Where does Ozone get it’s name?
From Greek derivative “to smell” - has distinct smell
ozone discovery timeline
- introduced to science in 1840 by Dr. C. Shoenbein
- 1845: ozone linked to oxygen
- 1863: ozone identified as O3
- 1872: existence in atmosphere confirmed
- 1870s to today: systematic observations
How is ozone formed?
O2 + sunlight —> O + O
O + O2 —> O3
What are the natural destructions of ozone?
- via UV radiation: O3 + UV –> O2 + O
- via interaction with chlorine (CL):
CL + O3 —> CLO + O2
CLO + O —> CL + O2
CLO = chlorine monoxide
Where is ozone primarily found?
stratosphere at 1 part per thousand
How and when is ozone created in the troposphere?
-can be created in the troposphere when hydrocarbons react with nitrogen oxides
- not good, leads to bas air quality
- O3 can aggravate asthma, etc.
Stratospheric Ozone
- good thing
- absorbs UV radiation
- ozone layer
- being depleted
What is the ozone layer?
- high concentration of ozone in the stratosphere
- is 0.00005% total atmospheric volume
Chlorofluorocarbon (CFCs) - composition, created for what and when, what was used prior
- single carbon, two chlorines, two fluorines
- created in 1928 as non-toxic, non-flammable refridgerant, trademarked as Freon
- prior we used ammonia, sulfur dioxide, and methyl chloride
- worldwide consumption in 1988 was at over 1 billion kgs
Why are CFCs a problem?
- CFCs dissolve in the sunlight
- A single Cl molecule floats around until it attacks an O3 molecule, pulling an O off it
- Chlorine atom and oxygen atom join to form chlorine monoxide
- A free oxygen pulls the O off the chlorine monoxide
- Once free, the chlorine atom is off to attack another ozone molecule
For each 1% decrease in ozone, UV radiation increases ___%
2%
Where is the greatest reduction in stratospheric ozone and why?
Antarctica due to combo of cold temperatures, formation of polar stratospheric clouds, and the Antarctic vortex
Montreal Protocol (1986)
international treaty to reduce CFC emissions and other ozone-depleting chemicals
What is the timeline of the Montreal Protocol
-1974: chemists Rowland and Molina presented evidence suggesting that breakdown of CFCs could destroy ozone
- initially criticized, but were invited to testify before Congress
- led to substantial funding to study problem
- 1976: National Academy of Sciences released report confirming hypothesis - US govt declared CFCs only be used in important things
- 1985: studies by British Antarctic Survey found “ozone hole”
- treaty has been revised about 7 times
- 1992: ozone hole began in northern hemisphere - pushed president Bush to accelerate US implementation of treaty
- replaced CFCs with HCFCs, which also deplete O3, so plan is for them to be phased globally by 2040
What is the Ozone Hole?
- the reduction in the amount of ozone of stratospheric ozone every year over Antarctica in its springtime (and now Greenland)
- any area under 220 Dobson units
Why is O3 reduction largely in Arctic/Antarctic regions?
- Antarctica winters have very strong circumpolar winds that isolate the atmosphere over Antarctica
- stratospheric clouds form, chlorine atoms attach themselves
- when sun returns to Antarctica in Spring (Sept), chlorine atoms are released, setting up ozone-destroying chain reaction that lasts 5-6 weeks, until ozone from lower latitudes can mix back into Antarctic atmosphere
