Characterization and source apportionment of PM2.5 in mixed function area during summer and winter, Beijing

Air particulate matter samples from mixed function area in Beijing were collected during Aug. and Dec. 2014. The chemical components consisted of organic carbon (OC) and elemental carbon (EC), 9 water-soluble ions, and 16elements in PM2.5 were analyzed. The chemical mass balance (CMB) method had been applied to identify the source of PM2.5. The results showed that the average daily mass concentration of PM2.5in summer was 73 μg/m3, which was lower than the relevant Chinese air quality standards. While in winter, the average daily mass concentration was 111 μg/m3, which was much higher than summer and the standards. The concentrations of OC and EC, and OC/EC ratio in winter were higher than in summer. And a linear correlation was identified between the OC and EC due to the same source apportionment. The secondary ions such as sulphate (SO42-), nitrite (NO3-) and ammonium (NH4+) were the most important compounds in the particles of this area, because they accounted for a large fraction of PM2.5 especially in summer. The concentration of chloride ion (Cl-) was increased in winter due to the coal combustion. The concentrations of Si, Ti, Fe, Zn and Al were in the range of 0.1~10 μg/m3; Pb, Cu, Mn, Cr, Ba and Sb 10~102 ng/m3; V, Ni, Co, Mo and Cd 0.1~10 ng/m3. The contents of all the elements were higher in winter than in summer. The results of the source apportionment showed that the major contributions of PM2.5 were second sulfate, motor vehicle exhausts and second nitrite in summer, while coal combustion, motor vehicle exhausts and raise dust in winter. © 2016, Chinese Society for Environmental Sciences. All right reserved.