Reaction kinetics and multi-sulfur products formation of sulfur-containing volatile organic compounds with OH radicals

Atmospheric sulfur-containing volatile organic compounds (sulfur-VOCs) have been recognized as crucial precursors for gaseous sulfuric acid (H2SO4), particulate sulfate and secondary organic aerosol (SOA) formation. However, their reaction kinetics and multi-sulfur product formation remain poorly understood. This study presents a systematic kinetic investigation into •OH-initiated oxidation of a series of sulfur-VOCs including thiols and sulfides. The reaction rate constants vary with molecular structure, with high reactivity observed for trimethylene sulfide and dimethyl disulfide. It was further demonstrated that under low-NOx conditions, sulfur-containing RO2 radicals can undergo bimolecular reactions forming low-volatility multi-sulfur products that enhance their SOA formation potential. Additionally, many sulfur-VOCs investigated in our chamber experiments are also identified from the emissions of algae samples collected from a major freshwater lake in China, and similar multi-sulfur oxidation products were observed after •OH oxidation. These findings advance the kinetic and mechanistic understanding of atmospheric sulfur-VOCs oxidation and suggest that the formation of low-volatility multi-sulfur products and inorganic sulfur-containing species may contribute to SOA production and new particle formation in marine and freshwater environments influenced by algal emissions.