Sulfur Isotope Effects. I. The Isotopic Exchange Coefficient for the Sulfur Isotopes 34S-32S in the System SO2g-HSO3-aq at 25, 35, and 45 degrees C.

Eriksen, Trygve E.; Vikane, Olav; Swahn, Carl‐Gunnar; Larsson, Ragnar; Nordén, Bengt; Sundbom, M.

doi:10.3891/acta.chem.scand.26-0573

Cited by 48 publications

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“…The weighted average α 34 is 1.0160±0.0013 at 0 • C, which results in a product δ 34 S change of +9.2±0.7 ‰ following the two bubblers. This is consistent with expectations for aqueous oxidation by H 2 O 2 (Eriksen, 1972a;Egiazarov et al, 1971) and is robust over a large range of flows and SO 2 concentrations. The gas temperature does not affect the measured fractionation since the collector is held at 0 • C and the quantity of gas passed through the sampling system is not sufficient to change the temperature within the collection system.…”

Section: E Harris Et Al: Sulfur Isotope Fractionation During Oxidatsupporting

confidence: 79%

“…For heterogeneous oxidation, equilibrium fractionation of 34 S/ 32 S during the uptake of SO 2 into solution and the subsequent acid-base equilibria has been measured in several studies. The results range between α het = 1.010 and 1.017 at 25 • C (Egiazarov et al, 1971;Eriksen, 1972a). So far, the isotopic effect of the terminating oxidation of S(IV) to S(VI) has not been investigated.…”

Section: Sulfur Isotopes In the Environmentmentioning

confidence: 99%

“…This shows that the terminating oxidation reaction has a negligible effect on isotopic fractionation, explaining why H 2 O 2 and O 3 produce the same fractionation factors despite very different mechanisms (Savarino et al, 2000). Eriksen (1972a) considers the equilibrium between 1 M NaHSO 3 at low pH as acid is constantly added to the system, thus the concentration of SO 2− 3 will be negligible. The experiments of Egiazarov et al (1971) consider the equilibration of 3 M NaHSO 3 at pH≈4, so unlike Eriksen (1972a) these results will include some equilibration to SO 2− 3 as well as significant production of S 2 O 2− 5 .…”

Section: Temperature-dependence Of Fractionation During Oxidation By mentioning

confidence: 99%

“…The major oxidants are H 2 O 2 , O 3 and O 2 , the latter being catalysed by Fe 3+ and other transition metal ions in a radical chain reaction pathway (Herrmann et al, 2000). The dissolution of SO 2 before oxidation follows several steps (Eriksen, 1972a): …”

Section: E Harris Et Al: Sulfur Isotope Fractionation During Oxidatmentioning

confidence: 99%

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Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H2O2, O3 and iron catalysis

et al. 2012

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Abstract. The oxidation of SO 2 to sulfate is a key reaction in determining the role of sulfate in the environment through its effect on aerosol size distribution and composition. Sulfur isotope analysis has been used to investigate sources and chemical processes of sulfur dioxide and sulfate in the atmosphere, however interpretation of measured sulfur isotope ratios is challenging due to a lack of reliable information on the isotopic fractionation involved in major transformation pathways. This paper presents laboratory measurements of the fractionation factors for the major atmospheric oxidation reactions for SO 2 : Gas-phase oxidation by OH radicals, and aqueous oxidation by H 2 O 2 , O 3 and a radical chain reaction initiated by iron. The measured fractionation factor for 34 S/ 32 S during the gas-phase reaction is α OH = (1.0089±0.0007) − ((4±5)×10 −5 )T ( • C). The measured fractionation factor for 34 S/ 32 S during aqueous oxidation by H 2 O 2 or O 3 is α aq = (1.0167±0.0019) − ((8.7±3.5)×10 −5 )T ( • C). The observed fractionation during oxidation by H 2 O 2 and O 3 appeared to be controlled primarily by protonation and acid-base equilibria of S(IV) in solution, which is the reason that there is no significant difference between the fractionation produced by the two oxidants within the experimental error. The isotopic fractionation factor from a radical chain reaction in solution catalysed by iron is α Fe = (0.9894±0.0043) at 19 • C for 34 S/ 32 S. Fractionation was mass-dependent with regards to 33 S/ 32 S for all the reactions investigated. The radical chain reaction mechanism was the only measured reaction that had a faster rate for the light isotopes. The results presented in this study will be particularly useful to determine the importance of the transition metal-catalysed oxidation pathway compared to other oxidation pathways, but other main oxidation pathways can not be distinguished based on stable sulfur isotope measurements alone.

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Section: E Harris Et Al: Sulfur Isotope Fractionation During Oxidatsupporting

confidence: 79%

Section: Sulfur Isotopes In the Environmentmentioning

confidence: 99%

Section: Temperature-dependence Of Fractionation During Oxidation By mentioning

confidence: 99%

Section: E Harris Et Al: Sulfur Isotope Fractionation During Oxidatmentioning

confidence: 99%

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Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H2O2, O3 and iron catalysis

et al. 2012

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“…8) and the first proton loss (Eq. 9) can be found by plotting the fractionation factors at pH = 2.1 and pH = 4 (Eriksen, 1972) against the fraction of HSO − 3 : The intercept at f (HSO − 3 ) = 0 gives the fractionation factor for hydration as α hydration = 1.0105 ± 0.0037, and the increase in fractionation at f (HSO − 3 ) = 1 gives the fractionation factor for the first proton loss as α K a 1 = 1.0042±0.0037 (Fig. 3).…”

Section: Dependence Of Isotopic Fractionation On Ph During Aqueous Oxmentioning

confidence: 99%

Fractionation of sulfur isotopes during heterogeneous oxidation of SO2 on sea salt aerosol: a new tool to investigate non-sea salt sulfate production in the marine boundary layer

et al. 2012

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Abstract. The oxidation of SO 2 to sulfate on sea salt aerosols in the marine environment is highly important because of its effect on the size distribution of sulfate and the potential for new particle nucleation from H 2 SO 4 (g). However, models of the sulfur cycle are not currently able to account for the complex relationship between particle size, alkalinity, oxidation pathway and rate -which is critical as SO 2 oxidation by O 3 and Cl catalysis are limited by aerosol alkalinity, whereas oxidation by hypohalous acids and transition metal ions can continue at low pH once alkalinity is titrated. We have measured 34 S/ 32 S fractionation factors for SO 2 oxidation in sea salt, pure water and NaOCl aerosol, as well as the pH dependency of fractionation.Oxidation of SO 2 by NaOCl aerosol was extremely efficient, with a reactive uptake coefficient of ≈0.5, and produced sulfate that was enriched in 32 S with α OCl = 0.9882±0.0036 at 19 • C. Oxidation on sea salt aerosol was much less efficient than on NaOCl aerosol, suggesting alkalinity was already exhausted on the short timescale of the experiments. Measurements at pH = 2.1 and 7.2 were used to calculate fractionation factors for each step from SO 2 (g) → multiple steps → SO 2− 3 . Oxidation on sea salt aerosol resulted in a lower fractionation factor than expected for oxidation of SO 2− 3 by O 3 (α seasalt = 1.0124±0.0017 at 19 • C). Comparison of the lower fractionation during oxidation on sea salt aerosol to the fractionation factor for high pH oxidation shows HOCl contributed 29 % of S(IV) oxidation on sea salt in the short experimental timescale, highlighting the potential importance of hypohalous acids in the marine environment.The sulfur isotope fractionation factors measured in this study allow differentiation between the alkalinity-limited pathways -oxidation by O 3 and by Cl catalysis (α 34 = 1.0163 ± 0.0018 at 19 • C in pure water or 1.0199 ± 0.0024 at pH = 7.2) -which favour the heavy isotope, and the alkalinity non-limited pathways -oxidation by transition metal catalysis (α 34 = 0.9905±0.0031 at 19 • C, Harris et al., 2012a) and by hypohalites (α 34 = 0.9882±0.0036 at 19 • C) -which favour the light isotope. In combination with field measurements of the oxygen and sulfur isotopic composition of SO 2 and sulfate, the fractionation factors presented in this paper may be capable of constraining the relative importance of different oxidation pathways in the marine boundary layer.

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Impact of aerosol direct effect on East Asian air quality during the EAST‐AIRE campaign

et al. 2016

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WRF‐Chem simulations were performed for the March 2005 East Asian Studies of Tropospheric Aerosols: an International Regional Experiment (EAST‐AIRE) Intensive Observation Campaign (IOC) to investigate the direct effects of aerosols on surface radiation and air quality. Domain‐wide, WRF‐Chem showed a decrease of 20 W/m2 in surface shortwave (SW) radiation due to the aerosol direct effect (ADE), consistent with observational studies. The ADE caused 24 h surface PM2.5 (particulate matter with diameter < 2.5 µm) concentrations to increase in eastern China (4.4%), southern China (10%), western China (2.3%), and the Sichuan Basin (9.6%), due to different aerosol compositions in these four regions. Conversely, surface 1 h maximum ozone was reduced by 2.3% domain‐wide and up to 12% in eastern China because less radiation reached the surface. We also investigated the impact of reducing SO2 and black carbon (BC) emissions by 80% on aerosol amounts via two sensitivity simulations. Reducing SO2 decreased surface PM2.5 concentrations in the Sichuan Basin and southern China by 5.4% and decreased ozone by up to 6 ppbv in the Sichuan Basin and Southern China. Reducing BC emissions decreased PM2.5 by 3% in eastern China and the Sichuan Basin but increased surface ozone by up to 3.6 ppbv in eastern China and the Sichuan Basin. This study indicates that the benefits of reducing PM2.5 associated with reducing absorbing aerosols may be partially offset by increases in ozone at least for a scenario when NOx and VOC emissions are unchanged.

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Sulfur Isotope Effects. I. The Isotopic Exchange Coefficient for the Sulfur Isotopes 34S-32S in the System SO2g-HSO3-aq at 25, 35, and 45 degrees C.

Cited by 48 publications

References 0 publications

Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H<sub>2</sub>O<sub>2</sub>, O<sub>3</sub> and iron catalysis

Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H<sub>2</sub>O<sub>2</sub>, O<sub>3</sub> and iron catalysis

Fractionation of sulfur isotopes during heterogeneous oxidation of SO<sub>2</sub> on sea salt aerosol: a new tool to investigate non-sea salt sulfate production in the marine boundary layer

Impact of aerosol direct effect on East Asian air quality during the EAST‐AIRE campaign

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Sulfur Isotope Effects. I. The Isotopic Exchange Coefficient for the Sulfur Isotopes 34S-32S in the System SO2g-HSO3-aq at 25, 35, and 45 degrees C.

Cited by 48 publications

References 0 publications

Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;, O&lt;sub&gt;3&lt;/sub&gt; and iron catalysis

Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;, O&lt;sub&gt;3&lt;/sub&gt; and iron catalysis

Fractionation of sulfur isotopes during heterogeneous oxidation of SO&lt;sub&gt;2&lt;/sub&gt; on sea salt aerosol: a new tool to investigate non-sea salt sulfate production in the marine boundary layer

Impact of aerosol direct effect on East Asian air quality during the EAST‐AIRE campaign

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Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H<sub>2</sub>O<sub>2</sub>, O<sub>3</sub> and iron catalysis

Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H<sub>2</sub>O<sub>2</sub>, O<sub>3</sub> and iron catalysis

Fractionation of sulfur isotopes during heterogeneous oxidation of SO<sub>2</sub> on sea salt aerosol: a new tool to investigate non-sea salt sulfate production in the marine boundary layer