The components and indicators that provide grounds for assessing water as mineral can include the degree of mineralization, the composition and ratio of dissolved substances in the water, gas content, pH reaction, and radioactivity.
Degree of mineralization of water. Water formed from melting ice in remote areas of Antarctica contains 0.005 g/L of dissolved substances, while groundwater in the Angaro-Lensky basin contains 700 g/L: a difference of 140,000 times — this is the range of salt content in natural waters. For waters classified as mineral, this range should obviously be significantly smaller, as water with dissolved salts up to 1 g/L is considered fresh and cannot be recognized as therapeutic based on this indicator.
In Kyrgyzstan, there are groundwater sources with dissolved salt content of less than 0.1 g/L (in high-altitude areas) to 600 g/L and more (in the Toktogul depression), thus fully and abundantly covering the entire range of mineralization of therapeutic waters.
Ionic composition of water. Along with the total amount of dissolved substances, the therapeutic properties of water depend on the composition of ions that determine the degree of mineralization. Most (over 75) elements of the periodic table of D.I. Mendeleev and many thousands of chemical compounds of both natural and artificial origin have been found in natural waters. However, the degree of mineralization of water is usually formed by six main components: cations of sodium, magnesium, calcium, and anions of chloride, sulfate ion, and bicarbonate ion; under certain specific conditions, potassium (in water from the influence zone of potassium salt deposits), iron, aluminum (in acidic waters), and carbonate ion (in highly alkaline waters) can also play an equal role.
Since the aforementioned ions determine the character of water mineralization, they are called macrocomponents, and the chemical type of water is determined by the predominance of one or several of them. For example, sodium chloride water predominantly contains chloride ion among anions and sodium ion among cations; it is evident that if the water contains an increased amount of bicarbonates and chlorides, but more chlorides than bicarbonate ions, it is called bicarbonate-chloride water.
So, how many types of water can be distinguished by name based solely on the combinations of the six main macrocomponents? 225 (the sulfate-chloride-bicarbonate sodium-magnesium-calcium water differs from chloride-sulfate-bicarbonate water with the same cation composition), and if we then try to account for the number of arithmetically possible combinations considering cases of high potassium, iron, aluminum, carbonate ion content, one can get confused by the large number of types and their complex naming. However, in practical balneology, about 40 types of water have been identified, of which around 30 have been reliably established in the depths of Kyrgyzstan — from sodium bicarbonate waters in the Fergana ridge in the valley of the Karakol River (eastern) to aluminum sulfate waters (commonly referred to as alum-sulfate) near the settlement of Isfana.
Microcomponent composition of water. Besides the substances contained in natural waters in amounts that determine their mineralization, the main mass of the dry residue obtained from evaporating water often contains components that have little effect on the degree of mineralization. Due to their insignificant concentrations, they are called microcomponents. However, it is often these microcomponents that provide the therapeutic effect of the water. Such microcomponents include iodine, bromine, iron, possibly barium, copper, molybdenum, zinc; among them is arsenic, as arsenic-containing water is consumed in dosed amounts, as it can cause poisoning.
To assess the therapeutic value of waters containing microcomponents, criteria have been introduced — lower concentration limits. Based on these, the balneological type is determined.
The extraction of barium, zinc, molybdenum, copper, and lithium therapeutic waters is not conducted in our country, but in some other countries rich in hydromineral resources, part of such waters is extracted. For example, in Hungary, therapeutic barium water is considered to be water containing 5 mg/L or more of barium, in Bulgaria and Hungary, lithium water — 1 mg/L of lithium, strontium water — 10 mg/L of strontium.
In Kyrgyzstan, there are groundwater sources with iron content (in mg/L) up to 120, zinc — 8, barium — 24, strontium — 80, lithium — more than 3 (Karakshur mineral water group in the Fergana ridge), metasilicic acid — up to 62 mg/L and 116.7 (sources Chon-Kyzyl-Su and Altyn-Arashan (southern) in Southern Issyk-Kul).
Radioactivity of water. Among the radioactive elements in groundwater, radium, uranium, and radon are most commonly found, but only based on radon content can water be classified as therapeutic. The criterion for such classification is the presence of radon of at least 5 nCi/L. In Kyrgyzstan, therapeutic radon waters are found in many places, but practically only thermal ones are used — at the resort of Jety-Oguz and in the sanatorium of Jilisu (Keregetash) in the Teskey Ala-Too mountains; the radon content here reaches 40 and 25 nCi/L, respectively.
Active reaction (pH) of water. The positive influence of water pH on the body manifests during bathing procedures and irrigations, when at low values of the hydrogen ion concentration indicator, the skin is "tanned," and its epidermis thickens, while at high values, skin elasticity improves, and sebum is washed away. However, the positive therapeutic influence is not provided by the active reaction itself, but by the properties of the water.
Organic substances in water. It is practically impossible to find groundwater that does not contain organic substances in amounts ranging from several mg/L (usually in groundwater from magmatic rocks) to 1000 mg/L (near oil and gas deposits). All therapeutic waters contain some amount (most often the first tens of mg/L) of various organic materials — bitumens (oils), humic and fulvic substances, carbon compounds, phenols, fatty acids, etc.
Most likely, the organic matter in mineral waters exerts a therapeutic effect when the water has a low content of mineral salts and dissolved organic matter with oil.
In the conditions of Kyrgyzstan, such a picture is rarely observed within the foothills of the Fergana Valley, and reliable information about the presence of such waters here is currently lacking: usually, where there is a water-oil contact, the mineralization of the water is high, and where the water is low in mineralization, there is no oil.
Carbon dioxide in water. Carbonated waters are the most widely used mineral waters in our lives, as they are used not only for treatment but also as table waters with mineralization of less than 2 g/L. The criterion for classifying carbonated waters as drinking is the content of free carbon dioxide (CO2) of over 500 mg/L. Anyone who has drunk carbonated water from a regular street soda fountain can judge this amount — its CO2 concentration is close to 1.5–2 g/L.
The solubility of gases is highly dependent on pressure and temperature. In a spring, an open bottle, or a glass, carbonated water is under atmospheric pressure, where the solubility of free CO2 primarily depends on the temperature of the water and is 3.1 g/L for water at 2°C, 2.3 g/L at 10°C, and 0.97 g/L at 40°C. All excess gas above the maximum soluble amount under these conditions bubbles up to the surface and escapes into the atmosphere, meaning it is practically impossible to drink carbonated water at a temperature of 20°C with a carbon dioxide content of 2 g/L.
If carbonated water is left in an open bottle, it becomes "flat" after a short time, although there are almost no visible gas emissions. Here, the law works according to which the pressure of free CO2 in water and in the air must balance, and since there is little carbon dioxide in the atmosphere, the remaining equilibrium amount in the water is not felt in taste.
This property of carbon dioxide — to quickly evaporate from water upon reaching the surface — necessitates that when filling therapeutic and table waters into bottles, they are additionally artificially carbonated, which requires a large amount of carbon dioxide during industrial bottling.
Out of 28 main groups of drinking mineral therapeutic and table waters provided by GOST 13 273-73, Kyrgyzstan has only 9 groups of carbonated waters and additionally 10 groups not provided by GOST due to low mineralization (less than 2 g/L), which in turn gives grounds to assert that Kyrgyzstan is the richest republic in Central Asia in terms of diversity and reserves of carbonated waters.
Hydrogen sulfide, hydrosulfide, and titratable sulfur in water. This component is very diverse: under the general name "total hydrogen sulfide" or sometimes "titratable sulfur," the following are hidden: free molecular hydrogen sulfide (H2S), hydrosulfide (HS~), thiosulfate (S2O32'-), sulfite (S032^), and sulfide (S2~).
The biologically active agents in therapeutic hydrogen sulfide (or sulfide) waters are molecular hydrogen sulfide and hydrosulfide ion. An equilibrium is always established between them depending on the active reaction of the medium (pH).
More important than the form of titratable sulfur for balneology is the total content of this sulfur. Based on this criterion, sulfide waters are divided into weakly sulfide (with total hydrogen sulfide content of 10–15 mg/L), medium concentration (50–100 mg/L), and strong sulfide (over 100 mg/L).
In Kyrgyzstan, waters containing hydrogen sulfide, whose presence even in small amounts is easily determined by the characteristic smell of rotten eggs, are quite common. The highest concentrations are observed in the zone of oil-bearing structures along the foothills of Fergana, with a record content (830 mg/L) established at the Changyr-Tash sulfide water deposit.
Temperature of mineral waters. Regardless of the presence of other indicators and properties, natural hot and warm waters have always been considered therapeutic by the people, and their outlets were given personal names — Hot Spring (Krasnodar Krai), Jilandy (Gorno-Badakhshan Autonomous Region), Altyn-Arashan and Jilu-Bulak (Eastern Issyk-Kul), etc. Meanwhile, modern balneology does not find significant differences between naturally and artificially heated water of the same composition.
However, in a natural setting, elevated water temperature is usually an unconditional sign of prolonged movement underground, resulting in the accumulation of balneologically active components and indicators in the water that were previously absent — silicic acids, radon, high alkalinity, etc.
When assessing water temperature as an indicator of therapeutic value, it is generally accepted that water with a temperature of less than 20°C is cold, 20–35°C is warm (subthermal), 35–42°C is hot (thermal), and over 42°C is very hot (high thermal).
In Kyrgyzstan, there are waters with temperatures of all the above values and almost in all administrative and physical-geographical areas.
The composition and properties of mineral waters are characterized by a great variety in the content of biologically active components and indicators, so it is not surprising that their therapeutic use is also very diverse. Often, the same water helps to relieve various ailments — depending on the regimen, dosage, consumption, use of other therapeutic means, and methods. This, in turn, means that only a doctor is entitled to give any recommendations regarding the therapeutic use of water, but even an experienced physician will most often not provide advice on this issue without conducting a comprehensive study of the patient.
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