UV induced mass‐independent sulfur isotope fractionation in stratospheric volcanic sulfate

J. Savarino (1) , A. Romero , J. Cole-Dai , S. Bekki , M. Thiemens

1 LGGE - Laboratoire de glaciologie et géophysique de l'environnement

Sulfuric acid aerosols produced in the stratosphere following massive volcanic eruptions possess a mass‐independent sulfur isotopic signature, acquired when volcanic SO 2 experiences UV photooxidation. The volcanic data are consistent with laboratory SO 2 photooxidation experiments using UV light at 248 nm (maximum absorption of ozone), whereas sulfur isotopic anomalies previously observed in Archean samples are consistent with photodissociation at 190–220 nm. A mechanism of SO 2 photooxidation, occurring in the early stage of a stratospheric volcanic plume, in the range of 220–320 nm (weak band absorption of SO 2 ), is also proposed. Since mass‐independent sulfur isotope anomalies in stratospheric volcanic sulfate appear to depend on the exposure of SO 2 to UV radiation, their measurements might therefore offer the possibility to determine the degree of UV penetration in the ozone‐absorption window for the present and past atmospheres. They can also be used to determine the stratospheric or tropospheric nature of volcanic eruptions preserved in glaciological records, offering the possibility to reassess the climatic impact of past volcanic eruptions.

Domaines: Sciences de l'environnement

J. Savarino, A. Romero, J. Cole-Dai, S. Bekki, M. Thiemens. UV induced mass‐independent sulfur isotope fractionation in stratospheric volcanic sulfate. Geophysical Research Letters, 2003, 30 (21), ⟨10.1029/2003gl018134⟩. ⟨hal-04418346⟩