Heavy Metal Pollution Characteristics And Pb And Hg Isotopes Implication In Surface Sediments From Xining Section Of Huangshui River

28 surface sediments samples were collected from Xining section of Huangshui River to investigate the geochemical characteristics,pollution characteristics and potential sources of heavy metals in surface sediments from Xining section of Huangshui River.The contents of heavy metals and isotope ratios of Pb and Hg in sediments were determined by Inductively Coupled Plasma-Mass Spectrometry(ICP-MS)and Mercury Analyzer.Statistical method,Pollution Load Index method and Potential Ecological Risk Index method were used to analyze the spatial distribution characteristics and pollution situation of Cr,Hg,Co,Ni,Cu,Zn,Pb and Cd in the surface sediments from Xining section of Huangshui River.The sources of heavy metals in surface sediments of Xining section of Huangshui River were analyzed by Correlation Analysis,Principal Component Analysis and Pb,Hg isotope analysis using statistical methods.The main conclusions are as follows.(1)The contents of Cr,Hg,Co,Ni,Cu,Zn,Pb and Cd in the surface sediments from Xining section of Huangshui River increased significantly from upstream to downstream.Pollution Load Index method showed that heavy metals in sediments of Xining section of Huangshui River were non-pollution to strong pollution,and the pollution load was medium.the Potential Ecological Risk Index method showed that the order of ecological risk of each heavy metal element was Hg>Cd>Co>Cu>Pb>Ni>Cr>Zn.The comprehensive Potential Ecological Risk Index(RI)of heavy metals showed that the samples with medium ecological risk or above accounted for 96.43%,and the Ecological Risk Index of each heavy metal in the surface sediments of Xining section of Huangshui River was Hg.(2)REE contents in surface sediments from Xining section of Huangshui River ranged from 89.75 to 217.58mg/kg,with an average of 153.56mg/kg.The variation trend of REE contents from 28 samples were consistent,and the changes of composition characteristics were small.LREE was relatively enriched,and HREE was relatively depleted with moderate negative Eu anomalies and without Ce anomalies.The source rock and mineral compositions of sedimentary rocks controlled the compositions of REE in surface sediments from Xining section of Huangshui River,while chemical weathering had no effect on the compositions of REE.The characteristic parameters,upper continental crust-normalized and chondrite-normalized REE patterns were close to soils in Qinghai and sediments in Yellow River,indicating that REE of surface sediments in Xining section of Huangshui River mainly came from weathered materials of Huangshui River and provided a partial source of REE in sediments of the Yellow River.(3)The elements of Co,Ni,Cu,Zn,Pb and Hg in the surface sediments of Xining section of Huangshui River may be affected by natural sources such as natural weathering of rocks and minerals,and industrial sources such as wastewater discharged from industrial production.Cd is mainly affected by agricultural and industrial production.Cr is mainly affected by natural weathering of rock minerals.(4)The results of Pb and Hg isotope analysis showed that Pb was mainly affected by natural sources such as soil parent material,human activities had little effect on it.Hg was mainly affected by coal combustion.