The use of flux-corer experiments in the determination of heavy metal re-distribution in and of potential leaching from the sediments

Metal dynamics between sediments, interstitial water and overlying water are particularly complex. The movement of metals, their availability, and possible toxicity are influenced by various chemical and physical reactions and factors such as oxygen/redox gradients, pH, grain size, etc. To study the impact of oxygen on the release from and the re-distribution of Cd, Pb, Zn and Cu in sediments, flux-corer experiments have been optimised and performed. The flux experiment was carried out using 3 identical sediment cores. The first (control) sediment core was completely characterised before, the two other cores after the experiment. Pore water extractions and sequential extractions were performed on 2 cm depth intervals throughout the 20 cm long sediment cores. In the flux experiment, the sediment cores were exposed to a small volume of overlying water, which was continuously renewed. The change of trace metal mobility was assessed by following concentration-changes in the outflow. It has been found by the use of the flux-corer experiment, that the Cd, Pb, Zn and Cu concentrations in the outflow are at least 3-6 times higher during oxic conditions. Flux-corer experiments can be useful tools to facilitate the study of the change of heavy metal mobility and distribution in the sediment induced by the change in surface water policy.