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.; Moreau, S.; Lannuzel, D. (2018). Influence of organic complexation on dissolved iron distribution in East Antarctic pack ice. Mar. Chem. 203: 28-37. https://dx.doi.org/10.1016/j.marchem.2018.04.005 In: Marine Chemistry. Elsevier: Amsterdam. ISSN 0304-4203; e-ISSN 1872-7581, more |  |
| Keyword | | | Author keywords | Iron speciation; Sea ice; Pack ice; Organic ligands; Southern Ocean |
| Authors | | Top | - Genovese, C., more
- Grotti, M.
- Pittaluga, J.
- Ardini, F.
| - Janssens, J.
- Wuttig, K.
- Moreau, S., more
- Lannuzel, D., more
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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 < 0.001) suggested that Fe-binding organic ligands control DFe distribution in Antarctic pack ice. Unlike results previously obtained for land-fast ice, Fe-binding organic ligands in pack ice were never saturated with iron (Lt/DFe > 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. |
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