Hydrogeochemistry of brines on the example of selected water phenomena in the Kłodawa Salt Mine (central Poland)

Chemical and isotopic studies of brines in salt mines are a key element in identifying their origins. This, in turn, is applied in determining the degree of water hazard. Studies of the chemical and isotopic composition of eight brine samples in two measurement series were carried out at the Kłodawa Inc. Salt Mine in 2022 for pH, electrolytical conductivity of water (EC), mineral alkalinity, total alkalinity, total hardness, carbonate hardness, non-carbonate hardness, HCO3−, Ca2+, Mg2+, Na+, K+, Ba2+, Li+, Sr2+, NH4+, Cl−, SO42−, NO3−, NO2−, Br−, F−, I−, CO32− ions as well as δ18O and δ2H in H2O. Analysed water phenomena were selected based on archival data which indicated their various chemical compositions. Using analyses based on hydrochemical indices and isotopic composition, it was found that the studied brines represented the isotopic composition of O and H in H2O typical of Zechstein brines, Paleo-infiltration waters, pre-Pleistocene infiltration waters and waters of mixed origin. Their salinity was mainly primary (inherent) in nature. The dominant processes affecting chemical transformations were ion exchange, precipitation and dissolution of sulphate minerals and halite, redox processes and, to a lesser extent, mixing of waters. The possible influence of inclusions on water chemistry was also found. Additionally, the analysis showed limitations in the applicability of selected hydrochemical indices.