To identify and apportion the sources of the ambient PM2.5 in the urban area of Hangzhou,China,PM2.5samples were collected at three sites in the city from April 2004 to March 2005.Water-soluble ions,metal elements,and total carbon（TC） in PM2.5 samples were analyzed.The results indicated that the 24-h mean concentrations of PM2.5 ranged from 17.1 to 267.0 μg/m~3,with an annual average value of 108.2 μg/m~3.Moreover,the seasonal mean values for PM2.5 in spring,summer,autumn,and winter were 116,73.1,114.2,and 136.0 μg/m~3.respectively.According to the Chinese ambient quality standard,at least 70% of the monitoring data exceeded the limit value.The total contribution of water-soluble ions,including F-,Cl-,NO3-,SO42-.NH4+,K+,and Na+.to PM2.5 mass varied from 32.3% to 36.7%.SO42-,NO3-,and NH4+were the main constituents of the ions,with contributions to PM2.5 varying from 14.1% to 14.7%,6.0%to 7.8%,and 6.4% to 7.7%,respectively.In addition,the annual mean mass fraction of TC in PM2.5 was27.8%.The annual average total contribution of the group of elements of Zn,Pb,Cu,Mn,Cr,Ni,Se,Mo.Cd,Sb,and Ag to the aerosol was in the range of 1.7-2.0%.Furthermore,positive matrix factorization was applied to analyze the PM2.5 data collected from the central area,and five factors were identified.The factor contributions to PM2.5 mass were 12.8%,31.9%,10.1%,17.2%,and 27.9%,respectively.Iron/steel manufacturing and secondary aerosol were the main sources for the fine particles.These findings may have significance for controlling the atmospheric contamination in the city.
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