福岛核事故后中国海域多介质中137Cs的长期变化及环境行为研究OA

To clarify the long-term variation of 137Cs in the China Seas after the Fukushima nuclear accident and the characteristics of its environmental responses across multiple media,this study systematically compiled publicly reported activity concentration data of 137Cs in seawater,surface sediments,and fish from the China Seas.Exponential decay fitting,segmented regression analysis,and parameter calculation were applied to evaluate the variation characteristics of 137Cs before and after 2013.The results showed that the activity concentratio of 137Cs in seawater of the China Seas generally followed an exponential decreasing trend before 2013 and exhibited a significant positive offset after 2013,with an additional annual multiplicative change rate of 5.8％.The corresponding rates for the Bohai Sea,East China Sea,and South China Sea were 16.9％,7.6％,and 3.2％,respectively,whereas no significant change was observed in the Yellow Sea.For the activity concentration of 137Cs in surface sediments,only the Yellow Sea exhibited a significant positive shift,whereas no significant systematic shift was observed in the other sea areas.The activity concentration of 137Cs in fish from the East China Sea showed a significant positive offset after 2013.Overall,the sediment distribution coefficients and bioconcentration factor for biota of 137Cs in the China Seas were(1.00±1.37)m3·kg-1 and(69.0±69.8)L·kg-1,respectively,which could provide reference values for establishing environmental behavior parameter databases for artificial radionuclides in the China Seas.Dose assessment indicated that the annual committed effective dose caused by consumption of fish from the China Seas was below the national annual effective dose limit for the public.This study suggests that the response of the activity concentration of 137Cs in the China Seas after the Fukushima nuclear accident shows clear media-specific and regional differences,highlighting the need for long-term,continuous,and multi-media monitoring.