UV induced mass independent sulfur
isotope fractionation in stratospheric
volcanic sulfate
J. Savarino, A. Romero, J. Cole-Dai, S. Bekki, and
M.H. Thiemens
Universität Heidelberg
Institut für Umweltphysik
Content
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Some explanations/definitions
Sulphur-Cycle
Summary of the paper
Questions
Discussion
Universität Heidelberg
Institut für Umweltphysik
What means d and D
d = ( Rsample/Rstandard – 1) x 1000
R = [33S]/[32S]
D33S = d33S – 1000 x [(1 + d34S/1000)0.515 – 1 ]  0
D36S = d36S – 1000 x [(1 + d34S/1000)1.90 –1 ]  0
Universität Heidelberg
Institut für Umweltphysik
Mass-dependent and massindependent fraction
• Mass dependent: only the different mass is
the cause of different fraction of the
isotopes
• Mass independent: fractionation caused by
something else as mass (example Photolyse
in the case of SO2)
Universität Heidelberg
Institut für Umweltphysik
Depth of penetration of solar
radiation through the atmosphere
Universität Heidelberg
Institut für Umweltphysik
Sulphur-Cycle
Universität Heidelberg
Institut für Umweltphysik
The sense behind it ?
• 1. determination of the degree of UV light affected S
oxidation in the atmosphere
• 2. Determination of the stratospheric and tropospheric
nature of volcanic eruptions -> reassess the climatic
impact of past volcanic eruptions (?)
„sulfur isotopic analysis of ice core volcanic sulfate can
be independent method to identify climatically
significant eruptions in the investigation of the climate
volcanic connection“
Universität Heidelberg
Institut für Umweltphysik
Observation
• Analysis of antarctic snow blocks, ice cores
and aerosol filter
• For volcanic sulfate, the S - isotopes
demonstrate a significant range of variations
• values d34S, d33S, d36S of aerosol and
background sulfate are all within small isotopic
ranges
• mass-independent sulfur isotopes anomalies in
the stratosphere appear to depend on the
exposure of SO2 to UV radiation (experiments
in the laboratory)
Universität Heidelberg
Institut für Umweltphysik
Plot of D33S and D36S sulfur
isotope anomalies of different
sulfate sources
?
Universität Heidelberg
Institut für Umweltphysik
Plot of D33S versus D34S and
Plot of D36S and D33S
Universität Heidelberg
Institut für Umweltphysik
My Questions to the authors
• Did you inspect carefully into the graphics?
C.f., why Cerro Hudson eruption is not
included in the D36S plot?
• Why they show only this two examples of
volcanic eruption, at least Tambora should
have been a better examble than Cerro
Hudson?
• .....?
Thanks
for your
attention
and tell
me - what
do you
think...!!!
Plot of D33S values versus
sample age
Farquar, 2000
Universität Heidelberg
Institut für Umweltphysik