Effect of Peroxidase Addition on Sorption, Desorption, and Binding of Phenolic Mixtures in Soil

Peroxidase enzymes can enhance the rate and extent of contaminant binding to soil organic matter and immobilize the contaminant within the soil matrix, and thus prevent its transport into the subsurface. This study focused on evaluating the binding of phenol, dichlorophenol, and naphthol, individually and as mixtures, on two sandy loams belonging to the Haynie series. U-ring-14 C-labeled target chemicals were used as radio tracers to track the distribution of the pollutant among various soil components. Bottle-point adsorption experiments with constant soil dosage were conducted for a period of seven days followed by sequential desorption of the " quickly desorbing " fraction with synthetic groundwater. The " slowly desorbing " chemicals were removed by multiple extractions with methanol. The chemicals associated with humic/fulvic acids and the soil (humin) fraction were determined by combustion of soil before and after alkali-extraction. Results illustrated that enzyme addition increased adsorption of phenol, and DCP and lead much more than desorption hysteresis, whether they were present alone or as a mixture. Addition of enzyme also resulted in dramatic enhancement in contaminant binding. The presence of co-contaminant did not affect adsorption or desorption of phenol or DCP, but to some extent decreased binding to HA/FA and soil humin fraction. Addition of enzyme did not enhance adsorption of naphthol but increased binding to HA/FA and soil humin fraction.