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Isotopic fingerprints of carbonyl sulfide (COS) in atmosphere and biosphere (KAISERJU19SF)

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  • Full or part time
    Prof Jan Kaiser
  • Application Deadline
    No more applications being accepted

Project Description

Carbonyl sulfide (COS) is a sulfur-analogue of CO2. It is the most abundant atmospheric sulfur compound and has a lifetime of 2 to 4 years. COS has industrial and natural sources, mostly the oceans. Its main sinks are plant and soil uptake, but due to its long lifetime, some COS reaches the stratosphere where it undergoes photolysis and oxidation to sulfate and forms the stratospheric aerosol layer (Fig. 1). This layer is of key importance for ozone chemistry, the radiation balance and Earth’s climate. Like CO2, COS is taken up during photosynthesis, but not released during respiration, making it a tracer for gross primary productivity (Asaf et al. 2013). However, overlap of plant and soil uptake limit the use of COS concentration alone for this purpose. Isotope measurements have recently found applications in fingerprinting COS sources and sinks including atmospheric oxidation pathways, and can potentially distinguish between plant and soil uptake.

1. A novel online method for isotope analysis of COS will be used for 13C and 34S measurements (Hattori et al. 2015) and further extended to polyisotopologues (13C16O34S) on mass-spectrometers with worldwide unique analyser and detector configurations.
2. The isotope fractionation during COS uptake by soils and vegetation will be determined using COS-enriched atmospheres, in order to provide constraints on the relative contributions of different COS sinks. Isotope fractionation during COS photolysis under realistic light conditions will be measured and used to verify the stratospheric sulfate aerosol budget.
3. Finally, the new method will be deployed on archived tropospheric and stratospheric samples to improve the global budget of COS for the quantification of gross photosynthesis rates.

Person specification and training
This PhD project requires good quantitative-analytical and experimental skills. A good Honours degree in science or engineering is required; an MSc is desirable. Training will be provided in isotope mass spectrometry, gas and vacuum systems, instrument control and numerical data analysis. Any scientific knowledge gaps can be filled by attending taught courses, e.g. in biogeochemical cycles and atmospheric chemistry. The project includes visits to international collaborators in the Netherlands.

For more information on the supervisor for this project, please go here:

Type of programme: PhD

Project start date: October 2019

Mode of study: Full time

Entry requirements: Acceptable first degree - Science or Engineering.
The standard minimum entry requirement is 2:1.

Funding Notes

This PhD project is offered on a self-funding basis. It is open to applicants with funding or those applying to funding sources. Details of tuition fees can be found at

A bench fee is also payable on top of the tuition fee to cover specialist equipment or laboratory costs required for the research. The amount charged annually will vary considerably depending on the nature of the project and applicants should contact the primary supervisor for further information about the fee associated with the project.


(i) Asaf D, Rotenberg E, Tatarinov F, Dicken U, Montzka SA, Yakir D (2013) Ecosystem photosynthesis inferred from measurements of carbonyl sulphide flux Nature Geosci 6:186 10.1038/ngeo1730

(ii) Hattori S, Toyoda A, Toyoda S, Ishino S, Ueno Y, Yoshida N (2015) Determination of the sulfur isotope ratio in carbonyl sulfide using gas chromatography/isotope ratio mass spectrometry on fragment ions 32S+, 33S+, and 34S+ Anal Chem 87:477 10.1021/ac502704d

(iii) Wang Y, Deutscher NM, Palm M, Warneke T, Notholt J, Baker I, Berry J, Suntharalingam P, Jones N, Mahieu E, Lejeune B, Hannigan J, Conway S, Mendonca J, Strong K, Campbell JE, Wolf A, Kremser S (2016) Towards understanding the variability in biospheric CO2 fluxes: using FTIR spectrometry and a chemical transport model to investigate the sources and sinks of carbonyl sulfide and its link to CO2 Atmos Chem Phys 16:2123 10.5194/acp-16-2123-2016

(iv) Barkley MP, Palmer PI, Boone CD, Bernath PF, Suntharalingam P (2008) Global distributions of carbonyl sulfide in the upper troposphere and stratosphere Geophys Res Lett 35:L14810 10.1029/2008GL034270

(v) Kaiser J, Röckmann T, Brenninkmeijer CAM, Crutzen PJ (2003) Wavelength dependence of isotope fractionation in N2O photolysis Atmos Chem Phys 3:303 10.5194/acp-3-303-2003

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