Identifying the Cause of Ozone Layer Depletion

The ozone layer protects Earth from harmful ultraviolet (UV) radiation. Its depletion is a major environmental concern.

Primary Cause of Ozone Depletion

The principal factor causing the depletion of the ozone layer is the emission of Chlorofluorocarbons (CFCs).

• CFCs are synthetic chemicals historically used in refrigerants, aerosol propellants, and solvents.
• When released into the atmosphere, CFCs rise to the stratosphere.
• Here, intense UV radiation causes them to decompose, releasing highly reactive chlorine atoms.
• These chlorine atoms act as catalysts in a destructive cycle, breaking down ozone molecules ($\text{O}_3$) much faster than they are naturally created. The simplified cycle involves:
  • $\text{Cl} + \text{O}_3 \rightarrow \text{ClO} + \text{O}_2$
  • $\text{ClO} + \text{O} \rightarrow \text{Cl} + \text{O}_2$
  This process significantly reduces the concentration of ozone in the stratosphere.

Evaluating Other Options

• Aviation fuels: Emissions from high-flying aircraft can release nitrogen oxides, which have a minor impact on ozone, but are not the primary cause.
• Volcanic eruptions: While volcanoes release various gases and particles, their direct impact on the large-scale depletion of the ozone layer is limited compared to CFCs.
• Radioactive rays: These are forms of high-energy radiation. They do not directly participate in the chemical reactions that deplete the ozone layer in the stratosphere.

Therefore, Chlorofluorocarbons are identified as the main culprits responsible for the depletion of the ozone layer.