scholarly journals Bayesian Simultaneous Estimation of Unsaturated Flow and Solute Transport Parameters from a Laboratory Infiltration Experiment

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1660 ◽  
Author(s):  
Anis Younes ◽  
Jabran Zaouali ◽  
Sabri Kanzari ◽  
Francois Lehmann ◽  
Marwan Fahs
Keyword(s):  
Mass Transport ◽  
Solute Transport ◽  
Unsaturated Flow ◽  
Soil Column ◽  
Accurate Estimation ◽  
Soil Parameters ◽  
Simultaneous Estimation ◽  
Transport Parameters ◽  
Undisturbed Soil ◽  
Infiltration Experiment

Numerical modeling has become an irreplaceable tool for the investigation of water flow and solute transport in the unsaturated zone. The use of this tool for real situations is often faced with lack of knowledge of hydraulic and soil transport parameters. In this study, advanced experimental and numerical techniques are developed for an accurate estimation of the soil parameters. A laboratory unsaturated flow and solute transport experiment is conducted on a large undisturbed soil column of around 40 cm length. Bromide, used as a nonreactive contaminant, is injected at the surface of the undisturbed soil, followed by a leaching phase. The pressure measurements at different locations along the soil column as well as the outflow bromide concentration are collected during the experiment and used for the statistical calibration of flow and solute transport. The Richards equation, combined with constitutive relations for water content and permeability, is used to describe unsaturated flow. Both linear and non-equilibrium mobile–immobile transport models are investigated for the solute transport. All hydraulic and mass transport parameters are inferred using a one-step Bayesian estimation with the Markov chain Monte Carlo sampler. The results prove that the pressure and concentration measurements are able to identify almost all hydraulic and mass transport parameters. The mobile–immobile transport model better reproduces the infiltration experiment. It produces narrower uncertainty intervals for soil parameters and predictive output concentrations.

scholarly journals Evaluation of Solute Transport in Undisturbed Soil Column under Steady Unsaturated Flow Conditions.

1997 ◽  
pp. 61-70
Author(s):  
Masato Horiuchi ◽  
Yoriteru Inoue ◽  
Shinsuke Morisawa ◽  
Barokah Aliyanta
Keyword(s):  
Solute Transport ◽  
Unsaturated Flow ◽  
Soil Column ◽  
Flow Conditions ◽  
Undisturbed Soil

A Two-Domain Approach to Model Solute Transport in an Undisturbed Soil Column using X-Ray CAT Scanning

2013 ◽  
Author(s):  
J. Perret ◽  
S.O. Prasher ◽  
A. Kanztas ◽  
and C. Langford
Keyword(s):  
Solute Transport ◽  
Soil Column ◽  
Undisturbed Soil ◽  
X Ray

scholarly journals A Nonlinear Solute Transport Model and Data Reconstruction with Parameter Determination in an Undisturbed Soil-Column Experiment

2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Gongsheng Li ◽  
De Yao ◽  
Yongzai Wang ◽  
Xianzheng Jia
Keyword(s):  
Inverse Problem ◽  
Solute Transport ◽  
Transport Model ◽  
Soil Column ◽  
Parameter Determination ◽  
Nonlinear Transport ◽  
Inversion Algorithm ◽  
Unknown Parameters ◽  
Undisturbed Soil ◽  
Optimal Perturbation

A real undisturbed soil-column infiltrating experiment in Zibo, Shandong, China, is investigated, and a nonlinear transport model for a solute ion penetrating through the column is put forward by using nonlinear Freundlich's adsorption isotherm. Since Freundlich's exponent and adsorption coefficient and source/sink terms in the model cannot be measured directly, an inverse problem of determining these parameters is encountered based on additional breakthrough data. Furthermore, an optimal perturbation regularization algorithm is introduced to determine the unknown parameters simultaneously. Numerical simulations are carried out and then the inversion algorithm is applied to solve the real inverse problem and reconstruct the measured data successfully. The computational results show that the nonlinear advection-dispersion equation discussed in this paper can be utilized by hydrogeologists to research solute transport behaviors with nonlinear adsorption in porous medium.

scholarly journals Study on Movement of Water and Salt through Soil Column and Utilization of Hydrus-1D Program to Simulate Five Scenarios of Crop Production in Salt Affected Paddy Soil

2015 ◽  
Vol 10 (1) ◽  
pp. 139
Author(s):  
Panom Chaiyasit ◽  
Piya Duangpatra ◽  
Visoot Verasan ◽  
Varawoot Vudhivanich
Keyword(s):  
Solute Transport ◽  
Bulk Density ◽  
Paddy Soil ◽  
Mung Bean ◽  
Soil Column ◽  
Breakthrough Curves ◽  
Pedotransfer Functions ◽  
Hydraulic Parameters ◽  
Transport Parameters ◽  
Hydrus 1D

<p class="zhengwen"><span lang="EN-GB">An experiment was conducted on the purpose to study movement of water and salt through soil column. Salt-affected paddy soil was assessed for its relevant transport parameters consisting of the hydraulic and the solute transport parameters. The hydraulic parameters included soil hydraulic conductivity (K<sub>s</sub>) and the van Genuchten’s parameters (θ<sub>s</sub>, θ<sub>r</sub>, α, and n). In this experiment the solute transport parameters was referred to the coefficient of Langmuir’s isotherm which consisted of k<sub>d</sub> and η. Experience showed that hydraulic parameters were sensitive to changes of soil bulk density (ρ<sub>b</sub>). Therefore pedotransfer functions describing the relations between these parameters with ρ<sub>b</sub> were established. Straight line functions were found for θ<sub>s</sub> and n, exponential functions were found for α and K<sub>s</sub>, and logarithmic function was found for θ<sub>r</sub>. Packing the soil in the physical column inevitably caused horizontal differentiation of different ρ<sub>b</sub>. Bulk density of each layer was estimated by analysis of water flow through soil column at steady-state. Then ρ<sub>b</sub> of each layer was calculated from the relation K<sub>s</sub> (ρ<sub>b</sub>). After the ρ<sub>b</sub> was known the van Genuchten’s parameters were calculated from the pedotransfer functions. A physical column of 4 inches diameter and 50 cm length was constructed. Sodium chloride solution EC 6 dS/m was fed on soil surface during the process of salinization and the feeding solution was changed to fresh water during the process of desalinization. Breakthrough solution was analyzed for Na concentration and the breakthrough curves were constructed. The relevant parameters as well as initial and boundary conditions were fed into Hydrus-1D on the purpose to simulate the breakthrough curves. Statistical comparison results using t-test and RMSE suggested that Hydrus-1D could be used successfully to monitor transport of water and salt through soil column.</span></p><p class="zhengwen"><span lang="EN-GB">Five scenarios concerning water and solute transport through soil profile under rice and mung bean cropping were simulated using Hydrus-1D. Simulation results suggested that continuous flooding was the most efficient way to leach soluble salts down to ground water. Wet/dry irrigation scheme for rice production could drain salts only when rice crop was in the first period of growth where crop water uptake was small. During later stages of growth concentration profile of Na remained almost unchange indicating negligible downward movement of salts. Leaving the soil to dry naturally during the dry season caused upward accumulation of salt to the degree smaller than cultivating mung bean since water content and hence the diffusion coefficient of the soil were higher and more favorable for upward salt diffusion than in the former case. Inserting the capillary rise hindering soil layer underneath mung bean root zone was found to retard upward diffusion of salt to the degree comparable to leaving the soil to dry naturally.</span></p>

scholarly journals Bayesian estimation of the hydraulic and solute transport properties of a small-scale unsaturated soil column

2016 ◽  
Vol 64 (1) ◽  
pp. 30-44 ◽  
Author(s):  
Paulo H. S. Moreira ◽  
Martinus Th. van Genuchten ◽  
Helcio R. B. Orlande ◽  
Renato M. Cotta
Keyword(s):  
Solute Transport ◽  
Transport Properties ◽  
Unsaturated Soil ◽  
Soil Column ◽  
Column Experiment ◽  
Richards Equation ◽  
Small Scale ◽  
Transport Parameters ◽  
Unknown Parameters ◽  
Concentration Data

Abstract In this study the hydraulic and solute transport properties of an unsaturated soil were estimated simultaneously from a relatively simple small-scale laboratory column infiltration/outflow experiment. As governing equations we used the Richards equation for variably saturated flow and a physical non-equilibrium dual-porosity type formulation for solute transport. A Bayesian parameter estimation approach was used in which the unknown parameters were estimated with the Markov Chain Monte Carlo (MCMC) method through implementation of the Metropolis-Hastings algorithm. Sensitivity coefficients were examined in order to determine the most meaningful measurements for identifying the unknown hydraulic and transport parameters. Results obtained using the measured pressure head and solute concentration data collected during the unsaturated soil column experiment revealed the robustness of the proposed approach.

scholarly journals Field scale variability of solute transport parameters and related soil properties

1997 ◽  
Vol 1 (4) ◽  
pp. 801-811 ◽  
Author(s):  
B. Lennartz ◽  
S. K. Kamra ◽  
S. Meyer-Windel
Keyword(s):  
Soil Properties ◽  
Solute Transport ◽  
Water Content ◽  
Soil Water ◽  
Soil Water Content ◽  
Preferential Flow ◽  
Type I ◽  
Transport Parameters ◽  
Undisturbed Soil ◽  
Soil Hydraulic

Abstract. The spatial variability of transport parameters has to be taken into account for a reliable assessment of solute behaviour in natural field soils. Two field sites were studied by collecting 24 and 36 small undisturbed soil columns at an uniform grid of 15 m spacing. Displacement experiments were conducted in these columns with bromide traced water under unsaturated steady state transport conditions. Measured breakthrough curves (BTCs) were evaluated with the simple convective-dispersive equation (CDE). The solute mobility index (MI) calculated as the ratio of measured to fitted pore water velocity and the dispersion coefficient (D) were used to classify bromide breakthrough behaviour. Experimental BTCs were classified into two groups: type I curves expressed classical solute behaviour while type II curves were characterised by the occurrence of a bromide concentration maximum before 0.35 pore volumes of effluent (MI<0.35) resulting from preferential flow conditions. Six columns from site A and 8 from site B were identified as preferential. Frequency distributions of the transport parameters (MI and D) of both sites were either extremely skewed or bimodal. Log-transformation did not lead to a normal distribution in any case. Contour maps of bromide mass flux at certain time steps indicated the clustering of preferential flow regions at both sites. Differences in the extent of preferential flow between sites seemed to be governed by soil structure. Linear cross correlations among transport parameters and independently measured soil properties revealed relations between solute mobility and volumetric soil water content at time of sampling, texture and organic carbon content. The volumetric field soil water content, a simple measure characterising the soil hydraulic behaviour at the sampling location, was found to be a highly sensitive parameter with respect to solute mobility and preferential flow situations. Almost no relation was found between solute transport parameters and independently determined soil properties when non-preferential and preferential samples were considered separately in regression analyses. Future work should concentrate to relate integrated parameters such as the infiltration rate or the soil hydraulic functions to solute mobility under different flow situations.

scholarly journals Field-scale solute transport parameters derived from tracer tests in large undisturbed soil columns

Soil Research ◽  
2014 ◽  
Vol 52 (1) ◽  
pp. 13 ◽  
Author(s):  
Dirk Mallants
Keyword(s):  
Solute Transport ◽  
Transport Model ◽  
Linear Regression Analysis ◽  
Local Scale ◽  
Time Domain Reflectometry ◽  
Hydrodynamic Dispersion ◽  
Transport Parameters ◽  
Field Scale ◽  
Soil Columns ◽  
Undisturbed Soil

Transport parameters obtained from laboratory tracer experiments were used to evaluate the stochastic form of the equilibrium convection–dispersion equation (CDE) in describing the transition of scale, i.e. from the column or local scale to a larger field scale. Local-scale solute breakthrough curves (BTCs) were measured in 1-m-long and 0.3-m-diameter undisturbed soil columns by means of time-domain reflectometry at six depths for a 79-h input pulse of chloride. The local-scale data were analysed in terms of the equilibrium CDE and the mobile–immobile non-equilibrium transport model (MIM). At the local scale, the MIM transport model better described the observed early breakthrough and the tailing of the BTC than did the CDE. A linear regression analysis indicated that the relationship between the hydrodynamic dispersion D and pore-water velocity v was of the form D = 31vl.92 (correlation ρv,D = 0.74). Averaging of the local-scale BTCs across the field produced a large-scale or field-scale mean BTC; at the greatest observation depth (0.8 m) the field-scale dispersivity <D>/<v> = λ equals 0.656 m. The results further showed that for large values of the mean dispersion coefficient, <D>, local-scale dispersion is an important mechanism for field-scale solute spreading, whereas the standard deviation, σD, and the correlation between v and D, ρvD, have negligible effects on field-scale transport. Stochastic stream tube models supplemented with statistical properties of local-scale transport parameters provide a practical and computationally efficient tool to describe heterogeneous solute transport at large spatial scales.

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