EFFECT OF DESORPTION AND INTRAPARTICLE MASS-TRANSFER ON THE AEROBIC BIOMINERALIZATION OF ALPHA-HEXACHLOROCYCLOHEXANE IN A CONTAMINATED CALCAREOUS SOIL

A laboratory study was performed to investigate the effects of desorption from soil aggregates on the biomineralization kinetics of α-hexachlorocyclohexane (α-HCH). Desorption and biodegradation of α-HCH in mixed soil suspensions at 20 °C were shown to be controlled by intraparticle mass-transfer processes. Two models were applied to the desorption and biodegradation kinetic data, a first-order model (FOM) and a sorption-retarded radial diffusion model (RDM). Only the RDM could explain the effect of aggregate size on HCH desorption and bioconversion rate. It also yielded the best fit to the desorption kinetic data. Estimated effective diffusivities were in the order of 5 × 10−17 m2/s. Biodegradation kinetics of α-HCH could only be described by the RDM by assuming that microorganisms could penetrate the inner parts of the aggregates. © 1990, American Chemical Society. All rights reserved.