Solid‐State Au/Hg Microelectrode for the Investigation of Fe and Mn Cycling in a Freshwater Wetland: Implications for Methane Production

Ma, Shuo; Luther, George W.; Keller, Jason K.; Madison, Andrew S.; Metzger, Édouard; Emerson, David; Megonigal, J. Patrick

doi:10.1002/elan.200704048

Cited by 20 publications

(23 citation statements)

References 29 publications

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“…As these are anaerobic reactions, rates below O 2 penetration depth (OPD) are given coupling, however, exists in freshwater sediments. Such coupling was also observed recently by Ma et al (2008) in a freshwater wetland.…”

Section: This Workmentioning

confidence: 53%

Carbon Cycling and the Coupling Between Proton and Electron Transfer Reactions in Aquatic Sediments in Lake Champlain

et al. 2010

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We used fine-scale porewater profiles and rate measurements together with a multiple component transport-reaction model to investigate carbon degradation pathways and the coupling between electron and proton transfer reactions in Lake Champlain sediments. We measured porewater profiles of O 2 , Mn 2? , Fe 2? , HS -, pH and pCO 2 at mm resolution by microelectrodes, and profiles of NO 3 -, SO 4 2-, NH 4 ? , total inorganic carbon (DIC) and total alkalinity (TA) at cm resolution using standard wet chemical techniques. In addition, sediment-water fluxes of oxygen, DIC, nitrate, ammonium and N 2 were measured. Rates of gross and net sulfate reduction were also measured in the sediments. It is shown that organic matter (OM) decomposes via six pathways: oxic respiration (35.2%), denitrification (10.4%), MnO 2 reduction (3.6%), FeOOH reduction (9.6%), sulfate reduction (14.9%), and methanogenesis (26.4%). In the lake sediments, about half of the benthic O 2 flux is used for aerobic respiration, and the rest is used for the regeneration of other electron acceptors produced during the above diagenetic reactions. There is a strong coupling between O 2 usage and Mn 2? oxidation. MnO 2 is also an important player in Fe and S cycles and in pH and TA balance. Although nitrate concentrations in the overlying water were low, denitrification becomes a quantitatively important pathway for OM decomposition due to the oxidation of NH 4 ? to NO 3 -. Finally, despite its low concentration in freshwater, sulfate is an important electron acceptor due to its high efficiency of internal cycling. This paper also discusses quantitatively the relationship between redox reactions and the porewater pH values. It is demonstrated here that pH and pCO 2 are sensitive variables that reflect various oxidation and precipitation reactions in porewater, while DIC and TA profiles provide effective constraints on the rates of various diagenetic reactions.

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Section: This Workmentioning

confidence: 53%

Carbon Cycling and the Coupling Between Proton and Electron Transfer Reactions in Aquatic Sediments in Lake Champlain

et al. 2010

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“…They reported that the iron pool in plant-free soils was 91 % Fe(II) and 9 % Fe(III), and concluded that iron reduction was the dominant anaerobic respiration pathway. Our data suggest that Ma et al (2008) witnessed the Fe(III) pool at a seasonal low due to temperature effects on the iron oxide pool size. If iron reducers were active, our data suggest rates of iron reduction would have been too low to detect (Table 1).…”

Section: Discussionmentioning

confidence: 69%

“…A previous study at our field site used voltammetric microelectrodes to study in situ redox species during the summer in vegetated and unvegetated soils (Ma et al 2008). They reported that the iron pool in plant-free soils was 91 % Fe(II) and 9 % Fe(III), and concluded that iron reduction was the dominant anaerobic respiration pathway.…”

Section: Discussionmentioning

confidence: 99%

Anaerobic Metabolism in Tidal Freshwater Wetlands: III. Temperature Regulation of Iron Cycling

Bullock

Sutton‐Grier

Megonigal

2012

Estuaries and Coasts

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Understanding the ecological processes that regulate the production and fate of methane (CH 4 ) in wetland soils is essential for forecasting wetland CH 4 emissions. Iron reduction is an important carbon mineralization pathway that is capable of suppressing CH 4 production in freshwater wetlands, but our understanding of temperature regulation of iron oxide respiration and the subsequent impacts on CH 4 production is limited. We tested the hypothesis that temperature regulates iron reduction rates indirectly through differential effects on Fe(II) oxidation versus Fe(III) reduction, which ultimately determines the size of the microbially labile, poorly crystalline Fe(III) pool. Our study indicates that rates of iron reduction are more sensitive to changes in temperature than rates of iron oxidation, which creates imbalance in the relative proportion of Fe(II) and Fe(III) in the poorly crystalline soil iron pool as temperatures change. Our results suggest that warmer temperatures can cause the Fe (III) oxide pool to decline, limiting the Fe(III) supply to iron reducers and relieving competition for organic carbon with methanogens.

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“…This persistent methanogenic pattern likely explains why we were unable to measure rates of Fe(II) accumulation in our iron reduction assays at this site. Microelectrode profiles taken near the sites used in this experiment suggested a role of manganese reduction at these sites (Ma et al 2008), but the observed CO 2 :CH 4 ratios in this experiment downplay this possibility. Interestingly, this methanogenic pattern was consistent in both the presence and absence of plants.…”

Section: Discussionmentioning

confidence: 70%

Anaerobic Metabolism in Tidal Freshwater Wetlands: I. Plant Removal Effects on Iron Reduction and Methanogenesis

Keller

Sutton‐Grier

Bullock

et al. 2012

Estuaries and Coasts

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Solid‐State Au/Hg Microelectrode for the Investigation of Fe and Mn Cycling in a Freshwater Wetland: Implications for Methane Production

Abstract: The solid-state voltammetric gold

Cited by 20 publications

References 29 publications

Carbon Cycling and the Coupling Between Proton and Electron Transfer Reactions in Aquatic Sediments in Lake Champlain

Carbon Cycling and the Coupling Between Proton and Electron Transfer Reactions in Aquatic Sediments in Lake Champlain

Anaerobic Metabolism in Tidal Freshwater Wetlands: III. Temperature Regulation of Iron Cycling

Anaerobic Metabolism in Tidal Freshwater Wetlands: I. Plant Removal Effects on Iron Reduction and Methanogenesis

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