Monitored natural attenuation (MNA) of chlorinated ethenes (CEs) has proven to be a cost-effective and environment-friendly approach for groundwater remediation. In this study, the complete dechlorination of CEs with formation of ethene under natural conditions, were observed at two CE-contaminated sites, including a pesticide manufacturing facility (PMF) and a fluorochemical plant (FCP), particularly in the deeply weathered bedrock aquifer at the FCP site. Additionally, a higher abundance of CE-degrading bacteria was identified with heightened dechlorination activities at the PMF site, compared to the FCP site. The reductive dehalogenase genes and 16 S rRNA gene were prevalent at both sites, even in groundwater where no CE dechlorination was observed. and was responsible for the complete dechlorination at the PMF and FCP site, respectively, indicating the distinct contributions of functional microbial species at each site. The correlation analyses suggested that has the potential to achieve the complete dechlorination at the FCP site. Moreover, the profiles of CE-degrading bacteria suggested that dechlorination occurred under Fe/sulfate-reducing and nitrate-reducing conditions at the PMF and FCP site, respectively. Overall these findings provided multi-lines of evidence on the diverse mechanisms of CE-dechlorination under natural conditions, which can provide valuable guidance for MNA strategies implementation.

中文翻译：

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揭示地下水中氯化乙烯的完整自然还原脱氯机制：功能基因分析的见解

监测氯化乙烯 (CE) 自然衰减 (MNA) 已被证明是一种经济高效且环境友好的地下水修复方法。在本研究中，在自然条件下，在两个 CE 污染场地（包括农药制造厂 (PMF) 和氟化工厂 (FCP)）观察到 CE 完全脱氯并形成乙烯，特别是在位于FCP 网站。此外，与 FCP 地点相比，PMF 地点的 CE 降解细菌丰度更高，脱氯活性更强。还原性脱卤酶基因和 16S rRNA 基因在这两个地点都很普遍，甚至在未观察到 CE 脱氯的地下水中也是如此。并分别负责 PMF 和 FCP 站点的完全脱氯，表明每个站点功能微生物物种的独特贡献。相关分析表明，有可能在FCP现场实现完全脱氯。此外，CE降解细菌的分布表明，PMF和FCP位点分别在铁/硫酸盐还原和硝酸盐还原条件下发生脱氯。总体而言，这些发现为自然条件下 CE 脱氯的多种机制提供了多方面的证据，可以为 MNA 策略的实施提供有价值的指导。