Abstract：
Hexachlorocyclohexane (HCH) isomers are persistent organic pollutants (POPs) with high toxicity, lipid solubility, chemical stability. Despite the current ban on usage of Lindane, residual contamination cannot be ignored, and HCH are frequently detected in groundwater and threaten human health. Cultures capable of degrading α-HCH, β-HCH, γ-HCH, and δ-HCH individually have been enriched in anoxic aqueous conditions. Compound-Specific Isotope Analysis (CSIA) was applied to examine the transformation mechanisms of different HCH isomers by the four enrichment cultures. 16S rRNA sequencing techniques were employed to examine the community composition of the enrichment cultures and detect changes in these communities resulting from adding individual HCH isomers. The results indicated that the ability of the enrichment cultures for dichloroelimination of HCH isomers was inconsistent. During dichloroelimination, different bond cleavage mode of β- and δ-HCH led to distinct isotopic effects. HCH isomers had significant impact on the microbial community, while different microbial communities showed comparable isotopic effects during the transformation of a specific HCH isomer. In addition, bacteria in the phyla Proteobacteria and Firmicutes were proposed as the dominant dechlorinators. This study provides a novel perspective on the mode of bond cleavage during HCH dichloroelimination and the effect of HCH on microbial communities, which could potentially support the evaluation of HCH transformation by CSIA and their effects on the microecosystems of groundwater.
摘要：
六氯环己烷（HCH）异构体是具有高毒性的持久性有机污染物（POPs），脂溶性，化学稳定性。尽管目前禁止使用林丹，残留污染不容忽视，和六氯环己烷经常在地下水中检测到，威胁人类健康。能够降解甲型六氯环己烷的培养物，β-HCH,γ-HCH,和δ-六氯环己烷分别在缺氧条件下富集。化合物特异性同位素分析（CSIA）用于检查四种富集培养物中不同HCH异构体的转化机制。采用16SrRNA测序技术来检查富集培养物的群落组成，并检测由于添加单个六氯环己烷异构体而导致的这些群落的变化。结果表明，富集培养物消除六氯环己烷异构体的能力不一致。在二氯消除期间，β-六氯环己烷和δ-六氯环己烷的不同键裂解模式导致不同的同位素效应。六氯环己烷异构体对微生物群落有重大影响，而不同的微生物群落在特定六氯环己烷异构体转化过程中表现出可比的同位素效应。此外,门变形杆菌和Firmicutes中的细菌被认为是主要的脱氯剂。这项研究为HCH二氯消除过程中的键裂解模式以及HCH对微生物群落的影响提供了新的视角，这可能支持CSIA对六氯环己烷转化及其对地下水微生态系统的影响的评估。
