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The marine geochemistry of iron and iron isotopes

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dc.contributor.advisor Edward A. Boyle. en_US Bergquist, Bridget A., 1973- en_US
dc.contributor.other Woods Hole Oceanographic Institution. en_US 2010-04-07T13:39:49Z 2010-04-07T13:39:49Z 2004 en_US 2004 en_US
dc.description Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and, the Woods Hole Oceanographic Institution), 2004. en_US
dc.description Includes bibliographical references. en_US
dc.description.abstract 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. en_US
dc.description.abstract (cont.) The main channel river dissolved Fe samples and suspended loads were isotopically similar ( -0.2 to -0.45%o relative to igneous rocks). The isotopically heaviest sample collected was dissolved Fe from an organic rich tributary, the Negro River (+0.16%o). In contrast, the suspended load from the Negro River was isotopically light (-1%o). The isotopically lightest sample from the Amazon region was shelf porewater (-1.4%o). In river water-seawater mixing experiments, the Fe isotopic signal of dissolved Fe of river water was modified by flocculation of isotopically heavy Fe. The observed range in the Fe isotopic composition of the natural samples including biological and aqueous samples demonstrates that significant and useful fractionation is associated with Fe biogeochemistry in the environment ... en_US
dc.description.statementofresponsibility by Bridget A. Bergquist. en_US
dc.format.extent 233 p. en_US
dc.language.iso eng en_US
dc.publisher Massachusetts Institute of Technology en_US
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. en_US
dc.rights.uri en_US
dc.subject Joint Program in Oceanography. en_US
dc.subject Earth, Atmospheric, and Planetary Sciences. en_US
dc.subject Woods Hole Oceanographic Institution. en_US
dc.title The marine geochemistry of iron and iron isotopes en_US
dc.type Thesis en_US Ph.D. en_US
dc.contributor.department Joint Program in Oceanography. en_US
dc.contributor.department Massachusetts Institute of Technology. Dept. of Earth, Atmospheric, and Planetary Sciences. en_US
dc.contributor.department Woods Hole Oceanographic Institution. en_US
dc.identifier.oclc 61048015 en_US

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