Full study notes for BEVAE-181 Block 3 Unit 9. Covers the definition of pollution and pollutants, biodegradable vs non-biodegradable pollutants, causes of environmental pollution, air pollution (natural, primary and secondary pollutants, SPM, acid rain, temperature inversion, smog), the Bhopal Gas Tragedy (1984) with ICMR findings, water pollution (biological, chemical, physical agents), water quality parameters (DO, BOD, COD, MPN, TDS), marine pollution, soil pollution (erosion, acidity), bioaccumulation and biomagnification (DDT food chain diagram), and noise pollution with sources, effects and control methods. Includes seven diagrams, SAQs, and terminal question answers. Free PDF download.
Unit 9 · Index
Pollution is any undesirable change in the physical, chemical, or biological characteristics of air, water, or soil that adversely affects life. This unit covers all major pollution types — air (primary/secondary pollutants, acid rain, smog), water (biological/chemical/physical agents, thermal, marine), soil (erosion, biomagnification), and noise — along with the Bhopal Gas Tragedy as a landmark case study.
Pollution = any undesirable change in the physical, chemical, or biological characteristics of environmental components (air, water, soil) that adversely affects life forms and life support systems of the biosphere. The agent that contaminates the environmental component is called the pollutant.
Point vs Non-Point Sources: Point sources are distinct confined sources — chimneys, discharge pipes/tunnels from industries or municipalities. Non-point (area) sources are diffused — runoff from construction sites, agricultural fields.
📌 Persistent Organic Pollutants (POPs): Non-biodegradable chemical substances that accumulate through food chains in humans. Nine chlorinated agro-pesticides (Aldrin, DDT, Chlordane, Dieldrin) and three chlorinated industrial products (Dioxin, PCBs) are listed as POPs.
Industrial processes + population growth → increasing consumption of energy and natural resources → steady rise in emissions of gases, chemicals, and wastes into air, water, soil.
| Item | Concentration 1950 | Concentration 1995 | Effect on Environment |
|---|---|---|---|
| Coal use | 884 million tons oil equivalent | 2,083 million tons | Climate change |
| Oil production | 518 million tons | 2,953 million tons | Climate change |
| Natural gas production | 180 million tons oil eq. | 2,128 million tons oil eq. | Climate change |
| Fertilizer use | 14 million tons | 125 million tons | Water pollution |
| CFC production | 42 thousand tons | 300 thousand tons | Ozone layer depletion |
| Human population | 2.55 billion | More than 5.6 billion | Changed land use and resource patterns |
Source: Vital Signs, 1995, World Watch Institute
Dry air: 78% nitrogen + 21% oxygen + 0.04% CO₂ + trace gases. Air pollution = any significant change in this composition. An average adult exchanges 6× more gas per day than daily food and water combined — so air quality is critically important.
| Pollutant Group | Key Sources | Major Effects |
|---|---|---|
| COₓ (CO, CO₂) | Combustion of fossil fuels, biomass burning, transport | CO₂ → greenhouse effect; CO binds to haemoglobin → asphyxia |
| SOₓ (SO₂, SO₃) | Coal/petroleum combustion, smelting, paper manufacturing | Severe lung damage; major precursor to acid rain; corrodes paints/metals |
| NOₓ (NO, NO₂, N₂O) | Fuel burning, fertilizer manufacturing, biomass burning | Forms PAN and HNO₃; suppresses plant growth; eye irritation |
| Hydrocarbons/VOCs (Methane, Benzene) | Gasoline evaporation, fuel burning, landfills, solvents | Carcinogenic effects; toxic to plants/animals; produce photochemical smog with sunlight |
| CFCs | Aerosol sprays, refrigeration, foam plastics | Stratospheric ozone depletion → more UV-B → skin cancer |
| Lead (Pb) | Leaded gasoline, lead smelting, paint | Neurotoxin; causes respiratory problems; carcinogenic |
| SPM (Particulates) | Fuel combustion, mining, construction, forest fires | PM₂.₅ → deep lung damage; blocks sunlight; reduces crop yields |
☁️ Delhi's Progress: Low sulphur diesel + ban on commercial vehicles >15 years old → decreasing SO₂ and NO₂ levels over past decade. Unleaded petrol drastically lowered lead levels in Indian city air.
i) Environmental ii) Non-degradable iii) Particulates iv) Humans v) Resource
On the night of December 2, 1984, during routine maintenance, a large quantity of water entered MIC storage tank no. 610. In early hours of December 3, 40 tonnes of toxic gases were released. Only a few ppm of inhaled gas causes violent coughing, swelling of lungs, bleeding, and death.
📊 ICMR Findings: Fibrosis of lungs, neurotic depression, anxiety and psychosis in 22.6% of exposed people. Children (up to age 5) suffered 2–4 times more fever, breathlessness, vomiting, cough. Spontaneous abortion rates among exposed women in 1990 were more than 3× that of unexposed women.
a)–v b)–iv c)–i d)–ii e)–iii
Water is a universal solvent — contamination is inevitable. Polluted water threatens health and aquatic life. Major human-generated sources: sewage, industrial waste, agricultural waste (fertilizers, pesticides).
| Parameter | Full Form | What It Measures | Interpretation |
|---|---|---|---|
| DO | Dissolved Oxygen | Amount of O₂ dissolved in water | Higher DO = cleaner water; Low DO = organic pollutants present |
| BOD | Biological Oxygen Demand | O₂ used by bacteria to decompose organic matter | High BOD = polluted water; High BOD → Low DO → life dies |
| COD | Chemical Oxygen Demand | O₂ needed to degrade organic chemical compounds | High COD = chemical industry effluents present |
| MPN | Most Probable Number | Detects E.coli and coliforms (indicators of sewage) | High MPN = human waste contamination in water |
| TDS | Total Dissolved Solids | Salts and solids dissolved in water | Excessive TDS = poor water quality; includes calcium, iron, nitrates, heavy metals |
🌊 Marine Pollution: ~210 million gallons of petroleum enter seas every year from extraction, transport, consumption. ~180 million gallons from natural seepage. Oil spills → aromatic hydrocarbons kill aquatic organisms; oil coats seabirds' feathers → destroys natural insulation and buoyancy → drowning. Millions of tonnes of plastics (est. 2,45,000 tonnes floating on sea water) found in stomachs of sea birds and fish.
i) Water ii) Aquatic iii) CPCB iv) Animals (seabirds, seals) v) BOD
Soil is only ~15 cm deep on land surface. Three ways humans degrade it: using it (agriculture/development), taking things from it (mining/deforestation), putting things into it (waste disposal).
Natural flora/fauna destroyed due to deforestation. IUCN estimates by 2050: up to 50,000 plant species will become extinct or threatened. Currently ~4,500 animal species + 20,000 plant species are threatened.
Loosening, detachment and removal of topsoil particles by wind/water. Reduces soil fertility; causes silting of rivers and water bodies. Excessive loss of topsoil = deposition in river beds = reduced river capacity.
Excess irrigation → salinisation → alkalinity (calcium carbonate deposits). Reduces fertility and makes certain crops impossible. Dry climate = more alkaline deposits. Wrong agricultural practices are primary cause.
Bioaccumulation: Entry of a pollutant into a food chain — increase in concentration from environment to first organism. Biomagnification: Increase in concentration from one food chain link to the next. Fat-soluble pollutants (DDT, PCBs) are retained in fatty tissues and become more concentrated at each higher level. This is why birds like bald eagle and brown pelican suffered reproductive abnormalities in 1950s–1960s from DDT.
Noise = any unwanted or exceedingly high levels of sound that can annoy, cause stress, or impair hearing ability. Measured in decibels (dB); high-pitched sounds more annoying than low-pitched at same intensity (measured in decibel-A or dbA).
Control measures: (i) Reduction of noise at source; (ii) Interruptions in the path of transmission; (iii) Protection of the receiver. Awareness, motivation, legislation, and strict implementation required. CPCB monitoring shows Deepawali noise levels in Delhi and Mumbai exceed 45 dbA limit for residential areas.
i) T ii) F (Excess loss of topsoil reduces soil fertility) iii) T iv) F (Fat-soluble pollutants biomagnify — retained in fatty tissues) v) F (Noise is unwanted) vi) T
Exam-style questions from the IGNOU textbook.
Pollution is any undesirable change in the physical, chemical, or biological characteristics of environmental components (air, water, soil) that adversely affects life forms and life support systems of the biosphere. The agent is called a pollutant.
Sources of Air Pollution:
Background: Union Carbide Corporation set up a pesticide plant in Bhopal in 1969. In December 1979, its Methyl Iso Cyanate (MIC) plant with 5,000 tonne capacity started production.
The Disaster: On the night of December 2, 1984, during routine maintenance, a large quantity of water entered MIC storage tank no. 610. In the early hours of December 3, 40 tonnes of toxic gases were released. No alarm was raised. No evacuation plan existed. The gas leak lasted less than 1 hour — yet killed about 2,500 people and seriously injured 1,00,000 people.
After Effects (ICMR Studies): Fibrosis of lungs, neurotic depression, anxiety, and psychosis in 22.6% of exposed people. Children (up to age 5 at disaster time) suffered 2–4× more illness. As late as 1990, spontaneous abortion rates among exposed women were more than 3× those of unexposed women. The nightmare continues.
Water pollution = any physical, biological, or chemical change that degrades water quality. Water, being a universal solvent, is easily contaminated.
Water Quality Parameters:
Soil pollution: Human activities degrade soil in three ways: (i) Using it (overagriculture, development), (ii) Taking from it (mining, deforestation), (iii) Putting into it (waste disposal, pesticides, fertilizers). Effects include biodiversity loss, soil erosion (reduces fertility, causes silting), acidity/alkalinity changes, and contamination by heavy metals and persistent organic pollutants.
Biomagnification: The increase in concentration of a pollutant from one level of a food chain to the next. Fat-soluble pollutants are retained in fatty tissues and concentrate at each higher level.
Example — DDT in Food Chain: DDT sprayed on agricultural fields runs off into water bodies (0.000003 ppm in water). Phytoplankton absorb and concentrate it (0.04 ppm). Small fish eat large quantities of plankton (0.5 ppm). Large fish eat many small fish (2 ppm). Fish-eating birds like Bald Eagle at the top (25+ ppm). At this concentration, DDT disrupts calcium metabolism → thin eggshells → eggs break during incubation → reproductive failure. This caused alarming declines in bald eagle and brown pelican populations in the 1950s–1960s.
Noise pollution: Any unwanted or exceedingly high level of sound that can annoy, cause stress, or impair hearing. Sound intensity measured in decibels (dB). A tenfold increase in sound intensity = 10 dB increase. The unit dbA measures both pressure and pitch.
Sources: Industrial operations and machines, vehicles and railways, aircraft, military arms, construction work, recreational appliances (crackers, loudspeakers, TVs).
Effects on Humans: Increased adrenalin levels, hypertension (high blood pressure), migraine, high cholesterol, gastric ulcers, insomnia, easy irritability, increased aggressive behaviour, psychological disorders, and most seriously — permanent damage to hearing ability.
Control: Three approaches: (i) Reduce noise at source (mufflers, soundproofing of industrial machinery); (ii) Interrupt transmission path (green belts, sound barriers); (iii) Protect the receiver (ear plugs/muffs for workers). CPCB monitoring shows Deepawali noise levels in Delhi/Mumbai exceed the 45 dbA residential limit.
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