Investigation On The Pollution Status Of Heavy Metals And Organic Pesticides In 18 Main Branches Of The Three Gorges Reservoir

In 2003,the Three Gorges Reservoir began to store water,increasing shipping,power generation and tourism,etc..However the river-type reservoirs have become typical channel reservoirs,which have reduced the ability of currents to disperse pollutants.Simultaneously,the effect of main flow on the tributaries weakens the selfpurification capability of the tributaries and exacerbates the risk of deterioration of the ecological environment of the entire Yangtze River basin.After consulting the literature,most of the domestic and foreign literature reports are about the pollution status of the main stream or a certain tributary of the Three Gorges Reservoir.They mainly focus on the investigation of heavy metal pollution,and there are few investigations of organic pollution,while there have been some days before now.So far no systematic report has been found on the pollution of heavy metals and organic matter in the main tributaries of the Three Gorges Reservoir.So it is necessary to update and supplement the data in a timely manner.Due to lead(Pb)and cadmium(Cd)are widely used,and if improper use of Pb and Cd will cause great harm to human health,therefore we selected Pb and Cd as the survey objects in this paper.Hexachlorocylcohexanes(HCH),an organochlorine pesticide,which had many advantages had been used widely before 1984 in China,but it is difficult to degrade and has great harm to human beings.Methyl parathion(MP)not only has equal effect with HCH,but also is easily degraded.Therefore MP is used instead of HCH.However,if MP is used improperly,it will also pose a great threat to human health.Pentachlorophenol(PCP),a persistent organic pollutants,has been widely used for sterilization,disinfection and antisepsis in China.However,the abuse of PCP will pose a serious threat to human health.Heavy metals and organics in water bodies are likely to accumulate in water sediments,and the heavy metals and organics will be released into the water when the external conditions change,not only threatening the survival of benthic organisms,but also endangering human health.Therefore,this study investigated the contents of Pb,Cd,PCP,MP and HCH in the waters and in the water sediments of the 18 tributaries of the Jiangjin-Yichang section of the Three Gorges Reservoir,including Qijiang River,Yipin River,Jialing River,Chaoyang River,Yulin River,Longxi River,Wujiang River,Quxi River,Longhe River,Dongxi River,Ruxi River,Zhuxi River,Tangxi River,Changtan River,Caotang River,Daning River,Baolong River and Qinggan River to provide scientific basis for the treatment of pollutants in the Three Gorges Reservoir and the rational use of Pb,Cd,PCP,MP and HCH.The study is as follows: 1.Detection and assessment of heavy metals in water of the 18 tributaries of the Jiangjin-Yichang section of the Three Gorges ReservoirIn this experiment,acid digestion was used to extract Pb and Cd in water and ICPAES was used to determination of the concentrations of Pb and Cd in water.This paper analyzed the differences in the concentrations of Pb and Cd in water during the impoundment period,natural flood season and dry season period for each section of four sample points with Duncan assuming the homogeneity of variance.And based on the assumption of homogeneity of LSD,it was analyzed whether there are significant differences in the contents of Pb and Cd in the 18 tributaries of water.Then,water quality of the 18 tributaries based on Pb and Cd was evaluated.The results showed that the water quality of the 18 tributaries based on Pb and Cd was mainly I-III.2.Detection and assessment of organics in water of the 18 tributaries of the JiangjinYichang section of the Three Gorges ReservoirIn this experiment,LLE was used to extract the organics in the water.The contents of MP and HCH in water was detected by GC-MS and The content of PCP in water was detected by HPLC.This paper analyzed the differences in the concentrations of PCP,HCH and MP in water during the impoundment period,natural flood season and dry season period for each section of four sample points with Duncan assuming the homogeneity of variance.And based on the assumption of homogeneity of LSD,it was analyzed whether there are significant differences in the contents of PCP,HCH and MP in the 18 tributaries of water.Then,the water quality of the 18 tributaries based on PCP,HCH and MP was evaluated.The results showed that the water quality of 18 tributaries based on PCP,HCH and MP was mainly I.3.Detection and assessment of heavy metals in the surface sediments from the 18 tributaries of the Jiangjin-Yichang section of the Three Gorges ReservoirIn this experiment,the collected sediments were first dried,sieved,and mixed.Then the appropriate amount of sample was weighed,digested with acid,extracted with methyl isobutyl ketone,and finally flame atomic absorption spectrometry was used to detect the contents of Pb and Cd in the surface sediments.Based on the assumption of homogeneity of LSD,it was analyzed whether there are significant differences in the contents of Pb and Cd in the surface sediments of the 18 tributaries and whether the contents of Pb and Cd exceeded the standard in the surface sediments of the 18 tributaries.The results showed that the concentration of Pb in the surface sediments of four rivers exceeded the standard,and the concentration of Cd in the surface sediments of a river exceeded the standard.4.Detection and assessment of organics in the surface sediments from the 18 tributaries of the Jiangjin-Yichang section of the Three Gorges ReservoirIn this experiment,the collected water sediments were first dried,sieved and mixed.The appropriate amount of sample was then weighed,dissolved in organic solvents,extracted by ultrasonic waves,extracted.MP and PCP need to be concentrated,and HCH is purified and dissolved in petroleum ether and measured after constant volume.GCECD was used to detect the contents of HCH in the surface sediments,GC-NPD was used to detect the content of MP in the surface sediments,and GC-FID was used to determine the content of PCP in the surface sediments.Based on the hypothesis of homogeneity of LSD,it was analyzed whether there are significant differences in the contents of PCP,HCH,and MP in the surface sediments of the 18 tributaries,and whether the contents of PCP,HCH,and MP exceeded the standard in the surface sediments of the 18 tributaries.The results showed that PCP in the surface sediments of the 18 tributaries did not exceed the standard and MP in the surface sediments of the 18 tributaries exceeded the standard,while BHC in the surface sediments of 7 tributaries exceeded the standard.