TY - JOUR

T1 - A review on recent developments in soil water retention theory

T2 - Interfacial tension and temperature effects

AU - Bachmann, Jörg

AU - Van Der Ploeg, Rienk R.

N1 - Copyright: Copyright 2008 Elsevier B.V., All rights reserved.

PY - 2002/8/1

Y1 - 2002/8/1

N2 - Study of soil physical processes such as water infiltration and redistribution, groundwater recharge, solute transport in the unsaturated zone, compaction and aeration in variably saturated soil hardly is possible without knowledge of the capillary pressure of the soil water as a function of the degree of saturation. Pore space topology, interfacial tension, and temperature probably are the most important physical factors affecting the capillary pressure at a given water content. Despite intensive research in the past decades on the water retention characteristics of soils, our knowledge of their response to varying ambient conditions is far from being complete. Current models of soil water retention as well as of hydraulic conductivity for unsaturated porous media often still use the simplified representation of the pore system as a bundle of cylindrical capillaries. Physical effects, like surface water film adsorption, capillary condensation and surface flow in liquid films, as well as volumetric changes of the pore space are often ignored. Consequently, physical properties of the solid phase surfaces, and their impact on water adsorption and flow, are often not considered. The objective of this contribution is to review various interfacial properties with possible application to the conventional water content - matric potential relation of soils. The ignoring of interfacial effects on the water retention of soils is widespread in the literature. The motivation of this paper is therefore to point out some of the more significant deficiencies of our current knowledge on the interaction of solid particle surfaces and the liquid phase in soil. We will first emphasize the impact of the wetting angle on the wetting of dry soil and to present the impact of interfacial tension of the liquid phase in the three-phase system. At low water content, the transition from capillary-bound water to adsorbed water and to wetting films is discussed separately, because of its impact on the rewetting process of dry soil. Finally, we discuss the impact of temperature on interfacial tension and water retention of soil as a second important interfacial process affecting directly the water retention of porous media.

AB - Study of soil physical processes such as water infiltration and redistribution, groundwater recharge, solute transport in the unsaturated zone, compaction and aeration in variably saturated soil hardly is possible without knowledge of the capillary pressure of the soil water as a function of the degree of saturation. Pore space topology, interfacial tension, and temperature probably are the most important physical factors affecting the capillary pressure at a given water content. Despite intensive research in the past decades on the water retention characteristics of soils, our knowledge of their response to varying ambient conditions is far from being complete. Current models of soil water retention as well as of hydraulic conductivity for unsaturated porous media often still use the simplified representation of the pore system as a bundle of cylindrical capillaries. Physical effects, like surface water film adsorption, capillary condensation and surface flow in liquid films, as well as volumetric changes of the pore space are often ignored. Consequently, physical properties of the solid phase surfaces, and their impact on water adsorption and flow, are often not considered. The objective of this contribution is to review various interfacial properties with possible application to the conventional water content - matric potential relation of soils. The ignoring of interfacial effects on the water retention of soils is widespread in the literature. The motivation of this paper is therefore to point out some of the more significant deficiencies of our current knowledge on the interaction of solid particle surfaces and the liquid phase in soil. We will first emphasize the impact of the wetting angle on the wetting of dry soil and to present the impact of interfacial tension of the liquid phase in the three-phase system. At low water content, the transition from capillary-bound water to adsorbed water and to wetting films is discussed separately, because of its impact on the rewetting process of dry soil. Finally, we discuss the impact of temperature on interfacial tension and water retention of soil as a second important interfacial process affecting directly the water retention of porous media.

KW - Capillary pressure

KW - Contact angle

KW - Interfacial tension

KW - Temperature

KW - Water adsorption

UR - http://www.scopus.com/inward/record.url?scp=0142010401&partnerID=8YFLogxK

U2 - 10.1002/1522-2624(200208)165:4<468::AID-JPLN468>3.0.CO;2-G

DO - 10.1002/1522-2624(200208)165:4<468::AID-JPLN468>3.0.CO;2-G

M3 - Article

AN - SCOPUS:0142010401

VL - 165

SP - 468

EP - 478

JO - Journal of Plant Nutrition and Soil Science

JF - Journal of Plant Nutrition and Soil Science

SN - 1436-8730

IS - 4

ER -