RESUMO
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.
Assuntos
Radioisótopos de Césio/toxicidade , Acidente Nuclear de Chernobyl , Monitoramento de Radiação , Poluentes Radioativos do Solo/toxicidade , Radioisótopos de Césio/química , Poluição Ambiental , Humanos , Cinza Radioativa , Rios , Poluentes Radioativos da Água/toxicidadeRESUMO
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.
Assuntos
Acidente Nuclear de Chernobyl , Monitoramento de Radiação , Cinza Radioativa , Poluentes Radioativos da Água , Radioisótopos de Césio/análise , Europa (Continente) , Sedimentos Geológicos , Cinza Radioativa/análise , Federação Russa , Poluentes Radioativos da Água/análiseRESUMO
Little information currently exists regarding the small-scale spatial variability of Chernobyl radiocaesium fallout and associated inventories. This contribution reports the results of a study of the variability of 137Cs inventories within the 2.18-km2 Lapki balka catchment located near Tula in central Russia. The local area was characterized by 137Cs inventories in excess of 200 kBq m-2 immediately after the Chernobyl accident and pre-existing bomb-derived inventories can be ignored in view of their very low magnitude. Field sampling and measurements included both collection of soil cores for subsequent laboratory analysis and in situ field measurements using a CORAD portable detector. The results obtained show evidence of a systematic south-north increase in the reference inventory across the basin, which must be taken into account when interpreting subsequent radiocaesium redistribution within the basin. Random spatial variability of 137Cs inventories of a similar magnitude to that reported for bomb-derived fallout was also documented. The extent of random spatial variability varied between different geomorphological units. Maximum variability, with coefficients of variation up to 20%, was associated with areas of sediment accumulation within the balka bottoms. Substantial variability (cv. typically ca. 15%) was found within flat cultivated areas and undisturbed areas both on the interfluves and on the balka sides, all of which could serve as reference sites. Minimum variability (cv. typically ca. 12%) was associated with the cultivated slopes with no evidence of sediment accumulation.
Assuntos
Agricultura , Radioisótopos de Césio/análise , Centrais Elétricas , Cinza Radioativa/análise , Liberação Nociva de Radioativos , Poluentes Radioativos do Solo/análise , Geografia , Monitoramento de Radiação/instrumentação , Monitoramento de Radiação/métodos , Análise de Regressão , Reprodutibilidade dos Testes , Federação Russa , UcrâniaRESUMO
This paper summarizes key findings and identifies the main lessons learnt from a 5-year (2002-2008) coordinated research project (CRP) on "Assessing the effectiveness of soil conservation measures for sustainable watershed management and crop production using fallout radionuclides" (D1.50.08), organized and funded by the International Atomic Energy Agency through the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture. The project brought together nineteen participants, from Australia, Austria, Brazil, Canada, Chile, China, Japan, Morocco, Pakistan, Poland, Romania, Russian Federation, Turkey, United Kingdom, United States of America and Vietnam, involved in the use of nuclear techniques and, more particularly, fallout radionuclides (FRN) to assess the relative impacts of different soil conservation measures on soil erosion and land productivity. The overall objective of the CRP was to develop improved land use and management strategies for sustainable watershed management through effective soil erosion control practices, by the use of ¹³7Cs (half-life of 30.2 years), ²¹°Pb(ex) (half-life of 22.3 years) and 7Be (half-life of 53.4 days) for measuring soil erosion over several spatial and temporal scales. The environmental conditions under which the different research teams applied the tools based on the use of fallout radionuclides varied considerably--a variety of climates, soils, topographies and land uses. Nevertheless, the achievements of the CRP, as reflected in this overview paper, demonstrate that fallout radionuclide-based techniques are powerful tools to assess soil erosion/deposition at several spatial and temporal scales in a wide range of environments, and offer potential to monitor soil quality. The success of the CRP has stimulated an interest in many IAEA Member States in the use of these methodologies to identify factors and practices that can enhance sustainable agriculture and minimize land degradation.