| As the captical city of Henan province and the traffic hub in China, Zhengzhou is faced with serious air pollution problem, especially fine particular matter(PM2.5) problem, which caused great concern among the government and ordinary people. Not only can PM2.5 reduce the visibility of air, causing haze, but it can carry various toxic substances including metal, bacteria, polycyclic aromatic hydrocarbons(PAHs) etc, and then invade the organism along with breathing. Considering those bad effects and serious situation, some effective measures and strictly standards has been taken by our country.In this study, PM2.5 samples were collected with quartz microfiber filters using a USA PM2.5 sampler(TE-6070 D Tisch Environmental) at roof of a four-storey building in Zhengzhou High-tech Zone. The sampling time was from April 2013 to December 2013, and the number of effective samples is 71. After sampling, all PM2.5 samples were prepared orderly to perform different chemical analysis. 7890 A with 5975 C GC-MS were used to analyze 33 n-alkane and 16 PAHs. The concentration character and seasonal variations of n-alkanes, PAHs and PM2.5 could be analyzed and some results showed that:(1) The daily concentrations of PM2.5 range from 56 to 698 μg/m3, nearly all exceeding the daily standard of China(75 μg/m3); the annual average of PM2.5 is 212 μg/m3, which is six times of annual standard of China(35 μg/m3); the seasonal variations of PM2.5 are clearly: winter > spring > autumn > summer, with the value of 356, 216, 170, 150 μg/m3.(2) The total concentrations of 33 n-alkanes in PM2.5 measured range from 47 to 2579 ng/m3, with an annual average of 396 ng/m3; the seasonal average values of 33 n-alkanes in PM2.5 identified in this study were 153, 145, 235, 1125 ng/m3, respectively, which is inconsistent with the seasonal trend of PM2.5; winter is still the most polluted season; the most abundant species in winter were in the middle section(C20-C30),accounting for 85% of the total alkanes, and in other seasons were C23-C33, accounting for 87, 92, 81% in spring, summer and autumn respectively.(3) The total concentrations of 16 PAHs in PM2.5 measured range from 28 to 648 ng/m3, with an annual average of 162 ng/m3, which is much higher than cities like Beijing, Dalian and the like; Winter is the most polluted season(average value: 275 ± 79 ng/m3), followed by autumn(average value: 166 ± 50 ng/m3), spring(average value: 113 ± 29 ng/m3), and summer(average value: 96 ± 36 ng/m3). The Benzo[a]pyrene(Bap) concentration obtained in this study was 12 ng/m3, exceeding nearly one order of magnitude of ambient air Ba P standard(annual average: 1 ng/ m3) in China.(4) The comparison of chemical component in PM2.5 showed: seasonal concentrations of PM2.5 and WSI showed strong consistency with winter > spring > autumn > summer; as for organic compounds, seasonal concentrations of PAHs, n-alkanes and OC were consistent with each other with winter and autumn most polluted. The ratio of OC/EC indicated the serious secondary organic aerosol pollution in the study area. The annual average concentrations of total water soluble ions were 95, 64, 72, 167 μg/m3 in spring, summer, autumn and winter, respectively, in keeping with the concentration trend of PM2.5. NO3-, SO42- and NH4+ were three major components, accounting for 86% of the total water soluble ions in PM2.5 and were consistent with the total seasonal concentration trends.(5) During the period of heavy pollution, daliy average values of PM2.5 range from 241 to 698 μg/m3, which were about 3 to 9 times of the standard of Environmental Ministry; as for compositions of PM2.5, the variation on proportion of organic compounds(including PAHs and n-alkanes, and OC) and EC were opposite with the concentration of PM2.5; while variation on proportion of WSI was consistent with the value of PM2.5. |
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