Premium
Measurement of the isotopic composition of dissolved iron in the open ocean
Author(s) -
Lacan F.,
Radic A.,
Jeandel C.,
Poitrasson F.,
Sarthou G.,
Pradoux C.,
Freydier R.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl035841
Subject(s) - seawater , fractionation , isotope fractionation , dissolved organic carbon , environmental chemistry , isotope , geotraces , water column , oceanography , water mass , composition (language) , circumpolar deep water , geology , chemistry , deep water , north atlantic deep water , chromatography , linguistics , physics , philosophy , quantum mechanics
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 57 Fe‐ 58 Fe 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 δ 57 Fe = −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: ∣Δ 57 Fe (plankton‐seawater) ∣ < 0.48‰.