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The Biogeochemistry of Marine Particulate Trace Metals

Daniel Ohnemus, Ph.D., 2014
Phoebe Lam, Advisor

Marine particles include living and non-living solid components of seawater, representing a dynamic and chemically diverse mixture of phases.  Through a combination of method development, basin-scale particulate collection and analyses, modeling, and field experiments, this thesis examines both the distributions of marine particulate trace metals and the underlying processes—inputs, scavenging, vertical and horizontal transport, and biotic uptake—in which marine particles participate.

I first present the results of an intercalibration exercise among several US laboratories.  We use inter-lab and intra-lab total elemental recoveries of these particles to determine our state of our intercalibration and to identify means of future improvement.  We present a new chemical method for dissolution of polyethersulfone filters and compare it to other total particle digestion procedures.  I then present the marine particulate distributions of the lithogenic elements Al, Fe, and Ti in the North Atlantic GEOTRACES section.  A one-dimensional multi-box model that describes lithogenic particle distributions is also proposed and its parameter sensitivities and potential implications are discussed.

I conclude with presentation of results from a series of bottle incubations in iron-limited waters using isotopically labeled Fe-minerals.  We demonstrate solubilization of minerals ferrihydrite and fayalite via transfer of isotopic label into suspended particles.