Monitoring And Analysis Of PAHs In The Ambient Air Of Dalian

With human society and economy advance and developing, coal, oil and other fossil fuels widely used in industrial production, transportation and life. In those processes, a lot of persistent organic pollutants are produced and becoming the world common concern. PAHs are a kind of typical persistent organic pollutants. They have high toxicity, persistent, transportation and bioaccumulation, therefore PAHs are potentially dangerous to the ecological environment and human health. It is one of the hot global topics. In this thesis, the concentration of PAHs in the ambient air of Dalian, a typical coastal city in China, was monitored and analysed. The PAHs pollution level of the air of Dalian was evaluated. The variation trend of PAHs concentrations in different seasons and in heating period and non-heating period were studied. And the distribution behavior of PAHs in gas phase and in particle phase were researched. The results show that:(1) The concentration of PAHs in DJU has not signifance difference with that in DMO.(2) The highest concentration of PAHs both in particle phase and in gas phase was in winter, and the minimum concentration was in summer. Dalian is a north city, the ambient temperature in winter was the lowest during the whole year. Coal was used for heating in winter, which increased the concentration of PAHs in the air. The highest ambient temperature was in summer, which made the PAHs evaporated more to the gas phase and the concentration of PAHs in the gas phase increased. In gas phase, the highest value of BaPeq was in summer, while the lowest value of BaPeq was in winter. However, in particle phase, the highest value of BaPeq was in winter, while the lowest value of BaPeq was in summer.(3) The concentration of PAHs in different seasons was:winter (195ng/m3)> autumn (122ng/m3)>spring (89ng/m3)> summer (70ng/m3). And the concentration of PAHs in heating period was much higher than that of in non-heating period.(4) From the annual average concentration of analyzed PAHs, the highest concentration of PAHs was Phe, then were Flua, Ant, Pyr, and Flu, while the lowest concentration of PAHs was DBahA and IcdP, and the other lower concentration of PAHs in the air including Ace, BkF, BbF, and BghiP.(5) The two-rings and three-rings PAHs were mainly existed in the gas phase, while the five-rings and six-rings PAHs were mainly existed in the particle phase. The distribution of four-rings PAHs changed with the different seasons. In winter, the four-rings PAHs were mainly existed in particle phase, while in summer they were mainly existed in gas phase. In spring and in autumn the concentration of four-rings PAHs in gas phase was comparable with that in particle phase.(6) The partition coefficient Kp of PAHs increased with their molecular weight. The identical PAH, the partition coefficient of it, Kp changed in different seasons, that was winter>fall>spring>summer.(7) There were good linear relationship between the gas-particle partition coefficient of PAHs, Kp with their octanol-air partitioning coefficient, Koa(R2=0.90) and with their sub-cooled vapor pressure, PL0(R2=0.88).