Journal of Earth Sciences and Geotechnical Engineering

The Variations of Gamma-Ray Attenuation Coefficients with Depth for Southwestern Nigerian Soil Types

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•                                                   Abstract
  
  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, μ_s , 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 μ_s 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 μ_s for the individual soil series are graphically displayed in this work. Regular monitoring and documentation of μ_s 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.