1 mark ewoldsen, ph.d. advanced placement environmental science teacher la cañada high school ozone...
TRANSCRIPT
1
Mark Ewoldsen, Ph.D.Mark Ewoldsen, Ph.D.Advanced Placement Environmental Science Teacher
La Cañada High SchoolLa Cañada High School
Ozone HoleOzone Hole
2
Two Atmosphere Two Atmosphere LayersLayers
• Stratosphere is above Troposphere Stratosphere is above Troposphere – Ozone Layer blocks UV radiation Ozone Layer blocks UV radiation
• Troposphere is where we liveTroposphere is where we live–Weather occurs hereWeather occurs here
• 72% of all air is below the cruising 72% of all air is below the cruising altitude of commercial airliners altitude of commercial airliners (33000 ft)(33000 ft)
3
Stratospheric Ozone Stratospheric Ozone (Good)(Good)
vs. vs.
Tropospheric OzoneTropospheric Ozone(Bad) (Bad)
4
Ozone – Two FacesOzone – Two Faces• Stratosphere – Good Ozone
–Blocks UV radiation–Hole caused by depletion due to
CFC’s• Troposphere – Bad Ozone
–Pollution • Photochemical smog • Eye irritant
5
Harmful effects of UV radiationHarmful effects of UV radiation
• Skin cancer such as melanoma(ultraviolet radiation can destroy acids in DNA)
• Suppression of immune systems
matrix.ucdavis.edu/tumors/tradition/ gallery-ssmm.html
7
Harmful effects of UV radiationHarmful effects of UV radiation
• Skin cancer such as melanoma(ultraviolet radiation can destroy acids in DNA)
• Suppression of immune systems• Cataracts and sun burning
www.snec.com.sg/clinical_services/ cataract.asp
http://www.wep.org.au/info/files/images/Amelia_and_the_kids.jpg
10
Harmful effects of UV radiationHarmful effects of UV radiation
• Skin cancer such as melanoma(ultraviolet radiation can destroy acids in DNA)
• Suppression of immune systems• Cataracts and sun burning• Adverse impact on crops and animals• Reduction in the growth of ocean
phytoplankton • Cooling of the Earth's stratosphere and possibly
some surface climatic effect• Degradation of paints and plastic material
Ozone Formation Ozone Formation
• Ozone forms a layer in the stratosphere, thinnest in the tropics (around the equator) and denser towards the poles.
• O2 + hv O + O
• (1) O + O2 O3
• wavelength ~ 240 nm
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
Natural Natural Ozone HoleOzone Hole
• Winter = no sunlight• Air in the polar
vortex can get very cold -80C
• Special clouds called Polar Stratospheric Clouds form as nitric acid trihydrate
• PSCs are crucial for ozone loss to occur
Since there is no sunlight, the air within the polar vortex can get very cold
The ozone hole builds up over the winter months, peaking at around September and breaking up
again by December, this data set from 2005
July
August
September
October
November
December
19
Destroying Good OzoneDestroying Good Ozone
20
21
Destroying Good OzoneDestroying Good Ozone
• Chloroflourocarbons were first created in 1928 as non-toxic, non-flamable refrigerants, and were first produced commercially in the 1930's by DuPont
• In 1974, a laboratory study demonstrated the ability of CFC's to catalytically breakdown Ozone in the presence of high frequency UV light
• Cl + O3 -> ClO + O2 ClO + O3 ---> 2 O2 + Cl• In a 1985, a study summarized data that had been
collected by the British Antartic Survey showing that ozone levels had dropped to 10% below normal January levels for Antarctica.
• http://www.nas.nasa.gov/About/Education/Ozone/history.html
22
A single chlorine atom A single chlorine atom removes about 100,000 removes about 100,000 ozone molecules before ozone molecules before
it is taken out of it is taken out of operation by other operation by other
substancessubstances
The frozen crystals that make up polar stratospheric clouds provide a surface for the reactions that free
chlorine atoms in the Antarctic stratosphere
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
26http://www.mmscrusaders.com/newscirocks/ozone/cfc.jpg
27
28
Montreal ProtocolMontreal Protocol• 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)
• 1995 (Vienna)
• 1997 (Montreal)
• 1999 (Beijing)
30
Area of Antarctica
Area of North America
