土地利用类型对喀斯特小流域汞关键再分配过程的影响研究

高汞的地质背景驱动了高强度汞的无序流动。高汞的地质背景叠加集中连片的喀斯特地貌以及超负荷的农业耕作，可能危及到西南喀斯特地区作为长江和珠江中上游重要的生态安全屏障的功能。研究表明，植被对于陆地生态系统汞的生物地球化学循环起着重要的作用，然而，土地利用类型对喀斯特地区汞的关键再分配过程的影响机制尚不清楚。因此，本项目以典型喀斯特小流域汞的关键再分配过程为研究对象，通过野外观测和实验室分析，采用同步辐射技术、新型动力学通量箱和汞同位素地球化学等技术手段，以明确不同土地利用类型条件下表层土壤汞的稳定性和剖面土壤汞的赋存形态及分布趋势，揭示不同土地利用类型条件下土壤汞的来源及积累特征，阐明土地利用类型对土壤-大气界面汞交换过程的影响机制。项目的实施，不仅有助于加深对陆地生态系统汞的生物地球化学循环的认识，对于减小高汞背景喀斯特地区汞的无序流动和发展健康可持续的农业生产也有重要意义。

The geological background of high mercury drives the high intensity disorderly flow of mercury. The high mercury geological background superimposed on the concentrated and contiguous karst landforms and overloaded agricultural farming and other factors may endanger the function of the Southwest Karst region as an important ecological security barrier in the middle and upper reaches of the Yangtze River and the Pearl River. Studies have shown that vegetation plays an important role in the biogeochemical cycle of mercury in terrestrial ecosystems. However, the impact mechanism of land use types on the key redistribution process of mercury in karst areas is still unclear. Therefore, this project takes the key redistribution process of mercury in two typical karst catchments as the research object. Through field observations and laboratory analysis, technical means such as synchrotron radiation technology, novel dynamic flux chamber and mercury isotope geochemistry are used to clarify the stability of mercury in surface soil and the occurrence speciation and distribution trend of mercury in soil profile under different land use types, reveal the source and accumulation characteristics of soil mercury under different land use types and clarify the influence mechanism of land use types on the process of air-surface Hg0 exchange. The successful implementation of the project will not only help to deepen the understanding of the biogeochemical cycle of mercury in terrestrial ecosystems, it is also of great significance for reducing the disorderly flow of mercury in karst areas with high mercury background and developing healthy and sustainable agricultural production.