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Evidence of preferential path formation and path memory effect during successive infiltration and drainage cycles in uniform sand columns.

Kapetas, L and Dror, I and Berkowitz, B (2014) Evidence of preferential path formation and path memory effect during successive infiltration and drainage cycles in uniform sand columns. J Contam Hydrol, 165. pp. 1-10.

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Abstract

The formation of preferential flow paths in the partially saturated zone, and in naturally structured media, is well known. This study examines non-uniform flow in uniform sand columns under different pressure and infiltration/drainage conditions. Experiments were carried out in a vacuum box, with applied suction set to three different heads, and with infiltration fixed at two different flow rates. Tailing observed in some conservative tracer breakthrough curves suggests the formation of immobile resident water pockets which slowly exchange mass with the flowing water fraction. The applied suction controlled the degree of water immobilization whereas flow rate had minimal effect on the dynamic behavior. Trapping and exchange of water occurred repeatedly during successive infiltration and drainage cycles, implying a (hysteretic) memory effect of the previously formed preferential flow paths. Flow and solute transport modeling suggests that these dynamics can be described by a mobile-immobile model that corroborates measurements suggesting preferential flow path formation. These findings have implications for the natural attenuation of contaminants in the partially saturated zone, but also for the persistence of a contamination source exposed to repeated conditions of infiltration and drainage.

Item Type: Article
Uncontrolled Keywords: Contaminant transport Old–new water Unsaturated zone Groundwater Models, Theoretical Porosity Silicon Dioxide Water Movements Water Pollutants, Chemical
Subjects: UNSPECIFIED
Divisions: Div D > Sustainable Development
Depositing User: Cron Job
Date Deposited: 17 Jul 2017 19:09
Last Modified: 20 Nov 2017 20:27
DOI: