| As typical POPs, PAHs are formed and released into the environment mainly through anthropogenic sources; SCCPs also exhibit the characteristics of POPs as industrial products. Both PAHs and SCCPs have properties of teratogenesis, carcinogenesis, and mutagenesis. Lanzhou is an important city with heavy chemical industries in Northwest China, where located numerous chemical and energy industries. Due to special landform and meteorological conditions, PAHs, SCCPs, and other pollutions were worse in Lanzhou Valley. The levels and sources of gas phase PAHs and their dry depositions were investigated in Lanzhou Valley. Potential lung cancer risks due to exposure to atmospheric PAHs were also assessed. The environmental levels of SCCPs, which have been listed as potential POPs, in atmospheric PM10 and water environment and risks to water environment were also studied. The spatial distributions and removal processes of gas phase PAHs and their dry depositions were obtained for the first time, and the gaps in knowledge of SCCPs contamination in Northwest China was filled.The atmospheric gas phase PAHs and their dry depositions were high-density spatial sampled using Passive Air Sampler(PAS) and Passive Dry Deposition(PAS-DD), the results showed that gas phase ∑15PAHs annually averaged concentration was 321.05±149.67 ng/m3, which was higher than those measured in developed countries, and similar with those measured in other cities across China; The annually averaged dry deposition fluxes of ∑15PAHs was 18.66±13.14 μg/(m2·d). This value was considerably higher than those reported in places nationally and internationally. Overall, the annually averaged atmospheric concentrations and dry deposition fluxes of ∑15PAHs were higher than that of background site, and higher levels of PAHs were found in the heating season. Phe was found to be the predominant compound in both atmospheric gas phase PAHs and dry deposition fluxes. Besides, Flu has the highest fraction in gas phase PAHs in the atmosphere. Whereas, the fraction of Flua and Pyr depositions were higher than other PAHs compounds in total deposition fluxes of ∑15PAHs, and also the fraction of heavy PAHs with 5 and 6 rings were increased in the dry deposition compared with that in gas phase; The similar composition patterns of PAHs in atmosphere and dry deposition between Lanzhou Valley and other national and international area indicated similarities in PAHs emission sources.The results of PAHs source apportionment using multiple approaches indicated that gas phase PAHs and their dry depositions could be traced back mainly to combustion and petroleum sources, which were largely contributed by vehicle emission, combustion and coking process, and this has been confirmed by principle component analysis. Combustion and coking process had stronger influence on PAHs contamination levels during the heating season. Vehicle emission contributed mostly to PAHs dry deposition and gas phase PAHs could be largely traced back to combustion and coking process during the non-heating season. Atmospheric concentrations and dry deposition fluxes of PAHs were directly related to traffic, locations of industries, and human activities in residential areas; Using the emission inventory of PAHs and HYSPLIT model, the source-receptor relationship of PAHs in Lanzhou Valley was assessed. Results showed that the atmospheric PAHs level in Lanzhou Valley was largely attributed to the local emission sources. The trajectories of trans-regional atmospheric transport and emission sources of PAHs were from Xining, the city located in the upstream of Lanzhou, might also contributed to PAHs contamination to Lanzhou during the heating season. On the other hand, the PAHs emissions from Lanzhou might also influence on the PAHs concentrations in downstream areas which might extend to parts of Ningxia, Sichuan, and Shanxi provinces.Lung cancer risks induced by inhalation exposure to atmospheric PAHs were assessed by using BaPeq concentration and a point-estimate approach. PAHs risk assessments suggested that lung cancer risk levels were higher than many developed countries but analogous to other cities in China; The risk levels were factors of one or two higher than that proposed by United States and European countries, which indicated that local population were under a high level of lung cancer risk due to exposing to atmospheric PAHs.The pollution levels of SCCPs in atmosphere were mornitored using Active High-volume Sampler in Lanzhou Valley, the concentrations of SCCPs in PM10 were 6.02±1.49 ng/m3 and 19.76±11.42 ng/m3 during the non-heating and heating seasons, respectively, indicating higher level during the heating season. Atmospheric concentration of SCCPs in Lanzhou were higher than that measured in background site and European and American countries, but similar to those measured in China. A strong relationship between PAHs concentration and PM10 mass concentration was also found. The mean SCCPs concentration in sediment in Lanzhou reach of Yellow River was 2.03±0.69 μg/g(dry weight) which was higher than that measured in developed countries, but similar to those reported in China. Daily averages concentrations of SCCPs in water and particle phase collected in Lanzhou reach of Yellow River were 37.45±12.61 ng/L and 54.06±25.78 ng/L, respectively. The SCCPs level in water was similar to those reported in China and other countries. However, SCCP concentrations in the sediment in Lanzhou were considerably lower than those measured in sewage sludge in China and other countries. There was no significant relationship between SCCPs concentration and TOC in sediment, it might be influenced by the low TOC of sandy sediment, and it also suggested that there might be SCCPs emission sources across Lanzhou Valley; SCCPs with 10 carbon and 6, 7 chlorine atoms were the predominant compounds. The structure of such composition was identical to the SCCPs products in China but differed from the results reported by other studies.SCCPs have much higher biotoxicity than other chlorinated paraffin compounds. Based on the criterion value proposed by National Institute of Advanced Industrial Science and Technology(AIST), results indicated that ecological risk levels due to exposure to SCCPs in the water environment were relatively low. |
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