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Understanding peatland hydrological processes and phenomena is critical for peatland management. Peat soils have a complex pore structure that affects hydrological processes. However, the micro-scale characteristics of peat pore space and their impact on hydraulic and transport properties have not been deeply investigated. This study characterized the pores in peat soil using 2D/3D X-ray computed tomography images and examined the connection between pore features and the simulated permeability. There were no apparent variations in porosity or pore morphology in different directions for peat soils with different degrees of decomposition at the pore scale. Peat soil with a high degree of decomposition had more numerous smaller pores with lower pore connectivity and higher tortuosity. Spherical pores were the highest proportion of total pores in peat soils, followed by ellipsoidal, long columnar, and branching pores. The diameters of spherical and ellipsoidal pores were small and isolated, and thus water in the peat soil flows preferentially through the more connected columnar and branching pores. The high permeability in peat soils was closely associated with the high porosity and abundance of well-connected and low tortuosity pore networks. The results of this study can provide insights into the underlying hydrological processes and also provide realistic parameters for use in multi-scale 3D digital soil-structure models and numerical simulations. [ABSTRACT FROM AUTHOR]

The pore geometry and topology properties of pore space in rocks are significant for a better understanding of the complex hydrologic and elastic properties. However, geometry and topology information about the sandstone pore structures is not fully available. In this study, we obtained the topological and geometrical pore parameters from a representative elementary volume (REV) for fluid flow in sandstone samples. For comparison, eight types of sandstones with various porosities were studied based on the X-ray micro-computed tomography technique. In this study, the REV size was selected based on the parameters from the respective pore network models (PNM), not just the porosity. Our analysis indicates that despite different porosity, all the sandstone samples have highly triangular-shaped pores and a high degree of pore structural isotropy. The high porosity group sandstones exhibit wider ranges of pore sizes than the low porosity group sandstones. Compared to the high porosity group sandstones, the low porosity group sandstones samples showing a higher global aspect ratio, indicating some pores exist in the form of bottlenecks. The pore topological properties of different sandstones show a high dependence of the porosity. The high porosity group sandstones obtain large coordination numbers, large connectivity densities and low tortuosities. The results from this study will help better understand the complex pore structure and the fluid flow in sandstone. [ABSTRACT FROM AUTHOR]