| The study of the physical and chemical characteristics of PM2.5, the effect of meteorological conditions and sources apportionment of PM2.5 in Kunming is of great significance for the prevention and control of air pollution in the plateau area against a background of the new ambient air quality standard has been published. A set of PM2.5 samples were collected from three sampling sites belonging to the regional air monitoring networks of Kunming(Jinding Mountain, Dongfeng Tung Road, Xishan Forest Park) during April 2013 to January 2014, the concentrations of PM2.5 and four kinds of chemical compositions were detected. The objectives of this study were to:(a)discuss the pollution characteristics of PM2.5 and chemical compositions; (b)analysis the the sources of the chemical compositions in PM2.5 by the method of Enrichment Factor (EF), ratio method, Principal Component Analysis (PCA); (c)investigate the influence of meteorological conditions on the concentrations levels of PM2.5 and chemical composition by the method of correlation analysis. The main conclusions are as follows:(1) Pollution characteristics of PM2.5 mass concentration:The annual mean concentrations of PM2.5 in Kunming was 72.69 (μg/m3, lower than the concentrations of PM2.5 in the Plain developed cities, exceeded the national ambient air quality second standard (35μg/m3). The spatial distribution characteristics of PM2.5 was industrial area (Jinding Mountain)>traffic area (Dongfeng Tung Road)>clean area (Xishan Forest Park), seasonal variation characteristics of PM2.5 was spring> winter> autumn> summer.(2) Pollution characteristics of inorganic elements in PM2.5:The concentration of inorganic elements ranged from 0.000 to 9.682μg/m3, the total concentration of 35 inorganic elements was 28.741 ug/m3, accounting for 22% of PM2.5 mass concentrations. Identify elements of soil wind dust (Ca, Si, Al, Na, Fe, K) was the highest, concentrations above 1.000 μg/m3, was the main inorganic elements. The concentrations of Al, Si, Ti, Fe in Kunming is lower than Shanghai, Guangzhou, Tianjin, Chengdu and Qingdao ect.developed cities, but the Ca concentration is much higher than the above cities, suggested that construction dust making a significant contribution to PM2.5 concentrations in the plateau cities.(3)Pollution characteristics of water soluble ions in PM2.5:The total concentration of 9 water soluble ion(Ca2+、Na+、K+、Mg2+、NH4+、F-、Cl-、NO3- and SO42-) was 12.93μg/m3, accounting for 9.5% of the mass concentration of PM2.5. SO42- and Ca2+ was one of the main components, accounting for 50.8% and 17.9% of the total ion content, respectively. As a kind of secondary ion (SO42- and NO3-), SO42- expressed an excellent positive correlation with SO2, the correlation of NO3- and NO2 was poorer, the value of SOR was 0.17-0.21, NOR was 0.01-0.02, which showed there were significant change process of the SO2 to SO42- in the atmosphere, NO3- didn’t exist quadratic transformation process.Compared with the plain cities such as Beijing, Tianjin, Jinan, the concentrations of secondary ion SO42-, NO3- and NH4+) in Kunming was relatively low, suggested that the PM2.5 bound-secondary components in the plateau city was less.(4) Pollution characteristics of PAHs in PM2.5:The concentration of 16 PAHs in Dongfeng Tung Road, Jinding Mountain, Xishan Forest Park in Kunming were 22.64 ng/m3,40.67ng/m3,22.07ng/m3,respectively, lower than the levels of PAHs in developed cities such as Beijing, Tianjin and Chongqing, ect. Pyr、CHR、BbF、BaP、BghiP、IND were the main monomers. The concentration of 6 monomers in Dongfeng Tung Road, Jinding Mountain, Xishan Forest Park accounted for 67.85%,69.21%,63.33% of ∑ PAHs, respectively. Result of health risk assessment of PAHs showed, the concentration of BaPeq at Jinding Mountain, Dongfeng Tung Road and Xishan Forest Park was 6.28, 4.00,2.94ng/m3, respectively, exceeded the national ambient air quality standard (2.5ng/m3) in China. BaP was the biggest contribution to toxic species, accounting for ∑ BaPeq 68.28-73.36%.(5) Pollution characteristics of carbonaceous in PM2.5:Average concentration of Organic Carbon(OC)and Elemental Carbon(EC) in Kunming were 20.32-22.5 μg/m3 and 3.38-7.67μg/m3. The value of TC/PM2.5 in winter and summer was 22.52%,24.03%, respectively. The value of OC/EC at three sampling points were greater than 2, suggested PM2.5 in Kunming exiting secondary sources. The value of OC/EC at Xishan Forest Park(clean area) was higher than Jinding Mountain and Dongfeng Tung Road, showed the levels of secondary organic pollution at Xishan Forest Park was higher than Jinding Mountain and Dongfeng Tung Road.. The value of OC/EC in summer was higher than winter, suggested quadratic transformation process" in summer was stranger than winter. The Secondary component accounted for 17.92-24.16%,11.48-16.85% ,11.38-17.83% of PM2.5 concentration at Xishan Forest Park, Jinding Mountain and Dongfeng Tung Road, respectively. Secondary pollution process in Kunming was relatively low. The attention should focused on the controlling of directed pollution sources in the process of PM2.5 reduction in Kunming.(6) The main source of inorganic elements and water soluble ion and its contribution rate:Soil source(23.49%), metal smelting and steel industry(20.59%), biomass combustion (11.68%), second source (11.63%), construction dust (8.61%). The PAHs in Jinding Mountain and Dongfeng Tung Road were mainly influenced by vehicle emission (50.80% and 40.20%), followed by coal combustion (35.55% and 39.23%), biomass combustion (7.30% and 7.98%); Xishan Forest Park was effected by vehicle emission (81.84%) and biomass combustion (9.73%), respectively.(7) The influence of meteorological factors:The concentrations of PM2.5 and inorganic elements were greatly influenced by wind speed, when the dominan wind direction was southwest winds, the pollutant concentration increased, it can be inferred that the levels of PM2.5 concentrations in Kunming PM2.5 may be influenced by the Anning industrial zone located in the southwest of Kunming. In addition, relative humidity, atmospheric pressure were the main factors influencing the levels of PM2.5 and inorganic element. The concentration of PAHs was negatively related to temperature, and positively correlated with Relative humidity. High atmospheric pressure and the input of air mass originated from the Qujing area were the cause of rising PAHs concentration in Kunming.(8)The multiple linear regression analysis was performed to predict PM2.5, inorganic elements and PAHs with meteorological parameters. The correlation coefficient of measured and calculated concentrations was 0.61 for PM2.5,0.51 for inorganic elements, and 0.55 for PAHs, suggested that the multiple regression models can be reliably used for future predictions of PM2.5, inorganic elements and PAHs. |
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