Air-water interfacial areas in unsaturated soils: Evaluation of interfacial domains

Molly S. Costanza-Robinson, Mark L Brusseau

Research output: Contribution to journalArticle

55 Citations (Scopus)

Abstract

A gas-phase miscible-displacement method, using decane as an interfacial tracer, was used to measure air-water interfacial areas for a sand with water Contents ranging from ∼2% to 20%. The expected trend of decreasing interfacial areas with increasing water contents was observed. The maximum estimated interfacial area of 19,500 cm-1 appears reasonable given it is smaller than the measured surface area of the porous medium (60,888 cm-1). Comparison of the experimental data presented herein with literature data provided further insight into the characterization of the air-water intterface in unsaturated porous media. Specifically, comparison of interfacial areas measured using gas-phase versus aqueous-phase methods indicates that the gas-phase method generally yields larger interfacial areas than the aqueous-phase methods, even when accounting for differences in water content and physical properties of the porous media. The observations are consistent with proposed differences in interfacial accessibility of the aqueous- and gas-phase tracers. Evaluation of the data in light of functional interfacial domains, described herein, yields the hypothesis that aqueous interfacial tracers measure primarily air-water interfaces formed by "capillary water," while gas-phase tracers measure air-water interfaces formed by both capillary and surface-adsorbed (film) water. The gas- and aqueous-phase methods may each provide interfacial area information that is more relevant to specific problems of interest. For example, gas-phase interfacial area measurements may be most relevant to contaminant transport in unsaturated systems, where retention at the air-water interface may be significant. Conversely, the aqueous-phase methods may yield information with direct bearing on multiphase flow processes that are dominated by capillary-phase behavior.

Original languageEnglish (US)
Pages (from-to)131-1317
Number of pages1187
JournalWater Resources Research
Volume38
Issue number10
StatePublished - Oct 1 2002

Fingerprint

Gases
Soils
air
Water
Air
gas
tracer
soil
Water content
gases
water
Porous materials
porous medium
water content
tracer techniques
porous media
Bearings (structural)
Multiphase flow
multiphase flow
pollutant transport

Keywords

  • Air-water interface
  • Interfacial tracer

ASJC Scopus subject areas

  • Environmental Science(all)
  • Environmental Chemistry
  • Aquatic Science
  • Water Science and Technology

Cite this

Air-water interfacial areas in unsaturated soils : Evaluation of interfacial domains. / Costanza-Robinson, Molly S.; Brusseau, Mark L.

In: Water Resources Research, Vol. 38, No. 10, 01.10.2002, p. 131-1317.

Research output: Contribution to journalArticle

@article{3405b4e037a04a82aad2bf492d53b561,
title = "Air-water interfacial areas in unsaturated soils: Evaluation of interfacial domains",
abstract = "A gas-phase miscible-displacement method, using decane as an interfacial tracer, was used to measure air-water interfacial areas for a sand with water Contents ranging from ∼2{\%} to 20{\%}. The expected trend of decreasing interfacial areas with increasing water contents was observed. The maximum estimated interfacial area of 19,500 cm-1 appears reasonable given it is smaller than the measured surface area of the porous medium (60,888 cm-1). Comparison of the experimental data presented herein with literature data provided further insight into the characterization of the air-water intterface in unsaturated porous media. Specifically, comparison of interfacial areas measured using gas-phase versus aqueous-phase methods indicates that the gas-phase method generally yields larger interfacial areas than the aqueous-phase methods, even when accounting for differences in water content and physical properties of the porous media. The observations are consistent with proposed differences in interfacial accessibility of the aqueous- and gas-phase tracers. Evaluation of the data in light of functional interfacial domains, described herein, yields the hypothesis that aqueous interfacial tracers measure primarily air-water interfaces formed by {"}capillary water,{"} while gas-phase tracers measure air-water interfaces formed by both capillary and surface-adsorbed (film) water. The gas- and aqueous-phase methods may each provide interfacial area information that is more relevant to specific problems of interest. For example, gas-phase interfacial area measurements may be most relevant to contaminant transport in unsaturated systems, where retention at the air-water interface may be significant. Conversely, the aqueous-phase methods may yield information with direct bearing on multiphase flow processes that are dominated by capillary-phase behavior.",
keywords = "Air-water interface, Interfacial tracer",
author = "Costanza-Robinson, {Molly S.} and Brusseau, {Mark L}",
year = "2002",
month = "10",
day = "1",
language = "English (US)",
volume = "38",
pages = "131--1317",
journal = "Water Resources Research",
issn = "0043-1397",
publisher = "American Geophysical Union",
number = "10",

}

TY - JOUR

T1 - Air-water interfacial areas in unsaturated soils

T2 - Evaluation of interfacial domains

AU - Costanza-Robinson, Molly S.

AU - Brusseau, Mark L

PY - 2002/10/1

Y1 - 2002/10/1

N2 - A gas-phase miscible-displacement method, using decane as an interfacial tracer, was used to measure air-water interfacial areas for a sand with water Contents ranging from ∼2% to 20%. The expected trend of decreasing interfacial areas with increasing water contents was observed. The maximum estimated interfacial area of 19,500 cm-1 appears reasonable given it is smaller than the measured surface area of the porous medium (60,888 cm-1). Comparison of the experimental data presented herein with literature data provided further insight into the characterization of the air-water intterface in unsaturated porous media. Specifically, comparison of interfacial areas measured using gas-phase versus aqueous-phase methods indicates that the gas-phase method generally yields larger interfacial areas than the aqueous-phase methods, even when accounting for differences in water content and physical properties of the porous media. The observations are consistent with proposed differences in interfacial accessibility of the aqueous- and gas-phase tracers. Evaluation of the data in light of functional interfacial domains, described herein, yields the hypothesis that aqueous interfacial tracers measure primarily air-water interfaces formed by "capillary water," while gas-phase tracers measure air-water interfaces formed by both capillary and surface-adsorbed (film) water. The gas- and aqueous-phase methods may each provide interfacial area information that is more relevant to specific problems of interest. For example, gas-phase interfacial area measurements may be most relevant to contaminant transport in unsaturated systems, where retention at the air-water interface may be significant. Conversely, the aqueous-phase methods may yield information with direct bearing on multiphase flow processes that are dominated by capillary-phase behavior.

AB - A gas-phase miscible-displacement method, using decane as an interfacial tracer, was used to measure air-water interfacial areas for a sand with water Contents ranging from ∼2% to 20%. The expected trend of decreasing interfacial areas with increasing water contents was observed. The maximum estimated interfacial area of 19,500 cm-1 appears reasonable given it is smaller than the measured surface area of the porous medium (60,888 cm-1). Comparison of the experimental data presented herein with literature data provided further insight into the characterization of the air-water intterface in unsaturated porous media. Specifically, comparison of interfacial areas measured using gas-phase versus aqueous-phase methods indicates that the gas-phase method generally yields larger interfacial areas than the aqueous-phase methods, even when accounting for differences in water content and physical properties of the porous media. The observations are consistent with proposed differences in interfacial accessibility of the aqueous- and gas-phase tracers. Evaluation of the data in light of functional interfacial domains, described herein, yields the hypothesis that aqueous interfacial tracers measure primarily air-water interfaces formed by "capillary water," while gas-phase tracers measure air-water interfaces formed by both capillary and surface-adsorbed (film) water. The gas- and aqueous-phase methods may each provide interfacial area information that is more relevant to specific problems of interest. For example, gas-phase interfacial area measurements may be most relevant to contaminant transport in unsaturated systems, where retention at the air-water interface may be significant. Conversely, the aqueous-phase methods may yield information with direct bearing on multiphase flow processes that are dominated by capillary-phase behavior.

KW - Air-water interface

KW - Interfacial tracer

UR - http://www.scopus.com/inward/record.url?scp=0036822364&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0036822364&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0036822364

VL - 38

SP - 131

EP - 1317

JO - Water Resources Research

JF - Water Resources Research

SN - 0043-1397

IS - 10

ER -