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The impact of changing surface ocean conditions on the dissolution of aerosol iron

The impact of changing surface ocean conditions on the dissolution of aerosol iron
The impact of changing surface ocean conditions on the dissolution of aerosol iron

The proportion of aerosol iron (Fe) that dissolves in seawater varies greatly and is dependent on aerosol composition and the physicochemical conditions of seawater, which may change depending on location or be altered by global environmental change. Aerosol and surface seawater samples were collected in the Sargasso Sea and used to investigate the impact of these changing conditions on aerosol Fe dissolution in seawater. Our data show that seawater temperature, pH, and oxygen concentration, within the range of current and projected future values, had no significant effect on the dissolution of aerosol Fe. However, the source and composition of aerosols had the most significant effect on the aerosol Fe solubility, with the most anthropogenically influenced samples having the highest fractional solubility (up to 3.2%). The impact of ocean warming and acidification on aerosol Fe dissolution is therefore unlikely to be as important as changes in land usage and fossil fuel combustion. Our experimental results also reveal important changes in the size distribution of soluble aerosol Fe in solution, depending on the chemical conditions of seawater. Under typical conditions, the majority (77-100%) of Fe released from aerosols into ambient seawater existed in the colloidal (0.02-0.4 innodatamum) size fraction. However, in the presence of a sufficient concentration of strong Fe-binding organic ligands (10 nM) most of the aerosol-derived colloidal Fe was converted to soluble Fe (<0.02 μm). This finding highlights the potential importance of organic ligands in retaining aerosol Fe in a biologically available form in the surface ocean.

Biogeochemistry, Climate change, Iron, Ligands, colloids, Marine aerosols
0886-6236
1235-1250
Fishwick, Matthew P.
30603435-7248-4915-9f08-b044f0f9adca
Sedwick, Peter N.
4f6c2a8e-afe2-4b89-a971-e8b086d40b48
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Worsfold, Paul J.
27675f89-7eee-45c5-821e-a381d8db9693
Buck, Kristen N.
a6cfcd5a-0aac-4e8d-8225-59e7faa00f53
Church, Thomas M.
f73e8b82-f784-4b9c-a66e-e304ed94dc7d
Ussher, Simon J.
089623db-1a7d-42b8-87d1-1f17395373b1
Fishwick, Matthew P.
30603435-7248-4915-9f08-b044f0f9adca
Sedwick, Peter N.
4f6c2a8e-afe2-4b89-a971-e8b086d40b48
Lohan, Maeve C.
6ca10597-2d0f-40e8-8e4f-7619dfac5088
Worsfold, Paul J.
27675f89-7eee-45c5-821e-a381d8db9693
Buck, Kristen N.
a6cfcd5a-0aac-4e8d-8225-59e7faa00f53
Church, Thomas M.
f73e8b82-f784-4b9c-a66e-e304ed94dc7d
Ussher, Simon J.
089623db-1a7d-42b8-87d1-1f17395373b1

Fishwick, Matthew P., Sedwick, Peter N., Lohan, Maeve C., Worsfold, Paul J., Buck, Kristen N., Church, Thomas M. and Ussher, Simon J. (2014) The impact of changing surface ocean conditions on the dissolution of aerosol iron. Global Biogeochemical Cycles, 28 (11), 1235-1250. (doi:10.1002/2014GB004921).

Record type: Article

Abstract

The proportion of aerosol iron (Fe) that dissolves in seawater varies greatly and is dependent on aerosol composition and the physicochemical conditions of seawater, which may change depending on location or be altered by global environmental change. Aerosol and surface seawater samples were collected in the Sargasso Sea and used to investigate the impact of these changing conditions on aerosol Fe dissolution in seawater. Our data show that seawater temperature, pH, and oxygen concentration, within the range of current and projected future values, had no significant effect on the dissolution of aerosol Fe. However, the source and composition of aerosols had the most significant effect on the aerosol Fe solubility, with the most anthropogenically influenced samples having the highest fractional solubility (up to 3.2%). The impact of ocean warming and acidification on aerosol Fe dissolution is therefore unlikely to be as important as changes in land usage and fossil fuel combustion. Our experimental results also reveal important changes in the size distribution of soluble aerosol Fe in solution, depending on the chemical conditions of seawater. Under typical conditions, the majority (77-100%) of Fe released from aerosols into ambient seawater existed in the colloidal (0.02-0.4 innodatamum) size fraction. However, in the presence of a sufficient concentration of strong Fe-binding organic ligands (10 nM) most of the aerosol-derived colloidal Fe was converted to soluble Fe (<0.02 μm). This finding highlights the potential importance of organic ligands in retaining aerosol Fe in a biologically available form in the surface ocean.

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More information

Published date: 2014
Keywords: Biogeochemistry, Climate change, Iron, Ligands, colloids, Marine aerosols

Identifiers

Local EPrints ID: 414026
URI: http://eprints.soton.ac.uk/id/eprint/414026
ISSN: 0886-6236
PURE UUID: d1ca8ec4-9cee-40f7-a7e1-52577f7f8b53
ORCID for Maeve C. Lohan: ORCID iD orcid.org/0000-0002-5340-3108

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Date deposited: 12 Sep 2017 16:32
Last modified: 06 Jun 2024 01:51

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Contributors

Author: Matthew P. Fishwick
Author: Peter N. Sedwick
Author: Maeve C. Lohan ORCID iD
Author: Paul J. Worsfold
Author: Kristen N. Buck
Author: Thomas M. Church
Author: Simon J. Ussher

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