SORPTION OF LOW-LEVELS OF NONIONIC AND ANIONIC SURFACTANTS ON SOIL - EFFECTS ON SORPTION OF TRITICONAZOLE FUNGICIDE

The sorption of two anionic surfactants and a series of seven nonionic alkylphenolethoxylate surfactants of increasing hydrophilic/lipophili c balance (HLB) in a loamy clay soil was evaluated. The effect of low doses of these surfactants on the sorption characteristics of the fung icide triticonazole was investigated. The critical micellar concentrat ion (CMC) of the surfactants in pure water and soil-water systems, and surfactant sorption were estimated by surface tension measurements us ing a batch equilibration technique. Triticonazole sorption, alone and in the presence of low doses of surfactants, was also measured by bat ch equilibration. CMC of the alkylphenol surfactants increased with th eir HLB. The sorption of surfactants increased with their lipophilicit y. CMC in the soil-water systems were considerably higher than in pure water. Sorption of the most lipophilic alkylphenol surfactants at the higher doses significantly increased triticonazole sorption. Proposed mechanisms are modifications of soil surface properties, and increase of soil organic carbon content. Sorption of the other nonionic and an ionic surfactants only resulted in monomeric surfactant concentrations in pore water, and did not affect triticonazole sorption. (C) 1998 So ciety of Chemical Industry.