Mineral waters of the Sudetic region (SW Poland) : selected problems

Mineralized waters used for medical treatment are common in the Sudetes. Due to reservoir rock types and the depth of groundwater circulation, two main types of groundwater deposits are distinguished. These are fissure deposits, the most often present in granites and gneisses, andfissure-porous deposits present first of all in sandstones. The main types of mineralized groundwater are CO2-rich waters, containing up to 99.5% of CO2 as the primary gas component, thermal waters characterized by the temperatures up to 87°C, which classifies these waters as the warmest in Poland, as well as radon waters, containing the highest activity concentrations of 222Rn, reaching above 2,000 Bq/dm3. All these groundwater types are infiltration waters. Discharge rates of the intakes in the Sudetes changes with time, which is influenced by changes in atmospheric parameters. The time of reaction is similar for all the intakes in the same hydrogeological structure. The process of mixing between the highly-mineralized, deep-circulation groundwater component and the shallow-circulation, low-mineralized component is intensely studied. Another problem is the presence of CO2 in the amount exceeding its solubility in the water. Juvenile CO2 flows from the deep crust through tectonic discontinuities, where it dissolves in groundwater, forming CO2-oversaturated waters, as well as itforms gas anomalies in soil air. CO2 concentrations may reach in soils more than 60 vol.%, and the flux of this gas reaches even 66 g/m2/d. Radon dissolves in groundwater in the zone of its out flow, where reservoir rocks are densely cracked, weathered, and cut by tectonic faults. The hydrogeochemical background of 222Rn in groundwater of the Sudetes is between 4 and 306 Bq/dm3