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| Titel |
Examining the effect of pore size distribution and shape on flow through unsaturated peat using computed tomography |
| VerfasserIn |
F. Rezanezhad, W. L. Quinton, J. S. Price, D. Elrick, T. R. Elliot, R. J. Heck |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 13, no. 10 ; Nr. 13, no. 10 (2009-10-28), S.1993-2002 |
| Datensatznummer |
250012033
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| Publikation (Nr.) |
 copernicus.org/hess-13-1993-2009.pdf |
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| Zusammenfassung |
| The hydraulic conductivity of unsaturated peat soil is controlled by the
air-filled porosity, pore size and geometric distribution as well as other
physical properties of peat materials. This study investigates how the size
and shape of pores affects the flow of water through peat soils. In this
study we used X-ray Computed Tomography (CT), at 45 μm resolution under
5 specific soil-water pressure head levels to provide 3-D, high-resolution
images that were used to detect the inner pore structure of peat samples
under a changing water regime. Pore structure and configuration were found
to be irregular, which affected the rate of water transmission through peat
soils. The 3-D analysis suggested that pore distribution is dominated by a
single large pore-space. At low pressure head, this single large air-filled
pore imparted a more effective flowpath compared to smaller pores. Smaller
pores were disconnected and the flowpath was more tortuous than in the
single large air-filled pore, and their contribution to flow was negligible
when the single large pore was active. We quantify the pore structure of
peat soil that affects the hydraulic conductivity in the unsaturated
condition, and demonstrate the validity of our estimation of peat
unsaturated hydraulic conductivity by making a comparison with a standard
permeameter-based method. Estimates of unsaturated hydraulic conductivities
were made for the purpose of testing the sensitivity of pore shape and
geometry parameters on the hydraulic properties of peats and how to evaluate
the structure of the peat and its affects on parameterization. We also
studied the ability to quantify these factors for different soil moisture
contents in order to define how the factors controlling the shape
coefficient vary with changes in soil water pressure head. The relation
between measured and estimated unsaturated hydraulic conductivity at various
heads shows that rapid initial drainage, that changes the air-filled pore
properties, creates a sharp decline in hydraulic conductivity. This is
because the large pores readily lose water, the peat rapidly becomes less
conductive and the flow path among pores, more tortuous. |
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