Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/31/1999
Publication Date: N/A
Technical Abstract: An isotopic exchange method was used to characterize the irreversibility of the sorption-desorption process of the insecticide imidacloprid and two of its metabolites, imidacloprid-urea and imidacloprid-guanidine, on a silty clay loam and a loamy sand soil. The exchange between 12C-pesticide molecules and 14C-labeled pesticide molecules in 24 h-preequilibrated soil suspensions was monitored and indicated that a fraction of the sorbed pesticide was resistant to desorption. A two-compartment model was applied to describe the experimental sorption data points as the sum of a reversible component and a non-desorbable, irreversible component, which was estimated from the isotopic exchange experiment. The isotopic exchange technique allowed accurate prediction of the sorption-desorption hysteresis during successive desorption cycles and appeared to be a suitable method to quantitatively characterize pesticide desorption from soil.