Characterization of chemical compositions in PM_2.5 and its impact on hazy weather during 16^th Asian games in Guangzhou

Aerosol samples for PM_2.5 were collected days and nights from 4 to 30 November 2010 in Guangzhou. The concentrations of organic carbon, element carbon, and water-solubility ions of all particle samples were determined by thermal/optical carbon analyzer and ion chromatography, respectively. In-situ online PM_2.5 mass concentrations, light extinction coefficients (b_ext), and selected meteorological parameters for this period were also measured. Temporal variation of PM_2.5 mass concentrations and its relationship with b_ext were discussed, and b_ext was reconstructed by revised IMPROVE formula. The results showed that the average mass concentration of PM_2.5 was (77.0±24.4) μg·m^-3 during the Asian Games period, which was 27.8% lower than that of the period before Asian Games. PM_2.5 and relative humidity were the dominant factors contributing to hazy weather. The average value of b_ext was 418 Mm^-1 during the Asian Games period, which was 28.3% lower than that of the period before Asian Games. The major contributors to b_ext included (NH₄)₂SO₄, POM, and LAC, which accounted for 87.0% of b_ext during the Asian Games period. A series of stringent air quality control measures were implemented by the Guangzhou Municipal Government and other cooperative cities, which greatly alleviated the hazy weathers in Guangzhou urban area during the Asian Games period.