Stratospheric Ozone Depletion

1. Stratospheric Ozone Depletion IB syllabus: 5.6.1-5.6.6 AP syllabus Ch 17, 18 Video – The Hole Story

2. Syllabus Statements • 5.6.1: Outline the overall structure and composition of the atmosphere • 5.6.2: Describe the role of ozone in the absorption of UV radiation. • 5.6.3: Explain the interaction between ozone and halogenated organic gasses. • 5.6.4: State the effects of UV radiation on living tissues and biological productivity. • 5.6.5: Describe three methods of reducing the manufacture and release of ozone-depleting substances • 5.6.6: Describe and evaluate the role of national and international organizations in reducing the emissions of ozone-depleting substances

3. vocabulary • Halogenated organic gases • Pollution • Non-point source pollution • Replenishablenatural capital

4. Atmospheric Structure • Layered structure – Troposphere, Stratosphere, Mesosphere, Thermosphere • Troposphere is layer next to earth’s surface – 75-80% of mass of earth’s air • Atmospheric composition  78% nitrogen, 21% oxygen, trace amounts of water, argon, carbon dioxide • Lapse rate – rate at which temperature declines with increasing altitude in the troposphere

5. Temperature Pressure Mesopause Stratopause Tropopause Layers of the Atmosphere Atmospheric pressure (millibars) 0 200 400 600 800 1,000 120 75 110 65 Thermosphere 100 90 55 80 Heating via ozone Mesosphere 45 70 Altitude (miles) Altitude (kilometers) 60 35 50 Stratosphere 40 25 30 15 Ozone “layer” 20 Heating from the earth Troposphere 10 5 Pressure = 1,000 millibars at ground level 0 –80 –40 0 40 80 120 (Sea Level) Temperature (˚C)

6. Ozone • Ozone is O3 formed from O + O2 • Found in the lower Stratosphere as the ozone layer – good protective qualities • Found in the Troposphere as a result of human pollution – bad qualities photochemical oxidant

7. Ozone Formation • O3+ UV  O + O2 • O + O  O2 • O + O2  O3 • It’s Replenishable

8. Ozone absorbs UV radiation • When UV strikes O3 it is absorbed and its energy used to break the chemical bond • O3 + UV  O + O2 • So UV doesn’t make it to the earth’s surface

9. Ozone Layer • Layer in the lower stratosphere • Keeps 95% of harmful UV radiation away • Seasonal depletion of ozone layer above Arctic & Antarctic, overall thinning everywhere but tropics • Depletion is serious long term threat to (1) humans, (2) other animals, (3) sun driven producers (plants) supporting food webs

11. CFC’s (Freons) • Discovered in 1930 • Chemically stable, odorless, nonflamable, nontoxic, noncorrosive  dream chemical in the troposphere • Coolants, Propellants, Sterilants, Fumigants • 1974 discovered to be lowering concentrations of stratospheric ozone • Immediate ban called for

12. CFC’s II • Large quantities being released – use, leaks, production of plastics • Remain in troposphere – unreactive, insoluble very stable • 11-20 years to rise to stratosphere • Release high energy Clatoms when exposed to UV which speed up breakdown of ozone • Each CFC lasts 65-385 years in stratosphere • Can break down up to 100,000 molecules of ozone

13. Summary of Reactions CCl3F + UV Cl + CCl2F Cl + O3 ClO + O2 Cl + O Cl + O2 Repeated many times Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breaking off a chlorine atom and leaving CFCl2. Sun Cl Cl C Once free, the chlorine atom is off to attack another ozone molecule and begin the cycle again. Cl F UV radiation Cl Cl O O A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2. The chlorine atom attacks an ozone (O3) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O2). Cl Cl O O O O O Cl The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO). O O O

14. Summary of Reactions • CCl3F + UV  Cl + CCl2F • Cl + O3 ClO + O2 • ClO + O  Cl + O2 Steps 2 + 3 are repeated many times causing massive destruction of ozone

15. Methyl Bromide • Other major ODC • Used as a pesticide and fumigant on crops • Kills nematodes, fungi, weeds

16. Remember that ozone breaks down naturally when it absorbs UV • This speeds up that process and limits the regeneration of O3 • Pollutants enhance O3 destruction  disturbing the equilibrium of the O3 production system

17. 400 October monthly means 350 300 Total ozone (Dobson units) 250 200 150 100 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year Decreasing ozone volume in fall over the poles

18. Seasonal Polar Thinning • Seasonal loss of ozone in summers over poles • Ozone hole is actually ozone thinning • Sunless winters, polar vortex causes swirling winds isolated from rest of atmosphere • Ice crystals in clouds collect CFC’s and speed release of Cl • Sun returns in spring / summer and frees large volumes of free Cl • Ozone thinning travels north to effect Aus, NZ, S. Am., S. Af.

19. 35 August 7, 2001 30 October 10, 2001 25 20 Altitude (kilometers) 15 10 5 0 5 10 15 Ozone partial pressure (milipascals)

20. Figure 18-29Page 474 30 Area of North America 25 20 15 Million square kilometers 10 Size of Ozone thinning 5 0 1979 1982 1985 1988 1991 1994 1997 2000 2003 2006 Year

21. Sept Ozone Loss Antarctic

22. March Ozone Loss Arctic

23. Human Health • Worse sunburn • More eye cataracts • More skin cancers • Immune system suppression Food and Forests • Reduced yields for some crops • Reduced seafood supplies from reduced phytoplankton • Decreased forest productivity for UV-sensitive tree species Wildlife • Increased eye cataracts in some species • Decreased population of aquatic species sensitive to UV radiation • Reduced population of surface phytoplankton • Disrupted aquatic food webs from reduced phytoplankton Air Pollution and Materials • Increased acid deposition • Increased photochemical smog • Degradation of outdoor paints and plastics Global Warming • Accelerated warming because of decreased ocean uptake of CO2 from atmosphere by phytoplankton and CFCs acting as greenhouse gases What are the effects? Effects on Humans, Plants, Animals & Global climate A 1% loss of stratospheric ozone equals a 2% increase in skin cancers & 1% increase in cataracts worldwide. Humans make cultural changes, others cannot

24. Ultraviolet A Ultraviolet B Thin layer of dead cells Hair Epidermis Squamous cells Basal layer Sweat gland Melanocyte cells Dermis Basal membrane Blood vessels Squamous Cell Carcinoma Basal Cell Carcinoma Melanoma

25. Solutions & Protection • Must immediately stop using ozone depleting chemicals • Long recovery time afterwards due to persistence in the atmosphere • Substitutes are available for most CFC uses • Hydrocarbons seem to be best for future

26. How can the manufacture and release of ODC be reduced? • Refrigerants can be recycled • Alternatives to gas blown plastics can be used • Alternative propellents – hydroflourocarbons – better but a potent greenhouse gas • Alternatives to methyl bromide can be used for fumigation and pesticides

27. Problems • Existing stockpiles were ok to use after the phase out • Old CFCs continue to leak out of junked cars and fridges • Black market trade in CFCs increasing because they are not made but still useful • China, India, Mexico have increased use and production of CFCs • Full recovery expected by 2050 if current decline continues

28. Montreal Protocol • 1987, 36 nations in Montreal • Cut emissions of CFCs by 30% between 1989 and 2000 • After 1989 ozone thinning info new meetings in 1990, 1992 formed new Copenhagen protocol, 177 nations  more stringent reductions required • UNEP involved in these agreements as well as an accelerated phase out for Korea, China, India • Montreal Multilateral Fund est’d for aiding transition • Also studying the relative effectiveness of the measures being taken

29. 15,000 No protocol 12,000 1987 Montreal Protocol 9,000 Abundance (parts per trillion) 6,000 1992 Copenhagen Protocol 3,000 0 1950 1975 2000 2025 2050 2075 2100 Year Ozone depleting chemical concentration Predictions in stratosphere

30. In the US • Government ratified Montreal Protocol agreeing stop production of CFC propellents • Taxes levied on CFC production and use • Corporations changing their ways • McDonalds (1987) – stopped use of styrofoam packaging • Caused foam packaging industry to stop use of all CFCs by 1988

31. Next… • Return to 1980 levels by 2050 • Assume countries follow agreement and don’t produce new ODC • Ozone loss has been cooling troposphere masking global warming’s real effects • Good precedent for global cooperation