The Kinetics of the Reaction of Ozone with Phenanthrene in Unsaturated Soils

Abstract

ABSTRACT The kinetics of the heterogeneous reactions of gaseous ozone with soil water, the soil matrix, and phenanthrene were investigated in a cycling batch reactor. The rate of ozone decomposition in soil water is described as a first-order rate expression with respect to the gaseous ozone concentration. The rate expression for the reaction of gaseous ozone with the soil matrix in moist soil can be described as second order overall, first order with respect to both gaseous ozone and soil organic matter concentrations. The rate of reaction for ozone with the soil matrix was observed to be independent of the ozone gas pore velocity (over the range of 0.18 to 23.4 cm/s), indicating that the overall reaction rate is dominated by chemical reactions rather than by interfacial mass transfer. During ozonation of a phenanthrene-contaminated soil, two pseudo-first-order kinetic regions with respect to the concentration of phenanthrene were observed. This is thought to be due to the nonuniformity of the surface di...