Hydrogeochemistry of the balneologic used groundwater in Germany and their relevance for geothermic projects

摘要

The groundwater chemistry is analyzed for waters in Germany which are used for balneotherapy, including determination of saturation indices and CO2 partial pressures with the computer program PHREEQC. Results show that sodium and chloride concentrations are limited at high ionic strength by the mineral phase halite (NaCl). At pH>6 the saturation indices for calcite (CaCO3) are around zero, therefore alimitation of calcium and carbonate concentrations in equilibrium with calcite is expected. Relatively high carbon dioxide partial pressures up to 2.5atm (approximate to bar) were also calculated. Astrong degassing is thus expected when in contact with the atmosphere, which should lead to precipitation of carbonate minerals. With higher ionic strength, the saturation index for gypsum (CaSO(4)2H(2)O) was around zero, therefore these water samples are expected to be in equilibrium with respect to gypsum. Fluoride concentrations seem to be limited by equilibrium with fluorite (CaF2). The saturation indices for chalcedony (calcedon) fall between -0.5 and +1, which suggests equilibrium with chalcedony or quartz.