Critical evaluation of a seaFAST system for the analysis of trace metals in marine samples

Impacts of COVID-19 and climate change on wastewater-derived substances in urban drinking water: Evidence from gadolinium-based contrast agents in tap water from Berlin, Germany

Anthropogenic gadolinium from MRI contrast agents has been detected in surface waters worldwide. It is released with the treated effluents of wastewater treatment plants, similar to other wastewater-derived substances (WWDS) such as pharmaceuticals and personal care products. We determined concentrations of the rare earth elements in tap water from Berlin, Germany, using an automated preconcentration procedure that is both time- and cost-efficient. Anthropogenic gadolinium concentrations in Berlin's tap water increased on average 30-fold between 2009 and 2021. However, the tap water composition responded quickly to the reduced number of MRI scans during the COVID-19 pandemic, and some districts show a decrease from 2016 to 2021. Since climate change causes groundwater levels to decline in many regions, this needs to be mitigated by artificial groundwater recharge with surface water. This will inevitably lead to an increase in WWDS in potable water, which can be cost-efficiently monitored using anthropogenic gadolinium as tracer.

Zinc stimulation of coastal productivity in low carbon dioxide environments

Zinc (Zn) is a key micronutrient used by phytoplankton for carbon (C) acquisition, yet there have been few observations of its influence on natural oceanic phytoplankton populations. In this study, we observed Zn limitation of growth in the natural phytoplankton community of Terra Nova Bay, Antarctica, due to low (~220 μatm) pCO2 conditions, in addition to primary iron (Fe) limitation. Shipboard incubation experiments amended with Zn and Fe resulted in significantly higher chlorophyll a content and dissolved inorganic carbon drawdown compared to Fe addition alone. Zn and Fe response proteins detected in incubation and environmental biomass provided independent verification of algal co-stress for these micronutrients. These observations of Zn limitation under low pCO2 conditions demonstrate Zn can influence coastal primary productivity. Yet, as surface ocean pCO2 rises with continued anthropogenic emissions, the occurrence of Zn/C co-limitation will become rarer, impacting the biogeochemical cycling of Zn and other trace metal micronutrients.

Distribution patterns of six metals and their influencing factors in M4 seamount seawater of the Western Pacific

Metals are crucial to the stability of marine ecosystems, and it is important to analyze their spatial heterogeneity. This study examined the distribution and influencing factors of six metals such as manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu) and cadmium (Cd) in M4 seamount of the Western Pacific. The results showed that the factors affecting the distribution of metals are complex. The concentration ranges of Mn, Fe, Co, Ni, Cu, and Cd in the M4 seamount were 0-0.05, 0-0.44, 0-0.0014, 0-0.082, 0.12-0.16, and 0-0.013 μg/L, respectively, roughly equivalent to those of other open seas, however, there were also some differences. Specifically, the distribution of ferromanganese nodules and Co-rich crusts, resulted in a significant increase in the concentration of metals such as Mn, Fe, and Co in the bottom. This study will significantly contribute to our understanding of the spatial heterogeneity of metals in seamount areas.

Persistent equatorial Pacific iron limitation under ENSO forcing

Projected responses of ocean net primary productivity to climate change are highly uncertain1. Models suggest that the climate sensitivity of phytoplankton nutrient limitation in the low-latitude Pacific Ocean plays a crucial role1-3, but this is poorly constrained by observations4. Here we show that changes in physical forcing drove coherent fluctuations in the strength of equatorial Pacific iron limitation through multiple El Niño/Southern Oscillation (ENSO) cycles, but that this was overestimated twofold by a state-of-the-art climate model. Our assessment was enabled by first using a combination of field nutrient-addition experiments, proteomics and above-water hyperspectral radiometry to show that phytoplankton physiological responses to iron limitation led to approximately threefold changes in chlorophyll-normalized phytoplankton fluorescence. We then exploited the >18-year satellite fluorescence record to quantify climate-induced nutrient limitation variability. Such synoptic constraints provide a powerful approach for benchmarking the realism of model projections of net primary productivity to climate changes.

Significant contribution of coastal fish-farm activities to the inventory of trace elements in coastal waters: Traced by ammonia and rare earth elements

In this study, we investigated the influence of fish-farm activities on the inventory of trace elements (Mn, Fe, Co, Ni, and Cu) in the coastal waters off the fish-farm plants on Jeju Island, Korea. NH₄⁺ and rare earth elements (REEs) were used as tracers to examine the production and removal processes. Relatively higher concentrations of trace elements were observed in the coastal waters and significantly correlated with NH₄⁺. Our results suggest that the excess dissolved trace elements in the coastal waters could be mainly produced inside fish farms, together with the production of NH₄⁺ and light-REEs (La to Nd). Although dissolved trace elements were found to be partially scavenged onto particles in the fish-farm rearing waters, indicated by the significant removal of particle-reactive Ce, these particles would be eventually discharged into the coastal ocean and release the dissolved trace elements back into the water columns.

Automated determination of gallium in seawater using seaFAST pre-concentration and high-resolution inductively-coupled plasma mass spectrometry

There has been increased interest in dissolved gallium (Ga) in natural waters due to its long residence time and its usefulness in tracking water masses; however, current analytical approaches are time consuming and labor intensive (e.g., magnesium hydroxide co-precipitation method, (Mg(OH)₂)) or have concerns such as carryover and sample recovery (automated resin column extraction). Ocean observing programs, such as GEOTRACES, recover hundreds of samples per expedition. There are both logistical (sample volume) and analytical (person-hour) demands to economically collect and analyze Ga. We present an automated isotope dilution method (using 99.8% enriched ⁷¹Ga) to determine Ga in seawater utilizing commercially available equipment while addressing the challenges of a) sample volume and sample pre-concentration factor, b) instrumental interferences, c) sample-sample carryover, d) sample recovery variability, and e) improving sample detection limits, accuracy and precision. A seaFAST SC-4DXS pico (Elemental Scientific, Inc.; ESI) was used to pre-concentrate 20 mL of sample on a Nobias PA1 resin column 67-fold before analysis in medium resolution on a ThermoFisher high-resolution inductively-coupled plasma mass spectrometer (HR-ICP-MS) equipped with an APEX Q FAST enabled spray chamber (ESI) to increase signal intensity and decrease instrument interferences. The new automated seaFAST method reproduced Ga concentrations determined by the Mg(OH)₂ method, but with greater precision (RSD <4%) and a lower detection limit (0.10 pmol L^-1). This method is ideal for high throughput applications and can be easily implemented using commercially available equipment.

Automated rapid solid-phase extraction system for separation and preconcentration of trace elements using carboxymethylated polyethyleneimine-type chelating resin

An automated system for the rapid separation and preconcentration of trace elements was developed. Carboxymethylated polyethyleneimine 600 (CM-PEI600), which is a partially carboxymethylated polyethyleneimine with a molecular weight of 600 Da, was used as a chelating resin to quantitatively recover trace elements under high-flow-rate conditions. For accurately and precisely determining trace elements, even with a rough control of the sample and eluent flow volumes, an internal standardization technique was employed for the solid-phase extraction and separation. A recovery test of the deionized water-based sample solution was conducted using this system, and good results, with a recovery of 92% or higher, were obtained for 11 elements (Cd, Co, Cu, Fe, Mn, Mo, Ni, Pb, Ti, V, and Zn). Eight elements present in certified groundwater and wastewater reference materials (ES-L-1 and EU-L) were separated and preconcentrated using this system. Almost all the determined values were within their tolerance intervals, and no significant differences were observed between the determined and certified values, demonstrating the validity of this method. The time required for the separation and preconcentration using approximately 100 mL of the sample solution was approximately 6.5 min, and theoretically, the system could be used to preconcentrate 17 samples in an hour because extraction and elution could be conducted simultaneously using two cartridges packed with the chelating resin. Using this system equipped with cartridges packed with CM-PEI600 resin, solid-phase extraction and the separation of multiple elements were performed simultaneously, automatically, and rapidly, enabling the accurate and precise determination of trace elements in environmental water and inorganic salts even by rapidly flowing the sample solutions using peristaltic pumps. Compared to NOBIAS Chelate PA-1, a commercially available chelating resin, the CM-PEI600 resin can recover trace elements even under an extremely high flow rate of approximately 50 mL min^-1.

Making waves: Time for chemical surface water quality monitoring to catch up with its technical potential

A comprehensive real-time evaluation of the chemical status of surface water bodies is still utopian, but in our opinion, it is time to use the momentum delivered by recent advanced technical, infrastructural, and societal developments to get significantly closer. Procedures like inline and online analysis (in situ or in a bypass) with close to real-time analysis and data provision are already available in several industrial sectors. In contrast, atline and offline analysis involving manual sampling and time-decoupled analysis in the laboratory is still common practice in aqueous environmental monitoring. Automated tools for data analysis, verification, and evaluation are changing significantly, becoming more powerful with increasing degrees of automation and the introduction of self-learning systems. In addition, the amount of available data will most likely in near future be increased by societal awareness for water quality and by citizen science. In this analysis, we highlight the significant potential of surface water monitoring techniques, showcase "lighthouse" projects from different sectors, and pin-point gaps we must overcome to strike a path to the future of chemical monitoring of inland surface waters.

Determination of Trace Metal (Mn, Fe, Ni, Cu, Zn, Co, Cd and Pb) Concentrations in Seawater Using Single Quadrupole ICP-MS: A Comparison between Offline and Online Preconcentration Setups

The quantification of dissolved metals in seawater requires pre-treatment before the measurement can be done, posing a risk of contamination, and requiring a time-consuming procedure. Despite the development of automated preconcentration units and sophisticated instruments, the entire process often introduces inaccuracies in quantification, especially for low-metal seawaters. This study presents a robust method for measuring dissolved metals from seawater accurately and precisely using a seaFAST and quadrupole Inductively Coupled Plasma Mass Spectrometer (ICPMS), employed in both offline (2016–2018) and online (2020–2021) setups. The proposed method shows data processing, including the re-calculation of metals after eliminating the instrumental signals caused by polyatomic interferences. Here, we report the blank concentration of Fe below 0.02 nmol kg−1, somewhat lower values than that have been previously reported using high-resolution and triple-quad ICPMS. The method allows for the accurate determination of Cd and Fe concentrations in low-metal seawaters, such as GEOTRACES GSP, using a cost-effective quadrupole ICPMS (Cdconsensus: 2 ± 2 pmol kg−1, Cdmeasured: 0.99 ± 0.35 pmol kg−1; Feconsensus: 0.16 ± 0.05 nmol kg−1, Femeasured: 0.21 ± 0.03 nmol kg−1). Between two setups, online yields marginally lower blank values for metals based on short-term analysis. However, the limit of detection is comparable between the two, supporting optimal instrumental sensitivity of the ICPMS over 4+ years of analysis.

Determination of Picomolar Titanium in Seawater by Isotope Dilution Multicollector Inductively Coupled Plasma Mass Spectrometry after Mg(OH)2 Coprecipitation

A new isotope dilution inductively coupled plasma mass spectrometry (ICPMS) method is developed to determine picomolar concentrations of titanium (Ti) in seawater. The method applies Mg(OH)₂ coprecipitation to concentrate Ti from seawater, and uses a new ⁴⁹Ti-⁴⁷Ti isotope dilution to eliminate the need for separating Ti from seawater Ca, resulting in an isobaric interference-free analysis by high-resolution multicollector ICPMS. The method uses a 1.8 mL seawater sample with a detection limit of 1.6 pmol L^-1 that is determined mainly by Ti contamination during sample preparation rather than by ICPMS sensitivity, instrumental Ti background, or isobaric interferences. An oceanographically consistent vertical profile of dissolved Ti in the Sargasso Sea near Bermuda is measured with this method.

Speciation of Inorganic Compounds in Aquatic Systems Using Diffusive Gradients in Thin-Films: A Review

The speciation of trace metals in an aquatic system involves the determination of free ions, complexes (labile and non-labile), colloids, and the total dissolved concentration. In this paper, we review the integrated assessment of free ions and labile metal complexes using Diffusive Gradients in Thin-films (DGT), a dynamic speciation technique. The device consists of a diffusive hydrogel layer made of polyacrylamide, backed by a layer of resin (usually Chelex-100) for all trace metals except for Hg. The best results for Hg speciation are obtained with agarose as hydrogel and a thiol-based resin. The diffusive domain controls the diffusion flux of the metal ions and complexes to the resin, which strongly binds all free ions. By using DGT devices with different thicknesses of the diffusive or resin gels and exploiting expressions derived from kinetic models, one can determine the labile concentrations, mobilities, and labilities of different species of an element in an aquatic system. This procedure has been applied to the determination of the organic pool of trace metals in freshwaters or to the characterization of organic and inorganic complexes in sea waters. The concentrations that are obtained represent time-weighted averages (TWA) over the deployment period.

Manganese co-limitation of phytoplankton growth and major nutrient drawdown in the Southern Ocean

Residual macronutrients in the surface Southern Ocean result from restricted biological utilization, caused by low wintertime irradiance, cold temperatures, and insufficient micronutrients. Variability in utilization alters oceanic CO₂ sequestration at glacial-interglacial timescales. The role for insufficient iron has been examined in detail, but manganese also has an essential function in photosynthesis and dissolved concentrations in the Southern Ocean can be strongly depleted. However, clear evidence for or against manganese limitation in this system is lacking. Here we present results from ten experiments distributed across Drake Passage. We found manganese (co-)limited phytoplankton growth and macronutrient consumption in central Drake Passage, whilst iron limitation was widespread nearer the South American and Antarctic continental shelves. Spatial patterns were reconciled with the different rates and timescales for removal of each element from seawater. Our results suggest an important role for manganese in modelling Southern Ocean productivity and understanding major nutrient drawdown in glacial periods.

A primary reference method for the characterization of Cd, Cr, Cu, Ni, Pb and Zn in a candidate certified reference seawater material: TEA/Mg(OH)2 assisted ID3MS by triple quadrupole ICP-MS/MS

A certified reference seawater material (CRM), UME CRM 1206 which was sampled from the Marmara Sea (40 31,423 N; 027 11, 333 E) with 27 psu of salinity is about to be released by Inorganic Analysis Laboratory of TÜBİTAK National Metrology Institute (UME). This paper represents the characterization measurements of Cd, Cr, Cu, Ni, Pb and Zn in this CRM. The use of a reference method by a single laboratory is one of the options for the characterization of a candidate CRM according to ISO 17034 [39]. This approach is used throughout this study with an introduction of a primary reference method. For this purpose, combination of triethylamine assisted Mg(OH)₂ co-precipitation and triple isotope dilution mass spectrometry (TEA/Mg(OH)₂-ID³MS) were developed and validated. This optimized co-precipitation protocol provided the recovery of target analytes within the range of 72%-92% which was the main advantage of TEA/Mg(OH)₂ method especially for Cd, Ni, Cu and Zn compared to NH₄OH assisted co-precipitation. Analytical performance of TEA/Mg(OH)₂-ID³MS were investigated under the optimum conditions. The results for matrix certified reference material were found to be not significantly different from the certified values based on the comparison of the results and certified values within their combined uncertainties. On the other hand, intermediate precision and repeatability of the developed method were found to be in the range of 0.34%-0.90% and 0.09%-0.49%, respectively. This study reports characterization measurements with their expanded uncertainties (k = 2) as 0.4327 ± 0.0071 ng/g for Cd, 2.442 ± 0.033 ng/g for Cr, 1.018 ± 0.012 ng/g for Cu, 4.568 ± 0.037 ng/g for Ni, 1.068 ± 0.016 ng/g for Pb and 8.521 ± 0.075 ng/g for Zn where the intermediate precision was found to be the main contributor to measurement uncertainty budget of TEA/Mg(OH)₂-ID³MS method for each analyte.

Characterization of alloying components in galvanic anodes as potential environmental tracers for heavy metal emissions from offshore wind structures

The impact of offshore constructions on the marine environment is unknown in many aspects. The application of Al- and Zn-based galvanic anodes as corrosion protection results in the continuous emission of inorganic matter (e.g. >80 kg Al-anode material per monopile foundation and year) into the marine environment. To identify tracers for emissions from offshore wind structures, anode materials (Al-based and Zn-based) were characterized for their elemental and isotopic composition. An acid digestion and analysis method for Al and Zn alloys was adapted and validated using the alloy CRMs ERM®-EB317 (AlZn6CuMgZr) and ERM®-EB602 (ZnAl4Cu1). Digests were measured for their elemental composition by ICP-MS/MS and for their Pb isotope ratios by MC ICP-MS. Ga and In were identified as potential tracers. Moreover, a combined tracer approach of the elements Al, Zn, Ga, Cd, In and Pb together with Pb isotope ratios is suggested for a reliable identification of offshore-wind-farm-induced emissions. In the Al anodes, the mass fractions were found to be >94.4% of Al, >26200 mg kg^-1 of Zn, >78.5 mg kg^-1 of Ga, >0.255 mg kg^-1 of Cd, >143 mg kg^-1 of In and >6.7 mg kg^-1 of Pb. The Zn anodes showed mass fractions of >2160 mg kg^-1 of Al, >94.5% of Zn, >1.31 mg kg^-1 of Ga, >254 mg kg^-1 of Cd, >0.019 mg kg^-1 of In and >14.1 mg kg^-1 of Pb. The n(²⁰⁸Pb)/n(²⁰⁶Pb) isotope ratios in Al anodes range from 2.0619 to 2.0723, whereas Zn anodes feature n(²⁰⁸Pb)/n(²⁰⁶Pb) isotope ratios ranging from 2.0927 to 2.1263.

Fast iron speciation in seawater by catalytic Competitive Ligand Equilibration-Cathodic Stripping Voltammetry with tenfold sample size reduction

Iron speciation analysis in seawater is a fundamental step to understand the cycling of this element in oceanic waters, in view of its central role in regulating primary productivity and its connection to global planetary cycles. At present, analytical procedures are the bottleneck for speciation analysis, in term of both time and sample size requirement. Here we present a novel instrumental configuration for the speciation analysis of iron by the Competitive Ligand Equilibration - Cathodic Stripping Voltammetry (CLE-CSV) procedure. The new system features a 1 mL microcell and a silver wire pseudoreference enabling a tenfold reduction of the sample volume. 2,3-dihydroxynaphthalene was used as the complexing ligand and atmospheric oxygen as the catalytic enhancer because they ensured the best analytical performances in terms of detection capabilities. The side reaction coefficient for the FeDHN complex α_Fe'DHN was calibrated against EDTA and an average value of 9.25 for logK'_Fe'DHN was calculated. The method was successfully validated in UV digested seawater using diethylenetriaminepentaacetic acid (DTPA), which has known stability constant for iron. The method was lastly applied to six samples from the Ross Sea water column (Antarctica), demonstrating its fit for purpose for the detection of trace amounts of iron ligands in seawater. Thanks to the employed instrumental configuration and the high sensitivity, the proposed method achieved a tenfold reduction in sample size, a tenfold increase in sensitivity compared with other methods employing DHN and halved the analysis time with respect to the fastest method reported in the literature. Half an hour is enough to measure a 12 point titration, making the analysis of at least three titrations per day feasible. It is expected that the application of this procedure will foster the sample throughput, thanks to the reduced analysis time, and make possible the analysis of limitedly available and challenging samples, like porewater and vent fluids via the tenfold reduction in sample size.

Development of an Automatic pH Adjustment Instrument for the Preparation of Analytical Samples Prior to Solid Phase Extraction

An automatic pH adjustment instrument was developed for the preparation of analytical samples prior to solid phase extraction, which is widely used as a pretreatment technique for the separation of sample matrixes and preconcentration of elements for analysis. Real-time monitoring of the sample pH condition was performed by observing the light signal intensity of the pH-sensitive wavelength of the pH indicating reagent. A light of pH-insensitive wavelength was selected as the reference light to cancel the signal intensity variation of the pH-sensitive light due to the difference of pH indicating reagent concentration, possible difference in transparency of sample vessels, and minute fluctuation of the light source. The pH condition was elevated by automatic addition of ammonia solution using a nebulizer in the flow line of which an electromagnetic valve was equipped. Open and close operation of the electromagnetic valve was controlled based on the difference between the real-time pH condition and the target pH condition. The effectiveness of the instrument was confirmed by using various pH indicating reagents and by analyzing trace elements in a seawater certified reference material.

An Automated SeaFAST ICP-DRC-MS Method for the Determination of 90Sr in Spent Nuclear Fuel Leachates

To reduce uncertainties in determining the source term and evolving condition of spent nuclear fuel is fundamental to the safety assessment. ß-emitting nuclides pose a challenging task for reliable, quantitative determination because both radiometric and mass spectrometric methodologies require prior chemical purification for the removal of interfering activity and isobars, respectively. A method for the determination of ⁹⁰Sr at trace levels in nuclear spent fuel leachate samples without sophisticated and time-consuming procedures has been established. The analytical approach uses a commercially available automated pre-concentration device (SeaFAST) coupled to an ICP-DRC-MS. The method shows good performances with regard to reproducibility, precision, and LOD reducing the total time of analysis for each sample to 12.5 min. The comparison between the developed method and the classical radiochemical method shows a good agreement when taking into account the associated uncertainties.

Genomic mosaicism underlies the adaptation of marine Synechococcus ecotypes to distinct oceanic iron niches

Phytoplankton are limited by iron (Fe) in ~40% of the world's oceans including high-nutrient low-chlorophyll (HNLC) regions. While low-Fe adaptation has been well-studied in large eukaryotic diatoms, less is known for small, prokaryotic marine picocyanobacteria. This study reveals key physiological and genomic differences underlying Fe adaptation in marine picocyanobacteria. HNLC ecotype CRD1 strains have greater physiological tolerance to low Fe congruent with their expanded repertoire of Fe transporter, storage and regulatory genes compared to other ecotypes. From metagenomic analysis, genes encoding ferritin, flavodoxin, Fe transporters and siderophore uptake genes were more abundant in low-Fe waters, mirroring paradigms of low-Fe adaptation in diatoms. Distinct Fe-related gene repertories of HNLC ecotypes CRD1 and CRD2 also highlight how coexisting ecotypes have evolved independent approaches to life in low-Fe habitats. Synechococcus and Prochlorococcus HNLC ecotypes likewise exhibit independent, genome-wide reductions of predicted Fe-requiring genes. HNLC ecotype CRD1 interestingly was most similar to coastal ecotype I in Fe physiology and Fe-related gene content, suggesting populations from these different biomes experience similar Fe-selective conditions. This work supports an improved perspective that phytoplankton are shaped by more nuanced Fe niches in the oceans than previously implied from mostly binary comparisons of low- versus high-Fe habitats and populations.

Assessment of leaching protocols to determine the solubility of trace metals in aerosols

Atmospheric deposition of aerosols to the ocean provides an important pathway for the supply of vital micronutrients, including trace metals. These trace metals are essential for phytoplankton growth, and therefore their delivery to marine ecosystems can strongly influence the ocean carbon cycle. The solubility of trace metals in aerosols is a key parameter to better constrain their potential impact on phytoplankton growth. To date, a wide range of experimental approaches and nomenclature have been used to define aerosol trace metal solubility, making data comparison between studies difficult. Here we investigate and discuss several laboratory leaching protocols to determine the solubility of key trace metals in aerosol samples, namely iron, cobalt, manganese, copper, lead, vanadium, titanium and aluminium. Commonly used techniques and tools are also considered such as enrichment factor calculations and air mass back-trajectory projections and recommendations are given for aerosol field sampling, laboratory processing (including leaching and digestion) and analytical measurements. Finally, a simple 3-step leaching protocol combining commonly used protocols is proposed to operationally define trace metal solubility in aerosols. The need for standard guidelines and protocols to study the biogeochemical impact of atmospheric trace metal deposition to the ocean has been increasingly emphasised by both the atmospheric and oceanographic communities. This lack of standardisation currently limits our understanding and ability to predict ocean and climate interactions under changing environmental conditions.

Pre-concentration of thorium and neodymium isotopes using Nobias chelating resin: Method development and application to chromatographic separation

The isotopes of thorium (Th) and neodymium (Nd) are used as tracers in oceanography, and are key parameters in the international GEOTRACES program. The very low concentrations of Th and Nd as well as the reactive nature of Th isotopes makes the analysis of seawater samples a complex process. Analysis requires time-consuming pre-concentration from over 5 L of seawater. We describe a method to simultaneously pre-concentrate dissolved Th and Nd from acidified seawater samples using the Nobias^® PA1L chelating resin. Prior to pre-concentration, hydrofluoric acid is added to the sample to stabilise Th, ammonium acetate buffer added (0.05 M), pH adjusted to 4.75, and then finally the prepared sample is pumped through the Nobias resin at a rate of 15 ml min^-1. Up to 6 samples can be processed simultaneously. Following elution in 3 M HNO₃, both elements are chromatographically separated and determined using Inductively Coupled Plasma Mass Spectrometry. Oxidation of the sample between all column separation steps, including after the initial Nobias resin, is important for obtaining maximum elemental recoveries. The method has >90% recovery with blank levels typically <10 pg for ²³²Th and <70 pg for Nd. Accuracy is excellent, as our reported values generally agree within 1% of the GEOTRACES intercalibration standards. The long-term analysis of these materials also indicates excellent reproducibility. The pre-concentration of Th and Nd using the Nobias resin is a time saving option compared to the widely used iron co-precipitation technique. Sample handling is also reduced, decreasing the risk of sample contamination. The simplicity of our suggested pre-concentration procedure makes it possible to be applied at sea.