Cadmium distribution in sediment profiles of the six main rivers in southern Taiwan

Dynamic cadmium distribution has been studied in six main rivers flowing through the largest, most highly developed and polluted area of southern Taiwan. Sediment profile samples were also analyzed for Cu, Cr, Zn, Ni, Pb, Co, Mn, Fe, carbonates, Mn-oxides, Fe-oxides and organic matter in order to characterize the geochemical environment and to identify the pollutant sources. Higher Cd concentrations (about 3.5 mg/kg) at depths of 0-10 cm have been detected in the samples of Yenshui, Ell-ren and Potzu rivers, associated to the history of industrial activity in their catchments. According to the linear correlation coefficient (r) between Cd and the geochemical components, carbonates are the primary Cd binding phase in the Ell-ren river (r=0.85), and Cd comes from the same pollutant sources of those containing Cr, Ni, Cu and Zn (r>0.80). Cadmium concentration in the Potzu and Peikang river sediments is probably due to waste deposits rich in Cr and Cu (0.54