Presentation on OZONE LAYER DEPLETION

What is the ozone layer?

The ozone layer is a deep layer in the stratosphere, encircling the Earth, that has large amounts of ozone in it. The layer shields the entire Earth from much of the harmful ultraviolet radiation that comes from the sun. 

Where is the ozone layer ?

The ozone layer lies between 10 and 50 kilometres above the Earth's surface.

It is in a region of the atmosphere called the Stratosphere. The Stratosphere completely surrounds the Earth with a thickness of about 33 kilometers in most places.

Formation of the Ozone Layer

One billion years ago, early aquatic organisms called blue-green algae began using energy from the Sun to split molecules of H2O and CO2 and recombine them into organic compounds and molecular oxygen (O2).

This solar energyconversion process is known as photosynthesis.Some of the photosynthetically created oxygen combined with organic carbon to recreate CO2 molecules.

The remaining oxygen accumulated in the atmosphere, touching off a massive ecological disaster with respect to early existing anaerobic organisms.As oxygen in the atmosphere increased, CO2 decreased.

High in the atmosphere, some oxygen (O2) molecules absorbed energy from the Sun's ultraviolet (UV) rays and split to form single oxygen atoms.These atoms combined (27k jpeg) with remaining oxygen (O2) to form ozone (O3) molecules, which are very effective at absorbing UV rays.The thin layer of ozone that surrounds Earth acts as a shield, protecting the planet from irradiation by UV light.

Advantages of ozone layer

Primarily, it blocks "UV-B", which other components of the atmosphere do not touch..

Helps to mitigate temperature, so that nights are a little warmer, and days a little cooler.

 

Different chemicals are responsible for the destruction of the ozone layer

Topping the list : chlorofluorocarbons (CFC’s) Catalyzed by halocarbons (carbon compounds

containing fluorine, chlorine, bromine and iodine)– Examples: CFCs and ClONO2

– man-made, non-toxic and inert in the troposphere– In the stratosphere are photolysed, releasing reactive

chlorine atoms that catalytically destroy ozone

Ozone-Depleting Substance(s) (ODS):

CFCs,

HCFCs,

halons,

methyl bromide,

carbon tetrachloride, and

methyl chloroform.

dangerous

Chlorine atoms from CFCs attack the ozone, taking away ozone and forming chlorine monoxide (ClO).

O3 + Cl O2 + ClO

Chlorine monoxide then combines with another oxygen atom to form a new oxygen molecule and a chlorine atom.

ClO + O Cl + O2

The chlorine atom is free to destroy up to 100,000 ozone molecules

Depletion process

Effect of depletion

On Human being/Animal /plants–

UV-B damages DNA, which results in cancer, mutation and reduced crop yield from any Earth-surface-dwelling organism

Skin cancer Eye damage such as cataracts Immune system damage Reduction in phytoplankton Damage to the DNA in various life-forms

– this has been as observed  in Antarctic ice-fish that lack pigments to shield them from the ultra-violet light (they've never needed them before)

Possibly other things too that we don't know about at the moment.

Effects of UV radiation on biological organisms

DNA damage …Maximum effect on small and single cell organism

Impaired growth and photosynthesis ...poor crop yields

Phytoplankton: ………………………...Reduced uptake of CO2

…………………………………………..mortality

…………………………………………..Impaired reproductive capacity

Nitrogen-fixing soil bacteria…………. Reduced, damaged

Human health effects:

Suppressed immune system……………..Enhanced susceptibility to infection

…………………………………………..Increase risk of Cancer

Dermatology (skin)……………………...Sunburn

…………….………………………….....Loss of skin elasticity (Premature aging)

…………….…………………………… Photosensitivity

Neoplasia (cancer)……………………....Melanocytic (malignant melanoma)

…………….………………………….....Squamous cell skin – cancer

…………….……………………………Basal skin – cancer

Still questionable if causes lip cancer or cancer of

the salivary glands

Oculur (Eye)….…………………….......Cataract

…………….…………………………....Pterygium

DNA & UV-B

DNA absorbs UV-B radiation

Changes shape in DNA

– Changes in the DNA molecule mean that enzymes cannot “read” the DNA code

– Results in mutated cells or the cells die

Cells have developed the ability to repair DNA

– A special enzyme arrives at the damage site

– removes the damaged section of DNA– replaces it with the proper components

This makes DNA somewhat resilient to damage by UV-B

Aquatic Ecosystems

PLANTS

The influence of the UV-B radiation on plant process.

Flowering UV-B radiation can alter

both the time of flowering as well as the number of flowers in certain species.

Differences in timing of flowering may have important consequences for the availability of pollinators.

The reproductive parts of plants, such as pollen and ovules are well shielded from solar UV-B radiation.

Amphibians

UV-B Effects on Human Over exposure may:– Increase risk of non-

melanoma and malignant melanoma skin cancer

Higher risks of malignant melanoma from severe sunburns – especially in childhood

Risk of malignant melanoma has increased 10%

Risk of nonmalignant melanoma has increased 26%

malignant

Non-malignant

www.ldeo.columbia.edu/.../ lectures/ozone_health/

-Suppress immune system-Accelerate aging of skin due high exposure-Cause an outbreak of rash in fair skin

Skin Protection Protect the skin against the solar radiation

using skin creams with SPF– The greater the numerical value of the SPF the

greater the protection Use lip balm with SPF Cover up

cornea is encountered first

then the lens

vitreous humor

Increases the risk of cataracts– Induces type of

protein that provokes cleaving (splitting) in the lens

– Leading cause of blindness

– The prevalence of cataract after age 30 is doubling each decade

Causes pterygium

Over Exposure to UV B….

Manifestations of…

Cataracts

Pterygium

Cancer

brought on by over exposure to UV-B

Protection Sunglasses with 100% UV block Wrap around sunglasses Eye protection for children Hats

Images of Antarctica Taken Indicate A Slow Recovery

Suggestions

What can an individual do to reduce Ozone depletion

You can make a difference by these actions: Unplug electronics from the wall when not in use Don't use regular incandescent light bulbs Switch to compact fluorescent light bulbs Follow 3R Rule - Recycle, Reduce, and Reuse Avoid heavily packaged products Carpool, bike, or walk instead of driving alone Plant a tree Buy fresh produce at you local farmer's market Use energy efficient appliances Limit private vehicle driving Use eco-friendly household cleaning products Avoid using pesticides Developing stringent regulations for rocket launches .Banning the use of dangerous nitrous oxide

Thank you

- PRESENTED by. Mr.P.R.TAMBE- MMS IV sem.