Depth profiles of methane oxidation potentials and methanotrophic community in a lab-scale biocover

The depth profiles of the CH₄ oxidation potentials and the methanotrophic community were characterized in a lab-scale soil mixture biocover. The soil mixture samples were collected from the top (0-10cm), middle (10-40cm), and bottom (40-50cm) layers of the biocover where most of methane was oxidized at the top layer due to consumption of O₂. Batch tests using serum bottles showed that the middle and bottom samples displayed CH₄ oxidation activity under aerobic conditions, and their CH₄ oxidation rates were 85 and 71% of the rate of top sample (8.40μmolgdry sample^-1h^-1), respectively. The numbers of methanotrophs in the middle and bottom were not significantly different from those in the top sample. There was no statistical difference in the community stability indices (diversity and evenness) among the methanotrophic communities of the three layer samples, even though the community structures were distinguished from each other. Based on microarray analysis, type I and type II methanotrophs were equally present in the top sample, while type I was more dominant than type II in the middle and bottom samples. We suggested that the qualitative difference in the community structures was probably caused by the difference in the depth profiles of the CH₄ and O₂ concentrations. The results for the CH₄ oxidation potential, methanotrophic biomass, and community stability indices in the middle and bottom layer samples indicated that the deeper layer in the methanotrophic biocover serves as a bioresource reservoir for sustainable CH₄ mitigation.