Small-scale contact angle mapping on undisturbed soil surfaces

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Title:Small-scale contact angle mapping on undisturbed soil surfaces
Creators:
Bachmann, Joerg; bachmann at ifbk dot uni-hannover dot de; Institute of Soil Science, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
Goebel, Marc-O.; Institute of Soil Science, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
Woche, Susanne K.; Institute of Soil Science, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
Journal or Publication Title:
Journal of Hydrology and Hydromechanics, 61, 1, pp. 3-8
Uncontrolled Keywords:Hydrophobicity, Sessile drop method, Soil water repellency, Water drop penetration time, Wettability

Abstract

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° and < 90°). 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 μL volume. Direct measurement on grain surfaces of the sand fraction is possible for grain sizes > 300 μm using drop volumes down to 0.1 μL. Geostatistical evaluation showed that the measurement grid scale is below the range of spatial dependency for droplets of 1 μL 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°, 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.

Official URL: http://147.213.145.2/vc/vc1.asp

Title:Small-scale contact angle mapping on undisturbed soil surfaces
Translated title:Small-scale contact angle mapping on undisturbed soil surfaces
Creators:
Bachmann, Joerg; bachmann at ifbk dot uni-hannover dot de; Institute of Soil Science, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
Goebel, Marc-O.; Institute of Soil Science, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
Woche, Susanne K.; Institute of Soil Science, Leibniz University Hannover, Herrenhäuser Str. 2, 30419 Hannover, Germany.
Uncontrolled Keywords:Hydrophobicity, Sessile drop method, Soil water repellency, Water drop penetration time, Wettability
Subjects:T Technology > TA Engineering (General). Civil engineering (General)
Divisions:Mathematics, Physics and Earth Sciences > Institute of Hydrodynamics > Journal of Hydrology and Hydromechanics
Journal or Publication Title:Journal of Hydrology and Hydromechanics
Volume:61
Number:1
Page Range:pp. 3-8
ISSN:0042-790X
Publisher:Institute of Hydrology of the Slovak Academy of Sciences and the Institute of Hydrodynamics of the Academy of Sciences of the Czech Republic
Related URLs:
URLURL Type
http://avi.lib.cas.cz/node/55Publisher
ID Code:7663
Item Type:Article
Deposited On:26 Mar 2013 15:39
Last Modified:26 Mar 2013 14:39

Citation

Bachmann, Joerg; Goebel, Marc-O.; Woche, Susanne K. (2013) Small-scale contact angle mapping on undisturbed soil surfaces. Journal of Hydrology and Hydromechanics, 61 (1). pp. 3-8. ISSN 0042-790X

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