| To investigate the distribution of inorganic elements concentrations of aerosol PM2.5 and characteristics of a single source and polycyclic aromatic hydrocarbons (PAHs) contaminations, two sampling site were set up, one being in the urban area (around Nanjing University in the Gulou district) and the other in the suburb region (on the campus of Nanjing University of Information Science and Technology), operating for December of 2002 to December of 2003 and also from July to August, 2005 to perform PM2.5 sampling, measure the composition and contents of PM2.5 elements and PAHs, and make a comparative study of the constituents, concentration level, temporal variation, concentration, pollution feature and sources of the aerosol as well as the contamination character of PAHs in both the areas, leading to the following conclusions.1) The elements of PM2.5 consist of those contained in PM2.5 from raised ground dusts, including Cr, Mg and Si, and also of anthropogenic pollutants of As, Fe, Ni, Pb, Zn, S, Al Ca, K, P, Na, V, Mn and Ti. Nanjing pollution is caused by sulfate oxides in soot and heavier in the suburb than in the urban area during spring and summer but lighter in autumn. The concentration coefficients are high for S, As, Pb and Zn, upon whose concentrations human activities exert greater effects.2) For PAHs they create more severe contamination in the urban than in the suburb area, with their mean concentration reaching 0.12-1.01 (0.19-5.06) ng/m~3 in the suburb (urban) area, and in the urban region the maximum concentration of benzopyrene as the strong agent for cancers attains 34.45 ng/m~3, a figure that is 34.5 times higher compared to that in the suburb. The total of PAHs is nearly 4 times higher in the urban area in association with heavy traffic.3) The proportions of two, three, four- and five-cyclic PAHs in the total content are, respectively, 4.70, 3.63, 37.48 and 54.22% for the urban area and 16.74, 8.56, 31.06 and 43.56% for the suburb region, indicating that the middle-high-number PAHs predominate considerably and burning sources make great contribution to PAHs production in both the areas.4) The total PAHs content is in higher linear correlation with that of BaP in both the parts of the city and, especially, strong correlation exists of BkF with BaP and BbF with BbP, illustrating that BkF and BaP are likely to be formed in the same process and BkF, BbF and BaP have identical predecessors in the atmospheric environment.5) Strong correlation occurs of Chry to BaP and of BaA to BaP in both the areas, thereby inferring that the generation of Chry may be relevant to the mechanism of free radical reaction in atmospheric photo-chemistry. It is deduced from the correlation of An, NI and Phen to BaP in the two portions of the city that the waste gases released from heavy traffic may contribute to producing An, NI and Phen and the correlativity of NaP with BaP shows that NaP has its correlation varying greatly in particle phase for the different areas, demonstrating that pollutants are affected considerably during their dispersion in the atmosphere.6) The total contribution (in percentage) of street raised, building, burning and smeltery dusts, to PM2.5 is 86.5 and 85.3%, respectively, for the urban and suburb area. The raised dusts rank first in the contribution to >50% of PM2.5 (in the suburb area) compared to ~70% PM2.5 originating from raised and building sources in the urban area. For the suburbs the contribution of soot is just next to that of raised dusts, followed by the contribution of smeltery dusts (-5%) and finally building pollutants. In the urban area the control over the release of raised and building dusts must be exercised, both of which have some inherent linkage. The municipal engineering, old houses demolishing and building areas produce clouds of dusts so that strict control over these links is the key approach to the improvement of air quality and for the city of Nanjing the effective restraint of the release of burning dusts remains crucial.
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