In situ measurement of effective vapor-phase porous media diffusion coefficients

Paul C. Johnson, Cristin Bruce, Richard L. Johnson, Mariush W. Kemblowski

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

Knowledge of the effective vapor-phase porous medium diffusion coefficient is important for many applications, including risk-based volatilization and vapor migration calculations and remediation performance estimates. A procedure for measuring the effective vapor-phase porous medium diffusion coefficient in situ is presented here. The approach utilizes transient changes in volume-averaged concentrations of an inert tracer gas, rather than changes in point concentration measurements, to determine the effective vapor-phase porous medium diffusion coefficient D(v)(eff). Measurements are made ever intermediate time frames (minutes - hours), and the procedure is easily altered to probe scales ranging from approximately 0.1-1 m. The data reduction leads to the determination of D(v)(eff)/(θ)(1/3), where θ(v) denotes the air-filled porosity. Given this reduced dependence on Θ(v) (relative to approaches based on transient point concentration changes), in many settings it would not be necessary to make independent measurements of moisture content and total porosity to determine D(v)(eff). For example, if θ(v) falls in the range 0.13 ≤ θ(v) ≤ 0.43 cm3-vapor/cm3-soil, then using an assumed value θ(v) = 0.28 would contribute to less than a 23% error in determining D(v)(eff) from experimental data. The theory, a general protocol, and an example field protocol are presented along with sample field data.

Original languageEnglish (US)
Pages (from-to)3405-3409
Number of pages5
JournalEnvironmental Science and Technology
Volume32
Issue number21
DOIs
StatePublished - Nov 1 1998

Fingerprint

in situ measurement
Porous materials
porous medium
Vapors
porosity
volatilization
Porosity
moisture content
remediation
tracer
probe
Remediation
Vaporization
air
Data reduction
gas
Moisture
Gases
Soils
soil

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Science(all)
  • Environmental Chemistry

Cite this

In situ measurement of effective vapor-phase porous media diffusion coefficients. / Johnson, Paul C.; Bruce, Cristin; Johnson, Richard L.; Kemblowski, Mariush W.

In: Environmental Science and Technology, Vol. 32, No. 21, 01.11.1998, p. 3405-3409.

Research output: Contribution to journalArticle

Johnson, Paul C. ; Bruce, Cristin ; Johnson, Richard L. ; Kemblowski, Mariush W. / In situ measurement of effective vapor-phase porous media diffusion coefficients. In: Environmental Science and Technology. 1998 ; Vol. 32, No. 21. pp. 3405-3409.
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