Speaker
Description
Under the current climate change, assessing water transfer and infiltration in soil, considered as complex porous medium, is a crucial point for estimating consequences of either heavy rain on runoff or of drought on plant water uptake. In both cases, variations in soil wettability due to amphiphilic materials is an overlooked point, but can greatly affect the infiltration and water transfer, such as water repellency in soil [Doerr2000,Orfánus2021,Bens2007].
A macroscopic model of the infiltration of a water drop into a porous medium is developed and applied to a soil containing amphiphilic molecules such as Exopolysaccharides (EPS) found in soil near plant roots [Bérard2020]. These molecules present a hydrophobic or hydrophilic property depending on the water content in soil. Experiments found in literature [Liu2012,Hapgood2002] or performed in our laboratory show two main behaviors :
i) When the soil is sufficiently moist, imbibition is immediate and rapid as in hydrophilic soils.
ii) In contrast, for a dry soil, the drop does not infiltrate immediately and the subsequent imbibition is slower and depending on the soil hydrophobicity, the drop may never infiltrate.
Models based on Richards Equation [Richards1931] in the soil and its variants [Beljadid2020,Landl2021] can only reproduce the rapid infiltration of regime i). We propose here to derive new equations describing the hydrophilic and hydrophobic interactions both in the soil and on the soil surface in contact with the water drop to describe all water infiltration regimes. In place of a contact angle to characterize the wettability of the soil surface, we introduce a free energy term which includes attractive and repulsive interactions, derived from the modeling of drop dynamics on a substrate [Thiele2018] and include the dependence of the surface wettability on the water saturation in the porous matrix [Doerr2000]. Concerning the soil, we recently developed a water-dependent hydrophobicity model [Beltrame2022] which has been extended to the case of amphiphilic molecules. In order to reproduce to interactions between water at soil surface and in the soil volume, and to be consistent with thermodynamic principles, we show that it is necessary to add a term inside the porous matrix that depends on both the saturation and the film height at the surface. The resulting equation system is a fourth order PDE system similar to the lubrication model with wettability. To our knowledge, it is the first time that wettability, both in the soil and on the soil surface, is accounted for to represent water infiltration. The numerical simulation of developed coupled equations is in agreement with the experiments of the infiltration of a drop on a thin layer of sand containing EPS. We retrieve the dependence of the Water Drop Penetration Time (WDPT) test with the concentration of amphiphilic molecules and soil moisture.
Moreover, we are able to reproduce the two regimes of the infiltration dynamics: instantaneous infiltration and progressive and slow infiltration depending on the initial water saturation of the soil.
References
[Beljadid2020] Beljadid, A., Cueto-Felgueroso, L., and Juanes, R. (2020). A continuum model of unstable infiltration in porous media endowed with an entropy function. Advances in Water Resources, 144:103684.
[Beltrame2022] Beltrame, P. and Cajot, F. (2022). Model of hydrophobic porous media applied to stratified media: Water trapping, intermittent flow and fingering instability. EPL, 138(5):53004. Publisher: EDP Sciences, IOP Publishing and Società Italiana di Fisica.
[Bens2007] Bens, O., Wahl, N. A., Fischer, H., and Hüttl, R. F. (2007). Water infiltration and hydraulic conductivity in sandy cambisols: impacts of forest transformation on soil hydrological properties. Eur J Forest Res, 126(1):101–109.
[Bérard2020] Bérard, A., Clavel, T., Le Bourvellec, C., Davoine, A., Le Gall, S., Doussan, C., and Bureau, S. (2020). Exopolysaccharides in the rhizosphere: A comparative study of extraction methods. Application to their quantification in Mediterranean soils. Soil Biology and Biochemistry, 149:107961.
[Doerr2000] Doerr, S. H., Shakesby, R. A., and Walsh, R. P. D. (2000). Soil water repellency: its causes, characteristics and hydro-geomorphological significance. Earth-Science Reviews, 51(1):33–65.
[Hapgood2002] Hapgood, K. P., Litster, J. D., Biggs, S. R., and Howes, T. (2002). Drop Penetration into Porous Powder Beds. Journal of Colloid and Interface Science, 253(2):353–366.
[Landl2021] Landl, M., Phalempin, M., Schlüter, S., Vetterlein, D., Vanderborght, J., Kroener, E., and Schnepf, A. (2021). Modeling the Impact of Rhizosphere Bulk Density and Mucilage Gradients on Root Water Uptake. Frontiers in Agronomy, 3.
[Liu2012] Liu, H., Ju, Z., Bachmann, J., Horton, R., and Ren, T. (2012). Moisture-Dependent Wettability of Artificial Hydrophobic Soils and Its Relevance for Soil Water Desorption Curves. Soil Science Society of America Journal, 76(2):342–349. _eprint: https://onlinelibrary.wiley.com/doi/pdf/10.2136/sssaj2011.008.
[Orfánus2021] Orfánus, T., Zvala, A., Čierniková, M., Stojkovová, D., Nagy, V., and Dlapa, P. (2021). Peculiarities of Infiltration Measurements in Water-Repellent Forest Soil. Forests, 12(4):472. Number: 4 Publisher: Multidisciplinary Digital Publishing Institute.
[Richards1931] Richards, L. A. (1931). CAPILLARY CONDUCTION OF LIQUIDS THROUGH POROUS MEDIUMS. Physics, 1(5):318–333.
[Thiele2018] Thiele, U. (2018). Recent advances in and future challenges for mesoscopic hydrodynamic modelling of complex wetting. Colloids and Surfaces A: Physicochemical and Engineering Aspects, 553:487–495.
| Participation | In-Person |
|---|---|
| Country | France |
| MDPI Energies Student Poster Award | No, do not submit my presenation for the student posters award. |
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