APPLICATION OF PB-210 IN SOILS

The gamma spectroscopic measurement of soil samples is described. Pb-210 data from a soil survey in western-Europe are briefly reviewed. The average Pb-210 flux from the atmosphere, as determined from Pb-210(exc) soil inventories, is 90 Bq m(-2) a(-1). A simple one-dimensional box-chain model is described. The model simulates the vertical, past depositional transport of natural and fall-out radionuclides in the soil. Simulation of measured Pb-210(exc), (CS)-C-134, Cs-137, and Am-241 soil profiles shows that mixing (bioturbation) is a very efficient transport mechanism. Lead seems to be strongly fixed to organic and clay particles. It is transported by the displacement of the organic and clay carrier substances. The mean residence time of lead, caesium, plutonium and americium in organic rich forest soils is in the order of 250-1000 years. An applicability study to investigate the use of Pb-210 in erosion problems showed erosion rates from 60-180 g m(-2) a(-1) on organic rich forest and meadow sites with 10 degrees-25 degrees slopes.