| Atmospheric PM2.5 pollution is a major concern in the atmosphere,and the atmospheric PM2 5 pollution in China is heavy,especially in the eastern region.As an important city in the Yangtze River Delta,the atmospheric PM2 5 pollution has attracted much attention.From September 2015 to September 2016,132 PM2.5 samples were collected from Suiyuan campus and Xianlin campus of Nanjing normal University.And 32 PM2 5 samples were collected from 8 sampling sites in different functional areas of Nanjing from December 2016 to January 2017.The concentrations and distribution characteristics of PM2.5,water-soluble ions,OC,EC and n-alkanes(C12-C33)were analyzed for these samples.The content and distribution characteristics of water-soluble ions,OC,EC and n-alkanes(C12?C33)were analyzed by means of factor analysis,formula and ratio method,respectively.The main characteristics and sources of air pollution in Nanjing are studied.The conclusions are as follows:(1)The air PM2 5 pollution in Nanjing is very serious.The rate of PM2.5 concentration in urban and suburban areas is only 31.82%,and there are obvious distribution characteristics of urban area>suburb,autumn>winter>spring>summer.The concentration of PM2.5 in different functional areas has the distribution characteristics of industrial area>traffic trunk road>residential area in winter.(2)The concentration of water soluble ions in PM2 5 in Nanjing is high,showing the change characteristics of urban area>suburb,night>day,autumn and winter season>spring and summer season,agricultural area>industrial area>residential area>traffic trunk road.Among them,SO42-,NO3-and NH4-are three main ions,which account for more than 90%of the total ion concentration.According to the NO3-/SO42-ratio,the contribution of atmospheric PM2.5 flowing source is higher than that of fixed source,night>daytime,urban area>suburb,winter>summer.The ratio of Yanion/Ecation indicates that the atmospheric particles in the urban and suburban areas are generally acidic.In addition,SO42-,NO3-and NH4+ in winter,spring and summer in the urban and suburban areas of Nanjing are mainly in the form of(NH4)2SO4 and NH4NO3,and they are mainly in the form of NH4HSO4 and NH4NO3 in autumn.(3)From the scale of the whole year,the concentration of OC and EC in PM2.5 of Nanjing urban and suburban areas has the characteristics of urban area>suburb,night>daytime.From the seasonal point of view,the concentration of OC and EC in PM2.5 of Nanjing urban and suburban areas has the seasonal variation characteristics of autumn>winter>spring>summer.(4)The concentration of n-alkanes in PM2.5 of Nanjing has the characteristics of suburb>urban area,day>night,autumn and winter seasons>spring and summer seasons.The concentration of n-alkanes in PM2.5 in winter in different functional areas of Nanjing city has the characteristics of industrial area>traffic trunk road>residential area>agricultural area.Through principal component analysis and calculation formulas of several main sources summarized by Bressi M et al,we analyzed the sources of PM2.5 in Nanjing city,suburb and different functional areas and conclude that:the secondary pollution of non-marine salt,such as sulfate,nitrate and ammonium salt,are the main source,and the contribution in autumn and winter is more prominent.At the same time,the contribution of sea salt and dust sources cannot be ignored,and it is more prominent in spring and summer.In addition,the contribution of dust sources in the suburbs is much higher than that in the urban areas.(5)By analyzing the source of n-ait is found that there are two main sources of atmospheric PM2.5 in the urban and suburban areas of Nanjing,such as fossil fuel combustion and higher plant wax,among which,the contribution of higher plant wax and other biological sources is obvious in spring,summer,winter in urban area and in summer and autumn in suburb,and dust sources such as ground dust and building dust are the most obvious in spring of suburb.Combined with the analysis of different functional areas,it is found that the winter air pollution in Nanjing mainly comes from the contribution of fossil fuel combustion and other man-made sources,but the contribution of natural sources such as higher plant wax is not obvious.Only the traffic trunk roads with more vegetation nearby and the natural sources such as higher plant wax in Tongshan orchard in Jiangning District contribute a little more. |
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