Bromine monoxide (BrO) is a halogen radical influencing atmospheric chemical processes, in particular the abundance of ozone. Furthermore, the molar bromine to sulphur ratio in volcanic gas emissions is a proxy for the magmatic composition of a volcano and potentially an eruption forecast parameter.

The talk focusses on the global BrO/SO₂ ratio, whose abundance in volcanic gas plumes can be derived simultaneously via differential optical absorption spectroscopy (DOAS), developed by Prof. Platt.

Using the high spatial resolution (3.5x5.5km²) of the TROPOMI satellite instrument, a global data-set of the BrO/SO₂ ratios inside 4000 volcanic plumes is derived. Based on this vast data-set information both on the magmatic composition – an important characteristic volcanic property – as well as the halogen chemistry inside volcanic plumes are derived.