Residence time, mineralization processes and groundwater origin within a carbonate coastal aquifer with a thick unsaturated zone

• Published in: Journal of hydrology (Amsterdam) Vol. 540; pp. 50 - 63
• Main Authors: Santoni, S., Huneau, F., Garel, E., Vergnaud-Ayraud, V., Labasque, T., Aquilina, L., Jaunat, J., Celle-Jeanton, H.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2016; Elsevier
• Subjects: Aquifers; Carbonates; CFCs; Chlorofluorocarbons; Coastal aquifer; Corsica; Earth Sciences; Flow pattern; Geochemistry; Ground-water flow; Groundwater; Hydrology; Mineralization; Origins; Residence time; Sciences of the Universe; SF6; SF6; Flow pattern; Residence time; CFCs; Coastal aquifer; Corsica
• ISSN: 0022-1694; 1879-2707
• DOI: 10.1016/j.jhydrol.2016.06.001

•CFCs and SF6 were used to evaluate groundwater residence time in a coastal aquifer.•CFCs can be used for carbonate aquifers with deep unsaturated zone.•Natural SF6 found in granites can constitute a direct tracer of groundwater origin. This study aims at establishing groundwater residence times, identifying mineralization processes and determining groundwater origins within a carbonate coastal aquifer with thick unsaturated zone and lying on a granitic depression. A multi-tracer approach (major ions, SiO2, Br−, Ba+, Sr2+, 18O, 2H, 13C, 3H, Ne, Ar) combined with a groundwater residence time determination using CFCs and SF6 allows defining the global setting of the study site. A typical mineralization conditioned by the sea sprays and the carbonate matrix helped to validate the groundwater weighted residence times from using a binary mixing model. Terrigenic SF6 excesses have been detected and quantified, which permits to identify a groundwater flow from the surrounding fractured granites towards the lower aquifer principally. The use of CFCs and SF6 as a first hydrogeological investigation tool is possible and very relevant despite the thick unsaturated zone and the hydraulic connexion with a granitic environment.