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

Cs-135/Cs-137 isotopic analyses represent an important tool for studying the fate and transport of radiocesium in the environment; in this work the Cs-135/Cs-137 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 Cs-135/Cs-137 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 Cs-135/Cs-137 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 Cs-135/Cs-137 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 Cs-135/Cs-137 isotope ratios between Sellafield, Chernobyl, and global nuclear weapons testing fallout indicate that Cs-135/Cs-137 isotope ratios can be utilized to discriminate between and track radiocesium transport from different nuclear production source terms, including major emission sources in Europe. (C) 2015 Elsevier Ltd. All rights reserved.