A Survey of the Causes of Surfactant‐Induced Changes in Hydraulic Conductivity

Effects of four soil surfactants on four soil-water properties in sand and silt loam

“…Adsorption isotherms show that surface tension falls slowly as surfactant concentration increases toward the CMC, and near the CMC, surface tension drops rapidly and shortly thereafter remains constant (Valoras et al, 1969;Tsujii, 1998). The argument might be made that at concentrations below the CMC, the surfactant monomers might adhere to the surfaces of air molecules either in solution or at the air-water interface of a water This potential problem was not discussed in numerous previous articles (Fitch et al, 1989;Kuhnt, 1993;Tumeo 1997;Henry et al, 1999;Bauters et al, 2000;Feng et al, 2002;Wiel-Shafran et al, 2006;Kostka et al, 2000;Lentz, 2007;Bashir et al, 2008;Oostindie et al, 2008;Urrestarazu et al, 2008). Other researchers have applied surfactant solution in setups similar to those used in this study for finding cumulative infiltration and capillary rise (AbuZrieg, 2003;Wiel-Shafran, 2006).…”

“…Researchers have postulated that surfactants either increase or decrease aggregate stability in soils, and hydrophobic coatings on water-repellent soil particles may produce the opposite effect as is seen in hydrophilic soils (Tumeo, 1997). Although the surface tension reduction achieved by surfactants should theoretically increase hydraulic conductivity, decreases in hydraulic conductivity are reported more often in literature.…”

“…Researchers have reported both increases and decreases in hydraulic conductivity due to surfactants, and the mechanisms of action have been debated since 1969 (Tumeo, 1997).…”

“…Their head bonds strongly with water, while their tail adsorbs to surfaces such as clay minerals, air molecules in pores, or hydrophobic organic substances in soil (Kuhnt, 1993;Tumeo et al, 1997). The net effect is an apparent lowering of the interfacial tension between air-water and soil-water surfaces (Rosen, 1989;Karagunduz, 2001).…”

Numerical demonstration of surfactant concentration-dependent capillarity and viscosity effects on infiltration from a constant flux line source

“…A second way surfactants can affect unsaturated flow is via surfactant-induced hydraulic conductivity modifications. Tumeo (1997) presents a survey of the major mechanisms that may contribute to surfactant-induced changes in hydraulic conductivity. Of relevance for the system studied in the present work (dissolved butanol and silica sand) is the reduction in hydraulic conductivity that occurs as viscosity increases with increasing butanol concentration.…”