Abiotic Methane Production Driven by Soil Reactive Oxygen Species

Methane (CH₄), which is a potent greenhouse gas, is predominantly produced in wetland soils through biological processes. Recent studies reveal that reactive oxygen species (ROS) can abiotically generate CH₄ via oxidative demethylation of organic compounds; yet, the environmental significance of this pathway remains unexplored. Here, we investigate the potential for reactive oxygen species (ROS)-driven CH₄ formation across diverse wetland soils during redox fluctuations. Using sterilized soils from 14 Chinese wetlands amended with a model methyl donor, we identified a linear relationship between hydroxyl radical (•OH) accumulation and CH₄ production, yielding 91 nmol·L⁻¹ CH₄ per nmol·L⁻¹ •OH. Mechanistic validation with citric acid and sodium citrate demonstrated that ligand-mediated iron chelation and acidification work together to enhance this pathway by preventing iron precipitation. Natural biomaterials, such as fish remnants and rice litter, acted as methyl donor hotspots, contributing approximately 50% of total CH₄ emissions during oxygenation. These findings establish ROS-driven CH₄ production as a pervasive abiotic pathway under ambient conditions. Our results underscore the necessity of reevaluating water management strategies in wetlands, where fluctuating water levels may inadvertently amplify abiotic CH₄ fluxes.