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

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 (b_scat,dry) and light absorption coefficient (b_abs) were 32.5 ± 15.5 Mm⁻¹ and 8.8 ± 4.7 Mm⁻¹, respectively. Diurnal cycles in b_scat,dry and b_abs were observed with peak values in the morning and at night. Both b_scat,dry and b_abs varied with wind speeds and directions, and thus affected by transport pathways. Chemical composition data for 12-h PM_2.5 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 (b_ext,dry = b_scat,dry + b_abs), respectively. Ammonium sulfate and organic matter were the dominant contributors to b_ext,dry, followed by elemental carbon, sea salt, fine soil, and ammonium nitrate. The six PM_2.5 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 b_ext,dry during the daytime and nighttime, respectively. Backward trajectory analysis further explored the impact of potential sources to b_ext,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.