| Polycyclic aromatic hydrocarbons?PAHs?is one kind of typical persistent organic pollutants with high toxicity,carcinogenicity and mutagenicity in the environment.PAHs in the atmosphere are mainly adsorbed on fine particals or exist in gas phase,and can converse between those two phases.PM2.5 is the main absorber of high-ring PAHs due to its smaller particle size.People exposed to the atmospheric environment can accumulate large amounts of PAHs through breathing and other ways,which would cause an irreversible damage to their health.Therefore,it is of great practical and theoretical significance to study the pollution characteristics,source characteristics and health risk for human caused by PAHs in PM2.5 and gas phase.The study was supported by the Natural Science Foundation of China?Grant NO.41271472?.The samples of PM2.5 and gas phase were collected from Minhang District of Shanghai for one year.The concentrations of the 16 kinds of USPA-priory PAHs were measured by the gas chromatography/mass spectrometer?GC/MS?,and the pollution characteristics were analyzed by the statistical methods.The dynamic changes of airflows in winter and summer haze period were simulated by the backward trajectory model.The adsorption mechanism of PAHs betweet PM2.5 and gas phase was studied,and the correlation between PAHs and other pollutants(such as O3,NO2,SO2,CO,and PM2.5)was analyzed using the air quality data at the same period.The source contribution of PAHs were discussed by using ratio method,factor analysis/multiple linear regression?FA/MLR?,positive definite matrix factorization?PMF?and HYSPLIT trajectory model.We made a comprehensive assessment of the health risks of PM2.5 and PAHs in gas phase to four types of population including adult males,adult females,minor males and underage females in Shanghai.The main conclusions were as follows:?1?The average and range of the total concentrations of 16 PAHs in PM2.5 in Shanghai were 7.14 ng·m-3 and 3.1922.26 ng·m-3,respectively.Seasonal variation was as follows:Winter>autumn>spring>summer and the main structures of PAHs were low molecular.However,the concentrations of 7 kinds of definitive carcinogenic PAHs?Ba A,CHR,BbFA,BkFA,BaP,IP and DBahA?were high.The average and range of the PAHs in gas phase were 27.24 ng·m-3 and 6.1353.97 ng·m-3,respectively.Seasonal variation was not significant and the main structures of PAHs were low molecular.However the concentrations of 7 kinds of definitive carcinogenic PAHs were low.?2?The results of gas-particle distribution theory showed that the atmospheric PAHs in Shanghai had not reached an equilibrium state in which the adsorption was the main process.On the other hand,the slope between lgKp and lg0deviated from-1probably due to the environmental factors.Both the concentrations of PAHs in PM2.5and gas phase were significantly positively correlated with the concentrations of PM2.5,SO2,NO2,and CO,the concentrations of O3 had a significant negative correlation with PAHs in PM2.5,but there was no significant correlation with PAHs in gas phase,indicating that some of PAHs participated in a series of photochemical reactions.However,the goodness of fitting was not very good because the environmental factors affected each other and the relationship was complex.?3?The dynamic analysis in winter and summer haze period found that a stable atmosphere would lead to the accumulation of pollutants which was the main reason of the haze reforming,and the haze in winter generally dissipated faster than that in summer.The analysis results of model potential source contribution function?PSCF?showed that the main potential source areas in winter haze in Shanghai were Jiangsu,Shandong,and northern Zhejiang,and the main diffusion areas were Yellow Sea and Bohai Sea.The main potential source areas in summer were Zhejiang and the main diffusion areas were same with in winter.The results of regional distribution analyzed by concentration-weighted trajectory?CWT?was similar with PSCF,in addition,it can be inferred that the PAHs in gas phase have a longer transmission distance than in PM2.5for the proportion of concentration weights in different regions.?4?Compared with the ratio method and FA/MLR,PMFcould yield a clear results of source categories for PAHs.Specifically,PAHs in PM2.5.5 were mainly from fuel wood combustion/motor vehicle emissions?38.71%?,steel industry emission?23.55%?,petroleum combustion/leakage source?20.98%?and stationary such as thermal power station emission?16.76%?.The source contributions in different seasons were quite different.PAHs in gas phase were mainly derived from fuel wood combustion/diesel combustion?45.96%?,industrial sources?29.98%?and coking?24.06%?.The source contribution had a small difference in different seasons.Spatially,the analysis results of the backward trajectory model were as follows:PAHs in summer was mainly affected by the south area of Shanghai;while PAHs in spring,autumn and winter were mainly affected by the inland of the north of China.PAHs in gas phase were more significantly affected by long-distance transmission than in PM2.5 which was similar to the results in haze period.?5?The carcinogenic and non-carcinogenic health risks caused by PAH exposure through respiratory pathways for four groups in Shanghai were as follows:The combined carcinogenic risk value(10-6)of PAHs in PM2.5 and gas phase for adult was slightly higher than the acceptable value(10-6)stipulated by USEPA,but it fitted the standards(10-610-5)set by our country,The carcinogenic risk value for underage was lower than 10-6.The 7 types of definitive carcinogenic PAHs in PM2.5 caused an equivalent carcinogenic risk(10-6)to adult males and females,and the value(10-7)was similar for underage males and females.Approximately,the carcinogenic risk values of the 5 kinds of PAHs?Ba A,CHR,Bb FA,BkFA,BaP?in gas phase were one order of magnitude lower than those in PM2.5.Under the superposition effect between PM2.5 and gas phase,there was the highest life expectancy loss for the adult males?19.12 min?and the least for the underage female?5.17 min?.None of the four groups had significant non-carcinogenic health risks in study. |
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