多氯联苯在典型沉积物中的微生物厌氧脱氯降解及其强化机制研究

Polychlorinated biphenyls (PCBs) are typical persistent organic pollutants. Their fate in the environment is of great concern. To date, the remediation of PCBs in sediments remains a particularly hot and difficult problem to solve. Despite microbial-catalyzed reductive dechlorination is believed to take place in natural sediments, little is known about the interactions among the physical/geochemical properties, microorganisms and PCB dechlorination, as well as how to effectively enhance PCB dechlorination. To overcome these obstacles, sediments collected from an electronic waste (e-waste) recycling site and a drinking water source site containing dioxin-like PCBs will be carefully examined for their dechlorination activities under a variety of physical/geochemical conditions. Gas chromatography coupled with micro-electron capture detector (GC-μECD) based PCB congener-specific analysis will be applied to track the shifts of PCB dechlorination rate, extent and pathways. Multiple molecular biology tools-quantitative polymerase chain reaction (qPCR), denaturing gel gradient electrophoresis (DGGE) and high throughput sequencing will be utilized to comprehensively qualify and quantify the shifts of microbial communities, dechlorinating bacteria and/or reductive dehalogenase genes. The relationships among the physical/geochemical properties, microorganisms and PCB dechlorination will be carefully studied and the results are expect to lead to a better understanding of the manipulation of physical/geochemical conditions on microbial-catalyzed PCB anaerobic dechlorination in the sediments. Furthermore, to effectively enhance PCB dechlorination, carbon sources, Fe(0), granular activated carbon, Fe(0) loaded granular activated carbon will be investigated for biostimulation of PCB dechlorination. Tetrachloroethene(PCE), halogenated benzoates, pentachloronitrobenzene and /or vitamin B12 will be examined to pre-enrich active dechlorinating bacteria. The active dechlorinating bacteria culture will be amended in sediments for bioaugmentation of PCB dechlorination. The recombinant rat hepatoma cell line (H4IIE-luc) which has a stable transfected luciferase reporter gene under the control of dioxin-responsive elements (DREs) will be utilized to characterize the sediments for their capacity and potency to induce Aryl hydrocarbon receptor (AhR)-mediated (so called dioxin-like) responses. The H4IIE-luc bioassays in conjunction with chemical analyses will be employed to comprehensively understand the ecological effect of enhanced dechlorination in sediments. In summary, this study is expected to better support monitored natural attenuation as a viable strategy for PCB in situ remediation in sediments.

多氯联苯（PCBs）作为公认的持久性有机污染物，其在环境中的转化归趋备受关注。近年来，PCBs污染沉积物的修复成为研究的热点和难点。在沉积物中PCBs可以通过微生物催化实现脱氯降解，但该降解方式受物理/地球化学因素、微生物因素的影响机制及脱氯强化机制都尚不明晰。本项目将分别选取电子垃圾拆卸区的PCBs重污染沉积物和有类二噁英PCBs检出的敏感水源地沉积物，全面考察各种常见物理/地球化学因素对PCBs脱氯降解的影响，通过跟踪监测探寻不同物理/地球化学条件下PCBs降解速率、效果和路径等的变化规律和脱氯相关微生物/基因的变化规律，揭示被研究沉积物中PCBs微生物厌氧脱氯的影响机制；并在此基础上通过生物刺激、生物强化方法的研究，深入阐释脱氯的强化机制；最后通过脱氯相关的生态毒理效应研究，综合评价PCBs微生物厌氧脱氯降解效果，为监测自然衰减法原位修复PCBs污染沉积物提供科学依据和技术支持。

多氯联苯（PCBs）在沉积物中能够通过厌氧微生物催化进行脱氯降解，而降解过程中地球化学因素的影响机制及微生物作用方式和机理尚不明晰，亟待全面考察并找出关键影响因子，实现对脱氯过程的调控。本项目围绕多氯联苯微生物脱氯展开研究，已发表SCI论文9篇，EI论文5篇，申请国家专利1项，培养研究生9名。取得主要研究成果如下：.（1）对典型浅水型湖泊太湖、白洋淀及典型深水型湖泊抚仙湖沉积物中多氯联苯分布特征进行调查并进行生态风险评估，结果表明抚仙湖沉积物中多氯联苯污染的生态风险较小，太湖和白洋淀沉积物中多氯联苯污染有一定的潜在生态风险。.（2）选取太湖沉积物配制微环境考察物理/地球化学因素对沉积物中多氯联苯微生物脱氯降解的影响，泥浆中多氯联苯初始浓度为(49.56±0.38) mg/kg，仅添加多氯联苯的T-1组在长达108周的反应期内，母体多氯联苯削减高达85%，微环境中多氯联苯以间位和对位脱氯为主；竞争电子受体SO42-，FeOOH和NO3-的添加，不同程度延长了多氯联苯脱氯反应的滞后期并抑制脱氯。.（3）对微生物群落结构进行分析，探究微生物、物理/地球化学因素和PCBs降解的相互作用机制，SO42-显著降低了微生物物种均匀度，三价铁显著降低了微生物物种丰富度和均匀度，而添加NO3-反应组微生物群落多样性随时间的增加呈现升高的趋势。脱氯相关菌Chloroflexi、Dehalococcoides 16S rRNA基因、还原脱卤酶基因ardA、rdh12均能指示T-1组和添加FeOOH的T-Fe组沉积物微环境脱氯反应的发生，Chloroflexi 16S rRNA基因、ardA、rdh12可以指示添加SO42-的T-S组脱氯反应的加快，且ardA、rdh12基因的所有指示均更加灵敏，Chloroflexi 16S rRNA和pcb A5可以指示添加NO3-的T-N组微环境脱氯反应的发生。.（4）考察了短链脂肪酸碳源、零价铁、活性炭及零价铁负载活性炭作为刺激剂对多氯联苯微生物脱氯的强化效果。结果表明上述物质均能够显著强化多氯联苯脱氯降解。.（5）对脱氯过程的生态毒理效应研究发现，降解过程不产生新的类二噁英多氯联苯。竞争电子受体SO42-和NO3-削弱了沉积物环境的解毒能力。短链脂肪酸碳源、零价铁、活性炭、零价铁负载活性炭的添加均有效降低了生态毒性。