A chemical and isotopic approach to investigate groundwater dynamics in a coastal aquifer

• DOI: 10.1016/j.catena.2022.106229
• Publication Date: 2022-03-20T21:50:12Z
• Authors: Silvina Carretero; Leandro Rodrigues...; Cristina Dapeña; Maximiliano Fabiano; Eduardo Kruse
• Keywords: Infiltration (HVAC); Saltwater intrusion; Capillary fringe

Fil: Fabiano, Maximiliano Emanuel. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina<br/>Fil: Rodrigues Capitulo, Leandro. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Cátedra de Hidrología General; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina<br/>The hydrogeological processes in two different zones of a sandy coastal aquifer of the province of Buenos Aires, Argentina, have been assessed on the basis of hydrochemical tools and environmental isotopes (2H and 18O). In general, groundwater in the sand dune barrier is either a Ca-HCO3 or a Na-HCO3 type, whereas in the coastal plain it is a NaCl type. In general terms, the isotopic composition of groundwater matches the average isotopic composition of the rainfall, which would indicate that there is no significant fractionation during the recharge process. However, the interpretation of data allowed the detection of different processes— rapid infiltration, selective infiltration, evaporation, mineral dissolution and mixing—in certain locations. The last process mentioned includes both natural lateral and vertical interface mixing, as well as the one generated by anthropogenic action (saline intrusion). There is a relationship between the variability of the isotopic contents and the thickness of the unsaturated zone. In the northern zone, its lesser thickness causes greater variability in isotopic contents, whereas in the southern zone a greater thickness is suggested by more homogeneous, clustered values. In both zones, selective infiltration was observed; they were represented by both highly depleted and highly enriched isotopic contents, as well as evaporation processes occurring prior to infiltration. Besides, in both zones it was possible to recognise the effects of the displacement of the freshwater–saltwater interface towards the continent as a consequence of intensive groundwater exploitation. The mixing percentage of salt water is about 51 % for both conservative elements oxygen-18 and chloride. The importance of the association of hydrochemical and isotopic methodologies stands out as a tool in the sustainable management of groundwater resources in coastal sand-dune regions.<br/>Fil: Carretero, Silvina Claudia. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina<br/>Fil: Dapeña, Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geocronología y Geología Isotópica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geocronología y Geología Isotópica; Argentina<br/>Fil: Kruse, Eduardo Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires. Universidad Nacional del Noroeste de la Provincia de Buenos Aires. Centro de Investigaciones y Transferencia del Noroeste de la Provincia de Buenos Aires; Argentina<br/>