Comparison of composition of PM2.5 between haze and non-haze periods from 2012.3 to 2013.2 in Beijing

Fine particles (PM_2.5) are complex compounds which are related to adverse health effects, visibility degradation and global climate change. A number of studies have focused on the components, sources and transportation of PM_2.5all over the world. As the capital of China，suffering from the dense population and heavy traffic, Beijing has experienced serious air pollution, which can be easily proved by the increasing number of low-visibility days.

In this study, we collected the daily PM_2.5 samples from 2012.3 to 2013.2 to get the continuous data. The components of PM_2.5 including ions, EC/OC and trace elements were obtained. Sulfate, nitrate, ammonium and organic matters (OM) are major components which account for more than 50% of PM_2.5. Clearly seasonal variations are observed. Trace elements are highest in spring and lowest in summer. OM in winter is almost 3 times higher than that in summer. The percentage of OM has a significantly negative correlation with PM_2.5 in summer and has no correlation with PM_2.5 in winter at the p = 0.05 level, while indicates that in summer, the formation of organic compound may less important than in winter. The differences between seasons when haze episode occurred and the changes between haze and non-haze period will be discussed.