Determination of the initial 137Cs fallout on the areas contaminated by Chernobyl fallout

The fallout radioisotope 137Cs is widely used to study rates and patterns of soil redistribution. This method requires the knowledge about the initial fallout of cesium in the study area. This paper describes the method of establishing the initial fallout of cesium for a study area which is contaminated by Chernobyl fallout. The study was carried out on the loess area near the Ujazd village (South-West Poland). The 137Cs activities for reference soil cores varied from 4.41(24) kBq/m2 to 5.97(26) kBq/m2. The average value of the reference inventory of 137Cs for the study area is 5.23(15) kBq/m2. The calculated contribution of the Chernobyl 137Cs fallout in the total cesium is equal 69 %. Moreover the annual values of the 137Cs fallout based on the precipitation data were calculated and presented. This study provides the method of calculating the 137Cs fallout connected with the nuclear weapon testing based on the precipitation data. Moreover, this study also indicated that the spatial variability on the highly contaminated by Chernobyl cesium study area is small (RSD about 10%) and thus it is possible to use the cesium method to study soil redistribution.