Characteristics And History Of Heavy Metal Content In Sediments Of The Nansi Lake

Heavy metal pollution has received widespread attention due to the toxic behavior,persistence,and bioaccumulation.Nansi Lake is the conveyance channel of South-to-North Water Transfer Project(east route)and is important for both drinking and irrigation water in Shandong province,rapid development of economy has led to the increasing pollution of heavy metals in sediment.In order to analyze the pollution characteristics and history of heavy metal in Nansi Lake surface sediment,Isotope dating,enrichment factor,multivariate statistical analysis,PMF model,geo-accumulation index,pollution load index and potential ecological risk factor were used to assess heavy metal pollution,the following results were obtained:1)The enrichment of Cd is the most obvious,reached medium enrichment level and significantly affected by human activities.The contribution of Cd to potential risk index is 76.1%,which is the decisive factor for ecological risk status of Nansi Lake.Cu and Pb had large geo-accumulation and pollution load index,which are two kinds of heavy metal that need to be monitored.The ecological risk level for Nansi Lake is medium,with some part of Zhaoyang Lake and Weishan Lake reaching high risk level.The upper lake basin had a larger area,accepted more pollutants and heavy metal diffusion was hindered,which resulted that pollution load of the upper lake is greater than that of the lower lake.2)According to the results of multivariate statistical analysis and PMF model,the sources of heavy metal in Nansi Lake surface sediment are mainly four categories:Natural source contribution elements are Cr,Co,Sc,Ni,Zn and part of Pb and Mn.Industrial source contribution elements are Pb,Cu,Mn and part of Cd and As.The main heavy metal of agricultural sources discharging are As and Cd,and the contribution to Cu,Cr and Zn is also objective.The main contributing elements of the traffic source are Pb,Cr and part of Ni and Zn.3)From 1896 to 1960,the sources of heavy metal in Nansi Lake were dominated by natural source and mining activities.From 1960 to 2006,the sources of heavy metals in Nansi Lake were natural source,coal consumption during industry production and agricultural production using fertilizers and pesticides.