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Diversity and activity of sulphur‐oxidizing bacteria and sulphate‐reducing bacteria in landfill cover soils

Sulphur bioconversion in landfill cover soils, including the metabolism of sulphur‐oxidizing bacteria (SOB) and sulphate‐reducing bacteria (SRB), is one of the important processes affecting H2S emission from landfills. In this study, two landfills with or without landfill gas collection and utilization system were investigated to characterize the role of biotic and abiotic factors affecting diversity and activity of SOB and SRB in the landfill cover soils. The results revealed that the potential sulphur oxidation rates (SORs) and sulphate reduction rates (SRRs) varied with landfill sites and depths. SOR was significantly correlated with pH and SO42−, while SRR was significantly related with pH. The populations of both SOB and SRB were low in the acidic landfill cover soils (pH = 4·7–5·37). Cloning and terminal restriction fragment length polymorphism profiles of soxB and dsrB showed that SOB including Halothiobacillus, Thiobacillus, Thiovirga and Bradyrhizobium, and SRB including Desulfobacca, Desulforhabdus and Syntrophobacter dominated in the landfill cover soils, and their distributions were affected mainly by pH value and organic matter contents of soils.