Multi-isotopic (d2H, d18O, d13C-TDIC, d18O-TDIC, 87Sr/86Sr) and hydrochemical study on fractured-karstic and detritic shallow aquifers in the Pampean region, Argentina

GLOK GALLI, M.; SILVA BUSSO, A.A.; TREZZA, M.A.; VADILLO PÉREZ, I.; QUIROZ LONDOÑO, O.M.; MARTÍNEZ, D.E.; BARREDO, S.P.

ISOTOPES IN ENVIRONMENTAL AND HEALTH STUDIES

TAYLOR & FRANCIS LTD

Lugar: Londres; Año: 2020 vol. 56 p. 513 - 532

1025-6016

Fluxes between fractured-karstified and detritic aquifers are commonly poorly understood in many environments. These two types of aquifers are in contact in the southeastern Pampean region in the Argentine Buenos Aires province, and the aim of this work is to analyze their relationship contributing to improve the hydrological model. A joint application of hydrochemical and multi-isotopic (δ2H, δ18O, δ13C-TDIC, δ18O-TDIC, 87Sr/86Sr) tools was used. TDIC, δ2H, δ18O and δ13C-TDIC allowed differentiating two main end members. Water in the Pampeano aquifer which is transferred from the fractured-karstic aquifer is characterized by high TDIC around 500-700 mg/L, more depleted water stable (δ18O) isotopes (about -5.5 ?) and high δ13C-TDIC (around -10.0 ?). The other end member is direct recharge water infiltrated into the Pampeano aquifer with TDIC values ranging from 400 to 500 mg/L, slightly enriched water stable isotopes (δ18O = -4.8 ?), and δ13C-TDIC in the range of soil CO2 and the result of reactions with calcrete concretions (from -20.0 to -9.0 ?). Dolomite dissolution is the main process controlling the chemistry of the low-mineralized (Mg-Ca-HCO3) waters, whereas the high-mineralized (Na-HCO3) waters are strongly influenced by ion-exchange reactions with adsorbed Ca2+ and Mg2+ and by evaporation.