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Hydrothermal vent sites found along mid-ocean ridges are sources of numerous reduced chemical species and trace elements. To establish dissolved iron (II) (dFe(II)) variability along the Mid Atlantic Ridge (between 39.5°N and 26°N), dFe(II) concentrations were measured above six hydrothermal vent sites, as well as at stations with no active hydrothermal activity. The dFe(II) concentrations ranged from 0.00 to 0.12 nmol L -1 (detection limit = 0.02 ± 0.02 nmol L -1 ) in non-hydrothermally affected regions to values as high as 12.8 nmol L -1 within hydrothermal plumes. Iron (II) in seawater is oxidised over a period of minutes to hours, which is on average two times faster than the time required to collect the sample from the deep ocean and its analysis in the onboard laboratory. A multiparametric equation was used to estimate the original dFe(II) concentration in the deep ocean. The in-situ temperature, pH, salinity and delay between sample collection and its analysis were considered. The results showed that dFe(II) plays a more significant role in the iron pool than previously accounted for, constituting a fraction >20 % of the dissolved iron pool, in contrast to <10 % of the iron pool formerly reported. This discrepancy is caused by Fe(II) loss during sampling when between 35 and 90 % of the dFe(II) gets oxidised. In-situ dFe(II) concentrations are therefore significantly higher than values reported in sedimentary and hydrothermal settings where Fe is added to the ocean in its reduced form. Consequently, the high dynamism of dFe(II) in hydrothermal environments masks the magnitude of dFe(II) sourced within the deep ocean., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

High quality observational data with a firm uncertainty assessment are essential for the proper validation of biogeochemical models for trace metals such as iron. Typically, concentrations of these metals are very low in oceanic waters (nM and sub nM) and ICP-MS is therefore a favoured technique for quantitative analysis. Uncertainties in the measurement step are generally well constrained, even at sub-nM concentrations. However, the measurement step is only part of the overall procedure. For the determination of trace metal solubilities from aerosols in the surface ocean, aerosol collection on a filter paper followed by a leaching procedure is likely to make a significant contribution to the overall uncertainty. This paper quantifies the uncertainties for key trace metals (cobalt, iron, lead and vanadium), together with aluminium as a reference element, for a controlled, flow through laboratory leaching procedure using filters collected from three different sampling sites (Tudor Hill (Bermuda), Heraklion (Crete) and Tel-Shikmona (Israel)) and water, glucuronic acid and desferrioxamine B as leachants. Relative expanded uncertainties were in the range of 12-29% for cobalt, 12-62% for iron, 13-45% for lead and 5-11% for vanadium. Fractional solubilities for iron ranged from 0.2 ± 0.1% to 16.9 ± 3.5%., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Two Guillemot carcases were dissected, each providing 12 discrete tissue samples and 3 samples of partially digested food. One hundred and five PCBs from the 209 PCBs determined by GCxGC-ToFMS were detected. The relative proportions of individual PCBs did not vary greatly within tissue types, although the PCB profile from undigested food could be distinguished. Enantiomer fractions (EFs) were determined for CB-95, CB-136 and CB-149 by GC-HRqToFMS. EFs in the partially digested food were near racemic, with high levels of enrichment for E1 CB-95 in the kidneys and liver (EF of 0.80 and 0.84 respectively). This provides some of the clearest evidence to date that fractionation takes place in the organs where metabolic biotransformation and elimination of PCBs occurs. Our findings also confirm the ability of non-lethal sampling techniques, such as collection of small (<1 g) blood samples, to provide PCB signatures that are representative of an individual organism., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

A flow injection manifold incorporating a solid phase chelating resin (Toyopearl AF-Chelate-650) is reported for the preconcentration of dissolved metals from seawater, with a focus on investigating the effect of the loading pH, wash solution composition and wash time. Cobalt, iron, lead and vanadium have been used as target analytes with contrasting oceanographic behaviour. Quadrupole ICP-MS has been used for detection to make the approach accessible to most laboratories and a collision/reaction cell has been incorporated to minimise polyatomic interferences. Results for the seawater CRM NASS-6 and two GEOTRACES reference materials were in good agreement with the certified/consensus values, demonstrating the suitability of the approach for the determination of trace metals in seawater. The experimental design used allowed a thorough investigation of the uncertainty contribution from each method parameter to the overall expanded uncertainty of the measurement. The results showed that the parameters making the largest contributions were the precision of the peak area measurement and the uncertainty associated with the slope of the calibration curve. Therefore, these are the critical parameters that should be targeted in order to reduce the overall measurement uncertainty. For iron, the wash blank also gave a measureable contribution., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A GC × GC-TOFMS installed with a Rtx-PCB (60 m × 0.18 mm × 0.18 μm) in the first dimension and Rxi- 17 (1.5 m × 0.1 mm × 0.1 μm) column in the second dimension was used to separate 188 out of 209 congeners. A further 12 congeners were identified through additional data processing resulting in the identification of a total of 200 congeners. However, caution is advised if these 12 congeners were to be used in quantitative assessments. The remaining 9 co-eluting congeners were three doublets (CB65 + CB62, CB160 + CB163 and CB201 + CB204) and one triplet (CB20 + CB21 + CB33). This method was tested on five Aroclors and resulted in the separation of all congeners present in the heavier Aroclor mixtures A1254 and A1260. The suitability of this method for applications in biological matrices was demonstrated on extracted whiting and guillemot liver samples which resulted in the identification of 137 individual PCBs in the whiting liver sample and 120 in the guillemot sample. Fingerprinting was able to show clear differences in the PCB signature of the two animals. This highlights the potential of this method for PCB fingerprinting in environmental forensics studies and other assessments that require congener specific analysis.

Macronutrient elements (C, N and P) and micronutrient elements (Fe, Co, Cu, Zn and Mn) are widely measured in their various physico-chemical forms in open ocean, shelf sea, coastal and estuarine waters. These measurements help to elucidate the biogeochemical cycling of these elements in marine waters and highlight the ecological and socio-economic importance of the oceans. Due to the dynamic nature of marine waters in terms of chemical, biological and physical processes, it is advantageous to make these measurements in situ and in this regard flow injection analysis (FIA) provides a suitable shipboard platform. This review, therefore, discusses the role of FIA in the determination of macro- and micro-nutrient elements, with an emphasis on manifold design and detection strategies for the reliable shipboard determination of specific nutrient species. The application of various FIA manifolds to oceanographic nutrient determinations is discussed, with an emphasis on sensitivity, selectivity, high throughput analysis and suitability for underway analysis and depth profiles. Strategies for enhancing sensitivity and minimizing matrix effects, e.g. refractive index (schlieren) effects and the important role of uncertainty budgets in underpinning method validation and data quality are discussed in some detail., (Copyright © 2013 Elsevier B.V. All rights reserved.)

In human exposure studies involving Polychlorinated Biphenyls (PCBs), it is useful to establish when an individual was potentially exposed. Age dating PCB exposure is complex but assessments can be made because different PCB congeners have different residence times in the human body. The less chlorinated congeners generally tend to have shorter residence times because they are biotransformed and eliminated faster than more chlorinated congeners. Therefore, the presence of high proportions of less chlorinated congeners is often indicative of recent exposure. The 2003-04 National Health and Nutrition Examination Survey (NHANES) dataset contains results for the concentration of 37 PCBs in a sub-sample of the US population. Multivariate statistical analysis of the NHANES data showed that less chlorinated congeners are not always biotransformed faster than higher chlorinated compounds. For example, PCB 28 (a tri-chlorobiphenyl) appears to be more resistant to biotransformation than PCB 101 and 110 (penta-chlorobiphenyls). Using statistical analysis of the NHANES data in conjunction with previously published studies on PCB persistence in humans, it was possible to identify the structural relationships that determine if a PCB is likely to be from a recent exposure (termed 'episodic') or from steady state exposure. Congeners with chlorine atoms in the 2,5- and 2,3,6-positions appear to be more susceptible to biotransformation whereas congeners with chlorine bonds in the 2,3,4- 2,4,5- 3,4,5- and 2,3,4,5-positions appear to be more persistent. This work shows that future investigations to date PCB exposure would benefit from the analysis of a wide range of congeners, including the selection of key congeners based not only on the degree of chlorination but also on the positions of the chlorine atoms on the biphenyl., (Copyright © 2013 Elsevier B.V. All rights reserved.)