南海北部海陆交互带土壤和沉积物中^(129)Ⅰ的分布特征及其影响因素

Distribution of Radioisotope ^(129)Ⅰin Soils and Sediments of the Sea-Land Interaction Zone in the Northern South China Sea and Its Influencing Factors

为保障我国核电工业健康有序发展,研究沿海核电站对周缘环境放射性的影响及关键排放产物在海陆交互带的地球化学行为至关重要。系统采集了我国南海海陆交互带58个表层土壤和海洋沉积物样品,采用氧化燃烧法结合共沉淀法分离和提纯碘,采用3MV加速器质谱仪(AMS)和电感耦合等离子体质谱仪(ⅠCP-MS)分别测量^(129)Ⅰ和^(127)Ⅰ。结果表明,区内昌江、防城港、阳江、岭澳和大亚湾核电站对周缘^(129)Ⅰ水平无明显影响;海陆交互带^(129)Ⅰ的主要来源为核武器试验的全球大气沉降和欧洲核燃料后处理厂排放的远距离传输。此外,不同利用类型的海陆交互带土壤对Ⅰ的富集作用具有明显的差异,呈现果园>林地>草地>农田的规律,而季风和降水对海陆交互带土壤中Ⅰ的分布影响较小。河流输入使河口和大陆架区海水中^(129)Ⅰ升高而^(127)Ⅰ降低,生物作用对陆坡和深海区^(129)Ⅰ和^(127)Ⅰ影响显著。

To ensure the healthy development of nuclear power industry in China,it is of great significance to understand the impact of coastal nuclear power plants on the surrounding environment and the geochemical behavior of key anthropogenic radionuclides in the sea-land interaction zone.58 surface soil and sediment samples were collected from the sea-land interaction zone of the northern South China Sea.Iodine was separated by oxidation combustion and coprecipitation,^(129)Ⅰand ^(127)I contents in the separated sample were measured by 3 MV Accelerator Mass Spectrometer(AMS)and Inductively Coupled Plasma Mass Spectrometry(ICP-MS),respectively.The result showed that the nuclear power plants located at Changjiang,Fangcheng port,Yangjiang,Ling’ao and Daya Bay had insignificant impact on the ^(129)Ⅰlevel in the environment.The main sources of ^(129)Ⅰin the sea-land interaction zone were the global fallout of nuclear weapon tests and the re-emission and long-distance transport of ^(129)Ⅰdischarged from European nuclear fuel reprocessing plants.Monsoon and precipitation rate had negligible impacts on the distribution of iodine(^(129)Ⅰand ^(127)I)in soils of the coastal interaction zone,while land utilization played an important role in the distribution of iodine(^(129)Ⅰand ^(127)I)in surface soils.The ^(129)Ⅰand ^(127)I concentrations in surface soils(<5 cm)of different land use types declined as Orchard>forest land>grassland>farmland.River input had a significant impact on the distribution of ^(129)Ⅰand ^(127)I in the marine sediment in estuaries-continental shelf areas,and biological effects were significant in the continental slope and deep sea area.