OZONE LAYER OZONE LAYER DEPLETIONDEPLETION

1.1. Why the hole in the atmospheric Why the hole in the atmospheric ozone layer above us?ozone layer above us?

2.2. What has been done about this?What has been done about this?

3.3. Why should I worry ourselves Why should I worry ourselves about the Ozone Layer Depletion?about the Ozone Layer Depletion?

Good life at the beach Good life at the beach threatened?threatened?

Mr. OZONEMr. OZONE: : Will I be able to continue Will I be able to continue enjoying this life without problems?enjoying this life without problems?

TheThe DiscoveryDiscovery

Team who discovered the hole 1985. From left: Joe Farman, Brian Gardiner, and Jonathan Shanklin

British Atlantic Survey Research station, Holly Bay, Antarctic coast

In 1985, using satellites, balloons, In 1985, using satellites, balloons, and surface stations, a team of and surface stations, a team of researchers had discovered a balding researchers had discovered a balding patch of ozone in the upper patch of ozone in the upper stratosphere, the size of the United stratosphere, the size of the United States, over Antarctica. States, over Antarctica.

Artist's view of the QuikTOMS spacecraft (image credit: NASA)

Total Ozone Mapping Spectrometer Total Ozone Mapping Spectrometer (TOMS)(TOMS)

Used by NASA to measure ozone Used by NASA to measure ozone concentrationsconcentrations

TOMS – a satellite-borne TOMS – a satellite-borne instrumentinstrument

TOMS launched in 1996 – makes TOMS launched in 1996 – makes 35 measurements every 8 seconds35 measurements every 8 seconds

Levels of ozone are measured in Levels of ozone are measured in Dobson units (DU), where 100 Dobson units (DU), where 100 DU is equivalent to a 1 millimeter DU is equivalent to a 1 millimeter thick layer of pure ozonethick layer of pure ozone

Earth’s AtmosphereEarth’s Atmosphere

•Ozone is a triatomic form of oxygen (O3) found in Earth’s upper and lower atmosphere.

•The ozone layer, situated in the stratosphere about 15 to 30 km above the earth's surface.

•Ozone protects living organisms by absorbing harmful ultraviolet radiation (UVB) from the sun.

•The ozone layer is being destroyed by CFCs and other substances.

• Ozone depletion progressing globally except in the tropical zone.

The ozone layer

www.epcc.pref.osaka.jp/apec/ eng/earth/ozone_layer_depletion/susumu.html

What is Ozone? Ozone What is Ozone? Ozone Layer?Layer?

Ozone (O3)Ozone (O3) is a highly-reactive from of oxygen. is a highly-reactive from of oxygen. Unlike oxygen (O2), ozone has a strong scent Unlike oxygen (O2), ozone has a strong scent

and is blue in color. and is blue in color. OzoneOzone exists within both the tropospheric and exists within both the tropospheric and

stratospheric zones of the Earth’s atmospherestratospheric zones of the Earth’s atmosphere In the troposphereIn the troposphere, ground level ozone is a , ground level ozone is a

major air pollutant and primary constituent of major air pollutant and primary constituent of photochemical smog photochemical smog

In the stratosphere,In the stratosphere, the the ozone layer is an ozone layer is an essential protector of life on earth as it absorbs essential protector of life on earth as it absorbs harmful UV radiation before it reaches the harmful UV radiation before it reaches the earth.earth.

Meteorological Meteorological mechanism mechanism

• Movement of air from Movement of air from one place to another in one place to another in the upper stratospherethe upper stratosphere

• Cold temperature in the Cold temperature in the upper atmosphere causes upper atmosphere causes nitric acid to freeze into nitric acid to freeze into crystals forming wispy crystals forming wispy pink cloudspink clouds

• Forms a vortex of tightly Forms a vortex of tightly twisted winds thus twisted winds thus forming a hole in the forming a hole in the upper atmosphere upper atmosphere

Hole Formation Based on Two different Hole Formation Based on Two different mechanisms:mechanisms:

Chemical Chemical MechanismMechanism

Different chemicals are responsible for the destruction of the ozone Different chemicals are responsible for the destruction of the ozone layer layer

Topping the list :Topping the list :• chlorofluorocarbons (CFC’s) chlorofluorocarbons (CFC’s) • man-made, non-toxic and inert in the troposphereman-made, non-toxic and inert in the troposphere• In the stratosphere are photolysed, releasing reactive chlorine In the stratosphere are photolysed, releasing reactive chlorine

atoms that catalytically destroy ozoneatoms that catalytically destroy ozone

A combination of low temperatures and A combination of low temperatures and elevated chlorine and bromine concentrations elevated chlorine and bromine concentrations are responsible for the destruction of ozone in are responsible for the destruction of ozone in the upper stratosphere thus forming a “hole”. the upper stratosphere thus forming a “hole”. (Kerr, 1987)(Kerr, 1987) www.met.sjsu.edu/~cordero/ education/education.htm

The Ozone LayerThe Ozone Layer

– What is the maximum concentration of ozone in the ozone layer?

• Maximum of absolute conc about 23 km (up to 1013 molecules/mL)• Maximum of relative conc about 35 km (up to 10 ppm)

• 16 – 35 km (above bkgd level)• Stratosphere contains about

90% of all atmospheric ozone• Total column ozone: ~300 DU

(1 DU = 0.3 cm thick layer at 1 atm)

CFC’s and ozone CFC’s and ozone depletiondepletion

Chlorofluorocarbons are Chlorofluorocarbons are created and used in created and used in refrigerators and air refrigerators and air conditioners. These conditioners. These chlorofluorocarbons are chlorofluorocarbons are not harmful to humans not harmful to humans and have been a benefit and have been a benefit to us. Once released into to us. Once released into the atmosphere, the atmosphere, chlorofluorocarbons are chlorofluorocarbons are bombarded and destroyed bombarded and destroyed by ultraviolet rays. In the by ultraviolet rays. In the process chlorine is process chlorine is released to destroy the released to destroy the ozone moleculesozone molecules

Destruction of ozone by Destruction of ozone by chlorinechlorine

Molecular oxygen is broken down in the stratosphere Molecular oxygen is broken down in the stratosphere by solar radiation to yield atomic oxygen, which then by solar radiation to yield atomic oxygen, which then combines with molecular oxygen to produce ozone. combines with molecular oxygen to produce ozone. The ozone is then destroyed by chlorine atoms.The ozone is then destroyed by chlorine atoms.

Ozone destruction by UV Ozone destruction by UV raysrays UV radiationUV radiation from the sun from the sun

releases the radicals Cl releases the radicals Cl and ClO.and ClO.

Ozone is a highly unstable Ozone is a highly unstable molecule so it readily molecule so it readily donates its extra oxygen donates its extra oxygen molecule to free radical molecule to free radical species such as hydrogen, species such as hydrogen, bromine, and chlorine. bromine, and chlorine.

These compound species These compound species act as catalysts in the act as catalysts in the breakdown of ozone breakdown of ozone molecules.molecules.

The ozone depletion The ozone depletion processprocess

Responsibility for ozone Responsibility for ozone damage each yeardamage each year

Global CFC productionGlobal CFC production

Ozone hole in September 2006Ozone hole in September 2006

“Largest hole in the record.”~Size of North America

Source: NASA

Ozone hole in Southern Ozone hole in Southern hemisphere October 1979 & hemisphere October 1979 &

19981998

Monthly means of total ozone in the Southern Monthly means of total ozone in the Southern Hemisphere observed with TOMS (Hemisphere observed with TOMS (Total Ozone Total Ozone Mapping Spectrometer)Mapping Spectrometer)

Images for October of 1979 (left) and 1998 (right). Images for October of 1979 (left) and 1998 (right).

Ozone concentration at the Ozone concentration at the center of ozone holecenter of ozone hole

Effects of UV rays on Aquatic Effects of UV rays on Aquatic EcosystemsEcosystems

Ozone depletion causes increases Ozone depletion causes increases in UV rays’s effects on aquatic in UV rays’s effects on aquatic ecosystems by:ecosystems by:

1. 1. decreasing the abundance of decreasing the abundance of phytoplankton – affects the food stock phytoplankton – affects the food stock for fishes and the absorption of CO2for fishes and the absorption of CO2

2. decreasing the diversity of aquatic 2. decreasing the diversity of aquatic organisms – reduces food stock and organisms – reduces food stock and also destroys several fish and also destroys several fish and amphibians.amphibians.

Effects of UV rays on Effects of UV rays on Terrestrial EcosystemsTerrestrial Ecosystems

Damage to plant cell DNA molecules - Damage to plant cell DNA molecules - makes plants makes plants more susceptible to more susceptible to pathogens and pests pathogens and pests

Reductions in photosynthetic capacity Reductions in photosynthetic capacity in in the plant - results in slower growth and the plant - results in slower growth and smaller leavessmaller leaves

Causes mutations in mammalian cells Causes mutations in mammalian cells and destroys membranesand destroys membranes

Harmful effects of UV rays Harmful effects of UV rays on peopleon people

Skin cancerSkin cancer

Premature aging (photoaging) of the Premature aging (photoaging) of the skin (different from normal skin (different from normal chronological aging)chronological aging)

Cataracts and eye disorders (corneal Cataracts and eye disorders (corneal sunburn and blindness)sunburn and blindness)

Immune system damageImmune system damage

Correlation between Ozone Correlation between Ozone depletion and skin diseasesdepletion and skin diseases