The Influence of Two Surfactants on Infiltration into a Water-Repellent Soil

Abstract

Water-repellency which affects infiltration, evaporation, erosion, and other water transfer mechanisms through soil has been observed under several natural conditions throughout the world. Surfactants can be used to mitigate the consequences of soil water repellency. The infiltration rates of two surfactants applied at concentrations of 500, 1000, 3000, and 5000 mg L−1 were measured on laboratory columns of sand treated to create a stable water-repellent system. All of these surfactant solutions had a surface tension equal to 0.035 N m−1 Drop-penetration times (DPT) of these solutions were also measured for these solutions. An aqueous ethanol solution with an identical surface tension as the surfactant solutions was also used. The DPT decreased and the infiltration rate increased as the surfactant solution concentration increased. The results are explained by adsorption of surfactant which caused an increase in surface tension of the solution. Adsorption of surfactants enhanced soil rewetting so that treated columns that were dried had high subsequent infiltration rates with water. Because the adsorption of surfactants greatly affects infiltration, prescription of surfactant treatment on a theoretical basis is not feasible. Although some basic concepts can be established, the utility of surfactants in managing water repellent systems will depend on empirical observations.