Presentation Slides for
Atmospheric Pollution:
History, Science, and Regulation
Chapter 11: Global Stratospheric Ozone Reduction
By Mark Z. Jacobson
Cambridge University Press, 399 pp. (2002)
Last update: March 28, 2005
The photographs shown here appear in the textbook and are provided
to facilitate their display during course instruction. Permissions for
publication of photographs must be requested from individual
copyright holders. The source of each photograph is given below the
figure and in the back of the textbook.
Column Abundance of Ozone
Figure 11.1
Latitude (degrees)
Ozone Column Abundance in 2000
Versus Latitude and Month
50
100
150
200
250
300
350
Ozone column abundance (DU)
400
450
Figure 11.2
400
Ozone (Dobson units)
Ozone (Dobson units)
Variation with Latitude of Yearly- and
Zonally-Averaged Ozone in ‘79, ‘99, ‘00
1979
350
2000
300
250
1999
Zonal and yearly average
200
-90
-60
-30
0
30
60
Latitude (degrees)
90
Figure 11.3
Vertical Profile of Ozone
O (ppmv)
Altitude (km)
Altitude (km)
40
3
30
20
O (molecules cm
3
-3
x 10
-12
Air (molecules cm
-19
x 5 x 10 )
10
)
-3
0
0
2
4
6
8 10 12 14
Figure 11.4
2500
2000
Far UV
Near UV
Visible
TOA
1000
UV-A
1500
UV-B
UV-C
Radiation intensity (W m-2 m-1)
Downward Solar Radiation at Top of
Atmosphere (TOA) and Ground
Ground
o
o
10 N, 5 W
August 3, 1990
Solar z enith angle 8.2
500
o
0
0.2
0.3
0.4
0.5
Wavelength (m)
0.6
Figure 11.5
Major Absorbers of UV
Radiation at Different Altitudes
Spectrum
Far-UV
Near-UV
UV-C
UV-B
UV-A
Wavelengths Dominant
(m)
Absorbers
0.01-0.25
N2
O2
Location of
Absorption
Thermosphere
Thermosphere
0.25-0.29
0.29-0.32
O3
O3
0.32-0.38
Particles
NO2
Particles
Stratosphere
Stratosphere
Troposphere
Polluted troposphere
Polluted troposphere
Polluted troposphere
Table 11.1
UV-B Trends
A 1% reduction in ozone results in roughly a 2% increase in UV-B
Observed UV-B changes 1970-1998
7% higher in NH midlatitudes during winter/spring
4% higher in NH midlatitudes during summer/autumn
6% higher in SH midlatitudes all year
130% higher in Antarctica during SH spring
22% higher in Arctic during NH spring
Sidney Chapman (1888-1970)
American Institute of Physics Emilio Segrè Visual Archives, Physics Today collection
Natural Ozone Production
O2(g) + h
Molecular
oxygen
O(1D)(g) + O(g)
 < 175 nm
Excited
Groundatomic state atomic
oxygen
oxygen
O2 (g) + h
M olecular
oxygen
O(g) + O(g)
Groundstate atomic
oxygen
 < 245 nm
M
O(1D)(g)
Excited
atomic
oxygen
O(g)
Groundstate atomic
oxygen
M
O(g) + O 2(g)
Ground- M olecular
state atomic oxygen
oxygen
O3(g)
Ozone
(11.1) - (11.4)
Natural Ozone Destruction
O3(g) + h
Ozone
O2(g) + O(1D)(g)
M olecular Excited
oxygen atomic
oxygen
 < 310 nm
O3(g) + h
Ozone
O2(g) + O(g)
M olecular Groundoxygen state atomic
oxygen
 > 310 nm
O(g) + O3(g)
Ground- Ozone
state atomic
oxygen
2O2(g)
M olecular
oxygen
(11.5) - (11.7)
Stratospheric NOx Production
N2O(g) + O(1D)(g)
Nitrous Excited
oxide
atomic
oxygen
NO(g) + NO(g)
Nitric oxide
(11.9)
NOx Ozone Catalytic Destruction
Cycle
NO(g) + O3(g)
Nitric
Ozone
oxide
NO2 (g) + O2(g)
Nitrogen Molecular
dioxide
oxygen
NO2(g) + O(g)
Nitrogen
Grounddioxide state atomic
oxygen
O(g) + O3(g)
Ground- Ozone
state atomic
oxygen
NO(g) + O2(g)
Nitric Molecular
oxide
oxygen
2O2(g)
M olecular
oxygen
(11.10) - (11.12)
Stratospheric HOx Production
1
O( D)(g) +
Excited
atomic
oxygen
H2O(g)
Water
vapor
OH(g)
Hydroxyl
radical
CH4(g)
M ethane
CH3(g)
M ethyl
radical
H2(g)
M olecular
hydrogen
OHg) +
Hydroxyl
radical
H
Atomic
hydrogen
(11.15)
HOx Ozone Catalytic Destruction
Cycle
OH(g) + O3(g)
Hydroxyl Ozone
radical
HO2(g) + O3(g)
Hydroperoxy Ozone
radical
2O3(g)
Ozone
HO2(g) + O2(g)
Hydroperoxy Molecular
radical
oxygen
OH(g) + 2O2(g)
Hydroxyl M olecular
radical
oxygen
3O2(g)
M olecular
oxygen
(11.16) - (11.18)
Removal of NOx and HOx From
Catalytic Cycles
NO2(g) + OH(g)
Nitrogen Hydroxyl
dioxide
radical
HO2(g) + NO2(g)
Hydroperoxy Nitrogen
radical
dioxide
HO2(g) + OH(g)
Hydroperoxy Hydroxyl
radical
radical
M
M
HNO3(g)
Nitric
acid
HO2NO2(g)
Peroxynitric
acid
H2O(g) + O2(g)
Water Molecular
vapor
oxygen
(11.13) - (11.19)
Percent difference in global ozone
from 1979 monthly average
from 1979 monthly average
Changes in Monthly-Averaged
Global Ozone From 1979-2001
5
El Chichon
(April, 1982)
M ount Pinatubo
(June, 1991)
0
-5
-10
1980
1985
1990
Year
1995
2000
Figure 11.7
Mount Pinatubo, June 12, 1991
Dave Harlow, United States Geological Survey
Percent
Percentdifference
d ifferenceininozone
ozo ne
from
from 1979
19 79monthly
month lyaverage
average
March- and October-Averaged
Ozone at High Latitudes Since 1979
40
20
El Chichon
(April, 1982)
0
-20
-40
M ount Pinatubo
(June, 1991)
o
60-90 N
March
60-90 o S
October
1980 1984 1988 1992 1996 2000
Year
Figure 11.9(a)
Ozone (Dobson units)
Ozone (Dobson units)
Variation with Latitude of October
Zonally-Averaged Ozone in ‘79, ‘99, ‘00
500
450
400
350
300
250
200
150
100
October zonal average
1979
2000
1999
-90
-60
-30
0
30
60
Latitude (degrees)
90
Figure 11.9(b)
500
Ozone (Dobson units)
Ozone (Dobson units)
Variation with Latitude of March
Zonally-Averaged Ozone in ‘79, ‘99, ‘00
450
March zonal average
1979
1999
400
2000
350
300
250
200
-90
-60
-30
0
30
60
Latitude (degrees)
90
Figure 11.10
Chlorofluorocarbons Are
Derived From Methane
H
H
C H
H
CH4 (Methane)
F
Cl
F
C
Cl
Cl
CFCl3 (CFC-11)
F
C
Cl
Cl
CF2Cl2 (CFC-12)
Chlorine Compounds
Chlorofluorocarbons
CFCl3 (CFC-11)
(1932)
CF2Cl2 (CFC-12)
(1928)
CFCl2CF2Cl (CFC-113) (1934)
Mixing ratio
(pptv)
Chemical
Lifetime (yr)
270
550
70
45
100
85
Hydrochlorofluorocarbons (HCFCs)
CF2ClH (HCFC-22)
(1943)
130
11.8
Other chlorinated compounds
CCl4 (Carbon tetrachloride)
CH3CCl3 (Methyl chloroform)
CH3Cl (Methyl chloride)
HCl (Hydrochloric acid)
100
90
610
10-1000
35
4.8
1.3
<1
Table 11.2
Bromine and Fluorine Compounds
Chemical
Bromocarbons-Halons
CF3Br (H-1301)
CF2ClBr (H-1211)
Mixing ratio Chemical
(pptv)
Lifetime (yr)
2
2
65
11
Other bromocarbons
CH3Br (Methyl bromide)
12
0.7
Fluorine compounds
CH2FCF3 (HFC-134a)
C2F6 (Perfluoroethane)
SF6 (Sulfur hexafluoride)
4
4
3.7
13.6
10,000
3200
Table 11.2
CFC sales (1000 metric tonnes/year)
Reported Sales of CFC-11 and
12 in 1976 and 1998
700
Total
Propellant
Blowing agent
600
500
Refrigerant
Other
400
CFC-11
300
CFC-12
200
100
0
1976
1998
1976
1998
Year
Figure 11.11, AFEAS (2000)
Figure 11.12
50
CCl4(g) Altitude (km)
Variations With
Altitude of CFCs and
Other Chlorinated
Compounds
30
CFC-12
20
Tropop ause
10
CFC-11
00
CFCl 3(g) + h
CFC-11
CFCl 2(g) + Cl(g)
Dichlorofluoro- Atomic
methyl radical chlorine
CF2 Cl2 (g) + h
CF2 Cl(g) + Cl(g)
CFC-12
HCFC-22
40
100 200 300 400 500 600
Mixing ratio (pptv)
Chlorodifluoro- Atomic
methyl radical chlorine
 < 250 nm
 < 230 nm
Chlorine Emission to Stratosphere
Chemical
Percent emission to stratosphere
Anthropogenic sources
CFC-12 (CF2Cl2)
CFC-11 (CFCl3)
Carbon tetrachloride (CCl4)
Methyl chloroform(CH3CCl3)
CFC-113 (CFCl2CF2Cl)
HCFC-22 (CF2ClH)
28
23
12
10
6
3
Natural sources
Methyl chloride (CH3Cl)
Hydrochloric acid (HCl)
15
3
Total
100
Table 11.3
Clx Ozone Catalytic Destruction
Cycle
Cl(g) + O 3(g)
ClO(g) + O 2(g)
Atomic Ozone
chlorine
Chlorine M olecular
monoxide oxygen
ClO(g) + O(g)
Chlorine
Groundmonoxide state atomic
oxygen
O(g) + O3(g)
Ground- Ozone
state atomic
oxygen
Cl(g) + O2(g)
Atomic M olecular
chlorine oxygen
2O2(g)
M olecular
oxygen
(11.23) - (11.25)
Removal of Clx From Catalytic
Cycles to Form Reservoirs
Cl(g) +
Atomic
chlorine
CH4(g)
Methane
CH3(g)
Methyl
radical
HO2(g)
Hydroperoxy
radical
O2(g)
Molecular
oxygen
H2(g)
Molecular
hydrogen
HCl(g) +
Hydrochloric
Hydrochloric
acie
acid
H2O2(g)
Hydrogen
peroxide
H(g)
Atomic
hydrogen
HO2(g)
Hydroperoxy
radical
M
ClO(g) + NO2(g)
Chlorine Nitrogen
monoxide dioxide
ClONO2(g)
Chlorine
nitrate
(11.26) - (11.27)
Brx Ozone Catalytic Destruction
Cycle
Br(g) + O 3(g)
Atomic Ozone
bromine
BrO(g) + O 2(g)
Bromine Molecular
monoxide oxygen
BrO(g) + O(g)
Bromine
Groundmonoxide state atomic
oxygen
O(g) + O3(g)
Ground- Ozone
state atomic
oxygen
Br(g) + O2(g)
Atomic M olecular
bromine oxygen
2O2(g)
M olecular
oxygen
(11.29) - (11.31)
Removal of Brx From Catalytic
Cycles to Form Reservoirs
Br(g) +
Atomic
bromine
O2(g)
Molecular
oxygen
HO2(g)
Hydroperoxy
radical
H2O2(g)
Hydrogen
peroxide
HBr(g) +
Hydrobromic
acid
HO2(g)
Hydroperoxy
radical
M
BrO(g) + NO2(g)
Bromine Nitrogen
monoxide dioxide
BrONO2(g)
Bromine
nitrate
(11.32) - (11.33)
Ozone Regeneration
(Dobson
column
ozoneunits)
Average global
(Dobson units)
Change in globally-averaged ozone column abundance during two
global model simulations in which all ozone was initially removed
and chlorine was present and absent, respectively.
350
300
No chlorine
250
200
150
With chlorine
100
50
0
0
10/1
100
200
300
1/7
4/17
7/26
Day and date of simulation
400
11/4
Figure 11.13
30
Area of N. America
250
200
25
Area of Antarctic
continent
150
100
50
1980
1985
1990 1995
Year
6 2) 2
Ozone hole area (106 km
)
km
Ozone minimum (Dobson units)
300
Ozone-hole area (10
Ozone minimum (DU)
Change in Size of Antarctic Ozone Hole
20
15
10
5
0
2000
Figure 11.14
Latitude (degrees)
Ozone Column Abundance on
October 1, 2000
50
100
150
200 250 300 350 400
Ozone column abundance (DU)
450
500
Figure 11.15
Summary of Ozone Hole Formation
Southern-Hemisphere winter (June-Sept.) without sunlight over
Antarctica --> cold
Polar vortex (jet stream) encircles Antarctica, confining air, cooling it
further
When temperatures drop below 195 K in the stratosphere, polar
stratospheric clouds (PSCs) form
On the surface of these clouds, “inactive” chlorine reservoirs, HCl(g)
and ClONO2(g), react to form Cl2(g), HOCl(g), ClNO2(g)
When sun rises in spring, sunlight breaks down new molecules into
“active” chlorine, which destroys ozone --> ozone hole
As air warm, PSCs melt, vortex breaks down, outside air brought in.
Ozone hole re-fills by November
Polar Stratospheric Clouds
Type I
Nitric acid trihydrate (NAT) HNO3-3H2O(s)
Form below 195 K
Comprise 90% of PSCs
Typical diameter: 1 m
Typical number concentration: 1 particle cm-3
Type II
Water ice H2O(s)
Form below 187 K
Comprise 10% of PSCs
Typical diameter: 20 m
Typical number concentration: <0.1 particle cm-3
Polar Stratospheric Clouds in
the Arctic (2000)
National Aeronautics and Space Administration
Heterogeneous Reactions
ClONO2(g) + H 2O(s)
Chlorine
Water-ice
nitrate
ClONO2(g) + HCl(a)
Chlorine
Adsorbed
nitrate
hydrochloric
acid
N2O5(g) + H 2O(s)
Dinitrogen Water-ice
pentoxide
N2O5(g) + HCl(a)
Dinitrogen Adsorbed
pentoxide hydrochloric
acid
HOCl(g) + HCl(a)
Hypochlorous Adsorbed
acid
hydrochloric
acid
HOCl(g) + HNO3(a)
Hypochlorous Adsorbed
acid
nitric
acid
Cl2(g) + HNO3(a)
Molecular Adsorbed
chlorine
nitric
acid
2HNO3(a)
Adsorbed
nitric
acid
ClNO2(g) + HNO3(a)
Chlorine
Adsorbed
nitrite
nitric
acid
Cl2(g) + H 2O(s)
Molecular Water-ice
chlorine
(11.34) - (11.38)
Active Chlorine Formation in Spring
Cl2(g) + h
M olecular
chlorine
2Cl(g)
Atomic
chlorine
 < 450 nm
HOCl(g) + h
Hypochlorous
acid
Cl (g) + OH(g)
Atomic Hydroxyl
chlorine radical
 < 375 nm
ClNO2(g) + h
Chlorine
nitrite
Cl(g) + NO2(g)
Atomic Nitrogen
chlorine dioxide
 < 370 nm
(11.39) - (11.41)
Dimer Mechanism
2 x ( Cl(g) + O3(g)
Atomic Ozone
chlorine
ClO(g) + ClO(g)
Chlorine
monoxide
Cl2O2(g) + h
M
Cl2O2(g)
Dichlorine
dioxide
ClOO(g) + Cl(g)
Chlorine Atomic
peroxy chlorine
radical
Dichlorine
dioxide
ClOO(g)
Chlorine
peroxy
radical
ClO(g) + O 2(g) )
Chlorine Molecular
monoxide oxygen
M
2O3(g)
Ozone
< 360 nm
Cl(g) + O2(g)
Atomic Molecular
chlorine oxygen
3O2(g)
M olecular
oxygen
(11.42) - (11.46)
Bromine-Chlorine Mechanism
Cl(g) + O 3(g)
ClO(g) + O 2(g)
Atomic Ozone
chlorine
Chlorine M olecular
monoxide oxygen
Br(g) + O 3(g)
BrO(g) + O 2(g)
Atomic Ozone
bromine
Bromine M olecular
monoxide oxygen
BrO(g) + ClO(g)
Bromine
monoxide
Chlorine
monoxide
2O3(g)
Ozone
Br(g) + Cl(g) + O 2(g)
Atomic Atomic Molecular
bromine chlorine oxygen
3O2(g)
M olecular
oxygen
(11.47) - (11.50)
Conversion of Chlorine
Reservoirs to Active Chlorine
1% Cl(g), ClO(g)
37%
ClONO (g)
2
62%
HCl(g)
Before PSC and photolysis
reactions
Figure 11.17
Melanin
Dark pigment in skin for protection against UV radiation
Developed originally in populations living under intense UV
radiation in equatorial Africa
Populations that migrated to higher latitudes became lighter due to
natural selection since some UV is needed to produce vitamin D
in the skin, and dark pigmentation blocks the little UV available at
higher latitudes for vitamin D production. Vitamin D necessary to
prevent bone fractures, bow legs, slow growth (rickets).
As populations moved across Asia to North America and down
toward equatorial South America, production of melanin again
became an advantage
Lighter skin color in equatorial South America than in equatorial
Africa due to shorter presence of population in South America
UV Effects on the Skin
Sunburn (erythema)
Skin reddening, blisters
Photoaging (accelerated aging of skin)
Loss of skin elasticity, wrinkles, altered pigmentation, decrease in
collagen
Skin Cancer
Basal-cell carcinoma (BCC) (79%)
Tumor develops in basal cells, deep in skin
Grows through skin and scabs
Doesn’t spread; removable by surgery, radiation, rarely fatal
Squamous-cell carcinoma (SCC) (19%)
Tumor develops in squamous cells, outside of skin
Appears as red mark
Spreads but removable by surgery, radiation, rarely fatal
Cutaneous melanoma (CM) (2%)
Dark-pigmented malignant tumor arising in melanocyte cell
Spread quickly; fatal in 1/3 of cases
CM as common as SCC in Northern Europe
Skin cancer rates increase from Equator to poles
Relatively high cancer rates in Australia/New Zealand
Lifetime exposure to UV not necessary to obtain skin cancer
UV Effects on the Eye
Snowblindness
Inflammation or reddening of the eyeball
Cataract
Loss in transparency of the lens
Blindness unless lens removed
Ocular melanoma
Cancer of iris and related tissues
Other UV Effects
Immune system effects
Reduces ability to fight disease and tumors
Effects on microorganisms (e.g., phytoplankton), animals, plants
Effects on global carbon and nitrogen cycles
Damage to phytoplankton reduces CO2(g) uptake
UV-B enhances photodegradation of plants, increasing CO2(g)
UV-B affects rate of nitrogen fixation by cyanobacteria
Effects on tropospheric ozone
Enhanced UV-B increases tropospheric ozone
Enhanced absorbing aerosols reduce UV-B, reducing ozone
Regulation of CFCs
June 1974: Effects of CFCs on ozone hypothesized by Rowland &
Molina
Dec. 1974: Bill to study, regulate CFCs killed in U.S. Congress
1975: Congress sets up committee to study CFC effects
1976: U.S. National Academy of Sciences releases report suggesting
long-term damage to ozone layer due to CFCs
1976: On basis of report, U.S Food and Drug Administration,
Environmental Protection Agency, Consumer Product Safety
Commission recommend phase out of spray cans in the U.S.
Oct. 1978: Manufacture/sale of CFCs for spray cans banned in U.S.
Regulation of CFCs
1980: U.S. EPA proposes limiting emission of CFCs from
refrigeration, but proposal rebuffed
1985: Vienna Convention.Initially 20 countries obligated to reduce
CFCs
1987: Montreal Protocol. Initially 27 countries agreed to limit CFCs
and Halons.
1990: London Amendments
1997: Copenhagen Amendments
Phaseout Schedule of CFCs
Year
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Montreal
Protocol
(1987)
100
100
100
80
80
80
80
80
80
50
50
London U.S. Clean Copenhagen
Amend. Amend.
Amend.
(1990) (1990)
(1992)
100
100
80
80
50
50
15
15
15
0
85
80
75
25
25
0
25
25
0
Eur. Com.
Schedule
(1994)
50
15
0
Table 11.4
Release (1000 metric tonnes/yr)
CFC Emission Since the 1930s
500
CFC-12
400
300
200
100
CFC-11
CFC-113
HCFC-22
HCFC-141b
HFC-134a
0
1930 1940 1950 1960 1970 1980 1990 2000
Year
Figure 11.18
Mixing ratio (pptv)
Mixing ratio (pptv)
CFC Mixing Ratios Over Time
600
550
500
450
400
350
300
250
200
CFC-12
CFC-11
1986 1988 1990 1992 1994 1996 1998 2000
Year
Figure 11.19
200
Mixing ratio (pptv)
Mixing ratio (pptv)
Chlorinated Gas Mixing Ratios
Over Time
150
100
CH 3 CCl 3 (g)
HCFC-22
CCl 4 (g)
50
0
1988 1990 1992 1994 1996 1998 2000
Year
Figure 11.19
15
Mixing ratio (pptv)
Mixing ratio (pptv)
HCFC and HFC Mixing Ratios
Over Time
10
5
HCFC-142b
HCFC-141b
HFC-134a
0
1993 1994 1995 1996 1997 1998 1999 2000
Year
Figure 11.19