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(M/EH122) Assessing the bioavailability of heavy metals in sediments, comparing Tubifex with DGT probes in three fresh water sediments. Stroomberg, Gerard1, Velzen, Martin1, Wegener, Jan Willem1, 1 ABSTRACT- Assesment of bioavailability of metals in sediments with the aquatic oligochaete Tubifex is hampered by the facts that the internal concentrations of some metals are regulated by the organism. Although cadmium and lead reach steady state within 7 days, internal concentrations of copper and zinc do respond to changes in the exposure conditions of the animals. Using a a-biotic technique, Diffusive Gradients in Thin-films (DGT), to asses the bioavailabilty of these four metals, only metals dissolved in the water above the sediment were accumulated onto the film. In order to assess the impact of the presence of Tubifex on the availability of the metals, an experiment was conducted using three fresh water sediments from different field locations. All sediments were placed in large glass beakers in a single tank filled with copper free water. Each sediment was placed in four beakers (20 cm deep) and submerged in the tank and left to rest for one month. One beaker with both Tubifex and a DGT probe, one beaker with only Tubifex, one beaker with only a DGT probe and one sediment beaker as a control. The DGT probes were 15 cm long, as to provide a depth profile on metal availability. The first 1 cm of the probe was left in contact with the water phase. After two weeks of exposure, samples were taken from the pore water, sediment and Tubifex. DGT probes were cut in 1 cm sections. All samples were analysed for metal content. Future research will focus on deployment of DGT probes in the field. Key words: Tubifex tubifex, diffusive gradients in thin-films, metals, sediment |
