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

The results of the extensive measurements of Cesium-137 (Cs-137) in virgin soils, plants, forest litter and lake bottom sediments of Altay Region in 1 992-1995 are presented. Analyses of the vertical soil profiles indicate tha t Cs-137 is present in the upper 5-20 cm of the soil. Crops and the majorit y of wild plants show no signs of contamination with Cs-137 even in areas w here soil is contaminated. A regional map of Cs-137 concentration is presen ted, which shows a highly irregular pattern of radio-cesium deposition from the nuclear tests on the Semipalatinsk Nuclear Polygon between 1949 to 196 2. This kind of lateral distribution of Cs-137 in Altay virgin topsoils can not be accounted for only by the distance from the nuclear testing site, on the contrary, it seems to be predominantly dependent on the weather condit ions and a pattern of rainfall at the time of Semipalatinsk explosions. The article discusses the factors causing the post-precipitation redistributio n of Cs-137 in the soil column and demonstrates that forest litter, lichen and lake bottom sediments can be used as sensitive indicators of the histor ical and current radioactive contamination.