Hydrogeochemistry and Stable Isotopes of a Solid Waste Disposal Area from Gualeguaychú, Entre Ríos, Argentina

Abstract

Major and trace elements, pH, electrical conductivity and organic matter were determined in groundwater and subsoil samples collected from an urban solid waste final disposal site (Gualeguaychú city, Argentina) in order to quantify leachate impact on the quality of these resources. Geochemical modeling results showed mixing process of pristine water and leachate in different proportions which promote, in turn, other processes in the free aquifer such as cation exchange, outgassing of carbon dioxide, precipitation and dissolution of minerals. Anomalous electrical conductivity values of subsoil samples confirmed the leachate impact too. Soilwater interaction allowed the development of natural attenuation processes in water: low dissolved organic carbon (DOC), iron and aluminum concentrations were associated with high amounts in subsoil. High clay content (smectites) and high cation exchange capacity, organic matter and metals analysis suggesting that the exchange and or sorption process were effective. δ13C-DOC constant values ratified the DOC sorption in sediments rather than oxidation. Other natural processes such evaporation and marine ingressions were detected through geochemical models. δ18O y δ2H values suggested not only a meteoric origin for the groundwater but also evaporation and mix process of waters. δ13C-DIC demonstrated that CO2 outgassing could have happened during the mixing.