Measurement of iron chemical speciation in seawater at 4°C: The use of competitive ligand exchange-adsorptive cathodic stripping voltammetry

Hassler, CS; Legiret, FE; Butler, ECV

Measurement of iron chemical speciation in seawater at 4°C: The use of competitive ligand exchange-adsorptive cathodic stripping voltammetry

Hassler, CS Legiret, FE Butler, ECV

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Publication Type:: Journal Article
Citation:: Marine Chemistry, 2013, 149 pp. 63 - 73
Issue Date:: 2013-02-01

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Field	Value	Language
dc.contributor.author	Hassler, CS	en_US
dc.contributor.author	Legiret, FE	en_US
dc.contributor.author	Butler, ECV	en_US
dc.date.issued	2013-02-01	en_US
dc.identifier.citation	Marine Chemistry, 2013, 149 pp. 63 - 73	en_US
dc.identifier.issn	0304-4203	en_US
dc.identifier.uri	http://hdl.handle.net/10453/27431
dc.description.abstract	Iron is mostly bound to poorly characterised organic ligands; thus, organic ligands are paramount in defining Fe biogeochemical cycling and its control on oceanic primary productivity. Since 1994, Fe chemical speciation has been determined by Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-AdCSV) at room temperature. However, chemical speciation is strongly dependent on temperature and some organic ligands can be temperature sensitive. Here, we compare the use of the CLE-AdCSV at room temperature and at 4°C-a temperature closer to that found in the Southern Ocean, one of the largest iron-limited regions. For both temperatures, similar detection limits and total Fe concentrations were found. However, at 4°C the analytical detection window (αFe(TAC)2) was shifted by 1.4-fold towards the detection of weaker ligands, resulting in up to 2-fold lower ligand concentrations as well as a 2- to 5-fold and 10- to70-fold lower conditional stability constants with inorganic Fe (Fe') and Fe(III), respectively. As a result, the Fe' concentration at 4°C was 2-fold greater, resulting in direct implication for Fe bioavailability. Results show that difference in Fe chemical speciation at 4°C was not solely explained by temperature effect on thermodynamics with the exchange ligands or the diffusion of the electroactive complex towards the Hg drop. Lowering analytical window during analysis at room temperature is proposed as a first estimate of temperature effect on iron chemical speciation. © 2013 Elsevier B.V.	en_US
dc.relation.ispartof	Marine Chemistry	en_US
dc.relation.isbasedon	10.1016/j.marchem.2012.12.007	en_US
dc.subject.classification	Oceanography	en_US
dc.title	Measurement of iron chemical speciation in seawater at 4°C: The use of competitive ligand exchange-adsorptive cathodic stripping voltammetry	en_US
dc.type	Journal Article
utslib.citation.volume	149	en_US
utslib.for	0399 Other Chemical Sciences	en_US
utslib.for	0402 Geochemistry	en_US
utslib.for	0405 Oceanography	en_US
pubs.embargo.period	Not known	en_US
pubs.organisational-group	/University of Technology Sydney
pubs.organisational-group	/University of Technology Sydney/Faculty of Science
utslib.copyright.status	closed_access
pubs.publication-status	Published	en_US
pubs.volume	149	en_US

Abstract:

Iron is mostly bound to poorly characterised organic ligands; thus, organic ligands are paramount in defining Fe biogeochemical cycling and its control on oceanic primary productivity. Since 1994, Fe chemical speciation has been determined by Competitive Ligand Exchange-Adsorptive Cathodic Stripping Voltammetry (CLE-AdCSV) at room temperature. However, chemical speciation is strongly dependent on temperature and some organic ligands can be temperature sensitive. Here, we compare the use of the CLE-AdCSV at room temperature and at 4°C-a temperature closer to that found in the Southern Ocean, one of the largest iron-limited regions. For both temperatures, similar detection limits and total Fe concentrations were found. However, at 4°C the analytical detection window (αFe(TAC)2) was shifted by 1.4-fold towards the detection of weaker ligands, resulting in up to 2-fold lower ligand concentrations as well as a 2- to 5-fold and 10- to70-fold lower conditional stability constants with inorganic Fe (Fe') and Fe(III), respectively. As a result, the Fe' concentration at 4°C was 2-fold greater, resulting in direct implication for Fe bioavailability. Results show that difference in Fe chemical speciation at 4°C was not solely explained by temperature effect on thermodynamics with the exchange ligands or the diffusion of the electroactive complex towards the Hg drop. Lowering analytical window during analysis at room temperature is proposed as a first estimate of temperature effect on iron chemical speciation. © 2013 Elsevier B.V.

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