Use of U-isotopes in exploring groundwater flow and inter-aquifer leakage in the south-western margin of the Great Artesian Basin and Arckaringa Basin, central Australia

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dc.contributor.authorPriestley, SCen_AU
dc.contributor.authorPayne, TEen_AU
dc.contributor.authorHarrison, JJen_AU
dc.contributor.authorPost, VEAen_AU
dc.contributor.authorShand, Pen_AU
dc.contributor.authorLove, AJen_AU
dc.contributor.authorWohling, DLen_AU
dc.date.accessioned2023-01-11T23:46:48Zen_AU
dc.date.available2023-01-11T23:46:48Zen_AU
dc.date.issued2018-11en_AU
dc.date.statistics2022-11-02en_AU
dc.descriptionThis is an open access article under the CC BY-NC-ND license.en_AU
dc.description.abstractThe distribution of uranium isotopes (238U and 234U) in groundwaters of the south-western margin of the Great Artesian Basin (GAB), Australia, and underlying Arckaringa Basin were examined using groundwater samples and a sequential extraction of aquifer sediments. Rock weathering, the geochemical environment and α-recoil of daughter products control the 238U and 234U isotope distributions giving rise to large spatial variations. Generally, the shallowest aquifer (J aquifer) contains groundwater with higher 238U activity concentrations and 234U/238U activity ratios close to secular equilibrium. However, the source input of uranium is spatially variable as intermittent recharge from ephemeral rivers passes through rocks that have already undergone extensive weathering and contain low 238U activity concentrations. Other locations in the J aquifer that receive little or no recharge contain higher 238U activity concentrations because uranium from localised uranium-rich rocks have been leached into solution and the geochemical environment allows the uranium to be kept in solution. The geochemical conditions of the deeper aquifers generally result in lower 238U activity concentrations in the groundwater accompanied by higher 234U/238U activity ratios. The sequential extraction of aquifer sediments showed that α-recoil of 234U from the solid mineral phases into the groundwater, rather than dissolution of, or exchange with the groundwater accessible minerals in the aquifer, caused enrichment of groundwater 234U/238U activity ratios in the Boorthanna Formation. Decay of 238U in uranium-rich coatings on J aquifer sediments caused resistant phase 234U/238U activity ratio enrichment. The groundwater 234U/238U activity ratio is dependent on groundwater residence time or flow rate, depending on the flow path trajectory. Thus, uranium isotope variations confirmed earlier groundwater flow interpretations based on other tracers; however, spatial heterogeneity, and the lack of clear regional correlations, made it difficult to identify recharge and inter-aquifer leakage. Crown Copyright © 2018 Published by Elsevier Ltden_AU
dc.description.sponsorshipThis study and paper were funded by the Government of South Australia's Department of Environment, Water and Natural Resources (DEWNR), Australia under its Bioregional Assessment Program on the Arckaringa Basin, and AINSE Ltd (Award PGRA; ALNSTU11404).en_AU
dc.identifier.citationPriestley, S. C., Payne, T. E., Harrison, J. J., Post, V. E. A., Shand, P., Love, A. J., & Wohling, D. L. (2018). Use of U-isotopes in exploring groundwater flow and inter-aquifer leakage in the south-western margin of the Great Artesian Basin and Arckaringa Basin, central Australia. Applied Geochemistry, 98, 331-344. doi:10.1016/j.apgeochem.2018.10.002en_AU
dc.identifier.issn0883-2927en_AU
dc.identifier.journaltitleApplied Geochemistryen_AU
dc.identifier.pagination331-344en_AU
dc.identifier.urihttps://doi.org/10.1016/j.apgeochem.2018.10.002en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/14310en_AU
dc.identifier.volume98en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectUranium isotopesen_AU
dc.subjectGround wateren_AU
dc.subjectAquifersen_AU
dc.subjectArtesian basinsen_AU
dc.subjectGeochemistryen_AU
dc.subjectAustraliaen_AU
dc.titleUse of U-isotopes in exploring groundwater flow and inter-aquifer leakage in the south-western margin of the Great Artesian Basin and Arckaringa Basin, central Australiaen_AU
dc.typeJournal Articleen_AU
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