土壤和底泥间隙水中汞-硫-铁纳米颗粒物的形成条件、结构特征及其在甲基汞生物合成中的作用

How to effectively reduce the production and accumulation of the potent toxin, methylmercury, has been the focus of the research on mercury pollution. Thus far, the mechanism of microbial production of methylmercury, particularly what forms of inorganic mercury can be methylated by anaerobic bacteria, remains poorly understood. The overarching goal of the proposed project is to elucidate the speciation and methylation potential of inorganic mercury in soil and sediment porewater, where microbial production of methylmercury often occurs. This research will study the effect of reduced iron, which is abundant in porewater, on the precursor of microbial production of methylmercury. Specifically, this research will investigate the reactions between mercury, sulfide and iron under various environmental conditions that lead to a series of products, including mercury-sulfide-iron nanoparticles. This research will evaluate the formation, stability and structure of these nanoparticles as well as their bioavailability to methylating microorganisms. This research will assess the potential mechanisms via which mercury-sulfide-iron nanoparticles deliver mercury into the cells of the methylating microorganisms for methylation, including dissolution, thiol ligand exchange and cell membrane penetration. This proposed project will help construct quantitative models for predicting methylmercury production based on environemntal parameters and provide insight to risk analysis and environmental remediation of mercury pollution.

如何有效降低具有强生物毒性的甲基汞的生成和积累是汞污染研究领域的热点和难点。目前，国内外学术界对于甲基汞生物合成的反应机理，特别是究竟哪种无机汞化合物可以被厌氧微生物转化为甲基汞尚缺乏系统准确的认识。本项目以阐明土壤和底泥间隙水这一甲基汞生成和积累的主要环境中无机汞的化学存在形式及其甲基化倾向为目标，研究该环境中大量存在的还原性铁对甲基汞生物合成前体物质的影响。本项目将研究不同环境条件下汞-硫-铁之间的相互作用，明确该过程的反应产物，特别是汞-硫-铁纳米颗粒物的形成条件、稳定性和结构特征；分析这种复合纳米颗粒物对于甲基化微生物的生物可利用性；考察纳米颗粒物向微生物细胞内部传递甲基汞前体物质的方式，包括溶解、巯基络合离子交换、穿越细胞膜等。本研究可为建立基于环境指标预测甲基汞合成的量化模型提供理论基础，对准确评价汞污染产生的环境风险，有效开展环境修复具有重要的理论意义和应用价值。

如何有效降低具有强生物毒性的甲基汞的生成和积累是汞污染研究领域的热点和难点。目前，国内外学术界对于甲基汞生物合成的反应机理，特别是究竟哪种无机汞化合物可以被厌氧微生物转化为甲基汞尚缺乏系统准确的认识。本项目以阐明土壤和底泥间隙水这一甲基汞生成和积累的主要环境中无机汞的化学存在形式及其甲基化倾向为目标，研究该环境中与汞共存的还原性铁、硫、天然巯基配体、碳纳米颗粒等对甲基汞生物合成前体物质的影响。重点研究了汞、硫、铁离子共沉淀过程、碳纳米颗粒和硫化亚铁纳米颗粒吸附无机汞离子过程形成含汞纳米颗粒物的作用机制，明确了天然巯基配体、微生物胞外多聚物的组分和浓度等厌氧间隙水化学条件对含汞纳米颗粒物的尺寸、形貌、元素组成、化学键成键情况、晶体结构、表面性质、团聚状态等结构特征的影响机制，揭示了纳米黑辰砂暴露晶面和颗粒物团聚状态对含汞纳米颗粒物与甲基化细菌细胞结合能力的重要作用，及其对含汞纳米颗粒物的生物可利用性和甲基化潜能的显著影响。本研究结果为将含汞纳米颗粒物这一新型甲基汞合成前体物质纳入甲基汞合成的定量预测模型提供了理论基础和关键参数，对准确评价汞污染产生的环境风险，有效开展环境修复具有重要的理论意义和应用价值。