The Study On Pollution Characteristics And Sources Of PM_2.5 In Typical Cities

Particulate matter (PM2.5) is an important indicator to measure the quality of the air, and it is also the main material which is harmful to human health and affects the climate. The source of atmospheric PM2.5 is complicated, and its chemical composition is various in terms of the area. Therefore, it’s important and meaningful to determine the main source of PM2.5 and the contribution rate of various sources for policy-making. A typical coastal city in the east was selected to set up four different sampling sites, and the atmospheric PM2.5 was collected to analyze in four months in 2015. The concentrations of PM2.5, inorganic elements, organic carbon, elemental carbon and water-soluble ions and polycyclic aromatic hydrocarbons (PAHs) were obtained, respectively.(1) The average concentration of PM2.5 was 76.8±53.1 ugμm3 during the sampling period, which was two times higher than the first grade of national atmospheric environmental quality standard, reflecting the serious air pollution. The research also showed that the concentrations of atmospheric PM2.5 had a tight connection with CO, the pollution elements such as K, Cd, As, Pb, Cu, Cr, Ni and other elements were enriched, the value of NO3-/SO42- was 0.67 and the value of OC/EC was 3.07. These characteristics all indicated that atmospheric PM2.5 mainly derived from motor vehicle exhaust and coal burning. In addition, the concentration distribution of atmospheric PM2.5 presented "winter> spring> autumn> summer. Furthermore, it suffered from multiple sources of pollution in winter and spring, mainly including NO3-、 SO42-、 NH4+、OC、EC; while it was much simpler in summer and autumn, dominated by pollution of SO42-. The atmospheric PM2.5 was generally acidic, the summer was more serious than the other seasons, while the atmosphere PM2.5 in spring was influenced significantly by the moving sources. Moreover, the study showed that the main source of PAHs in PM2.5 was coal burning.(2) The sources of PM2.5 were further identified by the chemical mass balance (CMB) receptor model. As the research indicated that the main sources of PM2.5 were motor vehicle exhaust and coal burning, which was consistent with the analysis of the chemical chacterisitcs of PM2.5. With comprehensive source apportionment, the main four sources of pollution were motor vehicle exhaust, coal burning, industrial emission and dusts, the contribution rate were 22.9%,21.4%,19.7%,16% and 20%, respectively.In summary, this study provided a reliable and theoretical basis for the development of the pollution prevention measures to atmospheric PM2.5 in the city of W to some extent.