Field monitoring and analysis of landfill gas emissions in a large-scale landfill in Hangzhou, China.

Landfill gas (LFG) harms human health and worsens the greenhouse effect. Long-term monitoring enables scientific assessment of environmental impacts. This paper presents a year-long observation of methane and volatile organic compounds (VOCs) concentrations and fluxes on the surface cover of a large-scale landfill in Hangzhou. Based on monitoring data, the LFG migration model was established to evaluate the gas containment effectiveness of different cover layers. It indicates that landfill cover systems effectively reduce methane and VOC emissions. Compared to the Phase II landfill, VOC fluxes on the surface of the Phase I landfill have decreased by over 50%, with the number of VOCs reducing from 19 to 11. Besides, the concentration and flux of LFG exhibit significant spatio-temporal heterogeneity. The permeation coefficient of GMB was determined by inverting the analytical model, and it was found to increase with rising temperature. This is due to increased gas molecule activity and heightened polymer segmental motion in GMBs at elevated temperatures. Additionally, it has been found that planting camphor trees on the cover layer can effectively reduce methane emissions, followed by Pyracantha fortuneana 'Harlequin' and Nerium. This is because camphor trees possess the deepest root systems and exhibit the strongest capacity for methane oxidation. Moreover, Pearson correlation analysis indicates a significant negative correlation between methane and VOC emissions. This is because methane oxidation consumes oxygen, thereby inhibiting VOC degradation. This study elucidates the migration and emission patterns of LFG, providing theoretical and data-driven support for the design and management of landfill cover systems.