| With the rapid development of urbanization and industrialization, there are large amounts of pollutants which have complex structure produced due to human activities, and these trace pollutants are persistent and are toxic for organism, which may cause potential ecological harm to the environment. Persistent toxic substances (PTS) are a kind of materials which can exist in environment for a long time, and they are quite recalcitrant to degradation though chemical or biochemical pathways. Furthermore, the massive research indicates that PTSs are also one important endocrine disrupting chemicals in humans and animals, with the negative effects of "carcinogenicity, teratogenicity, and mutagenicity", and they can accumulate in the food chain causing harm not only where they are produced and used but globally, and jeopardize the health of the human body finally. PTS can migrate and accumulate in air-water-sediment/soil through various ways, such as the atmospheric dry and wet deposition, surface runoff, sewage discharges and farmland irrigating water back, etc. which resulted in the pollution of environmental medias. OCPs, PAHs and PCBs are several typical PTS which are ubiquitous in the environment, have caused wide attention in the world. Monitoring and analyzing of these kinds of PTS occurrence level in environmental media, predicting the trend of PTS pollution, explaining and analyzing their source, and assessing their potential ecological risks may provide basic data for the establishment of related policies and for the prevention and control of environmental pollution.In this study, the city Hohhot and the Lake WuliangSuhai were selected for the main research area, the spatial distribution of OCPs, PAHs, PCBs and some heavy metals in water, sediment, some aquatic macrophytes and native fish were analyzed in the Wuliangsuhai Lake ecosystems, typical environmental media including pine needle, fall dust and soil of Hohhot city parks and farmland soils. Based on the physicochemical properties of PTS and their use histories, the regional distribution characteristics and sources of PTS were briefly analysis, and assessed the ecological risks of different target PTS, and made it possible to quantificational discrimination of ecological risk of target PTS in different environmental media.The main results and conclusions are shown as follows:1. An enrichment analysis method suitable for a variety of trace lindane, endosulfan, hexachlorobenzene in environmental aqueous samples was established. Under the optimized extraction conditions, the target recoveries were in range of97.3%-101.7%, the linear range was1.0-1000μg/L, and the detection limits was0.39-2.44μg/L. Finally, the established method was used to analyze those three OCPs in water samples collected from the Lake of Wuliangsuhai. With the help of Design-Expert, we optimized the pre-concentration methods of16OCPs in pine needles determined with a procedure of ASE-GC/MS. Under the optimized conditions, the recoveries of16OCPs ranged from82.6%to109.3%, and the detection limits was between0.3μg/L and2.8μg/L, which indicated that the optimized methods meet the requirements for analysis of trace amounts.2. The concentrations of OCPs, PCBs and PAHs in water, sediment, aquatic macrophytes, and different species fish of Wuliangsuhai lake ecological systems was systematically analyzed, the results showed that OCPs in the overlying water was in range of1.30-5.89ng/L, and which mainly derived from atmospheric dry and wet deposition or water-air exchange; The average concentration of PCBs in water was1.96ng/L, and the different chlorinated benzenes were in the sequence of4C1>5Cl>6C1>3Cl>7C1, PCB concentrations in the overlying water showed a trend of decrease year by year; The PAHs content variously changed with season, presented a slight trend with summer> winter, and the distribution of PAHs concentration was affected by salinity in water; Concentrations of OCPs in surface sediment was in range of1.79-6.59ng/g; Comparing with the Lake Daihai and Hulun, PAHs in Wuliangsuhai was in lower level; DDTs in surface sediments mainly origined from aerobic degradation, HCHs mainly came from the residues of agricultural historic use;PCB components were differences in sediment, and low-chlorinated biphenyls were the dominated congeners; PAHs in surface sediments mostly are the low molecular weight PAHs, wood, straw burning may be the main source, the potential ecological risks of low molecular weight PAHs should attract attention; OCPs and PCBs can be detected in all the three aquatic plants, and in a decreasing sequence of reed> myriophyllum spicatum> potamogeton pectinatus at the total amount, in different reed tissues shows roots> leaves> stems> spike. The amounts of PAHs content are Myriophyllum spicatum> reed> potamogeton pectinatus, in different reed tissues show leaves> roots> stems> spike. OCPs has been widely observed in fish, mainly in p,p’-DDD and alpha HCH, the sequence of OCPs accumulation is visceral> gill> skin>muscle. The results showed that PCBs occurs chiefly as four or five chlorinated benzene.3. The results of OCPs concentrations in the three environments media (pine needles, soil, dust) collected from Hohhot city parks have shown that higher DDTs concentrations were detected in soil and dust, and the content of OCPs presented a significant season variations that OCPs in winter higher than that in summer, the statistical differences between two seasons showed that the main source of OCPs in pine needles was the atmospheric particles deposition; The ratios of different PAHs congeners were utilizd to identify their origins, the results showed that the urban traffic, coal emissions and combustion of fossil fuels may be the main source of Hohhot park media.4. The concentration and distribution characteristics of OCPs and several heavy metals (Cu, Pb, Zn, Cr) in the suburban farmland soil of Hohhot city were analyzed, and the results suggested that soil types and cultivation ways have a great impact on the content of OCPs and heavy metals. In addition, the content of heavy metals in soil is also affected by soil pH, total organic carbon, soil microbes and local climate. The results of index of geo-accumulation illustrated that the pollution of Pb and Cu in some farmland soil is in or exceed moderate pollution, it should be paid more attention for this situation, the results of potential ecological risk index showed a relative high risk in farmland soil located in southwest of Hohhot city. |
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