Pesticide adsorption in a soii-water system in the presence of surfactants

In the present work changes in the adsorption of four 14C-labelled pesticides -diazinon, acephate, atrazine and ethofumesate- on a sandy loam soil, induced by application of anionic, cationic and nonionic surfactants - tetradecyltrimethylammonium bromide (TDTMA), sodium dodecyl sulphate (SDS) and polyoxyethylene sorbitanmonooleate (Tween 80)-, were determined using a batch equilibrium method. Three concentrations of each surfactant were used: lower, equal to or higher than the critical micellar concentration. The increases or decreases in the values of the Freundlich constant K for adsorption of the different pesticides by soil in the experiments revealed that the behaviour of pesticides in soil-water systems with micelle-forming surfactants mainly depends on the degree of hydrophobicity of the pesticide and the type of surfactant, as well as on the concentration of surfactant in the system.