Multiphase reactions of aromatic organosulfates with OH radicals: Kinetics, mechanisms, and environmental effects

Abstract. Aromatic organosulfates (aromatic OSs) are widely detected in the atmosphere and exhibit high abundance in urban areas. However, the atmospheric fate and environmental impacts of aromatic OSs remain poorly understood. In this study, we investigated the multiphase reaction of three aromatic OS (i.e., phenyl sulfate, p-tolyl sulfate, and 4-ethylphenyl sulfate) with OH radicals. The second-order reaction rate constant (k) of aromatic OSs with OH radicals were measured in the range of 4.29–6.38×10⁹ M^–1 s^–1 at different pHs. It is found that k values are similar for the homologues of aromatic OSs, whereas are slightly affected by the solution pH values. The multiphase reactions of aromatic OSs and OH radicals mainly yield functionalized OSs, along with fragmented OSs and inorganic sulfate. The observation of inorganic sulfate formation, for the first time, indicates that aromatic OSs can also be converted into inorganic sulfate in analogues to aliphatic OSs. Furthermore, generated chromophores and fluorophores (constituents of brown carbon, BrC) products can significantly enhance the light absorption capacity, particularly under acidic conditions. These findings provide new insights into the understanding of the fate of aromatic OSs in the atmosphere that they can rapidly undergo atmospheric transformation, affecting the atmospheric sulfur cycle and altering aerosol optical properties.