Biogenic Manganese Oxides Facilitate Iodide Oxidation at pH ≤ 5. Issue 3 (16th March 2018)

• Record Type: Journal Article
• Authors: Grandbois, Russell; Yeager, Chris; Tani, Yukinori; Xu, Chen; Zhang, Saijin; Beaver, Morgan; Schwehr, Kathy; Kaplan, Daniel; Santschi, Peter
• Is Part Of: Geomicrobiology journal. Volume 35:Issue 3(2018)
• Page Start: 167
• Page End: 173
• Publication Date: 2018-03-16
• Subjects: Bioremediation -- iodine -- manganese oxidation -- radionuclide -- subsurface microbiology; Geomicrobiology -- Periodicals; Biogeochemistry -- Periodicals; 579
• DOI: 10.1080/01490451.2017.1338795
• Languages: English
• ISSNs: 0149-0451

Abstract

ABSTRACT: Radioactive 129 I, a byproduct of nuclear power generation, can pose risks to human health if released into the environment, where its mobility is highly dependent on speciation. Based on thermodynamic principles, 129 I should exist primarily as iodide (I − ) in most terrestrial environments; however, organo- 129 I and 129 iodate are also commonly detected in contaminated soils and groundwater. To investigate the capability of biogenic manganese oxides to influence iodide speciation, 17 manganese-oxidizing bacterial strains, representing six genera, were isolated from soils of the Savannah River Site, South Carolina. The isolates produced between 2.6 and 67.1 nmole Mn oxides (ml −1 media after 25 days, pH 6.5). Results from inhibitor assays targeting extracellular enzymes and reactive oxygen species indicated that both play a role in microbe-induced Mn(II) oxidation among the strains examined. Iodide oxidation was not observed in cultures of the most active Mn-oxidizing bacteria, Chryseobacterium sp. strain SRS1 and Chromobacterium sp. strain SRS8, or the fungus, Acremonium strictum strain KR21–2. While substantial amounts of Mn(III/IV) oxides were only generated in cultures at ≥pH 6, iodide oxidation was only observed in the presence of Mn(III/IV) oxides when the pH was ≤5. Iodide oxidation was promoted to a greater extent by synthetic Mn(IV)O2 than biogenic Mn(III/IV) oxides under these low pH conditions (≤pH 5). These results indicate that the influence of biogenic manganese oxides on iodide oxidation and immobilization is primarily limited to low pH environments.