Synchrotron microtomographic quantification of geometrical soil pore characteristics affected by compaction
Soil compaction degrades soil structure and affects water, heat, and gas exchange as well as root penetration and crop production. The objective of this study was to use X-ray computed microtomography (CMT) techniques to compare differences in geometrical soil pore parameters as influenced by compac...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-05-01
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| Series: | SOIL |
| Online Access: | http://www.soil-journal.net/2/211/2016/soil-2-211-2016.pdf |
| Summary: | Soil compaction degrades soil structure and affects water, heat, and gas
exchange as well as root penetration and crop production. The objective of
this study was to use X-ray computed microtomography (CMT) techniques to
compare differences in geometrical soil pore parameters as influenced by
compaction of two different aggregate size classes. Sieved (diameter < 2 mm
and < 0.5 mm) and repacked (1.51 and 1.72 Mg m<sup>−3</sup>) Hamra soil
cores of 5 by 5 mm (average porosities were 0.44 and 0.35) were imaged at
9.6 μm resolution at the Argonne Advanced Photon Source (synchrotron
facility) using X-ray CMT. Images of 58.9 mm<sup>3</sup>
volume were analyzed using 3-Dimensional Medial Axis (3-DMA) software.
Geometrical characteristics of the spatial distributions of pore structures
(pore radii, volume, connectivity, path length, and tortuosity) were
numerically investigated. Results show that the coordination number (CN)
distribution and path length (PL) measured from the medial axis were
reasonably fit by exponential relationships P(CN) = 10<sup>−CN∕Co</sup> and
P(PL) = 10<sup>−PL∕PLo</sup>, respectively, where Co and PLo are the
corresponding characteristic constants. Compaction reduced porosity, average
pore size, number of pores, and characteristic constants. The average pore
radii (63.7 and 61 µm; <i>p</i> < 0.04), largest pore volume (1.58 and
0.58 mm<sup>3</sup>; <i>p</i> = 0.06), number of pores (55 and 50; <i>p</i> = 0.09), and
characteristic coordination number (3.74 and 3.94; <i>p</i> = 0.02) were
significantly different between the low-density than the high-density
treatment. Aggregate size also influenced measured geometrical pore
parameters. This analytical technique provides a tool for assessing changes
in soil pores that affect hydraulic properties and thereby provides
information to assist in assessment of soil management systems. |
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| ISSN: | 2199-3971 2199-398X |