Evaluation of the Bioavailability of Metals in Sediment from the Southern Coastal Wetland of the Qiantang Estuary by Using Diffusive Gradients in Thin Films Technique

Metal pollution has become an major issue governing the wetland ecosystem health. The southern coastal wetland of the Qiangtang Estuary are facing unusual perturbation due to rapid development along the embayment in recent decades. This study evaluated the bioavailability of metals (Cu, Pb, Cd, Cr and Zn) in the sediment of the southern coastal wetland of the Qiangtang Estuary using diffusive gradients in thin films (DGT) techniques and compared with several methods based on total metal content. The results showed that the contents of Cr, Pb, Cd and Cu in sediment, as detected using DGT, were considerably correlated with the exchangeable fraction and the content in Phragmites australis roots, while a weak correlation was observed for Zn. Therefore, DGT analysis could be used to evaluate the bioavailability and potential risk of Cr, Cd, Pb and Cu for P. australis . Quantitative indices, such as DGT concentration, bioaccumulation in P. australis , geoaccumulation index ( I geo ) and potential ecological risk index ( RI ), revealed that Cd was a major potential ecological risk factor along the southern coast wetland of the Qiantang Estuary, especially in the upstream region, which is potentially more vulnerable to the anthropogenic pollution.