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Sediment toxicity assessments must address bioaccumulation potential of bound contaminants. This potential has been associated with the desorption of chemicals including many mutagens and carcinogens from sediment into interstitial waters. Environmental impacts and health hazards of sediment-bound normal, alkylated and heterocyclic aromatic hydrocarbons are functions of their entry into food webs, the activation of promutagens, and bioaccumulation processes. Activation phenomena occurring in benthic organisms may generate genotoxic agents not extractable with non-polar solvents used for chemical analysis.
Co-solvent theory was applied to prepare aqueous-based extracts from petroleum contaminated sediments from Pass Fourchon, LA. Co-solvent solubilization of contaminants is thermodynamically related to partition coefficients which govern bioavailability to benthic organisms. Sediments were extracted into acetic acid co-solvent mixtures (0, 10, 20, and 50 %, in seawater) and mutagens mobilized into the extracts were detected by the Salmonella typhimurium mutagenicity assay with and without activation. Direct-acting mutagens were mobilized at all co-solvent concentrations, causing reversions in strain TA102, but not in TA97a, TA98, or TA100. Promutagens were detectable in all extracts after activation with Arochlor-induced rat liver S9. Increasing co-solvent strength seemed to suppress the extraction of water soluble mutagens but enhanced the extraction of lipophilic mutagens. Differing sensitivities were noted among the tester strains, with TA102 being most sensitive and TA98 showing no response to the mutagens. Mutagenicity varied among co-solvent concentrations, perhaps reflecting the mobilization of different arrays of compounds. Chemical analysis of co-solvent extracts by GC/MS yielded identifications of possible mutagenic constituents.
mutagens, sediments, co-solvent extraction, GC/mass spectrometry, risk assessment
Professor, Research Associate V, Louisiana State University, School of Veterinary Medicine, Aquatic Toxicology Laboratory, Baton Rouge, LA