| Global climate change along with the regional environment deterioration pose an impact on urban system within which physical processes and chemical contaminants are becoming more and more complex. High-speed urban life and human activities produce large amounts of toxic and hazardous pollutants into the environment. The explosive growth of urban population makes the urban ecosystem extremely fragile, facing many environmental problems to be solved, and it is a long way to resolve sustainable problems. For the persistent organic pollutants (POPs) in the urban environment, it is of great significance to study its enrichment, distribution characteristics and source apportionment. This study selected China’s largest industrial and commercial city-Shanghai as target, analyzing the enrichment, spatial distribution characteristics, and health risks of the PAHs in organic film on the glass surface. It reveals the evolution pattern and mechanism of PAHs in different seasons in organic film on the glass surface, and also initially explores the distribution rules of PAHs on vertical glass surface, and the difference of enrichment and distribution between indoor and outdoor glass surface are also researched. In order to elucidate the potential pollutants sources of PAHs on glass surface, the component spectrum of source fingerprints within environment is constructed, and the coupling relationship between PM2.5, PM10and PAHs on the glass surface is discussed.The concentration of PAHs on the glass surface in shanghai downtown is ranging from1348.5to4007.9ng/m2, which shows the following concentrarion gradient:traffic zone>business zone>cultural and educational areas>garden. The constitute of the PAHs are most predominantly by3-4rings, and Phe, Fl, Pyr and Chry are the main congener compounds.. For three major industrial areas of shanghai, Phe、Fl、Pyr、Chr and B[b+k]F are the main congener compounds of the PAHs on the glass surface. The concentration of the Nap and Phe is highest in Baoshan area and that of the control point which indicates the coal burning is the main source for the burden of PAHs. Through the macroscopical investigation of PAHs on the glass surface in downtown, suburbs and countryside, it is found that the concentration of PAHs in suburbs is lower than that of in urban and rural areas. It is mainly because of automobile exhaust emissioned into the air in downtown, which increases the atmospheric concentration of PAHs. The straw burning in rural area can increase concentrations of PAHs absorbed on glass surface. But there is little effect in the suburb area.The source of the PAHs in organic film on the glass surface is changing with different seasons, and also the concentration of PAHs in the air is also influenced by temperature, precipitation, humidity, wind direction and other weather conditions. It is found that pollutant emission sources and dominant wind play the role on the PAHs in the air. The high concentration of PAHs in spring mainly exist in north shanghai and south of Shanghai Pudong New Area, whereas the southeast of Pudong new area is the low area. This spatial distribution pattern shows that PAHs on glass surface is mainly controlled by the pollutant source. When in summer, Baoshan industrial zone in north, Wujing industrial zone in central, and Jinshan industrial in south are the areas with high concentration. Thus pollutant source is the key factor affecting PAHs. In particular, most of the central city is out of the high concentration area and this phenomenon may be because of the intense "heat island" and "rain island" effect. The "heat island" circulation brings the PAHs in the central city to settle down in the distant suburbs, and "rain island" effect makes the PAHs into other environmental media such as soil or water bodies by wet deposition process that can reduce the amount absorbed on the glass. High concentration areas of PAHs in autumn are extending on the basis of that of summer situation. The concentration of PAHs in central city is increasing, and the rural areas in Jinshan and Fengxian also show the high concentration. As the result of straw burning in rural areas surrounding Shanghai urban areas, the burning can produce lots of PAHs which has great of significance on PAHs adsorbed on the glass surface. High concentrations of PAHs in winter mainly observe in North Central of Shanghai (including the Wu Jing industrial area and Baoshan Industrial area). In winter, north central of shanghai is the high concentration area (including Wujing area and Baoshan area). Northwest or northeast is the dominant wind direction, so the PAHs generated by Jinshan Chemical industial area may migrate to Qiantangjiang River or into Zhejiang province with help of the wind, which has little effect on shanghai. The PAHs on glass surface is mainly Phe, Fl, Pyr and Chry in each season. In particular, the concentration of Nap is the most abundant compound in autumn than in other seasons, especially in rural areas, which may be caused by the straw burning. The content of PAHs has great difference in different seasons and functional areas. It indicates that weather condition is the dominant factor that can affect composition changes of PAHs under the condition of the background sources basically unchanged. PAHs in different functional areas and different seasons has different source. Except the conventional sources from coal and automobile exhaust, building earthwork, sand soil and raise dust is also the secondary pollution source, which cannot be ignored.Through the investigation of vertical distribution characteristics of PAHs on the surface, the study shows that PAHs content increased at first and then decreased with the increase of building floors. It reveals with the increase of building floors, gaseous and particulate PAHs content increased, and also implies that there is a relatively PAHs contamination layer of high upper and lower floors. There is a good correlation between PAHs and TOC in lower floors, but has an opposite trend from11to17layer. Organic film on glass surface basically exhibits the cumulative growth in linear trend, and there is good correlation between accumulation of PAHs and TOC. Through the comparison of PAHs on the glass surface between indoor and outdoor, the indoor is lower than the outdoor, and low-ring PAHs has nearly the same concentration either indoor or outdoor. But mass percentage of high-ring PAHs is higher in outdoor than that of in indoor.For the study of PAHs’potential source of pollution, the study constructs source spectral composition of PAHs in features medium. The road dust and deposition dust have the same component of PAHs within different particles in both Baoshan and Jinshan industrial areas. They are mainly Phe、Fl、Pyr、Chry、B[b+k]F and BaP, and it shows these PAHs congeners are the markers of road dust and deposition dust in the industrial area. The components of PAHs from burning of straw and weeds are mainly comprised of low-ring PAHs. The coagulation from exhaust pipe of diesel vehicles (trucks and buses) is mainly Nap, Phe, Fl and Pyr. In the meantime, Fl, Pyr, BaA, Chry, B[b+k]F, BaP, InP, BghiP and other high-ring PAHs are the certain marker compounds in vehicles powered by gasoline. The PAHs of lampblack from hood are mostly comprised of Nap. The PAHs of fumes and barbecue residues from exhaust fan are mainly Phe, Fl, Pyr and Nap. The components of PAHs in soil dust are mainly Phe, Fl, Pyr and Chry. They can be used as source marker in excavation of earth and topsoil at construction site.The concentration of PAHs on glass surface which is along with dominant wind direction in winter is between85.7and43.7ng/m2, PAHs concentration in urban and suburban areas are higher than in rural area, and the concentration of BaP on glass surface in Tangqiao is higher than in other samples. Except Shengang which characterized by four-rings PAHs, the other three samples are mainly three-rings groups. The concentration of PAHs within PM2.5and PM10is3.42～25.43ng/m2and3.56-26.69ng/m. Highest point is observed at Zhoupu(25.43ng/m3and26.69ng/m3) and the lowest one is in Shengang (3.42ng/m3and3.56ng/m3). Except Shengang, PAHs within PM2.5and PM10in other samples are mainly characterized by four-ring (27.47～41.1%), followed by five-ring (7.75～29.28%). The components of PAHs in Shengang are characterized by three-ring (49.35%), followed by four-ring (27.47%). This difference may be caused by the different source of pollutant and different content of particles in the air. As shengang is adjacent to East China Sea where has a relatively high air humidity, this may be the main factor affecting the concentration and components of PAHs in the air. PAHs within PM2.5and PM10in haze period are16.57ng/m3and16.59ng/m3, respectively, which is much higher than the non-haze period. The low-ring PAHs can easily reach equilibrium between glass surface and atmosphere in a short period, whereas that of high-ring PAHs hardly or even no equilibrium.The TEQ values of PAHs in organic film on glass surface from central city, industrial zone, urban-rural gradient and indoor and outdoor, is lower than the values of PAHs in air conditioning filter dust from office (1010ng/g), bedroom (901ng/g) and restaurants (782ng/g). It indicates that staying indoor for a long time is more dangerous than outdoor, and it is better to have regular window ventilation to reduce the adverse effects on health from toxic organic pollutants. Parent PAHs in the environment process often converted to other forms PAHs (methylated PAHs), and therefore it is inaccurate to interpret ecological and health risks for this study, with only reference of the parent PAHs. The Lifetime cancer risk model results indicate that swallowing process has smaller cancer risk. The cancer risk relatively high due to inhalation organic particles for different age groups. Children between the age of seven months and four years old have the most serious exposure risk through skin contact organic film. |
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