Here's the breakdown:
1. CFCs reach the stratosphere: CFCs, once widely used in refrigerants and aerosols, are very stable molecules and can persist in the atmosphere for decades. They eventually diffuse upwards into the stratosphere.
2. UV radiation breaks down CFCs: Strong UV radiation in the stratosphere breaks down CFCs, releasing chlorine atoms (Cl).
3. Chlorine atom becomes a free radical: The chlorine atom has a single unpaired electron, making it a highly reactive free radical (Cl•).
4. Chain reaction begins: This chlorine free radical reacts with ozone (O3), breaking it down into oxygen (O2) and an oxygen atom (O).
5. Chlorine regenerates: The chlorine atom then reacts with another ozone molecule, continuing the cycle and destroying multiple ozone molecules.
6. Long-lasting effect: Each chlorine atom can destroy thousands of ozone molecules before being removed from the stratosphere.
Here's the simplified reaction sequence:
* CFC + UV radiation → Cl• + other products
* Cl• + O3 → ClO• + O2
* ClO• + O → Cl• + O2
The net effect: This chain reaction results in the depletion of the ozone layer, which protects life on Earth from harmful UV radiation.
It's important to note that CFCs are now banned under international agreements, and the ozone layer is slowly recovering. However, the long lifespan of CFCs means that the effects of their release are still being felt today.
