Responses of methane oxidation to temperature and water content in cover soil of a boreal landfill

Methane oxidation in a cover soil of a landfill located in a boreal climate was studied at temperatures ranging from 1–19 °C and with water content of 7–34% of dry weight (dw), corresponding to 17–81% of water-holding capacity (WHC) in order to better understand the factors regulating CH4 oxidation at low temperatures. CH4 consumption was detected at all the temperatures studied (1–19 °C) and an increase in CH4 consumption rate in consecutive incubations was obtained even at 1 °C, indicating activation or increase in enzymes and/or microorganisms responsible for CH4 oxidation. CH4 consumption was reduced with low water content (17%WHC) at all temperatures. The response of CH4 consumption to temperature was high with Q10 values from 6.5 to 8.4 and dependent on water content: at 33%WHC or more an increase in water content was accompanied by a decrease in Q10 values. The responses of CH4 consumption to water content varied at different temperatures so that at 1–6 °C, CH4 consumption increased along with water content (33–67%WHC) while at 12–19 °C the response was curvilinear, peaking at 50%WHC. CH4 consumption was less tolerant (higher Q10 values; 6.5–8.4) of low temperatures compared to basal respiration (Q10 values for CO2 production and O2 consumption 3.2–4.0). Overall, the present results demonstrate the presence of CH4-oxidizing microorganisms, which are able to consume CH4 and to be activated or grow at low temperatures, suggesting that CH4 oxidation can reduce atmospheric CH4 emissions from methanogenic environments even in cold climates.