OBSERVATION AND ROLE OF THE FREE-RADICALS NO3, CLO, BRO AND IO IN THETROPOSPHERE

An attempt is made to obtain estimates of the average tropospheric abu ndance of nitrate radicals (NO3) and reactive halogen species (halogen oxide radicals and halogen atoms) on a global scale and thus to quant ify their possible impact on the oxidation potential of the tropospher e. For that purpose we combine new measurements with data that recentl y became available. It is found that the integrated formation of the r adicals is comparable to that of OH radicals in certain situations. Ho wever, it is argued that the effects of these radicals on the oxidatio n capacity of the troposphere are not necessarily additive. For instan ce, BrO could be an NO3-scavenger.