自养条件下微生物修复钒污染土壤的机理研究

Excessive vanadium from mining, smelting as well as its product application enters the environment and causes soil pollution. Vanadium polluted soil can also be the potential pollution source of groundwater. Microbial remediation possesses evident advantage, while available organic carbons decrease with the increased of depth under the surface, thus microbial remediation supported by autotrophic conditions are particularly important, however, limited studies have focused on this topic. In present study, processes and mechanisms of microbial vanadium (V) reduction under different autotrophic conditions will be investigated. Characteristics of microbial community structure succession and functional gene will be confirmed by Illumina high-throughput sequencing. Soil environmental factors such as humus and co-existed electron acceptors will also be studied, thus formation and distribution of different redox zones will be elucidated. Functional species will be fixed by stable isotope probing technique, then they will be purified and their vanadium (V) reduction processes as well as the influences of soil environmental factors will be researched. Mechanisms will also confirmed by field emission transmission electron microscopy, genomics, transcriptomics and proteomics. This study provides theoretical evidence to explore microbial gene resources for in situ microbial remediation of vanadium polluted soil.

钒矿开采、冶炼与钒制品使用过程导致大量的钒进入环境，造成土壤污染。受钒污染的土壤也是地下水的潜在污染源。微生物修复钒污染土壤优势明显，而地表下可获得的有机碳随着深度的增加而减少，自养条件支持的微生物修复尤为重要，但当前还鲜有报道。本项目拟研究不同自养条件下微生物还原五价钒的过程与机理，依托Illumina高通量测序技术，分析微生物群落结构演替特征并确定功能基因。探究腐殖质、共存电子受体等土壤环境因子的影响规律，进而明确氧化还原带的形成及分布规律。利用稳定同位素探针技术确定功能微生物。分离并验证功能微生物还原五价钒的过程及土壤环境因子的影响规律，综合运用场发射透射电镜技术、基因组学、转录组学、蛋白质组学等手段，解析功能微生物还原五价钒的作用机制。本项目为挖掘功能微生物基因资源，实现钒污染土壤的原位微生物修复提供理论依据。

钒矿开采、冶炼与钒的广泛使用导致大量的钒进入环境，造成土壤地下水严重污染。微生物可将毒性大、迁移性强的五价钒转化为低毒性、可自发沉淀的四价钒，微生物修复具有明显优势。针对地表下可获得的有机碳随着深度的增加而减少、额外添加有机碳容易造成二次污染的现实，本项目开展了自养条件下钒的微生物转化的研究，系统考察了单质硫、零价铁、天然马基诺矿、氢气作为电子供体时，厌氧微生物转化钒的过程、影响因素及机理，并确定了功能微生物及其作用途径。上述无机电子供体，均可有效支持微生物还原固定五价钒，单质硫和零价铁的效率，与常见有机电子供体相当，氢气的效率较低。通过微生物群落的分析，发现了氢自养耦合钒还原菌Dechloromonas和Hydrogenophaga、硫铁氧化耦合钒还原菌Thiobacillus，这在之前尚未报道过；在单质硫、零价铁体系中，主要通过微生物种间协同实现钒的高效去除，挥发性脂肪酸是主要的代谢媒介，主要的钒还原菌有Geobacter、Spirochaeta、Acetobacterium、Shewanella和Pseudomonas等。地质环境中常见电子受体硝酸盐、三价铁、硫酸盐显著影响钒的微生物还原，其中硝酸盐先抑制、后促进钒的还原过程，而三价铁、硫酸盐一直抑制钒的还原，并且其抑制程度随着氧化还原电位的减小而降低。通过功能微生物的代谢途径分析，发现反硝化基因，包括napA和nirS等的丰度在所构建的体系内显著增高，电子传递物质细胞色素c和NADH的浓度也显著提高，功能微生物的分泌物、细胞膜组分和细胞质组分，都能有效还原钒，场发射透射电镜确定了还原产物四价钒在细胞内和细胞外的分布。本项目利用高效无机电子供体有效促进五价钒的微生物还原，有助于加深对钒的生物地球化学过程的认识，并可为钒污染地质环境的有效修复，提供科学依据。