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This article in SSSAJ

  1. Vol. 48 No. 1, p. 3-6
    Received: May 23, 1983
    Accepted: Sept 14, 1983

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Measurement of Gas Diffusion Coefficient under Relatively Low Air-filled Porosity1

  1. A. Sallam,
  2. W. A. Jury and
  3. J. Letey2



Knowledge of the diffusion coefficient is necessary for modeling gas movement through soil. Various equations have been proposed relating apparent gas diffusion to soil parameters. A laboratory study was conducted to measure gas diffusion through soil at low air-filled porosity (0.05, 0.10, and 0.15) using an inert gas (Freon: CCl2F2). The Penman model DS/DA = 0.66a, where DA and DS are gas diffusion coefficients in air and soil, respectively, and a is the volumetric soil air content, greatly overestimated the measured DS at all porosities. The Millington-Quirk model DS/DA = a3.332, where φ is the soil porosity, had the same curve shape but slightly underestimated the measured DS. Much better agreement between calculated and measured DS was obtained by reducing the exponent 3.33 in the Millington-Quirk model to 3.10.

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