Computed Tomography-estimated Transport Velocity and Chemical Dispersivity in Undisturbed Geomedia

Transport of pollutants to groundwater through geomedia is of concern to environmental engineers and scientists. The objective of this study was to utilize computed tomography (CT) to evaluate chemical transport through several undisturbed geomedia core samples. Linear pore velocities, dispersion coefficients, and dispersivity values were spatially determined at the downstream end of the core samples. Research showed that one of eight core samples had preferential flow paths which was expected due to the type of material evaluated. CT-time averaged, CT cross-sectionally averaged, and outflow methods gave average values of 0.0789, 0.0818, and 0.140 mm/s, respectively. The time-averaged CT method and cross-sectionally averaged CT method gave similar values for dispersivity (3.57 and 3.89 mm, respectively) while the outflow method gave higher values (4.98 mm). Higher dispersivity values for the outflow method were attributed to additional dispersion through the column end-plate. Future studies can evaluate chemical adsorption and degradation processes.