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| Titel |
On-line Sulfur Isotope Determination by Hydride Generation coupled to MC-ICP-MS |
| VerfasserIn |
Nolwenn Callac, Olivier Rouxel, Emmanuel Ponzevera, Anne Godfroy |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039283
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| Zusammenfassung |
| In seafloor hydrothermal systems, Sulfur is an important element present in various forms
such as sulfate, elemental sulfur or sulfide in hydrothermal fluids and pore waters. Sulfur, as
either electron donor or acceptor, is one element that enables support for microbial life in the
deep biosphere. Traditionally, measurements of 34S/32S ratios (δ34S) are performed using
gas-source mass spectrometry (GS-MS) in which sulfur is introduced as gaseous SO2 or
SF6 species. We recently developed an alternate technique for the accurate and
precise determination of 34S/32S ratios in sulfur-bearing minerals using solution and
laser ablation multiple-collector inductively coupled plasma mass spectrometry
(MC-ICP-MS) (Craddock et al, 2008; Chemical Geology 253 p102–113). We examined and
determined rigorous corrections for analytical difficulties such as instrumental mass bias,
unresolved isobaric interferences, blanks, and laser ablation- and matrix-induced
isotopic fractionation. In particular, the use of high resolution sector-field mass
spectrometry has been shown to remove major isobaric interferences from O2+ while
standard–sample bracketing allowed the correcting instrumental mass bias of unknown
samples.
Here, we evaluate a new method for the direct determination of S isotope in
environmental samples using on-line generation of hydrogen sulfide coupled to MC-ICPMS.
It is expected that the introduction of volatile S-species in the plasma torch will lower the
minimum amounts of S required per analysis by more than 1 order of magnitude while
permitting matrix-free isotope analysis. An important aim of this study was to determine
optimal procedures to overcome analytical difficulties such as instrumental mass bias,
unresolved isobaric interferences, blanks, and isotope fractionation induced during hydrogen
sulfide generation. We initially applied this method to investigate the diversity of sulfur
isotope fractionations during microbial sulfur-reducing or sulfate-reducing at high
temperature. For that purpose, we used pure hyperthermophilic strains isolated from
deep-sea hydrothermal vents, including several sulfur- and sulfate-reducing archaea
strains and sulfate-reducing strains. These results will be discussed according to
the source of sulfide, the temperature of incubation, and type of microbial strains. |
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