垃圾填埋场覆盖黄土的甲烷氧化能力及其影响因素研究

利用西安江村沟填埋场不同覆盖时间的临时覆盖黄土和新鲜黄土掺堆肥配置的土样,开展了甲烷氧化培养瓶试验,培养历时最长达22d,研究了不同覆盖时间的覆盖黄土和不同堆肥掺量的新鲜黄土的甲烷氧化能力,以及含水量对覆盖黄土甲烷氧化能力的影响,分析了甲烷氧化过程中各组分气体体积变化关系.研究结果表明:不同覆盖时间的覆盖黄土的甲烷氧化能力相差很大,覆盖3~5年的黄土最大甲烷氧化能力达26.05~53.95μg CH4/(g×h), 而未覆盖的新鲜黄土几乎没有甲烷氧化能力.在新鲜黄土中掺入堆肥,能有效提高其甲烷氧化能力,且在堆肥掺量小于50%时,土样的最大甲烷氧化能力与堆肥掺量呈正比例关系.含水量对覆盖土的甲烷氧化能力有很大影响,黄土甲烷氧化的最适宜含水量约为20% ~ 30%.在甲烷氧化过程中,甲烷氧化菌将CH4中约44%的碳氧化为CO2,其余碳转化为甲烷氧化菌胞内物质.实际工程中进行覆盖层设计时,需要根据填埋场实际产气量和覆盖层导气性确定与甲烷通量相匹配的甲烷氧化速率,进而合理确定堆肥掺量.

Methane oxidation capacity of landfill cover loess and its impact factors

Batch tests with a duration up to 22 days were carried out on the loess samples to measure their methane oxidation capacity. Some loess samples were taken from the temporary covers with different durations of placement at Xi'an landfill, the others were produced by mixing fresh loess with different content of compost. The influence of moisture content on methane oxidation was also investigated. The relationships among the volume changes of different gas compositions during methane oxidation process were analyzed. The experiments demonstrated that the methane oxidation capacity of the covering loess depended significantly on the duration of placement on the landfill. The maximum methane oxidation capacity ranged from 26.05 to 53.95μg CH4/(g×h) for the temporary cover loess with a placement duration in between 3 and 5 years. The fresh loess had no methane oxidation capacity within 22 days of incubation. The admixture of fresh loess with compost significantly enhanced the methane oxidation capacity of the loess. When the compost content was less than 50%, the maximum methane oxidation capacity of loess increased linearly with an increase in the compost content. The moisture content of loess had a significant influence on the methane oxidation, and the optimum moisture content of loess for methane oxidation is 20% ~ 30%. During the methane oxidation process, about 44% of carbon in CH4 was oxidized to CO2, the rest carbon was converted to intracellular substances. In the design of a landfill final cover, the required methane oxidation capacity as well as the required compost addition should be determined according to the CH4 generation from the landfill and the gas permeability of the landfill cover.