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

Abstract. 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, and the reaction rates of dithiols and cyclic sulfides are generally higher than that of monothiols and acyclic sulfides. It was further demonstrated that under low NO_x, 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. 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.