Hydrogeological conditions and hydrogeochemistry of radon waters in the Zaeltsovsky–Mochishche zone of Novosibirsk, Russia

Hydrogeological and hydrogeochemical conditions, the concentrations of major and some minor ions, and ²²²Rn were determined in the Zaeltsovsky–Mochishche field in the southern part of West Siberia. The water abundance of sediments varies within a broad range, and water discharge yields of the wells are 25–110 m³/day. Waters are fracture-related, cold with the temperature of 6–10 °C, occurring at a depth of 50–200 m. All the wells penetrating granites and near-contact hornstones were tested for ²²²Rn content in groundwater. The type of groundwater in the zone is Ca HCO₃ and Ca–Na HCO₃ with total dissolved solids 322–895 mg/l. The concentrations of ²³⁸U and ²²⁶Ra do not exceed 0.098 mg/l and 1.9∙10–9 mg/l, respectively. The concentration of ²²²Rn in the groundwater of the Zaeltsovsky–Mochishche field is 11–801 Bq/l. The forms of uranium occurrence in radon waters are represented mainly by the uranyl-carbonate complexes of calcium Ca₂UO₂(CO₃)₃(aq) (61–75%) and CaUO₂(CO₃)₃²⁻ (25–36%).