HR: 0800h
AN: H21B-1339    [Abstracts]
TI: Functional Relationships among Soil-air Permeability, Soil-gas Diffusivity, and Saturated Hydraulic Conductivity in Undisturbed Soils
AU: * Kawamoto, K
EM: kawamoto@post.saitama-u.ac.jp
AF: Department of Civil and Environmental Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 3388570 Japan
AU: Moldrup, P
EM: pm@bio.auc.dk
AF: Environmental Engineering Section, Department of Life Sciences, Aalborg University, Sohngaardsholmsvej 57, Aalborg, 9000 Denmark
AU: Schjønning, P
EM: Per.Schjonning@agrsci.dk
AF: Danish Institute of Agricultural Sciences, Research Centre Foulum, Blichers, Allé, P.O Box 50, Tjele, 8830 Denmark
AU: Iversen, B V
EM: Bo.V.Iversen@agrsci.dk
AF: Danish Institute of Agricultural Sciences, Research Centre Foulum, Blichers, Allé, P.O Box 50, Tjele, 8830 Denmark
AU: Komatsu, T
EM: komatsu@post.saitama-u.ac.jp
AF: Graduate School of Science and Engineering, Saitama University, 255 Shimo-okubo, Sakura-ku, Saitama, 3388570 Japan
AB: Soil-pore geometric parameters including size distribution, total and air-filled porosity, pore tortuosity and connectivity strongly influence water and air flow in soils, and characterize soil-water and soil-gas transport parameters such as saturated hydraulic conductivity, soil-air permeability and soil-gas diffusivity. This study investigated functional relationships among the soil-pore dependent physical parameters in undisturbed soils and developed predictive expressions for soil-air permeability (k_a) as a function of air-filled porosity (ε) based on a reference point (soil-air permeability at -100 cm H₂O of soil-water matric potential (k_a,100) and corresponding air-filled porosity (ε₁₀₀)). We first measured saturated hydraulic conductivity, soil-air permeability, and relative soil-gas diffusivity on undisturbed soil cores from five Danish soils with depths of 10-540 cm (22 horizons and 96 samples in total). The soil-gas diffusivity and air permeability were measured at four different soil-water matric potentials (-16 (or 20), -50, -100, -150 (or -200) in cm H₂O). Relationships among measured datasets were examined. Second, we developed new k_a(ε) expressions based on relationships between measured k_a (including k_a,100) and soil-pore geometric parameters of ε₁₀₀ and Campbell pore size distribution index b. Two applicable expressions for estimating k_a,100(ε₁₀₀) that can be included in k_a(ε) were proposed. One is obtained by combining the Ball's equivalent pore diameter and the ε₁₀₀-based model for soil-gas diffusivity, and the other is obtained by a simple linear regression in a log (k_a,100)-log (ε₁₀₀) coordinate system. The new k_a(ε) expressions requires two parameters of ε₁₀₀ and b, compared to existing models that require measured k_a,100. Third, the new k_a(ε) expressions and existing models, including those based on saturated hydraulic conductivity, were tested against measured datasets. The new k_a(ε) expressions performed as well as the existing models in the case of ε₁₀₀ > 0.1 where predicted k_a,100 fitted well to measured k_a,100. However, there existed a relatively large discrepancy between predicted and measured k_a,100 in the case of ε₁₀₀ < 0.1 due to the large variability and uncertainty of measured k_a,100.
DE: 1847 Modeling
DE: 1875 Vadose zone
SC: Hydrology [H]
MN: Fall Meeting 2005