Environmental pollution notes

Pollution is an unwanted change in the physical, chemical or biological quality of the environment that harms human beings, other living things, resources or structures. A pollutant is the substance or energy (noise, heat, radiation) that brings that change. Primary pollutants leave the source as they are — SO₂, CO, raw sewage. Secondary form in the air — ozone, sulphates of acid rain. Biodegradable matter bacteria can break; non-biodegradable (plastic, heavy metals, many pesticides) accumulates. A point source is a chimney or a drain; a non-point source is field runoff or a city street.

Amount and sensitivity both matter: the same nitrogen fertiliser is a nutrient on the field and eutrophication in a pond. Natural sources exist — volcano dust, forest fire — but the industrial-age load is human. For every type the syllabus wants four rooms: definition, cause, effect, control. A local polluted site — a drain, a brick kiln, mine dust, a dump — is the field of those rooms.

Air pollution is an unwanted change in the composition of the atmosphere that harms living things, materials or climate. Causes: vehicles, power plants, industry, brick kilns, crop-residue and trash burning, mine dust, the household stove. Main pollutants — suspended particles (SPM / PM₂.₅–PM₁₀), sulphur dioxide, nitrogen oxides, carbon monoxide, lead, volatile organics, smog. London-type smog is SO₂ and smoke in cold damp air; photochemical smog is NOx and hydrocarbons in sunlight — ozone and PAN. Acid rain comes from SO₂–NOx; buildings, crops and lakes suffer. Greenhouse gases change climate over a long span; the health of air is here — asthma, bronchitis, heart, children’s lungs.

Control: catch at the source — electrostatic precipitator, bag filter, scrubber; catalytic converter and better fuel, CNG in vehicles; tall chimneys only spread, they do not remove; a green belt holds dust; do not burn stubble; public transport. Mine and kiln dust and city particles are local faces of the same heading. CO binds haemoglobin and cuts oxygen; PM₂.₅ enters deep lung.

Water pollution is an unwanted change in the physical, chemical or biological quality of water that makes it unfit for drinking, irrigation, industry or life in the water. Causes: domestic sewage, industry (dye, leather, sugar, metal), farm fertiliser–pesticide runoff, festival and city waste in a river, oil spills. Organic load eats dissolved oxygen (DO). BOD (biochemical oxygen demand) is the oxygen bacteria need to break organic matter — high BOD means more pollution. COD is chemical demand. Eutrophication is nutrients (N, P) driving an algal bloom, then oxygen crash, then dead fish — Unit 2’s fertiliser returns here. Pathogens in water bring cholera, typhoid, dysentery. Heavy metals (mercury, lead, arsenic, regional fluoride) reach top predators and people by biomagnification.

Control: sewage treatment (primary settling, secondary biological, tertiary nutrient/germ), industrial effluent on a standard, drains kept off the river, a belt at the reservoir edge, less fertiliser, oil barriers. In a dry region, groundwater fluoride and salt are already a problem; add nitrate and sewage and the well is a polluted point too. A field polluted site is often a riverbank or a drain — colour, smell, foam, dead fish are signs, not a lab report.

Soil pollution is chemicals or wastes in the soil that harm soil life, crops or groundwater. Causes: heavy fertiliser and pesticide, industrial and mine waste, heavy metals, plastic and oil on land, untreated sewage sludge, ash from burned e-waste, saline irrigation (Unit 2’s salinity becomes a pollutant here). The living skin of soil — earthworm, microbes — dies; residues enter the crop; rain carries pollutants to groundwater. Bare patches, low yield, contaminated vegetables are effects.

Control: organic manure, integrated pest management, safe landfill of hazardous waste, stop refinery leaks, crop rotation, phytoremediation (some plants take up metal) where it is scientific, do not burn plastic. Soil takes centuries to form — pollution spoils it faster even than Unit 2’s erosion. Mine dust sits in both air and soil, so one site can join two headings.

Do not mix this heading with Unit 2’s land degradation. Erosion, a gully and a bare slope are loss of soil as a resource. Pollution is chemicals and wastes in the soil — pesticide, metal, plastic, oil, saline irrigation. One field can show both. The official four rooms still apply: definition, cause, effect, control.

Marine pollution is pollution of seas and coasts. Causes: oil from tankers and wells, ship garbage, plastic and nutrients via rivers, coastal city sewage, dredging, sometimes dumped munitions. An oil film cuts light and gas exchange, sticks birds’ feathers, kills fish eggs. Plastic pieces are swallowed; microplastic sits in food chains. Nutrients make coastal eutrophication and dead zones (hypoxia). Coral pales from heat and from murk — climate touches it, so does waste.

Control: tanker standards, spill readiness, less plastic, coastal sewage treatment, saving mangrove and estuary (Unit 3’s high-production zone is hurt first). A landlocked state still sends plastic to the sea by river and canal — “marine” is not only a fisher’s paper.

Minamata (mercury in fish climbing to people) is the college books’ biomagnification example for the sea. An oil spill is both a film on water and tar on a beach; booms and skimmers are control at the surface, mangrove is control at the coast. Definition, cause, effect, control — the same four rooms as air or water.

Noise pollution is unwanted sound that harms health or wildlife. It is an energy pollutant, not a substance — measured in decibels (dB). Causes: traffic, industry, generators, building, loudspeakers, crackers, airports. Effects: hearing loss, stress, blood pressure, broken sleep, children’s study, wildlife communication. Night noise can harm more than day noise. WHO and Indian standards set different day–night limits for residential zones. Higher dB, more harm; long contact at about 80–90 dB can damage hearing.

Control: quieter machines at source, silencers, green belt and wall, zoning (school and hospital as quiet zones), limits on crackers and speakers, ear protection in industry, horn discipline. Sound spreads like air and is also absorbed — trees and distance help; a closed room can boom.

A quiet room is near 30 dB; ordinary speech near 60; long contact near 80–90 can damage hearing; around 120 is pain. Night limits are usually stricter than day limits in a residential zone. Horn and loudspeaker hours are the local face of this heading.

Thermal pollution is a rise (sometimes a fall) in the temperature of water or air that harms living things. The clean example is cooling water from thermal and nuclear plants released into river or sea. Warm water holds less dissolved oxygen; fish and eggs are sensitive; the algal balance breaks; some species leave. Urban concrete and vehicles make a “heat island” in air — related, but the syllabus centre here is water-heat.

Control: cooling towers, reuse of heat, do not dump hot water straight into the river, careful siting of plants, plant shade. Heat itself is not a poison; oxygen and enzyme limits make it one. Thermal pollution is not only hot wind; plant cooling water into a river is the textbook case.

Nuclear hazards are ionising radiation (α, β, γ, neutrons) and radioactive waste. Sources: power plants, uranium mines, medical X-ray/isotopes, weapons tests, accidents (Chernobyl, Fukushima — Bhopal is chemical, not nuclear). Effects depend on dose and time — burns, cancer, genetic damage, iodine to the thyroid, strontium to bone. A long half-life means waste is a risk for generations. Unit 2’s energy lesson can present nuclear as low-carbon; this lesson is its shadow.

Control: shielding, distant siting, deep geological holding of waste under watch, accident plans, no needless medical radiation, mine-tailings management. A person’s work is to follow official instructions on iodine or evacuation, not rumour. The syllabus prints “nuclear hazards” — peaceful use is not zero risk.

Urban solid waste is the mix of home, market and street — food, paper, plastic, glass, metal, sanitary. Industrial waste is slag, ash, sludge, sometimes hazardous chemicals. Biomedical and e-waste need separate rules. Causes: consumption, packaging, short product life, incomplete collection. Effects: blocked drains, polluted groundwater, methane, fire, animals and crows, disease vectors, marine plastic. An open heap is not management; a sanitary landfill is layers, liner, leachate collection.

The order of control: reduce, reuse, recycle (3R; a fourth R sometimes splits reject). Wet–dry sorting starts at the house. Compost and biogas are the path for food remains. Incineration saves space and risks dioxin — filters are needed. Industrial hazardous waste does not go on the ordinary heap. Extended producer responsibility for packaging is policy, not a slogan.

Prevention starts in conduct. Air: do not burn trash and leaves, keep the vehicle right, walk or bus where it works, fewer crackers. Water: no oil or paint in the drain, less soap-chemical, close leaks — Unit 2’s saving here also cuts pollution. Soil: not extra pesticide, do not bury plastic. Noise: horn, speaker. Waste: wet–dry split, a bag used again, e-waste to a shop or centre. Using less is the cheapest control.

The person is not a substitute for policy: a sewage plant is the city’s work. But a household open heap beats the plant. Naming a local polluted site — smell, dust, drain — joins Unit 1’s awareness. Reporting and panchayat pressure are civic roles, not only a switch.

A disaster is sudden large harm; management is a cycle — prevention, readiness, relief, rehabilitation. Flood: heavy rain, silt, deforestation, houses on the floodplain, dam gates (Unit 2). Effects: drowning, disease, crop, snakes and live wires. Management: warning, evacuation, clean drains and embankments, keep the floodplain empty, relief camps, boil water. Sudden urban waterlogging and a broken canal are flood-forms too.

Earthquake: plate motion, faults; Himalaya and the western edge of India are more sensitive, a desert plain is less but not zero (think in seismic zones; code numbers move). Richter is a measure of size. Harm comes from buildings, not only from shake. Readiness: building codes, heavy things low, drill — Drop, Cover, Hold; relief is rubble, medicine, gas and fire shut. A tsunami follows a coastal quake; this paper’s centre is building safety.

A cyclone is a spinning low over warm sea — in India the Bay of Bengal more often, the Arabian Sea also. Wind, rain and storm surge wreck the coast. Mangrove and coastal forest are a buffer (Unit 3–4 habitat as a shield). Management: weather-office warning, evacuation, cyclone shelters, boats ashore, cut power, relief. Named storms are examples; the principle is warning and evacuation, not a name-list.

A landslide is a hill slope breaking — rain, earthquake, road cutting, blast, trees removed (Unit 2’s man-induced). Himalaya and the Western Ghats stand in front. Check: drainage, walls, no building on a crack, a tree line, warning. The syllabus keeps four disaster names together — flood, earthquake, cyclone, landslide. Pollutant media change; the formula is one — control the source, do not spread the path, person and city both. Policy and law sit on that formula in Unit 6.