Heavy Metals in Dianshan Lake

In this study, the sediment of the Dianshan Lake, one of the major freshwater sources for Shanghai, was analyzed at varying depths to determine its historical environmental toxicity profile. Six heavy metal elements (Cd, Cr, Pb, Zn, Hg, and As) were analyzed, using a three step Sequential Extraction Procedure to determine the speciation of each metal, which gives a more accurate profile on their mobility and bioavailability(toxicity). The order of mobility was found to be Cd \u3e Pb \u3e Zn \u3e Cr \u3e Hg \u3e As. Levels of mobile species of Cr, Zn, Hg, and As were found to increase in the past decade, while Cd and Pb have remained constant. Peaks in mobile or total species concentration for Cr, Pb, and As are observable at 9-13 cm depth, corresponding to China\u27s rapid industrialization in the 1980\u27s