Implications of the distribution of δD in pore waters for groundwater flow and the timing of geologic events in a thick aquitard system

Hendry, M. Jim; Wassenaar, Leonard I.

doi:10.1029/1999wr900046

Cited by 125 publications

(192 citation statements)

References 28 publications

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“…The range of hydraulic conductivity values is based on values mentioned in literature for different clays. Hendry and Wassenaar (1999) report hydraulic conductivity values of the order of 10 -11 m/s and 10 -12 m/s for a clay-rich till and a massive, plastic clay respectively, Wemaere et al (2002) measured hydraulic conductivity values of 10 -10 m/s to 10 -12 m/s in Boom Clay samples and Keller et al (1989) present laboratory hydraulic conductivity values of a clayey till between 10 -11 m/s and 4.5 10 -11 m/s. The hydraulic conductivity values for the calculations are therefore between 10 -12 and 10 -10 m/s The hydraulic head gradient is taken as 0.02, which is of the same order as reported hydraulic gradients in low permeability environments of 0.014 (Hendry and Wassenaar 1999) and 0.02 (Mallants et al 2001).…”

Section: The Most General Form Of the Three-dimensional Advection-dismentioning

confidence: 99%

Review of the use of Péclet numbers to determine the relative importance of advection and diffusion in low permeability environments

2004

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In low permeability environments, transport by advection is often neglected based on a Péclet number criterion. Such a criterion usually states that if the Péclet number (Pe) is much smaller than 1, diffusion dominates over advection and transport may be modeled considering diffusion only. Unfortunately, up to 10 different Péclet number definitions exist and for a particular case these different definitions lead to very diverse Péclet number values, differing several orders of magnitude from each other. In this paper, the different Péclet number definitions are therefore evaluated on their ability to determine the relative importance of transport by advection and by diffusion in low permeability environments. This is done by comparing the results of the analytical solution for pure diffusion with the analytical solution for diffusion, advection and dispersion for a large number of different input parameter values. The relation between the different Péclet numbers and the difference between the calculated concentration considering diffusion only and the calculated concentration considering both diffusion and advection is studied. These calculations show that some Péclet number definitions are not well suited to decide whether advection may be neglected in low permeability media. Keywords Solute transport -Analytical solutions -Low permeability units -DiffusionResumen Frecuentemente se descuida el transporte por avección en ambientes de baja permeabilidad sobre la base del criterio del número de Péclet. Dicho criterio usualmente sostiene que si el número de Péclet (Pe) es mucho menor a 1, la difusión domina sobre la avección y es posible modelar el transporte considerando la difusión únicamente. Desafortunadamente existen 10 definiciones diferentes del número de Péclet y para un caso en particular estas diferentes definiciones conducen a valores de número de Péclet muy diversos los cuales difieren entre sí en varias magnitudes. Por lo tanto, en este artículo se evalúan las diferentes definiciones en base a su habilidad para determinar la importancia relativa del transporte por avección y difusión en ambientes de baja permeabilidad. Esto se lleva a cabo mediante la comparación de los resultados de la solución analítica para difusión pura con los de la solución analítica por difusión, avección y dispersión para un número amplio de diferentes valores como parámetro. Se ha estudiado la relación entre los diferentes números de Péclet y las diferencias entre la concentración calculada considerando difusión únicamente y considerando tanto difusión como avección. Estos cálculos muestran que algunas de las definiciones de los números de Péclet no son muy apropiadas par decidir si se puede descuidar la avección en medios de baja permeabilidad.Résumé Dans les milieux à faible perméabilité, le transport par advection est souvent négligeable lorsqu on se base sur le critère du nombre de Péclet. Un tel critère suggère habituellement que pour un nombre de Péclet beaucoup plus petit que 1, la diffusion domine sur l advect...

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Section: The Most General Form Of the Three-dimensional Advection-dismentioning

confidence: 99%

Review of the use of Péclet numbers to determine the relative importance of advection and diffusion in low permeability environments

2004

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“…Also, the till aquitard consists of only one geological unit, the Battleford Formation. The aquitard is also well characterized at the site (Hendry and Wassenaar, 1999). The site includes an instrumented peizometer well cluster, and is the subject of ongoing geochemical and hydrogeological investigations.…”

Section: Study Sitementioning

confidence: 99%

Azimuthal Resistivity to Characterize Fractures in a Glacial Till

Boris¹,

Merriam²

2002

Symposium on the Application of Geophysics to Engineering and Environmental Problems 2002

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Azimuthal resistivity was used to characterize fractures in a glacial till at the King site, near Birsay SK. The King site is a hydrogeological test site where the presence of fractures has been identified, but the fracture orientation was not previously known.Preliminary azimuthal resistivity surveys indicated that the site was electrically heterogeneous. There was no interpretable anisotropy in the azimuthal resistivity data. A revised methodology was developed where the effects of heterogeneity could be removed from the azimuthal resistivity data. A detailed 3D, isotropic, geoelectric model was developed for the site. This model was used to predict the azimuthal resistivity observations from an isotropic, heterogeneous earth. These predictions were removed from the observations, leaving the anisotropy. The process resulted in an interpretable anisotropy over portions of the site where the variations in resistivity varied by approximately a factor of two. However the process did not remove the heterogeneity from portions of the site with larger resistivity contrasts.

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“…18 O, δD, Cl -) in aquitards was shown to be dominated by molecular diffusion (Remenda et al, 1996;Guerrero et al, 1997;Hendry and Wassenaar, 1999). As pore water is retained for long periods within aquitards, its composition would be influenced by diagenetic processes (e.g., precipitation, adsorption, sulfide formation, remobilization, and biological degradation or uptake), causing the concentrations of chemical species in pore water to differ from free overlying water (Sacchi et al, 2001).…”

Section: Oxygen-18 (mentioning

confidence: 99%

“…Although aquitards play an important role in environment, geology, and hydrogeology, few studies have focused on the transport and geochemical reactions controlling solute concentrations in aquitards. Far less is presently known about aquitards than that of the behavior of solutes in aquifers (Hendry and Wassenaar, 2004;Timms and Hendry, 2008).Unlike transport of solutes in aquifers, which is dominated by advection, the transport of conservative tracers (e.g., δ18 O, δD, Cl -) in aquitards was shown to be dominated by molecular diffusion (Remenda et al, 1996;Guerrero et al, 1997;Hendry and Wassenaar, 1999). As pore water is retained for long periods within aquitards, its composition would be influenced by diagenetic processes (e.g., precipitation, adsorption, sulfide formation, remobilization, and biological degradation or uptake), causing the concentrations of chemical species in pore water to differ from free overlying water (Sacchi et al, 2001).…”

mentioning

confidence: 99%

Geochemical signature of aquitard pore water and its paleo-environment implications in Caofeidian Harbor, China

Liang

Jin

et al. 2013

Geochem. J.

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Oxygen-18 (18 O), deuterium (D), and chemical patterns were determined in pore water samples extracted from 100-m depth in Caofeidian Harbor, China. The stable isotopic composition indicates that aquitard pore water was of meteoric origin and was basically not influenced by evaporation. Seawater diffusion was identified as the main influence on the isotope signature of pore water, according to the δ 18 O profile and positive correlation between δ 18 O and Cl -. The chemistry of aquitard pore water is characterized by high total dissolved solids (TDS) decreasing with depth, ranging from 26.89 to 7.26 g/L. The same trend was observed for Cl -, Na + , and Mg 2+ , as influenced by seawater. However, the typical ion ratios (i.e., Cl/Br, Sr/Ba) of pore water change significantly in different sedimentary facies along the study profile due to the long-term reaction between pore water and sediment, further supporting the finding that pore water was not replaced by modern water or seawater. Therefore, during long-term aquitard residence, the chemical composition of pore water would be influenced by other processes such as reduction of sulfates and cation exchange. The rare earth elements (REEs) of pore water are mainly affected by water-rock interaction. The shale-normalized REE fractionation patterns display enrichment of heavy REEs (HREE) relative to light REEs (LREE) and even greater fractionation degree in marine sediment pore waters (as larger La/Yb NASC ). The relative reduction environment in the aquitard and preferential mobilization of Eu 2+ in the water-rock interaction lead to the development of positive Eu anomalies (1.13 < (Eu/Eu*) NASC < 1.98) and slightly positive Ce anomalies (-0.13 < (Ce/Ce*) NASC < 0.35).Keywords: pore water, aquitard, origin, geochemistry, China of aquitard pore water flowing into adjacent aquifers (Lee and Byrne, 1992;Guo et al., 1995). Although aquitards play an important role in environment, geology, and hydrogeology, few studies have focused on the transport and geochemical reactions controlling solute concentrations in aquitards. Far less is presently known about aquitards than that of the behavior of solutes in aquifers (Hendry and Wassenaar, 2004;Timms and Hendry, 2008).Unlike transport of solutes in aquifers, which is dominated by advection, the transport of conservative tracers (e.g., δ18 O, δD, Cl -) in aquitards was shown to be dominated by molecular diffusion (Remenda et al., 1996;Guerrero et al., 1997;Hendry and Wassenaar, 1999). As pore water is retained for long periods within aquitards, its composition would be influenced by diagenetic processes (e.g., precipitation, adsorption, sulfide formation, remobilization, and biological degradation or uptake), causing the concentrations of chemical species in pore water to differ from free overlying water (Sacchi et al., 2001). Based on the weaker hydrodynamic condition and specific chemical composition, together with the stable isotope information (e.g., δ18 O, δD, and δ 13 C), aquitard pore water has been used in studies of gro...

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Implications of the distribution of δD in pore waters for groundwater flow and the timing of geologic events in a thick aquitard system

Cited by 125 publications

References 28 publications

Review of the use of Péclet numbers to determine the relative importance of advection and diffusion in low permeability environments

Review of the use of Péclet numbers to determine the relative importance of advection and diffusion in low permeability environments

Azimuthal Resistivity to Characterize Fractures in a Glacial Till

Geochemical signature of aquitard pore water and its paleo-environment implications in Caofeidian Harbor, China

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