Pollution Characteristics Of Organochlorine Pesticides In Daling River Estuary

Organochlorine Pesticides (OCPs) is a kind of typical Persistent Organic Pollutants (POPs) with high toxicity, semi-volatility, environmental persistence and bio-magnification. Nowadays, OCPs have become the worldwide environment problem due to serious adverse effects on organisms. In order to provide extensive information of residue, pollution, distribution, sources and influencing factor of22OCP compounds, multi-media environment (soil, water, sediment) samples were collected from2011to2012of Daling River Delta. All the research would get pollution status of OCPs in the Daling River Delta, apply as the scientific for pollutant control and management, and have great significance for protecting people’s health and safety.In the first part of this thesis, gridded usage inventories of OCPs in Daling River Basin was established, and then based on which, the OCPs emission and residue are calculated. With the supporting of usage data, HCHs and DDTs usage inventory was allocated to a grid system with1/4°longitude by1/6°latitude resolution, which was established from Geographic Information System (GIS) and Access Database System. The total usage of HCHs and DDTs were estimated to be approximately18kt and910t between1952and1984. On the base of usage inventory, SGPERM model was application for calculating emission and residue. The total emission of HCHs and DDTs between1952and1984were5600t and510t. The residue of HCHs and DDTs were2.2t and10.2t in the year of2010.In the second part of this thesis, pollution characteristics of OCPs in soil of Linghai city were studied. The research shows that the22OCPs were detected with various in content in all the soil samples. HCHs and DDTs concentrations were detected with the high detection rates and residues. The results indicate that HCHs concentration in all soil samples and most DDTs concentration of soil samples were reached the first level of China’s "Soil Environment Quality Standard"(GB15618-1995), HCHs pollution was generally slight ecological risk and DDTs pollution was potential ecological risk for some geobiont and local bird. Compositional analysis indicate that HCHs and DDTs residues in soil were mainly from history use, but some areas have new sources which were lindane and dicofol in recently. With the aid of multi-variate geostatistics and GIS, spatial distribution of OCPs was studied with results showing that OCPs varied greatly in spatial distribution between types.In the third part of this thesis, pollution characteristics of OCPs in water of Daling River Delta were estimated. A total of22OCPs in surface water samplings were detected and HCHs and DDTs were the most dominant compounds in the water. Base on the health risk assessment, slight potential health risks of HCHs and DDTs in water may exist to organisms in Daling River Delta. There were lindane and dicofol input in recently years. The average concentration of HCHs in high water season was higher than that in low water season. HCHs in water presented in suspended particulate phase in high water season but dissolved phase in low water season. DDTs in water were mainly in suspended particulate phase. Geographical distributions of DDTs and HCHs from river area to coastal region were performed with the decreasing tendency. Total organic carbon in suspended particulate has influence on controlling OCPs’fate and transport in this area.In the fourth part of this thesis, pollution characteristics of OCPs in sediment of Daling River Delta were discussed. The results shows hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) were the most frequently detected contaminants. The decreasing trends of OCPs concentrations from Daling River to estuary area to coastal region in surface sediment were observed. With the information about the vertical distribution of radioactive activity of210Pb in Daling River Delta, give average sedimentation rates were1.12cm/a and dated back to1959. Trough the study of the vertical distribution characteristics of OCPs in the sediment core, the pollution history of OCPs in Daling River Delta was discussed. Compositional analysis of HCHs and DDTs indicated that new sources were lindane and dicofol in recently twenty years. Grain size plays important role on the residue and distribution of OCPs in sediment. The total organic carbon in the surface sediments had good correlation with OCPs. The temporal trends of HCHs and DDTs concentrations in the sediment core were affected by application history, emission and soil residues. Additionally, base on the available sediment quality guidelines, slight potential health risks of DDTs may exist to organisms in Daling River Delta. Fugacity fraction between water and sediment in the river revealing a net flux from water to sediment of HCHs and a net flux from sediment to water of DDTs (except wetland).