The effect of landscape factors on natural radioactivity of soils in Siberia

Data on uranium, thorium and potassium contents define natural radioactivity of native landscape soils of the Altai Territory, Altai Republic, Novosibirsk, and Kemerovo regions. These values change in different landscape conditions within a wide range, with average Th/U ratios of 3.1–3.9. The dependence of U and Th contents and Th/U ratio in soils on composition of soil-forming rocks was established at the example of Altai Territory. The natural variations of U, Th, K contents and Th/U ratios in soils under the identical landscape conditions, the influence of local situation changes, and U and Th distribution in landscape-geochemical catenae are demonstrated. The influence of soil types characterizing soil-forming processes is of a minor importance. The distribution down the soil sections is even, especially on rocks with homogeneous composition. The major variations of values are revealed in humus soil horizon. The scheme maps of Th/U ratio distribution in the upper soil horizons (humus and humus-accumulate) were constructed. The contents of U and Th and Th/U ratios in natural landscapes of Siberia corroborate an absence of anthropogenic radioactive contamination of the territory by these radionuclides.