Effects of plant radial oxygen loss on methane oxidation in landfill cover soil: A simulative study

Radial oxygen loss (ROL) by the spreading root systems of vegetation can improve soil aeration for subsequent oxidation of methane (CH₄) by microbes in landfill cover soils. This study proposes a theoretical model that elucidated the effects of ROL on microbial oxidation of CH₄ to understand landfill gas transportation and oxidation in landfill cover soils. Parametric analyses were conducted to investigate the effects of root depth, root architecture, and ROL rate on the CH₄ oxidation efficiency of landfill cover soils. The simulation results suggested that disregarding O₂ emissions by plants root systems could underestimate the CH₄ oxidation efficiency, especially when the water content ranged from 20% to 35%. Additionally, plants with a parabolic root architecture indicated 7-13% higher CH₄ oxidation efficiency than other root architectures, i.e., uniform, triangular, and exponential. The CH₄ oxidation efficiency increased rapidly at root depths less than 0.25 m. Therefore, plants characterized by a parabolic root architecture, longer root length, and higher ROL capacity should be selected as the preferred species for mitigating CH₄ emissions from landfills in humid areas.