环境有机配体介导硫化汞增溶过程的汞形态及其动力学研究

Mercury (Hg) is a global contaminant with health risks to people around the world, and its cycling in the environment involves complicated speciation and processes. Due to its extremely low theoretical solubility, mercury sulfide (HgS) is considered a major sink of mercury cycling, resulting in the sequestration of Hg in sediment and soil. However, organic ligands may promote the dissolution of HgS in the environment, which may play a key role in species distribution, mobility, reactivity, and methylation of mercury in the environment, depending on the species released from HgS dissolution. Due to lacking in studies directly investigating mercury species during organic ligand-promoted HgS dissolution and related dissolution mechanisms, little is currently known regarding the fundamental environmental chemistry of organic ligand-promoted HgS dissolution and its role in mercury cycling. Focusing on the key information on mercury species released from organic ligand-promoted HgS dissolution, this project will select thiol-containing small molecules and aquatic natural organic matter references as typical environmental organic ligands to study in the laboratory mercury speciation, chemical processes, and kinetics of HgS dissolution. The research will be further expanded to field study, by isolating HgS fraction from the sediment in a typical mercury-contaminated aquatic environment and investigating organic ligand-promoted dissolution of this HgS form present in the environment. It is expected that this study will reveal the environmental chemical mechanisms underlying organic ligand-promoted dissolution of HgS and provide fundamental information for an accurate evaluation on the overall role of organic ligand-promoted HgS dissolution in the biogeochemical cycling of mercury.

汞是具有广泛健康危害的全球性污染物，其在环境中的循环涉及多种形态和过程。由于理论溶解度极低，硫化汞常被认为是汞循环的终端形态，可将排放到环境的大部分汞固定在沉积物和土壤中。但自然环境中的有机配体可介导硫化汞增溶作用，这对汞在环境中的形态分布和迁移转化起着关键作用，且其作用大小与增溶所释放的汞形态密切相关。目前尚缺乏对有机配体介导硫化汞增溶所释放汞形态及増溶机制的研究，导致对这一重要环境过程及其在汞循环中的作用知之甚少。本项目针对有机配体介导硫化汞增溶过程释放的汞形态这一核心问题，选取小分子巯基化合物和水体天然有机质作为典型环境有机配体，实验研究配体介导下硫化汞增溶作用释放的汞形态、增溶机制及动力学过程，并扩展到现场环境，研究典型环境中提取的硫化汞组分在有机配体介导下的增溶过程。本项目有望揭示有机配体介导硫化汞增溶的环境化学过程机理，并为准确评估其在汞生物地球化学循环中的作用提供新的认识。

汞是具有广泛健康危害的全球性污染物，其在环境中的循环涉及多种形态和过程。由于理论溶解度极低，硫化汞常被认为是汞循环的终端形态，可将排放到环境的大部分汞固定在沉积物和土壤中。但自然环境中的有机配体可介导硫化汞增溶作用，这对汞在环境中的形态分布和迁移转化起着关键作用，且其作用大小与增溶所释放的汞形态密切相关。目前尚缺乏对有机配体介导硫化汞增溶所释放汞形态及増溶机制的研究，导致对这一重要环境过程及其在汞循环中的作用知之甚少。本项目针对有机配体介导硫化汞增溶过程释放的汞形态这一核心问题，通过比较目前通用的测定环境介质中硫化汞的方法，优化了硫化汞测定方法；研究了氧化增溶、络合增溶和光化学增溶过程在HgS溶解中的作用，明确了典型环境有机配体对HgS的增溶效应及其可能的增溶机制；表征了鸭儿湖总汞和甲基汞空间分布状况及汞污染现状，探讨了硫化汞溶解过程在已固化汞排放及水体汞循环中的作用，为准确评估硫化汞增溶过程在汞生物地球化学循环中的作用提供了新认识。