Eine Biotestbatterie als ökotoxikologisches Beurteilungsinstrument in der Bodensanierung: Am Beispiel TNT-kontaminierter Böden

The objective of the presented research was to address the suitability of a battery of bioassays for a site-specific ecotoxicological evaluation of contaminated soils. Experimental fields are located at an abandoned armament site where the topsoil was contaminated by the explosive 2,4,6-Trinitrotoluene (TNT) and several co-contaminants. At this site, different soil treatments were established at technical scale to investigate the efficiency of a newly developed phytoremediation technology. Being part of an extensive monitoring programme, the test battery was intended to evaluate changes of soil toxicity in the course of remediation. The battery was compiled of five rather standardised test methods used in ecotoxicology: a phytotoxicity test with garden cress (Lepidium sativum), a springtail reproduction test with Folsomia candida (Collembola) and soil respiration measurements (basal and substrate induced respiration). In addition to these soil assays two aquatic tests based on the luminescent bacterium Vibrio fischeri (acute toxicity and mutagenicity) were included to assess the toxicity of aqueous soil extracts. Biological data generated by the test battery reveal a differentiated toxicity of complex contaminated soil samples. Observed differences in toxicity are in relative agreement with a gradient of TNT-contamination between experimental fields as described by chemical analyses. The five bioassays revealed clear differences in sensitivity. The acute luminescent bacteria toxicity test conducted with soil leachates proved to be a sensitive screening indicator of water-extractable toxicity. Bioassay data from all treatment variants largely indicate a reduction of soil toxicity during a 17 months remediation period, supposedly reflecting decreased soil concentrations of nitroaromatic compounds as shown by chemical analyses. These observations indicate a positive impact of the remediation procedures applied, but further monitoring is essential.