Assessment of Selected Methods for Estimating Chemical Transport Parameters from Computed Tomographic Imaging

Groundwater vulnerability to pollutant transport through soil and geologic materials is an environmental concern. A study was conducted to evaluate selected methods for averaging pixels in computed tomography (CT) images obtained with dynamic chemical transport through several undisturbed core samples. Computed tomography scans of dynamic fluid transport studies allowed spatial estimates of transport pore velocity and dispersivity parameters. Group pixel averaging methods were used to determine these properties. Averaging methods ranged from 0.5 by 0.5 mm resolution to 10 by 10 mm resolution. Results showed that transport parameter estimates varied slightly as a function of which method was selected. These studies showed that the lower resolution images produced more consistent values as well as values approximating estimates determined from the core average experiments. Recommendations for future studies indicate accurate results are obtained with the 2 by 2 mm resolution (compromise between the highest resolution for more data and the lowest resolution for results similar to the core average). Experimental results appeared appropriate for the geomedia used in this study.