SEASONAL AND DIURNAL METHANE EMISSIONS FROM A LANDFILL AND THEIR REGULATION BY METHANE OXIDATION*1

Rates of methane emission from a Swedish landfill, measured by chamber technique and permanent frames, ranged between 0.034 and 20 mmol CH4m−2. h−1on average. The emissions followed a seasonal pattern, with the highest fluxes occurring between September and May. Methane concentrations in soil also followed a seasonal pattern, with a marked decrease during summers. Using the means of methane emission rates from frost-free periods, a stepwise regression model was made, that could explain 95% of the variation. Soil temperature turned out to be the dominating factor, explaining 85% when transformed to a second-degree function. Methane emissions were negatively correlated with soil temperature, which strongly suggests that biological methane oxidation is an important regulating factor. The activity of methane-oxidizing microorganisms was greatest around 0.5–0.6 m depth in the soil profile, and moisture at this level enhanced emissions. The tendency for methane emissions to be higher at night was probably due to the inhibitory influence of low soil temperatures on methane-oxidizing microorganisms.