地质高背景区铊的表生富集机理与环境影响效应研究

铊（Tl）是一种毒害重金属，是动植物体非必需元素。我国南方大面积地质高背景区土壤富集铊，铊表生富集及其可能造成的生态环境影响，是亟待解决的重要环境问题，但迄今对其表生富集形成机理及是否影响农产品质量安全的认识尚不明晰。本项目拟重点研究南方地质高背景区成土母岩-土壤界面铊赋存形态和铊稳定同位素组成特征，明确成土过程中铊赋存状态、生物有效性、铊同位素组成变化特征及其主控因子，揭示其表生富集机理；研究土壤-农作物界面铊迁移富集规律和铊同位素分馏特征，查明土壤-农作物系统铊迁移转化机制与主控因子，建立地质高背景农田铊污染识别指标，评估其污染生态风险，阐明其环境影响效应。研究成果有望在国际上率先揭示地质高背景区土壤铊生物有效性和铊同位素分馏特征，为理解和构筑地质高背景区铊表生迁移富集过程机制提供强有力的证据，为铊来源判别和生态风险评估提供重要理论指导，有重要的科学研究价值和实际指导意义。

Thallium (Tl) is a toxic and non-essential trace metal to flora and fauna. With respect to the enrichment of Tl in soils in large areas with high Tl geological background in South China, the supergene enrichment of Tl and possible associated eco-environmental risk present a vital environmental issue. However, little was known about the mechanism of Tl’s supergene enrichment in these soils and associated impact on local crop quality. This proposed project, for the first time, focusing on the high geogetic Tl contents in soils of South China, aims to characterize the geochemical fractions and isotope compositions of Tl in the parent rock-soil interface, to gain new insight into the dynamic characteristics of Tl’s occurrence states, bioavailability and isotope fractionation during pedogenesis, and to reveal the mechanism of supergene enrichment of Tl. The research will also focus on characterizing the mobility and enrichment of Tl and Tl isotope fractionation in the rhizosphere soil-crop system, and reveal Tl’s migration and transformation mechanism and associated key controlling factors. The study also tries to establish the identification index for geogenic Tl contamination, to assess its ecological risk, and to provide with a full understanding of the environmental impact effects. The outcomes of this study are to provide new insight into the bioavailability and isotope fractionation of Tl in the surface environment in areas with high Tl geological background. This insight is crucial to better understanding of the biogeochemical mobility, enrichment, and fate of geogenic Tl in the surface environment, and to enrich the knowledge about the source discrimination of geogenic Tl and associated ecological risk assessment.