Determination of High Resolution Pore Water Profiles of Trace Metals in Sediments of the Rupel River (Belgium) using Det (Diffusive Equilibrium in Thin Films) and DGT (Diffusive Gradients in Thin Films) Techniques

The techniques of diffusional equilibrium in thin films (DET) and diffusional gradients in thin films (DGT) were used to obtain high resolution pore water profiles of total dissolved and labile trace (mobilizable) metals in the sediments of the Rupel River, Belgium. DGT measures labile metal species in situ by immobilizing them on a resin gel after diffusion through a diffusive gel whereas for DET an equilibrium is established between the DET gel and the pore water. Concentrations of Pb and Zn obtained by DGT were in good agreement with the results obtained by centrifugation, and thus were well buffered by rapid equilibrium with the solid phase, whereas Fe, Mn and Cd were very tightly bound to the sediment phase and large differences were observed between the labile and the total metal concentrations. Cu, Zn, Co and Ni show intermediated behavior.