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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.

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In the Provence Alpes Côte d'Azur region (France), overproduction of apple (Malus domestica Borkh.) can result in a significant surplus (0–230 000 Mg per year between 1986 and 1995) which has to be used or destroyed. Among the possibilities for disposing of overproduction, land application is flexible and inexpensive. A field study was undertaken to identify the environmental risks and main biogeochemical processes involved when apple waste is applied to farm land. Three experimental plots receiving 0, 500, or 1000 Mg of apple ha−1 were studied. Soil solutions were collected at three depths (0–0.3, 0.3–0.6, and 0.6–0.9 m) at different times, pH and Eh were measured, major ions, metals, and total and carbonated alkalinity were analyzed. Rapid pH and Eh decrease (from 7.0‐5.5 for the pH and from +500 to −300 mV for the redox potential) were observed. The soil became reduced, thus causing the dissolution of Mn. Nitrogen immobilization and denitrification resulting from waste application explained NO−3 depletion in the soil. The formation of organic anions complexed the metals and major cations. Finally, the oxidation of the soil during drying created conditions which polluted less, emphasizing the importance of the choice of season for land application of organic waste.

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