Synergistic effect among Cl2, SO2 and NO2 in their heterogeneous reactions on gamma-alumina

Severe haze in China has been a global concern in recent years. Most studies about the mechanism of haze formation mare only focused on the heterogeneous reactions of SO2 and NO2 on mineral aerosols. However, little is known about the role of molecular chlorine (Cl-2) in those reactions. Here, we investigated the heterogeneous uptake of Cl-2, SO2 and NO2 on gamma-Al2O3 particles under different conditions using a quartz-based flow reactor. We found that the existence of gamma-Al2O3 seed aerosols significantly promotes the formation of secondary chloride, sulfate and nitrate aerosols, and Cl-2, NO2 and SO2 have synergistic effects when they react on gamma-Al2O3 surface under humid condition. The results also shows that Cl-2 can promote the formation of secondary sulfate and nitrate aerosols on gamma-Al2O3 surface. Moreover, Cl-2 is much easier to react with the surface of gamma-Al2O3 and form secondary CI- aerosol when comparing with NO2 and SO2, suggesting that Cl-2 is of great importance in atmospheric chemistry, it has the potential to alter the surface properties (e.g., chemical composition and fraction) of mineral aerosol, enhance the production of secondary inorganic aerosols in the troposphere, and thus cause adverse effects on the climate and human health. (C) 2017 Elsevier Ltd. All rights reserved.