Transport of arsenic in some affected soils of Indian subtropics

Soil Research ◽  
2014 ◽  
Vol 52 (8) ◽  
pp. 822 ◽  
Author(s):  
Indranil Das ◽  
Koushik Ghosh ◽  
D. K. Das ◽  
S. K. Sanyal
Keyword(s):  
Relative Concentration ◽  
Clay Content ◽  
Breakthrough Curves ◽  
Hydrodynamic Dispersion ◽  
Aluminium Content ◽  
Vertical Column ◽  
Retention Capacity ◽  
Column Study ◽  
Solute Permeability ◽  
Frictional Coefficients

An experiment on transport of aqueous arsenic (As) from both affected and unaffected soils of West Bengal, India, was conducted with the help of double-chambered columns in the laboratory. In the vertical column study, the sigmoid shape of breakthrough curves (BTCs) suggests hydrodynamic dispersion, whereas the inflexion of BTCs at a much lesser relative concentration indicates retention of As in the affected soils. In the horizontal column study, the affected soils showed lower mechanical filtration capacity and solute permeability and higher reflection coefficient, indicating greater As retention in these soils. The frictional coefficients for soil-water solute derived from the horizontal flow also indicate As retention by the affected soils. The As retention capacity of these soils was attributed to the greater clay content, illitic minerals, organic matter, specific surface area, and amorphous iron and aluminium content.

scholarly journals Imazapic interaction and mobility in soil cultivated with sugarcane in northeast Brazil

RBRH ◽  
2021 ◽  
Vol 26 ◽  
Author(s):  
Fernando Xavier de Assis ◽  
André Maciel Netto ◽  
Bruno Toríbio de Lima Xavier ◽  
Valmir Felix de Lima ◽  
João Paulo Siqueira da Silva
Keyword(s):  
Partition Coefficients ◽  
Biological Effects ◽  
Clay Content ◽  
Breakthrough Curves ◽  
Northeastern Brazil ◽  
Adsorption Potential ◽  
Soil Columns ◽  
Leaching Potential ◽  
Physical Chemical ◽  
Sorption Leaching

ABSTRACT In the plantation of sugarcane, Imazapic has used pre- or post-emergence, alone or in combination with other herbicides. When applied to the soil in pre-emergence, Imazapic can undergo the sorption, leaching and/or degradation processes due to physical, chemical and biological effects, besides being absorbed by weeds. The objective of this work was to evaluate the interaction and mobility of the Imazapic herbicide in the soil where the soil columns with a dystrophic Yellow Ultisol (YUd) and a dystrophic Red-Yellow Oxisol (RYOd) from northeastern Brazil were used. The higher adsorption potential of the RYOd is associated with higher clay content, higher Fed and Feo concentrations, and soil acidic pH. The CDE – 2 sorption sites model adequately represented the experimental data from the Imazapic breakthrough curves to the RYOd and YUd soils. From the Kd partition coefficients for RYOd and YUd, high values of the GUS index (5.94 and 7.04, respectively) were calculated, confirming the high leaching potential of the Imazapic molecule in these soils.

Pore-scale Mixing and the Evolution from Anomalous to Normal Hydrodynamic Dispersion

2021 ◽  
Author(s):  
Marco Dentz ◽  
Alexandre Puyguiraud ◽  
Philippe Gouze
Keyword(s):  
Porous Media ◽  
Large Scale ◽  
Molecular Diffusion ◽  
Pore Space ◽  
Breakthrough Curves ◽  
Heterogeneous Porous Media ◽  
Hydrodynamic Dispersion ◽  
Pore Scale ◽  
Sandstone Sample ◽  
Flow Variability

<p>Transport of dissolved substances through porous media is determined by the complexity of the pore space and diffusive mass transfer within and between pores. The interplay of diffusive pore-scale mixing and spatial flow variability are key for the understanding of transport and reaction phenomena in porous media. We study the interplay of pore-scale mixing and network-scale advection through heterogeneous porous media, and its role for the evolution and asymptotic behavior of hydrodynamic dispersion. In a Lagrangian framework, we identify three fundamental mechanisms of pore-scale mixing that determine large scale particle motion: (i) The smoothing of intra-pore velocity contrasts, (ii) the increase of the tortuosity of particle paths, and (iii) the setting of a maximum time for particle transitions. Based on these mechanisms, we derive an upscaled approach that predicts anomalous and normal hydrodynamic dispersion based on the characteristic pore length, Eulerian velocity distribution and Péclet number. The theoretical developments are supported and validated by direct numerical flow and transport simulations in a three-dimensional digitized Berea sandstone sample obtained using X-Ray microtomography. Solute breakthrough curves, are characterized by an intermediate power-law behavior and exponential cut-off, which reflect pore-scale velocity variability and intra-pore solute mixing. Similarly, dispersion evolves from molecular diffusion at early times to asymptotic hydrodynamics dispersion via an intermediate superdiffusive regime. The theory captures the full evolution form anomalous to normal transport behavior at different Péclet numbers as well as the Péclet-dependence of asymptotic dispersion. It sheds light on hydrodynamic dispersion behaviors as a consequence of the interaction between pore-scale mixing and Eulerian flow variability. </p>

scholarly journals Effect of Flow Rate and Particle Concentration on the Transport and Deposition of Bare and Stabilized Zero-Valent Iron Nanoparticles in Sandy Soil

2019 ◽  
Vol 11 (23) ◽  
pp. 6608
Author(s):  
Ibrahim ◽  
Awad ◽  
Al-Farraj ◽  
Al-Turki
Keyword(s):  
Flow Rate ◽  
Sandy Soil ◽  
Particle Deposition ◽  
Particle Concentration ◽  
Soil Column ◽  
Relative Concentration ◽  
Methyl Cellulose ◽  
Maximum Flow ◽  
Breakthrough Curves ◽  
Zero Valent Iron

Efficient application of nanoscale zero-valent iron (nZVI) particles in remediation processes relies heavily on the ability to modify the surfaces of nZVI particles to enhance their stability and mobility in subsurface layers. We investigated the effect of sodium carboxy-methyl-cellulose (CMC) polymer stabilizer, pH, particle concentration, and flow rate on the transport of nZVI particles in sand columns. Breakthrough curves (BTCs) of nZVI particles indicated that the transport of nZVI particles was increased by the presence of CMC and by increasing the flow rate. The relative concentration (RC) of the eluted CMC–nZVI nanoparticles was larger at pH 9 as compared to RC at pH 7. This is mainly attributed to the increased nZVI particle stability at higher pH due to the increase in the electrostatic repulsion forces and the formation of larger energy barriers. nZVI particle deposition was larger at 0.1 cm min-1 flow due to the increased residence time, which increases the aggregation and settlement of particles. The amount of CMC–nZVI particles eluted from the sand columns was increased by 52% at the maximum flow rate of 1.0 cm min-1. Bare nZVI were mostly retained in the first millimeters of the soil column, and the amount eluted did not exceed 1.2% of the total amount added. Our results suggest that surface modification of nZVI particles was necessary to increase stability and enhance transport in sandy soil. Nevertheless, a proper flow rate, suitable for the intended remediation efforts, must be considered to minimize nZVI particle deposition and increase remediation efficiency.

scholarly journals Iron Oxide-Coated Gravel Fixed Bed Column Study Performance to Remove Mixed Metals from Landfill Leachate

2019 ◽  
Vol 122 ◽  
pp. 01002 ◽  
Author(s):  
Ibrahim Yildiz ◽  
Banu Sizirici
Keyword(s):  
Iron Oxide ◽  
Fixed Bed ◽  
Breakthrough Curves ◽  
Fixed Bed Column ◽  
Desorption Process ◽  
Column Study ◽  
Regeneration Capability ◽  
Synthetic Leachate ◽  
Adsorption Desorption ◽  
Study Performance

Iron oxide-coated gravel as an adsorbent was employed in continuous fixed bed column study to remove Fe(II), Ni(II), and Zn(II) simultaneously in synthetic leachate samples. Experimental and modeled adsorption capacities derived from the breakthrough curves showed the adsorption capacity order of Zn(II)>Fe(II)> Ni(II). Iron oxide-coated gravel column removed 58.24% of Zn(II), 47.71% of Fe(II), and 39.45% of Ni(II). Desorption process was studied in order to test the regeneration capability of iron oxidecoated gravel. It was seen that 99.64 % of Ni(II), 99.54% of Fe(II) and 6.75% of Zn (II) were recovered through the first cycle of adsorption/desorption. In the second cycle, the recovery rates dropped to 81.4% for Ni(II), 80% for Fe(II) and 4% for Zn(II). Based on these results, iron oxide coated gravel has potential to remove mixed metal ions simultaneously in aqueous solutions.

scholarly journals Hydrodynamic dispersion characteristics of lateral inflow into a river tested by a laboratory model

2009 ◽  
Vol 13 (2) ◽  
pp. 217-228 ◽  
Author(s):  
P. Y. Chou ◽  
G. Wyseure
Keyword(s):  
Pore Water ◽  
Transport Model ◽  
Column Experiment ◽  
Breakthrough Curves ◽  
Water Velocity ◽  
Laboratory Model ◽  
Hydrodynamic Dispersion ◽  
Transport Parameter ◽  
Transport Parameters ◽  
Pore Water Velocity

Abstract. Groundwater and river-water have a different composition and interact in and below the riverbed. The riverbed-aquifer flux interactions have received growing interest because of their role in the exchange and transformation of nutrients and pollutants between rivers and the aquifer. In this research our main purpose is to identify the physical processes and characteristics needed for a numerical transport model, which includes the unsaturated recharge zone, the aquifer and the riverbed. In order to investigate such lateral groundwater inflow process, a laboratory J-shaped column experiment was designed. This study determined the transport parameters of the J-shaped column by fitting an analytical solution of the convective-dispersion equation for every flux on individual segments to the observed breakthrough curves of the resident concentration, and by inverse modelling for every flux simultaneously over the entire flow domain. The obtained transport-parameter relation was tested by numerical simulation using HYDRUS 2-D/3-D. Four steady-state flux conditions (i.e. 0.5 cm hr−1, 1 cm hr−1, 1.5 cm hr−1 and 2 cm hr−1) were applied, transport parameters including pore water velocity and dispersivity were determined for both unsaturated and saturated sections along the column. Results showed that under saturated conditions the dispersivity was fairly constant and independent of the flux. In contrast, dispersivity under unsaturated conditions was flux dependent and increased at lower flux. For our porous medium the dispersion coefficient related best to the quotient of the pore water velocity divided by the water content. A simulation model of riverbed-aquifer flux interaction should take this into account.

Gravity segregation during miscible displacement—re-investigation and re-interpretation

Soil Research ◽  
2007 ◽  
Vol 45 (5) ◽  
pp. 319 ◽  
Author(s):  
D. A. Rose ◽  
F. Abbas
Keyword(s):  
Cross Sections ◽  
Formal Analysis ◽  
Safety Margin ◽  
Breakthrough Curves ◽  
Hydrodynamic Dispersion ◽  
Immiscible Liquids ◽  
Saline Groundwater ◽  
Gravity Segregation ◽  
Dimensional Gravity ◽  
Miscible Liquids

When the liquid residing in a horizontal bed of porous material is displaced by another liquid of different density, the resulting hydrodynamic dispersion is modified by the formation of a tongue of denser liquid undershooting the less dense liquid, a phenomenon known as gravity segregation. An earlier account of gravity segregation contained a substantial error (that of an incorrect frame of reference for flow) and several printing mistakes. In this paper we (i) correct these errors, (ii) extend the analysis to describe the course of breakthrough in beds of rectangular and circular cross-sections, (iii) re-interpret the existing experimental evidence, and (iv) present new experimental results on the vertical and horizontal transport of ionic solutions of different concentrations and densities through inert and reactive porous materials, ballotini, and sepiolite, respectively. The behaviour of immiscible liquids is predicted by the non-dimensional gravity segregation number, β, segregation becoming more extreme as β increases. With miscible liquids, however, breakthrough starts later and ends earlier then predicted for immiscible liquids, mixing by hydrodynamic dispersion moderating the effect of segregation. Breakthrough curves are well fitted by CXTFIT 2.0; apparent coefficients of hydrodynamic dispersion vary much less with pore-water velocity in horizontal than in vertical flow, but retardation factors are not influenced by orientation. Although a formal analysis of the combined effect of gravity segregation and hydrodynamic dispersion was not possible, the statistically significant inverse relation between β and column Peclet number was explained qualitatively. Gravity segregation occurs during the intrusion of saline groundwater into coastal aquifers. The simple theory for immiscible displacement overestimates the actual intrusion that occurs with miscible liquids and so provides an effective safety margin.

Limitations in the use of electrical conductivity to monitor the behaviour of soil solution

Soil Research ◽  
2006 ◽  
Vol 44 (7) ◽  
pp. 695 ◽  
Author(s):  
D. A. Rose ◽  
F. Abbas ◽  
M. A. Adey
Keyword(s):  
Electrical Conductivity ◽  
Solution Concentration ◽  
Solute Concentration ◽  
Breakthrough Curves ◽  
Time Domain Reflectometry ◽  
Solid Particles ◽  
Bulk Solution ◽  
Hydrodynamic Dispersion ◽  
Wide Range ◽  
The Individual

Solutions of KBr and K2SO4 of various concentrations were separately displaced by deionised water through 2 contrasting saturated materials, inert solid particles (glass ballotini), and a reactive but non-swelling aggregated clay mineral (sepiolite) over a wide range of flow rates. The concentration of the individual ions in the effluent was analysed (Br– and K+ with ion-specific electrodes, SO42+ by ion chromatography) and that of bulk solution was measured by electrical conductivity (EC). For each displacement, the individual breakthrough curves (BTCs) for the anion, the cation, and the bulk solution were optimised by CXTFIT 2.0. In ballotini, the BTCs of the anion, cation, and solution were always congruent, the retardation factors did not differ significantly from unity, and the coefficients of hydrodynamic dispersion were identical. For sepiolite, the ions were separated; the bulk solution eluted faster than the cation, slower than the anions. Retardation factors were always less than unity for the anions, greater than unity for the cation, and close to but less than unity for the bulk solution, and became more extreme as the concentration of solute decreased. Dispersion coefficients were, however, unaffected by type of solute, concentration range, or particular ion/EC. The separation of ions means that the composition as well as the concentration of a solution changes continuously during flow through a reactive soil. Estimates of solution concentration from measurements of EC may thus fail to characterise adequately the movement of the individual components of the solution in such materials. This has implications for the interpretation of any leachate monitoring in reactive soils by methods based on the measurement of EC, such as time-domain reflectometry.

scholarly journals Immobilization of Powdered Coal Fly Ashes (CFAs) into CFA Beads and Column Studies on Color Removal from Pulp Mill Effluents Using These CFA Beads

2020 ◽  
Author(s):  
Musfiques Salahin ◽  
George Yuzhu Fu
Keyword(s):  
Pulp Mill ◽  
Breakthrough Curves ◽  
Color Removal ◽  
Column Studies ◽  
Column Study ◽  
Wide Range ◽  
Coal Fly Ashes ◽  
Powdered Coal ◽  
Pulp Mill Effluents ◽  
Operational Time

In this study, immobilization process of the three (3) powder CFAs was studied. The major results on immobilization process were briefly presented. A total number of fifteen (15) column studies from the combination of the five (5) types of CFAs beads and the three (3) PMEs samples were performed. In each column study, a set of aggregate parameters of flow rate, empty bed contract time, operational time, and throughput volume was studied, and the data was fitted to existing modeling of breakthrough curves. The overall operational time was 12–24-hour, color removal efficiencies were 40–90%, and throughput volume of treated PMEs was 10–14 bed volume. For the column study, the correlation coefficient R2 value for each combination indicated that the Thomas model had a better fit with the observed data than the Adams-Bohart model, and the color adsorption capacities of CFA beads varied in a wide range of 0.31–28.23 mg/g.

scholarly journals SOLUTE TRANSPORT MODELLING IN LOW-PERMEABILITY HOMOGENEOUS AND SATURATED SOIL MEDIA

2021 ◽  
Vol 36 (2) ◽  
pp. 25-32
Author(s):  
Muhammad Zaheer ◽  
Hadayat Ullah ◽  
Saad Ahmed Mashwani ◽  
Ehsan ul Haq ◽  
Syed Husnain Ali Shah ◽  
...  
Keyword(s):  
Solute Transport ◽  
Preferential Flow ◽  
Relative Concentration ◽  
Breakthrough Curves ◽  
Saturated Soil ◽  
Low Permeability ◽  
Transport Modelling ◽  
Variation Of Parameters ◽  
Solute Transport Modeling ◽  
Soil Media

Fickian and non-Fickian behaviors were often detected for contaminant transport activity owed to the preferential flow and heterogeneity of soil media. Therefore, using diverse methods to measure such composite solute transport in soil media has become an important research topic for solute transport modeling in soil media. In this article, the continuous-time random walk (CTRW) model was applied to illustrate the relative concentration of transport in low-permeability homogeneous and saturated soil media. The solute transport development was also demonstrated with the convection-dispersion equation (CDE) and Two Region Model (TRM) for comparison. CXTFIT 2.1 software was used for CDE and TRM, and CTRW Matlab Toolbox v.3.1 for the CTRW simulation of the breakthrough curve. It was found that higher values of determination coefficient (R2) and lower values of root mean square error (RMSE) concerning the best fits of CDE, TRM, and CTRW. It was found that in the comparison of CDE, TRM, and CTRW, we tend to use CTRW to describe the transport behavior well because there are prevailing Fickian and non-Fickian transport. The CTRW gives better fitting results to the breakthrough curves (BTCs) when β has an increasing pattern towards 2.00. In this study, the variation of parameters in three methods was investigated and results showed that the CTRW modeling approach is more effective to determine non-reactive contaminants concentration in low-permeability soil media at small depths.

Kinetics of H2S Sorption on Manganese Oxide and Mn-Fe-Cu Mixed Oxide Prepared by the Complexation Technique

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Pinar Caglayan ◽  
Sena Yasyerli ◽  
Irfan Ar ◽  
Gulsen Dogu ◽  
Timur Dogu
Keyword(s):  
Manganese Oxide ◽  
Mixed Oxide ◽  
High Surface ◽  
High Surface Area ◽  
Fixed Bed ◽  
Breakthrough Curves ◽  
Hydrogen Gas ◽  
Fixed Bed Reactor ◽  
High Porosity ◽  
Retention Capacity

Hydrogen sulfide sorption activities of manganese oxide and Mn-Fe-Cu mixed oxide sorbents were examined in a fixed bed reactor. Sulfur retention capacity of Mn-O sorbent was found to be quite high at 600 °C both in the absence and presence of hydrogen gas (0.17 and 0.14 g S/g sorbent, respectively). This sorbent has a high porosity and a relatively high surface area. Best regeneration temperature of this sorbent was found as 700 °C, with a gas stream containing 6% oxygen in nitrogen. Mn-Fe-Cu mixed oxide sorbent had a lower sulfur retention capacity (0.07 g S/g sorbent). However, both of these sorbents gave quite high initial sorption rate constants, resulting very sharp breakthrough curves. Deactivation model was shown to give good agreement with the experimental H2S breakthrough curves.

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