Federico Masis, Department of Agroecology, Aarhus University, Viborg, Denmark, Per Moldrup, Dept. of Biotech. Chem. and Environ. Engineering, Aalborg University, Aalborg, Denmark, Deepagoda Thuduwe Kankanamge Kelum Chamindu, Dept of Biotechnology, Chemistry, and Environmental Engineering, Aalborg University, Aalborg, Denmark, Markus Tuller, PO Box 210038, University of Arizona, Tucson, AZ and Lis W. de Jonge, Department of Agroecology, Aarhus University, Tjele, Denmark
Accurate prediction of saturated hydraulic conductivity (Ksat) is essential towards development of better distributed hydrological models and area-differentiated risk assessment of chemical leaching. The Ksat is often estimated from basic soil properties such as particle size distribution or, more recently, soil-air permeability. However, similar links to soil-gas diffusivity (Dp/Do, the ratio of gas diffusion coefficients in soil and pure air) have not been explored although gas diffusivity is a direct measure of the connectivity and tortuosity of the pore networks. Based on measurements for a coarse sandy soil, potential relationships between Ksat and Dp/Do were investigated. A total of 88 undisturbed soil cores were extracted from the topsoil of a field site, and Dp/Do (at four different matric potentials) and Ksat were measured in the laboratory. Water-induced and solids-induced tortuosity factors were obtained by applying a two-parameter Dp/Do model to measured data, and subsequently linked to the cementation exponent of the well-established Revil and Cathles predictive model for saturated hydraulic conductivity. Furthermore, a two-parameter model analogue to the Kozeny-Carman equation was developed for the Ksat - Dp/D0 relationships. All analyses implied strong and fundamental relations between Ksat and Dp/Do at all four different matric potentials. The promising links between Ksat and basic pore network characteristics should be further investigated for a wider range of soil types.