| Organochlorine pesticides (OCPs) are typical persistent organic pollutants (POPs), with characters of half-volatility, persistence, and high toxicity in the environment, and biological accumulation through the food web. OCPs are able to migrate between the different environmental media, proceed to long-range transport in the air, and lead to global environmental problems. In the early1970s, western developed countries had prohibited the use of OCPs as having recognized the hazard of OCPs residual in the environment. And in the following1983, the production and usage of OCPs were also banned in China. However, OCPs are still the most widespread POPs in the environment, due to their large use amount and slow degradation.The bay is not only the most important area for the connection and interaction between land and sea, but also the indispensable region for human survival and development. However, pollutants input to the bay from the interactions of land and sea would enter into the sediment of bay, and lead to the contaminants enrichment, especially the benthos amplification in the case of high concentrations of organic pollutants, which may exacerbate the organic pollution in the bay. Thus, having the information about the pollution transport between the bay and its catchment watershed is helpful and important to analyse the pollution status quo, assess the ecological risk, and control the pollution of the bay.Jinjiang River watershed is located in the southeast of Fujian Province, with the area of5629km2, accounted for5%of the whole province area, approximately. The economy of this watershed region is developed and the economic aggregate has been the highest in Fujian more than a decade. Quanzhou Bay is a semi-enclosed bay in the southeast coast of Fujian Province, adjacent to the west side of the straits of Taiwan. Jinjiang Rive and Luoyangjiang Rive inject into Quanzhou Bay from west side and north side, respectively. Compared with Luoyangjiang Rive, Jinjiang River is more important to Quanzhou Bay for offering more runoff and sand to the bay every year. And Jinjiang River watershed has also become the most important source region of pollution input to Quanzhou Bay.In this study, Jinjiang River watershed and Quanzhou Bay were selected as our case study to establish a multi-media fugacity model of OCPs to discuss the transport of OCPs from the watershed to the bay. And the historical trends of OCPs in sediment cores in Quanzhou Bay were studied. Combined with the simulation results of the multi-media fugacity model, this research attempted to estimate the historical pollution reserves of the Jinjiang River watershed and Quanzhou Bay.In the first part of this thesis, a multi-media fugacity model on the transport of OCPs form Jinjiang River watershed to Quanzhou Bay was established, which was used to study the geochemical behavior and the fate of OCPs from land to sea. In order to provide a more comprehensive and objective description of environment in the study area, the non-equilibrium, steady-state flow system model was built in this thesis including four environmental compartments (air phase, water phase, sediment phase and soil phase), and each compartment had a number of sub-cells, such as the air phase including air particle and air sub-cells, water phase including particle, biont and water sub-cells and so on. In order to know whether this model was suitable for this study, the molar concentrations of OCPs from the actual test were compared with the simulation value of OCPs molar concentrations. And the results showed that the value from the actual test and model simulation in water, sediment and soil phase were in good agreement, and concentration residuals were all less than one logarithmic unit. So, this model was able to perform the suitable simulation on the transport of OCPs from Jinjiang River watershed to Quanzhou Bay, as well as the distribution and fates of OCPs in Quanzhou Bay. The model results showed that the reserves distribution of HCHs and DDTs in environmental media were different. DDTs mostly accumulated in sediments, whereas HCHs prefered to accumulate in soil, compared with other environmental media. Thus, the storage capacities of soils and sediments for OCPs were significantly higher than water and air, and therefore, soils and sediments were the main storage media for OCPs in the environment in the study system.Modeling results of environmental migration indicated that the migration flux of HCHs from water to atmosphere was the highest (1.44kg/a), while the migration flux of DDTs from water to sediment was highest (29.6kg/a), when the system reached steady state. The migration fluxes of HCHs and DDTs from air to soil were both higher than the fluxes from air to water. The fluxes of HCHs from water to air were higher than the fluxes from water to sediment, while DDTs were on the opposite. For the soil phase, fluxes of HCHs and DDTs from soil to water were higher than to the air. As the transport from soil to bay water is mainly reflected in the supply of soil erosion to the bay, the transport of OCPs through the surface runoff from the Jinjiang River watershed to Quanzhou Bay was significant. In the air phase, the mainly behaviors of OCPs were atmospheric advection and degradation, with a small amount of migration to the soil and water phase. In the water phase, the mainly behaviors of OCPs were ocean current advection and migration from water to air and sediment, with degradation in a small amount. In the soil phase, the mainly behavior of OCPs was degradation, with a small amount of migration to the water and air. In the sediment phase, the mainly behavior of OCPs was to deep bury, with a small amount of degradation and resuspension.In order to assess the influence of the model input parameters to the model results, this study made sensitivity analysis of model parameters. The analysis showed octanol-water partition coefficient logarithm had greatest impact on the model outputs of HCHs and DDTs concentrations in various environmental phases of the study area, namely this parameter had the strongest influence on the modeling results.In the second part of this thesis, the high-resolution sedimentary records of OCPs in Quanzhou Bay were studied. With the information about the vertical distribution of radioactive activity of210Pb in the inner bay (QZ1) and outer bay (QZ2) of Quanzhou Bay, a constant initial210Pb concentration (CIC) model was used to give average sedimentation rates, the results were1.23cm/a in QZ1, and0.55cm/a in QZ2. And a constant rate of210Pb supply (CRS) model was applied to date each slice of sediment to obtain that QZ1(48cm) and QZ2(32cm) dated back to1953and1948, respectively.Historical trends of OCPs in Quanzhou Bay were obtained by applying the concentration of OCPs in each sediment slice back to the age sequence of sediment cores. There was a peak of deposition flux of HCHs in QZ1between1950and1960, but in the1950s, the use of pesticides in China was not in such high level, and this discrepancy might due to the heavy disturbance in inner bay with instable environment. A peak deposition flux of HCHs was found between1965and1970in QZ2, which was consistent with the heavy use of HCHs in1960s in China. The fluxes of HCHs and DDTs both showed peak values between1985and1992, which mainly because of the large-scale of beach reclamation and deforestation with farmland reclamation in the area of Quanzhou Bay in the mid-1980s, which allowed a lot of soil and surface runoff with OCPs residuals were carried into the Quanzhou Bay and deposited in the sediments.The deposition fluxes of OCPs in inner sediment core were lower than in outer one, whereas the sedimentation rates in inner core were higher than the rates in outer one. The reasons for this phenomenon might be from two aspects. Firstly, the depositional environment of inner bay was instability with many disturbances to affect the deposition of OCPs. Secondly, the outer bay might receive the pollution inputs from the outer sea water.The weak correlation were found between the deposition of DDTs and environmental factors, by the comparison and correlation analysis between the OCPs deposition chronological sequence and the historical hydrological and meteorological datas in mountain area of Jinjiang River watershed and coastal zone of Quanzhou Bay, such as temperature, precipitation and sediment load.Uncertainty analysis for the OCPs deposition chronological sequence showed the uncertainty of the210Pb dating method and the OCPs deposition process both might lead to the results not match the actual deposition ages of OCPs in this study.In the third part of this thesis, the historical reserves of OCPs in Jinjiang River watershed and Quanzhou Bay were estimated. Jinjiang River watershed is the most important area to deliver supplies to the Quanzhou Bay. And the pollution in Quanzhou Bay is the portrayal of the contamination in Jinjiang River watershed. With these information and several results from the multi-media fugacity model, the historical contamination fluxes of OCPs from Jinjiang River watershed to Quanzhou Bay could be work out. Therefore, based on the assumption of steady ratio of output in the research system, the proportions of OCPs reserves in individual environmental medium to the total reserves of the research system could be gained from the fugacity model of multi-media environment. With these proportion values and the OCPs deposition chronological sequence, the historical reserves of OCPs in Jinjiang River watershed and Quanzhou Bay were attempted to estimate.Total historical reserves of soils, atmosphere, water, sediment and the whole environment in Jinjiang River watershed and Quanzhou Bay in1950s,1960s,1970s,1980s were estimated. The results revealed that the reserves of HCHs and DDTs in the sediment of Quanzhou Bay in1950s,1960s,1970s,1980s were4.61kg and16.67kg,5.91kg and9.18kg,3.67kg and30.45kg,7.99kg and115.78kg. So the reserves of HCHs and DDTs in the whole stuty area in1950s,1960s,1970s,1980s were25.00kg and16.74kg,35.07kg and9.22kg,23.02kg and30.56kg,47.70kg and116.23kg, respectively. The reserves of HCHs and DDTs in the soil of the Jinjiang River watershed were19.60kg and0.06kg,28.04kg and0.03kg,18.65kg and0.08kg,38.27kg and0.35kg, respectively. The reserves of HCHs and DDTs in the air phase of study area in1950s,1960s,1970s,1980s were5.24g and0.24g,7.00g and0.09g,5.47g and0.33g,10.48g and1.16g, respectively. The reserves of HCHs and DDTs in the sea water of Quanzhou Bay in1950s,1960s,1970s,1980s were0.79kg and0.02kg,1.11kg and0.01kg,0.70kg and0.03kg,1.43kg and0.10kg, respectively.Overall, the historical reserves of HCHs and DDTs in various environmental media in the study region were basically in the order that1980s>1960s>1950s>1970s and1980s>1970s>1950s>1960s, respectively. The historical reserves orders of HCHs and DDTs were found different in this study, and the reason maybe the different types and quantities of pesticides were applied in different years. The estimated reserves of DDTs in the whole study area were one to three orders of magnitude less than the application amount of OCPs on the study area. The main reasons of this discrepancy were from the errors of the assumption of steady state in multi-media environmental fugacity model and the stable proportion of output reserves, the uncertainty from OCPs deposition chronological sequence, and the chose of actual values of OCPs application amount in the study area. |
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