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Unit 4 - Notes

CHE110

Unit 4: Environmental Pollution

1. Introduction to Environmental Pollution

Definition:
Environmental pollution is defined as the undesirable change in the physical, chemical, or biological characteristics of air, water, or land that causes harmful effects on the health, survival, or activities of humans or other living organisms.

Key Concepts:

  • Pollutant: Any substance that causes pollution (e.g., smoke, chemicals, noise).
  • Biodegradable Pollutants: Decompose rapidly by natural processes (e.g., sewage, paper).
  • Non-biodegradable Pollutants: Do not decompose or decompose very slowly (e.g., DDT, plastics, heavy metals).

2. Air Pollution

Definition

The presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or materials.

Types of Pollutants

  1. Primary Pollutants: Emitted directly from a source (e.g., , , , Particulate Matter).
  2. Secondary Pollutants: Formed in the atmosphere through chemical reactions between primary pollutants (e.g., Ozone, Peroxyacetyl nitrate - PAN, Smog).

Causes

  • Mobile Sources: Automobiles, airplanes (release Carbon Monoxide, Nitrogen Oxides).
  • Stationary Sources: Power plants, factories, refineries (release Sulfur Dioxide, particulates).
  • Area Sources: Burning wood, cities, livestock (Methane).
  • Natural Sources: Volcanic eruptions, dust storms, wildfires.

Effects

  • Human Health: Respiratory diseases (asthma, bronchitis), lung cancer, cardiovascular problems. Carbon monoxide reduces the oxygen-carrying capacity of blood.
  • Environmental: Acid rain, eutrophication, haze.
  • Photochemical Smog: A mixture of pollutants (mostly ozone) formed when nitrogen oxides and volatile organic compounds react to sunlight, creating a brown haze.

Control Measures

  • Equipment: Electrostatic precipitators, bag filters, and cyclone separators for particulates; wet scrubbers for gases like .
  • Automotive: Use of catalytic converters; shifting to unleaded petrol and CNG/EVs.
  • Policy: Implementation of Euro/Bharat Stage emission norms.

3. Water Pollution

Definition

The contamination of water bodies (lakes, rivers, oceans, groundwater) usually as a result of human activities.

Causes

  • Point Sources: Discharges from a specific location (e.g., discharge pipe from a factory).
  • Non-Point Sources: Diffuse sources (e.g., agricultural runoff containing pesticides and fertilizers).
  • Pathogens: Bacteria and viruses from untreated sewage.
  • Thermal Pollution: Hot water discharge from power plants decreasing dissolved oxygen.

Effects

  • Eutrophication: Excessive nutrients (nitrates/phosphates) induce algae growth (algal bloom), depleting oxygen and killing aquatic life.
  • Biological Magnification: Increase in concentration of toxic substances (like DDT or Mercury) at successive trophic levels in the food chain.
  • Diseases: Cholera, typhoid, dysentery from pathogen-contaminated water.

Control Measures

  • Wastewater Treatment Plants (WWTP):
    • Primary: Physical removal of solids.
    • Secondary: Biological decomposition of organic matter (activated sludge process).
    • Tertiary: Chemical removal of nutrients and pathogens (chlorination, UV).
  • Strict regulation on industrial effluents.

4. Soil Pollution

Definition

The build-up of toxic chemical compounds, salts, pathogens, or radioactive materials in the soil.

Causes

  • Agrochemicals: Excessive use of pesticides, insecticides, and chemical fertilizers.
  • Industrial Waste: Fly ash, metallic residues, chemical dumping.
  • Urban Waste: Plastics, electronic waste, medical waste.

Effects

  • Reduced Fertility: Imbalance in soil microbiome and nutrient content.
  • Toxic Crops: Plants absorb toxins, which then enter the human food chain.
  • Groundwater Contamination: Leachate from polluted soil seeps into aquifers.

Control Measures

  • Promoting organic farming and bio-fertilizers.
  • Bioremediation (using microorganisms to degrade pollutants).
  • Proper solid waste management (segregation and recycling).

5. Noise Pollution

Definition

Unwanted or excessive sound that can have deleterious effects on human health and environmental quality. Measured in Decibels (dB).

Causes

  • Industrial: Heavy machinery, generators, mills.
  • Transport: Road traffic, aircraft, railways.
  • Social Events: Loudspeakers, fireworks, construction activities.

Effects

  • Auditory: Temporary or permanent hearing loss (Threshold of pain is ~120-140 dB).
  • Non-Auditory: Hypertension, stress, sleep disturbance, annoyance, interference with communication.

Control Measures

  • Source Control: Silencers on vehicles, soundproofing machinery.
  • Transmission Control: Green belts (planting trees absorbs sound), noise barriers.
  • Legal: Zones of silence (near hospitals/schools), limiting loudspeaker usage times.

6. Radiation Pollution (Nuclear Hazards)

Definition

The physical pollution of air, water, and soil by radioactive materials.

Types and Causes

  • Ionizing Radiation: High energy (X-rays, Gamma rays) damaging to DNA.
  • Natural Sources: Cosmic rays, terrestrial radiation (Radon).
  • Anthropogenic Sources: Nuclear power plant accidents, improper disposal of nuclear waste, mining of uranium, nuclear weapon tests.

Effects

  • Somatic: Burns, fatigue, cancer, sterility, cataracts.
  • Genetic: Mutations passed to future generations, birth defects.

Control Measures

  • Strict safety protocols in nuclear plants.
  • Proper shielding (lead/concrete containers) for storage and transport.
  • Deep geological disposal of radioactive waste.

7. Emerging Pollutants & Special Topics

Emerging Pollutants

Pollutants that are not currently regulated but pose a potential threat.

  • Microplastics: Fragments <5mm found in oceans and human blood.
  • E-Waste: Discarded electronics releasing lead, cadmium, and beryllium.
  • PPCPs: Pharmaceuticals and Personal Care Products (hormones, antibiotics) found in water systems.

Fireworks and Ill-Effects

Fireworks release fine particulates (PM2.5, PM10) and heavy metals used for colors:

  • Copper: Blue (Respiratory irritant).
  • Cadmium: Batteries/Firecrackers (Carcinogen, kidney damage).
  • Lead: Oxidizer (Nervous system damage).
  • Magnesium: White sparks (Metal fume fever).
  • Impact: Massive spike in Air Quality Index (AQI) post-festivals, noise trauma to animals and infants.

8. Global Environmental Issues

Global Warming & Climate Change

  • Mechanism: The Greenhouse Effect. Greenhouse Gases (GHGs) like , Methane (), Nitrous Oxide (), and Water Vapor trap heat from the sun in the lower atmosphere.
  • Causes: Burning fossil fuels, deforestation (reduces absorption), cattle farming ().
  • Effects:
    • Rise in global average temperature.
    • Melting of polar ice caps and glaciers Sea level rise.
    • Extreme weather events (hurricanes, droughts).
    • Loss of biodiversity.

Ozone Layer Depletion

  • Location: Stratosphere (Good Ozone). Protects Earth from harmful UV-B radiation.
  • Causes: Ozone Depleting Substances (ODS) such as Chlorofluorocarbons (CFCs), Halons, and Carbon Tetrachloride used in refrigeration and aerosols.
  • Mechanism: UV radiation breaks down CFCs releasing Chlorine atoms. One Chlorine atom can destroy 100,000 Ozone molecules.
  • Effects: Increased skin cancer (melanoma), cataracts, damage to phytoplankton (affecting marine food chains).
  • Protocol: Montreal Protocol (1987) banned CFCs.

Acid Rain

  • Definition: Rain with a pH of less than 5.6.
  • Chemistry:
    • Sulfur Dioxide () + Water Sulfuric Acid ().
    • Nitrogen Oxides () + Water Nitric Acid ().
  • Effects:
    • Architecture: Stone leprosy (corrosion of marble/limestone monuments like the Taj Mahal).
    • Agriculture: Leaches nutrients (Ca, Mg) from soil; releases toxic Aluminum which damages roots.
    • Aquatic: Lowers pH of lakes, killing fish and eggs.

9. Impacts on Human Communities and Agriculture

Impacts on Human Communities

  1. Respiratory Health: Chronic Obstructive Pulmonary Disease (COPD), asthma, silicosis (occupational).
  2. Waterborne Diseases: Cholera, Giardiasis, Hepatitis A.
  3. Carcinogenic: Exposure to benzene, asbestos, and radiation leads to various cancers.
  4. Neurological: Lead and Mercury poisoning affects cognitive development in children (neurotoxicity).

Impacts on Agriculture

  1. Yield Reduction: Ozone and acid rain damage plant tissues and reduce photosynthesis.
  2. Soil Degradation: Salinization from poor irrigation and chemical accumulation renders land barren.
  3. Food Safety: Bioaccumulation of pesticides makes food unsafe for consumption.

10. Solid Waste Management

Types of Waste

  1. Municipal Solid Waste (MSW): Household trash (food, paper, plastic).
  2. Industrial Waste: Scrap metal, solvents, sludge.
  3. Hazardous Waste: Toxic, reactive, ignitable, or corrosive waste.

Control Measures (Urban & Industrial)

The 3R Principle (Hierarchy of Waste Management)

  1. Reduce: Generate less waste at the source.
  2. Reuse: Use materials again (e.g., glass bottles).
  3. Recycle: Process waste into new products (paper, aluminum).

Disposal Methods

  1. Sanitary Landfills: Engineered pits with liners to prevent leachate from contaminating groundwater; methane collection systems installed.
  2. Incineration: Burning waste at high temperatures. Reduces volume by 90% but may release dioxins if not filtered. Good for energy recovery (Waste-to-Energy).
  3. Composting: Biological decomposition of organic waste (aerobic or vermicomposting) to produce manure.
  4. Segregation at Source: Separating wet (biodegradable), dry (recyclable), and hazardous waste at the household/factory level.

11. Case Studies on Pollution

1. The Bhopal Gas Tragedy (Air/Industrial)

  • Date: Dec 2-3, 1984.
  • Place: Union Carbide India Ltd, Bhopal.
  • Event: Leakage of Methyl Isocyanate (MIC) gas.
  • Impact: Considered the world's worst industrial disaster. Thousands died immediately; long-term effects include blindness, respiratory issues, and birth defects.

2. Minamata Disease (Water)

  • Place: Minamata Bay, Japan (1950s).
  • Cause: Release of Methylmercury in industrial wastewater by Chisso Corporation.
  • Pathway: Mercury bioaccumulated in shellfish/fish eaten by locals.
  • Impact: Severe neurological damage, paralysis, coma, and death ("Dancing Cat Fever").

3. Chernobyl Disaster (Radiation)

  • Date: 1986.
  • Place: Ukraine (USSR).
  • Event: Explosion in Reactor 4 of the nuclear plant.
  • Impact: Released massive radioactive fallout across Europe. Increased thyroid cancer rates; a 30km exclusion zone remains uninhabitable.

4. The Great Smog of London (Air)

  • Date: 1952.
  • Cause: Burning of coal + weather inversion (cold air trapped pollutants).
  • Impact: 4,000 to 12,000 deaths due to respiratory failure. Led to the Clean Air Act of 1956.