Development of an approach to estimating mid- to long-term critical loads for radiocaesium contamination of cow milk in western Europe.

This paper describes the application of the critical load methodology, developed to set emission targets for atmospheric pollutants, to radioecology. The critical load can be redefined within radioecology as the radionuclide deposition at which radionuclide activity concentrations in a specified food product will exceed the maximum permitted level. An empirically based approach is described which provides estimates of critical load values for cow milk in the mid- to long-term after an accident when soil-to-plant transfer of radiocaesium is largely responsible for plant radiocaesium contamination. The areas identified as being most potentially vulnerable to radiocaesium deposition using this approach are those with extensive areas of organic soils such as western Scotland, parts of Ireland, The Netherlands and Denmark. The classification of European soil types into soil groups with significantly different soil-to-plant transfer of radiocaesium, and the allocation of a transfer value to each soil group provide the greatest uncertainties within this approach. Potential problems and deficiencies affecting the estimation of parameter values are discussed.