| Persistent organic pollutants (POPs) are a class of highly toxic persistent organic pollutants. Once they enter the environment, it is difficult to degrade, and long-distance transmission with airflow or water can make them reach to remote areas and even the Polar Regions. Therefore, POPs released from the source region can re-distribute through air and water in a large scale, even global redistribution. Recent studies indicated that high concentrations of POPs released from the tropical and subtropical regions can transport across the Pacific Ocean to high-latitude regions like Arctic.Moreover, POPs are easy to accumulate through the food chain, endangering the health of organism and human. Therefore, the pollution of persistent organic pollutants, and its geochemistry behavior, has caused widespread concern in the international community, and beame an important global environmental problem.Compared to the low-lying areas, high-latitude regions have low daytime air temperature and relatively high precipitation, and most experience long-lasting snow cover. Solar radiation fluxes are higher and air pressures are low. These climatic characteristics of high-latitude mountain regions will affect the environmental behavior of organic pollutants, leading POPs to settlement or stored in these areas. In addition, the high-latitude mountain regions have high biodiversity, and water in these areas is the main source of low altitude. Environmental pollutants in these areas cause potential harm to sensitive aquatic and terrestrial ecosystems. Therefore, the study of POPs in high-altitude mountains has great significance for the protection of the human resources environment. Zoige plateau wetland has great ecological value, and also is the hub connecting the Tibetan Plateau and the low-lying areas. So far, there is no research on the distribution and geochemistry behavior of POPs in this region.This paper selected Zoige plateau wetland as the research object, discussed distribution characteristics of POPs in the region, sources of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) in the atmosphere and atmospheric long-range migration, as well as the exchange of typical POPs in the the Zoige region between the atmosphere and surface, revealling the ecological and geochemical behavior of POPs in high altitude areas.The first part of this thesis discussed the atmospheric pollution characteristics of organochlorine pesticides and polychlorinated biphenyls. The active atmospheric analysis of organochlorine pesticides and polychlorinated biphenyls in different seasons (summer, winter and spring) in the wetland showed that: Ogrnaochlorine pesticide residues in Wetland atmosphere, especially of DDT levels, are still higher than the background region of our country and the world; the concentrations of ogrnaochlorine pesticides and polychlorinated biphenyls in winter are higher than in summer, showing the impact of monsoon on the characteristics of POPs in this region. The airflow trajectory analysis shows that: the monsoon from northwest in winter, making Zoige region affected by the high degree of atmospheric pollution in urban city in the direction of northwest. While in spring and summer, of relatively higher levels of DDT is carried by the southwest monsoon, indicating that monsoon circulation plays an important role of atmospheric long-range transport of POPs in high altitude clean areas like Zoige Wetland.The second part determinates the residues of OCPs and PCBs in typical wetland soils and dry soils in Zoige wetland protection zones. The results showed that the main organochlorine pesticide residues in Zoige wetland is HCH, SHCH accounted for a total OCPs compounds of44.24%. Based on the isomer composition analyze, informing that HCHs in the soil are from atmospheric air mass migration come from lindane using area, the concentrations of DDT isomers and their metabolites, lower than HCHs, accounting for37.37%of the total OCPs, and there is a good linear correlation between DDT analogues. This phenomena show that the highland pastures soil receptors of atmospheric pollutants, and before pollutants into the soil, they have been fully mixed in the atmosphere. Because of the high volatility, HCB only has little change in different sample point, and its concentration still higher than the other background areas of the world. PCBs in soils of the study area mainly detected low chlorinated PCB28and PCB52. In addition, the correlations of PCBs and OCPs in the soil between environmental factors show that the sampling location and the sources of pollution is the main reason leading to the concentration of POPs in the soil. Seasonal changes, the impact of land use types, as well as altitude and pH of the soil also play important role in the storage of POPs. In this study, OCPs and PCBs content and soil organic carbon (TOC) have good positive correlation.The third part of mainly studied the atmospheric particulate drop samples in different seasons (summer, winter and spring), and gaseous exchange between the atmosphere and surface in Zoige plateau wetland. The main component of atmospheric deposition is HCH, seasonal variations of deposition fluxes is winter> summer> spring. The precipitation in winter is the lowest all over the year, on the contrary, the deposition flux is the highest, showing the influence of the concentration of HCH under the change of monsoon and the scouring effect of snow on the pollutants in the atmosphere. The peak of deposition flux in winter is mainly due to the supply of heating in winter in the northern cities. Particulate matter content increased in the atmosphere in this season, the encounter of the hot air mass from south and the cold air mass rich in particulate matter from north, resulting the sedimentation peak of OCPs. The analyze of atmosphere and surface exchange of ogrnaochlorine pesticides showed the different exchange direction between soil and atmosphere in winter and summer. The reason of this phenomena revealing that the north wind prevailed in winter will carry the pollutants to the region, causing the absorption of OCPs in soil from the atmosphere, thereby slowing the speed to northward; when the southwest monsoon prevails, pollutants stored in the soil will release back into the atmosphere, participation in regional geochemical cycles, confirming the delay effect of soil distribution of POPs in the global scale.The fourth part mainly uses the multi-media fugacity model to simulate the migration of the four PCBs and OCPs in the cross-interface transmission and fate in Zoige plateau wetland. The simulation results showed that:Soil is the main reservoir of POPs in the region of Zoige plateau wetland. Among environmental media cross-interface migration, the most important transmission direction of all PCBs and OCPs are the atmosphere to soil migration and the migration from the atmosphere to water. The model sensitivity analysis showed that the atmospheric concentration of stratospheric input has the greatest impact of the output value in this model.Finally, through the work of the above four parts and the analysis of biological samples in Zoige region, discussed the atmospheric remote migration fate of OCPs and PCBs in this area. The compounds in gaseous form reached to Zoige region through atmospheric remote migration are HCHs, HCB, DDTs, PCB28, PCB52, and little endosulfan and PCB101. These compounds can stored in soil after wet deposition, but the composition changed and highlights the HCB and DDE. When they enter to forage, endosulfan are relatively enriched. While when we taking the yak body into account,β-HCH, a-HCH, HCB, endosulfan are the main compounds. The concentrations of β-HCH and endosulfan in the sources Atmosphere was not prominent, but they win after experienced a series of environmental geochemical processes, into the top of the grassland food chain. And the factor analysis of atmospheric remote migration impact of POPs showed that the model proposed in the literature on the migration ability of POPs compounds in atmospheric remote has some limitations, need further comprehensive analysis and re-modeling in the special areas like Zoige plateau wetland.The innovation of this study is:The plateau cold regions is the receiver and important reservoir of POPs. This study is the first analyze of the sources and long-range transport of POPs in Zoige plateau wetland, plateau grassland area of western China, revealing the input flux and the source of POPs in the alpine pasture regions of western China.Multi-media fugacity model was used to simulate migration trend of POPs, providing a reference for the fate of POPs in high-altitude but low background regions.Through the long time, multi-media and multi-angle research of POPs in Zoige, the result showed that the geographical location and the climatic conditions of this unique area cause the existing atmospheric remote migration model of POPs compounds in the region has a certain degree of the limitations. The results provide reliable data reference for POPs research in other high altitude areas. |
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