Effect of Soil Characteristics on Adsorption and Mobility of (14C)Diazinon

The adsorption and mobility of diazinon (O,O-diethyl O-2-isopropyl-6-methylpyrimidin-4-yl phosphorothioate) in 25 soils of different physicochemical properties were studied. The adsorption isotherms were found to conform to the Freundlich adsorption equation. Freundlich's constant, K, and the distribution coefficient, K d , were found to be highly significantly correlated (p<0.001) with the organic matter (OM) content when all soils or only those with an OM content above 2% were considered. There was also a significant correlation (p<0.01) OF K AND K d with the silt plus clay content of soils with an OM content below 2%. On the basis of the R f values obtained by TLC, the pesticide was found to be slightly mobile in 80% and immobile in 20% of the soils studied