SORPTION OF ORGANOPHOSPHORUS AND CARBAMATE INSECTICIDES BY SOIL

The adsorption and desorption of aldicarb, phorate, parathion, terbufos, and chlorpyrifos were studied in five soils with various organic matter contents. Sorption reached equilibrium in the soils within approximately 2 h. Sorption was positively correlated with organic matter content. Hysteresis was observed in adsorption and desorption isotherms. Adsorption decreased and desorption generally increased in soils oxidized by treatment with H2O2. Differences in the Freundlich κ constant among insecticides were correlated with the chemicals' water solubilities, partition coefficients, and parachors. Models were developed to explain the variability in adsorption and desorption constants. Adsorption occurred mainly through hydrophobic interactions with organic matter surfaces. © 1979, American Chemical Society. All rights reserved.