COMPARISON OF TOXICITY DETECTED BY 5 BIOASSAYS DURING BIOREMEDIATION OF DIESEL FUEL-SPIKED SOILS

Biodegradation of petroleum contaminants is an effective and generally inexpensive approach for reducing their concentrations in soils. Howe ver, little information is available on the toxicological status of co ntaminated soils and the fate of target hydrocarbons following bioreme diation. Four texturally distinct soils were contaminated with diesel fuel and bioremediated in microcosms at 22 degrees C, with moisture co ntents of 85% of soil water holding capacity, and nitrogen (N) and/or phosphorus (P) nutrient amendments. The progress of bioremediation was monitored using chemical and toxicological analyses. Soil toxicity wa s measured using five short-term bioassays: seed germination, red bloo d cell hemolysis, solid-phase Microtox, SOS-chromotest, and Toxi-chrom otest. Reductions in target compound concentration were not always pre dictive of reductions in soil toxicity. Conflicting trends were indica ted by the toxicity test results. For example, total petroleum hydroca rbon analysis revealed decreased hydrocarbon concentrations in all fou r soils following bioremediation but seed germination and seedling eme rgence data indicated increased soil toxicity. In contrast, the Microt ox test data indicated decreased toxicity in two of the four soils. Th ese results suggest that measurements of target contaminant concentrat ions should be complemented with several different soil toxicity bioas says, particularly when evaluating the ability of bioremediation to re duce the adverse effects of contaminants in soil. (C) 1998 by John Wil ey & Sons, Inc.