Lithium isotope dynamics of closed lake systems, Rottnest Island

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dc.contributor.authorMeredith, KTen_AU
dc.contributor.authorBaker, AAen_AU
dc.contributor.authorMartin, ANen_AU
dc.contributor.authorBischoff, Ken_AU
dc.date.accessioned2023-04-06T02:06:55Zen_AU
dc.date.available2023-04-06T02:06:55Zen_AU
dc.date.issued2019-04-09en_AU
dc.date.statistics2023-03-23en_AU
dc.description.abstractStable lithium isotopes (7Li) are useful for tracing hydrochemical processes such as water-sediment interactions and delineating the source of lithium (Li). Due to developments in trace element isotope methods, 7Li has proven to be a robust tracer of catchment processes and when used with traditional isotopic methods can provide deeper insights into environmental processes. Rottnest Island contains a number of permanent hypersaline lakes (with salinities over 330 g/L) that cover approximately 4.7 km2 area within a Pleistocene to mid-Holocene eolianite bedrock (Tamala Limestone). The lakes were once connected to the ocean but over thousands of years have become closed, and are now assumed to be driven by rainfall and evaporation cycles. This field-based study uses lithium isotope ratios measured on sediments and water to investigate Li dynamics of two closed lake systems on Rottnest Island, Western Australia. This work forms part of an ongoing six-year project. Four sediment cores were collected from the deepest sections of the lakes. Sediment samples were collected from textural or sedimentological changes in the cores and were ground and ashed at 450 C for at least 5 h. Column chromatography procedures were undertaken and Li isotope ratios were analysed by multi-collector inductively coupled plasma mass spectrometer. Sediment, shell, salt crusts, soil, palaeosol, microbialite, groundwater, lake water, rainfall and seawater end-members were analysed for 7Li, Li concentration, carbon-13 and oxygen-18. The results showed that the Li isotopes of the lake sediments ranged from +17.3h to +75.6h with an average of +42.4h(n = 25). All 7Li values for sediments lie between the soil (+16.5hand palaeosol (+68.5hvalues. Other end-members such as the microbialites (+23.9h, groundwaters (range from +22.8 to +35.7h, rainfall (+24.2h, bedrock (+21.0hand seawater (+33hsamples plot within this range. The shells (+6.3hand salt crusts (+15.6h were more depleted. The reported range in isotope values is the largest observed to date, and the enriched isotope values of the sediments are related to higher Li concentrations (R2=0.7). The processes responsible for this large variation suggest evaporation trends and the change in source materials (marine vs. terrestrial) over time. The lake sediment samples provide some of the first Li isotope measurements for coastal closed lake systems in Australia. The lakes on Rottnest Island have high environmental value for the region and form a sink for 7Li. Therefore, understanding the hydrochemical processes that lead to these conditions is important for interpreting the palaeoenvironmental history of the region.en_AU
dc.identifier.articlenumberEGU2019/EGU2019-3186en_AU
dc.identifier.booktitleGeophysical Research Abstractsen_AU
dc.identifier.citationMeredith, K., Baker, A., Martin, A., & Bischoff, K. (2019). Lithium isotope dynamics of closed lake systems, Rottnest Island. Paper presented to the EGU General Assembly 2019, Vienna, Austria, 7-12 April 2019. In Geophysical Research Abstracts, Vol. 21, EGU2019-3186. Retrieved from: https://meetingorganizer.copernicus.org/EGU2019/EGU2019-3186.pdfen_AU
dc.identifier.conferenceenddate12 April 2019en_AU
dc.identifier.conferencenameEGU General Assembly 2019en_AU
dc.identifier.conferenceplaceVienna, Austriaen_AU
dc.identifier.conferencestartdate7 April 2019en_AU
dc.identifier.otherEGU2019-3186en_AU
dc.identifier.urihttps://meetingorganizer.copernicus.org/EGU2019/EGU2019-3186.pdfen_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/14813en_AU
dc.identifier.volume21en_AU
dc.language.isoenen_AU
dc.publisherCopernicus GmbHen_AU
dc.subjectLithiumen_AU
dc.subjectIsotopesen_AU
dc.subjectLakesen_AU
dc.subjectIslandsen_AU
dc.subjectAustraliaen_AU
dc.subjectTrace amountsen_AU
dc.subjectWateren_AU
dc.subjectSedimentsen_AU
dc.subjectMass spectroscopyen_AU
dc.titleLithium isotope dynamics of closed lake systems, Rottnest Islanden_AU
dc.typeConference Abstracten_AU
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