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

In the present work changes in the adsorption of four C-14-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 polyoxpethylene 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. (C) 1996 Elsevier Science Ltd