Ozone Depletion AP ES 2/2008 Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breaking off a chlorine atom and leaving CFCl2. Figure 21-21 Sun Cl Cl F C Cl Page 485 Once free, the chlorine atom is off to attack another ozone molecule UV radiation and begin the cycle again. Cl Cl O O The chlorine atom attacks A free oxygen atom pulls an ozone (O3) molecule, Cl the oxygen atom off pulling an oxygen atom the chlorine monoxide Cl off it and leaving molecule to form O2. O O an oxygen O O molecule (O2). O The chlorine Cl atom and the O Summary of Reactions oxygen atom join CCl3F + UV Cl + CCl2F to form a chlorine O Cl + O3 ClO + O2 Repeated monoxide molecule O Cl + O Cl + O2 many times (ClO). 400 Figure 21-22 October monthly means Total ozone (Dobson units) 350 Page 485 300 250 200 150 100 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 Year 35 30 Figure 21-2311, 2003 August 6, 2003 October 25 Page 486 Altitude (kilometers) 20 15 10 5 0 5 10 15 Ozone partial pressure (milipascals) Natural Capital Degradation Effects of Ozone Depletion 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 Figur Ultraviolet A Ultraviolet B Thin layer of Figure 21-25 dead cells Page 487 Hair Epidermis Squamous cells Basal layer Sweat gland Melanocyte cells Dermis Basal cell Blood vessels Squamous Cell Carcinoma Basal Cell Carcinoma Melanoma DO NOT POST TO INTERNET Melanoma Figure 21-25bcd Page 487 Squamous Cell Carcinoma DO NOT POST TO INTERNET DO NOT POST TO INTERNET Basal Cell Carcinoma What Can You Do? Reducing Exposure to UV-Radiation • Stay out of the sun, especially between 10 A.M. and 3 P.M. • Do not use tanning parlors or sunlamps. • When in the sun, wear protective clothing and sun– glasses that protect against UV-A and UV-B radiation. • Be aware that overcast skies do not protect you. • Do not expose yourself to the sun if you are taking antibiotics or birth control pills. • Use a sunscreen with a protection factor of 15 or 25 if you have light skin. • Examine your skin and scalp at least once a month for moles or warts that change in size, shape, or color or sores that keep oozing, bleeding, and crusting over. If you observe any of these signs, consult a doctor immediately. Figur 15,000 21-27 Figure protocol Abundance (parts per trillion) No 12,000 Page 489 1987 9,000 Montreal Protocol 6,000 1992 Copenhagen 3,000 Protocol 0 1950 1975 2000 2025 2050 2075 2100 Year Animation CFCs destroying ozone animation. Click to view animation.
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