Ab initio calculations of sulfur isotope fractionation factor for H2S in aqua–gas system

Czarnacki, Maciej; Hałas, Stanisław

doi:10.1016/j.chemgeo.2012.05.007

Cited by 9 publications

(4 citation statements)

References 19 publications

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“…S isotopic fractionation in S 3 À and S 6 À2 Otake et al (2008) have discussed procedures for calculating S isotopic fractionation for various S species in aqueous solution. However, even the fractionation of H 2 S (aq) vs. H 2 S (g) is still uncertain both theoretically and computationally (Czarnacki and Halas (2012). We have evaluated 34 S-32 S fractionations at 298 and 723 K for a number of S-containing molecules, includingS 3 À and S 6 À2 to compare with the Otake study, with results shown in Table 9.…”

Section: Reactions Of Smentioning

confidence: 95%

Calculation of the properties of the S3− radical anion and its complexes with Cu+ in aqueous solution

Tossell

2012

Geochimica et Cosmochimica Acta

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Section: Reactions Of Smentioning

confidence: 95%

Calculation of the properties of the S3− radical anion and its complexes with Cu+ in aqueous solution

Tossell

2012

Geochimica et Cosmochimica Acta

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“…Considerable experimental and theoretical efforts have previously been made to determine the equilibrium isotope effect between H 2 S in the gas phase and solution (Fry et al, 1986a;Geβler and Gehlen, 1986;Otake et al, 2008;Czarnacki and Hałas, 2012;Eldridge et al, 2016). The enrichment factor (ε g-H2S ) was measured to be -0.5‰ at 22 °C (Fry et al, 1986a) and -0.8‰ at 25 °C (Geβler and Gehlen, 1986), while the calculated values were slightly larger and close to -1.0‰ at 25 °C (Czarnacki and Halas, 2012;Eldridge et al, 2016).…”

Section: Experimental Determination Of Equilibrium Sulfur Isotope Framentioning

confidence: 99%

“…For the sulfide system, equilibrium sulfur isotope fractionations have been explored experimentally by comparing the isotopic compositions of gaseous and total dissolved phases under different pH conditions that manipulate the proportion of the individual species (Fry et al, 1986a;Geβler and Gehlen, 1986). Theoretical studies have also used ab initio or density-functional theory to predict equilibrium distributions (Otake et al, 2008;Czarnacki and Hałas, 2012;Eldridge et al, 2016). Combined, these studies provide a consensus that gaseous H 2 S is depleted in 34 S relative to aqueous H 2 S at equilibrium, although the fractionation is only about 1‰ at 20°C.…”

Section: Introductionmentioning

confidence: 99%

Precise determination of equilibrium sulfur isotope effects during volatilization and deprotonation of dissolved H2S

Sim

Sessions

Orphan

et al. 2019

Geochimica et Cosmochimica Acta

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Sulfide (H 2 S, HS-, and S 2-) is ubiquitous in marine porewaters as a result of microbial sulfate reduction, constituting the reductive end of the biogeochemical sulfur cycle. Stable isotopes have been widely used to constrain the sulfur cycle, because the redox transformations of sulfur compounds, such as microbial sulfate reduction, often exhibit sizable kinetic isotope effects. In contrast to sulfate ion (SO 4 2-), the most abundant form of dissolved sulfur in seawater, H 2 S is volatile and also deprotonated at near neutral pH. Equilibrium isotope partitioning between sulfide species can therefore overlap with kinetic isotope effects during reactions involving sulfide as either reactant or intermediate. Previous experimental attempts to measure equilibrium fractionation between H 2 S and HShave reached differing results, likely due to solutions of widely varying ionic strength. In this study, we measured the sulfur isotope fractionation between total dissolved sulfide and gaseous H 2 S at 20.6±0.5°C over the pH range from 2 to 8, and calculated the equilibrium isotope effects associated with deprotonation of dissolved H 2 S. By using dilute solutions of Na 2 S, made possible by the improved sensitivity of mass spectrometric techniques, uncertainty in the first dissociation constant of H 2 S due to ionic strength could be better controlled. This in turn allowed us to close sulfur isotope mass balance for our experiments and increase the accuracy of the estimated fractionation factor. At equilibrium, aqueous H 2 S was enriched in 34 S by 0.7‰ and 3.1‰ relative to gaseous H 2 S and aqueous HS-, respectively. The estimated fractionation between aqueous H 2 S and HSlies between two earlier experimental reports, but agrees within the uncertainty of the measurements with a recent theoretical calculation.

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“…Therefore the kinetic fractionation factor is used for the following fractionation calculation. The fractionation between aqueous and gaseous hydrogen sulphide is negligible above 150 °C which enables us to compare the measured gaseous isotopic H 2 S composition to the modelled aqueous isotopic H 2 S composition (Czarnacki & Hałas, 2012;Eldridge et al, 2016). The modelled δ 34 S value of the aqueous hydrogen sulphide increased during the reaction path to close to 10‰, which is the measured composition for the gaseous H 2 S in the reservoir (King et al, 2014) (Figure 8b).…”

Section: Modelling Resultsmentioning

confidence: 71%

Reaction path modelling illustrating the fluid history of a natural CO2-H2S reservoir

Zwahlen¹,

Wogelius²,

Hollis³

et al. 2019

Applied Geochemistry

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Ab initio calculations of sulfur isotope fractionation factor for H2S in aqua–gas system

Cited by 9 publications

References 19 publications

Calculation of the properties of the S3− radical anion and its complexes with Cu+ in aqueous solution

Calculation of the properties of the S3− radical anion and its complexes with Cu+ in aqueous solution

Precise determination of equilibrium sulfur isotope effects during volatilization and deprotonation of dissolved H2S

Reaction path modelling illustrating the fluid history of a natural CO2-H2S reservoir

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