Relation between optical and chemical properties of dust aerosol over Beijing, China

[1] Characteristics of optical and chemical properties of dust aerosol over Beijing and their relation were studied in the spring dust season, 2006 to understand the impact of dust and anthropogenic aerosol on the regional climate. Two dust plumes (DS1 and DS2) were identified with contrasting physicochemical properties. Strong absorbing of aerosol at 439 nm was observed, probably due to the significant proportion of iron oxides in the dust aerosol other than black carbon. The transport pathways of dust, concentrations of pollutant precursors and meteorological conditions were the main factors affecting the mixing extent of pollutants with dust. Aerosol of DS1 was more “polluted” than that of DS2 and even non‐dust (ND) days. Pollution elements, i.e., Zn, As, Pb, S, and Cd, were greatly enriched in DS1; SO4 , NO3 , NH4 , and K significantly increased in dust storm episode, especially in DS1, indicating the strong heterogeneous chemical reaction occurred on dust and the mixing of dust with various pollutants during the long‐range/regional transport of dust plumes. Linear relationship between optical properties and aerosol chemical composition was found. Soluble ions, i.e., SO4 , NO3 , NH4 , and K, were the major contributors to the light extinction in fine particles, while mineral aerosol contributed more to that in coarse particles. Black carbon, as a strong light absorbing species, was found to contribute to the light extinction in both fine and coarse particles.