Assessment of the Water-Extractable Genotoxic Potential of Soil Samples from Contaminated Sites

A screening method for the evaluation of the water-extractable genotoxic potential of soil is proposed. Due to the low sensitivity of genotoxicity test systems, PAD-1 resin was used as solid phase to concentrate less hydrophilic compounds from aqueous soil extracts. Concentrated and nonconcentrated aqueous soil extracts from 19 soil samples were evaluated using three genotoxicity assays: the umu test according to the German standard method with Salmonella typhimurium TA1535/pSK1002, the NM2009 test with S. typhimurium NM2009, and the SOS Chromotest with Escherichia coli PQ37. All tests were performed according to a uniform protocol using microplates. Results indicate that the nonconcentrated water elutriates should be tested because the genotoxic potential of some soil samples is extremely high. Additionally, water elutriates should be concentrated by solid phase extraction to avoid false-negative results. The results of this study show that the genotoxic risk of sites contaminated with PAHs or mineral oils may be underestimated if only nonconcentrated samples are tested. The solid-phase extraction method with a concentration factor of 30 for these low soluble compounds is suitable for distinguishing between background genotoxicity of noncontaminated sites and anthropogenic contaminations.