ABSTRACT
Silicon (28% wt.) and aluminium (8%) are second and third most abundant elements in Earth’s crust. In groundwaters, including the medicinal ones, both elements occur in proportionally lower concentrations than the less abundant elements of lithosphere, such as Ca, Mg, Na, K. The primary sources of Si and Al in water are represented by alumino-silicate minerals. Various minerals have been indicated as a phases which could control the solubility of silicon and/or aluminium in water. Hydroxyaluminosilicate (HAS) colloids have been also suggested as such a phase (Schneider et al., 2004). In conjuction with that the formation and structure of synthetic HAS colloids, along with their ecotoxicological role were studied (e.g. Doucet et al., 2001; Exley, 2012). Evaluation of a large set of natural water chemical analyses suggested that one of HAS colloids, the HAS<sub>B</sub> type of a Al<sub>2</sub>Si<sub>2</sub>O<sub>5</sub>(OH)<sub>4</sub> composition, might be formed in groundwaters (Dobrzynski, 2007).<BR> This work presents an attempt to confirm this hypothesis by investigating the presence of HAS<sub>B</sub> colloid in groundwater. It includes analysis of 219 fresh and mineral groundwater samples from Poland, Spain, and Malaysia. An analytical method involving ion-exchange resin was first tested on synthetic solutions and then applied for indirect identification of HAS<sub>B</sub> in groundwaters. Additionally, the investigated water samples were subjected to micro- and ultra- filtration, and then the collected solids were analysed by XRD, EDS and SEM. The HAS colloids may have an important place in Si and Al hydro-geochemistry, especially in near-surface environments, and in eco-toxicology due to their role in limiting the concentration of bio-available and toxic aluminium species.<BR> This study concludes that the most promising conditions for the HAS<sub>B</sub> presence were found in silicon-rich medicinal waters from the Sudetes Mountains (Poland), especially from Swieradow Health Resort. The Si:Al molar ratio found in this work in eluates from resin prepared using waters from Swieradow showed values close to the theoretical ratio of 1:1.<BR> This work also discusses and indicates that the most preferential settings for formation of HAS colloids occur at the short groundwater turn-over time zone in crystalline aquifer-rocks. It also discusses the mechanism for masking the presence of HAS<sub>B</sub> colloids in water by other aluminosilicates. The presented results are still preliminary and require additional work aiming at development of analytical methods applicable for water suspensions rich in silicates.
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 H<sub>2</sub>SiO<sub>3</sub> (〜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 (CO<sub>2</sub>-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 HCO<sub>3</sub>-Ca-Mg type (TDS=1-5 g/L), 2) waters of HCO<sub>3</sub>-Cl-Na and Cl-HCO<sub>3</sub>-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 CO<sub>2</sub> content of 1600-3200 mg/L. The CO<sub>2</sub>-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.
ABSTRACT
Silicon (28% wt.) and aluminium (8%) are second and third most abundant elements in Earth’s crust. In groundwaters, including the medicinal ones, both elements occur in proportionally lower concentrations than the less abundant elements of lithosphere, such as Ca, Mg, Na, K. The primary sources of Si and Al in water are represented by alumino-silicate minerals. Various minerals have been indicated as a phases which could control the solubility of silicon and/or aluminium in water. Hydroxyaluminosilicate (HAS) colloids have been also suggested as such a phase (Schneider et al., 2004). In conjuction with that the formation and structure of synthetic HAS colloids, along with their ecotoxicological role were studied (e.g. Doucet et al., 2001; Exley, 2012). Evaluation of a large set of natural water chemical analyses suggested that one of HAS colloids, the HASB type of a Al2Si2O5(OH)4 composition, might be formed in groundwaters (Dobrzynski, 2007). This work presents an attempt to confirm this hypothesis by investigating the presence of HASB colloid in groundwater. It includes analysis of 219 fresh and mineral groundwater samples from Poland, Spain, and Malaysia. An analytical method involving ion-exchange resin was first tested on synthetic solutions and then applied for indirect identification of HASB in groundwaters. Additionally, the investigated water samples were subjected to micro- and ultra- filtration, and then the collected solids were analysed by XRD, EDS and SEM. The HAS colloids may have an important place in Si and Al hydro-geochemistry, especially in near-surface environments, and in eco-toxicology due to their role in limiting the concentration of bio-available and toxic aluminium species. This study concludes that the most promising conditions for the HASB presence were found in silicon-rich medicinal waters from the Sudetes Mountains (Poland), especially from Swieradow Health Resort. The Si:Al molar ratio found in this work in eluates from resin prepared using waters from Swieradow showed values close to the theoretical ratio of 1:1. This work also discusses and indicates that the most preferential settings for formation of HAS colloids occur at the short groundwater turn-over time zone in crystalline aquifer-rocks. It also discusses the mechanism for masking the presence of HASB colloids in water by other aluminosilicates. The presented results are still preliminary and require additional work aiming at development of analytical methods applicable for water suspensions rich in silicates.
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). 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. 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.