Env.sci Assg. 4

7/28/2019 Env.sci Assg. 4

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ACID RAIN

Rainwater that has a pH of less than that of natural rainwater (which is about 5.6 due todissolved carbon dioxide) is acid rain.

It is formed when sulphur dioxides and nitrogen oxides, as gases or fineparticles in theatmosphere, combine with water vapour and precipitate as sulphuric acid or nitric acid inrain, snow, or fog.

Causes of Acid Rain

The principal cause of acid rain is from human sources

1. Industrial factories, power-generatingplants and vehicles

2.

Sulphur dioxide and oxides of nitrogen are released during the fuelburning process

Natural Sources

1. Emissions from volcanoes and from biological processes that occur on the land, inwetlands, and in the oceans contribute acid-producing gases to the atmosphere

2. Effects of acidic deposits have been detected in glacial ice thousands of years old inremote parts of the globe

Formation of Acid Rain

When water vapour condeses, oras the rain falls, they dissolve inthe water to form sulphuricacid (H 2SO4) and nitric acid (HNO 3).

While the air in cleaned of the pollutants in this way, it also causes precipitation to becomeacidic, forming acid rain


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Effects of Acid Rain

1. Harmful to aquatic life2. Increased acidity in water bodies

3. Stops eggs of certain organisms (e.g.fish) to stop hatching4. Affects human health ( Brain damage, kidney problems, and Alzheimer's disease

has been linked to people eating "toxic" animals/plants . Respiratory problems,asthma, dry coughs,headaches and throat irritations) Leeching of toxins from thesoil by acid rain can be absorbed by plants and animals. When consumed, thesetoxins affect humans severely.

5. Changes population ratios6. Affects the ecosystem7. Harmful to vegetation (Water and soil systems lack natural alkalinity such as lime

base) 8. Increased acidity in soil9. Leeches nutrients from soil, slowing plant growth10. Leeches toxins from soil, poisoning plants11. Creates brown spots in leaves of trees, impeding photosynthesis12. Allows organisms to infect through broken leaves13. Accelerates weathering in metal and stone structuresEg. Taj Mahal inAgra, India

Preventive Measures

1. Reduce amount of sulphur dioxide and oxides of nitrogen released into theatomosphere

2. Use less conventional sources of energy (hence less fuel burnt)3. Use other sources of electricity (i.e. nuclear power, hydro-electricity, wind

energy ,geothermal energy, and solar energy)4. Use cleaner fuels5. Remove oxides of sulphur and oxides of nitrogen before releasing6. Flue gas desulphurization7. Catalytic Converters8. Coal that contains less sulphur9. "Washing" the coal to reduce sulphur content Consists of a wet scrubber and a

reaction tower equipped with a fan that extracts hot smoky stack gases from apower plant into the tower.


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GLOBAL WARMING

An average increase in the temperature of the atmosphere near the Earths surface and inthe troposphere, which can contribute to changes in global climate patterns is Global

Warming Causes Burning of fossil fuels (Coal/Crude oil) in

1. Power plants for generate electricity 2. fuels for transports (E.g. LPG, kerosene, fuel oil)3. Industrial processes (E.g. manufacture of cement, steel, aluminium)

Other greenhouse gases emission 1. Agriculture2. Forest fire3. Other land uses or Waste management

Example : Using natural gas to cook

CH4 + 2O 2 CO2 + 2H 2O

Besides carbon dioxide, other gases such as methane, chlorofluorocarbons, nitrogen

oxides and ozone also contribute to the greenhouse effect.

Formation of Green House Effect

Greenhouse gases in the atmosphere

Some infrared radiation is trapped

Greenhouse effect

Effect of Global Warming

Concentration of greenhouse gases in the atmosphere is highly increasing by humanactivities Leads to the increasing seriousness of global warming

Global surface temperatures

increased about 0.6C/century since the late19th century increased to 2C/century over the past 25 years


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Direct Temperature Effects

Increase in average temperature More extreme heat waves during the summer; Less extreme cold spells during the

winter Harmful to those with heart problems, asthma, the elderly, the very young and the

homeless

Climate-sensitive diseases

Increase the risk of some infectious diseaseso [particularly that appear in warm areas; are spread by mosquitoes and other

insects]o E.g. Malaria, dengue fever, yellow fever, encephalitis

Algal blooms occur more frequently as temperatures warm (particularly in areas withpolluted waters)

Diseases (e.g. cholera) accompanying algal blooms become more frequent

Air Quality

An increase in the concentration of ground-level ozone


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Damage lung tissue Harmful for those with asthma and other chronic lung diseases

Food supply

Rising temperatures and variable precipitation Decrease the production of staple foods in many of the poorest regions Increasing risks of malnutrition

Population displacement

Rising sea levels Increase the risk of coastal flooding (Necessitate population displacement)

Measures on controlling the problem

Government set some laws to limit the amount of pollutants produced by factories todevelop the skills of using renewable fuels , e.g.

solar energy, wind energy encourage the factories to replace fossil fuels byrenewable fuels, which would not cause environmental pollution

carry out energy saving scheme to reduce the pollution produced by burningfossil fuels

Grow more plants to reduce the pollutants e.g. CO 2

Citizens

reduce the use of plastic bags as burning plastic emit CH 4

recycle the resources, e.g. plastic, paper, glass etc reduce the use of sprays such as CFCs would be emitted out reduce the use of air-conditioner, which will emit CFCs use public transportation instead of private cars to reduce the pollutants

emitted by cars


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CLIMATE CHANGE

Climate is the average weather of an area. It is the general weather conditions, seasonalvariations and extremes of weather in a region. Such conditions which average over a long

period- at least 30 years is called climate.

From past 50 Years the worldhas recorded:

Hotter Summers

Warmer Winters

Increased Flooding

Severe Droughts More Intense Storms

and Rainfall

But bad weather in one place at one time does not prove theclimate is changing

During the past 50

years, the global surfacetemperature has risenby 0.6 C

Sea level has risen andsnow cover hasdecreased

Causes & Effects

Anthropogenic (man-made) activities are upsetting the delicate balance that has establishedbetween various components of the environment. Green house gases are increasing in theatmosphere resulting in increase in the average global temperature.

This may upset the hydrological cycle, result in floods and droughts in different regionsof the world, cause sea level rise, changes in agriculture productivity, famines and deathof humans as well as live stock.


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OZONE LAYER DEPLETION

The ozone layer is a deep layer in the stratosphere, encircling the Earth, that has largeamounts of ozone in it. Ozone concentration in about 24 km of the stratosphere i.e.

from 16 km to 40 Km away from earth is about 10 ppm

The layer shields the entire Earth from much of the harmful ultraviolet radiation thatcomes from the sun.

For nearly a billion years, ozone molecules in the atmosphere have protected life onEarth from the effects of ultraviolet rays.

CAUSES & Depletion Procedure

CFCs (chlorofluorocarbons)

Recently, chlorofluorocarbons (CFCs) were used a lot in industry and elsewhereto keep things cold and to make foam and soaps.

Strong winds carry CFCs up into the stratosphere where UV radiation breaksthem apart, releasing chlorine atoms.

Each chlorine atom can attack and break apart (destroy) as many as 100,000ozone molecules during the time it is in the stratosphere.

The chlorine from CFCs reduces (depletes) the amount of ozone in thestratosphere.

Other ozone-eating chemicals are pesticides such as methyl bromide, halons used in fireextinguishers, and methyl chloroform used in medicinal businesses.

OBSERVATION of Ozone Depletion

Scientists did predict that ozone depletion should peak around year 2010. As world-wide controls reduce the release of CFCs and other ozone-eating

substances, nature will repair the ozone layer. By year 2065 stratospheric ozone should return to the amount present in

1980. Until then, we can expect higher levels of UV radiation at the Earth's surface. We need to take care to avoid the bad health effects that could result from too

much UV radiation. Most countries have seen the threats created by ozone depletion and agreed

to a treaty called the Montreal Protocol. This Protocol will help humans to stop making and using ozone-eating

chemicals.


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MISCONCEPTIONS ABOUT THE OZONE LAYER DEPLETION

COMMON MISTAKE FACT

Global warming is caused by theozone hole which was created bychemicals like CFC etc.

The ozone layer protects the Earth from the Sunsharmful UV rays. Hole in the ozone layer has beencaused by chemicals released by humans.

CFCs are too heavy to reach the

stratosphere.

CFCs are commonly believed to be heavy. But

atmosphere gases are not sorted by weight. The windmixes the gases and they reach the atmosphere.

Effects of Ozone Layer Depletion (UV Exposure)

Skin Cancer an abnormal growth of skin tissues.

Premature aging make the skin thick, wrinkled, and leathery

Cataracts No longer have transparent lenses in their eyes

Other Eye Damages

Skin cancer around the eyes

Degeneration of the yellow spot

Suppression of Immunity Overexposure to UV radiation suppress properfunctioning of the body's immune system and natural defenses of skin

UV radiation weakens the immune system increases the chance of infection and disease

PROTECTING THE OZONE LAYER

The ozone layer must be protected. For this the use of CFCs has to be stopped. We must buy products that are labelled ozone friendly or CFC free. Substitutes for CFCs should be used. HCFCs are substitutes for CFCs.


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NUCLEAR ACCIDENTS AND HOLOCAUST

Nuclear accidents can occur at any stage of the nuclear fuel cycle. However, the possibilityof reactor accidents is viewed more seriously because the effects of reactor accidents aremore drastic.

Many estimates of hypothetical accidents in a nuclear power station are made. Suchestimates are made taking into consideration various parameters like reactor safetymeasures which if fail would release large amount of reactor contents, that is, radioactivedebris affecting a substantial portion of human population within a particular site in aparticular area.

The modern fusion bombs (nuclear bombs) are of the explosive force of 500 kilotons and 10megatons. In case of a world war total nuclear exchange of more than 5,000 megatons canbe expected. Nuclear bombardment will cause combustion of wood, plastics, petroleum,forests etc. Large quantity of black soot will be carried to the stratosphere. Black soot willabsorb solar radiations and won t allow the radiations to reach the earth. Therefore, coolingwill result. The infrared radiations which are re-radiated from the atmosphere to the earthwill have very less water vapours and carbon dioxide to absorb them. If they leave the loweratmosphere the green house effect will be disturbed and cooling will occur. Due to thiscooling effect, water evaporation will also reduce. Therefore, infra-red radiations absorbingwater vapours will reduce in the atmosphere. This will also cause cooling. In thestratosphere there won t be significant moisture to rainout the thick soot. So, due tonuclear explosions, a phenomenon opposite to global warming will occur. This is callednuclear winter. It may result in lower global temperature. Even the summer time willexperience freezing temperature. It will drastically affect crop production. Crop productivitywill reduce substantially causing famines and human sufferings.

The Chernobyl nuclear accident , 1986 has resulted in wide spread contamination byradioactive substances. (already mentioned in air pollution episodes). The devastationcaused by nuclear bombs are not only immediate but may be long lasting. Towards, the endof World War II, bombing of Dresden, Germany caused huge firestorms. This caused particleladden updrafts in the atmosphere.

In Nuclear holocaust in Japan 1945, two nuclear bombs were dropped on Hiroshima andNagasaki cities of Japan. One fission bomb was dropped on Hiroshima. This holocaust (largescale destruction of human lives by fire) killed about 100,000 people and destroyed the city.This forceful explosion emitted neutrons and gamma radiations. It had the force of 12kilotons of trinitrotoluene (TNT). The radioactive strontium (Sr90) liberated in the explosionresembles calcium and has the property of replacing calcium of the bones. As a result largescale bone deformities occurred in the inhabitants of these cities. Even after more than 50years the impacts of the nuclear fallout are still visible.

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Env.sci Assg. 4