Capturing water repellency cessation time by means of characteristic time method

verfasst von: Nasrollah Sepehrnia, Jörg Bachmann
Abstract: Persistence of water repellency is a significant physical key factor that governs water infiltration into unsaturated soil. We investigated water and ethanol infiltration using the characteristic time method (CTM), repellency index (RI), and the contact angle (CA) behavior for a comprehensive assessment on soil water repellency (SWR). We analyzed the impact of soil structure and thermal and wetting–drying treatments on water and ethanol infiltration. The first objective was to evaluate the CTM for water-repellent soils by partitioning characteristic and gravity infiltration behavior (I_char and I_grav) and to evaluate parameters like infiltration beginning (t_b) and gravity times (t_char and t_grav). The second objective was to characterize the CTM estimated water sorptivity (S_w), either as the S_ww (the hydrophilic state water sorptivity) or the S_wh (the hydrophobic state water sorptivity) to improve the calculation of water repellency cessation time (WRCT). Three soils with initial contact angles (CA_i) of 18°, 60°, and 90° (20 °C ± 3 °C) were additionally heated to temperatures of 40 °C and 60 °C resulting in CA_T40: of 23.6°, 56.4°, and 97.3° and CA_T60 of 18.5°, 88.0°, and 126.6°. The wetted state CA was determined for a wetting- and a rewetting-infiltration cycle (CA_we and CA_rewe) under –2 cm tension, followed by air-drying and further CA measurements (CA_air-dried). There was significant agreement (R² > 0.95) between the S_w evaluated by CTM and the S_wh, and excellent correspondence between t_char and the t_b. The relations between S_e, RI, CA_we, CA_rewe, CA_air-dried, and WRCT clearly showed dynamics and reversibility of SWR and also its dependence on persistence, even for the air-dried 20 °C soil with small CA_i. Persistence of SWR as characterized by the time components resulted in a long flow transition state (i.e., time development and respective changing relevance of capillary and gravity forces). Hence, missing experimental data has to be considered as the main barrier for modeling approaches. Further research is necessary to improve flexibility of the CTM code to reliably estimate S_w and S_wh with respect to persistence of SWR.
Organisationseinheit(en): Institut für Bodenkunde
AG Bodenphysik
Typ: Artikel
Journal: GEODERMA
Band: 427
ISSN: 0016-7061
Publikationsdatum: 01.12.2022
Publikationsstatus: Veröffentlicht
Peer-reviewed: Ja
ASJC Scopus Sachgebiete: Bodenkunde
Elektronische Version(en): https://doi.org/10.1016/j.geoderma.2022.116126 (Zugang: Offen)

BibTeX

@article{f4917fb84983402dab11e62500242361,
title = "Capturing water repellency cessation time by means of characteristic time method",
abstract = "Persistence of water repellency is a significant physical key factor that governs water infiltration into unsaturated soil. We investigated water and ethanol infiltration using the characteristic time method (CTM), repellency index (RI), and the contact angle (CA) behavior for a comprehensive assessment on soil water repellency (SWR). We analyzed the impact of soil structure and thermal and wetting–drying treatments on water and ethanol infiltration. The first objective was to evaluate the CTM for water-repellent soils by partitioning characteristic and gravity infiltration behavior (Ichar and Igrav) and to evaluate parameters like infiltration beginning (tb) and gravity times (tchar and tgrav). The second objective was to characterize the CTM estimated water sorptivity (Sw), either as the Sww (the hydrophilic state water sorptivity) or the Swh (the hydrophobic state water sorptivity) to improve the calculation of water repellency cessation time (WRCT). Three soils with initial contact angles (CAi) of 18°, 60°, and 90° (20 °C ± 3 °C) were additionally heated to temperatures of 40 °C and 60 °C resulting in CAT40: of 23.6°, 56.4°, and 97.3° and CAT60 of 18.5°, 88.0°, and 126.6°. The wetted state CA was determined for a wetting- and a rewetting-infiltration cycle (CAwe and CArewe) under –2 cm tension, followed by air-drying and further CA measurements (CAair-dried). There was significant agreement (R2 > 0.95) between the Sw evaluated by CTM and the Swh, and excellent correspondence between tchar and the tb. The relations between Se, RI, CAwe, CArewe, CAair-dried, and WRCT clearly showed dynamics and reversibility of SWR and also its dependence on persistence, even for the air-dried 20 °C soil with small CAi. Persistence of SWR as characterized by the time components resulted in a long flow transition state (i.e., time development and respective changing relevance of capillary and gravity forces). Hence, missing experimental data has to be considered as the main barrier for modeling approaches. Further research is necessary to improve flexibility of the CTM code to reliably estimate Sw and Swh with respect to persistence of SWR.",
keywords = "Capillary infiltration dynamics, Characteristic time method, Contact angle, Molecular interfacial properties, Persistence, Water repellency breakdown",
author = "Nasrollah Sepehrnia and J{\"o}rg Bachmann",
note = "Funding Information: We thank the Alexander von Humboldt Foundation for financial support of this project and donating post-doctoral fellowship to the first author. We thank Susanne K. Woche, Hanna B{\"o}hme, and Martin Volkmann for their assistance with soil sampling, sample preparation, and laboratory analysis. The authors greatly appreciate Prof. Mark Coyne, University of Kentucky, USA for proofreading the draft of the article. ",
year = "2022",
month = dec,
day = "1",
doi = "10.1016/j.geoderma.2022.116126",
language = "English",
volume = "427",
journal = "GEODERMA",
issn = "0016-7061",
publisher = "Elsevier",
}