Influence of the sample preservation mode to assess the chronic toxicity of an industrial effluent.

Abstract To improve the preservation of effluent samples, the contribution of refrigeration, freezing, and freeze-drying techniques to maintain the toxic characteristics of the samples was evaluated. To achieve this evaluation one acute test, three long-term toxicity tests, a biochemical test (P450 induction), and a mutagenicity test (Ames test) were used on the same industrial effluent. Refrigeration and freezing demonstrated a similar capacity of preservation. However, freezing should be recommended when the delay between sampling and the start of the bioassay exceeds 48 hr. Freeze-drying did not prove to be useful in that case but this could be due to methodological problems. Nevertheless, this technique allowed the detection of mutagenic compounds because of its aptitude to concentrate effluent samples. For the toxic evaluation of the samples the advantages of the use of a battery of biotests were confirmed and it was noted that the cladoceran ( Ceriodaphnia dubia ) reproduction test and the algal ( Selenastrum capricornutum ) growth test had a higher sensitivity within the three tests used.