Fall, Aidara Lamine und Fiedler, Sabine und Stahr, Karl
(2009)
Mineral distribution in soils of the coastal region of West-Central Senegal, West-Africa.
In: Jahrestagung der DBG 2009: Böden - eine endliche Ressource, September 2009, Bonn.
Kurzfassung
Coastal plain soils of West Africa are generally saline and acid, due to seawater intrusions and pyrite oxidation, respectively. The according processes affect the mineral weathering in different ways. The objectives of the present study were twofold: (1) investigate the mineral distribution in saline acid sulfate soils of the coastal area of the Sine Saloum basin, West-central of Senegal, in order to (2) determine the incidence of the landscape position, soil salinity and acidity on their formation and cristallinity. Four profiles located at two different landscape positions: floodplain (2) and low terrace (2) were investigated. The sampling transect was placed in such a way that influences of the landscape position could be reflected in soil properties. The widespread distribution of kaolinite and smectite in the entire toposequence and the influence of eolian dusts in such distribution trend remains the main finding of this study. The clay mineral assemblage in these soils appears therefore not in true equilibrium with the pedoenvironment. Furthermore, the oxidation of pyrite followed by the distribution of the main products (Fe2+ and SO42-) represents the major chemical process responsible for iron oxides (hematite and lepidocrocite) and jarosite formation. This work demonstrates that the mineral distribution in studied soils is less affected by the salinity and acidity than the landscape position which controls the water activity and the redox cycles of S and Fe materials.
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