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Which statement correctly describes ozone-layer depletion?

1. Ozone loss is less severe near the poles because NO2 freezes there and is therefore unavailable to remove ClO radicals.
2. Ozone depletion is more severe near the poles because ice crystals in polar clouds catalyze photochemical reactions that break down ozone through Cl• and ClO• radicals.
3. Freons, or chlorofluorocarbons, are inert and do not chemically react with ozone in the stratosphere.
4. Oxides of nitrogen also fail to react with ozone in the stratosphere.

Correct answer: Ozone depletion is more severe near the poles because ice crystals in polar clouds catalyze photochemical reactions that break down ozone through Cl• and ClO• radicals.

Solution

The correct option highlights that the unique conditions in polar regions, including the presence of ice crystals in polar stratospheric clouds, facilitate reactions that release chlorine radicals, which are highly effective in breaking down ozone molecules, leading to greater depletion compared to other areas.

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