The mechanism of sulfate aerosol formation: Chemical and sulfur isotopic evidence

Saltzman, E. S.; Brass, Garrett W.; Price, D.A.

doi:10.1029/gl010i007p00513

Cited by 109 publications

(109 citation statements)

References 10 publications

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“…Several atmospheric studies have also tried to infer the fractionation during this reaction. Seasonality in data, with lower δ 34 S values measured for sulfate in summer, could show that the gas-phase fractionation factor is less than the heterogeneous fractionation factor and probably less than 1 (Saltzman et al, 1983;Sinha et al, 2008a). However, seasonality may also be explained by changing sources or the temperature-dependence of fractionation factors (Caron et al, 1986;Novak et al, 2001;Ohizumi et al, 1997).…”

Section: Sulfur Isotopes In the Environmentmentioning

confidence: 99%

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: Sulfur Isotopes In the Environmentmentioning

confidence: 99%

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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“…It was fitted with a cascade impactor to collect size-fractionated particles on quartz filters as well as SO 2 . The SO 2 was trapped on a cellulose filter pretreated with potassium carbonate (K 2 CO 3 ) and a glycerol solution (Saltzman et al, 1983;Norman et al, 2004;Seguin et al, 2010). The sampling interval was 2 days, starting from 10:00 UTC.…”

Section: Field Description and Methodsmentioning

confidence: 99%

Biogenic, anthropogenic and sea salt sulfate size-segregated aerosols in the Arctic summer

et al. 2016

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Abstract. Size-segregated aerosol sulfate concentrations were measured on board the Canadian Coast Guard Ship (CCGS) Amundsen in the Arctic during July 2014. The objective of this study was to utilize the isotopic composition of sulfate to address the contribution of anthropogenic and biogenic sources of aerosols to the growth of the different aerosol size fractions in the Arctic atmosphere. Non-seasalt sulfate is divided into biogenic and anthropogenic sulfate using stable isotope apportionment techniques. A considerable amount of the average sulfate concentration in the fine aerosols with a diameter < 0.49 µm was from biogenic sources (> 63 %), which is higher than in previous Arctic studies measuring above the ocean during fall (< 15 %) (Rempillo et al., 2011) and total aerosol sulfate at higher latitudes at Alert in summer (> 30 %) (Norman et al., 1999). The anthropogenic sulfate concentration was less than that of biogenic sulfate, with potential sources being long-range transport and, more locally, the Amundsen's emissions. Despite attempts to minimize the influence of ship stack emissions, evidence from larger-sized particles demonstrates a contribution from local pollution.A comparison of δ 34 S values for SO 2 and fine aerosols was used to show that gas-to-particle conversion likely occurred during most sampling periods. δ 34 S values for SO 2 and fine aerosols were similar, suggesting the same source for SO 2 and aerosol sulfate, except for two samples with a relatively high anthropogenic fraction in particles < 0.49 µm in diameter (15)(16)(17). The high biogenic fraction of sulfate fine aerosol and similar isotope ratio values of these particles and SO 2 emphasize the role of marine organisms (e.g., phytoplankton, algae, bacteria) in the formation of fine particles above the Arctic Ocean during the productive summer months.

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“…range 0 to +4%0, leading authors to postulate that both processes are important, with one fractionation cancelling out the other [Saltzman et al, 1983].…”

mentioning

confidence: 99%

“…However, in view of the very complex and uncertain pathways, this must be considered to be highly uncertain. The best estimate for the fractionation during the oxidation of sulphur dioxide is 0-4%o, with the resulting sulphate enriched in the heavy isotope [Saltzman et al, 1983; Newman and Forrest, 1991 ]. The •534S values for sulphate and MSA should be related if they are derived from the same DMS pool [Calhoun and Bates, 1989].…”

mentioning

confidence: 99%

An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire

McArdle¹,

Liss²,

Dennis³

1998

J. Geophys. Res.

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The mechanism of sulfate aerosol formation: Chemical and sulfur isotopic evidence

Cited by 109 publications

References 10 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

Biogenic, anthropogenic and sea salt sulfate size-segregated aerosols in the Arctic summer

An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire

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The mechanism of sulfate aerosol formation: Chemical and sulfur isotopic evidence

Cited by 109 publications

References 10 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

Biogenic, anthropogenic and sea salt sulfate size-segregated aerosols in the Arctic summer

An isotopic study of atmospheric sulphur at three sites in Wales and at Mace Head, Eire

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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