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| Titel |
Si isotopes record cyclical dissolution and re-precipitation of pedogenic clay minerals in a podzolic soil chronosequence |
| VerfasserIn |
Jean-Thomas Cornelis, Dominique Weis, Les Lavkulich, Marie-Liesse Vermeire, Bruno Delvaux, Jane Barling |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088484
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| Publikation (Nr.) |
 EGU/EGU2014-2588.pdf |
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| Zusammenfassung |
| Soils are a major resource on the planet, acting as a key component for ecosystem function.
The secondary minerals in the clay fraction are important players in soil biogeochemical
processes as they provide a large reactive surface area. However, the origin and evolution of
secondary minerals in soils are not yet fully understood.
We determined the Si isotope compositions in the clay fraction of a podzolic soil
chronosequence and document light 28Si enrichment during pedogenesis that increases with
soil age. Relative to the original “unweathered” clay-size minerals in deepsoil (δ30Si =
-0.52±0.16 permil), the clay fraction of the topsoil eluvial horizon show less negative δ30Si
values (δ30Sifrom -0.33 to -0.10 permil), while the clay fraction of the subsoil illuvial
horizons is isotopically lighter (δ30Si from -0.60 to -0.84 permil). Geochemical and X-ray
diffraction analyses show that the on-going enrichment in light 28Si in pedogenic
minerals of illuvial subsoil horizons can only be related to the dissolution in the topsoil
horizon of clay minerals previously enriched in 28Si. The 28Si enrichment in the
clay fraction with pedogenesis and soil age provides consistent evidence for the
cyclical dissolution and re-precipitation of pedogenic minerals. Our study shows
that the successive generations of clay minerals occur over very short time scales
(ca. 300 years). This is instrumental in the evolution of the clay mineral genesis in
soils.
This soil-forming process has implications for the modeling of soil evolution. Given the
importance of clay minerals in the chemical cycles of elements, deciphering the origin of
pedogenic Si in clay mineral genesis is central to a better understanding of soil development
and associated terrestrial biogeochemical processes. |
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