Residence half-times of 137Cs in undisturbed surface soil in Nigeria based on measured soil concentration profiles.

Abstract

The transport of fallout 137 Cs within the Nigerian soil has been studied in this paper by a compartment model. The measured concentrations of the radionuclide in the soil layers were examined by the model in order to estimate the transport parameters of residence half-time and the migration velocity of the radionuclide in the soils. The residence half-times were observed to be short and decreased with soil depth with a mean ranging from 0.3 years at 0 -2cm soil depth in Akure site to 1.4 years at 10-15cm depth in Igbeti site. The migration velocity ν , calculated from the residence times with the consideration of the different thicknesses of the layers were observed to decrease slowly with depth at all the sampling sites with a range from 3.62 cm y -1 at Igbeti site to 8.21 cm.y -1 at Ikogosi site. The migration velocities obtained are quite higher than those reported in literature for global fallout.