Preliminary studies on radon concentration in CO2-rich mineral waters of the Elbrus area (Caucasus, Russia)

Abstract

The geological and geochemical conditions as well as radon concentrations of ten manifestations of СО2-rich waters in the Elbrus area are considered in this paper. Also, content of uranium and thorium were measured in waters and in host rocks. The data were compared with chemical and isotopic composition of associated gases. It is established that water bearing rocks are classified into rocks of low and normal radioactivity. The contents of uranium (<1.37 μg/L) and thorium (<0.3 μg/L) in the water are low. Measurements of radon concentrations in water and gas flux of mineral springs in the Elbrus area indicate that most of them are weakly radioactive (6–33 Bq/L, 25-350 Bq/m3, respectively). The CO2-rich mineral waters of the Tyrnyauz exhibit the highest level of radioactivity (33 Bq/L) within the Elbrus area. Isotopical gas studies have shown that within the Elbrus region there is a connection with the deep horizons of the Earth's crust, from which various fluids (water and gases) can rise to the surface. Although Rn values are low and cannot be used for medical purposes, natural objects with similar characteristics can be used to observe the state of the geological environment (e.g. earthquakes) and as natural laboratories to establish the mechanisms of deep gas migration to the surface.