Application of a battery of biotests for toxicity characterization of stormwater.

The environmental impacts of urban stormwater and road runoff have gained increasing interest during the last decade, an interest reinforced by the implementation of the EU Water Framework Directive with its clear statements on the need to tackle non-point sources of pollution. Although several studies dealing with toxicity assessment of urban wet-weather discharges have been published, the toxic impact of urban runoff is not well described in the literature. Wet-weather discharges can contain a complex combination of environmental pollutants and hence a chemical characterisation may not suffice in explaining its toxic potential. As an alternative monitoring strategy, the use of a battery of toxicity tests has been recommended as a more appropriate tool for screening and assessing the potential receiving water impacts of stormwater discharges, however, only a few such studies have been carried out. It is within this context that the current study, conducted within the DayWater project, aims to assess the order of magnitude of toxic effects of chemical constituents in water samples on a variety of biota (rather than specifically determine in situ toxicity) to enable the applicability of biotests as indicators for toxicity and hazard ranking of both sediments and the water samples to be evaluated.