Mineral waters from two tectonically active mountain systems within the Alpine-Himalayan orogenic belt, the Pamir and the Greater Caucasus (Elbrus region), were analyzed for
222Rn activity and
238U concentrations to establish correlations with geological conditions, physicochemical characteristics of water, and to
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Mineral waters from two tectonically active mountain systems within the Alpine-Himalayan orogenic belt, the Pamir and the Greater Caucasus (Elbrus region), were analyzed for
222Rn activity and
238U concentrations to establish correlations with geological conditions, physicochemical characteristics of water, and to assess the potential health risk associated with
238U and
222Rn. It was found that in mineral waters of the Pamir, the concentrations of
238U (0.004–13.3 µg/L) and activity of
222Rn (8–130 Bq/L) are higher than in the Elbrus area: 0.04–3.74 µg/L and 6–33 Bq/L, respectively. Results indicate that uranium mobility in water is strongly influenced by T, pH, and Eh, but is less affected by the age of host rocks or springs' elevation, whereas radon activity in waters depends on the age of rocks, spring elevation,
238U content, and values of δ
18O and δ
2H in water. This study reveals fundamental geological distinctions governing uranium and radon sources in the mineral waters of these regions. Isotopic evidence (
222Rn and
3He/
4He) demonstrates crustal radon sources prevail in Pamir, whereas the Elbrus system suggests mantle-derived components. The U concentrations do not exceed 30 µg/L, and most water samples (94%) showed
222Rn activities below 100 Bq/L, complying with the drinking water exposure limits recommended by the World Health Organization and European Union Directive. However, in intermountain depressions of the Pamirs, at low absolute elevations (~2300 m), radon concentrations in water can increase significantly, which requires special attention and study.
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