Chemical composition and source apportionment of the ambient PM2.5 in Hangzhou, China

To identify and apportion the sources of the ambient PM2.5 in the urban area of Hangzhou, China, PM2.5 samples 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 mu g/m(3), with an annual average value of 108.2 mu g/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 mu g/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 Nat, 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 was 27.8%. 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. (C) 2014 Published by Elsevier B.V. on behalf of Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.