Abstract:In situ megascale hydraulic diffusivities (D) of a confined loess aquifer were estimated at various scales (10 ≤ L ≤ 1500 m) by a finite difference model, and laboratory microscale diffusivities of a loess sample by empirical formulas. A scatter plot reveals that D fits to a single power function of L, providing that microscale diffusivities are assigned to L = 1 m and that differences in diffusivity observed between micro-and megascales are assigned to medium heterogeneity appraised by variations in the curva… Show more
“…Results are essential to the macroscopic aquifer composed of porous media without large heterogeneity, such as sandy aquifers containing rich groundwater resources. However, there are many problems associated with the upscaling of aquifers in real-world conditions (Dagan et al, 2013;Pacheco, 2013;Pacheco et al, 2015). Due to the large heterogeneity of natural aquifers, research results may be very different and can not be extrapolated to complex regional aquifer on a large scale.…”
Section: Pce Migration and Sgs Realizationsmentioning
Abstract. Groundwater can be stored abundantly in granulacomposed aquifers with high permeability. The microstructure of granular materials has important effect on the permeability of aquifers and the contaminant migration and remediation in aquifers is also influenced by the characteristics of porous media. In this study, two different microscale arrangements of sand particles are compared to reveal the effects of microstructure on the contaminant migration and remediation. With the help of fractal theory, the mathematical expressions of permeability and entry pressure are conducted to delineate granular materials with regular triangle arrangement (RTA) and square pitch arrangement (SPA) at microscale. Using a sequential Gaussian simulation (SGS) method, a synthetic heterogeneous site contaminated by perchloroethylene (PCE) is then used to investigate the migration and remediation affected by the two different microscale arrangements. PCE is released from an underground storage tank into the aquifer and the surfactant is used to clean up the subsurface contamination. Results suggest that RTA can not only cause more groundwater contamination, but also make remediation become more difficult. The PCE remediation efficiency of 60.01-99.78 % with a mean of 92.52 and 65.53-99.74 % with a mean of 95.83 % is achieved for 200 individual heterogeneous realizations based on the RTA and SPA, respectively, indicating that the cleanup of PCE in aquifer with SPA is significantly easier. This study leads to a new understanding of the microstructures of porous media and demonstrates how microscale arrangements control contaminant migration in aquifers, which is helpful to design successful remediation scheme for underground storage tank spill.
“…Results are essential to the macroscopic aquifer composed of porous media without large heterogeneity, such as sandy aquifers containing rich groundwater resources. However, there are many problems associated with the upscaling of aquifers in real-world conditions (Dagan et al, 2013;Pacheco, 2013;Pacheco et al, 2015). Due to the large heterogeneity of natural aquifers, research results may be very different and can not be extrapolated to complex regional aquifer on a large scale.…”
Section: Pce Migration and Sgs Realizationsmentioning
Abstract. Groundwater can be stored abundantly in granulacomposed aquifers with high permeability. The microstructure of granular materials has important effect on the permeability of aquifers and the contaminant migration and remediation in aquifers is also influenced by the characteristics of porous media. In this study, two different microscale arrangements of sand particles are compared to reveal the effects of microstructure on the contaminant migration and remediation. With the help of fractal theory, the mathematical expressions of permeability and entry pressure are conducted to delineate granular materials with regular triangle arrangement (RTA) and square pitch arrangement (SPA) at microscale. Using a sequential Gaussian simulation (SGS) method, a synthetic heterogeneous site contaminated by perchloroethylene (PCE) is then used to investigate the migration and remediation affected by the two different microscale arrangements. PCE is released from an underground storage tank into the aquifer and the surfactant is used to clean up the subsurface contamination. Results suggest that RTA can not only cause more groundwater contamination, but also make remediation become more difficult. The PCE remediation efficiency of 60.01-99.78 % with a mean of 92.52 and 65.53-99.74 % with a mean of 95.83 % is achieved for 200 individual heterogeneous realizations based on the RTA and SPA, respectively, indicating that the cleanup of PCE in aquifer with SPA is significantly easier. This study leads to a new understanding of the microstructures of porous media and demonstrates how microscale arrangements control contaminant migration in aquifers, which is helpful to design successful remediation scheme for underground storage tank spill.
“…Furthermore, according to the specific problem, considering laws of variation at different scales (small, medium, large) for each parameter can be of interest [25].…”
The importance of a law that, for an assigned porous medium, gives the variability of the hydraulic conductivity with the effective porosity is well known. Commonly this variability is represented by a power law at different scales, especially those of laboratory and field. Often it can be useful to have a scaling law valid for a single scale range, comprising both those of laboratory and field. Therefore investigation about the reliability of the laws representing the scaling behavior in the various intervals to which reference was made could be suitable.The purpose of this study is to provide evidence about the reliability of the scaling laws for laboratory, field and global (laboratory plus field) scaling ranges, verifying consistency with the expected proportionality between hydraulic conductivity and effective porosity for each of these. This verification was carried out using power-type scaling laws to two and four parameters respectively, and performing suitable moving averages of original data sets, in an attempt to reduce the inevitable measurement uncertainties. The experimental results, obtained with reference to the confined aquifer of Montalto Uffugo test field, show that there are no significant differences between the scaling laws considered and highlight the need to reduce the measurement uncertainties, which weigh heavily on the reliability of scaling laws. Keywords: Scaling law; Hydraulic conductivity; Effective porosity; Laboratory measurement, Field measurement. INFLUENCIA DE LA AMPLITUD DEL INTERVALO DE ESCALA EN LA DETERMINACIÓN DE LA CONDUCTIVIDAD HIDRÁULICA Y LA POROSIDAD EFECTIVA. EL CASO DE UN ACUÍFERO POROSA DEL SUR DE ITALIA La importancia de una ley que, para un dado medio poroso, describa la variabilidad de la conductividad hidráulica en función de la porosidad efectiva es bien conocida. Frecuentemente esta variabilidad está representada por una ley de potencia a diferentes escalas, especialmente las de laboratorio y de campo. A menudo es útil tener una ley de escalamiento válida para un cierto rango de escala incluyendo los de laboratorio y campo. Por esta razón, es oportuno investigar la confiabilidad de las leyes que representan este comportamiento de escalamiento en los diferentes intervalos a los cuales típicamente se hace referencia. El propósito de este estudio es proporcionar evidencia sobre la confiabilidad de las leyes de escalamiento para intervalos de escala válidos para laboratorio, campo y globales (laboratorio + campo), verificando la consistencia con la proporcionalidad esperada entre la conductividad hidráulica y la porosidad efectiva para cada uno de estos. Esta verificación se llevó a cabo utilizando leyes de escalamiento de potencia para dos y cuatro parámetros respectivamente, y tratando de reducir las inevitables incertidumbres de medición. Los resultados experimentales obtenidos con referencia al acuífero confinado del campo de prueba Montalto Uffugo, muestran que no hay diferencias significativas entre las leyes de escalamiento consideradas y se destaca la necesidad de reducir las incertidumbres de medición, las cuales tienen un alto peso sobre la fiabilidad de las leyes de escala. Palabras clave: ley de escalamiento; Conductividad hidráulica; porosidad efectiva; mediciones de laboratorio, medición de campo.
“…Results are essential to the macroscopic aquifer composed of porous media without large heterogeneity, such as sandy aquifers containing rich groundwater resources. However, there are many problems associated with the upscaling of aquifers in real-world conditions(Dagan et al, 2013;Pacheco, 2013;Pacheco et al, 2015). Due to the large heterogeneity of natural aquifers, research results may be very different and can not be extrapolated to complex regional aquifer on a large scale.…”
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