How Heterogeneous Pore Scale Distributions of Wettability Affect Infiltration into Porous Media

Abstract

Wettability is an important parameter that significantly determines hydrology in porous media, and it especially controls the flow of water across the rhizosphere—the soil-plant interface. However, the influence of spatially heterogeneous distributions on the soil particles surfaces is scarcely known. Therefore, this study investigates the influence of spatially heterogeneous wettability distributions on infiltration into porous media. For this purpose, we utilize a two-phase flow model based on Lattice-Boltzmann to numerically simulate the infiltration in porous media with a simplified geometry and for various selected heterogeneous wettability coatings. Additionally, we simulated the rewetting of the dry rhizosphere of a sandy soil where dry hydrophobic mucilage depositions on the particle surface are represented via a locally increased contact angle. In particular, we can show that hydraulic dynamics and water repellency are determined by the specific location of wettability patterns within the pore space. When present at certain locations, tiny hydrophobic depositions can cause water repellency in an otherwise well-wettable soil. In this case, averaged, effective contact angle parameterizations such as the Cassie equation are unsuitable. At critical conditions, when the rhizosphere limits root water uptake, consideration of the specific microscale locations of exudate depositions may improve models of root water uptake.

Plant growth‐promoting rhizobacteria mediate soil hydro‐physical properties: An investigation with Bacillus subtilis and its mutants

“…As demonstrated by Bentz et al. (2022), the presence of sporadic hydrophobic deposits can induce water repellency in an otherwise well‐wettable soil. Our results are consistent with their observations, suggesting that pore‐scale heterogeneity of bacteria/exudate distribution impacts soil wettability and infiltration.…”

“…Furthermore, because bacteria-incubated sand particles have greater contact angle values than untreated sand, the mixed wettability of sand particles in the columns could also cause nonuniform water distribution. As demonstrated by Bentz et al (2022), the presence of sporadic hydrophobic deposits can induce water repellency in an otherwise well-wettable soil. Our results are consistent with their observations, suggesting that porescale heterogeneity of bacteria/exudate distribution impacts soil wettability and infiltration.…”

Elucidating the role of water films on solute diffusion in unsaturated porous media by improved pore‐scale modeling

“…Nevertheless, this difference in the density ratio is not critical for the flow in a rigid porous media (e.g., hardened cement paste) as demonstrated in J. Bentz et al. (2022). For the solid phase boundary condition, a previous study of Pot et al.…”

“…The periodic boundary condition is employed at all surfaces of the simulation domain. Details on the implementation of boundary conditions as well as on a consistent unit conversion between arbitrary dimensionless lattice units and physical units are described in Bentz et al (J. Bentz et al, 2022). For this study, unit conversion is not relevant as only a simulation of the water distribution is carried out.…”

3–4D soil model as challenge for future soil research: Quantitative soil modeling based on the solid phase

“…The DEM‐based soil modeling was applied to analyze dynamics effects of tillage tools on soil loosening (Tamás et al., 2013). It allows incorporating local pore scale heterogeneity of soil mechanical (e.g., cohesion; Barbosa et al., 2020) and wettability properties (e.g., contact angle; Bentz et al., 2022). These studies, however, do not always take into account soil structural dynamics.…”