Key factors influencing the formation of sulfate aerosol on the surface of mineral aerosols: Insights from laboratory simulations and ACSM measurements

Abstract

A significant technique of combining simulation experiments with a long-term real-time field measurement was first deployed to explore impacts of various environmental factors on formations of sulfate aerosol on the surface of mineral aerosols as MgO in the different reaction systems, and synergistic impacts of these environmental factors on the formation of sulfate aerosols in the different seasonal systems, especially in haze days. Meanwhile, a new correction technique was developed to estimate the effective reaction area and initial uptake coefficient of SO2 on the MgO aerosol surfaces. The significant results showed that the reactions of SO2 on the MgO aerosol surfaces in the system of SO2-MgO-dark could produce a small amount of sulfate and a large amount of sulfite and bisulfite, while in the systems of SO2-MgO-hν and SO2-MgO-O3 produce a large amount of sulfate and a small amount of sulfite and bisulfite. The impacts of temperature T and relative humidity RH on the sulfate formation on MgO aerosol surfaces showed a single-peak mode under the UV light condition, respectively. The sensitivities of these environmental factors to the sulfate aerosol formation were found to follow the order of RH > UV >T > O3 > SO2. The revised initial uptake coefficient γ0.REV of SO2 on the MgO aerosols was always between γ0.BET and γ0.GEO, and much closer to actual value. The heterogeneous reaction mechanisms of SO2 on the MgO aerosol surfaces in the different reaction systems were obviously different. In the presence of water, light irradiation and O3 exerted crucially significant roles in promoting sulfate heterogeneous formation. The various environmental factors in the different seasonal systems, especially in haze days, showed different synergistic effects on sulfate aerosol formations. The sulfate aerosol formations in haze days were mostly impacted by RH, T, O3, and SO2 in spring, RH in summer, RH, T, and SO2 in autumn, and RH and SO2 in winter. The study will provide significant scientific bases for understanding and controlling haze pollution formation.