NIOS Class 12 Environmental Science Chapter 10 Environmental Pollution

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NIOS Class 12 Environmental Science Chapter 10 Environmental Pollution

Also, you can read the NIOS book online in these sections Solutions by Expert Teachers as per National Institute of Open Schooling (NIOS) Book guidelines. These solutions are part of NIOS All Subject Solutions. Here we have given NIOS Class 12 Environmental Science Chapter 10 Environmental Pollution Solutions, NIOS Senior Secondary Course Environmental Science Solutions for All Chapter, You can practice these here.

Environmental Pollution

Chapter: 10

Module 4: Contemporary Environment issues

Textual Question Answer

INTEXT QUESTIONS 10.1

1. Define pollutant and pollution. 

Ans: (a) Agents which cause environmental pollution are called pollutants.

(b) Addition to undesirable materials into the environment as a result of human activities.

2. Name any three devices that control pollution.

Ans: Filters, electrostatic precipitators and inertial collector.

3. State two means of controlling indoor air pollution.

Ans: (i) The wastes from the hospitals should be sterilised and treated properly. 

(ii) Kitchens and rooms should have proper ventilation and natural gas used to be promoted.

4. What is a PUC certificate? 

Ans: Pollution Control Certificate that ensures the levels of certain pollutants are not released in the exhaust of vehicles beyond the legal limits.

INTEXT QUESTIONS 10.2

1. What is noise and in which unit it is measured? 

Ans: Noise is defined as “sound without value” or “any noise that is unwanted by the recipient”.

Sound intensity is measured in Decibels (Db).

2. State two harmful effects of noise pollution.

Ans: Disturb sleep and emotional problems.

3. State two important indoor and two outdoor sources of noise pollution? Mention method of control for each of them.

Ans: Better designing and proper maintenance of vehicle, use of noise abatement measures, appropriate insulation and introduction of noise regulation for take off aircrafts, use of electric locomotives, using of sound proofing equipment.

INTEXT QUESTIONS 10.3

1. Name the metals which when in access in drinking water cause Minamata and Itai itai diseases.

Ans: Mercury and cadmium.

2. When fertilizers and sewage enter a water body phytoplankton and algae grow rapidly. What is this phenomenon called.

Ans: Eutrophication.

3. What is primary treatment? What is removed from water effluents during primary treatment.

Ans: Primary treatment removes suspended particulate matter and floating materials.

4. The water used for cooling purposes in industries may be drained industrial into rivers. To what extent does this raise the water temperature of the river? 

Ans: Increase in water temperature upto 10 to 150C above the ambient water temperature.

5. What effect does thermal pollution have on the swimming efficiency of fish?

Ans: Swimming efficiency of fish declines.

6. What effect does thermal pollution have on metabolism of aquatic animals?

Ans: Metabolism of aquatic animals increase and affect their growth.

7. State the term for residue left after primary treatment of waste water.

Ans: Sludge.

INTEXT QUESTIONS 10.4

1. Define soil pollution.

Ans: Addition of substances which adversely affect the quality of soil or fertility is known as soil pollution.

2. Why are plastic bags a big environmental nuisance?

Ans: Plastic bags are indestructible and create colossal environmental hazards.

3. Vermicomposting degrades organic waste into a useful substance. What is this substance used for? 

Ans: This substance is manure and used in agriculture.

INTEXT QUESTIONS 10.5

1. Which type of radiations are produced in a microwave oven? 

Ans: Non-ionizing radiations.

2. State the use of absorbed dose of radiation? 

Ans: Absorption of radiation to be the amount of energy deposited in the region of the body divided by the mass of the portion of the body that absorbed the radiation.

3. How much of radiation can damage internal organs upon its exposure for a few days.

Ans: Higher dozes (up to 100 rem) can damage internal organs upon exposure of it.

TERMINAL EXERCISE

1. Define the terms pollution and pollutant.

Ans: Pollution may be defined as addition of undesirable material into the environment as a result of human activities. 

The agents which cause environmental pollution are called pollutants. 

2. List the environmental problems faced by women inside the rural households. Suggest measures to reduce or eliminate them.

Ans: Rural households use traditional fuels like cow dung and wood, the burning of which generates harmful smoke. The smoke has carbon dioxide and carbon monoxide like toxic gases. Women working in rural households with such fuel are at a risk for respiratory diseases.

LPG (liquid petroleum gas) is a cleaner fuel than burning wood and cow dung. It is safer to use as well.

3. Why was CNG introduced as a fuel for automobiles in a city like Delhi? Has it made any difference?

Ans: Delhi is the most polluted city not only In India but in the world. Automobiles emit a lot of carbon monoxide, carbon dioxide, oxides of nitrogen, and hydrocarbons by burning petrol. CNG is a cleaner fuel than petrol or diesel. It emits fewer pollutants and left fewer residue after burning. The year of study by the researchers from 1991 till date showed a decline in the emission of substances like carbon monoxide.

4. Manufacture of chlorofluorocarbons is to be phased out as per ‘Montreal protocol’ Why?

Ans: Chlorofluorocarbons are generally used as a coolant in refrigerators. These cause the conversion of ozone back into molecular oxygen when released into the environment. This conversion is responsible for the thinning of the ozone layer. The thinning of the ozone layer is a threat to life-forms of the earth as this layer protects us from harmful UV rays of the sun that causes several diseases including skin cancers.

5. Describe an environmental friendly method to profitably dispose off human waste and cattle waste.

Ans: Human and cattle waste as well as agricultural waste can be used for the production of biogas. The methanogens like Methanococcus bacteria convert such wastes into biogas which can be used as fuel. The biogas plants that are set up in rural areas take very less cost for installation and provide more profit. Biogas production needs materials like wastes from humans, cattle as well as agricultural fields, Biogas is eco-friendly, which means it does not cause harm to the environment and is profitable as well. Biogas has methane, carbon dioxide, and a lesser amount of carbon monoxide. The bacteria that produce biogas from the human and cattle wastes work in the absence of oxygen.

6. Chemical fertilizers are useful to crops. In which way they cause environmental pollution?

Ans: Chemical fertilizers such as nitrates and phosphates are widely used to increase crop yield, but they also create serious environmental problems:

(i) Water Pollution: When fertilizers leach into rivers, ponds, and groundwater, they enrich the water with excess nutrients (mainly nitrogen and phosphorus).

(ii) Eutrophication: The nutrient enrichment promotes rapid growth of algae and phytoplankton. When these die and decompose, dissolved oxygen in water is depleted, leading to the death of fishes and other aquatic life.

(iii) Nitrate Poisoning: Animals and humans drinking water contaminated with nitrates may suffer from diseases like methemoglobinemia (“blue baby syndrome”) and other health hazards.

(iv) Soil Pollution: Long-term overuse of fertilizers also reduces soil fertility and disturbs natural microbial balance.

Thus, while fertilizers improve crop productivity, their uncontrolled use pollutes soil and water ecosystems, and threatens both human and animal health.

7. What steps can be taken to reduce pollution due to particulate matter from industries?

Ans: Several devices can control the emission of particles of dust and smoke into the environment. The use of filters, electrostatic precipitators, and scrubbers helps to reduce the emission of dust and smoke particles into the atmosphere. The filters are used to filter out the fine particles of dust and smoke from the gases pollutant. They can be made up of rigid or granular material that can be synthetic also. Electrostatic precipitators trap the charged particles of dust as they have oppositely charged ions. Thus they prevent the emission of harmful particulates into the environment. The scrubbers are generally a wet medium that absorbs the pollutant from the stream of gas. The medium can also include activated carbon or silica gel for the absorption of pollutants.

8. What is a PUC certificate? Is it necessary and for whom? In your opinion is it really useful?

Ans: A PUC certificate (Pollution Under Control certificate) is a document that certifies that the emissions from a vehicle are within the prescribed legal limits. It is mandatory for all motor vehicles in India to carry a valid PUC certificate, not only in Delhi but across the country. It is necessary because vehicles are a major source of air pollution, and regular checks help in controlling harmful emissions. The certificate is really useful, but only when tests are conducted honestly and strictly, without negligence or corruption. 

9. What is a medical waste? Why it is called hazardous waste? What is the safe way to dispose medical waste.

Ans: Medical waste is the waste generated from hospitals. Anatomical waste is hazardous as it can cause infections in healthy people. Gloves, wipes, and garments with body fluids are infectious waste. Treatment of thyroid uses radioactive iodine, which is kept in radioactive waste. Biomedical waste has the potential to cause diseases because of the infectious microbes present in the waste. It should be sterilized for its disposal. The autoclave is commonly used for sterilization purposes where a load of microbes present in the waste is reduced to a certain level and it becomes safe for disposal. Other ways are incineration, disinfection by chemicals, or irradiation. The waste generated from hospitals, biomedical waste is segregated and different colored disposal bags are used to dispose of different kinds of wastes. The healthcare workers, patients as well as the general public can be affected by the biomedical waste. The yelloW-colored bag is used for disposing of infectious waste. The red-colored container contains hazardous waste. The white-colored container is radioactive and the black-colored container has general medical waste.

10. Suggest the way to improve the water quality it has undergone primary treatment?

Ans:  After primary treatment, water quality can be improved by adopting secondary and tertiary treatment methods. In secondary treatment, biological processes such as the activated sludge process or trickling filters are used to remove dissolved and organic matter. In tertiary treatment, methods like chlorination, UV disinfection, ozonation, and advanced filtration are applied to kill bacteria and pathogens and to further purify the water. These steps make the water safe for reuse or discharge into natural water bodies. 

11. What are the causes and effects of thermal pollution on the life of aquatic animals like fish? What measures you would suggest to prevent thermal pollution?

Ans: The water used for cooling the pieces of machinery gets heated up during the cooling process. Aquatic animals are cold-blooded animals. they cannot adjust their internal body temperature on their own. Any change in the temperature of the external environment costs their survival. Fishes are badly affected by thermal pollution. Their efficiency of swimming has declined hence they can not escape easily from predators or chase their prey. The metabolism rate is increased and growth is very much affected. The water from the cooling of machinery should be kept in cooling ponds before releasing it into the water bodies directly.

12. What are ionizing and non-ionizing radiations? Give examples.

Ans: Ionizing radiations are those radiations that provide enough energy to an atom so that it could be displaced to its ground state to the excited state. Example- X Rays, gamma rays. Non-ionizing radiations generally lie in the visible spectrum and they can vibrate the atoms that are present in the medium through which the radiations pass. Example-radio waves, infrared waves.

13. List the possible damages caused to humans by radiation pollution.

Ans: Radiations from nuclear power plants or nuclear explosions have a deep impact on the people living in nearby areas. Radiations lead to cancers and some other permanent disabilities in humans. Radiations, especially ionizing radiations are harmful. They can penetrate deep into the internal organs and can cause damage. The mutations in the genetic material occurring due to long-term exposure to the radiation results in the formation of cancerous cells. The cell with mutated genes gets into the cell cycle, as a result, the growth of the cell occurs uncontrollably.

14. How can cancer be caused by radiation?

Ans: Radiation alters the genetic material of the cells. The cells then divide uncontrollably. The non-ionizing radiations like radio waves do not penetrate deep into the internal organs hence are not that much harmful as the ionizing radiations. Ionizing radiation like X-rays can penetrate the internal organs and the cells then behave abnormally hence divide uncontrollably to form the cancerous cell.

15. Briefly describe soil pollution, its causes and methods of control.

Ans: Soil pollution refers to the contamination of soil with unwanted and harmful substances that reduce its fertility and quality. Polluted soil loses its ability to support healthy plant growth, and the toxic substances often leach into groundwater, causing water pollution and affecting both humans and animals.

Causes of Soil Pollution:

(i) Excessive use of chemical fertilizers and pesticides – increases crop yield but leaves harmful residues in the soil.

(ii) Plastic waste – non-biodegradable, remains in soil for years, reduces fertility, and harms animals when ingested.

(iii) Industrial waste – chemicals, heavy metals, and other toxic substances discharged into soil.

(iv) Urbanization and deforestation – large-scale construction and land clearing degrade soil quality.

(v) Improper disposal of solid waste – garbage and biomedical waste pollute the soil.

Methods of Control:

(i) Use of organic manures and bio-fertilizers instead of chemical fertilizers.

(ii) Reduce and ban plastic bag usage; promote biodegradable alternatives.

(iii) Proper disposal and treatment of industrial waste before releasing into soil.

(iv) Bioremediation and vermicomposting to recycle organic waste.

(v) Afforestation and controlled land use to prevent soil degradation.