| Persistent Organic Pollutants (POPs) are a group of chemicals that persist in environment, bioaccumulate through the food web, and pose a risk of causing adverse effects to human health and the environment. POPs can reach regions where they have never been used or produced through long-range transport and threat the environment in the regions. Spatial identification of the relationship between sources and acceptors of POPs and understanding the causes of this relationship are the theoretical foundation to master the pollution trends of these chemicals on a regional or even a global scale, and make policies to control and reduce the pollution. This kind research on a national scale is lacking in China. While soil is one of the sink for POPs, and atmospheric transport is the most important pathway of many chemicals to undergo the long-range transport process.Technical HCH, one of POPs, was the mostly used insecticide in China from 1952 to 1984, andα-HCH, the major component of technical HCH, was selected as the targeted chemical in this study. The objective of this thesis is to study the pattern of the soil residues ofα-HCH in Chinese soil, the process to cause this residue patterns, and thereafter the relationship between source-receptor of the chemical.A multi-medium model has been developed based on a grid system with a 1/6°×1/4°latitude/longitude resolution to assessment long-period fate ofα-HCH in China environment. The model considers 4 matrixes, soil, air, water and sediment, and includes transfer and transport modules. The model was employed to simulate the transport and transfer ofα-HCH in 56 years from 1952 to 2007, to analyze the characteristics of its residues in soil during the use of technical HCH, to identify the major contaminated areas, and to quantify the contributions to these areas from different source regions by using inventory separation method. Both the temporal and spatial trends ofα-HCH residues in Chinese multi-media, soil in particular, were calculated by the model. The results of the modeled soil concentrations matched well with the measured data. The model result suggested thatα-HCH concentration pattern in soil in each grid cell was mainly affected by usage intensity and application modes of this chemical in the cell during the application period from 1952 and 1983, and was dominated by temperature, organic carbon content and porosity of soil after 1983.To identify quantitatively the contribution of different sources in China to theα-HCH budget national wide, the numerical simulations were performed for different scenarios. The results showed southern source was the remarkable contribution toα-HCH soil residue in Northeastern and mid-North China. The importance of the southern source has been stronger and it was predicted that over 50% ofα-HCH in Northeastern and mid-Northern soil will come from the southern sources in 2030 and 2041.The temporal and spatial pattern ofα-HCH air concentration in China in 2005 was simulated by atmospheric transport model CanMETOP and indicated that the transport ofα-HCH from southeast soil to northeast China mainly caused by East Asian monsoon occurred in summer, mainly in July. It was found that East Asian monsoon can carryα-HCH from soil in Southern China, and bring them to the Northeast, forming a much strong"pulse"ofα-HCH in the region with a air concentration even higher than that in the source region.Analysis on the meteorologic data during 1965-2007 shows thatα-HCH in southeast region was carryed into northeast China by air transport in summer of every year and maily in July.α-HCH transported into Northeast was concentrated by cyclone or lower air pressure and deposited into the environment of land surface by precipitation in the region.
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