Adsorption of dimethoate and 2,4-D on Jordan Valley soils and their environmental impacts

The adsorption process of dimethoate and 2,4-dichloro-phenoxy acetic acid (2,4-D) on Jordan Valley soils from aqueous solution at 25 C has been studied. The adsorption isotherms may be classified as L-type of the Giles classification. The K-ads values (Freundlich equation) vary between 1.01 (JV5) and 10.36 (JV7) for dimethoate insecticide and between 4.41 (JV5) and 14.87 (JV7) for 2,4-D herbicide, depending on the soil type. The adsorption of 2,4-D herbicide on soils in the study area is about threefold higher than that of dimethoate insecticide. The adsorption process of dimethoate and 2,4-D pesticides seem to be primarily controlled by the organic matter content of the soils and the clay content (most especially montmorillonite).