scholarly journals DETERMINATION OF TRANSPORT PARAMETERS FOR SOLUTES IN SALT-TREATED SOIL COLUMNS

2017 ◽  
Vol 48 (1) ◽  
Author(s):  
Bahia & Naser
Keyword(s):  
Sodium Chloride ◽  
Calcium Chloride ◽  
Peclet Number ◽  
Dispersion Coefficient ◽  
Breakthrough Curves ◽  
Retardation Factor ◽  
Transport Parameters ◽  
Péclet Number ◽  
Mixed Salts ◽  
Sodium And Potassium

A laboratory experiment was carried out at the Department of Soil Sciences and Water Resources, College of Agriculture, University of Baghdad. Silty clay soil was treated with three salt solutions (NaCl, CaCl2 and mixed NaCl–CaCl2). Homogeneously packed soil columns (10 cm, 40 cm) were leached six times using tap water. Effluent samples were collected to determine ion concentration Cl-, Ca++, Na+, K+ and Mg++. Breakthrough curves were used to estimate solute transport parameters (retardation factor, peclet number) using an analytical solution of convection-dispersion equation (CDE) by CXTFIT program. The results showed that relative concentration of chloride was increased rapidly with calcium chloride, which increased sodium leaching rate at starting of breakthrough curve. Sodium chloride increased water requirements for calcium displacement. Results indicated a good fitting of convection-dispersion equation with breakthrough curves data. The best-fit were used to calculate peclet number, retardation factor and dispersion coefficient. When soil was treated with calcium chloride, Peclet number of chloride was increased from 3.13 to 6.48, while it has been decreased for calcium, sodium and potassium. Sodium chloride decreased peclet numbers of chloride, calcium and sodium. Also mixed salts increased sodium peclet number from 1.01 to 9.02. Results showed, calcium chloride decreased retardation factor of chloride from 1.59 to 0.50, while it has been increased from 1.39, 1.58 to 175.00, 493.36 for each of sodium and potassium, respectively. Retardation factor of calcium was decreased when soil was treated with sodium chloride or mixed salts. Dispersion coefficient was decreased for chloride, and increased for calcium and magnesium. When soil was treated with calcium chloride, dispersion coefficients have been increased from 24.29, 25.56 to 40.51, 40.89 cm2hr-1 for sodium and potassium, respectively.

scholarly journals Temperature effect in potassium and nitrate ions in soil transport

2008 ◽  
Vol 28 (3) ◽  
pp. 438-447 ◽  
Author(s):  
Adriano D. M. A. Gonçalves ◽  
Jarbas H. Miranda ◽  
Paulo Rossi ◽  
José F. G. Sabadin ◽  
Marcos Y. Kamogawa
Keyword(s):  
Porous Medium ◽  
Dispersion Coefficient ◽  
Potassium Nitrate ◽  
Positive Influence ◽  
Retardation Factor ◽  
Nitrate Transport ◽  
Transport Parameters ◽  
Medium Temperature ◽  
Soil Transport ◽  
Solute Dynamics

When doing researches on solute dynamics in porous medium, the knowledge of medium characteristics and percolating liquids, as well as of external factors is very important. An important external factor is temperature and, in this sense, our purpose was determining potassium and nitrate transport parameters for different values of temperature, in miscible displacement experiments. Evaluated parameters were retardation factor (R), diffusion/dispersion coefficient (D) and dispersivity, at ambient temperature (25 up to 28 ºC), 40 ºC and 50 ºC. Salts used were potassium nitrate and potassium chlorate, prepared in a solution made up of 5 ppm nitrate and 2.000 ppm potassium, with Red-Yellow Latosol porous medium. Temperature exhibited a positive influence upon porous medium solution and upon dispersion coefficient.

Analysis of breakthrough curves: effect of mobile and immobile pore volumes

Soil Research ◽  
1984 ◽  
Vol 22 (1) ◽  
pp. 23 ◽  
Author(s):  
RS Pandey ◽  
SK Gupta
Keyword(s):  
Pore Volume ◽  
Peclet Number ◽  
Breakthrough Curves ◽  
New Technique ◽  
Péclet Number ◽  
A New Technique

A new technique of evaluating readily displaceable liquid has been outlined. The use of this technique has been illustrated for several breakthrough curves, highlighting the deviations in earlier estimates of pore volumes which are either positive or negative. The implication of these deviations has been discussed. The effect of this change in pore volume on Peclet number is presented. The prediction made with the new set of parameters is illustrated and compared with the observed data resulting in an overall improvement in predictions.

scholarly journals Determination of transport parameters for heavy metal in residual compacted soil using two methodologies

2006 ◽  
Vol 33 (7) ◽  
pp. 912-917
Author(s):  
Izabel Christina Duarte Azevedo ◽  
Cleidimar Rejane Nascentes ◽  
Antonio Teixeira de Matos ◽  
Roberto Francisco de Azevedo
Keyword(s):  
Heavy Metals ◽  
Dispersion Coefficient ◽  
Soil Column ◽  
Optimization Procedure ◽  
Retardation Factor ◽  
Hydrodynamic Dispersion ◽  
Column Test ◽  
Transport Parameters ◽  
Compacted Soil ◽  
Cumulative Mass

Values of the hydrodynamic dispersion coefficient and retardation factor obtained using the traditional and cumulative mass methods of column test analysis for zinc, manganese, and cadmium in a compacted soil are compared. The soil under study is from the B horizon of a residual gneissic tropical soil used for construction of the liner for the sanitary landfill in the District of Visconde do Rio Branco, Minas Gerais (MG), Brazil. To evaluate the behavior of landfill leachate heavy metals through the soil, soil column tests were performed on samples of compacted soil. A computational program that uses an optimization procedure to generate values of the hydrodynamic dispersion coefficient and retardation factor was developed to facilitate interpretation of the results obtained by the cumulative mass method. Values of the retardation factor and hydrodynamic dispersion coefficient were not influenced by the method of determination, even when a reduced number of effluent samples was used by the cumulative mass method. The use of the cumulative mass method, based on a reduced number of pore volumes, reduces the time and cost involved in the tests.Key words: heavy metals, column test, cumulative mass method.

scholarly journals RIGOROUS DERIVATION OF A HYPERBOLIC MODEL FOR TAYLOR DISPERSION

2011 ◽  
Vol 21 (05) ◽  
pp. 1095-1120 ◽  
Author(s):  
ANDRO MIKELIĆ ◽  
C. J. VAN DUIJN
Keyword(s):  
Dispersion Equation ◽  
Peclet Number ◽  
Perturbation Technique ◽  
Hyperbolic Model ◽  
Narrow Slit ◽  
Rigorous Derivation ◽  
Transport Parameters ◽  
Singular Perturbation Technique ◽  
Péclet Number ◽  
Hyperbolic Dispersion

In this paper, we upscale the classical convection-diffusion equation in a narrow slit. We suppose that the transport parameters are such that we are in Taylor's regime, i.e. we deal with dominant Péclet numbers. In contrast to the classical work of Taylor, we undertake a rigorous derivation of the upscaled hyperbolic dispersion equation. Hyperbolic effective models were proposed by several authors and our goal is to confirm rigorously the effective equations derived by Balakotaiah et al. in recent years using a formal Lyapounov–Schmidt reduction. Our analysis uses the Laplace transform in time and an anisotropic singular perturbation technique, the small characteristic parameter ε being the ratio between the thickness and the longitudinal observation length. The Péclet number is written as Cε-α, with α < 2. Hyperbolic effective model corresponds to a high Péclet number close to the threshold value when Taylor's regime turns to turbulent mixing and we characterize it by assuming 4/3 < α < 2. We prove that the difference between the dimensionless physical concentration and the effective concentration, calculated using the hyperbolic upscaled model, divided by ε2-α (the local Péclet number) converges strongly to zero in L2-norm. For Péclet numbers considered in this paper, the hyperbolic dispersion equation turns out to give a better approximation than the classical parabolic Taylor model.

Dispersion controlled by permeable surfaces: surface properties and scaling

2016 ◽  
Vol 801 ◽  
pp. 13-42 ◽  
Author(s):  
Bowen Ling ◽  
Alexandre M. Tartakovsky ◽  
Ilenia Battiato
Keyword(s):  
Mass Transport ◽  
Solute Transport ◽  
Surface Properties ◽  
Peclet Number ◽  
Dispersion Coefficient ◽  
Operating Conditions ◽  
Péclet Number ◽  
Porosity And Permeability ◽  
Matrix Porosity ◽  
The Impact

Permeable and porous surfaces are common in natural and engineered systems. Flow and transport above such surfaces are significantly affected by the surface properties, e.g. matrix porosity and permeability. However, the relationship between such properties and macroscopic solute transport is largely unknown. In this work, we focus on mass transport in a two-dimensional channel with permeable porous walls under fully developed laminar flow conditions. By means of perturbation theory and asymptotic analysis, we derive the set of upscaled equations describing mass transport in the coupled channel–porous-matrix system and an analytical expression relating the dispersion coefficient with the properties of the surface, namely porosity and permeability. Our analysis shows that their impact on the dispersion coefficient strongly depends on the magnitude of the Péclet number, i.e. on the interplay between diffusive and advective mass transport. Additionally, we demonstrate different scaling behaviours of the dispersion coefficient for thin or thick porous matrices. Our analysis shows the possibility of controlling the dispersion coefficient, i.e. transverse mixing, by either active (i.e. changing the operating conditions) or passive mechanisms (i.e. controlling matrix effective properties) for a given Péclet number. By elucidating the impact of matrix porosity and permeability on solute transport, our upscaled model lays the foundation for the improved understanding, control and design of microporous coatings with targeted macroscopic transport features.

scholarly journals Determination of the sodium retardation factor using different methods: Analysis of their characteristics and impact on the solute movement prediction in a structured Brazilian soil

2018 ◽  
Vol 22 (4) ◽  
pp. 281-289
Author(s):  
Vanessa Godoy ◽  
Gian Franco Napa-García ◽  
Lázaro Zuquette
Keyword(s):  
Prediction Models ◽  
Breakthrough Curves ◽  
Retardation Factor ◽  
Determination Method ◽  
Transport Parameters ◽  
Undisturbed Soil ◽  
Analytical Analysis ◽  
Initial Concentration ◽  
Preferential Pathways ◽  
The Impact

The retardation factor (Rd) is one of the main important solute transport parameters. Its value can vary significantly depending on the method used for its determination. In this paper, the sodium Rd is experimentally determined using undisturbed sandy columns to compare four methods of Rd determination and assess the impact of the chosen method in the prediction of sodium movement. Column experiments in undisturbed soil columns and analytical analysis were performed. The results showed that the soil has dual-porosity and preferential pathways. The breakthrough curves were in accordance with the soil’s physical characteristics. The Rd values ranged from 1.7 to 7.77 depending on the initial concentration and on the method used. These differences arise from the conceptual model of each Rd determination method. The experimental and analytical analysis indicated that the higher the Rd, the slower the movement. The methods that best reproduced the laboratory sodium movement were Ogata and Banks’ (1961), and Langmuir and Freundlich’s isotherms. The prediction models presented smaller errors with the increase of the initial concentration. In these cases, the predicted concentrations can be overestimated up to 22.5 % when using a not suitable method. Hence these results suggest that the Rd determination method can strongly affect the prediction of the sodium movement. Because of that, it is of vital importance to evaluate each method and how they can be adequate to the soil under investigation when determining Rd.

scholarly journals From “Black Box” to a Real Description of Overall Mass Transport through Membrane and Boundary Layers

Membranes ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 18
Author(s):  
Endre Nagy ◽  
Márta Vitai
Keyword(s):  
Mass Transport ◽  
Peclet Number ◽  
Porous Membrane ◽  
Black Box ◽  
Box Model ◽  
Transmembrane Pressure ◽  
Transport Parameters ◽  
Characteristic Parameters ◽  
Péclet Number ◽  
Dense Membrane

The “black box” model defines the enhancement, the polarization modulus, and the intrinsic enhancement, without knowing the transport mechanism in the membrane. This study expresses the above-mentioned characteristic parameters, simultaneously taking into account the mass transport expressions developed for both the polarization and the membrane layers. Two membrane models are studied here, namely a solution-diffusion model characterizing solute transport through a dense membrane and a solution-diffusion plus convection model characterizing transport through a porous membrane due to transmembrane pressure difference. It is shown that the characteristic parameters of the “black box” model (E, or ) can be expressed as a function of the transport parameters and independently from each other using two-layer models. Thus, membrane performance could be predicted by means of the transport parameters. Several figures show how enhancement and the polarization modulus varied as a function of the membrane Peclet number and the solubility coefficient. Enhancement strongly increased up to its maximum value when H > 1, in the case of transport through a porous membrane, whereas its change remained before unity in the case of a dense membrane. When the value of H < 1, the value of E gradually decreased with increasing values of the membrane Peclet number.

Analysis of partial breakthrough data by a transfer-function method

Soil Research ◽  
2006 ◽  
Vol 44 (2) ◽  
pp. 175 ◽  
Author(s):  
M. A. Mojid ◽  
D. A. Rose ◽  
G. C. L. Wyseure
Keyword(s):  
Transfer Function ◽  
Solute Transport ◽  
Calcium Chloride ◽  
Unsaturated Soils ◽  
Function Method ◽  
Sandy Loam ◽  
Breakthrough Curves ◽  
Time Domain Reflectometry ◽  
Transport Parameters ◽  
Transfer Function Method

A transfer-function method has been applied to determine solute-transport parameters from earlier sections of complete breakthrough data. Time-domain reflectometry allows the measurement of breakthrough data in unsaturated soil. In fine-textured soils, the flow of water must be kept low to maintain unsaturated conditions, and so experiments for a complete breakthrough of solute may last a very long time. Substantial savings of time and computer memory might be achieved if data could be analysed from an earlier section of breakthrough data. Data at 2 vertical positions (input at upper and response at lower position) from a complete breakthrough of calcium chloride applied as a pulse input to 4 unsaturated soils (coarse sand, sandy loam, clay loam, clay) were divided into 4 sets of increasing duration. Transport parameters of calcium chloride were determined by a transfer function, which results in similar values of the parameters from the last 3 datasets in all 4 soils. In the clay soil, however, because of erroneous breakthrough data the fit between the measured and estimated breakthrough curves (BTCs) was poor, but the transport parameters were consistent among different segments of data. We show that it is possible to determine successfully solute-transport parameters from partial breakthrough data, which include the peak of the response BTC. This transfer-function method is thus a powerful tool to shorten breakthrough experiments.

Shear Dispersion in a Rough-Walled Fracture

SPE Journal ◽  
2018 ◽  
Vol 23 (05) ◽  
pp. 1669-1688 ◽  
Author(s):  
Morteza Dejam ◽  
Hassan Hassanzadeh ◽  
Zhangxin Chen
Keyword(s):  
Peclet Number ◽  
Dispersion Coefficient ◽  
Coupled System ◽  
Fracture Aperture ◽  
Maximum Height ◽  
Fracture Roughness ◽  
Péclet Number ◽  
Relative Roughness ◽  
Shear Dispersion ◽  
Porous Walls

Summary An expression is analytically presented for the shear dispersion, or Taylor (1953) and Aris (1956) dispersion, of a solute transporting in a coupled system, which consists of a matrix and a rough-walled fracture. To derive a shear-dispersion coefficient in a fracture with rough and porous walls, the continuities of solute concentrations and their fluxes are imposed at the fracture walls. The dispersion coefficient for the coupled system is obtained as a function of the Péclet number and relative roughness, where the latter parameter is defined as the ratio of the maximum height of the roughness to the minimum half-aperture of the fracture. Several models for fracture-roughness geometry, including periodically and randomly shaped roughness models, are applied to study the effect of fracture-aperture variation on dispersion. The dispersion coefficient for all rough-walled fractures identifies three different regions in terms of the degree of relative roughness. The results show that for small values of the relative roughness (0&lt;ε≤0.1), the dispersion coefficient is at maximum for bell-shaped geometry and at minimum for triangular-shaped and randomly shaped geometries. When the relative roughness is within 0.1&lt;ε&lt;10, the dispersion is observed to be at maximum for rectangular-walled and at minimum for triangular-walled fractures. The results also reveal that for high values of the relative roughness (ε≥10), the dispersion is higher for bell-shaped roughness, whereas the triangular-walled fracture results in the lowest dispersion. It is found that for all roughness geometries an increase in either the Péclet number or relative roughness leads to an increase in the dispersion.

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