【作者】 李媛；

【导师】 郭华明；

【作者基本信息】 中国地质大学(北京) ， 地下水科学与工程， 2016， 博士

【摘要】 本研究以我国原生高砷地下水典型地区内蒙古河套盆地杭锦后旗作为研究区,将微宇宙实验与微生物分子生物学方法相结合,通过研究高砷地下水和沉积物中的微生物多样性及其群落结构特征,分析高砷含水层沉积物中的功能微生物群落,并与水文地球化学参数相结合,探讨微生物群落在高砷地下水运移富集过程中的作用机理。得到以下主要认识:（1）地下水样品的微生物多样性与砷污染水平有关,砷浓度相对较低的地下水样品的微生物多样性更大。细菌群落结构组成也随着地球化学条件（如氧化还原电位等）的变化而不同。（2）针对沉积物的高通量测序的CCA分析及beta多样性分布的聚类结果表明,取样深度、砷、硫和有机物含量等是影响沉积物细菌群落结构的主要因素;16S rRNA克隆文库结果也表明,沉积物微生物多样性随深度的增加而减小。（3）高砷含水层中的砷迁移受土著硝酸盐还原菌（如Pseudomonas sp.等）、铁还原菌（如Aquabacterium sp.、Thauera sp.、Georgfuchsia sp.、Methyloversatilis sp.、Clostridium sp.和Rhodoferax sp.等）、硫酸盐还原菌（如Spirochaetales sp.、Desulfuromonadales sp.、Geobacter sp.、Desulfobacca sp.和Desulfosporosinus sp.等）以及砷还原菌的影响。铁还原菌在氧化有机碳的同时,使铁氧化物发生还原性溶解,从而使铁氧化矿物表面的砷解放出来,促进地下水中砷的迁移。（4）沉积物中天然不稳定有机碳含量具有生物可利用性,足够支持上述微生物介导的生物化学活动。室内微宇宙实验证实,未加有机碳源的厌氧连续培养中,沉积物砷被大量释放出来,且所释放的砷以As（III）为主。（5）土著微生物对砷的归宿也有重要影响。X射线近边吸收结构分析显示,部分沉积物含有大量的与有机物和硫化物结合态的砷,且这些沉积物样品中存在大量的卤素呼吸菌Dehalococcoides和硫酸盐还原菌。在有机物存在的情况下,Dehalococcoides菌和Deltaproteobacteria的对As（V）、SO₄^2-和Fe（III）的还原作用可形成固态沉淀如Fe（II）-As（V）或As-S,将砷固定在黄铁矿中。（6）沉积物中存在与细胞质砷还原基因arsC（解毒）和呼吸砷还原基因arrA（呼吸）的功能基因,这些功能基因的存在促进了As（V）的还原。深层沉积物的微生物对As（V）还原作用更强,这与深层沉积物中存在异养砷还原菌（DARPs）有关,这些菌与已知的DARPs Desulfosporosinus Y5,Sulfurospirillum barnesii SES-3和Bacillus selenitireducens MLS10相似。更多还原

【Abstract】 In this study, microbially mediated arsenic release and mobiliaztion in high arsenic aquifers of Hetao Basin were studied using microscom experiments and microbial molecular methods, to analyse the geochemistry of groundwater and sediments, to investigate microbial community structure and diversity in groundwater and sediments with different geochemical characteristics, and to explore functional microbial communities in aquifer sediments enrichment culture. The following are the main points.First, the microbial community structures of groundwater changed substantially with depth at the same location. It indicated that a relatively higher bacterial diversity was present in the groundwater sample with lower arsenic concentration. Second, the CCA（Canonical Correlation Analysis） and the evolutionary tree drawed by beta diversity display the bacterial communites of the sediment samples were influenced by sample depth, As, S, TOC content significantly, which is in accordance with the comparison of clone libraries.Third, sequence analysis of 16S rDNA demonstrated that the sediment indigenous bacteria including NO₃^--reducing bacteria such as Pseudomonas sp., Fe（III）-reducing bacteria such as Aquabacterium sp.,Thauera sp.,Georgfuchsia sp.,Methyloversatilis sp., Clostridium sp., SO₄^2--reducing such as Spirochaetales sp.,Desulfuromonadales sp.,Geobacter sp.,Desulfobacca sp., Desulfosporosinus sp. and As（V）-reducing bacteria used the specific oxyanions as electron acceptor and played a significant role in reductive dissolution of Fe oxide minerals, reduction of As（V）, and release of arsenic from sediments into groundwater.Fourth, the natural organic matter in sediments was the potential electron donor for microbially mediated arsenic release from these aquifer sediments by the above bacteria. Microcosm experiments, using intact aquifer sediments, confirmed that high arsenic concentration especially As（III） was released in the batch without amendment of organic carbon.Fifth, indigenous bacteria also influenced the potential sequestration of As. Dehalococcoides sp. and sulfte reducing bacteria abundant in sediment sample with arsenic bound to organic matter and sulfides according to the sequential extraction results and XANES spectroscopy. Higher concentrations of organic matter may stimulate reduction of As（V）, SO₄^2- and Fe（III） by Dehalococcoides sp.and the Dletaproteobacteria. Arsenic can also remain in associated with the solid phase through precipitation of authigenic solids including Fe（II）-As（V） or As-S and the transformation of Fe minerals with subsequent As sequestration in the authigenic mineral.Finally, the 16S rRNA sequence anslysis and the results of functional gene ars C and arr A PCR amplification shows arsenic resistant bacteira and dissimilatory arsenate reducing prokaryotes（DARPs） are common in sediment samples which are related to As（V） reduction. As（V） was reduced remarkably in two deeper sediment encrichment cultures because of the existence of DARPs. Phylogenetic tree exhibited DARPs in the selected samples are close to DARPs Desulfosporosinus Y5,Sulfurospirillum barnesii SES-3 and Bacillus selenitireducens MLS10.更多还原