Allophane: a natural gel in volcanic soils with interesting environmental properties |
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Authors: | Thierry Woignier G Pochet H Doumenc P Dieudonné L Duffours |
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Institution: | 1.UR Seqbio IRD-PRAM, quartier petit Morne,Le Lamentin Cedex 2,France;2.la boratoire des collo?des, verres et nanocomposites,Université de Montpellier 2,Montpellier Cedex 5,France;3.Unité SOLS, Faculté d’ingénierie biologique, agronomique et environnementale,Université catholique de Louvain,Louvain-la-Neuve,Belgium;4.Prime Verre, ave. A Einstein,Parc technologique de la Pompignane,Montpellier,France |
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Abstract: | Volcanic (allophanic) soils are interesting in terms of the control of the greenhouse effect and the knowledge of the porous
features is of importance to understand the mechanism of C and N sequestration. These soils contain a peculiar clay: allophane
aggregates quite close to the synthetic mineral gels aggregates. These volcanic materials behave as gels during drying with
a large irreversible shrinkage that can modify the soil physical properties. Consequently, as for silica gels, we use the
CO2 supercritical drying procedure (SD) to control the drying step and to preserve the structural and textural properties of
the soils. The experimental results show that the N and C content in the soils is clearly dependent on the allophane content.
We also show that the textural properties, such as specific surface area, are higher for the supercritically dried samples,
compared to the classically dried samples, and SAXS results confirm the preserving effect of the SD. With these data, we propose
possible effects of the specific surface area on the C and N content of the allophanic soils. |
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Keywords: | Natural gel Supercritical drying Allophane C sequestration SAXS Andosols |
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