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

Rijkenberg, Micha J. A., Powell, Claire F., Dall'Osto, Manuel, Nielsdottir, Maria C., Patey, Matthew D., Hill, Polly G., Baker, Alex R. ORCID: https://orcid.org/0000-0002-8365-8953, 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). pp. 56-67.

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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.

Item Type:	Article
Additional Information:	Author acknowledgements: The authors thank the NERC Earth Observation Data Acquisition and Analysis Service (NEODAAS) for supplying data for this study. Satellite data were also provided by the Department of Meteorology (E. Highwood) of the University of Reading. We used the NAO index according to Hurrell as found on: www.cgd.ucar.edu/cas/jhurrell/nao.stat.winter.html. The authors gratefully acknowledge the NOAA Air Resources Laboratory (ARL) for the provision of the HYSPLIT transport and dispersion model and/or READY website (www.arl.noaa.gov/ready.html) used in this publication. We further want to express our gratitude to the Master and crew of FS Poseidon for support during the cruise. This research is funded by NERC as part of the UK-SOLAS programme, project grant number NE/C001931/1.
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User:	Rosie Cullington
Date Deposited:	26 Feb 2011 11:27
Last Modified:	24 Sep 2024 09:35
URI:	https://ueaeprints.uea.ac.uk/id/eprint/24803
DOI:	10.1016/j.marchem.2008.02.006

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