Chemical Fate\nof Particulate Sulfur from Nighttime\nOxidation of Thiophene

Sulfur-containing volatile organic compounds emitted\nduring wildfire\nevents, such as dimethyl sulfide, are known to form secondary aerosols\ncontaining inorganic sulfate (SO<sub>4</sub><sup>2–</sup>)\nand surfactant-like organic compounds; however, little is known about\nthe fate of sulfur in other emitted reduced organosulfur species.\nThis study aimed to determine the sulfurous product distribution resulting\nfrom the nighttime oxidation of thiophene as a model system. Ion chromatography\n(IC) and aerosol mass spectrometry (a mini aerosol mass spectrometer,\nmAMS) were used to constrain the proportions of sulfurous compounds\nproduced under wildfire-relevant conditions ([NO<sub>2</sub>]/[O<sub>3</sub>] = 0.1). With constraints from IC, results indicated that\nthe sulfurous particle mass consisted of 30.3 ± 6.6% SO<sub>4</sub><sup>2–</sup>, while mAMS fractionation attributed 24.5 ±\n1.6% of total sulfate signal to SO<sub>4</sub><sup>2–</sup>, 15.4 ± 1.9% to organosulfates, and 60.1 ± 0.9% to sulfonates.\nEmpirical formulas of organosulfur products were identified as C1–C8\norganosulfates and sulfonates using complementary mass spectrometry\ntechniques. This study highlights the nighttime oxidation of thiophene\nand its derivatives as a source of SO<sub>4</sub><sup>2–</sup> and particulate organosulfur compounds, which have important implications\nfor the atmospheric sulfur budget and aerosol/droplet physical and\nchemical properties.