Sources, Distributions And Fluxes Of Organochlorine Pesticides In Jiulong River-Estuary-Sea System

Production and use of organochlrine pesticides(OCPs) have been banned in most countries since the early 1970s.Because of their used largely,persistence and semi-volatility,OCPs are still the most widly spread POPs in the environment.As an important transport medium,water bodies play an important role in the fate and occurrence of OCPs in the environment.To date,studies of OCPs in the water environment focus primarily on the occurrence of OCPs in a local media(water, sediments and organisms).But the systematic studies are necessary on the transfer of OCPs especially in the river-estuary-sea system.In addition,few studies have been conducted to determine the fluxes of OCPs from major rivers to the coastal sea via riverine runoff in China.Thus studies on phase distribution and seasonal variation of OCPs in Jiulong river-estuary-sea were carried out.And sources of OCPs,factors affecting the distribution of OCPs in water body,and fluxes of OCPs from Jiulong river into the sea have been discussed and calculated.The result will help us understand deeply the transport of OCPs in river-estuary-sea water,and provide a theoretical basis for prevention of OCPs' pollution in water bodies.The main results are the following:1.Concentrations of OCPs,DDTs and HCHs in water in flood season were higher than those in the dry season.Compositions of DDTs and HCHs in dry season were identity in water bodies of Jiulong river.OCPs in water presented in dissolved phase in the sites of river and the upstream of estuary.In the downstream of estuary, OCPs were mainly in dissolved phase of water in normal season and flood season,but mainly in suspended particulate phase in dry season.Compared with the previous studies,the residual levels of OCPs in Jiulong river-estuary-sea have decreased. Concentrations of DDTs and lindane in Jiulong river(Beixi river and Xixi river) were lower than the state recommended limits of surface water(centralized drinking water) standards;Concentrations of DDTs and HCHs in Jiulong estuary and sea water also reached the limits of state seawater quality standards(class 1).2.Sources of OCPs in Jiulong river-estuary-sea water were different in different seasons by comparing the profiles of OCPs and the ER values ofα-HCH.OCPs in Beixi river mainly came from atmospheric deposition in dry season,while the local soil erosion contributed more in flood season.Some sites in the downstream of estuary and coastal waters show new inputs of HCHs and DDTs in dry season. Enantioselective breakdown ofα-HCH had been found in Jiulong river-estuary-sea water,and(+)α-HCH is more easily degraded.3.There are some positive correlation between SPM and suspended particulate OCPs and between DOC and dissolved OCPs separately,but some negative correlation between salinity and total OCPs.In addition,concentration of OCPs in water shows a high value in low tide,and a low value in high tide.4.The flux of total OCPs in water from Jiulong river into sea is 788.55 kg/a. HCHs in water tend to be transported into sea by dissolved phase,but DDTs tend to be transported into sea by suspended particulate phase.