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Preferential Flow Effects on Non-Equilibrium Solute Transport During a Series of Short Irrigation Events

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Pp. 201-204 in Preferential Flow, Water Movement and Chemical Transport in the Environment, Proc. 2nd Int. Symp. (3-5 January 2001, Honolulu, Hawaii, USA), eds. D. D. Bosch and K. W. King. St. Joseph, Michigan: ASAE  701P0006.(doi:10.13031/2013.2128)
Authors:   J. lvarez-Bened, R. Muoz-Carpena, C.M. Regalado, and L. Pi
Keywords:   Chemical transport, tracers

During soil solute transport events, preferential flow paths generate gradient concentrations between fast and slow moving regions dominated by different pore water velocities. Under a periodic irrigation regime, amid irrigation events, water flow decreases and solutes become more uniformly distributed through the soil regions due to diffusion. As a result of this effect, short irrigation events lead to breakthrough curves in which concentration perturbations reveal the relative importance of this phenomenon for a particular soil-water system. In this work, a computer controlled experimental setup is developed to evaluate the effect of an intermittent water regime in presence of preferential flow. A leaching experiment is carried out, consisting of 9 short irrigation events after application of Pentafluoro-Benzoic acid as a non-sorbable tracer. Effluent composition and volumes are used to study the concentration perturbations in the breakthrough curve. The magnitude of these perturbations, attributed to the influence of diffusive mass transfer between soil regions under different pore water velocities, was shown to be dependent on their position in the breakthrough curve, being more important at the initial stages. Additionally, time between irrigation events increased the magnitude of such perturbations.

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