Pollution Characteristics,Risk Assessment And Source Apportionment Of Heavy Metals In Sediments And Soils Of Poyang Lake Area

In this paper,the surface sediments of Poyang Lake and the agricultural soils around lake were taken as the research objects.Through the determination of heavy metal content,combined with ArcGIS,enrichment factor,single pollution index method,geoaccumulation index,potential ecological risk index method,principal component analysis,positive matrix factorization and Unmix model reveal the differences in the spatial distribution of heavy metals,evaluate the degree of pollution,potential ecological risk,and discuss the sources and contributions of pollution.The main research conclusions are as follows:(1)Except for the average contents of V and Cr in surface sediments of Poyang Lake did not exceed the soil background values of Jiangxi Province,the average contents of Cd,Mo,Hg,Cu,Pb,Zn,W,Sr,As,Ni,Co and Sb were 5.7,2.2,1.9,1.8,1.5,1.5,1.4,1.3,1.3,1.2,1.0 and 1.0 times of their respective background values.The average contents of Cr,Ni,Cu,Zn,Pb,Hg and As were lower than the risk screening values for soil contamination of agricultural land,and 51%of sediment samples had higher Cd contents than the risk screening values for soil contamination.The spatial distributions of Cr,Cu,Zn,Sr,Pb,Hg and As in sediments showed that the high content values were clustered near the river inlets of Ganjiang,Fuhe,Xinjiang,Raohe,while Co,Ni,Mo and Sb were obviously concentrated in the southern of lake region,the northeast region and the Xiushui into the lake.V,Cd and W gathered near Xiushui into the Lake,north into the mouth of the Yangtze River,and south branch of Ganjiang into the lake,respectively.(2)Except for V,Cr and Co,the average contents of Ni,Cu,Zn,Mo,Cd,Sb,W and Pb in agricultural soils around Poyang Lake exceeded the soil background values of Jiangxi Province.The average contents of Cr,Ni,Cu,Zn,Cd and Pb were lower than the risk screening values for soil contamination of agricultural land,and 55%of agricultural soil samples had higher Cd contents than the risk screening values for soil contamination,indicating that there may be Cd pollution risk in agricultural soils.The exceeding rates of background value of all heavy metals in the sampling points of Nanchang County,Jinxian County and Xinjian District ranked in the top three,probably because they accepted the "three wastes" discharged by various industrial bases and enterprises in the urban area of Nanchang,as well as pollutants from domestic sewage and agricultural non-point source in the surrounding cities and towns.There is a certain degree of weathering and erosion in the agricultural surface soil.Due to the soil erosion caused by the weathering,erosion,leaching and other processes of agricultural soil,part of the heavy metal elements are also lost with the soil,and the lost heavy metal entered the surface sediments of Poyang Lake eventually.(3)The assessment results by geo-accumulation index method indicated that the pollution degree of heavy metals in surface sediments of Poyang Lake was in the order of Cd>Mo>Hg>Cu>Pb>Zn>W>Sr>As>Ni>Co>Sb>Cr>V,among which Cd had the highest pollution degree,and the average pollution level of the whole lake reached partial moderate pollution.The average values of potential ecological risk of 10 heavy metals showed the order of Cd>Hg>As>Cu>Pb>Ni>Co>Cr>V>Zn,and the heavy metals in the whole lake had high comprehensive potential ecological risk.Cd and Hg were accounting for 59.7%and 25.3%to the comprehensive potential ecological risk,respectively.The pollution degree of heavy metals in agricultural soils around Poyang Lake showed the order of Cd>Mo>Zn>Cu>Sb>W>Pb>Ni>Cr>V>Co,and the average pollution level of Cd in whole lake reached partial moderate pollution.The pollution degree of Nanchang County was most serious and the cleanest was Poyang County.The average values of potential ecological risk of 8 heavy metals showed the order of Cd>Cu>Pb>Ni>Co>Cr>V>Zn,and the heavy metals had high comprehensive potential ecological risk.Poyang County had low comprehensive potential ecological risk,and Duchang County had high comprehensive potential ecological risk.The contribution rate of Cd to the comprehensive potential ecological risk was as high as 88.5%.(4)The source apportionment results of PCA and PMF indicated that the heavy metals in surface sediments from Poyang Lake were affected by mining and industrial activities,tailings and waste residue,agricultural activities,and natural source.They accounted for 38%,28%,19%and 14%of total contribution,respectively.Unmix model apportioned 5 pollution sources of heavy metals in agricultural soils around Poyang Lake.They are natural sources,copper mine tailings,agricultural activities,atmospheric deposition and industrial activities,with contribution of 7%,13%,20%,29%and 31%,respectively.The source apportionment results showed that the pollution of heavy metals of surface sediments and agricultural soils around Poyang Lake was mainly affected by mining and industrial activities.Therefore,we should increase monitoring,control and harness force of pollutant discharge of enterprise and the control of the flux of heavy metals into the lake of the 5 River.In addition,the environmental impact of industrial and mining enterprises should be evaluated regularly to reduce the pollution sources from the source into sediment and agricultural soil,and heavy metal pollution control should be carried out in a targeted way.