Ecotox-evaluation strategy for soil bioremediation exemplified for a PAH-contaminated site.

During a bioremediation of a PAH-contaminated site chemical and biological analyses were carried out. The biological investigations included ecotoxicological analyses in the aqueous extract, (Pseudomonas putida, Photobacterium phosphoreum, daphnids, algae, fish) and analyses in the soil with introduced organisms (plants, earthworms) and natural soil organisms (nematodes, microorganisms). In all test systems a correspondence between decreasing toxicity and degradation of the easily biodegradable PAHs was found. From investigations with aqueous extracts therefore not only conclusions on potential risks for groundwater can be drawn, but these tests also seem to allow risk assessments for soil inhabitants. Furthermore with these tests comprising dilution series the extent of toxicity for soil organisms can be quantified more precisely than with terrestrial investigations. Of all aquatic test systems a constant remaining toxicity was found only in the Microtox text. The test with Daphnia magna indicated the intermediate formation of organism specific toxic metabolites. Therefore useful information may be obtained with biological analyses which complement chemical analyses. For an extensive assessment of a contaminated site a test battery is advisable.