Multiple bioassays to evaluate ecotoxicity of polluted substrates

Potential ecotoxicity of three tunnel excavation materials conditioned with two different foaming conditioners (P and F, respectively) and lubricant were screened using a multi-endpoint bioassay approach. A modified OECD artificial soil was used as control soil (C) to screen only the effect of each conditioner. Acute toxicity bioassays were conducted with a selected set of test species (Dictyostelium discoideum, Daphnia magna, Hordeum vulgare and Lactuca sativa). Tests were done immediately after adding conditioners (t0), and after one (t7) and two weeks (t14) from P and F addition. Although substrates showed no toxic effect, the sensitivity of the test species and the toxicity endpoints varied. The D. discoideum were not affected by F exposure, showing morphology and fission rate rhythm (FRR) similar to that of C. Conversely, at t0 P inhibits the FRR, while t7 and t14 were comparable with C for cell division and morphology. The D. magna values of immobilization percentage (I%) were always lower than 10% (i.e., comparable with C), with the exception of one substrate+P in which I=10%. The germination index of L. sativa and H. vulgare ranged around 80% (i.e., no phytotoxicity) and the same trend was observed for mean root length. No significant time-effect (i.e., increasing conditioner biodegradation) were recorded with the exception of one substrates, with values that turned high at t14. Thus, substrates+conditioners were not toxic but with different sensitivity showed by multiple bioassays that revealed that this approach is suitable to be applied for a quick and exhaustive screening of soil toxicity.