Figure 9.

Examples of positron imaging of fluid transport processes in soil. A) Flow within a sand column with and without a cylindrical obstruction was imaged using positron emission tomography (PET) of [¹⁸F]FDG.¹¹⁵ B) PET imaging of ⁶⁴Cu and ¹⁸F in porous media consisting of sand- and silt-sized quartz coated with goethite and illite.¹²⁰ [⁶⁴Cu]Cu-MCPA complex moved slowly relative to a [¹⁸F]F⁻, which suggests Cu-MCPA interaction with goethite. A, B) Flow was driven from the bottom-up to reduce preferential flow channels and flow fingering and to allow escape of any gases formed during reactive flow. The PET imagery in A) was adapted from the Journal of Applied Physics, 76, Boutchko R, Rayz VL, Vandehey NT, O’Neil JP, Budinger TF, Nico PS, Druhan JL, Saloner DA, Gullberg GT, & Moses WW, Imaging and modeling of flow in porous media using clinical nuclear emission tomography systems and computational fluid dynamics, 74-81, Copyright (2012), with permission from Elsevier. The graphics in B were adapted from Ref. ¹²⁰ under Creative Commons Attribution International License CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).