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

Abstract

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 CH 4 oxidation at low temperatures. CH 4 consumption was detected at all the temperatures studied (1–19 °C) and an increase in CH 4 consumption rate in consecutive incubations was obtained even at 1 °C, indicating activation or increase in enzymes and/or microorganisms responsible for CH 4 oxidation. CH 4 consumption was reduced with low water content (17%WHC) at all temperatures. The response of CH 4 consumption to temperature was high with Q 10 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 Q 10 values. The responses of CH 4 consumption to water content varied at different temperatures so that at 1–6 °C, CH 4 consumption increased along with water content (33–67%WHC) while at 12–19 °C the response was curvilinear, peaking at 50%WHC. CH 4 consumption was less tolerant (higher Q 10 values; 6.5–8.4) of low temperatures compared to basal respiration ( Q 10 values for CO 2 production and O 2 consumption 3.2–4.0). Overall, the present results demonstrate the presence of CH 4-oxidizing microorganisms, which are able to consume CH 4 and to be activated or grow at low temperatures, suggesting that CH 4 oxidation can reduce atmospheric CH 4 emissions from methanogenic environments even in cold climates.