Final answer:
The natural mechanism that destroys ozone is photodissociation, where ozone molecules absorb UV light and break down. Human-made chemicals like CFCs release chlorine atoms that catalyze further breakdown of ozone, causing depletion of the ozone layer. The Montreal Protocol aims to reduce the use of such ozone-depleting substances.
Step-by-step explanation:
The mechanism for a naturally occurring reaction that destroys ozone in the atmosphere is photodissociation. Photodissociation is a process where a chemical compound is broken down by photons, such as the ultraviolet (UV) light from the sun. In the stratosphere, ozone (O3) molecules absorb UV radiation and are split into an oxygen molecule (O2) and a separate oxygen atom (O). This oxygen atom can then react with another oxygen molecule to reform ozone, or it can participate in a cycle that continues to absorb UV radiation and keep it from reaching the Earth's surface. However, the introduction of substances like chlorofluorocarbons (CFCs), when exposed to intense UV light, release chlorine atoms that catalyze the breakdown of ozone molecules, thus depleting the protective ozone layer.
Chemicals such as chlorine and bromine from human-made substances interrupt this cyclical process, leading to ozone depletion. The release of a chlorine atom from substances like CFCs follows a catalytic cycle that can destroy up to 100,000 ozone molecules, posing a significant threat to the ozone layer. This concern led to the implementation of the Montreal Protocol, an international agreement to phase out the production and use of ozone-depleting substances (ODS).