粤北佛冈花岗岩地质背景区土壤铊富集机理与环境效应研究

Thallium (Tl), a non-essential and highly toxic metal to plants and animals, could be easily enriched in outcrops as a “hidden health killer” with severe health impacts on human. Soils derived from natural weathering of granites in the north Guangdong Province are enriched in Tl, but little is known about its enrichment mechanism and environmental effects, which needs to be addressed immediately. Here we will investigate the characteristic and key controlling factors of transformation of Tl-bearing mineral phases, chemical speciation and stable isotopes of Tl for the interface between the Fogang granite, north Guangdong and its derived soils, which will provide important clues to understand the enrichment mechanism of Tl in soils. Besides, we will study the features of mobility and enrichment processes of Tl, Tl isotopes and key controlling factors in the interface between the arable soils (dry lands and paddy fields) and crops, and then evaluate the environmental effects of Tl-rich soils. This study is hopefully to unveil the features of supergene mobility and enrichment of Tl and Tl isotopes, and its environmental effects, which could enhance our understanding of the enrichment mechanism of Tl in soils derived from granites and has great significance in scientific research and practical guiding.

铊是动植物体非必需的、剧毒重金属元素；土壤铊易通过农作物富集，危害人体健康。粤北花岗岩地质背景区土壤富集铊，但其机理及潜在的环境影响效应尚不明晰，是亟待解决的重要环境问题。本项目拟以粤北佛冈花岗岩成土母质-土壤-农作物系统为研究对象，重点研究成土母质-土壤界面铊赋存形态、矿物相转化和铊同位素组成特征及其主控因子，揭示土壤铊富集机理；研究（旱地和稻田）土壤-农作物界面铊迁移富集过程规律和铊同位素分馏特征及主控因子，阐明土壤铊富集的环境影响效应。预期成果有望在国际上率先揭示花岗岩地质背景区铊表生迁移富集过程规律、铊同位素分馏特征及其环境影响效应，为理解和构筑花岗岩地质背景区土壤铊富集机制提供强有力的证据，有重要的科学研究价值和实际指导意义。

铊是动植物体非必需的、剧毒重金属元素；土壤铊易通过农作物富集，危害人体健康。花岗岩地质背景区土壤富集铊，但其机理及潜在的环境影响效应是亟待解决的重要环境问题。本项目以粤北佛冈-大东山花岗岩成土母质-土壤-农作物系统为研究对象，重点研究成土母质-土壤界面铊赋存形态、矿物相转化和铊同位素组成特征及其主控因子，揭示土壤铊富集机理及其环境影响效应。取得的主要认识如下：（1）证实了佛冈-大东山花岗岩地质背景区自然土壤存在Tl富集现象，是花岗岩原位风化的结果；（2）揭示了花岗岩地质背景区自然土壤铊的富集特征及花岗岩风化成土过程中Tl的迁移富集规律：Tl呈现出典型的“亲石性”地球化学特征，与Rb元素关系密切，在岩石系统中主要受控于钾长石，而在土壤系统中则主要受控于伊利石等富Rb粘土矿物；（3）明确了花岗岩及土壤系统中Tl的存在形态以残渣态为主，其生物有效态含量较低，较为稳定，但在一定条件下仍可能发生形态转化和迁移，对农田土壤安全造成潜在威胁；（4）发现了花岗岩风化成土过程中基岩-土壤界面存在显著的Tl同位素分馏现象，分馏程度高达15个epsilon单位。研究成果有望在国际上率先揭示花岗岩地质背景区铊表生迁移富集过程规律、铊同位素分馏特征及其环境影响效应，为理解和构筑花岗岩地质背景区土壤铊富集机制提供强有力的证据，有重要的科学研究价值和实际指导意义。