Sulfur isotope effects during the oxidation of thiosulfate by Thiobacillus versutus were found to be negligible. This result is considered in relation to other oxidative and reductive processes to assess which reactions are most likely to control the isotopic compositions of sulfur compounds in microbial sulfureta.

Revised delta(34)S reference values with associated expanded uncertainties (95% confidence interval (C.I.)) are presented for the sulfur isotope reference materials IAEA-S-2 (22.62 +/- 0.16 per thousand) and IAEA-S-3 (-32.49 +/- 0.16 per thousand). These revised values are determined using two relative-difference measurement techniques, gas source isotope ratio mass spectrometry (GIRMS) and dou...

An on-line method for S-isotope analysis is described. Samples are combusted in an elemental analyzer. SO2 is separated from other combustion gases by gas chromatography, and the gases enter the ion source of the mass spectrometer through a split interface. Integrated peak areas for %O2+ and %OZ+ are compared to the response for a standard gas sample to determine the 6% value. 6% values of samp...

It is generally thought that the sulfate reduction metabolism is ancient and would have been established well before the Neoarchean. It is puzzling, therefore, that the sulfur isotope record of the Neoarchean is characterized by a signal of atmospheric mass-independent chemistry rather than a strong overprint by sulfate reducers. Here, we present a study of the four sulfur isotopes obtained usi...

Sulfur isotope ratio data (δS) have been used to provide significant insights into global biogeochemical cycling over Earth history, providing a framework for reconstructing both global redox budgets and microbial metabolic activity. However, as the record of ancient oceanic conditions becomes better resolved, reports of coeval but divergent isotopic proxies are becoming increasingly common. Th...

Groundwater and sediment samples (~1 m depth) at sites representative of different groundwater pathways were collected to determine the aqueous speciation of sulfur and the fractionation of sulfur isotopes in aqueous and solid phases. In addition, selected sediment samples at 5 depths (from oxic to anoxic layers) were collected to investigate the processes controlling sulfur biogeochemistry in ...

Dissimilatory sulfate reduction serves as a key metabolic carbon remineralization process in anoxic marine environments. Sulfate reducing microorganisms can impart a wide range in mass-dependent sulfur isotopic fractionation. As such, the presence and relative activity of these organisms is identifiable from geological materials. By extension, sulfur isotope records are used to infer the redox ...

Sulfur isotopes in ancient sediments provide a record of past environmental conditions. The long-time-scale variability and apparent asymmetry in the magnitude of minor sulfur isotope fractionation in Archean sediments remain unexplained. Using an integrated biogeochemical model of the Archean sulfur cycle, we find that the preservation of mass-independent sulfur is influenced by a variety of e...