Physicochemical Limitations to the Biotransformation of Pentachlorophenol in Soil

Abstract

A chemical mass balance approach was employed to monitor rates and extent of pentachlorophenol (PCP) removal, mineralization, volatilization and bound residue formation in biologically active soils. For soils having an initial PCP mass loading of 10 mg/kg, 20 mg/kg, 40 mg/kg and 80 mg/kg, the extent of contaminant removal after 45 days of treatment was 93%, 63%, 51%, and 26% respectively. Over the same period, abiotic controls snowed an average PCP removal of 19%. Modeling PCP removal using first order kinetics resulted in rate constants of 0.065 ± 0.002, 0.019 ± 0.003, 0.015 ± 0.003, and 0.009 ± 0.001 day-1 for soils with initial PCP mass loadings of 10, 20, 40, and 80 mg/kg, respectively. Volatilization of PCP or its organic chemical intermediates was insignificant over the 45 day treatment period. The extent of PCP mineralization after 45 days of treatment was 8.8, 6.6, 3.0, and 1.3% for soils having initial PCP loadings of 10, 20, 40, and 80 mg/kg, respectively. By estimating the aqueous solubility of PCP in soil pore water, a simple physical-chemical model was developed to evaluate the biotreatment potential of PCP contaminated soils. Modeling results were used to delineate a range of environmental conditions under which biological treatment would be practical.