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8/3/2019 Air Pollution(2009 10)
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Air pollutionsources & effects
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Environmental Pollution
An undesirable change in the physical,chemical or biological characteristics ofenvironment
(Or)
Addition or excessive addition of certainmaterials to the physical environment
(Air, water, & lands), making it less fit orunfit for life
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Envelope of the earth
The atmosphere is the gaseous envelopethat surrounds the earth and constitutesthe transition between its surface and thevacuum of space.
The atmosphere is composed primarily ofnitrogen (N2) and oxygen (O2)
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Envelope of the earth
1.Thermosphere
2.Stratosphere
3.Mesosphere
4.Troposphere
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Troposphere
The first layer is called. People, plants,animals, and insects live in thetroposphere. It is the layer where allweather occurs
The troposphere begins at ground leveland extends 12km (7.5 miles) up into thesky where it meets with the second layercalled the stratosphere
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Stratosphere
The stratosphere begins at the 12km (7.5 mile)point and reaches 50km (21.1 miles) into the sky.
An important layer of atmosphere containingozone is located inside the stratosphere.
Ozone (O3) is a special form of oxygen, and theozone layer is very important to all life on earth.
Ozone blocks large amounts of solar ultraviolet
radiation from entering the troposphere.
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Mesosphere
The third layer is called the mesosphere.The mesosphere begins 50km (21.1miles)above the earth's surface.
Temperatures are warmest at the lowestlevel of the mesosphere and coldest at itshighest level.
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Thermosphere
The thermosphere begins 80km (49.7 miles) above theearth.
Temperatures in the thermosphere go up when movingfarther away from ground level due to the sun's energy.
The increase in temperature stops at this height, beyondwhich lies the exosphere. The exosphere is the highestlayer of the atmosphere.
The exosphere extends to 40,000 miles above theearth's surface.
The thermosphere and the exosphere together make upthe upper atmosphere.
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Giant safety blanket
The troposphere, stratosphere, mesosphere,
and thermosphere act together as a giant safetyblanket
They keep the temperature on the earth'ssurface from dipping to extreme icy cold that
would freeze everything solid, or from soaring toblazing heat that would burn up all life.
In the study of air pollution control the layers ofthe air that are most important are the
troposphere and the stratosphere
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Composition of air Air is a complex mixture made up of
many chemical components
The primary components of air arenitrogen (N2), oxygen (O2), andwater vapor (H2O)
About 99 percent of air is nitrogen(78%) and oxygen (21%)
The remaining percent includes trace
quantities of substances such ascarbon dioxide (CO2), methane(CH4), hydrogen (H2), argon (Ar) andhelium (He)
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Types of pollutants1.Primary pollutant :It is one that is emitted into theatmosphere directly from the
source of the pollutant andretains the same chemicalform
2.Secondary pollutant :It is one that is formed byatmospheric reactions ofprecursor or primary emissions
Secondary pollutantsundergo a chemical changeonce they reach theatmosphere
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Criteria Pollutants:Source of CO
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Source of NOX
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Source of Lead
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Secondary Pollutants
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Welfare Effects - Acid Rain
Acid rain" is a broad term used todescribe several ways that acids fall
out of the atmosphere
A more precise term is aciddeposition, which has two parts: wetand dry
Acid deposition occurs when
emissions of sulfur dioxide andnitrogen oxides in the atmosphere
react with water, oxygen, and oxidantsto form acidic compounds
These compounds fall to the earth ineither dry form (gas and particles) orwet form (rain, snow, and fog)
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Acid Rain
Acidity is measured in terms of pH on a
logarithmic scale from 1.0 to 14.0
A pH of 1.0 indicates high acidity, whereas a pHof 14.0 indicates high alkalinity; a pH of 7.0
indicates a neutral solution
Precipitation falling through a "clean"atmosphere is normally somewhat acidic, with apH of about 5.6. Acid rain, however, can have apH values below 4.0.
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Welfare Effects - Greenhouse Effect
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Greenhouse effect
The earth's climate is fueled by the sun
Most of the sun's energy, called solar radiation, isabsorbed by the earth, but some is reflected back into
space
Clouds and a natural layer of atmospheric gasesabsorb a portion of earth's heat and prevent it fromescaping into space
This keeps our planet warm enough for life and isknown as the natural "greenhouse effect
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Global warming
Scientific evidence shows that the greenhouse
effect is being increased by the release ofcertain gases into the atmosphere that cause theearth's temperature to rise, This is called "globalwarming"
Carbon dioxide, methane, particulate matter(especially black carbon or soot), nitrous oxide,fluorinated compounds, and ozone are some of
the compounds contributing to global warming
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Effects of global warming Continued emissions of greenhouse gases could
cause a 2.5
to 10
Fahrenheit rise in temperatureby the year 2100
This could lead to more extreme weather eventssuch as droughts and floods, threaten coastal
resources and wetlands by raising the sea level,and increase the risk of certain diseases byproducing new breeding sites for pests andpathogens
Agricultural regions and woodlands are alsosusceptible to changes in climate that could resultin increased insect populations and plant disease
This degradation of natural ecosystems could lead
to reduced biological diversity
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Welfare Effects - Stratospheric Ozone Depletion
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Stratospheric Ozone Depletion
The stratosphere, located about 6 to 31
miles above the earth, contains a layer ofozone gas that protects living organismsfrom harmful ultraviolet-B radiation (UV-B)from the Sun
UV-B (280 to 315 nanometer wavelength)has been linked to many harmful effects
including various types of skin cancer,cataracts, and harm to some crops, certainmaterials, and some forms of marine life
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Ozone Depletion
In the mid-1970s, it was discovered that somehuman-produced gases could cause stratosphericozone depletion
Gases containing chlorine and bromine accumulatein the lower atmosphere, are eventually transported
to the stratosphere and then converted to morereactive gases that participate in reactions thatdestroy ozone
Several substances have been associated with thestratospheric ozone depletion, includingchlorofluorocarbons (CFCs), halogens, carbontetrachloride, methyl bromide, and methylchloroform
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ozone depletion One example of ozone depletion is the annual ozone
"hole" over Antarctica that has occurred during theAntarctic spring since the early 1980s
Rather than being a literal hole, the ozone hole is alarge area of the stratosphere with extremely low
amounts of ozone
Ozone levels fall by over 60% during the worst years
Even over the United States, ozone levels are about 3percent below normal in the summer and 5 percentbelow normal in the winter
W lf Eff t S
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Welfare Effects Smog
It is the mixing of smoke particles from industrialplumes with fog that produces a yellow-blackcolor near ground level
Under the right conditions, the smoke and sulfur
dioxide produced from the burning of coal cancombine with fog to create industrial smog
The burning of fossil fuels like gasoline cancreate another atmospheric pollution problemknown as photochemical smog
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Photochemical smog
Photochemical smog is a condition that developswhen primary pollutants (oxides of nitrogen and
volatile organic compounds created from fossilfuel combustion) interact under the influence ofsunlight to produce a mixture of hundreds ofdifferent and hazardous chemicals known assecondary pollutants
Smog is the brownish haze that pollutes our air,particularly over cities in the summertime
Smog can make it difficult for some people tobreathe and it greatly reduces how far we cansee through the air.
Effects of smog
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Effects of smog Smog is a mixture of pollutants with ground-level ozone being
the main culprit
Increased levels of ground level-ozone are generally harmful toliving systems because ozone reacts strongly to destroy oralter many other molecules
Excessive ozone exposure reduces crop yield and forestgrowth
It interferes with the ability of plants to produce and store food,reducing overall plant health and the ability to grow andreproduce
The weakened plants are more susceptible to harsh weather,
disease, and pests
In addition, increases in tropospheric ozone lead to a warmingof earth's surface.
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Chemistry of pollutants
some equations and descriptions of the chemicalreactions that are involved in the production of commonprimary and secondary air pollutants.
Reactions producing:
Carbon Dioxide (CO2) Carbon Monoxide (CO)
Nitrogen Oxide (NO)Nitrogen Dioxide (NO2)
Ozone (O3)PAN gas (C2H3N2O5)Acid Rain (H2SO4)
Carbon Dioxide (CO2)
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Carbon Dioxide (CO2)
Carbon dioxide is mostly produced
through the burning of organic compounds(hydrocarbons). If these reactions arecomplete, the products are carbon dioxideand water
e.g. burning octane (petrol):
2C8H18 + 25O2 ==> 16CO2 + 18H2O
C b M id (CO)
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Carbon Monoxide (CO)
Carbon monoxide is mostly produced through the
incomplete burning of organic compounds(hydrocarbons). This occurs when the amount of oxygen available is
limited
e.g. burning octane (petrol):C8H18 + O2 ==> aCO2 + bCO + cH2O + unburnthydrocarbons
Where a, b, & cdepend on the amount of availableoxygen.
Nitrogen Oxide (NO)
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Nitrogen Oxide (NO)
Nitrogen oxide is produced through thecombination of oxygen and nitrogen from the airat very high temperatures.
This can occur naturally as the result of lightning
strikes but is more common in the hot cylindersof car engines as they burn fuel in air
Reaction:
N2 + O2(+high temperature ~ 2000 C) ==> 2NO
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Nitrogen Dioxide (NO2)Nitrogen dioxide is produced through the further reactionof nitrogen oxide with oxygen in the air.
This reaction is relatively fast and is increased further bythe presence of heat and sunlight.
Reaction: 2NO + O2 ==> 2NO2
Ozone (O3)Ozone in the troposphere (ground level) is producedfrom the combination of atmospheric oxygen.
This reaction is catalyzed by nitrogen dioxide andsunlight, making ozone a secondary pollutant.
Reaction: 3O2 ( + NO2 catalyst & sunlight) ==>2O3
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PAN gas (C2H3N2O5)PAN gas (peroxyacetalnitrate) is produced from thecombination of hydrocarbons, carbon dioxide and nitrogendioxide in the pressence of sunlight and heat. It has thefollowing structure:
Acid Rain (H2SO4)
Sulphuric acid is produced from the reaction of sulphurdioxide with ozone, the resulting sulphite ions then reactwith water vapour in the atmosphere to produce sulphuricacid.
Reactions: SO2 + O3 ===> SO3 + O2 SO3 + H2O ===> H2SO4
S ki i i j i t h lth
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Smoking is injurious to health
Which is dangerous to health, either
indoor smoking or out door smoking?The concentration of pollutants in the self
polluted air in a room of a smoker is higher
than that of out doors
What it contains?
Tobacco smoke contains at least 7polycyclic hydrocarbons and radioactivepolonium-210, which are carcinogens
S ki i i j i h l h
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Smoking is injurious to health
What are the health effects?
In smokers, the risk of developing anddying from lung cancer10 timesmorethan a non-smoker
The risk of lung diseasesis 6 timesandthat of heart diseasestwiceas comparedto a non-smoker.
Certain other diseases are also related tosmoking
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Smoking is Sweet poison
Who will be affected by smoking?
There is a world wide campaign to prohibitsmoking in public places as smokers affect
the health of even non-smoker, calledpassive smoker( i.e. who inhale tobaccosmoke passively)