High-Precision Measurements of 33S and 34S Fractionation during SO2 Oxidation Reveal Causes of Seasonality in SO2 and Sulfate Isotopic Composition

Harris, Eliza; Sinha, B.; Hoppe, P.; Ono, Shuhei

doi:10.1021/es402824c

Cited by 62 publications

(149 citation statements)

References 73 publications

(247 reference statements)

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“…However, sulfur isotope fractionation can confound apportionment. Harris et al (2013) reported sulfur isotope fractionation due to SO 2 oxidation, which depends on temperature and oxidation pathways. By solving isotope fractionation equations (Harris et al, 2013) for the average temperature during sampling for this study (∼ 5 • C), δ 34 S values of sulfate are 10.6 ± 0.7 ‰, 16.1 ± 0.1 ‰ and −6.22 ± 0.02 ‰ for homogeneous, heterogeneous and transition metal ion (TMI) oxidation, respectively.…”

Section: Aerosol Growthmentioning

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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Section: Aerosol Growthmentioning

confidence: 99%

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

et al. 2016

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“…For several years following large injections of SO 2 into the stratosphere, stratosphere-derived sulfate can dominate sulfate deposition in ice cores and, when corrected for background levels, can preserve the sulfur isotopic composition of stratospheric sulfate aerosols. Experimental studies demonstrate that OH oxidation of SO 2 (R1) does not produce mass-independent sulfur isotope anomalies (Harris et al, 2012(Harris et al, , 2013, so an additional oxidation mechanism is required to produce the mass-independent sulfur isotope signatures. Three reactions have been proposed to explain these isotope anomalies: excited-state photochemistry of SO 2 in the 250 to 350 nm absorption region (Savarino et al, 2003;Hattori et al, 2013), SO 2 photolysis in the 190 to 220 nm absorption region , and SO 3 photolysis (Pavlov et al, 2005).…”

Section: A R Whitehill Et Al: So 2 Photolysis As a Source For Sulfmentioning

confidence: 99%

SO2 photolysis as a source for sulfur mass-independent isotope signatures in stratospehric aerosols

et al. 2015

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Abstract. Signatures of sulfur isotope mass-independent fractionation (S-MIF) have been observed in stratospheric sulfate aerosols deposited in polar ice. The S-MIF signatures are thought to be associated with stratospheric photochemistry following stratospheric volcanic eruptions, but the exact mechanism responsible for the production and preservation of these signatures is debated. In order to identify the origin and the mechanism of preservation for these signatures, a series of laboratory photochemical experiments were carried out to investigate the effect of temperature and added O 2 on the S-MIF produced by two absorption band systems of SO 2 : photolysis in the 190 to 220 nm region and photoexcitation in the 250 to 350 nm region. The SO 2 photolysis (SO 2 + hν → SO+O) experiments showed S-MIF signals with large 34 S/ 32 S fractionations, which increases with decreasing temperature. The overall S-MIF pattern observed for photolysis experiments, including high 34 S/ 32 S fractionations, positive mass-independent anomalies in 33 S, and negative anomalies in 36 S, is consistent with a major contribution from optical isotopologue screening effects and data for stratospheric sulfate aerosols. In contrast, SO 2 photoexcitation produced products with positive S-MIF anomalies in both 33 S and 36 S, which is different from stratospheric sulfate aerosols. SO 2 photolysis in the presence of O 2 produced SO 3 with S-MIF signals, suggesting the transfer of the S-MIF anomalies from SO to SO 3 by the SO + O 2 + M → SO 3 + M reaction. This is supported with energy calculations of stationary points on the SO 3 potential energy surfaces, which indicate that this reaction occurs slowly on a single adiabatic surface, but that it can occur more rapidly through intersystem crossing. Based on our experimental results, we estimate a termolecular rate constant on the order of 10 −37 cm 6 molecule −2 s −1 . This rate can explain the preservation of mass independent isotope signatures in stratospheric sulfate aerosols and provides a minor, but important, oxidation pathway for stratospheric SO 2 . The production and preservation of S-MIF signals requires a high SO 2 column density to allow for optical isotopologue screening effects to occur and to generate a large enough signature that it can be preserved. In addition, the SO 2 plume must reach an altitude of around 20 to 25 km, where SO 2 photolysis becomes a dominant process. These experiments are the first step towards understanding the origin of the sulfur isotope anomalies in stratospheric sulfate aerosols.

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“…Using previous measurements of sulfur isotope fractionation factors characteristic of different oxidation pathways, e.g. oxidation by OH, H 2 O 2 or transition metal ion catalysis (Harris et al, 2012(Harris et al, , 2013a, the isotopic analyses made during HCCT-2010 allow dominant sulfate production pathways to be determined and resolved for different particle types, as described in Harris et al (2014).…”

Section: Measurement Sitesmentioning

confidence: 99%

Influence of cloud processing on CCN activation behaviour in the Thuringian Forest, Germany during HCCT-2010

et al. 2014

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Abstract. Within the framework of the "Hill Cap Cloud Thuringia 2010" (HCCT-2010) international cloud experiment, the influence of cloud processing on the activation properties of ambient aerosol particles was investigated. Particles were probed upwind and downwind of an orographic cap cloud on Mt Schmücke, which is part of a large mountain ridge in Thuringia, Germany. The activation properties of the particles were investigated by means of size-segregated cloud condensation nuclei (CCN) measurements at 3 to 4 different supersaturations. The observed CCN spectra together with the total particle spectra were used to calculate the hygroscopicity parameter κ for the upwind and downwind stations. The upwind and downwind critical diameters and κ values were then compared for defined cloud events (FCE) and noncloud events (NCE). Cloud processing was found to increase the hygroscopicity of the aerosol particles significantly, with an average increase in κ of 50 %. Mass spectrometry analysis and isotopic analysis of the particles suggest that the observed increase in the hygroscopicity of the cloud-processed particles is due to an enrichment of sulfate and possibly also nitrate in the particle phase.

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High-Precision Measurements of ³³S and ³⁴S Fractionation during SO₂ Oxidation Reveal Causes of Seasonality in SO₂ and Sulfate Isotopic Composition

Cited by 62 publications

References 73 publications

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

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

SO<sub>2</sub> photolysis as a source for sulfur mass-independent isotope signatures in stratospehric aerosols

Influence of cloud processing on CCN activation behaviour in the Thuringian Forest, Germany during HCCT-2010

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High-Precision Measurements of 33S and 34S Fractionation during SO2 Oxidation Reveal Causes of Seasonality in SO2 and Sulfate Isotopic Composition

Cited by 62 publications

References 73 publications

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

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

SO&lt;sub&gt;2&lt;/sub&gt; photolysis as a source for sulfur mass-independent isotope signatures in stratospehric aerosols

Influence of cloud processing on CCN activation behaviour in the Thuringian Forest, Germany during HCCT-2010

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High-Precision Measurements of ³³S and ³⁴S Fractionation during SO₂ Oxidation Reveal Causes of Seasonality in SO₂ and Sulfate Isotopic Composition

SO<sub>2</sub> photolysis as a source for sulfur mass-independent isotope signatures in stratospehric aerosols