A simplified 137CS transport model for estimating erosion rates in undisturbed soil

(CS)-C-137 is an artificial radionuclide with a half-life of 30.12 years which released into the environment as a result of atmospheric testing of thermo-nuclear weapons primarily during the period of 1950s-1970s with the maximum rate of (CS)-C-137 fallout from atmosphere in 1963. (CS)-C-137 fallout is strongly and rapidly adsorbed by fine particles in the surface horizons of the soil, when it falls down on the ground mostly with precipitation. Its subsequent redistribution is associated with movements of the soil or sediment particles. The Cs-137 nuclide tracing technique has been used for assessment of soil losses for both un-disturbed and cultivated soils. For undisturbed soils, a simple profile-shape model was developed in 1990 to describe the Cs-137 depth distribution in profile, where the maximum (CS)-C-137 occurs in the surface horizon and it exponentially decreases with depth. The model implied that the total (CS)-C-137 fallout amount deposited on the earth surface in 1963 and the (CS)-C-137 profile shape has not changed with time. The model has been widely used for assessment of soil losses on undisturbed land.