AVAILABILITY OF SORBED TOLUENE IN SOILS FOR BIODEGRADATION BY ACCLIMATED BACTERIA

Batch soil microcosms were used to evaluate the sorption and bioavailability of toluene in an organic soil containing acclimated bacteria. Most toluene sorption occurs rapidly but a small fraction (< 10%) sorbs at a much slower rate that continues to decrease over time. Toluene sorption appears to be a two-phase process (fast and slow) and true equilibrium may take a significant period of time to achieve. Measurement of both sorbed and solution phase toluene concentrations indicate that acclimated bacteria quickly utilize toluene under aerobic conditions. Within 2 days total toluene was reduced below measurable levels. Desorption of most toluene from soil is rapid, thereby becoming available to acclimated bacteria in the aqueous phase. However, a small quantity of toluene desorbs very slowly and becomes available for biodegradation at a rate limited by desorption. © 1990.