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Atmospheric pollutants are undesirable chemicals or particles present in the air responsible for atmospheric pollution. These pollutants are harmful to the environment, human health, plants, and animals. Atmospheric pollutants are either produced naturally or by industrial processes. In dense areas, human activities are the primary source of pollution.
- Degradable atmospheric pollutants quickly break down by natural processes.
- The slowly degradable pollutants remain active in the environment for decades.
- Earth's surface is surrounded by an atmosphere and it has five layers with different thicknesses at different heights.
- The troposphere is the first layer of the atmosphere that extends up to 10 km from the ground level where all organisms reside.
- Air Quality Index (AQI) measures the air pollution level on a scale of 0-500.
- The greater the value, the higher the concentration of pollutants present in the air.
Read More: Environmental Pollution
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Key Terms: Atmospheric Pollutants, Air Pollution, Particulate Matter, Stratospheric Pollution, AQI, Ozone layer, CFCs
Tropospheric Pollution
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Troposphere is the lowest layer closest to the earth’s surface where organisms live. Tropospheric pollution occurs because of the presence of undesirable gaseous or solid substances in the atmosphere.
- Troposphеric pollution is hazardous to human health, particularly thе rеspiratory and cardiovascular systеms.
- It can cause an increase in the prevalence of asthma, bronchitis, rеspiratory infеctions, and other rеspiratory illnesses.
- Long-tеrm air pollution exposure has also been linked to an increase in mortality rates.
Gaseous Pollutants
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Oxides of nitrogen, hydrogen, carbon, sulphur, and ozone are considered gaseous air pollutants.
- Hydrocarbons: Hydrocarbons are made up of carbons and hydrogen formed by partial combustion of automobile fuels. Hydrocarbons cause cancer. They are very harmful to plants and trees as they cause a breakdown of tissues, ageing, and shading of leaves and flowers.
- Oxides of Sulphur: Oxides of sulphur are produced by burning fossil fuels. The most common oxide pollutant of sulphur is Sulphur dioxide. It irritates the eyes resulting in redness and tearing. Studies reported that even a low concentration of sulphur dioxides can cause respiratory diseases. Sulphur dioxide In the presence of particulate matter oxidizes to sulphur trioxide.
2SO2(g) + O2(g) → 2SO3 (g)
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Particulate Matter
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The liquid droplets or the minute solid particles in the air are called particulate matter. They are present in smoke particles from fires, ash from industries, vehicle emissions, and dust particles.
- They are further classified into two different categories - viable and non-viable particulates.
- The viable particulates are the ones that are dispersed in the atmosphere for example - fungi, moulds, algae, etc.
- On the other hand, non-viable are classified depending on the size and nature of particulates.
- Smoke particulates are composed of a mixture of solids and liquid particles formed by organic matter combustion.
- For example, cigarette smoke, dry leaves, garbage, oil smoke, etc.
- Dust is composed of small solid particles (about 1ðm in diameter) formed during the grinding, attribution, and crushing of solid materials.
- Mits are formed by spray liquid particles and by condensation of liquid in the air. Sulphuric acid mist, herbicides, and insecticides are examples of mists.
- Fumes are produced by the condensation of vapours during distillation, sublimation, and boiling.
Read More: NCERT Solutions on Environmental Chemistry
Stratospheric Pollution
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The stratosphere is the next layer to the troposphere layer in the atmosphere that is extended from 10 to 15 km in height.
- The upper stratosphere consists of the ozone layer, dioxygen, and dinitrogen.
- The ozone layer protects the organism from the harmful ultraviolet rays coming from the sun.
- Ozone (O3) is the product of UV radiation reacting with dioxygen (O2) molecules.
- The UV radiation splits the oxygen molecules into free oxygen atoms (O).
- These oxygen atoms react with the oxygen molecule to form ozone.
- O2 (g) → O(g) + O(g)
- O(g) + O2(g) → O3(g)
- Thermodynamically, ozone is unstable and quickly breaks down into oxygen molecules.
- Chlorofluorocarbons (CFCs), also known as freons are the main reason for ozone layer depletion.
- CFCs produce radicals of chlorines and tend to deplete the ozone layer.
- The depletion of the ozone layer is a threat to all living organisms because the ozone layer blocks the harmful UV rays from the sun that can cause skin cancer.
Sources of Air Pollution
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The pollution in the air either be natural or caused due to human activities. Therefore, the classification of air pollution is.
Natural Source of Air Pollution
The natural source of air pollution includes:
- Wind-blown dust
- Forest fire smoke
- Ash from volcanic activities
- Pollen from flowers
- Gases like methane when organic matter decomposes.
Air pollution because of human activities
Pollution caused by humans include:
- Electric power generation
- Incineration
- Vehicle emissions
- Industrial production
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Effects of Air Pollution
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The effects of air pollution depend on the pollutant type, their concentration, and exposure duration. The effects of air pollution are:
- Asthma
- Lung cancer
- Pneumonia
- Chronic bronchitis
- Irritation to eyes, nose, and throat
- Chronic Obstructive Pulmonary Disease (COPD)
- Heart diseases
Things to Remember
- Atmospheric pollutants are harmful particles mixed up with the air and cause atmospheric pollution.
- Gaseous pollutants are the oxides of nitrogen, hydrocarbons, sulphur, and ozone present in the troposphere.
- AQI measures the quality of air in that region.
- The greater the AQI value, the higher concentration of air pollutants present.
- The main cause of ozone layer depletion is the release of chlorofluorocarbons (CFCs).
- Air pollutants can cause asthma, pneumonia, eye irritation, COPD, and heart diseases.
- Particulate Matter can be classified into two different categories - viable and non-viable particulates.
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Previous Year Questions
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Sample Questions
Ques. Name some non-degradable atmospheric pollutants that are harmful to living organisms. (2 Marks)
Ans. Some non-degradable atmospheric pollutants are plastic materials, dichloride-phenyl trichloroethane (DDT), nuclear wastes, heavy metals, and chemicals that are difficult to remove by natural processes from the environment and harmful to living organisms.
Ques. If the air quality index of any city is 350. Comment on the air quality of the city. (2 Marks)
Ans. The higher the value of AQI means the greater the concentration of air pollution present in the city. Therefore, an AQI value of 350 represents the hazardous air quality of the city.
Ques. Name the five atmospheric pollutants. (3 Marks)
Ans. The main 5 atmospheric pollutants are
- Ozone (O3)
- Carbon monoxide (CO)
- Particulate matter
- Nitrogen dioxide (NO2)
- Sulphur dioxide (SO2)
Ques. Explain the effects of atmospheric pollution on human health. (3 Marks)
Ans. Short and long-term exposure to air pollution can cause various diseases including
- The air pollutant can cause swelling, nasal irritation, and can even cause a runny nose.
- Air pollution can also cause lung damage and limit the functioning of the lungs
- Air pollution also has an impact on the heart - it can increase blood pressure and trigger the pre-existing condition of the heart.
Ques. What are the impacts of air pollutants on our environment? (5 Marks)
Ans. Air pollution and pollutants have several negative impacts on our environment that include
- Acid rain, which is precipitation, consists of sulphuric and nitric acid. Acid rain damages trees, forests, causes soil erosion, and turns water bodies like lakes, ponds, and rivers into acidification and makes water harmful to wildlife.
- Haze - It is a condition that occurs when sunlight hits the tiny pollutants in the air. Haze unclear the color, clarity, and texture of what we see.
- Ozone depletion - Substances like hydrochlorofluorocarbons, chlorofluorocarbons, and halons are causing ozone depletion. Depletion of ozone can increase the UV radiation effect on the earth’s surface and affect human health, damage crops, etc.
Ques. Give the difference between viable and non-viable particulate matter. Give examples of each. (2 Marks)
Ans. The particulate matter that is dispersed in the atmosphere for example - fungi, algae, moulds, etc. On the other side, the non-viable particulates are those particles that are classified according to their nature and size. For example - smog, dust, fumes, and milts.
Ques. What is the difference between biodegradable and non-biodegradable pollutants? Give examples of each. (2 Marks)
Ans. Those pollutants that can be broken down easily by natural processes are called biodegradable pollutants. Examples of degradable vegetables are discarded vegetables, urine, sewage, plants, etc. On the other hand, slowly degradable pollutants that remain in the environment for so long and cannot be degraded by natural processes are called nonbiodegradable pollutants. For example - metals, plastics, DDT, and nuclear wastes.
Ques. Give examples of natural sources of air pollutants. (3 Marks)
Ans. Natural sources of air pollutants are
- Forest fire smoke
- Volcanic eruptions
- Sea-salt spray
- Emission of pollen from plants
- Windblown dust
Ques. What is the main cause of ozone layer depletion? How harmful is depletion? (2 Marks)
Ans. The main cause of the depletion of the ozone layer is chlorofluorocarbon (CFCs), which is also known as freons. The depleted ozone layer allows UV radiation to reach the earth’s surface and affect human health, wildlife, trees, and deplete the soil quality.
Ques. What are the ways to reduce the growth of air pollutants? (3 Marks)
Ans. To reduce air pollutants, we should
- Use public transport
- Turn off the electricity when not in use
- Avoid using plastic bags
- Do not use crackers or fireworks
- Use filters for chimney
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