Assessment of X-Ray Micro-Ct Measurements of Porosity and Solute Concentration Distributions During Diffusion in Porous Geologic Media

Agbogun, Henry; Hussein, Esam M.A.; Al, Tom A.

doi:10.1615/jpormedia.v16.i8.10

Cited by 4 publications

(2 citation statements)

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“…Iodide content in natural soils is very low and typically ranges from 0.5 to 20 mg kg −1 (Whitehead, 1984). High water solubility of potassium iodide ( KI ) makes it very attractive as a dopant for dual‐energy X‐ray CT in porous media (Agbogun et al, 2013; Wildenschild et al, 2002, 2013).…”

Section: Methodsmentioning

confidence: 99%

“…The dual‐energy method was later expanded by combining the use of heavy elements (dopants or contrast agents) incorporated into the pore solution (Vinegar & Wellington, 1987; Wildenschild et al, 2002) or bound to organic matter (Peth et al, 2014; Van Loo et al, 2014), with synchrotron monochromatic beams at energy levels immediately below and above the photoelectric absorption edge of the dopant elements. Algebraic subtraction of the below‐edge images from those of the above‐edge visualizes the voxels with dopant presence (Agbogun, Hussein, & Al, 2013; Costanza‐Robinson, Harrold, & Lieb‐Lappen, 2008; Peth, 2010; Peth et al, 2014; Wildenschild et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Mass‐balance approach to quantify water distribution in soils based on X‐ray computed tomography images

Guber

Kutlu

Rivers

et al. 2020

European J Soil Science

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X‐ray computed tomography (CT) is commonly used in soil science to quantify distributions of pores, water and solids within soil samples. Particularly promising for liquid visualization is dual‐energy scanning of samples with added dopant solutions. The approach uses solutions of heavy elements as a proxy for the soil water and utilizes the abrupt increase of the mass attenuation coefficient of heavy elements when crossing an X‐ray absorption edge, detectable by dual‐energy CT scanning. However, a key step in visualization of the added liquid is image segmentation. In partially saturated soils, the X‐ray CT images consist of voxels with the presence of solid, liquid and gaseous phases in different ratios. These ratios are generally ignored by the traditional image segmentation methods, which separate image voxels into groups with either zero or complete saturation by either prevailing phase. The objective of this study was to develop and test a new physically based segmentation approach that accounts for partial saturation of image voxels by liquids. We combined a theoretical equation for detected photon intensity with the mass conservation equation to compute saturation of image voxels by dopant solution applied to the soil. This approach was tested on soil micro‐columns with potassium iodide (KI) solutions. The proposed approach outperformed the traditional segmentation methods, particularly at low and intermediate water contents. Tests conducted for KI solutions in the concentration ranges from 2 to 20% revealed deterioration of the method accuracy with decreasing dopant concentration in the soil. Based on the results of this study we recommend 10 wt% KI solution for quantifying spatial distribution of liquids in soils using dual‐energy X‐ray microtomography. Highlights We developed a new approach to quantify soil water distribution based on X‐ray CT. This approach accounts for partial saturation of image voxels by liquids. This approach outperforms the standard image segmentation methods. Its application is limited to using dual energy monochromatic X‐ray beams.

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