Characteristics Of Chemical Composition Of PM_2.5 In Handan

In order to explore the spatial, temporal, and chemical characteristics of PM2.5 pollution in Handan city, China, a comprehensive dataset including continuous online observations at four air quality monitoring stations in 2013 and 2014, and the concentrations including water-soluble inorganic ions, carbonaceous components, elements in PM2.5 samples collected in four representative seasons of 2013, 2014 and Jan. of 2015 are analyzed in this study. Also, PM2.5 samples collected in Handan before-and post-APEC are analyzed in this study to analyze the characteristics of PM2.5 pollution and assess the control strategies adopted during this period. The major conclusions are listed below:(1) PM2.5 has become the primary air pollutants of Handan, and its frequencies of being primary air pollutants are higher in polluted days. PM2.5 concentration decreases 16.5% from 2013(139 ?g/m3) to 2014(116 ?g/m3) on annual average. The variations of daily PM2.5 concentrations among two years are not pronounced. The variations of spatial PM2.5 concentrations are not obvious, indicating PM2.5 is nearly evenly spread over the study area.(2) SO42- dominates the TWSII(total water-soluble inorganic ions), accounting for 17.6% and 13.9% of the PM2.5 in 2013 and 2014, respectively. Compared with 2013, the concentrations of ionic species are lower in 2014, among them, the decrease of SO42- is most obvious(22.6%), then followed NO3-(18.9%). The particulate SO42- and NO3- are primarily formed through gas-phase SO2 oxidation, the heterogeneous reactions also occur in winter.(3) OC is responsible for 11.7% and 11.4% of PM2.5 in 2013 and 2014, respectively. The concentration of OC in 2014 decreases by 13.9% compared with 2013. The higher abundance of EC1 in carbonaceous aerosols(2013: 47.0%; 2014: 48.9%) indicates the important contributions of coal combustion and motor vehicle. Besides, the higher concentrations of OP, OC3 and OC4 emphasize the contributions from biomass burning and road dust.(4) Enrichment factor analysis shows that the major sources of V, Ca, Rb, Mn are soil. For Cu, Zn, Sb, Pb, Fe, they are simultaneously affected by natural and anthropogenic source. For Cu, Zn, Sb, Pb, Fe, anthropogenic source are their major souces. The contributions from coal combustion and steel to PM2.5 cannot be ignored. The mass balance shows that soil dust, organic materials and secondary ions are the major components of PM2.5.(5) The air quality of Handan has been improved during APEC, the decrease of PM2.5 is 38%, PM10 29%, SO2 14%, NO2 10%, CO 25%, O3 29%, respectively. During this period, the concentrations of SNA(SO42-、NO3-、NH4+) decreases 25%, while the carbonaceous components stay stable with a little decrease. The motor vehicles are the major souces of PM2.5 during this event, the contributions of biomass buring are less than road dust and construction dust.