RESUMO
PM10 and PM2.5 samples were collected in parallel in different function zones of Beijing during four seasons of 2005. The pollution level, distribution characteristics of the extractable organic matter (EOM) and relationship between EOM (PM10) and EOM (PM2.5) were illustrated. The results show that: the annual mean concentrations of organic compound in PM10 and PM2.5 are 41.39 microg/m3 and 34.84 microg/m3, being 1.44 times and 1.26 times higher than Ming Tombs site. The concentrations of EOM in winter are 67.04 microg/m3 (PM10) and 64.64 microg/m3 (PM2.5), which are 1.15 and 1.82 times, 2.06 and 2.26 times, 4.53 and 6.26 times higher than that in spring, autumn, summer, respectively. Ratios of EOM in PM2.5 to that in PM10 in different seasons exceed 0.60. In different function zones the concentrations of EOM present industrial and commercial zones > living, traffic and contrast zones. The influence of EOM (PM2.5) on EOM (PM10) in different districts are various. The order of annual concentrations of organic compositions is non-hydrocarbons > asphaltenes > aromatics > saturated hydrocarbon. The seasonal emissions of pollution sources play an important role in seasonality of compositions of EOM.