Chlorine and bromine atoms are the primary destroyers of ozone in the stratosphere. These atoms, originating from human-made chemicals like chlorofluorocarbons (CFCs), initiate chain reactions that break down ozone molecules (O3) into oxygen (O2). A single chlorine atom can destroy tens of thousands of ozone molecules before being removed from the stratosphere. This depletion of the ozone layer allows harmful ultraviolet (UV) radiation from the sun to reach the Earth's surface.
Ozone Depleting Substances and Processes
Several factors contribute to ozone destruction:
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Human-made chemicals: Chlorofluorocarbons (CFCs), halons, and other ozone-depleting substances (ODS) release chlorine and bromine atoms into the stratosphere, initiating ozone-depleting chemical reactions. [Source: Ozone Depletion. When chlorine and bromine atoms come into contact with ozone in the stratosphere, they destroy ozone molecules. One chlorine atom can destroy over 100,000 ozone molecules before it is removed from the stratosphere. Ozone can be destroyed more quickly than it is naturally created. (Sept 17, 2024)]
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Wildfires: Smoke from large wildfires injects particles into the stratosphere, providing surfaces for chemical reactions that accelerate the destruction of ozone. [Source: Wildfire Smoke Destroys Ozone - Eos, Wildfire smoke destroys stratospheric ozone] These reactions often involve chlorine compounds already present in the atmosphere.
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Space travel: The projected increase in space travel activities may also contribute to ozone depletion due to the release of exhaust gases into the stratosphere. [Source: Projected increase in space travel may damage ozone layer - NOAA]
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Nuclear war: Smoke from a nuclear war would inject massive amounts of soot and other particles into the stratosphere, leading to significant ozone destruction. [Source: Smoke from nuclear war would devastate ozone layer, alter climate]
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Natural Processes: While human activities are the primary driver of ozone depletion, natural processes also play a minor role. For example, nitrogen and hydrogen-containing gases in the stratosphere participate in reactions that convert ozone back into oxygen. [Source: Ozone and You | Ozone Secretariat] Iodine in desert dust can also trigger ozone-destroying chemical reactions. [Source: Iodine in desert dust destroys ozone | CIRES]
Other Reactive Gases
Besides chlorine and bromine, other reactive halogen gases also participate in ozone destruction. These gases can be categorized into reservoir gases (which don't directly destroy ozone) and highly reactive gases that directly participate in ozone-depleting reactions. [Source: Q8 What are the reactive halogen gases that destroy stratospheric ...]
