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(T/MF150) The role of salt marsh vegetation in the distribution patterns of heavy metals - a long term mesocosm study. Vorenhout, Michel1, Zorn, Mathilde1, Eijsackers, Herman1, 1 ABSTRACT- Ecosystems such as saltmarshes have an innate capacity for self-purification, strongly related to management (Vorenhout et al. 2000, ET&C). Due to restoration activities conducted in various sites, the influence of saltmarshes on the behaviour of heavy metals is of great interest to policy makers and scientists. In a long-term mesocosm experiment the influence of presence and development of vegetation on the behaviour and distribution of heavy metals has been studied. The vegetation influences the chemistry in the saltmarsh sediment via O2 leakage and production of organic matter. Oxygen-leakage changes the redox potential in the surroundings of the roots and organic matter changes the pH of the sediment via degradation processes. Both these changes are important for the partitioning of the heavy metals in a wetland. The mesocosm study is unique, due to the 10 year-period the experiment has been conducted so far. Three salt marsh mesocosms (5 x 15m each) with a tidal watermanagement were filled with sand in 1989 and polluted with harbour sediment in 1989 to 1993. In 1993 and 1999 the situation was assessed. The initial loss of half of the heavy metal load by 1993 did not continue. After ten years, the saltmarshes act as a sink for some metals (Cu, Zn), but Cd was lost from the sediment. To study the influence of the vegetation on the distribution in the sediment layers and biota, part of the Spartina anglica vegetation has been removed. The first results of this experiment showing the differences between vegetated and non-vegetated salt marshes, together with the results on PAH-distribution, will be presented. Key words: Saltmarsh, Heavy metals, Purifying function, Sink-source |
