Quantification of soil pore network complexity with X-ray computed tomography and gas transport measurements

Flow and transport of gases through soils are largely controlled by pore structural attributes. The quantification of pore network characteristics is therefore essential for accurate prediction of air permeability and gas diffusivity. In this study, the pore network characteristics of seven different soils subjected to 22 mo of field regeneration were quantified with X-ray computed tomography (CT) and compared with functional pore characteristics estimated from measurements of air permeability and gas diffusivity. Furthermore, predictive models for air permeability and gas diffusivity were developed based on CT-derived structural parameters and compared with previously proposed predictive models. Strong correlations between functional and pore geometry parameters were observed. The consideration of CT-derived air-filled porosity, pore network tortuosity and connectivity, and minimum equivalent pore diameter in predictive gas diffusivity and air permeability models significantly improved their performance. The obtained results suggest that the application of X-ray CT-derived pore-structural parameters has great potential for predicting gas diffusivity and air permeability.