Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Report on biotests applied to runoff and sediment pore water

To the best of our knowledge, the present study represents the largest collection of data on the ecotoxicity of stormwater samples. It was found that the potential ecotoxicological impact varies between storms at each site, between sites and in relation to its impact of different test organisms.

In relation to the performance of tests in a biotest battery, it was found that the Microtox test was the most sensitive of the three tests applied. Although issues with toxicity of blanks were encountered in the Microtox tests, the analysis of these procedural blanks enabled a baseline level of Microtox ecotoxicity to be identified against which the toxicity of stormwater samples could be meaningfully compared.

This is particularly important to keep in mind for interpreting Microtox data and decided when toxicity levels are of concern. The quantitative detection of toxicity was better in Microtox than in algal and rotifer tests. Thus, in 76% of the samples toxicity could be quantified in terms of EC-values when tested in the Microtox test whereas this was only possible for 39% of samples tested in algal tests. Some correlation between results of algal and rotifer tests and weak correlation between some rotifer and bacteria data.

The study support the use of a battery of biotests approach as the concomitant use of biotests resulted in a higher detection than would have been achieved using only a single test. The classification of stormwater toxicity suggested in the present study gives only an indication of the potential toxic impact of stormwater on organisms in the receiving waters. It is however noteworthy that most of the stormwater samples were classified as moderately to low toxic and that in only 10 of 38 tested samples could toxicity not be detected using the biotest battery.

The biotest approach allows for detection of toxicity of whole samples and also for ranking between samples based on the toxicity. The use of even simple toxicity identification procedures enabled conclusions to be drawn on the main compounds contributing to the toxicity of the whole sample.

Thus, it was found that addition of EDTA tends to reduce sample toxicity in comparison to the whole sample by a variable amount suggesting that metals make an important contribution to the total sample toxicity and concentrations of metals varies between storms. It was however also clear from the study that comprehensive chemical analyses will still be needed to verify results of TIE and to implement source tracking and elimination measures.

The metals found at the Stockholm site and organic compounds (most often polyaromatic hydrocarbons) found in other studies of stormwater will primarily be bound to suspended solids.

Suspended solids may settle as sediments in retention ponds or be transported to receiving waters during rain events. The resuspension tests included in the present study showed the potential toxic impact of sediment bound contamination and future activities should include toxicity tests of sediments and/or aqueous extracts hereof along with chemical analysis to identify priority pollutants. As a general rule for both water and sediment samples, chemical analysis and biotests should be used as complementary methods not as alternatives in vulnerability assessments of stormwater.

It is currently, however, primarily the results of chemical analyses, which form the basis for hazard and vulnerability assessments of stormwater discharges. Chemical analyses will only give information on the identity and quantity of single compound and will not reveal anything about the toxicity of the whole sample. The work carried out in T4.4 demonstrates the applicability of biotests for addressing issues of ecosystem vulnerability with the main benefit of including biotests being
detection and ranking of toxicity of whole stormwater samples. It is strongly recommended that a biotest approach is included in regulatory frameworks especially in relation to setting up a monitoring strategy in relation to fulfilling the needs for addressing the issues of Ecological status of receiving waters as outlined in the Water Framework Directive.

Biotests, Vulnerability, Toxicity, Algae, Rotifers, Microtox

Informazioni correlate

Reported by

Universite P. et M. Curie
UMR Sisyphe, Universite Paris 6, 4 place Jussieu
F-75005 Paris
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