Lithium and strontium isotope dynamics in a carbonate island aquifer, Rottnest Island, Western Australia

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dc.contributor.authorMartin, ANen_AU
dc.contributor.authorMeredith, KTen_AU
dc.contributor.authorNorman, MDen_AU
dc.contributor.authorBryan, Een_AU
dc.contributor.authorBaker, AAen_AU
dc.date.accessioned2022-11-25T04:20:57Zen_AU
dc.date.available2022-11-25T04:20:57Zen_AU
dc.date.issued2020-05-01en_AU
dc.date.statistics2022-11-25en_AU
dc.description.abstractWater-rock interactions in aquifer systems are a key control on water quality but remain poorly understood. Lithium (Li) isotopes are useful for understanding water-rock interactions, but there are few data available for groundwater aquifers. Here we present a Li isotope dataset for rainfall and groundwater samples from a carbonate island aquifer system: Rottnest Island, Western Australia. This dataset was complemented by strontium (Sr) isotope and major and trace element data for groundwaters, and leaching experiments on bedrock samples. The δ7Li values and 87Sr/86Sr ratios of fresh groundwaters ranged from +23 to +36‰ and 0.709167 to 0.709198, respectively. Mass balance calculations indicated that silicate weathering supplied ~60 and 70% of dissolved Li and Sr in fresh groundwaters, respectively, with the remainder provided by atmospheric input, and carbonate weathering; for major cations, the majority of calcium and sodium (Na) are supplied by carbonate weathering and atmospheric input, respectively. The estimated low proportion of Sr produced by carbonate weathering was surprising in a carbonate aquifer, and the 87Sr/86Sr data indicated that the silicate Sr source had low Rb/Sr and 87Sr/86Sr ratios. There was an increase in the maximum δ7Li values in fresh groundwaters (+36‰) relative to the maximum value in rainfall and seawater (ca. +31‰). As clay minerals are undersaturated in fresh groundwaters, this increase may be explained by Li isotope fractionation associated with ion-exchange reactions on clays and iron(oxy)hydroxides. In the more saline groundwaters, the minimum δ7Li values decreased with depth to +14.5‰, suggesting increased silicate mineral dissolution in the deeper aquifer. These results reveal the importance of water-rock interactions in a coastal carbonate aquifer, and demonstrate the usefulness of Li isotopes for tracing weathering reactions in an environmental setting where traditional weathering tracers, such as sodium and Sr isotopes, are less appropriate. Crown Copyright © 2020 Published by Elsevier B.Ven_AU
dc.description.sponsorshipThis work was supported Australian Research Council Linkage grant LP150100144.en_AU
dc.identifier.articlenumber136906en_AU
dc.identifier.citationMartin, A. N., Meredith, K., Norman, M. D., Bryan, E., & Baker, A. (2020). Lithium and strontium isotope dynamics in a carbonate island aquifer, Rottnest Island, Western Australia. Science of The Total Environment, 715, 136906. doi:10.1016/j.scitotenv.2020.136906en_AU
dc.identifier.issn0048-9697en_AU
dc.identifier.journaltitleScience of The Total Environmenten_AU
dc.identifier.urihttps://doi.org/10.1016/j.scitotenv.2020.136906en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/14098en_AU
dc.identifier.volume715en_AU
dc.language.isoenen_AU
dc.publisherElsevieren_AU
dc.subjectLithiumen_AU
dc.subjectStrontiumen_AU
dc.subjectCarbonatesen_AU
dc.subjectIsotopesen_AU
dc.subjectDynamicsen_AU
dc.subjectAquifersen_AU
dc.subjectGround wateren_AU
dc.subjectWestern Australiaen_AU
dc.titleLithium and strontium isotope dynamics in a carbonate island aquifer, Rottnest Island, Western Australiaen_AU
dc.typeJournal Articleen_AU
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