Peroxidase-Mediated Stabilization of 2,4-Dichlorophenol in a Model Humin-Mineral Geomaterial

Enhanced polymerization of phenolic contaminants induced by the application of the enzyme horseradish peroxidase (HRP) has drawn attention of many researchers due to its potential for remediation of contaminated soils. This study utilized 2,4-dichlorophenol (DCP) as a probe solute to evaluate the ability of HRP to stabilize pesticide derivatives in a model humin-mineral geomaterial. The model soil was derived from a natural surface soil treated with alkali to remove humic and fulvic acids. The resulting humin-mineral material had SOM content and chemical characteristics that were different from the parent soil. Sorption of DCP was complete within 24 hrs and most of the sorbed DCP was removed from the geomaterial by water and methanol suggesting weak solute-sorbent interactions. Phase distribution of DCP polymerization products (DPP) also appeared to be complete within 24 hrs, but a significantly higher amount of the solute was stabilized in the presence of HRP. The total extractable solute decreased, and DPP bound residues increased with contact time and initial solute concentration. These results illustrate the potential of utilizing HRP-mediated oxidation for in situ stabilization of pesticide derivatives, such as DCP, in humin-mineral geomaterials representative of soils found below the root zone.