Abstract

                                The effect of temperature, clay type, organic matter, pH and soil types of adsor- ption of carbendazim was investigated. Adsorption of carbendazim decreased with increase in temperature on both Ca-Montmorillonite and Ca-Kaolinite clays. Among. clay types, Ca-montmorillonite was superior in adsorbing this fungicide over Ca-Kaolinite. The adsorption of carbendazim was inferred to be through physical means under the specified conditions from the values of change in free energies. Adsorption was found to be highest on activated soils as reflected by their higher values of Freundlich's constants followed by natural and organic matter-free soils, respectively. The decre- ased adsorption of carbendazim on removing organic matter with H,O, pretreatment suggested the importance of organic master in adsorption The effect of pH on ads- orption of this fungicide revealed ionization of molecules through protonation at lower pH values. Thus carbendazim was adsorbed on soils in larger quantities as a result of protonation followed by ion-exchange process. Among soils, highest adsor- ption of this fungicide was found in laterite soils.

Key words :