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Changes in iron speciation following a Saharan dust event in the tropical North Atlantic Ocean

Changes in iron speciation following a Saharan dust event in the tropical North Atlantic Ocean
Changes in iron speciation following a Saharan dust event in the tropical North Atlantic Ocean
Concentrations of dissolved iron (DFe) and Fe-binding ligands were determined in the tropical Northeast Atlantic Ocean (12–30°N, 21–29°W) as part of the UK-SOLAS (Surface Ocean Lower Atmosphere Study) cruise Poseidon 332 (P332) in January–February 2006. The surface water DFe concentrations varied between 0.1 and 0.4 nM with an average of 0.22 ± 0.05 nM (n = 159). The surface water concentrations of total Fe-binding ligands varied between 0.82 and 1.46 nM with an average of 1.11 ± 0.14 nM (n = 33). The concentration of uncomplexed Fe-binding ligands varied between 0.64 and 1.35 nM with an average of 0.90 ± 0.14 nM (n = 33). Thus, on average 81% of the total Fe-binding ligand concentration was uncomplexed. The average logarithmic conditional stability constant of the pool of Fe-binding ligands was 22.85 ± 0.38 with respect to Fe3+ (n = 33). A transect (12°N, 26°W to 16°N, 25.3°W) was sailed during a small Saharan dust event and repeated a week later. Following the dust event, the concentration of DFe increased from 0.20 ± 0.026 nM (n = 125) to 0.25 ± 0.028 (n = 17) and the concentration of free Fe-binding ligands decreased from 1.15 ± 0.15 (n = 4) to 0.89 ± 0.10 (n = 4) nM. Furthermore, the logarithmic stability constants of the Fe-binding ligands south of the Cape Verde islands were distinctively lower than north of the islands. The absence of a change in the logarithmic stability constant after the dust event south of the Cape Verde islands suggests that there was no significant atmospheric input of new Fe-binding ligands during this dust event.
atmospheric input, aerosols, saharan dust, dry deposition, dissolved iron, organic iron complexation, equatorial atlantic ocean
0304-4203
56-67
Rijkenberg, Micha J.A.
549cc6d0-6f1a-432f-863a-2988abcb25d3
Powell, Claire F.
20ca5807-abae-44f0-83cb-78d73e5ca6d5
Dall'Osto, Manuel
7520b155-7a84-4019-b17d-aa09e4cd0092
Nielsdottir, Maria C.
7b1f99e9-79cc-4d73-a46f-5e231c3fcbad
Patey, Matthew D.
953bb9e5-e90f-4178-ae55-114c025137d2
Hill, Polly G.
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Baker, Alex R.
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Jickells, Tim D.
b3d89e13-a093-41bf-b721-786c25504962
Harrison, Roy M.
74964d49-ba58-47b5-ac97-8c72ddddb38a
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9
Rijkenberg, Micha J.A.
549cc6d0-6f1a-432f-863a-2988abcb25d3
Powell, Claire F.
20ca5807-abae-44f0-83cb-78d73e5ca6d5
Dall'Osto, Manuel
7520b155-7a84-4019-b17d-aa09e4cd0092
Nielsdottir, Maria C.
7b1f99e9-79cc-4d73-a46f-5e231c3fcbad
Patey, Matthew D.
953bb9e5-e90f-4178-ae55-114c025137d2
Hill, Polly G.
03ff729d-1c24-45f8-8bf7-3bcc9bf882e9
Baker, Alex R.
3a011c8c-c15a-4080-9602-6f3628fdca4a
Jickells, Tim D.
b3d89e13-a093-41bf-b721-786c25504962
Harrison, Roy M.
74964d49-ba58-47b5-ac97-8c72ddddb38a
Achterberg, Eric P.
685ce961-8c45-4503-9f03-50f6561202b9

Rijkenberg, Micha J.A., Powell, Claire F., Dall'Osto, Manuel, Nielsdottir, Maria C., Patey, Matthew D., Hill, Polly G., Baker, Alex R., Jickells, Tim D., Harrison, Roy M. and Achterberg, Eric P. (2008) Changes in iron speciation following a Saharan dust event in the tropical North Atlantic Ocean. Marine Chemistry, 110 (1-2), 56-67. (doi:10.1016/j.marchem.2008.02.006).

Record type: Article

Abstract

Concentrations of dissolved iron (DFe) and Fe-binding ligands were determined in the tropical Northeast Atlantic Ocean (12–30°N, 21–29°W) as part of the UK-SOLAS (Surface Ocean Lower Atmosphere Study) cruise Poseidon 332 (P332) in January–February 2006. The surface water DFe concentrations varied between 0.1 and 0.4 nM with an average of 0.22 ± 0.05 nM (n = 159). The surface water concentrations of total Fe-binding ligands varied between 0.82 and 1.46 nM with an average of 1.11 ± 0.14 nM (n = 33). The concentration of uncomplexed Fe-binding ligands varied between 0.64 and 1.35 nM with an average of 0.90 ± 0.14 nM (n = 33). Thus, on average 81% of the total Fe-binding ligand concentration was uncomplexed. The average logarithmic conditional stability constant of the pool of Fe-binding ligands was 22.85 ± 0.38 with respect to Fe3+ (n = 33). A transect (12°N, 26°W to 16°N, 25.3°W) was sailed during a small Saharan dust event and repeated a week later. Following the dust event, the concentration of DFe increased from 0.20 ± 0.026 nM (n = 125) to 0.25 ± 0.028 (n = 17) and the concentration of free Fe-binding ligands decreased from 1.15 ± 0.15 (n = 4) to 0.89 ± 0.10 (n = 4) nM. Furthermore, the logarithmic stability constants of the Fe-binding ligands south of the Cape Verde islands were distinctively lower than north of the islands. The absence of a change in the logarithmic stability constant after the dust event south of the Cape Verde islands suggests that there was no significant atmospheric input of new Fe-binding ligands during this dust event.

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More information

Submitted date: 3 April 2007
Published date: 16 May 2008
Additional Information: Actually deposited by Jane Conquer
Keywords: atmospheric input, aerosols, saharan dust, dry deposition, dissolved iron, organic iron complexation, equatorial atlantic ocean

Identifiers

Local EPrints ID: 52016
URI: http://eprints.soton.ac.uk/id/eprint/52016
ISSN: 0304-4203
PURE UUID: b7668ac1-9dad-4ddb-8fba-ad8684639286

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Date deposited: 03 Jun 2008
Last modified: 15 Mar 2024 10:21

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Contributors

Author: Micha J.A. Rijkenberg
Author: Claire F. Powell
Author: Manuel Dall'Osto
Author: Maria C. Nielsdottir
Author: Matthew D. Patey
Author: Polly G. Hill
Author: Alex R. Baker
Author: Tim D. Jickells
Author: Roy M. Harrison

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