Ozone depletion is the process of destruction of the ozone layer which can cause adverse effects on the living forms by many pollutants releases out from the vehicles, industries etc. Ozone layer depletion is one of the major environmental issues which is getting thinner day by day as a result of increasing pollution.
Before, knowing the term ozone depletion there are also some important terms and facts that can give us the whole idea about the phenomena i.e. “depletion of ozone”. In this context, we will discuss facts of ozone, the ozone layer, an ozone hole and last but not the least the ozone depletion.
Content: Ozone Depletion
- Definition of Ozone
- Generation of Ozone
- Ozone Layer
- UV radiation
- Ozone Hole
- Cause of Ozone Depletion
Definition of Ozone
To know the facts of ozone, there are some general, physical and chemical properties that are given below that gives a whole idea about ozone:
|Characteristics||General properties of ozone|
|Discoverer||Charles Fabrey and Henry Buisson in 1913|
|Location||Stratosphere of the atmosphere|
|Distance||16-40km from the earth surface|
|Characteristics||Physical properties of ozone|
|Physical state||Gaseous form|
|Colour||Blue coloured gas|
|Characteristics||Chemical properties of ozone|
|Polarity||It is a polar molecule|
|Solubility||More soluble in non-polar molecules like O2, CO2, CFCS etc. and less soluble in polar molecule like water|
A high concentration of ozone is found in the stratosphere region and some concentration is found in the troposphere of the atmosphere.
- O3 in the stratospheric zone considers being good as it protects us from the harmful UV rays and refers as “Good stratosphere ozone”.
- Whereas, O3 found in the troposphere region considers being bad. It acts as atmospheric pollutants that can cause many effects like respiratory hazards (asthma, bronchitis etc.), lungs damage, headaches, burning eyes etc. and it refers as “Bad troposphere (low level) ozone“.
Generation of Ozone
O3 is continuously generated and dissociated in the stratosphere, the phenomena known as “Chapman cycle”.
Formation of ozone: It involves the following steps:
- Firstly, dissociation of the oxygen molecule takes place under the presence of UV-light of wavelength (80-240nm).
- After that, the dissociated O-atom combines with the oxygen molecule to produce ozone in the stratosphere.
Dissociation of ozone: It involves the following steps:
Here, ozone absorbs UV-C photon of wavelength (200-300nm) and dissociates.
It refers to “Ozonosphere”. The ozone layer is a thin layer that acts as a protecting shield by absorbing harmful UV- radiations. It is situated in the lower portion of the stratosphere region. The ozone layer is present about 20-30km above the earth surface.
It absorbs up to 97-99% of UV-light less than the wavelength of 290nm. It contains a high concentration of ozone about 300-350 D.O. The level of ozone is measured by the Dobson unit that is named after the scientist G.M.B. Dobson. He first devised the instrument which he named “Dobson meter” (a simple spectrophotometer) to know the amount of ozone that overheads from the ground.
The thickness of the ozone varies, but generally;
- Near equator: It is thinner
- Near pole: It is thicker
It is non-ionizing radiation and is the part of electromagnetic rays whose wavelength ranges from 100-400nm.
UV radiation produces naturally by the sun in the form of solar energy. It can also be produced artificially by the mercury and tanning lamp. It was first discovered by Johann Wilhelm Ritter in the year 1801. The UV radiation is present between the X-rays and Visible light.
UV-light has wavelength more than X-ray but less than the visible light.
On the basis of penetration property, UV light is of three types:
|Types of UV-radiation||Wavelength (in nm)||Ozone absorption||Effects|
|UV-A||315-400||50%||Cause skin aging, wrinkles, DNA-damage leads to skin cancer.|
|UV-B||280-315||70-90%||Cause skin tanning, eye cataract etc.|
|UV-C||100-280||100%||This is blocked by the ozone therefore it does not show any effect.|
It was first seen in Antarctica continent in the year 1987. During that year, the ozone hole was observed between 12-24km altitudes. Later, it was investigated that the occurrence of ozone hole occurs annually during mid of August and September in the Antarctic continent.
The major factors involved in the cause of ozone hole is not known but there are some chlorine and its radicals that are responsible for this.
Cause of Ozone Depletion
The depletion of ozone in the stratosphere by the number of gaseous pollutants like nitric oxide (NO), nitrous oxide (N2O), chlorine (Cl), chlorofluorocarbons (CFCs) etc.
These gaseous pollutants react with the ozone to produce oxygen by which the net result is the depletion of ozone. The main causes of ozone depletion are as follows:
Nitrogen system: It causes 60% of ozone destruction.
Example: Nitrogen system can be explained by taking an example of nitrous oxide (N2O). Nitrous oxide produces in the soil and ocean first enters the atmosphere by the microbial activities and then to the stratosphere.
- In the stratosphere, N2O first reacts with the nascent oxygen in the presence of UV- light to form nitric oxide (NO).
- Then this nitric oxide reacts with the ozone to produce oxygen and acts as a powerful destroyer of ozone.
Hydrogen system: It causes 10% of ozone destruction.
Example: It can be explained by taking an example of hydroxyl (OH) group that is derived from the water molecule.
- Firstly, the water molecule reacts with the nascent oxygen to form a hydroxyl group.
- Later this hydroxyl group reacts with the ozone and produce oxygen and water.
Chlorine systems: It causes about 15-20% of ozone destruction.
Example: It can be explained by taking the example of CFCs
- Firstly, CFCl2 in the presence of UV light dissociates to form chlorine (Cl2).
- Then Cl2 reacts with the ozone to produce oxygen.
Other systems: There are several other compounds that deplete ozone is primarily halons. Halons are the chemical compounds that are widely used in the fire extinguishers.
Examples of halons: Bromoflourocarbons, Bromochloroflouro carbons etc.
Effects of ozone depletion
It is a serious issue that can cause a number of effects to the living organisms which categorizes into:
Effects on human health
- Skin cancer (sometimes refers as “malignant melanoma”).
- Eye cataract by direct exposure.
- Skin ageing
- The weakening of the immune system
- Skin infections
- tanning of skin
Effects on plants: The depletion of ozone affects the growth and development of the plant such as:
- Reduced growth of a plant
- Reduction in the efficiency of photosynthesis
- Production of smaller leaves
- Premature death
- Discolouration of leaves
Effects on the aquatic ecosystem:
- Decrease the photosynthetic efficiency of phytoplankton
- Effect development stages of fish, shrimp and other aquatic forms.
- Unbalance the marine ecosystem
- Interferes with the marine food chain indirectly
Control of ozone depletion
The control measures of ozone depletion can be done by following ways:
- Spread awareness about the ozone depletion.
- There should be restricted use of CFCs.
- Atomic nuclear explosions should be banned as they emit nitric oxide.
- The eco-friendly household cleansing product must be used.
- Rocket flight and high altitude aircraft should minimize.
- Unleaded gasoline should be used in the vehicles.
- Vehicles should be equipped with a catalytic converter.
- CFCs should be replaced with HCFC’s.
Depletion of ozone is a serious issue that drastically increases by the increase in environmental pollutants like nitrogen and chlorine radicals that depletes the ozone concentration. Some major steps should be taken to minimize or control this problem.