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

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.

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

10.21079/11681/41054 ◽

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.

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How are mineral and organic phases regulating burning-induced soil water repellency? Unravelling the crucial dynamics occurring in the Alps even at moderate fire intensities.

10.5194/egusphere-egu21-3533 ◽

2021 ◽

Author(s):

Sara Negri ◽

Beatrice Giannetta ◽

Daniel Said-Pullicino ◽

Luisella Celi ◽

Eleonora Bonifacio

Keyword(s):

Water Drop ◽

Aggregate Stability ◽

Water Repellency ◽

Beech Forest ◽

Mineral Surfaces ◽

Litter Cover ◽

Coarse Texture ◽

Fe Speciation ◽

Ft Ir ◽

Terrestrial Biomes

Wildfires play the role of ecosystem shapers in the majority of terrestrial biomes, altering canopy and litter cover and imposing strong modifications on soils. Organic matter (OM) content and composition, mineralogy, pH, aggregate stability and water repellency (WR) are among the main edaphic properties to be affected by heat. Various studies dealt with occurrence, extent and persistence of burning-induced soil WR, but the dynamics at the basis of its formation (and loss) are still widely unclear. In addition, the vast majority of research on this topic has been carried out in the Mediterranean, even if alpine environments are far from being untouched by fires. Our aims were therefore to provide insight into the key mechanisms regulating WR thermal alterations in a relatively understudied environment.Our sampling design aimed at collecting soils representative of the Western Italian Alps. Charring was simulated in the lab, at increasing temperatures (up to 300&#176; C), on a set of A soil horizons developed under pine and beech forest covers. Water drop penetration time (WDPT) was employed to test WR persistence. Soils were analyzed in terms of organic carbon (OC) and nitrogen contents, pH, texture and iron (Fe) oxides composition (Fe-DCB and Fe-pyrophosphate extracted). Fe-speciation and OM composition of some selected samples were further characterized using Fe K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy and Fourier transform-infra red (FT-IR) spectroscopy, respectively.WR was found to be extremely variable, event at room temperature. For samples exhibiting an increase in WR upon burning intensity, maximum repellency was observed at 200&#176; C. OC abundance (%) and coarse texture were found to be the main drivers of hydrophobicity in soil. WR was drastically lost when samples were exposed to temperatures higher than 200&#176;C. Above this threshold, pH systematically increased and OC (%) sharply decreased. The increasingly negative charge of mineral surfaces, mirrored by pH increase, seems to result in a significant C volatilization by OM desorption, eventually leading to a super-hydrophilic behavior in soil.Fe EXAFS allowed to evaluate different thermal-dictated pathways of Fe-speciation. The formation of more crystalline Fe-forms (e.g. hematite, meghemite) was observed above 200&#176; C. Even though a reduction in surface area should be expected when observing an increase in crystallization degree (potentially giving rise to greater WR), OM adhesion to mineral surfaces seems to be inhibited by the change induced in their charge. A reduction in the OM-bound Fe pool (pyrophosphate extracted) above 200&#176; C could be appreciated, supporting the interpretation of oxy-hydroxides transformations and OC (%) loss. &#160;The current investigation has been carried out to capture an in-depth picture of wildfire impacts on alpine soils, targeting factors responsible for WR enhancement and shred. Identifying the mechanisms regulating wildfire-related WR is a key issue, as the formation of hydrophobic layers in soil highly favors its erosion. Addressing such matters is crucial to tackle the issue of ecosystems recovery, considering that climate-change-related alterations in wildfires regimes are already causing the occurrence of more frequent and disruptive fires.

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Small variations of soil properties control fire-induced water repellency .

Spanish Journal of Soil Science ◽

10.3232/sjss.2014.v4.n1.03 ◽

2014 ◽

Vol 4 ◽

Author(s):

Jorge Mataix-Solera ◽

Lorena M. Zavala ◽

Antonio Jordán ◽

Gema Bárcenas-Moreno ◽

Elena Lozano ◽

...

Keyword(s):

Organic Matter ◽

Soil Properties ◽

Plant Species ◽

Water Repellency ◽

Soil Samples ◽

Soil Types ◽

Water Repellent ◽

Key Factors ◽

The Impact

Fire induced soil water repellency (WR) is controlled by many different factors (temperature reached, amount and type of fuel, etc.). Soil properties may determine the occurrence and intensity of this property in burned soils. The objectives of this paper are to make advances in the study of soil properties as key factors controlling the behaviour of fire-induced WR, and to study the impact of pre-fire SOM content and SOM quality in fire-induced soil WR. In this research, experimental laboratory burnings were carried out using soil samples from different sites with different lithologies, soil types and plant species. Soil samples taken from the same site differ only in quantity and quality of soil organic matter, as they were collected from under different plant species. All soil samples were heated in a muffle furnace at 200, 250, 300 and 350 ºC without the addition of any fuel load. WR was measured using the water drop penetration time test (WDPT). The results showed significant differences between soil types and plant species, indicating that small differences in soil properties may act as key factors controlling the development and persistence of WR reached, with burned soil samples ranging from wettable to extremely water repellent. The main soil property controlling the response was texture, specifically sand content. The quality of organic matter was also observed to have an effect, since soil samples from the same site with similar organic matter contents, but taken from beneath different plant species, showed different WR values after burning.

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

Journal of Hydrology and Hydromechanics ◽

10.1515/johh-2016-0001 ◽

2016 ◽

Vol 64 (2) ◽

pp. 133-140 ◽

Cited By ~ 20

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.

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Water-entry pressure in water repellent soils: a review

E3S Web of Conferences ◽

10.1051/e3sconf/202019502030 ◽

2020 ◽

Vol 195 ◽

pp. 02030

Author(s):

Xin Xing ◽

Sérgio D.N. Lourenço

Keyword(s):

Soil Water ◽

Water Repellency ◽

Water Entry ◽

Water Infiltration ◽

Water Repellent ◽

Key Factors ◽

Soil Water Repellency ◽

Factors Affecting ◽

Hydrophobic Compounds ◽

Entry Pressure

Water repellent soils can be naturally promoted (e.g. after wildfires) or synthetically induced by mixing with hydrophobic compounds (e.g. polydimethylsiloxane). The study of soil water repellency has lasted for over one century which implied the significant effect of soil water repellency on water infiltration, evaporation, soil strength, and soil stability. Water repellent soils can also be exploited by geotechnical engineers to offer novel and economical solutions for ground infrastructure. This paper synthesizes different methods for assessing soil water repellency based on varied indexes (e.g. contact angle, time for a drop to infiltrate) and with a focus on water entry pressure. Measurements of these parameters in synthetic water- repellent sands were taken, some results of which are summarized with discussion of key factors affecting water repellency. A comparison of these methods shows that water entry pressure can be more representative for assessing the water repellency of bulk samples.

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Post-fire soil water repellency, sorptivity, and the measurement of infiltration

10.5194/egusphere-egu21-13078 ◽

2021 ◽

Author(s):

Rose Shillito ◽

Markus Berli ◽

Teamrat Ghezzehei ◽

Ian Floyd

Keyword(s):

Water Repellency ◽

Accurate Method ◽

Silica Sand ◽

Water Repellent ◽

Field Methods ◽

Physically Based ◽

Soil Hydraulic Property ◽

Infiltration Tests ◽

The Relationship ◽

Common Field

Wildfires are frequently associated with the increased potential for runoff, flooding and debris flows during and after subsequent rainfall events. Specifically, wildfires can cause soils to become water repellent, which is believed to slow, if not halt, the infiltration of water into the soil. However, there exists no mechanistic way to determine the effect of post-wildfire water repellency on infiltration and runoff&#8212;until now. We have recently developed a simple physically-based model to account for the effect of water repellency on the soil hydraulic property of sorptivity. Further, since sorptivity is crucial to understanding the relationship between water repellency and post-fire infiltration, there is a need for a robust and accurate method to measure sorptivity in the field. All research was conducted in the laboratory using a fine silica sand, some of which was treated with ScotchgardTM to induce water repellency. Treated and untreated sand was mixed proportionally by weight to create various degrees of water repellent sand. Upward infiltration tests (wicking experiments) were used to validate the sorptivity model. Then, two common field methods (a 1D infiltrometer ring and a 3D tension infiltrometer) were used to measure downward infiltration and extract sorptivity data. Results showed that we able to predict sorptivity given the degree of water repellency and basic soil properties, that sorptivity measured using common field methods reflected the degree of water repellency, and that both downward infiltration measurement methods yielded similar sorptivity values.

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Testing soil water repellency in a Sicilian area two years after a fire

Journal of Agricultural Engineering ◽

10.4081/jae.2019.988 ◽

2019 ◽

Cited By ~ 1

Author(s):

Vincenzo Bagarello ◽

Giuseppe Basile ◽

Gaetano Caltabellotta ◽

Giuseppe Giordano ◽

Massimo Iovino

Keyword(s):

Soil Water ◽

Water Drop ◽

Soil Layer ◽

Soil Surface ◽

Water Repellency ◽

Soil Conditions ◽

Small Scale ◽

Water Repellent ◽

Soil Water Repellency ◽

Mountain Area

The water drop penetration time (WDPT) technique was applied in 2018 to check persistence of soil water repellency (SWR) in a Sicilian mountain area affected by a wildfire on June 2016. A total of four sites, that were severely water repellent immediately after burning, were sampled. Depending on the site, wettable soil conditions, less SWR and maintenance of a noticeable SWR were detected two years later. At the site showing a near-constant SWR, WDPTs were particularly high in the top soil layer (0-0.03 m) and they appreciably decreased more in depth. Signs of decreasing SWR in drier soil conditions and in association with coarser soil particles were also detected at this site. High gradients of the WDPT can occur at very small vertical distances and a depth increment of approximately 0.01 m should be appropriate to capture small-scale vertical changes in SWR, especially close to the soil surface. Occurrence of SWR phenomena is easily perceivable and explainable if an inverse relationship between WDPTs and antecedent soil water content is obtained. A direct relationship between these two variables is more difficult to interpret because infiltration times that increase in wetter soil are expected according to the classical infiltration theory. A hypothesis that should be tested in the future is to verify if WDPTs that decrease in drier soil conditions signal less SWR as a consequence of a reduced biological activity of the soil. Finally, long-term monitoring projects on longevity of fire effects on SWR should be developed, even because an in depth knowledge of the involved processes is relevant for the civil protection system.

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The effect of slash burning on the water repellency of forest soils at Vancouver, British Columbia

Canadian Journal of Forest Research ◽

10.1139/x83-052 ◽

1983 ◽

Vol 13 (2) ◽

pp. 353-355 ◽

Cited By ~ 18

Author(s):

G. S. Henderson ◽

D. L. Golding

Keyword(s):

Soil Water ◽

Water Drop ◽

Water Repellency ◽

Water Repellent ◽

Soil Water Repellency ◽

Naturally Occurring ◽

And Control ◽

Water Repellence ◽

Slash Burning ◽

Control Samples

Soil from 10 slash burned and 3 unburned clear-cuts was tested for water repellency by the water drop penetration method and compared with naturally occurring soil water repellency in uncut mature forest. There was no difference in soil water repellency between unburned clear-cuts and the uncut forest control. Soil was more frequently water repellent in slash burned sites (35% of samples) than in the control sites (21% of samples), but differences were significant only for the first 2 years after burning. All humus samples were severely water repellent. At the 0- to 4-cm depth below the humus, burned samples were more frequently repellent than control samples, but there was no difference at the 8- to 10-cm and 15+ cm depths. Water repellence decreased with depth in both burned and control sites.

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829 PB 311 WETTING AGENT EFFECTS ON TURF SOIL-WATER REPELLENCY

HortScience ◽

10.21273/hortsci.29.5.552b ◽

1994 ◽

Vol 29 (5) ◽

pp. 552b-552

Author(s):

John L. Cisar ◽

Karen E. Williams

Keyword(s):

Soil Water ◽

Soil Depth ◽

Water Drop ◽

Water Repellency ◽

Fine Sand ◽

Wetting Agent ◽

Water Repellent ◽

Soil Water Repellency ◽

Wetting Agents ◽

Over Time

Soil-water repellency is often a problem for turfgrass grown on sand soils. Wetting agents used to alleviate repellency often provide mixed results. We evaluated AquagroL and an experimental material (ACA 864) at 0, 7, 14, and 21ml/m2 applied monthly to tifgreen bermuda grown on a soil-water repellent Margate fine sand over 6 months. Alleviation of repellency was based upon water drop penetration time (WDPT). Wetting agents did not effect turf quality, cover, or discoloration. Wetting agents did not reduce repellency 1 month after initial application. At 2 months, ACA 864 at 21ml/m2 significantly reduced WDPT. With repeat applications, lower rates of ACA 864 provided reductions in WDPT similar to the highest rate of ACA 864, suggesting an additive effect over time. There was a decline in WDPT for all wetting agent treatments, except the control, over time. Repellency decreased with soil depth, and repeat wetting agent application reduced WDPT at lesser depth.

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An evaluation of the intrinsic sorptivity water repellency index on a range of New Zealand soils

Soil Research ◽

10.1071/sr9910353 ◽

1991 ◽

Vol 29 (3) ◽

pp. 353 ◽

Cited By ~ 77

Author(s):

MG Wallis ◽

DR Scotter ◽

DJ Horne

Keyword(s):

New Zealand ◽

Water Drop ◽

Water Repellency ◽

Water Infiltration ◽

Water Repellent ◽

Ethanol Droplet ◽

Wide Range ◽

Order Of Magnitude ◽

Moisture Conditions ◽

Short Time

Undisturbed cores were removed from the surface of 14 New Zealand soils with a wide range of textures. The sorptivity to ethanol and water was measured with a 'sorptivity tube' to determine the repellency index (Rl) of each soil. Texture and gravimetric water content were measured, and the water drop penetration time (WDPT) and molarity of ethanol droplet (MED) tests for water repellency were conducted on the soils. The RI measured all soils water repellent (RI> 1.95) at field moisture conditions, and was more sensitive than the WDPT or MED tests. The RI was used to demonstrate that water repellency reduced short-time water infiltration of all soils by approximately an order of magnitude. Actual and 'potential' infiltration was then compared with rainfall and irrigation intensities. This illustrated the hydrological significance of the phenomenon, even in soils which appeared to wet normally (low WDPT). In all soils the curves of cumulative infiltration versus the square root of time for both water and ethanol stayed linear long enough for sorptivity evaluation. However, at longer times the slope of the curve tended to increase for water sorption in the more repellent soils, but decreased consistently for ethanol.

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