Hydrological system in Quaternary clastic deposits, Mehedinţi County, Romania: isotope composition, chemistry and radiocarbon dating

Abstract

AbstractA groundwater geochemistry study was carried out on 24 samples collected from different springs and wells situated in a plateau area at an elevation of 200–300 m in the Mehedinţi County, southwestern Romania. The study was motivated by the fact that springs have represented the only source of potable water in the region, only recently completed by tens of metres-deep well drillings. Spring distributions and geological data reveal the presence of a multilayered system situated in the Lower Quaternary deposits. The mean δ18O and δD values of groundwater, −9.8 and −67.8‰, respectively, reflect the yearly weighted mean of the isotopic composition of precipitation, demonstrating locally derived recharge. The Piper ternary diagrams indicate that the dominant hydrochemical type is HCO3−–Ca2+–Mg2+ with transition towards higher SO42− and Mg2+ contents to the deeper aquifer. The anions vary from HCO3− with transition to no dominant type and with Cl− contents higher for the shallower aquifer. The sequence of abundance of cations is generally Ca2+ > Mg2+ > K+ > Na+ and for anions: HCO3− > SO42− > Cl− > NO3− > F−. Radiocarbon dating of dissolved inorganic carbon indicates a subrecent recharge of the aquifers. The vertical and lateral variations in groundwater chemistry may vary, and are influenced by lateral lithologic variation of the Quaternary clastic deposits. This is an unpredictable quality factor when taking the decision for the drinking water drill locations.