Sensitivity of epigean and hypogean freshwater macroinvertebrates to complex mixtures. Part I: Laboratory experiments.

The impact of waste storage on aquatic systems is a regulatory requirement in Europe, but it is nowadays only considered to a limited extent. The complexity of mixtures, which contain many inorganic and organic compounds, requires the use of combining chemical measurements with ecotoxicological observations. This research employed an integrated laboratory and outdoor mesocosms approach to assess the effects of mixtures on freshwater macroinvertebrates. The effects of percolates coming from water having percolated through maturated secondary smelting slags, on freshwater macroinvertebrates (molluscs, crustaceans and insect larvae) were investigated under laboratory conditions using a continuous flow-through testing apparatus. Lethality (LC50 96 and 240 h) was chosen as the endpoint. The results indicate that the difference in sensitivity of macroinvertebrates is correlated with their ability to regulate or neutralize contaminants in the mixture during short-term exposure. Moreover, differences in sensitivity were dependent on duration of exposure. Because of the variability of toxicity among mixtures coming from the same waste, bioassays are required to determine the toxicities of these mixtures.