Daytime SO2 chemistry on ubiquitous urban surfaces as a source of organic sulfur compounds in ambient air

The reactions of sulfur dioxide (SO2) with surface-bound compounds on atmospheric aerosols lead to the formation of organic sulfur (OS) compounds, thereby affecting the air quality and climate. Here, we show that the heterogeneous reaction of SO2 with authentic urban grime under near-ultraviolet sunlight irradiation leads to a large suite of various organic compounds including OS released in the gas phase. Calculations indicate that at the core area of Guangzhou, building surface uptake of SO2 is 15 times larger than uptake of SO2 on aerosol surfaces, yielding similar to 20 ng m(-3) of OS that represents an important fraction of the observed OS compounds (60 to 200 ng m(-3)) in ambient aerosols of Chinese megacities. This chemical pathway occurring during daytime can contribute to the observed fraction of OS compounds in aerosols and improve the understanding of haze formation and urban air pollution.

Automated summary

The reaction of sulfur dioxide (SO2) with surface-bound compounds on atmospheric aerosols leads to the formation of organic sulfur (OS) compounds, which affects air quality and climate. In this study, we demonstrated that the heterogeneous reaction of SO2 with authentic urban grime under near-ultraviolet sunlight leads to the release of various organic compounds, including OS, in the gas phase. Calculations showed that building surfaces in the core area of Guangzhou absorb 15 times more SO2 than aerosol surfaces, resulting in the production of about 20 ng/m3 of OS, which represents a significant fraction of observed OS compounds in aerosols in Chinese megacities.