Seasonal variations and chemical compositions of PM2.5 aerosol in the urban area of Fuzhou, China

Abstract The mass concentrations and chemical compositions (elements, water-soluble ions and carbonaceous species) of PM 2.5 aerosol were detected in the urban area of Fuzhou city across four seasons from April 2007 to January 2008. The mass concentrations of PM 2.5 ranged from 18.45 to 78.89 μg/m 3 , with the average value of 44.33 ± 16.30 μg/m 3 . The elemental compositions were dominated by Si, Ca, Fe, K, and Al. SO 4 2 − , NO 3 − , and NH 4 + were the major ions, contributing 24.3%, 9.9%, and 8.8% to the total PM 2.5 mass. The concentrations of above ions showed distinct seasonality of 2.2, 8.0, and 5.9 times higher in winter than those in summer, respectively. (NH 4 ) 2 SO 4 and NH 4 NO 3 were the main forms in summer and winter and NH 4 NO 3 mainly existed in autumn, while (NH 4 ) 2 SO 4 , NH 4 HSO 4 and NH 4 NO 3 existed in spring. The high NO 3 − /SO 4 2 − ratio suggested that vehicular exhaust made an important contribution to atmospheric pollution. TC occupied 24.1% of PM 2.5 mass, with a distribution of 19.2% OC and 4.9% EC. OC and EC had the common dominant sources in spring due to their strong correlation. The OC/EC ratio showed obviously seasonal distribution of 5.0 in spring, 2.7 in summer, 3.6 in autumn, and 4.2 in winter. The material balance analysis indicated that the fractions of major chemical species in PM 2.5 were in the following order: OM > sulfate > soil dust > nitrate > ammonium > EC > chloride.