Heterogeneous SO2 Oxidation in Sulfate Formation by Photolysis of Particulate Nitrate

• DOI: 10.1021/acs.estlett.8b00681
• Publication Date: 2019-01-05T00:13:59Z
• Authors: Masao Gen; Ruifeng Zhang; Dan Dan Huang; Yongjie Li; Chak K. Chan
• Keywords: Ammonium sulfate; Haze; Ammonium nitrate

Heterogeneous oxidation of sulfur dioxide (SO2) is suggested to be one the most important pathways for sulfate formation during extreme haze events in China, yet exact mechanism remains highly uncertain. We propose a much less explored pathway aqueous-phase SO2 particulate by NO2 and OH radicals produced from photolysis nitrate. Reactive uptake experiments with ammonium nitrate particles under ultraviolet irradiation show measured coefficients ∼10–5. Model calculations production rates, comparing known mechanisms O3, NO2, H2O2, transition metal ions, suggest that could contribute significantly overall at pH 4–6. This study provides new insight into current debate about typical conditions China.