Photochemical Soil Methane Emission

Lingering discrepancies in the global methane (CH4) budget and uncertainties associated with estimates of emissions have prompted efforts to identify novel sources of CH4, particularly among natural processes. We investigated a novel, natural abiotic source of CH4─photochemical emission from soil─and offer evidence that this is a common phenomenon, occurring in soils of diverse characteristics and under completely aerobic conditions. Among a suite of properties, the best predictor of light-induced CH4 emission was the amount of ketones, a finding consistent with known reactions in organic photochemistry. The existence of this phenomenon suggests that aerobic soils are an extensive terrestrial source of CH4 during daytime hours.