Landfill Methane Oxidation Response to Vegetation, Fertilization, and Liming
2000
Hilger, Helene A. | Wollum, Arthur G. | Barlaz, Morton A.
This study was conducted to evaluate the effects of vegetation, N fertilizers, and lime addition on landfill CH₄ oxidation. Columns filled with compacted sandy loam and sparged with synthetic landfill gas were used to simulate a landfill cover. Grass-topped and bare-soil columns reduced inlet CH₄ by 47 and 37%, respectively, at peak uptake; but the rate for both treatments was about 18% at steady slate. Nitrate and NH₄ amendments induced a more rapid onset of CH₄ oxidation relative to KCl controls. However, at steady state, NH₄ inhibited CH₄ oxidation in bare columns but not in grassed columns. Nitrate addition produced no inhibitory effects. Lime addition to the soil consistently enhanced CH₄ oxidation. In all treatments, CH₄ consumption increased to a peak value, then declined to a lower steady-state value; and all gassed columns developed a pH gradient. Neither nutrient depletion nor protozoan grazing could explain the decline from peak oxidation levels. Ammonium applied to grassed cover soil can cause transient reductions in CH₄ uptake, but there is no evidence that the inhibition persists. The ability of vegetation to mitigate NH₄ inhibition indicates that results from bare-soil tests may not always generalize to vegetated landfill caps.
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