Study On The Distribution, Release And Ecological Risk Of OCPs In Weishan Lake

As the vital buffer of the South-to-North Water Diversion East Route Project,Weishan Lake is drawing people’s attention to the internal pollution ant water quality.In order to investigate dynamic characteristics of the interaction of water diversionand Weishan Lake water quality, under the support of the Jiangsu Province NaturalScience Fund, this research collected the samples of overlying water and surfacesediment from July2009to February2013, tested and analyzed the composition andcontent of organic pollutants.111sediment and water samples were collected from thescene,511sediment and water samples were measured, and1533data was obtainedthrough the methods of data analysis. This research systematically studied the timeand space change tendency of the organic chlorine pesticide in Weishan Lake,established the release model of internal pollution, and made an ecological riskassessment to water quality of the Weishan Lake. The main conclusions are asfollows:1、The study analyzed physicochemical properties of water and sediment inWeishan Lake comprehensively through in site and indoor test, the results showed thatwater and sediment in Weishan Lake show a weak alkaline；The average annualtemperature of water is between4and26℃；The conductivity is between1230and1500us/cm, and the content of ion is higher; the particle size of sediment is between7.95and24.94μm; the content of organic matter in sediment is between4.02%and8.08%, and the distribution of organic matter is inhomogeneous.2、Extracting organic chlorine pollutants from water and sediment in WeishanLake by using liquid-liquid extraction and Soxhlet extraction method respectively,purifying and concentrating the extraction online with gel filtration chromatography,and analyzing the samples quantitatively and qualitatively with GC-MS and GC-ECD.Test results show that the relative deviation of the method is less than15%, andconsistent with the America USEPA analysis. Therefore, the method is suitable fordetermination of OCPs from water and sediment in Weishan Lake.3、Analyzing the composition characteristics, residual degree, the degree ofdistribution trend and main source of organic chlorine pesticides in water andsediments from Weishan Lake, and researching the stability and jumping of organicchlorine pesticides in water.①The main component of residual in water are γ-HCH,β-HCH and p,p’-DDE, and in sediment are β-HCH, δ-HCH and DDT from WeishanLake;②In water, the mean content of HCHs in low and high water period are 74.7ng/L and108.6ng/L respectively, and the mean content of DDTs in low and high water period are83.6ng/mL and99.5ng/L; In sediment, the mean content of HCHs is5.50ng/g, and the mean content of DDTs is5.47ng/g. Which compared with other domestic water environment is in the middle level of residual;③The content of OCPs in water and sediment both show decreasing trend from the shore of the lake to the center of the lake, and the lake outlet/inlet is higher than other regions, farming area is higher than non-farming region;④In water, the value of a-HCH/y-HCH is between0.01and2.3and it is far less than3, which indicating that the residual HCHs from water in Weishan Lake is mainly dominated by Lin Dan. The value of (DDD+DDE)/DDTs in most of the simple points are greater than0.5, and the value of DDD/DDE are all less than1, it shows that water is aerobic environment, and the source of DDT is older; In sediment, the value of (DDE+DDD)/DDTs is between1.24and3.40, more than1, and the content of DDD is lower than DDE, which indicating that most of DDT degraded into DDD and DDE, and the sediments are in the aerobic condition;⑤Taking the water in Weishan Lake as an example, analyzing the stability and jumping of γ-HCH, β-HCH and DDE from water quantitatively in Weishan Lake,by establishing the function model of describing heavy organic chlorine pesticides’stability and jumping in water. With the time-lapse, the stability of γ-HCH, β-HCH and DDE in water increase gradually, and the stability of β-HCH is similar to DDE and both of them are higher than γ-HCH; the jumping of the three kinds of organic chlorine pesticides shows that γ-HCH>β-HCH>DDE.4、he release kinetic characteristics of OCPs in the sediment under still water and turbulent conditions was simulated by a self-made device. Results indicated that:①Release rate and type of OCPs were different according to different conditions. Compared with under static condition, OCPs under turbulent conditions tended to release into the overlying water. Release rate during the first10days was high, then slowed down and reached steady release phase;②OCPs concentration in pore water was far higher than that in formation water and surface water, which reflected the pathway and force of OCPs diffusion;③Suitable surfactants had effect on the release of OCPs. Surfactants above CMC could stimulate the release of OCPs;④Combining the releasing characteristics of organic chlorine pesticides in static and turbulent state, according to the mass balance principle, deriving the release kinetics equation of organic chlorine pesticides from water in Weishan Lake: The value is2.0891d-1，0.4342d-1,0.1611d-1and2.1213d-1，0.2897d-1,1.1927d-1of α-HCH、γ-HCH and DD are respetively. The degree of fitting of the function is morethan80%, which showing that the equation can describe the release characteristics ofthe organic chlorine pesticides in sediments of Weishan Lake. Sampling shows thatthe water quality of south to north water diversion into the Yangtze River significantlybetter than Weishan Lake, and it is unavoidable organic chlorine pesticides insediments releases in water of Weishan Lake after water transfer, so that needs to bepaid close attention.5、Assessing the ecological risk of organic chlorine pesticides in the environmentof Lake Weishan, the results show that Compared with other regions at home andabroad lakes, HCHs and DDTs in water of Weishan Lake is high; The pollutiondegree of HCHs and DDTs in the sediments is higher than foreign river, while lowerthan other domestic regions.. The disclosure risk of OCPs was low, whilecarcinogenic risk was high. In general, OCPs residues in the water body of WeishanLake still had potential ecological risks to environment. Therefore, the governmentshould strengthen the pesticide management in this region.