Details
| Original language | English |
|---|---|
| Pages (from-to) | 3-8 |
| Number of pages | 6 |
| Journal | Journal of Hydrology and Hydromechanics |
| Volume | 61 |
| Issue number | 1 |
| Publication status | Published - Mar 2013 |
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.
Keywords
- Hydrophobicity, Sessile drop method, Soil water repellency, Water drop penetration time, Wettability
ASJC Scopus subject areas
- Environmental Science(all)
- Water Science and Technology
- Engineering(all)
- Mechanical Engineering
- Chemical Engineering(all)
- Fluid Flow and Transfer Processes
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In: Journal of Hydrology and Hydromechanics, Vol. 61, No. 1, 03.2013, p. 3-8.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Small-scale contact angle mapping on undisturbed soil surfaces
AU - Bachmann, Joerg
AU - Goebel, Marc O.
AU - Woche, Susanne K.
N1 - Funding Information: Acknowledgement. Financial support by The German Research Foundation (DFG, SPP 1315 Biogeochemical Interfaces in Soil, BA1359/9-2) is greatly appreciated. We greatly thank Prof. Jürgen Böttcher for the analytical data of the soil profile ‘Elze’. Copyright: Copyright 2013 Elsevier B.V., All rights reserved.
PY - 2013/3
Y1 - 2013/3
N2 - 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.
AB - 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.
KW - Hydrophobicity
KW - Sessile drop method
KW - Soil water repellency
KW - Water drop penetration time
KW - Wettability
UR - http://www.scopus.com/inward/record.url?scp=84875410557&partnerID=8YFLogxK
U2 - 10.2478/johh-2013-0002
DO - 10.2478/johh-2013-0002
M3 - Article
AN - SCOPUS:84875410557
VL - 61
SP - 3
EP - 8
JO - Journal of Hydrology and Hydromechanics
JF - Journal of Hydrology and Hydromechanics
SN - 0042-790X
IS - 1
ER -