A global perspective on Bromine monoxide composition in volcanic plumes derived from S5-P/TROPOMI

Bromine monoxide (BrO) is a halogen radical altering the atmospheric ozone chemistry, e. g. in polar regions, the stratosphere as well as volcanic plumes. In particular, the molar bromine to sulphur ratio in volcanic gas emissions is characteristic to the magmatic composition of a volcano.

The high spatial resolution of S5-P/TROPOMI (up to 3.5x5.5km²) and daily coverage offer the potential to detect BrO even during minor eruptions and determine BrO/SO₂ ratios during continuous passive degassing.

Here, we present a global overview of BrO/SO₂ molar ratios in volcanic plumes derived from a systematic investigation of two years (2018 and 2019) of TROPOMI data.

We retrieved BrO column densities as well as SO₂ column densities using Differential Optical Absorption Spectroscopy (DOAS) and calculated mean BrO/SO₂ molar ratios for each volcano. The calculated BrO/SO₂ molar ratios differ strongly between different volcanoes ranging between several 10^-5 and 10^-4. The data are classified and discussed with regard to several volcanic parameters –  more specific the volcanic region, volcano type (i. e. subduction zone, hotspot etc.) as well as activity level.