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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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