Geochemical self-organization

Ortoleva, P.

doi:10.1016/0009-2541(88)90428-7

Cited by 161 publications

(218 citation statements)

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“…Within the domain of reactive flow in unsaturated soils three main types of interfering instabilities occur: (i) reaction instabilities due to initial heterogeneities in the hydraulic properties with dissolution of wormholes and karst phenomena [1,[96][97][98][99][100][101][102][103][104][105], (ii) flow instabilities with moisture content fingering during the infiltration of a moisture front [106][107][108][109][110][111][112][113][114][115][116] and (iii) density instabilities due to local differences of solution densities [117][118][119][120][121][122][123][124]. However, the scope of this paper is not to investigate instability phenomena, but to propose a new approach that relates changes in mineral volumes and hydraulic properties.…”

Section: General Model Discussionmentioning

confidence: 99%

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Wissmeier

Barry

2009

Advances in Water Resources

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This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. ACCEPTED MANUSCRIPT AbsThe selective radius shift model was used to relate changes in mineral volume due to precipitation/dissolution reactions to changes in hydraulic properties affecting flow in porous media. The model accounts for (i) precipitation/dissolution taking place only in the water-filled part of the pore space and further that (ii) the amount of mineral precipitation/dissolution within a pore depends on the local pore volume. The pore bundle concept was used to connect pore-scale changes to macroscopic soil hydraulic properties. Precipitation/dissolution induces changes in the pore radii of water-filled pores and, consequently, in the effective porosity. In a time step of the numerical model, mineral reactions lead to a discontinuous pore-size distribution because only the water-filled pores are affected. The pore-size distribution is converted back to a soil moisture characteristic function to which a new water retention curve is fitted under physically plausible constraints. The model equations were derived for the commonly used van Genuchten/Mualem hydraulic properties. Together with a mixed-form solution of Richards' equation for aqueous phase flow, the model was implemented into the geochemical modelling framework PHREEQC, thereby making available PHREEQC's comprehensive geochemical reactions. Example applications include kinetic halite dissolution and calcite precipitation as a consequence of cation exchange. These applications showed marked changes in the soil's hydraulic properties due to mineral precipitation/dissolution and the dependency of these changes on water contents. The simulations also revealed the strong influence of the degree of saturation on the development of the saturated hydraulic conductivity through its quadratic dependency on the van Genuchten parameter . Furthermore, it was shown that the unsaturated hydraulic conductivity at fixed reduced water content can even r tract increase du ing precipitation due to changes in the pore-size distribution.

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Section: General Model Discussionmentioning

confidence: 99%

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Wissmeier

Barry

2009

Advances in Water Resources

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“…The Pi is the molar density of mineral i, and D is the dispersion coefficient for species in the aqueous fluid, is taken to be the same for all species, and is proportional to the magnitude of the flow velocity. The analysis of the conservation equations (10), in the limit of fast aqueous reaction, is given in chapter 3 of Ortoleva [ 1994]. Experimental and numerical studies [Arquis, 1994[Arquis, , 1995 show that the Brinkman equation adequately captures the velocity of the fluid in the boundary layer between the porous medium and the free fluid zone as well.…”

Section: Chemical Modelmentioning

confidence: 99%

Numerical modeling of reaction‐induced cavities in a porous rock

Ormond¹,

Ortoleva²

2000

J. Geophys. Res.

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Abstract. The interaction between mineral reaction and mass transport in a rock can lead to reaction front instability and the development of channel-like voids. This phenomenon is studied with a two-dimensional model accounting for the nonlinear feedback between flow, reaction, and matrix porosity-permeability evolution. In our model we calculate the flow field in both the porous medium and the reaction-induced voids, using the Brinkman equation. While a linear analysis cannot determine the length scale of the channels which can develop in a typical geological system, our simulations indicate that the channel size is actually unique and well characterized. While the onset of instability is favored at a preexisting heterogeneity, the channel growth and orientation is governed by the global flow pattern, even in an initially heterogeneous system.

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“…Merino, 1984Merino, , 1987Ortoleva et a1., 1980Ortoleva et a1., , 1982Ortoleva et a1., , 1986aOrtoleva et a1., y b, 1987Ortoleva, 1982Ortoleva, , 1984aOrtoleva, y b, 1987Ortoleva, , 1988Moore et a1., 1983;Fowler, 1988;Wang et a1., 1989 y otros colaboradores), que desarrollan un exhaustivo análisis de este tipo de procesos en busca de una modelización matemática cuantitativa.…”

Section: Antecedentesunclassified

Untitled

Gimeno¹,

Tena²,

Auqué³

et al. 1989

Estud. geol.

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La autoorganización geoquímica es el reflejo de la aplicación de una Ciencia más amplia, la Sinergética, al campo de la Geología. Se trata de una línea de investigación abierta muy recientemente y, por tanto, su planteamiento se encuentra todavía restringido al análisis de relativamente pocos fenómenos. Sin embargo, su estructura operativa y su concepción globalizadora la sitúan dentro de la actual tendencia unificadora de otras ramas de la Ciencia.En este artÍCulo se exponen los antecedentes de los que surge esta teoría y los principios fundamentales en que se basa, haciendo especial hincapié en el concepto de autoalimentación como mecanismo generador de determinados fenómenos, y en las variables y procesos que lo condicionan.Palabras clave: autoorganización groquímiaJ, sinergética, autoalimentaeión, modelización gecquímica. ABSTRACTGeochemical self-organization Introduce a synergetic view in modeling geological processes. It constitutes a new researching approach and so, its statment are restricted to analytical treatment of, relatively, few phenomena. However, the operative structUre and generalized conceptual basis endose this theory in the present unifying drift of Science.In this paper, a review of antecedents in the geochemical self-organization and a general outline of its basic ground are considered. Special emphasis is made in dealing with the feedback concept, as a triggering mechanism oC different phenomena, and in the related variables and processes.Key wonls: geochemical self-organization, synergetic, feed-back, geochemical modeling. IntroducciónLa actual tendencia de la Ciencia hacia la elaboración de teorías unificadoras, resulta todavía utópica en Geología, ya que sus leyes básicas carecen, por lo general, de la formalización matemática capaz de garantizar su fiable generalización.Esta carencia se debe básicamente a tres causas: 1) Los condicionantes espacio-temporales impuestos por el objeto de estudio dificultan extraordinariamente la utilización del método científico; 2) La enorme cantidad de variables que se manejan obliga a la introducción de gran número de hipótesis y supuestos iniciaies de dificil verificación; y 3) La propiedad intrínseca de ser sistemas abiertos y generalmente en desequilibrio hace imprescindible la determinación de las condiciones limitantes y de contorno para su modelización matemática, lo cual no siempre es inmediato.Teniendo en cuenta los puntos anteriores, es lógico que en este momento, y a pesar de las dificultades expuestas, uno de los objetivos primordiales en Geología sea la formulación de leyes básicas generalizadas o generalizables capaces de acomodarse y definir los complejos sistemas incluidos en este campo científico.Este objetivo se ha perseguido en muy diferentes ramas de la Geología utilizando distintos tipos de modelización matemática, pero nuestro interés se centra concretamente en su aplicación a determinados procesos petrogenéticos relacionados con crecimientos cristalinos y recristalizaciones (nódulos y concreciones, cementos bandeados, zonados cri...

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Geochemical self-organization

Cited by 161 publications

References 0 publications

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Effect of mineral reactions on the hydraulic properties of unsaturated soils: Model development and application

Numerical modeling of reaction‐induced cavities in a porous rock

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