Mixing and Reactive Fronts in the Subsurface

Rolle, Massimo; Borgne, Tanguy Le

doi:10.2138/rmg.2018.85.5

Cited by 61 publications

(58 citation statements)

References 167 publications

(225 reference statements)

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“…The warm (yellow) to cool (blue/black) coloring corresponds to liquid fraction (pure fluid at the base of the image, low liquid fraction ice at the top of the image). Image credit: (a)-adapted from Britney Schmidt/Dead Pixel FX, UT Austin; (b)-adapted from Rolle and Le Borgne (2019); and (c)-adapted from Worster and Rees Jones (2015).…”

Section: Numerical Modelmentioning

confidence: 99%

Entrainment and Dynamics of Ocean‐Derived Impurities Within Europa's Ice Shell

et al. 2020

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Compositional heterogeneities within Europa's ice shell likely impact the dynamics and habitability of the ice and subsurface ocean, but the total inventory and distribution of impurities within the shell are unknown. In sea ice on Earth, the thermochemical environment at the ice-ocean interface governs impurity entrainment into the ice. Here, we simulate Europa's ice-ocean interface and bound the impurity load (1.053-14.72 g/kg [parts per thousand weight percent, or ppt] bulk ice shell salinity) and bulk salinity profile of the ice shell. We derive constitutive equations that predict ice composition as a function of the ice shell thermal gradient and ocean composition. We show that evolving solidification rates of the ocean and hydrologic features within the shell produce compositional variations (ice bulk salinities of 5-50% of the ocean salinity) that can affect the material properties of the ice. As the shell thickens, less salt is entrained at the ice-ocean interface, which implies Europa's ice shell is compositionally homogeneous below~1 km. Conversely, the solidification of water filled fractures or lenses introduces substantial compositional variations within the ice shell, creating gradients in mechanical and thermal properties within the ice shell that could help initiate and sustain geological activity. Our results suggest that ocean materials entrained within Europa's ice shell affect the formation of geologic terrain and that these structures could be confirmed by planned spacecraft observations. Plain Language Summary Europa, the second innermost moon of Jupiter, likely houses an interior ocean that could provide a habitat for life. This ocean resides beneath a 10-to >30-km-thick ice shell which could act as a barrier or conveyor for ocean-surface material transport that could render the ocean chemistry either hospitable or unfavorable for life. Additionally, material impurities in the ice shell will alter its physical properties and thus affect the global dynamics of the moon's icy exterior. That said, few of the interior properties of the ice shell or ocean have been directly measured. On Earth, the composition of ocean-derived ice is governed by the chemistry of the parent liquid and the rate at which it forms. Here, we extend models of sea ice to accommodate the Europa ice-ocean environment and produce physically realistic predictions of Europa's ice shell composition and the evolution of water bodies (fractures and lenses) within the shell. Our results show that the thermal gradient of the ice and the liquid composition affect the formation and evolution of geologic features in ways that could be detectable by future spacecraft (e.g., by ice penetrating radar measurements made by Europa Clipper).

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Section: Numerical Modelmentioning

confidence: 99%

Entrainment and Dynamics of Ocean‐Derived Impurities Within Europa's Ice Shell

et al. 2020

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“…porous media | reactive transport | chaotic mixing | chemical gradients F luid mixing in porous media plays a key role in a range of natural and industrial systems (1)(2)(3). In these confined environments, mixing enables or limits reactions controlling the degradation of contaminants in the subsurface; the cycles of biogeochemical elements such as nitrogen, iron, and carbon; and the sequestration of CO2 in deep reservoirs (4)(5)(6)(7)(8)(9)(10).…”

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confidence: 99%

Stretching and folding sustain microscale chemical gradients in porous media

Heyman

Lester

Turuban

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Fluid flow in porous media drives the transport, mixing, and reaction of molecules, particles, and microorganisms across a wide spectrum of natural and industrial processes. Current macroscopic models that average pore-scale fluctuations into an effective dispersion coefficient have shown significant limitations in the prediction of many important chemical and biological processes. Yet, it is unclear how three-dimensional flow in porous structures govern the microscale chemical gradients controlling these processes. Here, we obtain high-resolution experimental images of microscale mixing patterns in three-dimensional porous media and uncover an unexpected and general mixing mechanism that strongly enhances concentration gradients at pore-scale. Our experiments reveal that systematic stretching and folding of fluid elements are produced in the pore space by grain contacts, through a mechanism that leads to efficient microscale chaotic mixing. These insights form the basis for a general kinematic model linking chaotic-mixing rates in the fluid phase to the generic structural properties of granular matter. The model successfully predicts the resulting enhancement of pore-scale chemical gradients, which appear to be orders of magnitude larger than predicted by dispersive approaches. These findings offer perspectives for predicting and controlling the vast diversity of reactive transport processes in natural and synthetic porous materials, beyond the current dispersion paradigm.

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“…Since the diffusion-reaction equation is the same of the diffusionreaction equation studied here, the mechanisms described here are also relevant for conventional dispersion processes. The effect of more complex mixing patterns induced by shear and stretching [46] could be investigated using a similar approach by considering stretching enhanced diffusion captured by lamella mixing models [47].…”

Section: Discussionmentioning

confidence: 99%

Enhanced and non-monotonic effective kinetics of solute pulses under michaelis–Menten reactions

Hubert

Aquino

Tabuteau

et al. 2020

Advances in Water Resources

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HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

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Mixing and Reactive Fronts in the Subsurface

Cited by 61 publications

References 167 publications

Entrainment and Dynamics of Ocean‐Derived Impurities Within Europa's Ice Shell

Entrainment and Dynamics of Ocean‐Derived Impurities Within Europa's Ice Shell

Stretching and folding sustain microscale chemical gradients in porous media

Enhanced and non-monotonic effective kinetics of solute pulses under michaelis–Menten reactions

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