High bromine oxide concentrations in the semi-polluted boundary layer

Bromine chemistry in the marine boundary layer is recognized to play an important role through catalytic ozone destruction, changes to the atmospheric oxidising capacity (by changing the OH/HO2 and NO/NO2 ratio) and oxidation of compounds such as dimethyl sulphide (DMS). However, the chemistry of bromine in polluted environments is not well understood and its effects are thought to be inhibited by reactions involving NOx (NO2 & NO). This paper describes long-path Differential Optical Absorption Spectroscopy (DOAS) observations of bromine oxide (BrO) at a semi-polluted coastal site in Roscoff, France. Significant concentrations of BrO (up to 7.5 ± 1.0 pptv) were measured during daytime, indicating the presence of unknown sources or efficient recycling of reactive bromine from bromine nitrate (BrONO2), which should be the major reservoir for bromine in a high NOx environment. These measurements indicate that bromine chemistry can play an important role in polluted environments.