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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
Article

Abstract

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.

Keywords

Breakthrough Curve Porous Glass Column Experiment Kinetic Sorption Tetrachloroethylene 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Appendix: Notation List and Units

b

aggregate radius, m

C

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

Cm

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

Co

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

Cp

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

Cw

concentration in the water phase, mol m−3

D

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

Da

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

Dao

molecular diffusivity in free air, m2 s−1

Dl

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

Do

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

Dw

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

Dwo

molecular diffusivity in free water, m2 s−1

H

Henry's constant, dimensionless

KH

Henry's constant, Pa (mol m−3)−1

Km

Equilibrium constant for vapour sorption, dim.less

Km

mass-transfer coefficient for vapour sorption, s−1

Ko

Equilibrium constant for solute sorption, dim.less

ko

mass-transfer coefficient for solute sorption, s−1

L

column length, m

m

= ɛ/(1−ɛ)

No

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

p

partial pressure, Pa

r

radial distance from centre of aggregate, m

t

time, s

V

average gas velocity in the macropores, m s−1

z

distance along macropore, m

αf

form factor with a value of 2 for spheres

ɛ

macropore porosity

ɛp

aggregate porosity

ρa

apparent density, kg m−3

ρp

apparent particle density, kg m−3

ρr

solid density, kg m−3

Τa

tortuosity of the gas-filled macropores

Τw

tortuosity of the water-filled aggregates

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References

  1. Chiou, C.T. and T.D. Shoup. 1985. Soil sorption of organic vapors and effects of humidity on sorptive mechanism and capacity. Environ. Sci. Technol. 19:1196–1200.Google Scholar
  2. Collin, M. and A. Rasmuson. 1988. A comparison of gas diffusivity models for unsaturated porous media. Soil Sci. Soc. Am. J. 52:1559–1565.Google Scholar
  3. Enfield, C.G., D.M. Walters, J.T. Wilson, and M.D. Piwoni. 1986. Behavior of organic pollutants during rapid-infiltration of wastewater into soil: II. Mathematical description of transport and transformation Hazard. Waste Hazard. Materials 3:57–76.Google Scholar
  4. Estes, T.J., R.V. Shah, and V.L. Vilker. 1988. Adsorption of low molecular weight halocarbons by Montmorillonite. Environ. Sci. Technol. 22:377–381.Google Scholar
  5. Fried, J.J. and M.A. Combarnous. 1971. Dispersion in porous media. In: V.T. Chow (Ed.), Advances in Hydroscience 7:169–282.Google Scholar
  6. Gierke J.S., N.J. Hutzler, and J.C. Crittenden. 1990. Modeling the movement of volatile organic chemicals in columns of unsaturated soil. Water Resour. Res. 26:1529–1547.Google Scholar
  7. Gierke J.S., N.J. Hutzler, and D.B. McKenzie. 1992. Vapor transport in unsaturated soil columns: Implications for vapor extraction. Water Resour. Res. 28:323–335.Google Scholar
  8. Gossett, J.M. 1987. Measurement of Henry's law constants for C1 and C2 chlorinated hydrocarbons. Environ. Sci. Technol. 21:202–208.Google Scholar
  9. Handbook of Chemistry and Physics. 64th ed., 1983–84. CRC Press, Boca Raton.Google Scholar
  10. Hayduk, W. and H. Laudie. 1974. Prediction of diffusion coefficients for non-electrolytes in dilute aqueous solutions. AIChE J. 20:611–615.Google Scholar
  11. Hutzler N.J., J.C. Crittenden, J.S. Gierke, and A.S. Johnson. 1990. Transport of organic compounds with saturated groundwater flow: Experimental results. Water Resour. Res. 22:285–295.Google Scholar
  12. Jury, W.A. and K. Roth. 1990. Transfer functions and solute movement through soil. Theory and applications. BirkhÄuser, Basel.Google Scholar
  13. Jury, W.A., D. Russo, G. Streile, and H. El Abd. 1990. Evaluation of volatilization by organic chemicals residing below the soil surface. Water Resour. Res. 26:13–20.Google Scholar
  14. Jury, W.A., W.F. Spencer, and W.J. Farmer. 1983. Behavior assessment model for trace organics in soil: IV. Model description. J. Environ. Qual. 12:558–564.Google Scholar
  15. Karickhoff, S.W., D.S. Brown, and T.A. Scott. 1979. Sorption of hydrophobic pollutants on natural sediments. Water Res. 13:241–248.Google Scholar
  16. Lyman, W.J., W.F. Reehl, and D.H. Rosenblatt. 1982. Handbook of chemical property estimation methods. McGraw-Hill, New York.Google Scholar
  17. Mackay, D. and W.Y. Shiu. 1981. A critical review of Henry's law constants for chemicals of environmental interest. J. Phys. Chem. Ref. Data 10:1175–1199.Google Scholar
  18. Mendoza, C.A. and E.O. Frind. 1990. Advective-dispersive transport of dense organic vapors in the unsaturated zone. 1. Model development. Water Resour. Res. 26:379–387 (1990).Google Scholar
  19. Millington, R.J. 1959. Gas diffusion in porous media. Science 130:100–102.Google Scholar
  20. Munz, Ch. and P.V. Roberts. 1987. Air-water phase equilibria of volatile organic solutes. J. Am. Water Works Assoc. 79: 62–69.Google Scholar
  21. Ong, S.K. and L.W. Lion. 1991. Mechanisms for Trichloroethylene vapor sorption onto soil minerals. J. Environ. Qual. 20:180–188.Google Scholar
  22. Pannwitz, K.H. 1985. Bestimmung von Konzentrationen organischer LösemitteldÄmpfe in Arbeitsbereichen — Teil I. DrÄgerheft 332:10–33.Google Scholar
  23. Peterson, M.S., L.W. Lion, and C.A. Shoemaker. 1988. Influence of vapor-phase sorption and diffusion on the fate of Trichloroethylene in an unsaturated aquifer system. Environ. Sci. Technol. 22:571–578.Google Scholar
  24. Pignatello, J.J. 1989. Sorption dynamics of organic compounds in soils and sediments. In: Sawhney, B.L. and K. Brown (Eds.). Reactions and movement of organic chemicals in soils. SSSA Spec. Publ. 22, Madison, Wisc., USA.Google Scholar
  25. Rasmuson, A. 1985. The influence of particle shape on the dynamics of fixed beds. Chem. Eng. Sci. 40:1115–1122.Google Scholar
  26. Rasmuson, A., T. Gimmi, and H. Flühler. 1990. Modeling reactive gas uptake, transport, and transformation in aggregated soils. Soil Sci. Soc. Am. J. 54:1206–1213.Google Scholar
  27. Schwarzenbach, R.P. and J. Westall. 1981. Transport of nonpolar organic compounds from surface water to groundwater. Laboratory sorption studies. Environ. Sci. Technol. 15:1360–1367.Google Scholar
  28. Shoemaker, C.A., T.B. Culver, L.W. Lion, and M.G. Peterson. 1990. Analytical models of the impact of two-phase sorption on subsurface transport of volatile chemicals. Water Resour. Res. 26:745–758.Google Scholar
  29. Sleep, B.E. and J.F. Sykes. 1989. Modeling the transport of volatile organics in variably saturated media. Water Resour. Res. 25:81–92.Google Scholar
  30. Spencer, W.F., M.M. Cliath, W.A. Jury, and L.Z. Zhang. 1988. Volatilization of organic chemicals from soil as related to their Henry's law constants. J. Environ. Qual. 17:504–509.Google Scholar
  31. Troeh, F.R., J.D. Jabro and D. Kirkham. 1982. Gaseous diffusion equations for porous materials. Geoderma 27:239–253.Google Scholar
  32. Van Brakel, J. and P.M. Heertjes. 1974. Analysis of diffusion in macroporous media in terms of a porosity, a tortuosity and a constrictivity factor. Int. J. Heat Mass Transfer 17:1093–1103.Google Scholar
  33. Wu, S. and P.M. Gschwend. 1986. Sorption kinetics of hydrophobic organic compounds to natural sediments and soils. Environ. Sci. Technol. 20:717–725.Google Scholar

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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