Ould Mohamedou A., Aventurier A., Barbiéro Laurent, Caruba R., Valles V. (1999). Geochemistry of clay dunes and associated pan in the Senegal Delta, Mauritania. Arid Soil Research and Rehabilitation, 13, p. 265-280. ISSN 0890-3069.
Titre du document
Geochemistry of clay dunes and associated pan in the Senegal Delta, Mauritania
Année de publication
1999
Type de document
Article
Auteurs
Ould Mohamedou A., Aventurier A., Barbiéro Laurent, Caruba R., Valles V.
Source
Arid Soil Research and Rehabilitation, 1999,
13, p. 265-280 ISSN 0890-3069
Since the construction of the anti-salting Diama dam, a resumption of aeolian deflation has been observed in the Senegal delta and particularly in Diawling National Park. It results in the formation of many clay dunes with high salt concentrations. The soft powdery structure observed on the soil surface, affected by aeolian deflation is due to rapid salt crystallization. In order to identify the mineralogy of the salt involved in this environment, the chemistry of soil and groundwater was studied along a transect from a pan to the associated clay dune. Equilibria computation and field and scanning electron microscope (SEM) observations indicated that the changes observed in the chemical facies of the solution were due to the following precipitation sequence : calcite to gypsum to halite. A progressive but significant fixing of Na+ onto the clay particles was observed. The calcite deposition in the soil was limited by exhibition of the potential acidity arising from the former mangrove site soils. It resulted in high equilibrating pCO2. This study intended to test a new extension to the Debye-Hückel law for concentrated chlorurated sodic waters. The relationship between chloride amounts and the residual alkalinity concept confirmed that calcite and gypsum formation and the exchanges between Na and Ca are the main phenomena responsible for the changes observed in the soil solution (r2 = 0.99). (Résumé d'auteur)
Plan de classement
Géochimie [064GEOCHI]
Descripteurs
EROSION EOLIENNE ; DUNE ; SOL DEGRADE ; SALINITE ; ALCALINISATION ; CALCITE ; GYPSE ; ARGILE ; EAU SOUTERRAINE ; SOLUTION DU SOL ; DELTA ; BARRAGE
