| In order to study the pollution of the fine particles and polycyclic aromatic hydrocarbons (PAHs) in ambient air in Taiyuan, the samples of PM2.5 and gas pollutants were collected in Taiyuan university of Science and Technology, during the period from August 2009 to April 2010. The compounds of PAHs were extracted by ultrasonic extraction method from aerosol samples, by Soxhlet extraction method from gas samples. The compounds of PAHs were analyzed by gas-chromatography mass spectrometry determination. Combined with meteorological data during the sampling period, this study reported levels of PM2.5 and PAHs concentrations, time and seasonal variations, described distribution balance of PAHs in the gas-particle phase, assessed the health risks of PAHs, and analysised the source of PAHs finally. Some results are listed below:1. The daily average concentration of PM2.5 was 222.60μg/m3 during the sampling time, and exceeded ambient air standards of EPA (EPA-NAAQS, 2006) 6.36 times.The highest seasonal average concentration of PM2.5 was 260.82μg/m3, in winter; and the lowest was 135.78μg/m3, in summer.The seasonal variation mainly should due to the emission of typical pollution sources and climate change. The concentration of PM2.5 in the day was higher than the night mostly. The correlations between PM2.5 and temperature, humidity, wind speed were ordinary. And the concentration between PM2.5 and wind speed was negative showed that the main source of PM2.5 pollution in Taiyuan was local source, not from other places. The main way of PM2.5 removal is wet deposition and air mass migration.2. The daily average concentration of PAHs was 744.48 ng/m3 during the sampling time. The average concentration PAHs in gas phase and particulate phase was 452.31 ng/m3 and 297.17 ng/m3, respectively. Compared to other cities, the pollution of PAHs in Taiyuan was very serious. The concentration of different rings number of PAHs was different: the highest was 3 rings PAHs (51.2% ofΣPAHs).But in particle phase, the highest concentration was 4 rings. The concentration ofΣPAHs in winter was 1710.97 ng/m3, the highest of four seasons; the next was the autumn and spring; the lowest ofΣPAHs was 310.10 ng/m3, in summer.The correlation betweenΣPAHs and temperature was strong positive. And other correlations, like betweenΣPAHs and humidity and wind speed, were generally ordinary in the all year. But in the winter, the correlations betweenΣPAHs and humidity, wind speed were strong positively and negatively, respectively. The state of gas-article distribution was balance all year, especially in autumn and winter. The seasonal sequence of Benzo (a) pyrene equivalent concentration (BEQ) was: winter> autumn> spring> summer. The annual average value of BEQ was 14.04 ng/m3 during the sampling time. That showed toxicity of PAHs in Taiyuan ambient air is serious.3. The qualitative source analysis of PAHs by ratios determines method showed that the sources of PAHs ware complex, including coal combustion emission and mobile sources emission. The quantitative source analysis of PAHs by principal component analysis method showed that the major sources of PAHs in Taiyuan ambience air were liquid fossil fuels combustion (including automobile emission ), coal combustion, biomass burning, coke emissions, et al. the combustion of liquid fossil fuels (including automobile emission and fuel oil combustion emission) has become a major source in different seasons.Especially in the summer, the contribution of liquid fossil fuel combustion emission has reached 54.92%.And in winter, due to heating and other reasons, the contribution of coal combustion emission increased, reached 32.94%. |
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