| Abstrakt: |
This study was conducted to evaluate the effects of vegetation, N fertilizers, and lime addition on landfill CH4oxidation. 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 CH4by 47 and 37%, respectively, at peak uptake; but the rate for both treatments was about 18% at steady slate. Nitrate and NH4amendments induced a more rapid onset of CH4oxidation relative to KCl controls. However, at steady state, NH4inhibited CH4oxidation in bare columns but not in grassed columns. Nitrate addition produced no inhibitory effects. Lime addition to the soil consistently enhanced CH4oxidation. In all treatments, CH4consumption 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 CH4uptake, but there is no evidence that the inhibition persists. The ability of vegetation to mitigate NH4inhibition indicates that results from bare‐soil tests may not always generalize to vegetated landfill caps. |
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