Experimental aluminization of vermiculite interlayers: An X-ray diffraction perspective on crystal chemistry and structural mechanisms

Lanson Bruno, Ferrage Eric, Hubert Fabien, Prêt Dimitri, Mareschal Louis, Turpault Marie Pierre, Ranger Jacques. 2015. Experimental aluminization of vermiculite interlayers: An X-ray diffraction perspective on crystal chemistry and structural mechanisms. Geoderma, 249-250 : 28-39.

Quartile : Q1, Sujet : SOIL SCIENCE

Résumé : Natural aluminization of swelling clay minerals is ubiquitous in acidic soils leading to the formation of hydroxy-interlayered (HI) minerals. This process has drawn special attention over the last 4–5 decades owing to the negative impact on soil fertility of the induced reduction of cation exchange capacity. Combination of chemical analyses and of X-ray diffraction profile modeling on a series of experimentally self-aluminized samples aimed at an improved description of HI minerals and more especially of their interlayer crystal chemistry. Both exchangeable alkali cations and hydroxy (Al, Fe) cations coexist within HI vermiculite interlayers. The latter form discontinuous gibbsite-like interlayer sheets with ~ 15% completeness, despite layer-to-layer distances similar to that of chlorite. From charge compensation considerations, the isolated hydroxy (Al, Fe) cation clusters bear ~ 1.5 positive charges per cation. Analysis of X-ray diffraction data indicates that aluminization of initially swelling interlayers is a layer-by-layer process leading to mixed layers composed of randomly interstratified swelling and aluminized layers, all aluminized layers likely hosting a similar number of hydroxy (Al, Fe) cations along the aluminization process. This model contradicts the widely accepted description of HI minerals as a solid solution between expandable 2:1 clay and aluminous chlorite end-members. As a consequence, the proportion of HI layers in the mixed layer is a robust estimate of aluminization progress and both the amount of extractible (Al, Fe) and the extent of CEC decrease are positively correlated to this essential parameter.

Mots-clés Agrovoc : chimie du sol, minéral argileux, vermiculite, sol argileux

Classification Agris : P33 - Chimie et physique du sol
P35 - Fertilité du sol

Champ stratégique Cirad : Axe 1 (2014-2018) - Agriculture écologiquement intensive

Auteurs et affiliations

• Lanson Bruno, Université de Grenoble (FRA)
• Ferrage Eric, Université de Poitiers (FRA)
• Hubert Fabien, Université de Poitiers (FRA)
• Prêt Dimitri, Université de Poitiers (FRA)
• Mareschal Louis, CIRAD-PERSYST-UMR Eco&Sols (FRA)
• Turpault Marie Pierre, INRA (FRA)
• Ranger Jacques, INRA (FRA)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/579326/)

Métriques

[ Page générée et mise en cache le 2024-12-19 ]