First Quantification of the Controlling Role of Humic Substances in the Transport of Iron Across the Surface of the Arctic Ocean

One of the main reasons behind our current lack of understanding of iron cycling in the oceans is our inability to characterize the ligands that control iron solubility, photosensitivity, reactivity, and bioavailability. We currently lack consensus about the nature and origin of these ligands. Here,...

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Bibliographic Details
Published in:Environmental Science & Technology
Main Authors: Laglera, Luis M., Sukekava, Camila, Slagter, Hans A., Downes, Javier, Aparicio-Gonzalez, Alberto, Gerringa, Loes J. A.
Format: Article in Journal/Newspaper
Language:English
Published: 2019
Subjects:
CATHODIC STRIPPING VOLTAMMETRY
BINDING LIGANDS
ORGANIC-MATTER
SOUTHERN-OCEAN
NATURAL-WATERS
SPECIATION
ESTUARINE
FE
SEAWATER
BIOGEOCHEMISTRY
Arctic
Arctic Ocean
Southern Ocean
Online Access:https://hdl.handle.net/11370/2dff06f6-32e3-4a42-90e3-1958bd6be016
https://research.rug.nl/en/publications/2dff06f6-32e3-4a42-90e3-1958bd6be016
https://doi.org/10.1021/acs.est.9b04240
https://pure.rug.nl/ws/files/108282623/acs.est.9b04240.pdf
Description
Summary:One of the main reasons behind our current lack of understanding of iron cycling in the oceans is our inability to characterize the ligands that control iron solubility, photosensitivity, reactivity, and bioavailability. We currently lack consensus about the nature and origin of these ligands. Here, we present the first field application of a new methodological development that allows the selective quantification of the fraction of Fe complexed to humic substances (HS). In the HS-rich surface Arctic waters, including the Fe-rich Transpolar Drift (TPD), we found that HS iron binding groups were largely occupied by iron (49%). The overall contribution of Fe-HS complexes to DFe concentrations was substantial at 80% without significant differences between TPD and non-TPD waters. Stabilization and transport of large concentrations of DFe across the surface of the Arctic Ocean are due to the formation of high concentrations of Fe-HS complexes. Competition of Arctic Fe-HS complexes with desferrioxamine and EDTA indicated that their stability constants are considerably higher than the stability constants previously found for riverine HS in temperate estuaries and HS standard material. This is the first case of identification of the ligand-dominating iron speciation over a specific region of the global ocean.

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