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| Titel |
Biogeochemistry of an Amazonian podzol-ferralsol soil system with white kaolin |
| VerfasserIn |
Y. Lucas, C. R. Montes, S. Mounier, M. Loustau Cazalet, D. Ishida, R. Achard, C. Garnier, B. Coulomb, A. J. Melfi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 9 ; Nr. 9, no. 9 (2012-09-28), S.3705-3720 |
| Datensatznummer |
250007297
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| Publikation (Nr.) |
 copernicus.org/bg-9-3705-2012.pdf |
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| Zusammenfassung |
The podzol-ferralsol soil systems, which cover great areas of Amazonia and
other equatorial regions, are frequently associated with kaolin deposits and
store and export large amounts of carbon. Although natural organic matter
(NOM) plays a key role in their dynamics, little is known about their
biogeochemistry. In order to assess the specific role of dissolved organic
matter (DOM) on NOM storage in deep horizons and to determine possible
relationships between kaolin formation and DOM properties, we studied the
groundwater composition of a typical podzol-ferralsol soil catena from
the Alto Rio Negro region, Brazil.
Groundwater was sampled using tension-free lysimeters placed according to
soil morphology. DOC, EH, pH, and dissolved Si, Al3+,
Fe2+, and Fe3+ were analyzed for all samples and values are given in a database.
Quantification of other dissolved ions, small carboxylic acids and
SUVA254 index and acid-base microtitration was achieved on selected
samples.
Part of the DOM produced by the hydromorphic podzols is directly exported to
the blackwater streams; another part percolates at greater depth, and more
than 90% of it adsorbs in the Bh-Bhs horizons, allowing carbon storage at
depth. Humic substances are preferentially adsorbed with regard to small
carboxylic compounds.
With regard to kaolin genesis, kaolinite precipitation is favored by Al
release from NOM mineralization within the Bh-Bhs and kaolin bleaching is
ensured by iron reduction due to acidity and relatively low EH.
Fe2+ mobility can be related to small EH variations and
enhanced by the significant concentration of small carboxylic acids. The
long-term result of these processes is the thickening of the kaolin, and it
can be inferred that kaolin is likely to occur where active, giant podzols are
close to a slope gradient sufficient enough to lower the deep water table. |
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