Redistribution of Chernobyl-derived radiocaesium across the landscape: Field observations and spatial modelling

¹ Utrecht Centre for Environment and Landscape Dynamics-UCEL, Faculty of Geographical Sciences, Utrecht University, P.O. Box 80115, 3508 TC Utrecht, The Nethedands
² VUJE Tmava a.s., Okruzna 5, 91864 Trnava, Slovakia
³ Department of Physical Geography, Odessa State I.I. Mechicov University, Shampansky Per. 2, 270058 Odessa, Ukraine

Abstract

In the framework of the EC-funded SPARTACUS project, redistribution of Chernobyl-derived radiocaesium at the catchment scale due to runoff and soil erosion and deposition was evaluated by means of rainfall experiments, soil sampling, and spatial modelling. Two GIS-embedded models have been developed, which simulate lateral radiocaesium transport at the event scale and long-term radiocaesium redistribution, respectively. The results from the rainfall experiments and model calculations demonstrate that from the runoff plots and on steep hill slopes where erosion rates are largest, the ¹³⁷Cs transport occurs mainly in particulate form. Due to internal deposition, the contribution of particulate ¹³⁷Cs transport to total ¹³⁷Cs transport decreases with increasing catchment size. During the fifteen years since the accident, soil contamination by radiocaesium has decreased by a factor of 3 to 4 at the steep hill slopes as a result of both radioactive decay and soil erosion. In the valley bottoms, inputs of radiocaesium attached to deposited soil particles have maintained the soil contamination at the 1986 level. The spatial patterns of radiocaesium gains and losses during individual rainfall events resemble the long-term patterns.