Download - Ozone depletion presentation Mr.P.R.Tambe
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.