O 3 zone Story Terry Deshler, Atmospheric Science Formation Importance Loss –Before 1985Before...
-
Upload
laurence-george -
Category
Documents
-
view
223 -
download
0
Transcript of O 3 zone Story Terry Deshler, Atmospheric Science Formation Importance Loss –Before 1985Before...
O3zone StoryTerry Deshler, Atmospheric Science
• Formation• Importance• Loss
– Before 1985
– After 1985
• Recovery• Relationship to global warming
• The end
Relationship to Global Warming • Peripheral• Ozone has a slight greenhouse effect, but
• Loss of ozone over Antarctica may have intensified the polar vortex and reduced the warming expected in Antarctica
• CFCs are a significant green house gas
• Reduction of CFCs largest single human action mitigating the current warming
The End?• No, we have to limit the release of CFCs
into the atmosphere from now on.
• The good news - the atmosphere will cleanse itself of present atmospheric chlorine.
• The bad news - it will take another 50 years to see the ozone hole above Antarctica disappear.
Ozone Formation
• O2 + h O + O
• Then, O + O + M O2 + M
• or O + O2 + M O3 + M (Ozone created)– Where will this primarily occur?
• Also, O3 + h ( > 310 nm) O2 + O
• and O3 + h ( < 310 nm) O2* + O* (UV absorption)
• O2* + O2 2O2 + thermal energy (Excess energy dumped
• O2* O2 + h ( = 1.3 m) in ozone layer)
Importance of ozone• Absorbs DNA damaging UV radiation
– This UV affects both animals and plants
• SH/NH differences - In summer UV radiation is 50% more intense in SH than NH. Australia - world leader in skin cancer– Reasons – 10% - Earth is closer to sun in SH summer than
NH summer– 20% - Antarctic ozone loss/clearer atmosphere– 20% - Unknown
Food Preservation
• 100 BC - 1700s, Early methods: Drying, Salting, Cool cellars/Spring houses, Pickling, Fermenting, Canning.
• Cooking -> could eat spoiled food - spices to hide the flavor.
• 1803 Ice Boxes - Thomas Moore invented the insulated box, with ice was in a separate container above the food storage area. Relied on stores of natural ice from frozen lakes and rivers.
• 1850s - Methods to artificially produce ice were developed.
• 1890 - Warm weather/rain lead to a shortage of natural ice. Spurred the development of mechanical refrigeration.
Refrigeration• 1918 - Kelvinator, First refrigerator introduced to American market.
• 1920s - Refrigerators used ammonia (NH4), sulfur dioxide (SO2), (toxic, odorous), and methyl chloride (CH3Cl), (toxic, no odor) - silent killer.
• 1928 - Thomas Midgley, Fridgidaire, dichlorodifluoromethane (CCl2F2)
• 1929 - Fridgidaire and DuPont joined to produce CCl2F2, and CFCl3 as Freon.
1974 - Molina and Rowland - simple question - What happens to CFCs released into the atmosphere? (awarded Nobel prize Chemistry 1995)
CCl3 F (F-11) + h ( < 240 nm, z > O3 layer) CCl2F + ClCCl2F2 (F-12) + h ( < 240 nm, z > O3 layer) CClF2 + Cl
• Then• Cl + O3 ClO + O2
• ClO + O Cl + O2
• Net: O3 + O O2 + O2
• This would occur above ozone layer altitudes above 30 km
Reservoir molecules
• 1975 - 1980 – Predicted ozone losses above 30 km were not observed. Reservoir molecules discovered.
– Cl + CH4 HCl + CH3
– ClO + NO2 ClONO2
– HCl and ClONO2 are reservoir species.1984 – Models predict 10% ozone loss in 100 years for current CFC production rates.
Ozone Profiles
McMurdo Station,
Antarctica
1986 - 1994
1994
1986 1987 1988
1989 1990 1991
1992 1993
Late winterspring
During Winter
Catalytic Cycle Polar Stratosphere– PSC particle + HCl + ClONO2 Cl2
– Cl2 + h Cl + Cl
– 2 [ Cl + O3 ClO + O]
– ClO + ClO + M ClOOCl + M (M=N2 or O2)
– ClOOCl + h Cl + ClOO
– ClOO + M Cl + O2 + M– h = Sun’s return
• Net 2O3 + h 3O2
• A single Cl atom can destroy more than100,000 ozone molecules.
• This cycle will continue until the NO2 and OH lost in the form of HNO3 in polar stratospheric clouds is replenished by mid latitude air, thus converting Cl back to its reservoir species.
Nitric acid/waterIce
Nitric acid/waterIce
Molina &Rowland,1974
ReservoirMoleculesDiscovered
MontrealProtocol, andamendments
Antarctic ozone holediscovered
0
400
800
1200
1600
Refrigerants
Foam ExpansionSolventsPropellants
Fire Extinguishants
1974Ozone Depletion
Hypothesis
1986Base Year for
Montreal Protocol
1996CFC PhaseoutComplete in
Developed Countries
CFCs HCFCs HFCs
Refrigerants
Other
Th
ousa
nd
s o
f to
nne
s
An Industry in Transition
1960 1980 2000 2020 2040 2060 2080 21001000
1500
2000
2500
3000
3500
4000
4500
Effe
ctiv
e E
qu
iva
len
t Str
ato
sph
eric
Ch
lori
ne
(pp
tv)
Years
Compliments of Paul Newmanand the Goddard automailer
Return