What substance is primarily responsible for ozone layer depletion?

What substance is primarily responsible for ozone layer depletion?

• A. Methane
• B. CO2
• C. CFCs
• D. Nitrogen oxides

Answer: (C)

Ozone layer depletion happens when certain chlorine- and bromine-containing compounds reach the stratosphere and are broken apart by UV light, releasing reactive halogens that destroy ozone molecules. Chlorofluorocarbons are the most impactful of these compounds because they are very stable in the lower atmosphere, so they travel up to the stratosphere intact. There, UV radiation frees chlorine atoms from the CFCs, and those chlorine atoms catalytically destroy ozone through a cycle that repeatedly converts ozone into ordinary oxygen. A single chlorine atom can participate in thousands of ozone destruction reactions before it’s removed from the cycle. Other substances listed don’t drive the depletion as strongly. Methane and CO2 are greenhouse gases with broad climate effects and can influence atmospheric chemistry indirectly, but they aren’t the primary agents breaking down ozone. Nitrogen oxides do participate in ozone chemistry as well, but their impact on the global ozone hole is smaller compared to the significant catalytic effect of chlorine from CFCs. So, chlorofluorocarbons are the primary culprits behind ozone layer depletion.

Ozone layer depletion happens when certain chlorine- and bromine-containing compounds reach the stratosphere and are broken apart by UV light, releasing reactive halogens that destroy ozone molecules. Chlorofluorocarbons are the most impactful of these compounds because they are very stable in the lower atmosphere, so they travel up to the stratosphere intact. There, UV radiation frees chlorine atoms from the CFCs, and those chlorine atoms catalytically destroy ozone through a cycle that repeatedly converts ozone into ordinary oxygen. A single chlorine atom can participate in thousands of ozone destruction reactions before it’s removed from the cycle.

Other substances listed don’t drive the depletion as strongly. Methane and CO2 are greenhouse gases with broad climate effects and can influence atmospheric chemistry indirectly, but they aren’t the primary agents breaking down ozone. Nitrogen oxides do participate in ozone chemistry as well, but their impact on the global ozone hole is smaller compared to the significant catalytic effect of chlorine from CFCs.

So, chlorofluorocarbons are the primary culprits behind ozone layer depletion.