Water, Air, and Soil Pollution

, Volume 68, Issue 1–2, pp 291–305 | Cite as

Transport of volatile chlorinated hydrocarbons in unsaturated aggregated media

  • Thomas Gimmi
  • Hannes Flühler
  • BjØrn Studer
  • Anders Rasmuson


Transport of volatile hydrocarbons in soils is largely controlled by interactions of vapours with the liquid and solid phase. Sorption on solids of gaseous or dissolved compounds may be important. Since the contact time between a chemical and a specific sorption site can be rather short, kinetic or mass-transfer resistance effects may be relevant.

An existing mathematical model describing advection and diffusion in the gas phase and diffusional transport from the gaseous phase into an intra-aggregate water phase is modified to include linear kinetic sorption on gas-solid and water-solid interfaces. The model accounts for kinetic mass transfer between all three phases in a soil. The solution of the Laplace-transformed equations is inverted numerically.

We performed transient column experiments with 1,1,2-Trichloroethane, Trichloroethylene, and Tetrachloroethylene using air-dry solid and water-saturated porous glass beads. The breakthrough curves were calculated based on independently estimated parameters. The model calculations agree well with experimental data. The different transport behaviour of the three compounds in our system primarily depends on Henry's constants.


Breakthrough Curve Porous Glass Column Experiment Kinetic Sorption Tetrachloroethylene 
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Appendix: Notation List and Units


aggregate radius, m


concentration in gas-filled macropores, mol m−3 (= mM)


sorbed concentration at the inter-aggregate sites, mol kg−1 dry solid


concentration in the soil organic matter after partitioning with the water phase, mol kg−1 dry solid


concentration in water-filled micropores expressed as an equivalent gas phase concentration (Eq. (7)), mol m−3


concentration in the water phase, mol m−3


apparent diffusivity in a porous medium (Eq. (19)), m2 s−1


apparent diffusivity in gas-filled macropores, m2 s−1


molecular diffusivity in free air, m2 s−1


dispersion coefficient in gas-filled macropores, tortuosity and constrictivity included, m2 s−1


molecular diffusivity (Eq. (19)), m2 s−1


apparent diffusivity in water-filled micropores, m2 s−1


molecular diffusivity in free water, m2 s−1


Henry's constant, dimensionless


Henry's constant, Pa (mol m−3)−1


Equilibrium constant for vapour sorption, dim.less


mass-transfer coefficient for vapour sorption, s−1


Equilibrium constant for solute sorption, dim.less


mass-transfer coefficient for solute sorption, s−1


column length, m


= ɛ/(1−ɛ)


flux from macropores to aggregates, mol m−2 s−1


partial pressure, Pa


radial distance from centre of aggregate, m


time, s


average gas velocity in the macropores, m s−1


distance along macropore, m


form factor with a value of 2 for spheres


macropore porosity


aggregate porosity


apparent density, kg m−3


apparent particle density, kg m−3


solid density, kg m−3


tortuosity of the gas-filled macropores


tortuosity of the water-filled aggregates


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Copyright information

© Kluwer Academic Publishers 1993

Authors and Affiliations

  • Thomas Gimmi
    • 1
  • Hannes Flühler
    • 1
  • BjØrn Studer
    • 1
  • Anders Rasmuson
    • 2
  1. 1.Institute of Terrestrial EcologyETH ZürichSchlieren
  2. 2.Department of Chemical Engineering DesignChalmers University of TechnologyGöteborg

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