亚热带与温带森林小流域生态系统汞的生物地球化学循环及其同位素分馏

Biogeochemical cycling and isotopic fractionation of mercury in subtropical and temperate forest ecosystem

汞是通过大气进行长距离传输的全球污染物,引起国际社会和学术界高度关注.陆地森林生态系统是全球物质循环最为活跃的地方,但其对全球汞的生物地球化学循环影响的认识还不清楚.同时,森林生态系统汞的生物地球化学循环过程可能对全球大气汞同位素组成产生重要的影响,但目前这两方面的研究还非常缺乏,制约了对全球尺度汞的生物地球化学循环深化规律的把握.本课题组拟在我国温带和亚热带选择3个森林小流域,首先系统开展森林小流域汞的质量平衡研究工作,深入刻画森林流域汞的生物地球化学演化规律,在此基础上开展流域汞的生物地球化学循环过程中汞同位素的分馏特征研究,最终建立流域尺度森林系统汞及其同位素的生物地球化学模型.该项目将极大推进对森林流域尺度汞的生物地球化学循环的认识,探讨森林生态系统与大气汞交换过程对全球尺度汞生物地球化学循环和对大气汞同位素组成的影响,为最终建立基于汞同位素的全球汞生物地球化学循环模型提供基础数据.

Mercury is regarded as a global pollutant due to the fact that it can be transported for a long distance in the atmosphere, and thus attracts attentions from both public sectors and scientific society. The mass exchanges in forest ecosystems are very active, but the role of forest ecosystem on global mercury geochemical cycling is still largely unknown. Meanwhile, the cycling of mercury in forest ecosystem may have altered mercury isotope ratios in the atmosphere. However, so far the knowledge on these two aspects is still lacking, hindering our understanding of the global cycle of mercury in the environment. In the project, we will select 3 small forest catchments from subtropical and temperate regions in China as our study areas. First of all, we will establish a detailed mercury mass balance in the ecosystems, and decipher the biogeochemical cycling of mercury in forest ecosystems. Based on this, we will investigate mercury isotope fractionation during mercury geochemical cycling processes in the forest ecosystems. Finally, we will develop biogeochemical cycling models in forest ecosystem for both mercury and mercury isotopes. Our project will advance our knowledge on mercury cycling in forest ecosystems, and discuss the impact of mercury exchange between atmosphere and forest on the global cycling of mercury in the atmosphere and on mercury isotope ratios in global atmosphere. In the end, our project will provide important data for the development of new generation global mercury models based on mercury isotope information.