“…In most cases, only the infinitesimal changes in these quantities are of practical interest, rather than their absolute values. As such, expressions can be derived by differentiating the above three thermodynamic functions and combining the First and Second Laws of thermodynamics (e.g., Edlefsen & Anderson, 1943; Gardner & Chatelain, 1947; Schroeder, 2000). These are …”
Section: Thermodynamic Treatment Of Soil Water Potentialmentioning
confidence: 99%
“…The preceding thermodynamic principles reveal a unique advantage of the Gibbs function in studying soil water potential over other thermodynamic potentials (e.g., Edlefsen & Anderson, 1943; Slatyer & Taylor, 1960), because temperature and external pressure (usually atmosphere) in Equation are generally easy to determine or control for soil systems (e.g., Gardner & Chatelain, 1947). A decade after the first formal definition of soil water potential by the ISSS in 1963 (Aslyng et al., 1963), this concept was updated again by the second Terminology Committee of Commission I with further detail, and more thoroughly from the perspective of thermodynamics: The total potential, ψ t , of the constituent water in soil at temperature T 0 , is the amount of useful work per unit mass of pure water, in J/kg, that must be done by means of externally applied forces to transfer reversibly and isothermally an infinitesimal amount of water from the state S 0 to the soil liquid phase at the point under consideration.…”
Section: Thermodynamic Treatment Of Soil Water Potentialmentioning
confidence: 99%
“…In most cases, only the infinitesimal changes in these quantities are of practical interest, rather than their absolute values. As such, expressions can be derived by differentiating the above three thermodynamic functions and combining the First and Second Laws of thermodynamics (e.g., Edlefsen & Anderson, 1943;Gardner & Chatelain, 1947;Schroeder, 2000). These are…”
Section: Thermodynamic Potentialsmentioning
confidence: 99%
“…The preceding thermodynamic principles reveal a unique advantage of the Gibbs function in studying soil water potential over other thermodynamic potentials (e.g., Edlefsen & Anderson, 1943;Slatyer & Taylor, 1960), because temperature and external pressure (usually atmosphere) in Equation 17are generally easy to determine or control for soil systems (e.g., Gardner & Chatelain, 1947). A decade after the first formal definition of soil water potential by the ISSS in 1963 (Aslyng et al, 1963), this concept was updated again by the second Terminology Committee of Commission I with further detail, and more thoroughly from the perspective of thermodynamics:…”
Section: Previous Interpretations Of Soil Water Potential Using Therm...mentioning
Soil water potential is a cornerstone in defining the thermodynamic state of soil water required to quantify phenomena such as water phase change, water movement, heat transfer, electric current, chemical transport, and mechanical stress and deformation in the earth's shallow subsurface environment. This potential has historically been conceptualized as free energy stored in a until volume of soil water. Though the concept of soil water potential has been evolving over the past 120 yr, a consensual definition is still lacking, and answers to some fundamental questions remain controversial and elusive. What are the origins and mechanisms for the free energy of soil water? Can the common mathematical expression of soil water potential as superposition of gravitational, osmotic, and matric potentials be used to define water phase transitions in soil? Are these major components of soil water potential independent or coupled? Is pore water pressure always tensile under unsaturated conditions? If so, how can soil water density be as high as 1.7 g cm −3 ? How do adsorptive soilwater interactions originating from the electromagnetic field around and within soil particles transfer to mechanical pore pressure? In this review, the authors (a) provide critical analysis of historical definitions of soil water potential to identify their strengths, limitations, and flaws; (b) synthesize the origins of electromagnetic energies in soil to clarify the fundamental differences between adsorptive and capillary soil water potential mechanisms; (c) introduce a recently emerging concept of soil matric potential that unifies contributions of adsorption and capillarity to soil water potential; and (d) illustrate the generality and promise of the unified definition of soil water potential for answering some of the fundamental questions that remain elusive to the hydrology, geoengineering, and geoscience communities.
“…In most cases, only the infinitesimal changes in these quantities are of practical interest, rather than their absolute values. As such, expressions can be derived by differentiating the above three thermodynamic functions and combining the First and Second Laws of thermodynamics (e.g., Edlefsen & Anderson, 1943; Gardner & Chatelain, 1947; Schroeder, 2000). These are …”
Section: Thermodynamic Treatment Of Soil Water Potentialmentioning
confidence: 99%
“…The preceding thermodynamic principles reveal a unique advantage of the Gibbs function in studying soil water potential over other thermodynamic potentials (e.g., Edlefsen & Anderson, 1943; Slatyer & Taylor, 1960), because temperature and external pressure (usually atmosphere) in Equation are generally easy to determine or control for soil systems (e.g., Gardner & Chatelain, 1947). A decade after the first formal definition of soil water potential by the ISSS in 1963 (Aslyng et al., 1963), this concept was updated again by the second Terminology Committee of Commission I with further detail, and more thoroughly from the perspective of thermodynamics: The total potential, ψ t , of the constituent water in soil at temperature T 0 , is the amount of useful work per unit mass of pure water, in J/kg, that must be done by means of externally applied forces to transfer reversibly and isothermally an infinitesimal amount of water from the state S 0 to the soil liquid phase at the point under consideration.…”
Section: Thermodynamic Treatment Of Soil Water Potentialmentioning
confidence: 99%
“…In most cases, only the infinitesimal changes in these quantities are of practical interest, rather than their absolute values. As such, expressions can be derived by differentiating the above three thermodynamic functions and combining the First and Second Laws of thermodynamics (e.g., Edlefsen & Anderson, 1943;Gardner & Chatelain, 1947;Schroeder, 2000). These are…”
Section: Thermodynamic Potentialsmentioning
confidence: 99%
“…The preceding thermodynamic principles reveal a unique advantage of the Gibbs function in studying soil water potential over other thermodynamic potentials (e.g., Edlefsen & Anderson, 1943;Slatyer & Taylor, 1960), because temperature and external pressure (usually atmosphere) in Equation 17are generally easy to determine or control for soil systems (e.g., Gardner & Chatelain, 1947). A decade after the first formal definition of soil water potential by the ISSS in 1963 (Aslyng et al, 1963), this concept was updated again by the second Terminology Committee of Commission I with further detail, and more thoroughly from the perspective of thermodynamics:…”
Section: Previous Interpretations Of Soil Water Potential Using Therm...mentioning
Soil water potential is a cornerstone in defining the thermodynamic state of soil water required to quantify phenomena such as water phase change, water movement, heat transfer, electric current, chemical transport, and mechanical stress and deformation in the earth's shallow subsurface environment. This potential has historically been conceptualized as free energy stored in a until volume of soil water. Though the concept of soil water potential has been evolving over the past 120 yr, a consensual definition is still lacking, and answers to some fundamental questions remain controversial and elusive. What are the origins and mechanisms for the free energy of soil water? Can the common mathematical expression of soil water potential as superposition of gravitational, osmotic, and matric potentials be used to define water phase transitions in soil? Are these major components of soil water potential independent or coupled? Is pore water pressure always tensile under unsaturated conditions? If so, how can soil water density be as high as 1.7 g cm −3 ? How do adsorptive soilwater interactions originating from the electromagnetic field around and within soil particles transfer to mechanical pore pressure? In this review, the authors (a) provide critical analysis of historical definitions of soil water potential to identify their strengths, limitations, and flaws; (b) synthesize the origins of electromagnetic energies in soil to clarify the fundamental differences between adsorptive and capillary soil water potential mechanisms; (c) introduce a recently emerging concept of soil matric potential that unifies contributions of adsorption and capillarity to soil water potential; and (d) illustrate the generality and promise of the unified definition of soil water potential for answering some of the fundamental questions that remain elusive to the hydrology, geoengineering, and geoscience communities.
Enthalpy and entropy of volatilization from dilute aqueous solutions for 26 volatile organic compounds (VOCs) have been determined using Henry's Law values reported in published literature. Based on the linearity of van't Hoff plots, for the temperature ranges common in soils, the differences in heat capacities of volatilization for reactants and products are very small for the VOCs studied.
When volatile solutes such as VOCs are present in soil water, soil‐gas concentration often nearly is in equilibrium with the dissolved solute. Setchinow salting coefficients are linearly related to dissolved partial molar volumes for halogenated aliphatic compounds. Based in part on approximations from this linear relationship, equilibrium deviations from Henry's Law behavior for dilute VOC concentrations due to capillary tension or the presence of ionic solutes are small for common soil conditions.
Since gas/water partitioning of VOCs if temperature‐sensitive and since annual soil moisture and temperature patterns vary geographically in documented fashion, geographically specific temporal patterns in soil‐gas VOC concentrations are predictable in vadose zones containing dissolved VOCs. A U.S. map depicting these general soil‐moisture and temperature patterns is provided. Gas concentrations in vadose zones containing dissolved VOCs tend to increase with increasing temperature and decreasing moisture content due to equilibrium partitioning effects.
Diagrams useful for understanding the results of soil‐gas surveys and the efficacy of various remediation options are provided. The effect of bubbles in VOC water‐sample vials on aqueous concentrations is shown to be very small. The effect of head‐space volume of soil samples on estimated soil‐gas concentrations can be large.
The various equations used by several authors to express the partial molar free energy of soil moisture as a function of certain parameters were compared with a "parent" equation derived in this paper; certain basic differences of approach apparently lead to results which are identical only under certain conditions; from the parent equation, equations with practical applicability are derived. The methods available for the experimental determination of the partial molar free energy of soil moisture are reviewed with special reference to the assumptions underlying the application of the freezing-point depression of soil moisture. (Abstract retrieved from CAB Abstracts by CABI’s permission)
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