Evaluation of the potential for dissolved oxygen ingress into deep sedimentary basins during a glaciation event

Geochemical conditions in intracratonic sedimentary basins are currently reducing, even at relatively shallow depths. However, during glaciation-deglaciation events, glacial meltwater production may result in enhanced recharge (Bea et al., 2011; and Bea et al., 2016) potentially having high concentrations of dissolved oxygen (O2). In this study, the reactive transport code Par-MIN3PTHCm was used to perform an informed, illustrative set of simulations assessing the depth of penetration of low salinity, O2-rich, subglacial recharge. Simulation results indicate that the large-scale basin hydrostratigraphy, in combination with the presence of dense brines at depth, results in low groundwater velocities during glacial meltwater infiltration, restricting the vertical ingress of dilute recharge waters. Furthermore, several geochemical attenuation mechanisms exist for O2, which is consumed by reactions with reduced mineral phases and solid organic matter (SOM). The modeling showed that effective oxidative mineral dissolution rates and SOMoxidation rates between 5 × 10-15 and 6 × 10-13 mol dm-3 bulk s-1 were sufficient to restrict the depth of O2 ingress to less than 200m.These effective rates are low and thus conservative, in comparison to rates reported in the literature. Additional simulations with more realistic, yet still conservative, parameters reaffirm the limited ability for O2 to penetrate into sedimentary basin rocks during a glaciation-deglaciation event.Fil: Bea, Sergio Andrés. Universidad Nacional del Centro de la Provincia de Buenos Aires. Rectorado. Instituto de Hidrología de Llanuras - Sede Tandil. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto de Hidrología de Llanuras - Sede Tandil; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Su, Danyang. University of British Columbia; CanadáFil: Mayer, Klaus Ulrich. University of British Columbia; CanadáFil: MacQuarrie, T. B.. University of New Brunswick; Canad

Aplicación de transporte reactivo al estudio de la movilidad del arsénico en la zona no saturada

Es ampliamente aceptado que el As contenido en las aguas subterráneas de la llanura Pampeana proviene de los propios sedimentos loéssicos que constituyen los acuíferos. Sin embargo, investigaciones recientes confirman la presencia de concentraciones de As relativamente anómalas dentro de la zona no saturada (ZNS), que podrían ser movilizadas hacia el acuífero por medio de las aguas de recarga, o por las variaciones del nivel freático. Sin embargo, comprender la dinámica del As en la ZNS es compleja ya que los principales procesos que controlan la movilidad del As (adsorción/desorción, la co-precipitación/co-disolución y las reacciones redox), están acoplados con los de flujo matricial y preferencial, la evapotranspiración, la infiltración y recarga. La modelación del transporte reactivo surge como una herramienta que permite estudiar en forma acoplada todos estos procesos. Este trabajo propone aplicar esta metodología para capturar la dinámica del As, y comprender los procesos que controlan su retención o liberación. La validación del modelo de flujo se realizó mediante información de tensiómetros, sondas de humedad y piezometría de una parcela experimental. Por su parte, el modelo hidroquímico se validó utilizando análisis químicos del agua poral de la ZNS. Los resultados de la modelación del transporte reactivo indican que la dinámica del nivel de las aguas subterráneas, y la competencia del sistema carbono por los sitios de adsorción sobre los óxidos/hidróxidos de hierro ejercerían el principal control sobre la disponibilidad del As en la ZNS.Publicado en: García, R. y Mariño, E. (Eds): Calidad del Agua Subterránea: Actas IX Congreso Argentino de Hidrogeología y VII Seminario Hispano-Latinoamericano Sobre Temas Actuales de la Hidrología Subterránea. Editorial Científica Universitaria UNCA. ISBN 978-987-661-222-

A process-based numerical approach to estimate forest groundwater consumption in flatland petrocalcic soils

Grasslands are extensively distributed in flatland areas around the world such as the Pampas in South-America. It is one of the most economically productive landscapes and, as in other regions, they are being replaced by forests at increasing rates. Soil salinization emerges as a negative consequence associated with water deficit and forest groundwater consumption (~250-500 mm/yr, in this region). Assessment of forest groundwater consumption is crucial in risk evaluation of soil salinization on flatland environments. For this aim, numerical modeling based on physical/biological processes and atmospheric boundary conditions was successfully applied in monitored grassland and afforested plots. Modeling results suggested a partial hydraulic disconnection between forest and phreatic aquifer due to the presence of petrocalcic horizons. Forest transpiration estimates were approximately ~13% of total groundwater usage. Forest water consumption was then restricted to that soil portions of above the petrocalcic horizons. Estimated forest transpiration rates (~723 mm/yr) were similar to and even exceed those reported in salinized sites with similar features. However, the risk of salinization of these soils was unlikely, because forest transpiration was restricted to the upper soil portions filled with fresh rain water. The petrocalcic horizon retained water and prevented both deep drainage and indirectly, soil salinization.Fil: Mujica, Claudio Ramon. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff"; ArgentinaFil: Milione, Germán Marcelo. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff"; ArgentinaFil: Bea, Sergio Andrés. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff"; ArgentinaFil: Gyenge, Javier Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce; Argentin

Modeling the influence of MgSO4 invariant points on multiphase reactive transport process during saline soil evaporation

In the present work, we modeled a laboratory experiment where a sand column saturated with a MgSO4 solution is subject to evaporation. We used a compositional formulation capable of representing the effect of geochemistry on flow and transport for concentrated solutions under extreme dry conditions. The model accounts for the water sink/sources terms due to hydrated mineral dissolution/precipitation and the occurrence of invariant points, which prescribe the water activity. Results show that the occurrence of the invariant points at the top of the domain could affect the vapor flux at the column top and salt precipitation along the column. In fact, the invariant points occurrence could explain the spatial fluctuation on the salt precipitates formation. Results also suggest that the complex hydrochemical interactions occurring during soil salinization, including osmotic effects, are crucial not only to understand the salt precipitation, but also the evaporation rate.Fil: Gamazo, P.. Universidad de la Republica; Uruguay. Universidad Politecnica de Catalunya; EspañaFil: Saaltink, M. W.. Universidad Politecnica de Catalunya; EspañaFil: Carrera, J.. Instituto de Diagnóstico Ambiental y Estudios del Agua; EspañaFil: Slooten, L. J.. Instituto de Diagnóstico Ambiental y Estudios del Agua; EspañaFil: Bea, Sergio Andrés. Universidad Nacional del Centro de la Provincia de Buenos Aires. Rectorado. Instituto de Hidrología de Llanuras - Sede Azul; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil; ArgentinaFil: Gran, M.. Universidad Politecnica de Catalunya; Españ

PROOST: object-oriented approach to multiphase reactive transport modeling in porous media

Reactive transport modeling involves solving several nonlinear coupled phenomena, among them, the flow of fluid phases, the transport of chemical species and energy, and chemical reactions. There are different ways to consider this coupling that might be more or less suitable depending on the nature of the problem to be solved. In this paper we acknowledge the importance of flexibility on reactive transport codes and how object-oriented programming can facilitate this feature. We present PROOST, an object-oriented code that allows solving reactive transport problems considering different coupling approaches. The code main classes and their interactions are presented. PROOST performance is illustrated by the resolution of a multiphase reactive transport problem where geochemistry affects hydrodynamic processes.Postprint (author's final draft

Modelación del Transporte Reactivo en el Salar del Pipanaco, Catamarca : Evaluación de hipotéticos escenarios de contaminación minera

El Salar del Pipanaco es una cuenca endorreica dentro de las Sierras Pampeanas de la Provincia de Catamarca. Sus recursos hídricos subterráneos están fuertemente comprometidos por importantes actividades agropecuarias dentro de la cuenca como mineras en cuencas vecinas que alimentan sus aguas subterráneas. La presencia de diques de colas mineras, y antecedentes de fugas, producto de años de explotación sobre las áreas de recarga de las aguas subterráneas, hace imperioso evaluar el alcance del impacto de hipotéticos vertidos mineros. La modelación del transporte reactivo ha sido utilizada para evaluar la migración de metales pesados (p.ej., Zn, Pb, etc.), y determinar aquellos parámetros fisicoquímicos que controlarían su movilidad y la capacidad de las aguas subterráneas para neutralizar estos vertidos ácidos. La alta alcalinidad de las mismas conjuntamente con la presencia de carbonatos jugarían un papel clave para controlar el pH, y por extensión la migración de los metales, al incrementar su retardo.Salar del Pipanaco is an endorheic sedimentary basin emplaced within the Sierras Pampeanas of the Catamarca Province. Its groundwater resources are strongly committed by important economic activities developed into the basin (e.g., the olive on the Pomán Valley along the Western flank of Sierras de Ambato), as well as other economic activities developed on the watersheds that recharge its groundwater system (mining). However, the presence of mining tailings and evidences of tailings leakage on the recharge areas make it important to evaluate both the heavy metals transport through the shallow aquifer (e.g., Zn, Pb), and those parameters that may control their mobility and the capacity of the groundwater to neutralize acid sources. The high alkalinity of the groundwater together with the mineral carbonate contents in the aquifer may play an important role to control the pH and so the metals migration downward.Universidad Nacional de La Plat

Influence of soil texture, climate and vegetation cover on secondary soil salinization in Pampas plains, South America

Land-use change from herbaceous to woody cover -or vice versa- largely affects water fluxes, which in turn can mobilize existing salts dissolved in the soil, and thereby negatively affect soil and/or water quality and site productivity. Secondary salinization was observed after afforestation at the Northern and Eastern subregions of the Río de la Plata Grassland. Based on this, our objective was to determine the degree of association between the climatic (e.g. water balance), edaphic (e.g. texture, presence of petrocalcic horizons) and biological factors (age of plantation, stand density and stand basal area) with the secondary salinization processes under the particular environmental conditions of the Austral Pampas. The lowest electrical conductivity (EC, µS.cm-1) values were found in sites with sandy-textured soils and negative water balance, regardless of tree canopy cover. When EC differences did occur between land uses of the same site (50% of the sites), in most cases - but not in all of them - the highest EC was measured under tree cover. When salinization was significant, no pattern was observed in the salt distribution along the soil profile. An increase of EC was associated with the oldest-unmanaged plantations, with mean age of 40 years, a period much longer than the productive rotation recommended. Under similar edaphic conditions where salinization was observed (i.e. clayed soils, with naturally high salt level), salinization was not significant in relatively young plantations (Fil: Milione, Germán Marcelo. Universidad Nacional del Centro de la Provincia de Buenos Aires; Argentina. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff"; ArgentinaFil: Mujica, Claudio Ramon. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas; Argentina. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff"; ArgentinaFil: Dominguez Daguer, Diego Rafael. Ministerio de Agricultura, Ganadería, Pesca y Alimento; ArgentinaFil: Bea, Sergio Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión de Investigaciones Científicas de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff". - Universidad Nacional del Centro de la Provincia de Buenos Aires. Instituto de Hidrología de Llanuras "Dr. Eduardo Jorge Usunoff"; ArgentinaFil: Fernandez, Maria Elena. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible - Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; ArgentinaFil: Gyenge, Javier Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible - Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; Argentin

Long-term fatigue and its probability of failure applied to dental implants

It is well known that dental implants have a high success rate but even so, there are a lot of factors that can cause dental implants failure. Fatigue is very sensitive to many variables involved in this phenomenon. This paper takes a close look at fatigue analysis and explains a new method to study fatigue from a probabilistic point of view, based on a cumulative damage model and probabilistic finite elements, with the goal of obtaining the expected life and the probability of failure. Two different dental implants were analysed. The model simulated a load of 178¿N applied with an angle of 0°, 15°, and 20° and a force of 489¿N with the same angles. Von Mises stress distribution was evaluated and once the methodology proposed here was used, the statistic of the fatigue life and the probability cumulative function were obtained. This function allows us to relate each cycle life with its probability of failure. Cylindrical implant has a worst behaviour under the same loading force compared to the conical implant analysed here. Methodology employed in the present study provides very accuracy results because all possible uncertainties have been taken in mind from the beginning