MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China.
MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China; College of Civil Engineering, Fuzhou University, China.
Waste Manag. 2020 Apr 15;107:54-65. doi: 10.1016/j.wasman.2020.03.026. Epub 2020 Apr 7.
The methane emission in a loess-gravel capillary barrier cover (CBC) in winter and summer was investigated by constructing a full-scale testing facility (20 m × 30 m) with a slope angle of 14.5° at a landfill in Xi'an, China. Weather conditions, methane emission, gas concentration, temperature, and volumetric water content (VWC) in the CBC were measured. The temperature and moisture in the CBC showed a typical seasonal pattern of warm and dry in summer and cold and wet in winter. Accordingly, the maximum methane oxidation rate and methane emission were higher in summer. The mean methane influx and methane emission decreased significantly as the VWC increased beyond 40% (i.e., a degree of saturation 0.85) at a depth of 0.85 m, which was near the loess/gravel interface. At this depth, more water was presented in the loess layer in the downslope direction due to capillary barrier effects, which increased the upslope methane emission. More dominant methane emission in the middle- and upper-section of the CBC occurred in summer than in winter as there was less soil moisture to facilitate methane transfer. The LFG balance showed that a significant fraction of the loaded LFG was not accounted in the flux chamber measurements due to the preferential flow along the edges of the CBC. The maximum methane oxidation rate was 93.3 g CH m d, indicating the loess-gravel CBC could mitigate methane emissions after landfill closure.
在中国西安的一个垃圾填埋场，通过构建一个具有 14.5°坡度角的全尺寸测试设施（20 m×30 m），研究了冬季和夏季黄土-碎石毛细屏障覆盖层（CBC）中的甲烷排放情况。测量了 CBC 中的天气条件、甲烷排放、气体浓度、温度和体积含水量（VWC）。CBC 中的温度和湿度呈现出夏季温暖干燥、冬季寒冷潮湿的典型季节性模式。因此，夏季的最大甲烷氧化速率和甲烷排放量较高。当 VWC 超过 40%（即饱和度为 0.85），深度为 0.85 m 时，甲烷通量和甲烷排放量显著下降，这接近黄土-碎石界面。在这个深度，由于毛细屏障效应，更多的水出现在下坡方向的黄土层中，这增加了上坡的甲烷排放。由于夏季土壤水分较少有利于甲烷迁移，CBC 中部和上部的甲烷排放更为显著。LFG 平衡表明，由于沿 CBC 边缘的优先流，通量室测量中未考虑到加载的 LFG 的很大一部分。最大甲烷氧化速率为 93.3 g CH m d，表明黄土-碎石 CBC 可以减轻垃圾填埋场关闭后的甲烷排放。
