GEOC 98 |
| Siderophores are biogenic chelating agents exuded in terrestrial and marine environments to increase the bioavailablity of ferric iron. Recent work suggests that both solid and aqueous manganese may affect siderophore speciation and thus siderophore-mediated iron transport. We studied the interaction of the trihydroxamate siderophore desferrioxamine B with several environmentally relevant minerals: hausmannite and manganite, lower-valence minerals typically produced by abiotic Mn(II) oxidation; two synthetic layer-type Mn(IV) oxides; and a biogenic oxide produced by a model organism, Pseudomonas putida MnB1. For pH 5-7, we find that all minerals studied dissolve by “reductive” dissolution, yielding Mn(II); for pH 7-9, “ligand-promoted” dissolution, which yields Mn(III)-siderophore complexes, is the predominant reaction pathway. Because reductive dissolution results in siderophore oxidation, Mn-oxide dissolution at acidic pH may provide a significant abiotic sink for siderophores in natural waters. At alkaline pH, the complexes produced may profoundly affect the aqueous speciation of siderophores as well as provide a source of reactive Mn(III)-complexes. |
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Physical Chemistry of Soil and Aquifer Systems: A Symposium in Honor of Garrison Sposito
1:30 PM-4:45 PM, Tuesday, 12 September 2006 Moscone Center -- Room 256, Oral
Division of Geochemistry |