Pore structure analysis via X-ray μCT: Enhancing soil macroaggregate models for water permeability and carbon sequestration

Abstract

Soil macroaggregates are crucial for carbon sequestration, water retention, and soil fertility. Their ecological functions are influenced by their pore characteristics. Yet, the relationship between pore structure and the movement of water and carbon within macroaggregates is not fully understood. In this study, the porosity, connectivity, and morphology of macroaggregate pores in three typical soil types in China were characterized. Additionally, water permeability and carbon sequestration were modeled based on in-situ CT-scanning images. The results indicated that the macropores within the macroaggregates serve as the primary channels for water permeability, while pore morphology of mesopores significantly influences carbon sequestration. The water permeability increased with the presence of macropores and enhanced connectivity within the macroaggregates. Dissolved organic carbon (DOC) showed a pronounced correlation with oblate pores across all samples, and a more intricate structure offered more surface area space, trapping additional carbon particles. The established model not only elucidates how various pore structures influence the transport of carbon particles and carbon sequestration but also simulates the structural changes in macroaggregates throughout the process. This allows for an intuitive understanding of water and carbon distribution and migration. This research presents an innovative simulation of water and carbon distribution within macroaggregates using micron-scale CT data.