Laboratory studies have shown that bromine nitrate (BrNO3) reacts on sulfuric acid and on ice particles. Here we investigate the potential role of BrNO3 in the marine boundary layer (mbl) assuming that it reacts on sea-salt particles as well. Using the chemical box model MOCCA we find that heterogeneous reactions of BrNO3 on aerosol particles could affect the chemistry in four major ways: 1) They increase loss of NOx (=NO+NO2) from the gas phase; 2) They accelerate loss of bromide and chloride from sea-salt aerosols. This dehalogenation occurs without the consumption of aerosol acidity; 3) The resulting loss of NOx and the increase of gas-phase bromine species both lead to O3 destruction; 4) The resulting increase of reactive chlorine species affects gas-phase hydrocarbons as well as S(IV) oxidation by HOCl in sea-salt aerosols. ¿ 1999 American Geophysical Union