RESUMEN
Vast areas of Europe were contaminated by the fallout of 137Cs and other radionuclides, as a result of the Chernobyl accident in 1986. The post-fallout redistribution of Chernobyl-derived 137Cs was associated with erosion and sediment transport processes within the fluvial system. Bottom sediments from lakes and reservoirs can provide a valuable source of information regarding the post-fallout redistribution and fate of 137Cs released by the Chernobyl accident. A detailed investigation of sediment-associated 137Cs in the bottom sediments of a reservoir in a Chernobyl-affected area in Central Russia has been undertaken. A new approach, based on the vertical distribution of 137Cs activity concentrations in the reservoir bottom sediment makes it possible to separate the initially deposited bottom sediment, where the 137Cs activity reflects the direct fallout of Chernobyl-derived 137Cs to the reservoir surface and its subsequent incorporation into sediment deposited immediately after the accident, from the sediment mobilized from the catchment deposited subsequently. The deposits representing direct fallout from the atmosphere was termed the "Chernobyl peak". Its shape can be described by a diffusion equation and it can be distinguished from the remaining catchment-derived 137Cs associated with sediment accumulated with sediments during the post-Chernobyl period. The 137Cs depth distribution above the "Chernobyl peak" was used to provide a record of changes in the concentration of sediment-associated 137Cs transported from the upstream catchment during the post-Chernobyl period. It was found that the 137Cs activity concentration in the sediment deposited in the reservoir progressively decreased during the 30-year period after the accident due to a reduction in the contribution of sediment eroded from the arable land in the catchment. This reflects a reduction in both the area of cultivated land area and the reduced incidence of surface runoff from the slopes during spring snowmelt due to climate warming.
Asunto(s)
Accidente Nuclear de Chernóbil , Monitoreo de Radiación , Ceniza Radiactiva , Contaminantes Radiactivos del Agua , Radioisótopos de Cesio/análisis , Europa (Continente) , Sedimentos Geológicos , Ceniza Radiactiva/análisis , Federación de Rusia , Contaminantes Radiactivos del Agua/análisisRESUMEN
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.