scholarly journals Assessment of The Dioxins Leaching Potentials In Selected Soils Through Breakthrough Curves (BTCs) Model

2021 ◽  
Author(s):  
Nida Gul ◽  
Bushra Khan ◽  
Ishaq Ahmad Mian Kakakhel ◽  
Syed Muhammad Mukarram Shah ◽  
Muhammad Saeed ◽  
...  
Keyword(s):  
Distribution Coefficient ◽  
Solute Transport ◽  
Groundwater Contamination ◽  
Breakthrough Curve ◽  
Breakthrough Curves ◽  
Retardation Factor ◽  
Normal Velocity ◽  
Soil Series ◽  
Seepage Velocity ◽  
Local Soil

Abstract The current study was to investigate the leaching and groundwater contamination potential of selected Dioxins, in local soil series. Solute transport was modelled through Breakthrough curve (BTC) plots, based on distribution coefficient (Kd), Retardation factor and Dispersivity, under normal velocity (20 cm day -1) and preferential or steady flow (50 cm day -1). In case of Dibenzo -p- Dioxin (DD), distribution coefficient values were found in order of Charsadda > Peshawar > Sultanpur series, while for 2 Chloro- p- Dioxin (2Cl-DD), the order was Charsadda > Sultanpur > Peshawar. However, the overall sorption was low. Under the normal velocity both of selected Dioxins (DD & 2Cl-DD), BTC plots relatively took longer time to reach the point of saturation as compared to high seepage velocity. However, the overall solute transport was found to be rapid. This behaviour showed that sorption of the Dioxins selected soil series is low and there is potential for leaching and groundwater contamination.

Comparative analyses of alternative breakthrough curves from cumulative mass column testing of soil–bentonite backfills

2020 ◽  
Vol 57 (8) ◽  
pp. 1197-1214 ◽  
Author(s):  
Charles D. Shackelford ◽  
Catherine S. Hong
Keyword(s):  
Steady State ◽  
Solute Transport ◽  
Breakthrough Curves ◽  
Retardation Factor ◽  
Dimensionless Time ◽  
Mass Ratio ◽  
Column Tests ◽  
Cutoff Walls ◽  
Cumulative Mass ◽  
Linear Regressions

The results of eight cumulative mass column tests were analyzed via several different methods to evaluate the dispersion coefficient, D, and the retardation factor, Rd, governing the migration of chloride (Cl−), potassium (K), and zinc (Zn) through soil–bentonite backfills for vertical cutoff walls. Regression of the measured relative (effluent) concentration (RC) breakthrough curves (BTCs) resulted in relatively accurate determinations of Rd, but relatively inaccurate determinations of D for all three solutes. Values of Rd based on dimensionless time, T, corresponding to an RC of 0.5 were underestimated for all three solutes due to the significance of diffusion on solute transport. With a few exceptions, Rd for K and Zn based on analyses of the steady-state portions of measured cumulative mass ratio (CMR) BTCs and T – CMR BTCs were relatively accurate, whereas analysis of measured T – CMR BTCs was more accurate for determining Rd of Cl−. Overall, there is no advantage to analyzing the results of cumulative mass column tests in the form of RC BTCs, whereas the CMR and T – CMR BTCs offer the advantage of determining Rd based on simple linear regressions of the steady-state portions of the BTCs, i.e., provided steady-state solute transport has been established.

scholarly journals Conjunctive Use of BTC and Batch Methods for Heavy Metal Transport

2020 ◽  
Author(s):  
Mohamed Fahmy Hussein ◽  
Hassan Khater
Keyword(s):  
Heavy Metal ◽  
Distribution Coefficient ◽  
Sandy Loam ◽  
Mathematical Formulation ◽  
Breakthrough Curves ◽  
Retardation Factor ◽  
Model Parameters ◽  
Dilute Solution ◽  
High Concentration ◽  
Theoretical Concepts

Abstract Marginal sediments can be used to combat punctual pollution by heavy metals in industrial zones. Such practice requires information on metal-concentration in the workshop discharge water. Knowledge about the reaction of the heavy metal with the sediment available in the landscape is of utmost importance. Modeling of batch experiments and breakthrough curves, BTC, supplies relevant information in this regard. We modeled the static batch-data by Freundlich isotherms for testing CdCl2 aqueous solutions equilibria with sandy loam sediment and the dynamic column-data by two codes, CfitM and CfitIM, under saturated water flow conditions. Three Cd-concentrations (5, 20, and 40 ppm) were employed to investigate the conjunction of using two procedures for obtaining the pertinent parameters for the transport of such a heavy metal and the design of the adequate Cd-trap. The results showed the deviations of the two techniques due to differences in their theoretical concepts, mathematical formulation, and performance. The batch method showed utility in supplying first guesses for the retardation factor, R, to insert into the 4-parameter analytical code, CfitIM, applied for column BTC modeling. The iteratively-obtained-parameters of the Freundlich equation were then employed to generate the distribution coefficient, k d. The generated value was, in turn, used to get more fair guess for the retardation factor, R, to use as a fixed-value in the CfitIM code to get an in-depth insight into the BTC dynamics and to obtain the other pertinent model parameters. The BTC runs indicated that the concentration controls the distinctive adsorption and transport rate and behavior of the heavy metal in the sediment column. The most dilute solution offered the highest Cd impediment, as shown by the most significant values for the distribution coefficient, k d, and retardation factor, R. The malfunction of the sediment as a trap appeared at Cd-concentrations four to eight folds higher than the most dilute solution. However, the loamy sand trap is successful when fed with a dilute aqueous solution. A set of successive traps is to arrange in tandem lines when moderate to high concentration is to discharge from an industrial workshop. The results emphasize the utility of the mutual use of these two lab procedures for the design of adequate traps and landfills and the simulation of more complex situations in the field. The point-pollution control needs to continue running batch and BTC experiments and to carry out their corresponding modeling.

scholarly journals Conjunctive Use of BTC and Batch Methods for Heavy Metal Transport

2020 ◽  
Author(s):  
Mohamed Fahmy Hussein ◽  
Hassan Khater
Keyword(s):  
Heavy Metal ◽  
Distribution Coefficient ◽  
Sandy Loam ◽  
Mathematical Formulation ◽  
Breakthrough Curves ◽  
Retardation Factor ◽  
Model Parameters ◽  
Dilute Solution ◽  
High Concentration ◽  
Point Pollution

Abstract Marginal sediments can be used to combat point-pollution by heavy metals in industrial zones. Such practice requires information on metal-concentration in the workshop discharge water. Knowledge about the reaction of the heavy metal with the sediment available in the landscape is of utmost importance. Modeling of batch experiments and breakthrough curves, BTC, supplies relevant information in this regard. We present the static batch results of Freundlich isotherms testing CdCl2 aqueous solutions equilibria with sandy loam sediments, along with column-data processed by the dynamic codes CfitM and CfitIM under saturated water flow conditions. Three Cd-concentrations (5, 20, and 40 ppm) were employed to investigate the conjunction of using two procedures for obtaining the pertinent parameters for the transport of such a heavy metal and the design of the adequate Cd-trap. The results showed the deviations of the two techniques due to differences in their theoretical concepts, mathematical formulation, and performance. The batch method showed utility in supplying first guesses for the retardation factor, R, to insert into the 4-parameter analytical code, CfitIM, applied for column BTC modeling. The iteratively-obtained-parameters of the Freundlich equation were then employed to generate the distribution coefficient, k d. The generated value was, in turn, used to get more fair guess for the retardation factor, R, to use as a fixed-value in the CfitIM code to get an in-depth insight into the BTC dynamics and to obtain the other pertinent model parameters. The BTC runs indicated that the concentration controls the distinctive adsorption and transport rate and behavior of the heavy metal in the sediment column. The most dilute solution offered the highest Cd impediment, as shown by the most significant values for the distribution coefficient, k d, and retardation factor, R. The malfunction of the sediment as a trap appeared at Cd-concentrations four to eight folds higher than the most dilute solution. However, the loamy sand trap is successful when fed with a dilute aqueous solution. A set of successive traps is to arrange in tandem lines when moderate to high concentration is to discharge from an industrial workshop. The results emphasize the utility of the mutual use of these two lab procedures for the design of adequate traps and landfills and the simulation of more complex situations in the field. The point-pollution control needs to continue running batch and BTC experiments and to carry out their corresponding modeling.

scholarly journals Conjunctive Use of BTC and Batch Methods for Heavy Metal Transport

2020 ◽  
Author(s):  
Mohamed Fahmy Hussein ◽  
Hassan Khater
Keyword(s):  
Heavy Metal ◽  
Distribution Coefficient ◽  
Sandy Loam ◽  
Mathematical Formulation ◽  
Breakthrough Curves ◽  
Retardation Factor ◽  
Model Parameters ◽  
Dilute Solution ◽  
High Concentration ◽  
Point Pollution

Abstract Marginal sediments can be used to combat point-pollution by heavy metals in industrial zones. Such practice requires information on metal-concentration in the workshop discharge water. Knowledge about the reaction of the heavy metal with the sediment available in the landscape is of utmost importance. Modeling of batch experiments and breakthrough curves, BTC, supplies relevant information in this regard. We present the static batch results of Freundlich isotherms testing CdCl2 aqueous solutions equilibria with sandy loam sediments, along with column-data processed by the dynamic codes CfitM and CfitIM under saturated water flow conditions. Three Cd-concentrations (5, 20, and 40 ppm) were employed to investigate the conjunction of using two procedures for obtaining the pertinent parameters for the transport of such a heavy metal and the design of the adequate Cd-trap. The results showed the deviations of the two techniques due to differences in their theoretical concepts, mathematical formulation, and performance. The batch method showed utility in supplying first guesses for the retardation factor, R, to insert into the 4-parameter analytical code, CfitIM, applied for column BTC modeling. The iteratively-obtained-parameters of the Freundlich equation were then employed to generate the distribution coefficient, k d. The generated value was, in turn, used to get more fair guess for the retardation factor, R, to use as a fixed-value in the CfitIM code to get an in-depth insight into the BTC dynamics and to obtain the other pertinent model parameters. The BTC runs indicated that the concentration controls the distinctive adsorption and transport rate and behavior of the heavy metal in the sediment column. The most dilute solution offered the highest Cd impediment, as shown by the most significant values for the distribution coefficient, k d, and retardation factor, R. The malfunction of the sediment as a trap appeared at Cd-concentrations four to eight folds higher than the most dilute solution. However, the loamy sand trap is successful when fed with a dilute aqueous solution. A set of successive traps is to arrange in tandem lines when moderate to high concentration is to discharge from an industrial workshop. The results emphasize the utility of the mutual use of these two lab procedures for the design of adequate traps and landfills and the simulation of more complex situations in the field. The point-pollution control needs to continue running batch and BTC experiments and to carry out their corresponding modeling.

A convective-dispersive-adsorptive flow model for solute transport in soils. I. Model description and some simulations

Soil Research ◽  
1981 ◽  
Vol 19 (1) ◽  
pp. 23 ◽  
Author(s):  
V Murali ◽  
LAG Aylmore
Keyword(s):  
Solute Transport ◽  
Computer Simulations ◽  
Numerical Solutions ◽  
Breakthrough Curves ◽  
Retardation Factor ◽  
Intermittent Flow ◽  
Simultaneous Occurrence ◽  
Model Description ◽  
Phase Concentration ◽  
Adsorption Desorption

Solute transport predictions are usually based on mathematical (analytical and numerical) solutions of partial differential equations describing convective-dispersive-adsorptive flow and ion-soil interactions. In this paper computer simulations based on a numerical model of solute transport in soil columns have been used to illustrate the significance of flow dynamics and adsorption-desorption parameters in determining the shape and position of solute breakthrough curves. Approximating non-linear isotherms of the form S = KCM, where S is adsorption phase concentration, Cis solution phase concentration, and K and M are constants, by linear isotherms of the form S = KC + � where E is the intercept, to facilitate the use of analytical solutions. has been shown to result in significant errors when the retardation factor fails to account for the intercept � (when � is zero, the retardation factor equals 1 + �K/�, where � is the bulk density and � is water content). Using the dynamic form of Freundlich adsorption, the importance of non-linearity in the equilibrium isotherms is demonstrated. Computer simulations have also been used to demonstrate the extreme importance of intermittent flow, the simultaneous occurrence of adsorption dynamics, ionic fixation and hysteresis during instantaneous adsorption and desorption in determining the transport of solutes in soils.

Parameter Determination for Chloride and Tritium Transport in Undisturbed Lysimeters during Steady Flow

1992 ◽  
Vol 23 (2) ◽  
pp. 89-104 ◽  
Author(s):  
Ole H. Jacobsen ◽  
Feike J. Leij ◽  
Martinus Th. van Genuchten
Keyword(s):  
Experimental Data ◽  
Unsaturated Flow ◽  
Transport Model ◽  
Time Moment ◽  
Breakthrough Curves ◽  
Coarse Sand ◽  
Retardation Factor ◽  
Parameter Determination ◽  
Model Parameters ◽  
Water Fraction

Breakthrough curves of Cl and 3H2O were obtained during steady unsaturated flow in five lysimeters containing an undisturbed coarse sand (Orthic Haplohumod). The experimental data were analyzed in terms of the classical two-parameter convection-dispersion equation and a four-parameter two-region type physical nonequilibrium solute transport model. Model parameters were obtained by both curve fitting and time moment analysis. The four-parameter model provided a much better fit to the data for three soil columns, but performed only slightly better for the two remaining columns. The retardation factor for Cl was about 10 % less than for 3H2O, indicating some anion exclusion. For the four-parameter model the average immobile water fraction was 0.14 and the Peclet numbers of the mobile region varied between 50 and 200. Time moments analysis proved to be a useful tool for quantifying the break through curve (BTC) although the moments were found to be sensitive to experimental scattering in the measured data at larger times. Also, fitted parameters described the experimental data better than moment generated parameter values.

Transport of Microorganisms in the Underground – Processes, Experiments and Simulation Models

1991 ◽  
Vol 24 (2) ◽  
pp. 309-314 ◽  
Author(s):  
G. Teutsch ◽  
K. Herbold-Paschke ◽  
D. Tougianidou ◽  
T. Hahn ◽  
K. Botzenhart
Keyword(s):  
Simulation Models ◽  
Mass Conservation ◽  
Breakthrough Curves ◽  
Conservation Equation ◽  
Retardation Factor ◽  
Natural Systems ◽  
Laboratory Setup ◽  
Preliminary Model ◽  
Sand And Gravel ◽  
Mass Conservation Equation

In this paper the major processes governing the persistence and underground transport of viruses and bacteria are reviewed in respect to their importance under naturally occurring conditions. In general, the simulation of the governing processes is based on the macroscopic mass-conservation equation with the addition of some filter and/or retardation factor and a decay coefficient, representing the natural “die-off” of the microorganisms. More advanced concepts try to incorporate growth and decay coefficients together with deposition and declogging factors. At present, none of the reported concepts has been seriously validated. Due to the complexity of natural systems and the pathogenic properties of some of the microorganisms, experiments under controlled laboratory conditions are required. A laboratory setup is presented in which a great variety of natural conditions can be simulated. This comprises a set of 1 metre columns and an 8 metre stainless-steel flume with 24 sampling ports. The columns are easily filled and conditioned and therefore used to study the effects of different soil-microorganism combinations under various environmental conditions. In the artificial flume natural underground conditions are simulated using sand and gravel aquifer material from the river Neckar alluvium. A first set of results from the laboratory experiments is presented together with preliminary model simulations. The large variety of observed breakthrough curves and recovery for the bacteria and viruses under investigation demonstrates the great uncertainty encountered in microbiological risk assessment.

A numerical study of the wave-induced solute transport above a rippled bed

1995 ◽  
Vol 299 ◽  
pp. 267-288 ◽  
Author(s):  
K. T. Shum
Keyword(s):  
Flow Field ◽  
Solute Transport ◽  
Concentration Profile ◽  
Vortical Flow ◽  
Sediment Surface ◽  
Normal Velocity ◽  
Advective Transport ◽  
Fluid Particles ◽  
Wave Induced ◽  
Rippled Bed

The role of wave-induced separated flow in solute transport above a rippled bed is studied from numerical solutions to the two-dimensional Navier–Strokes equations and the advection-diffusion equation. A horizontal ambient flow that varies sinusoidally in time is imposed far above the bed, and a constant concentration difference between the upper and lower boundaries of computation is assumed. The computed flow field is the sum of an oscillatory rectilinear flow and a vortical flow which is periodic both in time and in the horizontal. Poincaré sections of this flow suggest chaotic mixing. Vertical lines of fluid particles above the crest and above the trough deform into whorls and tendrils, respectively, in just one wave period. Horizontal lines near the bottom deform into Smale horseshoe patterns. The combination of high shear and vortex-induced normal velocity close to the sediment surface results in large net displacements of fluid particles in a period. The resulting advective transport normal to the bed can be higher than molecular diffusion from well within the viscous boundary layer up to a few ripple heights above the bed. When this flow field is applied to the transport equation of a passive scalar, two distinct features – regular temporal oscillations in concentration and a linear time-averaged vertical concentration profile – are found immediately above the bed. These features have also been observed previously in field measurements on oxygen concentration. Advective transport is shown to be dominant even in the region where the time-averaged concentration profile is linear, a region where vertical solute transport has often been estimated using diffusion-type models in many field studies.

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.

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