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

The results of the extensive measurements ofCesium-137 (137Cs) in virgin soils, plants,forest litter and lake bottom sediments of AltayRegion in 1992–1995 are presented. Analyses of thevertical soil profiles indicate that 137Cs ispresent in the upper 5–20 cm of the soil. Crops andthe majority of wild plants show no signs ofcontamination with 137Cs even in areas where soilis contaminated. A regional map of 137Csconcentration is presented, which shows a highlyirregular pattern of radio-cesium deposition from thenuclear tests on the Semipalatinsk Nuclear Polygonbetween 1949 to 1962. This kind of lateraldistribution of 137Cs in Altay virgin topsoilscannot be accounted for only by the distance from thenuclear testing site, on the contrary, it seems to bepredominantly dependent on the weather conditions anda pattern of rainfall at the time of Semipalatinskexplosions. The article discusses the factors causingthe post-precipitation redistribution of 137Cs inthe soil column and demonstrates that forest litter,lichen and lake bottom sediments can be used assensitive indicators of the historical and currentradioactive contamination.