Determination of Cobalt in Seawater by Catalytic Adsorptive Cathodic Stripping Voltammetry

Vega, Marisol; Berg, Constant M.G. van den

doi:10.1021/ac960214s

Cited by 107 publications

(67 citation statements)

References 31 publications

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“…Previous studies have verified the recovery of nonacidified total cobalt (Vega and van den Berg 1997;Saito and Moffett 2002). Total cobalt concentrations were determined using four to five standard additions of 25 pmol L Ϫ1 prepared from Fisher certified Co(NO 3 ) 2 stock solutions diluted in pH 2 Milli-Q water and polymethylpentene volumetric flasks.…”

Section: Methodsmentioning

confidence: 99%

Production of cobalt binding ligands in a Synechococcus feature at the Costa Rica upwelling dome

2005

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The Costa Rica upwelling dome (CRD; ϳ8.67ЊN and 90.6ЊW) was characterized chemically for cobalt and nickel abundances and speciation and biologically using cyanobacterial abundances and phylogeny. Total dissolved cobalt was 93 pmol L Ϫ1 at 90 m depth and decreased in surface waters to 45 pmol L Ϫ1 at 10 m. Cobalt was 40% labile at 90 m but was completely complexed by strong ligands at 10 m. A surface transect out of the dome showed decreasing total dissolved cobalt from 57 pmol L Ϫ1 to 12 pmol L Ϫ1 . Detection window studies showed that natural cobalt-ligand complexes have conditional stability constants greater than 10 16.8 and that competition with nickel did not release cobalt bound to organic complexes, consistent with natural cobalt ligands being Co(III) complexes. Synechococcus cell densities at the CRD are among the highest reported in nature, varying between 1.2 ϫ 10 6 and 3.7 ϫ 10 6 cells ml Ϫ1 . Phylogenetic analysis using the 16S-23S rDNA internally transcribed spacer showed the majority of clones were related to Synechococcus strain MIT S9220, while the remaining subset form a novel group within the marine Synechococcus lineage. In a bottle incubation experiment chlorophyll increased with cobalt and iron additions relative to each element alone and the unamended control treatment. Cobalt speciation analysis of incubation experiments revealed large quantities of strong cobalt-ligand complexes in the cobalt addition treatments (401 pmol L Ϫ1 ), whereas cobalt added to a 0.2-m filtered control remained predominantly labile (387 pmol L Ϫ1 ), demonstrating that the Synechococcus-dominated community is a source of strong cobalt ligands.Processes that influence the production of metal binding ligands in the surface ocean are not well understood. Many of the important biologically used metals (Fe, Cu, Zn, Co, and Cd) have a chemical speciation that is dominated by their complexation with strong organic ligands (e.g., Rue and Bruland 1995;Saito and Moffett 2001; Morel et al. and references therein;Morel et al. 2003). While the chemical structures of these metal-complexing ligands in the natural environment are currently unknown, their destruction by ultraviolet-irradiation provides evidence for their organic composition. Furthermore, conditional stability constants indicate these ligands are very strong, much stronger than most inorganic complexes (i.e., chloro or carbonate complexes).1 Corresponding author (mak@whoi.edu). AcknowledgmentsWe are grateful to co-chief scientists Ken Bruland and Dave Hutchins for providing space aboard the cruise, helpful discussions, and ancillary data. Thanks to G. Smith, J. Conn, and L. M. Lessin for water samples and nutrient and chlorophyll analyses. Thanks to the captain and crew of the R/V Melville. We are indebted to J. Waterbury, E. Webb, and two anonymous reviewers' comments on the manuscript and to Val Franck for helpful discussions.

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Section: Methodsmentioning

confidence: 99%

Production of cobalt binding ligands in a Synechococcus feature at the Costa Rica upwelling dome

2005

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“…Moreover, the bioavailability of those metals, which is probably not directly related to their total dissolved concentrations in the oceans (Ellwood and van den Berg, 2001;Wang et al, 2009;Dupont et al, 2010) is also poorly documented. While a very limited database does exist for some of these metals in the Mediterranean Sea (Boyle et al, 1985;Tankere et al, 1995;Vega and Van den Berg, 1997;Morley et al, 1997), there is no data on the bioavailable fraction of these metals for the Mediterranean waters. Identifying and quantifying those metals in atmospheric deposition and how they impact the distribution in the water column is essential for understanding the spatial and temporal distribution of diazotrophs and N 2 fixing activity in the Mediterranean Sea.…”

Section: Impact Of Saharan Dust Input On N 2 Fixationmentioning

confidence: 99%

Nutrient control of N<sub>2</sub> fixation in the oligotrophic Mediterranean Sea and the impact of Saharan dust events

et al. 2011

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Abstract.A better understanding of the factors controlling N 2 fixation is a pre-requisite for improving our knowledge on the contribution of N 2 fixation process in the nitrogen cycling. Trace-metal clean nutrient/dust addition bioassays (+P, +PFe, +dust) were performed at three stations located in the western, central and eastern Mediterranean Sea, in summer 2008 as part of the BOUM cruise. The main goals were (1) to investigate the nutrient factor(s) limiting N 2 fixation (uptake of 15 N 2 ) and (2) to evaluate the potential impact of a Saharan dust event on this biological process during the stratification period. Initially, surface waters at the three stations were DIP-depleted (<10 nM) while the DFe concentrations were relatively high (from 1.2 to 2.3 nM) most likely due to atmospheric iron accumulation in the surface mixed layer. At all stations, Saharan dust input relieved the ambient nutrient limitation of the diazotrophic activity as demonstrated by the strong stimulation of N 2 fixation (from 130 % to 430 %). The highest dust stimulation of N 2 fixation was recorded at the station located in the eastern basin. The response of diazotrophic activity to nutrient additions was variable between the sampled stations suggesting a spatial variability of the factor controlling N 2 fixation over the whole basin. At allCorrespondence to: C. Ridame (celine.ridame@upmc.fr) stations, N 2 fixation was not limited by Fe nor co-limited by P and Fe. At the western station, N 2 fixation was DIP limited while at the eastern one, N 2 fixation was first DIP limited, then was limited by one or several chemical element(s) released by dust. Our results demonstrated that a Saharan dust input was able to relieve these successive on going limitations. Very interestingly, at the station located in the central basin, N 2 fixation was not limited by the availability of P yet it was strongly stimulated by dust addition (x3.1). A chemical element or a combination of several, released by the added dust may have been responsible for the observed stimulations of N 2 fixation. These results indicated that Saharan dust pulses to the surface Mediterranean waters, in addition to P and Fe, could be a source of chemical(s) element(s) that are necessary for metabolic processes and therefore influence rates of N 2 fixation.

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“…Similarly, the combination of adsorptive stripping voltammetry and catalytic currents can also be used to decrease the limit of detection: thus, in the presence of the oxidant nitrite (NO 2 -), the adsorptive stripping determination of Co 2? (see the paragraph ''Adsorptive stripping voltammetry'') has a detection limit in the 10 -12 mol L -1 range [32].…”

Section: Catalytic Currentsmentioning

confidence: 99%

Voltammetric techniques of analysis: the essentials

Scholz

2015

ChemTexts

162

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This text is written for a course on instrumental methods of quantitative analysis. It summarizes the basic concepts of modern voltammetric techniques of analysis. The guiding concept of this text is to demonstrate how the ratio of faradaic to capacitive currents decides about the sensitivity of the techniques, and how this ratio can be increased by electronics, electrode construction and by chemical means. Finally, the advantages and disadvantages of voltammetric techniques of analysis are briefly described.

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Determination of Cobalt in Seawater by Catalytic Adsorptive Cathodic Stripping Voltammetry

Cited by 107 publications

References 31 publications

Production of cobalt binding ligands in a Synechococcus feature at the Costa Rica upwelling dome

Production of cobalt binding ligands in a Synechococcus feature at the Costa Rica upwelling dome

Nutrient control of N<sub>2</sub> fixation in the oligotrophic Mediterranean Sea and the impact of Saharan dust events

Voltammetric techniques of analysis: the essentials

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Determination of Cobalt in Seawater by Catalytic Adsorptive Cathodic Stripping Voltammetry

Cited by 107 publications

References 31 publications

Production of cobalt binding ligands in a Synechococcus feature at the Costa Rica upwelling dome

Production of cobalt binding ligands in a Synechococcus feature at the Costa Rica upwelling dome

Nutrient control of N&lt;sub&gt;2&lt;/sub&gt; fixation in the oligotrophic Mediterranean Sea and the impact of Saharan dust events

Voltammetric techniques of analysis: the essentials

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Nutrient control of N<sub>2</sub> fixation in the oligotrophic Mediterranean Sea and the impact of Saharan dust events