Iron redox process in clay minerals and its environmental significance
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Miami University / OhioLINK
2015
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ndltd-OhioLink-oai-etd.ohiolink.edu-miami14383882842021-08-03T06:32:33Z Iron redox process in clay minerals and its environmental significance Zhao, Linduo Geochemistry Geological The importance of microbial nitrate-dependent Fe(II) oxidation to iron biogeochemistry is well recognized. Past research has focused on oxidation of aqueous Fe2+ and structural Fe(II) in oxides, carbonates, and phosphate, but the importance of structural Fe(II) in phyllosilicates in this reaction is only recently studied. However, the effect of clay mineralogy on the rate and the mechanism of the reaction, and subsequent mineralogical end products are still poorly known. The objective of the first research was to study the coupled process of microbial oxidation of Fe(II) in clay mineral nontronite (NAu-2), and nitrate reduction by Pseudogulbenkiania species strain 2002, and to determine mineralogical changes associated with this process. Bio-oxidation experiments were conducted using Fe(II) in microbially reduced nontronite as electron donor and nitrate as electron acceptor to investigate cell growth on this process. The bio-oxidation extent under growth and nongrowth conditions reached 67% and 57%, respectively. Over the same time period, nitrate was completely reduced. Abiotic oxidation by nitrite partly accelerated Fe(II) oxidation rate under the growth condition. The oxidized Fe(III) largely remained in the nontronite structure, but secondary minerals such as vivianite, ferrihydrite, and magnetite formed depending on specific experimental conditions. The objective of the second research was to study microbially mediated redox cycles of Fe in nontronite (NAu-2). During the reduction phase, structural Fe(III) in NAu-2 served as electron acceptor, lactate as electron donor, AQDS as electron shuttle, and dissimilatory Fe(III)-reducing bacterium Shewanella putrefaciens CN32 as mediator. During the oxidation phase, biogenic Fe(II) served as electron donor and nitrate as electron acceptor. Nitrate-dependent Fe(II)-oxidizing bacterium Pseudogulbenkiania sp. strain 2002 was added as mediator in the same media. For all three cycles, structural Fe in NAu-2 was able to reversibly undergo three redox cycles without significant dissolution. Fe(II) in bioreduced samples occurred in two distinct environments, at edges and in the interior of the NAu-2 structure. The overall objective of the third study was to study biological nitrate-dependent Fe(II) oxidation in illite IMt-1 and the effects of bio-oxidation on clay mineral transformation. Our data demonstrated that Pseudogulbenkiania sp. strain 2002 was able to couple oxidation of structural Fe(II) in IMt-1 with reduction of nitrate to N2 with nitrite as a transient intermediate. Fe(II)-oxidizing bacteria caused clay mineral structure change, and facilitated the illite¿kaolinite and illite¿smectite transformations. The biogenic smectite was a transient phase. 2015-08-03 English text Miami University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=miami1438388284 http://rave.ohiolink.edu/etdc/view?acc_num=miami1438388284 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
| collection |
NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Geochemistry Geological |
| spellingShingle |
Geochemistry Geological Zhao, Linduo Iron redox process in clay minerals and its environmental significance |
| author |
Zhao, Linduo |
| author_facet |
Zhao, Linduo |
| author_sort |
Zhao, Linduo |
| title |
Iron redox process in clay minerals and its environmental significance |
| title_short |
Iron redox process in clay minerals and its environmental significance |
| title_full |
Iron redox process in clay minerals and its environmental significance |
| title_fullStr |
Iron redox process in clay minerals and its environmental significance |
| title_full_unstemmed |
Iron redox process in clay minerals and its environmental significance |
| title_sort |
iron redox process in clay minerals and its environmental significance |
| publisher |
Miami University / OhioLINK |
| publishDate |
2015 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=miami1438388284 |
| work_keys_str_mv |
AT zhaolinduo ironredoxprocessinclaymineralsanditsenvironmentalsignificance |
| _version_ |
1719438649872875520 |