Genotoxicity of bioremediated soils from the Reilly Tar site, St. Louis Park, Minnesota

An in vitro approach was used to measure the genotoxicity of creosote-conta minated soil before and after four bioremediation processes. The soil was t aken from the Reilly Tar site, a closed Superfund site in Saint Louis Park, Minnesota. The creosote soil was bioremediated in bioslurry, biopile, comp ost. and land treatment, which were optimized for effective treatment Mutag enicity profiles of dichloromethane extracts of the five soils were determi ned in the Spiral technique of the Salmonella assay with seven tester strai ns. Quantitative mutagenic responses in the plate incorporation technique w ere then determined in the most sensitive strains, YG1041 and YG1042. Mutag enic potency (revertants per microgram extract) in YG1041 suggested that co mpost, land treatment, and untreated creosote soil extracts were moderately mutagenic with Arochlor-induced rat liver (S9) but were nonmutagenic witho ut S9. However. the bioslurry extract was strongly mutagenic and the biopil e extract was moderately mutagenic either with or without S9. A similar tre nd was obtained in strain YG1042. The strong mutagenic activity in the bios lurry extract was reduced by 50% in TA98NR, which suggested the presence of mutagenic nitrohydrocarbons. Variation in reproducibility was 15% or less for the bioassay and extraction procedures. Bioavailability of mutagens in the biopile soil was determined with six solvents, water-soluble mutagens a ccounted for 40% of the total mutagenic activity and they were stable at ro om temperature. The mutagenic activity in the bioslurry and biopile samples was due to either the processes themselves or to the added sludge/manure a mendments. The in vitro approach was effective in monitoring bioremediated soils for genotoxicity and will be useful in future laboratory and in situ studies.