| Taiyuan is one of the main energy and heavy chemical base city in China. In recent years, the advancement of urbanization and the increase number of motor vehicles have brought a bad influence to the air quality of Taiyuan and caused the atmospheric particulate matters pollution seriously. In order to master the different size atmospheric particulate matters pollution in Taiyuan, and know the pollution characteristics of heavy metals in different size particulates, the study took samples from November 2012 to October 2013 at three sites, which are TISCO of Taiyuan industrial district, Liuxiang of Taiyuan commercial district and Shanxi university of Taiyuan education and residential area, respectively. PM2.5, PM5, PM10, TSP four size particles were obtained using sampler equipped with multistage cutter. The concentration of Fe, Pb, Cu, Ni, Cr, Cd, Mn, Zn in different size atmospheric particulates of three functional areas were determined by atomic absorption spectrophotometer, and the speciation distribution of heavy metals in PM2.5 and PM10 were analysed by BCR extraction method. The sources of heavy metals in the different diameter particles in Taiyuan were deduced by the method of enrichment factor and principal component analysis. Using transmission electron microscope and optical microscope to observe the morphology of particles and microscopic analyze its source.The results are:(1)The spatial distribution of content of the PM2.5, PM5, PM10, TSP characterized by:industrial zone> commercial area> education and residential district; The temporal distribution of content of PM2.5, PM5, PM10, TSP were highest in winter, minimum in summer, and middle in spring and autumn. The rain, snow, sandstorm, fog have caused influences on the concentration level of different size particles.(2) From the different sites, the highest concentration of Fe, Cu, Ni, Cr, Cd, Mn in atmospheric particulate matters in Taiyuan were at TISCO, the maximum content of Pb and Zn were at Liuxiang, the minimum content of heavy metals were at Shanxi university. From different seasons, the highest content of Fe, Zn, Cd, Cu in different particulates were in spring, next in autumn and winter, lowest in summer. However, the highest levels of Pb, Mn, Cr, Ni were in winter, next in spring and autumn, lowest in summer. From different size particles, the heavy metal of Pb, Mn, Zn, Ni, Cd were mainly enriched in PM2.5; Cr enriched in PM10; Cu enriched in PM5; Fe mainly enriched in PM2.5～100.Under the different circumstances, the content of heavy metals in particulates also had different changes accordingly.(3) According to the result of chemical speciation analysis, Pb, Mn, Ni and Zn were mainly distributed in exchangeable fraction and reducible fraction, shows high biological activity, harm to human; Cd and Cr were found abundantly in all four fractions, Cu mainly distributed in weak acid extraction and residual fraction in PM2.5, while equably distributed in four kinds forms in PM10, shows that once the environmental conditions change, they easy to release, also can harm to human; Fe was found bound to oxidizable fraction and residual fraction, the most less harm to the human.(4) The enrichment factor analysis showed that the enrichment factor of Cd, Zn and Pb were higher, mainly from man-made pollution; Cr and Ni were next; Mn was low, mainly from natural sources. The principal component analysis showed that the main source of heavy metals in atmospheric particles were metal smelting and organic synthesis industrial dust, coal dust, traffic vehicle emission and soil dust. From transmission electron microscope, the particles have five kinds morphology, that are dust collection, fly ash, sulfate particles, organic aggregate, mineral grains. Through optical microscope, the composition of winter particles are complicated, pollution is serious, next are spring and autumn, summer components decreased significantly. |
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