The characteristics of PM 2.5 and its chemical compositions between different prevailing wind patterns in Guangzhou

An intensive campaign for atmospheric pollution was carried out from October to November 2004 in Pearl River Delta Region (PRDR) of China in order to better understand the dominative factors for controlling air quality and impacts of pollutants on the regional environment. The object of this study aimed to investigate the characters and sources of particulates through the study of chemical compositions in different wind pattern in Guangzhou city. The ambient concentrations of mass, soluble species, and carbonaceous matter in PM2.5 particulates with time resolutions of 15 minutes, 15 minutes, and 12 hours were measured by TEOM, in-situ IC system, and carbon analyzer, respectively. During the sampling time, high concentrations of PM2.5 mass and its chemical compositions were found, which was comparable or higher than other measurements in mainland China. The average SO42-, NH4+, and NO3- concentrations were 38.6, 13.6, and 8.8 μg/m3, which accounted for 26.5%, 13.6%, and 5.7% of the total particulate mass, respectively. In the frontal system, biomass burning was the significant emission source and the great amount of SO42- and NH4+ particulates were observed in the aged secondary particulates, together with the dry prevailing northerly wind. In the local system, low value of sulfur oxidation ratio and high correlation coefficient between sulfate and elemental carbon were also observed under the prevailing southeasterly wind. It could be explained that the heterogeneous reaction of sulfate on soot particles causes high levels of NOx in Guangzhou. Great amount of SO2 would further convert to secondary sulfate particles through photochemical reactions during transport to the inner areas, which will cause more serious air pollutions in the southern China.