GEOC 139 |
| Barbara Sulzberger1, Edith Kaiser2, Laurence Meunier3, and Paul Borer1. (1) Department of Limnology, Swiss Federal Institute for Environmental Science and Technology (EAWAG), Ueberlandstrasse 133, P.O. Box 611, CH-8600 Duebendorf, Switzerland, (2) Limnological Research Center, Swiss Federal Institute for Environmental Science and Technology (EAWAG), Seestrasse 79, CH-6047 Kastanienbaum, Switzerland, (3) Department of Water Resources and Drinking Water, Swiss Federal Institute for Environmental Science and Technology (EAWAG), Ueberlandstrasse 133, P.O. Box 611, CH-8600 Duebendorf, Switzerland |
| Biogenic substances can enhance or reduce the rate of Fe(II) oxidation by O2, depending on the relative stability of Fe(II)- and Fe(III)-biogenic ligand complexes. Furthermore, Fe(II) oxidation by O2 is catalyzed by biological and mineral surfaces. Another factor affecting the kinetics of net Fe(II) oxidation is sunlight. We have measured slow decays of Fe(II) steady-state concentrations following irradiation of circumneutral natural water samples with simulated sunlight. This phenomenon can be explained in terms of continuous redox cycling of iron after irradiation by recycled reactive oxygen species and/or stabilization of Fe(II) by photochemically formed ligands. Reactive oxygen species, e.g., hydroxyl radicals produced in the Fenton reaction, drastically inhibited organic carbon utilization by riverine bacterioplankton. An important class of biogenic ligands is siderophores. They can prevent photochemically formed surface Fe(II) from being re-oxidized on the surface by enhancing its transfer into solution, thereby accelerating light-induced dissolution of Fe(III)-(hydr)oxides in oxic systems. |
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Microbially Mediated Manganese and Iron Oxidation in the Biosphere
8:00 AM-12:15 PM, Wednesday, March 31, 2004 Marriott -- Marquis NE, Oral
Division of Geochemistry |