Numerical simulation of isotope fractionation in steady-state bioreactive transport controlled by transverse mixing

Eckert, Dominik; Rolle, Massimo; Cirpka, Olaf A.

doi:10.1016/j.jconhyd.2012.08.010

Cited by 48 publications

(43 citation statements)

References 48 publications

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“…For instance, further research is needed to (i) formally upscale the complex interplay between advective and compound-specific diffusive properties to macroscopic descriptions of solute transport; (ii) identify and infer compound-specific mixing properties from high-resolution field characterization; (iii) evaluate the effects and the role of diffusion in complex three-dimensional flow topologies, where twisting and intertwining of flowlines can significantly affect dilution and reactive mixing; (iv) extend the investigation of coupled advective and diffusive processes to transport of electrolytes in porous media, where Coulombic interactions between charged species can considerably affect mass transport ; and (v) improve our capability to interpret isotopic signatures during degradation of contaminants in subsurface environments taking into account the effects of both physical and (bio)reactive processes (e.g., Bouchard et al, 2008;Eckert et al, 2012;Van Breukelen and Rolle, 2012).…”

Section: Discussionmentioning

confidence: 99%

On the importance of diffusion and compound-specific mixing for groundwater transport: An investigation from pore to field scale

Rolle

Chiogna

Hochstetler

et al. 2013

Journal of Contaminant Hydrology

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Section: Discussionmentioning

confidence: 99%

On the importance of diffusion and compound-specific mixing for groundwater transport: An investigation from pore to field scale

Rolle

Chiogna

Hochstetler

et al. 2013

Journal of Contaminant Hydrology

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“…volatilization, sorption) or dispersion. [19][20][21] Va riations of isotope ratios are thus good evidence that contaminant disappearance is due to reaction rather than dilution or sorption. Finally, the extent of isotope fractionation is proportional to the fractional conversion of the contaminant, which -provided that the KIEs and ε-values of a reaction are known -enables one to derive the extent of degradation from the comparison of isotope ratios.…”

Section: Environmental Chemistry In Switzerlandmentioning

confidence: 99%

Isotope Effects as New Proxies for Organic Pollutant Transformation

Hofstetter

Bolotin

Pati

et al. 2014

Chimia

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Assessing the pathways and rates of organic pollutant transformation in the environment is a major challenge due to co-occurring transport and degradation processes. Measuring changes of stable isotope ratios (e.g. (13)C/(12)C, (2)H/(1)H, (15)N/(14)N) in individual organic compounds by compound-specific isotope analysis (CSIA) makes it possible to identify degradation pathways without the explicit need to quantify pollutant concentration dynamics. The so-called isotope fractionation observed in an organic pollutant is related to isotope effects of (bio)chemical reactions and enables one to characterize pollutant degradation even if multiple processes take place simultaneously. Here, we illustrate some principles of CSIA using benzotriazole, a frequently observed aquatic micropollutant, as example. We show subsequently how the combined C and N isotope fractionation analysis of nitroaromatic compounds reveals kinetics and mechanisms of reductive and oxidative reactions as well as their (bio)degradation pathways in the environment.

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“…16 and 17 is that they allow a spatially variable representation of local hydrodynamic dispersion that can be directly linked to the spatially variable conductivity of heterogeneous porous media. Different empirical correlations have been proposed to relate the hydraulic conductivity to the grain size of unconsolidated materials; in this study we use the approximation of Hazen [55], which was adopted in previous simulations of solute transport in heterogeneous media [e.g., 56,57], and suggests a simple square root relation:…”

Section: Computational Experimentsmentioning

confidence: 99%

Longitudinal dispersion coefficients for numerical modeling of groundwater solute transport in heterogeneous formations

Lee

Rolle

Kitanidis

2018

Journal of Contaminant Hydrology

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Most recent research on hydrodynamic dispersion in porous media has focused on whole-domain dispersion while other research is largely on laboratory-scale dispersion. This work focuses on the contribution of a single block in a numerical model to dispersion. Variability of fluid velocity and concentration within a block is not resolved and the combined spreading effect is approximated using resolved quantities and macroscopic parameters. This applies whether the formation is modeled as homogeneous or discretized into homogeneous blocks but the emphasis here being on the latter. The process of dispersion is typically described through the Fickian model, i.e., the dispersive flux is proportional to the gradient of the resolved concentration, commonly with the Scheidegger parameterization, which is a particular way to compute the dispersion coefficients utilizing dispersivity coefficients. Although such parameterization is by far the most commonly used in solute transport applications, its validity has been questioned. Here, our goal is to investigate the effects of heterogeneity and mass transfer limitations on block-scale longitudinal dispersion and to evaluate under which conditions the Scheidegger parameterization is valid. We compute the relaxation time or memory of the system; changes in time with periods larger than the relaxation time are gradually leading to a condition of local equilibrium under which dispersion is Fickian. The method we use requires the solution of a steady-state advection-dispersion equation, and thus is computationally efficient, and applicable to any heterogeneous hydraulic conductivity K field without requiring statistical or structural assumptions. The method was validated by comparing with other approaches such as the moment analysis and the first order perturbation method. We investigate the impact of heterogeneity, both in degree and structure, on the longitudinal dispersion coefficient and then discuss the role of local dispersion and mass transfer limitations, i.e., the exchange of mass between the permeable matrix and the low permeability inclusions. We illustrate the physical meaning of the method and we show how the block longitudinal dispersivity approaches, under certain conditions, the Scheidegger limit at large Péclet numbers. Lastly, we discuss the potential and limitations of the method to accurately describe dispersion in solute transport applications in heterogeneous aquifers.

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Numerical simulation of isotope fractionation in steady-state bioreactive transport controlled by transverse mixing

Cited by 48 publications

References 48 publications

On the importance of diffusion and compound-specific mixing for groundwater transport: An investigation from pore to field scale

On the importance of diffusion and compound-specific mixing for groundwater transport: An investigation from pore to field scale

Isotope Effects as New Proxies for Organic Pollutant Transformation

Longitudinal dispersion coefficients for numerical modeling of groundwater solute transport in heterogeneous formations

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