Effets de la congélation sur la microstructure de tourbes. Apport de la micro- tomographie X à révéler tels effets de congélation.

Abstract : The impact of freezing on Sphagnum and Sphagnum Molinia decomposed peats was estimated from their morphological alterations in pore structure computed from 3D CT scanning images. This study investigates how the freeze during peat samples preparing in laboratory affects pore structure, using high-resolution (100 and 60μm) three-dimensional (3D) X-ray computed tomography (CT) and digital image processing of two peats sampled at a certain depths. Our results show that while the freezing technique is more and more frequently used, it alters the structure of the two peat materials studied. Not only tubular pores with a larger diameter were partially altered but many smaller pores also were produced by freezing. The later might be produced by the formation of ice crystals of similar size within the porous organic matrix water saturated or, as suggested by their 3D distribution, by the crystallization of the water in tubular pore too small to be identified before freezing with the X-ray microtomography used in this study but, after freezing, large enough discontinuously after ice crystals formation and their growth by water migration from the surrounding porous and water saturated organic matrix. Whatever le formation mechanism of these new pores visible after freezing on the 3D CT scanning images, our results show that the freezing technique is to be used with great care when the objective is to study the structure of peat materials, and that for peat materials similar to those studied here, it should be avoided.
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Submitted on : Thursday, April 11, 2019 - 10:22:23 AM
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Hassan Al Majou, Olivier Rozenbaum, Fatima Laggoun-Défarge, Sébastien Gogo, Emmanuel Le Trong, et al.. Effets de la congélation sur la microstructure de tourbes. Apport de la micro- tomographie X à révéler tels effets de congélation.. 14èmes Journées d’Étude des Sols, Jul 2018, Rouen- Normandie, France. ⟨insu-02081417⟩

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