| Atmospheric aerosol samples were collected with different size in the Campus of Nanjing Normal University and Nanjing College of Chemical Technology from January to October in2011. We discuss the spatial-temporal variation, particle size distribution characteristics and the sources of water-soluble ions, metal elements, polycyclic aromatic hydrocarbons (PAHs) and sulfur isotopes, and revealed the contribution ratio of various pollution sources in aerosol particles. The the main conclusions are as follows:(1) PM2.1-10and PM2.1mass concentration variations show the following decreasing order:winter>spring>autumn>summer; The average mass concentrations of Nanhua aerosol particles is higher compared to those in Nanshi, which is mainly due to the emissions of pollutants from local large chemical factories and steel enterprises;The concentrations of particulate matter in the two sampling points during winter and spring present three obvious peaks at the rangs of0.65～1.1μm,3.3-4.7μm and9～10μm,respectively. There is no obvious bimodal for the concentration of summer aerosols with a main peak falling in the accumulation mode (1.1～2.1μm); Size distribution of Nanshi particles in autumn is not significant, but Nanhua aerosols have a obvious peak at the range of0.65～1.1μm;(2)Water-soluble ion concentrations in the two sampling points have an obvious seasonal variation:winter>spring>autumn>summer; SO42-, NO3-, Ca2+, Mg2+and Na+are the major water-soluble ions in aerosols, with a similar size distribution characteristics, SO42-,NO3-, Cl-have peaks of size distribution at the rangs of<0.43μm,1.1-2.1μm and3.3～4.7μm, respectively. The peak of NH4+, K+is at0.65～1.1μm of fine-grained segment, however, Ca2+, Mg2+, Na+have a peak in the conrse mode (3.3～4.7μm); Factor analysis shows that vehicle exhaust, coal combustion, soil, building dust and biomass burning are the main sources for Nanjing atmospheric aerosols;(3) Element As in Nanshi and Nanhua aerosols mainly presents in PM2.1in autumn and winter, and mainly in PM21-10in spring and summer; Pb and Cd are mainly enriched in PM2.1, while Hg and Zn have a relatively uniform distribution in PM2.1and PM2.1-10; As and Zn in Nanshi aerosols have a strong correlation, Hg and As, Pb, Zn in Nanhua aerosols all have strong correlation, Cd and Pb are also significantly correlated; Factor analysis shows that metal elements pollution are mainly from coal combustion, vehicle exhaust and industrial sources;(4) PAHs in Nanjing atmospheric aerosols vary as an order of winter>spring>autumn> summer, and PAHs pollution in winter is more serious; PAHs-PM2.1/PAHs-PM10annual average ratio of Nanshi and Nanhua are0.56and0.55, respectively, showing that PAHs are mainly distributed in fine particles; Total PAHs concentrations of PM2.1-10and PM2.1in Nanhua are higher than those in Nanshi, which is mainly due to the pollutants emission around the sampling points; Characteristic ratios and factor analysis show that PAHs are mainly from vehicle exhaust and coal combustion;(5) The annual average values of834S in Nanshi and Nanhua aerosols are around5.96‰and6.16‰respectively, indicating that the main sulfur source in aerosols is from coal combustion; The values of δ34S in the two sampling points have the same seasonal variation: winter>autumn>spring>summer.δ34S values in summer are generally lower than those in other seasons, which is chiefly ascribed to the emission of biogenic sulfur; The values of δ34S in Taihu aerosol samples ranged from4.46to9.87‰,δ34S values in summer are generally higher than those in spring, which is contrary to the δ34S changes in Nanjing aerosol, and it is primarily due to the influence of phase oxidation of SO2. Meanwhile, there is a remarkable sulfur isotope mass-independent fractionation effect in Taihu aerosols, we propose that sulfur isotope anomaly in Taihu aerosols is mainly related to the oxidation of SO2in the stratosphere, which provides the basis for a further study of the composition of multiple isotope in Nanjing atmospheric aerosols. |
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