Volatile OrganicCompound Emissions from Pollutedand Natural Soils: Influences of Environmental Factors

Volatile organic compounds (VOCs) impact urban air quality and human health. Soil represents a potentially important source of VOCs. However, the VOC emission characteristics of soils from different urban and natural environments remain unclear. In this study, the composition and flux of VOCs emitted from various soil types were examined. Results reveal significantly elevated VOC emissions from polluted soils, with levels 2 orders of magnitude higher than those from their natural counterparts. Influences of light, soil water content, and temperature on VOC emissions were explored. Light exposure notably enhanced the emissions of certain VOCs, such as acetonitrile, from highly polluted industrial soils. Simultaneously, reductions in VOCs such as terpenes were observed, possibly driven by photochemical degradation processes. By comparison, soils from less polluted environments exhibited minimal changes in VOC emissions under light exposure, emphasizing the distinct behaviors of different soil types. Soil water content was inversely correlated with VOC emission rates, likely due to reduced soil porosity and permeability at higher moisture levels, whereas temperature exhibited intricate effects on soil emissions that varied with VOC species. Factors such as soil VOC storage, VOC “affinity” to soil, and microbial activities may play roles and warrant future investigation. Results from this study highlight soil emissions as non-negligible contributors to ambient VOC levels and underscore the crucial impacts of environmental factors in modulating these emissions.