USDA-Agricultural Research Service, Soil and Water Management, St. Paul, MN 55108, USA.
Waste Manag. 2011 May;31(5):823-32. doi: 10.1016/j.wasman.2009.12.018. Epub 2010 Jan 21.
In order to understand the limits and dynamics of methane (CH(4)) oxidation in landfill cover soils, we investigated CH(4) oxidation in daily, intermediate, and final cover soils from two California landfills as a function of temperature, soil moisture and CO(2) concentration. The results indicate a significant difference between the observed soil CH(4) oxidation at field sampled conditions compared to optimum conditions achieved through pre-incubation (60 days) in the presence of CH(4) (50 ml l(-1)) and soil moisture optimization. This pre-incubation period normalized CH(4) oxidation rates to within the same order of magnitude (112-644 μg CH(4) g(-1) day(-1)) for all the cover soils samples examined, as opposed to the four orders of magnitude variation in the soil CH(4) oxidation rates without this pre-incubation (0.9-277 μg CH(4) g(-1) day(-1)). Using pre-incubated soils, a minimum soil moisture potential threshold for CH(4) oxidation activity was estimated at 1500 kPa, which is the soil wilting point. From the laboratory incubations, 50% of the oxidation capacity was inhibited at soil moisture potential drier than 700 kPa and optimum oxidation activity was typical observed at 50 kPa, which is just slightly drier than field capacity (33 kPa). At the extreme temperatures for CH(4) oxidation activity, this minimum moisture potential threshold decreased (300 kPa for temperatures <5°C and 50 kPa for temperatures >40°C), indicating the requirement for more easily available soil water. However, oxidation rates at these extreme temperatures were less than 10% of the rate observed at more optimum temperatures (∼ 30°C). For temperatures from 5 to 40°C, the rate of CH(4) oxidation was not limited by moisture potentials between 0 (saturated) and 50 kPa. The use of soil moisture potential normalizes soil variability (e.g. soil texture and organic matter content) with respect to the effect of soil moisture on methanotroph activity. The results of this study indicate that the wilting point is the lower moisture threshold for CH(4) oxidation activity and optimum moisture potential is close to field capacity. No inhibitory effects of elevated CO(2) soil gas concentrations were observed on CH(4) oxidation rates. However, significant differences were observed for diurnal temperature fluctuations compared to thermally equivalent daily isothermal incubations.
为了理解填埋场覆盖土壤中甲烷（CH(4)）氧化的极限和动态，我们研究了加利福尼亚两个垃圾填埋场的日覆盖土壤、中间覆盖土壤和最终覆盖土壤中 CH(4)氧化作为温度、土壤湿度和 CO(2)浓度的函数。结果表明，与通过在存在 CH(4)（50 ml l(-1)) 和土壤湿度优化的情况下进行 60 天预培养达到的最佳条件相比，现场采样条件下观察到的土壤 CH(4)氧化有显著差异。该预培养期使所有检查的覆盖土壤样本中的 CH(4)氧化率归一化为相同数量级（112-644 μg CH(4) g(-1) day(-1))，而没有这种预培养时，土壤 CH(4)氧化率的变化范围为四个数量级（0.9-277 μg CH(4) g(-1) day(-1))。使用预培养的土壤，估计 CH(4)氧化活性的最小土壤水分势阈值为 1500 kPa，这是土壤萎蔫点。从实验室培养来看，当土壤水分势比 700 kPa 更干燥时，氧化能力的 50%受到抑制，而最佳氧化活性通常在 50 kPa 时观察到，这只是略低于田间持水量（33 kPa）。在 CH(4)氧化活性的极端温度下，这个最小水分势阈值降低（<5°C 时为 300 kPa，>40°C 时为 50 kPa），表明需要更易获得的土壤水。然而，在这些极端温度下的氧化速率小于最适温度（约 30°C）下观察到的速率的 10%。对于 5 至 40°C 的温度，CH(4)氧化的速率不受 0（饱和）至 50 kPa 之间的土壤水分势的限制。土壤水分势的使用使土壤变异性（例如土壤质地和有机质含量）相对于土壤水分对甲烷营养菌活性的影响标准化。这项研究的结果表明，萎蔫点是 CH(4)氧化活性的较低水分阈值，最佳水分势接近田间持水量。升高的 CO(2)土壤气体浓度对 CH(4)氧化速率没有抑制作用。然而，与热等效的每日等温培养相比，昼夜温度波动有显著差异。
