The reactions of sulfur dioxide (SO 2 ) 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 SO 2 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 SO 2 is 15 times larger than uptake of SO 2 on aerosol surfaces, yielding ~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.

The competitive adsorption behavior, the synergistic catalytic reaction, and deactivation mechanisms under double components of sulfur-containing volatile organic compounds (VOCs) are a bridge to solve their actual pollution problems. However, they are still unknown. Herein, simultaneous catalytic decomposition of methyl mercaptan (CH 3 SH) and ethyl mercaptan (C 2 H 5 SH) is investigated over lanthanum (La)-modified ZSM-5, and kinetic and thermodynamic results confirm a great difference in the adsorption property and catalytic transformation behavior. Meanwhile, the new synergistic reaction and deactivation mechanisms are revealed at the molecular level by combining with in situ diffuse reflectance infrared spectroscopy (in situ DRIFTS) and density functional theory (DFT) calculations. The CH 3 CH 2 * and SH* groups are presented in decomposing C 2 H 5 SH, while the new species of CH 2 *, active H* and S*, instead of CH 3 * and SH*, are proved as the key elementary groups in decomposing CH 3 SH. The competitive recombining of SH* in C 2 H 5 SH with highly active H* in dimethyl sulfide (CH 3 SCH 3 ), an intermediate in decomposing CH 3 SH, would aggravate the deposition of carbon and sulfur. La/ZSM-5 exhibits potential environmental application due to the excellent stability of 200 h and water resistance. This work gives an understanding of the adsorption, catalysis, reaction, and deactivation mechanisms for decomposing double components of sulfur-containing VOCs.