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Influence of organic complexation on dissolved iron distribution in East Antarctic pack ice

Genovese, C, Grotti, M, Pittaluga, J, Ardini, F, Janssens, J, Wuttig, K ORCID: 0000-0003-4010-5918, Moreau, S ORCID: 0000-0001-9446-812X and Lannuzel, D ORCID: 0000-0001-6154-1837 2018 , 'Influence of organic complexation on dissolved iron distribution in East Antarctic pack ice' , Marine Chemistry , pp. 1-10 , doi: 10.1016/j.marchem.2018.04.005.

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Abstract

Since Antarctic sea ice covers an area larger than the Antarctic continent itself, the discovery that it can fertilize the Southern Ocean with iron (Fe) has fostered a new breadth of research in recent years. In order to test the hypothesis that Fe-binding organic ligands control the distribution of dissolved iron (DFe) in Antarctic pack ice, iron organic speciation was investigated in samples collected during the Sea Ice Physics and Ecosystem eXperiment-2 (SIPEX-2) voyage in Austral winter/spring 2012. Dissolved Fe was measured using sector field inductively coupled plasma mass spectrometry, and iron organic speciation parameters were determined by competitive ligand equilibration - adsorptive cathodic stripping voltammetry method, using 1-nitroso-2-naphthol (NN) as the added ligand. The concentration of Fe-binding organic ligands (Lt) ranged from 4.9 nM to 41 nM (average of 14.9 ± 8.4 nM, n = 34), and was always higher than the corresponding DFe (average of 7.5 ± 4.5 nM, n = 34). Conditional stability constants (log K′Fe’L = 11.7–13.0) were similar to those previously observed in land-fast ice. Concentrations of DFe and Lt displayed similar depth profiles; their strong correlation (Spearman's ρ = 0.80, p 1). Estimates showed that pack ice would have released 0.45 μmol/m2/d of Lt during spring melt, 0.21 μmol/m2/d of which are free from Fe binding, and hence available for further complexation. Therefore, it is suggested that this excess of Fe-free ligands may play a key role in controlling the solubility of free or newly formed Fe in surface waters before the peak of primary production, outcompeting the Fe-binding organic ligands already present in seawater.

Item Type: Article
Authors/Creators:Genovese, C and Grotti, M and Pittaluga, J and Ardini, F and Janssens, J and Wuttig, K and Moreau, S and Lannuzel, D
Keywords: sea ice, ligands, iron, Antarctica
Journal or Publication Title: Marine Chemistry
Publisher: Elsevier Science Bv
ISSN: 0304-4203
DOI / ID Number: 10.1016/j.marchem.2018.04.005
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© 2018 Elsevier B.V. All rights reserved.

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