Behavior and fate of surfactants in soil

Abstract

Although a growing number of investigations have dealt with selected aspects of the behavior of surfactants in soil and their effects on various soil properties, systematic approaches like those applied to pesticides or heavy metals are still rare. Considering that soil is exposed to a considerable quantity of surfactants, it would appear necessary to do more intensified research in this field. Based on a comprehensive review of the literature, the author briefly outlines the behavior and fate of surfactants in soil and presents a synopsis from the viewpoint of a pedologist. Even at low concentrations, surfactants seem to alter soil physics, soil chemistry, and soil biology significantly, whereby sorption processes play a dominant role. The report tries to integrate the most important research results in this field and to interpret them against the background of the complex structure of the soil system.

Effect of detergents from laundry greywater on soil properties: a preliminary study

“…The main cause of K sat reduction can be rationalized as a small pore clogging in the soil due to the adsorption of surfactant. Surfactant effects on water infiltration and on percolation in soils are a function of soil type and surfactant characteristics (Kuhnt 1993). Surfactants decrease the capillary rise of water in soil columns when mixed with sands or clayey soils by decreasing water surface tension (Smith and Gillham 1999).…”

Influence of Anionic Surfactant on Saturated Hydraulic Conductivity of Loamy Sand and Sandy Loam Soils

“…Surfactants are not all degradable in aquifers; they may be adsorbed on mineral surface and sediments, or transported with aqueous solutions [14]. Kuhnt (1993) demonstrated how the adsorbed surfactants can change the physical, chemical, and biological properties of soils [15], e.g., create water-repellent soils [16], and evidence also suggests that accumulated surfactant in soils is harmful to both agricultural productivity and environmental sustainability [17,18].…”

“…At this point, the hydrophobic non-polar regions make maximum contact with one another to form a hydrocarbon-like core, with the hydrophilic polar-regions in maximum contact with water [19]. This formation of micelles will in turn (1) reduce the surface tension and interfacial tension of the aqueous solution [9,15,16]; and (2) enhance the solubility of water-insoluble compounds such as hydrophobic organic compounds (HOC) [9,14]. The resulting surfactants may then be potentially used in the in-situ flushing of HOC from soils [20,21].…”

“…In their comparison of three surfactants (Triton X-100, Aerosol 22 and HDTMA) on the infiltration rate of three soil types (clay, clay loam, and loam), Mingorance et al (2007) observed that each surfactant shifted the infiltration rate at various levels for a given soil type, with a specific surfactant either increasing or decreasing the infiltration rate in the various soils under study [25]. Kuhnt (1993) noted that surfactant may either increase or decrease the infiltration rate, with the shift depending upon the degree of soil water repellency, the method employed to apply the surfactant, and the effects of the surfactant on surface tension and the liquid/solid contact angle [15].…”

“…Many studies were undertaken to analyze the collapse of soil aggregates induced by anionic surfactant [15,25,26]. Since the reduced surface tension leads to higher wettability of primary particles, aggregates lose their stability more easily making the particles more prone to dispersion.…”