Contributions of aerosol composition and sources to particulate optical properties in a southern coastal city of China

Abstract

The contributions of chemical composition and emission sources to aerosol optical properties were evaluated for a coastal city in southern China. The average dry light scattering coefficient (bscat,dry) and light absorption coefficient (babs) were 32.5 ± 15.5 Mm−1 and 8.8 ± 4.7 Mm−1, respectively. Diurnal cycles in bscat,dry and babs were observed with peak values in the morning and at night. Both bscat,dry and babs varied with wind speeds and directions, and thus affected by transport pathways. Chemical composition data for 12-h PM2.5 samples were used with the revised IMPROVE algorithm and a Hybrid Environmental Receptor Model to evaluate aerosol composition and source contributions to dry light extinction (bext,dry = bscat,dry + babs), respectively. Ammonium sulfate and organic matter were the dominant contributors to bext,dry, followed by elemental carbon, sea salt, fine soil, and ammonium nitrate. The six PM2.5 sources identified were secondary sulfate source, biomass burning, marine emission, fugitive dust, traffic-related emission, and shipping emission. Marine emission and secondary sulfate source were the largest contributors of bext,dry during the daytime and nighttime, respectively. Backward trajectory analysis further explored the impact of potential sources to bext,dry at Sanya from surrounding regions. The results of our study would be useful for improving models of radiative effects from different sources in this area.