Stratospheric Ozone Depletion
Taylor Westphal
What is Ozone? What is a DU?
• Ozone is O3, created by disassociation of O2 by
UV light, one molecule of which joins a nearby
O2 molecule to form ozone.
• From NASA’s ozonewatch: “One Dobson Unit
is the number of molecules of ozone that
would be required to create a layer of pure
ozone 0.01 millimeters thick at a temperature
of 0 degrees Celsius and a pressure of 1
atmosphere”.
Chlorofluorocarbons (CFC)
Used for many refrigerants, aerosols,
and solvents. Chlorine from CFCs is
not soluble like Cl from natural
sources, and is able to get into the
stratosphere. The Cl reacts with O3
and during which reaction, the ozone
is destroyed and the Cl is freed to
react with more ozone. A single Cl
molecule can reside in the
stratosphere for decades and destroy
as many as 100,000 ozone molecules
Ozone “Hole”
• Formed seasonally during the southern
hemisphere winter due to Polar Stratospheric
Clouds (PSCs), which are complex, and have to
do with the extreme air temperature and
circulation.
• These unusual clouds (sometimes water,
sometimes acids) provide a surface for CFCs to
react with ozone, speeding the reaction and
significantly reducing the amount of ozone in the
atmospheric column.
The Ozone Hole: Winter vs. Summer
Montreal Protocol
• Passed in 1987.
• Similar agreements were attempted starting in
the 70’s.
• If followed, ozone layer could potentially recover
by 2050.
• Sometimes cited as the most successful
international agreement ever, being ratified by
196 states.
• No trouble from chemical industry, CFC patents
had expired anyway, good chance to find a
profitable replacement.
Who cares, right?
Some Potential Effects
• Skin cancer.
• Damages to various aspects of plant health.
• Damages to Phytoplankton health. Being the
foundation of the ocean food chain: damage
to the ocean ecosystem.
• Direct damage to reproductive development
of various fish, crustaceans, amphibians, etc.
• Colorful shirts will fade faster.
Anecdote.
Protect Yourself from UV
References:
Wikipedia:
http://en.wikipedia.org/wiki/Ozone_depletion
EPA:
http://www.epa.gov/ozone/strathome.html
NASA:
http://ozonewatch.gsfc.nasa.gov/facts/ozone.html