Status: this preprint was under review for the journal ACP but the revision was not accepted.
Aqueous phase oxidation of bisulfite influenced by nitrate photolysis
Lu Chen,Lingdong Kong,Songying Tong,Kejing Yang,Shengyan Jin,Chao Wang,and Lin Wang
Abstract. Nitrate aerosol is ubiquitous in the atmosphere, and it can exit in both solid aerosol particles and fog and cloud droplets. Nitrate in the aqueous and particulate phase can undergo photolysis to produce oxidizing active radicals, which will inevitably affect various atmospheric chemical processes. However, the role of nitrate aerosols in these atmospheric photochemical processes remains unclear. In this study, the effects of nitrate photolysis on the aqueous phase oxidation of bisulfite under different conditions were investigated. Results show that nitrate photolysis can significantly promote the oxidation of bisulfite to sulfate. It is found that pH plays a significant role in the reaction, and ammonium sulfate has significant impacts on regulating the pH of solution and the enhancement of sulfate production. We also found an apparent synergism among halogen chemistry, nitrate and its photochemistry and S(IV) aqueous oxidation, especially the oxidation of halide ions by the nitrate photolysis and by the intermediate peroxymonosulfuric acid (HSO5−) produced by the free radical chain oxidation of S(IV) in acidic solution leads to the coupling of the redox cycle of halogen with the oxidation of bisulfite, which promotes the continuous aqueous oxidation of bisulfite and the formation of sulfate. In addition, it is also found that O2 is of great significance on nitrate photolysis for the conversion of HSO3−, and H2O2 generation during the nitrate photolysis is verified. These results provide a new insight into the heterogeneous aqueous phase oxidation pathways and mechanisms of SO2 in cloud and fog droplets and haze particles.
How to cite. Chen, L., Kong, L., Tong, S., Yang, K., Jin, S., Wang, C., and Wang, L.: Aqueous phase oxidation of bisulfite influenced by nitrate photolysis, Atmos. Chem. Phys. Discuss. [preprint], https://doi.org/10.5194/acp-2020-806, 2020.
Received: 02 Aug 2020 – Discussion started: 31 Aug 2020
The role of nitrate aerosol in atmospheric SO2 oxidation remains unclear. We investigated the effects of nitrate on the aqueous phase oxidation of bisulfite under different conditions. We found the important roles of nitrate photolysis, pH, ammonium and O2 in the oxidation of bisulfite to sulfate, the generation of H2O2, and the synergism with halogen chemistry. These results provide a new insight into the heterogeneous aqueous phase oxidation of SO2 in cloud and fog droplets and haze particles.
The role of nitrate aerosol in atmospheric SO2 oxidation remains unclear. We investigated the...