Summary. The transport of fallout Cs-137 within the Nigerian soil has been studied in this paper by the compartment and the diffusion-convection models. The measured concentrations of the radionuclide in the soil layers were examined by the models in order to estimate the accumulation and migration velocity of the radionuclide in the soils of the study area. The transport parameters of residence half-time, migration velocity, diffusion coefficient and the convective velocities of the radionuclide were evaluated. The mean residence half times ô of the radionuclide in the soil layers were observed to range 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 was observed to range from 3.62 cm y-1 at Igbeti to 8.21 cm.y-1 at Ikogosi site. The range of the diffusion coefficient obtained is 0.002 ­ 1.002 cm2 per year while the convective velocity  ranged from 0.007 to 1.00. The migration velocities were quite higher than those reported in literature for global fallout while the diffusion rate of the radionuclide is slower compared to literature values.


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(*) Dr. Isaac Rotimi Ajayi is Associate Professor and Head of the Department of Physics at Adekunle Ajasin University in Akungba, Akoko, Ondo State, Nigeria. He obtained a Ph.D in 1994 at the University of Ibadan in Nigeria. He started teaching physics in Ondo State University in 1990. His current research field is environmental radioactivity. Dr. Ajayi has been a Regular Associate of the Abdus Salam ICTP since 2006.

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