The Gamma-Ray transmission method was used in this
work to experimentally determine the attenuation coefficients of soil layers
collected at eight locations in Southwestern Nigeria at depths of 0-15, 15-30,
30-50, 50-70, 70-90, and 90-120cm into the soil profile. Undisturbed samples
from Iwo, Ondo, Egbeda, Itagunmodi, Okemessi, Mamu, Origo and Jago soil series
of Southwestern Nigeria were collected in June 2006 and using gamma-ray energy
pairs of 122 and 1112 keV and 344 and 1408 keV obtained from europium-152 (152Eu ) radionuclide, the mass attenuation coefficients for soil, ìs , at varying soil depths of these series were
calculated. The measured attenuation coefficients are observed to vary
exponentially with photon energy for all the soil series studied in this work.
The variation of ìs with soil depth show
that in all the series, the top soil (0-15cm depths) is least attenuating with
gamma ray penetrability decreasing down the profile. The variations of ìs for the individual soil series are graphically
displayed in this work. Regular monitoring and documentation of ìs over a long period of time can be used to develop
(mathematical) models for the variation of this important soil physical
property in this part of the world.