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The quantification of particle transport through soil is of great importance for estimating the potential risk of adsorbing contaminants leaching into groundwater. In the present study, we investigated the mobilization of natural soil particles in an undisturbed soil column (diameter = 0.3 m, height = 0.66 m). We tested the effects of physicochemical properties of soil and infiltrating water on the mobilization and transport of soil particles. A square pulse of water was applied at the top of the column. Water was allowed to drain freely at the bottom of the column. We tested two rainfall intensities (11 and 23 mm h−1), three ionic strengths (10−5, 10−3, and 10−1 M), and two initial moisture contents (0.34 and 0.38 m3 m−3). For the whole set of infiltration experiments, the concentration of eluted particles was correlated with the drainage flow intensity, particularly during transient flow. Particle leaching during steady flow varied with the boundary and initial conditions. The highest mobilization of particles was observed for deionized water, the highest infiltration rate and the highest initial soil moisture content. Particle mobilization was limited for high ionic strength associated with the divalent cation Mg2+ During transient flow, mechanical detachment by hydrodynamic shear could lead to particle mobilization. During steady flow, the ionic strength of the incoming solution may alter the energy potential at the soil–water interface, and thus have an effect on the mobilization rate as well.

[1] Understanding particle movement in soils is a major concern for both geotechnics and soil physics with regard to environmental protection and water resources management. This paper describes a model for mobilization and preferential transport of soil particles through structured soils. The approach combines a kinematic-dispersive wave model for preferential water flow with a convective-dispersive equation subject to a source/sink term for particle transport and mobilization. Particle detachment from macropore walls is considered during both the steady and transient water flow regimes. It is assumed to follow first-order kinetics with a varying detachment efficiency, which depends on the history of the detachment process. Estimates of model parameters are obtained by comparing simulations with experimental particle breakthrough curves obtained during infiltrations through undisturbed soil columns. Both water flux and particle concentrations are satisfactorily simulated by the model. Particle mobilization parameters favoring both attachment and detachment of particles are related to the incoming solution ionic strength by a Fermi-type function.Citation: Majdalani, S., E. Michel, L. Di Pietro, R. Angulo-Jaramillo, and M. Rousseau (2007), Mobilization and preferential transport of soil particles during infiltration: A core-scale modeling approach, Water Resour. Res., 43, W05401,