Heterogeneous reaction of SO on CaCO particles: Different impacts of NO and acetic acid on the sulfite and sulfate formation.

Despite the heterogeneous reaction of sulfur dioxide (SO) on mineral dust particles significantly affects the atmospheric environment, the effect of acidic gases on the formation of sulfite and sulfate from this reaction is not particularly clear. In this work, using the in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique, we employed a mineral dust particle model (CaCO) combined with NO and acetic acid to investigate their effects on the heterogeneous reaction of SO on CaCO particles. It was found that water vapor can promote the formation of sulfite and simulated radiation can facilitate the oxidation of sulfite to sulfate. The addition of NO or acetic acid to the reaction system altered the production of sulfate and sulfite accordingly. There was a synergistic effect between NO and SO that promoted the oxidation of sulfite to sulfate, and a competitive effect between acetic acid and SO that inhibited the formation of sulfite. Moreover, light and water vapor can also affect the heterogeneous reaction of SO with the coexistence of multiple gases. These findings improve our understanding of the effects of organic and inorganic gases and environmental factors on the formation of sulfite and sulfate in heterogeneous reactions.