Methane Emission From Municipal Solid Waste Landfill And Oxidation Factor In Landfill Cover Soils

Landfill has become an important source of anthropogenic methane emissions.Soil cover is recognized as a key technology for mitigating landfill methane emissions.In order to fully understand the methane emissions from landfill and oxidation efficiency in landfill cover soils,this study takes Beijing Asuwei landfill as the research object,using the static chamber method to conduct a comprehensive monitoring of methane emission from landfill.Based on the results of long-term fixed point monitoring and special seasonal strengthening monitoring,the relationship between methane emission flux and related factors and temporal and spatial variation of methane emission were analyzed.Based on the experiment results and the investigation data,the inversion model and the CH₄/CO₂ ratio method were used to evaluate the methane oxidation factor.The main conclusions of this paper are as follows:（1）Through 10 long-term fixed-point monitoring,results show that the average monthly methane emission flux value fluctuates in a large range,up to 3⁵ orders of magnitude.However,methane emission flux showed obvious seasonal variation,which exhibited that the high value appeared near the winter,and the low value appeared in summer.Based on the results of strengthening monitoring by IDW spatial interpolation analysis,the methane emission flux value at 200⁸00 mg m^-2h^-1 accounted for 39.62% of the monitoring area in summer;the methane emission flux value at 3300¹4200 mg m^-2h^-1 accounted for 44.32% of the monitoring area in Autumn.The hot spot area of methane emission in autumn was the same as that in summer,but the methane emission flux value was significantly higher than that in summer,which was about 16 times that of the same area in summer.（2）Methane and carbon dioxide emission fluxes maintain a high degree of synchrony.The correlation analysis showed that methane and carbon dioxide emission fluxes had significant positive correlation（r=0.861,P<0.01）.In addition,there was a significant negative correlation between methane emission flux and atmospheric temperature（r=-0.897,P<0.01）;The methane emission flux was positively correlated with atmospheric pressure（r=0.775,P<0.01）;There was no significant correlation between methane emission flux and atmospheric relative humidity（P>0.05）.（3）The results of inversion model show that the methane oxidation factor in the landfill cover soils shows a seasonal pattern.The highest value of methane oxidation factor appeared in June,the lowest value appeared in February,and the values in summer and autumn are obviously higher than those in winter and spring.The annual methane oxidation factor is in the range of 0.01 to 0.82 and the average is 0.42,which is higher than the default value of IPCC（0.1）.（4）The CH₄ / CO₂ ratio method analysis showed that the change ratio of CO₂ / CH₄ ratio was 0.90 12.64,and the variation range of method oxidation factor in different soil depth was 0.16 0.88,the average value was 0.55.