金属硫化物微生物氧化过程中硫的价态、物相转变及同位素地球化学意义

The oxidation of sulfides is responsible for the generation of acid mine drainage and acid rock drainage, which leads to further contamination around polymetallic mining areas. It has been well demonstrated that microorganisms play crucial roles in the oxidation processes. The study area for this project is Tongling polymetallic deposit. Oxidative decomposition process of metal sulfide in acid mine environment is studied by mineralogical analysis methods. Decomposition of sulfides often results in the dissolution of carbonate minerals in the surrounding rock and the formation of secondary minerals. Identifying the species of primary sulfide minerals and secondary minerals, and the associated relationship between secondary minerals, analyzing sulfur isotope fractionation caused by primary sulfide and secondary sulfate minerals, these work are helpful to find traces of biological, chemical weathering and further explore the microbial activity in transformation of secondary minerals, which have important theoretical and practical significance in the remediation of pollution. We select representative bacteria (A.ferrooxidans) isolated in mine environment to interact with sulfides in laboratory, then investigate the properties of reaction interface between sulfides and bacteria and secondary minerals sediment generated during the experiments. By monitoring the valence changes of element S and its isotope fractionation caused by valence change and secondary minerals forming in different experimental stages, we may investigate the microscopic mechanism of microbial sulfide interaction in the micro-nano scale, and evaluate the environmental effect of microbial sulfide interaction.

金属硫化物的氧化分解作用是导致矿山环境污染，酸性矿山排水、酸性岩石排水形成的重要因素。在此过程中，微生物的作用至关重要。选择安徽铜陵多金属矿山为研究区，通过矿物学分析手段，研究金属硫化物在矿山酸性环境下的氧化分解过程；硫化物的分解往往造成围岩中碳酸盐矿物的溶蚀并形成次生矿物，查明体系中原生矿物组合及次生矿物的种类和伴生关系，分析原生硫化物及不同次生硫酸盐矿物造成的S同位素分馏，寻找生物痕迹，进而探讨化学风化和微生物活动造成的矿物之间的相互转化，对矿山环境污染研究和治理提供理论依据；选择矿山环境中代表性微生物氧化亚铁硫杆菌和金属硫化物开展相互作用的模拟实验，系统分析微生物与硫化物反应界面特征及次生沉淀，通过监测反应过程中元素S的价态变化以及价态变化和不同阶段次生矿物造成的S同位素分馏，进而从微纳米尺度上探讨微生物－硫化物界面作用的微观机制，评价微生物－硫化物相互作用的环境效应。

金属硫化物的氧化分解作用是导致矿山环境污染，酸性矿山排水、酸性岩石排水形成的重要因素。本研究以安徽铜陵多金属矿山环境中典型的岩石露头及尾矿库为研究背景，利用矿物学及地球化学分析手段，通过对风化成因次生矿物的种类、形态、成分差异以及其固定重金属离子能力等的研究，酸性矿山排水及尾矿库对周边环境的综合分析，探讨了次生矿物的形成机理及元素As的赋存、迁移形式，进而评估其对环境的影响。. 野外样品分析结果显示，碳酸盐-硫化物共存体系的风化作用导致多种次生矿物的生成，包括石膏、硬石膏、针铁矿、赤铁矿、单质硫和黄钾铁矾、施氏矿物等。硫化物矿物的风化使得周围环境酸化，导致方解石溶解。方解石富集的区域pH值最高，其周围pH逐渐降低，依次形成方解石-石膏/硬石膏-铁（氢）氧化物-高铁硫酸盐 4个矿物带。. 在硫化矿物的风化过程中，元素As及重金属离子一部分进入次生矿物相，另一部分通过溶解态形式进入地表及地下水，从而对环境造成污染。由于碳酸盐岩具有较强的酸中和能力，从而可以有效阻止硫化物风化产生酸性矿山排水，降低对水土的污染。通过老鸦岭尾矿库酸性矿山排水对周边环境的毒性研究以及杨山冲尾矿库对周边环境影响的综合分析认为，可以利用尾矿库的深层渗滤水来原位处理尾矿库产生的酸性矿山排水。