Re-examination of Cs-137 depth profiles in undisturbed soils in Northern Germany

Knowledge of the evolution of Cs-137 vertical profile in soils after a surface contamination is crucial for predicting the transfer to human food chains and/or groundwater contamination. The objective of this study is the re-examination the vertical distribution of Cs-137 originating from the Chernobyl accident and nuclear weapons fallout at undisturbed soil profiles in northern Germany sampled in 1992 and 1994 and recently in 2014 at two identical locations. The goals are to measure and compare the depth distributions between the two sampling dates and also between the two regions. Moreover, a mathematical model based on the convection-dispersion equation will be fitted to the data of each soil core. The comparison between profiles taken at different times is expected to provide more reliable modelling results. For both locations, the first one characterised as Orthic Podsol and the second one as Umbric Gleysol, Cs-137 could be detected until 72 cm respectively 48 cm depth. Results, in general, demonstrate decreasing activity concentrations with depth with values ranging from about 29.5 to 0.1 Bq/kg and from about 11.5 to 0.1 Bq/kg respectively. Additionally, the expected downward migration of Cs-137 between the past and recent soil core is observed.