Stratospheric Ozone Depletion - AP Environmental Science

1. What is the main reason for seasonal variation in ozone depletion?

   Sunlight availability. UV radiation drives chemical reactions, so depletion peaks during polar spring.

2. Which atmospheric phenomenon enhances ozone depletion at the poles?

   Polar vortex. Circular wind patterns isolate polar air, creating conditions for severe depletion.

3. How do UV rays contribute to the breakdown of CFCs?

   They provide energy to release chlorine. High-energy UV photons break carbon-chlorine bonds, releasing reactive chlorine.

4. Which gas is released from HCFCs that still affects the ozone layer?

   Chlorine. HCFCs contain some chlorine but much less than CFCs, reducing ozone impact.

5. Identify one health effect of increased UV radiation due to ozone depletion.

   Skin cancer. UV-B radiation damages DNA in skin cells, leading to malignant tumors.

6. Identify a human activity that releases ozone-depleting substances.

   Use of aerosol sprays. Aerosols historically contained CFCs as propellants, releasing them into the atmosphere.

7. What is the global warming potential (GWP) of CFCs compared to CO₂?

   High GWP. CFCs trap thousands of times more heat than carbon dioxide per molecule.

8. Which gas is a byproduct of CFC breakdown that also affects ozone?

   Chlorine monoxide (ClO). This radical forms when chlorine reacts with ozone, continuing destructive cycles.

9. Which month typically shows the largest ozone hole over Antarctica?

   September. Antarctic spring brings sunlight that triggers chemical reactions depleting ozone.

10. What is the relationship between ozone depletion and cataracts?

    Increased UV exposure causes cataracts. Higher UV-B levels damage eye lenses, leading to clouding and vision problems.

11. Name a factor that can naturally repair the ozone layer.

    Chemical reactions forming $O_3$. Natural photochemical processes continuously create new ozone from oxygen molecules.

12. What is the expected timeline for full recovery of the ozone layer?

    Mid-21st century. Recovery depends on continued compliance with international ozone protection agreements.

13. What is one major goal of the Vienna Convention?

    Protect the ozone layer. This 1985 framework established international cooperation for ozone layer protection.

14. What is the primary human-made source of ozone-depleting substances?

    Industrial chemicals. Manufacturing processes release CFCs, HCFCs, and other synthetic ozone depleters.

15. What does the abbreviation 'CFC' stand for?

    Chlorofluorocarbon. These synthetic compounds contain carbon, fluorine, and chlorine atoms.

16. What happens to CFCs in the stratosphere that causes ozone depletion?

    UV light breaks them down, releasing chlorine. Photolysis by UV radiation breaks C-Cl bonds, freeing reactive chlorine atoms.

17. Name a natural source of halogens that can deplete ozone.

    Volcanic eruptions. Volcanic emissions can release chlorine and bromine compounds into the stratosphere.

18. Which protocol amendment accelerated the phase-out of CFCs?

    London Amendment. This 1990 amendment strengthened CFC phase-out timelines and added new substances.

19. What term describes the depletion of ozone over the Arctic?

    Arctic ozone depletion. Similar to Antarctic ozone hole but typically less severe due to different conditions.

20. How does the Montreal Protocol contribute to climate protection?

    Reduces greenhouse gases. CFCs are potent greenhouse gases, so eliminating them helps climate protection.

21. What is the significance of the Dobson Unit in ozone measurement?

    Measures total ozone column. This unit quantifies the total amount of ozone in a vertical atmospheric column.

22. What role do refrigerators play in ozone depletion?

    Release CFCs as refrigerants. Old refrigerators contain CFC coolants that escape when units are improperly disposed.

23. Identify the type of UV radiation most affected by ozone depletion.

    UV-B radiation. This wavelength range (280-315 nm) increases most when ozone levels drop.

24. Name a substitute for CFCs with no ozone-depleting potential.

    Hydrofluorocarbons (HFCs). These contain no chlorine or bromine, so they don't harm the ozone layer.

25. What type of radiation does the ozone layer primarily absorb?

    Ultraviolet (UV) radiation. Ozone molecules absorb UV-B and UV-C radiation, protecting life on Earth.

26. How long can CFCs remain in the atmosphere contributing to ozone depletion?

    Up to 100 years. CFCs have extremely long atmospheric lifetimes, causing persistent ozone depletion.

27. Which substance replaced CFCs due to its lower ozone-depleting potential?

    Hydrochlorofluorocarbons (HCFCs). These transitional chemicals have shorter lifespans and contain less chlorine than CFCs.

28. What does UV-B radiation do to living organisms?

    Damages DNA. UV-B breaks chemical bonds in DNA, causing mutations and cellular damage.

29. What is the role of polar stratospheric clouds in ozone depletion?

    They provide surfaces for chlorine activation. Ice crystals convert stable chlorine compounds into reactive forms that destroy ozone.

30. What is the term for the area of significant ozone thinning over Antarctica?

    Ozone hole. This seasonal phenomenon occurs due to polar vortex conditions and chemical reactions.

31. What is the primary cause of stratospheric ozone depletion?

    Chlorofluorocarbons (CFCs). These synthetic chemicals break down in the stratosphere, releasing ozone-destroying chlorine atoms.

32. Identify the atmospheric layer where ozone depletion occurs.

    Stratosphere. This layer contains about 90% of Earth's ozone, located 10-50 km above Earth's surface.

33. Which element in CFCs is most responsible for ozone depletion?

    Chlorine. When CFCs break down, chlorine atoms catalytically destroy thousands of ozone molecules.

34. What is the primary environmental consequence of ozone layer depletion?

    Increased UV radiation. Less ozone means more harmful UV-B radiation reaches Earth's surface.

35. What is the effect of ozone layer recovery on UV radiation levels?

    Decreased UV radiation. As ozone layer heals, it will better absorb UV radiation reaching Earth.

36. Name the international treaty aimed at reducing ozone-depleting substances.

    Montreal Protocol. This 1987 agreement successfully phased out production of ozone-depleting chemicals worldwide.

37. Which chemical reaction describes ozone formation in the stratosphere?

    $O_2 + UV \rightarrow 2O$; $O + O_2 \rightarrow O_3$. UV splits oxygen molecules, then atomic oxygen combines with $O_2$ forming ozone.

38. How does chlorine affect ozone molecules in the stratosphere?

    It catalyzes the breakdown of $O_3$. One chlorine atom can destroy thousands of ozone molecules through catalytic cycles.

39. Identify the unit used to measure the concentration of ozone.

    Dobson Unit (DU). Named after ozone researcher Gordon Dobson, measures atmospheric ozone thickness.

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