Sulfate, as a major component of aerosol particles, greatly contributes to haze formation and affects global climate change. Although formation pathways of sulfate aerosols from the conversion of SO_(2) have been extensively studied, the discrepancy between field observations and model simulations suggests that there are still unknown sulfate sources. Herein, we report for the first time a photoinduced SO_(2) uptake and oxidation pathway in Beijing urban PM_(2.5) aerosols. In comparison with the NO_(2)- and O_(3)-induced SO_(2) oxidation pathways, this SO_(2) photo-oxidation in Beijing urban PM_(2.5) could make an important contribution to the daytime sulfate formation. Reactive species, such as ~(•)OH radicals and H_(2)O_(2), are the major oxidants leading to sulfate formation in PM_(2.5). The water-soluble matter (WSM) and water-insoluble organic matter (WISOM) in PM_(2.5) were identified as the main photo-oxidant producers. Our work highlights an important daytime sulfate source in the atmosphere and provides new insight into the photochemical aging of ambient aerosols.
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Beijing National Laboratory for Molecular Sciences, Key Laboratory of Photochemistry, CAS Research/Education Center for Excellence in Molecular Sciences, Institute of Chemistry, The Chinese Academy of Sciences;
