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(79-14) Influence of storing time on measured toxicity within Whole Effluent Assessment. De Maagd, P. Gert-Jan*,1, Kerkum, Lia1, Rotteveel, Serge1, 1 RIZA, P.O. Box 17, Lelystad, The Netherlands ABSTRACT- Within the Dutch Whole Effluent Assessment (WEA) procedure the quality of effluents is assessed based on acute and chronic toxicity, bioaccumulation, genotoxicity and persistence. For that purpose effluent samples are taken and transported to laboratories in which a series of tests is performed. One of the key-issues within the validation of test procedures within WEA is whether or not during storage an effluent sample remains representative for the actual effluent it is taken from. Sorption, volatilisation and degradation in the sample can be expected to lead to a reduced toxicity with storage time, especially since no preservative compounds can be added to samples used in bioassays. In the present study the acute toxicity of four industrial waste water samples from various origins is studied as a function of storage time. In the present study the influence of storage time at −20°C is assessed using acute toxicity tests at four taxonomic levels ( Microtox™-test, algae, daphnids and fish). The toxicity was assessed on fresh samples, and on samples that were stored for 3 days, 2 weeks, 2 months and 6 months at −20°C. For fish and Microtox™ no signifcant changes in toxicity were found for any of the samples. The results of the algae tests showed a high variability hampering a straightforward interpretation of test results. For daphnids a clear time-dependent reduction in toxicity (up to a factor 3) was found for one sample. Although no extreme losses in toxicity were found, no general rule for advisable maximum storage time could be deduced. It may be advised to check the constancy of toxicity if long storage times are needed, for example when a TIE (toxicity identification and evaluation)-study is performed. Key words: effluent, storage, bioassays, Whole Effluent Assessment |
