ISSN:
1365-2389
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Geosciences
,
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
The inability to predict flow and transport behaviour based on a priori information demonstrates the lack of knowledge we currently have concerning transport-relevant properties or processes, or both. We present an approach in which the behaviour of effective solute transport at the scale of a soil column (100 mm) is predicted by taking into account the spatial structure of the hydraulic properties at the local scale (1 mm). The local absorption coefficients obtained from X-ray tomography, which are linearly related to bulk density, are used as local proxy for hydraulic properties. As a first approximation, two density classes were distinguished, and the three-dimensional structure of the hydraulic properties was implemented in a model of flow and transport. The local hydraulic properties were obtained from a network model, except for the absolute value of the hydraulic conductivity function which was measured. Model simulations were compared with a measured breakthrough curve determined on the same soil sample. The two agreed well, although the local hydraulic properties and parameter structure were determined independently with respect to a breakthrough experiment. Predictions of solute transport at the column scale were sensitive to the difference in saturated hydraulic conductivities of both materials, but not to the local dispersivities. The simulations demonstrate that (i) assuming validity of the Richards equation and the convection–dispersion equation on the local scale leads to a good description of the effective flow and transport behaviour at the column scale without making any assumptions about the governing processes at that scale; (ii) the dispersion parameters, which are notoriously difficult to determine, need not be determined since their effect is included explicitly; and (iii) local absorption coefficients can be used as a local proxy for the parameter field of the hydraulic properties.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1046/j.1365-2389.2000.00282.x
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