Chernobyl fallout in three areas of upland pasture in West Cumbria.

The ConCentrations of '"Cs and "'Cs originating from the Chernobyl fallout have been measured in the standing vegetation of three upland pastures over a ?+ear period. An exponential decay curve has been used in the past to dewrib the concentrations on agricultural cropsover a shon time span (about 2W days). However. a bener fit to the later stages of the present Wear span can be obtained by a power curve or a double exponential. Examples of the curves fined by differenf methods are given and a range of predicted values calculated tor the time to retllrn to preGhernobyl levels. Total inventories for the three pastures were established with sites at Corney Fell, Ennerdale and Wastwater containing 16M0, 122w and 14 1W Bq m-' '"Cs. respectively. On these sites the preChernobyl contribution of '37Cs is calculated as 17%. 38% and 34%. in all three soils whch are a peat, brown podzolic soil and a brown earth the main deposition of the Chernobyl material is held in the top layers which are highly organic. This has important implications for the long'term persistence of the radiocaesium in upland ecosystems: the root mat of the grassy Vegetation dominates the top layers and the potential for recycling Is large.Examples of the curves fined by differenf methods are given and a range of predicted values calculated tor the time to retllrn to preGhernobyl levels. Total inventories for the three pastures were established with sites at Corney Fell, Ennerdale and Wastwater containing 16M0, 122w and 14 1W Bq m-' '"Cs. respectively. On these sites the preChernobyl contribution of '37Cs is calculated as 17%. 38% and 34%. in all three soils whch are a peat, brown podzolic soil and a brown earth the main deposition of the Chernobyl material is held in the top layers which are highly organic. This has important implications for the long'term persistence of the radiocaesium in upland ecosystems: the root mat of the grassy Vegetation dominates the top layers and the potential for recycling Is large.