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It is considered as silent zone because in hospitals sound intensity increases the heart beat altering respiratory patterns of patients etc.but in schools it affects the teaching and learning process.

The thin layer of ozone around the atmosphere that prevents entry of harmful UV rays is called ozone shield. Methane and CFCs are the two ozone depleting substances.

Chlorofluorocarbons (CFCs) release active chlorine (Cl atom) when acts with UV rays and Cl atoms degrade ozone releasing molecular oxygen. Depletion of ozone allows the entry of UV-B radiation to the earth which damages DNA causes mutation leading to skin cancer in humans and also rate of photosynthesis decreases in plants.

(b) Radioactivity

Correct Answer is: (d) Ozone

Lakes as a storage of rain water provides drinking water, improves ground water level and preserve the fresh water bio-diversity and habitat of the area where in occurs.

In terms of services lakes offer sustainable solutions to key issues of water management and climatic influences and benefits like nutrient retention, influencing local rainfall, removal of pollutants, phosphorous and nitrogen and carbon sequestration.

Biochar is a long term method to store carbon. To increase plants ability to store more carbon, plants are partly burnt such as crop waste, waste woods to become carbon rich slow decomposing substances of material called Biochar. It is a kind of charcoal used as a soil amendment. Biochar is a stable solid, rich in carbon and can endure in soil for thousands of years. Like most charcoal, biochar is made from biomass via pyrolysis. (Heating biomas in low oxygen environment) which arrests wood from complete burning.

Biochar thus has the potential to help mitigate climate change via carbon sequestration. Independently, biochar when added to soil can increase soil fertility of acidic soils, increase agricultural productivity, and provide protection against some foliar and soil borne diseases. It is a good method of preventing waste woods and logs getting decayed instead we can convert them into biochar thus converting them to carbon storage material.

Process of heating biomass in low oxygen environment is called as Pyrolysis.

Carbon sequestration is the process of capturing and storing CO₂ which reduces the amount of CO₂ in the atmosphere with a goal of reducing global climate change.

(c) Appiko movement

Every human activity leaves a mark just like our footprint. This Carbon foot print is the total amount of green house gases produced by human activities such as agriculture, industries, deforestation, waste disposal, buring fossil fuels directly or indirectly. It can be measured for an individual, family, organisation like industries, state level or national level. It is usually estimated and expressed in equivalent tons of CO₂ per year.

The burning of fossil fuels releases CO₂ and other green house gases. In turn these emissions trap solar energy and thus increase the global temperature resulting in ice melting, submerging of low lying areas and inbalance in nature like cyclones, tsunamis and extreme weather conditions.

To reduce the carbon foot print we can follow some practices like

1. Eating indigenous fruits and products 

2. Reduce use of your electronic devices 

3. Reduce travelling 

4. Do not buy fast and preserved, processed, packed foods 

5. Plant a garden 

6. Less consumption of meat and sea food. Poultry requires little space, nutrients and less pollution comparing cattle farming.

7. reduce use of Laptops (when used for 8 hours, it releases nearly 2 kg. of CO₂ annually)

8. Line dry your clothes. 

(Example: If you buy imported fruit like kiwi, indirectly it increases CFP. How? The fruit has travelled a long distance in shipping or airliner thus emitting tons of CO₂ )

The tribal women of Himalayas protested against the exploitation of forests in 1972. Later on it transformed into Chipko Movement by Sundarlal Bahuguna in Mandal village of Chamoli district in 1974. People protested by hugging trees together which were felled by a sports goods company. Main features of Chipko movement were,

1. This movement remained non political 

2. It was a voluntary movement based on Gandhian thought. 

3. It was concerned with the ecological balance of nature 

4. Main aim of Chipko movement was to give a slogan of five Fs – Food, Fodder, Fuel, Fibre and Fertilizer, to make the communities self sufficient in all their basic needs.

1. Deforestation: The conversion of forested area into a non- forested area is known as deforestation. 

2. Afforestation: Afforestation is planting of trees where there was no previous tree coverage and the conversion of non forested lands into forests by planting suitable trees to retrieve the vegetation.

Chipko movement.

Social forestry refers to the management of forests and afforestation on barren lands with the purpose of helping the environmental, social and rural development and benefits.

Agroforestry is an integration of trees, crops and livestock on the name plot of land. The commercial Agroforestry trees are casuarina and Eucalyptus.

1. Cloth / Jute bags 

2. Plantain leave, palmyra plates as plates 

3. Metal cups 

4. Earthen pots or ceramic wares 

5. Paper made flags

1. Training on tree growing methods 

2. Publicity and propaganda regarding tree growing 

3. Formation of demonstration plots 

4. Raising and supply of seedlings on subsidy 

5. Awareness creation among school children and youth about the importance of forests through training and camps

Clean Development Mechanism (CDM) is defined in the Kyoto protocol (2007) which provides project based mechanisms with two objectives to prevent dangerous climate change and to reduce green house gas emissions. CDM projects helps the countries to reduce or limit emission and stimulate sustainable development.

An example for CDM project activity, is replacement of conventional electrification projectswith solar panels or other energy efficient boilers. Such projects can earn Certified Emission I Reduction (CER) with credits scores, each equivalent to one tonne of CO , which can be counted towards meeting Kyoto targets.

CFCs are widely used refrigerants. They are discharged in lower parts of atmosphere but however more upward and reach the stratosphere where UV rays act upon them releasing chlorine atoms which degrade ozone releasing molecular oxygen. CFCs added to stratosphere in this way have permanent and continuing effects on ozone. 

Therefore, it is suggested to reduce its emission as far as possible.

CFCs find wide use as refrigerants. CFCs discharged in the lower part of atmosphere move upward and reach stratosphere. In stratosphere, UV rays act on them releasing chloride atoms. Chloride atoms degrade ozone, releasing molecular oxygen. Whatever CFCs are added to the stratosphere have permanent and continuing effects on ozone. These have resulted in ozone hole.

GREEN HOUSE EFFECT AND GLOBAL WARMING:  

The term ―Greenhouse effect has been derived from a phenomenon that occurs in greenhouse.

In a greenhouse the glass panel lets the light in, but does not allow heat to escape. Therefore the greenhouse warms up, very much like inside a car that has been parked in the sun for a few hours. 

The greenhouse effect is a naturally occurring phenomenon that is responsible for heating of Earth‘s surface and atmosphere.

Without greenhouse effect the average temperature at surface of earth would have been a chilly -18° C rather than the present average of 15°C. 

Clouds and gases reflect about one-fourth of the incoming solar radiation and absorb some of it but half of incoming solar radiation falls on Earth‘s surface heating it, while a small portion is reflected back. 

Earth‘s surface re-emits heat in the form of infrared radiation but some part of this does not escape into space because of atmospheric gases (e.g. carbon dioxide, methane etc).

The molecule of these gases radiate heat energy and a major part of which again comes to Earth‘s surface, thus heating it up once again. 

Carbon dioxide and methane – are commonly called as greenhouse gases because they are responsible for greenhouse effect.

Increase in the level of greenhouse gases has led to considerable heating of Earth leading to global warming orenhanced green house effect. 

During the past century, the temperature of Earth has increased by 0.6 °C.

CO₂, CH4, N₂O, chlorofluorocarbons or CFCs

Particulate matter will pollute the air

(i) Particulate matter will pollute the air.

(ii) Vehicular pollution can be controlled by : 

Use of CNG/ Phasing out of old vehicles/ Use of unleaded petrol / Use of low sulphur fuel / Use of catalytic converters / Application of stringent pollution level.

Certain substances react with ozone present in the stratosphere and destroy the ozone. They are called ozone depleting substances or ODS. The majors ODS are CFCs, halons (gases used in fire extinguisher i. e. like bromo chloride fluoro methane), N₂O, CH4, Cl etc.

The most harmful UV-radiation is UV- C have a range of 100-280 nm. They are absorbed by oxygen molecules of atmosphere. The next goes to UV-B with a range of 280-32 nm wavelength.

Antarctic air circulating over the polar region is called polar vortex.

Correct Answer is: (c) O₃ 

(b) Rio de Janeiro

(c) Poly hydroxy biphenyl based compounds

Correct Answer is: (c) Decibel

(c) Pesticides

(d) Peroxyacetyl nitrate

Ozone is found in the layer of the atmosphere called the Stratosphere. It acts as a protective covering that absorbs ultraviolet (UV) radiation from the Sun. The ozone molecule (O₃ ) consists of three oxygen atoms. It is formed when atmospheric oxygen (O₂ ) on exposure to solar radiation breaks into two oxygen atoms; each atom then joins up with a single oxygen atom. The ozone molecule is unstable. It soon decays again to form molecular oxygen. This cycle is a continuous process in the upper reaches of the stratosphere.

The large-scale global warming will have significant impact on people and nature. As global average temperatures rise, precipitation patterns could be, affected. Extreme wet and dry conditions can be expected (flooding and desertification). Coastal areas shall become more vulnerable to storm surges as sea level rises. Plant and animal species will migrate or disappear in response to climate change.Global warming can directly affect the flora and fauna. This could also result in shortage of food and even lead to food crisis; and affect the health of the people and organisms.

Correct Answer is: (a) Copper

Electronic waste or e-waste describes discarded electrical electronic devices as well as any refuse created by discarded electronic devices and components and substances involved in their manufacture or use. Their disposal is a growing problem because electronic equipment frequently contains hazardous substances.

In a personal computer, for example, there may be lead (Pb) in the cathode ray tube (CRT) and soldering compound, mercury (Hg) in switches and housing, and cobalt (Co) in steel components, among other equally toxic substances. E-wastes are basically PCB (Polychlorinated bipheny) based, which are non-degradable.

(d) iii and iv

The socio-economic benefits are:  

(1)  Employment generation  

(2)  Import substitution 

Eutrophication is the natural aging of a lake by biological enrichment of its water. In a young lake, the water being cold and clear, does not support much life. But with time, streams draining into the lake introduce nutrients such as nitrogen and phosphorus, which encourage the growth of aquatic organisms. As the lake’s fertility increases, plant and animal life begins to develop and organic remains begin to be deposited on the lake’s bottom. Over the centuries, as silt and organic debris pile up, the lake grows shallower and warmer. Now, the warm water organisms replace those that live in a cold environment. Marsh plants take root in the shallows and begin to fill in the original lake basin. Eventually, the lake develops large masses of floating plants (bog), finally converting into land.

The process of nutrient enrichment of water and consequent loss of species diversity is referred to as Eutrophication. 

Natural Eutrophication: 

• Streams draining into the lake increase nutrients like nitrogen and phosphorus. 
• Increase in nutrient encourages growth of aquatic organisms.
• Over centuries, as silt and organic debris pileup the lake grows shallower and warmer. 
• Warm-water organisms dominate over that thrive in a cold environment. 
• Marsh plants take root in the shallows and begin to fill in the original lake basin.
• Eventually the lake gives way to large masses of floating plants (bog), finally converting into land

Pollutants from man‘s activities like effluents from the industries and homes can radically accelerate the aging process. This phenomenon is called Cultural or Accelerated Eutrophication.

Eutrophication

• It is defined as the natural aging of a lake by biological enrichment of its water. 

• Water in a young lake is cold and clear to support life. 

• With time, it is enriched with nutrients by streams draining into it. 

• This encourages growth of aquatic life—plant and animal life. 

• Organic remains deposit at the bottom of the lake and with time makes the water warmer. 

• Eventually, floating plants develop in the lake, finally converting into land. 

• According to climate, size of lake and other factors, natural ageing of lake may span thousands of years. 

• The accelerated aging of lakes due to sewage and agricultural and industrial wastes is called cultural or accelerated eutrophication.

Cause: 

• Heated (thermal) waste waters flowing out of electricity-generating units. E.g. thermal power plants. 

Effects: 

• Thermal wastewater eliminates or reduces the number of organism sensitive to high temperature. 
• Enhance the growth of plants and fish in extremely cold areas but only after causing damage to the indigenous flora and fauna.

Causes: 

• Sewage and agricultural and industrial wastes. 
• Prime contaminants are nitrates and phosphates. 

Effects: 

• Unsightly scum and unpleasant odors. 
• Robbing the dissolved oxygen form water. 
• Pollutant inflow kills the fish. 
• Decomposition of dead fish causes further depletion of DO.  
• Finally a lake can literally choke to death.

(a) Sustainable development

Agenda 21 aims at achieving global sustainable development.

So, the correct answer is:

a. sustainable development.

Biomagnification

High concentrations of DDT disturb calcium metabolism in birds, which causes thinning of eggshell and their premature breaking, eventually causing decline in bird populations.

Platinum and palladium.

The particulate and gaseous pollutants are released from thermal power plants which lead to harmful effects. 

These pollutants can cause:

i. breathing or respiratory symptoms when inhaled. 

ii. irritation, inflammations and damage to lungs and premature death.

Precautionary measures include use of electrostatic precipitators by which 99% of the particulate matters can be removed from the exhaust.

Catalytic converters have expensive metals like platinum-palladium and rhodium as catalysts. As exhaust emission passes through catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water, and carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas.

Unleaded petrol is the best fuel for such vehicles.