compound-specific radiocarbon analysis
    
    Polycyclic aromatic hydrocarbons (PAHs) form one of the most important classes of persistent pollutants (Blumer 1976). Some PAHs are carcinogenic and mutagenic. Owing to their adverse effect on human/ecological health and widespread distribution around in the environment, identification of the sources of PAHs is of special concern (Pedersen et al. 2004). Thus, elucidating and evaluating the source of PAHs is of importance for being essential to achieving better source control and pollution abatement. PAHs are generally produced through the incomplete combustion of organic matter (e.g., fossil fuels, biomass, or detrital organic materials) and emitted to the atmosphere. Because of their hydrophobic nature, once these semi-volatile organic compounds enter aquatic environments through atmospheric deposition, PAHs accumulate in the underlying sediment and are stored for a long time. Especially, sediments from urban reservoirs such as moats and canals provide an ideally homogenized natural archive of particle-borne pollution, integrating the input over the past several decades as a result of the combined processes of deposition, runoff, water mixing, and sedimentation. So far, the source apportionment of PAHs using natural level radiocarbon is used as a useful tracer to sedimentary and aerosols, for example, for industrial countries (Asian megacities) and urban reservoirs (Kanke et al., 2004; Kumata et al., 2006, 2024). The purposes of this study were to quantitatively apportion modern and fossil sources of PAHs by determining radiocarbon and δ13C contents of individual PAHs extracted from an urban reservoir, namely, one of the moats surrounding the Imperial Palace (the Sakurada Moat), located in the central Tokyo metropolitan area, which is recognized as one of the most urbanized areas in the world. samples and to reconstruct historical trends of the relative inputs of PAHs from fossil fuel combustion and biomass burning. In this conference, we present radiocarbon and δ13C data of sedimentary PAHs and source apportionment of PAHs using the Markov Chain Monte Carlo-driven Bayesian modeling.
    
    Reference:
    Kanke, H.,et al. (2004) NIMB, 223-224, 460-465., Kumata, H., et al. (2006). Environ. Sci. Technol., 40(11), 3474-3480., Kumata, H.,et al. (2024) Radiocarbon,in press.
    
    Speaker: Masao Uchida (NIES-TERRA AMS facility, National Institute for Environmental Studies)
  - 63
    
    Source Attribution of Atmospheric CO2 Using Δ14C and δ13C as Tracers in Chinese Megacities
    
    Identifying the sources of atmospheric Carbon dioxide (CO2) is an important prerequisite for developing effective mitigation strategies. Here we conducted regular observations of the atmospheric CO2 mixing ratio and its carbon isotope compositions (i.e., Δ14C and δ13C) in Xi'an and Beijing during winter, to estimate source contributions of CO2 emissions in Chinese megacities. The results showed that CO2 emissions in both Xi'an and Beijing originated mainly from fossil-fuel sources, which contributed 65 ± 3% and 82 ± 2% of the total CO2 enhancement, respectively, during the sampling period; the results also revealed a substantial biogenic CO2 contribution during winter. We further separated the fossil-fuel sources into contributions from coal, oil and natural gas combustions. We found that coal combustion was the dominant anthropogenic source in Xi'an, accounting for 54 ± 4% of the total fossil-fuel emissions, and oil and natural gas contribute almost equally to the emissions. In contrast, emission from natural-gas combustion was the main fossil-fuel source in Beijing, accounting for more than half of the total fossil-fuel emissions, whereas, coal combustion contributed only 17 ± 10%. These top-down results are generally consistent with emission inventory when seasonal variations of emissions are considered; some differences between the two methods indicated that the inventory for Xi'an might be underestimating the emissions from oil consumption. This study confirms the potential of direct verification between top-down and bottom-up methods from the perspective of source attribution. We further combined inventory data sets and Δ14C measurements to quantitatively evaluate the contribution of human respiratory emission in Beijing, and further isolate the emissions from fossil fuels and biogenic CO2 sources. We found that the human respiratory emissions could increase atmospheric CO2 concentration by about 2 ppm, accounting for 14% ± 6% of average CO2bio concentration in winter. This study highlights the importance of human respiration in carbon emissions in megacities and has implications for a better understanding of the regional carbon budget.
    
    Speaker: Peng Wang
  - 64
    
    Vertical measurements of atmospheric CO2 and 14CO2 at the northern foot of the Qinling Mountains in China
    
    Air at different heights within 2000 m at the northern foot of the Qinling Mountains were sampled by unmanned aerial vehicle to study the vertical variations and sources of atmospheric CO2 and 14CO2. The CO2 concentrations mainly exhibited a slight decreasing trend with increasing height during summer observations, which was in contrast to the increasing trend that was followed by a subsequent gradual decreasing trend during early winter observations, with peak CO2 levels (443.4 ± 0.4–475.7 ± 0.5 ppm) at 100–500 m. The variation in vertical concentrations from 20 to 1000 m in early winter observations (21.6 ± 19.3 ppm) was greater than that in summer observations (14.6 ± 14.3 ppm), and the maximum vertical variation from 20 to ~2000 m reached 61.1 ppm. Combining Δ14C and δ13C vertical measurements, the results showed that fossil fuel CO2 (CO2ff, 56.1 ± 15.2%), which mainly come from coal combustion (81.2 ± 3.4%), was the main contributor to CO2 levels in excess of the background level (CO2ex) during early winter observations. In contrast, biological CO2 (CO2bio) dominated CO2ex in summer observations. The vertical distributions of CO2ff in early winter observations and CO2bio in summer observations were consistent with those of CO2 during early winter and summer observations, respectively. The strong correlation between winter CO2bio and ΔCO (r = 0.81, p < 0.01) indicated that biomass burning was the main contributor to CO2bio during early winter observations. Approximately half of the air masses originated from the Guanzhong Basin during observations. The results provide insights into the vertical distribution of different-sources of atmospheric CO2 in scientific support of formulating carbon emission-reduction strategies.
    
    Speaker: Dan Liang
  - 65
    
    A Novel Method For Preparing Uranium-236 Samples In Seawater By Coprecipitation Technology For Accelerator Mass Spectrometry
    
    Uranium-236 serves as a widely utilized analytical tool for detecting environmental radioactive contamination and tracking natural processes. Given the low concentration of 236U in environmental samples, Accelerator Mass Spectrometry (AMS) emerges as a highly sensitive mass spectrometry method. Based on the AMS system at Guangxi Normal University (GXNU-AMS), we have developed and evaluated a novel approach for analyzing 236U in seawater samples. This method primarily involves the coprecipitation of Fe(OH)3 from actinides, followed by the extraction and purification of uranium using UTEVA ion exchange resin. To assess the extraction efficiency, we utilized alpha spectrometry (AS) and inductively coupled plasma mass spectrometry (ICP-MS), achieving a remarkable recovery rate of 85%. Furthermore, its applicability was validated through AMS tests on target samples, confirming its effectiveness in analyzing 236U in seawater. This method offers robust technical support for environmental radioactive research, holding significant implications for the field.
    
    Speaker: Weixin Chen (Guangxi Normal University)
  - 66
    
    AMS measurements of tritium in graphite from a decommissioned reactor
    
    The measurement of tritium by accelerator mass spectrometry (AMS) is a precise technique for determining tritium content. This technology is characterized by small sampling, high accuracy, and selectivity, making it a favorable method for measuring tritium in solids. In the process of measuring tritium by AMS, it is necessary to prepare the tritium-containing sample into the chemical form of TiH₂. This typically involves steps such as sample extraction, purification, and conversion into TiH₂. The accuracy of tritium AMS measurements is influenced by the quality of sample preparation, the performance parameters of the instrument, and the operational precision during the measurement. In this study,the compact 200kV single-stage AMS (GXNU-AMS) of Guangxi Normal University was used to determine the concentrations of ³H and ¹⁴C accumulated in irradiated graphite from a decommissioned reactor.
    
    Speaker: Junsen Tang (College of Physics and Technology, Guangxi Normal University, Guilin, Guangxi 541004, China)
  - 67
    
    AMS Radiocarbon Dating Analysis of Charcoal Samples from Natib Volcano: Implications for Volcanic Activity and Nuclear Power Plant Siting in the Bataan Volcanic Arc, Philippines
    
    Located within the Bataan volcanic arc of the Philippines is the potentially active Natib Volcano, situated on the western flank of Luzon Island near a decommissioned Bataan nuclear power plant (BNPP). As the Philippine government explores nuclear power as part of its energy mix, attention has shifted towards repurposing the former BNPP. However, despite its classification as potentially active, research on the volcanic activity of Natib Volcano is limited to proving the safety of BNPP rehabilitation.
    
    This study utilizes accelerated mass spectrometry (AMS) to obtain radiocarbon age dates of charcoal samples collected on Carabao Island, approximately 55 kilometers southeast of the flank of Natib volcano, Philippines. The lithology of the island predominantly consists of volcaniclastic and clastic rocks of dacitic and andesitic compositions. The four-centimeter (4-cm) thick charcoal layer is overlain by lapilli tuff and underlain by porphyritic andesite. Geochemical analyses, focusing on the comparison of major oxides and trace elements across volcanic data sets from various sources, revealed a strong correlation of magmatic evolution processes between the volcaniclastic deposits found in the same stratigraphy as the charcoal and the volcanic materials from the Western Bataan Lineament, particularly those from Mt. Natib and Mt. Mariveles. The radiocarbon dating of charcoal fragments from this region yielded age dates of 24,565 ± 281 BP, 24,885 ± 257 BP and 22,252 ± 218 BP years from three samples in the area, which are tentatively calibrated to the calendar year of 26,897 ± 302 BC (100%), 27,113 ± 219 BC (97.8%), and 24,675 ± 311 BC (100%), respectively. These ages supplement the previously obtained C14 age of 27,000 ± 630 years.
    
    This newly determined age enhances our understanding of Mt. Natib's volcanic history and contributes to the known age of magmatism of the Bataan Volcanic Complex. The findings have implications for the potential site of nuclear power plants in the region, further confirming the status of Mt. Natib as a potentially active volcano.
    
    Speaker: Ms Alexandria Tanciongco (Department of Science and Technology - Philippine Nuclear Research Institute)
  - 68
    
    An alternative method to improve AMS 14C dating for paleoclimate and environment studies in Chinese Loess Plateau
    
    We applied the high temperature pyrolysis-combustion technique to 2 last glacial loess-paleosol sequences in the Chinese Loess Plateau (CLP) to partition the total soil organic carbon (SOC) into pyrolysis labile-recalcitrant and pyrolysis inert SOC fractions for accelerator mass spectrometry radiocarbon (AMS 14C) dating analysis to explore which SOC fraction yields more reliable AMS 14C chronology for climate stratigraphy studies in the southern and eastern CLP. The dating results of pyrolysis labile-recalcitrant and pyrolysis inert fractions from 2 loess-paleosol sites show similarities in 2 aspects: (1) almost all loess samples show 14C dates of pyrolysis inert SOC compounds older than that of pyrolysis labile-recalcitrant molecules consistent with the general consensus that SOC molecular groups with stronger activation energy have older 14C ages; (2) dating results from the upper-middle loess profiles show good correlations with loess depths but deviated one from another in the lower loess profile. In addition to previous studies in the region , the comparison of soil morphology and climate proxies between loess-paleosol sequences indicate that climate-induced SOC content、soil texture and depositional mode matter strongly to AMS 14C dating range and accuracy. Our pyrolysis-combustion technology provides an alternative method to assess AMS 14C dates of different SOC fractions in molecular levels to improve chronology for paleoclimate and environment studies in the CLP.
    
    Speaker: Mr yi Yang (Beijing Normal University)
    
    An alternative method to improve AMS 14C dating for paleoclimate and environment studies in Chinese Loess Plateau.docx
  - 69
    
    Analysis of Tongatapu Island groundwater system using radiocarbon dating and hydrochemical data
    
    Groundwater, the world's critical freshwater resource, is currently facing significant challenges from overexploitation and depletion, particularly on small islands such as Tongatapu in the Kingdom of Tonga. This study aimed to analyze the groundwater system of the island by integrating radiocarbon dating and water quality analysis. Groundwater samples were collected from coastal areas and springs across the island to evaluate recharge processes and current water quality conditions. The age of the groundwater was estimated using radiocarbon analysis, and a detailed assessment of water quality parameters, such as pH and electrical conductivity, was conducted. This combined approach aims to provide an initial understanding of groundwater dynamics in Tongatapu, highlighting the age, recharge rates, and chemical properties of the aquifers. The results are expected to contribute significantly to the development of effective water management strategies for small carbonate islands, addressing the challenges related to water scarcity, pollution, and aquifer overexploitation.
    
    Speaker: Naoto Fukuyo (Geological Survey of Japan)
  - 70
    
    Background value reduction in 10Be/ 9Be measurement of 1MV AMS
    
    The background value of 10Be/9Be in 1MV AMS was originally ~10-14, so the use was limited for the measurement of low-value Be samples. Therefore, we started research to lower the background value without significantly changing the existing equipment itself. First, a sample with a low background value was obtained. Next, various attempts were made on the existing equipment to increase the energy of the tandem to the maximum value of 1.1 MV, and the Ar stripper gas pressure in the middle of the tandem was also adjusted and used, and the ion value after the Ar stripper gas was changed from 1+ to 2+, and the Si3N4 foil was tested by changing the thickness. Finally, it succeeded in lowering the background value of 10Be/9Be without installing additional Magnet or ESA in the equipment, and it was possible to measure the Be sample with a low value by reaching the background value of 10Be/9Be near 10-15.
    
    Speaker: Junghun Park (KIGAM)
    
    Be_ abstract_AMS16.docx
  - 71
    
    Bomb 14C recorded by tree rings in China- A brief summary
    
    Atmospheric nuclear weapons tests caused a dramatic increase of atmospheric 14CO2 with a peak around 1964, thereafter, bomb 14C became a powerful tool for dating recent carbonaceous material. There are lots of observational atmospheric 14CO2 records and reconstructed 14CO2 records based on annual tree rings covered bomb peak in the world, and they were compiled by Hua et al. in 2022. In China, however, continuous atmospheric 14CO2 records since the 1950s are scarce, and only several tree ring 14C records were reported. Here, we summarized four published tree ring bomb 14C records and three new records from our latest research between 27°N and 47°N in China. The results show the Δ14C of these records are generally higher than the average level in mid-latitudes of the Northern Hemisphere (NH zone 2 defined by Hua et al. (2022)) during the period of 1964-1989. This phenomenon is likely due to the impact of the atmosphere nuclear testing at Semipalatinsk (Kazakhstan), and the effect of Lop Nor nuclear weapons tests in Northwest China is not obvious. A local Suess effect began to appear in the records from urban and suburban sites since 1990s, of which the ecological half-life (T1/2,e , ~10.5 years) is shorter than that of remote sites. T1/2,e of records in remote sites range from 10.66 to 12.38 years, with an average of 11.54 years, are close to the level of the tree ring records in South Korea and Japan. It may suggest the impact of atmosphere diffusion is not very different. What should be highlighted is that these bomb 14C records of tree rings in China presents apparent differences with those records in similar latitudes in the other regions, therefore, there could be an additional uncertainty when the average bomb 14C value in the world (e.g. average in NH zone 1, 2 or 3) were used to dating recent samples in China. To solve the above-mentioned problem, more tree ring AMS-14C data in wider area in China are desired.
    
    Speaker: Xiaohu Xiong (Institute of Earth Environment, CAS)
    
    Abstract.docx
  - 72
    
    Development of 129I measurement technology with the home-made compact AMS facility at CIAE
    
    129I is a long-lived nuclide with very low nature level, but the presence of 129I in the environment has changed significantly since the beginning of the nuclear era. Accelerator mass spectrometer (AMS) is the most sensitive method for 129I measurement, which is widely used in environmental monitoring, geological evolution dating, nuclear activities tracking and other fields. For further expanding the applications of 129I, a home-made compact AMS facility has been developed by China Institute of Atomic Energy (CIAE), recently. In this paper, the measurement technology of 129I has been established with this facility. Charge state 2+ is selected at high-energy side and transmission efficiency of 55% for 127I2+ is obtained. The measurement sensitivity of 129I/127I≈1.5×10-14 has been achieved. At present, this facility can be used for routine measurement of 129I.
    Keywords: 129I, compact AMS, home-made, measurement technology
    
    Speakers: Wenhui Zhang, Ming He (中国原子能科学研究院)
    
    Development of 129I measurement ---AMS16 confenrence.docx
  - 73
    
    Experimenting solutions of Lithium reduction for radiocarbon measurement with 1 MV AMS at charge state 2+
    
    A 1MV AMS was installed at IHEG-CAGS in 2023. We usually measure 14C at charge state 2+ because beam transmission yield reaches maximum value at a terminal voltage of 1000 kV. However, when 2+ ions are used for the 1MV 14C analysis, interference by the 7Li2 molecular ions is severe in some cases. Therefore, it was necessary to investigate the source of Li interference.
    Herein, we give some experimenting solutions of Lithium reduction for radiocarbon measurement with 1 MV AMS at charge state 2+.
    
    Speaker: Hui Zhang
  - 74
    
    Imprint of stratosphere-troposphere-exchange on 10Be deposition in Greenland and Antarctica ice cores
    
    The 10Be record from the Northern Greenland NEEM ice core has been found to significantly correlate with the mid-latitude tropopause pressure on both seasonal and annual scales, highlighting the potential of applying ice core 10Be records to study the past stratosphere-troposphere exchange at mid-latitudes. However, a comprehensive study is required to determine if this relationship holds for 10Be records from other ice cores in Greenland and Antarctica. In this study, we review the available high-resolution 10Be records from Greenland and Antarctica over the last hundred years, finding that most of these records show significant correlations with mid-latitude tropopause pressure. However, the 10Be composite records from Greenland or Antarctica could not strengthen this relationship, suggesting different transport pathways to the different ice core locations in polar region. Finally, we discuss the potential of using solar storm events as "natural experiments" to investigate past stratosphere-troposphere exchange.
    
    Speaker: Minjie Zheng (Lund University)
  - 75
    
    Late Pleistocene reconstruction using sedimentary major elements and Be-10 from Lake Biwa, Japan
    
    Advances in Accelerator Mass Spectrometry (AMS) have made palaeoclimate reconstructions using meteoric cosmogenic nuclides available for a wide range of environments, including ocean, lake and ice cores (Raisbeck et al., 2007; Yokoyama et al., 2016; Behrens et al., 2022). Here, we report a Be-10 record for the past 45,000 years using sediments from Lake Biwa, the largest lake in Japan. The core was obtained in 2007, and the Be-10 concentration was measured using the previously reported method (Yokoyama et al., 2019). The Be-10 measurement was performed at the Micro Analysis Laboratory, Tandem Accelerator, University of Tokyo (Matsuzaki et al., 2020). The reconstructed Be-10 fluxes show fluctuations and are correlated with the major element fluxes also measured for the sediments. They are controlled by regional climate changes during the Late Pleistocene, probably induced by changes in the East Asian monsoon.　
    
    Raisbeck, G. M. et al., Clim. Past, 3, 541–547, 2007.
    Yokoyama, Y. et al., Proc Natl Acad Sci U S A. Mar 1;113(9):2354-9, 2016.
    Behrens, B.C. et al., Quat. Sci. Adv., 7, Article 100054, 2022.
    Matsuzaki, H. et al., Nucl. Instr. Meth. Phys. Res. B463, 55-63, 2020.
    
    Speaker: Takahiro Aze (Atmosphere and Ocean Research Institute, the University of Tokyo)
  - 76
    
    METHODS FOR CHEMISTRY AND PREPARATION OF LOW-CL CONCENTRATION SAMPLES FOR STABLE CHLORINE ISOTOPE MEASUREMENTS WITH AMS
    
    Introduction: Cl is a volatile element and can be lost during formation and evolution of planetary bodies, which can lead to fractionation of its two stable isotopes, 35Cl and 37Cl. Stable Cl isotope variations (reported as δ37Cl, in parts per thousand (‰), relative to standard mean ocean chloride (SMOC) [1]) have been measured in many lunar samples and have produced a wide range from -4‰ to +81‰ [2-7]. This variation has led to various interpretations of how the fractionation was produced, from degassing during accretion, magma ocean, or volcanic phases of lunar evolution [3, 4].
    Chlorine isotope measurements from two methods, SIMS and IRMS, have produced significantly different results, leading to difficulties in interpreting δ37Cl data, which led us to develop a method for high precision (~1-4‰ with 10 µg Cl, 2σ) stable Cl isotope measurements using the cesium sputter negative ion source of an accelerator mass spectrometry (AMS) system [8].
    This work is the next step in developing the chemistry and methods required to dissolve, separate, and measure samples from highly fractionated, low Cl concentration materials such as those found in astromaterials from the Moon, Mars and 4 Vesta [2-7,9-12]. Here we will present progress toward a method that can efficiently extract small amounts of Cl from a silicate matrix. Our approach involves bulking with Br carrier following HF digestion to efficiently scavenge Cl with a Ag(Br+Cl) precipitation. The Ag(Br+Cl) is then re-dissolved and Cl is chemically separated from Br via anion exchange chromatography. This will enable sample preparation with microgram-scale Cl masses, to ultimately prepare samples for measurement using the cesium sputter AMS method [8]. The presented experiments are aimed at establishing a robust column separation procedure, potential sources of Cl contamination, and isotope fractionation in the column.
    Discussion: We were able to fully separate the 50 µg of added Cl from 500 µg of added Br using anion exchange resin, enabling this method for use in scavenging micrograms of Cl from low mass or low-Cl astromaterials. In a natural sample, the Cl and Br would be co-precipitated together and re-dissolved to be loaded into anion exchange columns.
    Our finding that the column chemistry slightly fractionates the Cl samples can likely be precisely quantified and accounted for with further measurements or may not be present with other forms of resin, which will be tested.
    The current source of Br standard solution adds approximately 4 µg of Cl per ml to the sample. In addition to exploring a new Cl-free Br source, cleaning the Br solution of Cl using this anion exchange method will be tested.
    Anderson et al. [8] outlined how to measure stable chlorine isotopes using only the Cs sputter source of an AMS facility at high precision. This work represents an important next step to being able to fully dissolve rock samples and scavenge small masses of Cl for stable Cl isotopic measurements of low mass or low-Cl concentration lunar and meteoric samples with AMS.
    Future tests will use different chemical forms of resin such as the OH- form to quantify any Cl fractionation or contamination and note any process changes.
    Conclusion: We have shown the ability to chemically separate Cl from Br, representing important initial steps toward a method for scavenging small Cl masses from natural samples for stable Cl isotope measurements with AMS.
    Applications of this sample preparation method coupled with the high precision measurement of stable chlorine isotopes shown in [8] to problems in planetary science and astrophysics will be discussed.
    Acknowledgments: Prepared in part by LLNL under Contract DE-AC52-07NA27344; LLNL-ABS-858930.
    References: [1] Kaufman et al. (1984) Nature, 309, 338-340. [2] Wang et al. (2019) Sci. Rep., 9, 5727. [3] Sharp et al. (2010) Science, 329(5995), 205-214. [4] Boyce et al. (2018) EPSL, 500, 205-214. [5] A.H. Treiman et al., (2014) Am. Mineral. 99 (10) 1860-1870 [6] J.J. Barnes et al. (2016) EPSL 447, 84-94. [7] J.J. Barnes, et al. (2018) Geochem. Cosmochim. Acta, 266, 144-162. [8] T. S. Anderson et al. (2022) Int. J. Mass Spectrom. 477, 116849. [9] C.K. Shearer et al. (2018) Geochem. Cosmochim. Acta 234, 24-36. [10] J.T. Williams et al. (2016) Meteoritics Planet Sci. 51 (11), 2092-2110. [11] A.R. Sarafian et al. (2017) Earth Planet Sci. Lett. 459, 311-319. [12] T.J. Barrett et al. (2019) Geochem. Cosmochim. Acta, 266, 582-597.
    
    Speaker: Tyler Anderson (Lawrence Livermore National Laboratory)
  - 77
    Performance and inter-comparison tests of the MICADAS at the radiocarbon laboratory of Henan University, China
    
    Introduction
    Radiocarbon Laboratory of Henan University was primitively established in 2017, and introduced a compact accelerator mass spectrometer (AMS) – a 200 KV mini carbon dating system (MICADAS) in 2023, which had greatly improved the testing capacity of the laboratory. Here we present the performance of MICADAS.
    The laboratory can accurately measure the weight of the sample through the microbalance. Through the elemental analyzer (EA) and the carbonate treatment system (CHS), the organic and inorganic carbon samples can be burned at high temperature or dissolved by phosphoric acid to prepare carbon dioxide. Then it enters the fully automatic graphyization system (AGE-3) to reduce carbon dioxide into graphite with hydrogen under the catalysis of iron powder (or directly for gas measurement), and then makes a solid sample target through the pneumatic pressure device (PSP), and then puts it into the target disk for sample measurement.
    The test results of IAEA-C7、IAEA-C8 and OII show high accuracy and precision, and stability of the MICADAS. The mean pMC value for PHA was 0.18±0.07, corresponding to around 52,000 years, with a low background.
    
    Speaker: Mr 亚飞魏 (河南大学)
    
    henuposter.pptx
  - 78
    
    Status report of the sample chemical preparation for 10Be and 26Al at LN2C : Part 2 : Improving the targets quality prior AMS measurements.
    
    The extractions of beryllium and aluminum samples by ion exchange resins prior AMS, depend heavily on the quality of quartz purity. However, even with meticulous purification, objectives to guarantee sufficient AMS current are not always achieved.
    Using a well-known natural sample that had already been studied and purified, quantitative multi-elements (B, Be, Al, Ti, Ca, Na, K, Mg, Fe) monitoring by ICP-OES was carried out. Aliquots were collected in the various eluted fractions (Boron fraction, Beryllium and Aluminum fractions) as well as in the precipitates and supernatants from intermediate purification stages, before and after each column step. The composition of the final Be fraction was then characterized. Using the routine protocol, elements such as Ti, Al and other minor elements were still present. Test targets have thus been prepared to observe the potential influence of these elements on the quality of the AMS measurement and the interest to update the protocol to eliminate the unwanted interferences.
    Prior to AMS measurement BeO is mixed with niobium powder in a 1:1 ratio, homogenized then pressed into copper cathode. To avoid problem in the mixing process, we explore the possibility to add a solution of Nb (or Fe) with Be precipitate before the oxidation stage. After oxidation, the sample will be taken straight out of the crucible and added to the cathode. This has already been investigated ([1] , [2] ), it allows better homogenization of the Nb/sample mixture with a precisely controlled amount of Nb and will reduce target preparation time.
    
    Ref:
    [1] A-M Berggren, G. Possnert, A. Aldahan, Enhanced beam currents with co-precipitated niobium as a matrix for AMS measurements of 10Be. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Volume 268, Issues 7–8, 2010, Pages 795-798. doi.org/10.1016/j.nimb.2009.10.033.
    [2] A. Walker, A. J. Hidy, S. R. Zimmerman, S. J. Tumey, T. Brown, S. M. Braumann, R. Schwartz, J. M. Schaefer. Less is more: optimizing 9Be carrier addition for AMS analysis of 10Be at CAMS. 15th International Conference on Accelerator Mass Spectrometry. Program and abstracts 2021
    
    Speaker: Dr Stéphanie Gairoard (CEREGE LN2C)
  - 79
    
    The preliminary study on the correction of “Reservoir Effect" in lacustrine sediments.
    
    The correction of " Reservoir Effect" in lake sediments is a particularly challenging issue in radiocarbon chronology. The controlling factors of Reservoir Effect and how to correct for it remain unclear. A research team systematically reviewed the past 20 years of lake studies in different climatic regions of China, and systematically investigated the 14C ages and correction methods used in 81 lake studies. The study found that climate-vegetation cover and the distribution of carbonates around the lake are the main factors controlling the radiocarbon reservoir effect. In eastern China, the average 14C reservoir age is about 500 years, which is related to relatively dense vegetation. However, in northwestern China and the Tibetan Plateau, the widespread carbonate bedrock may significantly increase the radiocarbon reservoir age, typically around 1500 and 2500 years, respectively. The segmented linear regression model provides a more reliable method for 14C reservoir age correction, which takes into account the changes in sedimentary facies and sedimentation rates. It is worth mentioning that when the 14C age significantly deviates from the time series, the age anomaly may indicate significant impacts related to climate and environmental change research.
    
    Speakers: 鹏程 (中国科学院地球环境研究所) , 卫健周 (中国科学院地球环境研究所) , 郁达炊 (中国科学院地球环境研究所)
  - 80
    
    Ultra-trace Analysis meets Radiochemistry: Studying the Behaviour of Pa-231 in the Environment
    
    Uranium mining and milling activities contribute to the release of natural uranium and its decay products into the environment. This may lead to potential radiological risks. While U-238 and its decay products are routinely monitored, the behaviour of the U-235 decay products is either not considered, or only estimated based on the U-238 decay chain in radiological assessments [1].
    Pa-231 is one of the few long-lived isotopes in the U-235 decay chain. It has a half-life of 3∙10^5 years and lacks analogues in the U-238 decay series. Hence, it is necessary to study Pa-231 to learn about the transport and possible accumulation of U-235 decay products in the environment that might differ from the U-238 decay series [2].
    In this talk, I will present two different approaches to studying the behaviour of Pa-231 in the environment. First, we use the short-lived isotope Pa-233 (half-life 27 days) as an analogue to study the interaction of Pa with plants. Using gamma spectroscopy and autoradiography, we provide an insight into the translocation and accumulation patters of Pa in Sand Oat (Avena strigosa).
    To check if the results from the Pa-233 experiments are transferable to real life environmental situations we are planning to measure Pa-231 in the environment using Accelerator Mass Spectrometry (AMS). This ultra-sensitive method is capable of measuring minute concentrations of long-lived radionuclides. Especially actinides can be measured to unparalleled sensitivity. The measurement of Pa-231 is not yet an established procedure at most AMS laboratories, but there are multiple ongoing efforts to develop such a procedure [2,3]. The main challenges are the complications in chemical sample preparation, particularly Pa losses due to sorption on lab equipment.
    We have developed and adapted chemical sample preparation procedures for multiple environmental samples including water from a uranium mine, riverbank soil and plants. First, the Pa is leached from each environmental sample using a specific protocol. Then, Pa needs to be separated from the environmental matrix, where each sample material comes with its own challenges. I will give an overview of different leaching mechanisms and elemental separation methods we tested for separating Pa from environmental samples, focussing on where we lose Pa in the sample preparation and how to avoid these losses.
    
    _ [1] Beaugelin-Seiller, K., et al., J. Environ. Radioact., 2016, 151, 114-125.
    [2] Medley, P., et al., Nucl. Instrum. Methods Phys. Res. B, 2019, 438, 66-69.
    [3] Christl, M., et al., Nucl. Instrum. Methods Phys. Res. B, 2007, 262, 379-284.
    
    Speaker: Janis Wolf (Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, Germany)
  - 81
    
    An in situ cosmogenic 14C extraction system at Xi’an AMS Center
    
    In situ radiocarbon（14C）is produced within minerals at the earth’s surface by a number of spallation reactions. Due to its relatively short half-life of 5730 years, it serves as a unique cosmogenic nuclide tool for the measurement of measuring rapid erosion rates (>10–3 cm yr–1) and events occurring over the past 25,000 years. At Xi'an AMS Center, we have developed and constructed a new vacuum system specifically designed for extracting in situ 14C from quartz samples. Puried quartz samples are degassed and heated to 1600-1650℃ in a high temperature resistance furnace without the use of a fluxing agent. Carbon fraction within the quartz crystal lattice is liberated and oxidized to CO2 in an O2-He mixed atmosphere. The CO2 is subsequently captured through a series of cryogenic traps and hot Ag and Cu wool/mesh, and converted to graphite for accelerator mass spectrometry (AMS) measurement. One major challenge encountered in measuring in situ 14C is establishing a low and reproducible system blank and efficient extraction of the in situ 14C component. Our initial experiments reveal a high blank level and a low extraction efficiency. Through the optimization of the extraction steps, the continuous running of the high temperature furnace and the effective control of all various system components in multiple conditional tests, a lower process background level and stable extraction efficiency are obtained. These results demonstrate that our system is capable of extracting in situ 14C from quartz for surface exposure dating.
    
    Speaker: Ms Hua Du (Institute of Earth Environment, Chinese Academy of Sciences)
    
    AMS16 Abstract-Duhua.docx
  - 82
    
    Coevolution of glacial retreat and regional climate on the Tibetan Plateau and surrounding mountains from the Global Last Glacial Maximum to Early Holocene based on a compilation of 10Be exposure ages
    
    The Tibetan Plateau and its surrounding mountains (TPSM) has experienced glacier expansion during the Global Last Glacial Maximum and punctuated retreat during the following deglaciation. Preserved moraines provide a reliable record for glacier extent and their terrestrial cosmogenic exposure dating marks the transition of glacial advance or stasis to one of recession. As a wide geographic domain, when and how the glaciers retreated on the TPSM during the last termination remains unclear. In order to investigate this issue, we recalculated 1077 boulder 10Be exposure ages from 239 moraines spanning the period of 26.5-10 ka ago using the LSDn scaling model and the Probabilistic Cosmogenic Age Analysis Tool. We divided the TPSM into seven regions and utilized the kernel density estimate method to calculate the summed probability distribution of moraine ages and compared the peaks to identify phases of glacier activities for these regions. The results show that the initiation of glacier retreat on TPSM began synchronously at ca 22 ka, aligning with worldwide glacier retreat in response to the onset of summer insolation rise on the mid-latitude Northern Hemisphere. Phases of moraine abandonment concentrated at five peak stages, i.e., 22-20 ka, 19-18 ka, 17-16 ka, 14.5-12.9 ka and 11.6-10 ka, broadly corresponding to the periods of thousand-year enrichment of δ18O from the Greenland ice core. Synchronous retreat over the entire TPSM occurred at 22-20 ka, 19-18 ka, 14.5-12.9 ka. Asynchronous retreat at 17-16 ka was not observed in Pamir and NE Tibet, which is likely a result of the sustained influence of the Westerlies over these regions. An exposure age peak at 11.6-10 ka data was absent on Central Tibet, NE Tibet and Tianshan, which is likely a bias due to the lack of chronology for the remote and perched moraines in these regions. We suggest that 17-16 ka was a major adjustment in atmospheric circulation from glacial to interglacial state over the TPSM.
    
    Speaker: Chaogang Zheng (Nanjing Normal University)
  - 83
    
    Continuous Holocene increase of the radiocarbon reservoir age at Lake Kanas, southern Altai Mountains, related to peat/soil erosion and climatic wetting
    
    Radiocarbon (14C) dating of the total organic carbon (TOC) content of lacustrine sediments is usually affected by a 14C reservoir effect and the 14C dates are often systematically older than the true ages, due to the input of carbon from different sources. Therefore, when using TOC's radiocarbon data to build the age-depth relation, it is necessary to accurately deduct the radiocarbon reservoir age. However, due to the possible diachronic variation of the reservoir effect in sediments, it is difficult to deduct the this effect. We collected TOC samples from the Holocene sediments of Lake Kanas, in the southern Altai Mountains, for AMS 14C dating and compared the results with AMS 14C ages based on terrestrial plant macrofossils from the same depths. The results show that the reservoir ages progressively increased from ∼0 to ∼2800 yr between ∼9700 cal BP and ∼530 cal BP. As the lake catchment was glaciated prior to the Holocene, and Holocene soils and peats are the main sources of the TOC in the lake sediments, we argue that soil erosion is the major factor contributing to the progressive increase in the reservoir age. Based on previously reported evidence for increasing moisture in central Asia and glacier advances in the mid-to-late Holocene, we suggest that the intensified soil erosion on the hillslopes was caused by increased precipitation during the mid-to-late Holocene and by anthropogenic forest clearance after 1500 cal BP.
    
    Speaker: 辉辉曹 (兰州大学)
  - 84
    
    Developing OC/EC Separation Equipment for Accurate Radiocarbon Source Attribution and Carbon Cycle Modelling
    
    The Rafter Radiocarbon Lab, through the CarbonWatch-Urban project, is developing detailed CO2 emissions information for all towns and cities in New Zealand. Tracking fossil fuel CO2 emissions traditionally involves radiocarbon measurements of atmospheric CO₂ to separate fossil fuel from natural CO2 fluxes. In contrast, this study aims to further separate CO2 and carbon monoxide (CO) from wood burning and fossil fuel combustion sources utilizing aethalometer and radiocarbon measurements of organic carbon (OC) and elemental carbon (EC) derived from aerosol samples. An aethalometer measures black carbon absorption at multiple wavelengths, allowing separation of black carbon derived from fossil fuel and biogenic (wood burning) combustion. Radiocarbon measurements are essential to calibrate the aethalometer separation of biogenic and fossil black carbon. These measurements will together be used in a tracer ratio approach to partition CO2 and CO from these sources. This is particularly important in New Zealand cities, where there is a substantial CO2 and CO source from wood burning used for home heating.
    This study proposes the use of an advanced pre-treatment process based on the methodology developed by Dusek et al (2014), which involves the thermal separation of OC and EC at specific temperatures under oxygen gas flow. The samples will be heated in a controlled environment in oxygen atmosphere, with OC combusted at lower temperatures and EC at higher ones, ensuring precise separation. The resultant CO₂ from each fraction will then be subjected to radiocarbon analysis. Our OC/EC thermal separation system is built as an additional module of an existing vacuum system designed for ramped pyrolysis radiocarbon separation, taking advantage of the similar equipment needed.
    This approach not only supports more effective environmental policies and interventions but also enhances our understanding of the complex dynamics of carbon in the atmosphere. This research underscores the importance of advanced analytical techniques in environmental science, particularly in the context of climate change mitigation and air quality management.
    
    Speaker: Kilho Sung (GNS Science)
    
    AMS-16 abstact_Kilho Sung_Developing OC-EC Separation Equipment_c.docx
  - 85
    
    Development of a method to extract and date of carbonised material in pottery: Research aimed at overcoming the issues of marine reservoir effects in Hokkaido, Japan
    
    The purpose of this study is to establish a method for extracting charcoal from inside pottery and measuring its radiocarbon date. We proposed a new method that uses X-ray equipment to search for carbonised grains embedded within earthenware and directly date these grains in relation to grain cultivation in the Japanese archipelago [1]. This method allows us to obtain data on the introduction of crops without contamination, even from archaeological sites where flotation was not conducted or carbonised grains have not been detected. It is also possible to clarify the relationship between grains and associated pottery types.
    In this presentation, we report an analysis of Kouren-4 site (Early Jomon period in Hokkaido, Japan) using this method. The dates of charred residues on pottery in Hokkaido can be compared with charcoal, providing data that is several hundred years older. Estimated age difference were caused by marine foods which might reflect the upwelling of old sea water for western part of North Pacific. We present the radiocarbon dates for the carbonised materials in the pottery (insects, seeds, twigs, etc.) to approximately 4700-4900 BP. These dates were several hundred years newer than the charred residues on the pottery. This new attempt is expected to overcome the issues of marine reservoir effects.
    
    References
    [1] Obata, H. and Kunikita, D. 2022 A new archaeological method to reveal the arrival of cereal farming: Development of a new method to extract and date of carbonised material in pottery and its application to the Japanese archaeological context. Journal of Archaeological Science 143, 105594.
    
    Speaker: Dai Kunikita (Graduate School of Humanities and Human Sciences, Hokkaido University)
  - 86
    
    Development of AMS 14C dating preparation laboratory at the Beijing Normal University
    
    The development of the AMS 14C dating preparation laboratory has been completed in the Beijing Normal University (BNU). There are 2 lines of home-made CO2 generation vacuum systems and 4 lines of home-made graphitization vacuum systems. For CO2 generation, a pyrolysis-combustion vacuum system with an infrared gas analyzer, ultrapure O2 and Ar gas supply systems, a manometer with a pressure transducer to measure pressure variations from vacuum (-760 mmHg) to ~2.5 atmospheric pressure, a CO2 purification system and a 12-port vacuum line to extract and are installed. These vacuum systems are used together with other apparatus to extract variable organic and inorganic carbon fractions through thermal decomposition and fractional acid reaction for AMS 14C dating analysis. For graphitization, 44 close-spaced hydrogen-iron reaction vessels to reduce CO2 are installed in 4 vacuum lines each with online monitoring systems on a dozen of CO2 reduction rate simultaneously, ultrapure H2 gas supply systems, CO2 purification systems, and a manometer with a pressure transducer to measure pressures from vacuum (-760 mmHg) to 2.2 atmospheric (30 psi) ranges on each vacuum lines. By the mid-2024, the BNU 14C preparation laboratory had completed >500 graphitization of unknown-aged organic, inorganic, and bone collage sample preparation with nearly 200 standard, blanks, and other testing specimens. The BNU-AMS 14C preparation laboratory begins to provide AMS 14C dating services for samples of gas, water DIC, soil, loess, dune sand, lacustrine, wood shaving, charcoal fragment, organic remains, bone collagen, tooth enamel bioapatite, carbonate minerals, eggshells, stalagmite, and tufa samples.
    
    Speaker: Prof. Hong Wang (Beijing Normal University)
    
    BNU-AMS 14C dating prep lab.docx
  - 87
    
    Difficulty and complexity interpreting cosmogenic nuclide data in cave settings -- a case study in multilevel karst system in Atapuerca, northern Spain
    
    In this paper we revisit cosmogenic nuclide analysis from multilevel karst system in Atapuerca mountain range to discuss difficulty and complexity in interpretating cosmogenic data not only for chronology but also for sediment dynamics, i.e., provenance, transport pathway and depositional processes. Atapuerca is situated in the western end of Europe, and is among the key sites in the study of early human evolution. The site consists of a multilevel karst system developed within the Cretaceous limestones that make the “Sierra de Atapuerca” mountain range, where several cave infills have been exposed by a railway cutting in early 1900s. Since 1980s, excavation of the sites has revealed rich records of archaeological and paleontological remains, including one of the earliest human fossils outside Africa dated ~1.2 Ma, as well as a new homo species, Homo antecessor, dated ~0.8-0.9 Ma. Efforts to constrain chronological framework have paralleled. Paleomagnetism identified B/M boundary indicating the sites extend from Early to Middle Pleistocene. Several early attempts by U-series, OSL and ESR have been successful at certain degree, with some unresolved discrepancies. Recent advancement in OSL and ESR provided better chronological constraints in key sites including Gran Dolina. In this study, we revisited previously measured 10Be-26Al data together with some new data from Gran Dolina, Cueva del Silo and associated river terraces proximity to the sites, to discuss analytical feasibility and difficulty applying quartz 10Be-26Al method to largely karstic environment, and complexity interpretating such data not only for burial ages but also for sediment dynamics from its origin, to potential prior-burial and reworking, and to accumulation rate. Nevertheless, approaching the problems with multiple geochronological methods (e.g., paleomagnetism, ESR, OSL) and comparing with paleontological and archaeological evidence provide invaluable opportunities to test and validate assumptions and model for burial age calculations based on cosmogenic nuclides.
    
    Speaker: Dr Toshiyuki Fujioka (CENIEH)
  - 88
    
    Dual carbon isotopes (δ13C and Δ14C) were used to reveal the main sources and input fluxes of dissolved inorganic carbon in a karst reservoir in winter
    
    Understanding the sources and fluxes of dissolved inorganic carbon (DIC) in karst reservoirs is essential for regional carbon cycling studies, particularly concerning the "karst effect". This study utilized dual carbon isotopes (δ13CDIC and Δ14CDIC) to estimate the contribution rates and input fluxes of DIC from various sources in the Aha Reservoir (AHR), located in southwestern China. Our results indicated that the DIC concentrations (22.33-32.79 mg·L-1) and δ13CDIC values (-10.02‰ to -8.55‰) were nearly homogeneous both vertically in the water column and laterally across the reservoir (p > 0.05). The Δ14CDIC values (-246.31‰ to -137.86‰) exhibited homogeneous along the vertical profile, while significant differences were observed horizontally (p ＜ 0.05). Horizontally, the Δ14CDIC values at the mouths of the inflowing rivers decreased from -149.57±10.27‰ to -232.85±2.37‰. We found that the inflowing rivers contributed the largest portion of DIC to AHR, accounting for 70% of the total input. Groundwater and atmospheric CO2 contributions were relatively minor, at 18% and 12%, respectively. The DIC input fluxes from the inflowing rivers were quantified as follows: Jinzhong River 2.01 t/(km2·mon), Youyu River 1.29 t/(km2·mon), and Baiyan River 1.03 t/(km2·mon). This study highlights the significant impact of anthropogenic activities on DIC input in AHR. The discharge of industrial and domestic wastewater had a larger influence than agricultural activities and acidic mine wastewater inputs. These findings underscore the critical need to manage and mitigate the impacts of human activities on karst reservoir ecosystems.
    
    Speaker: Dr Xia Yu (College of Resources and Environmental Engineering, Guizhou Institute of Technology)
    
    Abstract.pdf
  - 89
    
    Fossil and Non-Fossil Carbon Contents in the Tropical Indian Aerosols
    
    Atmospheric aerosols have serious impacts on the Earth’s climate system directly by scattering and absorbing solar radiation and indirectly by acting as cloud condensation nuclei. They also cause adverse effects on human health and play an important role in atmospheric chemistry. Although carbonaceous aerosols that represent a large fraction of fine aerosol mass have been extensively studied, their origins and atmospheric processing are not fully understood yet in the tropical Indian aerosols. To apportion the fossil and non-fossil carbon in the tropical carbonaceous aerosols from the Indian region, we collected atmospheric aerosols (PM10) on day- (approximately 6:00–18:00 LT) and nighttime (18:00–6:00 LT) bases in winter (January 23 to February 6, n = 29) and summer (May 22–31, n = 20) 2007 from a mega‐city, Chennai (13.04°N; 80.17°E) located in the southeast coast of India. We measured the radiocarbon (14C), a unique tracer for distinct fossil and non-fossil carbon, isotope ratios of total carbon (TC) in the PM10 using the Accelerator Mass Spectrometry (AMS). In addition, carbonaceous components, molecular composition and distributions of various organic classes of compounds and their stable carbon isotopic composition (13C) in TC were measured. Here we report the characteristics of 14C in TC (percent of modern carbon (pMC)), together with the comparison with carbonaceous components and molecular marker species in PM10. Based on the results obtained, we discuss the importance of contemporary sources and aging of the tropical carbonaceous aerosols, including their diurnal and seasonal changes, in the southeast coastal region of India.
    
    Speaker: Dr Masao Uchida (National Institute for Environmental Studies)
    
    Abstract_14C in Chennai PM10_AMS16_Pavuluri et al.docx
  - 90
    Graphitization of atmospheric CO$_{2}$ from whole air samples with the new ALF-NewAge system
    
    The atmospheric concentration of carbon dioxide (CO$_{2}$) has been increasing steadily since industrialization. Emission of $^{14}$C-free CO$_{2}$ from the combustion of fossil fuels, such as coal, oil or gas, reduces the $^{14}$CO$_{2}$ to $^{12}$CO$_{2}$ ratio in the atmosphere. When the background $^{14}$CO$_{2}$ level is known, the local surplus of fossil CO$_{2}$ can be calculated using the measured CO$_{2}$ concentration and $^{14}$CO$_{2}$ abundance at a given site (e.g. Levin et al. 1989). However, the measurement of atmospheric $^{14}$CO$_{2}$ from whole-air samples by AMS requires meticulous sample preparations. That includes the isolation of CO$_{2}$ from other atmospheric gases and its subsequent graphitization to form uniform graphite targets for $^{14}$C measurements by AMS.
    
    Here, a new fully automated air loading facility (ALF), together with a new dedicated graphitization line (NewAge), is presented. The system allows for the simultaneous graphitization of up to 10 air samples, standard or reference gases that are stored in 3L glass cylinders at typically 1.6 bar (NORMAG Germany). The NewAge graphitization unit is based on the principles of the established AGE graphitization line (Wacker et al. 2010): The isolation of CO$_{2}$ from air is performed by a molecular sieve trap, from where it is directly transferred to the reaction tubes by thermal release. This approach omits the use of liquid nitrogen and vacuum lines that are present in similar systems. A significant redesign compared to the original AGE system optimizes the new system for air samples by including a new dedicated air sampling trap, which allows for a high airflow of over 750 ml/min when sampling. Further, the number of reactors has been increased from 7 (AGE) to 10 (NewAge) while at the same time reducing the footprint of the system.
    
    Overall, the NewAge system allows for a high air sample throughput (20 - 30 samples per work day) with minimal user input. First results showing the reproducibility of standards and references as well as the blank level are presented for the system.
    
    References
    
    Levin, I, Schuchard, J, Kromer, B, Münnich KO. 1989. The continental european Suess effect. Radiocarbon, 31(3):431-440.
    
    Wacker, L, Němec, M, Bourquin, J. 2010. A revolutionary graphitisation system: Fully automated, compact and simple. Nucl. Instrum. Meth. B 268(7):931-934
    
    Speaker: Dr Philip Gautschi (ETH Zurich, Laboratory of Ion Beam Physics)
  - 91
    
    Interaction of slow ions with laser light – the ILTIS injector beamline at the 1-MV AMS facility HAMSTER in Dresden
    
    Suppression of isobars for AMS profits from studying element selective interactions of slow ions with photons or in collisions with other atoms. Negative ions extracted from an ion source can be slowed down to near-thermal energies in an ion cooler consisting of a buffer gas filled radio-frequency quadrupole. The slow ions collide with the buffer gas and can be overlapped with a laser beam. These processes are utilized to suppress isobaric interferences in element selective neutralizations or transformations of the injected anions. Such a device expands the repertoire of measured isotopes to nuclides previously restricted to large AMS facilities as documented in experiments at the ion-laser-interaction mass spectrometer ILIAMS at the VERA (Vienna Environmental Research Accelerator) facility, among them $^{36}$Cl or $^{26}$Al from extraction of AlO$^{–}$ [1,2] and non-classical AMS radionuclides such as $^{135}$Cs and $^{137}$Cs [3].
    The new AMS system called HAMSTER (Helmholtz Accelerator Mass Spectrometer Tracing Environmental Radionuclides) will expand the capabilities of radionuclide measurements at HZDR. A second injection line to the 1-MV Pelletron tandem accelerator holds such a novel ion cooler developed in a collaboration between VERA and the HZDR, the so-called Ion Linear Trap for Isobar Suppression ILTIS.
    The injector around ILTIS is delivered by NEC and is equipped with a MC-SNICS ion source, followed by an electrostatic analyzer, options for beam attenuation and a magnet before and after the ion cooler, each allowing for fast beam switching. Low-current Faraday Cups and sensitive beam profile monitors enable mass analysis of the beam before and after the ion cooler at the pA level.
    In addition to the combination with the 1-MV accelerator, the new injector can be operated independently for testing purposes in parallel to conventional AMS measurements running from another ion source. The control of the different beamline components will be conducted by an EPICS based control system.
    I will present the potential of interaction for studying new long-lived radioisotopes based on measurements of $^{135}$Cs and $^{137}$Cs at VERA as well as our design of the ILTIS injector and first impressions and results from the setup of this system at HZDR.
    
    Refs:
    [1] Lachner et al., 2019, $^{36}$Cl in a new light: AMS measurements assisted by ion-laser interaction,
    10.1016/j.nimb.2019.05.061
    [2] Lachner et al., 2021, Highly sensitive $^{26}$Al measurements by Ion-Laser-InterAction Mass Spectrometry, 10.1016/j.ijms.2021.116576
    [3] Wieser et al., 2023, Detection of $^{135}$Cs & $^{137}$Cs in environmental samples by AMS, 10.1016/j.nimb.2023.02.013
    
    Speaker: Johannes Lachner (1) Helmholtz-Zentrum Dresden-Rossendorf (HZDR), Dresden, Germany)
  - 92
    
    Investigation of small sample preparation for 14C-AMS based on AGE-3 Automated Graphitization Equipment
    
    Abstract: Accelerator Mass Spectrometry (AMS) is considered to be the ultra-sensitivity technique for 14C isotope analysis at present, however, high-quality 14C data are heavily dependent on the sample graphitization. Relying on AGE-3 from Ionplus, the graphitization process not only improves the sample processing efficiency but also reduces the sampling cost compared to the traditional method, and is characterized by high graphite yield, stable beam currents and low background. This study is based on the equipment for the preparation of small samples carbon masses ranging from 0.02 to 1 mg for the modern carbon standard sample OXII, the laboratory secondary standard Humic Acid (HA) and the background sample C1, the limits of the device for small sample preparation were explored, the amount of modern and dead carbon contamination introduced into the process was estimated, and the small sample preparation capability of the automated graphitization equipment was evaluated. The experimental set-up, calibration method and initial results will be detailed in this contribution.
    Key word: Accelerator Mass Spectrometry (AMS); 14C Sample preparation; Trace sample; AGE-3
    
    Speaker: 立欣张 (天津大学地球系统科学学院)
    
    Abstract-zhangLixin.docx
  - 93
    
    Measurement of 14C in the environmental samples around nuclear facilities in Korea
    
    Monitoring the fluctuations of radiocarbon in environmental samples (air, biological, groundwater, etc.) around nuclear facilities is a commonly used tool to assess the safe operation of the facility. Measurements of radiocarbon in environmental monitoring programs around the nuclear facility are primarily performed using liquid scintillation counters, which are known to be capable of assessing levels of approximately 0.2 Bq/g-C. However, the instability of the LSC method due to the magnitude and fluctuation of the background counts and the measurement of carbon absorption weight require the need for method validation. However, AMS (Accelerator Mass Spectrometry) has very excellent precision and accuracy for the measurement of radiocarbon and a lower limit of detection than that of LSC. Therefore, this study evaluated the accuracy of the measurement method of radiocarbon in environmental samples collected around nuclear facilities (nuclear power plants and research reactor) in Korea using LSC by comparing it with the results of AMS.
    
    Speaker: Jong-Myoung Lim (Korea Atomic Energy Research Institiute)
    
    16th AMS conference_JM LIM.docx
  - 94
    
    Multi-proxy palaeoenvironmental record of the past 4600 years from Beloe Lake, northwestern Altai, Russia
    
    Beloe Lake (51°17’40” N, 82°38’50” E, 530 m a.s.l.) is a foothill lake in the northwestern Altai of Russia. Twenty-five AMS 14C dates on sedimentary TOC and plant remaining samples were obtained from a 193-cm long core to construct the chronology of the lake sediment sequence. Additionally, 210Pb and 137Cs dating were applied to the uppermost 20 cm sediments of the core to complement the chronologic framework. The measurements of TOC and TN by EA and 0.5N HCl leaching elemental concentrations measured by ICPOES provide high-resolution climate change and human impact over the past 4600 years. I (2660-2500 BC): high surface runoff and lake productivity due to wet and warm conditions; II (2500-2330 BC): salinity abruptly decrease (Ca and Sr) indicate a dry condition; III (2330-2170 BC): decreasing in terrestrial input, but the lake was well-mixed; IV (2170-1510 BC): terrestrial elements were remained low, and limnological factors changed due to the limited waterbody, such as variations in pH, temperature; V (1510-1050 BC): a small pulse of TOC and Mn indicated a wet condition; VI (1050-640 BC): increasing in surface runoff and waterbody was observed, showing a wet climate; VII (640 BC-40 CE): relatively high TOC, terrestrial elements and metal concentrations resulted from enhanced catchment erosion in wet and warm climates; VIII (40-220 CE): a sudden drop in concentrations due to the dry condition; IX (220-540 CE): TOC increased but Sr decreased indicate wet and high-level water condition; X (540-710 CE): a mild dry condition resulted in a gentle decrease in element concentration; XI (710-1070 CE): a significant increase in terrestrial elements showed a wet condition; XII (1070-1210 CE): Si and TOC concentrations indicated terrestrial input decreased associated with dry condition; XIII (1210-1950 CE): the lake had very low sedimentation, perhaps due to enhanced surface frozen period during the Little Ice Age; XIV (1950-2022 CE): TOC and heavy metal elements increase showed lake became fresh and activity. The lake was fresh and low productivity resulted from wet and warm climates and human impact.
    This study is supported by the Russian Science Foundation (RSF) (grant No.22-47-08001) to Kazan Federal University (KFU).
    
    Speaker: Dr Tzu-Tsen Shen (Instrumentation Center, National Taiwan University)
  - 95
    
    Preperation of metallic calcium samples for 41Ca dating
    
    Calcium is a major element in the biosphere and lithosphere. Its cosmogenic isotope 41Ca, with a half-life of 99 thousand years1, can trace environmental processes at an age scale beyond the reach of 14C.
    Here,we achieved the analysis of 41Ca in environmental samples using ATTA, and a single analysis requires 80mg of metallic calcium. In addition, we have developed a process for preparing metallic calcium samples from different types of environmental samples for the application of 41Ca dating. The sample types and extraction efficiency are granite (40%), loess (60%), bone (90%), seawater(90%), foraminifera (90%), and coral (90%), respectively.
    
    Speaker: huimin zhu (USTC)
    
    AMS16 Abstract.docx
  - 96
    
    Processing of micro radiocarbon samples and samples with sulphur contamination
    
    For nearly three decades, the Centre for Accelerator Science at ANSTO has been conducting radiocarbon analyses using solid sample ion sources. To accommodate smaller samples, we developed both Laser Heated Furnaces (LHFs) and Micro-Conventional Furnaces (MCFs) over a decade ago. These innovations have significantly expanded our capabilities, enabling the analysis of samples containing as little as a few micrograms of carbon (µgC), including those with sulphur content.
    The LHF, with a reaction volume of approximately 0.25 mL, uses an infrared laser to directly heat the Fe catalyst in a quartz crucible, with temperature measured indirectly by infrared thermometry. We routinely utilize LHFs to graphitise in-situ 14C quartz samples containing just 1-40 µgC. Conversely, the MCF, featuring a small tube furnace for catalyst heating, has a slightly larger minimum reaction volume of 0.9 mL. This design is optimized for processing samples with around 5-300 µgC. The MCF's capacity has been demonstrated through the processing of thousands of samples in recent years, ranging from Antarctic ice core gases to mud wasp nests associated with Australian Aboriginal rock art.
    The radiocarbon analysis and calibration of such small samples necessitate the preparation of numerous small standard samples and blanks (14C free samples) that carry a similar carbon mass (Cmass). To accomplish this, we employ a set of custom-built two-valve gas splitting vessels with splitting ratios varying between 1/100 to 1/3. These vessels not only enable the division of one large gas sample into multiple small samples of similar Cmass but also can produce many small samples with different Cmass by varying the ratio. Moreover, the vessel can be connected with LHF and MCF directly for sample splitting just prior to graphitization, enhancing efficiency and significantly reducing contamination of small standards and blanks.
    In certain instances, the presence of sulphur in small sediment-based mud wasp nests and in-situ 14C samples has interrupted the graphitisation process. To overcome this, we found that the addition of extra silver wires to solid samples (sediment) before combustion, or the re-combustion of gas samples at 650°C with silver wires was effective. This technique has proven successful, allowing us to process 100% of rock art and in-situ 14C samples affected by sulphur contamination, ensuring the integrity and accuracy of our radiocarbon analyses.
    
    Speaker: Dr Bin Yang
  - 97
    
    Status report of the sample chemical preparation for 10Be and 26Al at LN2C : Part 1 : quartz purification
    
    Since the acceptance of the 5MV AMS ASTER (CEREGE, Aix en Provence), the national laboratory LN2C is routinely measuring 10Be and 26Al for the scientific community. Previously based on a solvent extraction using EDTA and CCl4, we moved in 2008 due to the end of CCl4 production and to change for a safer chemistry, to a separation by ion exchange chromatography using anionic and cationic resins. But prior to this step, the sample purification quality is for one of the most important steps. The purification is a time-consuming and costly process. It is important that each step is carried out with the utmost care, using the most appropriate purification techniques that must be the most environmentally friendly.
    In this study, we will present how to get a pure quartz and we will focus on two persistent minerals: feldspars and muscovite. These latter minerals may persist after acid etching and yield to a significant reduction in the target emissivity in the AMS source. To define the limit beyond which the presence of these minerals mixed with quartz has an impact on sample preparation and AMS measurements, we prepared mixtures of geological samples by adding different proportion of feldspars, or/and micas with pure quartz. ICP-OES analyses were carried out to determine variations in aluminum concentration related to the proportion of feldspars or micas as well as a multi-element analyses to track B, Be, Al, Ti, Ca, Na, K, Mg, Fe, along the different steps of Be and Al extraction processes. Targets for AMS measurements were then prepared to define what are the critical values for which the quality of AMS measurement is impacted.
    To eliminate feldspars, we tested an effective, fast, and environmentally friendly method based on magnetite addition combined with a magnetic separation (Lacumin and Quercioli, 1993). For micas, we tested other techniques: flotation, heavy liquor, sieving and high-current magnetic separation.
    
    References
    [1] Silke Merchel, Andreas Gärtner, Sabrina Beutner, Bodo Bookhagenc , Amelié Chabilan, Attempts to understand potential deficiencies in chemical procedures for AMS: Cleaning and dissolving quartz for 10Be and 26Al analysis. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms Volume 455 (2019), p. 293-299
    [2] Lacumin and Quercioli, A new technique for quantitative separation of quartz from feldspars. European Journal of Mineralogy Volume 5 Number 4 (1993), p. 677 - 678
    
    Speaker: Laetitia Léanni (CEREGE LN2C)
  - 98
    
    Trace amounts of iodine were isolated from soil samples for AMS measurements.
    
    Iodine, as an essential biophilic element, is widely present in living organisms and crucial for human life activities. Among iodine isotopes, only iodine-127 is a stable nucleus, while iodine-129 has the longest half-life (1570 million years). Therefore, it is particularly important to isolate iodine from soil samples and utilize AMS to measure the ratio of iodine-129 to iodine-127 for analyzing the level of environmental nuclear contamination. In this study, a method involving the addition of a carrier to precipitate iodine as silver iodide forming milligram-level iodine targets was developed. Using a tube furnace to generate high temperatures, iodine was volatilized from soil samples, and the released iodine vapor was collected with an alkaline trapping solution. 1 mg of carrier iodine was added to the trapping solution, and all iodides were reduced to iodide ions through oxidation-reduction reactions. A 1 ml solution was taken for stable iodine measurement using ICP-MS. Adding silver nitrate to the solution produced a precipitate. Impurities in the precipitate were dissolved and washed away with ammonia solution to obtain silver iodide precipitate. The precipitate was dried, mixed with niobium powder, pressed into a target, and measured with AMS to obtain the ratio of the two isotopes. This method can accurately determine the ratio of iodine-129 to iodine-127 content, with broad potential applications in environmental monitoring and geological dating.
    
    Speaker: Mr Wenqiao Liu (GUANG XI NORMAL UNIVERSITY)
- 18:15
  
  Dinner Restaurant，Ground floor
  
  Restaurant，Ground floor
Tuesday, 22 October
- Registration in the lobby of the Conference Hotel Lobby of the Conference Hotel
  
  Lobby of the Conference Hotel
- Plenary GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Convener: Prof. Anton Wallner (HZDR)
  - 99
    
    The environmental tracing studies using Chinese loess 10Be at Xi’an AMS Center
    
    The Xi'an AMS Center is equipped with a 3 MV accelerator mass spectrometer for multi-nuclides measurements, which provides a background of 10Be/9Be ratio up to 1.56×10-16, giving us favorable conditions to carry out environmental tracing study by using Chinese loess 10Be. Chinese loess-paleosol sequences are considered as one of three pillars for the global change research, along with marine sediments and ice cores. However, paleomagnetic studies showed that geomagnetic polarity reversals recorded in Chinese loess, such as the Matuyama/Gauss (M/G) reversal (a key time marker for Quaternary/Neogene boundary) and Brunhes-Matuyama (B/M) reversal, were found to be asynchronous with those in marine sediments. Such asynchroneities led to a long-standing debate over the uncertainties of the loess time scale and climatic correlation between terrestrial and marine records. To resolve these problems, we developed Residual Trace Approach (RTA) to disentangle the global geomagnetic and climate signals in Chinese loess 10Be, and reinvestigated the M/G and B/M boundaries using 10Be from loess sections. The results showed that the 10Be-traced M/G and B/M reversals were in fact synchronous with the records from marine sediment, settling the long-disputed question of the apparent asynchroneities of the two important geomagnetic reversals between terrestrial and marine sediments. We further reconstructed geomagnetic field variations for the last ~870 kyr and, for the first time, identified 13 consecutive geomagnetic excursions in loess which provide key time markers for Chinese loess-paleosol sequences. As by-product, we also quantitatively reconstructed multi-time scale Asian monsoon (AM) rainfall using loess 10Be. We proposed that the AM rainfall was mainly modulated by the low latitude insolation gradients and the Earth’s eccentricity can modulate the amplitude of the precession signal in AM rainfall.
    
    Speaker: Weijian Zhou (Institute of Earth Environment, Chinese Academy of Sciences)
    
    AMS16_Abstract_Zhou Weijian.pdf
- Applications in Archaeology GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  AMS tools to study and date ancient humans and human activity.
  
  Convener: Prof. Hong-Chun Li
  - 100
    
    Radiocarbon-based chronological researches on Chinese civilization
    
    The research on the Origin and Development of Chinese Civilization is a hot topic and involving many complex questions, such as the elements, process and paths of civilization. To establish the precision chronological frame is one of the most important aspects related to Chinese Civilization. The major scientific research project about Chinses civilization supported by the state that combines natural science and humanities and social sciences conducts multi-level and comprehensive research on the origin and progress, nature and characteristics of Chinese civilization. It reveals the process and reasons for the formation of Chinese civilization and proves the fact that the history of Chinese civilization spans over 5,000 years and explains the reference significance of Chinese civilization to current human development from both theoretical and practical perspectives. The research team from Peking University has made important contributions to chronological research, and has conducted radiocarbon dating research using accelerator mass spectrometry on dozens of important sites, providing high-precision dating data for accurately estimates the ages of key points and major historical events. It provides a solid chronological support for the study of the origin and early development of Chinese civilization. Around 5300 years ago, central cities and primitive religious sites with an area of over 1 million square meters emerged in the middle and lower reaches of the Yellow River, the Yangtze River, and the Western Liao River basin. About 4300 years ago, the civilization process in various parts of China underwent transformation, with the important feature of the rise of the center on Central Plains. Around 4000 years ago, a new era has begun with the beginning of the period of dynasties.
    
    Speaker: Xiaohong Wu (Peking University)
  - 101
    
    Introducing 'Horsepower: China, Mongolia and the steppe'
    
    From the second millennium BC, two great cultures formed, traded and fought across Eurasia – one based on horses and herding that stretched from Mongolia to the European steppe, and the other, to the south that consisted of established and newly formed states from the Middle East to the Chinese Central Plains.
    
    Horsepower: interactions between China, Mongolia and the steppe 2000–0 BC studies these relationships between China and neighbouring Mongolia and Central Asia by exploring the trade in horses. It also looks at the associated material culture associated with horseback riding or the driving of vehicles, and the metal supply from China to the north and northwest.
    
    Combining scientific techniques in genetics (DNA analysis), radiocarbon chronology and metallurgical analysis with theories of cosmology, aesthetics and performance plus new archaeological excavation in Mongolia and China, this project examines early state formation in Mongolia and China in the first two millennia BC.
    
    The current presentation serves two purposes: firstly, introducing the 'Horsepower' project to the international community; and, secondly, presenting a database intended to contain ALL 14C dates thus far produced pertaining to archaeological sites within the boundaries of modern day China.
    
    Speaker: Richard Staff (School of Archaeology, University of Oxford & British Museum)
  - 102
    
    Radiocarbon dating reveals a 20,000-year sequence of Australian Aboriginal Rock Art
    
    A decade long research project has revealed a chronological sequence of Australian Aboriginal rock art that spans, at least, 20,000 years.
    
    The Kimberley region in north-western Australia is renowned for its rich concentration of rock art, traditionally believed to originate from the Pleistocene. Despite its cultural and historical importance, the direct radiometric dating of the older art is not possible as it was rendered using ochre pigment. Attempts to date the art, therefore, rely on establishing age constraints through the dating of material overlying or underlying the paintings. Until now, the scarcity of suitable material meant there was very limited geochronological evidence to support its Pleistocene antiquity and insufficient results to date the different styles of rock art.
    
    Our research project developed techniques to radiocarbon date the more abundant, small mud wasp nests commonly found in contact with rock art. Employing statistical analyses, we determined that hundreds of wasp nest ages were necessary to confidently estimate the age span of the five main Kimberley rock art styles. Between 2015 and 2023, we collected over 600 mud wasp nest samples (median mass 260 mg). For the 565 samples prepared for AMS measurement, the median carbon mass was just 25 micrograms so the ability to reliably measure microgram-sized samples was crucial.
    
    Our findings, based on 440 radiocarbon dated wasp nests in relation to rock art, establish a Kimberley stylistic sequence spanning at least 20,000 years. Notably, the great majority of the paintings in our study area date back to the period between 20,000 and 10,000 years ago, encompassing the Last Glacial Maximum to the terminal Pleistocene.
    
    Speaker: Damien Finch (University of Melbourne)
- Applications in Astrophysics and Nuclear Sciences GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  From the surface of Earth to meteorites and interstellar space. Using the AMS to help understand processes and phenomena within our universe; AMS methods for monitoring nuclear emissions, identifying sources of emissions, and the management of nuclear waste.
  
  Convener: Prof. Anton Wallner (HZDR)
  - 103
    
    On some unsettled half-lives of AMS radionuclides
    
    Half-lives ought to be accurate, and preferably precise as well. In the recently published review on half-lives of long-lived radionuclides (Heinitz et al., 2022), several cases were mentioned where multiple half-life measurements on a specific radionuclide were incompatible with each other within the reported uncertainties. We call these “unsettled” half-lives. There are also cases where only very old half-life measurements (50 to 60 years ago) exist, which may need confirmation.
    The direct way to determine a long half-life follows from the radioactive decay law: dN/dt = -λ$\cdot$N,
    where N is the number of radionuclides, dN/dt is its decay rate (activity), and λ the decay constant related to the half-life via λ = ln2/t$_{1/2}$. Both N and dN/dt need to be measured accurately and independently to obtain the half-life.
    The half-life of $^{10}$Be can be considered as a good example of how early (trivial) mistakes were corrected and eventually an accurate and precise half-life value of (1.387$\pm$0.012)$\times$10$^{6}$ y was established from two independent measurements (Korschinek et al., 2010, Chmeleff et al., 2010).
    In this contribution, we want to discuss unsettled half-lives of some radionuclides where AMS was partly involved in the half-life measurement itself, and which are of interest for applications through AMS measurements. Among others, these comprise the radionuclides $^{32}$Si, $^{39}$Ar, $^{53}$Mn, $^{59}$Ni, $^{79}$Se, $^{135}$Cs, and $^{146}$Sm.
    We will discuss some ongoing and planned half-life measurements on these radionuclides, which hopefully will lead to a firmly accepted value. The number of radionuclides in the sample whose activity needs to be measured is a crucial input for a half-life determination. Different methods to measure radionuclide concentrations (e.g. AMS, ICP-MS) will be mentioned. In particular, a critical assessment of the measurement of absolute isotope ratios with AMS will be presented, In some cases, geophysical half-life measurements can also be combined with physical measurements to confirm or refute half-life values.
    
    S. Heinitz, I. Kajan, and D. Schumann, How accurate are half-life data of long-lived radionuclides? Radiochim. Acta 110/6-9 (2022) 589-608.
    G. Korschinek et al., A new value for the half-life of $^{10}$Be by heavy-ion elastic recoil detection and liquid scintillation counting. Nucl. Instr. Meth. Phys. Res. B 268 (2010) 187–191.
    J. Chmeleff et al., Determination of the half-life of $^{10}$Be by multicollector ICP-MS and liquid scintillation counting, Nucl. Instr. Meth. Phys. Res. B 268 (2010) 192–199.
    
    Speaker: Walter Kutschera (University of Vienna, Faculty of Physics, Isotope Physics, A-1090 Vienna, Austria)
  - 104
    
    How competitive can compact AMS systems be in nuclear waste characterisation?
    
    At the Centro Nacional de Aceleradores (CNA, Seville, Spain), research efforts are being devoted to exploring the limits of the 1 MV AMS system to analyse several radioisotopes present in nuclear waste that pose serious analytical challenges to radiometric techniques. The focus has been placed on 41Ca, 36Cl, and actinides radionuclides (239,240,241Pu, 236,238U, 237Np, 241,243Am and 244,245,246Cm). 41Ca and 36Cl have stable isobars, 41K (6.73% isotopic abundance) and 36S (0.0158% isotopic abundance), respectively, which cannot be fully suppressed in our system using techniques based on stopping power difference as is done in conventional AMS facilities. Our alternative approach is based on i) the removal of K (41K) or S (36S) through optimised radiochemical methods and ii) the indirect control of the 41K or 36S count rates mimicking the detector signal of 41Ca and 36Cl, respectively, using other stable K and S isotopes with well-known isotopic abundances. The obtained results this way point out to minimum atomic ratios of 10-12 for 41Ca/40Ca (3 mBq/g of Ca), and 10-9 for 36Cl/35Cl (0.1Bq/g of Cl). It has been observed that the interference from 36S and 41K originates from the metallic matrix of the cathode rather than from the samples. As for actinides, efforts have been devoted to simplifying the existing radiochemical methods and the measurement techniques for environmental samples. Using one UTEVA® and one DGA® resin in tandem, the U, Np and Pu species on the one hand, and Am and Cm on the other, respectively, are sequentially separated from nuclear waste matrixes. Subsequently, the target nuclides for each fraction (236,238U, 237Np, and 239,240,241Pu for the U+Pu+Np AMS sample; 241,243Am and 244,245,246Cm for the Am+Cm AMS sample) are analysed on the 1 MV AMS system. In this work, the status of the AMS analysis on nuclear waste at the CNA and first results for samples from the decommissioning of a Spanish nuclear reactor (i.e. resin, sludge, and concrete) will be presented and discussed.
    
    Speakers: Dario Sanchez Jimenez (Universidad de Sevilla) , Dr Elena Chamizo-Calvo (Universidad de Sevilla) , Prof. José María López-Gutiérrez (Universidad de Sevilla)
    
    2024 AMS conference ABSTRACT.pdf
  - 105
    
    r-Process Radioisotopes from Near-earth Supernovae and Kilonovae
    
    The astrophysical sites where r-process elements are synthesized remain mysterious: it is clear that neutron star mergers (kilonovae, KNe) contribute, and some classes of core-collapse supernovae (SNe) are also possible sources of at least the lighter r-process species. The discovery of 60Fe on the Earth and Moon implies that one or more astrophysical explosions have occurred near the Earth within the last few Million years (Myr), probably SNe. Intriguingly, 244Pu has recently been discovered in deep-sea deposits spanning the past 10 Myr, a period that includes two 60Fe pulses from nearby supernovae. 244Pu is among the heaviest r-process products, and we consider whether it was created in the supernovae, which is disfavored by nucleosynthesis simulations, or in an earlier kilonova event that seeded 244Pu in the nearby interstellar medium that was subsequently swept up by the supernova debris. Accelerator mass spectrometry (AMS) measurements of 244Pu and searches for other live isotopes could probe the origins of the r-process and the history of the solar neighborhood, including triggers for mass extinctions, e.g., that at the end of the Devonian epoch, motivating the calculations of the abundances of live r-process radioisotopes produced in SNe and KNe that we present here. Given the presence of 244Pu, other r-process species such as 93Zr, 107Pd, 129I, 135Cs, 182Hf, 236U, 237Np, and 247Cm should be present. Their abundances and well-resolved time histories could distinguish between the SN and KN scenarios, and we discuss prospects for their detection in deep-ocean deposits and the lunar regolith samples returned to Earth by missions such as Chang'e and Artemis.
    
    Speaker: Xilu Wang (Institute of High Energy Physics, Chinese Academy of Sciences)
- 10:20
  
  coffee break Lobby , 2nd Floor
  
  Lobby , 2nd Floor
- Applications in Archaeology GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  AMS tools to study and date ancient humans and human activity.
  
  Convener: Prof. Hong-Chun Li (NTU)
  - 106
    
    Cosmogenic exposure dating the Pre-Columbian archaeological structures at Tiwanaku, Bolivia
    
    We use in-situ cosmogenic 10Be to date the construction of stone platform from the Kalasasaya UNESCO Heritage archaeological site at the ancient city of Tiwanaku, Bolivia. The unique site is located within the altiplano valley of Tiwanaku at 3870 masl near the southern shores of Lake Titicaca. The monuments at Tiwanaku were constructed as ceremonial and civic buildings of exceptional precision and quality by an Andean civilization, who were precursors of the Inca Empire. The pillars, ~5 meters tall and of square meter section, frame the outer perimeter wall of the 120m square Kalasasaya Platform which is made of andesite and sandstone blocks quarried from outcropping bedrock tens of kilometres distant and at ~ 4300 masl. The date of construction of Tiwanaku is unknown. Earliest settlement is believed to be at least ~3,000 years ago and archeological evidence supports a drought-based empire collapse in the first half of the 12th century. Radiocarbon dating of construction material and other debris ranges from 300 to 950 AD. At its apogee Tiwanaku settlement is estimated to have extended over an area of as much as 6 sq km and to have housed between 70,000 and 125,000 inhabitants. We gained permission to sample the very tops of 3 of these pillars, multi-meter size cuboid sandstone blocks excavated at the quarries, bedrock surfaces of the cavity from where blocks originated, and unmodified bedrock outcrop. We were able to re-orient extracted blocks back into their original excavated cavity and thus determine pre- excavated buried and post-excavated exposed vertices which allowed us to measure how long ago the block was carved out of bedrock and rotated in the process.
    Our results show that the cosmogenic signal in platform pillar tops is dominated by inheritance but that blocks had been quarried as recently as 2500-3500 years ago, the age range depending on the magnitude of the steady state erosion rate for the site and choice of attenuation length. Details of sampling, 10Be measurements and age calculations will be presented.
    
    Speaker: David Fink (ansto)
  - 107
    
    AMS 14C dating of lead carbonate, a new chronological tool for archaeology: example from the Grandmont Abbey cemetery, France
    
    Absolute dating of lead carbonates - cerussite (PbCO3) and hydrocerussite (2PbCO3.Pb(OH)2 - by the radiocarbon method have been developed recently. Lead white cosmetics, pigments and paints have been successfully dated (Beck et al., 2018- 2020; Hendriks et al., 2019; Messager et al., 2021, 2022). The dating was made possible by the lead white synthesis method, which uses horse manure as a source of CO2 to form carbonates. It was thus demonstrated that carbon of organic origin had been incorporated during this synthesis, as also observed by Strydonck et al. (2016) in the corrosion products of a lead coffin.
    In this study, a similar approach is being attempted on lead carbonates formed by in situ corrosion of lead bottles found in burials in the cemetery of the Grandmont Abbey (France). Since 2013, a multidisciplinary team from the University of Picardie has been carrying out research on the site of the Grandmont Order's motherhouse. Lead was used extensively in the architecture of the abbey church, thanks in particular to the patronage of Henry II Plantagenet in the second half of the 12th century, who supplied large quantities of lead from England. When the monastery was founded around 1124, lead was chosen to make eulogy bottles, which were placed in contact with the body in the graves. Lead carbonates were taken during the restoration of bottles for radiocarbon dating. Samples were prepared by thermal decomposition and measured using the AMS ARTEMIS/LMC14. The consistency of the results obtained on both lead carbonates and bones (rarely preserved) suggests that the formation of lead carbonates is indeed the product of corrosion of the metal by an organic substance, linked to the decomposition of the bodies. Thus, 14C dating of lead corrosion gives access to the date of burial, and opens up new perspectives in cases where the bones are no longer present or poorly preserved.
    
    Speaker: Dr Lucile BECK (CEA)
  - 108
    Compound-specific radiocarbon dating of lipids in pottery via SFE-pcGC
    
    Radiocarbon dating plays a pivotal role in establishing reliable chronologies in both archaeological and paleoenvironmental studies, spanning over 55,000 years. Pottery, pervasive throughout the Holocene archaeological record, offers a crucial avenue for dating human activity, employing a combination of relative methods such as typology and seriation, alongside absolute techniques. Traditional radiocarbon dating of pottery often relies on carbon fractions from various origins, such as temper or associated organic materials like bone and charcoal. However, inaccuracies can arise from relative dating as a result of stratigraphic uncertainties and poor preservation, whilst the direct dating of different carbon fractions may not accurately reflect the timing of vessel use. Over the past decades, researchers have pursued an alternative avenue; leveraging lipid residues, particularly fatty acids absorbed into pottery walls during the processing and storage of plant and animal-derived foods, for radiocarbon dating [1, 2]. This approach holds promise for delivering highly accurate measurements directly correlating to the use of vessels. At the Oxford Radiocarbon Accelerator Unit, efforts have been made to refine this methodology through compound-specific radiocarbon dating of pottery, employing advanced techniques such as supercritical fluid extraction (SFE) coupled with preparative capillary gas chromatography (pcGC). The adoption of SFE may represent a substantial leap forward, since it has been demonstrated to yield 95% more lipid residue than traditional solvent extraction [3]. This presentation will compare SFE yields to the acidic methanol extraction method. Here, we delineate the developed methodology and present preliminary findings, including analyses conducted on pottery samples sourced from archaeological sites with well-established chronologies.
    
    E. Casanova, et al., Accurate compound-specific 14C dating of archaeological pottery vessels. Nature 580, 506–510 (2020).
    
    A. W. Stott, et al., Radiocarbon Dating of Single Compounds Isolated from Pottery Cooking Vessel Residues. Radiocarbon 43, 191–197 (2001).
    
    T. Devièse, et al., Supercritical Fluids for Higher Extraction Yields of Lipids from Archeological Ceramics. Analytical Chemistry 90, 2420–2424 (2018).
    
    Speaker: Dr Qian Ma (Oxford Radiocarbon Accelerator Unit, School of Archaeology, University of Oxford)
  - 109
    
    Assessing the Reservoir Effect in Radiocarbon Dating of Archaeological Sites Dependent on Freshwater Resources
    
    The preservation of bone collagen at many ancient archaeological sites in Southern China is often poor, complicating the process of effective radiocarbon dating. To address this, our study has employed a method focused on extracting hydroxyproline—a non-essential, but abundant amino acid in collagen involved in human metabolism. This approach was chosen due to its presumed stability and abundance in archaeological bone. Nonetheless, we observed that hydroxyproline is susceptible to the freshwater reservoir effect, which results in anomalously old radiocarbon ages compared to those of contemporaneous plant or wooden artifacts. This effect, while generally less impactful than its marine counterpart, can significantly skew radiocarbon dating results at sites heavily reliant on freshwater resources.
    
    Our analysis at sites such as the Banpo in Xi'an and the Qujialing in Hubei, which are characterized by extensive fish remains and fishing tools, reveals a clear dependency on freshwater biota. By analyzing single amino acids, we found that the radiocarbon ages of essential amino acids (e.g., leucine, isoleucine, and methionine) were consistently younger by 60-100 years compared to non-essential amino acids (e.g., aspartic acid, glutamic acid, and alanine). This pattern indicates a significant influence of the freshwater reservoir effect.
    
    Our findings highlight the necessity of considering this effect when conducting radiocarbon dating at sites with a strong reliance on freshwater resources. Ignoring this factor could lead to substantial errors in the chronological reconstruction of past human activities. Thus, incorporating adjustments for the freshwater reservoir effect is crucial for accurate and reliable dating of archaeological remains.
    
    Speaker: Dr Zihan Li (Nanjing University)
- Applications in Astrophysics and Nuclear Sciences GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  From the surface of Earth to meteorites and interstellar space. Using the AMS to help understand processes and phenomena within our universe; AMS methods for monitoring nuclear emissions, identifying sources of emissions, and the management of nuclear waste.
  
  Convener: Prof. Walter Kutschera (University of Vienna, Faculty of Physics)
  - 110
    
    $^{60}$Fe and $^{182}$Hf nucleosynthesis via double neutron capture
    
    The long-lived radionuclides Fe-60 (t$_{1/2}$=2.6 Myr) and Hf-182 (t$_{1/2}$=8.9 Myr) are sensitive monitors to the neutron environment under different stellar conditions. Production of both nuclides requires neutron fluxes high enough to compete with the decay of the shorter-lived nuclides Fe-59 (t$_{1/2}$=44 d) and Hf-181 (t$_{1/2}$=42 d) which separate Fe-60 and Hf-182 from stable isotopes Fe-58 and Hf-180. Such conditions are predicted for the s (slow neutron capture) process in massive stars only at their late burning phases, e.g., shortly before they end in a supernova, as well as in the r process (rapid neutron capture). The site and frequency of the r process is heavily debated and attributed either to some rare cases of supernovae or neutron star mergers.
    On Earth, (n,α) reactions do not contribute to their natural production as the parent nuclides for both cases are not stable. Fission yields are also very low, consequently, both Fe-60 and Hf-182 are very rare on Earth. Accordingly, any presence of either nuclides on Earth may indicate signatures of interstellar influx with their nucleosynthesis within a time period of a few half-lives. Indeed, two distinct interstellar Fe-60 influxes had been found in terrestrial and lunar archives demonstrating recent (within 10 Myr) and ‘nearby’ supernova activity (<150 pc distance). No interstellar Hf-182 had been detected so far. This reflects either the expected low production yields of Hf-182 or a low interstellar influx into the solar system. However, more importantly, the difficulty to chemically extract and measure Hf-182 at the expected low concentrations in terrestrial archives makes detection of interstellar Hf-182 extremely challenging.
    The production yields of both nuclides at astrophysical energies are not yet measured and predictions are highly uncertain. This is crucial not only for interpreting the supernova-produced Fe 60 data, but also for Hf-182, as both, s and r process may contribute to an interstellar signal, potentially still undetected in terrestrial or lunar archives.
    In this contribution, we present new and precise data for both double neutron-capture reactions as well as give an outlook on Fe-60 production via 63Ni(n,α). Samples, highly enriched in Fe-58, Ni-62 and Hf-180, were irradiated at the nuclear reactor at the Institut Laue-Langevin (ILL), Grenoble, with a high, predominantly thermal, neutron flux. At the Atominstitut in Vienna, additional Fe-58 samples were exposed to a mix of thermal and epithermal neutrons extending the energy range to the astrophysical interesting keV-energies. The induced Fe-59 and Hf-181 activities were utilised as intrinsic monitors for the neutron fluence. After the decay of intermediate Fe-59, the produced Fe-60 was measured with AMS at the ANU. The number of Hf-182 nuclides, however – owing to the much higher capture cross sections – was high enough for a direct activity measurement of the irradiated sample without the need for AMS.
    These new experimental data will provide important anchor points for a better understanding of heavy element nucleosynthesis in massive stars and explosive stellar environments.
    
    Speaker: Anton Wallner (HZDR)
  - 111
    
    Search for Interstellar $^{60}$Fe, $^{244}$Pu and $^{247}$Cm in a Pacific Ferromanganese Crust
    
    The radionuclide $^{60}$Fe(t$_{1/2}$ = 2.6 Myr) is a tracer for recent nucleosynthesis in massive stars and core-collapse supernovae, whereas the longer-lived radionuclide $^{244}$Pu (t$_{1/2}$ = 81 Myr) is synthesized in the astrophysical r-process. The nucleosynthesis site of the r-process is heavily debated in the astrophysics community with rare supernovae and neutron star mergers being the prime candidate sites.
    In contrast to freshly synthesised $^{60}$Fe, $^{244}$Pu, due to its much longer half-life, could accumulate in the interstellar medium over geological timescales. A time-resolved profile of $^{60}$Fe and $^{244}$Pu abundances would provide important information about the site of the r-process and interstellar medium dynamics. The r-process nuclide $^{247}$Cm (t$_{1/2}$ = 15.6 Myr) with a shorter half-life than $^{244}$Pu could additionally serve as an independent clock for r-process nucleosynthesis in the galaxy when compared to $^{244}$Pu.
    
    The search for $^{60}$Fe and $^{244}$Pu on Earth with AMS resulted in the discovery of both interstellar radionuclides. Two distinct global influxes of interstellar $^{60}$Fe around 2.4 Myr [e.g. 1,2] and 7 Myr ago [e.g. 2,4] into marine archives, a recent $^{60}$Fe influx into Antarctic snow [3] as well as a corresponding influx of interstellar $^{244}$Pu into a marine ferromanganese crust [4] were reported. The time-resolution of the $^{244}$Pu profile was so far insufficient to fully relate the influx characteristics of $^{244}$Pu to that of $^{60}$Fe. Up to now, no interstellar $^{247}$Cm has been detected on Earth.
    
    In this contribution, we report on a new time-profile of $^{60}$Fe and $^{244}$Pu in a Pacific ferromanganese crust. The acquired $^{60}$Fe profile shows two pronounced peaks of $^{60}$Fe influxes with improved timing. A continuous r-process $^{244}$Pu influx was discovered with a time-resolution of 1 Myr over the last 10 Myr owing to the extraordinarily high total efficiency of Pu AMS of 1% achieved in this project. Recent work on detecting interstellar $^{247}$Cm in the same archive will be presented.
    
    [1] Knie et. al., Phys. Rev. Lett. 93 (2004).
    
    [2] Wallner et al., Nature 532 (2016).
    
    [3] Koll et al., Phys. Rev. Lett. 123 (2019).
    
    [4] Wallner et al., Science 372 (2021).
    
    Speaker: Dominik Koll (The Australian National University & TU Dresden & Helmholtz-Zentrum Dresden-Rossendorf)
  - 112
    
    Simultaneous Extraction of Cosmogenic and Interstellar Radionuclides from Lunar Soil
    
    Various nucleosynthetic processes contribute to the creation of the chemical elements in the universe. The rapid neutron capture process ($r$-process) alone produces over half of the elements heavier than iron and is uniquely capable of synthesizing the actinides. Recent $r$-process events in the solar neighbourhood can leave fingerprints in the solar system, such as the pure $r$-process radionuclide $^{\textrm{244}}$Pu (t$_{1/2}\,\sim\,$81$\,$Myr). The extraordinary improvements in the $^{\textrm{244}}$Pu detection efficiency in recent years made it possible to detect live interstellar $^{\textrm{244}}$Pu in deep-sea ferromanganese crusts via AMS $-$ confirming ongoing $r$-process nucleosynthesis in the solar neighbourhood [1]. We have now extended our search for interstellar $^{\textrm{244}}$Pu and also for supernova-produced $^{\textrm{60}}$Fe (t$_{\textrm{1/2}}\,$=$\,$2.6$\,$Myr) to a different archive, lunar soil. The absence of geological processes leads to the accumulation of radionuclides over much longer time periods, leading to potentially higher signals and enabling mapping of the interstellar influx up to hundreds of millions of years into the past [2,3]. Alongside the search for interstellar radionuclides, we also measured various cosmogenic radionuclides with half-lives in the order of a million years in these lunar samples $-$ suitable to study the samples' exposure histories. The radionuclides $^{\textrm{10}}$Be, $^{\textrm{26}}$Al, and $^{\textrm{41}}$Ca are measured at HZDR in Dresden and $^{\textrm{53}}$Mn at the ANU in Canberra. An effective sample preparation method ensuring optimal extraction of all radionuclides from the same sample and simultaneously providing high chemical yields is important here.
    
    This contribution presents a chemical separation procedure based on existing recipes [4,5] to simultaneously extract eight elements from one lunar soil sample. This method was first tested on lunar simulants and then applied on an Apollo 11 soil sample, also investigating different leaching and digestion procedures. Data for 12 lunar soil samples will be presented for all cosmogenic nuclides. Additionally, we will provide insights into preliminary $^{\textrm{60}}$Fe data and updates on the quest for interstellar $^{\textrm{244}}$Pu.
    
    [1] Wallner, A., et al. (2021) Science, 372(6543), 742-745.
    [2] Fields, B. D. and Wallner A. (2023) Annu. Rev. Nucl. Sci. 73, 365-395.
    [3] Fimiani, L. et al. (2016) Phys. Rev. Lett. 116, 151104.
    [4] Merchel, S. and U. Herpers (1999) Radiochim. Acta 84, 215.
    [5] Koll, D. et al. (2022) Nucl. Inst. Meth. B 530, 53.
    
    Speaker: Sebastian Zwickel (Helmholtz-Zentrum Dresden-Rossendorf & TU Dresden)
  - 113
    
    AMS and ICP-MS Measurements of Radioimpurities Pb-210 and K-40 for the SABRE South Dark Matter Experiment
    
    DAMA/LIBRA (DArk MAtter/Large sodium Iodide Bulk for RAre Processes) is a low-background NaI:Tl crystal detector array in the Gran Sasso underground laboratory in Italy. It has been measuring purported dark matter signals for over two decades. DAMA/LIBRA reported an annual modulation signal in the 2 to 6 keV energy region that is claimed to be from dark matter [1]. SABRE (Sodium-iodide with Active Background REjection) South, located at the Stawell Undergrond Physics Laboratory (SUPL) in Australia, will provide an alternate and independent dark matter signal measurement with the same detector material as DAMA/LIBRA but with a higher sensitivity [2].
    
    Ultra-high purity of the NaI:Tl crystals is a crucial feature of direct dark matter detectors. Radioimpurities in the detector material may mimic dark matter and must be studied and quantified. The metrology group at the Australian National University (ANU) is developing chemical procedures for ultra-sensitive measurements of radioimpurities with accelerator mass spectrometry (AMS) and inductively coupled plasma mass spectrometry (ICP-MS) towards qualification of SABRE materials. This study focuses on the radionuclides $^{210}$Pb and $^{40}$K, which are expected to be the dominant radioimpurities in the crystals impacting the background.
    
    $^{210}$Pb (half-life of 22.2 yr) is a part of the uranium decay series and therefore naturally occurring in environment. Due to a limited amount of NaI available for radioimpurity analysis, not enough intrinsic lead can be extracted to produce an adequately large AMS sample. Therefore, it is essential to add an optimal lead carrier material with a low $^{210}$Pb content to increase the size of the NaI sample. Potential carriers were measured via AMS at the 14 UD pelletron accelerator at the ANU, as well as at the 1 MV VEGA accelerator at the Australian Nuclear Science and Technology Organisation in Sydney. Due to the relatively short half-life of $^{210}$Pb, carriers obtained from aged constructions were measured to have the lowest $^{210}$Pb/Pb ratios in the order of 10$^{-16}$, two orders of magnitude lower than previously reported [3].
    
    Due to its long half-life, the radioimpurity $^{40}$K (half-life of 1.25 Gyr) is of primordial origin. The amount of the stable potassium isotope $^{39}$K was measured via ICP-MS. The well-known natural abundances of these two isotopes were used to determine the amount of $^{40}$K in NaI.
    
    [1] R. Bernabei et al., Eur.Phys.J.C 67 (2010): 39-49.
    [2] E. Barberio et al., Eur.Phys.J.C 83.9 (2023): 878.
    [3] M. B. Froehlich et al., Nucl. Instrum. Meth. B 529 (2022): 18-23.
    
    Speaker: Dr Zuzana Slavkovská (The Australian National University)
- 12:00
  
  lunch Restaurant，Ground floor
  
  Restaurant，Ground floor
- Actinide Techniques and Applications GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Discussions on the applications of actinide series elements.
  
  Convener: Prof. Marcus Christl (ETH Zurich)
  - 114
    
    Actinides measurements on the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA, Seville, Spain): How far can we go?
    
    The AMS technique was implemented for the first time in Spain in 2005, with the arrival at the Centro Nacional de Aceleradores (CNA, Seville) of the first compact and multi-elemental system put in the market by High Voltage Engineering Europa (HVEE, Amersfoort, The Netherlands). Since then, actinides measurement techniques have been in constant development at the CNA. To date, 236U, 237Np, 239Pu, 240Pu and 241Pu can be considered consolidated radionuclides and are routinely measured in a variety of samples [1,2]. Recently, the AMS technique has been setup for 233U [3] and 244Pu [4] analysis. The limelight is now put on Am and Cm analysis.
    
    The compact design of the spectrometer constraints the abundance sensitivity that can be obtained for those nuclides neighboured in mass by naturally occurring isotopes. This is the case of 236U, neighboured by 235U and 238U, and 233U, neighboured by 232Th, 234U and 235U, for which background isotopic ratios of 10-10 (i.e. 236U/238U) and of 5x10-11 (i.e. 233U/238U) have been demonstrated, respectively [3,5]. It has been observed that the survival of molecular isobars in 3+ charge state can limit the sensitivity of the technique is the stripper gas settings are not properly adjusted. This can be especially critical for the extremely minor 244Pu, due to the survival of the diatomic trication 232Th12C3+ [4]. Recent studies on Am (241Am and 243Am) and Cm (244Cm, 245Cm and 246Cm) isotopes point out to detection issues related to the presence of lanthanides (mostly Dy isotopes) in the sample, due to occurrence of pile-up events from 2+ molecular fragments mimicking the electronics signal of 3+ actinides ions in the detector (e.g. 162Dy2+ and 243Am3+). Thus, the best performance of the AMS technique for actinides analysis in environmental samples can be achieved if: i) the AMS technical parameters are thoroughly adjusted in every case (i.e. slits settings and stripper gas pressure), and ii) the radiochemistry of the samples is optimized so that Th is suppressed from the U, Np and Pu samples, and lanthanides from the Am and Cm samples [7].
    
    At the CNA, a synergy between both research fields, AMS technique and radiochemistry, has been achieved, so that the most minor and demanding actinides radionuclides can be analysed in a variety of environmental matrixes. In this work, the overall performance of the technique will be presented. Besides, examples of the most recent studies carried out at the CNA illustrating the potential of the U, Pu and Am isotopic vectors to gain information on the anthropogenic sources of actinides to the environment will be given.
    
    [1] M. López-Lora, E. Chamizo, I. Levy, M. Christl, N. Casacuberta, T.C. Kenna, 236U, 237Np and 239,240Pu as complementary fingerprints of radioactiveeffluents in the western Mediterranean Sea and in the Canada Basin (Arctic Ocean), Sci. Total Environ. 765 (2021) 142741. https://doi.org/10.1016/J.SCITOTENV.2020.142741.
    [2] M. López-Lora, G. Olszewski, E. Chamizo, K. Pettersson, M. Eriksson, Plutonium Signatures in a Dated Sediment Core as a Tool to Reveal Nuclear Sources in the Baltic Sea, Environ. Sci. Technol. (2023). https://doi.org/10.1021/acs.est.2c07437.
    [3] E. Chamizo, M. López-Lora, M. Christl, Performance of the 1 MV Accelerator Mass Spectrometry system at the Centro Nacional de Aceleradores for the analysis of 233U at environmental levels, Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms. 533 (2022) 81–89. https://doi.org/10.1016/J.NIMB.2022.10.019.
    [4] E. Chamizo, M. López-Lora, I. Levy, V. Lérida, Reaching environmental levels of 244Pu by Accelerator Mass Spectrometry at the Centro Nacional de Aceleradores, J. Environ. Radioact. (submitted (2024).
    [5] E. Chamizo, M. López-Lora, Accelerator mass spectrometry of 236U with He stripping at the Centro Nacional de Aceleradores, Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms. 438 (2019) 198–206. https://doi.org/10.1016/j.nimb.2018.04.020.
    [7] M. López-Lora et al., This conference: Sequential extraction of U, Np, Pu and Am from sediment samples for AMS studies at the Centro Nacional de Aceleradores (CNA, Spain).
    
    Speaker: Dr Elena Chamizo (Centro Nacional de Aceleradores (CNA), Universidad de Sevilla, Sevilla, Spain)
  - 115
    
    Fallout isotopes $^{239-241,244}$Pu and $^{236}$U in a lake sediment from New Zealand
    
    Fallout from nuclear weapons tests in the 1950s and 1960s has been used for many years as a chronological marker in sediment cores. $^{137}$Cs in fallout has been detected by gamma spectroscopy, and used to validate $^{210}$Pb dating [1]. However, with its half-life of 30 years, $^{137}$Cs activity is reducing and it is now difficult to detect with good precision, especially in the southern hemisphere where fallout is significantly less than in the north.
    
    With the use of AMS, plutonium fallout is readily detectable and has been used increasingly in place of $^{137}$Cs [2, 3]. The high sensitivity of the Vega AMS system at ANSTO enables the detection of the rarer isotopes $^{241}$Pu and $^{244}$Pu in such sedimentary records, in addition to the $^{239}$Pu and $^{240}$Pu that is has been measured in the past. For some studies, the fallout isotope $^{236}$U has also been measured [3].
    
    In the current study, a detailed profile of the isotopes $^{239-241,244}$Pu and $^{236}$U has been obtained. The sediment core was taken from Lake Marion, a sub-alpine lake with a small catchment in a natural forest environment, in the Doubtful Range in the northern part of the South Island, New Zealand.
    
    The data show distinct variations in isotopic ratios with depth in the core. These can be interpreted as reflecting the transition from PPG-dominated fallout to Arctic-dominated fallout through the atmospheric weapons testing period. The $^{244}$Pu/$^{239}$Pu ratio is strongly correlated with $^{240}$Pu/$^{239}$Pu, as may be expected, while the $^{236}$U/$^{239}$Pu appears to be anti-correlated with $^{240}$Pu/$^{239}$Pu.
    
    [1] P.G. Appleby, Three decades of dating recent sediments by fallout radionuclides: a review, The Holocene 18 (2008) 1.
    [2] S.G. Tims et al., Plutonium as a tracer of soil and sediment movement in the Herbert River, Australia, Nucl. Instr. and Meth. B 268 (2010) 1150.
    [3] S.K. Marx et al., Examining the response of an eastern Australian mangrove forest to changes in hydro-period over the last century, Estuarine, Coastal and Shelf Science 241 (2020) 106813.
    
    Speaker: Michael Hotchkis (ANSTO)
  - 116
    
    Assessing the contamination sources of actinides (236U, 237Np, 239Pu, 240Pu, 241Am, 243Am) in sedimentary reservoirs from the northwestern Black Sea
    
    A.J. López-Fuentes1,2, E. Chamizo2, M. López-Lora2,3, J. Mantero1, J.M. Abril4, M. Ilie5, T. Sava5, G. Ion6
    
    1Department of Applied Physics II, E.T.S.A., University of Seville, Seville, Spain
    2Centro Nacional de Aceleradores (CNA), Seville, Spain
    3Department of Atomic, Molecular and Nuclear Physics, Physics Faculty, University of Seville, Seville, Spain
    4Department of Applied Physics I, E.T.S.I.A, University of Seville, Seville, Spain
    5Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest, Romania
    6National Institute of Marine Geology and Geo-Ecology (GeoEcoMar), Bucharest, Romania
    
    Scarce data exist on the presence of anthropogenic radionuclides in the Black Sea. This region might have been affected by different regional contamination sources, such as the Chernobyl accident in 1986 (former Soviet Union, now Ukraine), the fallout due to the atmospheric tests carried out by former Soviet Union, or leakages from the different nuclear facilities on its borders. These sources coexist with the global fallout (GF) signal from the atmospheric testing of thermonuclear weapons mainly in the 1950s and the 1960s.
    
    This work reports results on 137Cs and anthropogenic actinides in three sediment cores from the northwestern Black Sea, with the aim of assessing the contamination sources to this understudied marine region. Those results are complemented by a 210Pb dating. The samples were provided by the Horia Hulubei National Institute of Physics and Nuclear Engineering (HH-IFIN) and the National Institute of Marine Geology and Geo-Ecology (GeoEcoMar), both in Bucharest, Romania.
    
    Firstly, natural occurring radionuclides (210Pb, 214Pb and 214Bi) and 137Cs were characterized by gamma spectrometry at the University of Seville, Spain. Subsequently, the samples were chemically processed to separate: i) Pu, Np and U in the three target cores; and ii) additionally, Am in one of the cores, following the radiochemical method described in (M. López-Lora, this conference). The presence of 236U, 237Np, 239Pu, 240Pu, 241Am and 243Am was then investigated on the 1 MV Acceleration Mass Spectrometry (AMS) system at CNA, Seville, Spain.
    
    Results on the atomic ratios 240Pu/239Pu, 236U/238U and 243Am/241Am will be presented for an evaluation of the contamination sources and assess the studied elements in the context of an anoxic environment like the Black Sea.
    
    Speaker: Antonio Jesús López Fuentes (University of Seville)
    
    Abstract_AMS16_AJLF.docx
- Applications in Archaeology GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  AMS tools to study and date ancient humans and human activity.
  
  Convener: Prof. Hiroyuki Matsuzaki (The University of Tokyo)
  - 117
    
    Refining the chronology of two archaeological sites in south Russia since middle bronze age by 14C dating
    
    AMS 14C dating results on the samples from three archaeological sites: one is the Early Bronze Age in the Stanitsa Dinskaya, Krasnodar kray, North Caucasus, Southern Russia (45°14'42.258"N, 39°12'26.573"E) and two sites of the Early Iron Age in the Samara region, Middle River Volga area: Koptevo (50.1976N, 53.323E) and Manchikha (53°19'32.7"N, 50°06'6.2"E). There is very little radiocarbon dating for these archaeological cultures, so it is important for refining the chronology. During excavations of 6 mounds at the Dinskaya site, valuable findings were discovered, such as wooden carts, which are characteristic of the Novotitorovskaya culture of the Early Bronze Age, remains of people and animals, ceramic and bronze vessels, gold jewelry, etc. During detailed sampling, charcoals, human bones and teeth from different burials of four mounds at the Dinskaya site for AMS 14C dating were taken. Archaeological research has shown that the mounds contain materials belonging to several cultures of the Early Bronze Age. All AMS 14C data are given as the average of three burial materials with significant of 2 sigma Cal yr BP. It has been established that burials from four mounds at the Dinskaya site have the following radiocarbon age in the decreasing order in years ago: Early Yamnaya 4780±215, North Caucasian culture 4715±190, Catacomb culture 4690±155, Novotitorovskaya culture 4690±160, for this culture data on the analysis of charcoals is 4520±165, charcoals were taken from the same burials as the teeth. The 14C dates from charcoals are somewhat younger than those obtained from tooth analysis. In the 1st mound of the Dinskaya site, 6.5 m high, there was an entrance rich Sarmatian burial with a gold jewelry, large bronze cauldron, weapons and other finds, age 2015±145 Cal yr BP. Thus, the necropolis of the Dinskaya site with 6 mounds was built over a period of 100 years during the Early Bronze Age. We also dated materials from two settlements of the Early Iron Age of the Belogorsk culture in the Samara region of River Volga area. For 14C dating charcoal, animal bones and teeth were used. The average of two AMS 14C dates obtained from animal remains of the Manchikha site is 2320±190 Cal yr BP, from the charcoal – 2200±145 Cal yr BP. For the Koptevo settlement, two close dates were obtained: 2490±135 Cal yr BP and one date differs from them – 2190±120 Cal yr BP. Thus, the settlements of the Belogorsk culture included in the widespread Ananyin community functioned in the Samara region of Middle River Volga area during 2300–2500 yrs ago. Judging by the literature information, our radiocarbon AMS dates fit into the periods previously established for these archaeological communities.
    We thank archaeologists and anthropologists for providing ancient materials for 14C dating: Sheremetyev A.G., Kochetov Yu.E., Denisov A.V., Volkova E.M., Abramova A.N.
    The work was carried out within the framework of the State Assignment № 0191-2019-0046
    
    Speaker: Hong-Chun Li (NTU)
    
    5. TEZIS from Valentina.pdf
  - 118
    
    Radiocarbon and ivory live together in perfect harmony
    
    Extant elephant species have been protected from excessive international commercial trade by the Convention on International Trade in Endangered Species of Wild Flora and Fauna at least since 1989. However, the legal protection usually allows for some exemptions, such as antiques, that might serve as a loophole for trade in modern ivory.
    Comparison of the individual legislations of chosen states reveals that the term elephant antique ivory stands for different time periods throughout the globe. Radiocarbon dating is a powerful method of providing an objective age of ivory to distinguish legal from illegal. The analysis is generally successful for ivory dating between 1956 and 2017 covering the infamous big slaughters of African elephants. Ivory from 1947 to 1955 and younger to 2017 is not distinguishable by the method alone from ivory coming before 1947. Even though successful, the radiocarbon result may not be satisfactory or useful, as it is too vague for a specific legislative frame.
    On a robust group of radiocarbon data of ivory confiscated in the Czech Republic in recent years, we will demonstrate how the legislation affects the radiocarbon dating ability to serve as evidence of a wildlife crime. If the legislative definition of antique does not respect the limitation of the method, the ratio of useless analysis increases. We will introduce an ideal legislative solution that maximizes the number of analysis that can decide whether the ivory is legal or illegal.
    
    Speaker: Katerina Pachnerova Brabcova (1. Nuclear Physics Institute of the CAS; 2. Faculty of Science, Institute for Environmental Studies, Charles University)
  - 119
    
    A Study on the Life History of “Nanhai(南海) I” shipwreck
    
    This study dated the tree ring sequence ages of the upper deck, hull deck, mast holes, keel, etc. of the “Nanhai(南海) I” shipwreck using the method of AMS radiocarbon dating. The data were corrected using Bayesian methods by Oxcal calibration software. The samples representing the time of ship sinking, such as various plant seeds and animal bones, were also dated. According to the calibration results, “Nanhai(南海) I” shipwreck was probably built between 900 and 1000 AD. It was repaired between 1020 and 1050 AD. After combining the correction of the unearthed porcelain with the manufacture data written on its bottom, the sank date can be a certain year from 1183-1212 AD. Based on the radiocarbon dating, it could be inferred that “Nanhai(南海) I” shipwreck could have navigated about 200-300 years.
    
    Speaker: Jianfeng Cui (1. School of Archaeology and Museology, Peking University)
- 14:30
  
  coffee break Lobby , 2nd Floor
  
  Lobby , 2nd Floor
- Applications in Climate Studies GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  Paleoclimate, ocean and sea ice evolution, glaciations, and climate reconstruction using AMS methods.
  
  Convener: Prof. Hiroyuki Matsuzaki (The University of Tokyo)
  - 120
    
    Monthly and annual variations of 10Be fallout in the early 21st century recorded in a Greenland ice core
    
    Cosmogenic 10Be is produced by spallation reactions between galactic cosmic rays and nitrogen and oxygen atoms, mainly in the lower stratosphere and upper troposphere. Since the intensity of galactic cosmic rays is modulated by solar/geomagnetic fields, 10Be serves as a proxy for solar activity and the paleointensity of the Earth's magnetic field (Beer et al., 2012).
    
    The 10Be produced is immediately oxidized and then falls to the surface, usually attached to aerosols. Approximately 65 % of 10Be is estimate to be produced in the stratosphere and 35% in the troposphere (Beer et al., 2012). Stratospheric 10Be is thought to have an average residence time of one to two years, to be well mixed in the latitudinal direction by the Brewer-Dobson circulation, and to enter the troposphere mainly at mid-latitudes. It is then transported to higher latitudes by atmospheric circulation in the troposphere and is removed within several days to weeks along with the 10Be produced in the upper troposphere (e.g. Heikkilä et al., 2009). These atmospheric behaviors may allow 10Be variations recorded in high resolution ice cores to serve as unique chemical tracers associated with specific stratospheric/tropospheric processes (e.g. Pedro et al., 2011; Zheng et al., 2020).
    
    In this study, we present a quasi-monthly 10Be record from 2000 to 2020 CE obtained from an ice core drilled in 2021 from the southeastern dome (67°11'30" N, 36°28'13" W) of the Greenland ice sheet (hereafter as SE-Dome II). An accurate age model was constructed based mainly on annual layer counting using the seasonality of H2O2 concentration in SE-Dome II (Kawakami et al., 2023). The 10Be concentrations ranged from 0.27×10^4 to 1.74×10^4 atoms/g. Seasonal variations characterized by an increase from late spring to early summer were evident in the 10Be profile throughout the period. On the other hand, the annually averaged 10Be concentration correlates well with the 10Be production rate in the atmosphere estimated from neutron monitor observations and a production model (Poluianov et al., 2016), but with a lag of one to two years. In contrast to the 10Be concentration, the annually averaged 10Be flux does not correlate well with the 10Be production, suggesting that solar activity reconstructions from the SE-Dome II 10Be record should use concentrations rather than fluxes. Recently, an advanced chronology of SE-Dome II has been proposed based on an oxygen isotope correlation with the output of an oxygen isotope GCM, a similar approach to that had already been used for an ice core from a nearby site (Furukawa et al., 2017). Based on this new chronology as well, both seasonal and annual variations of 10Be recorded in the SE-Dome II ice core will be further discussed.
    
    Speaker: Dr Kazuho Horiuchi
  - 121
    
    Post-glacial wildfire documents in the high mountains of Taiwan
    
    Even with annual rainfall > 2000 mm, many wildfires in alpine coniferous forests were reported in the > 3000 m-high mountains of Taiwan (up to 3952 m). Most of these historic wildfires occurred in spring, the driest season in Taiwan, demonstrating their close relationship with climatic dryness. We have undertaken extensive geomorphic surveys in the Taiwan’s high mountains and found the prevalence of charcoals, the products of paleo-wildfires, in the < 1 m-thick sandy colluviums capping the mountains (particularly below the bamboo grasslands). So far, these charcoals have yielded as many as 102 radiocarbon dates; the sampling sites of these dates cover most of the major mountain areas. Only two of the dates (9070 – 8800 cal BP) from the Nanhu Mountain in northern Taiwan are older than 5 ka; 57 dates cluster around 4780 – 3170 cal BP (mostly 4.4 – 3.4 ka) with two prominent peaks around 4.3 ka (n = 11) and 3.9 ka (n = 17); other 43 dates are distributed somewhat evenly over the last 3 ka. Our data suggest that after the Holocene climate optimum, the high mountains of Taiwan ever experienced a climate condition dry enough to bred wildfires at a regional scale. We infer that during this dry (and cool) period, aeolian and creeping processes in the region were enhanced, which facilitated the deposition of fine-grained materials on hillslope (and thus the preservation of the charcoals).
    
    Key words: Wildfire; Radiocarbon date; Holocene climate optimum; Taiwan orogen
    
    Speaker: Fang-yu Li (National Chung Cheng University)
  - 122
    
    Paleoenvironmental and climatic changes in Altai Krai of Russia during the past 1700 years: Insights from the sedimentary feature, elemental geochemistry and pollen record
    
    A 64-cm long core from Zolotoe Lake (51°51'28.74''N, 80°15'59.16''E) located in the ribbon forest of the Kulundinsky plain of the West Siberian Lowland of Russia has been dated with AMS 14C dating on sediment total organic carbon (TOC) samples, and 210Pb and 137Cs dating. A clear sharp peak in the 137Cs profile corresponding to 1964 CE appeared at the 12-14 cm depth. The 210Pb profile demonstrates exponential decay from the surface down to about 19 cm depth, with relatively unchanged levels below 19 cm, indicating no excess 210Pb. Currently, AMS 14C dates of six samples in the core show: 1) strong nuclear bomb 14C signal (Fm = 1.0787); 2) 145145 Cal yr BP at 22-24 cm; and 3) 1690135 Cal yr BP at 62-64 cm; 4) all dates are in good stratigraphic order. Measurements of TN, TOC and C/N, as well as elemental concentrations in 0.5N HCl leach and Aqua Regia dissolution fractions measured by ICP-OES, and pollen assembles, have been done. Based on sediment features and geochemical data, we classify five zones of the studied core: I (200-440 CE), fine grey sediments: The lake was relatively small and low productivity but high salinity, shown by low TOC%, high C/N and Sr/Ca, Mg and Na contents. II (440-980 CE), dark grey slit: The lake expanded and deepened with decreasing salinity indicated by decreasing C/N, Sr/Ca, Sr, Mg and Na contents. At the end of this zone when was the beginning of the Medieval Warm Period (WMP), the lake became a large and stable lake with increasing productivity, reflected by rising TOC, AL Ca and Sr contents. III (980-1800 CE), dark brown sandy slit: Lake Zolotoe during the first half of this zone expanded further and deepened with increased productivity but decreased salinity reflected by increased TOC, reduced Sr/Ca, C/N, AL Mg and Na contents. High AL Ca and Sr contents might be resulted from increased productivity. However, the lake during the second half seemed remained stable with low salinity but high productivity during the Little Ice Age. IV (1800-1970 CE), light brown muddy clay: During this period, both TOC and C/N decreased, indicating reduced productivity. The sharp decrease in AL Ca and Sr reflected decrease in productivity from 1940 to 1970, perhaps attributed to a cooling temperature. V (1970-2022 CE), brownish fine mud: The lake became fresh and stable with recovered productivity. Human impact may influence the lake sedimentation.
    
    Speakers: Eslam Mohamed Ali Mitwally, Prof. Hong-Chun Li (Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan, ROC)
    
    Abstract-22-Al-03-Eslam-Final.docx
  - 123
    
    Reliable radiocarbon dating through small snail shells
    
    In late Quaternary loess-palaeosol deposits, snail shells are often the only radiocarbon dating material available for building a chronology. However, the reliability of radiocarbon dating different small snail shells remains an open question. Here, we collected different small snail shells from a loess-palaeosol sequence located in central China to test the radiocarbon ages of snail shells. Both solid graphite target AMS (accelerator mass spectrometry) and gas AMS measurements were performed to evaluate the reliability and possible contamination of small shells of different sizes for radiocarbon dating. The 14C ages of the graphitized samples were generally consistent with the corresponding OSL ages, indicating the reliability of small-snail-shell 14C dating in Chinese loess deposits. The ages of the surface fractions of the small snail shells were close to the ages of the interior parts, and contamination after chemical treatment was limited, revealing that the fossil snail shells behaved as a closed system during burial. In addition, the gas measurement results further demonstrated the different degrees of reliability among various snail species. For minute taxa, such as Vallonia and Pupilla, their shells can mainly reveal reliable 14C ages. For larger taxa, such as Cathaica and Metodontia, much attention should be given to selecting appropriate shells. Large individuals and snail hatchlings may contain considerable amounts of old carbon, and only small shells larger than newly incubated snails (<10 mm and > 2 mg) can provide reliable 14C ages. Our study shows that the limestone effect on the radiocarbon ages obtained from most small snail shells is negligible, thus providing a great potential method to constrain the accurate ages of late Quaternary loess deposits.
    
    Speaker: Dr Yao Gu (Nanjing University)
  - 124
    
    81Kr dating with 1 kg of polar ice
    
    81Kr is a cosmogenic isotope with half-life of 229 ka. Its dating range is 20-1500 ka, which covers many applications for polar ice. 81Kr can provide absolute, radiometric ages and do not rely on continuous stratigraphy. Thus it is complementary to conventional ice dating techniques and is particularly valuable for disturbed ice samples. 81Kr-dating on 200 kg blue ice samples from the Taylor Glacier has been demonstrated in 2014, using the Atom Trap Trace Analysis (ATTA) method. Over the past decade, there has been continuous efforts to reduce the sample size so that 81Kr-dating can be applied on deep ice cores, especially the stratigraphically disturbed ones. In this talk, I will present some of our works along this journey and report our recent technical breakthrough on the all-optical ATTA method. By using the optical excitation scheme in ATTA, the memory effect is significantly suppressed, allowing us to reduce the sample size to 1 kg. The performance of the new all-optical ATTA dating method has been verified with ice core samples from Taylor glacier. Recently we have performed 81Kr-dating on the bottom ice from the GISP2 site in Greenland. The results may shed light on the evolution history and stability of the Greenland ice sheet.
    
    Speaker: Prof. Wei Jiang (中国科学技术大学)
    
    AMS16 abstract.docx
- Manufacturers Session GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Manufacturers Session
  
  Convener: Prof. Hongtao Shen (Guangxi Normal University)
  - 125
    
    High Voltage Engineering Europa: Advancing AMS Technology
    
    High Voltage Engineering Europa B.V. (HVE) is a leader in the design, manufacture, and service of particle accelerator systems for scientific and industrial applications. As the largest and most diverse producer in this field, HVE offers a comprehensive range of high-quality products, including ion accelerator systems, accelerator mass spectrometers (AMS), ion implanters, and ion beam analyzers. HVE’s innovative solutions are tailored to meet the specific needs of our global clientele, ensuring superior performance and reliability. Our services encompass initial design, installation, maintenance, and customer support throughout the system's lifecycle.
    AMS at its Best
    HVE offers state-of-the-art AMS systems for precise isotope analysis, suitable for applications in archaeology, geology, biomedicine and many other areas of science. HVE’s AMS product line features several different models, each designed to provide exceptional performance and reliability. Our team of experts continually pushes technological boundaries, ensuring our customers receive the most advanced solutions. HVE’s commitment to quality is evident in our rigorous standards and constant investment in research and development.
    Global Presence
    With a strong international presence, HVE serves a diverse clientele worldwide, delivering top-tier accelerator technology and comprehensive support wherever needed. Our global reach ensures we meet the demands of clients across various industries and scientific disciplines.
    For more information, visit https://www.highvolteng.com.
    
    Speaker: Matthias Klein
  - 126
    
    Current product range and latest technical developments at Ionplus AG, Switzerland
    
    We present a brief overview of Ionplus’ latest product range, showcasing both established products and latest developments. In the first part of the talk, we cover the current state of well-established products such as MICADAS, the high precision radiocarbon AMS system, GIS, the CO2 gas interface, and MILEA, the multi-isotope system, along with various peripheral devices.
    A particular focus will be placed on the latest additions to the Ionplus product portfolio: the even more compact radiocarbon AMS, LEA, and the High Throughput gas Interface (HTI), which enable highly automated CO2 gas measurements on a small footprint, occupying less than 4 x 2 m2. Moreover, the optional magazine storage robot, AMC, can increase the number of available measurement cathodes from 39 in a standard MICADAS magazine to up to around 400 during more extensive and largely unsupervised measurement campaigns.
    In the second part of the talk we give a brief insight into ongoing development efforts to further integrate AMS into the biomedical and materials industry. In 2023, Ionplus was awarded the Swiss Innosuisse grant, which supports these developments over a 2.5 year funding period. We outline the various work packages comprising AMS system and peripheral design, software development, and regulatory (GxP) integration efforts.
    We conclude with a brief outlook on future projects, including the integration of peripherals (e.g. GIS) into a new software platform.
    
    Speaker: Sascha Maxeiner
  - 127
    
    National Electrostatics Corp: Product Overview & Discussion
    
    We present a brief overview of the National Electrostatics Corp. (NEC) AMS systems over the last 30 years, leading the transition from multi-MV tandems to compact sub-MV tandems, CAMS, XCAMS and UAMS, and even lower energy single-stage SSAMS and the positive ion system, PIMS.
    
    We will also discuss three recent beamline components that are now being installed in NEC state-of-the-art AMS systems. We will describe the result of the evolution of the ubiquitous NEC BPM80 beam-profile monitor series into the stepper-motor driven BPM90 series and present data from a new low-current BPM model capable of measuring beam location and profile for beam currents from 1 picoamp to over 12microamp, an eight-decade range.
    
    We will also describe a current-measuring system that is also capable of measuring sub-pA beam currents, and the new variable Pulsed Beam Attenuator that facilitated the testing of the two low-current components.
    
    Speaker: Mark Sundquist (National Electrostatics Corp.)
  - 128
    
    miDose Solutions Product Overview & Discussion
    
    miDose Solutions is a growing Polish company established in 2018 following the development and patenting of innovative solutions at the Silesian University of Technology.
    The Company was founded to provide a novel dose rate measurement systems, the μDOSE system, and answer the needs and specific requirements of the trapped charge dating (TCD) community. After years of gained experience, we developed the enhanced μDOSE+ system, as well as the just-released fully automated 14C combustion and graphitization system, μGraphiline, to further facilitate researchers and the dating community.
    We proudly provide reliable equipment for accurate measurements, as we aim to advance the state of knowledge in environmental, earth and archeological sciences as a whole, and our μDOSE and μDOSE+ systems are currently used in laboratories worldwide, including Europe, Asia, Australia and the USA.
    
    Speaker: Konrad Tudyka (Silesian University of Technology)
- Poster Session A: (The poster dimensions should be 120 cm in height and 80 cm in width.) Lobby and Hallway , 2nd Floor ((Poster session A should be taken down at the end of the session, while Poster session B is being set up.))
  
  Lobby and Hallway , 2nd Floor
  
  (Poster session A should be taken down at the end of the session, while Poster session B is being set up.)
  
  Poster Session A
- 18:00
  
  Dinner Restaurant，Ground floor
  
  Restaurant，Ground floor
Wednesday, 23 October
- Registration in the lobby of the Conference Hotel Lobby of the Conference Hotel
  
  Lobby of the Conference Hotel
- Plenary GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Convener: Prof. Peter Steier (University of Vienna – Faculty of Physics, Isotope Physics, Vienna, Austria)
  - 129
    
    New developments in Ion-Laser InterAction Mass Spectrometry
    
    Interferences from isobars typically restrict the applicability of AMS to selected long-lived radionuclides. The novel Ion-Laser InterAction Mass Spectrometry (ILIAMS) technique at the Vienna Environmental Research Accelerator (VERA) can overcome this limitation in many cases by highly-efficient isobar removal at eV-energies in a gas-filled radiofrequency quadrupole. The virtually complete suppression of isobars serves two objectives: A great number of nuclides can be measured for the first time with AMS while others become accessible at environmental levels – even on low terminal voltage AMS-systems – with the benefit of unprecedented detection efficiencies and blank values. This opens exciting possibilities in environmental radioactivity ($^\text{90}$Sr, $^\text{99}$Tc, $^\text{135,137}$Cs), astrophysics ($^\text{44}$Ti, $^\text{53}$Mn, $^\text{182}$Hf), and Earth science ($^\text{26}$Al, $^\text{36}$Cl, $^\text{41}$Ca) research. [1] At AMS-15, we have reported on the excellent performance of ILIAMS for $^\text{26}$Al and $^\text{36}$Cl. Here we highlight the recent developments for the technique across the entire nuclear chart.
    ILIAMS exploits differences in detachment energies (DE) within elemental or molecular isobaric systems by neutralizing anions with DEs smaller than the photon energy via laser photodetachment. In addition, molecular interactions with a buffer gas can further enhance isobar suppression, e.g., via breakup of $^\text{41}$KF$_{\text{3}}^-$ into $^\text{41}$KF$_{\text{2}}^−$ and F, or via O-pickup of $^\text{182}$WF$_{\text{5}}^−$ forming $^\text{182}$WF$_{\text{5}}$O$_{\text{x}}^-$.
    With at least eleven orders of magnitude suppression of both Mg and K, ILIAMS-assisted AMS enables the detection of $^\text{26}$Al/$^\text{27}$Al (~10$^{-10}$, extraction of AlO$^-$) and $^\text{41}$Ca/$^\text{40}$Ca (10$^{-11}$−10$^{-13}$ extraction of CaF$_{\text{3}}^-$) directly from crushed stony meteorites containing intrinsic ~1% Al and Ca, respectively [2,3]. The presence of isobars originating from the natively abundant elements (13-20% Mg, ~1‰ K) does not cause any analysis problems making radiochemical separation redundant. Measurements of $^\text{41}$Ca in chemically untreated concrete from nuclear decommissioning and coral sand samples clearly demonstrate the huge potential of this newly-established instrumental AMS (IAMS) technique. It is opening routes to high-sample throughput analysis, reasonable and fast provenance checks for (extra-)terrestrial origin and nuclear clearance.
    At the upper end of the nuclear chart, the laser-induced suppression of U during measurements of Np constitutes the first non-chemical isobar discrimination in AMS in the actinide region.
    Finally, for $^{\text{90}}$Sr, highly efficient ILIAMS-suppression of the isobaric interference $^{\text{90}}$Zr enables a blank value of $^{\text{90}}$Sr/Sr < 5$\times$10$^{-16}$ at an overall Sr-detection efficiency of 4$\times$10$^{-4}$. This corresponds to a detection limit of <0.016$\,$mBq, i.e., 2$\times$10$^{\text{4}}$ atoms or 3$\,$ag of $^{\text{90}}$Sr in a sample of mg of stable Sr – at least a factor 100 better than any other known technique of measurement. Recently, we have successfully demonstrated the tremendous potential of this technique for $^{\text{90}}$Sr in the measurement of contemporary coral aragonite and seawater samples of less than 500$\,$ml, and the analysis of $^\text{90}$Sr concentration in small samples of soils and other environmental archives after adding Sr carrier.
    Ackn.: This project received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101008324 (ChETEC-INFRA) and No 824096 (RADIATE), and grants from the Austrian Science Fund (FWF): I 4803-N and P 31614-N28. (Extra-)terrestrial samples were kindly provided by A. Bischoff (U Muenster), A. Gaertner & K. Schniebs (Senckenberg Dresden), Forst- und Landwirtschaftsbetrieb der Stadt Wien, K. Pachnerová Brabcová (Czech Academy of Science, Prague).
    References: [1] Martschini et al., Radiocarbon 64 (3) (2022) 555. [2] Bischoff et al., accepted for Meteorit. Planet. Sci.. [3] Bischoff et al., submitted to Meteorit. Planet. Sci..
    
    Speaker: Martin Martschini (University of Vienna - Faculty of Physics)
    
    Martschini_etal_AMS16_final.pdf
- Actinide Techniques and Applications GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  Discussions on the applications of actinide series elements.
  
  Convener: Prof. Elena Chamizo (Centro Nacional de Aceleradores (CNA), Universidad de Sevilla)
  - 130
    
    Minor actinides radionuclides to reveal sources of anthropogenic radioactivity to the Baltic Sea
    
    The most studied actinide radionuclides to unravel contamination sources in general environmental samples have been 238Pu, 239Pu, 240Pu and 241Am. In the last few years, thanks to the development of ultra-sensitive Mass Spectrometry techniques like AMS, this list has been expanded to other less studied and minor actinides nuclides providing key information on the source terms. 236U and 237Np AMS techniques have been fully established [1,2]. The lack of an appropriate isotopic tracer for 237Np studies has been overcome using 242Pu as a non-isotopic tracer [2,3]. AMS techniques have been pushed to the limit to assess the analysis of the most minor actinides radionuclides such as 233U, 241Pu, 242Pu and 244Pu [4,5]. Overall, it has been constated that the combined study of the 233U/236U, 241Pu/239Pu, 242Pu/239Pu and 244Pu/239Pu atom ratios is a promising tool to unravel multiple contamination sources in complex scenarios.
    The Baltic Sea marine environment has been historically exposed to multiple local and regional actinides sources: i) atmospheric debris from the Chernobyl accident (1986), ii) liquid releases from Sellafield and La Hague nuclear reprocessing facilities transported through the North Sea, iii) authorized radioactive discharges from nuclear facilities in the Baltic Sea region, and iv) possible leakages from dumping sites within this marine region [6]. These sources coexist with the baseline levels imposed by the atmospheric nuclear tests (945-1980) or global fallout. Although the Baltic Sea has been one of the most studied areas regarding the distribution of anthropogenic radionuclides, long-lived actinides have been scarcely investigated and there are still many open questions about their source terms and distribution.
    This work focuses on the study of a sediment core from the Tvären Bay, directly impacted by the liquid releases from the Studsvik Nuclear facility (east coast of Sweden), since 1959 up to now. This core preserves a sediment record since the 1950s, being a key natural reservoir to study the scarcely documented historical releases from Studsvik. In a previous study, the analysis of the full Pu isotopic vector (238Pu, 239Pu, 240Pu, 241Pu, 242Pu and 244Pu) on the 1 MV AMS system at the Centro Nacional de Aceleradores (CNA, Seville, Spain) allowed us to assess the Pu sources in this area and to reconstruct the liquid release history for Pu [7]. The results show the presence of highly enriched 239Pu, probably originating from the Swedish nuclear program in the 1960s-1970s and the handling of high burn-up nuclear fuel in later years. Moreover, new results on 237Np, 233U and 236U have been obtained. The 233U/236U atomic ratio has been studied to unravel the 236U inputs, revealing an intense release of 236U in the 1970s. In contrast, a minor contribution is observed in the case of 237Np. This work is now being expanded to study 241Am and 243Am.
    References
    [1] Fifield LK (2008) Quat Geochronol 3:276–290.
    [2] López-Lora M, Chamizo E (2019) Nucl Instrum Methods Phys Res B 455:39–51.
    [3] López-Lora M, Levy I, Chamizo E (2019) Talanta 200:22–30.
    [4] Hain K, Steier P, Froehlich MB, et al (2020) Nat Commun 11:1275.
    [5] Steier P, Hrnecek E, Priller A, et al (2013) Nucl Instrum Methods Phys Res B 294:160–164.
    [6] HELCOM (2018) Baltic Sea Environment Proceedings No. 151
    [7] López-Lora M, Olszewski G, Chamizo E, et al (2023) Environ Sci Technol.
    
    Speaker: Mercedes López-Lora (Universidad de Sevilla)
  - 131
    
    Actinides and 129I Analyses with the 300 kV Multi-Isotope Low-Energy AMS
    
    The 300 kV Multi-Isotope Low-Energy AMS (MILEA) system was developed by ETH Zurich and Ionplus AG, Switzerland for the ultra-sensitive measurement of long-lived nuclides, such as 14C, 129I, actinides, 10Be, 26Al and 41Ca. The negatively charged ions (such as C-, I-, AnO-) were extracted from the target sample in a Cs-sputtering ion source, and injected into a low-energy analysis system, including a 90° low-energy ESA (r=534 mm) and a 90° magnet (r=450 mm). Then the ion beam was introduced into a vacuum insulated high voltage platform with the maximum acceleration voltages of 300 kV, where He gas as stripping gas was fed. Meanwhile, the incident negative ions were transformed into positive ions and the molecules were break up. After focusing of different charge states and molecular break-up products using the following electrostatic quadrupole triplet lens, the ion beam passed through the high energy side, which consists of twoagnets (90◦ and 110◦ bending angles) with a 120◦ ESA in between. While the ion currents of stable nuclides or high abundance nuclides (e.g. 12C, 127I, 235U, 238U, etc.) were measured by one of seven movable Faraday cup behind the high energy magnet 1. The rare nuclides (14C, 239Pu, 240Pu, 241Pu, 242Pu, 243Am, 241Am, 244Cm, 233U, 236U, etc.) were counted with a low noise two-anode gas ionization detector (GID).
    For the determination of long-lived actinides (237Np, 239Pu, 240Pu, 241Pu, 244Pu, 241Am, 244Cm, 233U, 236U, 235/238U), An3+ ions were selected, and transmission from injector to HE cup is more than 36% at the terminal voltage of about 260 kV in accelerator. The AMS target preparation method was optimized by adding 0.4 mg Fe and 0.1 mg Ti to co-precipitate the Am and Cm, Pu and Np. The overall detection efficiencies were 8.8 × 10-4 for Pu, 6.3 × 10-4 for Np, 3.1× 10-4 for Am and 7.2 × 10-4 for Cm after 2 h of sputtering time. The correction factors of Pu/Np and Am/Cm were 1.39-1.41 and 0.39-0.43, respectively. The abundance sensitivity of 239/238 reached an optimal value of (2.1 ± 0.6) ×10-13. For the measurement of 236U/238U ratios at (6.98 ± 0.32) ×10-11, the single sample scatters were between 0.9% and 1.4%. For129I measurement, the127I transmission from injector to HE cup was more than 50.9% using I2+, and the 129I transmission from HE cup to detector was more than 95.6%. The 129I/127I ratio of WWI was (2.0-3.7) × 10-14. For the measurement of standard solution with 129I/127I ratio at 3.98 × 10-14, 9.95 × 10-14, 100.37 × 10-14, the precisions were 0.41%, 0.71%-0.75%, 0.20%-0.22%, respectively. The performance of the AMS system is shown in Table 1.
    
    Table 1 The performance of 300 kV Multi-Isotope Low-Energy AMS (MILEA) system for actinides, 14C and 129I
    Nuclide Transmission Blank Precision Detection limit
    Actinides > 36% (2.1 ± 0.6)×10-13 (239/238) 236U/238U ≤ 1.4% 237Np: 0.005 fg (1.3 × 10-10 Bq)
    239Pu: 0.005 fg (1 × 10-8 Bq)
    240Pu: 0.002 fg (2 × 10-8 Bq)
    241Pu: 0.003 fg (1.1 × 10-5 Bq)
    241Am: 0.03 fg (3.8 × 10-6 Bq)
    244Cm: 0.004 fg (1.2 × 10-5 Bq)
    C-14 > 46% 14C/12C < 1.34 × 10-15 14C/12C < 0.2% -
    I-129 > 50% 129I/127I: (2.0-3.7) × 10-14 129I/127I < 0.4%
    
    For dose assessment in the event of internal exposures at nuclear facilities and nuclear power plants, the analytical methods for actinides (Pu isotopes, 237Np, 241Am, 244Cm) in urine bioassay have been developed using sequential separation and AMS determination, and the detection limits obtained in this work were 10-17-10-18 g/d in 1.0-1.6 L of urine samples. For the environmental tracer and monitoring studies, series of analytical methods for actinides and 129I in seawater, soil, sediment, aerosol have also been developed in China Institute for Radiation Protection.
    
    Speaker: Maoyi Luo
    
    AMS大会摘要-luo.docx
  - 132
    
    First measurement of 236U concentration in the Arctic seawater in 2022 at the MALT, The University of Tokyo
    
    The Annual discharges and the ratio of 129I/236U from the nuclear reprocessing plants are different, the concentration of 129I, 236U, and the ratio of 129I/236U are novel tracers for the transit time of the Arctic Ocean circulation.
    We developed a new 236U-AMS with the time-of-flight detector system at the MALT, The University of Tokyo. To improve sensitivity and decrease background by increasing the extract beam intensity, the sample preparation procedures for the Iron-Uranium co-precipitation ratio and the mixed Nb powder ratio were optimized.
    The depth profile of the Chukchi Sea and the Beaufort Sea in the Arctic Ocean during the MR22-06C cruise of R/V Mirai were measured by 236U-AMS at MALT.
    
    Speaker: Takeyasu Yamagata (The University of Tokyo)
    
    Yamagata.pdf
- Applications of Cosmogenic Isotopes GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Applications involving isotopes created via cosmic ray activation and spallation. Topics include exposure dating and groundwater tracing.
  
  Convener: Prof. David Fink (ansto)
  - 133
    
    Extreme solar events recorded in cosmogenic nuclides
    
    Solar eruptions (solar flares and coronal mass ejections) are known to cause various space–weather phenomena in the Sun–Earth system that can have severe impacts on modern society. As the magnitude of a solar eruption increases, its frequency of occurrence decreases, but the severity of its impact increases. Therefore, it is important to understand the long-term characteristics of extreme solar eruptions. To investigate such extreme solar eruptions on a timescale that exceeds that of modern observations, we have used cosmogenic nuclides such as 14C, 10Be, and 36Cl. Because solar energetic particles (SEPs) that originate from solar eruptions have sufficient energy to produce cosmogenic nuclides, as also do galactic cosmic rays, extreme SEP events cause rapid increases (spikes) in cosmogenic nuclide concentrations.
    To date, several cosmogenic nuclide spikes have been found e.g., in 774 CE, 993 CE, around 660 BCE, and 7176 BCE, via analyses of 14C in tree rings and of 10Be and 36Cl in ice cores. The magnitudes of these events have been estimated to be several dozen times larger than that of the largest SEP event observed using modern instruments. We are currently conducting a long-term exploration of extreme SEP events by analyzing the 14C concentrations in tree rings. In this presentation, we report the latest updates regarding our SEP event exploration and event candidates reported recently.
    
    Speaker: Fusa Miyake (Nagoya University)
  - 134
    
    Radionuclides in Lunar Cores: Gauges of Particle Flux and AMS Measurement Capability
    
    Radionuclides are ideal gauges for monitoring the energetic particle environment of the lunar surface and near sub-surface. The physics of the production mechanisms of the radionuclides and the production rates are known. The measurement of radionuclides in depth profiles from the lunar surface has allowed us to better characterize both the galactic and cosmic ray fluxes in addition to identifying some of the processes and time-scales for processes that garden the upper layer of the lunar surface.
    Often overlooked in the measurement and reporting of these radionuclide profile data are the demands that they place on the measurement technique, and consequently, what can be said about the robustness of these measurements. Over the years AMS laboratories have conducted many comparisons of 10Be, 26Al, 36Cl, and 41Ca standards and a few reference materials. In general, the concordance between laboratories and reproducibility of these measurements is excellent. But standards are prepared from homogenous solutions, samples are typically derived from complex geologic materials that vary in composition from one sample to the next. The radionuclide measurements from lunar cores conducted over many decades represent yet another means to assess the robustness of the chemical extraction techniques, AMS precision, normalization standards, and reproducibility of the entire technique.
    The figure below shows a comparison of AMS measurements of 26Al along with 26Al measurements conducted by decay counting in Apollo 17 drill core [Fruchter et al. (1976, 1979)]. The precision of the AMS measurements is better than decay counting, but the agreement between the two different techniques is striking. Also shown is a comparison of 36Cl measurements taken decades apart [Nishiizumi et al. (1984, 1989)]; the upper portion which isn’t exponential reflects solar cosmic ray production. The agreement is excellent, both profiles show the same exponential behavior and concentrations.
    
    References:
    Nishiizumi et al. (1984) EPSL 70:157-163; Nishiizumi et al. (1989) Proc. 19th LPSC, 19:305-307; Fruchter et al. (1976) Proc. 9th LPSC, 9:2019-2032; Fruchter et al. (1979) Proc. 10th LPSC, 10:1243-1251
    
    Speaker: Marc Caffee (Purdue University)
    
    LunarCores_Abstract.pdf
  - 135
    
    Annual 10Be record in travertine covering 1510-1701: a new proxy for reconstructing annual solar activity
    
    Previous research has revealed that the 10Be record in laminated travertine has significant potential for reconstructing past high-resolution solar activity. However, the depositional processes of atmospheric 10Be into travertine have not been entirely resolved, therefore the methodology for extracting the production signal is not well established. In this study, we present an annually resolved 10Be record from Baishuitai travertine covering 1510-1701 CE, along with environmental proxies, discuss the potential influence of climatic/environmental variations on the travertine 10Be record, and propose an improved correction methodology for extracting the atmospheric 10Be production signal from the travertine. We show that 10Be deposition in travertines has two environmental impacts: the transport efficiency of atmospheric 10Be into travertine and the additional 10Be inflow from overland flow caused by rainfall. We demonstrate that these effects can be corrected based on iron and potassium contents, and the resulting corrected record reasonably agrees with ice-core and tree-ring data, indicating that 10Be in travertine can be a good proxy for probing the past annual solar activity.
    
    Speaker: Hongyang Xu (华东师范大学)
    
    Abstract_AMS16.docx
- 10:20
  
  coffee break Lobby , 2nd Floor
  
  Lobby , 2nd Floor
- Actinide Techniques and Applications GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  Discussions on the applications of actinide series elements.
  
  Convener: Prof. Stephan Winkler (Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany)
  - 136
    
    The Zurich Sea Water (ZSW) intercomparison for $^{236}$U and other actinides
    
    In 2011, during the Fenice11 expedition to the Tyrrhenian Sea, a total of about 350$\,$L of sea water samples were collected and prepared as large volume intercomparison sample for $^{236}$U/$^{238}$U. In this contribution, the results of the intercomparison will be presented.
    
    All samples were filtered through several 0.45$\,\mu$m membrane filters and collected in a 400$\,$L plastic tank. Afterwards, the pH value was adjusted to 3. After some months of equilibration time, the seawater was filled into 35 ten liter plastic cubitainers ready for shipment. One or two cubitainers were sent out to each participating lab. The labs were asked to apply their standard sample processing procedures, with the primary goal of returning information on the $^{236}$U/$^{238}$U ratio. Additionally, an interest in $^{236}$U-, $^{238}$U-, and other actinide-concentrations of the sample was communicated.
    
    The ZSW intercomparison sample was processed in six different chemistry labs and measured on six different mass spectrometers, five AMS systems and one MC-ICP-MS system. All labs returned information on the $^{236}$U/$^{238}$U ratio of the intercomparison sample and most of them provided results on $^{236}$U and $^{238}$U concentrations. Additionally, some laboratories reported $^{233}$U/$^{238}$ ratios and results on Pu-isotopes. Furthermore, indicative concentration values for Am-, and Np-isotopes were reported for the ZSW sample.
    
    The analysis of the reported U-isotopic data shows that the scatter, indicated by the one sigma uncertainty for a single measurement, of the $^{236}$U/$^{238}$U ratios and the $^{236, 238}$U-concentrations is 5% and 3%, respectively. A $\chi^2$-analysis shows that the external error (lab-scatter) is 1-2% and 3% for the $^{236, 238}$U-concentrations and the $^{236}$U/$^{238}$U ratios, respectively.
    
    The consensus value for the $^{236}$U/$^{238}$U ratio and the $^{236, 238}$U-concentrations of the ZSW sample will be presented. Also, indicative values for Pu-isotopes will be presented but the number of contributing labs is too small for providing a consensus value. The fact that the ZSW sample has been characterized by many different (A)MS labs makes it a valuable internal standard for quality control not only for the analysis of anthropogenic U-isotopes in seawater.
    
    Some of the $^{236}$U-measurements were performed on the newly installed MILEA system at ETH Zurich. In addition to the above results, the MILEA setup for U-isotopes will be presented and discussed. The MILEA system provides an abundance sensitivity at the order of 10$^{-13}$ in the mass range of the actinides and thus allows determining the $^{236}$U/$^{238}$U ratio in samples containing U from both, anthropogenic and natural sources.
    
    Speaker: Dr Marcus Christl (ETH Zurich, Laboratory of Ion Beam Physics)
  - 137
    
    Survey of naturally occurring 236U with direct-AMS
    
    From a multi-isotope direct-AMS survey of 310 uranium ore concentrates (UOCs), 236U/238U ratios from 2x10-12 to 2x10-7 are measured. However, a range from low-10-12 to mid-10-10 is expected from directly mined natural uranium ore minerals. This upper-end discrepancy would normally be attributed to inputs of spent fuel materials, but the numerous occurrences and the lack of economic reasons to recycle anything in the front stage of UOC production make the abnormally high 236U/238U ratios rather perplexing. When plotted against the 187Os/188Os ratios, which were also obtained in the survey, the high 236U/238U results are seen to occur around the value of 187Os/188Os = 10, a none-random pattern as might be anticipated from unwitting contaminations. The 187Os/188Os ratios measured reflect mostly the Os impurities contained by the UOCs. They might be affected by the Os impurities contained by the chemicals used for the UOC manufacture, but these chemicals are ultimately derived from Crust materials in which 187Os/188Os ratios are typically within 0.1 and 1. Thus, the observed correlations between 236U/238U and 187Os/188Os favor those measured high 236U/238U ratios being natural. This work also calls for further studies of naturally occurring 236U/238U in a wider range of native uranium-bearing minerals. Meanwhile, it is a reminder that any such studies are best done using direct-AMS without chemical sample pretreatment to better avoid anthropogenic 236U that is pervasively present in the environment today. It also calls for efforts combatting the AMS ion source memory effects. To secure unambiguous natural 236U surveys, an approach is described that combines UF5- production directly from powdered native samples and ion source reconfiguration to minimize background.
    
    Speaker: Dr XIAOLEI ZHAO (BEIJING NORMAL UNIVERSITY)
    
    20240416 - Survey of naturally occurring 236U with direct-AMS.docx
  - 138
    
    The measurement method of 239Pu with the developed compact AMS system
    
    Abstract: The compact AMS devices are the tendency of AMS development. Based on the previously developed air-insulated AMS, the compact AMS device with a terminal voltage of 0.25 MV has been established. In this paper, a low detection limit measurement method for 239Pu using compact accelerator mass spectrometry (AMS) has been presented. A measurement technique for 239Pu was established based on the systematic study of ion extraction, transmission, and ion detection using this device. The measurement performance is tested using standard samples and blank samples. The detection limit of 239Pu is about 0.1fg, and the measurement uncertainty of standard samples meet within 5%. This device is currently available for routine measurement of 239Pu samples.
    
    Speaker: Dr Qingzhang Zhao (中国原子能科学研究院)
  - 139
    
    Optimisation of ion source efficiency for AMS analysis of the rarest known naturally-occurring radioisotope $^{244}$Pu
    
    The recent discovery of naturally-occurring $^{244}$Pu [1,2] has been made possible by achieving high overall detection efficiency for plutonium by AMS [3]. Overall efficiency is determined by a combination of ionisation efficiency, charge state yield and beam transmission through the AMS system. Of these, ionisation efficiency remains as the principal limitation, with few instances where efficiency greater than 1% has been reported. Using the Vega AMS system at ANSTO, we have achieved reproducible ionisation efficiency, for formation of PuO anions, of 3-4%. However, the achievement of high overall efficiency has come at the cost of operational efficiency, as it can take of the order of 10 hours to fully consume each sample.
    
    We have performed a series of tests to understand what determines ionisation efficiency, focussed on plutonium AMS, and to seek improvements where possible.
    
    In the standard method used at ANSTO, plutonium samples are dispersed in iron oxide and mixed with niobium powder as ‘binder’. An initial observation made by us was that the overall efficiency (number of atoms detected / number of atoms in the sample, with sample run to exhaustion) is linearly proportional to the total mass of the iron oxide + niobium mixture.
    
    We have performed a series of tests by varying the following sample parameters: (i) recess depth of material in cathode; (ii) use of layered samples; (iii) varied binder / iron oxide mix; (iv) different cathode materials; (v) different binder; (vi) varied sample surface area. We have also checked the molecular composition of the Pu anions: PuO$_{x}^{-}$ of extracted beams for x = 0 to 3.
    
    The results will be reported and compared to a sputtering model that has been developed to account for the observed variation in count rates versus time as the sample is consumed. In the course of these tests, a maximum ionisation efficiency of 6% has been observed for PuO anions.
    
    [1] A. Wallner et al. Science, 372 (2021) 742.
    [2] D. Koll, PhD Thesis, ANU and TUD, 2023.
    [3] M.A.C. Hotchkis et al. Nucl. Inst. and Meth. B 438 (2019) 70.
    
    Speaker: Michael Hotchkis (ANSTO)
- Applications of Cosmogenic Isotopes GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Applications involving isotopes created via cosmic ray activation and spallation. Topics include exposure dating and groundwater tracing.
  
  Convener: Prof. David Fink (ansto)
  - 140
    
    A first minimum in-situ 10Be age for the Tswaing Meteor Crater, South Africa.
    
    The well-preserved Tswaing Meteor Crater– aka Pretoria Saltpan – with a diameter of 1130 m is located ca. 40 km NNW of Tshwane (Pretoria). It has been a subject of several scientific investigations. The crater is formed on a ca. 2 Ga Nebo Granite, the acid phase, of the Bushveld Complex (Lebowa Granite Suite). The interior structure floor is not far removed from the local ground water level and hence the floor is partially filled by a highly saline lake (Tswaing means the place of salt). The elevation of the rim over the present structure floor is ~120 m, while it rises about 60 m above the surrounding plain. The rim, with minimal seasonal brush, has a fair number of granitoid boulders. These are thought to have been uprooted during the cratering event from the Nebo granite basement bedrock. The basement rock is some 200 m below the current floor. The drill cores from this lake give a unique insight into past climate and flora of the region (Partridge et al. 1993, Kristen et al. 2007, Metwally et al. 2014, Scott 2016).
    
    The meteorite impact origin of Tswaing was largely inferred from morphological observations and was later supported by structural and experimental fission track measurements (Reimold et al., 1992). The currently accepted age of 220±50 ka the is based on fission track dating (Storzer et al. 1993). However, this is an average over wildly varying measuements. While a similar result age was inferred by the core drilling on the crater floor that revealed an infilling consisting of 90 m of organic lacustrine sediments, this is based on extrapolation from the average infilling rate of 50 cm/ka of the radiocarbon dated section of the core (Partridge et al, 1993). This rate also has evident significant variance over the first 20 m of the core.
    
    The boulders from the ejecta of the impact around the rim of the crater present an excellent opportunity to independently verify the age of the cratering event through the exposure ages of these boulders by cosmogenic radionuclides using accelerator mass spectrometry. To this end we collected 15 samples from around rim, pre-treated them, and processed selection of 10 at the Helmholtz-Zentrum Dresden-Rossendorf for AMS analysis. Here we will present first results from the AMS measurement of the samples, a contextual interpretation, and the implications for the actual age of the Tswaing impact crater.
    
    References:
    Kristen, I., et al. "Hydrological changes in southern Africa over the last 200 Ka as recorded in lake sediments from the Tswaing impact crater." South African Journal of Geology 110.2-3 (2007): 311-326.
    Metwally, A. A., et al. "Holocene palynology and palaeoenvironments in the Savanna Biome at Tswaing Crater, central South Africa." Palaeogeography, Palaeoclimatology, Palaeoecology 402 (2014): 125-135.
    Partridge, T. C., et al. "The Pretoria Saltpan: a 200,000 year southern African lacustrine sequence." Palaeogeography, Palaeoclimatology, Palaeoecology 101.3-4 (1993): 317-337.
    Reimold, Wolf Uwe, et al. "Pretoria Saltpan crater: Impact origin confirmed." Geology 20.12 (1992): 1079-1082.
    Scott, L. "Fluctuations of vegetation and climate over the last 75 000 years in the Savanna Biome, South Africa: Tswaing Crater and Wonderkrater pollen sequences reviewed." Quaternary Science Reviews 145 (2016): 117-133.
    Storzer, Dieter, Christian Koeberl, and Wolf Uwe Reimold. "The age of the Pretoria Saltpan impact crater, South Africa." In Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 3: NZ p 1365-1366 (SEE N94-20636 05-91). Vol. 24. 1993.
    
    Speaker: Vela Mbele (iThemba LABS, South Africa)
  - 141
    
    Temperature-forced runoff changes in arid areas of central asia inferred from 10Be exposure ages of river terraces
    
    Understanding the hydrological changes on context of global warming is of special significance for the security and sustainable development in vast arid areas of Central Asia. The sustainability of river runoff, as the major freshwater source in arid Central Asia, is of special concerns because millions of people suffer from water stress. However, our understanding of the freshwater mechanisms in arid Central Asia has been limited by the paucity of long-term records and the inconsistency of available information. Here, we reconstructed the first and longest record of freshwater supply in Central Asia by river terrace 10Be exposure ages in Tarim Basin. These exposure ages, integrating with the chronological data of the river terraces and the 10Be exposure ages of the moraines across Central Asia, provide a deep insight into the hydrology dynamics of Central Asia. The results show that the river terraces are developed through erosion and incision of the alluvial deposits by high river power, and thus the 10Be exposure ages indicate the periods with high river power. The high river runoff corresponded to alpine glacier expansions in Central Asia, indicating that meltwater is the dominant source of the freshwater in Central Asia. The high river runoff displayed a close link to low temperatures on both orbital and millennial time scales during the past 280 ka, indicating that the low temperature, rather than increased precipitation or meltwater associated with global warming, drove the freshwater supply in Central Asia. All these lines of evidence suggest that both the river discharges and alpine glaciers as water reservoirs would decrease in the future with global warming in arid Central Asia, implying an increasing water crisis with global warming in the future.
    
    Speaker: Prof. Bing Xu ( Institute of Geology and Geophysics, Chinese Academy of Sciences)
    
    Abstract of EAAMS-9 by Xu et al 2023.docx
  - 142
    
    Meteoric 10Be analysis of a deeply weathered dolomite soil profile in the central Guizhou Plateau, SW China
    
    The Guizhou Plateau is a typical subtropical mountainous karst area where carbonate rocks contain very few insoluble residues causing the slow soil production rate. Moreover, serious soil erosion leads to karst rocky desertification and land degradation in this area. Quantification of soil formation age and rate thus is vital for understanding carbonate weathering and scientifically evaluating the sustainability of soil resources. Meteoric 10Be and element geochemical analysis were applied in a regolith profile with a thickness of ~3 meters on the early Triassic dolomite bedrock at Pingba, Guizhou, SW China. Unlike the regular “bulge” or “decline” type, the concentrations of meteoric 10Be increase with soil depth and enrich at the soil-rock interface. We suggest that this trend is controlled by soil pH that averages with value of 5 in soil and it abruptly increases to more than 8 at the soil-rock interface. This geochemical barrier results in Be isotopes and some other elements precipitating in the alkaline region. Correcting for potential losses of meteoric 10Be based on 9Be mass losses in the regolith profile, the minimum soil residence age was estimated to be 0.53 Ma. The related maximum soil production rate of 5.37 m/Ma was evaluated for the Pingba profile, which is faster but does not conflict with a previous estimation of 1.27 m/Ma from acid-insoluble residue contents. This work is the first attempt of meteoric 10Be employed on the carbonate regolith, not only providing a choice for the soil study in the karst area but also expanding the knowledge of meteoric 10Be geochemical behaviors in different soil types.
    
    Speaker: Yu Liu (Institute of Geochemistry, CAS)
    
    liuyu-14 AMS abstract.docx
  - 143
    
    Surface denudation on soil-mantled hillslope in bedrock-dominated landscape: A weathering profile perspective from the eastern margin of Tibetan Plateau
    
    Landscape evolution is a fundamental and vital topic in natural geography science, which is of great significance for understanding Earth’s dynamics, climate change, geohazard prevention and human habitability. Surface denudation, referring to the sum of chemical weathering and physical erosion, is an essential process to drive landscape shaping and transformation. In details, chemical weathering refers to the process of the alteration of bedrock to saprolite by chemical reactions, after which saprolite can be mechanically disrupted into mobile soils that can be transported from hillslopes to streams and rivers by physical erosion. Recently, in-situ 10Be depth profiling provides a powerful perspective for quantifying the surface denudation rates and studying the historical records of landscape denudation along geologic timescales. When combining in situ 10Be analysis with geochemical methods such as mass balance calculation using an immobile element within a weathering profile, one can explicitly extract the respective proportion of chemical weathering and physical erosion from a certain 10Be-derived denudation rate.
    Therefore, this study conducted the measurement of geochemical compositions and in situ 10Be concentrations of a granitic weathering profile from a high-relief landscape on the eastern margin of Tibetan Plateau. Geochemical mass balance calculation suggests that chemical weathering mainly occurred in the saprock zone. 10Be concentrations in the soil are significantly lower than those in the uppermost saprolite, suggesting that the soil should be an external cover rather than an in situ weathering product from the underlain saprolite. Depth variations of the measured 10Be concentrations cannot match the steady-state modeling curve, indicating that the weathering profile should be involved with an unsteady-state denudation regime. Variation of 10Be concentrations in the saprolite/saprock zone at the shallow depths ( < 200 cm) that should have been controlled by the spallation of neutrons, instead, show an obvious signal of significant muonic production, implying that this layer should be derived from a deeper part that was suddenly exposed to the surface in a certain timing in the past by an abrupt denudation event such as landsliding. Finally, we proposed a conceptual model involved with unsteady denudation incorporating a landslide event. This model well explains the depth variation of 10Be concentrations, which yielded best-fitting results for the denudation rate of weathering profile (D) is 2.0 g m-2 yr-1, the occurrence time of landslide (t) is 11.6 kyr ago, and the depth of landsliding surface (XL) is 4.0 m. Together with the geomorphic parameters from traditional GIS-based analysis, this study may provide new insights into the coupling of chemical weathering and physical erosion under contrasting denudation regimes and the response of landscape evolution to tectonic forcing and, probably, the prediction of potential landslides in tectonically-active regions.
    
    Speaker: Dr Wei Wei
- 12:00
  
  lunch Restaurant，Ground floor
  
  Restaurant，Ground floor
- Applications of Cosmogenic Isotopes GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Applications involving isotopes created via cosmic ray activation and spallation. Topics include exposure dating and groundwater tracing.
  
  Convener: Dr Fusa Miyake (ISEE, Nagoya University)
  - 144
    
    Constraining erosion rates and landscape evolution with in-situ 10Be and 26Al cosmogenic nuclides at Table Mountain, Antarctica
    
    Surface weathering and permafrost exhumation rates in the Transantarctic Mountains are important for understanding landscape evolution, determining onset of persistent polar climate conditions, and refining East Antarctic Ice Sheet response to past climate perturbations. We report cosmogenic 10Be and 26Al in bedrock, erratics, a 3m permafrost depth-profile and cobbles embedded within Sirius Group sediments at Table Mountain, McMurdo Dry Valleys, to quantify apparent erosion rates at high elevation, hyper-arid polar landscapes. Including recalculated 10Be and 26Al concentrations from Table Mountain (Ivy-Ochs et al., 1995), Beacon sandstone bedrock, adjacent to Sirius Group sediments, give apparent erosion rates ranging from 0.04 – 0.39 m/Myr (average=0.17±0.12; n=11) that on average are ~5 times lower than 10Be-based cobble erosion rates, 0.16 – 2.7 m/Myr (average=0.85±0.82; n=7), embedded within the Sirius Group surface. 26Al/10Be ratios show a negligible bedrock or cobble burial history. Assuming secular equilibrium conditions for exposed bedrock, the larger cobble erosion rate and spread suggests that emergence of Sirius Group cobbles has been an ongoing process for at least the past few millions years – after exhumation they experience increased production allowing a larger 10Be inventory until steady state commensurate with surface production. Equivalent minimum (zero-erosion) exposure ages are much younger than their inferred Miocene depositional age derived from stratigraphic correlations and noble gas exposure ages, leading to data interpretation as maximum erosion rate. 10Be and 26Al depth profiles show distinct exponential attenuation, suggesting no vertical mixing or post-depositional disturbance of Sirius Group permafrost. Depth profile modelling, interpreted within erosional steady state conditions, results in a best fit surface exhumation rate of 0.53±0.13 m/Myr, and zero inheritance. In contrast, Sirius Group denudation at Table Mountain based on geochemical profiling meteoric 10Be diffusion (Dickinson et al., 2012) is an order of magnitude lower than results from our in-situ 10Be permafrost profile.
    
    Speaker: David Fink (ansto)
  - 145
    
    Beryllium-10 enhancement over the Laschamp excursion recorded in a deep-sea sediment core from the Indian sector of the Southern Ocean
    
    The Laschamp geomagnetic dipole low, associated with a pronounced geomagnetic excursion that occurred at about 41.5 ka, has been studied in several authigenic beryllium isotope records from deep-sea sediments. However, such records from the Southern Hemisphere were scarce. In this study, we analyzed the authigenic beryllium isotope (the 10Be/9Be ratio) from 48 to 29 ka in a sediment core (the DCR-1PC core) from the Del Can ̃o Rise (46°01'S, 44°15'E), the Indian sector of the Southern Ocean. The 10Be/9Be ratio showed a sharp increase to a maximum at 40.3 ka, followed by a gradual decrease. Given the behavior of the 10Be/9Be ratio and the uncertainty in the age model of the core, we conclude that this increase faithfully reflects the 10Be enhancement caused by the Laschamp geomagnetic dipole low. However, comparisons with authigenic beryllium isotope records from northeastern Atlantic and equatorial Pacific sediments showed a lower rate of the Laschamp peak enhancement in the Southern Hemisphere record. This suggests either the existence of a hemispheric difference in 10Be production /fallout or the influence of pre-/post- depositional smoothing, or both.
    
    Speaker: Dr Kazuho Horiuchi
  - 146
    
    Study on the dating method of 26Al in deep-sea ferromanganese crust
    
    The deep-sea ferromanganese crust (DSFC) is not only an ideal archive for recording the history of the Earth’s evolution, but also a natural reservoir for rich in a variety of metal elements. As one of the most important cosmogenic nuclides, as well as an ideal indictor of natural events since Quaternary, 26Al has not been as widely used in chronological studies as 14C, 10Be etc., due to the influence of factors such as measurement sensitivity and 26Al in situ production. The survey and exploration of 26Al dating method to a typical deep-sea ferromanganese crust were re-conducted based on previous research. A crust with a more rational stratigraphic structure was selected, the experimental method was further optimized, background interfering nuclides were analyzed, and 10Be data were still used as a control. The final results show that the 26Al dating is feasible for application to deep-sea ferromanganese crusts.
    
    Speaker: Kejun Dong (天津大学)
  - 147
    
    $^{53}$Mn development at CologneAMS and its application to cosmogenic nuclide burial dating
    
    Age determination of sediments in arid and hyper-arid regions poses challenges due to the absence of age-indicating fossils. As part of the collaborative research cluster 1211 of the German Research Foundation “Earth - Evolution at the Dry Limit” we are improving cosmogenic radionuclide dating in order to gain a better insight into the geological dynamics of, e.g., the Atacama Desert or the Namib.
    In this contribution we discuss a novel approach using Accelerator Mass Spectrometry (AMS) to measure the cosmogenic $^{53}$Mn/$^{3}$He concentration in iron-titanium oxides (hematite, magnetite, titanomagnetite, ilmenite). $^{53}$Mn, with a half-life of T $\approx \ 3.7$ Ma, has the potential to extend the upper limits of cosmogenic nuclide burial dating into the Miocene, as compared to the typically Pliocene upper limit of the more commonly used $^{26}$Al/$^{10}$Be pairing.
    $^{3}$He is measured using noble gas mass spectrometry whereas $^{53}$Mn requires AMS with a tandem accelerator of high terminal voltage, exemplified by the 10 MV FN tandem accelerator at the University of Cologne. The system consists of a multi cathode SNICS ion source by NEC, a low and a high energy mass filter containing a magnet and an electrostatic analyzer each, a gas-filled magnet for suppressing the isobar $^{53}$Cr and a gas ionization detector. The sample preparation is done in-house at the institute for Geology and Mineralogy.
    Systematic optimization, including the development of a Bragg-type gas ionization detector and enhanced stability of the accelerator voltage via position measurement of the $^{55}$Mn beam in the offset cup, has resulted in stable conditions for the measurement of $^{53}$Mn, achieving a low blank level of $^{53}$Mn/$^{55}$Mn = $(3.3\ \pm \ 3.4)\ \cdot \ 10^{-14}$.
    Our contribution includes an overview of the sample preparation, the current limits in terms of age determination, $^{53}$Mn results from Namibian and Chilean iron oxide surface samples and a discussion of their implications for advancing our understanding of the geomorphological dynamics.
    
    Speakers: Gereon Hackenberg (University of Cologne, Institute for Nuclear Physics, Germany) , Markus Schiffer (University of Cologne, Institute for Nuclear Physics, Germany)
- Radiohalide Techniques and Applications GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  AMS analysis of radionuclides as environmental tracers within geological, hydrological, and atmospheric systems.
  
  Convener: Prof. Hou Xiaolin (Xi’an AMS Center, Institute of Earth Environment, Chinese Academy of Sciences)
  - 148
    
    Improvement of Cl-36 measurements at the Tsukuba 6 MV AMS facility
    
    Long-lived nuclides $^{10}$Be, $^{14}$C, $^{26}$Al, $^{36}$Cl, $^{41}$Ca, $^{90}$Sr, and $^{129}$I have been successfully detected with the 6 MV accelerator mass spectrometer at the University of Tsukuba [1]. $^{36}$Cl is one of the most difficult radionuclides to measure due to contamination with the interfering isobaric $^{36}$S. Sulfur itself is easily present in the environment, making its removal difficult. In order to separate and discriminate $^{36}$S, we have studied acceleration conditions, methods to reduce $^{36}$S in the beam itself emitted from the Cs sputtering ion source, and to separate and identify the spectrum between $^{36}$Cl and $^{36}$S incident on the detector [2]. To reduce $^{36}$S, we compared the material of the cathode in which the sample is loaded, a copper cathode filled with AgBr powder and a cathode with Ta metal attached. The sample cathode made of Cu, filled with AgBr, and with a 1 mm diameter hole had the lowest contamination of $^{36}$S. When the sample volume is large, AgCl is placed on the entire surface. In addition, we attempted to suppress $^{36}$S contamination by covering the surface of the wheel disk with a 0.5 mm Ta plate. As a result, the contribution of $^{36}$S was reduced by a factor of 50. $^{36}$Cl detection performances of Cl$^{5+}$ (30.0 MeV), Cl$^{7+}$ (48.0 MeV), and Cl$^{8+}$ (54.0 MeV) were compared by acceleration at 6 MV. We also compared how the spectrum separation changes with the gas pressure in the gas ionization chamber. As a result, background values were ~3 × 10$^{-15}$ for all charge numbers q=5+, 7+, and 8+. Cl$^{7+}$ (48.0 MeV) is commonly used for $^{36}$Cl AMS at the University of Tsukuba because the beam transmittance is as high as about 14% and the effect of interfering nuclides on the spectrum is small. In this presentation, we will report on progress in $^{36}$Cl AMS detection techniques and applied researches with the 6 MV tandem accelerator.
    References
    [1] K. Sasa et al., Nucl. Instrum. Methods Phys. Res. B, 437 (2018) 98.
    [2] S. Hosoya, K. Sasa et al., Nucl. Instrum. Methods Phys. Res. B, 438 (2018) 131.
    
    Speaker: Dr Kimikazu Sasa (University of Tsukuba)
  - 149
    
    129I at MILEA
    
    $^{129}$I is one of the AMS radionuclides which benefits most from a compact and low-energy AMS system. The interfering stable isobar $^{129}$Xe is completely suppressed as it does not form negative ions, thus high energies are not required for isobar separation in the detector. Mass separation needs to be high enough to discriminate against the stable isotope $^{129}$I. The HE side of a compact low-energy AMS system can be equipped with two magnets and an electrostatic analyzer (ESA), providing excellent suppression of neighboring masses, in particular of the stable isotope $^{127}$I and of a potential interference from $^{128}$Te. As one of the heavier AMS nuclides $^{129}$I requires high magnetic fields in combination with large bending radii, even more so when the measurements are performed at high ion energies. This is often compensated with the selection of a high charge state with a low yield at the high energy (HE) side to bring the magnetic rigidity down for reasonably sized magnets. In contrast at lower energies (around a few 100 keV) the most probable charge state 2+ can be selected and with He stripping transmissions of >50% are achieved. Furthermore, the use of the 2+ charge state avoids mass/charge ambiguities at other charge states (e.g. 3+).
    All these benefits are implemented at the 300 kV multi-isotope AMS system MILEA, which was built from more than 10 years of experience of $^{129}$I at the first compact 500 kV multi-isotope AMS system Tandy. Here we describe the MILEA system, review the key aspects of the performance and discuss challenges that still arise: Destruction of molecules of same mass are key for all AMS measurements; at the low charge state 2+ we control the rate of surviving molecules with the stripper gas pressure and thus by the number of collisions. Attention must be paid to molecules other than $^{127}$I$^1$H$_2^-$ that do not scale with the $^{127}$I current and can occur in natural samples. Another critical component is the ion source. Due to the volatility of iodine, cross-talk between samples can limit the performance for samples with low $^{129}$I content.
    We show that with careful selection of the source parameters we can control the cross-talk and are able to measure Woodward Iodine down to $1\times10^{-14}$ while having high transmission of >50% and measure the nominal ratio with >90%. The optimized performance combined with the reduced complexity of the AMS measurement at MILEA are beneficial particularly for high throughput applications such as $^{129}$I as an ocean tracer.
    
    Speaker: Christof Vockenhuber (ETH Zurich, Laboratory of Ion Beam Physics)
  - 150
    
    Iodine-129 in ice and coral cores as candidate golden spikes for the Anthropocene
    
    The Anthropocene is a proposed geological epoch that will mark when humans have irreversibly affected the Earth. One of the primary requirements to formally establish this is a Global Boundary Stratotype Section and Point (GSSP) or “golden spike” – a record of a planetary signal marking the new epoch’s beginning. Last July 2023, it was announced that the leading candidate for the Anthropocene’s golden spike are the fallout peaks of 14C (T1/2 = 5,730 y) and 239+240Pu (T1/2 = 24,110 y and 6,560 y for 239Pu and 240Pu, respectively) from nuclear weapons testing in the 1960s recorded in a lake sediment core from Canada. However, in early 2024, the International Commission on Stratigraphy rejected the proposal to establish the Anthropocene as a new epoch. Among the reasons is that the proposed GSSP may not be definitive enough and that the chosen radionuclides’ half-lives may not be sufficiently long for their signals to be observable in the far future and are, thus, not durable.
    
    In this regard, here we show the 129I time series record in an ice core from the SE-Dome site, Greenland and from several coral cores from the Philippines. We find that 129I in ice core and corals record almost the entire history of the nuclear age in excellent detail at annual to sub-annual time resolution. More specifically, 129I in these records reflects signals from nuclear weapons testing, the Chernobyl and Fukushima Accidents, and various signals from nuclear fuel reprocessing. The quantitative relationships between 129I in the core records and these human nuclear activities have been established using numerical models. Similar signals are observed in other records from various environments worldwide, such as in sediments and tree rings. This global ubiquity and synchronicity are comparable to those of the 14C and 239+240Pu bomb signals, but the much longer half-life of 129I (T1/2 = 15.7 My) makes it a more durable golden spike. Furthermore, rather than existing as a single or a few bomb peaks, 129I clearly distinguishes before and after the proposed Anthropocene event because of the minuscule natural 129I levels before 1950 compared to the consistently elevated 129I levels after 1950 from human nuclear activities. For these reasons, the 129I in ice and coral cores can be considered an excellent candidate for the Anthropocene golden spike.
    
    Speaker: Dr Angel Bautista VII (DOST - Philippine Nuclear Research Institute)
    
    AMS16 Anthropocene.docx
  - 151
    
    Methodology and Tracing Applications of long-lived Anthropogenic radioiodine
    
    Radioactive iodine is a key concern for the transport and dispersion of radioactive pollutants and radiation exposure evaluation during nuclear accidents and nuclear emergency preparedness, as well as for understanding the atmospheric cycling of iodine. However, atmopsheric 129I is difficult to measure due to its low concentration in remote areas, away from nuclear pollution sources. This presentation will introduce a series of methods for sensitive determination of 129I and its species in atmosphere, ocean and land. Furthermore, a brief review will be given on the applications of iodine-129 in atmospheric cycling, radioactive proxy for defining the onset of the Anthropocene and nuclear environmental safety.
    
    Speaker: Luyuan Zhang (Institute of Earth Environment, CAS)
  - 152
    
    Latitudinal variation of atmospheric 129I/127I ratio in Spain
    
    129I (T1/2 = 15.7 × 106 y) is a radionuclide whose presence in the environment changed strongly due to the emissions from the two largest nuclear fuel reprocessing plants in Europe: Sellafield (UK) and La Hague (France). Most of the 129I has been discharged to the sea, but part of it is released as gaseous 129I. Liquid discharges of 129I mostly travelled from these plants to the North Sea and then to the Arctic along the Norwegian coast. The geochemical cycle of iodine includes continue interchanges between different environmental compartments, including the atmosphere, where it can travel long distances despite its short residence time. 129I can be a tracer of atmospheric processes. Besides, it can be an indicator of the presence of shorter-lived iodine isotopes released in nuclear accidents. However, there are not many recent data on the presence of 129I in the atmosphere.
    In this work we present the results for atmospheric 129I/127I isotopic ratios over four cities in Spain: Bilbao (43°15′N), Seville (37°23′N), Malaga (36°43′N) and La Laguna (28°29′N) during the first three months of 2023. The evolution of the isotopic ratios was very similar in the four cases, revealing a common origin of 129I. The results showed 129I/127I isotopic ratios in the order of 10-10 to 10-8 for the four cities but showing a clear dependence on latitude. Highest ratios were measured in Bilbao, the most septentrional city, while the lowest ones were found on La Laguna, placed in the Canary Island. In average, 129I/127I ratios were a factor of 4.5 higher in Bilbao than in La Laguna during this period. Finally, it could also be observed that the values found in Sevilla were in the same range than the ones measured in 2013, previously to the closing of the Sellafield reprocessing plant.
    
    Speaker: Jose Maria Lopez-Gutierrez (Universidad de Sevilla)
    
    AMS-16_abstract_filters.docx
- 15:10
  
  coffee break Lobby , 2nd Floor
  
  Lobby , 2nd Floor
- Applications of Cosmogenic Isotopes GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Applications involving isotopes created via cosmic ray activation and spallation. Topics include exposure dating and groundwater tracing.
  
  Convener: Prof. Marc Caffee (Purdue University)
  - 153
    
    Cosmogenic Be-10 in fine-grained quartz from shale
    
    In situ-produced Be-10 is routinely used in the mineral quartz for measuring exposure times and erosion rates. Most previous applications have focused on relatively coarse mineral grains (typically greater than 100 microns) in sandstone, quartz veins, or igneous and metamorphic rocks. Here we report Be-10 measurements from fine-grained quartz extracted from shale bedrock and sediment. Shale typically contains 25% or more quartz, but because it is fine-grained it has been considered difficult to purify. Quartz grains less than 10 microns in size are also subject to ejection and implantation of Be-10 during the production reactions, creating potential complications.
    
    We purify quartz from shale using hot phosphoric acid after combustion of organics and dissolution of clays in hot sodium hydroxide. Centrifugation of the fine-grained minerals after each step rapidly settles the micron-sized quartz. Heavy minerals are separated by centrifugation in lithium heteropolytungstate. We have obtained pure quartz for size fractions ranging from 1-100 microns. Preliminary results suggest that grains finer than 5 microns may contain meteoric Be-10; experiments are underway to identify the source of this contamination.
    
    We have conducted field experiments in the layered rocks of the southern Appalachian Mountains, USA, where mountain ridges are held up by resistant sandstone while valleys are typically underlain by shale and limestone. Our initial results in Shenandoah Valley indicate that shale in the valley floor has a denudation rate similar to the long-term rate of river incision, while previous research shows that sandstone ridges are eroding much more slowly. Our results suggest that mountain relief is growing in this region due to lowering of the shale- and limestone-floored valleys.
    
    Speaker: Darryl Granger (Purdue University)
  - 154
    
    A protocol for estimating accurate denudation rates based on terrestrial cosmogenic nuclides
    
    Terrestrial cosmogenic nuclides provide a crucial tool in geomorphology, however evaluation and correction of systematic uncertainties remains a challenge in estimating denudation rates of land surfaces. Subsurface nuclide production involves distinct processes by neutron and muons, which have different contribution ratios and attenuation lengths for accumulating any nuclides such as chlorine-36 in calcite in carbonate rocks and beryllium-10 or aluminum-26 in quartz in silicates. Therefore, at a given point in time, the nuclide amount present on an eroding ground surface has resulted from accumulation through each production path on different timescales. The muon contribution to the total nuclide abundance increases with the denudation rate, which accumulates the nuclide on a longer timescale. Generally, nuclide production rate changes with time with varying cosmic-ray flux, and hence different scaling factors apply for evaluating the local nuclide production rates on different timescales. However, the current scheme does not take temporal changes in the nuclide production rate into account for calculating denudation rates. In this report, we discuss the importance of this issue by comparing ordinary analytical solutions with quasi-analytical evaluation using time-integrated scaling factors for the denudation rates, as well as with results of numerical integration of nuclide accumulation under sequential changes in the nuclide production rate. An appropriate protocol is then presented for calculating accurate denudation rates based on the concentrations of terrestrial cosmogenic nuclides in various types of geomorphological samples.
    
    Speaker: Yuki Matsushi (Kyoto University)
  - 155
    
    A Statistical Method for Treating the ``Negative-Age'' and ``Negative-Atom-Number'' Conundrums in Radioisotope Dating
    
    In radioisotope dating, statistical fluctuations of atom counts or decay counts can sometimes lead to unphysical results, such as negative counts after subtracting the background or negative apparent ages near the boundaries of the dating range. How to treat these boundary cases with a unified approach and give proper estimates on age limits and confidence intervals is an important issue in radioisotope dating. In this work, we combine the Feldman-Cousins likelihood-ratio ordering method for interval estimation, a Frequentist approach to make consistent transitions from the choice of one-sided limits to two-sided confidence intervals, and a Bayesian method to treat the background uncertainties. This data treatment method naturally eliminates the unphysical results. We use $^{81}$Kr dating and Atom Trap Trace Analysis as an example to illustrate the advantages. This method can be generalized to other radioisotopes and ultra-sensitive analysis techniques.
    
    Speaker: Mr Weikang Hu
  - 156
    
    Calculation of cosmic ray shielding factor in different terrains
    
    The rate of production of cosmogenic nuclides is not only related to altitude and latitude, but also to topographic occlusion and the elemental composition of rock formations. Due to the occlusion of the terrain, it is necessary to establish a shielding factor calculation model in practical geoscience applications. In this paper, five geometric shapes of terrain are considered: slope, surface protruding hemisphere, spherical wall pit, spherical pit, cylindrical pit, and the numerical solution of each shielding factor is calculated by MATLAB program, and the corresponding terrain shielding factor calculation formula is fitted, which is convenient for geologists to apply them to the calculation of the concentration of nuclides in common terrain, and compared with the AMS measurement of nuclide concentrations in different terrains, the existing theory can be improved. It provides a practical calculation method for the calculation of the production rate and exposure age of cosmogenic nuclides in geophysics.
    
    Speaker: Dingxiong Chen (College of Physics and Technology, Guangxi Normal University, Guilin, Guangxi 541004, China)
- Radiohalide Techniques and Applications GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  AMS analysis of radionuclides as environmental tracers within geological, hydrological, and atmospheric systems.
  
  Convener: Prof. Philippe Collon (University of Notre Dame)
  - 157
    
    Tracing environmental processes using long-lived radionuclides in Xi’an AMS Center
    
    A series of analytical methods have been developed for sensitive and accurate determination of long-lived 129I, 14C, plutonium and uranium isotopes in various environmental samples, such as soil, sediment, water, air, and vegetation samples in the Xi’an AMS center using the 3MV tandem AMS, MICDAS AMS and other mass spectrometry methods. An overall investigation of artificial radioactivity in terrestrial and the adjunct sea environment of China has been implemented in the past 15 year to obtain their distribution and sources, in order to understand their dispersion and transfer pathways and environmental impact. In general, a relative higher level of anthropogenic radionuclides, e.g. 129I, 239, 240Pu, were observed in North China compared to South China. No significantly enhanced levels of anthropogenic radionuclides were observed in the surrounding area of Lop Nor nuclear weapons testing sites (300-600 km distance to the center of the testing site) were measured, due to the desert and hard bed of dried salt lake topography and geography in Lop Nor region. The measured 240Pu/239Pu atomic ratios in all environmental samples except a few samples from northeast Xinjiang were around 0.16-0.20, which are similar to the ratio of the global fallout of atmospheric nuclear weapons tests (0.18), indicating most of the plutonium and many other anthropogenic radionuclides originated from global fallout. Significantly lower 240Pu/239Pu ratios of 0.11-0.13 were observed in soil samples collected from northeast corner of Xinjiang, this might result from the transport of the close-in deposition of Semipalatinsk nuclear weapons tests in 1950-1963.
    The 129I and Pu isotope level in the surface soil shows a gradually declined trend from North to South China, and relative higher level were observed in North China, especially in the eastern inner Mongolia at the west side of the Greater Khingan Mountains and Yinshan Mountains, this is attributed to the long-distance transport of gaseous 129I by dominant westerlies wind in this region from Europe, where large amount of 129I was discharged to the seas and atmosphere from Sellafield and La Hague spent fuel reprocessing plants. The mountain topography and climate condition in the eastern Inner Mongolia promoted the deposition and retention of 129I in the region. These hypotheses were confirmed by the measured distribution of 129I in the sediment cores collected from Jiaozhou Bay, East China Sea and Tal lake in Philippine, which showed constantly higher level of 129I in the upper layer sediment (after 1980), and the decreased inventory of 129I in the sediment core from north location to south location in Asia (Fan et al. 2016; Zhang et al. 2019; Zhao et al. 2021a, b). The declined 129I level from North to South China resulted from the transport of reprocessing derived 129I dispersed to North China to South Asia by East Asia winter monsoon.
    The level of 129I in the China Sea shows a higher concentration in the north (Yellow Sea and Bohai) compared to the south (East China Sea and South China Sea). Meanwhile a high 129I/127I atomic ratios in the coastal seawater, especially the estuarine seawater were much higher than the open seawater, and in the surface seawater compared to the deep water. The 129I/127I atomic ratios in seawater is much lower than that in river or lake water. The high 129I in the estuarine and costal water is attributed to the terrestrial input of 129I through rivers by leaching and transport of 129I deposited in on the land, and the high deposition of 129I in North China compared to South China. A significantly increased 240Pu/239Pu ratios (0.25-0.35) was observed in the seawater and sediment in the China Seas, clearly showing the contribution of the continuous resuspension of radioactive substance in the PPG nuclear weapons tests site and its long-distance transport through the North Equator and Kuroshio Currents. A remarkable Fukushima 137Cs signal was observed in the South China Sea and West Pacific Ocean, especially in the middle and subsurface layer, which was transported to this region from Fukushima through a long-distance transport via water circulation.
    Acknowledgements: Many colleagues and students contributed to this work, Yukun Fan, Luyuan Zhang, Peng Cheng, Qi Liu, Ning Chen, Xue Zhao, Yanyun, Wang, Mengting Zhang, Shan Xing, Weichao Zhang, Dongxia Zhang, Dan Liu, Jialin Liu, Miao Fang, Zhao Huang, etc. This work was also supported by Chinese Academy of Sciences, Ministry of Science and Technology of China, National Nature Science Foundation of China.
    
    Speaker: Xiaolin Hou (Institute of Earth Environment, Chinese Academy of Sciences)
    
    AMS abstract- Application of AMS for Tracing Environmental Process.docx
  - 158
    
    Study on natural iodine isotope system
    
    Iodine isotopes (stable 127I and long-lived radioactive 129I with half-life 15.7 million year) in natural environment have potentially various applications, utilizing as a dating tool or an index of comic-ray intensity variation with millions to 10-million-year time scale. For these purposes, iodine isotope system in natural environment should be understood comprehensively. Important issues are:
    1. Iodine dynamics in the environment.
    Inventories of iodine in various sites and transition among them should be elucidated.
    2. 129I sources and assimilation of the iodine dynamic system.
    Production rate of 129I by the cosmic ray and 238U spontaneous fission and how well is the produced 129I is mixed with the ambient iodine should be evaluated. This is related to the equilibrium 129I/127I ratio. Does the globally equilibrium 129I/127I ratio exist like radiocarbon?
    
    Speaker: Hiroyuki Matsuzaki (The University of Tokyo)
    
    Matsuzaki_Iodine_system.pdf
  - 159
    
    129I concentration in breastmilk and its dose to infants’ thyroid
    
    Radiation exposure dose and potential health risks remain a crucial aspect of public health particularly given the use of the linear no-threshold model which postulates any exposure to radiation can result in harm. The concentration of several long-lived radionuclides has increased in the environment through human nuclear activities. Many of these radionuclides are alpha and beta emitters which if ingested in sufficient quantities, may impact human health. This paper demonstrates a reliable and reproducible method for the measurement of 129I in human breastmilk, then assessed it dose to infant thyroid.
    The procedure used here was a refinement of a method that already established. the 129I in breastmilk ranged from 1.26x108 atoms/L to 6.64x108 atoms/L with a median of 2.10 x108 atoms/L, and the 129I/127I ratio ranged from 1.27x10-10 to 9.9x10-10 with a median of 2.13x10-10. There results suggest a strong correlation between 127I and 129I concentrations in breastmilk. We noticed the similarity in isotopic ratios between breastmilk and the Canadian cow’s’ milk, indicating that the milk of both cows and humans may be a reflection of the 129I concentration of their local environment and the food ingested.
    The results confirm that humans are exposed to the 129I from birth through their mother breastmilk, giving them an average dose of 1.10 x10-4 Bq/year and thyroid dose rate equal to 5.92 x10-10 Sv/year.
    
    Speaker: Fahad Almarshadi (University of Ha'il)
  - 160
    
    The distribution of the 129I radioisotope concentration in surface waters across Romania
    
    The increasingly wide range of human activities in the nuclear field, such as nuclear weapons technologies, nuclear reactors for energy production, spent nuclear fuel reprocessing plants, and nuclear waste repositories, has correspondingly increased the importance of monitoring and preventing nuclear pollution.
    In the early stages of nuclear pollution, the quantities of dispersed radioactive material in the environment can be extremely small, undetectable by most nuclear monitoring techniques. The accelerator mass spectrometry technique using 129I is suitable for detecting very small increases in nuclear pollution even in the early stages when they are not yet hazardous in terms of contamination level.
    In this research, we continue our work of determining 129I concentrations by analyzing water samples collected from across the entire territory of Romania. The aim is to map the current level of 129I concentration in order to assess the potential impact of future nuclear contaminations at the Romanian and Southeast European levels. The results obtained will complete the global map of 129I distribution created by Xuegao Chen et al. in 2015, where there is currently a lack of data concerning Romania.
    
    Speaker: Mrs Melania Beatrice Istrati (Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering)
    
    abstract Melania Istrati.pdf
  - 161
    
    Isotopic Evidence Unveils Fossil Fuels Contribution to Atmospheric Iodine
    
    Iodine is a crucial nutrient for public health, and its presence in the terrestrial atmosphere is a key factor in determining the prevalence of iodine deficiency disorders. While oceanic iodine emissions decrease at lower sea surface temperature, the primary contributors to atmospheric iodine can vary from oceanic sources in summer to other sources in winter. However, the specific sources and their respective contributions have remained unexplored. Fortunately, the atomic ratio of 129I to 127I significantly differs between nuclear activity and fossil fuels like coal and petroleum, which formed millions to billions of years ago. This distinction makes 129I a valuable tool for identifying iodine sources. In our study, we for the first time took this advantage of iodine isotopes to successfully identify the sources of atmospheric iodine and estimate their contributions based on the analyses of PM2.5 samples collected in four Chinese metropolises. This research enhances our comprehension of the impact of human activities on iodine levels in the environment, and may add important information on addressing iodine deficiency-related health concerns and comprehending stratospheric ozone depletion.
    
    Speaker: Yukun Fan (Institute of Earth Environment, Chinese Academy of Sciences)
- Poster Session B: (The poster dimensions should be 120 cm in height and 80 cm in width.) Lobby and Hallway , 2nd Floor
  
  Lobby and Hallway , 2nd Floor
  - 162
    
    129I in precipitation from Xi’an, China in 2011: influence of the Fukushima nuclear accident
    
    During the Fukushima nuclear accident in March 2011, large amounts of radionuclides were released into the environment. Some of them were transmitted and dispersed over long distances, e.g. 131I, which is harmful to human. However, 131I has a short half-life (8 days), and if environmental samples are not collected and measured in time after the nuclear accident, it will be difficult to detect 131I since it will decay away after several months of the accident, making it difficult to assess the environmental impact of 131I. Another radioiodine released during the accident, long-lived 129I (with half-life of 15.7 million years) will remain in the environment for a long time. It has the same chemical properties and environmental behavior as 131I. The 129I/131I ratio of radioiodine released by the accident has been studied. By measuring 129I content in environmental samples after the accident, and compared with the 129I background level before the accident，131I distribution can be reconstructed. During the period from March to April, 2011, 131I was detected in aerosol samples, precipitation and other environmental samples in China. For example, 131I was detected in the aerosol samples in Xi 'an from 23th March to 27th April 2011. Precipitation is the main pathway for iodine transferring from the atmosphere to the land. However，there is no reported data of 131I in precipitation in Xi 'an in 2011. Precipitation samples were collected in 2011, which could be used to study the influence of the Fukushima nuclear accident in Xi 'an, via measuring the 129I to estimate the 131I level. The 129I concentration and 129I/127I ratio of precipitation samples collected at Xi’an from February to July 2011 were analyzed by AMS. The concentration of 129I ranged from 1.0×107 atoms/L to 81.8×107 atoms/L with an average of 10.3×107 atoms/L, and the atomic ratio of 129I/127I ranged from 0.64×10-9 to 26.73 ×10-9 with an average of 4.47×10-9. According to the origination of the air mass during precipitation and the concentration of 129I originated from the Fukushima accident in aerosols, which was estimated based on the reported activity of 131I in aerosols in Xi'an in 2011, and compared with the 129I in precipitation in Xi’an before 2011, it was possible that the impact of the Fukushima accident was not strong.
    
    Speaker: 宁陈 (中国科学院地球环境研究所)
    
    Abstract for meeting AMS-16- Ning Chen -Poster preferred.docx
  - 163
    
    Current status of BINP AMS and MICADAS facilities, working at AMS Golden Valley, Russia
    
    The radiocarbon laboratory “AMS Golden Valley” was established in 2020 in Novosibirsk, Russia. At the present moment laboratory provides routine 14C analyses of various samples: collagen, cellulose, humic acids, carbonates from sediments, food soot, methane from seeps, CO2 dissolved in water etc. The main focus of the laboratory is to determine the age of archaeological artifacts by radiocarbon dating, some of the work is being carried out with 14C labels in the area of biomedical application of AMS, in particular to study the penetrating ability of aerosols in the tissues of laboratory mice and the selectivity of oncolytic viruses.
    Laboratory is equipped with two accelerator mass spectrometers: BINP (Budker Institute of Nuclear Physics) AMS facility and MICADAS-28. In 2022 AMS Golden Valley passed the Glasgow International Radiocarbon Intercomparison. Current status of the laboratory will be presented. BINP AMS facility is undergoing modernization to improve reliability and performance. MICADAS-28 continues to perform routine measurements of user samples.
    
    Speaker: Alexey Petrozhitskiy (Budker Institute of Nuclear Physics of SB RAS, Novosibirsk State University, Institute of Archaeology and Ethnography SB RAS)
    
    2024_05_31 Abstract Petrozhitskiy AMS16 (3) fin.docx
  - 164
    
    Deciphering circulation patterns, timescales and mixing in the Arctic and North Atlantic Oceans: insights from radionuclide transient tracers – the TITANICA project
    
    The ERC-funded project entitled TITANICA (A New Era of Transient Tracers in the Arctic and Atlantic Ocean) embarked on its official journey in July 2021, with the aim to decipher circulation patterns, transport timescales and mixing in the Arctic and subpolar North Atlantic oceans. The novelty of TITANICA is the use of a new set of transient radionuclide tracers (129I, 236U, 39Ar and 14C), a quartet that allows studying and constraining oceanographic processes on timescales of years to millennia. In particular, releases of 129I and 236U from European Nuclear Reprocessing Plants (NRPs) are used as powerful tracers of Atlantic waters circulation on their journey through the Arctic Ocean and subsequent entrainment into the overflow waters in the Nordic Seas and Labrador Sea (Wefing et al., 2021; Casacuberta&Smith). In addition, the cosmogenic radionuclides 14C and 39Ar are reemerging today as a powerful dual tracer to reassess the long ventilation timescales of the deep and bottom waters in the Arctic Ocean. In this talk, we will present a compilation of results from 15 oceanic expeditions covering the Arctic Ocean basins, the subpolar North Atlantic (mostly Labrador Sea, Irminger Sea and seas around Iceland) and the main gates connecting both oceans (i.e. Fram Strait, Davis Strait and Sta. Anna Trough). In the Arctic Ocean and Fram Strait, we have reevaluated transit time distributions of Atlantic waters in years 2020/2021 (Payne et al., submitted) and used these tracers to estimate storage of anthropogenic carbon (Raimondi et al., 2024). Latest results of cosmogenic tracers 14C and 39Ar in the deep Arctic Basins provide with new estimates of ventilation timescales, reassuring the isolation of these waters from any anthropogenic imprint. In the subpolar North Atlantic, the combination of 129I and 236U proved to be an additional tool to constrain water mass mixing and origin of overflow waters, a signal that can be chased down to Bermuda. TITANICA has sailed half of its journey, so this story is far from over…
    
    Speaker: Habacuc Pérez-Tribouillier (Laboratory of Ion Beam Physics)
  - 165
    
    Detection of lithological control on landslide type and pattern using 10Be dilution
    
    Determining the landslide type and pattern which are greatly conditioned by the lithological properties of the land surface, is vital for evaluating geo-hazard risk for different area and understanding regional landscape evolution pattern. Landslides could supply substantial deep-seated, low-nuclide debris from hillslope into channel network, resulting in a dilution of the detrital cosmogenic nuclide concentration in fluvial sediments. At present, the cosmogenic nuclide dilution model for fluvial sediments has been shown to evaluate the landslide depth and quantify landslide-derived sediment yield, which could be used as the criteria for determining the landslide type and pattern. Here, we presented a detrital 10Be concentrations dataset obtained from Minjiang catchment located in the eastern margin of the Tibetan Plateau, where shows contrasting lithological conditions, and attacked by coseismic landslides during 2008 Wenchuan earthquake. Sampling sub-catchments were carefully selected to cover a range of landslide distribution and to be representative of specific lithology. The presumable model parameters were evaluated and constructed through multifaceted geospatial analyses. The scaling factors for evaluating landslide depth and sediment yield were obtained inversely from the diluted 10Be concentrations and corresponding landslide inventory. Our data allow us to characterize in detail the lithological control on landslide type and pattern for the Minjiang catchment from the differential nuclide concentration dilution of fluvial sediments for areas with different lithologies. In addition, we also use them to solidify our quantitative understanding of landslide response to basement lithology setting, that can be ported into other environments or locations as a refined tool.
    
    Speaker: Mr Jiajun Peng (Kyoto University)
  - 166
    
    East vs West: comparing the rates of landscape change in the southern African region.
    
    For channel incision rate determination and comparison, bedrock samples from sections of the Olifants River (n = 10) in the dry tropical/subtropical Kruger National Park, as well as samples from sections of the Orange River (n = 20), in the arid Northern Cape were collected. Using cosmogenic in-situ 10Be in pure quartz, average incision rates determined from granitic samples of the Olifants River indicate that the channel is incising at a rate of 26.4 ± 1.77 m/Ma, while granitic and quartzitic samples from along the Orange River produce a slower average rate of 6.89 ± 0.45 m/Ma, implying considerably slower channel evolution in the west. These rates fall within a very wide range of previously determined rates of erosion and channel incision across various southern Africa of 0.2 – 255 m/Ma landforms. The roughly four times faster channel incision rate along the Olifants River, compared to that of the Orange River, suggest that the prevailing long-term climate is a driver on erosion and apparent exposure ages, where the wetter east yields faster rates and younger apparent exposure ages, while the drier west, slower rates and older apparent exposure ages. Quartzitic rates of incision are also seen to be slower than those of granitic composition along the Orange River, suggesting a further lithological control on the rates of erosion and landscape change. Although the southern African landscape has been considered tectonically quiescent, the data presented here imply that landscape evolution is not uniform, and that is prevailing long-term climate variability and lithology are the primary drivers of differential erosion across the region.
    
    Speaker: Rivoningo Khosa (iThemba LABS)
    
    AMS16_Abstract_Khosa et al..pdf
  - 167
    
    In situ produced cosmogenic 10Be and 36Cl measurement in Serra do Cipó marble
    
    Over the last twenty years, the use of cosmogenic nuclides has allowed a spectacular growth in the quantification of processes in the earth sciences. Besides the field of accelerator mass spectrometry, the accurate application of these approaches implies that the nuclide production rates are well known. During the last decade, a lot of work has been done in the field of production rate calibration, but less work has been done in the production rate calibration within different minerals to expand the applicability of the cosmogenic nuclides to new environments or lithological settings.
    Even if one can get a good idea of what the production rate of a given mineral can be based on numerical simulations on experimentally determined cross sections, sometimes the energy ranges of these experiments are not comparable to the entire natural energy range, and this may yield large uncertainties in the production rate determinations.
    In this work, we will present a second attempt at the determination of the production rate of $^{10}$Be in carbonate ($^{10}$Be-carb) in natural samples collected along a 10 m depth profile in a Brazilian marble from Serra do Cipó mountain range (Minas Gerais). These $^{10}$Be-carbs will be compared to $^{36}$Cl measured within the same carbonate as well as the $^{10}$Be measured in the fine quartz fraction embedded in the marble. To do so, a simple chemical protocol has been established to eliminate the atmospheric $^{10}$Be that may be adsorbed on the sample surface.
    Even though the expected exponential decrease is well observed for the three datasets, the relative production ratios between them are totally unexpected and will be presented and discussed during the workshop.
    
    Speaker: Dr Regis Braucher (CEREGE CNRS LN2C)
  - 168
    
    In-situ erosion rate revealed by Be-10 at Kiio-shima Island, Wakayama Prefecture, Japan
    
    Multiple marine terraces, presumed to have been formed by uplift with the Nankai Trough Earthquake, are recognized in the Shionomisaki area, Wakayama Prefecture. These marine terrace surfaces can be used to investigate the crustal deformation history in this area, if those abandonment ages can be determined. Surface exposure dating (SED) using cosmogenic radionuclides(CRNs) is an applicable dating method for this area, where little or no marine terrace deposits. When this method is applied to strong eroding areas, the erosion rate of the target area is an important parameter because ignoring the effect of erosion will lead to underestimation, and the age cannot be limited enough if the erosion rate isn't determined. Therefore, in this study, we attempted to estimate the erosion rate in this area as a preliminary step for dating. Quartz Porphyry is distributed over most of Kiio-shima. The Quartz Porphyry contains quartz grains of visible size (< 10 mm in diameter), but their quartz content is not as high as that of Granite. Therefore, this rock has almost not been used for SED because of the difficulty of extracting quartz. If a measurement method can be established for this type of rock, the applicability of SED can be extended. The analysis of CRNs for Quartz Porphyry is another purpose of this research.
    Samples were collected from the highest and one level below terraces on the island. These terrace surfaces are considered to have lost their original topographic surface by erosion after their abandonment. The SOS-H001 site is on the island's west side, where the ridge-top tor and its roots are exposed and unweathered Quartz Porphyry can be seen over the entire artificial scarp. On the other hand, site SKN-H002 is located on the island's east side, where a soil layer, a weathered layer, and heavily weathered Quartz Porphyry are observed from top to bottom in order. As some of those samples were collected with a relatively low amount of quartz, they resulted in a large measurement error by Accelerator Mass Spectrometry. Despite the large error, their 10Be concentrations at both sites almost show an attenuation trend with depth from the surface.
    The erosion rates obtained by the fitting model were 27 +22/-17 mm/kyr at site SOS-H001 and 130 +270/-58 mm/kyr at site SKN-H002. The erosion rate at site SOS-H001 indicates the weathering erosion rate of the tor. Based on these results, the erosion rate at site SOS-H001 can be used to estimate the exposure age of Quartz Porphyry samples collected from directly exposed rock such as tor on Kiio-shima Island.
    
    Speaker: Yoshiki Shirahama (ERI, the University of Tokyo)
  - 169
    
    Iodine-129 deposition from atmosphere in the sample preparation rooms for AMS.
    
    Through the chemical treatment of samples with high I-129 concentrations, the workspace used to prepare samples tends to become gradually contaminated. Such contamination may lead to overestimated I-129 in accelerator mass spectrometry (AMS) analyses. Environmental contamination monitoring of I-129 from the atmosphere in sample preparation rooms was performed at ten Japanese institutions, including University of Tsukuba. The sampling was carried out in July and August 2022, and February 2023. The ambient level of atmospheric I-129 in each room was estimated from the measured concentrations in the alkali trap solutions that were left for two or three weeks [1]. To check the difference in the I-129 contamination risks from atmosphere between inside and outside the facility, the sampling bottles were left at places outside the seven institutions, where the rainwater never entered the bottles. I-129 contamination risk [atoms cm$^{-2}$ day$^{-1}$] were calculated from I-129 concentration [atoms g$^{-1}$]. The experimental procedure was performed according to previously described experimental methods [1], except that we used a different carrier reagent “Old Iodine” with an I-129/I-127 ratio of 2 × 10$^{−14}$ and performed AMS at Tsukuba University system [2]. In most of the institutions, the amounts of I-129 are on the order of 10$^{3}$ or 10$^{4}$ atoms cm$^{-2}$ day$^{-1}$ in the rooms, which are one or two orders of magnitude lower than the environmental background level, 3 × 10$^{5}$ atoms cm$^{-2}$ day$^{-1}$ [3]. A clear difference is not found between the I-129 contamination risks from atmosphere inside and outside. This suggests that there is almost no I-129 contamination risk of the samples from atmosphere.
    
    This work was supported by the KAKENHI under grant Nos. of 22H04441 and 22H02001.
    
    [1] M. Matsumura et al., Anal. Sci. 36 (2020) 631-636.
    [2] K. Sasa et al., Nucl. Instrum. Meth. Phys. Res. B 437 (2018) 98-102.
    [3] M. Matsumura et al., Geochemical Journal 52 (2018) 155-162.
    
    Speaker: Dr Kimikazu SASA (University of Tsukuba)
  - 170
    
    New cosmogenic nuclide dating laboratory in CENIEH, Spain
    
    CENIEH, located in Burgos, northern Spain, is dedicated to human evolution research worldwide, including Atapuerca, a world heritage archaeological site where among the oldest human fossils in Europe has been discovered. To support the needs of characterising geological and sedimentological context of archaeological sites, the institute also features a wide range of geological analysis (e.g., laser diffraction grain size analyser, XRD/XRF, SEM, digital mapping) and geochronology laboratories, such as palaeomagnetism, OSL, ESR and U-series dating. In 2020, cosmogenic nuclide dating research line has been launched to strengthen the existing geochronological capabilities in the centre, particularly, for timescales at early-mid Pleistocene and beyond. To date, we have established a procedure for routine target preparation for 10Be and 26Al from quartz. The current projects include landscape studies in Iberian Peninsula and elsewhere, as well as human evolution studies from Africa to Europe to Asia. In this paper, we present the general setup of the laboratory and procedure, the capacity and quality control, and current projects.
    
    Speaker: Dr Santiago Padilla (CENIEH)
  - 171
    
    Radiocarbon intercomparison by a 1MV AMS at IHEG-CAGS AMS lab in China
    
    Herein, we give an overview of the operating status and performance of the 1MV AMS system. The long-term measurements of the standard and blank samples indicated that the results for IHEG-CAGS AMS were accurate and stable and of high sensitivity.
    
    Speaker: Hui zhang
  - 172
    
    Report on a MICADAS Workshop
    
    In September of this year a 2-day MICADAS (MIni CArbon DAting System) workshop was held to discuss (1) best practices, advances, successes, and issues encountered with the MICADAS, (2) solutions and potential approaches to address any common problems, and (3) best communication mechanisms for a user group. Outcomes of the meeting and plans for a follow up workshop are presented.
    
    Speaker: Mark Roberts (Woods Hole Oceanographic Institution)
  - 173
    
    Sequential extraction of U, Np, Pu and Am from sediment samples for AMS studies at the Centro Nacional de Aceleradores (CNA, Spain)
    
    During the last decades, the scientific community has dedicated efforts to expand the list of radionuclides that can be measured by the ultra-sensitive AMS techniques on either traditional or compact facilities. To date, 239Pu, 240Pu and 236U are consolidated radionuclides in AMS. In the last few years, the most minor actinides isotopes have been put in the limelight: 233U, 241Pu, 242Pu, 244Pu and 241Am [1-3]. To make the most of those AMS advances for environmental studies, it becomes necessary to adapt and/or improve the current sample preparation methods according to the specific requirements of those new and more challenging radionuclides.
    The Centro Nacional de Aceleradores (CNA, Sevilla, Spain) has hosted a 1 MV multi-elemental AMS system since 2005. This system was the first prototype of compact AMS designed and manufactured by the Dutch company High Voltage Engineering Europa (HVEE, Amersfoort). The measurement techniques for Pu isotopes (i.e. 239Pu, 240Pu, 241Pu, 242Pu, 244Pu), 233U, 236U and 237Np have been implemented at this facility [4-6] and the possibilities for 241Am and 243Am have been recently explored [7]. They are based on the extraction of monoxide anions (e.g. PuO-) from the ion source, the selection of the 3+ charge state (e.g. Pu3+) after the stripping on He gas at about 650 kV (35% yield), and their final analysis from the total energy signal provided by a gas detector. Complementary, important efforts have been made to develop reliable radiochemical procedures for the sequential extraction of actinides from environmental samples, meeting the requirements of the simple design of the 1 MV CNA.
    In this work, we present the latest advances in actinides radiochemistry developed at the CNA for sediment samples. The goal is to set up a sequential method allowing the separation of uranium, plutonium, neptunium, and americium from sediments, so that: i) the extremely low concentrations of 233U, 241Pu, 242Pu,244Pu or 243Am can be analyzed, in addition to those of 239Pu, 240Pu, 236U and 241Am; and ii) 237Np can be reliably normalized to the non-isotopic tracer 242Pu. The proposed procedure is based on a Fe(OH)2 co-precipitation of actinides after the leaching of the samples, followed by a sequential extraction of actinides using TEVA® (Pu+Np), UTEVA® (U) and DGA® (Am) resins. The efficient removal of Th from both Pu and U fractions becomes mandatory, due to the constated survival of the molecules 232Th12C3+ and 232Th1H3+ during the analysis of 244Pu and 233U, respectively. Moreover, for 243Am and 241Am analysis, lanthanides (i.e., Dy isotopes) need to be cleaned from the Am fraction to prevent undesired pile-up events from 2+ molecular fragments, making it necessary to introduce an additional TEVA® resin in the procedure. Results on the chemical yield for the different species and on the performance of the method will be presented and discussed.
    
    References
    [1] Hain K, Steier P, Froehlich MB, et al (2020) Nat Commun 11:1275.
    [2] Steier P, Hrnecek E, Priller A, et al (2013) Nucl Instrum Methods Phys Res B 294:160–164.
    [3] Christl M, Dai X, Lachner J, et al (2014) Nucl Instrum Methods Phys Res B 331:225–232.
    [4] López-Lora M, Chamizo E (2019) Nucl Instrum Methods Phys Res B 455:39–51.
    [5] Chamizo E, López-Lora M (2019) Nucl Instrum Methods Phys Res B 438:198–206.
    [6] Chamizo E, López-Lora M, Christl M (2022) Nucl Instrum Methods Phys Res B 533:81–89.
    [7] E. Chamizo. This conference: Actinides measurements on the 1 MV AMS system at the Centro Nacional de Aceleradores (Spain): How far can we go?
    
    Speaker: Dr Mercedes López-Lora (Centro Nacional de Aceleradores (CNA), Universidad de Sevilla, Sevilla, Spain )
  - 174
    
    Silicon-32 as a potential tool for soil accretion dating and carbon sequestration of coastal wetlands and assessing their risk of sea level rise
    
    Title: Silicon-32 as a potential tool for soil accretion dating and carbon sequestration of coastal wetlands and assessing their risk of sea level rise
    Authors: Peng Zhou,1, 2, 3† Juan Zhang,1,4† Dongmei Li ,1, 2, 5 Lifeng Zhong,3 Wei Zhou,3
    1Nansha Islands Coral Reef Ecosystem National Observation and Research Station & Key Laboratory of Marine Environmental Survey Technology and Application of of Ministry of Natural Resources (MNR), Guangzhou 510300, China;
    2South China Sea Ecological Center, MNR, Guangzhou 510300, China;
    3Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000;
    4South China Sea Marine Forecast and Hazard Mitigation Center, MNR, Guangzhou 510310, China;
    5Key Laboratory of Global Change and Marine-Atmospheric Chemistry, MNR, Xiamen 361005, China
    *Correspondence: samzhou2@126.com (P.Zhou), zj@hyyb.org(J. Zhang);Tel.: +86-20-89111586 (P.Zhou); Fax: +86-20-84457983. †These authors contributed equally to this work.
    
    Abstract: The basic pathway to carbon neutrality includes "emission reduction" and "sink enhancement". Coastal wetlands (mangroves, seagrass beds, salt marshes) as important "blue carbon" pools in the world, have functions for regulating global climate, promoting the degradation of pollutants, carbon sequestration, but how to improve the efficiency of blue carbon sequestration and maintain the stability of blue carbon pool and assess whether they adapt to future sea level rise (SLR) is a hotspot under global climate warming. Cosmogenic silicon-32 ( a half-life of approximately 150 years) has a potential tool for dating soil vertical accretion in coastal wetland to fill the dating gap (100-1000 years) that lies between those chronologies based on the shorter-lived isotopes of 228Thex and 210Pb, and those based on the longer-lived 14C. It will play a key role improving the efficiency of blue carbon sequestration and maintaining the stability of blue carbon pool of coastal wetlands and assessing their risk of sea level rise under globe climate warming. Because carbon storage and sequestration in coastal wetland sediments (soils) need undergoing need undergoing centennial timescales. At present, the 210Pb (T1/2=22.3a) dating technique is often used estimate carbon burial and sources and to assess carbon storage and sequestration in coastal wetland sediments within the decadal timescale (<100a). However, coastal wetland carbon in sediments within the centennial timescale (<1000a) are few studied today.
    Therefore, it is of great importance to carry out the accretion rate of coastal wetlands based on natural 210Pb and cosmogenic 32Si (T1/2≈150a) dating techniques. By analyzing organic carbon and nitrogen, biogenic silica, and their chemical and isotopic fingerprints in soil cores, it is possible not only to understand their spatial and temporal distributions, but also to assess the sources of organic matter/carbon through numerical modeling and to explore the stability of the sedimentary carbon pools in coastal wetlands over a 1000a time scale. This is important for assessing the stability of carbon pools, the sustainability and potential of carbon sinks, and predicting the impact of future global changes on the vulnerability of coastal wetlands.
    Keywords: Coastal wetland; 32Si dating method; Soil accretion rate; carbon sequestration; Sea level rise
    Funding: This research was funded by Science and Technology Development Foundation of South China Sea Bureau, Ministry of Natural Resorces of P. R. China (23YD03), the Fund of Key Laboratory of Global Change and Marine-Atmospheric Chemistry, Ministry of Natural Resources (MNR) (GCMAC202207), and by the Youth Talent Support Program of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai) (SML2021SP316).
    
    Speaker: 鹏周 (自然资源部南海生态中心)
    
    paper Silicon-32 as a potential tool for soil accretion dating and carbon sequestration of coastal wetlands.docx
  - 175
    
    Single-year radiocarbon measurement of Japanese tree rings of the first millennium BCE.
    
    The chronology from the 10th century BCE is of great importance for the archaeology of the Japanese archipelago and East Asia. We have continued AMS radiocarbon dating of Japanese trees with tree ring ages, and some of the results have been included in a calibration curve IntCal20. As a result, the shape of the calibration curve was revised from the 1st to the 3rd century CE. However, the data employed were measured in the 2000s with uncertainties, and most of the measurements were based on a sample of five rings.
    Since the Miyake Event of 775CE was detected, the radiocarbon dating of tree rings has become based on single years. In the Japanese archipelago, conventional dendrochronology has been possible only for cypress and cedar trees, and the range has been about 3,000 years in the past. However, the oxygen isotopic dendrochronology put to practical use in the 2010s changed the situation completely. Oxygen isotope ratios of cellulose in tree rings reflect the amount of precipitation. They are highly synchronous regardless of tree species in the Japanese archipelago under the influence of the Asian monsoon. A master chronology of the past 5,000 years has already been completed for the Japanese archipelago, and many tree rings can now be dated in various regions.
    Again, we have decided to conduct AMS radiocarbon measurements of single-year Japanese tree rings from the first millennium BCE. Some have already been reported (e.g., Sakamoto et al. 2023), and the presenting samples filled in the gaps, consisting of tree rings from the 9th century BCE and the 5th to the 6th century BCE. In addition, we have attempted to detect 660 BCE events using two new samples to verify the dating by oxygen isotope ratio dendrochronology.
    This work was supported by JSPS KAKENHI Grant Number JP22H00026.
    
    Speaker: Prof. Minoru Sakamoto (National Museum of Japanese History)
  - 176
    
    Single-year radiocarbon measurements on trees from the United Kingdom 1 BCE – 330 CE
    
    The current radiocarbon calibration curve for the northern hemisphere, IntCal20, represents a major update of the previous calibration curve, IntCal13. Over the first half of the first millennium CE, IntCal20 is based on over 550 calibration datapoints, in comparison to IntCal13, which was based on just over 100. In general, the calibration data and, thus, the two curves follow each other closely. There is, however, a more appreciable divergence between c. CE 50 and c. CE 250. The reason that IntCal20 diverges from IntCal13 in this period is that it includes new data from two Japanese trees, which produce older ages than the current data from North American and European trees only during the late first and second centuries CE. The datasets are more compatible at later times, including with the single-year data on European trees.
    
    We present single-year measurements on Irish oak from across this period, including a replicate analysis of rings from the same tree measured independently at ETH Zürich, the University of Groningen, and the National Museum of Japanese History. This study aims to contribute towards providing reliable calibration for archaeologists working on European sites during this time frame, and attempts to investigate whether inter-laboratory variation may be the cause of the observed offsets.
    
    Speaker: Dr Michael W. Dee (University of Groningen)
  - 177
    
    Status and recent progress of the AMS system at NIES-TERRA
    
    The NIES-TERRA AMS facility, the NEC 5 MV tandem Pelletron AMS, was installed in 1995 and started operation in 1997 for various environmental studies. In 2015 and 2016, we made substantial improvements to the system, such as the installation of a new type of ionizer (multi-cathode source of negative ions by cesium sputtering, MC-SNICS), reconstruction of the beamlines, and exchange of related electronic instruments, as well as special repairs, including adjustments to the beamlines and exchange of the terminal bellows. For the past several years, we have focused on the small mass 14C measurements using a new system as well as the development of a small amount of graphite preparation system (Uchida et al., 2023a). Associated with the application of small mass 14C analysis, we have focused on compound-specific radiocarbon analysis of PAHs, lipid biomarkers, and black carbon in sediment, soil, and carbonaceous aerosol (Uchida et al., 2023b, Kumata et al., in press, Pavuluri et a., in press). In addition, recently, we started development of the 129I and 10Be measurements in cooperation with the MALT AMS facility at the University of Tokyo. In this conference, we present the status report of routine 14C measurements and preliminary reports and the progress of 129I measurements in our system.
    
    References: Uchida et al., 2023a, NIMB,536, 144-153, Uchida et al., 2023b, NIMB 538,64-74, Kumata et al., Radiocarbon, in press, Pavuluri et al., Radiocarbon, in press
    
    Speaker: Masao Uchida (NIES-TERRA AMS facility, National Institute for Environmental Studies)
  - 178
    
    The Establishment of East Asia Accelerator Mass Spectrometry Association
    
    Accelerator Mass Spectrometry (AMS) technique was emerged as a discipline in the 1970’s, after the demonstrating that tandem accelerators are suited to the detection of 14C in natural materials for radiocarbon age dating (14C/12C < 10E-12). Since then, over 50 rare isotopes at such low abundances, from tritium to curium, have been detected using accelerators of varying sizes. Methods are continually being developed for smaller facilities and for better isotope detection sensitivity. AMS applications are similarly growing, new areas including biofuel content evaluation, climate history studies, nuclear environmental monitoring and pharmaceutical micro dosing.
    The total number of world-wide AMS facilities has been more than 160, and early AMS laboratories were mainly built in the Americas and Europe. But in the past 20 years, AMS construction in East Asia has been on the rise, the number of AMS equipment has got to 54 in total, almost 1/3 of that in the world. The East Asia Accelerator Mass Spectrometry Symposia (EA-AMS) began 20 years ago as a compliment to the International AMS Conferences. And EA-AMS attracts specialists with diverse interests, from AMS application users to technique developers, to students just starting out in the field.
    To strengthen mutual cooperation and friendship between the East Asia AMS Labs, Prof Weijian Zhou from Institute of Earth Environment, CAS proposed to establish an Association of East Asia AMS, and the proposual was discussed in the final session in the EA-AMS9 meeting and received unanimous approval from all attending representatives. Dr. Zhao Xiaolei from Beijing Normal University was elected as the conference secretary general, with the assistance of Dr. Liu Qi from the Institute of Earth Environmentc CAS.
    The goals of EA-AMSA include but not limited to:
    - to jointly apply grants and funding from governments and institutions;
    - to promote effective cooperation among the East Asia AMS Laboratories in scientific research, in forms of both field exploration and laboratory experimentation;
    - to exchange samples for inter-laboratory comparison and reference materials for analytical technique development.
    - to expand social influence and seek various resources for our community.
    As proposed and discussed during the 9th Symposium of East Asia Accelerator Mass Spectrometry at KIST, we have agreed to form an association of the EA-AMS facilities to promote collaboration within our community. On 5th march, 2024, the association website had been online, we put up a webpage for our presence in the conference management system run by Chinese Academy of Sciences. The link is: https://eaams.casconf.cn/, more than 1/3 of the AMS labs in East-Asia area had feedbacked and put their information on the website. And all EA-AMS facilities are welcome to contact us to join EA-AMSA, to be listed on this web page. The historic and recent news regarding to EA-AMS and related activities had been posted.
    
    Speaker: Dr Qi Liu (Institute of Earth Environment, CAS)
    
    EAAMS Association Abstract.docx
  - 179
    
    A new 1 MV AMS facility at IGCAS in Guiyang, China
    
    Institute of Geochemistry, Chinese Academy of Sciences (IGCAS), has installed a universal 1 MV AMS in February 2022. Manufactured by National Electrostatics Corporation, the United States of America, it is equipped with a 40 cathodes MC-SNICS ion source, a 90° injection magnet (mass energy product 5 amu-MeV), a model 3SDH-1 pelletron accelerator, a 90° high energy analysis magnet (mass energy product 36 amu-MeV), a 90°, 1.00 meter radius electrostatic spherical analyzer, a 45° B/Be separation magnet (mass energy product 36 amu-MeV) and a 2 channel gas detector. It is designed for high precision measurement of isotopes 10Be, 14C, 26Al and 41Ca. A clean chemistry laboratory has been developed for 10Be and 26Al chemical processing of samples. In addition, a sample preparation laboratory with automatic graphitization equipment (Aeon CEGS 12X) has also been setup for carbon sample preparation. Chemical procedural blanks of all the three isotope ratios can be routinely lower than 5×10-15. Furthermore, performance data for 10Be, 14C and 26Al and machine background will be reported as well.
    
    Speaker: Yu Liu (Institute of Geochemistry, CAS)
    
    IGCAS-16th AMS abstract.docx
  - 180
    
    A new HVE 1 MV multi-element AMS system at IHEG-CAGS AMS lab in China
    
    A 1 MV Accelerator Mass Spectrometer(AMS) dedicated to measuring 14C as well as capabilities to measure 10Be, 26Al, 41Ca, 129I, was installed at IHEG-CAGS（Institute of Hydrogeology and Environmental Geology, Chinese Academy of Geological Sciences）in 2023. This multi-element AMS was developed by HVE and the results of an acceptance test demonstrated that its ability to achieve precision for 14C,10Be,26Al and 129I to 0.13,1.25,2.61 and 0.39% levels,with background values of 5.4×10-16, 1.4×10-15, 8.5×10-16 and 6.4×10-14 respectively.
    
    Speaker: Hui Zhang
  - 181
    
    Calculation of the rate of production of cosmogenic nuclides
    
    Calculate the production rate of cosmic nuclides in a certain place in the matter, use the flux of primary particles and secondary particles of particles reaching the earth's atmosphere, use software to simulate the process of particles bombarding objects, obtain the energy spectrum of particles and secondary particles at different depths, and calculate the production rate of different cosmogenic nuclides through the nuclear reaction cross-section data of the cross-section database, which is convenient for geologists to apply them to the calculation of the concentration of cosmic nuclides in the common terrain, and the model provides users with an effective method to study the production of cosmic nuclides on the earth's surface。
    
    Speaker: Dingxiong Chen (College of Physics and Technology, Guangxi Normal University, Guilin, Guangxi 541004, China)
  - 182
    
    Cosmogenic 32Si as a potential tracer for the global marine silicon cycle processes: A review
    
    Title: Cosmogenic 32Si as a potential tracer for the global marine silicon cycle processes: A review
    Authors: Haoxiang Zhong,1 Peng ZHOU,2,3 LI Dongmei 2
    1Guangzhou Maritime University, Guangzhou 510725, PR China;
    2South China Sea Ecological Center of Ministry of Natural Resources (MNR), Nansha Islands Coral Reef Ecosystem National Observation and Research Station, & Key Laboratory of Marine Environmental Survey Technology and Application of MNR, Guangzhou 510300, China;
    3Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai, 519000）
    Corresponding authors. E-mail addresses: samzhou2@126.com (P. Zhou). Tel.: +862089111586 (P. Zhou); Fax: +862084457983. †These authors contributed equally to this work.
    
    Abstract: Silicon is the second most abundant element (27.7%) after oxygen in the Earth's crust. It plays an important role in regulating primary productivity and carbon cycling in the oceans. Cosmogenic 32Si (a half-life of approximately 150 years) is the only long-lived radioisotope, which can be produced by cosmic rays impinging on atmospheric 40Ar and falling as precipitation on lands (partly into oceans through runoff) and oceans. 32Si is taken up by siliceous organisms (e.g., diatoms), partly recycled, and partly eventually transported to the seafloor as biogenic silica (BSi). This paper summarizes 32Si and silicon cycling studies in nearshore (including estuaries), continental shelf waters, and the open ocean. Recent studies have demonstrated that 32Si can independently constrain diagenetic processes controlling Si storage in marine sediments. Biogenic silica (BSiopal) is rapidly altered toauthigenic clay phases (BSiclay) to variable extents depending on depositional environment. In tropical sediments, 32Si is in mineral rather than biogenic (reactive) silica pools used to constrain the silica cycle. Coastal reactive Si burial rates are likely 20-30% higher globally than previously estimated. Tropical and subtropical deltas store 3.5–3.9 Tmol/yr of Si as authigenic clay(BSiclay), and temperate proximal coastal zones store ~1 Tmol/yr. Global sedimentary Si sink via reverse weathering reactions is 2 to 3 times the current estimates and exceeds the Southern Ocean siliceous ooze.
    Keyword: silicon-32; a cosmic-ray-produced radioactive nuclide; global marine silicon cycle; oceanography
    Funding: This research was funded by CAS Henan Industrial Technology Innovation & Incubation Center (2024123), by Science and Technology Development Foundation of South China Sea Bureau, Ministry of Natural Resorces of P. R. China (23YD03), the Fund of Key Laboratory of Global Change and Marine-Atmospheric Chemistry, Ministry of Natural Resources (MNR) (GCMAC202207).
    
    Speaker: 皓想仲 (广州航海学院)
    
    paper Cosmogenic 32Si as a potential tracer for the global marine silicon cycle processes A review.docx
  - 183
    
    Development of a numerical model of BINP AMS facility
    
    Routine $^{14}$C analysis of user samples is performed with two accelerator mass spectrometers at AMS Golden Valley: BINP AMS facility, developed by Budker Institute of Nuclear Physics, Russia and MICADAS-28 facility, developed by IonPlus AG, Switzerland. The laboratory has international index GV and provides $^{14}$C analyses of various samples: collagen, cellulose, humic acids, carbonates from sediments etc. The main focus of the laboratory is to determine the age of archaeological artifacts.
    BINP AMS is currently undergoing modernization, the main objectives of which are to increase the reliability of operation and improve the performance of this installation. One of the key conditions for the success of this upgrade is a detailed simulation of the beam dynamics in an accelerator section. A numerical model of the installation was built, and based on the simulation results, the modernization of some ion-optical elements was proposed.
    
    Speaker: A.V. Ivanov (Budker Institute of Nuclear Physics)
  - 184
    
    Discovery and correction of loess susceptibility decline relying on cosmogenic 10Be record in loess
    
    Attributed from combination of AMS-measured cosmogenic 10Be record in loess with RTA mathematical trace method, decline of loess susceptibility in the Xifeng 0-870Ka profile is unexpectedly revealed by the uptilting of the RTA-reconstructed 0-870Ka atmospheric 10Be production rate Pr curve and is indubitably certificated by high similarities R2≈0.9 (or r=0.94) shown in the linear regression between both measured or both corrected 10Be concentration Be(M) and the susceptibility SUS(M) in the same sample all the time within 0-870Ka interval. Then, the “inversion correction” method (“μcorrection”) of loess susceptibility decline is developed to recover the declined susceptibility and the “Indirect Verification of Golden Standard” method is adopted to assess accuracy of the μ-corrected Xifeng 0-870Ka loess susceptibility.
    The μ-correction has shown that the average decline amount (or average correction amount) of the Xifeng 0-870Ka loess susceptibility is as high as 87%. And the “Indirect Verification of Golden Standard” has indicated almost complete similarity r = 0.99 and acceptable relative standard deviation of point to point difference RSD = 4.43% between the verifying curve related to the Golden Standard of Verification and the examined curve related to the recovered susceptibility, which inconceivably manifests that decline rule of loess susceptibility accumulated in the specific Xifeng 0-870Ka profile is in almost complete similarity (r=0.9914) to the decay rule of the 10Be atoms due to unknown mechanism.
    
    Speaker: Prof. 茂柏陈 (Institute of Earth Environment,CAS)
  - 185
    
    Distribution of I-129 in the terrestrial environment after the Fukushima Daiichi Nuclear Power Plant accident
    
    A significant amount of radioactive material was released　into the environment after the accident　at the Fukushima Daiichi Nuclear Power Plant (FDNPP) on March 11, 2011, with atmospheric emissions commencing on March 12 and peaking during March 15–16 and 20–22 (TEPCO, 2012). Anthropogenic sources such as nuclear-fuel reprocessing plants had already increased the I-129 level in the environment above its natural background (I-129/I-127 = 1.5 × 10 $^{–12}$; e.g., [1]). Total amounts of radionuclides discharged into the atmosphere were estimated to be 8.1 GBq for I-129 (T$_{1/2}$ = 1.57 × 10$^{7}$y) [2] and 120 – 200 PBq for I-131 (T$_{1/2}$ = 8.02 d) [3] released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. Although the accident-derived I-131 in soil extinguished in a few months, the long-lived I-129 can be used as a tracer to retrospectively infer the level of I-131. We mentioned at AMS-15, the I-129/ I-131 atomic ratio in 5-cm-long surface soils of Fukushima area for reconstruction of the I-131 deposition using the long-lived I-129, average ratio of I-129/ I-131 was estimated to be 26.0 ± 5.7 corrected to the time of earthquake, on March 11, 2011[4].
    Several years were passed, I-129 released into the environment exists through repeated deposition and resuspension. We investigated the concentration of I-129 and isotopic ratio of I-129/ I-127 in river water in Fukushima Prefecture, the sampling was conducted at five sites on the Niida-River, once per year, from 2014 to 2020. Sample measurements were performed using AMS at the MALT, The University of Tokyo [5] until 2015 and at UTTAC, The University of Tsukuba [6] thereafter. As a results, the I-129 concentrations were in the range (0.35-2.8) × 10$^{8}$ atoms L$^{-1}$ and the I-129/ I-127 ratio was (0.51-4.6) × 10$^{-8}$. Generally, values are high at the earliest sampling time and appear to have stabilized since then.
    
    This work was supported by the KAKENHI under grant Nos. of 15H02340, 19H04252 and 22H02001.
    
    [1] J. E. Moran, et al., Environ. Sci. Technol. 33 (1999) 2536–2542.
    [2] X. L. Hou, et al., Environ. Sci. Technol. 47 (2013) 3091–3098.
    [3] M. Chino et al., J. Nucl. Sci. Technol. 48 (2011) 1129–1134.
    [4] K. Sasa, et al., AMS-15 (2021) A6.05.
    [5] H. Matsuzaki et al., Nucl. Instrum. Meth. Phys. Res. B 361 (2015) 63-68.
    [6] K. Sasa et al., Nucl. Instrum. Meth. Phys. Res. B 437 (2018) 98-102.
    
    Speaker: Dr Kimikazu SASA (University of Tsukuba)
  - 186
    
    Investigating the Iodine-129 levels of Seawater and Coral Core in the West Philippine Sea
    
    Iodine-129 is a long-lived radionuclide introduced into the environment through human nuclear activities (HNAs) such as nuclear accidents, nuclear fuel reprocessing, and nuclear weapons testing. It is considered an excellent oceanographic proxy and tracer of HNA-derived radionuclide due to its biophilic nature, conservative behavior, and sufficiently long residence times in the ocean.
    Here, we present data from 119 seawater samples from all over the Philippines and one coral core from the WPS analyzed for I-127 and I-129 concentrations and ratios using inductively coupled plasma mass spectrometry (ICP-MS) and accelerated mass spectrometry (AMS) to provide a more extensive spatial and geographical picture of the I-129 levels in the WPS.
    
    Results show that 129I/127I ratios of WPS seawater samples occur at around 3.22 to 5.87 x 10-11, roughly 49-72% greater than those from other parts of the Philippines. Moreover, findings suggest that the elevated levels previously detected in corals and seawater have been sustained until now and are isolated only in the WPS. Notably, the calculated I-129 concentration in both seawater and coral samples are 1-2 magnitudes higher than the pre-nuclear level in the ocean, which indicate that the source of elevation in the study area is anthropogenic likely coming local sources around the region.
    
    We expect our current work to provide updated information on 129I concentrations in the WPS, which is crucial for understanding potential health risks, threats to the marine environment, and nuclear safety and security. Data generated from this study can serve as a basis for policy makers in crafting recommendations aimed to mitigate risks associated with radioactive materials in the marine environment.
    
    Speaker: Angel Bautista VII (DOST - Philippine Nuclear Research Institute)
    
    I-129 levels of Seawater and Coral Core in the WPS.docx
  - 187
    
    Investigating the North Equatorial Current bifurcation of nuclear bomb radionuclides from the Pacific Proving Grounds through iodine-129 in coral cores along the East Philippine coast
    
    In the Western Equatorial Pacific, a significant portion of ocean radioactivity is contributed by aboveground nuclear weapons tests (ANWTs) conducted in the Pacific Proving Grounds (PPG) during the 1950s. These radioactive materials can reach the Philippines through the North Equatorial Current (NEC), which splits into the Kuroshio (northward) and Mindanao (southward) currents upon hitting the country’s eastern coast. Iodine-129, a long-lasting fission product (t1/2 = 15.7 Ma), is used as a tracer for ANWTs and other human nuclear activities (HNAs) due to its well-known behavior in the environment. While previous 129I studies have focused on the northern Philippines, little is known about the southern regions affected by the NEC bifurcation. To investigate this, we present coral 129I/127I time series records from two sites in the eastern coast of the Philippines, one each from locations along the Kuroshio (i.e., referred to as Calaguas) and Mindanao (i.e., referred to as Cantilan) currents. 127I and 129I Measurements were done using inductively coupled plasma mass spectrometer (ICP-MS) and accelerator mass spectrometer (AMS), respectively. Results show that both sites exhibit low 129I/127I ratios before the year 1950 (i.e., natural 129I), followed by distinct bomb peaks between the 1950s to 1960s from ANWTs, then a steady increase of about (0.4 to 0.5) x 10-12 per year from 1960s onwards from nuclear fuel reprocessing (NFR) interspersed with distinct peaks from historical nuclear accidents such as the Chernobyl and Fukushima accidents. Mathematical simulations that were performed to determine the quantitative relationships between the 129I signals in the coral samples from both sites and these HNAs show that 129I from ANWTs were transported and divided almost equally and between the north and south bifurcations of the NEC. This study is instrumental for understanding better the past impacts of HNAs and the relevant complex oceanographic processes in the great Pacific Ocean.
    
    Speaker: Mr Jeff Darren Valdez (DOST - Philippine Nuclear Research Institute)
    
    Abstract_AMS16_JDGValdez_2.docx
  - 188
    
    Radiocarbon dating of modern marine organisms living in hadal trench
    
    Hadal trenches (6000-11000 m) constitute 45% of the ocean depths range and have the ecology of the deepest places on earth. The understanding of the life history of hadal trench organisms is limited due to the lack of a proper dating method. Though radiocarbon has the potential for dating modern organisms in trenches, the lack of a 14C dating method limited the application of 14C in marine organisms. Here we will show the 14C dating method for modern hadal organisms by the example of amphipods. First, the radiocarbon tracing study reveals that the organic carbon of hadal amphipods mainly comes from the production in the surface water. Then a synthetic curve for the 14C variation in the West Pacific Ocean (WPO) for the past 70 years was built up by the data of proxy of 14C content in surface water. The apparent ages of amphipods' muscle tissues are calibrated according to the WPO curve. These results indicate greater longevity of hadal amphipods than the ones in shallow water, which is consistent with the ages estimated by the body length and growth rate. The relation between the apparent age and real age of amphipods needs further interdisciplinary studies. This method can be applied extensively to marine organisms in the deep sea, whose organic carbon source also comes from the production in surface water.
    
    Speaker: Ning Wang (State Key Laboratory of Isotope Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China)
  - 189
    
    Report on the on-site acceptance tests of the 1MV multi-element AMS system at Beijing Normal University
    
    Beijing Normal University acquired a 1MV multi-element AMS system from High Voltage Engineering Europa; the system is now commissioned after some delay. This advanced 1MV system is uniquely configured to accommodate efficient transmission of all elements from light to heavy, including an additional detector line dedicated to 10Be detection with overall beryllium ion transmission efficiency matching those of 5-6 MV systems. For the main detector line, both the low- and high-energy magnet boxes are electrically insulated so that a rapid sequential isotope selection mode can be used for data acquisition, in measurements of up to 10 different actinide isotopes at 1 Hz rate. In this report, all data (10Be, 14C, 26Al, 41Ca, 129I, 236U, 239,240Pu) from the recently completed on-site acceptance tests are presented, with selected aspects discussed in more details.
    
    Speaker: Dr XIAOLEI ZHAO (BEIJING NORMAL UNIVERSITY)
    
    20240608 - BNU-AMS OSAT Report.docx
  - 190
    
    Status of low-energy AMS detection of Iodine-129 at CNA: performance and background correction
    
    $^{129}I (T_{1/2} = 15.7 My)$ is present in all environmental compartments and has a very conservative behaviour in water. Its presence in the environment is mainly due to the nuclear fuel reprocessing plant discharges, whose history is relatively well-known. These characteristicsenter code here make of it an excellent hydrological tracer. For this and other applications, $^{129}I$ is one of the radionuclides most frequently measured by Accelerator Mass Spectrometry.
    $^{129}I$ measurements are routinely performed at CNA (Sevilla, Spain) by a 1MV AMS system manufactured by High Voltage Engineering Europe (HVEE, The Netherlands) in 2005. Charge state selection after acceleration has evolved from 4+ to 3+ and now to 2+, especially after the stripping gas change from Ar to He, which has provided a strong increase in the accelerator transmission up to more than 40% in this last charge state.
    The instrumental background level has not changed sensitively after the last stripper gas and charge state selections, showing typical isotopic ratios of $^{129}I/^{127}I=2-3x10^{-13}$. This background is caused by different effects, including contamination and interference from neighbouring isotopes as $^{127}I$. The influence is especially relevant when measuring samples with low $^{127}I^{2-}$ currents, as the contamination makes the isotopic ratios increase. In order to carry out a complete subtraction of the background, a double correction is carried out at CNA, based on the continuous analysis of instrumental blanks with different AgI/Nb proportions, which present a range of $I^{-}$ currents and isotopic ratios. In this presentation, the different experiments performed for the measurement optimisation as well as the background subtraction procedure will be presented.
    
    Speaker: Victoria Lérida-Toro (Centro Nacional de Aceleradores)
    
    AMS-16_abstract_VLT_JML2.docx
  - 191
    
    Status of the XCAMS facility at Tianjin University
    
    The compact 14C AMS system extended for 10Be and 26Al (XCAMS) has been installed at Tianjin University for 7 years already, since October 2017. More than seven thousand samples have been successfully measured and analyzed. The cosmogenic nuclides of 14C, 10Be and 26Al have been widely applied to related fields such as earth systems and environmental sciences. The system was gradually smoothed and optimized based on a series of standard, blank and real samples measurement, based on these measurements and applications. On the other hand, two sets of automated graphitization devices were purchased to meet the requirement of 14C measurement for increasing applications. The current experimental conditions, routine measurements of nuclides, optimization of methods, experimental results and outlook of the XCAMS at Tianjin University will be briefly presented in this paper.
    
    Speaker: Mr Kejun Dong (Tianjin University)
  - 192
    
    Status report of JAEA-AMS-TONO
    
    In the Tono Geoscience Center, Japan Atomic Energy Agency (JAEA), the investigation of deep underground environments for R&D programs related to the geological disposal of High-Level Radioactive Waste (HLW) has been performed by using various dating systems, including Accelerator Mass Spectroscopy. The JAEA-AMS-TONO facility owns three accelerator mass spectrometers (AMS). Two of these are for measuring actual samples, and one is a test device for the development of an ultra-compact AMS for measuring carbon-14. These AMSs are used to carry out scientific research into deep geological formations carried out by the organization, as well as to measure the age of requested samples under the facility utilization system.
    
    The two AMSs for measuring actual samples that can be used for dating are JAEA-AMS-TONO-5MV (15SDH-2 manufactured by NEC, maximum acceleration voltage 5.0 MV) and JAEA-AMS-TONO-300kV (4103Bo-2 manufactured by HVEE, maximum acceleration voltage 300 kV), and both can measure four nuclides; carbon-14 ($^{14}$C), beryllium-10, aluminum-26, and iodine-129. Additionally, using the JAEA-AMS-TONO-5MV, we are developing technology for measuring chlorine-36 ($^{36}$Cl), which is useful for dating underground water, and investigating methods for removing sulfur using cells. The ultra-compact AMS for $^{14}$C measurement is a device that uses ion channeling to separate molecules of the same mass and is currently undergoing demonstration tests with the aim of becoming a general-purpose $^{14}$C measurement device.
    
    Furthermore, sample preparation techniques have been improved for $^{36}$Cl and small-mass $^{14}$C measurements by the AMSs. In our study, the small-mass graphitization was performed by a third-generation automated graphitization equipment (AGE3, IonPlus AG).
    
    Speaker: Dr Akihiro Matsubara (PESCO Co., Ltd)
  - 193
    
    Towards AMS measurements of Nb-91, Nb-94 and Mo-93 produced in fusion environment
    
    One of the main advantages of nuclear fusion in comparison to fission is that any radioactive waste produced is future fusion reactors is expected to be low-level waste (LLW) at least 100 years after the end of its operation. The activation of the structural material would be caused by the expected high fluences of high-energy neutrons (14.1$\,$MeV) produced by the deuterium-tritium fusion reaction. In order to confirm that these materials will meet the LLW criteria, the simulations of the production of radionuclides must be validated experimentally activating them with much lower neutron fluences from the same reaction. Such fluences are currently available using research fusion reactors and accelerator-based neutron generators. One example is the recent campaign of irradiation in the Joint European Torus (JET) reactor at the Culham Centre for Fusion Energy [1]. While some of these radionuclides can be experimentally measured by radiometric techniques, such as $\gamma$-spectrometry or liquid scintillation counting, for most long-lived radionuclides the expected activities are below the detections limits of these techniques. Three examples are $^{91}\mathrm{Nb}$, $^{94}\mathrm{Nb}$ and $^{93}\mathrm{Mo}$, which would be produced in molybdenum-containing materials, like stainless steel 316.
    
    The main challenge for the measurement of these radionuclides by accelerator mass spectrometry (AMS) is the interference caused by their stable isobars: $^{91}\mathrm{Zr}$ in the case of $^{91}\mathrm{Nb}$; $^{94}\mathrm{Zr}$ and $^{94}\mathrm{Mo}$ in the case of $^{94}\mathrm{Nb}$; and $^{93}\mathrm{Nb}$ in the case of $^{93}\mathrm{Mo}$. The Ion-Laser InterAction Mass Spectrometry (ILIAMS) setup of the 3-MV-AMS facility at the University of Vienna, VERA (Vienna Environmental Research Accelerator) has already proven its capabilities to deal with this challenge for several other radionuclides [2]. This setup is based on the selective photodetachment of the anions with photon energies capable of suppressing the stable isobar anion, without doing the same for the radionuclide of interest. Preliminary studies show that laser photodetachment with a 355 nm laser would allow measurements of $^{91,94}\mathrm{Nb}$ when selecting the $\mathrm{NbO}_3^{-}$ anion for injection into the accelerator, suppressing both $\mathrm{ZrO}_3^{-}$ and $\mathrm{MoO}_3^{-}$ anions. On the other hand, $\mathrm{NbO}_2^{-}$ anions get detached by laser light with a wavelength of 637 nm, but do not affect $\mathrm{MoO}_2^{-}$ anions, which makes this setup suitable for $^{93}\mathrm{Mo}$ measurements.
    
    [1] Packer, L.W. et al., (2021), "Technological exploitation of the JET neutron environment: progress in ITER materials irradiation and nuclear analysis", Nuclear Fusion 61, 116057
    
    [2] Martschini, M. et al., (2022), "5 years of ion-laser interaction mass spectrometry - status and prospects of isobar suppression in AMS by lasers", Radiocarbon 64, 555-568
    
    Speakers: Carlos Vivo-Vilches (University of Vienna, Faculty of Physics, Isotope Physics, Vienna, Austria) , Martin Martschini (University of Vienna, Faculty of Physics, Isotope Physics, Vienna, Austria)
    
    VivoVilches_etal-AMS16.pdf
  - 194
    
    A decade of 1MV accelerator mass spectrometry in Romania – expanding the range of measurable isotopes
    
    In Romanian scientific research, there was already vast experience in the field of accelerator mass spectrometry. In 2012, this research field received a strong development boost when a new Cockcroft Walton type 1 MV HVEE tandetron AMS system was installed at the National Institute for Physics and Nuclear Engineering (IFIN-HH), Bucharest. After the acceptance tests carried out by High Voltage Engineering Europa (HVEE), AMS system was commissioned only for isotopes 14C, 10Be, 26Al, and 129I.
    In parallel with the routine isotope measurements, in the last 10 years we have expanded the range of measurable isotopes at our AMS machine. Thus, new procedures have been developed that allow high-sensitivity measurements of boron, tritium and plutonium (239, 240, 242). These developments will enable new applications using these isotopes at our AMS facility.
    Tritium is the primary fuel in nuclear fusion and its behavior inside the tokamak, as well as its contamination of its walls, are intensively studied in the Euratom program. Tritium has applications in medicine as a marker, as well as in environmental science. By determining the concentration of tritium in tree rings near nuclear facilities, the history of nuclear pollution can be established.
    Determining very low concentrations of boron in graphite is useful in classifying graphite used as a moderator in nuclear fission reactors, particularly during decommissioning procedures of such installations and for the preparation of new neutron moderators.
    Plutonium is an important tracer in monitoring nuclear pollution in the environment and in determining the origin of radioactive materials based on the isotopic ratio of plutonium, particularly when discerning the illicit nature of certain materials. Additionally, other applications of plutonium are found in fields such as astrophysics, archaeology, geology, medicine, and others.
    
    Speaker: Dr Alexandru Razvan Petre (Horia Hulubei National Institute for R&D in Physics and Nuclear Engineering)
    
    abstract Alexandru Petre.pdf
  - 195
    
    Al-26 and Be-10 measurements at DREAMS, HZDR – an update
    
    DREAMS, the DREsden AMS-facility, in operation since 2011 is based on a 6 MV Tandetron (manufactured by High Voltage Engineering Europa) and shared with other research groups at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR). DREAMS has been applied primarily in the measurement of cosmogenic isotopes. However, with radiocarbon not in the mix, a focal point has always been the routine measurement of $^{10}$Be and $^{26}$Al. Over the years, we have improved the AMS facility in various aspects for increased performance, particularly for these two isotopes. In this report we will give details on the performance of our routine measurements over the past 12 years of operation with a focus on the impact of methodological developments since 2021. We will present our recent investigations and improvements on the performance of $^{10}$Be and $^{26}$Al measurements, highlight key challenges remaining, and point to potential future optimisations. Finally, we have reinvestigated our in-house standard material for $^{26}$Al against the standards provided by Nishiizumi (2004) – “KNSTD” - to ensure compatibility of reported results with exposure-age calculators such as CRONUS-Earth.
    
    Speaker: Georg Rugel (Helmholtz-Zentrum Dresden-Rossendorf)
  - 196
    
    BAMS: a new compact 14C AMS system at CEDAD (Centre of Applied Physics, Dating and Diagnostics), University of Salento for biomedical and pharmaceutical research
    
    In the frame of the PRP (Pathogen Readiness Platform) project funded through the post-pandemic Italian plan for recovery and resilience (PNRR: Piano Nazionale Ripresa e Resilienza) the installation of a new compact Accelerator Mass Spectrometry system is planned at CEDAD (Centre of Applied Physics, Dating and Diagnostics), Department of Mathematics and Physics “Ennio de Giorgi”, University of Salento. The new system is expected to provide an essential asset for drug-development by Biomedical Accelerator Mass Spectrometry (BAMS) which will be adopted as a powerful bio-analytical method for human studies in the areas of pharmacology and toxicology. The new system will assist classic DMPK (Drug Metabolism and Pharmacokinetics) studies where 14C is used as a tracer in drug development for evaluating the distribution and binding of novel drug candidates allowing the use of low-level drug doses. Microdosing and microtracing will result in a more cost and time effective drug development pipeline. For this application the main requested features for the AMS system are: 14C sensitivity at least in the 10-15 range (14C/12C ratio), uncertainty better than 0.3% and 0.5 % for solid and gas samples, respectively and high sample throughput.
    The new set-up will be formed by a new dedicated 14C AMS system manufactured by High Voltage Engineering Europa Mod. HVEE 4102Bo operated at a terminal voltage of 210 kV. The system is based on a multicathode S-110C hybrid ion source capable of accepting both solid and gas samples handled by a dedicated gas interface. The tandem accelerator is operated by a vacuum insulated power supply, incorporated into the vacuum vessel and operating at a maximum terminal voltage of 210 kV. The system is equipped with permanent magnets ensuring reduced power consumption (2.5 kW) and is equipped with a dedicated system for automatic tuning and data analysis. The reduced footprint of the machine (approximately 3 x 2.8 m) will allow its installation in the hall where the Tandetron accelerator (HVEE Mod. 4130HC) is installed and in operation.
    The general features of the system are presented as well as preliminary results obtained during preliminary tests and future projects.
    
    Speaker: Gianluca Quarta (University of Salento)
  - 197
    
    CAMS/LLNL Cs Sputter Ion Source Operating Conditions for C–Production
    
    Over the last several decades what was originally a General Ionex Corp. Model 846 high-intensity multi-sample negative ion source has been heavily modified to become what is now the Center for AMS at Lawrence Livermore National Laboratory’s (CAMS/LLNL) general use Cs Sputter Negative Ion Sources. One of these CAMS/LLNL ion sources currently in operation at CAMS is used predominately for natural level 14C measurements using the AMS system based around the CAMS HVEC FN accelerator. In order to optimize the operations of this ion source for such 14C measurements, we have delved into the performance of the ion source under reasonable variation of various source parameters. The results obtain in these studies will be presented and discussed.
    
    Speaker: Dr Tom Brown (Center for AMS, LLNL USA)
  - 198
    
    Enhanced Sensitivity in the Detection of 129I Using Accelerator Mass Spectrometry at the University of Notre Dame
    
    The isotope $^{129}$I, with a half-life of 15.7 million years, serves critical roles ranging from an environmental tracer of fission products to a significant marker in nuclear astrophysics. Due to its low natural terrestrial abundance (approximately one part per trillion), accelerator mass spectrometry (AMS) offers a robust method for its detection, accurately distinguishing the $^{129}$I signal from the stable isotope $^{127}$I in aqueous samples. Recent advancements in our beamline configuration and time-of-flight detection systems at the University of Notre Dame’s Nuclear Science Laboratory have significantly increased our measurement sensitivity for $^{129}$I. This study presents a comprehensive analysis of reference standards, highlighting the enhanced detection capabilities achieved. The modifications to the AMS system, improved time-of-flight resolution, detailed analysis results, and implications for environmental and astrophysical applications will be discussed. In particular, we will highlight our collaboration with the nuclear theory group at Notre Dame, and how future experiments may be used to build upon advancements made by Wang et al. (2021, 2023) on the understanding of certain astrophysical processes (Wang, X., Clark, A. M., Ellis, J., et al. 2021, r-Process Radioisotopes from Near-Earth Supernovae and Kilonovae), (Wang, X., Clark, A. M., Ellis, J., et al. 2023, Proposed Lunar Measurements of r-process Radioisotopes to Distinguish the Origin of Deep-sea $^{244}$Pu).
    
    This work is supported by the National Science Foundation Grant No. NSF PHY-2011890.
    
    Speaker: David Lund (University of Notre Dame)
  - 199
    
    Exploration of 41Ca dating
    
    The cosmogenic isotope 41Ca with a half-life of 99,000 years can serve as a dating tracer for environmental processes. Employing the atom-trap trace analysis (ATTA) method, we realized a precision of 10% on the 41Ca/Ca ratio at the level of 10−17 with the lowest measured 41Ca/Ca ratio standing at (1.99 ±0.34) ×10−17.
    For 41Ca exposure dating, we have developed a 41Ca production model, which is based on the CRONUSscalc program and LSDn scaling model, enabling the calculation of instantaneous 41Ca production rates at any given geographical location and historical period. Integrating 41Ca/Ca measurements and the 41Ca production rate, we conducted a demonstration application of 41Ca exposure dating of glacial moraines in the eastern Tibetan Plateau.
    Regarding burial dating, we are exploring its feasibility for marine environmental samples. We have mapped the global spatial distribution of 41Ca in the ocean and conducted tests on a series of foraminifera and coral samples.
    
    Speaker: Weiwei Sun (University of Science and Technology of China)
  - 200
    
    Iodine-129 as an environmental tracer of salinity and freshwater leachates in Boracay Island, Philippines
    
    Iodine-129 is a long-lived radioisotope considered an excellent environmental tracer due to its unique and conservative properties. Groundwater and seawater samples collected from Boracay island, southwestern Philippines, in April 2022 were analyzed for iodine-129, iodine-127, and stable isotopes of H and O. One groundwater sample with elevated salinity suspected due to seawater intrusion was proven to be caused by other factors as indicated by low 129I/127I supported by stable H and O isotopes. Moreover, two seawater samples had relatively low I-129 values, indicating possible freshwater dilution from a nearby treatment plant. In general, 129I/127I ratios measured in seawater were 10 to 14 times higher than prenuclear level (I129/I127(prenuclear) = 1.50 x 10-12), while groundwater 129I/127I ratios were measured to be 1.5 to 14 times higher than prenuclear level indicating effects of anthropogenic inputs. Since no known nuclear activities are recorded in the country, the anthropogenic I-129 must have originated from transboundary sources and transported by atmospheric deposition and ocean currents. Our results demonstrate the use of I-129 as a tracer of anthropogenic inputs in the water resources of Boracay island and also provide essential data in evaluating the possible effects of various NPPs along the seas of the Philippines in the future.
    
    Speaker: Mr Jeff Darren Valdez (DOST - Philippine Nuclear Research Institute)
    
    Abstract_AMS16_JDGValdez.docx
  - 201
    
    MALT-AMS：current activity after 30 years history
    
    MALT (Micro Analysis Laboratory, Tandem accelerator, The University of Tokyo) is an ion beam analysis facility consist of a negative ion source, injection analysis system, a 5MV tandem accelerator, a high energy analysis system, and beam courses each dedicated for ion beam analysis method. Among various beam analysis techniques, AMS (Accelerator Mass Spectrometry) is one of most important. The completion of MALT was in 1993. After the early beam test, the formal operation had started in 1995. Since then, it has been 30 years. This presentation will look back the history of MALT-AMS as well as report current activity.
    
    Speakers: Hiroyuki Matsuzaki (The University of Tokyo) , Ms Yoko Tsuchiya (The University of Tokyo)
    
    Matsuzaki_MALT_status.pdf
  - 202
    
    Performance report of the NTUAMS Lab during 2020-2024
    
    Hong-Chun Li*, Tzu-Tsen Shen, Satabdi Misra, Mitwally E. M. A.
    Department of Geosciences, National Taiwan University, Taipei 106319, Taiwan
    
    The AMS 14C dating Lab (Lab code is NTUAMS) in the Department of Geosciences at the National Taiwan University was established in 2012 equipped with a 1.0 MV Tandetron Model 4110 BO-Accelerator Mass Spectrometer (AMS) made by High Voltage Engineering Europa B.V. (HVE) in Netherlands. Since 2013, the lab has been providing 14C dating on organic and inorganic carbon samples including sediment and peat cores, stalagmites, foraminifera shells, bones, etc. We have built up three graphitization lines and a home-made semi-automatic EA-graphitization system for producing graphite. In order to avoid 2Li+ interference, the AMS is running 14C3+ mode with a transmission rate of 18% instead of 14C2+ which has a transmission rate of 48%. For each batch of samples, at least three OXII, three background samples (BKG made from anthracite for organic carbon and NTUB made from limestone for inorganic carbon) and two known-age inter-comparison samples (distributed by University of Glasgow) were measured together. This study presents a total of 5050 graphite targets measured during 2020~2024. The target numbers measured in 2020, 2021, 2022, 2023 and 2024 (four months) were 1356, 1357, 1164, 1159 and 435, respectively. From the data results, the summaries of OXII, BKG, NTUB, inter-comparison samples are given. The AMS has a blank 14C/12C ratio between 5e-16 and 2e-15. The 14C/12C ratios of OXII, BKG and NTUB are about 1.2e-12, 6e-15 and 4e-15, respectively. The measured ages of the inter-comparison samples agree well with their consensus values. A recent study of our lab on a known historic archaeological site in central China illustrates that the 14C ages of bone collagen and charcoal samples not only agree well with the late Shang dynasty, but also time difference from the two sub-sites in the area. With our reliable 14C dating facility, many applications in geology, archaeology, environment and synthetic industry have been done.
    
    Keywords: NTUAMS Lab, standard and background, inter-comparison samples, semi-automatic graphitization system, applications
    
    Speaker: Chun-Yen Chou ( Department of Geosciences National Taiwan University)
    
    Report of the NTUAMS Lab for AMS 16 Chou et al.pdf
  - 203
    
    Preliminary tests of the new 6MV-AMS in IGGCAS，Beijing
    
    A new 6 MV tandem accelerator entered the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS), Beijing in 2023. Similar model accelerators (18SDH-2, National Electrostatics Corp., USA) were previously installed in Tsukuba, Japan and Ansto, Australia in 2014. Drawing from these prior experiences, the IGG accelerator was specifically designed for multi-nuclide AMS measurements, focus on high-sensitivity detection of 10Be, 14C, 26Al, 36Cl, 41Ca, and 129I.
    
    Following one year of construction and conditioning efforts, the IGG-AMS is now capable of conducting accurate carbon-14 measurements (~0.3% for IAEA series standards) with background levels below 0.2 pMC. Sample preparation involves the use of an auto-graphitization device called CEGS from AEON Crop., USA – marking its first introduction into China.
    
    For beryllium-10 analysis, the high terminal voltage allows direct separation of both beryllium-10 and boron-10 in the gas detector without relying on degrader foil technique assistance. Initial tests using beryllium-10 standards indicate that we are approaching parameters to achieving high overall efficiency and counts per second (CPS). However, further improvements are necessary to enhance the performance across all isotopes.
    
    Speaker: 实陈 (中国科学院地质与地球物理研究所)
    
    摘要.docx
  - 204
    
    Readout system of pixelated silicon detector for compact AMS
    
    $^{14}$C is one of the most useful isotopes and has been widely utilized for radiocarbon dating in various fields, such as archaeology, environmental science, geology, and space and earth sciences. Yamagata University (YU) installed a compact accelerator mass spectrometry (YU-AMS, Fig. 1) system in March 2009 [1]. Two automated graphitization lines, AGL-I and AGL-II, were also installed in YU dedicated to $^{14}$C measurement [2,3]. The AMS system is based on a 0.5 MV Pelletron accelerator (CAMS) developed by National Electrostatics Corporation. This is the first CAMS system to be installed in a university in Japan.
    　Recently, we have developed a pixelated silicon detector (PSD) for the position-sensitive detector on a focal plane of YU-AMS system as shown in Fig. 2 [4]. The active area and thickness are 16 × 16 mm$^2$ and 320 µm, respectively. The active area is segmented into 64 channels (8 × 8) each with an electrode pad of 2 × 2 mm$^2$. The characteristics of the PSD were investigated by irradiating $\alpha$ particles from an $^{241}$Am source. The energy resolution of 22.4 keV (FWHM) is obtained for 5.486 MeV $\alpha$ particles. The PSD was installed at the focal plane of the beamline of the YU-AMS system and its performance was investigated using $^{14}$C beam. The two-dimensional count map of the $^{14}$C beam was successfully obtained by the PSD. The PSD can be utilized for not only the tuning of the optimal parameters of the AMS system such as low- and high- energy bending magnets but also for the monitoring of the $^{14}$C beam during $^{14}$C measurements. We are currently developing the new low-noise preamplifier and data acquisition system of the PSD. It is expected that the performance of the newly developed PSD and the readout system enable effective beam diagnostics, and hence, the precise isotope measurements in other AMS facilities including the positive ion mass spectrometry (PIMS) systems. In this conference, we will present the recent development of the PSD.
    
    References
    [1] F. Tokanai, K. Kato, M. Anshita et al., “Compact AMS system at Yamagata university”, AIP Conf. Proc. 1336 (1), 70–74 (2011).
    [2] F. Tokanai, K. Kato, M. Anshita et al., “Present status of YU-AMS system”, Radiocarbon 55 (2–3), 251–259 (2013).
    [3] T. Moriya, M. Takeyama, H. Sakurai et al., “Status of the AMS system at Yamagata University”, Nucl. Instrum. Methods Phys. Res. B 439, 94–99 (2019).
    [4] F. Tokanai, T. Moriya, M. Takeyama et al., “Development of pixelated silicon detector for AMS study”, Nucl. Instrum. Methods Phys. Res. B 552, 165353 (2024).
    
    Speaker: Dr Mirei Takeyama (Yamagata University)
    
    AMS-16_abstract_fig.pdf
  - 205
    
    Study on the migration behaviour of Fukushima accident-derived I-129 from land area to the marine environment
    
    The March 2011 accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in Japan resulted in the massive release of high-volatility fission products, including $^{129}$I (8.1 GBq) and $^{131}$I (120–160 PBq). The long-lived $^{129}$I (T$_{1/2}$ = 15.7 million years) is one of the important radionuclides that we need to evaluate its migration behaviour from Japan’s land area to the marine environment because of its relatively high chemical reactivity, biological concentration in the marine ecosystem, and affinity for the thyroid gland although it is less radiologically harmful than the short-lived $^{131}$I (T$_{1/2}$ = 8.02 days). The present study aimed to evaluate the following three points: 1) the source and the discharge of particulate $^{129}$I in the Niida River, 2) $^{129}$I distribution in the marine sediment around the mouth of the Niida River, and 3) $^{129}$I distribution in the seawater and the marine organism in an area close to the FDNPP. In the Niida River system where the upstream is in the relatively high-contaminated area located 30–40 km northwest of the FDNPP, total suspended solids (SS) each month from December 2012 to January 2014 were continuously collected at the Haramachi site (5.5 km upstream from the river mouth) of the downstream river by installing the time-integrative SS sampler. Marin surface sediments (0–3 cm depth) were collected at the two sites within 2 km from the mouth of the Niida River. On the other hand, seawater samples of 2 L in water depths of 0 m, 5 m, 10 m, 15 m, and 20 m, and rockfish were collected at a site 6 km south-southeast of the FDNPP in July 2014. The iodine in SS, sediment, and rockfish of 0.2–0.5 g was volatilized and trapped in an organic alkaline solution by pyrohydrolysis method. After adding 2 mg iodine carrier to the trap solution and the filtered water sample of 1 L, the iodine was isolated and precipitated as AgI. The $^{129}$I/$^{127}$I ratio of AgI targets was measured using an AMS system at the Micro Analysis Laboratory Tandem Accelerator (MALT), The University of Tokyo. $^{127}$I in the trap solution and the water sample were measured by an ICP-MS. The original $^{129}$I activities and $^{129}$I/$^{127}$I ratios in the samples were calculated using $^{127}$I concentration obtained from ICP-MS and $^{129}$I/$^{127}$I ratio obtained from AMS. $^{129}$I activities and $^{129}$I/$^{127}$I ratios in SS of the Niida River were 0.9–4.1 mBq kg$^{−1}$ and (2.5–4.4)×10$^{−8}$, which were strongly correlated with the total dry weight of monthly SS samples with correlation coefficient (R$^{2}$) of over 0.79. $^{129}$I activity and $^{129}$I/$^{127}$I ratio in SS were considered to infer the source of SS (relatively high-level contaminated upstream area or low-level contaminated downstream area). Meanwhile, the discharged particulate $^{129}$I at the Haramachi site were estimated to be 7.7–12 kBq month$^{−1}$ from September to October 2013. Therefore, a relatively massive amount of particulate $^{129}$I from the upstream was transported to the downstream of the Niida River from September to October 2013. $^{129}$I activities in the surface marine sediments from two sites within 2 km from the mouth of the Niida River were 5.8–8.4 Bq kg$^{−1}$, 2–3 orders of magnitude lower than that of SS at Haramachi site of the Niida River. The $^{129}$I activity in surface seawater 40 months after the accident was 2.2 µBq L$^{−1}$, 2 times larger than the previous $^{129}$I data in surface seawater 3 months after the accident. $^{129}$I activities in the rockfish were 42–48 µBq kg$^{−1}$, approximately 20–400 times larger than that of seawater of the same site.
    
    Speaker: Tetsuya Matsunaka (Kanazawa University)
  - 206
    
    The 6 MV multi-nuclide AMS system at the University of Tsukuba: Status report after 10 years of operation
    
    The 6 MV multi-nuclide AMS system at the University of Tsukuba has been in operation for 10 years since 2014 [1]. The injector has two cesium sputtering negative ion sources: the 40-sample MC-SNICS and the MCG-SNICS gas/solid hybrid ion source. The accelerator with the 6 MV Pelletron tandem (National Electrostatics Corp, 18SDH-2) has a gas stripper tube and a foil changer with 80 foil holders for the charge exchange reaction. Carbon stripper foils are used mainly for obtaining highly charged ions in $^{36}$Cl, $^{41}$Ca and $^{90}$Sr AMS. The rare-particle detection line has a 22.5° ESA for filtering energy-to-charge-state ratios (E/Z) with a resolution of E/dE = 200. A five-electrode dE-E gas-ionization detector is installed as the end station of the detection system. Highly sensitive detections of $^{10}$Be, $^{14}$C, $^{26}$Al, $^{36}$Cl, $^{41}$Ca, and $^{129}$I have been performed [2], with background levels of 10$^{-14}$ to 10$^{-15}$ for these isotope ratios. In addition, AMS analytical techniques for $^{90}$Sr, $^{135}$Cs, $^{210}$Pb, and other nuclides are being developed. Currently, $^{90}$Sr AMS is performed in isotopic ratio ranges of 10$^{-9}$ to 10$^{-13}$ with a total beam energy of 51.7 MeV [3]. The $^{90}$Sr/Sr AMS background is 6 × 10$^{-13}$ (~ 3 mBq $^{90}$Sr). The radioactive halogens for $^{36}$Cl and $^{129}$I have been the main research nuclides at the 6 MV multi-nuclide AMS system. In this presentation, we will report on the progress of AMS detection techniques and applications using multi-nuclides for anthropogenic and cosmogenic tracers in the environment.
    
    References
    [1] K. Sasa et al., Nucl. Instrum. Methods Phys. Res. B, 361 (2015) 124.
    [2] K. Sasa et al., Nucl. Instrum. Methods Phys. Res. B, 437 (2018) 98.
    [3] K. Sasa et al., J. Nucl. Sci. Technol., 58(1) (2021) 72.
    
    Speaker: Dr Kimikazu Sasa (University of Tsukuba)
  - 207
    
    The Centre of Applied Physics, Dating and Diagnostics (CEDAD) at the University of Salento: 25 years and still growing
    
    The CEDAD-Centre of Applied Physics, Dating and Diagnostics was established at the University of Salento in 1999 in the frame of a large scale research project funded by the Italian Ministry of Research and Education. The first core of the centre was a 3 MV Tandetron accelerator (Mod. HVEE 4130HC) initially equipped with only one high energy ion implantation beamline which was then upgraded for Accelerator Mass Spectrometry 14C dating becoming the first Italian center for research and service in radiocarbon dating.
    Since then, while fulfilling its initial mission of serving as national 14C dating facility, it had undergone relevant upgrades with the installation of five more beamlines. Currently the facility hosts six beamlines for ion irradiation, in vacuum and in air Ion Beam Analysis, AMS of rare nuclides and a nuclear microprobe. An hybrid ion source accepting both solid and gas samples is also in operation and is used to feed the original AMS 14C beamline. A general overview of the current status of the facility is presented in terms of instrumental developments and research projects in fields spanning from archaeology and geochronology to forensic and environmental sciences.
    
    Speaker: Lucio Calcagnile (CEDAD-Dept. of Mathematics and Physics, University of Salento)
  - 208
    
    The first 1000 days of MILEA.03 life
    
    Since 2021, the first Czech accelerator mass spectrometry laboratory have been operating at the Nuclear Physics Institute of the Czech Academy of Sciences in Řež, near the capital city of Prague. Its primary purpose is to conduct radiocarbon measurements. The Czech Radiocarbon Laboratory (international code CRL) can provide precise results for radiocarbon dating and other applications of 14C analysis. The samples encompass archaeological artifacts, forensic evidence, and environmental samples, contributing to a better understanding of human history and civilization development, aiding in criminal investigations, environmental protection efforts, and biocarbon determination.
    The contribution summarizes the age portfolio and types of samples analysed in the laboratory, as well as the processing strategy flowchart for different matrices and contaminations, and implementing robust quality control measures. Additionally, we will discuss the 14C measurement parameters achievable with MILEA, including the unique combination with gas interface system. We will also address challenges and potential solutions encountered during the implementation and operation of our new AMS system. By sharing our experiences and best practices, we aim to facilitate the smooth integration and optimal operation of AMS facilities worldwide, thus advancing the capabilities and accessibility of radiocarbon dating.
    
    Speaker: Dr Katerina Pachnerova Brabcova (Nuclear Physics Institute of the CAS)
  - 209
    
    The Lawrence Livermore National Laboratory’s CAMS Accelerator Facility
    
    The Lawrence Livermore National Laboratory’s CAMS Accelerator Facility (CAMS) has been in operation since the late 1980’s. CAMS currently encompasses three electrostatic tandem-type accelerators with pelletron charging systems, and one elevated deck AMS system. Over the years, CAMS has established AMS measurement capabilities for 3H, 7Be, 10Be, 14C, 26Al, 36Cl, 41Ca, 63Ni, 90Sr, 99Tc, 129I, and various actinides, including 233-238U, 236-237Np, and 239-244Pu. CAMS has also established capabilities in high-energy ion implantation for materials modification and radiation damage studies, and in isotope production and nuclear physics experiments.
    
    Since the last published description of CAMS, a significant number of hardware additions to our facility have been made, and further additions are in the process of being installed or planned. The additions completed and in operation include 1) a heavy isotope AMS beamline that allows the transport of ions up to actinide masses and also allows fast bouncing between those heavy isotopes 2) a high mass resolution low-energy injection magnet with a large pole face gap, which allows clear transport of high mass negative ions with high mass resolution, and 3) a beamline designed for and dedicated to high energy ion implantation work involving projectile ions ranging from protons to actinides, and to isotope production and nuclear physics experiments. The most significant in-progress addition to the CAMS facility is the installation of a Gas-Filled Magnet (GFM) beamline which has been designed to allow useful isobaric resolution up to at least the transition metal elements.
    
    Aspects of the current operations and capabilities of the CAMS Accelerator Facility will be presented, and similar aspects of the in-progress and intended systems will also be discussed.
    
    This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344.
    
    Speaker: Dr T. A. Brown (CAMS LLNL USA)
  - 210
    
    A Deep Learning Approach of Artificial Neural Network with Attention Mechanism to Predicting Marine Biogeochemistry data
    
    Marine biogeochemistry data is helpful for researchers to have a more comprehensive understanding of elemental changes in the marine environment. Some important marine biogeochemistry data are not available directly or in a short time due to technical and cost constraints. Therefore, the supplementation of marine biogeochemistry data is essential. Machine learning method is one of the effective methods to supplement marine biogeochemistry data. However, current machine learning methods based on RF and ANN often struggle to effectively capture the intricate features of ocean data, resulting in suboptimal prediction accuracy. To solve this problem, we develop a novel deep learning method called Artificial Neural Network with attention mechanism (ANN-att) for predicting marine biogeochemistry data. We compare and evaluate the performance of RF, ANN, and ANN-att based on two widely-used ocean datasets in marine biogeochemistry: GLODAP v2.2022 and MOSAIC 2.0. Our results show that the prediction accuracy of the ANN-att method is higher than other methods by 6% for GLODAP v2.2022 and 30% for MOSAIC v.2.0. Additionally, the prediction maps of surface ocean dissolved O2 in global marine and Δ14C in the West Pacific demonstrate that ANN-att has a significant advantage in predicting marine biogeochemistry data with stronger nonlinear characteristics.
    
    Speaker: Mr Mingzhi Liu (中国海洋大学)
  - 211
    
    Basin-wide distributions of meteoric 10Be in river water, sediments and soils --implications for understanding long-term Earth surface denudation in China’s karst rock desertification areas
    
    Karst rocky desertification has been a very serious environmental issue in the southwestern China. Heavy metal elements entering the surface ecosystem through the dissolution of carbonates in such areas increases the pollution risk to the farmland soils. Here we present preliminary results of a new attempt of determining long-term soil erosion rate using isotope ratios of the meteoric cosmogenic nuclide 10Be to the mineral-derived stable isotope 9Be (10Be/9Be ratio). River water, river-bed sediments, suspended sediments, and soil samples were collected from the drainage of the Wujiang River (in the Yangtze River system) and Beipanjiang River (in the Pearl River system) in Guizhou Province, where rocky desertification is widely distributed. For comparison, water, sediment and soil samples from valley areas with severe soil erosion in the western Yunnan Province were also studied. Here, large amount of sediment comes from the Lancing River (renamed as the Mekong River in Southeast Asian countries) and the Nuking River (renamed as the Salween River in Myanmar), making the application of the 10Be/9Be ratio in deciphering the history of the long-term weathering process and stability of the soil in the limestone areas a challenging task. Along with the beryllium isotope data, major and trace elements in rocky desertification areas will be presented. This leads to the establishment of spatial distributional patterns of meteoric 10Be/9Be ratio and concentration levels, distributional features and potential sources of eight heavy metal elements (Cr, Ni, Cu, Cr, Cd, Pb, As, Hg). Comparisons of results for samples collected under the pristine conditions of typical rocky desertification areas and under human disturbance conditions (such as farming and building of dams) allows us to assess the effect anthropogenic activities on chemical weathering. For this purpose, soil, water and sediment samples in the upper and lower reaches of four dams in Wujiang River were collected and the results will be discussed. The dissolved 9Be concentrations in the river water samples vary from <0.5 to >10 nM. Both the 9Be and meteoric 10Be concentrations in the sediments show wide variability, resulting in the 10Be/9Be ratio in a range from 2×10-10 to 2×10−8 (atoms/atoms). The results of this study will not only provide valuable information on the processes regulating Be isotopic distribution in karst areas, but also serving as a basis for the long-term soil erosion rate estimation from hillslope scale to an entire river basin scale, and its relation with heavy metal migration and transport in the rocky desertification areas.
    
    Speaker: Yongliang Yang (Key Lab of Eco-geochemistry (MNR), China)
    
    Shang_PKU_sub.pdf
  - 212
    
    Compact AMS at PKU - 20 years’ progress in instrumentation and application
    
    A compact AMS was installed at Peking University in September 2004. The instrument was the fourth of newly developed low energy compact Pelletron model 1.5SDH AMS manufactured by the National Electrostatics Corp. Here we reflect major instrumental improvements and applications associated with the instrument over the past 20 years. The 500kV compact AMS was upgraded for 10Be measurements in two phases. The first phase involved installation of a silicon nitride foil in front of the electrostatic deflector near the focal plane of 10Be as passive boron degrader and replacement of the Si detector originally for radiocarbon detection at the end of the beam line with a high-resolution ΔE-Eres gas ionization chamber, allowing for 10Be identification. In the second phase, a 90-bending magnet with 350 mm radius was added after the electrostatic deflector for the re-focusing of the 10Be ions. The gas detector for 10Be was mounted after the additional magnet. The upgraded spectrometer remains compact and requires no more space than the original instrument. The new system allows quick shifts for 10Be set-up without affecting any parameters for radiocarbon measurements. An overall transmission of 5-6% for 10Be was achieved with the 10Be/9Be background level down to 2.4x10-15. Recently, a control system including MBS system controller, PPCI, PXI chassis and ACT chassis was installed to replace the original CAMAC-based system, providing assurance for the compact AMS to make high quality measurements in many years ahead. The instrumental upgrade was accompanied by the improvement in sample preparation. The hydrogen method line was rebuilt with increased output capacity and remains dedicated to dating applications. A new line using sealed tube zinc reduction method was set up for geoscience applications and a special line for bio and medical applications was constructed. As for applications, PKU AMS remains to serve as a most trusted dating facility for Chinese archaeology and Quaternary communities, contributing to the fields of human evolution, origins of agriculture, origins of Chinese civilization and Paleolithic archaeology as well as Quaternary paleoclimate changes. Over the last 20 years, PKU compact AMS has also facilitated exciting integration of AMS applications into Earth system science. This was started with the use of 14C in estimating afforestation soil turnover, fossil fuel derived CO2 in the air and in the carbonaceous aerosols, then followed by a large-scale investigation of the full-depth seawater 14C in the South China Sea, Indian Ocean and the NW Pacific. Other applications supported by the compact AMS are found in the field from the environmental monitoring of nuclear power plant facilities to the development of innovative drugs.
    
    Speaker: Liping Zhou (Peking University)
    
    Zhou_PKU_sub.pdf
  - 213
    
    Determination of Th-230 and Th-228 in Small-Volume Seawater by Accelerator Mass Spectrometry for Marine Carbon Sink Accounting
    
    Thorium isotopes Th-234, Th-230 and Th-228 are important tracers for estimating carbon fluxes in the ocean via the biological pump. However, conventional radiological methods for Th-230 and Th-228 in seawater require large-volume samples (100-1000 L), limiting the large-scale application of Th isotopes in carbon sink accounting. This study aims to develop an accelerator mass spectrometry (AMS) method for simultaneous determination of dissolved and particulate Th-230 and Th-228 in small-volume (10 L) seawater samples.
    The proposed analytical procedure includes: 1) Establishing an efficient preconcentration and purification protocol for Th in 10 L seawater with >80% recovery; 2) Developing an AMS method for Th-230 and Th-228 to achieve >0.2% total detection efficiency; 3) Minimizing procedural blanks to enable quantification of Th-230 and Th-228 in 10 L seawater.
    To validate the developed method, seawater profile samples will be collected from one station in the South China Sea. Dissolved and particulate Th-234, Th-230 and Th-228 in these samples will be analyzed using the small-volume procedure and compared with conventional large-volume analyses. Particulate organic carbon (POC) export fluxes at different depths will also be estimated using a particle dynamics model, and if possible, compared with sediment trap results.
    The small-volume AMS method is expected to greatly reduce sampling time and cost while increasing observation density. This technical advancement will provide the international oceanographic community with an effective tool for quantifying and monitoring deep-sea carbon fluxes across vast ocean basins. Improved spatial and temporal coverage of POC export flux data will enhance our understanding of the global ocean carbon cycle and its response to climate change. Furthermore, this research will contribute to the global effort in assessing the potential of marine carbon sequestration as a nature-based solution for mitigating climate change.
    
    Speaker: Mu Lin (Institute of Geology and Geophysics, Chinese Academy of Sciences)
  - 214
    
    Earthquake-enhanced dissolved carbon cycles in ultra-deep ocean sediments
    
    Hadal trenches are unique geological and ecological systems located along subduction zones. Earthquake-triggered turbidites act as efficient transport pathways of organic carbon (OC), yet remineralization and transformation of OC in these systems are not comprehensively understood. Here we measure concentrations and stable- and radiocarbon isotope signatures of dissolved organic and inorganic carbon (DOC, DIC) in the subsurface sediment interstitial water along the Japan Trench axis collected during the IODP Expedition 386. We find accumulation and aging of DOC and DIC in the subsurface sediments, which we interpret as enhanced production of labile dissolved carbon owing to earthquake-triggered turbidites, which supports intensive microbial methanogenesis in the trench sediments. The residual dissolved carbon accumulates in deep subsurface sediments and may continue to fuel the deep biosphere. Tectonic events can therefore enhance carbon accumulation and stimulate carbon transformation in plate convergent trench systems, which may accelerate carbon export into the subduction zones.
    
    Speaker: Rui Bao (Ocean University of China)
  - 215
    
    Establishing detection limits and optimal sample-matrix composition for an enhanced actinide determination using the ETH MILEA system
    
    In this study, the detection limits for Pu, U, and Am isotopes are presented, demonstrating the ETH MILEA system's capability to identify these isotopes at ultra-trace levels. Additionally, the impact of varied matrix compositions, specifically iron and niobium content, on the detection efficiency of these actinides was investigated. Larger matrices were observed to be advantageous for extended measurement times, particularly benefiting lower-concentration samples. These findings were then applied to determine isotopic concentrations in small-volume environmental samples collected from areas near the Fukushima Nuclear Power Plant and the North Sea.
    
    This research forms an integral part of the ongoing MetroPOEM project, which aims to harmonize different mass spectrometry methods for the determination of radioactive pollutants in the environment. Our results also contribute to improving actinide measurements in the fields of tracer oceanography and nuclear forensics.
    
    Speaker: Habacuc Pérez-Tribouillier (Laboratory of Ion Beam Physics)
    
    Abstract_actinides_HPerezTribouillier.pdf
  - 216
    
    Glacial meltwater-produced high lake levels on the Tibetan Plateau during the late Quaternary period， using Be-10
    
    High lake levels across the Tibetan Plateau (TP) have attracted much attention, but the mechanisms driving the lake level rises are still debated. Dramatic lake expansions over the past decades are mainly ascribed to the additional water supply from accelerated glacial melting and precipitation increasing. Throughout the late Quaternary higher lake levels have been attributed primarily to enhanced monsoonal precipitation with glacial meltwater being a lesser contributor. We use absolute dating of the shorelines and glacial moraines, combined with modeled ice volumes, to examine the synchronicity of high lake levels and glaciations in the Nam Co’s catchment in the western side of the Nyainqentanglha Mountains, and Linggo Co and Duoge Co North around the Puruogangri ice field on the TP. We find that lake water levels during Pleistocene are much higher than those during Holocene. The conspicuously exposed paleo-shoreline at 20-27 m above the current level of Nam Co in the southern TP formed during multiple short-lived periods at similar water levels that likely were initiated during Marine Isotope Stage (MIS) 6. This shoreline was subsequently re-sculpted in MIS 3. The second highest shoreline (14-18 m) was formed during the deglaciation associated with MIS 4 and reshaped during the last deglaciation. Four shorelines of Linggo Co in the innermost TP were formed during MIS 6 (25 - 29 m), MIS 4 (82-89 m), MIS 3 (94 m) and the Last Glaciation Maximum (LGM) (66 m). The shoreline associated with MIS 6 is lower in altitude than late-formed shorelines associated with MIS 4, MIS 3 and the LGM. The earlier shorelines are well-preserved and their ages are not significantly underestimated by later higher water-level processes, suggesting that the high lake levels were short-lived. The periods during which these two clearly discernible shorelines of Nam Co and four shorelines of Linggo Co were at their widest extent appear consistent with the timings of the extensive local glacial advances, suggesting that high lake levels were correlated with these glaciations. High water levels of glacier-fed lakes also appear synchronous with the local glaciations during the last glacial period across the semi-arid areas on the TP and its surrounding mountains. The climates conditions during MIS 6, MIS 4, MIS 3, the LGM, and the last deglaciation were generally colder and drier, but the lake levels during these periods were higher than those of the Holocene, suggesting that the increasing precipitation was not a major factor for these high lake levels. The reconstructed ice volume losses during LGM, MIS 3 and MIS 4 in the Nam Co’s catchment are equivalent to a rise of 66-75 m in the Nam Co’s water levels. We suggest that paleoglaciers would have contributed substantial meltwater to maintain high water levels for shore time for glacier-fed lakes during late Quaternary on the TP, and it implies that the increase of the water levels for present-day glacial meltwater-fed lakes would not last for a long time.
    
    Speaker: Prof. Chaolu Yi (北京年代科技，西藏大学，中科院青藏所)
  - 217
    
    Measurement techniques for 236U with a compact AMS system
    
    236U has an important role as an emerging tracer in geochemical and oceanographic studies. A new compact AMS device at the China Institute of Atomic Energy (CIAE) enables efficient transmission of actinides. In this study, we focus on its capabilities to analyze uranium isotopes, mainly for 236U measurements. Compared to the air-insulated AMS system, which is the previous generation of the device at CIAE, we have reduced the footprint of the whole system by half. The compact AMS system (0.25 MV) maintains extremely high measurement sensitivity, which has been tested with 129I and 239Pu, by using a new simple Bragg detector and installing a second magnet on the HE-side. Besides, the compact accelerator implements gap acceleration and gas distribution control techniques that greatly suppress charge exchange processes.
    In order to establish the measurement techniques for 236U with the compact AMS system, the background and sensitivity for 236U/238U will be studied and analyzed in detail. Then, accurate measurements of 236U and other rare uranium isotopes such as 233U will be carried out.
    
    Speaker: Mr 建良李 (中国原子能科学研究院)
  - 218
    
    Methodological Research on ECR+AMS for Tracing the Authenticity of Medicinal Herbs
    
    The authenticity of traditional Chinese medicinal herbs refers to the superior quality and significant efficacy of herbs from specific regions due to unique geographical and climatic factors. This concept holds an important place in traditional Chinese medicine. Scientific analysis and testing are crucial for ensuring the quality of medicinal herbs and enhancing clinical efficacy.
    Conventional mass spectrometers cannot simultaneously measure ratios such as 13C/12C and 14C/12C, nor can they measure 2H/H, 3H/H, and 17O/16O, 18O/16O at the same time. Therefore, it is challenging to distinguish the true production areas of medicinal herbs that belong to the C3 plant category.
    ECR+AMS (Accelerator Mass Spectrometry with a Electron cyclotron resonance ion source) is an advanced analytical technique with ultra-high sensitivity and detection limits ranging from femtograms to attograms (10^-15 to 10^-18 grams). It can be a primary method for detecting the authenticity of medicinal herbs. By using AMS to detect isotopic fingerprints and establish a corresponding spectral database, it can serve as a technical support for the identification, evaluation standards, and quality control system of authentic medicinal herbs, allowing nuclear-derived technology to benefit all of humanity.
    
    Speaker: JIANPING SONG (Southern Zhejiang Institute of Radiation Medicine and Nuclear Technology Applications)
  - 219
    
    Paired radiocarbon measurements on European and North American oak from Historic Buildings in England
    
    English oak is the most common timber found in Historic Buildings in England, although conifer is used widely in the post medieval period and fine-grained oak panels were imported from around the Baltic from the middle ages. The network of ring-width reference chronologies for English oak over the past millennium is generally robust, and it is unusual to find long (> 100 rings) and well-replicated (> 5 samples) site chronologies that cannot be dated using dendrochronology is unusual.
    
    Collaborative research with North American colleagues on a group of such chronologies, which on architectural grounds probably date to the eighteenth or nineteenth century CE, suggests that they are indeed of this date and were imported from the East Coast of North America (Crone et al. in prep). Radiocarbon wiggle-matching of single-ring samples was used on a number of these sites to validate the tree-ring dating proposed.
    
    This presented the opportunity to compare these measurements with those on single-ring samples of English oak dated to the same calendar years. The weighted mean offset observed (5.4±3.1 BP, n=46) is not statistically significant.
    
    Crone, A, et al. in prep. American oak imports to the British Isles in the 18th and early 19th centuries: the dendrochronological evidence, Dendrochronologia
    
    Speaker: Dr Michael W. Dee (University of Groningen)
  - 220
    
    Peakless distribution and migration model of 239+240Pu in typical Chinese core samples
    
    Based on data from 45 soil cores, 35 lake sediment cores, and 29 sea sediment cores in China, this study found a type of 239+240Pu peakless distribution cores in soil, lakes, and marine environments, and discussed the phenomenon of 239+240Pu peakless distribution. The results show that there were two main types of peakless distribution of 239+240Pu in soil core samples: one that the 239+240Pu specific activity increased with depth, and the other that the 239+240Pu specific activity decreased with depth; when using a Convection Dispersion Equation(CDE) model to simulate the migration behavior of 239+240Pu in soil cores, the apparent convection rate showed a positive correlation with the 239+240Pu maximum depth (n=45, R2=0.847). There was only one type of peakless distribution of 239+240Pu in lake and ocean core samples: the 239+240Pu specific activity decreased with depth. Meanwhile, the sedimentation rate of lake core samples (n=35,R2=0.921) or the maximum apparent convection rate of marine core samples (n=29, R2=0.949) also showed a positive correlation with the 239+240Pu maximum depth. The maximum apparent convection rate of the exchangeable 239+240Pu in the peakless distribution core sample was close to the sedimentation rate, and the maximum apparent convection rate didn't affect the vertical distribution of 239+240Pu in the core sample.
    
    Speaker: Yanan Huang (南宁师范大学)
  - 221
    
    Production of 236U/238U Reference Standards for Accelerator Mass Spectrometry Measurements
    
    $^{236}$U is a rare isotope of uranium, naturally occurring with an abundance of less than 100 parts per trillion. The ability to detect it and make isotopic ratio measurements has applications ranging from nuclear forensics and nonproliferation to energy production and environmental protection. Currently, Accelerator Mass Spectrometry (AMS) is the only technique sensitive enough to accurately measure $^{236}$U/$^{238}$U isotopic ratios as they exist in naturally occurring ores in the range of $^{236}$U/$^{238}$U =10$^{-14}$-10$^{-10}$. Some AMS facilities have demonstrated their capabilities to make these measurements already, however the lack of any known reference standard has required the use of absolute measurements, notoriously difficult to do using AMS, resulting in increased uncertainties in measurements and a reliance on knowledge of systematic effects. Using a reference standard prepared for other forms of mass spectrometry, we are attempting to create a series of AMS suitable standards through dilution with depleted uranium. The techniques used to produce these materials and analysis of them using AMS will be discussed. Additionally, changes to our time of flight detection system and how they improve our detection limits will be presented alongside a call for collaboration with other facilities to help validate our technique and isotopic ratios.
    
    This work is supported by the National Science Foundation Grant No. NSF PHY-2011890 and the Nuclear Regulatory Commission Award No. 31310019M0037.
    
    Speaker: Philippe Collon (University of Notre Dame)
  - 222
    
    Reanalysis of the formation mechanism of the Cold Water Belt in the southern Okhotsk Sea using I-129 as chemical tracer
    
    The southern Okhotsk Sea is an excellent fishing ground, producing 352 kton year$^{-1}$ of scallops, crabs, salmon, etc. Fed by the Soya Warm current (SWC, high salinity) and the East Sakhalin Current (ESC, cold and low salinity), surface water of the southern Okhotsk can be grouped into Coastal and Offshore areas.
    The Cold Water Belt (CWB) is formed by the upwelling of cold subsurface seawater. Hence, the CWB exhibits high biological production (Mustapha and Saitoh, 2009). The formation mechanism of the CWB has been studied leaving 2 theories: 1. The upwelling due to resonance and 2. The elevation of thermocline through baroclinic-wave adjustment. However, both theories allocate the source of the CWB before and after Soya Strait (at the intermediate cold water, ICW), respectively. To elucidate the nutrients’ cycle at the southern Okhotsk Sea, it is indispensable to clarify the formation mechanism of the CWB. Along a wide range of oceanographic parameters, $^{129}$I extracted from seawater as AgI was measured using accelerator mass spectrometry at the University of Tsukuba.
    Prior to this study we found that $^{129}$I is carried southward by the ESC. Likewise, in the surface waters $^{129}$I (Offshore > Coastal) anti-correlates with salinity. In this study, after an identification of the different water masses based on their physical properties, we found that 1. The highest $^{129}$I/$^{127}$I ratio was observed at OSW’s subsurface (1.33-1.53 x 10$^{-10}$), which is modified by Sea Ice melting. 2. Dense-SWC, as Japan Sea’s winter-mixed water, has higher $^{129}$I/$^{127}$I ratios than SWC, but lower than Okhotsk Sea surface water (offshore area). 3. It is likely that ICW does not have a high $^{129}$I/$^{127}$I ratio. 4. The CWB had a low $^{129}$I/$^{127}$I ratio (< 1.10 x 10$^{-10}$), even lower than ICW’s.
    From the difference in $^{129}$I/$^{127}$I ratios of the endmembers, it is likely that the main water mass conforming the CWB would have origins at the of Japan Sea’s subsurface waters. Therefore, the upwelling due to resonance would be the most suitable. Such mechanism has been previously theorized as follows: when a stratified barotropic flow passes through the shallow (50 m depth) Soya Strait, internal Kelvin waves cause a nonlinear resonance with the seafloor, provoking a large boundary surface displacement that causes the lower layer to rise (Mitsudera et al., 2011a) at the Cape Krillion (at the left respect to the passing flow), whereas the baroclinic adjustment generated after the strong upwelling causes a strong baroclinic jet in the surface layer along the SWC axis and a dome–like structure in the subsurface layer (Mitsudera et al., 2011b). To quantify the role of the bottom Ekman upwelling (the second mechanism), a mass balance among endmembers including $^{129}$I/$^{127}$I ratios, TS, chlorophyll-a and macronutrients data will be presented at the conference.
    
    Speakers: Dr Rodrigo Mundo (Instituto de Investigaciones Tropicales de El Salvador) , Dr Tetsuya Matsunaka (Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Japan)
    
    AMS16_2024＿RM1.docx
  - 223
    
    Research activities after a decade of the installation of a single stage accelerator mass spectrometry at the Atmosphere and Ocean Research Institute, the University of Tokyo
    
    A single-stage accelerator mass spectrometer at the Atmosphere and Ocean Research Institute, The University of Tokyo was installed in 2013 and has been running stably for the past 10 years. Various types of samples have been analyzed, including geology, biology, oceanography, archaeology, etc., in active collaboration with national and international institutions. Precision for 14C/12C measurements on standard samples has been achieved to better than 0.1% due to improvements in the operating software system and increased number of standard measurements per run, and small-scale radiocarbon measurements down to 10-30 micrograms C have been constantly carried out. Stable operating conditions have been maintained and the average annual operating hours have reached 8100 hours/year for the last three years, allowing us to measure as many as 2520 samples/year (excluding the number of standard samples). Some recently developed in-house apparatus including the automated graphitisation apparatus has enabled us to produce a high throughput system. The expansion of the building to twice the size of the current building will provide us with the space to install planned newly designed systems. We will introduce some of these recent systems during the presentation.
    
    Speaker: Yusuke Yokoyama (Atmosphere and Ocean Research Institute, The University of Tokyo)
  - 224
    
    Spatial distribution and transportation paths of 236U the Beibu Gulf, South China Sea
    
    In order to investigate the spatial distribution and source of 236U in the Beibu Gulf, we collected and analyzed 36 surface sediments using accelerator mass spectrometry (AMS). Prior to AMS measurement, the abundance of 238U,235U and 234U were determined by inductively coupled plasma mass spectrometry (ICP-MS). By combining the counts of 234U and 236U in the AMS measurement with the value of U isotope abundance, we can obtain the 236U/236 atomic ratio. The 236U-AMS experiment is currently ongoing. We aim to determine the transport path of 236U in this area through analysis of its concentration combined with ocean current movements.
    
    Speaker: Yongjing Guan (Guangxi Key Laboratory for Relativistic Astrophysics, School of Physical Science and Technology, Guangxi University)
    
    AMS 16 abstract.docx
  - 225
    
    Status of the French Accelerator Mass Spectrometry (AMS) Facility ASTER
    
    ASTER AMS facility, part of the LN2C (National Laboratory for Cosmogenic Nuclides) is involved in its own beam line development to fulfil the stringent requirements of the AMS technic and the always increasing quality measurements required by the Geosciences community applications. Since the acceptance tests in March 2007, routine measurement conditions for the long-lived radionuclides 10-Be and 26-Al has been established. In 2023, Sample throughput as high as over 3000 unknowns has been reached for 10-Be and around 600 for 26-Al. Moreover, unacceptable cross-contamination for volatile elements had been largely solved by a first ion source upgrade [1]; this have allowed more than 789 36-Cl samples measurements.
    
    Major instrumental developments occurred between 2015 and 2020: The Acquisition of a new high intensity ion source, the SO-110C, latest version of the HVE SO-110 sputter ion source with a carrousel capacity of 200 samples stored in a separate vacuum chamber minimized, cross-talk between samples, lowered the source background and reduced source maintenance by providing good access to the source head and the disposable items while minimizing the effort for alignment of parts. Moreover, this latest upgrade of the source increased the sputter voltage capability to 12 kV. This ion source is performing 26-Al and 10-Be measurements the previous ion source version SO-110B is still dedicated to 36-Cl measurements.
    
    During acceptance tests, this new source design produced 1 μA analysed current for 27Al− and up to 20 μA for 9BeO-. So, concerning 10Be, the enhancement of the stable current level with respect to the precedent ion source design is impressive allowing minimal measurement time losses and uncertainties. However, regarding aluminium, we have mixed results, measuring several targets that have provided 27-Al- current lower than expected between 500 and 700 nA and all the data show that the current dropped so fast; actually, within a time span of 10 mn to 30mn it dropped below 200 nA.
    
    Based on this conclusion, in 2020 Aster team has acquired a new beam line introducing a gas-ﬁlled magnet (GFM) in front of a new GIC focused on 26-Al measurements improvements. The new strategy is to use AlO - ions that provide ionization yield about an order of magnitude higher compared to the commonly used Al- ions.
    
    Tests has been delayed due to Covid pandemia, but the GFM is now connected to the 0° exit port of existing vertical 30o magnet provided with a degaussing unit.
    Following the completion of the on-site installation, the equipment has been subjected to an acceptance test that shown that the equipment is in operating condition. Data acquisition system was demonstrated by performing a batch of twelve (12) AMS analyses (26-Al/27-Al isotopic ratios) using four (4) aluminum reference samples, proving this way the functionality of the GFM setup using Al- current. Al5+ was then selected after the accelerator, whose terminal voltage was set at 5 MV.
    Even if the GFM setup is designed to support AlO- injection, the suppression of the MgO- interference needs indeed to be optimized. In the present state of our experiment with GFM detection system we can only manage some functionality without expecting performance specifications. More investigation have to be performed with the help of the constructor HVEE that are willing to collaborate with us to improve our results. Until then, 26-Al AMS measurements are still performed on the original beamline machine setup.
    
    References: [1] M. Arnold et al., NIMB 268 (2010) 1954.
    
    Speaker: Mr KARIM KEDDADOUCHE (CNRS cerege UMR7730)
  - 226
    
    The first 14CAMS Facility in Latin America: LAC-UFF over 15 years of operation
    
    The Radiocarbon Laboratory of the Fluminense Federal University (LAC-UFF) has been pivotal in radiocarbon dating by Accelerator Mass Spectrometry and its applications in Latin America since its inception in 2009 (Anjos et al. 2013; Macario et al. 2013; 2015). Over the past 15 years, LAC-UFF has engaged in diverse research activities and collaborations. These have spanned cultural and natural heritage conservation, paleo vegetation and paleo sea level reconstructions, the determination of renewable fractions for biofuel certification, biopolymers, pharmaceuticals derived from natural and synthetic materials, and forensic science.
    
    The sample preparation laboratory has expanded significantly, incorporating new vacuum systems and analyzing a wide variety of sample materials, such as otoliths, stromatolites, vermetids, bones, and pottery (Oliveira et al. 2021). Installed in 2012, the NEC 250 kV single-stage AMS system (SSAMS) at LAC-UFF has been instrumental in measuring the 14C content of thousands of graphite samples, both reference materials and unknowns. Significant improvements in the system and in measurement and analysis protocols have been made over the years to enhance the precision and accuracy of results (Linares et al. 2015; Castro et al. 2015). For instance, in 2019, the stripper gas was switched from argon to helium, enhancing the system transmission and consequently improving statistics of measurements, positively impacting results (Carvalho et al. submitted).
    
    Throughout its operation, LAC-UFF has continuously refined its protocols and methodologies for 14C AMS determination, aiming to maintain best practices in radiocarbon dating. The laboratory is dedicated to advancing scientific knowledge, preserving cultural heritage, supporting forensic investigations, and contributing to sustainable development practices in Brazil and beyond.
    
    References
    
    Anjos, R. M., et al. "Towards a complete 14C AMS facility at the Universidade Federal Fluminense (Niterói, Brazil): sample preparation laboratory tests." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 294 (2013): 173-175.
    
    Carvalho, C. et al. (submitted to Radiocarbon) “LAC-UFF SSAMS System Status Report after 12 years”
    
    Castro, M. D. et al. "New software for AMS data analysis developed at IF-UFF Brazil." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 361 (2015): 526-530.
    
    Linares, R. et al. "Radiocarbon measurements at LAC-UFF: Recent performance." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 361 (2015): 341-345.
    
    Macario, K. D. et al. "The Brazilian AMS Radiocarbon Laboratory (LAC-UFF) and the intercomparison of results with CENA and UGAMS." Radiocarbon 55.2 (2013): 325-330.
    
    Macario, K. D., et al. "Advances in the graphitization protocol at the Radiocarbon Laboratory of the Universidade Federal Fluminense (LAC-UFF) in Brazil." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 361 (2015): 402-405.
    
    Oliveira, F., et al. "LAC-UFF status report: current protocols and recent developments." Radiocarbon 63.4 (2021): 1233-1245.
    
    Speaker: Prof. Kita Macario (LAC-UFF (Radiocarbon Laboratory of the Fluminense Federal University), Physics Institute)
  - 227
    
    Tree-ring dating of Alerce timbers commercially imported into Japan
    
    Alerce (Fitzroya cupressoides) is rare and long-lived cypress growing in southern Chile and adjacent Argentina. Considerable effort has been devoted to developing millennium-long tree-ring chronologies of Alerce, and this has led to a 5682-year-long tree-ring width chronology, which is the longest for the Southern Hemisphere. In this study, tree-ring dating was conducted using Alerce timbers, which were commercially imported into Japan before forbidding its international commerce under Convention on International Trade of Endangered Species. We measured annual growth rings to an accuracy of 0.001 mm. Standardized ring-width series was then cross-dated against several tree-ring chronologies so far developed using Alerce from the region. It turned out that many samples were shown to have groups of micro-rings that could not be cross-dated. We therefore selected samples with relatively wide rings. A total of five samples were successfully cross-dated, covering the period 693–1058 CE. The sharp radiocarbon spike observed globally at 774–775 CE was well reproduced using one of our dated samples, which provides independent support for the dating of tree rings. Specifically, our spike appears in 774 CE, which is one year earlier than those observed in the Northern Hemisphere. The event is considered to have occurred within the boreal growing season (June to August) of 774 CE. Tree-ring chronologies from temperate regions of the Southern Hemisphere lag those from the Northern Hemisphere by approximately six months, owing to the phase difference of the extratropical growing seasons between hemispheres. Our spike found in 774CE is therefore consistent with the previous findings. In fact, radiocarbon data previously reported using another Alerce tree also starts the spike in 774 CE. While the sample size is limited in this study, tree-ring dating based on ring widths works for the Alerce timbers commercially imported into Japan.
    
    Acknowledgements. We thank Yoshiko Saito, Yuki Hata, and Maiko Yamaguchi for their assistance in our tree-ring analysis. This research was funded by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (Grant nos, 20H00035, 22H00026, 22H00738, and 23H04845).
    
    Speaker: Masaki Sano (National Museum of Japanese History)
    
    AMS16_abstract_submitted_msano.docx
- 18:40
  
  Dinner Restaurant，Ground floor
  
  Restaurant，Ground floor
Thursday, 24 October
- Registration in the lobby of the conference Hotel Lobby of the Conference Hotel
  
  Lobby of the Conference Hotel
  
  Chairperson: Prof. Shen, Hongtao
- Plenary GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Convener: Prof. Xiaolin Hou
  - 228
    
    Radiocarbon constraints on organic carbon sources, transport and burial in China marginal seas
    
    Constraining the sources, transport, and burial of OC in marine sediments is of fundamental importance for understanding the carbon cycle on a range of spatial and temporal scales. Marginal seas receive substantial terrestrial inputs from rivers and comprise hotspots for both organic carbon (OC) burial and remineralization. However, much remains unknown about factors that control the sources, transport processes and burial history of OC in response to natural and anthropogenic processes in marginal seas. Here we employ novel approaches of dual carbon isotopic (Δ14C and δ13C) measurements of both bulk OC and especially source-specific biomarkers to gain deeper insights into the fates of terrestrial organic carbon in China marginal sea systems. We systematically assess the characteristics of riverine and marine sediments, quantify the contributions of different-sourced and different aged OC and reveal their spatial distributions, and then constrain the burial efficiencies of terrestrial OC in China marginal seas. We also explore the role of transport processes (e.g., hydrodynamic sorting) in alteration and evolution of OC along the river-estuary-coastal ocean continuum. Our results reveal that estuaries serve as critical zones for OC degradation and aging, which in turn affect OC burial in marginal seas. By applying the same approaches in down-core sediments, we examine the longer-term controls on OC composition, age and burial over centennial to millennial timescales, revealing the distinct variations and mechanisms for terrestrial OC fates in China marginal seas. Overall, these findings suggest both sources and hydrodynamic processes during transport exert strong influence on the fate of OC, with important implications for the role of river-dominated marginal seas in the global carbon cycle.
    
    Speaker: Meixun Zhao (Ocean University of China)
- Memorial Session GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  This session will be dedicated to honoring the memory of our late predecessors who have made significant contributions to the field of accelerator mass spectrometry. It will be an opportunity for us to reflect on their legacy and celebrate their achievements that have paved the way for current and future advancements in AMS.
  
  Convener: Prof. Xiaolin Hou
  - 229
    
    A long-lasting and unforgettable scientific achievements and personality: Göran Possnert 1951-2022
    
    Ala Aldahan1 and Xiaolin Hou2
    1Department of Geosciences, United Arab Emirates University, Al Ain, UAE
    2Xi’an AMS Center, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, China
    Göran Possenrt was a remarkable, innovative and sympathetic scientist who was always open to new challenges and endeavors. His sense of humor let him engage easily with everyone and he was an inspiration to young colleagues, many of whom would go on to flourish in the research areas that he pioneered. Göran passed away on October 10, 2022 leaving behind enormous national and international research materials on human culture, environment and climate. His contributions to the development and advance of accelerator mass spectrometry, among other scientific interests, were vital to the progress of this scientific field. He opened the field of AMS radiocarbon analysis and other cosmogenic isotopes for a wide range of applications. Göran’s contributions to radiocarbon research were through technological tools and applications. The development of technological tools includes setting up and technical expansion of 3 AMS systems, the 7 MV EN tandem accelerator, the 5 MV Pelletron tandem accelerator and the Green-MICADAS low energy accelerator as well as the testing of Intracavity OptoGalvanic Spectroscopy for measurements of C-14. In sample preparation technology, he developed methodology for materials that hold a minute amount of carbon, such as iron artifacts, separation of alkaloid for radiocarbon dating and ultra-small sample preparation method down to a few μg C samples for analysis of DNA and other biomedical targets. He participated in several international radiocarbon laboratory intercomparisons and laboratory comparisons for other cosmogenic isotopes. On the application side of radiocarbon, he contributed to a wide range of research extending from life science to biomedical applications, including understanding tumor growth dynamics, postnatal neurogenesis in the human amygdala with cell turnover rates comparable to the hippocampus, the dynamics of cell generation and turnover in the human heart, the lifespan and turnover of microglia in the human brain and how diploid hepatocytes drive physiological liver renewal in adult humans. Göran made many contributions to the radiocarbon-archeological research such as a full list of radiocarbon dates for woolly mammoth and other species of the mammoth fauna available from Wrangel Island, northeast Siberia, Russia, and the dating of many Viking and museums artifacts. In the natural environment, he provided radiocarbon time scale and the dating of many sediments, plant remains, tree rings, carbon-bearing minerals and materials for the revision and calibration of the last 40 kyr for climatic, historical and environmental analyses. Among such archives, the Vedde Ash Bed (mid-Younger Dryas) and the Saksunarvatn Ash (early Holocene), which are important regional stratigraphic event markers in the North Atlantic, the Norwegian Sea, and the adjacent land area and he contributed to The Circum-Arctic Sediment CArbon DatabasE (CASCADE). The contributions of Göran in the development of sample preparation and AMS systems for the measurements of Be-10, I-129 and Cl-36 include: setting up AMS beamlines and needed accessories to perform the measurements, establishing internal standards and background materials for the analytical control and setting up chemical separation labs dealing with all types of solid, liquid and gas targets. The applications in the field of cosmogenic isotopes, other than C-14, were enormous and covered many parts of the world, environmental settings and materials. Examples include analysis of Be-10 and I-129 in ice, precipitation, marine and fresh water, aerosols, sediments, rocks, tree rings and organic materials. The applications comprise finding evidence for solar storms in the past and their effects on space weather, reconstruction of the geomagnetic dipole moment variations for the last glacial period, investigating the Late Holocene pathway of Asian Summer Monsoons, and tracing marine water circulation in different parts of the world and environments. These contributions aimed to document processes occurring in the Earth’s surface environment and atmosphere and utilize these archives for a better understanding of changes in our environment and climate in the past, present and future.
    
    Speaker: Prof. Aldahan Ala (United Arab Emirates University)
    
    AMS 16 Ala Aldahan abstract, 2024.docx
  - 230
    
    Ingeborg Levin: A retrospective of her scientific accomplishments, radiocarbon and atmospheric 14CO2 research
    
    In February 2024, the radiocarbon community suffered a great loss with the passing of Ingeborg Levin, a prominent figure in the field.
    This tribute commemorates her scientific journey, which began in 1978 with her diploma thesis "Regional Modelling of Atmospheric CO2 Based on C-13 and C-14 Measurements." Throughout her career, she focused on studying various trace gases, such as CH4, N2O, CO, H2, 222Rn and SF6, while integrating data from isotopologues whenever possible.
    
    Her research into global radiocarbon activity in atmospheric CO2 and its implications for the global carbon cycle remained a central passion. With a focus on radiocarbon analysis, her primary goal was to accurately pinpoint global and regional sources and sinks of the most critical greenhouse gases.
    
    For years, she served as a role model for many young and established scientist, played a key role within the WMO GGMT community, respected not only for her expertise but also cherished as a supportive colleague and friend.
    
    Through her involvement, Ingeborg emphasized the need for a precise and cohesive data foundation for future greenhouse gas studies. This awareness inspired her to champion the establishment of the European research infrastructure ICOS (Integrated Carbon Observation System).
    In this tribute, we reflect on Ingeborg's enduring impact on radiocarbon research and the profound influence her work continues to have in the field today.
    
    Speaker: Dr Ronny Friedrich (Curt-Engelhorn-Center Archaeometry)
  - 231
    
    Environmental and landscape evolution from Be-10 record in sediments of arid regions (UAE)
    
    Natural landscape evolution is strongly linked to the climatic and tectonic settings of a region. Consequently, indicators of landscape changes through time can provide vital information on climate and tectonic changes in the past. Be-10 data from arid regions, although challenging due to the difficulties of finding well preserved archives, can contribute to a better understanding of climate change in the past. Here, we have conducted a large-scale sampling of variable sediments (sand dunes, wadi deposits, terraces, alluvial fans, loess and Sabkha) from different environmental and tectonic settings in the UAE (lat. 23~26o and long. 52~56o) with the aim of investigating landscape evolution during the Quaternary. In addition to Be-10, we use geomorphic, sedimentologic and tectonic information to provide a picture of the environmental variability in the region. Based on topography, the region was divided into highlands, alluvial plains, sand dunes and coastal Sabkha. Due to the large textural variability of the sediments and to get comparable results, we used a grain size fraction < 200 micrometers for the chemical extraction of Be-10. The AMS analysis of Be-10 was performed in the Tandem Laboratory, Uppsala University. The results of Be-10 indicate a range of 1-33×107 atoms/g with an average of 6.4×107 atoms/g and highest values found in the alluvium deposits of the highlands and the lowest in the sand dunes region. Be-10 of the coastal sediments was rather constant, at a value of 6~7×107 atoms/g. These results indicate Be-10 concentrations that are lower than what is expected from latitude-zonal models. However, the recent global atmospheric Be-10 production models suggest low production and deposition at low latitudes. The mineralogic difference between the deposits (silicates, carbonate or evaporite) did not show a clear effect on Be-10 values. The low rainfall in the region (50~250 mm/y) means that most of the Be-10 deposition is related to dry fallout. This is also well illustrated by the higher values in the relatively rainy highlands compared to the rain-poor sand dunes region. These highlands have been subjected to tectonic uplift and sea level changes that have affected erosion and depositional rates. The occurrence of tillite-like deposits and water-ice erosional features in the highland along incised valleys suggest formation of ice bodies (likely small winter glaciers) in this region, which was most likely during the ice ages. The effort to produce carbon-14 dates from the alluvial terraces at the sides of the incised wadies was difficult due to the absence of organic matter. We, however, used carbonate material (stalagmitic and other groundwater drip carbonate forms) collected from a cave in the bedrocks of the area, where the C-14 data indicate infinite ages (older than 40000 years). Although estimating ages based only on 10Be data is problematic, particularly for sediments without other age controls, the 10Be in samples at different stratigraphic levels within the alluvial terraces indicates a range of 1-20×107 atoms/g. The highest concentration is found in the youngest terrace beds, which indicate a large span in Be-10 (likely ages too) that has associated with terraces development in the area. The variability of the Be-10 concentration in the terraces reflects changes in the primary concentrations during deposition, leaching/enrichment in the terrace profile and addition/removal by wind. The 10Be concentration in the modern fluvial sediments of the wadis, sandy-muddy samples of a wadi bed, indicates concentrations of 14~17×107 atoms/g, which is relatively lower than the highest value in the terrace beds. We are working on linking Be-10 production/depositional models in the region with sedimentation episodes, rainfall rate and erosion rates. The addition of new Be-10 data from arid regions to the global register of soils and sediments is vital for the comprehensive understanding and accurate modeling of Be-10 global deposition and the link to climate change in the past. Göran Possnert has contributed to this project in all its aspects and the authors are honored by his dedication and enthusiasm. He passed away in 2022 and for ethical reasons and scientific integrity, his name was not included in the authorship list to avoid any possible conflicts during publication.
    
    Speaker: Peng Chen (Hohai University)
- Sample Preparation Techniques GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Sample separation and preparation methods for achieving lower backgrounds, higher yields, and stronger ion beam currents.
  
  Convener: Dr Kunihiko Nishiizumi (University of California, Berkeley)
  - 232
    
    20 years of progress on the sealed-tube zinc reduction method of graphitization for 14C AMS measurement at the UCI KCCAMS facility
    
    We report here the progress of the sealed tube zinc reduction method for graphitization over the past 22 years at the W. M. Keck Carbon Cycle AMS facility (KCCAMS) at the University of California, Irvine, USA. Since the publication of the method in 2007, we have significantly improved and expanded this technique. First, we have further decreased the background associated with combustion and graphitization to a F14C of 0.00015 (approximately 52,000 14C YBP). Second, we are now able to graphitize samples as small as a few µg C by using a smaller reaction tube and a thermal gradient graphitization approach from room temperature to 450°C (Walker and Xu, 2019). The small carbon mass graphite (3-10 µg C) can produce currents of approximately 1 μA μg C−1 (he12C+) with a low extraneous carbon blank (0.5–0.7 µg C) when measured at KCCAMS. Third, we have demonstrated that the method is capable of handling samples with a high sulfur content (up 21.5%S). Fourth, the method can be adapted to a single-step process, combining combustion and graphitization, making it a convenient method for graphitizing certain types of samples, such as AMS swipes. Once sealed inside the Pyrex tube under vacuum, sample graphite is preserved indefinitely. We have tested graphite prepared more than 10 years ago and found no change during storage. This makes the method especially useful for users without their own AMS, costly semi-automated H2 reduction lines, and for time intensive sample extraction methods (e.g. compound-specific measurements).
    
    Speaker: Dr Xiaomei Xu (University of California, Irvine)
    
    Abstract AMS16_Xu.docx
  - 233
    
    Removal of hydrogen sulfide in carbon dioxide for radiocarbon AMS analysis
    
    A method of hydrogen sulfide removal in water (for DIC radiocarbon analysis) or carbon dioxide gas was investigated. By using a silver nitrate solution in diluted nitric acid in a gas wash device, or a trap filled with silver nitrate impregnated silica gel, the hydrogen sulfide was easily removed from the carbon dioxide. The cleaned CO2 is pure enough to get reduced by hydrogen on the iron catalyst for graphite AMS measurement. The blank of this clean-up method is negligible. It will not change the isotopic composition of the CO2. This method is applied to some hydrogen sulfide containing samples successfully.
    
    Speaker: Dr Mark Roberts (Woods Hole Oceanographic Institution)
  - 234
    
    10Be and 26Al sample preparation at the GXNU-AMS laboratory
    
    10Be and 26Al sample preparation at the GXNU-AMS laboratory
    
    Kaiyong Wu1, Hongtao Shen1, 2, Linjie Qi1, He Ouyang1, Guofeng Zhang1, Junsen Tang1, 2, Dingxiong Chen1, Xinyi Han1, Xinya Huang1, Lingrong Du1, Weixin Chen1, Wenqiao Liu1
    1. College of Physics and Technology, Guangxi Normal University, Guilin Guangxi 541004, China
    2. Guangxi Key Laboratory of Nuclear Physics and Nuclear Technology, Guilin Guangxi 541004, China
    Corresponding author. Email: shenht@gxnu.edu.cn
    
    Since the 1980s, significant progress has been made in the study of cosmogenic nuclides, of which 10Be and 26Al have been widely used. The invention of accelerator mass spectrometry (AMS) has facilitated widespread application of 10Be and 26Al exposure dating and erosion rates in chronological studies. Quartz, due to its simple composition of silicon and oxygen, is an ideal mineral for generating both 10Be and 26Al , making it a preferred material for cosmic nuclide dating. In this work, Be and Al were effectively separated from Fe and Mg by chemical precipitation based on previous experimental methods. The separation of beryllium and aluminum was achieved by a specialized column instrument with a 12-cm length and a 1.5-cm inner diameter containing Dowex 50W-X8 (H+) cation exchange resin with a particle size of 100-200 mesh. In order to improve the separation efficiency and recovery of beryllium and aluminum, hydrochloric acid solutions of different concentrations were used. The sample preparation process and separation and purification methods for beryllium and aluminum are still being optimized. The goal is to further optimize the extraction and separation of the cosmogenic nuclides 10Be and 26Al from quartz. In addition, this work aims to provide an optimized chemical analytical method to meet the demand for 10Be/26Al measurements in the 3MV AMS system at GXNU.
    
    Speaker: Mr Kaiyong Wu (Guangxi Normal University)
    
    吴凯勇摘要.docx
- 10:20
  
  coffee break Lobby , 2nd Floor
  
  Lobby , 2nd Floor
- Memorial Session GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  This session will be dedicated to honoring the memory of our late predecessors who have made significant contributions to the field of accelerator mass spectrometry. It will be an opportunity for us to reflect on their legacy and celebrate their achievements that have paved the way for current and future advancements in AMS.
  
  Convener: Prof. Aldahan Ala (United Arab Emirates University)
  - 235
    
    Seawater circulation in the Nordic Seas and Arctic traced by reprocessing derived 129I using AMS analysis
    
    Seawater circulation and interaction are important processes for pollutant dispersion and environmental and climate change. Salinity and temperature are the conventional parameters, which were widely used for the identification of water masses and circulation in the oceans. Generally, small differences in these two parameters are difficult to detect, which makes precise and accurate identification of water circulation problematic. This is particularly important for some locations where the water masses have very similar physiochemical features. Part of the problem can be resolved by using a marine water tracer more sensitive than salinity and temperature to the changes in water parcels and circulation. 129I has been proven to be well suited for such purposes, as the isotope is a long-lived radionuclide (T½=15.7 Ma) with a high solubility and conservativity in marine water. As a high-yield fission product from 235U and 239Pu, anthropogenic 129I is the dominant source in present-day environments. Among the major release sources of the isotope are the two spent nuclear fuel reprocessing plants at Sellafield and La Hague that have discharged a huge amount of 129I to the Irish Sea and the English Channel, accounting for more than 90% of the total human releases of 129I. This reprocessing derived 129I is therefore an ideal and unique tracer for the accurate identification of the dispersion of water-soluble pollutants and water circulation in marine environments, especially in the Nordic Seas and the Arctic. However, the analysis of 129I requires the use of accelerator mass spectrometry, which is amenable in some laboratories worldwide. Furthermore, the speciation of iodine in the environment is another feature that needs to be considered during the analysis of the isotope. In the past 25 years, we have analyzed a series of seawater and seaweed samples in the Nordic Seas and the Arctic for 129I and 127I, as well as their chemical species. This presentation aims to summarize all these investigations, highlight the major achievements, and show some perspectives. Göran Possnert has contributed to the data in all its aspects, and the authors are honored by his dedication and enthusiasm. He passed away in 2022, and for ethical reasons and scientific integrity, we put his name on the authorship list as we shall present data and conclusions that he has approved.
    
    Acknowledgements: Many colleagues and formal students contributed to this work, including Justin Gwynn, Peng Yi, Peng He, Maoyi Luo, Luyuan Zhang, Keliang Shi, Yukun Fan and Qi Liu. This work was also supported by Nordic Research Foundation and the Chinese Academy of Sciences.
    
    Speaker: Prof. Xiaolin Hou (Institute of Earth Environment, Chinese Academy of Sciences)
    
    AMS abstract Hou for Memorial session Xiaolin-Ala.docx
  - 236
    
    Göran Possnert and his importance for the Lund radionuclide research
    
    The passing of Göran Possnert in October 2022 marked a significant loss to the cosmogenic radionuclides community. His pioneering work laid the foundation for many advancements in this area, and his contributions continue to influence current research and methodologies. The cosmogenic radionuclide group in Lund, led by Raimund Muscheler, has cooperated with Göran Possnert since 2007, focusing on 10Be and 36Cl measurements from ice cores with applications in solar and geomagnetic reconstructions. Göran’s extensive knowledge and innovative approach enabled our group to achieve several significant milestones, including identifying sun-climate relationships for the first time over the last glaciation period (Adolphi et al., 2014), the first ice core evidence for the extreme solar storms in 775/4 A.D. (Mekhaldi et al., 2015), the latest geomagnetic reconstruction over the glacial period based on the Greenland ice cores (Zheng et al., 2021), and much more. He was instrumental in supporting not only PhD but also master projects in our group. The legacy of Goran’s work continues through the many researchers he mentored and the significant contributions he made to our understanding of radionuclides in ice cores. As we honor his memory, we acknowledge the profound impact he had on our work and express our deep gratitude for his invaluable contributions. His legacy will continue to inspire and guide us in future endeavors.
    
    Speaker: Minjie Zheng (Lund University)
  - 237
    
    I-129 in water of the Celtic Sea, the English Channel and beyond: sources and environmental impact
    
    The English Channel (the Channel) and the Celtic Sea represent a major transport pathway of Atlantic water to the North Sea, with anthropogenic I-129 added to the water parcels. The major source of this I-129 is the liquid discharges from the La Hague nuclear reprocessing facility of I-129 into the Channel that have been going on for the last 60 years, with an estimated total amount exceeding 7000 kg by the end of 2024. The fate of this discharged I-129 in the Channel is not entirely clear, but a large part of it is transported with the marine currents or deposited in the Channel bottom and a smaller part is transferred to the atmosphere. The understanding of 129-I distribution in the Channel is further complicated by the speciation forms of the isotope. Although the liquid discharge from the nuclear facility is dominated by the iodide species, occurrence of both iodide and iodate was observed in marine waters in addition to the organic iodine. To shed light on some of the 129-I occurrence forms and distribution pattern in the Channel and beyond, data on 129-1 and 127-1 and their species that were acquired from several investigations are presented. The data reveal large variation in the I-129 concentration and speciation forms as the isotope is transported from the Channel. The variations in the I-127 were less bracketed and strongly correlated with the marine water salinity. The transport pathways are predominantly northward, but leaks with high I-129 transport southward were also detected. The data also indicate that the major speciation form of the isotopes is iodate (IO3) with a varying ratio of iodide to iodate. Despite the relatively large amount of data on I-129 in the North Sea, accurate transport pathways are still disputable. However, the available data suggest extensive transport along the European continental margin, with some conversion of iodate into iodide by mostly the addition of water from the European rivers. The environmental impact of I-129 is presently not well understood, as calculations of radioactivity based on the concentration in marine water indicate acceptable levels. However, analysis of I-129 in seafood products from the Channel may add new perspective to this issue.
    
    Speaker: Peng He (Chengdu University of Technology)
- Sample Preparation Techniques GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Sample separation and preparation methods for achieving lower backgrounds, higher yields, and stronger ion beam currents.
  
  Convener: Dr Xiaomei Xu (University of California, Irvine)
  - 238
    
    10Be AMS MEASUREMENTS AND CHRONIC BERYLLIUM DISEASE (CBD)
    
    10Be AMS MEASUREMENTS AND CHRONIC BERYLLIUM DISEASE (CBD)
    Kunihiko Nishiizumi, Space Sciences Laboratory, University of California, Berkeley, CA 94720-7450, USA. (kuni@berkeley.edu)
    
    Beryllium and Be compounds, especially inhalation of very small particles or fumes, are known to be extremely toxic materials. Although the occupations with the highest risk are likely Be mining and machining, AMS researchers who process and measure 10Be are also at risk. Although most 10Be researchers are aware of the toxicity of Be, many nonetheless do not take the risk seriously. I have experienced circumstances that have brought home in a personal manner this risk. I hope this experience will galvanize all researchers who handle Be compounds to remain vigilant regarding the risks of Be. There are two types of beryllium diseases, acute and chronic beryllium disease (CBD), but the former is now rare and not important for AMS researchers. Patients with CBD experience several symptoms including shortness of breath, cough, night sweats, fatigue, chest pain, and weight loss. Symptoms may develop within months to 30 - 40 years after exposure to Be. Since CBD is an immune system response that is only people have beryllium sensitization (allergy to Be) develop symptoms, it is important to get a diagnosis of beryllium sensitization first.
    Immune sensitization to beryllium can be detected by a blood test technique: beryllium lymphocyte proliferation test (BeLPT), which measures the white blood cells’ reaction to Be. BeLPT is a complicated, time-consuming, and relatively expensive test. Only three laboratories, Oak Ridge Institute for Science Education (ORISE), National Jewish Health Center, and Cleveland Clinic perform the BeLPT in US (2019 update) (e.g. 1).
    Over 45 years, I have handled more than 150 g of BeO, perhaps giving me the dubious distinction of handling more Be, perhaps by one to two orders of magnitude, than anybody in AMS community I have known. With the help of EH&S at Lawrence Berkeley National Lab (LBNL), I have participated in the BeLPT every ~3 years. The blood samples were sent to two of above labs because it requires two abnormal results to identify beryllium sensitization. In addition, a high-resolution chest CT scan, chest x-ray, and pulmonary function test were performed.
    I will describe complicated BeLPT and some suggestions / practices of prevention of beryllium disease at the meeting.
    References:
    1. Beryllium lymphocyte proliferation testing (BeLPT), DOE-SPEC-1142-2019.
    
    Speaker: Kunihiko Nishiizumi (University of California, Berkeley)
    
    CBD_Abstract_Final.pdf
  - 239
    
    A gas sample preparation method for radiocarbon at the GXNU-AMS laboratory
    
    A method for preparing gas samples was established in Guangxi Normal University. The method consists of three parts: introducing nitrogen to exhaust the impurity, releasing the gas and circulating CO2 , purifying CO2 and graphitization. A series of atmospheric samples were prepared to verify the feasibility and stability of this method. Moreover, the carbon content corresponding to the atmospheric samples of different volumes has a linear relationship with CO2 pressure collected by the sample preparation system. The measurement results of the accelerator mass spectrometer (GXNU-AMS) in our laboratory show that the beam current of 12Cˉ for each sample is greater than 30uA. The pollution introduced during the gas sample preparation process is less than 3×10ˉ15. In summary, the gas sample preparation method has the characteristics of high efficiency and low pollution.
    
    Speaker: Xinyi Han (Guangxi Normal University)
  - 240
    
    A tree-ring cellulose extraction device adapted to radiocarbon analysis
    
    Tree-ring cellulose is a commonly used material for radiocarbon analysis. Extracting cellulose is labor-consuming and several devices that enable batchwise extraction have been developed. However, these devices bear the risk of sample contamination. The present study describes a new device which improves upon two aspects of currently available devices. First, to prevent cross-sample-contamination, we redesigned the drainage module to enable independent removal of chemical waste from each individual sample funnel. Second, we added covers to the sample funnels to reduce the risk of external contamination. Cellulose purity (i.e., holocellulose) was confirmed by Fourier Transform Infrared (FTIR) Spectroscopy. Furthermore, accuracy of the radiocarbon analysis was confirmed by results of 14C-blank samples and samples of known age. In conclusion, while maintaining labor-saving, our modified device significantly reduces the risk of sample contamination during extraction of tree-ring cellulose.
    
    Speaker: Mr Pengyu Lin (School of Geography and Ocean Science, Nanjing University)
- New and Updated Facilities GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Report on new and updated AMS facilities.
  - 241
    
    The new 3.0 MV Universal Accelerator Mass Spectrometer GANA at Guangxi Normal University
    
    GANA (Guangxi Accelerator for Nuclear Analysis) is a new 3.0 MV universal Accelerator Mass Spectrometer (AMS) at Guangxi Normal University (GNU), and it supports the analysis of elements ranging from 10Be to 244Pu at 3 MV terminal voltage. Manufactured by High Voltage Engineering Europa B.V., the Netherlands, GANA is equipped with a 50-sample ion source, a high-resolution 120-degree injection magnet, a 90-degree high-energy analysis magnet (mass-energy product 185 MeV-AMU, supports 244Pu+5 at 18MeV ), a 65-degree, 1.7 m radius electric analyzer, and a 4 channel gas ionization detector. The 3.0 MV Tandetron accelerator features a high-voltage terminal that supports both gas and foil stripping, with Argon or Helium as selectable stripper gases. To minimize the pressure in the acceleration tubes, the terminal uses a differential pumping system with two turbomolecular pumps. Post-acceleration, a pump restriction minimizes the flow of stripper gas into the high-energy side analyzing beamlines, maintaining a pressure of low 10-8 mbar. This low pressure is crucial for minimizing low-angle scattering on gas particles, thereby achieving high abundance sensitivity for actinides. The rare ions of interest are identified in a multi-anode gas ionization chamber, whereas the stable ones are measured as current in offset Faraday cups with an internal slit system for stabilizing the terminal voltage. A switching magnet in the high-energy beamlines allows using a separate beamline for ion beam analysis.
    
    In this presentation, we will discuss the specifications of the new AMS equipment and report on the acceptance test results for 10Be, 14C, 26Al, 129I, and actinide analyses.
    
    Speaker: Prof. Hongtao Shen (Guangxi Normal University)
- 12:00
  
  lunch Restaurant，Ground floor
  
  Restaurant，Ground floor
- 13:30
  
  AMS lab tours. Field trip to the other Forbidden City in China - Jingjiang Princes' City, Duxiu Hill and East West Street GNU and Guilin City
  
  GNU and Guilin City
- Conference Banquet GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
Friday, 25 October
- Registration in the lobby of the Conference Hotel Lobby of the Conference Hotel
  
  Lobby of the Conference Hotel
- Plenary GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Convener: Prof. XIAOLEI ZHAO (BEIJING NORMAL UNIVERSITY)
  - 242
    
    Retrospective view on progress and recent developments in AMS technology
    
    Modern AMS instruments are still following design concepts of the pioneering experimental setups as invented during the early times of AMS. However, measurement procedures have undergone a continuous evolution. Groundbreaking progress was made when molecular isobaric interferences could be eliminated by collisional interaction of swift ions with the stripper gas atoms. Radiocarbon detection, still the most important AMS discipline, has advanced most significantly by introducing vacuum insulated high voltage stages, He as stripper gas, fixed field magnetic spectrometers, optimized ion optics, and compact instrument designs. Today, such almost tabletop sized instruments are commercially available and capable to measure carbon isotopic ratios with sup permille precision and measurement quality is more and more no longer limited by the instrumental capabilities but rather by the reproducibility of the sample preparation procedures. This has boosted applications of radiocarbon analyses in many different research fields, making it to a widespread standard analytic technique rather than an exotic experimental endeavour. The analytical progress achieved over the past decades has opened a great potential as well for applications of Be-10, Al-26, Ca-41, I-129, and actinides measurements. Instruments using terminal voltages of less the 1 MV, He as stripper gas and utilizing the 3+ charge state obtain high ion transport efficiencies for actinide nuclides. They are not interfered by stable isobars and can be identified with optimized gas ion detectors at low ion energies. But also, in cases of nuclides with stable isobar interferences such as Be-10, dedicated low energy instruments can provide suitable measurement performance for a wide variety of applications. Here, elaborated ion identification techniques and optimized ion optical designs are crucial to achieve competitive efficiencies and background levels. However, there is still a need for AMS instruments based on large accelerator facilities. Isobar suppression of medium heavy nuclides such as Cl-36, Mn-53 or Fe-60 rely on substantial ion energies above 40 MeV to exploit the energy loss differences of isobaric ions. This may change soon, when isobar suppression technique at very low ion energies such as RF cooler in combination with lasers beams become mature. This presentation will review major AMS development steps and highlight latest progress in AMS measurement technology.
    
    Speaker: Prof. Hans-Arno Synal (Ionpuls AG)
- New Isotopes Methodologies GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  Developments in ion injection and instrumentation interfacing for AMS. Topics include ion production, gas source AMS, and gas chromatography interfacing.
  
  Convener: Prof. Kimikazu Sasa (University of Tsukuba)
  - 243
    
    The 90s – Exciting opportunities for AMS at the Heavy Ion Accelerator Facility
    
    The mass region between 90 and 100 amu is home to several long-lived radionuclides that are interesting for various applications of AMS. Two examples are $^{93}$Zr, and $^{99}$Tc with half-lives of ~1.6 Ma, and ~211 ka respectively. Both isotopes are high-yield fission products and were produced and distributed in the environment by atmospheric nuclear weapons tests and nowadays are produced in large quantities in nuclear power plants. In addition to fission, $^{93}$Zr is also created by neutron capture on stable $^{92}$Zr due to usage of zirconium alloys for cladding of nuclear fuel rods. The neutron capture cross sections of $^{92}$Zr for thermal energies (~25 meV) as well as for stellar energies (tens of keV) are not well known. These cross sections are important for nuclear industry, nuclear waste management and for modelling the astrophysical slow neutron capture process, respectively. Technetium-99 can serve as an ocean current tracer and owing to its high mobility and long half-life, it is an important radionuclide for long-term dose-assessment and radiotoxicity.
    The high achievable particle energies (>200 MeV) at the Heavy Ion Accelerator Facility (HIAF) and our dedicated 8-anode ionisation chamber are ideal to tackle the challenging separation of $^{93}$Zr and $^{99}$Tc from their respective isobars, $^{93}$Nb and $^{99}$Ru.
    For 93Zr, detection limits of $^{93}$Zr/$^{92}$Zr ~10$^{-12}$ were achieved, however currently no well-defined $^{93}$Zr AMS reference material exists. In collaboration with the Institute Laue-Langevin and HZDR we produced well-defined amounts of $^{93}$Zr via neutron-induced fission on $^{235}$U in two uranium-oxide targets. Addition of known amounts of stable Zr carrier and extraction of the Zr resulted in primary reference samples with known $^{93}$Zr/Zr ratios. Currently cross calibrations of secondary reference materials (neutron-irradiated ZrO$_{2}$) to these materials are being conducted at HIAF.
    First AMS measurements of $^{99}$Tc were performed in the early 2000s at HIAF [1,2] and in collaboration with the University of Vienna they are currently refined. In the absence of a stable Tc isotope, we follow the approach described in Koll et al [3]. The Tc is dispersed in a Nb$_{2}$O$_{5}$ matrix, extracted from the ion source as TcO$^{-}$ and measured relative to stable $^{93}$Nb. A precision of ~10% and blank levels in the order of 10$^{7}$ $^{99}$Tc atoms per sample were achieved, allowing for measurement of the $^{99}$Tc content in various environmental samples. Recent investigations showed that using a degrader consisting of a stack of nine 1 μm thick silicon nitride foils in combination with our multi-anode ionisation chamber increases the Tc-Ru separation and improves the normalisation by a factor of two, arriving at the same blank levels. The degrader foil technique will be explored for other AMS isotopes in this mass region, where $^{90}$Sr with two protons less than its isobar $^{90}$Zr is a particularly interesting candidate.
    
    [1] Fifield et al., Nucl. Instrum. Meth. B 168, 427 (2000). doi: 10.1016/S0168-583X(99)01094-0
    [2] Wacker et al., Nucl. Instrum. Meth. B 223-224, 185 (2004). doi: 10.1016/j.nimb.2004.04.038
    [3] Koll et al, Nucl. Instrum. Meth. B 438, 180 (2019). doi: 10.1016/j.nimb.2018.05.002
    
    Speaker: Stefan Pavetich (The Australian National University)
  - 244
    
    Tracking down Tc-99 in the environment
    
    Concentrations of the anthropogenic radionuclide $^{99}$Tc (t$_{1/2}$ = 2.1$\times$ 10$^5$ yrs) have been extensively studied in the Irish Sea, where the Sellafield reprocessing plant is responsible for high concentrations of 2$\times$ 10$^9$ atoms/ml. However, a comprehensive understanding of its global distribution and physico-chemical behavior in the environment remains limited. The accurate determination of $^{99}$Tc concentrations in samples distant from contamination sources requires detection methods with exceptionally high sensitivities of better than 10$^7$ atoms/sample or prohibitively large sample volumes.
    
    In AMS of $^{99}$Tc effective suppression of the stable isobar $^{99}$Ru and establishment of a reliable normalization method are imperative. Various strategies can be employed for the suppression of $^{99}$Ru: at the Vienna Environmental Research Accelerator (VERA), we investigate an approach using a 3 MV tandem accelerator coupled with the Ion-Laser InterAction MS (ILIAMS) setup. It has been shown that because of different detachment energies, $^{99}$RuF$_5^−$ can be suppressed by a factor of up to 105 using a 532 nm-laser, making extraction of $^{99}$TcF$_5^−$ a viable option for ILIAMS [1]. For normalization to $^{93}$NbF$_5^−$ extracted from the same sample, the reproducibility of the method was significantly improved by a factor of 3 by optimization of ion source parameters.
    
    At AMS-facilities equipped with large accelerators that can reach >10 MV terminal voltage, another approach can be pursued. The Australian National University (ANU) uses a 15 MV tandem accelerator, so that the ions are accelerated to ~190 MeV and $^{99}$Ru and $^{99}$Tc are separated in an 8-anode ionization chamber. The minute differences in their energy loss characteristics are only observable at these high ion energies [2]. Normalization to $^{93}$NbO$^-$ current extracted from the sputter matrix [3] achieved a precision of 10%. Technical details of this technique are presented in the contribution from Stefan Pavetich.
    
    Implementing this latter approach, we not only met the criteria for sensitivity and reproducibility but also marked a significant milestone by effectively analyzing a comprehensive set of samples from different environmental reservoirs. Among these were 1 g peat bog samples and 10 L water samples from the Pacific Ocean and European rivers. By employing chemical preparation techniques and subsequent AMS measurement we successfully determined ultra-trace levels of $^{99}$Tc.
    
    References:
    [1] Martschini et al. Radiocarbon 64(3) (2022), doi: 10.1017/RDC.2021.73
    [2] Wacker, et al., Nucl Instrum Methods Phys Res B 223-224 (2004), doi: 10.1016/j.nimb.2004.04.038
    [3] Koll et al., Nucl Instrum Methods Phys Res B 438 (2019), doi: 10.1016/j.nimb.2018.05.002
    
    Speaker: Stephanie Adler (University of Vienna)
    
    Adler-AMS16-abstract.pdf
  - 245
    
    Reveal atmospheric phenomena using cosmogenic 10Be and 7Be base on AMS analysis
    
    The 10Be/7Be ratio is a sensitive tracer for the study of atmospheric transport, particularly with regard to stratosphere-troposphere exchange. Measurements with high accuracy and efficiency are crucial to 7Be and 10Be tracer studies. Full stripping method of 7Be have been carried out by few larger AMS. However, for low energy AMS that is difficult to obtain efficient full stripping Be, the method of 7Be measurement using non-fully stripping is a blank field, which is more widely applicable for all AMS. Firstly, the preparation procedures of rain samples that is suitable for 7Be and 10Be by AMS measurement at same target have been established. 7Be analysis has been performed to by full stripping method, which completely removed 7Li due to its electronic structure, using more homogeneous Si3N4 as a secondary stripping film, and same way for 10Be. 7Be/9Be background was less than 2×10-16. On the other hand, study for non-full stripping method to 7Be has been analyzed by AMS. The magnitude of suppression for isobaric 7Li has been discussed at each stage, and another interference 14N were found and analyzed. Due to the full stripping method was not used, it makes for it possible to analyze 7Be with lower energy AMS, which is ultra-low efficiency to obtain 7Be4+. The non-full stripping method is generally method for 7Be analysis especially for low energy AMS. In addition, we discussed quality control and data calibration methods. A preliminary study of environment applied was carried out using 7Be and 10Be by 3MV AMS. The ratio of 10Be/7Be and concentration of 10Be and 7Be of rainwater collected in Xi'an have been obtained.
    
    Speaker: Prof. Yun-Chong Fu (Institute of Earth Environment, CAS)
- New and Updated Facilities GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Report on new and updated AMS facilities.
  
  Convener: Prof. XIAOLEI ZHAO (BEIJING NORMAL UNIVERSITY)
  - 246
    
    HAMSTER – a new universal 1-MV AMS facility at HZDR with ion cooler and SIMS capabilities
    
    The new dedicated AMS facility HAMSTER (Helmholtz Accelerator Mass Spectrometer Tracing Environmental Radionuclides) is being set up at HZDR as a universal and flexible AMS system that allows for routine measurements of nuclides across the whole chart of nuclides but has also a focus on implementing new technical developments.
    HAMSTER is based on a 1-MV Pelletron accelerator. It consists of three independently operating beam injection systems: an MC-SNICS ion source is coupled via a 90° ESA to a third-order correction low-energy injection magnet. Upstream a second MC-SNICS connects via a 45° ESA to an ion-cooler setup which is sandwiched between two magnets. This system then merges to the beamline mentioned above towards the injection magnet. Both of these two low energy beamlines include fast beam switching, beam attenuators and at all waists full beam diagnostics capabilities for low-intensity ion currents. Finally, another ion beam from a dynamic SIMS setup (CAMECA IMS 7f Auto), previously connected to the DREAMS 6-MV system (HVEE Tandetron), can be injected into the AMS beamline for Trace Element Accelerator Mass Spectrometry (TEAMS) measurements.
    The high-energy side corresponds to NEC’s ‘Actinide AMS’ system, as first realized at the VEGA system at ANSTO, Sydney. It includes two high-energy magnets, both with fast bouncing capability, and with the option of quasi-simultaneous measurements of up to 8 isotopes. As an additional feature, we have added a Wien filter before the first high-energy magnet for further background reduction, primarily for heavier isotopes.
    HAMSTER accordingly requires a significantly larger footprint compared to state-of-the-art compact AMS systems. It allows to analyse ‘all isotopes’ from Be up to the super-heavies. Special focus was a setup aiming for a high measurement efficiency as well as implementing the options of full beam diagnostics at all waists with the objective to facilitate further technical developments for rare isotope detection.
    A new ion cooler ILTIS (Ion Linear Trap for Isobar Suppression) had been developed in-house in collaboration with the Univ. of Vienna (J. Lachner et al., this conference) to utilise and explore the potential of ion-laser interaction for detection of new AMS nuclides. NEC’s Accelnet software will be integrated into our general EPICS-based control software, which is presently under development at HZDR.
    HAMSTER will be located in a dedicated new building that houses also three labs for sample handling and sample preparation, which add to the two chemistry labs already in use since about 15 years. The new facility is operated as a dedicated AMS system - with the 6-MV DREAMS facility still being used in parallel. However, considering the improved isobar suppression, the new actinide AMS capabilities and the stable isotope capabilities, with HAMSTER we will extend our research portfolio significantly beyond DREAMS’s primary focus on cosmogenic nuclides.
    
    Speaker: Anton Wallner (HZDR)
  - 247
    
    A home-made compact multi-isotope AMS system at CIAE
    
    Developing the compact AMS system for multi-isotope measurement is the tendency for AMS system development. After developing single stage 0.2MV-AMS system dedicated for 14C measurement and air-insulated 300KV-AMS system used for heavy nuclei measurement, A compact multi-isotope AMS system which can be used for 14C,26Al, 236U,239Pu etc. measurement has been developed at CIAE. Utilizing the compact design of the AMS system, The floor space of the compact AMS system is about 25m2 which is half of the air-insulated 300KV AMS system.
    The structure of the AMS system is shown in Figure 1. The ion source is 40-sample negative sputter ion source. The injection system consists of a 90◦ double focus spherical electrostatic analyzer (ESA) and a double focus 90◦ injection magnet with a deflection radius of 650 mm for both the ESA and the injection magnet. The accelerator is a compact accelerator with a total length of 1.1 m and a terminal voltage of 260 kV. An electrostatic quadrupole was installed after the accelerator for beam focusing. After that, a double focus 90◦ analyzing magnet and a 90◦ double focus ESA and with a deflection radius of 650 mm for both the ESA and the analyzing magnet. In order to improve the mass resolution, another 70◦ analyzing magnet with deflection radius of 700 mm is equipped behind the ESA ,finally, a gas detector with 30 nm silicon nitride membranes as entrance windows is used.
    The performances of the AMS system have been tested with 129I and 239Pu. The transmission efficiency of 127I for charge state of 2+ is more than 50% at accelerator’s terminal voltage of 0.2 MV, and the sensitivity of 129I/127I=1.5×10-14 has been obtained; The detection limitation of better than 0.1fg for 239Pu at accelerator’s terminal voltage of 0.23 MV has been achieved. The performances of 14C, 26Al, 236U etc. are under developing.
    
    Fig.1 The schematic diagram of the AMS system
    
    Speaker: Ming He (中国原子能科学研究院)
    
    A home-AMS compact AMS ---AMS16 confenrence(2).docx
  - 248
    
    The NAUTILUS project: The story of an AMS facility on the move
    
    NAUTILUS (NAval Ultra-Trace Isotope Laboratory Universal Spectrometer) combines Secondary Ion Mass Spectrometry (SIMS) with a Single Stage 300kV Accelerator Mass Spectrometer system (SSAMS) to produce a single setup unlike any other in the world for spatially resolved trace-element and isotope analysis [1]. Initially designed and built at the United States Naval Research Laboratories (NRL), it was decommissioned only 2 years after becoming fully operational due to a realignment of the research focus of a number of groups at NRL. NAUTILUS was transferred in August 2023 to the University of Notre Dame (ND) to pursue its research “career” in an academic setting broadening its range of research activities. At the start of disassembly NAUTILUS was still 100% functional, all systems were connected to power and the system under vacuum. NAUTILUS was carefully disassembled and fully documented by members of the Institute for Structure and Nuclear Astrophysics (ISNAP) of the University of Notre Dame and crated and shipped to ND where it awaits reassembly.
    The University of Notre Dame has approved $1.5M for the construction of a new building north of campus and the hiring of a research faculty to supervise its reassembly and future operations. NAUTILUS will be operated jointly by the Department of Engineering and ISNAP as a University research facility, and will as such support a number of research programs: ranging from actinide research both from the ND Energy Center and the ISNAP AMS group, to the training of the next generation of experts in Nuclear Nonproliferation and the development of new capabilities for the detection, identification and characterization of nuclear weapons development. NAUTILUS will also support a basic Radiocarbon AMS program for the department of Anthropology as well as research programs from NASA meteoritic research groups and other outside users. This talk will present both the challenges of the move as well as present certain aspects of the NAUTILUS future scientific program.
    
    This work is supported by the Notre Dame Office of Research, The ND College of Science and the ND College of Engineering.
    
    [1] E. Groopman et al, J. Anal. At. Spectrom., 2020, 35, 600
    
    Speaker: Prof. Philippe Collon (University of Notre Dame)
- 10:20
  
  coffee break Lobby , 2nd Floor
  
  Lobby , 2nd Floor
- Applications in Oceanography GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Using the AMS to study sedimentation rates and records, or tracing ocean currents.
  
  Convener: Prof. Marcus Christl (ETH Zurich)
  - 249
    
    Exploring the lowest levels of environmental $^{90}$Sr/Sr compared to $^{236}$U/U in carbonates and seawater using a new, highly sensitive Accelerator Mass Spectrometry technique
    
    Strontium-90 ($^{90}$Sr) is an anthropogenic radionuclide, which, due to its radiological relevance, has been most intensively monitored in the past. In terms of initial activity, over 630 PBq of this radionuclide have been distributed globally from stratospheric fallout of bomb-testing, and there are more localized contributions from tests, accidents, and releases from reprocessing plants. In the past, massive sample sizes (up to 100 l of seawater or 100 g of coral aragonite) were required, even right after the peak period of global fall-out from bomb testing. On the other hand, the high amount of strontium dissolved in seawater complicates the use of mass spectrometric methods, as an isotopic abundance sensitivity of at least 1·10$^{−15}$ is required to detect the estimated main signal. With recent advances in isobar separation techniques in accelerator mass spectrometry (AMS) at the University of Vienna, this requirement has come within reach, offering new research possibilities. The new technique uses an ion-cooler and laser-photo-detachment to suppress the stable isobar $^{90}$Zr almost completely. With initial test samples we could confirm an isotopic abundance sensitivity of 8·10$^{−16}$ $^{90}$Sr/Sr, sufficient for application to ocean water samples. In this presentation, we will show comparison of $^{90}$Sr to $^{236}$U, another ocean tracer that has been studied intensively recently. We will present results from contemporary coral skeleton material, the methods, requirements, and impact of sample preparation. Further, we present the first results from ocean water samples and the sample preparation and blank levels for these types of samples.
    Finally, we explain our sample preparation scheme to extract $^{236}$U, simultaneously with $^{90}$Sr, for multi-isotope applications of both.
    
    Speaker: Dr Stephan Winkler (Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany)
  - 250
    
    Seawater circulation analysis in the Southern and Indian Oceans by cross-sectional I-129 observation
    
    The Southern Ocean is suitable for detecting water masses containing anthropogenic $^{129}$I (T$_{1/2}$: 15.7 million years) tracer since $^{129}$I in the Southern Ocean is 3–6 orders of magnitude lower than that in the Northern Hemisphere. This study aimed to clarify seawater circulation in the Southern Ocean by vertical cross-sectional observations of dissolved $^{129}$I and water mass structure analysis from the Southern Ocean to the Indian Ocean, where few studies have been conducted. Seawater was sampled horizontally and vertically at six sites in the Southern and Indian Oceans (maximum depth: 5,230 m) during the JAMSTEC MR19-04 voyage (December 2019–February 2020) and horizontally at 15 sites from Australia to Showa Station in Antarctica during the National Institute of Polar Research SR21 voyage (November 2021–March 2022). After adding 1 mg of $^{127}$I carrier (Deepwater iodine, $^{129}$I/$^{127}$I: 1×10$^{–14}$) per 500 ml of seawater, iodine was purified by solvent extraction, and silver iodide targets were prepared. The $^{129}$I/$^{127}$I ratio of the target was measured using an accelerator mass spectrometer at the University of Tsukuba and normalized using the S-Purdue reference material ($^{129}$I/$^{127}$I: 8.378×10$^{–12}$). In the Antarctic Circumpolar Current (ACC) region of the Southern Ocean, anthropogenic $^{129}$I was rarely observed in the horizontal and vertical directions (maximum depth: 5,230 m) and was below the pre-nuclear activity level and Tsukuba AMS quantification limit. Anthropogenic $^{129}$I was observed in the surface layer from the northern area of the Southern Ocean to the Indian Ocean, and the relationship between the horizontal distribution of $^{129}$I and water temperature, salinity, and $^{226}$Ra provided information on the boundary between the Indian Ocean surface waters and the ACC. The vertical distribution of $^{129}$I in the Indian Ocean decreased with increasing depth from the surface. At the southernmost site in the South Ocean, two spike layers of $^{129}$I above pre-nuclear activity level were identified at 201 m and 1,670 m water depths, and an upper $^{129}$I spike was also observed in the isodensity layer at one site to the north.
    
    Speaker: Tetsuya Matsunaka (Kanazawa University)
  - 251
    
    Temporal Changes of Iodine-129 in the Canada Basin Over the Past Decade
    
    The Arctic, a region highly sensitive to global climate change, has experienced a temperature increase exceeding four times the global average rate since the onset of the industrial era. Concurrently, warmer and saltier Atlantic water is encroaching further northward into the Arctic Ocean, driving the phenomenon known as "atlantification." These shifts have led to significant Arctic sea ice loss and alterations in seawater thermohaline structure, potentially impacting Arctic ocean currents. Understanding the response mechanisms of these currents to climate change is crucial for comprehending and addressing the broader impacts of climate change. Notably, substantial quantities of iodine-129 (¹²⁹I) have been discharged directly into the North Atlantic from nuclear fuel reprocessing plants (NFRPs). Enriched with NFRP-derived ¹²⁹I, Atlantic Waters penetrate the Arctic region via the Fram Strait and the Barents Sea, rendering ¹²⁹I an ideal tracer for tracking Arctic currents. While numerous studies have utilized ¹²⁹I to investigate ocean currents in the Eurasian Basin of the Arctic Ocean, research in the Canada Basin, characterized by equally intricate current structures, remains scarce. Here, we present a decade-long analysis of temporal changes in ¹²⁹I concentrations at two stations (NAP and CB, Fig. 1) within the Canada Basin spanning from 2013 to 2023. Our findings reveal a diminishing influence of Atlantic water on the surface of the Canada Basin over time. In the early 2010s, ¹²⁹I concentrations in the intermediate layer of both stations remained consistent, suggesting a common source. However, by the late 2010s, the concentration of ¹²⁹I in the intermediate layer of the NAP station significantly surpassed that of the CB station, indicative of a shift in ocean currents, likely influenced by changes in the Arctic Oscillation and potentially linked to atlantification.
    
    Speaker: Dr Yuanzhi Qi (The University of Tokyo)
    
    AMS-16 abstract_Yuanzhi Qi.pdf
  - 252
    
    Pre-aged terrigenous organic carbon biases ocean ventilation-age reconstructions in the North Atlantic
    
    Over the last deglaciation, ventilation of ocean circulation has been key regulators of deep-sea carbon release, controlling climate change on centennial to millennial time scales. However, paleoceanographic reconstructions documenting changes in deep-ocean ventilation using 14C- foraminifera dating, may bear multidimensional explanations, obfuscating the roles of ocean ventilation played on climate evolution. Here, we show that previously inferred poorly ventilated conditions in the North Atlantic were linked to enhanced pre-aged organic carbon (OC) input during Heinrich Stadial 1 (HS1). The 14C age of sedimentary OC was approximately 13,345 ± 692 years older than the coeval foraminifera in the central North Atlantic during HS1, which is coupled to a ventilation age of 5,169 ± 660 years. Old OC was mainly of terrigenous origin and exported to the North Atlantic by ice-rafting. Remineralization of old terrigenous OC in the ocean may have contributed to, at least in part, the anomalously old ventilation ages reported for the high-latitude North Atlantic during HS1. This study provides a new organic geochemical explanation for anomalous deep-water ventilation 14C ages, and provides unique insights for global carbon cycle under extreme climatic events.
    
    Speakers: Yipeng Wang (Ocean University of China) , Rui Bao (Ocean University of China)
- New Isotopes Methodologies GOLDEN CASSIA (金桂厅), 2nd Floor
  
  GOLDEN CASSIA (金桂厅), 2nd Floor
  
  Developments in ion injection and instrumentation interfacing for AMS. Topics include ion production, gas source AMS, and gas chromatography interfacing.
  
  Convener: Stefan Pavetich (The Australian National University)
  - 253
    
    Identifying Old Ice and Water with Atom Trap Trace Analysis
    
    The long-lived noble-gas isotope 81Kr is the ideal tracer for old water and ice with ages of 0.1 – 1 million years, a range beyond the reach of 14C. 81Kr-dating, a concept pursued over the past six decades, is now available to the earth science community at large. This is made possible by the development of the Atom Trap Trace Analysis (ATTA) method, in which individual atoms of the desired isotope are captured and detected. ATTA possesses superior selectivity, and is thus far used to analyze the environmental radioactive isotopes 85Kr, 39Ar, 41Ca, and 81Kr. These isotopes have extremely low isotopic abundances in the range of 10^-17 to 10^-11, and cover a wide range of ages and applications. In collaboration with earth scientists, we are dating groundwater and mapping its flow in major aquifers around the world, and dating old ice from the deep ice cores of Antarctica, Greenland, and the Tibetan Plateau. For an update on this worldwide effort, please google “ATTA Primer”.
    
    Speaker: Prof. Zheng-Tian Lu (University of Science and Technology of China)
  - 254
    
    The search of 28Si doubly charged negative ion by Accelerator Mass Spectrometry
    
    Here we search the 28Si doubly charged negative ion (28Si DCNI) with Accelerator Mass Spectrometry (AMS). Five kinds of silicon including samples made of Si, Si+Fe, Si3N4, SiO2+Fe, and Si3N4+Fe were prepared to find 28Si DCNI. These samples were loaded into an AMS, which was a tandem type machine with a negative ion source by cesium sputtering (SNICS). The ions produced from these samples went through the AMS and were measured in ΔE-Eresdual of an ionization detector. The existence of the 28Si DCNI (28Si2-) was originally believed to be in the spectrum of ΔE-Eresdual of the AMS.
    
    Speaker: Junghun Park (KIGAM)
    
    Si_AMS16_abstract.docx
  - 255
    
    Counting Ar-42 atoms at the 10^-21 isotopic-abundance level
    
    Atom Trap Trace Analysis (ATTA) is a technique that utilizes laser to selective capture and detect individual atoms of the desired isotope. This technique loads atoms into a magneto-optical trap (MOT) through laser cooling and trapping, realizing high sensitivity and detection efficiency of the desired isotope.
    Due to the use of multi-photon repetitive excitation in the experiment, the ATTA method has extremely high isotope selectivity and has been successfully applied to the detection of Ar-39 with an abundance level of 10^-17.
    In recent years, we have significantly improved the counting rate and detection efficiency of the Ar isotope ATTA device, and developed a strong flow mass spectrometry isotope pre-concentration method. These advancements have enabled us to successfully detect Ar-42 (with a half-life of 33 years) atoms in the air with an isotopic-abundance level of only 10^-21 using single atom counting method.
    Previously, people used dark matter detectors detecting the decay of Ar-42 from tons of liquid argon to calculate the natural abundance of Ar-42. The sample consumption in this work is only 1-2L of gaseous argon, and the final measured natural abundance of Ar-42 is (5.4±0.8)×10^-21, which is twice more accurate than previous measurements. This work demonstrates the lowest detection limit that can be achieved by all current ultra-sensitive isotope detection methods.
    
    Speaker: Zhaofeng Wan
    
    AMS16摘要.docx
  - 256
    
    Radio-argon dating and its application in the ocean
    
    Cosmogenic Ar-39 dating is an emerging technique in tracing groundwater flow, dating mountain glacier ice, and mapping ocean circulation. With a half-life of 268 years, its dating range covers from 50 to 1800 years. Atom Trap Trace Analysis (ATTA) is a laser-based method that trapping and detecting individual neutral isotope atoms in a magneto-optical trap, with high selectivity and sensitivity. We have realized an ATTA system of Ar-39 in environmental samples. The system is capable of analysing small (1 - 5 kg) environmental water or ice samples, and achieves a count rate of 100 atoms/h for Ar-39 at the modern isotopic abundance level of 8E-16. These advances allow us to determine the Ar-39 age in its dating range with precisions better than 15%. Case studies in the Western Pacific and the South China Sea were applied to trace the ocean current. And, a new age scale was conducted by Ar-39 in Guliya Glacier on Tibet Plateau.
    
    Speaker: Dr Guo-Min YANG
- 12:00
  
  lunch Restaurant，Ground floor
  
  Restaurant，Ground floor
- Applications in Oceanography GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Using the AMS to study sedimentation rates and records, or tracing ocean currents.
  
  Convener: Prof. Liping Zhou (Peking University)
  - 257
    
    Presence of 233U, 236U, 237Np, 239Pu and 240Pu in the continental shelves of Angola and Namibia
    
    The Southern Atlantic continental shelf of Africa is an almost blank area regarding available information on the presence of anthropogenic radionuclides, namely actinides. The coast of Namibia, part of the northern Benguela Upwelling System, was the target of the first two studies reporting 236U, 237Np, 239Pu and 240Pu in seawater [1,2]. The obtained 236U and 237Np inventories and the measured 240Pu/239Pu atom ratios in a seawater column were consistent with the global fallout source. Additionally, evidence of a different geochemical behaviour of 236U and 237Np in coastal seawater was observed.
    
    In this work, new results on the presence of the above-mentioned radionuclides in seawater samples collected from two transects along the shelves of Angola at 10ºS and 17ºS, and one along the Namibian shelf at 22ºS, will be presented. Additionally, the profiles of 233U, 236U, 238U, 239Pu and 240Pu, in a sediment core collected at 120 m depth from the upwelling cell will be presented and discussed. Thus, more information on the Pu, U and Np contamination sources in the region and on the geochemical behaviour of 236U and 237Np in coastal seawater and sediments will be provided.
    
    This study was carried out as a collaborative effort of different institutions and in the frame of the existing agreement between the IAEA Marine Environment Laboratories and the CNA. The seawater samples were collected during the NANSEN expedition in 2019 and the sediment core during the sampling campaign along the Namibian continental shelf in 2014. Sample processing was carried out at the CNA as well as the analysis of 236U, 237Np and 239,240Pu in the seawater samples and of 239Pu and 240Pu in the sediment core at the CNA (Seville, Spain) [3,4]. The 233U/238U and 236U/238U atom ratios in the sediment core samples were analysed on the compact AMS system MILEA at the ETH (Zürich, Switzerland) [5]. The 238U concentrations in the sediment core were determined by ICPMS at the University of Seville.
    
    [1] M. López-Lora, E. Chamizo, M. Rožmarić, D.C. Louw, Presence of 236U and 237Np in a marine ecosystem: The northern Benguela Upwelling System, a case study, Sci. Total Environ. 708 (2020) 135222. https://doi.org/10.1016/J.SCITOTENV.2019.135222.
    [2] M. Rozmaric, E. Chamizo, D.C. Louw, M. López-Lora, O. Blinova, I. Levy, B. Mudumbi, A.K. van der Plas, R. Garcia Tenorio, P. McGinnity, I. Osvath, Fate of anthropogenic radionuclides (90Sr, 137Cs, 238Pu, 239Pu, 240Pu, 241Am) in seawater in the northern Benguela upwelling system off Namibia, Chemosphere. 286 (2022) 131514. https://doi.org/10.1016/J.CHEMOSPHERE.2021.131514.
    [3] M. López-Lora, I. Levy, E. Chamizo, Simple and fast method for the analysis of 236U, 237Np, 239Pu and 240Pu from seawater samples by Accelerator Mass Spectrometry, Talanta. 200 (2019) 22–30. https://doi.org/10.1016/J.TALANTA.2019.03.036.
    [4] M. López-Lora, E. Chamizo, Accelerator Mass Spectrometry of 237Np, 239Pu and 240Pu for environmental studies at the Centro Nacional de Aceleradores, Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms. 455 (2019) 39–51. https://doi.org/10.1016/j.nimb.2019.06.018.
    [5] M. Christl, P. Gautschi, S. Maxeiner, A.M. Müller, C. Vockenhuber, H.A. Synal, 236U analyses with the ETH Zurich MILEA prototype system, Nucl. Instruments Methods Phys. Res. Sect. B Beam Interact. with Mater. Atoms. 534 (2023) 61–71. https://doi.org/10.1016/J.NIMB.2022.11.009.
    
    Speakers: Mrs Elena Chamizo (Centro Nacional de Aceleradores (CNA), Universidad de Sevilla, Sevilla, Spain) , Prof. Rafael García-Tenorio (Centro Nacional de Aceleradores (CNA), Universidad de Sevilla, Sevilla, Spain)
  - 258
    
    Distribution and sources of anthropogenic 233,236U in the South China Sea
    
    Uranium-233 (233U) and uranium-236 (236U) in the environment mainly originate from human nuclear activities. Based on the long half-lives and high solubility of uranium, 236U and 233U can be used as powerful tracers for the investigation of oceanographic and environmental processes. However, insufficient work limits the understanding of the source items of anthropogenic 233,236U in the South China Sea (SCS) and the assessment of their environmental process, which are of great importance to the identification of potential radioactive pollutant sources. This study, for the first time, reported the 236U and 233U levels of 64 surface seawaters collected in the SCS from August to September 2018. The measured 236U/238U and 233U/238U atomic ratios are (0.99-1.15)E–9 and (1.1-49.5)E–12, which are respectively higher than their natural backgrounds of E–14-E–10 and E–14-E–11, indicating that the SCS were obviously affected by the human nuclear activities. In comparison to the reprocessing-plant-affected 236U/238U in the Baltic Sea (1.42-22.5)E–9, the input of anthropogenic 236U to the SCS is mainly from the contribution of the global fallout. Furthermore, by performing the 129I/236U-236U/238U mixing model, our data demonstrated that the global fallout was the major contributor to the 236U in the SCS at the moment of sampling. This study aims to open up an avenue for the study of uranium-isotope tracing and add essential information for future assessments of environmental radioactivity in the SCS.
    
    Speaker: Yanyun Wang (Insititute of Earth Environment, Chinese Academy of Sciences)
  - 259
    
    Carbon cycle in the polar oceans based on 14C perspectives (14C in the polar oceans)
    
    The development of 14C measurement techniques and icebreaking research vessels especially encourage and support polar research using 14C. Research examining 14C in polar oceans in the context of climate change has led to considerable insight into the marine carbon cycle. The Amundsen Sea, in West Antarctica, is experiencing rapid ice melting because of a warming climate. As found in previous studies conducted in these seasonally ice-free areas, nutrients released from melting ice sheets and upwelled by buoyant melt water stimulate surface primary production, which in return increases the surface uptake of CO2 in these regions. To address this carbon discharge, we conducted radiocarbon analysis of dissolved organic carbon in water samples collected near the melting ice shelf in the Amundsen Sea. Our finding indicates the deep water in the regions is going through a biological process under the influence of meltwater input. Further sampling will be needed for the investigation of the role of meltwater in downstream ecosystems. The impact of warming induced melting sea ice and glaciers on marine biogeochemical cycles, future environmental challenges and research directions have also been summarized. The limitations of existing 14C research in polar regions can be addressed through well-designed and continuous investigation, data and sample sharing, and the development of state-of-the-art 14C measurement techniques.
    
    Speaker: LING FANG
  - 260
    
    Vertical distributions of I-129 in the Southern Canada Basin and the prospect of combining U-236
    
    Radionuclides present in the marine environment predominantly stem from human activities, notably emanating from nuclear fuel reprocessing plant and nuclear weapons testing. Notably, Sellafield and La Hague facilities in Europe have been significant sources of ¹²⁹I emissions into the Atlantic Ocean. Subsequently, ¹²⁹I transported via ocean currents reaching the Canada Basin. The current system in the Canada Basin is intricate and changes by years, this study is based on the most recent data from our laboratory, collected in 2023. The dynamics in the Canada Basin ocean current system intertwined with climate changes. A thorough analysis of currents system serves to enhance our comprehension of Arctic climate change. This study investigates two depth profiles of the St.14 (72.4°N, 155.4°W) and St.32 (74.0°N, 162.0°W) in this region. In the vertical dimension, the ¹²⁹I/¹²⁷I ratio exhibits a minimum (2×10^–10) followed by maximum (138×10^–10) values. Based on the ratio, the water column divided to freshwater mixed layer (0–20 m), Pacific-origin water (20–100 m), Atlantic-origin water (200–1000 m), and bottom aged water mass (~2000 m), with vertical mixing layer existing between these water masses. However, relying solely on analysis of ¹²⁹I presents limitations. We aim to attain a more precise determination of the water mass movement. The different proportions of each source and input functions result in differing ¹²⁹I/²³⁶U atomic ratio across different sources and time scales. Consequently, the ¹²⁹I/²³⁶U atomic ratio is highly sensitive for analyzing the origins of water mass. This distinctive characteristic enables a more detailed analysis of the pathway and mixing regime of the water mass. The dual-tracer method offers a sensitive and robust approach to investigating ocean current circulation and vertical mixing processes.
    
    Speaker: Mr Xinru Xu (Department of Nuclear Engineering and Management, School of Engineering, The University of Tokyo)
    
    AMS 16th Absract.pdf
- Reference Materials, Carriers, Intercomparisons GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  The investigation of reference materials, new carriers, and AMS intercomparisons.
  
  Convener: Prof. Liping Zhou (Peking University)
  - 261
    
    Establishing matrix backgrounds and radionuclide concentrations for the metrology of new, SI-traceable isotope standards for the determination of key radioactive pollutants in the environment by (accelerator) mass spectrometry
    
    For its ultimate success, the zero-pollution ambition of the European Green Deal requires highly sensitive and state-of-the-art detection techniques to determine ultra-low amounts of pollutants in the environment. Mass spectrometry has become a key method for the determination of non-radioactive polluting elements, and is also of increasing importance for the detection of long-lived radionuclides. The MetroPOEM (Metrology for the Harmonisation of Measurements of Environmental Pollutants in Europe) project has been designed to bridge the gap between the radiometric techniques and mass spectrometry by comparing and linking both techniques, thus significantly improving measurement uncertainties and detection limits. As an important part of achieving this aim, this project will develop new reference materials, resulting in SI-traceable measurement procedures tracking the sources of pollution by commonly available mass spectrometers. The MetroPOEM Project Consortium has 22 Partners in 14 countries. The project is funded by the EU through the European Association of National Metrology Institutes (EURAMET).
    The radioactive pollutants identified as the most significant for this project are $^{236}$U, $^{237}$Np, $^{239}$Pu, $^{240}$Pu, $^{241}$Am, and $^{90}$Sr. For these pollutants, project partners will create both single isotope activity standards available in 6 dilutions each, and multi-isotope solutions. Finally, these solutions will be used to create a solid and a liquid reference material mimicking typical environmental matrixes, enabling a full proficiency test based on a directly SI-traceable material. These materials will then be disseminated to participating laboratories for an inter-laboratory comparison.
    In the area of radioactive pollutants accelerator mass spectrometry (AMS) is making an important and unique contribution. AMS offers the lowest isotopic abundance detection limits for the actinide isotopes, which has been demonstrated over many years by the pioneering actinide AMS system of the Vienna Environmental Research Accelerator (VERA). Recently, a new generation of small AMS systems, such as the Multi Isotope Low Energy AMS system MILEA designed by ETH Zurich and Ionplus AG, and operated at several labs worldwide including ETH Zurich, offer an efficient way for precise measurements at low levels for actinides. In a further advance in AMS, a new isobar separation system at the VERA facility for 90Sr, has shown that AMS is also the most sensitive method overall for the latter isotope. Meanwhile, at the Helmholtz-Zentrum Dresden-Rossendorf a new dedicated system – HAMSTER – advancing over the state-of-the-art for heavy isotopes and other isotopes is currently being implemented, however, only the actinide sample preparation laboratories are operational at this stage.
    Here we present first results and details of our AMS determination of single and multi-isotope solutions and matrix backgrounds for the solid and the liquid reference material at both the facilities of ETHZ and University of Vienna, controlling for systematic effects of different systems and mass spectrometry methods. These measurements will represent an important step for the final deliverables of the MetroPOEM Project.
    
    Speaker: Dr Stephan Winkler (Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany)
    
    AMS-16 MetroPOEM S Winkler 2.0_final.docx
  - 262
    
    Reproducibility and accuracy of actinide AMS – measurement limits from high-precision studies on $^{235}$U(n,$\gamma$)$^{236}$U
    
    Actinide-AMS has grown into an important discipline for environmental and geological sciences, for oceanography, but also nuclear (astro)physics. Nuclear data requests in nuclear physics continue to challenge the present limits in accuracy and abundance sensitivity of actinide detection. Exploring these limits is the primary motivation of this presentation.
    In recent years, significant effort has been spent to reduce uncertainties and regain lost knowledge in nuclear data. In particular, a major focus is to better understand the validity of the numerous cross-section data that were obtained decades ago. These activities are motivated by the urgent need for improved, safer, and highly accurate nuclear data for optimised designs of advanced reactor concepts, small modular reactors, nuclear fusion reactors, and next generation nuclear power plants (Gen IV) and accelerator driven systems (ADS).
    For such nuclear applications accurate actinide data are crucial, e.g., requiring uncertainties <2-3% for capture reactions of U and some Pu isotopes. Recent data evaluations based on state-of-the-art statistical methods highlighted the importance of proper data treatment including ‘complete’ uncertainty analysis. Adding a new independent method for such measurements helps to identify unrecognized systematic uncertainties in the existing nuclear database: the combination of activation and subsequent AMS detection offers here a powerful and complementary tool to measure these cross sections, largely independent of previous methods as it is based on a direct count of the produced nucleus. However, AMS had been applied only very recently for measurements on actinides.
    One example is the cross-section value for $^{235}$U neutron-capture at near thermal energies. The thermal capture is defined as a so-called thermal neutron constant and believed to be known to better than 1%. Despite its importance, direct measurements are rare (only two older data exist for thermal energies), usually done as a ratio to fission, and they exhibit large uncertainties, thus its knowledge is based primarily on indirect information.
    We present systematic investigations of neutron-capture measurements of $^{235}$U and $^{238}$U targets for samples irradiated with neutrons at four different facilities covering neutron energies from ultra-cold and cold to thermal. The goal was to produce cross-section data with highest accuracy, qualifying eventually as an independent reference for the neutron standard library.
    Two different sets of uranium samples were activated under identical conditions for each neutron irradiation. The samples were dissolved and individual aliquots were then spiked with several independent but well-known reference isotopes ($^{233,236,238}$U, $^{239,242}$Pu, provided by EC JRC Geel, Belgium), relative to which the neutron-produced radionuclides were measured.
    To properly estimate the final data accuracy, results from six repeated AMS measurements were used, allowing to estimate the measurement reproducibility by covering unknown uncertainties beyond counting statistics and other unknown systematic uncertainties. A comparison of these data provides the present limits in the measurement accuracy of heavy-ion AMS.
    
    Speaker: Anton Wallner (HZDR)
- 15:30
  
  coffee break Lobby , 2nd Floor
  
  Lobby , 2nd Floor
- Summary statement & Awards, Discussion for the next conference, Closing of AMS16 GRAND BALLROOM (宴会厅), 2nd Floor
  
  GRAND BALLROOM (宴会厅), 2nd Floor
  
  GULIN BRAVO HOTEL (桂林宾馆)，14 Ronghu Road, Guilin, 541002, China
  
  Convener: Prof. Hongtao Shen (Guangxi Normal University)
- 17:50
  
  Dinner Restaurant，Ground floor
  
  Restaurant，Ground floor
Saturday, 26 October
- Post conference excursion Option A: Li River Scenery (As one of china's top tourist destinations, the Li River is honored to be the largest and most beautiful karst gallery of the world. http://www.liriver.com.cn ); West Street; Guilin karst cave; "Impression of Liu Sanjie" (a spectacular night show)
  
  Li River Scenery (As one of china's top tourist destinations, the Li River is honored to be the largest and most beautiful karst gallery of the world); West Street; Guilin karst cave; "Impression of Liu Sanjie" (a spectacular night show).
- Post conference excursion Option B: Jinkeng Terraces(Perfect for shutterbugs and hikers): The largest terraced area in Longji; The most magnificent scenery;Cable cars available; Ethnic Minority Red Yao visit.

The 16th International Conference on Accelerator Mass Spectrometry

GRAND BALLROOM (宴会厅), 2nd Floor

Overview

Lobby of the Conference Hotel

Restaurant，Ground floor

Lobby of the Conference Hotel

GRAND BALLROOM (宴会厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby, 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Restaurant，Ground floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby , 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby and Hallway , 2nd Floor

( Poster session A should be set up in the morning.)

Restaurant，Ground floor

Lobby of the Conference Hotel

GRAND BALLROOM (宴会厅), 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby , 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Restaurant，Ground floor

GRAND BALLROOM (宴会厅), 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

Lobby , 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby and Hallway , 2nd Floor

(Poster session A should be taken down at the end of the session, while Poster session B is being set up.)

Restaurant，Ground floor

Lobby of the Conference Hotel

GRAND BALLROOM (宴会厅), 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby , 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Restaurant，Ground floor

GRAND BALLROOM (宴会厅), 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

Lobby , 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

Lobby and Hallway , 2nd Floor

Restaurant，Ground floor

Lobby of the Conference Hotel

GRAND BALLROOM (宴会厅), 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby , 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Restaurant，Ground floor

GNU and Guilin City

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby of the Conference Hotel

GRAND BALLROOM (宴会厅), 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby , 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

GOLDEN CASSIA (金桂厅), 2nd Floor

Restaurant，Ground floor

GRAND BALLROOM (宴会厅), 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Lobby , 2nd Floor

GRAND BALLROOM (宴会厅), 2nd Floor

Restaurant，Ground floor