1. Arthur N. Samel Chair, Department of Geography Bowling Green State University & Chief Reader, Advanced Placement Environmental Science Program

2. The concentration of O 3 near the earth’s surface is minute ~40 ppb

3. Location of stratospheric O 3

4. Atmospheric O 3 concentration as a function of height/altitude

5. Stratospheric Ozone “Cycle” : 2O 3 + → 2O 2 + O ( < 290 nm; UV-B; 90% absorption) 2O 2 + 2O → 2O 3 O 2 + → 2O ( < 240 nm; UV-C; 100% absorption) 2O + O 2 → 2O 3

6. CFCs … Oh NO!!!

7.  CFCs are extremely stable molecules in the troposphere and become well mixed.  It takes many years (60-100) for CFC molecules to enter the stratosphere.  Once in the stratosphere, CFCs absorb UV-C radiation, dissociate, and Cl- radicals are released.

8. Stratospheric Ozone Destruction : CFCs CFC + → CFC + Cl ( < 215 nm; UV-C) O 3 + → O 2 + O ( < 290 nm; UV-B) Cl + O 3 → ClO + O 2 ClO + O → Cl + O 2 A single Cl - radical can reside in the stratosphere for nearly a decade and disrupt the formation of several hundred thousand O 3 molecules. Increased UV-B reached Earth’s surface

9.  What is a greenhouse gas ?  Transparent to insolation  Absorbs outgoing terrestrial radiation

10.  Is O 3 an atmospheric greenhouse gas?  How can the destruction of stratospheric O 3 enhance the atmospheric greenhouse effect?  Does the destruction of stratospheric O 3 contribute to warming in the troposphere?

11. Energy emission spectra of Sun and Earth (A) and absorption of energy in the Earth’s atmosphere (B). UV-B absorption in the stratosphereIR absorption in the troposphere

12. DU = thickness of compressed atmospheric O 3 at 0°C * 100. (e.g., 4mm = 400 DU)

13. Bar graph of area with Antarctic low O 3 concentrations (< 220 DU) during October and November (area of North America ~ 24 million km 2).

14. Monthly average total O 3 Northern Hemisphere spring

15. Bar graph of area with Arctic low O 3 concentrations (< 300 DU) during February and March.

16.  Increased rate of skin cancers  Increased frequency of cataracts  Decreased phytoplankton productivity  Decreased photosynthesis rates  Decreased plant growth rates

17. Atmospheric O 3 concentration as a function of height/altitude

18. NOx VOCs NO x Sources Tropospheric Ozone Formation : 2NO + O 2 → 2NO 2 NO 2 + → NO + O O + O 2 → O3

19. Various sources of VOCs

20. Ozone formation occurs through the following sequence of reactions. The sequence is almost always initiated by the reaction of various VOC or CO with the OH radical [ R1, R2 ]. This is followed by the conversion of NO to NO 2 (through reaction with HO 2 or RO 2 radicals), which also regenerates OH [ R3, R4 ]. NO 2 is photolyzed to generate atomic oxygen, which combines with O 2 to create O 3 [ R5, R6 ].

21. Variation in ground level O3 concentration during a typical 24-hour day

23. New York City, July 10, 2007 New York City, July 16, 2008

24. L.A. City Hall, 1953 L.A. City Hall, 2005

25. Number of days when the 1-hour federal O 3 standard was exceeded in Los Angeles as well as the 1-hour peak concentration

26.  Is O 3 an atmospheric greenhouse gas?  Does the formation of tropospheric O 3 enhance the atmospheric greenhouse effect?

27. Factors that contribute to atmospheric warming and cooling and our level of understanding

28. Global Warming Potentials (GWP) and Atmospheric Lifetimes (Years) Used in the Inventory Gas Atmospheric Lifetime 100-year GWPa 20-year GWP 500-year GWP Carbon dioxide (CO 2 ) 50-200 1 1 1 Methane (CH 4 )b 12±3 21 56 6.5 Nitrous oxide (N 2 O) 120 310 280 170 HFC-23 264 11,700 9,100 9,800 HFC-125 32.6 2,800 4,600 920 HFC-134a 14.6 1,300 3,400 420 HFC-143a 48.3 3,800 5,000 1,400 HFC-152a 1.5 140 460 42 HFC-227ea 36.5 2,900 4,300 950 HFC-236fa 209 6,300 5,100 4,700 HFC-4310mee 17.1 1,300 3,000 400 CF 4 50,000 6,500 4,400 10,000 C 2 F 6 10,000 9,200 6,200 14,000 C 4 F 10 2,600 7,000 4,800 10,100 C 6 F 14 3,200 7,400 5,000 10,700 SF 6 3,200 23,900 16,300 34,900

29. Net 100-year Global Warming Potentials for Select Ozone Depleting Substances Gas Direct Netmin Netmax CFC-11 4,600 (600) 3,600 CFC-12 10,600 7,300 9,900 CFC-113 6,000 2,200 5,200 HCFC-22 1,700 1,400 1,700 HCFC-123 120 20 100 HCFC-124 620 480 590 HCFC-141b 700 (5) 570 HCFC-142b 2,400 1,900 2,300 CHCl 3 140 (560) 0 CCl 4 1,800 (3,900) 660 CH 3 Br 5 (2,600) (500) Halon-1211 1,300 (24,000) (3,600) Halon-1301 6,900 (76,000) (9,300)