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Atmospheric input of manganese and iron to the ocean: Seawater dissolution experiments with Saharan and North American dusts

Mendez, Jeffrey and Guieu, Cecile and Adkins, Jess (2010) Atmospheric input of manganese and iron to the ocean: Seawater dissolution experiments with Saharan and North American dusts. Marine Chemistry, 120 (1-4). pp. 34-43. ISSN 0304-4203.

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Dissolution of wind blown dust is a major source of iron, manganese and other trace nutrients in the ocean. Kinetic and thermodynamic values for the release of metals from dust are needed for computer models which incorporate dust as part of their ocean system. Here we investigate both the thermodynamic and kinetics parameters involved in the dissolution of metals from dust in seawater. We added dust from the Sahara and the Western United States in five different concentrations (0.01–5.0 mg/L) representative of those concentrations found in seawater after dust events, to open-ocean Pacific seawater. Sub-sampling of the reaction vessels took place on days 1, 2, 4, 7, 14, and 35 for the kinetic study. Results show different apparent thermodynamic constants for manganese (Mn) and iron (Fe). The final Mn concentrations are proportional to the added dust concentration. Fe concentrations reach a maximum of less than 2 nM, independent of the quantity and type of dust added. The Fe dissolution kinetics are faster than our sampling resolution. The first order rate constant for the dissolution of Mn from the Western US and Sahara dusts were 0.94 ± 0.04 (nmol Mn/day mg Dust), and 0.22 ± 0.01 (nmol Mn/daymg Dust) respectively. We conclude that, Mn concentrations are limited by available Mn on the dust surface, while Fe concentrations are limited by the ligand concentrations in the seawater, which ultimately are determined by the biological community.

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Additional Information:© 2008 Elsevier. Received 10 July 2008; accepted 28 August 2008. Available online 9 September 2008. We would like to acknowledge Marith Reheis (USGS) for kindly providing the U.S. dust, Stéphane Moustier (CEREGE-France) for the grain-size distribution measurements, Kristen Buck (UC Santa Cruz) for the seawater ligand measurements, Diego Fernandez for his expertise with the ICP-mass spectrometer, and James Morgan for insightful discussions. This work was partly supported by the National Science Foundation (grant OCE-0502642), by the Comer Science and Education Foundation, and by the European FAIRY Program (Marie Curie Int. Fellowships — Contract MOIF-CT-2004-002918).
Funding AgencyGrant Number
Corner Science and Education FoundationUNSPECIFIED
European FAIRY Program Marie Curie Int. FellowshipsMOIF-CT-2004-002918
Subject Keywords:Iron; Manganese; Aerosol; Dust dissolution; Marine chemistry
Issue or Number:1-4
Record Number:CaltechAUTHORS:20100715-090913021
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:19064
Deposited By: Tony Diaz
Deposited On:15 Jul 2010 20:16
Last Modified:03 Oct 2019 01:51

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