Pollution — Types and Sources

Answer the following questions

Question 1

Define pollution. How is it caused?

Answer

The presence or introduction of a substance in the environment that is harmful or has poisonous effects, is called pollution.

Pollution is caused by improper management of resources or by careless human activities. They may be caused naturally or by human activities.

Question 2

State the causes of soil pollution.

Answer

The causes soil pollution are deposition of solid waste, accumulation of non-biodegradable material and toxic chemicals etc., which come from the following sources:

1. Industrial waste — Industrial waste containing chemicals, when dumped in soil, cause soil pollution. For example, fly ash from thermal plants, chemicals from oil refineries pollute the soil.
2. Urban commercial and domestic waste — Non-biodegradable wastes like glass, plastic, polythene bags remain in the soil for a long time.
3. Chemical fertilizers — Chemical fertilizers when used, disturb the natural balance of the soil. They also contaminate water bodies through run-off.
4. Biomedical waste — Hospital wastes containing plastics, metal needles and chemicals are dumped in soil.
5. Pesticides — Pesticides show permanent accumulation in soil in the form of nitrates and phosphates.

Question 3

State the effects of freshwater pollution. How is it caused?

Answer

The effects of freshwater pollution are:

1. Eutrophication and death of aquatic animals — Nitrate and phosphate accumulate in water bodies with run off water. They may be derived from fertilizers and detergents. They overstimulate the growth of aquatic plants and algae, resulting in eutrophication.
2. Disturbance in aquatic ecosystem — Leached heavy metal and chemicals may kill aquatic animals and plants disturbing the aquatic ecosystem.
3. Oil spill results in a layer of oil over the water surface, insulating the water from the atmosphere. This lowers the level of dissolved oxygen in water and ultimately leads to loss of aquatic life.
4. Many industries dump hot water in the freshwater bodies which raises the temperature of water and causes adverse effects on the aquatic creatures.

Freshwater pollution is caused due to:

1. Natural sources — The natural sources are gases, animal waste, living organisms, soil, minerals (Nickel, Cobalt, Lead and Mercury etc.) and other pollutants soluble in water.
2. Human sources — Urbanization and industrialization have resulted in excessive water pollution. The human sources of water pollution can be classified as follows:
   1. Sewage and Domestic waste
   2. Industrial waste
   3. Agricultural waste
   4. Nuclear waste
   5. Oil spills
   6. Thermal pollution

Question 4

How do agricultural wastes harm the environment?

Answer

Agricultural wastes harm the environment in the following way:

1. Agriculture, including commercial livestock and poultry farming is a source of many organic and inorganic pollutants in surface waters. Pesticides from agricultural run off, metals and processed chemicals are also major sources of water pollutants.
2. Excess nitrates and phosphates lead to Eutrophication in water bodies which leads to loss of aquatic life and disturbs the aquatic ecosystem.
3. Chemical fertilizers and pesticides contain potassium and phosphorus, which are released in water bodies through run-off water. This also affects the plant growth in the soil.
4. Radio-tracers extensively used in agriculture are also responsible for radiation pollution.

Question 5

Which gases are emitted through refrigerators and air-conditioners?

Answer

Chlorofluorocarbons are the gases emitted through refrigerators and air-conditioners.

Question 6

Differentiate between the natural and man-made sources of pollution.

Answer

Question 7

What is meant by oil spill?

Answer

The leakage or spill of oil in the sea causes a layer of oil spreading on the surface of water. This is known as oil spill. The oil spread on the sea water acts as an insulating layer between air and water. Due to this, the oxygen of the atmosphere cannot mix with water and causes death of aquatic creatures.

Question 8

How is oil spill caused?

Answer

Oil spill may be caused in the following ways:

1. waste oil from city drains, tankers
2. leakage from oil well
3. accidental oil spill

Question 9

What is meant by radiation?

Answer

The emission of highly charged particles and electro-magnetic rays from radioactive substances is called radiation.

Question 10

Explain the following terms :

(a) Smog

(b) Pollutants

(c) CFC

(d) Eutrophication

Answer

(a) Smog — The term 'smog' is derived from 'smoke + fog' as it is formed due to mixing of smoke and fog. Smog is common in industrial areas in winters. It reduces visibility and is unhealthy for humans, animals and plants.

(b) Pollutants — The substances or materials that cause pollution are called pollutants. They are harmful for the environment and living beings. They can be natural such as volcanic ash or man-made like plastic.

(c) CFC — CFC or Chlorofluorocarbons are the synthetic chemical compounds which are used as refrigerant or cooling agent in AC and refrigerators. When these chemicals are released in atmosphere, they split due to ultraviolet rays and damage the ozone layer.

(d) Eutrophication — The process by which the excess phosphates and nitrates lead to over growth of algae and other aquatic plants in a water body, depleting the oxygen of water, is called Eutrophication.

Question 11

Write a short note on the following:

(a) Radiation

(b) Oil spill

(c) Air pollution

(d) Noise pollution

Answer

(a) Radiation — Radiation pollution is the emission of highly charged particles and electromagnetic rays entering the earth's atmosphere. Sources of radiation may be natural or man-made. Natural sources consist of cosmic rays that pollute the life supporting systems like air, water and soil. Man-made sources consist of waste water from nuclear power stations, mining of uranium ore, waste from hospitals where isotopes are used for diagnostic and therapeutic purposes etc.

(b) Oil spill — The leakage or spill of oil in the sea cause a layer of oil spreading on the water. This is known as oil spill. The oil spread on the sea water acts as an insulating layer between air and water. Due to this, the oxygen of the atmosphere cannot mix with water. It leads to death of aquatic animals due to deficiency of dissolved oxygen. The birds cannot fly as their feathers are oil-soaked.

(c) Air pollution — The contamination of air with harmful gases and particles is called air pollution. Natural sources of air pollution consist of volcanic eruption, dust storms and forest fires. Man-made sources consist of burning of fossil fuels, use of CFCs, industrial and construction wastes etc. Air pollution leads to poor air quality which further result in breathing problems, lung diseases, smog, damage to buildings and also disrupts ecological balance.

(d) Noise pollution — Any sound that causes annoyance is regarded as noise and is considered as a source of pollution. Sound level of about 80 decibels causes noise pollution. The sources of noise pollution are aeroplanes,trains, loud-speakers, fire crackers and industries etc. Noise pollution cause discomfort, deafness, high blood pressure, palpitation, headache etc.

Question 12

What kind of pollution is produced by brick kilns?

Answer

Brick Kilns cause air pollution. They use coal to burn the bricks. They give out huge quantity of carbon dioxide and particulate matter such as smoke, dust which is very harmful. Brick kilns cause air pollution.

Question 13

How is thermal pollution caused?

Answer

The thermal power plants release the recycled hot water into the rivers and sea causing water pollution. The hot water raises the temperature of the water body. It can lead to a decrease in the dissolved oxygen level in the water while also increasing the biological demand of aquatic organisms for oxygen.

Question 14

What are the sources of radioactive pollution?

Answer

The sources of radioactive pollution are:

1. Natural sources — Cosmic rays emit radioactive radiation.
2. Man-made sources — waste water from nuclear power plant, waste generated during nuclear weapon testing, mining and processing of uranium ore, waste generated from hospitals and research laboratories where radioisotopes are used, X-ray waste, nuclear accidents, nuclear bomb explosions and use of radio tracers.

Question 15

How do water bodies get contaminated by the effluents from industries?

Answer

Water bodies get contaminated by the effluents from industries in following ways:

1. Waste and sewage generated by industry can get into the water supply, introducing large organic pollutants into the ecosystem.
2. Most of the industries release chemicals like chlorides, sulphides, carbonates, nitrates and metal like Zinc, Mercury, Copper, Chromium, etc. in the rivers or their water sources.
3. Water can become contaminated with toxic or radioactive material from the industry, mine sites and abandoned hazardous waste sites.
4. Air pollution leads to acid precipitation which lower the overall pH of lakes, streams, and ponds; thereby killing vital plants and affecting the whole food chain.
5. Leaching of heavy metals from soil into the water bodies leads to contamination of water. It may kill aquatic flora and fauna.

Question 16

What is the difference between primary and secondary pollutants?

Answer

Question 17

How does urbanization cause air pollution?

Answer

Urbanization has resulted in concentration of industries around the cities. Big and small industries, power plants, brick kilns create air pollution. Also there are numerous vehicles in the urban areas creating a lot of air pollution. Urbanization causes air pollution in following ways:

1. The burning of fuels in automobiles and aeroplanes lead to emission of Carbon Monoxide and Hydrocarbons containing nitrogen and oxygen.
2. Industries like il refinery discharge Ammonia, Hydrocarbons and Sulphur oxide. Aluminium plants release fluoride dust.
3. Burning of garbage lead to emission of carbon dioxide and nitrogen oxide.
4. Brick kilns also release huge quantity of Carbon dioxide and particulate matters.
5. Use of cleansing agents release chemicals like Ammonia and chlorine, causing indoor pollution.
6. Use of radioactive elements or use of isotopes(medical purpose) lead to emission of α, β and γ radiations.

Choose the correct option

Question 1

Which of the following reasons is the main cause of Acid rain?

1. Due to the emission of CO2 in the air
2. Due to the emission of Carbon Monoxide in the air
3. Due to the emission of Sulphur dioxides in the air
4. All the above

Answer

Due to the emission of Sulphur dioxides in the air

Question 2

Which of the following is a secondary pollutant?

1. Smoke
2. Ozone
3. Sulphur dioxides
4. Dust

Answer

Ozone

Question 3

SPM stands for

1. Suspended Poisonous Matter
2. Soluble Poisonous Material
3. Smoky Particulate Matter
4. Suspended Particulate Matter

Answer

Suspended Particulate Matter

Question 4

Which of the following chemical compounds is mainly responsible for the formation of ozone hole?

1. CO₂
2. CFC
3. SO₂
4. NO

Answer

CFC

Question 5

Study the picture and identify which type of environmental pollution is mainly caused by the activity practised here.

1. Noise pollution
2. Water pollution
3. Air pollution
4. Radioactive pollution

Answer

Air pollution

Question 6

Study the picture and identify the type of environmental pollution caused here.

1. Soil pollution
2. Water pollution
3. Air pollution
4. Radioactive pollution

Answer

Water pollution

Question 7

Thermal pollution is caused by

1. the discharge of fertilizer on the Water body
2. the discharge of domestic waste in the water body
3. the discharge of hot water of thermal power plants in the water body.
4. All the above

Answer

The discharge of hot water of thermal power plants in the water body

Question 8

Which of the following is not a man-made source of radioactive pollutant?

1. Wastes from the nuclear power stations
2. Mining & processing of Uranium Ore
3. Cosmic rays
4. X-ray wastes

Answer

Cosmic rays

Question 9

Study the picture and identify the type of environmental pollution caused here.

1. Soil pollution
2. Noise pollution
3. Air pollution
4. Radioactive pollution

Answer

Noise pollution

Question 10

Which of the following is not a man-made source of air pollution?

1. Automobile pollution
2. Forest fires
3. Industrial pollution
4. Brick Kilns

Answer

Forest fires

Give reasons for the following

Question 1

Noise pollution is prevalent in towns and cities.

Answer

Noise pollution is prevalent in towns and cities due to a large number of vehicles on the roads, numerous construction projects like building of flyovers, metro and high rises, aeroplanes, trains, loud-speakers, high-pitched music, fire crackers, etc. Moreover, often no noise barriers or sound-absorbing materials are installed in public spaces and noise limits are not enforced.

Question 2

Acid rainfall is a result of the burning of fossil fuel.

Answer

Acid rainfall is a result of the burning of fossil fuels because the combustion of these fuels releases pollutants such as sulphur dioxide (SO₂) and nitrogen dioxide (NO₂) into the atmosphere. These pollutants can react with water, oxygen, and other chemicals in the atmosphere to form acidic compounds, such as sulphur acid (H₂SO₄) and nitric acid (HNO₃). These acidic compounds then mix with precipitation, such as rain or snow, and fall to the ground as acid rainfall.