Sources of Pollution
ICSE Class 9 · Geography · Chapter 17
What this chapter covers
- What a source of pollution is
- Sources of noise pollution
- Sources of air pollution
- Sources of water pollution
- Sources of soil pollution
- Sources of radiation pollution
- Linking sources to types of pollution
Key points
- A source of pollution is the place, activity or object from which a pollutant or harmful energy is released; sources may be fixed, such as factories, or moving, such as vehicles.
- One source often causes several types of pollution; a thermal power station pollutes the air, water and soil and is also noisy.
- Noise pollution comes from traffic (engines, tyres and especially horns), factories, construction sites, loudspeakers and firecrackers, and airports.
- Air pollution comes from vehicles (carbon monoxide, oxides of nitrogen, hydrocarbons, soot and road dust), industries (thermal power stations, steel, cement, refineries, brick kilns) and the open burning of garbage and crop residue.
- The Bhopal gas tragedy of 1984 shows how a single industrial source can release deadly pollution at once.
- Domestic waste, chiefly untreated sewage, is the largest source of water pollution in India; less than a third of urban sewage is treated.
- Industrial effluent carries chemicals, dyes, heavy metals and heat into rivers, as from the tanneries of Kanpur and the dyeing units of Tiruppur.
- The sea is polluted by sewage and effluent from coastal cities, by plastics, and by oil from tankers, ships and offshore oil fields.
- Soil is polluted by excess chemical fertilisers, by bio-medical waste dumped without treatment, and by persistent pesticides such as DDT and endosulfan.
- Radiation pollution comes from X-rays used carelessly or too often, and from radioactive fallout and waste from nuclear plants, as in the Chernobyl (1986) and Fukushima (2011) accidents.
Questions answered
What is meant by a source of pollution? Why is it important to know the source of a pollutant?
A source of pollution is the place, activity or object from which a pollutant, or harmful energy such as sound or radiation, is released into the environment. Knowing the source shows where control must begin, and stopping a pollutant at its source is easier and cheaper than cleaning it up after it has spread.
Name five sources of noise pollution. Which of them is the most widespread in Indian cities, and why?
Traffic, factories, construction sites, loudspeakers and airports. Traffic is the most widespread because vehicles run on every road for most of the day and night, and the frequent use of horns at crowded junctions adds greatly to the noise of engines and tyres.
Why are airports a serious source of noise for people living near them?
A jet taking off produces about 140 dB near the runway and remains loud along the flight path for several kilometres. Many Indian airports now have residential colonies close to their runways, so people hear aircraft every few minutes, and night flights disturb their sleep.
Name three pollutants present in vehicle exhaust and state how any one of them is formed.
Carbon monoxide, oxides of nitrogen and unburnt hydrocarbons (diesel soot is also accepted). Carbon monoxide is formed when fuel burns with too little oxygen, as happens in idling engines and poorly maintained vehicles.
Give two reasons why vehicular pollution is worse in traffic jams.
Engines idle for long periods, so fuel burns incompletely and more carbon monoxide and unburnt hydrocarbons are given out. Many vehicles are packed into a small area, so their exhaust collects in the street instead of spreading out.
Explain why coal-fired thermal power stations are a major source of air pollution in India.
Most of India's electricity is produced by burning coal, and Indian coal has a high ash content of 30 to 45 per cent. Burning it releases sulphur dioxide, oxides of nitrogen and carbon dioxide, along with huge quantities of fly ash that settle on the surrounding land.
Why is the open burning of garbage especially harmful when the garbage contains plastic?
Plastic burnt at the low temperature of an open fire gives out thick smoke and toxic substances such as dioxins and furans, which are among the most poisonous chemicals known, and the smoke stays close to the ground where people breathe it.
Distinguish between domestic waste and industrial waste as sources of water pollution, with one example of each.
Domestic waste comes from homes and the daily life of towns and consists mainly of sewage, kitchen and bathroom waste water and garbage; an example is untreated sewage from Delhi's drains entering the Yamuna. Industrial waste is effluent discharged by factories and carries chemicals, metals, dyes or heat; an example is chromium-laden waste from the tanneries of Kanpur entering the Ganga.
Past board exam questions
ICSE 2019 sample paper · 2 marks
Explain how industrial waste and vehicular emission act as the source of air pollution.
Show answer
Industries burn coal and oil and release smoke containing sulphur dioxide, nitrogen oxides, carbon monoxide, dust/particulate matter and toxic gases into the air. Vehicles burn petrol and diesel and emit carbon monoxide, nitrogen oxides, hydrocarbons, lead and fine particles through their exhaust. These pollutants mix with the air and pollute it.