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HBr, in the stratosphere, ozone is continuously being
formed via the Chapman mechanism. However, halogen radicals such as bromine and
chlorine (released from anthropogenic and some natural sources) catalyze the
breakdown of ozone which results in a net ozone loss:
O3 + Br----> BrO + O2
A reservoir species is a compound whose formation breaks the destruction
cycle by taking the halogen radical out of the cycle. Two examples are HCl and
HBr. Unfortunately, the success of HBr as a reservoir species is very limited
due to the fact that it photodissociates quickly and easily. Thus, the ozone
depleting effects of bromine are, atom for atom, more severe than those of
chlorine.
[Graedel, T.D. and Paul Crutzen. Atmospheric Change: an Earth system
perspective; 1993; Freeman Press.]
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