Hydrogeochemical and stable isotope data of Groundwater of a multi-aquifer system: Northern Gafsa basin - Central Tunisia

Mokadem, N., Demdoum, A., Hamed, Y., Bouri, S., Hadji, R., Boyce, A. , Laouar, R. and Sâad, A. (2016) Hydrogeochemical and stable isotope data of Groundwater of a multi-aquifer system: Northern Gafsa basin - Central Tunisia. Journal of African Earth Sciences, 114, pp. 174-191. (doi:10.1016/j.jafrearsci.2015.11.010)

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Abstract

The hydrodynamic of the multi-aquifer system (the Continental Intercalaire “ C.I ” and the Complex Terminal “ C.T ”) of the North Gafsa basin is largely determined by tectonics (Tebessa - Gafsa fault). The composition of groundwater is controlled by complex reactions at gas-liquid-solid “mineralogical composition of associated rocks” interfaces, which depend on the natural surrounding and potential anthropogenic impact. The hydrochemical data (major ion geochemistry) indicate that these groundwaters are characterized by the dominance a Ca-Mg-HCO3/SO4 and Na-Cl-NO3 water types. Geochemical pattern is mainly controlled by the dissolution of halite, gypsum and/or anhydrite as well as by the incongruent dissolution of carbonate minerals. The pH of these samples range from 6.54 to 8.89, supporting the conclusion that the H2CO3/HCO3 couple control pH buffering. Oxygen-18 (δ18O‰SMOW) and deuterium (dD‰SMOW) isotopic data show the exchange between the groundwater and the rock (water-rock interaction) and the evaporation effect. The isotopic content of the boreholes waters is of mixed Mediterranean - Atlantic origin and is opposite to the quantity of rainwater distribution, both in space and time in the study area. This is due to its geographical situation in the southern and south-western of the Mediterranean Sea and between the Atlas area and the Sahara Platform. The concentrations of the isotopic composition of the groundwater are significantly higher than the rainwater. This is indicative of the dissolution of salts and other processes modifying the rainwater geochemical composition during infiltration into the vadose zone. The hydraulic interconnection of these components of the system has led to the evolution of these interesting groundwater types.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Boyce, Professor Adrian
Authors: Mokadem, N., Demdoum, A., Hamed, Y., Bouri, S., Hadji, R., Boyce, A., Laouar, R., and Sâad, A.
College/School:College of Science and Engineering > Scottish Universities Environmental Research Centre
Journal Name:Journal of African Earth Sciences
Publisher:Elsevier B.V.
ISSN:1464-343X
Copyright Holders:Copyright © 2015 Elsevier
First Published:First published in Journal of African Earth Sciences 2015
Publisher Policy:Reproduced in accordance with the copyright policy of the publisher.

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