Redox species in a reducing fjord: equilibrium and kinetic considerations

Emerson, Steven; Cranston, R E; Liss, P. S.

doi:10.1016/0198-0149(79)90101-8

Cited by 243 publications

(97 citation statements)

References 17 publications

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“…Several studies of manganese oxidation by such geochemical approaches have led to the conclusion that biological catalysis must be occurring (Emerson et al 1979;Wollast et al 1979). Further studies by a combined microbiological and geochemical approach (Emerson et al 1982) confirmed 1247 that the rates observed in nature were due to bacterial activity.…”

mentioning

confidence: 83%

Microbial mediation of Mn(II) and Co(II) precipitation at the O₂/H₂S interfaces in two anoxic fjords1

Tebo

Nealson

Emerson

et al. 1984

Limnology & Oceanography

144

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We studied the potential for bacterial catalysis of Mn(II), Co(H), and Fe(III) precipitation at the 02/H2S interfaces in Saanich Inlet, British Columbia, and in Framvaren Fjord, Norway. In Saanich Inlet the interface is below the photic zone, but in Framvaren Fjord it is within the region of significant light penetration. Biological catalysis of metal removal was measured as the binding of radioactive isotopes as a function of time in the presence and absence of poisons which do not measurably interfere with the solution chemistry of manganese. In a region just above the oxic/ anoxic interface in Saanich Inlet, the binding of Co(I1) and Mn(I1) was inhibited by the bacterial poisons, but Fe(III) precipitation was not. Measurements of the oxidation state of the particulate material indicated a slightly higher Mn(IV):Mn(II) ratio in the region of dissolved Mn(B) precipitation, confirming that manganese was being oxidized and not simply bound, In both fjords, binding was either stronger or more rapid under air saturation than under conditions of oxygen limitation, suggesting that O2 is the electron acceptor during manganese oxidation. In Framvaren

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mentioning

confidence: 83%

Microbial mediation of Mn(II) and Co(II) precipitation at the O₂/H₂S interfaces in two anoxic fjords1

Tebo

Nealson

Emerson

et al. 1984

Limnology & Oceanography

144

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“…Although MnO, is the thermodynamically stable form of Mn in oxygenated waters, manganese oxides often oc-I This research was supported by ONR Contract N-000 14-80-C-0273 and by a contract from the Ocean Assessments Division, National Ocean Service, NOAA. cur in seawater as Mn(W) or as mixtures of different oxidation states (Grill 1982;Emerson et al 1982;Kalhorn and Emerson 1984). These oxides can be reduced to soluble Mn(I1) in anoxic environments such as occur in the bottom waters of many fjords (Emerson et al 1979) and in reducing sediments. There is also evidence that manganese oxides can be reduced chemically or photochemically in oxygenated seawater by reactions involving organic compounds (Sunda et al 1983;Stone 1983).…”

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confidence: 99%

Microbial oxidation of manganese in a North Carolina estuary1

Sunda

Huntsman

1987

Limnology & Oceanography

124

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Experiments were conducted with 54Mn(II) to determine the kinetics of particulate manganese formation in seawater from the lower Newport River estuary, North Carolina. Dissolved Mn was rapidly converted into particles at constant rates that ranged from 0.36 to 6.2% h-r (0.62-3.5 nmol liter-l h-l), yielding turnover times of the dissolved manganese pool of 0.7-l 1 d. Dissolved Mn turnover rates increased with temperature (Q10 = 2) up to a maximum at 25"-35°C and also increased with the ratio of particulate to dissolved Mn. These two factors explained most of the variation in the observed turnover rates.Sample deoxygenation reduced the formation of particulate 54Mn by 94% and virtually all the particulate 54Mn formed in natural oxygen-containing samples could be dissolved by 10 PM ascorbic acid, a strong reducing agent. These results indicated that the formation of particulate 54Mn resulted primarily from the oxidation of Mn(I1) to manganese oxides (MnO,). The oxidation rates, however, were much too rapid to be accounted for by abiotic mechanisms, and the rate was reduced by 97% following heat sterilization of the seawater. In addition, the rates conformed to the Michaclis-Menten enzyme kinetics model with V,,, equal to 1.2 x lO-8 mol liter-' h-' and K, equal to 1.9 x lo-' M. These findings provide strong evidence that oxidation of Mn in the estuarine samples is microbially catalyzed. This catalysis appears to be instrumental in the rapid redox cycling of Mn and in the scavenging of dissolved Mn onto particles in aquatic systems.

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“…Reduction in anoxic basins is demonstrated by Cranston and Murray (1978) and by Emerson et al (1979). The latter assume that Cr(VI) is readily reduced below the oxic--anoxic boundary (although their results do not quite confirm this), but that Cr(III) is less rapidly oxidized above this boundary.…”

Section: Sinks For Chromiummentioning

confidence: 73%

“…Elderfield (1970) supposed that the kinetics of oxidation for Cr(III) to Cr(VI) are slow, which would explain the apparent absence of thermodynamic equilibrium. Emerson et al (1979) and Cranston and Murray (1978) showed that the Cr(III)/Cr(VI) ratio responds to changes in the redox conditions. Schroeder and Lee (1975) carried out experiments on the oxidation of Cr(III) in model freshwaters.…”

Section: Stability Of Cr (Iii)-and Cr (Vi)-species In Seawatermentioning

confidence: 99%

Chromium(III) — chromium(VI) interconversions in seawater

Weijden

Reith

1982

Marine Chemistry

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Van der Weijden, C.H. and Reith, M. 1982. Chromium(III)--chromium(VI) interconversions in seawater. Mar. Chem., 11: 565--572.The stable form of dissolved chromium in oxygenated seawater is Cr(VI). But Cr(III)-species are also present at an analytically significant level. It is shown that Cr(III) is oxidized only slowly by dissolved oxygen, and that manganese oxide is a strong catalyst for such oxidation. However, the low oceanic concentration of suspended MnO2 impedes the conclusion that the former process is quantitatively less important than the latter one. The distribution of dissolved chromium among Cr(VI)-and Cr(III)-species is probably kinetically controlled.

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Redox species in a reducing fjord: equilibrium and kinetic considerations

Cited by 243 publications

References 17 publications

Microbial mediation of Mn(II) and Co(II) precipitation at the O₂/H₂S interfaces in two anoxic fjords1

Microbial mediation of Mn(II) and Co(II) precipitation at the O₂/H₂S interfaces in two anoxic fjords1

Microbial oxidation of manganese in a North Carolina estuary1

Chromium(III) — chromium(VI) interconversions in seawater

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Redox species in a reducing fjord: equilibrium and kinetic considerations

Cited by 243 publications

References 17 publications

Microbial mediation of Mn(II) and Co(II) precipitation at the O2/H2S interfaces in two anoxic fjords1

Microbial mediation of Mn(II) and Co(II) precipitation at the O2/H2S interfaces in two anoxic fjords1

Microbial oxidation of manganese in a North Carolina estuary1

Chromium(III) — chromium(VI) interconversions in seawater

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Product

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Microbial mediation of Mn(II) and Co(II) precipitation at the O₂/H₂S interfaces in two anoxic fjords1

Microbial mediation of Mn(II) and Co(II) precipitation at the O₂/H₂S interfaces in two anoxic fjords1