X-ray microtomography analysis of soil pore structure dynamics under wetting and drying cycles

Pires, Luiz F.; Auler, Andr� C.; Roque, Waldir L.; Mooney, Sacha J.

Abstract

The soil water retention curve is one of the most important properties used to predict the amount of water available to plants, pore size distribution and hydraulic conductivity, as well as knowledge for drainage and irrigation modeling. Depending on the method of measurement adopted, the water retention curve can involve the application of several wetting and drying (W-D) cycles to a soil sample. The method assumes soil pore structure is constant throughout however most of the time soil structure is dynamic and subjected to change when submitted to continuous W-D. Consequently, the pore size distribution, as well as other soil morphological properties can be affected. With this in mind, high resolution X-ray Computed micro-Tomography was utilized to evaluate changes in the soil pore architecture following W-D cycles during the procedure of the water retention curve evaluation. Two different soil sample volumes were analyzed: ROIW (whole sample) and ROIHC (the region close to the bottom of the sample). The second region was selected due to its proximity to the hydraulic contact of the soil with the water retention curve measurement apparatus. Samples were submitted to the following W-D treatments: 0, 6 and 12 W-D. Results indicated the soil changed its porous architecture after W-D cycles. The image-derived porosity did not show differences after W-D cycles for ROIW; while for ROIHC it increased porosity. The porosity was also lower in ROIHC in comparison to ROIW. Pore connectivity improved after W-D cycles for ROIHC, but not for ROIW. W-D cycles induced more aligned pores for both ROIs as observed by the tortuosity results. Pore shape showed changes mainly for ROIW for the equant and triaxial shaped pores; while pore size was significantly influenced by the W-D cycles. Soil water retention curve measurements showed that W-D cycles can affect water retention evaluation and that the changes in the soil morphological properties can play an important role in it.

Citation

Pires, L. F., Auler, A. C., Roque, W. L., & Mooney, S. J. (2020). X-ray microtomography analysis of soil pore structure dynamics under wetting and drying cycles. Geoderma, 362, Article 114103. https://doi.org/10.1016/j.geoderma.2019.114103

• Journal Article Type: Article
• Acceptance Date: Nov 18, 2019
• Online Publication Date: Jan 3, 2020
• Publication Date: Mar 15, 2020
• Deposit Date: Nov 22, 2019
• Publicly Available Date: Jan 4, 2021
• Journal: Geoderma
• Print ISSN: 0016-7061
• Electronic ISSN: 1872-6259
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 362
• Article Number: 114103
• DOI: https://doi.org/10.1016/j.geoderma.2019.114103
• Keywords: Soil structure; Pore shape; Pore size distribution; Soil micromorphology; 3D image analysis
• Public URL: https://nottingham-repository.worktribe.com/output/3354758
• Publisher URL: https://www.sciencedirect.com/science/article/pii/S0016706119307037?via%3Dihub
• Additional Information: This article is maintained by: Elsevier; Article Title: X-ray microtomography analysis of soil pore structure dynamics under wetting and drying cycles; Journal Title: Geoderma; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.geoderma.2019.114103; Content Type: article; Copyright: © 2020 The Authors. Published by Elsevier B.V.
• Contract Date: Nov 22, 2019