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Predicting the Gas Diffusion Coefficient in Repacked Soil

Water-Induced Linear Reduction Model

^a Environmental Engineering Lab., Dep. of Civil Engineering, Aalborg Univ., Sohngaardsholmsvej 57, DK-9000 Aalborg, Denmark
^b Dep. of Crop Physiology and Soil Science, Danish Institute of Agricultural Sciences, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark
^c Dep. of Civil and Environmental Engineering, Faculty of Engineering, Hiroshima Univ., 1-4-1 Kagamiyama, Higashi-Hiroshima, 739, Japan
^d Soils and Biogeochemistry, Dep. of Land, Air and Water Resources, Univ. of California, Davis, CA 95616 USA

View larger version (23K): [in a new window]   Fig. 1 Gas diffusivity in completely dry porous media (sands, soils, glass beads, combinations hereof, glass wool, steel wool). Measured data (Penman, 1940; Taylor, 1949; van Bavel, 1952; Currie, 1960; Papendick and Runkles, 1965; and Reible and Shair, 1982) and predictions by three classical gas diffusivity models, Eq. [2] through [4]

View larger version (26K): [in a new window]   Fig. 2 Comparison of gas diffusivity in completely dry porous media (open circles, same data as in Fig. 1) and in wet soil. Predictions by the Marshall (1959) model, Eq. [3], for dry soil, and the new WLR (Marshall) model, Eq. [6], for wet soil

View larger version (41K): [in a new window]   Fig. 3 Performance of the WLR(Marshall) model, Eq. [6], when tested against gas diffusivity data for nine differently textured, sieved, and repacked soils. For comparison, the Marshall (1959) model, Eq. [3], for gas diffusivity in dry soil is shown. (a) through (f) data from this study, (g) through (h) data from Xu et al. (1992) at four different soil total porosities, the range of total porosity for each soil is shown and used in Eq. [6], and (i) data from Karimi et al. (1987)

View larger version (23K): [in a new window]   Fig. 4 Performance of the three new WLR models, Eq. [5] through [7], when tested against data for Yolo loam (data from Petersen et al., 1994). The dotted, vertical line represents soil total porosity,

View larger version (42K): [in a new window]   Fig. 5 Scatter-plot comparison of model performance when tested against gas diffusivity data for 11 differently-textured, sieved and repacked soils. (a) through (f) Test of six different models against all data , and (g) through (i) test of the three new WLR models, Eq. [5] through [7], against low relative gas diffusivities,

View larger version (29K): [in a new window]   Fig. 6 Test of the WLR(Marshall) model, Eq. [6], against gas diffusivity data for a clay loam at five different soil total porosities (data from Arah and Ball, 1994). For comparison, the Marshall (1959) model for gas diffusivity in dry soil is shown