Spatial and Temporal Reconstruction of Chernobyl (137)Cs Initial Fallout Field on Soil Within upper Lokna River Basin

The study area is located within the upper Lokna River basin with a catchment area of about 35 km(2). The schematic map of (137)Cs initial fallout after the Chernobyl disaster in 1986 on soil was drawn. The method of selecting reference sites and soil sampling scheme are given in detail-for statistically correct description of radionuclide initial fallout field. 12 soil samples were selected from each of the six reference sites to characterize the average amount of radionuclide in the upper 30 cm of the soil profile. Additionally, some single sampling points were used on erosion-stable areas adjacent or located within the catchment, as well as the "truncated" samples of the radionuclide inventory from the catchment bottom. The cesium soil contamination in 1986 immediately after the Chernobyl accident was restored taking into account the half-life of (137)Cs. The schematic map adequately correlated with the aerial photography data performed by Hydromet in 1986.