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(30-05) Biotest-directed fractionation and identification: a suitable tool for determination of realistic exposure situations? Grote, Matthias*,1, Walter, Helge1, Brack, Werner1, Vrana, Branislav1, Schüürmann, Gerrit1, Blanck, Hans2, Altenburger, Rolf1, 1 UFZ - Center for Environmental Research, Leipzig, Germany2 Botanical Institute, Göteborg, Sweden ABSTRACT- Biotest-directed fractionation and identification is a procedure to unravel site specific contaminants by linking biotests and chemical analysis which has recently been applied to various environmental samples. A sample or a sediment extract is subject to several fractionation steps followed by biotesting and chemical analysis of the effective fractions leading to a list of potentially toxic substances. Finally a confirmation step is performed in order to be sure that the toxicity found is caused by the suspected substances. However, this confirmation step is more or less a purely technical validation of the methodology. As generally this procedure is conducted with sediment extracts it does not allow to draw conclusions about the relevance of the identified toxicants for the bulk water. A wider understanding of this confirmation step is needed which accounts for aspects of bioavailability and milieu factors as pH and light intensity to make a site specific estimation of the relevance of the identified toxicants. In the present study a biotest-directed toxicity identification was performed for sediment extracts from the Baltic Sea using aquatic organisms (algae and bacteria) as detectors for toxicity resulting in a list of toxicants consisting mainly of PAHs. Subsequently the identified toxicants were analysed in the water body above the sediment using passive sampling devices. As several PAHs are considered to be phototoxic the influence of light on their toxicity was determined and their relevance at the site is discussed. Key words: sediment contamination, algae biotest, biotest-directed fractionation |
