Hydrogeochemical Relationships between Spring and Subsurface Waters in the Dindefello Area of South Eastern Senegal

Seybatou Diop^1*, Fary Diome¹, Momar Samb¹, Raphael Sarr²

¹Institute of Earth Sciences, Faculty of Sciences and Techniques, Cheikh Anta Diop University of Dakar, Dakar, Senegal.
²Department of Geology, Faculty of Sciences and Techniques, Cheikh Anta Diop University of Dakar, Dakar, Senegal.

DOI: 10.4236/jwarp.2014.619156                

Abstract

The analytical results of water samples collected from the Dindefello Plain area revealed the dominant major ions of bicarbonate, silica, calcium, magnesium and sodium, in order of decreasing relative abundance. Spring water exhibited a very low, i.e. similar to rainwater, mineralization status, unlike groundwater. To better understand the origin of mineralization, the data were further analyzed for interrelationships between parameters and for mineral-water relationships using speciation calculations. This provided various tenuous lines of evidence for speculating various modes of groundwater mineralization. Hydrochemical evaluation of major ions suggested an early stage of mineralization which could be attributed to mineral breakdown driven by pH in the vadose zone under the leaching action of H⁺. Conceivably the soil in recharge areas supplies CO₂ to infiltrating rainwater, thus adding to the amount of aqueous CO₂ (H₂CO₃) already entrapped from the atmosphere. Then, H⁺ ions, produced from the dissociation of aqueous CO₂ (), reacts along groundwater flow paths with the carbonaceous-sulfated and silicated minerals, resulting in the observed major ion chemistry. The spatial variations in the groundwater chemistry indicated that the type of bedrock aquifer has an effect on the water chemistry.

Keywords

Senegal, Dindefello, Groundwater Mineralization, Springwater, Hydrogeochemical Evolution, Chemical Weathering

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Bassot, J.P. (1966) Geological Study of Eastern Senegal and Its Guinea-Malian Borders. Memoires du BRGM, 40, 322 p.
[2]	Villeneuve, M. (1984) Geological Study of the SW Border of the West African Craton—The Pan-African Suture and the Evolution of the Proterozoic—Paleozoic Sedimentary Basins on the NW Gondwana Margin. These Doctorat d’Etat, Universite d’Aix-Marseille III, 552 p.
[3]	Villeneuve, M. (1989) The Geology of the Madina Kouta Basin (Guinea-Senegal) and Its Significance for the Geodynamic Evolution of the Western Part of the West African Craton during the Upper Proterozoic Period. Precambrian Research, 44, 305-322. http://dx.doi.org/10.1016/0301-9268(89)90050-8
[4]	Delor, C., Coueffe, R., Goujou, J.-C., Diallo, D.P., Theveniaut, H., Fullgraf, T., Ndiaye, P.M., Dioh, E., Blein, O., Barry, T.M.M., Cocherie, A., Le Metour, J., Martelet, G., Sergeev, S. and Wemmer, K. (2010) Explanatory Notes to the 1/200,000 Geological Map of Senegal, Saraya—East Kedougou Sheet. Ministere des Mines, de l’Industrie, de l’Agro-Industrie et des PME, DMG, Dakar, 195 p.
[5]	Diop, S. (1998) Contribution to the Hydrogeology of the Fractured Aquifers Developed within the Crystalline Area of Eastern Senegal: Isotope-Hydrogeochemical Investigations and Water Balances in the Kedougou Area (Districts of Bandafassi, Salemata, Fongolimbi and Saraya). Munster Forsch Geol Palaont, 84, 175-259.
[6]	Hem, J.D. (1985) Study and Interpretation of the Chemical Characteristics of Natural Water. 3rd Edition, US Geological Survey Water-Supply Paper 2254, University of Virginia, Charlottesville, 263 p.
[7]	Travi, Y., Gac, J.Y., Fontes, J.Ch. and Fritz, B. (1987) A Survey of the Chemical and Isotopic Composition of Rainwater in Senegal. Geodyn, 2, 43-53.
[8]	Drever, J.I. (1988) The Geochemistry of Natural Waters. 2nd Edition, Prentice-Hall, Englewood Cliffs, 437 p.
[9]	Reesman, A.L., Picket, E.E. and Keller, W.D. (1969) Aluminum Ions in Aqueous Solutions. American Journal of Science, 267, 99-113. http://dx.doi.org/10.2475/ajs.267.1.99
[10]	Roberson, C.E. and Hemd, J.D. (1969) Solubility of Aluminium in the Presence of Hydroxide, Fluoride and Sulphate. US Geol. Survey Water Supply Paper 1827-C, 37 p.
[11]	Freeze, R.A. and Cherry, J.A. (1979) Groundwater. Prentice-Hall, Inc., Englewood Cliffs, 588 p.
[12]	Garrels, R.M. and Christ, C.L. (1965) Solutions, Minerals and Equilibria. W. H. Freeman, San Francisco, 450 p.
[13]	Garrels, R.M. and MacKenzie, F.T. (1967) Origin of the Chemical Compositions of Some Springs and Lakes. In: Equilibrium Concepts in Natural Water Systems, Advances in Chemistry Series, Vol. 67, American Chemical Society, Washington DC, 222-242. http://dx.doi.org/10.1021/ba-1967-0067.ch010
[14]	Hem, J.D. (1977) Surface Chemical Processes in Groundwater Systems. Second International Symposium on Water-Rock Interaction, Strasbourg, 17-25 August 1977, IV 76-IV 85.
[15]	White, D.E., Hemd, J.D. and Waring, G.A. (1963) Chemical Composition of Subsurface Waters. In: Data of Geochemistry, 6th Edition, US Geological Survey Professional Paper 440-F, Reston, 67 p.
[16]	Mitchell, J.K. (1993) Fundamentals of Soil Behavior. John Wiley & Sons, Inc., 2nd Edition, New York, Chichester, Brisbane, Toronto, Singapore, 437 p.
[17]	Krauskopf, K.B. (1967) Introduction to Geochemistry. McGraw-Hill Book Co., New York, 721 p.
[18]	Langmuir, D. (1971) The Geochemistry of Some Carbonate Ground Waters in the Central Pennsylvania. Geochimica et Cosmochimica Acta, 35, 1023-1045. http://dx.doi.org/10.1016/0016-7037(71)90019-6
[19]	Heathcote, J.A. (1985) Carbonate Chemistry of Recent Chalk Groundwater in a Part of East Anglia, UK. Journal of Hydrology, 78, 215-227. http://dx.doi.org/10.1016/0022-1694(85)90102-7
[20]	Drake, J.J. and Wigley, T.M. (1975) The Effect of Climate on the Chemistry of Carbonate Groundwater. Water Resources Research, 11, 958-962. http://dx.doi.org/10.1029/WR011i006p00958
[21]	Keller, C.K. (1991) Hydrochemistry of a Clayey Till 2—Sources of CO2. Water Resources Research, 27, 2555-2564.
[22]	Polzer, W.L. and Hem, J.D. (1965) The Dissolution of Kaolinite. Journal of Geophysical Research, 70, 6233-6240. http://dx.doi.org/10.1029/JZ070i024p06233