Downward Migration of Chernobyl-Derived Radionuclides in Soils in Poland and Sweden

The Chernobyl accident on April 26, 1986 resulted in significant fallout of ¹³⁷Cs and ^239,240Pu on surface soils throughout northern Europe. There is a substantial amount of information that is embedded in the distribution of radionuclides with depth in a soil profile that may be extracted to characterize and quantify erosion rates and mechanisms, understand watershed retention and sediment delivery ratios, trace sediment source regions, constrain sediment budgets, calculate watershed inventories and residence times, determine transit distance and transit time of sediment and pollutants, refine our ability to predict dose exposure rates, determine exposure from food-chain transfer, and plan environmental remediation and clean-up. Moreover, ignoring this evidence may lead to a real risk of drawing incorrect conclusions from an incomplete understanding of the radionuclide profiles. Therefore, there is a need to better understand their downward migration in soils. Despite the use of these radionuclides and their activity-depth profiles, little is known about how the profile shapes develop or why they differ with location. Presented here are soil profiles and Hydrus-1D model simulations of ¹³⁷Cs, ²¹⁰Pb_xs and ^239,240Pu from the Lazy, Tulowice and Bor za Lasem sites in Poland and the Hille and Skogsvallen sites in Sweden so that the profiles of these nuclides may be compared with those obtained previously to better understand the downward migration.