The soil elemental (oxides) composition variation of three Brazilian soils submitted to the application of wetting
and drying (W–D) cycles was measured in order to evaluate the possible changes in the calculated soil mass attenuation
coefficient (μ) as a function of the cycles.Measurements of μ by using radioactive sources of 241Amand
137Cs were also performed. Gamma-ray computed tomography (CT)was used as a tool to evaluate the impact of
changes in μ induced by the cycles in determinations of soil bulk density (ds). Themeasured and calculated values
of μ presented good agreement. Significant modifications were not observed in the total elemental composition
of the soils after the application ofW–D cycles. As a consequence only slight changes in μ were observed. However,
the use of CT allowed concluding that even small changes in μ can cause some change in ds.