Atmospheric Monitoring

First satellite detection of volcanic OCIO

25 March 2014

A large volcanic OClO and BrO plume could be tracked from ENVISAT SCIAMACHY jointly with EOS Aura MLS and OMI observations for 5 days after the June 2011 eruption of Puyehue-Cordón Caulle (PCC). Previous measurements of Volcanic chlorine oxides as ClO and OClO (a species formed by the reaction of BrO and ClO) or molecular chlorine were obtained using ground-based instruments: this is the first time that reactive chlorine of volcanic origin has been detected from space.

The early plume of the PCC eruption shows low abundances of BrO and OClO, and is rich in SO2. According to the authors this can be explained by an efficient scavenging of halogen halides (HCl and HBr) by water, ice, or ash in the early stage of the eruption. Another possibility is a time shift in the initial volcanic emissions of halogens compared to SO2, resulting, e.g., from differences in magmatic solubility. The evidence for volcanic halogens activation for many days points to a very efficient recycling mechanism of halogen oxides on the surface of volcanic aerosols.

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