Uranium isotopes in groundwater from the continental intercalaire aquifer in Algerian Tunisian Sahara (Northern Africa)

• Published in: Journal of environmental radioactivity Vol. 100; no. 8; pp. 649 - 656
• Main Authors: Chkir, N., Guendouz, A., Zouari, K., Hadj Ammar, F., Moulla, A.S.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 01-08-2009; Elsevier
• Subjects: 234U/ 238U; Activity ratio; Algeria; Aquifers; Assessments; Compartments; Discharge; Disequilibrium; Earth sciences; Earth, ocean, space; Environmental Monitoring; Exact sciences and technology; Fresh Water - chemistry; Geography; Groundwater; Hydrogeology; Hydrology. Hydrogeology; Isotope geochemistry; Isotope geochemistry. Geochronology; Kinetics; Mobility; Radioactivity; Solubility; Tunisia; Uranium; Uranium - analysis; Uranium isotopes; Water Movements; Water Supply; North Africa; Algeria; Tunisia; Africa; Sahara; Tunisia, Chott; Mobility; Disequilibrium; Uranium; 234U/ 238U; Activity ratio; Solubility; mobility; oxidation-reduction conditions; ground water; hydrogeology; uranium disequilibrium; migration of elements; U-238/U-234; water-rock interaction; aquifers; U; isotopes; solubility; residence time; uranium
• ISSN: 0265-931X; 1879-1700
• DOI: 10.1016/j.jenvrad.2009.05.009

The disequilibrium between
234U and
238U is commonly used as a tracer of groundwater flow. This paper aims to identify uranium contents and uranium isotopic disequilibria variation in groundwater sampled from deep Continental Intercalaire aquifer (southern Algeria and Tunisia). Large variations in both U contents (0.006–3.39
ppb) and
234U/
238U activity ratios (0.4–15.38) are observed. We conduct a first assessment in order to verify whether the results of our investigation support and complete previous hydrogeological and isotopic studies. The dissolved U content and
234U/
238U activity ratio data were plotted on a two-dimensional diagram that was successfully utilized on sharing the CI aquifer into different compartments submitted to different oxidising/reducing conditions and leads also to distinguished two preferential flow paths in the Nefzaoua/Chott Fejej discharge area. Uranium isotopes disequilibrium indicate that ranium chemistry is mainly controlled by water–rock interaction enhanced by long residence time recognised for this aquifer.