Mineralization potential for phenol in subsurface soils

The mineralization of 14C-phenol to 14CO2 was determined in each horizon of four contrasting soil profiles using a modification of the approach used to determine heterotrophic potential in aquatic environments. Short-term mineralization rates were determined at 12 concentrations ranging from 5 to 10,000 μg phenol kg-1 dry soil and the data were reduced using a hyperbolic saturation model similar to that used for describing enzyme kinetics. The kinetic terms V/sub max/ and K were estimated using nonlinear regression. Phenol was mineralized in all soil samples at each concentration examined. The V/sub max/ values ranged from 0.018 to 22.4 ng phenol kg-1 dry soil s-1; K values ranged from 20 to 2355 μg phenol kg-1 dry soil. Generally within each soil profile, V/sub max/ tended to decline with increasing depth; however, the magnitude and pattern of this decline varied widely according to soil type. The V/sub max/ in the Ap horizons (3-15 cm) ranged from 2.49 to 13.8 ng kg-1 dry soil s-1. The V/sub max/ in the B22t horizons (30-101 cm) ranged from 0.839 to 2.65 ng kg-1 s-1, and V/sub max/ in the deepest horizons (81-187 cm) ranged from 0.145 to 4.75 ng kg-1 dry soil s-1. This study indicates that soil horizon and soil type are important determinants of the biodegradation of phenol, a potential ground water pollutant, as it passes through the soil column