Structure and distribution of allophanes, imogolite and proto-imogolite in volcanic soils

Levard Clément, Doelsch Emmanuel, Basile-Doelsch Isabelle, Abidin Z., Miche Hélène, Masion Armand, Rose Jérôme, Borschneck Daniel, Bottero Jean Yves. 2012. Structure and distribution of allophanes, imogolite and proto-imogolite in volcanic soils. Geoderma, 183-184 : 183-184.

Quartile : Q1, Sujet : SOIL SCIENCE

Résumé : Despite half a century of intensive research, the structure and presence of short-range ordered aluminosilicates in volcanic soils is still the focus of debate. Imogolite is easily distinguishable because of its tubular structure, whereas allophane compounds-usually described as spheres-are harder to identify, especially because of their variable structure and occurrence patterns. In addition, the local structure of allophanes can be very similar to that of proto-imogolite (imogolite precursor). Strangely, this similarity is seldom considered in most characterization studies. In this context, our study focuses on the structure of two Al-rich short range-ordered aluminosilicates of two different origins, from: (i) an Andosol B horizon (Andosol sample); and (ii) a weathered pumice grain (pumice sample). These natural samples were compared to a synthetic proto-imogolite. The three samples were analyzed using experimental tools that are commonly used for the identification of these nanophases (chemical composition, X-ray diffraction, nuclear magnetic resonance, Fourier transform infrared spectroscopy and transmission electron microscopy). The three samples exhibited the same local structure, but significant differences were observed at a larger scale. The pumice sample clearly showed ring-shaped particles, while the Andosol sample and the synthetic proto-imogolite were amorphous. Our results suggest that poorly ordered proto-imogolite, rather than Al-rich allophones and imogolites, is present in Andosol horizons. We believe that the mineralogy of these phases needs to be reassessed along with their growth mechanisms.

Mots-clés Agrovoc : sol volcanique, propriété physicochimique du sol, structure chimique, silicate, Andosol, rayon x, spectroscopie infrarouge, spectroscopie RMN

Mots-clés géographiques Agrovoc : La Réunion, France

Mots-clés complémentaires : Nanoparticule

Classification Agris : P33 - Chimie et physique du sol

Champ stratégique Cirad : Hors axes (2005-2013)

Auteurs et affiliations

• Levard Clément, CNRS (FRA)
• Doelsch Emmanuel, CIRAD-PERSYST-UPR Recyclage et risque (FRA) ORCID: 0000-0002-7478-4296
• Basile-Doelsch Isabelle, IRD (REU)
• Abidin Z., Ehime University (JPN)
• Miche Hélène, Aix-Marseille université (FRA)
• Masion Armand, CNRS (FRA)
• Rose Jérôme, CNRS (FRA)
• Borschneck Daniel, CNRS (FRA)
• Bottero Jean Yves, CNRS (FRA)

Source : Cirad - Agritrop (https://agritrop.cirad.fr/564118/)

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