| To understand the transport and bioavailability of heavy metals in the surface sediment of Daliao River system, nine samples of surface sediment were collected. Clay content, pH, and Eh of these sediment samples were measured. Total contents and chemical speciation of Cu, Pb, Zn and Ni in the sediment were determined. In addition, the concentrations of Cu, Pb, Zn and Ni in the pore water of the sediment were determined separately by DGT (diffusive gradient in thin film) method and traditional centrifuge method. The total contents of Cu, Pb, Zn and Ni in the sediment were 16.8-49.2, 12.9-55.8, 38.7-152.8 and 18.1-39.0 mg/kg, respectively. The ratios of DGT measured concentrations c(DGT) to heavy metal concentrations in pore water were lower than 0.5, showing lower replenishment of these metals from solid to the liquid and lower bioavailability of the metals in the sediments. Correlation analysis showed that c(DGT) of Cu was significantly influenced by Cu in the carbonate fraction (r=0.633，p<0.05), while c(DGT) of Pb was influenced by Pb in the exchangeable fraction (r=0.617, p<0.05). Ni in the exchangeable, Mn oxides, organic matter (OM) and Fe oxides fractions may contribute to thec(DGT) of Ni (r>0.650, p<0.05). In addition, pH was also an important factor influencing the release of heavy metals from solid to liquid in sediments. |
