Influence of soil properties on sorption-desorption of imidacloprid

Sorption-desorption studies of imidacloprid (1-[(6-chloro-3-pyridinyl)methyl]-N-nitro-2-imidazolidinimine) were conducted using the batch equilibration method with seven U.S. soils varying in their physicochemical properties. Initial imidacloprid concentrations ranged from 3 to 300 mu g L-1. Sorption coefficients K-f and the soil properties organic carbon and CEC gave the higher single correlation coefficients; the latter due to the positive correlation between OC and CEC. Sorption was irreversible and desorption hysteresis in general was greater at low soil solution concentrations. K-f values were lower at 1:5 soil:solution ratio than at 1:1, suggesting a possible effect of a soluble soil component, such as salt concentration, on sorption; no significant differences in pH between solutions were detected.