Characterization of chemical compositions in PM2.5 and its impact on hazy weather during 16th Asian Games in Guangzhou

: Aerosol samples for PM2.5 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,, mass concentrations, light extinction coefficients (bext), and selected meteorological parameters for this period were also measured. Temporal variation of PM,, mass concentrations and its relationship with bext were discussed, and bext was reconstructed by revised IMPROVE formula. The results showed that the average mass concentration ol PM2.5 was (77.0 +/- 24.4) microg.m-3 during the Asian Games period, which was 27.8% lower than that of the period before Asian Games. PM2.5 and relative humidity were the dominant factors contributing to hazy weather. The average value of bx, 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 bext included (NH4) 2SO4, POM, and LAC, which accounted for 87.0% of bext 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.