Institute of Radiation Safety and Ecology, NNC RK, Kurchatov, Kazakhstan.
PLoS One. 2023 Jan 6;18(1):e0278581. doi: 10.1371/journal.pone.0278581. eCollection 2023.
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.
为了全面了解生态系统周围的放射性生态状况，对作物产品的安全性进行预测评估，并为放射性污染地区制定合理的恢复策略，有必要获取土壤中放射性核素的垂直分布数据。本研究对原塞米巴拉金斯克试验场（STS）试验场外地区（即未进行核武器或放射性战争剂核效应试验的地区）土壤中的放射性核素垂直分布进行了调查。在整个塞米巴拉金斯克试验场，以 5 厘米的间隔，分层采集土壤样本，深度达 30 厘米。在整个研究区域，大多数高活度浓度的放射性核素都集中在 0-5 厘米的土壤层中。通过 γ、β 和 α 谱仪对采集的土壤样本中主要的人为放射性核素的活度浓度进行了测定。结果，在 0-5、5-10、10-15、15-20、20-25 和 25-30 厘米土壤层中，确定了 137Cs、241Am、90Sr 和 239+240Pu 的活度浓度范围。在传统的“背景”区域，即 0-5 厘米土壤层，平均包含（整个土壤剖面深度的总活度浓度百分比）：137Cs-83%，239+240Pu-87%和 90Sr-38%。对于 1953 年羽流，这些值分别为 92%、83%和 73%。在 0-5 厘米土壤层中，1951 年羽流的值分别为：137Cs-93%，239+240Pu-93%和 90Sr-59%。在所有研究区域，放射性核素的最低浓度都出现在 20-30 厘米深的地方。90Sr 是在土壤中向下迁移能力最强的放射性核素。研究发现，基于检测到的活度，土壤中放射性核素的垂直迁移率如下（降序排列）：90Sr＞137Cs＞239+240Pu＞241Am。还计算了确定 0-20 和 0-30 厘米土壤覆盖层中放射性核素活度浓度与 0-5 厘米表土中该放射性核素活度浓度之比的系数。这些系数可根据 0-5 厘米土壤层中放射性核素的活度浓度来估算各土壤采样点的放射性核素含量。
