Transcript Natural” O3 Destruction - University of Missouri

“Natural” O3 Destruction
Water:
H2O + UV light 
•H +
•OH
Free Radicals:
Unpaired electrons
Uncharged
Very reactive
Convert O3 to O2
NO
2 N2O
+ O2  4 NO
(soil bacteria)
NO + O3  NO2 + O2
energy +N2 + O2  2 NO
Energy = lightning or jet engine
Chlorofluorocarbons (CFCs)
• Natural means don’t account for O3 loss
• Even with seasonal cycles
• Main suspect: CFCs
– Cl + F + C
– Man-made, gases
– Unreactive (non-toxic, non-flammable,
cheap)
Uses:
Coolants, propellants, styrofoam…
Related: Halons (C and F or Br – no Cl)
Inert CFCs?
Upper atmosphere = high energy UV  bonds break
2 •Cl + 2 O3

•Cl

CFC (or halon) + UV
2 ClO• + O2
2 ClO•  ClOOCl
ClOO• + •Cl
ClOOCl + UV 
ClOO• 
Cl•
+
Catalytic cycle
O2
Fig.2.15
Why do we care about energy?
Reactions require energy
If light has enough E, the reaction occurs
If not, the reaction will not occur, no matter how much
light you put in!
You won’t get a tan from standing in front of a radio
- no matter how long!
In the Greenhouse (3.1)
• Avg. Temp. - Compare Earth to Venus:
Based on distance:
Earth
0°F
Venus
212°F
Actual
59°F
840°F
Why?
Heat is held in longer by CO2 and H2O
in the atmosphere
Fig.03.02
Fig. 3.2
Greenhouse Gases
Absorb IR radiation - trap heat
CO2 & H2O (also methane, CH4)
- No change in water
CO2 is on the rise
More now than 150 years ago
Earth temp. has changed
Greenhouse Effect
Process where gases trap heat
Heat stays and warms the planet
Needed for life – planet would freeze otherwise
Too much = bad
“Enhanced greenhouse effect”
Energy return of > 81%  avg. temp. increase
History of Our Atmosphere
• Early atmosphere: 1000X CO2
• Bacteria used CO2, made sugars
6 CO2 + 6 H2O  C6H12O6 + 6O2
(glucose)
Consumed
Produced
How do we know?
Core samples from the ocean
Bacterial remains tell temp.
Magnetic alignment tells when
(relate to Earth’s magnetic core)
“Heavy water” composition of ice
More heavy water = higher temp.
Trapped bubbles
Tell conc. of CO2 when bubble formed
Fig.3.4
Theory:
Global warming:
Caused by high CO2 and CH4 levels
Possible: High CO2 and CH4 levels are a result
of warming, not a cause
Fact: CO2 and CH4 trap heat and do contribute
Recent Evidence
Atmospheric CO2 is increasing
Global temps. are increasing
Fig. 3.5
Fig. 3.6
Other Factors
Orbital changes
Temp maxima
Major and minor ice ages
Doesn’t entirely account for temp. changes
Airborne dust – volcanic activity
Cloud cover – weather patterns
Greenhouse gases