Data on the transfer of artificial radionuclides from the environment to the food supply is necessary for internal dose assessment. There is a necessity for expanding and improving the available information on these factors in order to make better dose models for specific scenarios. This paper describes the results of a field experiment with broiler chickens on the transfer factor (F f) and concentration ratio (C R) for the long-term intake of 241 Am and 137 Cs with grass meal and soil. The broilers were divided into two groups, each group had nine subgroups and each subgroup had three broilers. The radionuclide concentrations in the feed and the thigh muscle, thigh bone, and liver of 54 broilers divided between the grass meal and soil groups were evaluated by gamma spectrometry for 241Am and 137Cs. The duration of feeding with "contaminated" sources ranged between 1-70 days. The equilibrium stage of 241 Am in muscle and bone occurs on the 1 st and 40 th day, respectively; for 137 Cs in muscle-30 th days of intake and for liver and bone-7 th days. For 241 Am, the liver did not reach equilibrium stage during the 70 days of intake. F f of 137 Cs in the "forage-muscle" and "soil-muscle" systems were determined as 1.9±0.3 and 0.18±0.05; F f of 241 Am in the "soil-muscle" system was-7.5×10 −5 .
The article addresses the pattern of vertical distribution of the major long-lived man-made radionuclides 137Cs, 241Am, 90Sr and 239+240Pu in soils of the Semipalatinsk Test Site. Areas of different contamination with radionuclides are discussed – places of aboveground nuclear and fusion tests conducted at the ‘Experimental Field’ site, the fallout in the form of plumes within the Semipalatinsk Test Site, areas of radiological warfare agent tests at the ‘4А’ site, areas of meadow ecosystems associated with radioactively contaminated water streams from test adits of the ‘Degelen’ testing site, conventionally ‘background’ areas of the test site, in which no nuclear or fusion tests were conducted. In the course of research, differences were revealed in the vertical distribution of radionuclides of interest in soils of the above areas. Differences are attributed to the pattern of how contamination with radionuclides is formed and to abiotic and biotic factors such as physical and chemical soil properties, moistening conditions, human activity and others. Based upon findings, recommendations were developed, aimed at the optimization of research into the vertical distribution of radionuclides in the soil cover of the former Semipalatinsk test Site. In particular, it was found that when undertaking such research, it was sufficient to confine oneself to dividing a territory by the soil type and restrict the research depth to 30 cm.
Data on the vertical distribution of radionuclides in the soil is necessary to fully understand the radioecological situation around ecosystems, give predictive estimates to how safe crop products are and justify a rehabilitation strategy for radioactively contaminated areas. A study was conducted to investigate the vertical distribution of radionuclides in soils of the former Semipalatinsk Test Site (STS) territory beyond its testing sites, that is, in areas in which no nuclear weapons or nuclear effects of radiological warfare agents were tested. Soil was sampled layerwise all over the Semipalatinsk Test Site down to 30 cm deep at a 5-cm spacing. Most of high activity concentrations of radionuclides all over the study area were detected in the 0–5 cm soil layer. Activity concentrations of the major man-made radionuclides were determined in soil samples collected by γ-, β and α-spectrometry. As a result, ranges of activity concentrations of 137Cs, 241Am, 90Sr and 239+240Pu were determined in 0–5, 5–10, 10–15, 15–20, 20–25, 25–30 cm soil layers. In the conventionally ‘background’ area, the 0–5 cm soil layer, on average, contains (the percentage of total activity concentration across the soil profile depth): 137Cs– 83%, 239+240Pu– 87% and 90Sr– 38%. For the 1953 plume, these values were 92%, 83% and 73%, respectively. Values for the 1951 plume in the 0–5 cm soil layer were: 137Cs– 93%, 239+240Pu– 93% and 90Sr– 59%. The minimum concentration of radionuclides are observed 20–30 cm deep in all areas studied. 90Sr is the most mobile radionuclide from the perspective of its ability to travel deep down the soil. The study found out that the nuclide vertical migration rates downward in soils based on detected activity were as follows (in descending order): 90Sr– 137Cs– 239+240Pu– 241Am. Coefficients that determine the ratio of the activity concentration of the radionuclide in the 0–20 and 0–30 cm soil cover layers to that of this radionuclide in the 0–5 cm topsoil were calculated. These coefficients enable to estimate the radionuclide inventory at each soil sampling point from their activity concentration in the 0–5 cm soil layer.
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