典型污染区域河流底泥中氯代有机磷阻燃剂的厌氧微生物降解

Organophosphate flame retardants (OPFRs) have been considered as a kind of emerging persistent organic pollutants. Especially, some chlorinated OPFRs are suspected to be carcinogenic, posing higher health risks to ecosystems and humans than non-chlorinated OPFRs. River sediments are usually a main pool of chlorinated (including non-chlorinated) OPFRs and thus readily contaminated. Anaerobic microbial degradation is proposed as a major factor affecting the environmental behavior and fate of chlorinated OPFRs in river sediments. Little is known about the anaerobic microbial degradation of chlorinated OPFRs, although two aerobic bacteria strains have been reported to be able to degrade chlorinated OPFRs efficiently. This research project thus aims to explore the anaerobic microbial degradation of OPFRs in river sediments and the underlying mechanisms. More specifically, we will collect river sediments from three representative sites contaminated by OPFRs, and investigate the responses of composition and function of microbial communities in the sediments using next generation high-output sequencing technologies. Based on this, we will establish microcosms with selected sediments to study the degradation dynamics, metabolites and pathways of three representative chlorinated OPFRs by anaerobes in the sediments. The associated changes in composition and function of microbial communities in the sediments will be also characterized. We will further isolate anaerobic bacterial strains that can degrade chlorinated OPFRs efficiently, and explore the characteristics of these anaerobes in degrading chlorinated OPFRs and the genomic basis for their properties in the degradation. The results generated by this project will not only improve our understanding of the roles of anaerobes in affecting the environmental behavior and fate of chlorinated OPFRs in river sediments but also have significant implications for risk assessment and remediation of sites contaminated by chlorinated OPFRs.

有机磷阻燃剂（OPFRs）是一类新型的持久性有机污染物，尤其是氯代OPFRs有潜在的致癌性，对生态环境和人体健康具有严重危害。河流底泥是氯代OPFRs重要聚集地，而厌氧微生物降解是影响氯代OPFRs在底泥中环境行为和归趋的重要因素。但是，目前只分离到两株能降解氯代OPFRs的好氧菌，而对氯代OPFRs厌氧生物降解的研究尚未见报道。因此，本项目拟选择典型污染区域河流作为研究靶区，通过高通量测序技术研究河流底泥微生物群落结构和功能对OPFRs污染的响应机制；构建微宇宙模拟实验体系，研究河流底泥中氯代OPFRs厌氧生物降解动力学、降解产物和降解途径；从底泥中分离氯代OPFRs的高效降解菌株，研究其降解氯代OPFRs的特征和基因组学基础；以期揭示典型污染区域河流底泥中氯代OPFRs的厌氧微生物降解过程和机制，为氯代OPFRs污染场地的风险评估、污染控制和生物修复提供重要的理论依据和微生物修复材料。

氯代有机磷酸酯（OPFRs）是在厌氧环境（地下水、沉积物、地下土壤）中广泛检出的一类新兴污染物，然而关于氯代OPFRs在厌氧条件下还原转化过程却并不清楚。本项目以磷酸三（2-氯乙基）酯（TCEP）、磷酸三（1-氯-2-丙基）酯（TCPP）和磷酸三（1,3-二氯-2-丙基）酯（TDCPP）为目标化合物，开展了典型污染区域河流沉积物中氯代OPFRs厌氧生物降解过程和机制研究，取得的主要结果如下：1）首次阐明了电子垃圾拆解地河流沉积物中厌氧微生物对不同结构氯代OPFRs的降解和转化速率，通过16S rRNA基因扩增子测序分析揭示了主要参与氯代OPFRs降解和转化过程的微生物门类；2）结合氘代水实验，首次证明了氯代OPFRs通过单电子转移（自由基机制）进行还原脱氯，脱氯产物随即发生C-O键断裂生成二酯产物和烯烃，烯烃可以被进一步还原成烷烃；3）成功富集了可以高效厌氧转化TCEP、TCPP和TDCPP的含Dehalococcoides的菌群，通过定量聚合酶链反应和宏基因组学单菌草图组装技术证明了Dehalococcoides是氯代OPFRs厌氧生物转化过程的主要驱动者，参与TCEP和TCPP生物转化的Dehalococcoides属于不同的Dehalococcoides mccartyi亚组；4）揭示了参与TCEP和TCPP生物转化的Dehalococcoides分别包含14和15个还原脱卤酶（rdh）基因，其中13个和12个rdh基因在TCEP和TCPP还原转化过程中均能进行转录表达，表明它们可能分别参与了TCEP和TCPP的还原转化过程；5）首次阐明了TCEP在汽车拆解地沉积物中的厌氧降解途径和机制。另外，我们还拓展研究了硫化亚铁、硫化纳米零价铁非生物还原转化氯代OPFRs的机制，为氯代OPFRs的污染控制和生物修复提供重要的理论依据和修复材料。目前，已在Environmental Science & Technology、Water Research等国内外重要学术刊物上发表SCI论文13篇。