Characterization of three atmospheric aerosol episodes at a coastal site in China: Implications for regional transport of air pollution

Abstract

Size-selective atmospheric aerosol samples, collected between March 28 and April 8 2002 in Changdao, a small island in eastern China, were characterized by analysis of elements, ions, organic and elemental carbon, lead isotopes, and single particles. On the basis of compositional differences and remote sensing information, three distinct aerosol pollution episodes were identified. The first was dominated by fine particles with a substantial contribution from biomass burning emissions and industrial lead-containing particles from inland China at least 800 kilometers away. The second was characterized by coarse and aged secondary calcium sulfate particles and primary calcium sulfate particles from local industrial sources as well as windblown mineral dust. The third was a typical Asian Dust event with a source region on the border between China and Mongolia at a distance of around 1000 kilometers. Abundant sulfate particles found at the beginning of the Asian Dust event were predominantly ammonium sulfates in the fine fraction and calcium and ammonium sulfates in the coarse fraction. The major portion of the pollutants and the dust front of the event arrived in separate air masses. Although the three events occurred in quick succession they were quite different in terms of size distribution, chemical composition, sulfate speciation, source types, and source geographic locations. Biomass burning, industrial emission, coal combustion, and mineral dusts were identified as sources of the Asian continental outflow.