Systematic investigation of bromine monoxide in volcanic plumes from space by using the GOME-2 instrument

摘要

During recent years, volcanic emissions turned out to be a natural source ofbromine compounds in the atmosphere. While the initial formation process ofbromine monoxide (BrO) has been successfully studied in local ground-basedmeasurements at quiescent degassing volcanoes worldwide, literature on thechemical evolution of BrO on large spatial and temporal scales is sparse. Thefirst space-based observation of a volcanic BrO plume following the Kasatochieruption in 2008 demonstrated the capability of satellite instruments tomonitor such events on a global scale.In this study, we systematically examined GOME-2 observations from January2007 until June 2011 for significantly enhanced BrO slant column densities(SCDs) in the vicinity of volcanic plumes. In total, 772 plumes from at least37 volcanoes have been found by using sulphur dioxide (SO) as a tracerfor a volcanic plume. All captured SO plumes were subsequently analysedfor a simultaneous enhancement of BrO and the data were checked for apossible spatial correlation between the two species. Additionally, the meanBrO/SO ratios for all volcanic plumes have been calculated by theapplication of a bivariate linear fit.A total number of 64 volcanic plumes from at least 11 different volcanoesshowed clear evidence for BrO of volcanic origin, revealing large differencesin the BrO/SO ratios (ranging from some 10 to several 10)and the spatial distribution of both species. A close correlation betweenSO and BrO occurred only for some of the observed eruptions or just incertain parts of the examined plumes. For other cases, only a rough spatialrelationship was found. We discuss possible explanations for the occurrenceof the different spatial SO and BrO distributions in aged volcanicplumes.