Contaminant occurrence and migration between high- and low-permeability zones in groundwater systems: A review

You, Xueji; Liu, Shuguang; Dai, Chaomeng; Guo, Yiping; Zhong, Guangfa; Duan, Yanping

doi:10.1016/j.scitotenv.2020.140703

Cited by 72 publications

(27 citation statements)

References 148 publications

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“…(8) into Eq. (1) and dividing both sides of the equations by ϕ i (z)θ i (t) at the same time results in (9) Introducing the constant λ, Eq. ( 9) can be split into two separate ordinary differential equations as (10) (11) The solutions of Eq.…”

Section: General Solution 221 Concentration In Contaminated Soilmentioning

confidence: 99%

“…As for the following numerical simulation, the first numerical example (i.e., numerical example A) corresponds to the same assumption condition with the present analytical solution, and the second numerical example (i.e., numerical example B) further considers the maximum contribution of advection and mechanical dispersion to diffusion-controlled transport. It is noted again that under the condition of low head, permeability coefficient and Peclet number, the transport of contaminant is diffusion-controlled [6][7][8][9]. When considering the role of advection and mechan-ical dispersion in the process of diffusion-controlled transport, the hydrodynamic dispersion coefficient D ri in the ith layer can be defined as [36].…”

Section: Verification Of the Present Solutionmentioning

confidence: 99%

“…It should be pointed out that under the coupling effect of multiple fields, the contaminant source of the repository is likely to diffuse to the adjacent soil and water with great difficulty to repair again, which seriously threatens the environmental health [3][4][5]. In the above cases, molecular diffusion induced by concentration differences is the key factor for the contaminant diffusion to the adjacent soil or cover layer because of its low hydraulic conductivity of the clay (e.g., < 10 -7 cm/s), low leachate head (e.g., < 0.3 m), and small Peclet number [6][7][8][9]. Besides, diffusive transport problem comprehensively exists in the engineering materials, such as compacted clay liner [10,11], underwater cap [12], geosynthetic clay lining [13], and composite liners [14,15].…”

Section: Introductionmentioning

confidence: 99%

“…Unless otherwise specified, the basic parameters used in the following calculations (i.e., Fig.3to Fig.8) are:H = 1m, h 1 = 0.5 m, T v = 0.129 or 0.279, C 0 = 0.1 mol/L, D v1 = 3.3 × 10 -10 m 2 /s, D v2 = 6.8 × 10 -10 m 2 /s, n 1 = 0.25, n 2 = 0.5.It should be pointed out again that S di = 0, ∞ and finite values (i = 1, 2) represent the non-diffusion, full diffusion and imperfect diffusion boundaries.As for the following numerical simulation, the first numerical example (i.e., numerical example A) corresponds to the same assumption condition with the present analytical solution, and the second numerical example (i.e., numerical example B) further considers the maximum contribution of advection and mechanical dispersion to diffusion-controlled transport. It is noted again that under the condition of low head, permeability coefficient and Peclet number, the transport of contaminant is diffusion-controlled[6][7][8][9]. When considering the role of advection and mechan-…”

mentioning

confidence: 99%

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An analytical solution for one-dimensional contaminant transport in a double-layered contaminated soil with imperfect diffusion boundaries

Sheng

Zhang

et al. 2021

Environmental Engineering Research

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An analytical method is proposed to solve the contaminant transport in a double-layered contaminated soil with imperfect diffusion boundaries. By virtue of the separation of variables scheme, the governing equation for contaminant diffusion is split into two ordinary differential equations, and the corresponding general solutions are obtained. By utilizing the initial, continuity and boundary conditions of the system, and the orthogonality of trigonometric functions, the analytical solution for contaminant concentration in the double-layered contaminated soil is derived, which can be further used to describe the average degree of diffusion. The reliability and accuracy of the developed solution is verified by comparing with the existing analytical solution and numerical simulation results. Selected numerical examples are further presented to analyze the influence of the imperfect diffusion boundaries on the spatial/time distribution of contaminant concentration, average degree of diffusion and mass flux. The results show that greater imperfect diffusion capacity coefficients lead to lower contaminant concentration distribution within the entire depth range and higher average degree of diffusion for a given time. Particularly, it only takes 23.32 years to complete the entire diffusion process when imperfect diffusion capacity coefficients are infinite. The developed solution can provide useful guidance for engineering practice.

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Section: General Solution 221 Concentration In Contaminated Soilmentioning

confidence: 99%

Section: Verification Of the Present Solutionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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An analytical solution for one-dimensional contaminant transport in a double-layered contaminated soil with imperfect diffusion boundaries

Sheng

Zhang

et al. 2021

Environmental Engineering Research

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“…In these studies, diffusion was identified as the main mechanism responsible for the migration of the dissolved chemical substances through the clays. Apart from diffusion, which is a physical process, clay also attenuates the transport of dissolved contaminants through chemical processes, for example, complexation and adsorption [5][6][7][8], ultimately causing the groundwater cleanup time to be longer than expected [9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Influence of Clay on Solute Transport in Saturated Homogeneous Mixed Media

et al. 2021

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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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Évaluation de la dispersion des valeurs de perméabilité estimées par les méthodes Dupuit, Thiem et Boulton sur des essais de pompage répétés dans un aquifère libre

Peyraube,

Villanueva,

Lastennet

et al. 2023

Hydrogeol J

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Contaminant occurrence and migration between high- and low-permeability zones in groundwater systems: A review

Cited by 72 publications

References 148 publications

An analytical solution for one-dimensional contaminant transport in a double-layered contaminated soil with imperfect diffusion boundaries

An analytical solution for one-dimensional contaminant transport in a double-layered contaminated soil with imperfect diffusion boundaries

Influence of Clay on Solute Transport in Saturated Homogeneous Mixed Media

Évaluation de la dispersion des valeurs de perméabilité estimées par les méthodes Dupuit, Thiem et Boulton sur des essais de pompage répétés dans un aquifère libre

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