| The PM2.5 is refers to the aerosol granule that its aerodynamics diameter is smaller or equal to 2.5um. It not only has very big harm to the human body health but also to the environment. Moreover, it is the important reason to the reducing of the city atmospheric visibility. Therefore, the study about PM2.5 has become a hotspot in the environment research in the recent years. Compared with other country and areas, the PM2.5 pollution was more seriously and the proportion it occupied in TSP and PM10 was quite higher in Beijing, which caused seriously affects to people's life and the health. Therefore, five sampling sites were adopted in Beijing according to the main wind direction to collect the PM2.5. After weighed the samples, its chemical composed was analysed by ICP-MS and their character and rules were studied. Main research contents and results in the articles are as follows :⑴The mass concentration of PM2.5 in Beijing showed obviously temporal changeing, as the original emission nearly all the same, the weekly concentration of PM2.5 had clearly dispersion between 5～45ug/m3; the mass concentration of PM2.5 in heavily polluted period was about three times higher than the others weekly concentration. The monthly change of mass concentration of PM2.5 represented as follows: November >October >September ( the concentration in December was comparable with the concentration in September ), which accounted for that the most heavily polluted month not only appeared in winter months, but also in autumn months as a result of the atmospheric circumfluence changing.⑵The concentration of PM2.5 in daytime was higher than nighttime in the urban sampling sites where the human activity had relatively distinction day and night, such as the Zoology Center, the Long Palace(chang gong) Restaurant and the Observatory, and the changing rule was not obviously in suburb sampling sites such as the Bei'an He and YangTian Cun.⑶In the fine particles which is about PM2.5 of Beijing, the concentration of K and Ca was more higher and the micro element Zn and Pb was the most highest. By contrast, the pollution of Pb was worse in Beijing than any other city.⑷The concentration of Ca and K were much higher in Beijing's PM2.5 composition, the sequences of those elements were : Ca>K>Fe>Al>Na>Mg; the concentration of Zn and Pb were higher than other microelemnts, from top to bottom were: Zn>Pb>Mn>Cu>As。Compared with other cities, the Pb pollution in PM2.5 of Beijing was more serious.⑸During heavy polluting period, the PM2.5 concentrations from all measure point went up apparently, however, the inorganic elements stayed in the mean level; for the heating period, concentrations of Ti and Ga were higher than non-heating period, but the coal fuel in Beijing had related high Ti concentration, which meaned coal-fire did impact the PM2.5 concentration in Beijing⑹The result of enrichment factor indicated that the element which was K,S,Pb and As were enriched relative to their natural abundance in the crust soil and also suggested that these elements were related to anthropogenic behavior. Four main sources of fine particles were identified by factor analysis and then we can concluded that namely soil, vehicular emissions and coal burning and smelting industry were the main source of the PM2.5 in Beijing.
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