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1. EGEE 102 – Energy Conservation
And Environmental Protection
Ozone and Environment

2. Ozone
• Ozone layer
• From Wikipedia, the free encyclopedia
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• Ozone-oxygen cycle in the ozone layer.
• The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the
Sun's ultraviolet radiation. It contains high concentration of ozone (O3) in relation to other
parts of the atmosphere, although still small in relation to other gases in the stratosphere.
The ozone layer contains less than 10 parts per million of ozone, while the average ozone
concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone
layer is mainly found in the lower portion of the stratosphere, from approximately 15 to 35
kilometers (9.3 to 21.7 mi) above Earth, although its thickness varies seasonally and
geographically.[1]
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3. • The ozone layer was discovered in 1913 by the French physicists
Charles Fabry and Henri Buisson. Measurements of the sun showed
that the radiation sent out from its surface and reaching the ground on
Earth is usually consistent with the spectrum of a black body with a
temperature in the range of 5,500–6,000 K (5,227 to 5,727 °C), except
that there was no radiation below a wavelength of about 310 nm at the
ultraviolet end of the spectrum. It was deduced that the missing
radiation was being absorbed by something in the atmosphere.
Eventually the spectrum of the missing radiation was matched to only
one known chemical, ozone.[2] Its properties were explored in detail by
the British meteorologist G. M. B. Dobson, who developed a simple
spectrophotometer (the Dobsonmeter) that could be used to measure
stratospheric ozone from the ground. Between 1928 and 1958, Dobson
established a worldwide network of ozone monitoring stations, which
continue to operate to this day. The "Dobson unit", a convenient
measure of the amount of ozone overhead, is named in his honor.
3

4. • In 1976 atmospheric research revealed that the
ozone layer was being depleted by chemicals
released by industry, mainly chlorofluorocarbons
(CFCs). Concerns that increased UV radiation due to
ozone depletion threatened life on Earth, including
increased skin cancer in humans and other
ecological problems,[4] led to bans on the chemicals,
and the latest evidence is that ozone
depletion ,slowed or stopped. The United Nations
General Assembly has designated September 16 as
the International Day for the Preservation of the
Ozone Layer.
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5. • The ozone layer absorbs 97 to 99
percent of the Sun's medium-frequency
ultraviolet light (from about 200 nm to
315 nm wavelength), which otherwise
would potentially damage exposed life
forms near the surface.[3]
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6. • Venus also has a thin ozone layer at an
altitude of 100 kilometers from the
planet's surface.
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7. • Scientists in this age are working around the clock to
develop Hydrofluorocarbons (HFCs) to take the place
of hydrochlorofluorocarbons (HCFCs) and
chlorofluorocarbons (CFCs) for use in vehicle air
conditioning. Hydrochlorofluorocarbons are powerful
greenhouse gases, but they are not able to deplete
ozone. Chlorofluorocarbons, on the other hand,
significantly contribute to climate change, which
means Hydrofluorocarbons continue to be the better
alternative until safer alternatives are available.
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8. • The chlorine and bromine free radicals
react with ozone molecule and destroy
their molecular structure, thus depleting
the ozone layer. One chlorine atom can
break more than 1, 00,000 molecules of
ozone. Bromine atom is believed to be
40 times more destructive than chlorine
molecules.
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9. • Destruction of the Ozone Layer - The
Causes
• Chlorofluorocarbons (CFCs) have been
identified as the main cause of the
destruction to the ozone layer, but there
are also compounds containing bromine,
other halogen compounds and also
nitrogen oxides which cause damage.
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10. • CFCs were discovered by Thomas
Midgeley in the 1930s as a cheap, non-
flammable coolant for refrigerators.
They have been used in refrigerators,
air conditioning, fast food packaging
and propellants. CFCs are very stable,
they decay slowly and so endure in the
atmosphere for up to a century.
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11. • CFCs rise and gradually accumulate in
the stratosphere where they are broken
down by the sun's ultraviolet light, so
releasing chlorine atoms. The chlorine
attacks the ozone, one chlorine atom
can help to destroy 100,000 ozone
molecules.
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12. • What are ozone depleting substances?
• Ozone depleting substances are man-made gases that destroy
ozone once they reach the ozone layer. The ozone layer sits in
the upper atmosphere and reduces the amount of harmful ultra
violet radiation that reaches Earth from the sun. Ultraviolet
radiation can have detrimental effects on both humans and the
environment such as inducing skin cancer and cataracts,
distorting plant growth and damaging the marine environment.
• Ozone depleting substances include:
• chlorofluorocarbons (CFCs)
• hydrochlorofluorocarbons (HCFCs)
• hydrobromoflurocarbons (HBFCs)
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13. • halons
• methyl bromide
• carbon tetrachloride
• methyl chloroform.
• They have been used as:
• refrigerants in commercial, home and
vehicle air conditioners and refrigerators
• foam blowing agents
• components in electrical equipment
• industrial solvents

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Ozone
• O3
• a gas composed of three atoms of
oxygen
• bluish gas that is harmful to breathe
• Nearly 90% of the Earth's ozone is in
the stratosphere and is referred to as
the ozone layer
• Ozone absorbs a band of ultraviolet
radiation called UVB

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Ozone-Depleting
Substance(s) (ODS):
• CFCs,
• HCFCs,
• halons,
• methyl bromide,
• carbon tetrachloride, and
• methyl chloroform.

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Various sources

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Effects of OLD
• -- Skin Cancer (melanoma and
nonmelanoma)
-- Premature aging of the skin and other
skin problems
-- Cataracts and other eye damage
-- Immune system suppression

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The Antarctic Ozone
Hole
• The ozone hole is
defined as the area
having less than 220
dobson units (DU) of
ozone in the
overhead column
(i.e., between the
ground and space).
Source: http://jwocky.gsfc.nasa.gov/multi/recent_ozone91200.gif

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http://www.cpc.ncep.noaa.gov/products/stratosphere/sbuv2to/ozone_hole_plot.gif

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What can we do?
• Make sure that technicians working on your
car air conditioner, home air conditioner, or
refrigerator are certified by an EPA approved
program to recover the refrigerant (this is
required by law).
• Have your car and home air conditioner units
and refrigerator checked for leaks. When
possible, repair leaky air conditioning units
before refilling them.

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What can we do?
• Contact local authorities to properly dispose
of refrigeration or air conditioning equipment.
• Protect yourself against sunburn. Minimize
sun exposure during midday hours (10 am to
4 pm). Wear sunglasses, a hat with a wide
brim, and protective clothing with a tight
weave. Use a broad spectrum sunscreen with
a sun protection factor (SPF) of at least 15
and 30 is better.

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Ground level Ozone
Formation
• Secondary Pollutant
• VOCs+ NOx  Ozone
• In presence of sunlight
• Ozone + NOX + HCs  Smog (haze)

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Photochemical Smog
NO
CO, RH
NO2
CO
HC
O3
CO
PAN
Haze
6:00AM 12NOON 3:00 PM

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Smog Sources
Source: http://www.epa.gov/oar/oaqps/regusmog/smog.html

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Sources of Volatile
Organic Carbons

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Sources of NOx

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What can We do?
• Keep your automobile well tuned and
maintained.
• Carpool, use mass transit, walk, bicycle,
and/or reduce driving, especially on hot
summer days.
• Be careful not to spill gasoline when filling up
your car or gasoline-powered lawn and
garden equipment. During the summer, fill
your gas tank during the cooler evening hours.

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What can we do?
• Make sure your car's tires are properly
inflated and your wheels are aligned.
• Participate in your local utility's energy
conservation programs.
• Seal containers of household cleaners,
workshop chemicals and solvents, and
garden chemicals to prevent VOC from
evaporating into the air. Dispose of them
properly.