Pollution Characteristics,speciation And Source Analysis Of Heavy Metals In Dongting Lake

Dongting Lake is the second largest freshwater lake in China,which is located in Hunan province of China,which is known as " Nonferrous Metal Village ".This province is rich in nonferrous metals,is an important production base of heavy metals in China.The exploitation of the upstream metal mineral resources,the paper making around the lake area,and the large amount of sewage discharged from the chemical industry cause many heavy metals to be carried into the lake,which has caused great harm to the water environment and human health.Although the study of heavy metals in Dongting Lake has been reported,but most of them for a single medium to study,the pollution characteristics of heavy metals in Dongting Lake can not be understood comprehensively and systematically.Therefore,it is very important to study the heavy metal pollution in the water environment of Dongting lake,not only comprehensively and systematically understand the occurrence of heavy metals in Dongting Lake water environment,but also reveal the accumulation and migration of heavy metals in the heterogeneous media.In this study,the Dongting Lake as the research object,select 15 representative national control points,Sampling in the 2016 season.research the characteristics of Cr,Cu,Cd,Zn,Ni,As,Hg,and Pb in the surface water,surface sediments and fish body in the Dongting Lake,respectively.The health risk assessment method,land accumulation index and potential ecological risk index method were used to evaluate the risk grade;The correlation analysis and principal component analysis were used to analyze the source.The results of the study are as follows:(1)The concentrations of heavy metals in the surface water were lower than the standard limits of GB 3 "surface water environmental quality standard"(3838-2002),the contention of heavy metals in surface water of Dongting Lake is decreased in the order of Zn>As>Cu>Ni>Pb>Cr>Cd>Hg;The spatial distribution of heavy metals in surface water of Dongting Lake is decreased in the order of East Dongting Lake > South Dongting Lake >Dongting Lake;The health risk level of heavy metals in the surface water of Dongting Lake is basically between 10-11 and 10-5,which is lower than the recommended limit of EPA,Low risk level,The average annual risk of chemical carcinogens on human health is far more than theannual risk of non carcinogens,Children are more vulnerable to heavy metal pollution than adults.The contention of heavy metals in surface sediment of Dongting Lake is decreased in the order of Zn>Cr>Pb>Cu>Ni>As>Cd>Hg,compared with the corresponding background value,Cd exceeded the most serious,is the primary pollutant;The concentration of the river and its delta area is relatively high,the heavy metal accumulation is serious,and the pollution of the South Dongting Lake is the most serious;Index of accumulation shows that:Cd is the primary pollutant,belongs to moderate pollution;The potential ecological risk index RI value ranged from 179.93 to 1066.48,with an average value of 489.39,belonging to high ecological risk,South Dongting Lake is the most serious pollution,with high ecological risk.The contents of heavy metals in muscle of different fish were lower than the limits of the relevant standards in china,shows that carnivorous fish heavy metal content> omnivorous fish>herbivorous fish,benthic and pelagic organisms were larger than the upper and middle layers;The THQ value and TTHQ value of the fish were less than 1,no significant health risk.The order of TTHQ values of heavy metals in various fish species is:Crucian carp> catfish>lobster> silver carp> red eye trout> carp> grass carp> bream fish.(2)The heavy metals Cr,Hg,Zn,As,Ni and Cu in the surface sediments were dominated by residual state,accounting for more than 60%;Pb is mainly based on reducible state(B2),and Cd is mainly based on weak acid extractable state(B1);The results of the ratio of secondary phase and primary phase distribution shows that the RSP values of Cd and Pb were all greater than 1,but Cd belongs to heavy pollution,Pb belongs to moderate pollution;The rest of the elements belong to non pollution,and the average value of RSP is less than 1.(3)Pollution source analysis of heavy metals in surface water and sediments of Dongting Lake using Pearson correlation coefficient and principal component analysis.Cu,Zn,Cd,Ni and Pb in the surface water were mainly derived from domestic sewage,industrial wastewater and agricultural non-point source pollution;Cr and As are mainly controlled by non-ferrous metal mining and the introduction of tributaries.There are 3 main sources of heavy metals in surface sediments,Cu,Zn,As and Pb are dominated by industrial and mining waste water;Cr and Ni were affected by natural factors,domestic sewage and agricultural runoff,and Cd and Hg were mainly affected by the inflow of water into the lake.