REPRESENTATIVE EVALUATION OF PHYTOTOXICITY - RELIABILITY AND PECULIARITIES

In order to evaluate the ecotoxicological potential of various hazardo us wastes deposited in old salt mines, various phytotoxicity rests, i. e. the Lepidium, Lemna, and Chlamydomonas tests were performed. The ev aluation was accomplished by analyzing leachates, obtained by extracti on of the samples with brines, matching in their composition to the sa lt occurring in the mines. As reported previously (WUNDRAM et al., 199 6), the salinity of these samples causes severe difficulties performin g reliable ecotoxicity tests with Lepidium and Lemna. Additionally, va rious other effects aggravate the reliability of the ecotoxicity tests . Comparison between leachates produced with brines and those obtained by extracting the samples with pure water reveal drastic differences in the toxicity determined. Surprisingly, these variations only partia lly are due to differences in the solubility of toxic compounds in bri nes and pure water. Mainly they are caused by compensatory effects of the brines. At least in the case of the root elongation test with Lepi dium, the major reason for such compensation seems to be the induction of stress growth by various factors. The results on the differences i n ecotoxicity reported demonstrate that ecotoxicity tests always have to be performed with various organisms and suitable control assays in order to obtain reliable results.