| With the growth of population, rapid development of industry, the soil contamination by persistent organic pollutants (POPs) has become more and more serious by leachate from waste solids, dry and wet deposition, and sewage irrigation. Due to their carcinogenicity, mutagenicity and teratogenicity, as well as endocrine disruptive activity, POPs contamination has increasingly aroused general concern. POPs in soil may contaminate the air, surface water and underground water by volatilization, diffusion and transfer. They easily accumulate in organism by bioconcentration and biomagnification, and finally endanger the health of human beings. So soil contamination by POPs is a key problem to be urgently solved and investigated. The contamination levels, spatial distribution, isomeric composition, possible sources and potential ecological risk of POPs including PAHs, OCPs, PBDEs and PCBs from soil in Shanghai urban areas and agricultural fields were systematically investigated. The study aimed to understanding the soil contamination status and potential risk posed by typical POPs in Shanghai region,and to providing the scientific basis for implementing the POPs convention. The main conclusions are summarized as follows:1. The results showed that the total concentrations of 22 PAHs (ΣPAHs) ranged from 442 to 19700μg kg-1 in urban soil and from 141 to 2370μg kg-1 in agricultural soil of Shanghai, with means of 3780μg kg-1 and 757μg kg-1, respectively. The seven possible carcinogenic PAHs (Σ7CarPAHs) accounted for higher percentage ofΣPAHs. Among different sampling areas, the higher levels of PAHs were found in the roadside, followed by greenbelt, commercial district, park, residential district, and the low concentrations of PAHs were found in agricultural soil. The composition of PAHs was characterized by the high molecular weight PAHs, among which Flu, Pyr, BbF and Chr were most dominant components. The good correlations among the individual PAHs were observed. The contents of individual PAHs were not correlated with soil total organic carbon (TOC) in urban soil; on the contrary, there were significant correlations between soil TOC and individual PAHs in agricultural soil. The principal component analysis (PCA) and PAHs isomeric ratios indicated that PAHs in soil from Shanghai originated mainly from combustion. The risk assessment suggested that soil PAHs carcinogenic potential merited attention at present contamination level in urban areas.2. The total concentrations of 24 OCPs ranged from 3.28 to 94.7μg kg-1 in urban soil and from 3.16 to 265μg kg-1 in agricultural soil of Shanghai, respectively. Among different sampling areas, the higher levels of PAHs were found in the greenbelt and park in urban soil, while the higher contaminated areas were distributed in south regions of Shanghai agricultural field (including Fengxian, Nanhui and Jinshan districts). According to the measured concentrations and detection frequencies, HCHs, DDTs, HCB and heptachlor epoxide were the most dominant compounds among the OCPs. The different compositions of DDTs, HCHs, Chlordane and endosulfan indicated that the residues of these compounds in most soil samples originated from historical application, besides slight recent introduction at some sampling locations. The correlation analysis showed there were no significant relations between TOC and OCPs. The soil quality of Shanghai was classified as low pollution by OCPs. The risk assessment showed that HCH residues in soil did not pose much risk to the geobiont therein, while DDTs posed some risk to the birds and geobiont.3. The concentrations ofΣPBDEs ranged from 22.3 to 889 ng kg-1 in urban soils and 41.7 to 962 ng kg-1 in agricultural soil, and BDE 209 varied from 0.291 to 2910 and from 33.2 to 796 ng kg-1, respectively. BDE 209 was the predominant congener detected among the 44 congeners detected in soil, consisting with the fact that technical deca-BDE mixture is the dominant technical PBDE mixture used in China. Meanwhile, PBDEs homologues analysis and PCA revealed that the major source of PBDEs in Shanghai might be associated with the prevalent use of deca-BDE as a flame retardant, in addition penta-BDE also had contribution on PBDEs contamination in one-third soil samples. Furthermore, high level of PBDEs contamination was observed in north Shanghai because of the rapid development of urbanization and industrialization in the area, while high PBDEs content in urban area were distributed in greenbelts and commercial districts because of point-sources contamination. The correlation analysis showed there were significant relations between TOC and individual PBDEs, suggesting important influence of soil TOC on PBDEs contamination.4. For PCBs contamination, 74 PCB congeners in urban areas and 62 PCB congeners in agricultural fields were identified, and the concentrations ofΣPCBs ranged from 232 to 11300 ng·kg-1 in urban soil and 71.7 to 2530 ng·kg-1 in agricultural soil, with means of 3060 ng·kg-1 and 534 ng·kg-1, respectively. For the urban sites, the higher PCB concentrations in the soil samples were found in commercial and greenbelt area, followed by park, residential and roadside sites, but the differences are not significant. The high level of PCBs were detected in BS2, SJ6, JS4 and FX4 in agricultural fields. The relative content of low weight molecular PCBs were higher in the rural sites than those in urban sites in Shanghai. PCBs homologues analysis and PCA revealed that PCBs in Shanghai might originate from Aroclor1242 and 1254 in urban areas, and Aroclor1242 in agricultural fields. The correlation analysis showed that there was relatively good correlation among the individual PCBs and soil TOC, suggesting important influence of soil TOC on PCBs contamination. Compared with related reports, the level of PCBs contamination was low in the studied areas.
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