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- Bohlin, Madeleine, et al.
(författare)
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High-precision determination of lithium and magnesium isotopes utilising single column separation and multi-collector inductively coupled plasma mass spectrometry
- 2018
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Ingår i: Rapid Communications in Mass Spectrometry. - : Wiley. - 0951-4198 .- 1097-0231. ; 32:2, s. 93-104
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Tidskriftsartikel (refereegranskat)abstract
- Rationale Li and Mg isotopes are increasingly used as a combined tool within the geosciences. However, established methods require separate sample purification protocols utilising several column separation procedures. This study presents a single-step cation-exchange method for quantitative separation of trace levels of Li and Mg from multiple sample matrices.Methods The column method utilises the macro-porous AGMP-50 resin and a high-aspect ratio column, allowing quantitative separation of Li and Mg from natural waters, sediments, rocks and carbonate matrices following the same elution protocol. High-precision isotope determination was conducted by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS) on the Thermo Scientific NEPTUNE Plus fitted with 1013Ω amplifiers which allow accurate and precise measurements at ion beams <0.51 V.Results Sub-nanogram Li samples (0.3-0.5 ng) were regularly separated (yielding Mg masses of 1-70 μg) using the presented column method. The total sample consumption during isotopic analysis is <0.5 ng Li and <115 ng Mg with long-term external 2σ precisions of ±0.39‰ for δ7Li and ±0.07‰ for δ26Mg. The results for geological reference standards and seawater analysed by our method are in excellent agreement with published values despite the order of magnitude lower sample consumption. Conclusions The possibility of eluting small sample masses and the low analytical sample consumption make this method ideal for samples of limited mass or low Li concentration, such as foraminifera, mineral separates or dilute river waters.
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- Henderiks, Jorijntje, et al.
(författare)
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Algal constraints on the Cenozoic history of atmospheric CO2?
- 2006
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Ingår i: Geochimica et Cosmochimica Acta. - : Elsevier BV. - 0016-7037.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Future acidification of the oceans due to raised carbon dioxide levels will cause a drastic change in ocean chemistry that has not been experienced for at least the last 650,000 years, and will likely reduce marine calcification.Coccolithophores, calcareous haptophyte algae, constitute a key biological group subjected to this global process. The rate at which the natural populations can acclimatise or adapt to changes in ocean chemistry is an essential factor in how their natural feedback mechanisms will operate in future.Novel experiments testing the environmental tolerance of different extant coccolithophore species to various conditions of seawater carbonate chemistry reveal the need to consider species-specific effects when evaluating whole ecosystem responses to elevated pCO2 (Langer, 2006). Specifically, PIC/POC ratios in Coccolithus pelagicus appeared unaffected by the range in CO2 tested (Langer, 2006), which to date remains unexplained.We argue that the evolutionary history of the Coccolithus genus, which originated in the early Paleocene, holds not only invaluable information on how species evolve within ‘planktic super-species’ (de Vargas, 2004) whilst keeping rather conservative coccolith morphologies, as will be demonstrated. It potentially is also a crucial factor in constraining maximum levels of atmospheric CO2 experienced in the geological past.
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