AIR POLLUTION
Definition of air pollution
Air pollution is a result of industrial and certain domestic activity. An ever-increasing use of fossil fuels in power plants, industries, transportation, mining, construction of buildings, stone quarries had led to air pollution. Air pollution may be defined as the presence of any solid, liquid or gaseous substance including noise and radioactive radiation in the atmosphere in such concentration that may be directly and indirectly injurious to humans or other living organisms, plants, property or interferes with the normal environmental processes.
Types of air pollutants
(1) Suspended particulate matter, and
(2) Gaseous pollutants like carbon dioxide (CO2), NOx etc.
Particulate air pollutants, their sources and effects
Pollutant | Sources | Effects |
Suspended Particulate Matter (SPM) / Dust | Smoke from domestic, industrial, and vehicular sources | · Depends on specific composition; reduces sunlight and visibility; increases corrosion; causes pneumoconiosis, asthma, cancer, and other lung diseases |
Fly Ash | Part of smoke released from chimneys of factories and power plants | · Settles on vegetation and houses; adds to SPM in the air; leachates contain harmful materials |
Particulate pollutants
- Particulate matter suspended in air are dust and soot released from the industrial chimneys. Their size ranges from 0.001 to 500 µm in diameter. Particles less than 10µm float and move freely with the air current. Particles which are more than 10µm in diameter settle down. Particles less than 0.02 µm form persisent aerosols. Major source of SPM (suspended particulate matter) are vehicles, power plants, construction activities, oil refinery, railway yard, market place, industries, etc.
Fly ash
- Fly ash is ejected mostly by thermal power plants as by products of coal burning operations. Fly ash pollutes air and water and may cause heavy metal pollution in water bodies. Fly ash affects vegetation as a result of its direct deposition on leaf surfaces or indirectly through its deposition on soil. Fly ash is now being used for making bricks and as a land fill material.
Lead and other metals particles
- Tetraethyl lead (TEL) is used as an anti-knock agent in petrol for smooth and easy running of vehicles. The lead particles coming out from the exhaust pipes of vehicles is mixed with air. If inhaled it produces injurious effects on kidney and liver and interferes with development of red blood cells. Lead mixed with water and food can create cumulative poisoning. It has long term effects on children as it lowers intelligence.
- Oxides of iron, aluminum, manganese, magnesium, zinc and other metals have adverse effect due to deposition of dust on plants during mining operations and metallurgical processes. They create physiological, biochemical and developmental disorders in plants and also contribute towards reproductive failure in plants.
Smog
- Smog is a type of air pollution that creates a hazy or foggy atmosphere, reducing visibility and affecting air quality. Originally used in the early 1900s to describe a blend of smoke and fog, the term “smog” referred to pollution from coal-burning, especially common in industrial areas. Today, smog is still prevalent in densely populated cities with high levels of industrial and vehicular emissions.
- Smog forms when pollutants such as nitrogen oxides, volatile organic compounds (VOCs), and other harmful particles are released into the atmosphere from sources like factories, vehicles, and power plants. These pollutants react chemically in the presence of sunlight, creating a harmful mixture. When combined with fog or high humidity, this reaction produces a thick haze, further reducing visibility and posing risks to public health.
Annual average concentration of pollutants in ambient air in residential and industrial areas (year 2000) mg/m3 in 24 hours
Gaseous pollutants
Power plants, industries, different types of vehicles – both private and commercial use petrol, diesel as fuel and release gaseous pollutants such as carbon dioxide, oxides of nitrogen and sulphur dioxide along with particulate matter in the form of smoke. All of these have harmful effects on plants and humans. some of these pollutants, their sources and harmful effects.
Gaseous air pollutants: their sources and effects
Pollutant | Source | Harmful Effects |
Carbon Compounds (CO, CO₂) | · Automobile exhaust, burning of wood & coal | • Respiratory problems • Greenhouse effect |
Sulphur Compounds (SO₂, H₂S) | · Power plants, refineries, volcanic eruptions | • Respiratory problems in humans • Loss of chlorophyll in plants (chlorosis) • Acid rain |
Nitrogen Compounds (NO, N₂O) | · Motor vehicle exhaust, atmospheric reactions | • Irritation in eyes and lungs • Low productivity in plants • Acid rain damages metals & stones |
Hydrocarbons (benzene, ethylene) | · Automobiles, petroleum industries | • Respiratory problems • Carcinogenic (cancer-causing) |
SPM (Suspended Particulate Matter) | · Thermal power plants, construction activities, metallurgical processes, automobiles | • Poor visibility, breathing problems • Lead interferes with red blood cell development • Causes diseases & cancer • Smog formation worsens asthma |
Fibres (cotton, wool) | · Textile & carpet weaving industries | • Lung disorders |