CHARACTERIZATION OF MAGNETITE FROM COLUMBIA RIVER SEDIMENTS
Maya Navarro1, Miranda Bradley2, Paul Tratnyek2.
1DePaul University, Chicago, IL, 2Institute of Environmental Health, Oregon Health and Science University, Portland, OR.
Sediments in the Columbia River contain iron oxides, which are significant to the biogeochemistry of the ecosystem. Magnetite (Fe3O4), an iron oxide mineral, has unique redox properties, specifically because it contains both ferrous (Fe2+) and ferric (Fe3+) iron that allows it to sequester contaminants such as uranium by reduction. In this study, the variability of the redox properties of magnetite are measured in sediment samples from 6 locations along the Columbia River as well as in samples that have intentionally been oxidized or reduced prior to experimentation. We hypothesize that these properties will vary based on the mineral composition and condition of the outer shell of material that coats the particles, which is oxidized when exposed to oxygen or when reducing another material in the environment. Powder disk electrodes (PDEs) of each sample are tested in a 3-electrode cell using linear polarization resistance, linear sweep voltammetry, electrical impedance spectroscopy, and cyclic voltammetry techniques. The resulting plots are used to determine how electrons behave at the surface of the material and the potential for environmental reactivity. The differences in these different types of surface composition are expected to be observable using these forms of electrochemical testing. Preliminary results show a correlation between the material’s ability to conduct charge and its geographic origin. The variability in these data suggests the possibility of differences among the redox properties of magnetite from various locations.