Ozone Depletion

What is the ozone layer and where is it found?

• The ozone layer is the layer of the atmosphere at an altitude of 15 to 40 km (stratosphere)

• What is Ozone?• Ozone is a molecule

made of three oxygen atoms

• What is the function of the ozone layer?

• ozone absorbs ultraviolet solar radiation.

So…What’s the issue with the ozone layer?• These satellite images below show the growth of the

ozone hole (blue, then purple, then red) over the past two decades.

How is ozone depleted?

Chloroflouorocarbons (CFC’s)

Chlorofluorocarbons (CFCs) are hydrocarbons in which some or all of

the hydrogen atoms are replaced by chlorine

and fluorine.

They are used in coolants for

refrigerators and air conditioners and in

cleaning solvents. They were also used as a

propellant in spray cans of everyday products such as deodorants,

insecticides, and paint.

Their use is now restricted because they

destroy ozone molecules in the

stratosphere

The chemical reaction that destroys ozone.

Chemical equation for this process…CFCl3 + UV Light CFCl2 + ClCl + O3 ClO + O2ClO + O Cl + O2

The free chlorine atom is then free to attack another ozone moleculeCl + O3 ClO + O2ClO + O Cl + O2

and again ...Cl + O3 ClO + O2ClO + O Cl + O2

and again... for thousands of times• In this way, a chlorine atoms act as a catalyst.

How Does the Ozone Hole Form?During the dark polar winter, strong circulating winds over Antarctica, called the polar

vortex, separate cold air from surrounding warmer air.

The air within the vortex grows extremely cold.

Polar stratospheric clouds form at altitudes of about 21,000 m during the Arctic

and Antarctic winter or early spring, when air

temperatures drop below –80°C.

On the surfaces of polar stratospheric clouds, the

products of CFCs are converted to molecular

chlorine.

When sunlight returns to the South Pole in the

spring, molecular chlorine is split into two chlorine atoms by UV radiation.

The chlorine atoms rapidly destroy ozone.

The destruction of ozone causes a thin spot, or ozone hole, which lasts for several

months.

If ozone is also being produced as air pollution, why does this ozone not repair

the ozone hole in the stratosphere?• Ozone is very chemically reactive. It can

chemically burn your lungs (Good up high…bad near by)

• Ozone produced by pollution breaks down or combines with other substances in the troposphere long before it can reach the stratosphere to replace ozone that is being destroyed

Why is a hole in the ozone a problem?

As the amount of ozone in the stratosphere

decreases, more UV light is able to pass through the atmosphere and

reach Earth’s surface.

UV light is dangerous to living things because it

damages DNA, the genetic material that contains the information that

determines inherited

characteristics.

Exposure to UV light makes the

body more susceptible to skin

cancer, and may cause other

damaging effects to the human body.

What are the effects of thinning ozone layer on humans?

• As the amount of ozone decreases, more UV light is able to pass through the atmosphere and reach Earth’s surface.

• UV light damages DNA • Exposure to UV light makes

the body more susceptible to skin cancer, and may cause other damaging effects to the human body.

High levels of UV light can kill single-celled organisms called phytoplankton that live near the surface of the ocean disrupt ocean food chains and reduce

fish harvests

Decrease in phytoplankton could cause an increase in the amount of carbon

dioxide in the atmosphere.

UV light could be especially damaging for amphibians, such as toads, because

they lay eggs that lack shells in the shallow water of ponds and streams. UV light at natural levels kills many eggs of some species by damaging

unprotected DNA.

UV light can damage plants by interfering with photosynthesis. This

damage can lower crop yields

Effects of ozone thinning on animals and plants

What have we done to protect the ozone layer?

Montreal

group of nations made an agreement, called the Montreal Protocol, to sharply limit their production of CFCs.

1987Copenhagen

_ At a second conference in Copenhagen, Denmark in 1992, developed countries agreed to eliminate most CFCs by 1995

1992

2007 was the 20th anniversary of the Montreal Protocol:

• "The Montreal Protocol has been a resounding success," said Richard Stolarski, a speaker at the symposium from NASA's Goddard Space Flight Center, Greenbelt, Md. "The effect can be seen in the leveling off of chlorine compounds in the atmosphere and the beginning of their decline."

• Since the Montreal Protocol was signed on Sept. 16, 1987, more than 100 nations have agreed to limit the production and release of compounds, notably human-produced chlorofluorocarbons, known as CFCs. CFCs and a list of other compounds are known to degrade the layer of ozone in the stratosphere that shields life from the sun's ultraviolet radiation. That process gives rise to the ozone hole above Antarctica.

Other forms of Pollution….NOISE!!!

• A sound of any kind is called a noise.

• Some noises are unnecessary and can cause noise pollution.

• Health problems that can be caused by noise pollution include loss of hearing, high blood pressure, and stress.

• Noise can also cause loss of sleep, which may lead decreased productivity at work and in the classroom.

Other forms of Pollution….

• LIGHT!!!!!• Light pollution does not present a direct

hazard to human health, but it does negatively affect our environment.

• The use of inefficient lighting in urban areas is diminishing our view of the night sky.

• In urban areas, the sky is often much brighter than the natural sky.

Describe in 1 sentence what is happening in the diagram below.

• The hole in the ozone has grown significantly over the past two decades over the continent of antarctica

What causes ozone depletion?

• A - Acid Rain• B - Volatile Organic Compounds• C - Chloroflourocarbons• D - Thermal Inversion

What happens to chlorine after it breaks down one molecules of ozone?

• A – It move on to break down another molecule of ozone

• B – It creates acid rain• C – It destroys aquatic ecosystems• D – It disappears

What does “good up high – bad near by” mean?

• Ozone in the stratosphere is helpful because it protects us from harmful UV radiation

• Ozone on the ground level is toxic to humans and breaks down before reaching the stratosphere – so it can’t be used to replace the missing ozone

What are some effects on people from ozone depletion?

• UV rays can cause genetic damage that can lead to skin cancer or other health problems

What have we done about the hole in the ozone layer?

• A - We are moving ground level ozone into the stratosphere

• B - CFC’s were no longer produced and later banned from use

• C – We are cleaning up the CFC’s from the atmosphere over antarctica

• D - Nothing