Abstract:Chlorinated methanes including carbon tetrachloride, chloroform, dichloromethane, and chloromethane are widely present in the soil and underground water at contaminated sites. With high toxicity, high stability, strong volatility, and resistance to biodegradation, chlorinated methanes have aroused public concern about their threats to environmental, ecological, and human health. Microbial dechlorination has gained attention as an environmental-friendly and cost-effective remediation strategy. This review systematically summarizes the microbial dechlorination mechanisms of chlorinated methanes, with a focus on the dechlorination process catalyzed by reductive dehalogenases in typical organohalide-respiring bacteria such as Dehalobacter and Desulfitobacterium, as well as metabolic pathways (e.g., the Wood-Ljungdahl pathway) for dichloromethane mineralization. In addition, this review highlights key environmental factors influencing microbial dechlorination efficiency and explores the substrate inhibition effects caused by the coexistence of multiple pollutants. Furthermore, the potential of indirect dechlorination mediated by microbial generation of compounds such as iron sulfide (FeS) is explored. Finally, a microbe-mineral synergistic dechlorination strategy is proposed, which integrates the advantages of abiotic reductive materials and organohalide-respiring microorganisms to achieve efficient and complete degradation of chlorinated methanes. This review provides theoretical foundations and technical insights for the in-situ remediation of chlorinated methane-contaminated sites.
