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A Laboratory Analysis of the Effect of Macropores on Solute Transport
Author(s) -
Wildenschild D.,
Jensen K. H.,
Villholth K.,
Illangasekare T. H.
Publication year - 1994
Publication title -
groundwater
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.84
H-Index - 94
eISSN - 1745-6584
pISSN - 0017-467X
DOI - 10.1111/j.1745-6584.1994.tb00655.x
Subject(s) - macropore , environmental science , soil water , soil science , water table , groundwater , outflow , hydrology (agriculture) , water flow , dns root zone , geology , chemistry , geotechnical engineering , mesoporous material , biochemistry , oceanography , catalysis
Macropores play an important role in many soils in relation to ground‐water contamination by providing preferential pathways from the root zone to the water table. Surface‐applied agrochemicals may hereby be carried quickly to the shallow ground water. The reduced retention combined with a small contact area between the flowing water and the soil implies that little removal from physical, chemical, and microbiological processes may take place, thus increasing the risk of ground‐water contamination. A laboratory procedure for evaluating the effect of macropores in a given soil is proposed and tested. The procedure involves the following sequence of experiments on two undisturbed soil monoliths: (1) measurements of the distribution of outflow, (2) measurements of breakthrough curves, (3) dye application for visual observation of macropores; and (4) horizontal slicing of the monoliths to measure macropore distribution and continuity of macropores. The experimental procedure is based on well‐documented techniques that combined will provide evidence on the significance of macropores in relation to ground‐water contamination and guidance for selecting the appropriate model for simulating flow and transport at the field in question. The laboratory procedure was tested on two large, undisturbed soil monoliths (30 cm in diameter) removed from the unsaturated zone at a clayey moraine agricultural field in Denmark. This soil was known to have many macropores. The investigations documented the strong influence of these structures on flow and transport suggesting that a traditional flow and transport model would be inadequate for simulating the processes occurring in the field.