Speciation and Bioavailability of Heavy Metals in Sediments Taken from Wetland in the Huaihe River Basin

摘要

The fractions of heavy metals in sediment cores taken from the riverine wetland located in the Huaihe River Basin, China, were analyzed using BCR (European Communities Bureau of Reference) sequential extraction techniques. The results revealed that the total concentrations of Cd, Cr, Cu, Pb, and Zn ranged from 0.09-0.38, 47.6-70.2, 14.0-92.1, 19.6-35.9, and 53.8-227.0mgkg-1, respectively. The significant increase in the values of enrichment factors (EF) and the geoaccumulation index (Igeo) from about 4cm depth layer and maximum values approaching 5 and 1 near the surface, respectively, indicated the rapid growth of pollutant discharge especially for Cd, Cu, and Zn in recent years. Furthermore, the proportions of the different fractions (i.e.,acid extractable, reducible, oxidizable, and residual fractions) of Cd, Cr, Cu, Pb, and Zn had changed drastically. The significant increases in the proportions of reactive forms (acid extractable, reducible, and oxidizable fractions) of heavy metals from about 4cm depth layer to top layer suggested a marked increase in the mobility and bioavailability of Cd, Pb, Cu, and Cr. Finally, significant positive correlations between total organic carbon (TOC) and reactive fractions suggested that heavy metals, especially reactive fractions, tended to be absorbed by organic materials. The most significant trend in increases indicated that Cd and Cu possessed the most conspicuous mobility and bioavailability. In addition, larger proportions of reactive fractions of Zn indicated that Zn had constant mobility and posed a significant ecological risk to aquatic organisms in the riverine wetland.