High-precision determination of lithium and magnesium isotopes utilising single column separation and multi-collector inductively coupled plasma mass spectrometry

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

High-precision determination of lithium and magnesium isotopes utilising single column separation and multi-collector inductively coupled plasma mass spectrometry.

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 1013  Ω 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 δ7 Li and ±0.07‰ for δ26 Mg. 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

Diffusive processes in aqueous glass dissolution

Abstract: High level nuclear waste is often immobilised in a borosilicate glass for disposal. However, this glass corrodes in contact with aqueous solutions. To predict radionuclide releases from wasteforms, their dissolution mechanisms must be understood. Understanding glass dissolution mechanisms presents a challenge across numerous other disciplines and many glass dissolution models still remain conflicted. Here we show that diffusion was a significant process during the later stages of dissolution of a simplified waste glass but was not evidenced during the initial stages of dissolution. The absence of measurable isotopic fractionation in solution initially supports models of congruent dissolution. However, the solution becoming isotopically lighter at later times evidences diffusive isotopic fractionation and opposes models that exclude diffusive transport as a significant mechanism. The periodically sampled isotopic methodologies outlined here provide an additional dimension with which to understand glass dissolution mechanisms beyond the usual measurement of solution concentrations and, post-process, nano-scale analysis of the altered glass

Variability in the Concentration of Lithium in the Indo‐Pacific Ocean

Lithium has limited biological activity and can readily replace aluminium, magnesium and iron ions in aluminosilicates, making it a proxy for the inorganic silicate cycle and its potential link to the carbon cycle. Data from the North Pacific Ocean, tropical Indian Ocean, Southern Ocean and Red Sea suggest that salinity normalized dissolved lithium concentrations vary by up to 2%–3% in the Indo‐Pacific Ocean. The highest lithium concentrations were measured in surface waters of remote North Pacific and Indian Ocean stations that receive relatively high fluxes of dust. The lowest dissolved lithium concentrations were measured just below the surface mixed layer of the stations with highest surface water concentrations, consistent with removal into freshly forming aluminium rich phases and manganese oxides. In the North Pacific, water from depths >2,000 m is slightly depleted in lithium compared to the initial composition of Antarctic Bottom Water, likely due to uptake of lithium by authigenically forming aluminosilicates. The results of this study suggest that the residence time of lithium in the ocean may be significantly shorter than calculated from riverine and hydrothermal fluxes.Key Points: Li/Na ratios vary by up to 2%–3% in the Indian and Pacific Oceans. Authigenic formation of aluminosilicates slightly deplete deep‐water lithium concentrations in the North Pacific. The residence time of lithium in the ocean is 240,000 ± 70,000 years, based on removal from North Pacific deep‐water.Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659MoES, Indian National Centre for Ocean Information Services http://dx.doi.org/10.13039/501100004814National Science Foundation USAhttps://doi.pangaea.de/10.1594/PANGAEA.94188

Seawater lithium concentration data from the Indian and Pacific ocean

A total of 603 seawater samples were analysed for their lithium concentrations. The seawater samples were collected during eight research expeditions. All seawater lithium concentrations were normalised to TEOS-10 absolute salinity of 35 g/kg. Most seawater samples were collected using Niskin bottles and filtered using 0.22 µm filters. Exceptions are samples UW1-UW26 that were collected from the underway water system of RV Kilo Moana during cruise CDisK-IV, and surface water samples from the Red Sea that were collected using a bucket lowered from the deck of a container ship. Samples from cruises SOE09, RS2015 and RS2018 were not filtered. The seawater samples were collected during the following cruises: CDisK-IV from Hawaii to Alaska in 01-30 August 2017; SN105 from Goa to Mauritius, samples collected during 7-16 December 2015; RS2015 from the Bay of Bengal to the Mediterranean Sea, samples collected during 27 December 2015 to 3 January 2016; RS2018 from the Bay of Bengal to the Mediterranean Sea, samples collected during 23-31 March 2018; SOE09 in the Indian sector of the Southern Ocean in 12 January - 21 February 2017; JR274 in the Atlantic sector of the Southern Ocean between 9 January and 12 February 2013; D357 and JC068 sailed from South Africa to South America, mostly along 40°S, cruise D357 in 18 October – 22 November 2010, and cruise JC068 in 24 December 2011 – 27 January 2011

Seawater and aerosol lithium concentration data

A total of 603 seawater samples and 125 aerosol samples were analysed for their lithium concentrations. The seawater samples were collected during eight research expeditions. All seawater lithium concentrations were normalised to TEOS-10 absolute salinity of 35 g/kg. Most seawater samples were collected using Niskin bottles and filtered using 0.22 µm filters. Exceptions are samples UW1-UW26 that were collected from the underway water system of RV Kilo Moana during cruise CDisK-IV, and surface water samples from the Red Sea that were collected using a bucket lowered from the deck of a container ship. Samples from cruises SOE09, RS2015 and RS2018 were not filtered. The seawater samples were collected during the following cruises: CDisK-IV from Hawaii to Alaska in 01-30 August 2017; SN105 from Goa to Mauritius, samples collected during 7-16 December 2015; RS2015 from the Bay of Bengal to the Mediterranean Sea, samples collected during 27 December 2015 to 3 January 2016; RS2018 from the Bay of Bengal to the Mediterranean Sea, samples collected during 23-31 March 2018; SOE09 in the Indian sector of the Southern Ocean in 12 January - 21 February 2017; JR274 in the Atlantic sector of the Southern Ocean between 9 January and 12 February 2013; D357 and JC068 sailed from South Africa to South America, mostly along 40°S, cruise D357 in 18 October – 22 November 2010, and cruise JC068 in 24 December 2011 – 27 January 2011. Daily aerosol samples were collected from the Pacific Ocean during CLIVAR-CO2 Repeat Hydrography Sections P16 and P2. The P16 section follows 150°-152°W and was divided into two legs, a southern leg from 17°S to 71°S in January-February 2005, and a northern leg from 16°S to 56°N in February-March 2006. CLIVAR-CO2 section P2 from Japan to San Diego, along 30°N was visited in June-August 2004. The aerosol data from both CLIVAR-CO2 sections include aerosol lithium concentration measured following digestion in HF:HNO3:HCl mixture and corrected for sea-salt contributions (Li xs total), the P16 data also includes aerosol lithium extracted with ultrapure deionised water (≥18 MΩ) by pulling 100 mL of deionised water within ten seconds through the filter (Li xs MQ). The aerosol dataset also includes calculation of lithium deposition flux based on the local rain rate

Aerosol lithium concentration data from the Indian and Pacific ocean

A total of 125 aerosol samples were analysed for their lithium concentrations and deposition flux. Daily aerosol samples were collected from the Pacific Ocean during CLIVAR-CO2 Repeat Hydrography Sections P16 and P2. The P16 section follows 150°-152°W and was divided into two legs, a southern leg from 17°S to 71°S in January-February 2005, and a northern leg from 16°S to 56°N in February-March 2006. CLIVAR-CO2 section P2 from Japan to San Diego, along 30°N, was visited in June-August 2004. The aerosol data from both CLIVAR-CO2 sections include aerosol lithium concentration measured following digestion in HF:HNO3:HCl mixture and corrected for sea-salt contributions (Li xs total), the P16 data also includes aerosol lithium extracted with ultrapure deionised water (≥18 MΩ) by pulling 100 mL of deionised water within ten seconds through the filter (Li xs MQ). Aerosol lithium deposition flux was calculated based on the local rain rate

Variability in the Concentration of Lithium in the Indo‐Pacific Ocean

Funder: MoES, Indian National Centre for Ocean Information Services; Id: http://dx.doi.org/10.13039/501100004814Abstract: Lithium has limited biological activity and can readily replace aluminium, magnesium and iron ions in aluminosilicates, making it a proxy for the inorganic silicate cycle and its potential link to the carbon cycle. Data from the North Pacific Ocean, tropical Indian Ocean, Southern Ocean and Red Sea suggest that salinity normalized dissolved lithium concentrations vary by up to 2%–3% in the Indo‐Pacific Ocean. The highest lithium concentrations were measured in surface waters of remote North Pacific and Indian Ocean stations that receive relatively high fluxes of dust. The lowest dissolved lithium concentrations were measured just below the surface mixed layer of the stations with highest surface water concentrations, consistent with removal into freshly forming aluminium rich phases and manganese oxides. In the North Pacific, water from depths >2,000 m is slightly depleted in lithium compared to the initial composition of Antarctic Bottom Water, likely due to uptake of lithium by authigenically forming aluminosilicates. The results of this study suggest that the residence time of lithium in the ocean may be significantly shorter than calculated from riverine and hydrothermal fluxes

Genomics and Physiology of a Marine Flavobacterium Encoding a Proteorhodopsin and a Xanthorhodopsin-Like Protein

Riedel T, Gómez-Consarnau L, Tomasch J, et al. Genomics and Physiology of a Marine Flavobacterium Encoding a Proteorhodopsin and a Xanthorhodopsin-Like Protein. PLOS ONE. 2013;8(3): e57487.Proteorhodopsin (PR) photoheterotrophy in the marine flavobacterium Dokdonia sp. PRO95 has previously been investigated, showing no growth stimulation in the light at intermediate carbon concentrations. Here we report the genome sequence of strain PRO95 and compare it to two other PR encoding Dokdonia genomes: that of strain 4H-3-7-5 which shows the most similar genome, and that of strain MED134 which grows better in the light under oligotrophic conditions. Our genome analysis revealed that the PRO95 genome as well as the 4H-3-7-5 genome encode a protein related to xanthorhodopsins. The genomic environment and phylogenetic distribution of this gene suggest that it may have frequently been recruited by lateral gene transfer. Expression analyses by RT-PCR and direct mRNA-sequencing showed that both rhodopsins and the complete β-carotene pathway necessary for retinal production are transcribed in PRO95. Proton translocation measurements showed enhanced proton pump activity in response to light, supporting that one or both rhodopsins are functional. Genomic information and carbon source respiration data were used to develop a defined cultivation medium for PRO95, but reproducible growth always required small amounts of yeast extract. Although PRO95 contains and expresses two rhodopsin genes, light did not stimulate its growth as determined by cell numbers in a nutrient poor seawater medium that mimics its natural environment, confirming previous experiments at intermediate carbon concentrations. Starvation or stress conditions might be needed to observe the physiological effect of light induced energy acquisition