scholarly journals Quantifying the effect of subcritical water repellency on sorptivity : a physically based model

2021 ◽  
Author(s):  
Rose Shillito ◽  
Markus Berli ◽  
Teamrat Ghezzehei
Keyword(s):  
Contact Angle ◽  
Hydraulic Conductivity ◽  
Subcritical Water ◽  
Water Drop ◽  
Water Repellency ◽  
Quantitative Model ◽  
Saturated Hydraulic Conductivity ◽  
Silica Sand ◽  
Water Repellent ◽  
Burned Areas

Soil water wettability or water repellency is a phenomenon that can affect infiltration and, ultimately, runoff. Thus, there is a need to develop a model that can quantitatively capture the influence of water repellency on infiltration in a physically meaningful way and within the framework of existing infiltration theory. The analytical model developed in this study relates soil sorptivity (an infiltration parameter) with contact angle (a direct measure of water repellency) for variably saturated media. The model was validated with laboratory experiments using a silica sand of known properties treated to produce controlled degrees of water repellency. The measured contact angle and sorptivity values closely matched the model‐predicted values. Further, the relationship between the frequently used water drop penetration time test (used to assess water repellency) and sorptivity was illustrated. Finally, the direct impact of water repellency on saturated hydraulic conductivity was investigated due to its role in infiltration equations and to shed light on inconsistent field observations. It was found that water repellency had minimal effect on the saturated hydraulic conductivity of structureless sand. A quantitative model for infiltration incorporating the effect of water repellency is particularly important for post‐fire hydrologic modeling of burned areas exhibiting water repellent soils.

The impact of heating on the hydraulic properties of soils sampled under different plant cover

Biologia ◽  
2009 ◽  
Vol 64 (3) ◽  
Author(s):  
Viliam Novák ◽  
Ľubomír Lichner ◽  
Bin Zhang ◽  
Karol Kňava
Keyword(s):  
Hydraulic Conductivity ◽  
Soil Water ◽  
Water Retention ◽  
Water Drop ◽  
Sampling Site ◽  
Water Repellency ◽  
Saturated Hydraulic Conductivity ◽  
Soil Water Repellency ◽  
The Impact ◽  
Penetration Time

AbstractThe impact of heating on the peristence of water repellency, saturated hydraulic conductivity, and water retention characteristics was examined on soils from both forest and meadow sites in southwest Slovakia shortly after a wet spell. The top 5 cm of meadow soils had an initial water drop penetration time WDPT at 20°C of 457 s, whereas WDPT in the pine forest was 315 s for the top 5 cm and 982 s if only the top 1 cm was measured. Heating soils at selected temperatures of 50, 100, 150, 200, 250 and 300°C caused a marked drop in water drop penetration time WDPT from the initial value at 20°C. However, samples collected in different years and following an imposed cycle of wetting and drying showed much different trends, with WDPT sometimes initially increasing with temperature, followed by a drop after 200–300°C. The impact of heating temperature on the saturated hydraulic conductivity of soil was small. It was found for both the drying and wetting branches of soil water retention curves that an increase in soil water repellency resulted in a drop in soil water content at the same matric potential. The persistence of soil water repellency was strongly influenced by both the sampling site and time of sampling, as it was characterized by the results of WDPT tests.

scholarly journals Biological soil crusts cause subcritical water repellency in a sand dune ecosystem located along a rainfall gradient in the NW Negev desert, Israel

2016 ◽  
Vol 64 (2) ◽  
pp. 133-140 ◽  
Author(s):  
Hannes Keck ◽  
Vincent John Martin Noah Linus Felde ◽  
Sylvie Laureen Drahorad ◽  
Peter Felix-Henningsen
Keyword(s):  
Subcritical Water ◽  
Water Drop ◽  
Water Repellency ◽  
Biological Soil Crusts ◽  
Water Repellent ◽  
Rainfall Gradient ◽  
Soil Crusts ◽  
Water Redistribution ◽  
Local Water ◽  
Wilhelmy Plate Method

AbstractThe biological soil crusts (BSCs) in the NW Negev cause local water redistribution by increasing surface runoff. The effects of pore clogging and swelling of organic and inorganic crust components were intensively investigated in earlier studies. However, the effect of water repellency (WR) was not addressed systematically yet. This study investigates subcritical WR of BSCs in three different study sites in the NW Negev. For this purpose, three common methods to determine soil WR were used: (i) the repellency index (RI) method (ii) the water drop penetration time (WDPT) test and (iii) the Wilhelmy plate method (WPM). Furthermore, the potential influence of WR on local water redistribution is discussed and the applied methods are compared. We found the BSC to be subcritically water repellent. The degree of WR may only affect water redistribution on a microscale and has little influence on the ecosystem as a whole. The RI method was clearly the most appropriate to use, whereas the WDPT and the WPM failed to detect subcritical WR.

scholarly journals Effect of kaolinite and Ca-montmorillonite on the alleviation of soil water repellency

2011 ◽  
Vol 50 (No. 8) ◽  
pp. 358-363 ◽  
Author(s):  
P. Dlapa ◽  
S.H. Doerr ◽  
Ľ. Lichner ◽  
M. Šír ◽  
M. Tesař
Keyword(s):  
Water Drop ◽  
Water Repellency ◽  
Silica Sand ◽  
Water Repellent ◽  
Mineral Surfaces ◽  
Adhesion Forces ◽  
Key Factors ◽  
High Adhesion ◽  
Phase Water ◽  
Amphiphilic Organic Compounds

The effects of adding 1–3% (weight) kaolinite or Ca-montmorillonite on the wettability of silica sand, made highly water repellent with stearic acid, was studied during wetting and prolonged drying phases at 50°C. The persistence of water repellency was estimated with the water drop penetration time (WDPT) test. After wetting water repellency disappeared in all the samples. During the drying phase, water repellency re-appeared in all samples (untreated and clay-treated) as the water content decreased below 1%. Repellency did, however, not reach pre-wetting levels. The effect of clay additions on water repellency differed strongly between the two clay types. Kaolinite reduced WDPT, while Ca-montmorillonite caused an increase in WDPT in the already highly repellent sand. Potential mechanisms for the alleviation effectiveness of kaolinite are proposed, with key factors being the high adhesion forces between water and clay mineral surfaces, and the ability kaolinite to disperse. In the case of Ca-montmorillonite, its lower affinity for water may lead to a displacement of water molecules at mineral surfaces by amphiphilic organic compounds, which may result in increased repellency. This phenomenon clearly requires further investigation.

scholarly journals Evaluation and remediation of post-wildfire slope stability

2020 ◽  
Vol 205 ◽  
pp. 04007
Author(s):  
Mahta Movasat ◽  
Ingrid Tomac
Keyword(s):  
High Speed ◽  
Xanthan Gum ◽  
Water Repellency ◽  
Soil Improvement ◽  
Dust Control ◽  
Water Repellent ◽  
Civil Infrastructure ◽  
Burned Areas ◽  
Treated Sample ◽  
Experimental Laboratory

Catastrophic mudflows and landslides triggered by rainfall can occur suddenly and move with high speed, damaging electrical and civil infrastructure and threatening human and wildlife. Due to the climate change and extreme weather increase, it is likely that wildfires and consequently mudflows will increase in frequency in the future. The risk of mudflows and landslides increases in post-wildfire areas mainly because of water repellent soil which forms on slopes. Water repellency, or hydrophobicity, can occur due to the burning of the accumulated organic matter in soil. Hydrophobicity repels water and prevents infiltration of water into the soil, which results in soil erosion, mudflows and landslides. In this study, a series of experimental laboratory tests are conducted on regular, hydrophobic and Xanthan gum-treated hydrophobic sand. Xanthan gum, which is an environmentally friendly biopolymer, can be substituted for chemical material used for soil improvement and decrease the CO2 emissions and enhance environmental slope protection. Xanthan gum can enhance the inter-particle cohesion and can hold a large amount of water and consequently help the recovery of the vegetation. Contact angle, direct shear and rain simulation tests are conducted on samples. Results show that in Xanthan gum treated slope the rate of erosion and the risk of mudflow decreases. It is also observed that the Xanthan gum treated sample can retain more water and consequently decreases the rate of wind erosion and helps the dust-control in burned areas.

Field measurement of soil water repellency and its impact on water flow under different vegetation

Biologia ◽  
2007 ◽  
Vol 62 (5) ◽  
Author(s):  
L’ubomír Lichner ◽  
Paul Hallett ◽  
Debbie Feeney ◽  
Olívia Ďugová ◽  
Miloslav Šír ◽  
...  
Keyword(s):  
Hydraulic Conductivity ◽  
Forest Soil ◽  
Soil Water ◽  
Water Flow ◽  
Water Repellency ◽  
Water Repellent ◽  
Dry Spell ◽  
Physically Based ◽  
Low Levels ◽  
The Impact

AbstractNumerous recent laboratory studies have shown that vegetation can influence soil water flow by inducing very low levels of water repellency. In this study we extended on this previous research by developing a field-based test using a miniature infiltrometer to assess low levels of water repellency from physically based measurements of liquid flow in soil. The field-based test was verified through a simple laboratory experiment and then applied to determine the impact of vegetation and antecedent soil water content. The soil hydraulic properties determined were hydraulic conductivity, sorptivity, as well as the persistence and index of water repellency. Tests were conducted following a dry spell and wet spell on (1) forest soil (0 cm depth), (2) glade soil (0 cm depth) and (3) glade soil (50 cm depth). It was found that both the persistence and index of water repellency, R, decreased in the order as follows: forest soil > glade soil (0 cm) > glade soil (50 cm) for both dry and wet spell. The range of values of R was 0.28 (wettable) to 360 (highly water repellent), which affected hydraulic conductivity k r(−2 cm). R increased and hence k r(−2 cm) decreased in the order: forest soil < glade soil (0 cm) < glade soil (50 cm) for both the dry and wet spell. There were clear interactions between vegetation and changes to water flow caused by presence of repellency.

scholarly journals Ultrahydrophobic Textiles Using Nanoparticles: Lotus Approach

2008 ◽  
Vol 3 (4) ◽  
pp. 155892500800300 ◽  
Author(s):  
Karthik Ramaratnam ◽  
Swaminatha K. Iyer ◽  
Mark K. Kinnan ◽  
George Chumanov ◽  
Phillip J. Brown ◽  
...  
Keyword(s):  
Contact Angle ◽  
Water Contact Angle ◽  
Contact Angle Hysteresis ◽  
Water Repellency ◽  
Textile Material ◽  
Water Repellent ◽  
Complete Wetting ◽  
Water Contact ◽  
Lotus Effect ◽  
Textile Materials

It is well established that the water wettability of materials is governed by both the chemical composition and the geometrical microstructure of the surface.1 Traditional textile wet processing treatments do indeed rely fundamentally upon complete wetting out of a textile structure to achieve satisfactory performance.2 However, the complexities introduced through the heterogeneous nature of the fiber surfaces, the nature of the fiber composition and the actual construction of the textile material create difficulties in attempting to predict the exact wettability of a particular textile material. For many applications the ability of a finished fabric to exhibit water repellency (in other words low wettability) is essential2 and potential applications of highly water repellent textile materials include rainwear, upholstery, protective clothing, sportswear, and automobile interior fabrics. Recent research indicates that such applications may benefit from a new generation of water repellent materials that make use of the “lotus effect” to provide ultrahydrophobic textile materials.3,4 Ultrahydrophobic surfaces are typically termed as the surfaces that show a water contact angle greater than 150°C with very low contact angle hysteresis.4 In the case of textile materials, the level of hydrophobicity is often determined by measuring the static water contact angle only, since it is difficult to measure the contact angle hysteresis on a textile fabric because of the high levels of roughness inherent in textile structures.

Water Repellency Control of Oxygen-Free Copper Surface by Diamond-Cut Micro Grooves

2015 ◽  
Vol 9 (4) ◽  
pp. 396-402 ◽  
Author(s):  
Kazuma Asakura ◽  
◽  
Jiwang Yan
Keyword(s):  
Contact Angle ◽  
Flat Surface ◽  
Water Drop ◽  
Water Repellency ◽  
Copper Surface ◽  
Industrial Applications ◽  
Burr Formation ◽  
Wide Range ◽  
Grooved Surface ◽  
Maximum Contact

Improving water repellency of a metal surface is required in a wide range of industrial applications. In this study, the water repellency control of an oxygen-free copper surface was attempted by generating micro V grooves on the surface by using ultraprecision cutting technology. The results showed that the maximum contact angle of a water drop on a micro V-grooved surface could be as high as approximately twice that of a flat surface. The contact angle depended strongly on the direction, depth, pitch of the grooves, and burr formation at the edges of the micro grooves. A method for controlling burr formation was proposed.

scholarly journals The impact of vegetation on hydraulic conductivity of sandy soil

2008 ◽  
Vol 2 (No. 2) ◽  
pp. 59-66 ◽  
Author(s):  
L. Lichner ◽  
T. Orfánus ◽  
K. Novákova ◽  
M. Šír ◽  
M. Tesař
Keyword(s):  
Hydraulic Conductivity ◽  
Forest Soil ◽  
Sandy Soil ◽  
Preferential Flow ◽  
Water Drop ◽  
Water Repellency ◽  
Forest Site ◽  
Meadow Soil ◽  
Capillary Suction ◽  
The Impact

The objective of this study was to assess the impact of vegetation on the hydraulic conductivity of sandy soil at the locality Ml&aacute;ky II at Sekule (southwest Slovakia). The measurements were taken on the surface of a meadow (Meadow site), a 30-year old Scots pine (Pinus sylvestris) forest (Forest site) and a glade (Glade site). In the glade, the measurements were also taken in the depth of 50 cm (Pure sand) to reduce the influence of vegetation on the soil properties. It was found that the unsaturated hydraulic conductivity k<sub>r</sub>(&minus;2 cm) as reduced due to the soil water repellency increased in the same order: Forest soil &lt; Glade soil &asymp; Meadow soil &lt; Pure sand, similarly as decreased the water drop penetration time t<sub>p</sub>: Forest soil &gt; Glade soil &asymp; Meadow soil &gt; Pure sand, which could refer to an inverse proportionality between the capillary suction and hydrophobic coating of the soil particles. The saturated hydraulic conductivity K<sub>s</sub> increased in the following order: Meadow soil &lt; Glade soil &asymp; Forest soil &lt; Pure sand; more than two-times higher K<sub>s</sub> at both the Forest and Glade sites than that at the Meadow site could be the result of both the patchy growth of vegetation with some areas of bare soil at the Glade site and the macropores (dead roots) in more homogeneous humic top-layer at the Forest site. The share B<sub>r</sub> of flux through the pores with radii r longer than approximately 0.5 mm decreased in the order: Forest soil &raquo; Meadow soil &gt; Glade soil &raquo; Pure sand, revealing the prevalence of preferential flow through macropores (dead roots) in the Forest site and a negligible share of macropores in the Pure sand.

Sign in / Sign up

Export Citation Format

Share Document