THE VARIABILITY OF CHERNOBYL CS RETENTION IN THE WATER COLUMN OF LAKES IN THE ENGLISH LAKE DISTRICT, 2 YEARS AND 4 YEARS AFTER DEPOSITION

Radiocaesium activity was measured in 26 lakes in the English Lake Dis trict (North - West England) in 1988 and in 1990. Several lakes showed measurable Cs activity, even though calculations suggested that. by t hese 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 illitic clay minera l content in the sediment, point to remobilisation from fibrous peat s oils (peat bogs) within the catchment as the source of residual Cs act ivity in the water column. Loss rates of up to 2.2% of the catchment i nventory per annum were observed. Extrapolation of these arguments sug gests that all lakes in catchments containing soils poor in clay miner als are likely to receive significant radiocaesium contributions from the catchment, considerably increasing the recovery time after an acci dental input.