Use of caesium-137 and lead-210 as tracers in soil erosion investigations

Recent years have seen increasing interest in the potential for using caesium-137 as a tracer in soil erosion investigations and caesium-137 measurements are now accepted as an effective and valuable means of producing retrospective information on medium-term rates and patterns of soil redistribution. There are, however, two important limitations to the general application of the approach. These involve the complications introduced by inputs of Chernobyl-derived radiocaesium in many areas of Europe and the relatively low caesium-137 inventories encountered in some parts of the globe where fallout rates were low. Unsupported lead-210, a natural fallout radionuclide, can offer a viable alternative to caesium-137 as a sediment tracer in many environments. In addition, when used in combination with caesium-137, it offers potential as a complementary tracer, which can provide additional information on the erosional history of a site. The results of a study of soil redistribution within a small cultivated field at Butsford Barton, Colebrooke, Devon, UK, aimed at comparing the estimates provided by caesium-137 and unsupported lead-21 Omeasurements, are presented. These results confirm the potential for using unsupported lead-210, both as an alternative to, and in combination with, caesium-137 in soil erosion investigations.