福岛核事故释放的137Cs在西北太平洋海水中输运的模拟与预测

摘要

2011-03-11日本福岛核电站放射性物质发生泄漏事件,本研究基于MASNUM(Laboratory of Marine Science and Numerical Modeling)海洋环流模式,建立了西北太平洋海洋放射性物质输运扩散模式,对事故释放的137Cs在海洋中的输运和扩散过程进行了20 a的模拟与预测.根据与观测资料的比较,验证了所建立的模式具备模拟放射性物质在海洋中的输运扩散过程的能力.结果显示:至2015年,137Cs表层活度浓度已经扩散至整个中国海域,活度浓度值在0.01 Bq/m3左右;事故发生10 a后,研究海域137Cs表层活度浓度趋于均匀,为0.20~0.60 Bq/m3左右;20 a后,137Cs在海洋表层的活度浓度要小于0.15 Bq/m3.垂向扩散的结果显示:事故发生10 a后,黄海海域137Cs垂向分布较为均匀,东海东部陆架海域活度浓度高于西部海域,且上层海水中137Cs活度浓度高于底层海水,南海北部海域137Cs活度浓度高于南部海域,且略小于黄海和东海;至2030年,中国近海137Cs的活度浓度的垂向分布趋于均匀,南海略高于黄海和东海;日本海137Cs活度浓度主要集中在表层,最大活度浓度出现在2016年,约为0.20 Bq/m3;西北太平洋海域137Cs活度浓度要高于其他4个海域;2030年以后,整个海域137Cs活度浓度在水平和垂向分布均趋于均匀,均小于0.15 Bq/m3.%On March 11,2011,significant amounts of radioactive contaminants were leaking into the air and oceans causing by the Fukushima Daiichi nuclear power plant (FD-NPP) accident.Based on a two-time-level,three-dimensional numerical ocean circulation model (named MASNUM),we established a high resolution Northwest Pacific Ocean radionuclides transport model to simulate and predict the transport of the leaking radioactive isotope 137Cs resulting from the nuclear accident in 20 years.According to the comparison with the observation data,the established radionuclides transport model was validated effective and reliable.The results show: the surface concentration of 137Cs had spread to the whole China seas in 2015,with the concentration about 0.01 Bq/m3;the surface concentration tend to be evenly distributed in 10 years,at around 0.20~0.60 Bq/m3;till 2030,the concentration in surface ocean is less than 0.15 Bq/m3.The vertical diffusion results show: in 2020,the concentration of 137Cs in the Yellow Sea are roughly the same in the vertical distribution;the concentration of 137Cs is larger in the east of the East China Sea than the west area,where the concentration in the surface layers is larger than the bottom layers;the concentration in the northern South China Sea is larger than that in the southern seas,and a slightly smaller than the Yellow Sea and the East China Sea;the 137Cs concentration vertical distribution becomes homogeneous in the China seas in 2030;The high concentration in the Japan Sea will concentrate in the surface layer,with a maximum value of 0.20 Bq/m3 in 2016.The 137Cs concentration in the Northwest Pacific Ocean with a maximum concentration is larger than the other four seas.The 137Cs concentration of the entire area will be affected to be consistent in horizontal and vertical distribution in 20 years,with the low concentration less than 0.15 Bq/m3.