The influence of NaBr/NaCl ratio on the Br(-) catalyzed production of halogenated radicals

The activation of Br- and Cl- to atomic Br and Cl in sea-spray aerosol was investigated in smog-chamber experiments. In the presence of O3, hydrocarbons and NaCl aerosol alone no activation was observed. By adding Br- to the aerosol, the chain reaction: Br + O3 ==> BrO, BrO + HO2 ==> HOBr, HOBr ==> HOBr(aq), HOBr(aq) + H+ + Br- ==> Br2 (6), HOBr(aq) + H+ + Cl- ==>BrCl(7) was verified. The step from reaction (6) to (7) is accompanied by a decrease of the Br-/Cl- ratio from 1/600 to less than 1/2000. In the absence of sulphate, the chain is initiated by the reaction of OH(aq) with Br-.