Influence of Clay on Solute Transport in Saturated Homogeneous Mixed Media

In this study, four homogeneous porous media (HPM1-HPM4), consisting of distinct proportions of sand-sized and clay-sized solid beads, were prepared and used as single fracture infills. Flow and nonreactive solute transport experiments in HPM1-HPM4 under three flow rates were conducted, and the measured breakthrough curves (BTCs) were quantified using conventional advection-dispersion equation (ADE), mobile-immobile model (MIM), and continuous time random walk (CTRW) model with truncated power law transition time distribution. The measured BTCs showed stronger non-Fickian behaviour in HPM2-HPM4 (which had clay) than in HPM1 (which had no clay), implying that clay enhanced the non-Fickian transport. As the fraction of clay increased, the global error of ADE fits also increased, affirming the inefficiency of ADE in capturing the clay-induced non-Fickian behaviour. MIM and CTRW performed better in capturing the non-Fickian behaviour. Nonetheless, CTRW’s performance was robust. 12.5% and 25% of clay in HPM2 and HPM3, respectively, decreased the flowing fluid region and increased the solute exchange rate between the flowing and stagnant fluid regions in MIM. For CTRW, the power law exponent ( β CTRW ) values were 1.96, 1.75, and 1.63 in HPM1-HPM3, respectively, implying enhanced non-Fickian behaviour. However, for HPM4, whose clay fraction was 50%, the β CTRW value was 1.87, implying a deviation in the trend of non-Fickian enhancement with increasing clay fraction. This deviation indicated that non-Fickian behaviour enhancement depended on the fraction of clay present. Moreover, increasing flow rate enhanced the non-Fickian transport based on β CTRW .

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Multiscale Roughness Influence on Conservative Solute Transport in Self-affine Fractures

10.5194/hess-2018-203 ◽

2018 ◽

Author(s):

Zhi Dou ◽

Brent Sleep ◽

Hongbin Zhan ◽

Zhifang Zhou ◽

Jinguo Wang

Keyword(s):

Numerical Simulations ◽

Solute Transport ◽

Large Scale ◽

Breakthrough Curves ◽

Nonlinear Flow ◽

Small Scale ◽

Single Fracture ◽

Advection Dispersion ◽

Flow Features ◽

Conservative Solute Transport

Abstract. In this article, the influence of multiscale roughness on transport of a conservative solute through a self-affine fracture was investigated. The fracture roughness was decomposed into two different scales (i.e., a small-scale stationary secondary roughness superimposed on a large-scale non-stationary primary roughness) by a wavelet analysis technique. The fluid flow in the single fracture was characterized by Forchheimer's law and exhibited nonlinear flow features such as eddies and tortuous streamlines. The results indicated that the small-scale secondary roughness was primarily responsible for the nonlinear flow features. Numerical simulations of asymptotic conservative solute transport showed non-Fickian transport characteristics (i.e., early arrivals and long tails) in breakthrough curves (BTCs) and in residence time distributions (RTDs) with and without consideration of the secondary roughness. Analysis of multiscale BTCs and RTDs showed that the small-scale secondary roughness played a significant role in enhancing the non-Fickian transport characteristics. Removing small-scale secondary roughness delayed the arrival time and shortened the tail. The peak concentrations in BTCs decreased as the secondary roughness was removed, implying that the secondary roughness could also enhance the solute dilution. Fitting the one-dimensional (1D) Fickian advection-dispersion equation (ADE) to the numerical BTCs resulted in considerable errors that decreased with the small-scale secondary roughness being removed. The 1D mobile-immobile model (MIM) provided a better fit to the numerical BTCs and inclusion of the small-scale secondary roughness in numerical simulations resulted in a decreasing MIM mobile domain fraction and an increasing mass exchange rate between immobile and mobile domains.

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Non-Fickian Solute Transport in a Single Fracture of Marble Parallel Plate

Geofluids ◽

10.1155/2018/7418140 ◽

2018 ◽

Vol 2018 ◽

pp. 1-9 ◽

Cited By ~ 2

Author(s):

Xiaosan Yan ◽

Jiazhong Qian ◽

Lei Ma ◽

Mu Wang ◽

Aofeng Hu

Keyword(s):

Electrical Conductivity ◽

Solute Transport ◽

Breakthrough Curves ◽

Transport Processes ◽

Single Fracture ◽

Experimental Conditions ◽

Monitoring Method ◽

Subsurface Hydrology ◽

Advection Dispersion ◽

The Right

Accurate prediction of solute transport processes in a fracture aquifer is an important task not only for proper management of the groundwater but also for pollution control. A key issue of this task is how to accurately obtain the experimental data and to analyze the solute transport in fracture in subsurface hydrology, which would greatly help us to understand the releasing mechanism and transport of the solute in a fracture. In this study, a fracture experiment is conducted in a laboratory based on previous studies. The fracture used with a length of 60 cm and a width of 10 cm is sealed with glass glue to avoid leakage of tracer due to uneven fracture walls. The sodium chloride (NaCl) solute is injected from the left of the fracture. And an electrical conductivity monitoring system is installed on the right of the fracture. Then breakthrough curves (BTCs) of solute transport are fitted using the classical advection-dispersion equation (ADE) and the truncation power-law function (TPL) model in the package of the continuous time random walk (CTRW). The results show that the flow satisfies non-Darcian law in the experimental conditions, which can be better fitted using the Forchheimer equation and Izbash equation. The solute transport presents non-Fickian phenomena and shows a long tailing. The fitting results of the TPL model are far better than ADE in fitting the long tailing at three different flow velocities. Furthermore, electrical conductivity monitoring method not only is effective but also has an advantage of no disturbance to water and concentration fields in a fracture.

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Experimental Study and Models Comparison for Solute Transport through Riparian Zones

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1073-1076.1604 ◽

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.

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

Lithosphere ◽

10.2113/2021/7998907 ◽

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.

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Identification and Estimation of Solute Storage and Release in Karst Water Systems, South China

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17197219 ◽

2020 ◽

Vol 17 (19) ◽

pp. 7219

Author(s):

Liang Zhang ◽

Mingming Luo ◽

Zhihua Chen

Keyword(s):

Solute Transport ◽

Water Level ◽

Groundwater Remediation ◽

Tracer Tests ◽

Water Systems ◽

Breakthrough Curves ◽

Karst Water ◽

Transport Pathways ◽

Advection Dispersion ◽

Storage Rate

Solute storage and release in groundwater are key processes in solute transport for groundwater remediation and protection. In karst areas where concentrated recharge conditions exist, pollution incidents can easily occur in springs that are hydraulically connected to densely inhabited karst depressions. The intrinsic heterogeneity common in karst media makes modeling solute transport very difficult with great uncertainty. Meanwhile, it is noteworthy that solute storage and release within subsurface conduits and fissures exhibit strong controlling function on pollutant attenuation during underground floods. Consequently, in this paper, we identified and estimated the solute storage and release processes in karst water systems under concentrated recharge conditions. The methodology uses the advection–dispersion method and field tracer tests to characterize solute transport in different flow paths. Two solute transport pathways were established (i.e., linear pathway (direct transport through karst conduits) and dynamic pathway (flow through fissures)). Advection–dispersion equations were used to fit the breakthrough curves in conduit flow, while the volume of solute storage in fissures were calculated by segmenting the best fitting curves from the total breakthrough curves. The results show that, greater recharge flow or stronger dynamic conditions leads to lower solute storage rate, with the storage rate values less than 10% at high water level conditions. In addition, longer residence time was recorded for solute exchange between conduits and fissures at the low water level condition, thereby contributing to a higher solute storage rate of 26% in the dynamic pathway.

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Modelling solute transport in homogeneous and heterogeneous porous media using spatial fractional advection-dispersion equation

Soil and Water Research ◽

10.17221/245/2016-swr ◽

2018 ◽

Vol 13 (No. 1) ◽

pp. 18-28 ◽

Cited By ~ 12

Author(s):

G. Moradi ◽

B. Mehdinejadiani

Keyword(s):

Sensitivity Analysis ◽

Solute Transport ◽

Dispersion Equation ◽

Dispersion Coefficient ◽

Breakthrough Curves ◽

Heterogeneous Porous Media ◽

Average Pore ◽

Advection Dispersion ◽

Estimated Parameters ◽

Heterogeneous Soil

This paper compared the abilities of advection-dispersion equation (ADE) and spatial fractional advection-dispersion equation (sFADE) to describe the migration of a non-reactive contaminant in homogeneous and heterogeneous soils. To this end, laboratory tests were conducted in a sandbox sizing 2.5 × 0.1 × 0.6 m (length × width × height). After performing a parametric sensitivity analysis, parameters of sFADE and ADE were individually estimated using the inverse problem method at each distance. The dependency of estimated parameters on distance was examined. The estimated parameters at 30 cm were used to predict breakthrough curves (BTCs) at subsequent distances. The results of sensitivity analysis indicated that average pore-water velocity and dispersion coefficient were, respectively, the most and least sensitive parameters in both mathematical models. The values of fractional differentiation orders (α) for sFADE were smaller than 2 in both soils. The scale-dependency of the dispersion coefficients of ADE and sFADE was observed in both soils. However, the application of sFADE to describe solute transport reduced the scale effect on the dispersion coefficient, especially in the heterogeneous soil. For the homogeneous soil, the predicting results of ADE and sFADE were nearly similar, while for the heterogeneous soil, the predicting results of sFADE were more satisfactory in comparison with those of ADE, especially when the transport distance increased. Compared to ADE, the sFADE simulated somewhat better the tailing parts of BTCs and showed the earlier arrival of tracer. Overall, the solute transport, especially in the heterogeneous soil, was non-Fickian and the sFADE somewhat better described non-Fickian transport.

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Numerical and experimental study on solute transport through physical aquifer model

Water Science & Technology Water Supply ◽

10.2166/ws.2021.281 ◽

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.

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Biochar caged zirconium ferrite nanocomposites for the adsorptive removal of Reactive Blue 19 dye in a batch and column reactors and conditions optimizaton

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2020-1749 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Shazia Perveen ◽

Raziya Nadeem ◽

Shaukat Ali ◽

Yasir Jamil

Keyword(s):

Experimental Data ◽

Low Dose ◽

Fixed Bed ◽

Breakthrough Curves ◽

Adsorption Efficiency ◽

Fixed Bed Column ◽

Flow Rates ◽

Adsorptive Removal ◽

Reactive Blue 19 ◽

Pseudo Second Order

Abstract Biochar caged zirconium ferrite (BC-ZrFe2O5) nanocomposites were fabricated and their adsorption capacity for Reactive Blue 19 (RB19) dye was evaluated in a fixed-bed column and batch sorption mode. The adsorption of dye onto BC-ZrFe2O5 NCs followed pseudo-second-order kinetics (R 2 = 0.998) and among isotherms, the experimental data was best fitted to Sips model as compared to Freundlich and Langmuir isotherms models. The influence of flow-rate (3–5 mL min−1), inlet RB19 dye concentration (20–100 mg L−1) and quantity of BC-ZrFe2O5 NCs (0.5–1.5 g) on fixed-bed sorption was elucidated by Box-Behnken experimental design. The saturation times (C t /C o = 0.95) and breakthrough (C t /C o = 0.05) were higher at lower flow-rates and higher dose of BC-ZrFe2O5 NCs. The saturation times decreased, but breakthrough was increased with the initial RB19 dye concentration. The treated volume was higher at low sorbent dose and influent concentration. Fractional bed utilization (FBU) increased with RB19 dye concentration and flow rates at low dose of BC-ZrFe2O5 NCs. Yan model was fitted best to breakthrough curves data as compared to Bohart-Adams and Thomas models. Results revealed that BC-ZrFe2O5 nanocomposite has promising adsorption efficiency and could be used for the adsorption of dyes from textile effluents.

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Regional variation of recession flow power-law exponent

Hydrological Processes ◽

10.1002/hyp.11441 ◽

2018 ◽

Vol 32 (7) ◽

pp. 866-872 ◽

Cited By ~ 9

Author(s):

Swagat Patnaik ◽

Basudev Biswal ◽

Dasika Nagesh Kumar ◽

Bellie Sivakumar

Keyword(s):

Power Law ◽

Regional Variation ◽

Power Law Exponent ◽

Flow Power

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Growth Rate Exponents of Richtmyer-Meshkov Mixing Layers

Journal of Applied Mechanics ◽

10.1115/1.2164510 ◽

2005 ◽

Vol 73 (3) ◽

pp. 461-468 ◽

Cited By ~ 10

Author(s):

Timothy T. Clark ◽

Ye Zhou

Keyword(s):

Flow Field ◽

Power Law ◽

Mixing Layer ◽

Power Laws ◽

Mixing Layers ◽

Spatial Gradients ◽

Power Law Exponent ◽

Virtual Time ◽

Time Origin ◽

Density Ratios

The Richtmyer-Meshkov mixing layer is initiated by the passing of a shock over an interface between fluid of differing densities. The energy deposited during the shock passage undergoes a relaxation process during which the fluctuational energy in the flow field decays and the spatial gradients of the flow field decrease in time. This late stage of Richtmyer-Meshkov mixing layers is studied from the viewpoint of self-similarity. Analogies with weakly anisotropic turbulence suggest that both the bubble-side and spike-side widths of the mixing layer should evolve as power-laws in time, with the same power-law exponent and virtual time origin for both sides. The analogy also bounds the power-law exponent between 2∕7 and 1∕2. It is then shown that the assumption of identical power-law exponents for bubbles and spikes yields fits that are in good agreement with experiment at modest density ratios.

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