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Abstract Background Floodplains are biodiversity hotspots and provide numerous ecosystem services. In recent decades, however, 70–90% of Europe's floodplains have been structurally degraded. Accordingly, many (inter-)national programs aim to restore and protect floodplain ecosystems. The success of such measures also depends on the chemical contamination, especially of floodplain soils and sediments, which serve as sinks and sources for a variety of pollutants. In this study, we assess the current ecotoxicological status of a floodplain restoration site along the Main river (Frankfurt am Main, Germany) and estimate its development potential with respect to the influence of a local industrial plant and potential legacy contaminations. We therefore use in vitro effect-based methods (EBMs) testing for baseline toxicity, mutagenicity, dioxin-like and estrogenic activities, coupled with chemical analysis. Results Of all water bodies analyzed, the overall toxicity was highest in two flood depressions. In the respective water phase, estrogenic activities exceeded the environmental quality standard and sediment samples were positive for all tested endpoints. Chemical analysis of these sediments revealed high concentrations of polycyclic aromatic hydrocarbons. Soil samples from frequently flooded areas showed the highest mutagenic potential for both frameshift and point mutations with and without metabolic activation. The industrial effluent showed baseline toxic, mutagenic, and dioxin-like activities, that were highly diluted in the Main river. Respective sediments, in turn, showed significantly elevated activities and chemical contamination downstream of the industrial discharge. Conclusion Based on the results of this study, we rate the overall ecotoxicological status of a recently established tributary and groundwater-fed ponds as good, and identified two flood depressions near the Main river as hot spots of contamination. We assume that the observed mutagenicity in the floodplain soils is related to legacy contaminations from former aniline and azo dye production. In terms of the development potential of the floodplain restoration site, we emphasize considering the remobilization of pollutants from these soils and suppose that, in the long term, pollution of the Main river and the local industrial plant may negatively impact sediment quality in its tributaries. With this study, we confirmed the utility of in vitro EBMs for identifying chemically and ecotoxicologically relevant sites.
Kuschik-Maczollek et al. (Mon,) studied this question.