title: Three dimensional imaging of porosity and tracer concentration distributions in a dolostone sample during diffusion experiments using X-ray micro-CT.
abstract: X-ray micro-computed tomography (micro-CT) techniques for measuring the three-dimensional (3-D) distributions of diffusion-accessible porosity (φ(d)) and temporal tracer-concentrations (C(t)) within a dolostone sample subjected to solute diffusion are developed and tested in this work. The φ(d) and C(t) measurements are based on spatially resolved changes in X-ray attenuation coefficients in sequentially acquired 3-D micro-CT datasets using two (calibration and relative) analytical approaches. The measured changes in X-ray attenuation coefficient values are a function of the mass of X-ray absorbing potassium-iodide tracer present in voxels. Mean φ(d) values of 3.8% and 6.5% were obtained with the calibration and the relative approaches, respectively. The detection limits for φ(d) measurements at individual voxel locations are 20% and 36% with the calibration and the relative methods, respectively. The detection limit for C(t) are 0.12 M and 0.22 M with the calibration and the relative approaches, respectively. Results from the calibration method are affected by a beam-hardening artifact and although results from the relative approach are not affected by the artifact, they are subject to high detection limits. This work presents a quantitative assessment of micro-CT data for studies of solute transport. Despite limitations in precision and accuracy, the method provides quantitative 3-D distributions of φ(d) and C(t) that reflect solute diffusion in heterogeneous porous geologic media.
authors.affiliation: Department of Earth Sciences, University of New Brunswick, Fredericton, New Brunswick, Canada E3B 5A3.
authors.forename: H M D
authors.initials: HM
authors.lastname: Agbogun
authors.forename: Tom A
authors.initials: TA
authors.lastname: Al
authors.forename: Esam M A
authors.initials: EM
authors.lastname: Hussein
mesh_terms: D002138:Calibration; D004058:Diffusion; D019015:Geologic Sediments; D021621:Imaging, Three-Dimensional / Q000379:methods*; D016062:Porosity; D011193:Potassium Iodide / Q000032:analysis*; D055114:X-Ray Microtomography / Q000379:methods*
chemical_list: D011193:Potassium Iodide