Measurement of the isotopic composition of dissolved iron in the open ocean

This work demonstrates for the first time the feasibility of the measurement of the isotopic composition of dissolved iron in seawater for a typical open ocean Fe concentration range (0.1–1 nM). It also presents the first data of this kind. Iron is preconcentrated using a Nitriloacetic Acid Superflo...

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Bibliographic Details
Published inGeophysical research letters Vol. 35; no. 24
Main Authors Lacan, F., Radic, A., Jeandel, C., Poitrasson, F., Sarthou, G., Pradoux, C., Freydier, R.
Format Journal Article
LanguageEnglish
Published Washington, DC Blackwell Publishing Ltd 01.12.2008
American Geophysical Union
Subjects
Earth sciences
Earth, ocean, space
Exact sciences and technology
iron isotopic composition
Ocean, Atmosphere
open ocean
Sciences of the Universe
seawater
Antarctic Ocean
PSW, Antarctic, Atlantic Sector
PS, Antarctic Ocean
AS, Tropical Atlantic, Circumpolar Deep Water
sea water
resins
Quaternary
Bias
accuracy
Isotopic composition
concentration
Deep water
upper Quaternary
Uptake
Anion exchange
Neptune
acids
corrections
isotope fractionation
organic materials
phytoplankton
iron
plankton
Feasibility
Cenozoic
Phanerozoic
Holocene
Atlantic
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ISSN0094-8276
1944-8007
DOI10.1029/2008GL035841

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Summary:This work demonstrates for the first time the feasibility of the measurement of the isotopic composition of dissolved iron in seawater for a typical open ocean Fe concentration range (0.1–1 nM). It also presents the first data of this kind. Iron is preconcentrated using a Nitriloacetic Acid Superflow resin and purified using an AG1x4 anion exchange resin. The isotopic ratios are measured with a MC‐ICPMS Neptune, coupled with a desolvator (Aridus II), using a 57Fe‐58Fe double spike mass bias correction. Measurement precision (0.13‰, 2SD) allows resolving small iron isotopic composition variations within the water column, in the Atlantic sector of the Southern Ocean (from δ57Fe = −0.19 to +0.32‰). Isotopically light iron found in the Upper Circumpolar Deep Water is hypothesized to result from organic matter remineralization. Shallow samples suggest that, if occurring, an iron isotopic fractionation during iron uptake by phytoplankton is characterized by a fractionation factor, such as: ∣Δ57Fe(plankton‐seawater)∣ < 0.48‰.
Bibliography:ark:/67375/WNG-4PXGN7X3-4
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ArticleID:2008GL035841
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ISSN:0094-8276
1944-8007
DOI:10.1029/2008GL035841