NIOS Environmental Science (333) Notes/Answer| Chapter-5|Environmental Pollution

NIOS Environmental Science (333) Notes/Answer| Chapter-5|Environmental Pollution. Important questions for NIOS Environmental Science (333) Questions Answers brings you latest queries and solutions with accordance to the most recent pointers SOS . Students will clear all their doubts with regard to every chapter by active these necessary chapter queries and elaborate explanations that area unit provided by our specialists so as to assist you higher. These queries can facilitate students prepare well for the exams thanks to time constraint . NIOS Environmental Science (333) Notes/Answer| Chapter-5|Environmental Pollution

HS 2nd years Solutions (English Medium)

NIOS Environmental Science (333) Notes/Answer| Chapter-5|Environmental Pollution

Very Short Questions: Marks: 1/2

1. Fill in the blanks :

a) The term pollution is derived from the latin word __________ 

Ans: Pollutionem 

b) 70% of iron is found in __________of the human body.

Ans: Haemoglobin

c) The ground water contains__________ amount of iron.

Ans: 0.5 to 100mg/liter.

d) One CFC molecule can destroy __________ number of ozone molecules.

Ans: 1,00,000

Short Questions with Answers: ▸▸ Marks: 4/5

1. Give one reason for the increase in human population. 

Ans: Improved agricultural practices have helped in increasing food production, hence food became available leads to increase in human population. 

2. What is deforestation?

Ans: Deforestation is when humans remove or clear large areas of forest lands and related ecosystems for non-forest use. These include clearing for farming purposes, ranching and urban use. In these cases, trees are never re-planted.

3. List any three human activities that have resulted into desert formation.

Ans: Over exploitation/uncontrolled grazing/indiscriminate felling of trees/intensive and uneconomic exploitation of water resource leading to fall in water table/ uneconomic land use for agriculture.

4. Define pollutant and pollution. 

Ans: Agents which cause environmental pollution are called pollutants. Addition to undesirable materials into the environment as a result of human activities is called pollution.

5. State two means of controlling indoor air pollution. 


  1. Use of wood and dung cakes should be replaced by cleaner fuels such as biogas, kerosene or electricity.
  2. Improved stoves for looking like smokeless chullahs have high thermal efficiency and reduced emission of pollutants including smoke.

6. What is removed from water effluents during primary treatment.

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

7. How the secondary Pollutants are formed?

Ans: The Secondary pollutants are formed by the natural causes or chemical reaction from the primary pollutants. 

8. Which type of water is not fit for drinking?

Ans: Water for drinking by humans must be free from pathogenic microorganisms and other substances which are hazardous to health. If the water sample is highly turbid, highly coloured or with objectionable taste should be rejected.

9. Which diseases are caused by the presence of fluoride in water? 

Ans: Dental fluoresces and skeletal fluoresces are the diseases caused by presence of fluoride in water.

10. What are the auditory effects of noise pollution?

Ans: The auditory effects of noise are imparing of hearing which may cause auditory fatigue and defines.

11. How does rapid industrialization add fuel to pollution? 

Ans: Industrial processes like chemical plants, metallurgical plants, smelters, pulp and paper mills, cotton and textile mills, petroleum refineries, synthetic rubber manufacturing plants etc. produce about 20% of air pollution.

In factories and mines around the world hundreds of thousands of workers are daily exposed to a large variety of toxic or poisonous substances that lead to deadly diseases such as silicosis, foetal disorders, paralysis, skin allergies, pneumoconiosis etc. In textile industries workers constantly inhale cotton dust. Similarly in a flour mill, workers constantly inhale flour dust, asbestos dust in asbestos manufacturing mills, silica dust in factories making bangles and glass wares etc.

12. What are outdoor air pollutants

Ans: Outdoor air pollutants :

Vehicles are the sources of the highest amount of pollutants like 

  • Immoderate chemical substances
  • Particulates
  • Sulphur-di oxide
  • Carbon monoxide and carbon di oxide
  • Ozone
  • Lead

13. What is Safe Water:

Ans: Any kind of water is not safe for drinking unless a chemical test is carried out. Safe water is suitable for household activities along with personal cleanliness. Packaged water should be used for drinking. In some special activities like dialysis (medical sector), cleaning contact lens or food processing and manufacturing medicines, highly sophisticated water is essential.

14. What are the sources of soil pollution?

Ans: The following sources have been found to be responsible for soil pollution

  1. Industrial wastes
  2. Urban wastes 
  3. Agricultural practices/wastes
  4. Municipal wastes
  5. Radioactive pollutants
  6. Biological agents

15. Mention some sources of noise pollution

Ans: The sources of noise pollution may be

  1.  Natural
  2.  Man-made

a) Natural: The natural source of noise pollution is thunder.

b) Man-made: Noise pollution is mainly caused by the different activities of man. The automobiles such as trucks, buses, scooters, fire extinguisher vehicles, police vans, ambulances etc., the trains, the aeroplanes, industries, factories, loud speakers, musical instruments, sirens, blast of explosions etc. produce unwanted sounds. During dewali, people of all ages enjoy firecrackers. The noise produced by the crackers exceeds the permissible level. During the other festivals people use different forms of noise producers.

NIOS Class 12th Environmental Science (333) Notes/Question Answer

ChaptersChapters NameLink
Chapter 1Basic Concept of EnvironmentClick Here
Chapter 2Ecological ConceptClick Here
Chapter 3Biodiversity and its conservationClick Here
Chapter 4Natural ResourcesClick Here
Chapter 5Environmental PollutionClick Here
Chapter 6Social Issues and EnvironmentClick Here
Chapter 8 (A)Disaster Management: Responsibilities and PrecautionsClick Here
Chapter 8 (B)Road SafetyClick Here

Long Questions with Answers ▷▷ Marks: 10

1. Define Pollutant and contaminant. How will you classify pollutants?

Ans: Pollutant: A substance present in nature, in greater than natural abundance due to human activities, which ultimately has a detrimental effect on the environment.

Examples: Carbon monoxide, sulphur di oxide, arsenic, fluorides, lead, cadmium etc. 

Contaminant: A substance which does not occur in nature, but is introduced by human activities into the environment. Contaminant is also a pollutant. Example Fluorine from chlorofluorocarbons, food additives, paints etc.

Classification of pollutants Pollutants may be of two types- primary and secondary on the basis of their forms they exist in the environment after their release.

Primary pollutants: These pollutants are released directly from an identifiable source and exist as such in the environment. Examples are oxides of sulphur, oxides of nitrogen, hydrocarbons etc.

Secondary pollutants: These pollutants are derived from the primary pollutants by chemical reactions or by natural causes. Example hydrocarbons and nitrogen oxides react in presence of sunlight to form peroxy acetyl nitrate (PAN) as secondary pollutant.

2. What are the causes of environmental Pollution? 

Ans: Both natural and anthropogenic activities are responsible for environmental pollution, but the impact of the latter is severe and sometimes irreversible. Sometimes the natural causes may also be more dangerous. Natural Earthquake, volcanoes, eruption, excessive rainfall (flood), landslides, storms, weathering of rocks etc.

Anthropogenic or Man made – Population increase, deforestation, industrial and automobile exhausts, burning of fossil fuel, war, construction works

3. Mention some methods for Prevention and control of air pollution

Ans: Chemists always have to play a key role in protecting the environment from the adverse effects of the chemicals. The chemists have to think of the following points while involved in manufacturing different chemicals or design some new pathways for synthesis of chemicals.

  • Synthetic methods should be designed to maximize the incorporation of all materials used in the process into the final products.
  • Wherever practicable, synthetic methodologies should be designed to use and generate substances that possess little or no toxicity to human health and the environment. 
  • It is better to prevent waste than to treat or clean up waste after it is formed.
  • The use of auxiliary substances (eg. solvents, separation agents etc.) can be avoided wherever possible
  • Energy requirements should be minimized. 
  • A raw material for feedstock should be renewable rather than depleting.
  • They should encourage plantation programmes in the industrial site in particular. 
  • Less polluting fuels should be used. 
  • Use of non-conventional sources of energy should be encouraged.
  • Proper Environmental Impact Assessment for any developmental work must be done. 
  • Strict rules and regulations can help in controlling air pollution.

4. What are the sources of water pollution 

Ans: The following sources have been identified as the sources of water pollution

  1. Domestic wastes
  2. Industrial effluents
  3. Agricultural wastes
  4. Run off from urban areas 
  5. Soluble effluents
  6. Oil spills
  7. Seepage pits
  8. Refuse dumps
  9. Solid wastes
  10. Thermal pollutants
  11. Radioactive nuclides
  12. Particulates and atmospheric gases
  13. Infectious agents etc.

5. How to categorise Vehicular emissions as a pollutant?

Ans: It is the most dangerous form of air pollution. In spite of introducing stringent laws, adopting new standards, changing the fuel characteristics, modifying the design of vehicles etc. studies reveal that vehicular pollution is increasing day by day. 

The principal pollutants emitted by vehicles are

  • Carbon monoxide (CO)
  • Hydrocarbons (HC) 
  • Oxides of nitrogen (NOx) and
  • Suspended particulate matter (SPM) 

Petroleum based vehicles also emit polynuclear aromatic hydrocarbons and aldehydes in trace amounts. Depending upon the sulphur content of the fuel, varying amount of sulphur dioxide (SO) may also be emitted. In addition the exhaust gases from petrol based fuel vehicles also contain lead particles and sometimes lead compounds because of the addition of tetraethyl lead. Diesel vehicles contribute more NOx and particulate matter.

The pollution load from vehicular exhausts depends on

  • characteristics of the fuel
  • efficiency of combustion 
  • types of engine used
  • age of the vehicle
  • congested traffic
  • poor road condition
  • outdated automotive technology etc. 

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

Ans: The industrial wastes prior to disposal should be properly treated for removing hazardous materials. The sewage water can be treated to make it safe for disposal into water bodies like rivers, lakes etc. The treatment involves three stages: primary, secondary and tertiary. This includes 

  1. sedimentation, 
  2. coagulation/flocculation, 
  3. filtration, 
  4. disinfection, 
  5. softening and 
  6. aeration. 

The first four steps are of primary treatment. The first three steps are involved in primary treatment to remove suspended particulate matter. Secondary treatment removes organic solids, left out after primary treatment, through their microbial decomposition.

Effluents after secondary treatment may be clean but contain large amounts of nitrogen, in the form of ammonia, nitrates and phosphorus which can cause problems of eutrophication upon their discharge into a receiving water body such as river, lake or pond. The tertiary treatment is meant to remove nutrients, disinfect for removing pathogenic bacteria, and aeration removes hydrogen sulphide and reduce the amount of carbon dioxide and make water healthy and fit for aquatic organisms. This treatment of waste water or sewage is carried out in effluent treatment plants especially built for this purpose. The residue obtained from primary treatment is one known as sludge.

7. What are the protective measures to keep drinking water sources clean and safe?

Ans: To keep drinking water sources clean and safe the following measures should be adopted:

  1.  Location: Water sources should be on a higher location at least 10m to 15 m away from polluting sources like latrine, soak pits, garbage etc.
  2. Plateform: A cement concrete plateform around the tube wells and ring wells extending Im in all directions having gentle slope outwards towards a drain should be built. These platforms should be free from cracks and damages.
  3. Drain: Water sources should have sound drainage systems to check stagnancy. Waste water should not be allowed to accumulate in these areas.
  4. Covering: The mouth of a ring well should always be covered at all times to prevent foreign materials from entering it. 
  5. Lining: The lining of a ring well should be built of stones set in cement upto a depth of at least 6m so that water enters from the bottom and not from the sides.

8. State three reasons for deforestation. 


(i) Developmental activities

As humans began leading a settled life, crop fields, building, roads, industries, schools, hospitals, railway and irrigation canals etc. became necessary developmental activities. Forests were cleared to meet the need for land needs for the above developmental activities. 

(ii) For timber and wood 

Wood is used in building construction, making furniture and other articles for human use. Trees that yield wood grow in forests and were cut down for timber. Use of firewood for cooking and heating etc. also contributes to deforestation.

(iii) Shifting cultivation : 

Shifting cultivation is a system of crop cultivation involving cleaning of forest and burning the fallen trees to clear the land for raising crops. Crops are grown on the cleared area for a few years and abandoned after a few years as the land loses its fertility. Thereafter a new forest areas is cleared for cultivation and the same cycles is repeated

9. What are the effects of soil pollution


  1. Industrial wastes consist of a variety of chemicals which are extremely toxic. Chemicals like acids, alkalis, pesticides (weedicides, fungicides, insecticides, rodenticides), heavy metals etc. affect soil fertility and ultimately affect human health.
  2. Some of the persistent toxic organic chemicals inhibit the non-target organisms, soil flora and fauna and reduce soil productivity. These chemicals accumulate in the food chain and ultimately affect man and other animals.
  3. Sewage sludge has many types of pathogenic microorganisms which may cause various diseases. Varieties of soil transmitting diseases like giardiasis, tetanus etc. are caused by soil pollution.
  4. Nitrogen and phosphorus from the fertilizers in soil reach nearby water bodies with agricultural run-off and cause eutrophication.
  5. The problem of radioactive wastes dumped into the soil is more complicated. This is so because every radioactive element like radium, uranium, thorium, plutonium etc. can remain active in soil for thousands of years. Since radioactive wastes are produced in huge quantities and have higher activation energy, they create an extremely difficult public health problem.

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