Natural Radionuclides in Soils in the Area of the Elkon Plateau Uranium Deposit in South Yakutia

The radioecological situation of the mothballed geological survey site at the Elkon Plateau deposit in the Aldan Highlands was assessed by field radiometry. It was found that the extraction of a huge mass of radioactive rocks to the surface from underground mine workings (adits, mines) has significantly increased the area with an elevated background radiation of 1.0–12.0 µSv/h and more. The studies have shown that under conditions of anthropogenic contamination, the determining factors of migration, distribution, and accumulation of natural radionuclides in soils, besides their chemical properties, are humid climate, genetic features of radioactive ore, presence of permafrost rocks, soil-forming processes, and organic matter content. In the existing conditions of mountain taiga landscapes, the intensity of wind dispersion of radionuclides from dumps is significantly lower than that of hydrogenic dispersion. Active leaching of uranium from the dump rocks led to a dramatic disturbance of the radioactive equilibrium between radium and the parent radionuclide towards its excess in the soils of the Akin Creek Valley. Prolonged uncontrolled environmental impact of radioactive dumps contributed to the accumulation of uranium and radium in soils to levels of low- (14 252–66 836 Bq/kg) and medium-activity (102 294–601 987 Bq/kg) solid radioactive waste. At present, the problem of environmental contamination with natural radionuclides in the Elkon uranium ore mining district remains extremely urgent and requires close attention of nature conservation specialists.