Search results for: Carl I. Steefel

Items from 1 to 20 out of 49 results

article

Multi-scale Model of Reactive Transport in Fractured Media: Diffusion Limitations on Rates

Sergi Molins, David Trebotich, Bhavna Arora, Carl I. Steefel, more

Transport in Porous Media > 2019 > 128 > 2 > 701-721

Reactive transport in fractured media is conceptualized as a multi-scale problem that couples a pore-scale component, which comprises Navier–Stokes flow, multi-component transport and aqueous equilibrium in the fracture, and a Darcy-scale component, which comprises multi-component diffusive transport, aqueous equilibrium and mineral reactions in the porous matrix. The model that implements this multi-scale...

article

Predicting the impact of land management decisions on overland flow generation: Implications for cesium migration in forested Fukushima watersheds

Erica R. Siirila-Woodburn, Carl I. Steefel, Kenneth H. Williams, Jens T. Birkholzer

Advances in Water Resources > 2018 > 113 > C > 42-54

The effects of land use and land cover (LULC) change on environmental systems across the land surface's “critical zone” are highly uncertain, often making prediction and risk management decision difficult. In a series of numerical experiments with an integrated hydrologic model, overland flow generation is quantified for both present day and forest thinning scenarios. A typhoon storm event in a watershed...

article

Investigating calcite growth rates using a quartz crystal microbalance with dissipation (QCM-D)

Bo Cao, Andrew G. Stack, Carl I. Steefel, Donald J. DePaolo, more

Geochimica et Cosmochimica Acta > 2018 > 222 > C > 269-283

Calcite precipitation plays a significant role in processes such as geological carbon sequestration and toxic metal sequestration and, yet, the rates and mechanisms of calcite growth under close to equilibrium conditions are far from well understood. In this study, a quartz crystal microbalance with dissipation (QCM-D) was used for the first time to measure macroscopic calcite growth rates. Calcite...

article

Effects of sulfate and magnesium on cement degradation under geologic CO2 sequestration conditions

Jilong Guo, Bo Cao, Carl I. Steefel, Jiawei Chen, more

International Journal of Greenhouse Gas Control > 2017 > 63 > C > 118-125

For safer geologic CO₂ sequestration (GCS), it is important to understand CO₂-brine-cement interactions, which affect wellbore integrity. However, potential effects of sulfate and magnesium ions on cement degradation under GCS conditions are not well understood. Here Class H Portland cement were reacted in brines containing 0.05M sulfate and/or magnesium ions under both GCS (50°C and 100atm CO₂) and...

article

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

Estela Reinoso-Maset, Carl I. Steefel, Wooyong Um, Jon Chorover, more

Geochimica et Cosmochimica Acta > 2017 > 207 > C > 298-321

Uranyl oxyhydroxide minerals are important weathering products in uranium-contaminated surface and subsurface environments that regulate dissolved uranium (U) concentrations. However, dissolution rates for this class of minerals and associated dissolution mechanisms have not been previously reported for circumneutral pH conditions, particularly for the case of flow through porous media. In this work,...

article

Evaluation of accessible mineral surface areas for improved prediction of mineral reaction rates in porous media

Lauren E. Beckingham, Carl I. Steefel, Alexander M. Swift, Marco Voltolini, more

Geochimica et Cosmochimica Acta > 2017 > 205 > C > 31-49

The rates of mineral dissolution reactions in porous media are difficult to predict, in part because of a lack of understanding of mineral reactive surface area in natural porous media. Common estimates of mineral reactive surface area used in reactive transport models for porous media are typically ad hoc and often based on average grain size, increased to account for surface roughness or decreased...

article

Expanding the role of reactive transport models in critical zone processes

Li Li, Kate Maher, Alexis Navarre-Sitchler, Jenny Druhan, more

Earth-Science Reviews > 2017 > 165 > C > 280-301

Models test our understanding of processes and can reach beyond the spatial and temporal scales of measurements. Multi-component Reactive Transport Models (RTMs), initially developed more than three decades ago, have been used extensively to explore the interactions of geothermal, hydrologic, geochemical, and geobiological processes in subsurface systems. Driven by extensive data sets now available...

article

Identifying geochemical hot moments and their controls on a contaminated river floodplain system using wavelet and entropy approaches

Bhavna Arora, Dipankar Dwivedi, Susan S. Hubbard, Carl I. Steefel, more

Environmental Modelling & Software > 2016 > 85 > C > 27-41

Geochemical hot moments are defined here as short periods of time that are associated with disproportionally high levels of concentrations (biogeochemically-driven or transport-related) relative to longer intervening time periods. We used entropy and wavelet techniques to identify temporal variability in geochemical constituents and their controls along three transects within a contaminated floodplain...

article

Effects of pore-scale precipitation on permeability and flow

Catherine Noiriel, Carl I. Steefel, Li Yang, Dominique Bernard

Advances in Water Resources > 2016 > 95 > C > 125-137

The effects of calcite precipitation on porous media permeability and flow were evaluated with a combined experimental and modeling approach. X-ray microtomography images of two columns packed with glass beads and calcite (spar crystals) or aragonite (Bahamas ooids) injected with a supersaturated solution (log Ω = 1.42) were processed in order to calculate rates of calcite precipitation with a spatial...

article

Evaluation of mineral reactive surface area estimates for prediction of reactivity of a multi-mineral sediment

Lauren E. Beckingham, Elizabeth H. Mitnick, Carl I. Steefel, Shuo Zhang, more

Geochimica et Cosmochimica Acta > 2016 > 188 > C > 310-329

Our limited understanding of mineral reactive surface area contributes to significant uncertainties in quantitative simulations of reactive chemical transport in subsurface processes. Continuum formulations for reactive transport typically use a number of different approximations for reactive surface area, including geometric, specific, and effective surface area. In this study, reactive surface area...

article

Molecular Dynamics Simulations of Anion Exclusion in Clay Interlayer Nanopores

Christophe Tournassat, Ian C. Bourg, Michael Holmboe, Garrison Sposito, more

Clays and Clay Minerals > 2016 > 64 > 4 > 374-388

The aqueous chemistry of water films confined between clay mineral surfaces remains an important unknown in predictions of radioelement migration from radioactive waste repositories. This issue is particularly important in the case of long-lived anionic radioisotopes (¹²⁹I^-, ⁹⁹TcO ₄^- , ³⁶Cl^-) which interact with clay minerals primarily by anion exclusion. For example, models of ion migration in clayey...

article

Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment

Bhavna Arora, Nicolas F. Spycher, Carl I. Steefel, Sergi Molins, more

Biogeochemistry > 2016 > 127 > 2-3 > 367-396

Flood plains play a potentially important role in the global carbon cycle. The accumulation of organic matter in flood plains often induces the formation of chemically reduced groundwater and sediments along riverbanks. In this study, our objective is to evaluate the cumulative impact of such reduced zones, water table fluctuations, and temperature gradients on subsurface carbon fluxes in a flood...

article

Dissolution rate of borosilicate glass SON68: A method of quantification based upon interferometry and implications for experimental and natural weathering rates of glass

Jonathan P. Icenhower, Carl I. Steefel

Geochimica et Cosmochimica Acta > 2015 > 157 > C > 147-163

Rates of glass dissolution from laboratory and field studies are often considered to be irreconcilable, although potential causes for the difference, such as solution saturation state and increasing surface area from progressive weathering, have not been explored in depth. The dissolution rate of SON68 glass, the non-radioactive analog of the French R7T7 composition, was determined in a single-pass...

article

Chemical affinity and pH effects on chlorite dissolution kinetics under geological CO2 sequestration related conditions

Shuo Zhang, Li Yang, Donald J. DePaolo, Carl I. Steefel

Chemical Geology > 2015 > 396 > C > 208-217

The kinetic dissolution of Flagstaff Hill chlorite (CCa-2 from Clay Minerals Society), (Mg_4.55Al_1.23Fe_0.12)(Al_1.04Si_2.96)O₁₀(OH)₈, was investigated using a well-mixed flow-through reactor at 100°C, pH values ranging from 3.0 to 7.5, and variable saturation states. The objective was to measure the dependence of chlorite dissolution rate on pH as well as on degree of undersaturation under conditions...

article

ParCrunchFlow: an efficient, parallel reactive transport simulation tool for physically and chemically heterogeneous saturated subsurface environments

James J. Beisman, Reed M. Maxwell, Alexis K. Navarre-Sitchler, Carl I. Steefel, more

Computational Geosciences > 2015 > 19 > 2 > 403-422

Understanding the interactions between physical, geochemical, and biological processes in the shallow subsurface is integral to the development of effective contamination remediation techniques, or the accurate quantification of nutrient fluxes and biogeochemical cycling. Hydrology is a primary control on the behavior of shallow subsurface environments and must be realistically represented if we hope...

article

A reactive transport benchmark on heavy metal cycling in lake sediments

Bhavna Arora, S. Sevinç Şengör, Nicolas F. Spycher, Carl I. Steefel

Computational Geosciences > 2015 > 19 > 3 > 613-633

Sediments are active recipients of anthropogenic inputs, including heavy metals, but may be difficult to interpret without the use of numerical models that capture sediment-metal interactions and provide an accurate representation of the intricately coupled sedimentological, geochemical, and biological processes. The focus of this study is to present a benchmark problem on heavy metal cycling in lake...

article

Benchmarks for multicomponent reactive transport across a cement/clay interface

Nicolas C. M. Marty, Olivier Bildstein, Philippe Blanc, Francis Claret, more

Computational Geosciences > 2015 > 19 > 3 > 635-653

The use of the subsurface for CO₂ storage, geothermal energy generation, and nuclear waste disposal will greatly increase the interaction between clay(stone) and concrete. The development of models describing the mineralogical transformations at this interface is complicated, because contrasting geochemical conditions (Eh, pH, solution composition, etc.) induce steep concentration gradients and a...

article

Benchmark problems for reactive transport modeling of the generation and attenuation of acid rock drainage

K. Ulrich Mayer, Peter Alt-Epping, Diederik Jacques, Bhavna Arora, more

Computational Geosciences > 2015 > 19 > 3 > 599-611

Acid rock drainage (ARD) is a problem of international relevance with substantial environmental and economic implications. Reactive transport modeling has proven a powerful tool for the process-based assessment of metal release and attenuation at ARD sites. Although a variety of models has been used to investigate ARD, a systematic model intercomparison has not been conducted to date. This contribution...

article

Benchmarks for multicomponent diffusion and electrochemical migration

Pejman Rasouli, Carl I. Steefel, K. Ulrich Mayer, Massimo Rolle

Computational Geosciences > 2015 > 19 > 3 > 523-533

In multicomponent electrolyte solutions, the tendency of ions to diffuse at different rates results in a charge imbalance that is counteracted by the electrostatic coupling between charged species leading to a process called “electrochemical migration” or “electromigration.” Although not commonly considered in solute transport problems, electromigration can strongly affect mass transport processes...

article

Reactive transport benchmarks for subsurface environmental simulation

Carl I. Steefel, Steven B. Yabusaki, K. Ulrich Mayer

Computational Geosciences > 2015 > 19 > 3 > 439-443

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INFONA - science communication portal

Search results for: Carl I. Steefel

Multi-scale Model of Reactive Transport in Fractured Media: Diffusion Limitations on Rates

Predicting the impact of land management decisions on overland flow generation: Implications for cesium migration in forested Fukushima watersheds

Investigating calcite growth rates using a quartz crystal microbalance with dissipation (QCM-D)

Effects of sulfate and magnesium on cement degradation under geologic CO2 sequestration conditions

Rates and mechanisms of uranyl oxyhydroxide mineral dissolution

Evaluation of accessible mineral surface areas for improved prediction of mineral reaction rates in porous media

Expanding the role of reactive transport models in critical zone processes

Identifying geochemical hot moments and their controls on a contaminated river floodplain system using wavelet and entropy approaches

Effects of pore-scale precipitation on permeability and flow

Evaluation of mineral reactive surface area estimates for prediction of reactivity of a multi-mineral sediment

Molecular Dynamics Simulations of Anion Exclusion in Clay Interlayer Nanopores

Influence of hydrological, biogeochemical and temperature transients on subsurface carbon fluxes in a flood plain environment

Dissolution rate of borosilicate glass SON68: A method of quantification based upon interferometry and implications for experimental and natural weathering rates of glass

Chemical affinity and pH effects on chlorite dissolution kinetics under geological CO2 sequestration related conditions

ParCrunchFlow: an efficient, parallel reactive transport simulation tool for physically and chemically heterogeneous saturated subsurface environments

A reactive transport benchmark on heavy metal cycling in lake sediments

Benchmarks for multicomponent reactive transport across a cement/clay interface

Benchmark problems for reactive transport modeling of the generation and attenuation of acid rock drainage

Benchmarks for multicomponent diffusion and electrochemical migration

Reactive transport benchmarks for subsurface environmental simulation

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