Imagerie par résonance magnétique du transport et de la rétention des colloïdes dans les sols

Abstract : The ability to predict transport and retention of colloidal particles is a major environmental concern as such particles can carry adsorbed pollutants towards the groundwater or be pollutants themselves. The models currently used to predict the fate of colloids in soils are based on mechanisms inferred from breakthrough curves (evolution of concentration as a function of pore volume or time) after injection of particles into a column of porous media. In this thesis we aim to complement this comprehension with internal measurements by Magnetic Resonance Imaging (MRI).MRI provides 1D and/or 2D distribution of contrast agent particles in time along the sample axis during transport experiment through a porous medium. This technique, together with the study of breakthrough curves gives a global approach. We performed several transport experiment in columns of porous media of increasing complexity: glass beads, sand, soil aggregates, and undisturbed soil.From transport experiments in model porous media we show that dispersion is less important than expected and strongly dependent on entrance effects in the column. This dependence is also observed for adsorption. Experiments in soil aggregates showed a strong adsorption but also a constant release, dependent on the flow rate. Finally, rain experiments in undisturbed sol columns allowed following water content and particles as a function of time
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Alizée Lehoux. Imagerie par résonance magnétique du transport et de la rétention des colloïdes dans les sols. Géophysique [physics.geo-ph]. Université Paris-Est, 2016. Français. ⟨NNT : 2016PESC1131⟩. ⟨tel-01542079⟩

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