Response of chlorinated hydrocarbon transformation and microbial community structure in an aquifer to joint H₂ and O₂

Hydrogen (H₂) and oxygen (O₂) are critical electron donors and acceptors to promote the anaerobic and aerobic microbial transformation of chlorinated hydrocarbons (CHCs), respectively. Electrochemical technology can effectively supply H₂ and O₂ directly to an aquifer. However, the response of CHC transformation and microbial community structure to joint H₂ and O₂ are still unclear. In this work, microcosms containing different combinations of H₂ and O₂ were constructed with natural sediments and nine mixed CHCs. The joint H₂ and O₂ microcosm (H₂/O₂ microcosm) significantly promoted the biotransformation of trichloroethylene (TCE), trans-dichloroethene (tDCE) and chloroform (CF). Illumina sequencing analyses suggested that a particular microbial community was formed in the H₂/O₂ microcosm. The specific microbial species included Methyloversatilis, Dechloromonas, Sediminibacterium, Pseudomonas, Acinetobacter, Curvibacter, Comamonas and Acidovorax, and the relative abundance of the tceA, phe and soxB genes synchronously increased. These results suggested that some specific microbes are potential CHC converters using H₂ and O₂ as energy sources, and aerobic and anaerobic transformations exist simultaneously in the H₂/O₂ microcosm. It provides a theoretical basis for establishing efficient green remediation technologies for CHC contaminated aquifers.