Seasonal CH₄ and CO₂ effluxes in a final covered landfill site in Beijing, China

As the main solid waste disposal method in China, landfill sites are considerable sources of methane (CH₄) and carbon dioxide (CO₂). This study characterized the seasonal variation of CH₄ and CO₂ effluxes at a large and well-managed final covered landfill site in China. A three-year monitoring program was conducted. There were two different seasonal variation patterns for hotspot and non-hotspot' CH₄ and CO₂ effluxes. For non-hotspots, the CH₄ and CO₂ effluxes' seasonal variations were mainly affected by the seasonal change of the landfill's cover soil respiration activity, particularly the CH₄ oxidation capability. CH₄ had a higher efflux in winter; in other seasons, the CH₄ efflux fluctuated around 0; the CO₂ effluxes were (1) increased in spring and peaked in summer or early autumn; (2) then, they decreased to a minimum value in late autumn or early winter; and (3) fluctuated with the CH₄ efflux in winter. The CH₄ emissions in winter account for 60.4-84.4% of the all year outputs. For the hotspots', the CH₄ and CO₂ effluxes seasonal variations were mainly determined by the seasonal change of the landfill cover's soil gas permeability. The ratio of CH₄ emissions in winter to the all year outputs range from 17.4 to 68.7%.