Speaker
Description
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.
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