Impact of Rock Weathering on the Chemical Composition of Groundwater Determined by Inverse Modeling in Large Sedimentary Basins

This study focuses on the geochemistry of groundwater in a large sedimentary Eocene aquifer system. The main goals of the investigation are determining the influence of rock weathering and quantifying the inputs from each of the end-members (i.e., silicate, carbonate, evaporite) by using an inverse method approach of mass budget equations. We report here the results obtained on 42 groundwater samples collected in a large aquifer (The) in the Adour- Garonne district (SW France). Mass budget equations solved using an inverse method allowed us to estimate the contribution of the different sources among which, carbonate inputs dominate, evaporites often play a secondary role, and silicate inputs may be important.