OZONE DEPLETION

EFFECTIVE FILTER 200 – 315 nm – UV radiations in wavelength

OZONE LAYER

20

The ozone layer is a layer is a layer in the earth’s atmosphere which contains 90% of atmospheric ozone (O3). The ozone layer is found in the lower portion of the stratosphere from about 20 to 30 km above earth’s surface. It’s thickness varies seasonly and geographically.

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FORMATION OF OZONE LAYER

The ozone layer or the ozone forms by conversion of atmospheric oxygen(O2) into ozone (O3), this process is called as Chapman cycle . The oxygen get photolyzed by U.V.rays to form oxygen radical.

U.V. Light

O2

2O

The oxygen radical then react with molecular oxygen and forms ozone molecule (O3).

At the same time ozone gets reduce to oxygen by reacting with oxygen radical.

O3O2

2O

O3O2O

So, ozone is constantly get created and destroyed by Chapman cycle, which is a natural process.

DOBSON UNIT A unit of measurement for the total amount

of ozone in the atmosphere above a point on the earth's surface,

One Dobson unit being equivalent to a layer of pure ozone 0.01 mm thick at standard temperature and pressure.

The Dobson unit is named after Gordon Dobson, who was a researcher at the University of Oxford. In the 1920s, he built the first instrument to measure total ozone from the ground, now called the Dobson ozone spectrophotometer

OZONE DEPLETION

Decrease in concentration of ozone and thinning of ozone layer is called Ozone depletion.

From industries and our day to day life many gases like Chlorofluorocarbons (CFC’s) , Hydro- chlorofluorocarbons (HCFC’s) , halons, halogens, etc. get evolved in atmosphere which are mainly responsible for ozone depletion, as it contains or produce Chlorine (Cl) atom.

let’s take look at the process of ozone depletion---

PROCESS OF OZONE DEPLETION

Due to solar radiation i.e. U.V. Rays CFC’s , HCFC’s breaks and form Cl atom which react with ozone molecule and forms Chlorine monoxide (ClO). Chlorine monoxide then reacts with oxygen radical to form Chlorine atom and molecular oxygen.

Cl O3

U.V. Light

ClO O2

ClO O Cl O2

NET REACTION :

O3O2

2U.V. Light

O

As Cl atom acts as a catalyst , one single Cl atom can destroy much amount of ozone molecules.

Each chlorine radical can destroy 1,00,000 molecules of ozone

OZONE HOLEAs a result of ozone depletion, over

Antarctica the ozone hole is formed. This ozone hole leads to melting of ice of Antarctica, increase in sea level and other harmful effects on it’s environment.

OZONE DEPLETING SUBSTANCESOzone depleting substances are

mainly CFC’s, HCFC’s, Halons, etc. which are found in Refrigerators, Cleaning agents, sprays, Pesticides, Air conditioners, car emissions, etc.

EFFECT OF OZONE DEPLETIONDue to ozone depletion harmful U. V. Rays such

as UV-B Radiation reaches to earth which leads to harmful effects on animals, plants, aquatic life as well as on humans also. Effect on Aquatic System: Affects phytoplankton, fish, larval crabs. Decrease in amount of phytoplankton increase the CO2 in atmosphere which contribute the global warming. Effect on Materials: Degradation of paints and plastics. Effect on Climate: Global Warming (Increasing the Average temperature of the Earth’s surface).

Effect on Human Health: Damage genetic materials in the cells. Leads to more people suffering from Cataracts. Causes cancer, allergies and some other infectious disease.

10% depletion in ozone layer results in 30% increase in skin cancer infection.

PREVENTIONS Limit private vehicle driving to decrease vehicle emissions. By using Eco-friendly household or other cleaning agents. Avoid excess use of pesticides. Replacing CFC’s by other material which are less damaging. Manufacturing and using of ozone depleting chemicals must be stopped, etc.

But, for controlling ozone depletion the most important thing is to aware people about it, and that’s why International Environmental Community declared 16 September as a World Ozone Day .

The Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the Vienna Convention for the Protection of the Ozone Layer) is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion.