Which statement about chlorine in the stratosphere is true?

Which statement about chlorine in the stratosphere is true?

• A. It is introduced mainly by natural volcanic emissions
• B. It is introduced mainly by human-made refrigerants
• C. It has no role in ozone depletion
• D. It is neutralized quickly by sunlight

Answer: (B)

Chlorine in the stratosphere drives ozone loss through catalytic cycles, and most of it comes from human-made refrigerants. Compounds like CFCs and related halons travel up to the stratosphere, where UV light breaks them apart and releases chlorine atoms and radicals. These chlorine species repeatedly destroy ozone: for example, chlorine reacts with ozone to form chlorine monoxide and O2, and then chlorine monoxide reacts with atomic oxygen to regenerate chlorine and produce more O2. Because the chlorine is regenerated, a single atom can destroy many ozone molecules, amplifying the effect. Volcanic emissions do contribute some chlorine, but they are not the main source. And sunlight doesn’t quickly neutralize chlorine’s role; instead, it helps convert stable reservoir forms (like HCl and ClONO2) back into reactive chlorine, sustaining the catalytic depletion cycles.

Chlorine in the stratosphere drives ozone loss through catalytic cycles, and most of it comes from human-made refrigerants. Compounds like CFCs and related halons travel up to the stratosphere, where UV light breaks them apart and releases chlorine atoms and radicals. These chlorine species repeatedly destroy ozone: for example, chlorine reacts with ozone to form chlorine monoxide and O2, and then chlorine monoxide reacts with atomic oxygen to regenerate chlorine and produce more O2. Because the chlorine is regenerated, a single atom can destroy many ozone molecules, amplifying the effect.

Volcanic emissions do contribute some chlorine, but they are not the main source. And sunlight doesn’t quickly neutralize chlorine’s role; instead, it helps convert stable reservoir forms (like HCl and ClONO2) back into reactive chlorine, sustaining the catalytic depletion cycles.