Ozone Hole

Understanding Ozone http://royal.okanagan.bc.ca/mpidwirn/atmosphereandclimate/ozonehole.html

Discovered in 1839 by German scientist Christian Friedrich SchonbeinPale blue, unstable molecule made of three oxygen atomsVital to life in the stratosphere Harmful to plants and humans in the troposphereConcentration: stratosphere up to 15 ppm at about 25 kmFormed when atomic oxygen (O) from higher parts of the atmosphere collides with molecular oxygen (O2) in the stratosphereUV radiation splits the ozone back to O and O2 and it can form another ozone molecule

http://www-imk.fzk.de/topoz-iii/ataglanz/ozonbild.html http://www-imk.fzk.de/topoz-iii/ataglanz/ozonbild.html

http://www-imk.fzk.de/topoz-iii/ataglanz/ozonzerst.htmlhttp://www-imk.fzk.de/topoz-iii/ataglanz/ozonzerst.html

The Ozone HoleFirst discovered in 1985: observations from Antarctica extend back into 1950’s.Characterized as a rapid depletion of ozone over Antarctica during spring. Ozone hole season, Spring (August – October) Ozone hole located over mainly over Antarctica. Ozone hole recovers by late December

Ozone hole caused by human chemicals (CFC’s)Ozone hole not present in early 1970’s

science.widener.edu/svb/ atmo_chem/oct15.html

Ozone hole stabilizesOctober 17, 2001WASHINGTON (CNN) -- A hole in the Earth's protective ozone layer is about the same size as in the past three years, according to scientists at the National Oceanic and Atmospheric Administration,

who predict it will hold steady in the near future.

Satellite data show the hole over Antarctica, which allows more harmful solar radiation to

reach the Earth, peaked this year at about 10 million square miles (26 million square km), roughly the size of North America.

http://www.cnn.com/2001/TECH/space/10/17/ozone.hole.size/index.html

History of Ozone Depletion

CFCs developed in 40’s and 50’sCFCs developed in 40’s and 50’sRefrigerants, propellants, fire retardantsRefrigerants, propellants, fire retardants

1970’s CFCs detected in atmosphere.1970’s CFCs detected in atmosphere.Many of these have long atmospheric lifetimes (10’s to 100’s of Many of these have long atmospheric lifetimes (10’s to 100’s of years)years)

1974 Rowland and Molina propose that CFC’s can destroy 1974 Rowland and Molina propose that CFC’s can destroy ozone in the stratosphere.ozone in the stratosphere.

CFCs broken apart by UV radiation forming chlorine which can CFCs broken apart by UV radiation forming chlorine which can destroy ozone quickly:destroy ozone quickly:

O3 +Cl ClO+ O2 (Catalytic Reaction)ClO+O Cl+O2

Chlorofluorocarbons or CFCs

First produced by General Motors First produced by General Motors Corporation in 1928, CFCs were Corporation in 1928, CFCs were created as a replacement to the created as a replacement to the toxic refrigerant ammoniatoxic refrigerant ammonia

CFCs have also been used as a CFCs have also been used as a propellant in spray cans, cleaner propellant in spray cans, cleaner for electronics, sterilant for for electronics, sterilant for hospital equipment, and to produce hospital equipment, and to produce the bubbles in Styrofoamthe bubbles in Styrofoam

CFCs are cheap to produce and very stable compounds, lasting up to 200 years in the atmosphereMany countries have recently passed laws banning nonessential use of these chemicals. Nevertheless, by 1988 some 320,000 metric tons of CFCs were used worldwide.

Action of CFCs

CFCs created at the Earth's surface drift CFCs created at the Earth's surface drift slowly upward to the stratosphere where slowly upward to the stratosphere where UV radiation from the sun causes their UV radiation from the sun causes their decomposition and the release of decomposition and the release of chlorinechlorineChlorine in turn attacks the molecules of Chlorine in turn attacks the molecules of ozone converting them into oxygen ozone converting them into oxygen moleculesmolecules

Cl + OCl + O33 »»» ClO + O »»» ClO + O22

ClO + O »»» Cl + OClO + O »»» Cl + O22

Ultraviolet light hits a chlorofluorocarbon (CFC) molecule, such as CFCl3, breakingoff a chlorine atom and leaving CFCl2.

UV radiation

Sun

Once free, the chlorine atom is off to attack another ozone moleculeand begin the cycle again.

A free oxygen atom pulls the oxygen atom off the chlorine monoxide molecule to form O2.

The chlorine atom and the oxygen atom join to form a chlorine monoxide molecule (ClO)

The chlorine atom attacksan ozone (O3) molecule, pulling an oxygen atom off it and leaving an oxygen molecule (O2).

Cl

Cl

ClC

F

Cl

Cl

OO

Cl

OO

O

ClO

OO

ClO

O

http://www.clas.ufl.edu/users/dlsmith/Lecture_11.html

A single chlorine atom A single chlorine atom removes about removes about 100,000 ozone 100,000 ozone

molecules before it is molecules before it is taken out of operation taken out of operation by other substancesby other substances

Current measurements indicate that the amount of ozone in the stratosphere of the low and middle latitudes has decreased by about 3% with estimates that it will decrease by10% by 2025

Low and Middle Latitudes

Harmful effects of UV radiation.

Skin cancer (ultraviolet radiation can destroy acids in DNA)Cataracts and sun burningSuppression of immune systemsAdverse impact on crops and animalsReduction in the growth of ocean phytoplankton Cooling of the Earth's stratosphere and possibly some surface climatic effectDegradation of paints and plastic material

matrix.ucdavis.edu/tumors/tradition/ gallery-ssmm.html

www.snec.com.sg/clinical_services/ cataract.asp

Conclusion

Ozone Depletion Exists and effects certain areas of the Earth more than othersCurrently, one in five North Americans and one in two Australians will develop some form of skin cancer in their lifetimeWith a sustained 10% decrease in stratospheric ozone, an additional 300,000 non-melanoma and 4,500 melanoma skin cancers could be expected world-wide, according to UNEP estimates.

Effects of Ozone Depletion

Natural Capital Degradation

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

Montreal Montreal ProtocolProtocol

An international treaty designed to protect the ozone layer phasing out production of number of substances

believed to be responsible for ozone depletion Effective January 1, 1989 Five revisions

1990 (London) 1992 (Copenhagen) accelerated the phasing out of key

ozone- depleting chemicals. 1995 (Vienna) 1997 (Montreal) 1999 (Beijing)

Ozone Depleting Chemicals

Chlorofluorocarbons (CFCs)Chlorofluorocarbons (CFCs)HalonsHalonsMethyl bromideMethyl bromideCarbon tetrachlorideCarbon tetrachlorideMethyl chloroformMethyl chloroformHydrogen chlorideHydrogen chloride

Former Uses of CFCsAir Conditioners

Refrigerators

Spray cans

Cleaners for electronic parts

Sterilizing medical instruments

Fumigants for granaries and cargo ships

Air Conditioners

Refrigerators

Spray cans

Cleaners for electronic parts

Sterilizing medical instruments

Fumigants for granaries and cargo ships

Solutions: Protecting the Ozone LayerSolutions: Protecting the Ozone Layer

CFC substitutes CFC substitutes

Montreal Protocol Montreal Protocol

Copenhagen ProtocolCopenhagen Protocol

Fig. 21-25 p. 489Fig. 21-25 p. 489