135Cs/137Cs isotopic composition of environmental samples across Europe: Environmental transport and source term emission applications

Abstract

(135)Cs/(137)Cs isotopic analyses represent an important tool for studying the fate and transport of radiocesium in the environment; in this work the (135)Cs/(137)Cs isotopic composition in environmental samples taken from across Europe is reported. Surface soil and vegetation samples from western Russia, Ukraine, Austria, and Hungary show consistent aged thermal fission product (135)Cs/(137)Cs isotope ratios of 0.58 ± 0.01 (age corrected to 1/1/15), with the exception of one sample of soil-moss from Hungary which shows an elevated (135)Cs/(137)Cs ratio of 1.78 ± 0.12. With the exception of the outlier sample from Hungary, surface soil/vegetation data are in quantitative agreement with values previously reported for soils within the Chernobyl exclusion zone, suggesting that radiocesium at these locations is primarily composed of homogenous airborne deposition from Chernobyl. Seawater samples taken from the Irish Sea show (135)Cs/(137)Cs isotope ratios of 1.22 ± 0.11 (age corrected to 1/1/15), suggesting aged thermal fission product Cs discharged from Sellafield. The differences in (135)Cs/(137)Cs isotope ratios between Sellafield, Chernobyl, and global nuclear weapons testing fallout indicate that (135)Cs/(137)Cs isotope ratios can be utilized to discriminate between and track radiocesium transport from different nuclear production source terms, including major emission sources in Europe.

Fukushima Daiichi reactor source term attribution using cesium isotope ratios from contaminated environmental samples

“…Results from our group, Zheng et al [17] and Taylor et al [8] for one such material (IAEA-375) are [8] White triangles represent grass, bark, and moss samples analyzed by Shibahara et al [20] White dots A, B, and C represent particulate tape sample datapoints for hourly 137 Cs airborne concentrations given by Tsuruta et al [3] (see also Fig. 5) shown in Supplementary have not yet reported values for IAEA-375, personal communications between our group and Dr Shibahara have revealed that both our groups have made measurements that are within statistical agreement for the reference material IAEA-156 (with errors in the 4% 2σ range; exact results from our group on this material have been reported elsewhere [38] [8] for the J-village soil (which is located~30 km south of the FDNPP site). While a much larger set of analyses at known locations to the south is needed for definitive determination of the extent of homogeneity in the 135 Cs/ 137 Cs isotopic composition to the south/southwest of the FDNPP site, currently available 135 Cs/ 137 Cs isotope data from locations in this direction appear to have a consistent 135 Cs/ 137 Cs isotope ratio of~0.376 (which is slightly higher than the value of 0.34 ± 0.01 previous reported by Zheng et al for samples to the northwest [8] ).…”

“…While Shibahara et al . (Kyoto University Research Reactor Institute, Osaka, Japan) have not yet reported values for IAEA‐375, personal communications between our group and Dr Shibahara have revealed that both our groups have made measurements that are within statistical agreement for the reference material IAEA‐156 (with errors in the 4% 2σ range; exact results from our group on this material have been reported elsewhere). Agreement between measurements made by our group, Shibahara et al ., and Zheng et al .…”

Analysis of cesium isotope compositions in environmental samples by thermal ionization mass spectrometry-3

“…These values are significantly higher than those of the plant samples, as shown in Table 2. The 135 Cs/ 137 Cs isotopic ratio of IAEA-156 obtained in this study was in agreement with that of IAEA-373 obtained in this study and the reported data for IAEA-156 [25], within error; these values were used as the 135 Cs/ 137 Cs isotopic ratio of the nuclear material released in the accident at CNPP. The average analytical error was ∼0.1% for the 135 Cs/ 137 Cs isotopic ratio determined in a previous analysis of Cs in plant samples [2][3][4], while the analytical errors for the 135 Cs/ 137 Cs ratio in this study was higher than that of the previous study.…”

“…It was confirmed that the three-time method was required for the recovery of Cs from the soil samples in this study (except for samples OK01 and OK03) and the IAEA-156 and IAEA-373 standard reference materials. In the case of the one-time method, the observed mass spectra were influenced by impurities, as also observed by Snow and coworkers [25]. However, in the previous study [2][3][4], the analytical error for the plant sample data showed a weaker dependence on the concentration of 137 Cs; the magnitude of the error was also lower than that of the soil sample.…”

“…The plot shows that the error was correlated with the concentration of 137 Cs. In the reports by Snow et al [25][26][27], the error in the 135 Cs/ 137 Cs isotopic ratio was not influenced by the loading amount in the range of 1-5 Bq. The error obtained in this study might not be strongly influenced by the Cs loading based on this result ( Figure 1 shows the dependence of the error on the concentration of 137 Cs); the results presented by Snow et al also showed a good correlation with this dependency.…”