Development and application of a new sessile drop contact angle method to assess soil water repellency

verfasst von: J. Bachmann, A. Ellies, K. H. Hartge
Abstract: Existing methods for determining the contact angle as a measure of the water repellency of soils are either indirect, or cumbersome and time-consuming. Our objective was to develop a new method that is simpler than the existing procedures like the capillary rise method and that still yields accurate and reproducible results. To this end, we applied the so-called sessile drop method. To obtain the needed plane sample surface and to reduce geometrical effects, a single layer of air-dry soil particles is sprinkled on double-sided adhesive tape. Eight droplets of deionized water are placed carefully on this horizontal particle layer. Immediately after sample preparation, the contact angle at the three-phase boundary was measured with a goniometer-fitted microscope. In order to test the new method, contact angle measurements were carried out with wettable soil material that was hydrophobized, and with soils showing a wide range of natural water repellency. Both wettable silt and sand were made hydrophobic with Dimethyldichlorosilane and diluted with untreated soil to obtain a defined variation in the solid surface tension. Contact angle measurements showed a nonlinear decrease with increasing amounts of wettable particles in the 40-90°contact angle domain. Generally, the contact angle decrease was predictable and could be described with an empirical model. For volcanic ash soils showing a wide range of repellency, the contact angles of different, narrowly sieved soils fractions (<20 μm, 20-38 μm, 38-63 μm, and 63-100 μm) were within the range of 25-110°. The impact of the different sieved soil fractions on the contact angles was found to be small. Measurements performed with independent replicates showed good reproducibility across the whole range of contact angles. (C) 2000 Elsevier Science B.V.
Organisationseinheit(en): Institut für Bodenkunde
AG Bodenphysik
Externe Organisation(en): Universidad Austral de Chile
Typ: Artikel
Journal: Journal of hydrology
Band: 231-232
Seiten: 66-75
Anzahl der Seiten: 10
ISSN: 0022-1694
Publikationsdatum: 29.05.2000
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Gewässerkunde und -technologie
Elektronische Version(en): https://doi.org/10.1016/S0022-1694(00)00184-0 (Zugang: Unbekannt)

BibTeX

@article{65cadc46a5e94ba78da2f8e3d7522e93,
title = "Development and application of a new sessile drop contact angle method to assess soil water repellency",
abstract = "Existing methods for determining the contact angle as a measure of the water repellency of soils are either indirect, or cumbersome and time-consuming. Our objective was to develop a new method that is simpler than the existing procedures like the capillary rise method and that still yields accurate and reproducible results. To this end, we applied the so-called sessile drop method. To obtain the needed plane sample surface and to reduce geometrical effects, a single layer of air-dry soil particles is sprinkled on double-sided adhesive tape. Eight droplets of deionized water are placed carefully on this horizontal particle layer. Immediately after sample preparation, the contact angle at the three-phase boundary was measured with a goniometer-fitted microscope. In order to test the new method, contact angle measurements were carried out with wettable soil material that was hydrophobized, and with soils showing a wide range of natural water repellency. Both wettable silt and sand were made hydrophobic with Dimethyldichlorosilane and diluted with untreated soil to obtain a defined variation in the solid surface tension. Contact angle measurements showed a nonlinear decrease with increasing amounts of wettable particles in the 40-90°contact angle domain. Generally, the contact angle decrease was predictable and could be described with an empirical model. For volcanic ash soils showing a wide range of repellency, the contact angles of different, narrowly sieved soils fractions (<20 μm, 20-38 μm, 38-63 μm, and 63-100 μm) were within the range of 25-110°. The impact of the different sieved soil fractions on the contact angles was found to be small. Measurements performed with independent replicates showed good reproducibility across the whole range of contact angles. (C) 2000 Elsevier Science B.V.",
keywords = "Contact angle, Hydrophobic soil, Volcanic ash soil",
author = "J. Bachmann and A. Ellies and Hartge, {K. H.}",
note = "Copyright: Copyright 2004 Elsevier Science B.V., Amsterdam. All rights reserved.",
year = "2000",
month = may,
day = "29",
doi = "10.1016/S0022-1694(00)00184-0",
language = "English",
volume = "231-232",
pages = "66--75",
journal = "Journal of hydrology",
issn = "0022-1694",
publisher = "Elsevier",
}