The effect of landfill leachate irrigation on soil gas composition: Methane oxidation and nitrous oxide formation

The treatment of landfill leachate by irrigation of the recultivation layer of landfills sites might interfere with greenhouse gas cycling in the soil through alteration of the microbial methane oxidation capacity and promotion of nitrous oxide formation. The interaction of landfill leachate irrigation, methane oxidation and nitrous oxide formation was investigated in a compost - gravel recultivation substrate with and without landfill gas fumigation during a two year lysimeter experiment. Microbial methane oxidation started 3 days after landfill gas addition, and it was promoted by less than 150 mm of landfill leachate application. While long term landfill leachate irrigation negatively affected methane oxidation corresponding to the increasing soil moisture content. In respect to nitrous oxide, formation was low under landfill gas fumigation, while landfill leachate application triggered nitrous oxide production. Only low amounts (< 200 mm) might avoid increasing greenhouse gas concentrations in landfill leachate irrigated soil.