Small-scale contact angle mapping on undisturbed soil surfaces

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Bachmann, Joerg; Goebel, Marc-O.; Woche, Susanne K.: Small-scale contact angle mapping on undisturbed soil surfaces. In: Journal of Hydrology and Hydromechanics 61 (2013), Nr. 1, S. 3-8. DOI: http://dx.doi.org/10.2478/johh-2013-0002

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Sum total of downloads: 264




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Research of the last years pointed out that most soils are neither completely hydrophilic nor hydrophobic, but exhibit a subcritical level of water repellency (i.e. contact angle, CA > 0 degrees and < 90 degrees). Soil water repellency (SWR) is mainly caused by organic compounds of different origin and structure, showing the relevance of biofilms and organic coatings present at many particle surfaces. Despite the importance of SWR for hydraulic processes like preferential flow phenomena, generation of heterogeneous moisture patterns, or surface run-off generation, detailed investigations on the spatial variability of SWR at various scales have rarely been carried out. We introduce a new and easy-to-apply operation for measuring the spatial distribution of SWR using a modified sessile drop method for direct optical assessment of CA at a small scale. The specific objectives of this paper are to apply a sampling and preparation technique that preserves the original spatial arrangement of soil particles and to characterize soil wettability in terms of CA at a high spatial resolution. Results revealed that the sampling and preparation technique allows determination of CA at the millimeter scale using droplets of 1 mu L volume. Direct measurement on grain surfaces of the sand fraction is possible for grain sizes > 300 mu m using drop volumes down to 0.1 mu L. Geostatistical evaluation showed that the measurement grid scale is below the range of spatial dependency for droplets of 1 mu L volume, but not for measurements on single grains (pure nugget effect). Results show further that the small-scale differences in wettability, especially for CA < 90 degrees, cannot be detected by the conventional WDPT test. From these findings it can be concluded that the proposed technique allows the identification of small-scale variations in wettability that may promote the formation of heterogeneous flow fields and moisture patterns in soil under unsaturated conditions.
License of this version: CC BY-NC-ND 3.0 Unported
Document Type: Article
Publishing status: publishedVersion
Issue Date: 2013
Appears in Collections:Naturwissenschaftliche Fakultät

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pos. country downloads
total perc.
1 image of flag of Germany Germany 173 65.53%
2 image of flag of United States United States 31 11.74%
3 image of flag of China China 14 5.30%
4 image of flag of France France 5 1.89%
5 image of flag of Korea, Republic of Korea, Republic of 4 1.52%
6 image of flag of Iran, Islamic Republic of Iran, Islamic Republic of 4 1.52%
7 image of flag of No geo information available No geo information available 3 1.14%
8 image of flag of Russian Federation Russian Federation 3 1.14%
9 image of flag of Czech Republic Czech Republic 3 1.14%
10 image of flag of Canada Canada 2 0.76%
    other countries 22 8.33%

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