16-1Geochemical analysis of acidulous medicinal waters (Carpathian Mountains, SE Poland) for finding new water rich in dissolved silica / 日本温泉気候物理医学会雑誌

ABSTRACT

  Silicon generates interest in ecology, biology and medicine due to the recognized role it plays in living organisms in controlling bio-available aluminium and its toxicity. In Poland, silicon is regarded as a desired component in balneotherapy, with threshold value for siliceous medicinal water of 70 mg/L H₂SiO₃ (〜0.9 mM). In the Carpathians, mineral/medicinal waters occur in flysch rocks, in hundreds of sites where they are partly used for balneology. Most of these waters represent the acidulous (CO₂-rich) type. In contrast, only seven intakes are documented as sources of siliceous medicinal waters. Three main groups of acidulous waters occur in the Carpathians 1) “simple” acidulous waters of HCO₃-Ca-Mg type (TDS=1-5 g/L), 2) waters of HCO₃-Cl-Na and Cl-HCO₃-Na types (TDS=10-30 g/L), and 3) waters from mixing of the above-mentioned types (Rajchel, 2012). Usually, high silicon concentration is found in thermal and/or alkaline groundwater. Unfortunately, Carpathian acidulous waters have low-enthalpy (T=6.4-20.3°C) and are slightly acidic or near-neutral (pH=5.2-7.7).<BR>  The presented geochemical study of water from 93 intakes throughout Polish Carpathian Mountains aimed at determining hydro-geochemical conditions conducive to finding new sites with Si-rich groundwater as viable source of medicinal water. It was reported that groundwater rich in silicic acid provide benefits in detoxifying body from aluminium and therapy of aluminium-related diseases (e.g. Exley et al., 2006). This study was focused on waters containing above 0.5 mM Si, suggested to be more effective in therapy (op.cit.). Silica-enriched groundwater is present in various geological-settings (Dobrzynski & Exley, 2010; Dobrzynski et al., 2012), but its therapeutic potential seems to be still underrated.<BR>  We found that silicon in concentrations above 0.5 mM occurs in mineral waters with ionic strength (I) of 0.02-0.3 M. The pH of Si-enriched waters varies between 5.8 and 6.6, which corresponds to free CO₂ content of 1600-3200 mg/L. The CO₂-mediated hydrolytic decay of silicate minerals is responsible for increased concentration of dissolved silicon. Geochemical modelling demonstrates that waters are close to chemical equilibrium with rock-forming feldspars. The prospective areas for finding new siliceous waters in Polish Carpathian Mountains are Poprad River Valley and Kroscienko-Szczawnica spas. The highest Si concentrations are expected to be found in groundwater which originate in the deeper part of the simple-acidulous water zone, and in geological structures where these waters mix with deeply-occurring chloride waters.