Typologie physico-chimique et métallique des eaux du fleuve Sénégal au niveau de la ville de Rosso (Mauritanie)

L’étude concerne une analyse de la typologie physico-chimiques et métalliques des eaux du fleuve Sénégal : Cas du delta Mauritanien localisé dans la ville de Rosso. L’évaluation de 19 variables est effectuéepar dosage volumétrique et spectroscopique (spectroscopie d'absorption atomique Flamme et Four, ICP) selon le Rodier au cours de la périoded’étude dans les deux saisons de l'année 2006 : Saison froide ''Septembre'' et saison sèche ''Mars''. Les résultats montrent que :- Parmi 19 variables physicochimiques et métalliques évalués seules 14déterminent la typologie physicochimique du milieu étudié. - Deux groupements de relevées sont différenciés. Le premier rassemble des relevés tous effectués en été et caractérisés par des concertations élevés en Ca2+, Mg2+, Na+, Zn2+ et faibles en NO3- et K+ . Le second  groupement est formé par des relevés hivernaux présentant des caractéristiques physicochimiques opposées à celles des relevés dupremier groupement. L’effet du facteur « saison » est donc bien dégagé.Pour les teneurs en Al 3+ et le Sr2+ le facteur saison n’intervient pas. En outre, l’activité domestique et les rejets des eaux usées favorisent la pollution organique de certaines parties de la zone prospectée alors que les rejets des eaux usées industrielles de la sucrerie sénégalaise C.S.S. polluent en Al2+ et Sr2+ d’autres stations. Mais, d’une manière générale les teneurs des éléments chimiques évalués sont dans les nomes de l’eau d’irrigation.Mots-clés : eau potable, eau usée, pollution, concentration métallique, paramètres physico-chimiques, fleuve Sénégal, Mauritani

Argan Oil Exerts an Antiatherogenic Effect by Improving Lipids and Susceptibility of LDL to Oxidation in Type 2 Diabetes Patients

In this study, we investigate the effect of argan oil consumption on serum lipids, apolipoproteins (AI and B), CRP, and LDL susceptibility to oxidation in type 2 diabetic patients which are known to have a high level of cardiovascular risk due to lipid abnormalities and lipid peroxidation. For that, 86 type 2 diabetic patients with dyslipidemia were randomized to one group consuming 25 mL/day of argan oil during 3 weeks and control group consuming 20 g/day of butter in breakfast. After argan oil intervention, serum triglycerides decreased by 11.84%, (P = 0.001), total chol by 9.13%, (P = 0.01), and LDL-chol by 11.81%, (P = 0.02). However, HDL-chol and Apo AI increased (10.51%, P = 0.01 and 9.40%,  P = 0.045, resp.). Susceptibility of LDL to lipid peroxidation was significantly reduced by increasing of 20.95%, (P = 0.038) in lag phase after argan oil consumption. In conclusion, we show for the first time that consumption of argan oil may have an antiatherogenic effect by improving lipids, and the susceptibility of LDL to oxidation in type 2 diabetes patients with dyslipidemia, and can therefore be recommended in the nutritional management of type 2 diabetes

Influence de la maturation des sols de mangrove sur la déflation éolienne et la formation des dunes argileuses dans le delta du fleuve Sénégal

L'étude des dunes argileuses est largement employée pour la reconstitution des paléo-environnements. L'arrêt de la sédimentation éolienne est généralement attribuée à des modifications climatiques ou hydrologiques. Notre étude, menée dans le delta du fleuve Sénégal, montre que des transformations internes de la couverture pédologique peuvent induire des modifications de la partie superficielle des sols et arrêter la déflation éolienne, sans modifications des conditions environnementales. (Résumé d'auteur

Geochemistry of clay dunes and associated pan in the Senegal Delta, Mauritania

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

Soil cover and landscape evolution in the Senegal floodplain: a review and synthesis of processes and interactions during the late Holocene

International audienc

Polyphasic origin of salinity in the Senegal delta and middle valley

Saline areas are a major obstacle to the development of sustainable irrigated agriculture in the Senegal valley. They have been attributed to the incorporation of marine salts in the sediments during the last marine transgression. However, this does not explain their geomorphological situation and geochemical features. They are distributed as strips about 100-200 m wide and several kilometers long,which are composed of two parallel substrips, one located in the depressions of former creek beds, and the other on higher ground on the southern bank. In these two substrips, the chemical composition of salinity and its distribution in the soil suggest that it arises from more than one source. Comparison of saline areas of the middle valley with present-day salt accumulation in the delta suggests a four-stagesalinization process, which involves evaporation from a shallow watertable, aeolian salt accumulation as clay dunes, deep transformation of shell beds into gypseous layers under temporary acid conditions inducedby oxidation of pyrite under the mangrove vegetation, and secondary salinization by runoff. The four-stage model agrees with a regional salinity chemical database and the geomorphology of the saline areas.In the Senegal valley, the lower middle valley and the delta can therefore be regarded as a chrono sequence, the recent salinity features occurring in the delta and the more developed ones upriver at the limit of the marine transgression