A TROPOMI-based survey of stationary BrO sources

Bromine monoxide levels in the troposphere are usually very low. Under certain conditions, local concentrations can be enhanced, and if the enhancement is large enough, it can be detected in satellite observations using UV absorption spectroscopy.

Most satellite BrO observations focus on polar regions, where many BrO enhancements occur every spring, resulting in local ozone depletion and impacting atmospheric mercury chemistry. BrO enhancements are also observed in some volcanic plumes, and the BrO-to-SO2 ratio can help better understand magma conditions and possibly even predict changes in volcanic activity. Enhanced tropospheric BrO levels have also been detected in satellite data near salt lakes and salt marshes.

In this study, 8 years of TROPOMI BrO slant columns have been evaluated for stationary BrO signals indicating local sources. In addition to the emissions from Rann al Katch, the Dead Sea, and the Great Salt Lakes, which have already been reported in earlier work, many more local BrO enhancements could be identified, mostly linked to salt lakes and salt marshes. The BrO hotspots are evaluated for potential artefacts from enhanced albedo, surface spectral reflectance, and scene inhomogeneity. For the signals deemed real, the seasonal variation is analysed, and the magnitude of the BrO enhancement is estimated.