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Sulfide Oxidation across Diffuse Flow Zones of Hydrothermal Vents

Sulfide Oxidation across Diffuse Flow Zones of Hydrothermal Vents The sulfide (H2S/HS−) that is emitted from hydrothermal vents begins to oxidize abiotically with oxygen upon contact with ambient bottom water, but the reaction kinetics are slow. Here, using in situ voltammetry, we report detection of the intermediate sulfur oxidation products polysulfides [ $$ {\text{S}}_{\text{x}}^{2 - } $$ ] and thiosulfate [ $$ {\text{S}}_{ 2} {\text{O}}_{ 3}^{ 2- } $$ ], along with contextual data on sulfide, oxygen, and temperature. At Lau Basin in 2006, thiosulfate was identified in less than one percent of approximately 10,500 scans and no polysulfides were detected. Only five percent of 11,000 voltammetric scans taken at four vent sites at Lau Basin in May 2009 show either thiosulfate or polysulfides. These in situ data indicate that abiotic sulfide oxidation does not readily occur as H2S contacts oxic bottom waters. Calculated abiotic potential sulfide oxidation rates are <10−3 μM/min and are consistent with slow oxidation and the observed lack of sulfur oxidation intermediates. It is known that the thermodynamics for the first electron transfer step for sulfide and oxygen during sulfide oxidation in these systems are unfavorable, and that the kinetics for two electron transfers are not rapid. Here, we suggest that different metal catalyzed and/or biotic reaction pathways can readily produce sulfur oxidation intermediates. Via shipboard high-pressure incubation experiments, we show that snails with chemosynthetic endosymbionts do release polysulfides and may be responsible for our field observations of polysulfides. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aquatic Geochemistry Springer Journals

Sulfide Oxidation across Diffuse Flow Zones of Hydrothermal Vents

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References (71)

Publisher
Springer Journals
Copyright
Copyright © 2011 by Springer Science+Business Media B.V.
Subject
Earth Sciences; Hydrogeology; Geochemistry
ISSN
1380-6165
eISSN
1573-1421
DOI
10.1007/s10498-011-9136-1
Publisher site
See Article on Publisher Site

Abstract

The sulfide (H2S/HS−) that is emitted from hydrothermal vents begins to oxidize abiotically with oxygen upon contact with ambient bottom water, but the reaction kinetics are slow. Here, using in situ voltammetry, we report detection of the intermediate sulfur oxidation products polysulfides [ $$ {\text{S}}_{\text{x}}^{2 - } $$ ] and thiosulfate [ $$ {\text{S}}_{ 2} {\text{O}}_{ 3}^{ 2- } $$ ], along with contextual data on sulfide, oxygen, and temperature. At Lau Basin in 2006, thiosulfate was identified in less than one percent of approximately 10,500 scans and no polysulfides were detected. Only five percent of 11,000 voltammetric scans taken at four vent sites at Lau Basin in May 2009 show either thiosulfate or polysulfides. These in situ data indicate that abiotic sulfide oxidation does not readily occur as H2S contacts oxic bottom waters. Calculated abiotic potential sulfide oxidation rates are <10−3 μM/min and are consistent with slow oxidation and the observed lack of sulfur oxidation intermediates. It is known that the thermodynamics for the first electron transfer step for sulfide and oxygen during sulfide oxidation in these systems are unfavorable, and that the kinetics for two electron transfers are not rapid. Here, we suggest that different metal catalyzed and/or biotic reaction pathways can readily produce sulfur oxidation intermediates. Via shipboard high-pressure incubation experiments, we show that snails with chemosynthetic endosymbionts do release polysulfides and may be responsible for our field observations of polysulfides.

Journal

Aquatic Geochemistry – Springer Journals

Published: May 31, 2011

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