The variability of Chernobyl Cs retention in the water column of lakes in the English Lake District, two years and four years after deposition

Radiocaesium activity was measured in 26 lakes in the English Lake District (North-West England) in 1988 and in 1990. Several lakes showed measurable Cs activity, even though calculations suggested that, by these times, levels of Chernobyl fallout should have been undetectable in almost all lakes. Several factors, including negative correlations between Cs activity levels in the water column and ilitic clay mineral content in the sediment, point to remobilisation from fibrous peat soils (peat bogs) within the catchment as the source of residual Cs activity in the water column. Loss rates of up to 2.2% of the catchment inventory per annum were observed. Extrapolation of these arguments suggests that all lakes in catchments containing soils poor in clay minerals are likely to receive significantly radiocaesium contributions from the catchment, considerably increasing the recovery time after an accidental input. (Author)