NIOS Class 12 Environmental Science Chapter 10
INTEXT QUESTIONS 10.1
1. Define pollutant and pollution.
Ans: (a) Agents that cause environmental pollution are called pollutants.
(b) Addition of undesirable materials into the environment as a result of human activities.
2. Name any three devices that control pollution.
Ans: Filters, electrostatic precipitators, inertial collectors, scrubbers (any three)
3. State two means of controlling indoor air pollution.
Ans: Any two.
- Use of wood and dung cakes should be replaced by cleaner fuels such as biogas, kerosene, or electricity.
- Improved stoves for cooking, like smokeless chullahs, have high thermal efficiency and reduced emission of pollutants, including smoke.
- The house designs should incorporate a well-ventilated kitchen.
- Use of biogas and CNG (Compressed Natural Gas) needs to be encouraged.
- Those species of trees, such as baval (Acacia nilotica), which are least smoky should be planted and used.
- Indoor pollution due to the decay of exposed kitchen waste can be reduced by covering the waste properly.
- Segregation of waste, pretreatment at source, and sterilization of rooms will help in checking indoor air pollution.
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 units is it measured?
Ans: Decibels (Db)
2. State two harmful effects of noise pollution.
Ans: Disturb sleep, emotional problems, annoyance (any two)
3. State two important indoor and two outdoor sources of noise pollution? Mention the method of control for each of them.
Ans: Better designing and proper maintenance of vehicles, use of noise abatement measures, appropriate insulation, and introduction of noise regulation for take-off aircraft, use of electric locomotives, and use of soundproofing equipment.
INTEXT QUESTIONS 10.3
1. Name the metals which, when in excess 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 into rivers. To what extent does this raise the water temperature of the river?
Ans: Increase in water temperature up to 10 to 15 °C 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 the metabolism of aquatic animals?
Ans: The Metabolism of aquatic animals increases and affects their growth.
7. State the term for residue left after primary treatment of wastewater.
Ans: Sludge
INTEXT QUESTIONS 10.4
1. Define soil pollution.
Ans: Addition of substances that 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 a colossal environmental hazard.
3. Vermicomposting degrades organic waste into a useful substance. What is this substance used for?
Ans: This substance is manure and is used in agriculture.
INTEXT QUESTIONS 10.5
1. Which types of radiation are produced in a microwave oven?
Ans: Non-ionizing radiations
2. State the use of absorbed dose of radiation.
Ans: Absorption of radiation is 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 radiation can damage internal organs upon its exposure for a few days?.
Ans: Higher doses (up to 100 rem) can damage internal organs upon exposure to it.
TERMINAL EXERCISE
1. Define the terms pollution and pollutant.
Ans: Pollution may be defined as the addition of undesirable material into the environment as a result of human activities. The agents that cause environmental pollution are called pollutants. A pollutant may be defined as a physical, chemical, or biological substance unintentionally released into the environment that is directly or indirectly harmful to humans and other living organisms.
2. List the environmental problems faced by women inside the rural households. Suggest measures to reduce or eliminate them.
Ans: In congested areas, slums, and rural areas, burning of firewood and biomass results in a lot of smoke. Children and ladies exposed to smoke may suffer from acute respiratory problems, which include a runny nose, cough, sore throat, lung infection, asthma, difficulty in breathing, noisy respiration, and wheezing.
3. Why was CNG introduced as a fuel for automobiles in a city like Delhi? Has it made any difference?
Ans: Use of cleaner fuels such as biogas, CNG, and electricity prevents air pollution.
4. Manufacture of chlorofluorocarbons is to be phased out as per the ‘Montreal Protocol’. Why?
Ans: Chlorine from chemicals such as chlorofluorocarbons (CFCs) used for refrigeration, air conditioning, etc, causes damage to the ozone lay. Chlorine contained in the CFCs, on reaching the ozone (O3) layer, splits the ozone molecules to form oxygen (O2). The amount of ozone, thus reduced, which cannot prevent the entry of UV radiation and creates an ozone hole over the Arctic and Antarctic regions. This is known as the ozone hole. This permits passage of UV radiation through Earth’s atmosphere, which causes sunburn, cataract in the eyes leading to blindness, skin cancer, reduced productivity of forests, etc. Under the “Montreal Protocol,” amended in 1990, it was decided to completely phase out CFCs to prevent damage to the ozone layer.
5. Describe an environmentally friendly method to profitably dispose of human waste and cattle waste.
Ans: Human and animal waste could be used to generate biogas that will prevent soil pollution in the landfill. The organic matter from domestic, agricultural, and other waste should be segregated and subjected to vermicomposting, which generates useful manure as a byproduct. Kitchen waste can also be used for making compost through various methods, which can be used for enriching soil and adding manure for house plants.
6. Chemical fertilizers are useful for crops. In what way do they cause environmental pollution?
Ans: Chemical fertilizers that run off can pollute water bodies. When fertilizers and sewage enter a water body, phytoplankton and algae grow rapidly, in a phenomenon called eutrophication. Fertilizers and pesticides from agricultural use, which reach soil as run-off and land filling by municipal waste, are a growing cause of soil pollution.
7. What steps can be taken to reduce pollution due to particulate matter from industries?
Ans:
- Particulate matter from the gas stream can be removed using a filter made of fibrous materials like cloth, granular material like sand, a rigid material like a screen, or any mat like a felt pad.
- The emanating dust is charged with ions, and the ionized particulate matter is collected on an oppositely charged surface.
- Inertial collectors can be used that work on the principle that the inertia of SPM in a gas is higher than its solvent, and as inertia is a function of the mass of the particulate matter, this device collects heavier particles more efficiently.
8. What is a PUC certificate? Is it necessary, and for whom? In your opinion, is it really useful?
Ans: In cities like Delhi, motor vehicles need to obtain a Pollution Under Control (PUC) certificate at regular intervals. This ensures that levels of pollutants emitted from vehicle exhaust are not beyond the prescribed legal limits. Yes, it is a really useful measure to control the rising air pollution.
9. What is medical waste? Why is it called hazardous waste? What is the safe way to dispose of medical waste?
Ans: Waste generated from hospitals is called medical waste. It includes the soiled bandages, used syringes, wipes, garments, body fluids, etc. These can be highly contagious and should be treated carefully. Such biomedical waste, such as sharp materials, such as syringes, must be sterilized before disposal. Incineration is the other option for treating this waste.
Hospitals must segregate biomedical waste into separate colour-coded bags and must dispose of it as per the laws specified.
10. Suggest a way to improve the water quality that has undergone primary treatment?
Ans: The residue obtained from primary treatment one known as sludge, which will undergo secondary and tertiary treatments.
- Secondary treatment removes organic solids, left out after primary treatment, through their microbial decomposition. Still, water contains large amounts of nitrogen, which will be removed in the tertiary treatment.
- The tertiary treatment is meant to remove nutrients, disinfect to remove pathogenic bacteria, and aeration removes hydrogen sulphide and reduces the amount of carbon dioxide and making the water healthy and fit for aquatic organisms.
11. What are the causes and effects of thermal pollution on the life of aquatic animals like fish? What measures would you suggest to prevent thermal pollution?
Ans: An increase in water temperature decreases dissolved oxygen in water, which adversely affects aquatic life.
Aquatic plants and animals in the warm tropical water live dangerously close to their upper limit of temperature, particularly during the warm summer months.
- Discharge of hot water into a water body affects feeding in fish, increases their metabolism, and affects their growth.
- Their swimming efficiency declines.
- Running away from predators or chasing prey becomes difficult.
- Their resistance to diseases and parasites decreases.
One of the best methods of reducing thermal pollution is to store the hot water in cooling ponds and allow the water to cool before releasing it into any receiving water body.
12. What are ionizing and non-ionizing radiations? Give examples.
Ans:
- Ionizing radiations cause ionization of atoms and molecules of the medium through which they pass. Electromagnetic radiations such as short wavelength ultraviolet radiations (UV), X-rays and gamma rays, and energetic particles produced in nuclear processes, electrically charged particles like alpha and beta particles produced in radioactive decay, and neutrons produced in nuclear fission, are highly damaging to living organisms.
- Non-ionizing radiations are constituted by the electromagnetic waves at the longer wavelength of the spectrum, ranging from near infra-red rays to radio waves. These waves have enough energy to excite the atoms and molecules of the medium through which they pass, causing them to vibrate faster, but not strong enough to ionize them. Eg., In a microwave oven, the radiation causes water molecules in the cooking medium to vibrate faster and thus raises their temperature.
13. List the possible damages caused to humans by radiation pollution.
Ans: The biological damage resulting from ionizing radiations is generally termed radiation damage.
- Large amounts of radiation can kill cells, which can dramatically affect the exposed organism as well as possibly its offspring.
- Affected cells can mutate and result in cancer.
- A large enough dose of radiation can kill the organism.
Radiation damage can be divided into two types:
- (a) Somatic damage (also called radiation sickness): Somatic damage refers to damage to cells that are not associated with reproduction. Effects of somatic radiation damage include reddening of the skin, loss of hair, ulceration, fibrosis of the lungs, the formation of holes in tissue, a reduction of white blood cells, and the induction of cataract in the eyes. This damage can also result in cancer and death.
- (b) Genetic damage: Genetic damage refers to damage to cells associated with reproduction. This damage can subsequently cause genetic damage from gene mutation, resulting in abnormalities. Genetic damages are passed on to the next generation.
14. How can cancer be caused by radiation?
Ans: Radiation can affect cells in the body. The affected cells could be damaged or lead to cancerous growth. Another way radiation leads to cancer is by causing a mutation in the gene. A genetic mutation leads to cancer.
15. Briefly describe soil pollution, its causes and methods of control.
Ans: Addition of substances that adversely affect the quality of soil or its fertility is known as soil pollution. Solid waste, such as garbage and sewage, causes soil pollution when it is carelessly disposed of. Medical and industrial waste, acid rain, and dry deposition of pollutants also add to soil pollution. The main sources of soil pollution are,
- Plastic bags that are made from low-density polyethylene (LDPE) are non-degradable.
- Flyash, chemical residues, metallic or nuclear waste, etc., from industries.
- Agricultural chemicals, especially fertilizers and pesticides, pollute the soil.
Control measures for soil pollution
- Indiscriminate disposal of solid waste should be avoided.
- Stop the use of plastic bags and instead use bags of degradable materials like paper and cloth.
- Sewage should be treated properly before being used as fertilizer and landfills.
- The organic matter from domestic, agricultural, and other waste should be segregated and subjected to vermicomposting, which generates useful manure as a byproduct.
- The industrial wastes before disposal should be properly treated to remove hazardous materials.
- Biomedical waste should be separately collected and incinerated in proper incinerators.
