Ozone in the troposhere is determined by photochemical production and destruction,
During
It is still not fully understood how salts are transported from the ocean and oxidized to become reactive halogen species in the air. Other halogens (chlorine and iodine) are also activated through mechanisms coupled to bromine chemistry.[6] The main consequence of halogen activation is chemical destruction of ozone, which removes the primary precursor of atmospheric oxidation, and generation of reactive halogen atoms/oxides that become the primary oxidizing species.[6] The oxidation ability originally influenced by ozone is weakened, while the halogen species now holds the oxidation ability. This changes the reaction cycles and final products of many atmospheric reactions. During ozone depletion events, the enhanced halogen chemistry can effectively oxidize reactive gaseous elements.[4]
The different reactivity of halogens as compared to OH and ozone has broad impacts on atmospheric chemistry. These include near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere.[6] The deposition of reactive gaseous mercury (RGM) in snow from oxidation by enhanced halogens increases the bioavailability of mercury.[4] Recent changes in the climate of the Arctic and state of the Arctic sea ice cover are likely to have strong effects on halogen activation and ozone depletion events. Human-induced climate change affects the quantity of snow and ice cover in the Arctic, altering the intensity of nitrogen oxide emissions.[4] Increment in background levels of nitrogen oxide apparently strengthens the consumption of ozone and the enhancement of halogens.