Modeling the influence of an artificial macropore in sandy columns on flow and solute transfer

Understanding and modeling both flow and solute transport within heterogeneous soils, such as a macroporous soil, are of primary concern nowadays in tackling the problem of predicting water resources and soil contamination. Traditional conceptual approaches have proven inadequate for describing preferential solute transfer through macropores and the dependence of such transfer on macropore characteristics (continuity, tortuosity, hydraulic properties, etc.). The enhancement of preferential flow and nonreactive solute transfer through a cylindrical macropore in a sandy matrix has been studied under hydric conditions through laboratory column experiments. Numerical modeling based on the Darcy-Buckingham Law for both the macropore and matrix along with macropore-matrix system geometry is not able to generate an accurate fit. An additional modeling step has indicated that the preferential flow path zone must be considered as extending around the macropore. Such a result illustrates that the major effect of macropores may be much more significant than would be predicted through the typical, conceptual dual-permeability approaches and thus deserves further research. (C) 2009 Elsevier B.V. All rights reserved.