Water Transport in Unsaturated Nonisothermal Salty Soil: I. Experimental Results

Abstract

This paper presents observed soil moisture redistribution within unsaturated soil in response to imposed boundary temperatures. Both salinized and solute‐free soil conditions are studied. Two different uniform initial soil water contents and solute concentrations are used for the salinized soil columns. Likewise, two different uniform initial soil water contents are used for solute‐free soil columns. High and low boundary temperatures are similar for all of the soil columns. Thus, the experiments are designed to directly observe the impacts of thermal, soil matric, and osmotic gradients on redistribution of soil water. In all cases, appreciable amounts of water move in the direction of decreasing temperature within the soil columns. This is not a general rule of soil water movement, but a result of the uniform initial water content, the presence of solute, and the imposed boundary temperatures under salinized soil, or the initial water content and the imposed boundary temperatures under solute‐free soil. For both solute‐free and salinized soils, the net amount of transported water to achieve steady‐state conditions is greater for low initial water content than for high initial water content. Therefore, the steady‐state variations in the soil moisture content increased by decreasing the initial moisture content. When the same initial water content is used for both salinized and solute‐free soils, the net water transported to achieve steady‐state conditions is greater for the solute‐free soil than for salinized soil. These observations indicate clearly that solute concentration affects soil water transport with unsaturated, nonisothermal conditions.

Dynamic effects on capillary pressure–Saturation relationships for two‐phase porous flow: Implications of temperature

“…[1][2][3][4][5][6][7][8] In addition, temperature variation may affect such flows where the hydraulic properties of the porous media such as hydraulic conductivity and water retention are temperature dependent. [9][10][11][12] Conventional approaches for modeling of immiscible two-phase flow in porous media involve the use of an extended version of Darcy's law 3,13,14 for multiphase flows in conjunction with the use of constitutive relationships between capillary pressure, saturation, and relative permeability (P c -S-K r ) based on quasi-static conditions. 15,16 These P c -S-K r relationships are highly nonlinear in nature and depend on flow hydrodynamics (dynamic/static) conditions, capillary and viscous forces, contact angles, grain size distribution, surface tension, boundary conditions, fluid properties, and length scales of observation.…”

Method for Maintaining One‐Dimensional Temperature Gradients in Unsaturated, Closed Soil Cells

“…Providing one-dimensional temperature conditions in laboratory soil columns remains challenging. Prunty and Horton (1994) noted that laboratory studies aimed at one-dimensional temperature conditions (e.g., Nassar and Horton, 1989;Bach, 1992) often demonstrated evidence of ATI. This interference creates a radial temperature distribution, in addition to the axial temperature distribution from imposed boundary conditions, thus altering the coupled processes of heat and water movement within the column.…”

“…Prunty, 1992), unlike the linear or convex distributions frequently reported in the literature (cf. Nassar and Horton, 1989). This concavity comes from the nonlinear distribution of thermal properties associated with water redistribution in response to thermal gradients (Prunty and Horton, 1994).…”

Rapid Migration of Radionuclides Leaked from High-Level Water Tanks: A Study of Salinity Gradients, Wetted Path Geometry and Water Vapor Transport

“…water-vapor partial pressure; aqueous-phase density; aqueous-phase viscosity; aqueous phase enthalpy; and osmotic pressure were also incorporated into the solution schemes. Calculation of the osmotic pressure required introduction of an osmotic efficiency coefficient to express the degree to which dissolved salt would be effective in reducing the total pressure (Nassar and Horton, 1989). Calculation of this coefficient required estimation of the water film thickness for different Hanford sediments as a function of pressure head.…”