Hydrogeochemical evolution and groundwater mineralization of shallow aquifers in the Bas-Saint-Laurent region, Québec, Canada

This study presents the first regional groundwater hydrogeochemical portrait of the Bas-Saint-Laurent region (BSL), a region shaped by the Appalachians, a strong Quaternary glacial heritage, and coastal dynamics from the St. Lawrence Estuary. The proximity of BSL’s aquifers to St. Lawrence Estuary and its geological history with the past Goltwait Sea transgression create unique issues with respect to groundwater mineralization and sustainability in the region. The study is based on the distribution of major and trace elements and stable isotope signatures of water and inorganic carbon (δ18O, δ2H, δ13CDIC) in 145 groundwater samples collected in private and municipal wells distributed evenly over the study area. Groundwater shows a wide range of composition as indicated by the seven facies revealed by their composition of major elements. Ca-HCO3 and Na-HCO3 facies mainly dominate the regional groundwater composition, representing respectively 66 and 20% of the samples. Nevertheless, no significant relation...