ABSTRACT
Hydrogeological and geochemical data together with geochemical modelling were used to identify main flow directions and the origin of water mineralization in a regional deep aquifer system located in the Aquitaine Basin. Four geochemical processes were identified (dissolution, redox, acid–base reaction, and ion exchange), which explain most of the observed spatial variability in groundwater composition. Combining geochemical modelling and hydrologic data allowed the identification of the most likely water pathways at the aquifer scale. In addition, concentrations of several ions were used to highlight aquitard–aquifer interactions. A complementary study was performed to estimate mass fluxes between the two units. Processes such as leakage, diffusion and mineral dissolution followed by diffusion from an overlying aquitard were investigated. Results suggest that the composition of the major aquitards may impact significantly on the chemistry of the aquifer water.
