Tropospheric ozone depletion events

[1] Apart from absorbing UV-B radiation and converting solar energy into heat in the stratosphere, ozone in the troposphere provides greenhouse effect and controls the oxidation capacity of the atmosphere.

[3] Nitrogen oxides play a key role in recycling active free radicals (such as reactive halogens) in the atmosphere and indirectly affect ozone depletion.

[5] During springtime in the polar regions of Earth, unique photochemistry converts inert halide salt ions (e.g. Br−) into reactive halogen species (e.g. Br atoms and BrO) that episodically deplete ozone in the atmospheric boundary layer to near zero levels.

The exact sources and mechanisms that release bromine are still not fully understood, but the combination of concentrated sea salt in a condensed phase substrate appears to be a pre-requisite.

These include near complete removal and deposition of mercury, alteration of oxidation fates for organic gases, and export of bromine into the free troposphere.