Influence of a Nonionic Surfactant on the Water Retention Properties of Unsaturated Soils

Abstract

Surfactants are widely used in household products, industrial pro-100 g L Ϫ1) of the formulated herbicide product and 0.1 cesses and as adjuvants to improve the delivery and effectiveness of to 0.5% (1 to 5 g L Ϫ1) of the spray tank solution. As a agrochemicals. Due to their amphiphilic nature, surfactants tend to accumulate at gas-liquid and solid-liquid interfaces, and thus, have result, the amount of surfactant applied to agricultural the potential to influence water flow and retention in unsaturated lands can be substantial, particularly if repeated herbisoils. The objective of this study was to investigate the effects of a cide applications are required throughout the growing nonionic surfactant, Triton X-100, on the interfacial properties and season. capillary pressure-water content relationships of F-70 Ottawa sand Due to their amphiphilic properties, possessing both and Appling soil. In the presence of surfactant, soil water contents hydrophilic and lipophilic moieties, surfactants tend to decreased incrementally as the surfactant concentration was increased accumulate or adsorb at gas-liquid and solid-liquid interfrom 0 g L Ϫ1 up to the critical micelle concentration (CMC) of Triton faces. Below the surfactant concentration at which miX -100 (0.15 g L Ϫ1). Over the same surfactant concentration range, celles begin to form, the critical micelle concentration the surface tension of water decreased from 7.2 ϫ 10 Ϫ2 J m Ϫ2 to 3.2 ϫ (CMC), interfacial adsorption of surfactants typically 10 Ϫ2 J m Ϫ2 while solid-liquid contact angle decreased from 40؇ to 10؇. No further changes in interfacial properties or soil water characteris-results in a lowering of both the surface tension of water tics were observed at surfactant concentrations above the CMC. The and the contact angle between the solid and aqueous experimental results were used to develop and evaluate alternative phases (Rosen, 1989). Therefore, the water holding cascaling approaches to describe concentration dependent changes in pacity of soils is likely to decrease in the presence of soil water characteristics based on the van Genuchten model. A scaling surfactants. This phenomenon could increase the depth factor that incorporated both surface tension and content angle relaof infiltration during spray events, and create a positive tionships provided accurate predictions of soil water retention curves pressure gradient between regions of surfactant-rich and over a range of surfactant concentrations. A simplified form of the surfactant-free soil water (Tschapek et al., 1981, 1991; scaling factor also was developed, on the basis of a single fitting Karkare et al., 1993; Karkare and Fort, 1993). Karkare parameter without the need for surface tension and contact angle data. Although further validation of the simplified scaling factor will and Fort (1993) reported that soil water content was be required, this approach offers an efficient means to describe the substantially altered in the presence of surfactants, with effects of concentration dependent change...

Effect of impurities in description of surface nanobubbles

“…Results demonstrate that for significantly high surface coverage of impurities, the (gas-side) contact angle can significantly reduce and indeed exhibit a value close to that suggested by experimental findings [7,19]. Such lowering of the contact angle is similar to that which are suggested by experimental evidences of equilibrium adsorption of common surfactants to water [36,37]. The…”

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

“…Although the structure and function of the molecules of the wide number of surfactants vary widely, all possess a hydrophilic "head" group and a hydrophobic "tail" group (Karagunduz, 2001). 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).…”

“…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). This is especially noticeable when the soil particles have hydrophobic, or water repellent, coatings (Doerr et al, 2007;Kostka et al, 2007;Hallett, 2008).…”

“…The anionic polymer XPAM increased water retention: seepage rates decreased with increasing XPAM dosages in five soil types (Lentz, 2007). A soil-remediation surfactant formulated to increase drainage, Triton-X, produced the opposite effect of substantially reducing soil water content (Karagunduz et al, 2001). Adding an anionic surfactant to seed-germinating growth media increased the media's total water holding capacity in proportion to surfactant dosage, and the available water increased significantly after adding surfactant (even at the lowest dose) to the media (Urrestarazu et al, 2008).Capillary rise was found to decrease significantly when anionic and nonionic surfactants were tested in sand columns, with the decrease in direct proportion to surfactant concentration (Wiel-Shafran et al, 2006).…”

Effect of Pore-Water Surface Tension on Tensile Strength of Unsaturated Sand

“…Using this relationship, matric suction in any unsaturated soil system wetted with surfactant is scaled by the ratio of the surface tension of the solution to the surface tension of the water (or any reference liquid). Karagunduz et al (2001) reported that in addition to surface tension, the presence of surfactant might also alter the contact angle of the liquid-gas interface.…”