Formation and transformation of manganese(III) intermediates in the photochemical generation of manganese(IV) oxide minerals

Zhang, Tengfei; Liu, Lihu; Tan, Wenfeng; Suib, Steven L.; Qiu, Guohong

doi:10.1016/j.chemosphere.2020.128082

Cited by 11 publications

(3 citation statements)

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“…Homogeneous oxidation of aqueous Mn(II) by dissolved O 2 is thermodynamically unfavorable (at pH < 8) and kinetically hindered due to high activation energy of the reaction, ,, yet there are many physical and chemical factors that drive abiotic formation and transformation of Mn-oxides. Mn(II) can be oxidized to Mn(III) by ROS (e.g., O 2 •– , 1 O 2 , OH • ) produced through abiotic pathways including Fe(II) oxidation, nitrate photolysis, , illumination of humic substances, and illumination of metal oxides in desert varnish . Further Mn(III) oxidation by ROS and/or disproportionation results in rapid Mn(IV)-oxide formation. , Mineral surfaces, such as Fe-oxides and Mn-oxides, also catalyze Mn(II) oxidation via interfacial catalysis and/or electrochemical reactions − at rates equivalent to or faster than biological oxidation. , Products of Mn(II) oxidation and Mn-oxide phase transformations are highly dependent on pH conditions (e.g., SI Figure S1) and mineral surface properties (e.g., semiconductivity, particle size, ions). ,,− For instance, the presence of transition metals (e.g., Co and Ni), high concentrations of uranyl, and thallium have all been shown to mediate changes in Mn-oxide crystallinity or phase transformation.…”

Section: Manganese In Terrestrial Ecosystems: Occurrence and Characte...mentioning

confidence: 99%

“…•− , 1 O 2 , OH • ) produced through abiotic pathways including Fe(II) oxidation, 36 nitrate photolysis, 37,38 illumination of humic substances, 39 and illumination of metal oxides in desert varnish. 40 Further Mn(III) oxidation by ROS and/or disproportionation results in rapid Mn(IV)oxide formation.…”

Section: Manganese In Terrestrial Ecosystemsmentioning

confidence: 99%

“…40 Further Mn(III) oxidation by ROS and/or disproportionation results in rapid Mn(IV)oxide formation. 37,38 Mineral surfaces, such as Fe-oxides and Mn-oxides, also catalyze Mn(II) oxidation via interfacial catalysis and/or electrochemical reactions 41−43 at rates equivalent to or faster than biological oxidation. 44,45 Products of Mn(II) oxidation and Mn-oxide phase transformations are highly dependent on pH conditions (e.g., SI Figure S1) and mineral surface properties (e.g., semiconductivity, particle size, ions).…”

Section: Manganese In Terrestrial Ecosystemsmentioning

confidence: 99%

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A Critical Review on the Multiple Roles of Manganese in Stabilizing and Destabilizing Soil Organic Matter

Santos

Butler

et al. 2021

Environ. Sci. Technol.

128

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Manganese (Mn) is a biologically important and redox-active metal that may exert a poorly recognized control on carbon (C) cycling in terrestrial ecosystems. Manganese influences ecosystem C dynamics by mediating biochemical pathways that include photosynthesis, serving as a reactive intermediate in the breakdown of organic molecules, and binding and/or oxidizing organic molecules through organo-mineral associations. However, the potential for Mn to influence ecosystem C storage remains unresolved. Although substantial research has demonstrated the ability of Fe- and Al-oxides to stabilize organic matter, there is a scarcity of similar information regarding Mn-oxides. Furthermore, Mn-mediated reactions regulate important litter decomposition pathways, but these processes are poorly constrained across diverse ecosystems. Here, we discuss the ecological roles of Mn in terrestrial environments and synthesize existing knowledge on the multiple pathways by which biogeochemical Mn and C cycling intersect. We demonstrate that Mn has a high potential to degrade organic molecules through abiotic and microbially mediated oxidation and to stabilize organic molecules, at least temporarily, through organo-mineral associations. We outline research priorities needed to advance understanding of Mn–C interactions, highlighting knowledge gaps that may address key uncertainties in soil C predictions.

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