A Case Study Of Sediment Quality Assessment In Heavy Metal Polluted River

This study discussed the sediment quality assessment of heavy metals in surface sediment from Xiangjiang river (Hengyang-Zhuzhou and Yueyang sections). Geochemical properties of sediments and the contents and speciation and distribution of heavy metals in surface sediments from a 370km length section of Xiangjiang river were studied. The relationship between the speciation of heavy metals and their environmental factors have also been described. Based on Equilibrium Partitioning approach and Potential Ecological Risk method, this study established a heavy metals quality assessment method and assessed the heavy metals quality in surface sediment from Xiangjiang river with this method.Contents of Cu, Pb, Zn, Cd, Cr, As in sediments from Xiangjiang river were all higher than background values. Of these 6 heavy metals, Cd was the most polluted element, especially in Hengyang Shuikoushan area where the content of Cd reached 170.25μg/g. Cu, Pb, Zn, Cr, As in this area were also very high and their values were 514.49 pg/g,2246.09μg/g,3656.94μg/g,231.98μg/g, 408.88μg/g, exceeding their background values by 30,90,51,340,4,20 times, respectively.Four major metals Cu, Pb, Zn, Cd, in sediment from Xiangjiang river existed mainly in extractable fraction. Percentage of contents of these elements reached to 70.84-97.07μg/g. Different natures of elements cause various speciation characteristics. Cu, Pb existed mainly in reducible fraction, and Zn, Cd existed mainly in weak soluble fraction. Bioavailability for four metals varied in the order of Cd>Pb>Zn>Cu.The results show that Cd was the most contaminated heavy metal in the sediment from Xiangjiang river. The result implies that emissions from enterprises along the river was a major impact factor for the spatial distribution of heavy metals in the sediment in Xiangjiang river area.The results of heavy metals quality assessment in sediment trom Xiangjiang River show that Hengyang upper (Ⅰ), Hengyang middle (Ⅲ), Hengyang lower (Ⅲ), Zhuzhou (Ⅱ), Yueyang upper (Ⅱ), Yueyang lower (Ⅱ).