Pollution Characterizations And Source Apportionment Of Polycyclic Aromatic Hydrocarbons In Atmosphere Of Xi’an City, China

Polycyclic aromatic hydrocarbons(PAHs) in atmosphere,a group of ubiquitous persistent toxic substances possessing careinogenic,mutagenic and immunotoxic properties,have become an issue of increasing concern in recent decades.However, these researches are always focus on PAHs which absorbed on the aerosol,and the whole phase PAHs including gas phase and particulate phase has been paid less attention.In this thesis, we have researched pollution characterizations and source apportionment of PAHs from August,2008 to July,2009 in Atmosphere of Xi’an,by using membrane and polyurethane foam (PUF).25 PAHs compounds have been identified by gas chromatogram-mass spectrum (GC-MS) including 16 PAHs in EPA priority pollutants. The results showed the concentrations of∑16PAHs in TSP and gas phase were 6.86～198.84 ng/m3 (average concentration:48.74ng/m3),22.14～472.46ng/m3(average concentration:146.07 ng/m3), respectively. Two and three ring PAHs dominated in the gas phase, while five and six ring PAHs were mainly adsorbed on the particle phase.Analysising of PAHs composition, content, carcinogenic and seasonal variation, main results are as follows:Seasonal variation of the PAHs total amount is winter> autumn>spring>summer,and the proportion of PAHs is seasonal different; Health risk assessment was discussed using toxic equivalency factors (TEFs) of benzo(a)pyrene, which indicated contributions of particle phase PAHs to carcinogenic were much higher than that of gas phase PAHs; There is a good correlation between phenanthrene(Phe), fluorene(Flo), fluoranthene(Flu) and∑16PAHs, but benzo(a)pyrene (BaP) is different, and Above all prove that Phe, Flo, Flu and PAHs have similar pollution source;Good correlation was found between gas-particle partition coefficients and the respective sub-cooled vapor pressures of PAHs. Ambient temperature was predominating factor influencing the variation of PAHs concentrations and wind speed is followed;Gas phase, particle phase, the total concentration of∑16PAHs and meteorological parameters is partial correlation analyszed by using SPSS software,and it showed that the concentration of∑16PAHs and temperature is significantly correlated; Gas phase, particle phase, the total concentration of∑16PAHs and pollution index is partial correlation analyszed,and it showed that the concentration of∑16PAHs and the API index of SO2 is significantly correlated.Ratio analysis illustrated that gasoline and diesel burning were the main source of PAHs during non-heating period, and gasoline、diesel and coal were the main source of PAHs during heating period.Contribution of different PAHs sources was calculated by applying factor analysis and multipe linear regression method. The contributions of major sources were quantified as 55.33% from coal/coking,29.28% from gas,15.38% from vehicle during heating period,and 50.38% from vehicle,27.53% from coal/gas, 22.09% from coking during non-heating period. It Complies with the composition of primary energy consumption.Finally, according to the source of PAHs,we propose measures to reduce PAHs.