Composition
 Nitrogen: 78.1%
 Oxygen: 20.9%
 Other Gases:
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Argon : 0.9%
CO2 : ~370 ppm: Green House Gas
Methane: Green House Gas
Ozone: blocks UV radiation
Dust: solid particles in the atmosphere
Water Vapor: a major player in atmospheric circulations

Since water vapor is lighter than the atmosphere. Introduction
of water vapor causes vertical movement (convection) in the
atmosphere
Structure
 Troposphere: 0-11 km elevation, the weather layer,
temp. drops with elevation
 Tropopause
 Stratosphere 11-45 km, little vertical motion,
contains ozone layer, Temp rises with elevation
 Stratopause
 Mesosphere: >45 km
 Ambient Air Pollution:
 Ground level tropospheric air pollution. It is air
pollution all around us.
 Criteria Air Pollution:
 Originated with the Clean Air Act of 1970
 EPA identified six most serious pollutant in the ambient
air
 CO, O3, SO2, NO, PM (particulate matter) and Pb
(Lead)
 VOC (Volatile Organic Pollutants):
Criteria Air Pollutant
 These are produced in large amounts – hence higher
risk
 Exhausts from motor vehicles account for about half of
these emissions
 In many major cities, criteria air pollutants cause eye
and respiratory irritation, head ache and other
ailments.
 Outdoor Pollution
 Indoor Pollution
 Primary Pollution
 Secondary Pollution
Carbon Monoxide (CO)
 Product of incomplete combustion of carbon
 Accounts for 50% of all air pollutants
 Accounts for 11% of all hospital admission of elderly patients
for congestive heart failure
 Iron atom in hemoglobin in blood picks up oxygen from
lungs and takes it to the cells. CO has 250 X more affinity for
the iron atom compared to Oxygen
 Organs get less oxygen: heart and brain gets affected first
 Headache dizzinessfatigue, drowsiness  coma 
death
 US ambient air standard for CO is 9 ppm averaged over
8 hours. If it exceeds one time in a year , the area is
violating standards.
Ground level Ozone
 Ozone O3 has three oxygen atoms
 Major component of photochemical smog (which also contain nitrates
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and nitrogen oxides)
Nox + VOC  (Sunlight, High Temp, stagnant air O3
Automobiles are the main producers of precursors, also power plants,
aeroplanes
EPA considers Ozone as the “most … intractable air pollutant in urban
areas”.
Effects on People: see the table
Effects on Plants and trees: causes more damage to plants than all other
air pollutants combined
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Crop loss in USA 5-10%
World wide 35% of the crops grow in areas with high O3
More harmful when combined with other pollutants like acid rain
Trees and forests are also adversely affected
Ozone is a major component of SMOG
 Smog = unhealthy mixtures of air pollutants over urban areas
1. Industrial (gray air) smog = industries burn coal or oil
2. Photochemical (brown air) smog = Produced by light-driven
reactions of primary pollutants & normal atmospheric compounds
 Irritates eyes, noses, and throats
 Vehicle inspection programs in the U.S. have decreased smog
Nitrogen oxides (give it brown hazy color) + VOCs + heat + sunlight
= O3 + other photochemical oxidants + aldehydes
Industrial smog
Photochemical smog
 17.16
Ozone Levels
Concentration (ppm)
Air Quality
<0.05
Good: No health impact expected
0.051 – 0.100
Moderate: Unusually sensitive people should consider
prolonged exertion outdoors
0.101 – 0.150
Unhealthy for sensitive group: Active children and
adults with asthma or other respiratory diseaes should
avoid prolonged outdoor exertion
0.151-0.200
Unhealthy: Active children and adults and those with
respiratory diseases should follow the advise above.
Children should limit prolonged outdoor exertion
0.201 – 0.300 Alert
Very Unhealthy: Active children and adults, and
those with respiraory diseases should avoid all outdoor
exertion. Others, especially children should limit
outdoor exertions
How to reduce Ozone pollution?
 Reduce NOx and VOC emissions from Automobiles
 1970 CAA – emissions fell 90%
 But more autos and increased miles driven = high Nox and VOC
 New Ozone standard
 Low VOC and NOx does not necessarily reduce O3
 Between 1990 to 1992, # of cities in US exceeding old O3 standard
(<.12 ppm) fell from 97 to 56
 Reduced emissions from power plants, vapor recovery nozzles in
Gas stations, cleaner burning gasoline
 Restricting Formaldehyde emissions because Formaldehyde causes
more O3 formation than other VOCs
 New EPA standard : 0.08 ppm – 1/3rd of US cities do not comply
even with the old standard (0.12 ppm) – LA has > 0.20 ppm on 30 40 days
Sulfur Gases
 >50 million tons of SO2 emitted worldwide
 2/3rd from combustion of coal in power plants
 Rest mostly from Petroleum refining, smelting
 Natural Sources: sea water, bacteria, planktons, plants
 Volcanic eruption: Mt Pinatubo (1991) ejected 20 million
tons – caused global cooling
Sulfur dioxide (SO2)
 SO2 gas reacts with moisture to form sulfuric acid
which causes irritation and aggravates asthma, heart
disease. Mucous membrane in eye, lungs affected
 Forms aerosols (suspension of fine liquid or solid
particles in air) of sulfuric acid (wet condition) or
sulfates (dry condition) – can inflame lungs if inhaled
 Environmental Effects:
 Forms blue haze that blocks sunlight
 Causes acid deposition (acid rain)
 Harms stratospheric O3
Nitrogen Oxides (NOx)
 NO (nitric oxide), NO2 (nitrogen dioxide), N2O (nitrous
oxide)
 Sources: at high temp atmospheric N2 combines with O2
 Motor vehicles (50%), Electric utilities (25-30%), industrial
furnaces (14%)
 Natural sources: Lightning, soil microbes, volcanoes
 Same as SO2: irritation, haze, acid rain, global cooling,
ozone destruction
 But also is precursor of Ozone formation – SO2 is not
 Deposited on earth acts as a plant nutrient – can be very
harmful in high concentrations
Particulate Matter (PM)
 Solids suspended in air
 Accounts for 10% of US air pollution
 Can vary in composition and size
 Sulfates, nitrates, metals, dust, biological matters
 Gaseous pollutants can condense into PMs
 Caused silicosis, black lung diseases (coal miners),
mesothelioma from asbestos
 Coarser PM can be sneezed out, PM 10 is regulated by EPA,
PM 2.5 even more dangerous--- can cause inflamation in
Lungs. Very fine PM can cause cancer
 Causes Haze , lowers visibility– can cause other problems
Sources:
 PM10 = dust from farms, mines, or roads, pollens
 PM2.5 = mostly from combustions– diesel motor
vehicles, electric power plants, industrial operations like
steel mills, fly ash
 Construction sites, agricultural activities, wood burning
stoves
 Chloride salts in coastal areas
 EPA standard :
 PM10 < 50 μg/m3. PM2.5 <15 μg/m3
 PM2.5 contains different chemicals in east coast
comapred to west coast
 We don’t know which component is most harmful
 Sulfates, nitrates, soot, metal oxides?
 Controlling combustion sources
Lead
 Causes Brain damage, nervousness, apathy
 Inner city children more at risk
 Tetraethyl Lead was used as a octane booster in
gasoline
 Lead was used in paints
 Now both use banned with dramatic reduction of lead
in atmosphere and in average blood levels
 Lead mobilized many years ago is still a problem:
 Old paints, solder of old water pipes, roadside soil
contaminated by leaded gasoline…
 Other pollutants like Hg, Cd, Pb, Zn, As can be of
concern near mines and smelters
Volatile Organic Chemicals (VOC)
 Combustion sources: Motor vehicles, aeroplanes, farm machineries,
lawn mowers..
 Incomplete combustion, idling
 Evaporation during filling of gas tanks
 Non-combustion sources:
 Petroleum refineries, chemical plants
 Dry cleaners
 Paint shops, garages, print shops
 Bakeries – emit ethanol formed by action of yeast
 Sewage treatment plants, composting
 Natural Sources: Trees emit VOCs. 90% of VOCs in Maine is from
Trees.
 Terpene can contribute to Ozone formation
 Reducing VOC emission: CAA – VOC dropped by 30% between
1970 and 1985
Acid Rain
 Any rain more acidic than normal rain (pH=5). Carbonic,
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Sulfuric and Nitric acids
SO2 dissolves in water to form Sulfuric acid: main ingredient
of acid rain. NOx  Nitric acid. CO2 Carbonic acid
Industrialized areas more affected. pH=4.2 in US Northeast
In the United States, roughly 2/3 of all SO2 and 1/4 of all
NOx come from electric power generation that relies on
burning fossil fuels, like coal.
Granitic terrains more affected than limestone terrains
Affects plant growth, contaminates lakes and groundwater,
man made structures, cause algal blooms, releases heavy
and toxic metals from sediments
Acid deposition
 Originates from burning fossil fuels that release sulfur
dioxide and nitrogen oxides
 These compounds react with water to form sulfuric and
nitric acids
Acidic
precipitation
in the U.S.
Acid Deposition: Effect of Life in Water
pH
Effect of Life in water
6
Snails and Crayfish begin to die
5
Fish eggs do not hatch, some fish die
4.5 to 5
Fish species like Bass and Trout begin to die
4
Many flies and frogs begin to die
US emission of criteria pollutants,
2006
 In 2006, the U.S.
emitted 137 million
tons of the 6 major
pollutants
Health Effects
 Respiratory diseases = damage to
tissue (asthma, bronchitis,
emphysema)
 ½ of all lungs examined in
autopsies in US show damage
 Lead to lung cancer
 Heart disease, immune
suppression, reduced mental
function
 1 in 5 people live with
dangerously polluted air
 Reduced life expectancy
 5-10 yrs if you live in LA
(150 days of hazardous breathing)
 24, 000 people/yr die in the US
Los Angeles, CA
Air pollution has decreased since 1970
 Total emissions of the 6 monitored pollutants have declined
 Cap-and-trade program for SOx.

Enabled the 110 most polluting power plants to buy and sell SO2 pollution
rights.
 But CO2 emissions have been increasing
Areas in the U.S. fail air quality standards
Ozone Hole
Ozone is harmful at Ground level
At 15 km above surface UV ray reacts
with Oxygen to produce Ozone. This
Ozone absorbs UV ray and shields
earth’s surface
• 1% reduction in ozone causes 3% rise in skin cancer in
light-skinned people plus increased cataract,
melanoma, gene mutation, immune system damages
UVA: longest wavelength: not damaging
UVC: shortest wavelength: highly damaging, absorbed by oxygen
UVB: intermediate wavelength: absorbed by Ozone
Destruction of Ozone
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Ozone in the upper atmosphere can be destroyed by the
exhaust of hi-altitude aircrafts and more seriously by
CFCs(Chlorofluorocarbons) which were used as a
refrigerant and in aerosol spray cans (e.g., Freon)
40 billion lbs of CFC produced since 1931 and 90% of this
released to the atmosphere
The released CFC either dissolves in seawater or go into
Troposphere where they remain for many decades and are
harmless
Some of the CFC escape to stratosphere, absorb UV ray and
releases Chlorine which act as a catalyst to break Ozone
molecule
Destruction of Ozone
 Chlorine + Ozone = ClO(Chlorine Monoxide) + O2
 A single chlorine atom can destroy 100,000 ozone molecules
 ozone hole is more pronounced in polar regions
 In polar stratosphere, extreme cold removes nitrogen compounds,
which normally inactivate chlorine, from the stratosphere
 Release of reactive chlorine is also catalyzed by fine ice crystals in
stratosphere
 At present both the Arctic and Antarctic are affected by
ozone hole
 Sulfate aerosols as from Mt Pinatubo also destroys Ozone
layer
Ozone Hole
 UV rays reaching Antarctica each spring has
increased from 20 to 200% every year since 1980s
 Production of algae and bacteria in contact with
seawater has decreased by 15% since the late
1980s
 Marine Phytoplanktons are severely stressed
 This in turn, will affect animals higher in the food
chain.
Ozone Hole
Ozone Hole over Antarctica and N. America
Present scenario
 Montreal Protocol (1987, 1990)
 Signed by more than 70 nations
 Stipulates phasing out of CFCs and other ozone
depleting compounds by 2000
 Hesitancy on part of China
 Substitutes not totally safe
 Latest data indicate that ozone hole is not expanding
CO2 needs to be added to the list!
 Not regulated as a
pollutant under the
U.S. Clean Air Act.
 But most emissions are
CO2
 A greenhouse gas
 Contributes to global
climate change
In the US…
Sources of C02
 US emissions
1. 40 %
Petroleum
products
2.
34 % coal
3.
20 % natural
gas
Greenhouse Effect
 In a greenhouse, light enters but IR cannot escape
 CO2 in atmosphere allows light rays to enter but traps
IR
 CO2 % in atmosphere has increased from 280 ppm in
pre-Industrial time to present day value of 375.64 ppm
(2003 data)
Rise in atmospheric CO2 in the last two decades
Greenhouse Effect: Is it Real?
 How much CO2=How much rise of T?
 More T = more evaporation = more cloud = Less
Temp…
 Real rise or natural fluctuation?
 Data for the last 10ka indicate upto 6 °C fluctuation
 Little ice age (1450 – 1850)
Global Temperature Rise
Methane (CH4) concentration
ppb
Other Greenhouse Gases
 Methane, water vapor, nitrous oxide
 Rice paddy, extraction of fossil fuel, raising of live
stock (bovine flatulence) cause increase in
methane
 Cutting of forests kills CO2 sink
 Some effects might be opposite of CO2: SO2
 Temperate regions more resilient
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Colder climate will have longer growing season
 Marginal areas to be hard hit
 More flooding, heat waves…
Greatest air pollution problem: Global Warming
•
www.nelson.wisc.edu/outreach/energy2006
Evidence to Support Global Warming
 Intergovernmental Panel on Climate Change (IPCC)
 An international panel of scientists and government officials
established in 1988
 Generated reports on the synthesis of scientific information concerning
climate change
 4th Assessment report 2007
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Documents observed trends in surface temperature, precipitation patterns,
snow and ice cover, sea levels, storm intensity
The IPCC concluded that it is more than 90%
likely that most global warming is due to humans
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The Debate over climate change is over
84% of people surveyed think humans contribute to global warming
Predicts future changes
Temperatures will rise 0.2 degree Celsius per decade
Greenhouse Effect: Problems
 Rise of temperature : Drier climate?
 Melting of Ice Caps: ultimate reduction of soil
moisture (up to 40%)
 If all the ice melted sea level will rise by 75m
inundating 20% of the Earth’s land area. No
Florida!!
 Even a partial melting of Antarctica ice cap will
raise sea level by 3 to 6m. Fear of calving from Ross
Ice Shelf
Rising sea levels
 IPCC predicts mean sea level to be 18-59 cm (7-23 in)
higher than today’s at the end of the 21st century
Predictions from two models
By 2030, Illinois will have
a climate like Missouri’s.
By 2090, it will have a
climate like Oklahoma’s.
Green = Canadian
model
Blue = Hadley model
Halting emissions
• California’ s Global Warming Solutions Act
• Cut greenhouse gas emissions 25% by 2020
• 10 NE states launched the Regional Greenhouse Gas Initiative (RGGI)
in 2007
• cap-and-trade program for C emissions from power plants
Fig. 15-22, p. 371
Kyoto Protocol
 Conference: Dec 1-11, 1997 in Kyoto, Japan
 Six Greenhouse gases were targeted (CO2, CH4, NOx, CFC-
substitutes)
 Their emission to be reduced below 1990 levels as follows:
EU: 8%, US: 7%, Japan 6%
The reduction will be done in a 5 year period between 2008-2012
Emission can be traded in global market
Creation of carbon sinks like afforestation can be balanced against
emission
 Developing countries to benefit from “clean” technology
 The protocol will be open for signature in March, 1998, has to be
ratified by countries producing 55% of the emissions: reached in
2004 after Russia signed it.
 Entered into force: Feb 16, 2005 US pulled out of it in 2001
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