Dating Groundwater

Davis, Stanley N.; Bentley, Harold W.

doi:10.1021/bk-1982-0176.ch011

Cited by 26 publications

(5 citation statements)

References 42 publications

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“…For aquifers for which the chemistry is well understood, interpreted carbon-14 ages are within ±20 percent of the actual value (Davis and Bentley, 1982). In areas where present-day recharge may not reflect the composition of recharge for older groundwater, the greatest source of uncertainty in interpreting carbon-14 data is in determining the initial chemistry, carbon-14 activity, and δ 13 C composition of the recharge water.…”

Section: Limitations Of Carbon-14 Interpretationsmentioning

confidence: 92%

Hydrogeologic controls and geochemical indicators of groundwater movement in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California

Teague¹,

Izbicki²,

Borchers³

et al. 2019

Scientific Investigations Report

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Section: Limitations Of Carbon-14 Interpretationsmentioning

confidence: 92%

Hydrogeologic controls and geochemical indicators of groundwater movement in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California

Teague¹,

Izbicki²,

Borchers³

et al. 2019

Scientific Investigations Report

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“…Although methods exist for dating old groundwater (e.g. excess 4He generated by decay of uranium and thorium, 234U/238U disequilibrium dating, and I4C and 36Cl dating), these all suffer from potentially severe problems in extracting and/or interpreting the data (Davis and Bentley 1980). Most of the present approaches are strongly model-dependent so that correct age determinations presuppose valid geochemical models of the aquifer.…”

Section: Groundwater Dating (''Kr)mentioning

confidence: 99%

Method for counting noble gas atoms with isotopic selectivity

et al. 1985

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A method has been developed for direct counting of noble gas atoms and has been demonstrated for selected isotopes of krypton. In principle, a few atoms of the noble gases argon, krypton, xenon and radon can now be counted with isotopic selectivity whether stable or radioactive. A concept was originated in which a laser method would be used to count noble gas atoms of a particular isotope that are moving freely in an enclosure. As the concept developed, a parallel with Maxwell's sorting demon became quite obvious since our plan was to sort out only atoms of a given type (2 selection), e.g. krypton atoms, from any other atom in the enclosure and then to sort the atom by isotope ( A selection) before removing the atom from the gas compartment. The plan was to count each atom as it was stored in a target until all atoms were counted. Thus, our realisation of Maxwell's demon can remember each atom as it is counted until all of them have been sorted out from background atoms. Development of several special components was required to carry out these objectives.Resonance ionisation spectroscopy ( RIS) is quantum-state selective, yet an efficient method for the ionisation of free atoms. However, to accomplish this Z-selective ionisation for the noble gases requires lasers in the far vacuum ultraviolet (vuv) region. Extensive theoretical work was done to guide experiments for vuv generation with lasers. This was especially important for generating 116.5 nm radiation for the first excitation step in the RIS of krypton. The laser experiments themselves led to the development of a laser system, driven by a Nd : YAG pump, that could produce the necessary 116.5 nm radiation at a 10 Hz rate with about 500 nJ per pulse. It should be somewhat easier to produce the radiation needed for RIS of argon. Very effective schemes for xenon have already been demonstrated.In spite of the considerable advances made for vuv generation using lasers, the effective volume for ionisation of krypton in a single laser pulse remained below 10-3cm3. Thus, nearly lo7 laser pulses would be required to find all of the atoms

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“…The concept of "groundwater age" has been described in several studies (Davis and Bentley 1982;Sanford 2011;IAEA 2013) as the average age of the water molecules in a sample or the average residence time of those molecules in the subsoil (Bethke and Johnson 2008). McCallum et al (2015) provide a detailed description of the terms that are commonly used for groundwater age.…”

Section: Introductionmentioning

confidence: 99%

Characterization of the functioning of the Motril–Salobreña coastal aquifer (SE Spain) through the use of environmental tracers

et al. 2020

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Environmental tracers were used to characterize the origin and determine the age of the groundwater in the Motril-Salobreña aquifer (south-eastern Spain). The stable isotope concentrations (δ 18 O/δ 2 H), compared to the results obtained in previous studies, indicate that most of the recharge during the sampling period was from irrigation return flow and the carbonate Escalate aquifer. The combined dating of 3 H, 3 He, 4 He, 85 Kr, and 39 Ar allowed establishing the presence of modern water throughout the aquifer, although with different mixing percentages. Thus, there is a large zone characterized by a fluvial domain with 100% young waters (< 5 years) due to the circulation of water through an area of high permeability sediments. In the discharge zone of the aquifer, older water is located (age > 170 years), and the percentage of young water is reduced (22.5%). This is explained by the greater distance that groundwater travels (aquifer thicknesses is over 250 m) and the lower permeability of the aquifer in the deeper sectors.

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Dating Groundwater

Cited by 26 publications

References 42 publications

Hydrogeologic controls and geochemical indicators of groundwater movement in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California

Hydrogeologic controls and geochemical indicators of groundwater movement in the Niles Cone and southern East Bay Plain groundwater subbasins, Alameda County, California

Method for counting noble gas atoms with isotopic selectivity

Characterization of the functioning of the Motril–Salobreña coastal aquifer (SE Spain) through the use of environmental tracers

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