Toxicity and genotoxicity of industrial soils polluted by polycyclic aromatic hydrocarbons (PAHs)

Three soil samples polluted by PAH were assessed for both acute (Vibrio fischeri Microtox® test], Daphnia magna, Thamnocephalus platyurus) and chronic (Pseudokirchneriella subcapitata) toxicity, as well as for genotoxicity (Vibrio fischeri M169, Mutatox® test]). Bioassays were performed on soil water leachates and on soil solvent extracts to characterise not only the fraction of water soluble pollutants but also to evaluate less soluble and soil-bound pollutants. The toxicity of the water leachates was low to moderate (from 0 to 30 toxic units) whereas the toxicity of the methanol extracts was about 100 to 10,000 toxic units. Although only slightly toxic, the genotoxicity of water leachates was clearly demonstrated. This finding shows that acute and chronic toxicity assays alone may not be sufficient to characterize soil hazards. A step procedure to characterise soil ecotoxicity is therefore proposed which allows one to study the pollutant mobility, toxicity and genotoxicity. It can be used to identify the hazard, to classify soil hazards and thus map contaminated sites, to assess the success of treatment and finally to monitor rehabilitated sites.