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Synergistic Dissolution of Manganese Oxides as Promoted by Siderophores and Small Organic Acids
Author(s) -
Saal Lauren B.,
Duckworth Owen W.
Publication year - 2010
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2009.0465
Subject(s) - dissolution , siderophore , oxalate , chemistry , manganese , ligand (biochemistry) , inorganic chemistry , aqueous solution , chelation , oxide , metal , solubility , organic acid , organic chemistry , receptor , biochemistry , gene
Recent studies have revealed that siderophores, biogenic chelating agents that strongly complex Fe(III) and other hard metals, may function in concert with low‐molecular‐mass organic acids (LMMOAs) to facilitate Fe (hydr)oxide dissolution via synergistic reactions. The siderophore desferrioxamine B (DFOB) may also participate in a number of chemical reactions at Mn (hydr)oxide surfaces. The goal of this study was to determine the rates and products of δ‐MnO 2 , a layer type Mn(IV) oxide, dissolution as promoted by LMMOA–DFOB mixtures. As with Fe (hydr)oxides, the rate of DFOB‐promoted dissolution of δ‐MnO 2 is strongly influenced by the presence of the LMMOAs citrate and oxalate. In the presence of DFOB, citrate increases the dissolution rate relative to the sum of dissolution rates from corresponding single‐ligand systems by promoting both Mn(III)HDFOB + complex formation and Mn(II) production in a pH‐dependent mechanism. In contrast, oxalate–DFOB mixtures produce predominantly Mn(II), with rates enhanced up to threefold from the sum of dissolution rates in single‐ligand systems at acidic pH values. We investigated possible mechanisms to describe this synergistic dissolution processes by building on observations of single‐ligand systems. These results suggest that biological exudation of LMMOAs in conjunction with siderophores may allow the selection of dissolution products, including regulation of the formation of potentially reactive aqueous Mn(III) complexes.