Application of a sediment quality triad and different statistical approaches (Hasse diagrams and fuzzy logic) for the comparative evaluation of small streams.

In order to evaluate the ecotoxicological contamination of 12 aquatic sites in streams within the catchment area of the Neckar River, a sediment quality triad (SQT) approach was applied. In contrast to Chapman's original triad approach, not only sediments, but also surface waters were examined. In brief, to obtain a comprehensive insight into the potential ecotoxicological hazard, both acute toxicity and more specific effects such as mutagenic, genotoxic, teratogenic, dioxin- and estrogen-like responses were recorded. Different statistical methods (ranking, cluster analyses, Hasse diagram techniques, and fuzzy logic) for the evaluation and presentation of the SQT data were compared with respect to the needs of environmental decision-making. Results document advantages and disadvantages of the methods applied for the evaluation and classification of data within the complex data matrixes. The ranking procedure presented as well as the Hasse diagram technique seem to be suitable tools to elucidate the pattern of the ecotoxicological load. However, these classification methods require expert knowledge to interpret the ranking results with respect to decision-making in environmental sciences and policy. In contrast, fuzzy logic allows both to develop site-specific expert systems in order to assess the ecotoxicological burden and to give insight into the pattern of the contamination.