The marine geochemistry of iron and iron isotopes

This thesis addressed questions about the Fe cycle by measuring detailed profiles and transects of Fe species in the ocean and also by exploring the use of a new tracer of Fe, Fe isotopic fractionation. In the subtropical and tropical Atlantic Ocean, transects and profiles are presented for dissolved Fe ([less than]0.4 m), soluble Fe ([less than]0.02 gm), and colloidal Fe (0.02 to 0.4 Im). Surface dissolved Fe distributions reflect atmospheric deposition trends with colloidal Fe following dust deposition more strongly than the soluble fraction of Fe. Observed surface maxima and shallow minima in dissolved Fe were always due to variations in the colloidal Fe fraction. Deep-water dissolved and colloidal Fe concentrations vary with water mass source, age, and transport path. Elevated dissolved Fe concentrations ([greather than]1 nmol/kg) were associated with an oxygen minimum zone in the tropical Atlantic at 100N, 45 degrees W. Fractionation of iron isotopes could be an effective tool to investigate the geochemistry of iron. Trace metal clean plankton tows, river samples, aerosol leachates, and porewater samples were measured for their iron isotopic composition using a GV Instruments IsoProbe Multi-collector ICPMS. The Fe isotopic composition of plankton tow samples varied by over 4%o (in 56Fe/54Fe). North Pacific plankton tow samples had isotopically lighter Fe isotopic compositions than samples from the Atlantic. The overall isotopic range observed in the Amazon River system was 1.5%o, with variability observed for different types of tributaries.

Department dc:contributor.department

Joint Program in Oceanography

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2004

Author dc:creator

• Bergquist, Bridget A., 1973-

Advisor dc:contributor.advisor

• Edward A. Boyle.

• Joint Program in Oceanography.
• Earth, Atmospheric, and Planetary Sciences.
• Woods Hole Oceanographic Institution.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/53550

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/53550