Pollution and it's Types | General Awareness for SSC CGL PDF Download

Atmospheric Pollution

Atmospheric pollution refers to the introduction of undesirable substances into the atmosphere that negatively impact plants, animals, and humans. This pollution can result from both natural processes and human activities. There are two main types of atmospheric pollution: tropospheric and stratospheric.

• Tropospheric Pollution: This can be either gaseous or particulate.
• Stratospheric Pollution: This affects the stratosphere and involves different pollutants.

Pollutants: Substances causing pollution are known as pollutants. They fall into two categories:

• Primary Pollutants: These remain in the environment in their original form, such as sulfur dioxide (SO₂) and nitrogen dioxide (NO₂).
• Secondary Pollutants: These are formed from the reaction of primary pollutants, including peroxyacetyl nitrate (PAN), ozone (O₃), and aldehydes.

Pollutants from the Steel/Iron Industry: The iron and steel industry contributes to air, water, and soil pollution. Air pollutants include carbon monoxide (CO), sulfur dioxide (SO₂), nitrogen oxides (NOₓ), carbon dioxide (CO₂), hydrogen sulfide (H₂S), PAN, lead (Pb), nickel (Ni), and cadmium (Cd). Water pollutants include organic matter, oils, metals, acids, sulfides, and sulfates.

Major Gaseous Air Pollutants

• Sulfur Dioxide (SO₂): Highly toxic to both humans and plants, even at low concentrations. It can cause respiratory issues like bronchitis and asthma, as well as eye and throat irritation. In plants, it hampers chloroplast formation, leading to chlorosis. SO₂ also contributes to acid rain when it reacts with particulate matter and water to form sulfuric acid (H₂SO₄), which damages structures and materials.

• Oxides of Nitrogen (NOₓ): This group includes nitric oxide (NO), a colorless, odorless gas, and nitrogen dioxide (NO₂), a brown gas with a pungent odor. NO₂ is toxic to tissues, causing leaf fall and reducing photosynthesis rates in plants. It also contributes to smog and can irritate eyes, as well as affect the liver and kidneys. NO₂ reacts with moisture to form nitric acid (HNO₃), a component of acid rain.

• Carbon Monoxide (CO): This gas is highly poisonous as it forms a stable complex with hemoglobin in the blood, reducing oxygen transport to organs and tissues. The carboxyhemoglobin complex is about 200 times more stable than the oxygen-hemoglobin complex, leading to symptoms like headaches, weakness, and asphyxia. Soil microorganisms can help reduce carbon monoxide levels.

• Hydrocarbons: Consisting only of carbon and hydrogen, hydrocarbons are produced from incomplete combustion of fuels and anaerobic decomposition of organic matter. Methane (CH₄) is a major hydrocarbon pollutant. High levels of hydrocarbons can be carcinogenic and cause plant damage. They also react with nitrogen oxides to create secondary pollutants.

Prevention and Control of Air Pollution

• Combustion: Organic pollutants are burned to convert them into less harmful carbon dioxide (CO₂) and water (H₂O).
• Absorbers: Gaseous pollutants are removed by passing them through absorbers.
• Fabric Filters: Gases containing dust are filtered through fabric to trap particles, which are collected while the purified gases are released.
• Electrostatic Precipitators: Aerosol-containing gases pass through electrostatic precipitators, where particles are electrically charged and collected on electrodes, allowing clean gases to be discharged.

• Greenhouse Effect: The Earth's atmosphere allows most sunlight to reach and warm the surface. However, greenhouse gases like carbon dioxide, methane, and water vapor trap the heat radiated back from the Earth. This process, known as the greenhouse effect, is crucial for maintaining temperatures that support life on our planet. Without it, Earth would be extremely cold.
• Global Warming: An increase in the concentration of greenhouse gases intensifies the greenhouse effect, leading to global warming. This phenomenon can cause the melting of ice caps and glaciers, resulting in rising sea levels.

Acid Rain

• Formation: Acid rain occurs when oxides of nitrogen and sulfur in the air dissolve in rainwater, forming nitric and sulfuric acids.
• Effects: Acid rain corrodes buildings, monuments (like the Taj Mahal), and statues. It also makes soil more acidic, degrading soil quality and reducing forest and agricultural productivity. Additionally, acid rain leaches heavy metals such as lead, copper, mercury, and aluminum from soil and rocks, contaminating water sources and posing health risks.
• Health Impacts: Lead, often released from vehicle exhausts, is highly toxic and can cause anemia, brain damage, convulsions, and death. Other heavy metals and certain pesticides, like DDT, can lead to kidney and liver damage, and neurological issues.

The Taj Mahal and Marble Cancer

• Issue: The Taj Mahal, a renowned tourist attraction in Agra, faces discoloration of its white marble due to air pollution. Industries around Agra release sulfur dioxide and nitrogen dioxide, which contribute to acid rain. This acid rain accelerates the deterioration of the marble, a phenomenon known as "marble cancer."
• Actions: To protect the Taj Mahal, the Supreme Court has mandated that local industries use cleaner fuels like CNG and LPG, and that vehicles in the area switch to unleaded petrol.

Particulates

• Definition: Particulates are tiny solid particles and liquid droplets suspended in the air, including dust, smoke, mists, and bacteria.

Smog

Classical Smog: This type occurs in cool, humid climates and is primarily composed of sulfur dioxide (SO₂) and particulate matter from burning fuels. It is chemically reducing.

• Components and Effects: Ozone in photochemical smog has a pungent smell and can cause respiratory issues and damage rubber products. Peroxyacetyl nitrate (PAN) and aldehydes present in this smog irritate the eyes and are highly toxic to plants, causing damage like bronzing and glazing of leaves.
• Control Measures: Photochemical smog can be mitigated using free radical traps, which react with the precursors of smog. Installing efficient catalytic converters in vehicles also helps reduce the release of nitrogen oxides and hydrocarbons.