Multiple Effects of Humic Components on Microbially Mediated Iron Redox Processes and Production of Hydroxyl Radicals

Microbially mediated iron redox processes are of great significance in the biogeochemical cycles of elements, which are often coupled with soil organic matter (SOM) in the environment. Although the influences of SOM fractions on individual reduction or oxidation processes have been studied extensive...

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Published inEnvironmental science & technology Vol. 56; no. 22; pp. 16419 - 16427
Main Authors Han, Ruixia, Wang, Zhe, Lv, Jitao, Zhu, Zhe, Yu, Guang-Hui, Li, Gang, Zhu, Yong-Guan
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 15.11.2022
Subjects
Aquatic plants
Biogeochemical cycles
Biogeochemical Cycling
Electron transfer
Ferric Compounds
Fractions
Free radicals
Fulvic acids
Humic acids
Humic Substances - analysis
Hydroxyl Radical
Hydroxyl radicals
Iron - chemistry
Iron oxides
Microorganisms
Organic matter
Organic soils
Oxidation
Oxidation-Reduction
Peat
Reduction
Soil - chemistry
Soil organic matter
Soils
redox cycle
iron
hydroxyl radical
dissimilatory iron-reducing bacteria
soil organic matter
reactive oxygen species
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Summary:Microbially mediated iron redox processes are of great significance in the biogeochemical cycles of elements, which are often coupled with soil organic matter (SOM) in the environment. Although the influences of SOM fractions on individual reduction or oxidation processes have been studied extensively, a comprehensive understanding is still lacking. Here, using ferrihydrite, Shewanella oneidensis MR-1, and operationally defined SOM components including fulvic acid (FA), humic acid (HA), and humin (HM) extracted from black soil and peat, we explored the SOM-mediated microbial iron reduction and hydroxyl radical (•OH) production processes. The results showed that the addition of SOM inhibited the transformation of ferrihydrite to highly crystalline iron oxides. Although FA and HA increased Fe­(II) production over four times on average due to complexation and their high electron exchange capacities, HA inhibited 30–43% of the •OH yield, while FA had no significant influence on it. Superoxide (O2 •–) was the predominant intermediate in •OH production in the FA-containing system, while one- and two-electron transfer processes were concurrent in HA- and HM-containing systems. These findings provide deep insights into the multiple mechanisms of SOM in regulating microbially mediated iron redox processes and •OH production.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.2c03799