THE USE OF FLUX-CORER EXPERIMENTS IN THE DETERMINATION OF HEAVY-METALRE-DISTRIBUTION IN AND OF POTENTIAL LEACHING FROM THE SEDIMENTS

Metal dynamics between sediments, interstitial water and overlying wat er are particularly complex. The movement of metals, their availabilit y, and possible toxicity are influenced by various chemical and physic al reactions and factors such as oxygen/redox gradients, pH, grain siz e, etc. To study the impact of oxygen on the release from and the re-d istribution 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-w as completely characterised before, the two other cores after the expe riment. Pore water extractions and sequential extractions were perform ed on 2 cm depth intervals throughout the 20 cm long sediment cores. I n the flux experiment, the sediment cores were exposed to a small volu me of overlying water, which was continuously renewed. The change of t race metal mobility was assessed by following concentration-changes in the outflow. It has been found by the use of the flux-corer experimen t, that the Cd, Pb, Zn and Cu concentrations in the outflow are at lea st 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 sur face water policy. (C) 1998 IAWQ. Published by Elsevier Science Ltd.