EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Modelling the tropospheric and stratospheric sulfur isotopes in a column model for volcanically quiescent periods

Juhi Nagori1, Narcisa Nechita-Bândă1, Masumi Shinkai2, Sebastian Danielache2, Thomas Röckmann1, and Maarten Krol1,3
Juhi Nagori et al.
  • 1Utrecht University, Institute of Marine and Atmospheric Research (IMAU), Physics, Utrecht, Netherlands (
  • 2Sophia University, Faculty of Science and Technology Department of Materials and Life Science, Tokyo, Japan
  • 3Wageningen University, Meteorology and Air Quality (MAQ), Environmental Sciences, Wageningen, Netherlands

It is debated how much stratospheric sulfate aerosol (SSA) in volcanically quiescent times is replenished by carbonyl sulfide (COS) oxidation products. The atmospheric COS budget is also currently uncertain, with missing sources and sinks. Isotopic analysis can be used to allocate the missing sources of COS and also to further constrain the relevance of COS to SSA. The measured tropospheric isotopic signature of COS (δ34S) ranges from 10-14 ‰ (Kamezaki et al., 2019; Angert et al.,2019; Hattori et al., 2020; Davidson et al., 2020), whereas SSA δ34S is constrained by only one single measurement at 18 km of 2.6 ‰ (Castleman, 1974). We use an atmospheric column model to constrain the COS isotopic budget and understand the contribution of COS to sulfate. We find that the COS tropospheric signal is determined by the signatures of its precursors (carbon disulfide, CS2, and dimethyl sulfide, DMS) and fractionation during plant uptake and oxidation. Photolysis of COS is important in the stratosphere; the isotopic signal of COS propagates through sulfur dioxide (SO2) to sulfate in the stratosphere. The model can reproduce δ34S between 1-5 ‰ in the lower stratosphere, which encapsulates the observations from Castleman (1974).


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  • Davidson, C., Amrani, A., & Angert, A. (2020). Tropospheric carbonyl sulfide mass-balance based on direct measurements of sulfur isotopes.
  • Hattori, S., Kamezaki, K., & Yoshida, N. (2020). Constraining the atmospheric OCS budget from sulfur isotopes. Proceedings of the National Academy of Sciences, 117(34), 20447-20452.
  • Kamezaki, K., Hattori, S., Bahlmann, E., & Yoshida, N. (2019). Large-volume air sample system for measuring 34S∕ 32S isotope ratio of carbonyl sulfide. Atmospheric Measurement Techniques, 12(2), 1141-1154

How to cite: Nagori, J., Nechita-Bândă, N., Shinkai, M., Danielache, S., Röckmann, T., and Krol, M.: Modelling the tropospheric and stratospheric sulfur isotopes in a column model for volcanically quiescent periods, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-14316,, 2021.

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