Isotopic and chemical considerations in radiocarbon dating of groundwater within the arid Tucson Basin, Arizona.

Persistent Link:
http://hdl.handle.net/10150/191002
Title:
Isotopic and chemical considerations in radiocarbon dating of groundwater within the arid Tucson Basin, Arizona.
Author:
Wallick, Ed.
Issue Date:
1973
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
A chemical-isotopic equilibrium model was developed for adjustment of radiocarbon ages of groundwater from the arid Tucson basin for dilution of the initial groundwater C-14 activity by the solution of soil calcite having a C-14 of 25 ± 19% modern. Input to the model consisted of the laboratory chemical analyses for Ca⁺⁺, Mg⁺⁺, Na⁺, H₄SiO₄, SO₄⁼, HCO₃⁻, CO₃⁼, NO₃⁻, and pH, and δ C-13 for the total dissolved carbon in the groundwater. Output consisted of the equilibrium chemical composition of the groundwater, the ratio of soil CO₂ derived to total dissolved carbon, Q, and δ C-13 of total dissolved carbon, H₂CO₃, HCO₃⁻, and CO₃⁼, and δ C-13 for the soil CO₂ and calcite that initially dissolved in the surface water as it equilibrated with soil minerals. Radiocarbon age of the groundwater is computed from the equation T = 8270 ln [(Q + (1-Q) A(CaCO₃)/Am] where T is the age in years before A.D. 1950, A(CaCO₃) is the soil calcite activity and Am is the measured activity for the dissolved carbonate in the groundwater, both with respect to modern wood. The validity of the model was tested by comparing the predicted values for δ C-13 (CO₂), δ C-13 (CaCO₃) with measured values for samples from the Tucson basin. δ C-13 (CO 2) calculated = (-12.9 ± 1.9) per mil PDB. δ C-13 (CO2) measured = (-15.1 ± 2.8) per mil PDB. δ C-13 (CaCO3) calculated = (-3.9 ± 1.7) per nil PDB. δ C-13 (CaCO3) measured = (-3.6 ± 1.7) per mil PDB. On the basis of these results, the model adequately describes the natural system and may prove useful in future radiocarbon dating work in desert regions.
Type:
Dissertation-Reproduction (electronic); text
Keywords:
Hydrology.; Groundwater -- Arizona -- Tucson Basin.; Radioisotopes in hydrology.
Degree Name:
Ph. D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Long, Austin

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleIsotopic and chemical considerations in radiocarbon dating of groundwater within the arid Tucson Basin, Arizona.en_US
dc.creatorWallick, Ed.en_US
dc.contributor.authorWallick, Ed.en_US
dc.date.issued1973en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractA chemical-isotopic equilibrium model was developed for adjustment of radiocarbon ages of groundwater from the arid Tucson basin for dilution of the initial groundwater C-14 activity by the solution of soil calcite having a C-14 of 25 ± 19% modern. Input to the model consisted of the laboratory chemical analyses for Ca⁺⁺, Mg⁺⁺, Na⁺, H₄SiO₄, SO₄⁼, HCO₃⁻, CO₃⁼, NO₃⁻, and pH, and δ C-13 for the total dissolved carbon in the groundwater. Output consisted of the equilibrium chemical composition of the groundwater, the ratio of soil CO₂ derived to total dissolved carbon, Q, and δ C-13 of total dissolved carbon, H₂CO₃, HCO₃⁻, and CO₃⁼, and δ C-13 for the soil CO₂ and calcite that initially dissolved in the surface water as it equilibrated with soil minerals. Radiocarbon age of the groundwater is computed from the equation T = 8270 ln [(Q + (1-Q) A(CaCO₃)/Am] where T is the age in years before A.D. 1950, A(CaCO₃) is the soil calcite activity and Am is the measured activity for the dissolved carbonate in the groundwater, both with respect to modern wood. The validity of the model was tested by comparing the predicted values for δ C-13 (CO₂), δ C-13 (CaCO₃) with measured values for samples from the Tucson basin. δ C-13 (CO 2) calculated = (-12.9 ± 1.9) per mil PDB. δ C-13 (CO2) measured = (-15.1 ± 2.8) per mil PDB. δ C-13 (CaCO3) calculated = (-3.9 ± 1.7) per nil PDB. δ C-13 (CaCO3) measured = (-3.6 ± 1.7) per mil PDB. On the basis of these results, the model adequately describes the natural system and may prove useful in future radiocarbon dating work in desert regions.en_US
dc.description.notehydrology collectionen_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.typetexten_US
dc.subjectHydrology.en_US
dc.subjectGroundwater -- Arizona -- Tucson Basin.en_US
dc.subjectRadioisotopes in hydrology.en_US
thesis.degree.namePh. D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairLong, Austinen_US
dc.contributor.committeememberSimpson, Eugene S.en_US
dc.contributor.committeememberDamon, Paulen_US
dc.contributor.committeememberDutt, Gordon R.en_US
dc.identifier.oclc213395789en_US
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