Cesium-137 in the environment of the Altay Region (Russia)

The results of the extensive measurements of Cesium-137 (¹³⁷Cs) in virgin soils, plants, forest litter and lake bottom sediments of Altay Region in 1992-1995 are presented. Analyses of the vertical soil profiles indicate that ¹³⁷Cs is present in the upper 5-20 cm of the soil. Crops and the majority of wild plants show no signs of contamination with ¹³⁷Cs even in areas where soil is contaminated. A regional map of ¹³⁷Cs concentration is presented, which shows a highly irregular pattern of radio-cesium deposition from the nuclear tests on the Semipalatinsk Nuclear Polygon between 1949 to 1962. This kind of lateral distribution of ¹³⁷Cs in Altay virgin topsoils cannot be accounted for only by the distance from the nuclear testing site, on the contrary, it seems to be predominantly dependent on the weather conditions and a pattern of rainfall at the time of Semipalatinsk explosions. The article discusses the factors causing the post-precipitation redistribution of ¹³⁷Cs in the soil column and demonstrates that forest litter, lichen and lake bottom sediments can be used as sensitive indicators of the historical and current radioactive contamination.