Microbial oxidation of CH4 at high partial pressures in an organic landfill cover soil under different moisture regimes

The uptake and utilization of CH4 at high concentrations (5–18% vol.) and different soil moistures were followed for samples from a landfill cover soil with a high organic matter content. Measurements of the utilization of CH4 and O2, and production of CO2 indicated that the activity of methanotrophic organisms accounted for most of the O2 respiration. At water saturation, CH4 oxidation rates decreased with time, probably because NH+4 accumulated. Denitrification rates, estimated based on both N2 and N2O production, were positively related to soil moisture and only slightly influenced by the extent of CH4 oxidation. Total phospholipid fatty acid concentrations increased, and concentrations of phospholipid fatty acids, typical for obligate methanotrophic bacteria (e.g. 16:1ω8 and 18:1ω8), increased in the CH4-amended samples, indicating growth of both type I and type II methanotrophs.