J. Savarino, A. Romero, J. Cole-Dai, S. Bekki, and M.H. Thiemens 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 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 mass- independent 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