The effect of wetting and drying cycles on soil chemical composition and their impact on bulk density evaluation: An analysis by using XCOM data and gamma-ray computed tomography

•Can the wetting and drying cycles cause changes on soil chemical composition?•Can these modifications affect the soil mass attenuation coefficient (μs)?•Measured and calculated values of μs presented good agreement.•CT showed that small changes in μs can cause slight soil bulk density alterations.

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 241Am and 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). The measured and calculated values of μ presented good agreement. Significant modifications were not observed in the total elemental composition of the soils after the application of W-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.