Lateral gas transport in soil adjacent to an old landfill: factors governing emissions and methane oxidation

Field investigations of lateral gas transport and subsequent emissions in s oil adjacent to an old landfill in Denmark were conducted during a 1-year p eriod. A significant seasonal variation in the emissions with high carbon d ioxide and low methane fluxes in the summer (May to October) was observed. This was attributed to methane oxidation. Diurnal measurements during a dro p in barometric pressure showed that the fluxes of landfill gas changed dra matically within a very short time. The concentrations and the soil moistur e content in the upper part of the soil profile had significant influence o n the fluxes, as did the distance from the landfill border, temperature, ba rometric pressure and the pressure gradient. Statistical analyses proved th at soil moisture described the largest part of the variation. No methane is emitted during the summer. Calculations and isotope analyses showed that v ery high fractions of the laterally migrating methane were oxidised.