How Does the Ozone Layer Protect Life on Earth?
Ozone is a highly reactive gas that is basically composed of three oxygen atoms. In Earth's atmosphere, more precisely in the stratosphere layer and lower atmosphere layer that is the troposphere this ozone occurs. It can be both natural as well as man-made. Ozone affects life on earth, either in a good way or bad way it depends where it is situated in the atmosphere of the earth.
The stratospheric ozone is formed naturally from the interaction of solar ultraviolet radiation with molecular oxygen. This layer of ozone protects the earth's surface from harmful ultraviolet radiation.
The troposphere ozone layer is formed from photochemical reactions primarily. These reactions occur between two major classes of air pollutants that are not orphan oxide and Volatile organic compounds. These reactions are traditionally being dependent upon heat and light resulting in a greater concentration of ozone in the atmosphere during the summer season. Ozone can be both advantageous as well as hazardous; it is completely dependent upon its location. This article will give you a brief knowledge about the ozone layer. The topics that you are going to study here include the definition of ozone, elemental Properties of ozone as a whole, properties layer, importance of the ozone e layer, depletion of the ozone layer, and other information. At the end of this article, you are being provided with the Frequently Asked Questions related to the ozone layer. It will help you to clear your queries. Vedantu has designed this article especially for you to understand the basics of our ozone layer.
What is Ozone?
Ozone is a natural gas present within the atmosphere of our planet. Well, how is ozone formed? Three oxygen atoms form the ozone layer on the upper atmosphere of the Earth's surface. The layer of atmosphere in which the ozone layer lies is called the stratosphere. Hence, you get the ozone layer formula - O3. The ozone structure indicates that it is quite unstable and much more reactive as compared to oxygen (O2). It implies it is easy to form and decompose when interacting with other compounds. The O3 can deplete and decompose when it collaborates with human-made compounds in the stratosphere.
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Diagram showing where the Ozone layer lies and distance between different layers in Earth's atmosphere.
On the other hand, Ozone gas also exists near the Earth's surface, in the lower atmosphere called the troposphere. Here chemical responses between air pollutants from gasoline smoke, vehicle exhaust, and other emissions create O3 that is, however, toxic to people and plants alike.
Today this protective ozone layer is depleting because of the presence of chlorofluorocarbon compounds (CFC) in the atmosphere. These compounds mix with other gases present in the environment and enter the Earth's stratosphere. In the presence of ultraviolet rays, these agents deliver chlorine radicals in the air to produce oxygen molecules and chlorine monoxide. As a result, the ozone layer depleted. The ultraviolet radiation from the sun is able to enter the Earth's atmosphere directly. These ultraviolet radiations can cause a lot of harm to humans as well as other organisms living on earth. As for Humans, they are prone to diseases such as skin cancer, cataract, and other immune weakening diseases.
Element Properties
Symbol: O3
Atomic Weight: 48
Solubility: 570 mg/l bij 20 °C
Energy: 142,3 KJ/mol (34,15 kcal/mol)
Melting Point: -192.2 °C
Boiling Point: -112 °C
Critical Temperature: -12,1 °C
Binding Degree: 116 °
Critical Pressure: 5460 kPa
Density: 2,14 kg O3/m3 bij 0°C 1013 mbar
Relative Density (in air): 1,7 kg/m3
Electrochemical Potential: 2,07 volt
Properties of O₃
Ozone is a form of oxygen called a triatomic allotrope of oxygen. The molecule in the ozone structure comprises three atoms.
This form of oxygen is a pale blue and irritating gas that even at low concentrations is combustible and lethal in nature.
O3 absorbs solar ultraviolet radiation when naturally produced in the Earth's stratosphere in little quantities. Otherwise, the UV sunlight could lead to drastic destruction to living organisms on our planet. Ozone can control the ultraviolet range extending between 220 - 290 nm of the atmospheric spectrum.
Another significant property of O3 is that it is highly reactive, especially when exposed to heat. In the presence of heat, it even decomposes back to oxygen, which is known as the thermal decomposition process. This process can spontaneously happen at roughly 300 degrees Celsius. When the temperature rises, it creates an exothermic reaction that causes the breakdown of ozone to an oxygen atom as well as an oxygen molecule.
The boiling point of ozone is −112 °C (−169.6 °F) that turns into violet-blue crystals on solidifying whereas its melting point is -192.2 (−314 °F).
Preparation of Ozone Layer
You might be wondering how the ozone layer is formed? Don't worry; here we will clear out all your confusion regarding the preparation of ozone.
The preparation of ozone is done in a two-step reactive method in the stratosphere region of the earth's surface. Firstly, an oxygen molecule decomposes by sunlight into two oxygen atoms. Afterward, the oxygen atoms interact with another oxygen atom to form O3.
However, is this the only way you get ozone? Definitely not, men, today can even create ozone gas. So, how is the ozone formed by us? All you require for the preparation of ozone is a machine and oxygen molecules to create ozone gas. The ozone-producing machine is called an ozonizer, which is an apparatus generally used as a water or air purifier. The O3 in this device swoops bacteria to eliminate them.
Scientists use a similar methodology in the laboratory for the preparation of ozone. Instead of sunlight just use a high voltage electric current. The dry oxygen is placed in an ozonizer in this process. Then a salient electric current, which is a high voltage electrical current zaps through the oxygen molecule that transforms the oxygen molecule into O3 gas.
The equation for ozone formation is as follows:
3O2 + energy = 2O3
Importance of Ozone Layer
One of the most important uses of the ozone layer for our environment is that it saves every single living being on the planet from the harmful UV rays of the sun. As a shield to Earth, it protects us from physical and environmental damage that UV radiation can cause.
Further, human-produced ozone gas is used for water and air purification.
Other uses of ozone layer gas are to help eliminate any unwanted toxic substances from the environment. It is suitable for various industrial purposes.
Ozone Layer Depletion
Halogen gases are the reasons behind ozone layer depletion. Bromide, halons, Chlorofluorocarbons, hydrochlorofluorocarbons, methyl, and chloride are called ozone-depleting substances or ODS. They release at the surface, spread all over in the air, and go from the lower atmosphere to the upper atmosphere through wind transport patterns. These gases further create chlorine and/or bromine that are capable of ozone layer depletion by destroying the stratosphere in the presence of ultraviolet rays.
Apart from the natural factors, scientists believe that somewhat stratospheric ozone is also damaging because of human actions such as human-made chemicals.
Fun Facts
Volcanic eruptions may shoot substances into the stratosphere, which causes an increased risk of ozone layer depletion. And if this layer keeps depleting it will be very difficult for humans to survive on earth as most of the rays may enter the earth's surface. Along with it, many human activities are also responsible for the depletion of oxygen.
Zone layer: In Antarctica, there is a hole in the ozone layer. This hole is known as an ozone hole. Due to various human activities, there is depletion of the ozone layer and in Antarctica, due to its depletion, a complete hole is formed.
In 1840 Schönbein first made an electrical ozone generating machine
FAQs on Ozone Layer: Structure, Preparation, and Importance
1. What is the ozone layer and where is it located in the atmosphere?
The ozone layer is a natural, protective shield of ozone (O₃) gas located in the stratosphere, the second layer of Earth's atmosphere. It is most concentrated at an altitude of approximately 15 to 35 kilometres. Its primary function is to absorb the majority of the Sun's harmful ultraviolet (UV) radiation, preventing it from reaching the Earth's surface and protecting living organisms.
2. How is ozone naturally formed in the stratosphere?
Ozone is formed through a natural photochemical process in the stratosphere. High-energy ultraviolet (UV-C) radiation from the sun strikes an oxygen molecule (O₂), splitting it into two separate oxygen atoms (O). Each of these highly reactive oxygen atoms can then combine with another oxygen molecule (O₂) to form an ozone molecule (O₃). This process is a continuous cycle of formation and breakdown, maintaining a dynamic equilibrium of ozone concentration.
3. What are the main causes of ozone layer depletion?
The primary cause of ozone layer depletion is the release of man-made chemicals known as Ozone-Depleting Substances (ODS). The most significant of these are:
- Chlorofluorocarbons (CFCs): Once widely used in refrigerators, air conditioners, aerosol sprays, and cleaning solvents.
- Halons: Used in fire extinguishers.
- Carbon Tetrachloride: Used in industrial processes.
4. How exactly do CFCs destroy ozone molecules in a chain reaction?
In the stratosphere, UV radiation breaks the strong carbon-chlorine bonds in a CFC molecule, releasing a highly reactive chlorine free radical (Cl•). This single chlorine atom then acts as a catalyst in a destructive cycle:
- The chlorine atom collides with an ozone molecule (O₃), stealing an oxygen atom to form chlorine monoxide (ClO•) and leaving behind a normal oxygen molecule (O₂).
- The chlorine monoxide molecule (ClO•) then reacts with a free oxygen atom (O) present in the stratosphere, which releases the chlorine atom (Cl•) and forms another oxygen molecule (O₂).
5. What is the difference between stratospheric 'good ozone' and tropospheric 'bad ozone'?
The effect of ozone depends entirely on its location in the atmosphere.
- Stratospheric Ozone ('Good Ozone'): This is the naturally occurring ozone in the stratosphere that forms the protective ozone layer. It is beneficial as it shields the Earth from harmful UV-B radiation.
- Tropospheric Ozone ('Bad Ozone'): This ozone is found at ground level in the troposphere. It is a secondary air pollutant and a key component of smog. It is not created naturally but is formed by chemical reactions between nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. It is harmful to breathe and can damage crops and ecosystems.
6. Why does the 'ozone hole' form specifically over Antarctica?
The 'ozone hole' is not a literal hole but an area of significant seasonal thinning of the ozone layer. It forms over Antarctica due to a unique combination of factors during the southern winter:
- Extreme Cold: The formation of Polar Stratospheric Clouds (PSCs), which only occur at very low temperatures (-78°C).
- Chemical Reactions: These ice clouds provide a surface for chemical reactions that convert inactive, stable chlorine compounds into more reactive forms.
- Sunlight: When sunlight returns in the Antarctic spring (September-October), it provides the energy to break apart these reactive compounds, releasing a massive amount of chlorine radicals that trigger rapid ozone destruction.
7. Why is the stratospheric ozone layer considered crucial for life on Earth?
The stratospheric ozone layer is vital because it absorbs approximately 97-99% of the Sun's harmful medium-frequency ultraviolet (UV-B) radiation. Without this protective shield, increased UV-B exposure at the Earth's surface would lead to severe consequences, including:
- Increased rates of skin cancer and eye cataracts in humans.
- Suppression of the immune system.
- Damage to terrestrial plant life, including crops.
- Harm to marine ecosystems by affecting phytoplankton, the base of the aquatic food web.
8. Is the ozone layer healing, and what role did the Montreal Protocol play?
Yes, scientific evidence shows that the ozone layer is slowly healing. This recovery is a direct result of the Montreal Protocol on Substances that Deplete the Ozone Layer, an international treaty signed in 1987. This landmark agreement successfully orchestrated a global phase-out of the production and consumption of ODS like CFCs. Because these chemicals have a long atmospheric lifespan, the recovery process is gradual, but the ozone hole is shrinking, and full recovery is anticipated by the middle of the 21st century.
