Geochemists from Tomsk and their Chinese colleagues have found out why alkaline mineral water from Jiangxi province is abnormally low in salts. This discovery will help find new similar sources, according to the press service of the Russian Science Foundation.
“We believe that their secret lies in the interaction of the thermal waters with the rock. The pH values continuously rise due to the absence of neutralizing acids, and the alkaline environment and high temperatures accelerate the processes of secondary mineral formation. Therefore, the elements do not accumulate in the solution, but are immediately bound by new minerals,”says Elena Zappa from Tomsk Polytechnic University.
Countless geysers and other hot springs are known on Earth in the vicinity of volcanoes or crustal faults. Passing through the heated layers of rocks, the water is enriched with minerals, the list and concentration of which vary greatly for different parts of the planet.
For example, in the Chinese province of Jiangxi, there are more than one hundred mineral water sources rich in nitrogen and carbon dioxide. They have long attracted the attention of not only local residents who use water for drinking and hot baths, but also scientists who are interested in the unusual chemical composition of water.
The fact is that there are almost no mineral compounds in the water from the hot streams of Jiangxi, moreover, it has a high level of alkalinity. While mineral water from other alkaline sources is completely uncommon - the higher the pH level, the more salts it contains.
To find out what this anomaly is connected with, Russian scientists and their Chinese colleagues went on an expedition three years ago to sources located near Nanchang, the capital of Jiangxi province.
There they collected water samples, analyzed them on site and in the laboratory, and were able to find the answer to this riddle. In doing so, the scientists relied on the concept developed by Professor Stepan Shvartsev, one of the largest Soviet and Russian hydrochemists and geologists.
In accordance with his ideas, water moving through rocks not only dissolves them and accumulates certain molecules and ions, but also continuously forms new minerals, some of which remain in the rock. Accordingly, the balance between the appearance of new substances and the dissolution of old ones determines the composition of the water that has reached the Earth's surface.
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For example, observations by Zappa and her colleagues of nitrogen water sources have shown that their composition is related to how the water interacts with various aluminosilicates (minerals containing aluminum, silicon and oxygen), as well as iron and sulfur compounds.
Carbonic waters are formed differently: a more acidic environment interferes with interaction with aluminosilicates and the appearance of new minerals, including calcite and other carbonates. Therefore, carbonic waters accumulate minerals better than nitrogen waters.
Accordingly, knowing where the rocks are necessary for such reactions, geologists can find sources of alkaline waters beneficial for athletes, diabetics and carriers of many other serious diseases.