Infiltration Experiments Research Articles

A bimodal extension of the ARYA&PARIS approach for predicting hydraulic properties of structured soils

• Bimodal Arya&Paris hydraulic properties were developed based on soil structure. • The bimodal PTF provides better prediction of un/saturated hydraulic conductivity. • The bimodal PTF predicts well the spatial variability of the hydraulic properties. The main purpose of this paper is to develop a bimodal pedotransfer function to obtain soil water retention (WRC) and hydraulic conductivity (HCC) curves. The proposed pedo-transfer function (PTF) extends the Arya and Paris (AP) approach, which is based on particle size distribution (PSD), by incorporating aggregate-size distribution (ASD) into the PTF to obtain the bimodal WRC. A bimodal porosity approach was developed to quantify the fraction of each of the porous systems (matrix and macropores) in overall soil porosity. Saturated hydraulic conductivity, K 0 , was obtained from WRC using the Kozeny-Carman equation, whose parameters were inferred from the behaviour of the bimodal WRC close to saturation. Finally, the Mualem model was applied to obtain the HCC. In order to calibrate the PTF, measured soil physical and hydraulic properties data were used, coming from field infiltration experiments from an irrigation sector of 140 ha area in the “Sinistra Ofanto” irrigation system in Apulia, southern Italy. The infiltration data were fitted by using both bimodal and unimodal hydraulic properties by an inverse solution of the Richards equation. The bimodal “measured” hydraulic properties were then used to calibrate the scaling parameter (α AP ) of the proposed bimodal AP ( bimAP ) PTF. Similarly, for the sake of comparison with the bimodal results, the unimodal hydraulic properties were used to calibrate the α AP of the classical unimodal AP ( unimAP ) PTF. Compared to the unimAP PTF, the proposed bimAP significantly improves the predictions of the mean WRC parameters and K 0 , as well as the prediction of the shape of the whole HCC. Moreover, compared to the unimodal approach, it also allows to reproduce statistics of the hydraulic parameters (for example, variance) similar to those observed in the calibration dataset. Multiple linear regression (MLR) was also applied to analyse the sensitivity of the bimodal α AP parameter to textural and structural features, confirming significant predictive effects of soil structure.

Contact and Infiltration Behavior of Al Melt and Al-B4C Composite

In the present study, the authors used sessile drop method to simulate the contacting and infiltration behavior between Al melt and Al–B4C composite. In order to track the penetration distance of the metal melt infiltrate into the Al-B4C composite matrix when the infiltration is not obvious, element Si was added into the metal melt as the tracer agent. The Al-10%Si melt was dropped onto the Al-B4C composite substrate at 913K. The changes of droplet bottom size, height, and contact angle during the spreading and penetration with Al-B4C composite substrate surface are investigated by infiltration experiment equipment. The process of the droplet infiltrating into the Al-B4C composite can be divided into two stages: (a) a slow infiltration stage that the contact angle changes slowly; (b) a quick infiltration stage with the rapidly-changed contact angle. The content of B4C and the pores in the composite plays an important role on the infiltration of the droplet. The higher the density, the easier the infiltration proceeds.

Spatial Patterns of Infiltration on a Bench Terraced Hillslope in Kigezi Highlands, South-Western Uganda

The spatial patterns of infiltration on bench terraced hillslopes are not fully understood. Moreover, these patterns are pivotal for assessing hydrological processes affecting water distribution, surface flow and soil erosion, and groundwater recharge. Our objective was to determine the spatial patterns of steady-state infiltration rates on a bench terraced hillslope; and assess the influence of soil properties on the infiltration process. We employed Geo-Information Science (GIS) to stratify the terraced bench hillslope into three slope position sequences, namely, Upslope, Middle slope, and Downslope. Besides, in each slope position segment, a bench terrace was randomly selected; and later stratified into three plot segments, namely, Upper (A), Middle (B), and Bottom (C), for purposes of conducting infiltration experiments. At each plot segment, three infiltration experiments were replicated to ascertain the intra-bench and inter-bench terrace steady-state infiltration rates. The experimental field design consisted of three slope position sequences, three plot segments, and three replicates, hence, leading to a total of twenty-seven (27) experiments. The infiltration measurements were conducted using a standard double-ring infiltrometer. We sampled soil for two different depths, namely; 0-15 cm and 15-30 cm, at each infiltration experiment to establish its relationship to the infiltration process. Using a Spatial Autocorrelation tool embedded in ArcGIS 10.2, we analysed the spatial patterns of infiltration along the hillslope. Furthermore, a Two-Way analysis of variance (ANOVA) was used to determine differences between the means of the infiltration rates across the hillslope sequences. Descriptive Statistics were used to investigate the Degree of Variability in infiltration rates. Results showed that beyond 15 m, infiltration rates vary significantly (P<0.018) from 5 cm hr-1 to 40 cm hr-1 between the bench terraced hillslope sequences, with a mean rate of 21 cm hr-1. Intra-bench steady-state infiltration rates varied higher in the Bottom (C) compared to Upper (A) and Middle (B) segments, especially in the Upslope sequence, where rates varied from 6 cm hr-1 to 20 cm hr-1 with a coefficient of variation (CV) of 45%. The clay content in the soil had a significant influence (P<0.003) on infiltration in the study sites of the hillslope with a correlation coefficient (R, r2 = -0.5). We concluded that the spatial patterns of infiltration on a bench-terraced hillslope are influenced by slope position. Infiltration is higher at the Downslope and Middleslope bench terraces as compared to the Upslope bench terrace. Soil texture and the structural condition of the bench terraces themselves play a cardinal role in the variations in infiltration. Within the bench terraced land parcels, infiltration is higher on the downslope and lower in the upslope positions. Since percent clay content increased with slope, it was noted as a fundamental soil characteristic affecting infiltration within the bench terraces. Our recommendation was that in bench terraces where steady-state infiltration was high such as in downslope and middle slope positions, the terrace bunds should be strengthened with grass and stone embarkments to consolidate them coherently. This strategy may reduce terrace bund breakages and consequently counter surface flow on the bench terraced hillslope. Besides, in areas where low steady-state infiltration rates were recognised, such as the upslope position, agronomic practices should be enhanced.

Sizes of crab burrows regulate water–salt transport of tidal marsh wetlands

In recent years, scholars have paid increased attention to the ecological role of crab burrows, particularly their impact on the hydrological processes of saltmarsh wetlands. This study aims to investigate the influence of crab burrows on soil water and salt transport and to understand the ecological significance of crab burrows in coastal wetlands from the perspective of ecohydrological processes. We combined a field sample survey and an indoor soil column infiltration experiment to analyze the differences in infiltration time, soil water content, and soil electrical conductivity (EC) between different experimental groups. Consequently, the results showed that the size of crab burrow diameter varies significantly in different areas of the coastal wetland, influenced by tidal creek and sea–land distances, with larger burrow diameters in areas around 5 m from the tidal creek. Large-diameter burrows (2.5 cm × 6) are more conducive to salt transport due to their preferential water conductivity to the underlying soil vertically, small-diameter burrows (0.5 cm × 6) could promote water infiltration uniformly and maintain good soil water retention capacity. This study's results provide insights into the hydrological connectivity and spatial distribution of salinity in coastal wetlands. Additionally, the positive impact of burrows on the water–salt environment of coastal wetland sediments may also provide new ideas for coastal wetland restoration.

Experimental Investigation of the Different Polyacrylamide Dosages on Soil Water Movement under Brackish Water Infiltration.

The use of soil conditioners in conjunction with brackish water irrigation is critical for the efficient development and use of brackish water as well as the enhancement of the structure of saline soil and stimulating crop growth. This study investigated the effects of different polyacrylamide (PAM) dosages (0, 0.02%, 0.04%, and 0.06%) on the water flow properties of sandy loam during brackish water infiltration using one-dimensional vertical and horizontal soil column infiltration experiments. The results showed that: (1) PAM could lower the soil infiltration rate and increase soil water retention performance under brackish water infiltration conditions. (2) PAM had a significant effect on the parameters of the Philip and Kostiakov infiltration models. The soil sorption rate S and the empirical coefficient λ were the smallest, and the empirical index β was the largest when the PAM dosage was 0.04%. (3) PAM dosage displayed a quadratic polynomial connection with the soil saturated water content and the saturated hydraulic conductivity. The soil saturated water content was highest when the PAM dosage was 0.04%, the intake suction hd of the Brooks-Corey model increased by 15.30%, and the soil water holding capacity was greatly improved. (4) Soil treated with PAM could absorb more water under the same soil water suction, whereas the soil unsaturated hydraulic conductivity and its growth rate decreased. The soil saturated diffusion rate Ds, as well as the soil water diffusion threshold, rose. Finally, the 0.04% PAM dosage could improve soil hydrodynamic characteristics under brackish water infiltration, which is beneficial for the efficient utilization of brackish water.

Interaction Between Brackish Water Intermittent Infiltration and Cultivated Soil Environment: A Case Study From Arid Piedmont Plain of Northwest China

Brackish groundwater was widely used in arid areas which may cause soil salinization and groundwater environmental declines. To ensure the sustainable development of agriculture in arid areas, brackish water intermittent infiltration experiments were conducted in Southern Xinjiang, Northwest China between June to September 2018, and Hydrus-2D numerical simulation was used to analyze the underground pipe drainage systems. The field experiments were carried out during cotton growth stages after the first freshwater flood infiltration and salt washing. Two control experiments were, respectively, designed as freshwater (0.68 g/L) and brackish water (1.66 g/L) with water amount of 1.0 Q = 572 mm. Other eight groups (1.05–1.40 Q) were compared to analyze the effect of soil salt leaching by increasing the brackish water amount. The results showed that the soil moisture content was almost less than the field capacity of 0.203 at depth of 0–60 cm before each infiltration due to roots water uptake, and the soil water holding capacity rate was lower than 0.2 after 5 days under 1.20–1.40 Q brackish water treatments. Variation of EC1:5 at depth of 0–30 cm was less than 0.5 dS/m. Salt mainly accumulated at the depth of 40–60 cm whether the water amount was excessive or insufficient even under the fresh water infiltration. The optimal brackish water amount was 1.15 Q = 657.8 mm, and the soil total salinity was less than 0.55 dS/m (EC1:5) and reached mild salinization degree. Numerical simulations were used based on the 2018 field experimental results and extended by another 10 years. The soil salt accumulated to 1.10–2.99 dS/m (EC1:5) at the depth of 40–60 cm during 0–30 days. The no salinization area expanded to depth of 40–45 cm after 120 days and reduced during non-infiltration period due to evaporation effect. The soil salt was gradually leached and less than 0.55 dS/m (EC1:5) after 10 years. The optimized leaching–drainage system could not only provide a low salinity soil condition for cotton growth and realize sustainable cultivation but also greatly protect the soil and groundwater environment.

Parameters of infiltration models affected by the infiltration measurement technique and land-use

The measurement method (MM) and the land-use (LU) are two soil structure-related attributes that are available in infiltration experiments. This study aims to hypothesize that measurement technique and land-use might be good predictors of the performance of infiltration parameter values and models. The Soil Water Infiltration Global (SWIG), which includes about 5000 experiments worldwide and assembled in the Institute of Agrosphere in Jülich, Germany, was used. Except for the known properties such as texture, measurement method, and land-use, changes [...]

Influence of fiber/matrix interface on the texture evolution and fracture toughness of C/C

This study was conducted to obtain a more in-depth insight into the role of fiber/matrix interface on the texture and mechanical performance of carbon fiber reinforced carbon composites (C/C). In this study, a series of isothermal chemical vapor infiltration (ICVI) experiments were performed on the deposition of pyrocarbon (PyC) onto carbon fibers (CFs) and pre-oxidized fibers (PFs). The results showed that the graphitization degree and orientation angle (OA) of the fiber and matrix of the PF-SL were relatively low compared with the CF-SL. Most importantly, the OA of CF-SL between the interfaces was much higher than that of PF-SL. Besides, a low texture transition layer with a width of tens of nanometers was observed between the fiber/matrix interfaces, which may reduce the lattice distortion and interfacial energy. In addition, the fracture toughness of CF-SL was higher than that of PF-SL, which was attributed to interfacial differences. Further, PF-SL had a coarser interface than CF-SL due to the carbonization reaction during ICVI, which induced gas escape and PF shrinkage and bulges on the surface.

Infiltration Assessments on Top of Yungang Grottoes by Time-Lapse Electrical Resistivity Tomography

Water plays a vital role in the weathering process of grottoes. Precipitation is a main water source in the grotto hosting mountain rock. In this study, time-lapse electrical resistivity tomography was adopted to track the movement of infiltrated water in a profile in the Yungang Grottoes. Our one-year monitoring data indicated a good resistivity response to rainfall in the shallow unconsolidated soil layers. There were only resistivity decreases in the near surface 5 m across the whole monitoring profile, and resistivity values quickly returned to a neutral state after the rain stopped. Based on the analysis of a typical rainfall event during the rainy season, we found that the infiltrated water cannot continuously move downwards to recharge local groundwater. It moves horizontally to a nearby gully due to the existence of a hydraulic conductive fine sand layer and low permeable mudstone and sandstone base rocks. An artificial infiltration experiment was carried out to further verify the fate of infiltrated water. Based on mass balance analysis, with 10 m3 of infiltrated water, it only saturated dry soil in the top 1.36 m soil layer on average and this was roughly consistent with our field borehole wetting front verifications at 1.2 and 1.3 m. There were limited horizontal expansions from the infiltrated water. Therefore, based on our monitoring data and analysis, infiltrated water was not the main source of the water involved in the weathering process of the Yungang Grottoes.

Effect of brackish water irrigation on the movement of water and salt in salinized soil

Abstract In China, fresh water resources are scarce, while brackish water resources are abundant. Reasonable utilization of brackish water is one of the important measures to alleviate the contradiction of water shortage. In order to study the effect of brackish water irrigation on water and salt transport in saline-alkali soils, one-dimensional brackish water infiltration experiments of soil columns were conducted. The influence of brackish water with different salinities on water and salt transport in salinized soil was compared and analyzed. The results showed that under brackish water irrigation, the Kostiakov model could better simulate the change in soil infiltration rate with time, the soil infiltration capacity had a positive response to the salinity of irrigation water. There was a good linear relationship between cumulative infiltration and the wetting front distance. Under different salinity conditions, the depth of soil desalination, Na+, and Cl− removal is different, which are inversely proportional to the degree of salinity; with the increase in the salinity of irrigation water, the water salt content and the concentration of Na+ and Cl− increased gradually, but the difference in the desalination zone was not obvious. Therefore, brackish water irrigation has a certain effect on the distribution of water and salt in saline soil.

Risk assessment of groundwater pollution during GLDA-assisted phytoremediation of Cd- and Pb-contaminated soil

Using biodegradable chelate agents during phytoremediation of heavy metal contaminated soil is a growing consensus. However, the potential risk of groundwater pollution and the corresponding quantification during biodegradable chelate-assisted phytoremediation is currently ignored. This study provides a risk-assessment framework containing the practical boundaries and the transport model of chelate-metal complexes and metals at the subsoil, to quantify and predict the leaching risk of biodegradable N,N-bis(carboxymethyl)glutamic acid (GLDA)-induced phytoremediation during heavy rainfall. The case of ethylenediaminetetraacetic acid (EDTA)-assisted phytoremediation was also considered. Here, adsorption experiments and percolation experiments were conducted based on the subsoil to obtain adsorption parameters and hydrodynamic parameters. Optimal parameters derived from inverse fitting and the boundary condition originated from pot leaching experiments were used for the framework establishment and Hydrus-1D simulation. Results showed that fewer GLDA-metal complexes were adsorbed on the soil particles compared with metals, inferring their great mobility in the subsoil. However, the chemical and physical non-equilibrium process indicated by the asymmetric breakthrough curves of the percolation experiments would also affect the transport behavior of contaminants in the sub-vadose zone. In addition, adsorption parameters and optimal hydrodynamic parameters aptly described breakthrough curves of the chelate-metal complexes, and could better predict their transport behavior at the subsoil. Opposite to the previous findings, prediction results showed that heavy rainfall during GLDA-assisted phytoextraction resulted in Cd and Pb pollution in shallow groundwater, where the pollution degree was related to properties of the soil horizon, depth of the water table, and types of contaminants. The degradation feature of GLDA-metal complexes would fail to keep groundwater from heavy metal contamination at the sub-vadose zone with high permeability. Thus, we recommend our risk-assessment framework to optimize the operating condition before utilizing the biodegradable chelate-assisted phytoremediation.

Does macropore flow in no-till systems bypass mobile soil nitrogen after harvest?

Reduced tillage practices, including no-till, have been proposed to reduce NO3- leaching in agricultural soils. However, this is not universally supported by experimental data, and the effect of reduced tillage on NO3- leaching is likely connected to the interaction between macropore flow and resident solutes. To investigate this, we carried out infiltration experiments on intact soil cores from conventionally tilled (CT) and no-till (NT) plots, recording resident concentrations and breakthrough curves (BTCs) of three solutes (a tritium pulse, resident Br- tracer and native NO3-). We then fitted a dual porosity model implemented in HYDRUS-1D, to the experimental BTCs. By assuming different initial solute distributions between phases, we investigate possible bypass mechanisms. In the lysimeter experiment, leaching of all solutes initiated and peaked earlier in NT compared to CT, indicating increased macropore flow. However, total leached NO3- was greater in CT, and higher resident NO3- concentrations were found after the experiment in NT, suggesting an overall bypass effect. In the fitted dual porosity model, saturated water contents in the mobile phase were six times smaller in NT than in CT, with smaller horizontal solute transfer rates for NO3- than for Br-. The optimal initial proportion of total resident NO3- in the mobile phase was 7.5% in NT and 65% in CT. Our results suggest a bypass effect of native resident NO3- in NT soils related to a smaller volume of soil involved in macropore flow. Added solutes, however, remain susceptible to quicker leaching in NT compared to CT under intense precipitation.

Bioorthogonal Equipping CAR-T Cells with Hyaluronidase and Checkpoint Blocking Antibody for Enhanced Solid Tumor Immunotherapy.

Adoptive cellular therapy utilizing chimeric antigen receptor redirected T (CAR-T) cells has shown impressive therapeutic effects on hematological malignancies. In contrast, the efficacy of CAR-T therapies in treating solid tumors is still poor, which is largely due to inefficient penetration into solid tumors and the immunosuppressive tumor microenvironment. Herein, we engineered hyaluronidase (HAase) and the checkpoint blocking antibody α-PDL1 on the CAR-T cell surface via highly efficient and biocompatible bioorthogonal click chemistry to improve their therapeutic effects on solid tumors. The modified HAase degrades hyaluronic acid and destroys the tumor extracellular matrix, allowing CAR-T cells to penetrate deeply into solid tumors, as evidenced by in vitro infiltration experiments and in vivo biodistribution studies. In addition, in vitro cytotoxicity studies showed stronger antitumor activity of α-PDL1-decorated cells than traditional CAR-T cells. Importantly, HAase- and α-PDL1-engineered CAR-T cells showed better therapeutic efficacy on two solid tumor models and did not cause significant systemic side effects. In this work, we provide a simple, efficient, and biologically safe chemical strategy to engineer traditional CAR-T cells for enhanced therapeutic efficacy on solid tumors, which can be extended to other adoptive cellular immunotherapies and holds great potential for clinical application.

Soil macroporosity and water flow in the root zone of oases in hyper‐arid regions

AbstractThe characteristics of soil macropores and water infiltration are closely connected to the growth of plant roots and their root zone environment. However, it is unclear how the root zone environment of oasis farmlands regulates the development of soil macropores and water flow in hyper‐arid regions. The objective of this study was to investigate soil macropores and their effect on water flow under irrigated oasis farmlands using a combination of X‐ray computed tomography (CT) and dye tracer. It was hypothesized that the integration of CT and dye tracer could clearly reveal preferential flow through biopores and large pores of oasis soils. A helical medical CT scanner was used to quantify more information about soil macropores in the root zone, along with an in situ single‐ring dye infiltration experiment to reveal water flow in three different oasis farmlands (piedmont oasis farmland, marginal oasis farmland, and old oasis farmland). Soil macroporosity was 0.44% under crop rows, while soil macroporosity in the interrows was only 0.30% across the oasis farmlands. Biopores contributed 73% of the volume of the total macropores under crop rows. The stable infiltration rate in the interrows was 0.3 mm min−1, which was significantly (p < 0.05) less than that under crop rows (0.7 mm min−1). Water flow under crop rows were mainly transported in biopores and large pores. The contribution of macropores to preferential flow under crop rows was 4.8 times larger than interrows. The integration of CT and dye tracer was a more holistic technique, which adequately revealed that oases had preferential flow affected by biopores and large pores, resulting in higher solute and contaminant transport.Key Points Soil macropores and preferential flow affected by crop roots were investigated in hyper‐arid regions. The integration of CT and dye tracer adequately identified preferential flowpaths of oasis soils. Biopores were larger under crop rows than interrows. Preferential flow transported in biopores and large soil pores under crop rows.

Numerical models of pressure-driven fluid percolation in rock salt: nucleation and propagation of flow pathways under variable stress conditions

Success of our ongoing energy transition largely depends on subsurface exploitation. The subsurface can act as a “battery” to store energy dense fluids such as hydrogen, or a “host” to sequester unwanted substances such as carbon dioxide or radioactive waste. On the other hand, these operations cause the subsurface pressure and/or temperature to change and induce various (or cyclical) loadings to the surrounding formations. Their operational safety crucially hinges upon the subsurface integrity. The most imminent risk is nucleation of cracks that can lead to loss of mechanical integrity. Unlike hydraulic fracturing in geoenergy applications where one deliberately initiates cracks at certain targets, we normally design a system to avoid fracturing. At the designing stage, we thus have no prior knowledge of crack initiation locations or propagation paths. And, the computational designing tools should be able to assess the fracturing risk without such prior knowledge. In this study, we compared three computational approaches that do not require prescribed crack geometries—the discrete element method, the lattice element method, and the variational phase-field approach—against percolation experiments on rock salt. The experimental results show different fracture propagation paths depending on the boundary loads. The fracture geometries were reasonably matched by all approaches despite some differences in path irregularities. While the variational phase-field approach predicts relatively regular fracture paths, the paths predicted by the discrete and the lattice element methods are more irregular. These irregularities may seem more comparable to intergrain failure in real rocks, but they are also necessary triggers for fracture initiation in the discrete and the lattice element methods. In contrast, the fracture initiation in the variational phase-field approach is a realization of the energy minimization in the system, and the grain level descriptions are absent in the current formulation. These findings highlight their predictive capabilities and gaps to be bridged between the grain and continuum scales for field-scale applications.

Impact of hydro-chemical conditions on structural and hydro-mechanical properties of chalk samples during dissolution experiments

The importance of karst reservoirs for water resources, and their complexity in terms of structural properties and hydraulic responses, require a better understanding of the formation and location of conduits in these systems, in particular for chalk reservoirs. For this purpose, we conduct laboratory experiments of acid solutions injection in chalk core samples using a homemade experimental device. Three different flow rates and two acid concentrations are applied on six samples at atmospheric conditions with Peclet numbers ranging from 0.1 to 1.7 and Damköhler numbers from 10−6 to 10−3. Hydraulic and chemical measurements are carried out during the experiments, while petrophysical characterization is conducted on the samples before and after the reactive percolation experiments. The analysis of these data shows an increase in permeability of the rock samples due to calcite dissolution, which is associated with the creation of preferential conduits. We also observe that the initial structural properties control the dissolution regime with the following main conclusions. For homogeneous systems, the overall dissolution rate and percolation time are directly linked to the considered flow rate and injected acid concentration. For heterogeneous systems, (i) pre-existing large-scale structural heterogeneities control the location of newly created paths while reducing the value of the dissolution rate, and (ii) micro-scale heterogeneities result in highly heterogeneous general structures, which are responsible for channels formation while applying low Damköhler numbers.

On shapes of cumulative infiltration curves

Water infiltration into soil is the key process in the water cycle, and understanding and predicting infiltration is essential for water management. Measurements of cumulative infiltration are a common part of soil hydrological characterization. Such measurements provide the cumulative infiltration curve (CIC), i.e. dependence of the amount of infiltrated water on time. The classic, usually anticipated CIC shape is the concave increase section transitioning to the linear section. However, other shapes were also observed. The objectives of this work were (a) to use the unique large international infiltration database SWIG to define distinctly different types of CIC shapes, and (b) to see if basic soil properties, land use, and infiltration measurement method can indicate what type of non-classic CIC shapes can be expected in site-specific conditions. Examination of 5023 CIC led to the definition of 12 types of CIC shapes. About 1/3 of SWIG datasets had non-classic CIC shapes. The shape types were visually discernible in most cases. A technique was suggested to distinguish the shape types if needed. The classification tree divided all datasets with non-classic CIC shapes into most similar inside and most different from each other groups. The infiltration measurement method, the clay content, and the organic carbon content were the most influential predictors of the shape type in this classification. Several non-classic shapes were previously related to soil structure and hydrophobicity. The relatively large fraction of non-classic CIC indicates the need to design infiltration experiments accounting for possible non-classic CIC, and the need for the cautious application of common infiltration equations, most of which were developed to simulate classic CIC shapes.

Percolation Experiment Across 10-Year-Old Interface between Opalinus Clay and Portland Concrete

Percolation Experiment Across 10-Year-Old Interface between Opalinus Clay and Portland Concrete

On the three‐parameter infiltration equation of Parlange et al. (1982): Numerical solution, experimental design, and parameter estimation

AbstractSoil water infiltration is central to hydrologic studies and lends itself for detailed experimentation and mathematical–physical modeling. The most rigorous of these approaches numerically solve Richards’ equation, possibly coupled through a heterogeneous soil to a surface water routine and groundwater model. This approach is computationally expensive and prone to mass balance errors and overparameterization. Analytic solutions of the infiltration process obviate the need for specification of hydraulic functions and simplify computation and inverse determination of soil properties. This paper investigates the usefulness of Parlange's three‐parameter infiltration equation for forward and inverse modeling of vertical infiltration experiments. This quasi‐exact implicit solution of Richards’ equation, also credited to Haverkamp and coworkers in recent literature, is valid for the entire infiltration event, matches cumulative infiltration data from different soils and its (super‐)parameters, S, Ks, and β, exhibit a solid mathematical–physical underpinning. Nonetheless, Parlange's equation has not entered mainstream use for infiltration simulation and data analysis in the absence of a robust, exact and efficient numerical solution. This paper builds upon the recent work of Jaiswal et al. and presents theory, algorithms, and source codes of two numerical procedures for forward and inverse modeling of Parlange's infiltration equation. We illustrate the procedures using measured infiltration data from the Soil Water Infiltration Global (SWIG) database. Our findings highlight the potential of Parlange's equation for infiltration modeling and hydraulic characterization of the soil sorptivity, S [L T−1/2], saturated hydraulic conductivity, Ks [L T−1], and unitless coefficient, β. Parlange's infiltration equation provides a powerful alternative to mathematically more convenient explicit infiltration equations that suffer physical underpinning and/or a limited time validity.

A Mathematical Model for Transport and Growth of Microbes in Unsaturated Porous Soil

In this work, we develop a mathematical model for transport and growth of microbes by natural (rain) water infiltration and flow through unsaturated porous soil along the vertical direction under gravity and capillarity by coupling a system of advection diffusion equations (for concentration of microbes and their growth-limiting substrate) with the Richards equation. The model takes into consideration several major physical, chemical, and biological mechanisms. The resulting coupled system of PDEs together with their boundary conditions is highly nonlinear and complicated to solve analytically. We present both a partial analytic approach towards solving the nonlinear system and finding the main type of dynamics of microbes, and a full-scale numerical simulation. Following the auxiliary equation method for nonlinear reaction-diffusion equations, we obtain a closed form traveling wave solution for the Richards equation. Using the propagating front solution for the pressure head, we reduce the transport equation to an ODE along the moving frame and obtain an analytic solution for the history of bacteria concentration for a specific test case. To solve the system numerically, we employ upwind finite volume method for the transport equations and stabilized explicit Runge–Kutta–Legendre super-time-stepping scheme for the Richards equation. Finally, some numerical simulation results of an infiltration experiment are presented, providing a validation and backup to the analytic partial solutions for the transport and growth of bacteria in the soil, stressing the occurrence of front moving solitons in the nonlinear dynamics.