scholarly journals Numerical and experimental study on solute transport through physical aquifer model

2021 ◽  
Author(s):  
Muskan Mayank ◽  
Pramod Kumar Sharma
Keyword(s):  
Porous Media ◽  
Numerical Model ◽  
Solute Transport ◽  
Breakthrough Curves ◽  
Time Dependent ◽  
Environmental Concerns ◽  
Transport Parameters ◽  
Spatial Moments ◽  
Advection Dispersion ◽  
Simplifying Assumptions

Abstract Environmental concerns have drawn much research interest in solute transport through porous media. Thus, contaminants of groundwater permeate through pores in the ground, and adsorption attenuates the pollution concentration as the pollutants adhere to the solid surface. Mathematical models based on certain simplifying assumptions have been used to predict solute transport. The transport of solutes in porous media is governed by a partial differential equation known as the advection-dispersion equation. In this study, a two-dimensional numerical model has been developed for solute transport through porous media. Results of spatial moments have been predicted and analysed in the presence of both constant and time-dependent dispersion coefficients. Afterward, a numerical model is used to simulate experimentally observed breakthrough curves for both conservative and non-conservative solutes. Thus, transport parameters are estimated through numerical simulation of observed breakthrough curves. Finally, this model gives the best simulation of observed breakthrough curves, and it can also be used in the field scale.

scholarly journals Experimental Research on the Thresholds of Scale-Dependent Dispersivity of Solute Transport

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 3) ◽  
Author(s):  
Ruigang Zhang ◽  
Mingxi Chu ◽  
Yong Liu ◽  
Dun Wu ◽  
Wenyong Zhang
Keyword(s):  
Porous Media ◽  
Solute Transport ◽  
Threshold Value ◽  
Breakthrough Curves ◽  
Heterogeneous Porous Media ◽  
Travel Distance ◽  
Asymptotic Model ◽  
Linear Scale ◽  
Advection Dispersion ◽  
Early Arrival

Abstract The conventional advection-dispersion equation (ADE) has been widely used to describe the solute transport in porous media. However, it cannot interpret the phenomena of the early arrival and long tailing in breakthrough curves (BTCs). In this study, we aim to experimentally investigate the behaviors of the solute transport in both homogeneous and heterogeneous porous media. The linear-asymptotic model (LAF solution) with scale-dependent dispersivity was used to fit the BTCs, which was compared with the results of the ADE model and the conventional truncated power-law (TPL) model. Results indicate that (1) the LAF model with linear scale-dependent dispersivity could better capture the evolution of BTCs than the ADE model; (2) dispersivity initially increases linearly with the travel distance and is stable at some limited value over a large distance, and a threshold value of the travel distance is provided to reflect the constant dispersivity; and (3) compared with the TPL model, both the LAF and ADE models can capture the behavior of solute transport as a whole. For fitting the early arrival, the LAF model is less than the TPL; however, the LAF model is more concise in mathematics and its application will be studied in the future.

Experimental Study and Models Comparison for Solute Transport through Riparian Zones

2014 ◽  
Vol 1073-1076 ◽  
pp. 1604-1608
Author(s):  
Zhou Chen ◽  
Jin Guo Wang ◽  
Wen Zhang Zhang ◽  
Jia Hui Shi
Keyword(s):  
Solute Transport ◽  
Riparian Zone ◽  
Tracer Tests ◽  
Breakthrough Curves ◽  
Advection Dispersion ◽  
Early Arrival ◽  
Models Comparison ◽  
Silt Layer ◽  
Better Than ◽  
Peak Value

Solute transport through riparian zone was studied experimentally and numerically with the consideration of silt layer. The silt layer had markable change on flow field and lead to a significant variation of the breakthrough curves (BTCs). BTCs of solute tracer tests show non-Fickian features as early arrival of peak value and long tailings. BTCs were fitted by advection dispersion equation (ADE), mobile and immobile model (MIM) and the continuous time random walk (CTRW) models. MIM and CTRW can fit BTCs better than ADE and MIM fit better on the capture of the peak value and CTRW fit better in description of the long tailing.

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>

A time-space Hausdorff derivative model for anomalous transport in porous media

2019 ◽  
Vol 22 (6) ◽  
pp. 1517-1536 ◽  
Author(s):  
Yingjie Liang ◽  
Ninghu Su ◽  
Wen Chen
Keyword(s):  
Porous Media ◽  
Solute Transport ◽  
Water Flow ◽  
Dispersion Model ◽  
Mathematical Formulation ◽  
Breakthrough Curves ◽  
Flow In Porous Media ◽  
Time And Space ◽  
Time Space ◽  
Constant Diffusion

Abstract This paper presents a time-space Hausdorff derivative model for depicting solute transport in aquifers or water flow in heterogeneous porous media. In this model, the time and space Hausdorff derivatives are defined on non-Euclidean fractal metrics with power law scaling transform which, respectively, connect the temporal and spatial complexity during transport. The Hausdorff derivative model can be transformed to an advection-dispersion equation with time- and space-dependent dispersion and convection coefficients. This model is a fractal partial differential equation (PDE) defined on a fractal space and differs from the fractional PDE which is derived for non-local transport of particles on a non-fractal Euclidean space. As an example of applications of this model, an explicit solution with a constant diffusion coefficient and flow velocity subject to an instantaneous source is derived and fitted to the breakthrough curves of tritium as a tracer in porous media. These results are compared with those of a scale-dependent dispersion model and a time-scale dependent dispersion model. Overall, it is found that the fractal PDE based on the Hausdorff derivatives better captures the early arrival and heavy tail in the scaled breakthrough curves for variable transport distances. The estimated parameters in the fractal Hausrdorff model represent clear mechanisms such as linear relationships between the orders of Hausdorff derivatives and the transport distance. The mathematical formulation is applicable to both solute transport and water flow in porous media.

scholarly journals Comparison of Surface Roughness and Transport Processes of Sawed, Split and Natural Sandstone Fractures

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2530 ◽  
Author(s):  
Sascha Frank ◽  
Thomas Heinze ◽  
Stefan Wohnlich
Keyword(s):  
Surface Roughness ◽  
Tracer Tests ◽  
Breakthrough Curves ◽  
Transport Processes ◽  
Natural Fracture ◽  
Transport Parameters ◽  
Fracture Surfaces ◽  
Advection Dispersion ◽  
Hydraulic Aperture ◽  
Surface Morphologies

In single fractures, dispersion is often linked to the roughness of the fracture surfaces and the resulting local aperture distribution. To experimentally investigate the effects of diverse fracture types and surface morphologies in sandstones, three fractures were considered: those generated by sawing and splitting, and a natural sedimentary fracture. The fracture surface morphologies were digitally analyzed and the hydraulic and transport parameters of the fractures were determined from Darcy and the tracer tests using a fit of a continuous time random walk (CTRW) and a classical advection–dispersion equation (ADE). While the sawed specimen with the smoothest surface had the smallest dispersivity, the natural fracture has the largest dispersivity due to strong anisotropy and non-matching fracture surfaces, although its surface roughness is comparable to the split specimen. The parameterization of the CTRW and of the ADE agree well for β > 4 of the truncated power law. For smaller values of β, non-Fickian transport processes are dominant. Channeling effects are observable in the tracer breakthrough curves. The transport behavior in the fractures is controlled by multiple constraints such as several surface roughness parameters and the equivalent hydraulic aperture.

Simulation of Contaminant Transport in a Fractured Porous Aquifer

2007 ◽  
Vol 129 (9) ◽  
pp. 1157-1163
Author(s):  
Sergei Fomin ◽  
Vladimir Chugunov ◽  
Toshiyuki Hashida
Keyword(s):  
Solute Transport ◽  
Contaminant Transport ◽  
Time Derivative ◽  
Surrounding Rock ◽  
Time Dependent ◽  
Confined Aquifer ◽  
Closed Form Solutions ◽  
Advection Dispersion ◽  
Porous Aquifer ◽  
Fractional Time Derivative

Solute transport in the fractured porous confined aquifer is modeled by the advection-dispersion equation with fractional time derivative of order γ, which may vary from 0 to 1. Accounting for diffusion in the surrounding rock mass leads to the introduction of an additional fractional time derivative of order 1∕2 in the equation for solute transport. The closed-form solutions for concentrations in the aquifer and surrounding rocks are obtained for the arbitrary time-dependent source of contamination located in the inlet of the aquifer. Based on these solutions, different regimes of contamination of the aquifers with different physical properties are modeled and analyzed.

scholarly journals Preselection of a sorption model based on a column test: the algorithm and an example of its application

2021 ◽  
Author(s):  
Marek Marciniak ◽  
Monika Okońska ◽  
Mariusz Kaczmarek
Keyword(s):  
Mathematical Model ◽  
Breakthrough Curve ◽  
Breakthrough Curves ◽  
Transport Processes ◽  
Column Experiments ◽  
Transport Parameters ◽  
Sorption Model ◽  
Advection Dispersion ◽  
Conservative Tracer ◽  
Reactive Tracer

AbstractIn order to describe the contamination of saturated porous media, it is necessary to find an appropriate mathematical model that includes processes occurring in aquifers, such as advection, dispersion, diffusion, and various kinds of sorption. The identification of parameters of those processes is possible through laboratory column experiments, which result in records of breakthrough curves for a conservative tracer and a reactive tracer. An algorithm leading to the preliminary selection of the mathematical model that best describes transport processes of the reactive tracer in the experimental column is proposed in this article. A study published previously presented a sensitivity analysis for an arbitrarily adopted variability of the transport parameters. The analysis involved examining changes in the shape of breakthrough curves caused by the alteration of each parameter value. Specially defined indicators called descriptors were proposed to quantitatively describe the breakthrough curves. Then, formulas were proposed to determine the percentage deviations of descriptors of the breakthrough curve obtained for the reactive tracer in relation to the descriptors of the breakthrough curve of the conservative tracer. In the work described in this article, the deviations are analyzed and an algorithm is proposed that allows the preselection of the most suitable sorption model out of the five discussed simple (one-site) and six hybrid (two-site) models. The algorithm can facilitate and accelerate the interpretation of column experiments of contaminant transport in a porous medium. An example is provided to illustrate the usability of the proposed algorithm.

Solute transport in dual conduit structure: experiment and modelling

2020 ◽  
Author(s):  
Chaoqi Wang ◽  
Xiaoguang Wang ◽  
Samer Majdalani ◽  
Vincent Guinot ◽  
Hervé Jourde
Keyword(s):  
Solute Transport ◽  
Peak Concentration ◽  
Dispersion Model ◽  
Tracer Tests ◽  
Breakthrough Curves ◽  
Physical Models ◽  
Length Ratio ◽  
Tracer Transport ◽  
Transport Parameters ◽  
Total Length

&lt;p&gt;An important phenomenon often encountered when interpreting tracer tests in karst aquifers is the occurrence of dual-peaked breakthrough curves (BTCs). The dual-peaked BTCs are usually attributed to tracer transport through a conduit system consisting of a dual-conduit structure: an auxiliary conduit that deviates from the main conduit at the upstream and converges back at the downstream. In order to understand how the geometric configuration of the dual-conduit structure influences the BTCs, laboratory experiments utilizing plastic tubes were conducted. The physical models were constructed by varying: 1) the total length of the conduits, while fixing the length ratio; 2) length ratio between the two conduits, while fixing the length of the main conduit; and 3) conduits connection angle. The tracer experiments are then fitted by a Multi-Region Advection Dispersion model and a Transfer Function model to derive effective transport parameters. This allows us to quantitatively compare the experimental results, and thus to analyse the conduit geometry effects on solute transport and to compare the performance of the two models.&lt;/p&gt;&lt;p&gt;Results show that the dual-conduit structure causes the double peaks of BTCs. Keeping the length ratio of the two conduits and increasing their total length leads to a larger separation of the two peaks of the BTCs. Keeping the length of main conduit while increasing the length of the secondary conduit causes similar effects. As (&amp;#952;&lt;sub&gt;1&lt;/sub&gt;-&amp;#952;&lt;sub&gt;2&lt;/sub&gt;) increases, the first peak concentration value decreases, the second peak concentration value increases.&lt;/p&gt;&lt;p&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: karst, lab experiment, dual-peaked BTCs, modelling&lt;/p&gt;

Sign in / Sign up

Export Citation Format

Share Document