Topic 3.2 - Ozone Depletion


OZONE

  • A Highly reactive gas

  • Composed of three oxygen atoms…

    • O + O2 -> O3

  • There is only 3 molecules of ozone for every ten million molecules of air.


  • Triatomic oxygen molecule

  • Max concentration is ~10 ppm, occurring in Stratosphere (15-30 km)

    • Stratosphere contains 90% of all ozone (good)

    • Tropospheric ozone (bad) from auto emissions


OZONE LAYER

  • The ozone layer is a layer of gas consisting of O3 molecules

  • Ozone gas can be created or destroyed by the sun’s UV rays.


WHERE IS THE OZONE LAYER?




ULTRAVIOLET (UV) RAYS?

  • UV rays are the most common and harmful rays that come to Earth from the sun.


OZONE DEPLETION

  • the weakening of the ozone layer due to human activity, causing thinning and a hole to appear and ultraviolet rays to enter into the Earth.


ULTRAVIOLET RADIATION

  • UV rays penetrate the Earth's Atmosphere at slightly different wavelengths called UV-A, UV-B, and UV-C rays.

    • UVA rays are most common and cause skin aging and wrinkling. Tanning beds usually use UVA rays.

    • UVB rays cause sunburns, cataracts and the immune system.

    • UVC rays, the most dangerous, are absorbed by our one layer.


CAUSE OF OZONE DEPLETION

Chlorofluorocarbons (CFCs) 

  • A chemical used to make refrigerators, home insulation, plastic foam, and throw away food containers.

    • Discovered in the 1930s by scientist Thomas Midgley.

    • Non-toxic, non-flammable, and non-reactive with other chemical compounds.

    • Made up of chlorine, fluorine, and carbon

  • Very stable

  • Non-toxic

  • Non-corrosive

  • Inexpensive “Dream Chemical”

  • CFCs are used for:

    • Coolant in refrigerators and air conditioners

    • Propellant in aerosol sprays

    • Cleaner for electronics

    • Bubbles in plastic foams

    • Insulations

    • Sterilizing medical instruments

    • Fumigants for granaries and cargo ships




HOW ARE WE AS HUMANS AFFECTING THE OZONE LAYER?

  • Since 1928, CFCs have been produced, originally as nonflammable refrigerants for use in refrigerators, and eventually for use in fire extinguishers, dry cleaning agents,pesticides, degreasers, adhesives, and as propellants for aerosol products.

  • As these CFCs have been released into the atmosphere, the level of ozone in the stratosphere has decreased.


What Causes Depletion?

  • Too good to be true:

    • 1974 study at UC Irvine Indicated threat to ozone layer fromCFCs

    • Shock to the $28 billion per year CFC industry–DuPont and other chemical companies.


THE DESTRUCTION OF OZONE

  • CFCs are transported to the stratosphere

  • It is broken down by ultraviolet rays

  • Releases chlorine, which then becomes part of the process that destroys ozone

  • The ozone molecule is replaced by oxygen molecules

  • The chlorine can deplete the ozone up to 100,000 times faster than unabated depletion

  • In 1985, Joe Farman of British AA survey measured dramatic loss in ozone.



OZONE-OXYGEN CYCLE

  • Free radicals, like chlorine ,act as catalysts to the decomposition step (breaking down ozone)

  • These Catalysts Speed up the reaction.


OZONE DEPLETION: WHAT CAUSES DEPLETION?

  • CFCs remain stable in troposphere due to reactivity

  • Over 11-20 years they get lifted into stratosphere by convection and drift

  • Once in stratosphere they break down by UV rays releasing highly reactive chlorine atoms (with others) that in a chainreaction break apart ozone

  • Each CFC molecule lasts in stratosphere for 65-385 years

    • Can convert 100,000 of O3to O2 during that time.

    • DuPont and others fought findings until 1988 when they admitted problems.

    • 1995 Nobel Prize Chemistry

  • CFCs are not the only culprit:

    • Halons

    • Hydrogen chloride

    • Methyl bromide

    • Carbon tetrachloride

    • Methyl chloroform


LOSS OF THE OZONE LAYER : REASONS FOR CONCERN

  • Increased incidence and severity of sunburn

  • Increase in eye cataracts

  • Increased incidence of skin cancer

  • Immune system suppression

  • Increase in acid deposition

  • Lower crop yields and decline in productivity


EFFECTS OF OZONE DEPLETION

DISEASES

  • UV rays are the most common and harmful rays that come to Earth from the sun.

  • Causes skin cancer and kills the environment

  • EPA estimates, by 2075, 60 million people will get skin cancer, 10 million of that population is expected to die.


LIFE CYCLES (Introduction)

  • Disrupts flow of food chain because of decreased reproduction.

  • Simple organisms could be wiped out resulting in biological disruptions for some species above them.


PLANT LIFE

  • 100 out of 200 plants are sensitive to ozone depletion.(50%)

  • If food chains are disrupted,consumers won’t have anything to feed on.


OCEAN LIFE

  • Plankton would be affected(they won’t be able to survive)

  • Fish wouldn’t have the nutrients they need.

  • The fish will die out, and the secondary consumers won’t have anything to feed on and they will eventually die out as well.


THE OZONE HOLE

  • Since the 1970’s the ozone hole has been increasing in size over the Antarctic.

  • For the first time, in September of 2000,the ozone hole became so large it actually left populated areas of southern Chile fully exposed to the effects of the Sun’s UVrays.


SOLUTIONS THAT ADDRESS OZONE DEPLETION

  • Don’t use the air conditioner or use it less often. Open up windows.

  • Don’t open the refrigerator for too long. Get only what you need, don’t linger.

  • Refrain from using aerosol cans. You can use paper towels to wipe off the dust.

  • Fire extinguishers are essential, but to prevent using them, you can try to prevent fires from occurring.

  • Don’t use hairsprays.


MONTREAL PROTOCOL

  • Montreal Protocol: an international agreement to discontinue products with harmful chemicals affecting the ozone layer and instead replace them for an ozone friendly brand.


SOLUTIONS: PROTECTING THE OZONE LAYER

  • CFC Substitutes

    • Substitutes do exist


  • 1987 Montreal Protocol

    • 36 nations

    • Goal: reduce CFCs by 35% by 2000



  • 1992 Copenhagen Protocol

    • Protocol accelerated phase out


  • Good News: The ozone layer should recover in fifty years if there are no further harmful effects.



So what are we doing about it?

  • After the discovery of ozone depletion in the late 1970’s, many countries agreed that something must be done worldwide to stop the production of man-made, ozone harmful products.

  • The international community adopted the Vienna Convention in1985 followed by the Montreal Protocol in 1987.

  • The latest reports confirm that it has led to the phasing out of about 95% of the consumption of Ozone-Depleting Substances (ODS) listed in the agreement. In turn, this has led to the prospect of the ozone layer recovering by 2050 to 2075.

  • Furthermore, the phasing out of ODS has helped to fight climate change since many of these chemicals are also powerful greenhouse gasses. According to a recent study, the phasing out of substances under the Protocol led to more reductions in greenhouse gasses than what is foreseen under the Kyoto Protocol.


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.

  • 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 Volatile Organic Chemicals (VOCs) from evaporating into the air. Dispose of them properly