Heterogeneous Reaction of OH Radicals with Terbuthylazine on Self-synthesized Silica Particles in an Aerosol Smog Chamber at Different Temperatures

Significant Conversion of Organic Sulfur from Hydroxymethanesulfonate to Inorganic Sulfate and Peroxydisulfate Ions upon Heterogeneous OH Oxidation

“…HMS is known to be secondary in nature and can be formed from the nucleophilic addition of bisulfite (HSO 3 – ) or sulfite (SO 3 2– ) ion to formaldehyde (HCHO) in the aqueous phase. ,− While significant progress had been made regarding the understanding of abundance and formation mechanisms of HMS, its subsequent transformation kinetics and mechanisms remain unclear. HMS exhibits a surface affinity and tends to migrate to the air–liquid interface. ,, It adopts an arrangement with the methylene pointing out of the bulk (i.e., the bulk aerosol solution phase), the hydroxyl group pointing into the bulk, and the C–S bond pointing slightly out of the bulk. , This makes it more likely to be oxidized by gas-phase oxidants (e.g., hydroxyl radical (OH) and ozone (O 3 )) near the gas-aerosol interface (termed heterogeneous oxidation). − In addition, OH oxidation of sulfonates (e.g., MSA) is known to produce inorganic sulfur species (e.g., sulfate (SO 4 2– ) ion). − Given that sulfur in its inorganic and organic forms exhibit very different physicochemical properties including surface activity, water uptake, and cloud condensation nuclei activity, it is desirable to understand the conversion rates and mechanisms between the organic sulfur and inorganic sulfur forms upon oxidation.…”