Relating caesium-137 and soil loss from cultivated land

Because of the limitations associated with traditional methods of measuring rates of soil erosion, such as erosion plots, the fallout radionuclide caesium-137 (137Cs) has been increasingly used in recent years as an alternative approach to estimating rates of soil redistribution on both cultivated and noncultivated areas. The successful application of the 137Cs approach depends heavily on the availability of reliable conversion models for converting measurements of 137Cs redistribution, relative to the local reference inventory, to estimates of soil redistribution rates. In the absence of empirical conversion models, most studies have made use of theoretical conversion models. The assumptions made by such theoretical models are frequently untested and they thus remain largely unvalidated. This contribution describes the results of a measurement programme involving nine experimental plots located in southern Italy, aimed at validating several of the basic assumptions commonly associated with the use of mass balance models for estimating rates of soil redistribution on cultivated land from 137Cs measurements. Overall, the results confirm the general validity of these assumptions. However, several other assumptions and process representations incorporated into such models still require testing and elucidation.