Surfactants and soil water evaporation and migration

Abstract

1. Water evaporation from soil and sand columns is smaller when the surfactant is placed on the surface, and larger when it is located at the bottom. Water evaporation from soil and sand mixed with the surfactant is as high as without the surfactant. 2. The fact that water evaporation from soil and sand depends on the location of the surfactant in the column is accounted for by the dominant role of migration but not by the suppressive action of the surfactant film on water evaporation. 3. Water migration from sites with surfactant towards sites without surfactant is caused by two pressures: the capillary and the additional pressure arising from the spreading of the surfactant. 4. The importance of the additional pressure on water migration is shown by experiments which rule out the existence of a capillary pressure difference.