Contribution of sulfate-reducing bacteria in the formation of hydrogen sulfide in coal seams of Hancheng mining area, China

Coalbed hydrogen sulfide (H2S) is a toxic and corrosive gas, it’s very important for researching the origin of H2S in coalbed and related metabolic characteristics of microbes in the bioconversion of coal. The purpose of this study is to clarify the contribution and influencing factors of bacterial and sulfate-reducing bacterial (SRB) communities in the Taiyuan Formation (Nos. 5 and 11 coal seams) of the Hancheng mining area, by using gas composition testing, water quality measurements, 16S rRNA amplicon sequencing, and fluorescence real-time quantitative (qPCR) analysis. The results indicate that the coal seam gas is mainly composed of methane with a trace amount of H2S ranging from 4 to 56 ppm. The H2S content exhibits a positive correlation with the SRB gene copy number within the range of ∼30 to 200 copies/mL, indicating a strong association between the production of H2S and the contribution of SRB in the study area. The presence of Desulfobulbus, Desulfovibrio, Desulfomicrobium, Desulfotomaculum, Desulfobacca, Thermosinus, Desulfococcus, Desulfarculus, and Syntrophobacter genus from the coalbed-produced water further proves that H2S is reduced in dissimilatory sulfate reduction (DSR) pathway. Bacteria and SRB play a critical role in the conversion of coal organic matter through biodegradation. SRB community composition is more related to total organic carbon, total dissolved solids, SO42- and trace elements. This study gives an in-depth explanation of the formation of H2S in coalbed and provides novel views in toxic gas removal in future gas exploitation.