Metal speciation and pollution assessment of Cd and Pb in intertidal sediments of Donghai Island, China

The speciation contents of Cd and Pb were investigated with the modified BCR method on the intertidal sediments of Donghai Island, China. For 24 surface samples of eight sections, the order was residual>exchangeable>oxidable>reducible for Cd and residual>reducible>oxidable>exchangeable for Pb; the four-fraction summation and single fraction concentration of Cd and Pb all decreased gradually from west to east because of different TOC; from high tidal zones to low tidal zones, the four-fraction summation, the residual fraction and its percentage all increased gradually due to the influence of the decreasing particle size of surface sediments. No accordant changing rule was found for the vertical distribution of Cd and Pb. About 32.0% of Cd and 36.9% of Pb for the nonresistant fraction presented the evidence of anthropogenic enrichment. The Risk Assessment Code suggested that a low risk for Pb and a medium risk for Cd to the intertidal environment.