核能利用在给人类带来利益的同时也存在着隐患。自1945年以来，全球各地的核活动向环境中释放了大量的放射性核素。这些放射性核素主要波及的地区以及对人体的辐射剂量是社会关注的焦点，它直接关系着每个人的切身利益。然而，由于核试验或核事故所释放出的短寿命核素在核事故之后迅速衰减至可探测水平以下，使辐射危害评估变得十分困难。因此，对于早期核活动对我国环境的影响的认知目前还较为有限。本课题拟通过分析我国西北地区湖泊沉积物中的长寿命核素129I，并结合其它指标如137Cs，210Pb等，评估历史中不同时期的核事件对当地环境的影响情况；重建核事故或不同阶段核爆时研究区域短寿命核素131I的环境水平，并估算当地人群接收到的辐射剂量；甄别邻国早期核活动释放的放射性物质对我国核环境安全的影响情况，为我国国防安全、政府决策和环境外交提供科学数据，还可以为利用环境放射性核素进行环境过程示踪研究提供基础数据支持。

The nuclear power can bring human the benefit as well as the potential risk. Since 1945, the nuclear activities around the world have released a great number of radioactivity to the environment. The main areas affected by these radionuclides and the level of human radiation exposure have become a large concern of the public, being related to everyone’s interest. However, the short-lived radionuclides decayed rapidly to the level under the limit of detection in a quite short time after a nuclear event, making it impossible to assess the environmental radioactivity. Therefore, the understanding of the historical nuclear activities on the environment in China was limited. By analysis of 129I combined with 137Cs and 210Pb, this project aims to assess this envionmental impact in northwestern China, to reconstruct the environmental 131I level in investigated areas when the nuclear accident or nuclear test took place, and identify the contribution by nuclear event in neighbouring countries, aiming to provide scientific proof for government policy and environmental diplomacy as well as the study of tracing the environmental processes.