A modeling study of the impact of heterogeneous reactions on mineral aerosol surfaces on tropospheric chemistry over East Asia

Abstract

Nine heterogeneous reactions (uptake of H 2O 2, HNO 3, HO 2, N 2O 5, NO 2, NO 3, O 3, OH and SO 2 on mineral aerosol surfaces) are incorporated into a Regional Air Quality Model System (RAQMS) to investigate their impacts on tropospheric chemistry in East Asia during the dust storm period in March 2006. Comparison with observations shows the model system well represents the behaviors of the gaseous and aerosol species. Most of the reaction probability γ values used for this study are the best estimation specifically for dust samples from deserts of China, derived from analysis of a number of recent laboratory studies. There are large variations in gas and aerosol concentrations while taking heterogeneous reactions on mineral aerosol surface into account, especially during dust storm events. The domain-averaged monthly mean percentage changes in SO 2, NO 2, O 3, HNO 3, NH 3, total sulfate, total nitrate and total ammonium concentrations are −4.4%, −3.8%, −2.1%, −22.0%, 12.7%, 6.6%, 26.1%, and −9.5%, respectively below 3 km. These changes indicate the considerable perturbation of heterogeneous reactions on mineral aerosol surface to tropospheric chemical system and components. The strength of heterogeneous reactions is determined by both reaction probability and gas precursor concentration. Among the nine reactions, dust uptakes of HNO 3, SO 2, and N 2O 5 exert relatively large influences on the other chemical components, whereas the reactions regarding H 2O 2, HO 2, and OH have little impacts.