me3003 - module one part two.pdf

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Notes for ME3003 Environmental Studies for

Mechanical EngineersModule 1 part 2

Topics covered - Global warming, climate change, acid rain,ozone layer depletion, nuclear accidents.

Reference for the notesBook 1 : [1] Environmental Studies by Mr. Benny Joseph


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Greenhouse effect (abbreviated as GHE) Process which occurs naturally which helps in heating of earths surface

and atmosphere.

Gases Like CO 2, CH 4 and water vapor absorb long wave radiation from

surface of earth (trap heat) ,similar to glass of greenhouse.

The earths temp would have been -18 o C if GHE was absent.

As solar energy passes thru surface (s/f) of earth,

Reflection by clouds and particles to space - 26 % of energy

Absorption by clouds, ozone and other gases, particles - 19 %

Passing thru earth s/f - 55% (51+4)Reflected by earth s/f - 4%

Reaching earth s/f - 51%

(used in heating s/f, evaporation of water, snow and ice melting,

photosynthesis) 1


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Sun

Absorptionby surface

HeatConversion

Long wave radiationto space

More Heat gainand radiation again

Greenhouse Gases

Greenhouse Gases like CO 2, CH 4 ,water vapor absorb longwave radiation from surface of earth (trap heat)

Greenhouse effect

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Amount of heat added by GH gases to atmosphere depends on their

concentration (has been increasing since Industrial Revoln.). Increase of

Earths temperature due to GHE is called Global Warming . Modeling

indicates (doubling CO 2 -> 2-3 O C rise in temp) , causes evaporation in

oceans, more cloudy, clouds reflect more counteraction of GHE.

Greenhouse effect and Global Warming

Greenhouse gases - CO 2 (accounts for 55 % GHE)

- Chlorofluorocarbons - CFC (accounts for 25%)

- Methane CH 4 (accounts for 15%)

- Nitrous Oxide - N 2O (accounts for 5%)- Ozone O 3 (not quantified)

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Causes climate changes in world. Climate conditions determine availability of food, water

resources etc. They influence

Water Resources - quality, quantity and availability for irrigation, industrial use,

electricity generation impacted due to change in precipitation and increased

evaporation.

Coastal Resources rise in sea level, inundation of land.

Energy and Transportation water transport impacted because of flooding, lower

river level.

Oceans complicated effect (increase water vapor content but their thermal holding

capacity reduces GW. Phytoplanktons (biological CO 2 pump) remove anthropogenic

CO 2 (reason for GW).

Vegetation Changes in vegetation affect hydrological cycle. Changes in precipitation(lower rainfall) causes drought, fire susceptibility, insect damage, more CO 2 means

more photosynthesis.

Global Climate glacier melt, cold water addition alters sea currents of Atlantic ocean

which are heat conveyors. Drastic effect : Northern Hemisphere (may become colder)

Southern Hemisphere (may become drier).

Global Warming Effects

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Global Warming Effects (continued)

Using less polluting fossil fuels, wind, solar energy use, fuel cell or

electric vehicles.

Use of biofuel (Ethanol, Biodiesel), reduces CO 2 emission from

automobiles.

Design of compact and complete towns involving lesser need for

driving, encourages bicycles, walking etc.

Practicing sustainable farming and forestry, (traps carbon in soilsand plants).

Global Warming

Solutions

Health (cause mortality due to heat).

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Climate ChangeClimate Average weather (temperature, rainfall, humidity) pattern in a locality over many

years.

Climate change influenced by either heat coming into earth or going out of atmosphere.

Caused by increased fossil fuel- burning since Industrial Revln; increases GH gas

concentration (CO 2, CH 4, N 2O, HFC (hydro), PFC(per), SF 6), more GW, so climate changes.

Dealing with Climate change Energy Supply - Increasing use of (hydro, solar, wind, geothermal sources).

Transport More cleaner and fuel efficient vehicles.

Buildings More efficient appliances, cooking stoves, alternate refrigerant fluids.

Industry More efficient equipment, heat and power recovery, control of gas emissions.

Agriculture Better grazing and crop mgmt to improve carbon storage of soil, better

manure mgmt to reduce CH 4 emissions, N 2O emissions in nitrogen fertilizer applications. Forests Afforestation, reduce deforestation.

Waste waste incineration with energy recovery, composting organic waste.

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Acid RainsWhen Rain water has pH < 5.7 , it is called acid rain.Causes

1) SO 2 by burning of fossil fuels and from industrial plants

2SO 2 + O2 2SO 3This reaction is influenced by sunlight, temp, humidity, hydrocarbons, particulates etc.

SO 3 + H2O H2SO 4 (Sulphuric Acid)

2) Nitrogen Oxides released from power plants and vehicles

SO 2 (g) H2O (l)+ H2O (l) H2O (l)+

4NO 2 + 2H 2O 4HNO 3+ O2

2NO + O 2 2NO 2

SO 2 + H2O H2SO 3 (Sulphurous Acid)

(Nitric Acid)Effects

On Vegetation - Plant nutrients are washed away from soil. Makes soil acidic, aids

release of Al, Cu ions which harm plants.

Aquatic Life (If pH < 4.5 affects Ca metabolism in fish).

Building materials get damaged (e.g. Limestone, Marble).

Corrosion of metals promoted. 7


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Oz layer denser at poles than equator. Oz (O 3) in stratosphere protects earth

from harmful UV rays which can cause skin cancer, damage to vegetation, etc.

Ozone (abbreviated as Oz) layer depletion Ozone naturally occurs in stratosphere of earth as a layer. It is formed when UV

radiation from sun strikes stratosphere and splits oxygen molecule (O 2) into

atoms (O) reaches . Atomic oxygen combines quickly and forms ozone.

Chapmans eqns. (Eqns. 1-4) form oz layer. So oz layer also called as chapman

layer.

O 2 + h O + O (Eqn. 1)

O + O 2 O 3 (Eqn. 2)

O 3 +h O 2 + O (Eqn. 3)

O 2 + O O 3 (Eqn. 4)

Even if UV splits ozone, it can re-form quickly. Net oz concentration is a net result

of these reactions.

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Measuring depletion of ozone

In DOBSON Unit - total amount of ozone in an overhead column of atmosphere.

Measures how thick the layer would be if it is compressed to 1 layer at 0 o C under

pressure of one atmosphere acting over it.Effects of depletion

Causes skin cancer, eye cataract, reduces natural immunity, damages life and

vegetation due to depletion.

Steps of control

Many ODC (ozone depleting chemicals phased out of use in uses as aerosols,

refrigerant etc.)

Proper equipment maintenance so that CFCs are not released into atmosphere.

Ozone (abbreviated as Oz) layer depletion Chlorofluorocarbon (CFC), broken down by sunlight, release Cl atoms, and act as catalysts in

destruction of ozone.

Cl +O 3 ClO + O 2

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Nuclear Accidents

The possibility of their occurrence when radioactive materials are used,

transported or stored. e.g. of sites are : Nuclear power plants, research centers,

hospitals, industries, major highway etc.

Radioactive materials pose danger because these emit radiations which are

harmful for body cells. Radiation cannot be detected by sight, smell etc.

Nuclear accidents/disasters have potential to cause catastrophic destruction,

death etc.

Effects

Skin hardening, cancer, death, chronic illness etc. depending on amount of

radiation absorbed and duration of exposure.

Ways of minimizing damageDistance - More the distance from source, lesser is the radiation.

Shielding More heavier and denser the materials separating person from source, better

is the shielding.

Time - Lesser the time of exposure, more safer it is.10


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End of Module1 part 2 notes

me3003 - module one part two.pdf

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