Characterization of mixing and dilution in heterogeneous aquifers by means of local temporal moments

Cirpka, Olaf A.; Kitanidis, Peter K.

doi:10.1029/1999wr900354

Cited by 159 publications

(142 citation statements)

References 43 publications

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“…The influence of incomplete mixing on mixing-induced reactions has recently won much attention and been reported in many literatures [36][37][38][39][40][41]. The key point for this is that a fundamental difference exists between spreading and mixing processes.…”

Section: Reactants Mixing and Reaction Productmentioning

confidence: 99%

Pore-Scale Modeling of Mixing-Induced Reaction Transport through a Single Self-Affine Fracture

et al. 2018

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This pore-scale modeling study in single self-affine fractures showed that the heterogeneous flow field had a significant influence on the mixing-induced reaction transport. We generated the single self-affine fracture by the successive random additions (SRA) technique. The pore-scale model was developed by coupling the Navier-Stoke equation (NSE) and advection-diffusion equation with reaction (ADER). Eddies were captured in the self-affine fracture due to the increasing Reynolds number and the sudden expansion of aperture. The flux-weighted breakthrough curves (BTCs) of reaction product showed the typical non-Fickian characteristics (i.e., "early arrival" and "heavy tail"). It was found that the reactant was involved in eddies and then reacted inside the eddy-controlled domain. Consequently, eddies played a significant role in delaying the mass exchange process between the eddycontrolled domain and the main flow channel, which resulted in the "heavy tail" in BTCs. As the Reynolds number increased, the breakthrough time increased while the concentration peaks of BTCs decreased. Furthermore, the dilution index presenting the exponential of the Shannon entropy of a concentration probability distribution was used to quantify the degree of reactant mixing. The results showed that the quantification of dilution for nonreaction transport was in good agreement with the outcomes of mixing-induced reaction transport. The high Reynolds number and Peclet number had a negative influence on the mixing process at the early time whereas they led to the enhanced mixing process at the late time.

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Section: Reactants Mixing and Reaction Productmentioning

confidence: 99%

Pore-Scale Modeling of Mixing-Induced Reaction Transport through a Single Self-Affine Fracture

et al. 2018

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“…In general, ensemble dispersion coefficients tend to overestimate the impact of heterogeneities on the dispersive mixing process describing artificial ensemble averaging effects. Especially, the real mixing behavior at the concentration front is much better described by the effective than by the ensemble dispersion coefficient, which can be very essential in modeling reactive transport as shown in [8].…”

Section: General Conceptsmentioning

confidence: 99%

Multiscale Modeling of Nonlinearly Adsorbing Solute Transport

Attinger¹,

Micha²,

Kinzelbach³

2003

Multiscale Model. Simul.

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Abstract. We focus our investigations on hydrologic subsurface transport processes of a solute dissolved in groundwater. Moreover, the solute adsorbs nonlinearly on the soil matrix. Starting with transport in homogeneous media, we introduce a new methodology to identify transport parameters from dissolved solute concentration data. Transport in heterogeneous media is investigated by using a stochastic modeling approach. For mildly heterogeneous media we construct a perturbation theory around the homogeneous nonlinear theory and derive explicit expressions for asymptotic and transient large-scale transport parameters. Asymptotically, we find that the large-scale parameters are exactly the same as for linearly adsorbing transport. Differences between transport with linear and nonlinear adsorption become apparent for transient times. The characteristic time or length scales to reach the asymptotic regime depend on the grade of the nonlinearity: the smaller the Freundlich exponent p, the larger the characteristic time or travel distance. The theoretical results are verified in a semianalytical approach. Ensemble and effective dispersion coefficients are obtained from integral expressions by means only of homogeneous concentration data. We found an excellent agreement between the analytical predictions and the semianalytical results.

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“…These two moments can be used to directly infer seepage velocity v and dispersion coefficient D from BTC data for a one-dimensional system (Cirpka and Kitanidis, 2000).…”

Section: A1 Binary Diffusion Coefficientmentioning

confidence: 99%

Experimental study on retardation of a heavy NAPL vapor in partially saturated porous media

Kleinknecht

Class

Braun

2017

Hydrol. Earth Syst. Sci.

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Abstract. Non-aqueous-phase liquid (NAPL) contaminants introduced into the unsaturated zone spread as a liquid phase; however, they can also vaporize and migrate in a gaseous state. Vapor plumes migrate easily and thus pose a potential threat to underlying aquifers. Large-scale column experiments were performed to quantify partitioning processes responsible for the retardation of carbon disulfide (CS 2 ) vapor in partially saturated porous media. The results were compared with a theoretical approach taking into account the partitioning into the aqueous phase as well as adsorption to the solid matrix and to the air-water interface. The experiments were conducted in large, vertical columns (i.d. of 0.109 m) of 2 m length packed with different porous media. A slug of CS 2 vapor and the conservative tracer argon was injected at the bottom of the column followed by a nitrogen chase. Different seepage velocities were applied to characterize the transport and to evaluate their impact on retardation. Concentrations of CS 2 and argon were measured at the top outlet of the column using two gas chromatographs. The temporal-moment analysis for step input was employed to evaluate concentration breakthrough curves and to quantify dispersion and retardation. The experiments conducted showed a pronounced retardation of CS 2 in moist porous media which increased with water saturation. The comparison with an analytical solution helped to identify the relative contributions of partitioning processes to retardation. Thus, the experiments demonstrated that migrating CS 2 vapor is retarded as a result of partitioning processes. Moreover, CS 2 dissolved in the bulk water is amenable to biodegradation. The first evidence of CS 2 decay by biodegradation was found in the experiments. The findings contribute to the understanding of vapor-plume transport in the unsaturated zone and provide valuable experimental data for the transfer to field-like conditions.

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Characterization of mixing and dilution in heterogeneous aquifers by means of local temporal moments

Cited by 159 publications

References 43 publications

Pore-Scale Modeling of Mixing-Induced Reaction Transport through a Single Self-Affine Fracture

Pore-Scale Modeling of Mixing-Induced Reaction Transport through a Single Self-Affine Fracture

Multiscale Modeling of Nonlinearly Adsorbing Solute Transport

Experimental study on retardation of a heavy NAPL vapor in partially saturated porous media

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