[Characterising seasonal variation and spatial distribution of PM2.5 species in Shenzhen]

To investigate the effect of meteorological characteristics on PM2.5 chemical composition and the spatial distribution of different PM2.5 species in Shenzhen, 24-h PM2.5 samples were collected every six days from December 2008 to December 2009. The sampling network included an industrial site at Baoan, an urban site at Luohu and a seaside site at Yantian. Water-soluble inorganic ions and carbonaceous material (organic carbon and elemental carbon) were analyzed. The industrial site showed a much higher concentration than that of other two sites of organic matter, elemental carbon and nitrate, which presented the obvious difference of local emissions. But for the concentration of sulfate and ammonium of three different sites nearly stayed at the same level and indicated that they were mainly influenced by regional transport. OC/EC had the characteristics of the industrial site < the urban site < the seaside site, which implied that the industrial site had less secondary organic matter and more primary pollution sources. As the subtropical maritime monsoon climate is the dominant meteorological feature of the Pearl River Delta with a southwesterly transport and abundant rain in spring and summer, in contrast to a northwesterly transport and little rain in fall and winter, the PM2.5 pollution was much more serious in winter than in summer. Compared with the results of the similar experiment in 2004, the concentration of sulfate in PM2.5 has significantly declined because of the measures of reducing the emission of sulfer dioxide. But the pollution of vehicle emissions has become significant.