| Researching the concentration,characteristics and sources of urban atmospheric PM2.5 and O3,identifying their key components affecting the air quality,and revealing the internal correlations among the contaminants have an important scientific significance for people to realize the complex situation of air pollution and formulate scientific and effective control measures.Characterized by its high elevation,low air pressure,low oxygen content,high intensity of solar radiation,higher forest coverage,etc.,the atmospheric environment of the Yunnan-Guizhou Plateau is quite different from that of the cities in Eastern China plains,and is still short of systematic observations and studies.By obtaining the concentration of PM2.5 and O3 from 9 other typical Chinese cities,and the data of VOCs,O3 and PM2.5 chemical components from 3 sampling points of the Kunming area,and establishing a Kunming local open source(soil dust,construction dust and road dust)PM2.5 source spectrum,this paper studied the pollution characteristics and meteorological factors of atmosphere O3 and PM2.5 of typical cities in China,by means of the phase relations,Pearson correlation coefficient method,principal component analysis method,ratio method,chemical quality balance receptor model and the air mass consequent trajectory model system,with emphasis on the sources and internal relationships of O3 and PM2.5 in Kunming,a typical city of the Yunnan-Guizhou Plateau.The conclusions are shown as follows:(1)The analyses on the concentration levels of atmospheric PM2.5 and O3 in the plateau city Kunming and 8 other cities showed that the concentration distribution of PM2.5 had obvious regional characteristics.The Midwest cities(Wuhan and Chengdu),the Northeast ones(Harbin,Shenyang and Beijing),the East coastal ones(Shanghai and Guangzhou),and the Southwest ones(Kunming and Lhasa)on the plateaus had the highest,the higher,the lower,and the lowest concentration of PM2.5,respectively.The concentration of 03 presented an obvious latitudinal feature.The cities such as Shanghai,Lhasa,Wuhan and Chengdu around 30 degrees at north latitude had the highest concentration of O3,whereas those including Beijing,Shenyang,Harbin,Kunming and Guangzhou in further north and south trended a concentration decrease of O3.(2)The correlation studies on the mass concentration of PM2.5 and O3 in the 9 typical cities of China showed that Kunming in summer had significantly a positive correlation with the other cities,except Beijing and Harbin.This was closely related to the photochemical reaction of the active atmosphere in summer.In the spring,autumn and winter however,the 9 cities had the weaker correlation of mass concentration of PM2.5 and O3,especially in Beijing,which was largely affected by the pollutant diffusion of its surrounding urban agglomeration,thus the correlation became significantly weaker.(3)Based on the correlation analyses on the mass concentration of PM2.5 and O3 and meteorological parameters in the 9 typical cities of China,the multiple linear regression equations of meteorological parameters and PM2.5 and O3 were established,and the accuracy of the equation was verified by comparing calculated values and measured values.(4)It was revealed in the analyses of chemical composition of atmospheric PM2.5 that the atmospheric PM2.5 concentration levels of 35 inorganic elements in Kunming City were between the range 0.0-9.68μg/m3,and their total concentration was 28.741μg/m3,accounting for 22.0%of the PM2.5 mass concentration.The total concentration of 9 kinds of soluble ions,i.e.,Ca2+,Na+,K+,Mg2+,NH4+,F-,Cl’ NO3and SO42-was 12.93μg/m3,accounting for 9.5%of PM2.5 mass concentration.The average concentration of OC and EC in the summer was 20.32±10.6μg/m3 and 3.38±1.80μg/m3,respectively,while that in the winter was 22.51±9.15μg/m3 and 7.67±5.82μg/m3.The SOC contribution in the Xishan Forest Park was 7.99μg/m3 in the summer,thus indicating a relatively strong atmospheric photochemical reaction in the forest areas.The researches on the correlation coefficient of the mass concentration of atmospheric PM2.5 and its main chemical components(elements,ions,carbon and PAHs)and O3 in Kunming showed that the formation process and source of the PM2.5 and O3 were significantly correlated.The mean concentration of 16 kinds of PAHs in PM2.5 was 28.26ng/m3,and the PAHs came mainly from vehicle exhaust and coal combustion sources.(5)The main sources of PM2.5 in Kunming City were analyzed by means of the CMB model.The results showed that the highest annual sharing rate of PM2.5 was motor vehicle exhaust dust(27.5%),which was followed by construction of cement dust(15.5%),coal smoke dust(15.4%),soil dust(13.4%),metallurgical dust(8.8%),and ammonium sulfate dust(5.7%)which was the lowest.The diagnosis index of goodness of fit of the source contribution value in the source fitting calculation of the secondary sulfate(ammonium sulfate)was better than a simple one,indicating that there was the higher secondary ammonium sulfate contribution in the atmospheric PM2.5 of Kunming which was located in a control area of sulfur dioxide rain.Using OC/EC minimum ratio method,the total mass of SOC in the PM2.5 in Kunming was obtained,making up 9.5%.It could be estimated that the ratio of the secondary particles(organic and inorganic ones in all)in Kunming area was 15.2%,the high temperature with strong ultraviolet rays in summer was beneficial to particle generation of these two kinds,and their highest proportion accounted for 23.8%of the PM2.5.(6)The potential ability of VOCs-generating ozone in Kunming urban area was analyzed by adopting ozone generation potential method,and the results showed that the contribution of OFP was from maximum to minimum as follows,in summer:OFP contribution olefins(52.01%)>alkane(24.58%)>aromatic hydrocarbon(23.41%),in autumn:olefins(49.12%)>aromatic hydrocarbon(43.02%)>alkane(7.86%),and in winter:the aromatic hydrocarbon(60.02%)>alkane diene(39.98%).Foreign bodies in summer having as much as 23.82%of the ozone generating potential emissions of volatile organic compounds indicated that in summer a large number of vegetation was an important precursor of ozone generation in Kunming City.(7)The correlations of the secondary composition of PM2.5 and O3 were studied through the analyses of the atmospheric PM2.5 environmental sample components in Kunming,finding that the higher correlations existed between secondary inorganic particles and ozone. |
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