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Methane distribution surrounding closed landfill sites in China

Methane as a green gas has been a concern for a long time. The emission of landfill gas and the release of dissolved methane in water in contaminated sites surrounding the landfills are two main sources of methane contributing to surface air. The distribution of methane in leachate, air and groundwater around the closed Erfei Shan landfill was investigated and the effects of redox species in leachate plume on methane distribution were also discussed in this paper. The result showed a high concentration of dissolved methane was determined in raw leachate (up to 46.07 mg l−1) and in the shallow groundwater (up to 27.95 mg l−1) near the landfill. Methane was depleted where elevated concentrations of sulfate were observed at 7–10 m under ground level. The average methane concentrations by volume in the surface air surrounding the landfill for SA1, SA2, SA3 and SA4 were 55.09, 118.29, 14.01 and 87.22 mg l−1, respectively. The surface methane concentrations were related to their emission sources and low levels of methane emissions can last a long time, even after the landfill is closed.