Hydrogeochemical features of groundwater in Republic of Moldova within the limits of secondary mineral formation processes modeling

Abstract

For the first time in the hydrogeological area of the Republic of Moldova, this paper addresses the role of ionic equilibria in the formation of secondary minerals in the “groundwater-rock” system. Potable waters from phreatic and interstratal aquifers were studied. Phreatic waters are mainly supersaturated with calcite, dolomite, and magnesite. In the case of aluminosilicates, the processes are characterized by the formation of clay minerals (kaolinite and illite). Waters from the Middle Sarmatian aquifer were saturated with calcite, dolomite, and magnesite, while the aluminosilicate minerals are in a state of stability and geochemical equilibrium, being in disequilibrium only with anorthite. Thermodynamic calculations for the Lower Sarmatian aquifer showed that the waters are supersaturated with carbonates. Regarding aluminosilicate minerals, geochemical stability is observed with kaolinite, montmorillonite, analcime, illite, and muscovite, while no geochemical equilibrium with gibbsite was recorded. For the Upper Cretaceous aquifer, the equilibrium diagrams reflect predominant saturation with calcite and dolomite, and lower saturation with magnesite. Aluminosilicate minerals (kaolinite, montmorillonite, and, rarely, gibbsite) form stability fields. No geochemical stability is observed with analcime, albite, and anorthite. Thus, the obtained results demonstrate the importance of secondary minerals in the formation of potable groundwater quality and the necessity of monitoring standardized chemical elements.