SO2 photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism

Shohei Hattori; Johan Albrecht Schmidt; Matthew Stanley Johnson; Sebastian O. Danielache; Akinori Yamada; Yuichiro Ueno; Naohiro Yoshida

doi:10.1073/pnas.1213153110

SO₂ photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism

Shohei Hattori, Johan Albrecht Schmidt, Matthew Stanley Johnson, Sebastian O. Danielache, Akinori Yamada, Yuichiro Ueno, Naohiro Yoshida

Department of Chemistry

42 Citations (Scopus)

Abstract

Natural climate variation, such as that caused by volcanoes, is the basis for identifying anthropogenic climate change. However, knowledge of the history of volcanic activity is inadequate, particularly concerning the explosivity of specific events. Some material is deposited in ice cores, but the concentration of glacial sulfate does not distinguish between tropospheric and stratospheric eruptions. Stable sulfur isotope abundances contain additional information, and recent studies showa correlation between volcanic plumes that reach the stratosphere and mass-independent anomalies in sulfur isotopes in glacial sulfate. We describe a mechanism, photoexcitation of SO2, that links the two, yielding a useful metric of the explosivity of historic volcanic events. A plume model of S(IV) to S(VI) conversion was constructed including photochemistry, entrainment of background air, and sulfate deposition. Isotopologue-specific photoexcitation rates were calculated based on the UV absorption cross-sections of 32SO2, 33SO2, 34SO2, and 36SO2 from 250 to 320 nm. The model shows that UV photoexcitation is enhanced with altitude, whereasmass-dependent oxidation, such as SO2 + OH, is suppressed by in situ plume chemistry, allowing the production and preservation of amass-independent sulfur isotope anomaly in the sulfate product. The model accounts for the amplitude, phases, and time development of 33S/34S and 36S/33S found in glacial samples. We are able to identify the process controlling mass-independent sulfur isotope anomalies in the modern atmosphere. This mechanism is the basis of identifying the magnitude of historic volcanic events.

Original language	English
Journal	Proceedings of the National Academy of Sciences of the United States of America
Volume	110
Issue number	44
Pages (from-to)	17656-17661
Number of pages	6
ISSN	0027-8424
DOIs	https://doi.org/10.1073/pnas.1213153110
Publication status	Published - 29 Oct 2013

Keywords

Atmosphere
Climate Change
Light
Models, Chemical
Photochemistry
Sulfur Dioxide
Sulfur Isotopes
Volcanic Eruptions

UN SDGs

This output contributes to the following UN Sustainable Development Goals (SDGs)

Access to Document

10.1073/pnas.1213153110

Cite this

Hattori, S., Schmidt, J. A., Johnson, M. S., Danielache, S. O., Yamada, A., Ueno, Y., & Yoshida, N. (2013). SO₂ photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism. Proceedings of the National Academy of Sciences of the United States of America, 110(44), 17656-17661. https://doi.org/10.1073/pnas.1213153110

SO₂ photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism. / Hattori, Shohei; Schmidt, Johan Albrecht; Johnson, Matthew Stanley et al.
In: Proceedings of the National Academy of Sciences of the United States of America, Vol. 110, No. 44, 29.10.2013, p. 17656-17661.

Research output: Contribution to journal › Journal article › Research › peer-review

Hattori, S, Schmidt, JA, Johnson, MS, Danielache, SO, Yamada, A, Ueno, Y & Yoshida, N 2013, 'SO₂ photoexcitation mechanism links mass-independent sulfur isotopic fractionation in cryospheric sulfate to climate impacting volcanism', Proceedings of the National Academy of Sciences of the United States of America, vol. 110, no. 44, pp. 17656-17661. https://doi.org/10.1073/pnas.1213153110

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abstract = "Natural climate variation, such as that caused by volcanoes, is the basis for identifying anthropogenic climate change. However, knowledge of the history of volcanic activity is inadequate, particularly concerning the explosivity of specific events. Some material is deposited in ice cores, but the concentration of glacial sulfate does not distinguish between tropospheric and stratospheric eruptions. Stable sulfur isotope abundances contain additional information, and recent studies showa correlation between volcanic plumes that reach the stratosphere and mass-independent anomalies in sulfur isotopes in glacial sulfate. We describe a mechanism, photoexcitation of SO2, that links the two, yielding a useful metric of the explosivity of historic volcanic events. A plume model of S(IV) to S(VI) conversion was constructed including photochemistry, entrainment of background air, and sulfate deposition. Isotopologue-specific photoexcitation rates were calculated based on the UV absorption cross-sections of 32SO2, 33SO2, 34SO2, and 36SO2 from 250 to 320 nm. The model shows that UV photoexcitation is enhanced with altitude, whereasmass-dependent oxidation, such as SO2 + OH, is suppressed by in situ plume chemistry, allowing the production and preservation of amass-independent sulfur isotope anomaly in the sulfate product. The model accounts for the amplitude, phases, and time development of 33S/34S and 36S/33S found in glacial samples. We are able to identify the process controlling mass-independent sulfur isotope anomalies in the modern atmosphere. This mechanism is the basis of identifying the magnitude of historic volcanic events.",

keywords = "Atmosphere, Climate Change, Light, Models, Chemical, Photochemistry, Sulfur Dioxide, Sulfur Isotopes, Volcanic Eruptions",

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AU - Yamada, Akinori

AU - Ueno, Yuichiro

AU - Yoshida, Naohiro

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AB - Natural climate variation, such as that caused by volcanoes, is the basis for identifying anthropogenic climate change. However, knowledge of the history of volcanic activity is inadequate, particularly concerning the explosivity of specific events. Some material is deposited in ice cores, but the concentration of glacial sulfate does not distinguish between tropospheric and stratospheric eruptions. Stable sulfur isotope abundances contain additional information, and recent studies showa correlation between volcanic plumes that reach the stratosphere and mass-independent anomalies in sulfur isotopes in glacial sulfate. We describe a mechanism, photoexcitation of SO2, that links the two, yielding a useful metric of the explosivity of historic volcanic events. A plume model of S(IV) to S(VI) conversion was constructed including photochemistry, entrainment of background air, and sulfate deposition. Isotopologue-specific photoexcitation rates were calculated based on the UV absorption cross-sections of 32SO2, 33SO2, 34SO2, and 36SO2 from 250 to 320 nm. The model shows that UV photoexcitation is enhanced with altitude, whereasmass-dependent oxidation, such as SO2 + OH, is suppressed by in situ plume chemistry, allowing the production and preservation of amass-independent sulfur isotope anomaly in the sulfate product. The model accounts for the amplitude, phases, and time development of 33S/34S and 36S/33S found in glacial samples. We are able to identify the process controlling mass-independent sulfur isotope anomalies in the modern atmosphere. This mechanism is the basis of identifying the magnitude of historic volcanic events.

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KW - Light

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KW - Photochemistry

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