Speaker
Description
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.
| Student Submission | No |
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