Character and Sources Identification of Heavy Metals Contamination in Sediment from the Core Sediment in Nanshan Lake,the Zhalong Wetland

NSH2 sediment core from Nanshan Lake in the south of Zhalong wetland was studied,which was a typical lake for both empolder and aquaculture.The vertical distributions of heavy metals(Hg,Cd,Pb,Cr,As,Mn,Ag,Cu,Co,Fe and Zn) were investigated.The method of principal component analysis(PCA) was adopted to apportion the sources of heavy metals,and particle size,combined with 210 Pbex dating data were used to indicate characteristics,sources and polluted history of heavy metals in lake sediments since 1829.The results showed that: ① the trend of changes in accumulation in the sedimentation was rather slow in the earlier stage,then was fast in the middle stage,and finally slowed down again in the later stage.The history of elements pollution is correspondent with the production of human activities and policies of soil and water conservation of Nanshan Lake;② the contents of all elements varied smoothly before 1957,and which fluctuated slightly from 1957 to 1985.The contents of Hg,Cd and Ag increased obviously since 1985.The sources of heavy metals determined were mainly from sewage,the loss of fertilizers,and combustion of fuel such as coal and gasoline;③ natural sources of the degradation of organic matter,rock weathering and erosion,as well as the source of industrial emissions,with the contributions of 50.14%,19.90% and 10.32%,respectively.High potential risk of heavy metals existed in NSH2 sediment core.Hence,enough attention must be paid to the pollution control of lakes.Therefore,this study can provide basic data for help wetland ecological environment improvement in Zhalong wetland.