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.