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Air Pollution
Chapter 18
South Asia’s
Massive Brown Cloud
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Asian Brown Cloud-2 miles thick
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Causes
Chemical composition- dust, smoke, ash,
Areas impacted (India, Bangladesh, and
China)
Reduced photosynthesis by about 7%
Air pollution connects the world –LA
2 weeks to circle the globe
Steps taken in China and India to reduce
air pollution coal to natural gas
Air Pollution in Shanghai, China,
18.1 The Atmosphere Consists of
Several Layers
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Divided into layers based on temperature changes
from differences in absorption of incoming solar
energy
Atmosphere varies in
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Density-higher at sea level than top of mountain
Atmospheric pressure -decreases with altitude –less
gas molecules at higher altitudes
 Influenced by Gravity-pulls gas molecules towards
Earth’s surface
Air Movements in the Troposphere Play a Key Role in
Earth’s Weather and Climate
 Troposphere
 75–80% of the earth’s air mass
 Closest to the earth's surface
 0-11 km above sea level
 Chemical composition of air
Nitrogen 78%
 Oxygen 21%
 H20, CO2, trace amounts of others (Ar)
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Weather, climate and all life forms exist here
Involved in chemical cycling
Upper boundary = tropopause
As altitude increases, temperature decreases
The Stratosphere Is Our Global Sunscreen
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Stratosphere
11-50 km above Earth's surface
 Similar composition to the troposphere, with 2
exceptions
Much less water (1/1000)
 O3, ozone layer
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 As
altitude increases, temperature increases
 Air motion is horizontal
 Airplanes fly here
OZONE O3 – our global sunscreen
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Keeps 95 + % of UV rays from Earth's
surface
Allows humans and other life to exist on earth
Helps protect humans from sunburn, cancer,
cataracts and damage to the immune system
Prevents oxygen in the troposphere from being
converted to ozone, a harmful pollutant which
causes smog and damage to plants. (Less heat
to form ozone)
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50-80 km
Mesosphere
As altitude increases, temperature
decreases
Very little O3
Middle atmosphere – Air thin, pressure
low,
Need oxygen to live in this region. Air
quite cold -90°C (-130°F) near the top of
mesosphere
Thermosphere
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Altitude increases, temperature
increases
“Hot layer” – oxygen molecules
absorb energy from solar rays
warming the air. Very few atoms and
molecules in this region.
Intense UV – breaks O2 and N2 bonds
International Space Station is here
Comparison of the lower
atmosphere with the higher
atmosphere
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Continuous mixing
Constant, uniform
chemical composition
Fairly constant temp
over a 24 hour period
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Still air – slow
diffusion of gases
Different composition
at different heights
Wide temperature
variations
The Earth’s Atmosphere Is a Dynamic
System with Four Layers
18.2 What are the major
outdoor air pollution problems?
Air Pollution Comes from
Natural Sources
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Air pollution: presence of chemicals in
atmosphere in concentrations high enough
to harm organisms
Natural sources
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Dust blown by wind
Pollutants from wildfires and volcanoes
Volatile organics released by plants – mold
and terpenes
Air Pollution Comes from
Human Sources (anthropogenic)
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Human sources: mostly in industrialized
and/or urban areas
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Stationary sources - power and industrial
plants
Mobile sources - cars, buses
Air Pollution in the Past:
The Bad Old Days
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Discovery of fire-may have started air pollution
problem
Middle Ages-haze of wood smoke over densely
populated urban areas
Industrial Revolution-late 1700’s coal being
burned for factories and homes-increase in
respiratory diseases
London, England
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1850s
1952: yellow fog-lasted 5 days-killed over 4,000
Clean Air Act of 1956
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The London Smog of 1952
 London naturally has very calm air, and
regularly experiences thick sea fog.
 The weather turned unusually cold,
causing the residents to burn greater
amounts of coal to heat their homes.
 This combined with a temperature
inversion to create a thick smog of
sulfur dioxide over the city.
 The number of fatalities is unknown,
but estimated to be 4,000- 12,000.
16
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United States
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1948: Donora, PA; first U.S. air pollution
disaster-coal burning factories, steel
mills, zinc smelter and sulfuric acid
trapped in fog
1963: New York City - killed 300
Global problem
Air Pollution History
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The Donora Fluoride Fog of 1948
 In late October, the town of Donora experienced
a temperature inversion.
 The town is located along the Monongahela
River south of Pittsburgh, within a small valley.
 The main employer of the town was a US Steel
Zinc smelting plant.
18
Donora Fluoride Fog
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19
Emissions of sulfur dioxide, nitrogen
dioxide, and fluoride from the zinc
smelting plant began to accumulate.
The smog became so thick that driving
was impossible.
The plant itself did not cease operations
until 4 days later.
The smog finally broke up as a rainstorm
entered the area after 5 days.
Donora Fluoride Fog
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20
A total of 20 residents died; About a third
to a half of the town’s entire population of
14,000 became sickened.
Donora experienced higher than normal
mortality rates for 10 years afterwards.
Noon in
Donora
Some Pollutants in the Atmosphere
Combine to Form Other Pollutants
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Primary pollutants- chemical emitted directly
into air
Secondary pollutants- when primary
pollutants react with each other to form new
harmful chemicals – ozone, PANs, HNO3
Air quality improving in developed countries
Much more needs to be done in developing
countries
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Indoor pollution: big threat to the poor
1 in 6 live in area where air is bad
Sources and Types of Air Pollutants
polyacrylonitrile (PAN)
What Are the Major
Outdoor Air Pollutants?
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Carbon oxides
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Carbon monoxide (CO) – colorless,
odorless, highly toxic-car exhaust, open
fires, tobacco smoke
 Reduces
body
ability of blood to transport oxygen to
Carbon dioxide (CO2) colorless, odorless
 Sources 93% from carbon cycle, rest from
burning fossil fuels, clearing
forests/grasslands
 Human health and environmental impactGlobal Warming
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What Are the Major Outdoor Air Pollutants?
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Nitrogen oxides (NO) and nitric acid (HNO3)
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Sources-car engines and coal burning plants
Acid deposition-reacting with water vapor
Photochemical smog-sun and traffic
Human health and environmental impact
Sulfur dioxide (SO2) and sulfuric acid
(H2SO4)
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Colorless, bad smell
Sources – 1/3 from sulfur cycle, 2/3 humans-coal in
electrical plants and industrial plants
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Human health and environmental impact-Asian Brown
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cloud
What Are the Major Outdoor Air Pollutants?
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Particulates
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Suspended particulate matter (SPM)
Fine
 Ultrafine
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Sources-dust, wild fires, sea salt (~62%)
cars, tobacco smoke, coal burning (~38%)
Human health and environmental impact
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Toxic particulates (Pb, PCBs and Cd) can cause
reproductive problems, cancer, reduce visibility and
corrode metals
 60,000-70,000 premature deaths/year
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What Are the Major Outdoor Air Pollutants?
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Ozone (O3) – a secondary pollutant
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An unstable molecule that readily reacts to shed a
single O2 atom
Human and environmental impact
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Volatile organic compounds (VOCs)
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Organic compounds as gas in atmosphere
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Hydrocarbons and terpenes (C10H15 emitted
by leaves of plants)
Sources-mainly plants and wetlands, oil wells,
landfills, cows and termites: other sources =
benzene, vinyl chloride, industrial solvents
Human and environmental impact
 Leukemia, blood disorders, immune system
damage
Chemical Reactions That Form Major
Outdoor Air Pollutants
Detecting Air Pollutants
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Chemical instruments
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Satellites-Asian Brown Cloud
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Unmanned aircraft
2 miles thick, 1-3 miles above ground, covers
much of India, Bangladesh and China- satellites
tracked its movement- even across the Pacific
Ocean to California!
Nanotechnology-nanodetectors?
Biological indicators
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Lichens-fungus and algae
- are always absorbing air as a source of
nourishment
Natural Capital: Lichen Species,
Vulnerability to Air Pollutants
Old mans beard sickens
in the presence of SO2
Yellow Evernia also
sickens in SO2
Lead Is a Highly Toxic Pollutant
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Does not break down in the environment
Sources-toys, paint, water pipes, red,
long-lasting lipsticks
Human health and environmental impact
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Most vulnerable – children under 6 and
fetuses
Neurotoxin-about 200 kids die per year
Lead Is a Highly Toxic Pollutant
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Reduction of lead (Pb)
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Unleaded gasoline
Unleaded paint
Still problems
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2007: toys with Pb paint recalled
Older buildings- Pb- based paint peeling,
Pb contaminated dust, water
pipes/faucets
Global bans on lead in gasoline and paint
would be helpful- China just phased on
leaded gasoline 5 years ao.
Burning Coal Produces Industrial Smog
(gray-air smog)
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Chemical composition = sulfur dioxide,
suspended droplets of sulfuric acid
(mostly from coal burning),
suspended solid particles and
droplets
Carbon from coal and oil converted
to CO and CO2
Unburned carbon ends up as
particulate matter in air (soot)
Reduction of this smog in urban
cities of the United States
China and Smog
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Each year 358,000 Chinese die from
air pollution (some estimate as many
as 750,000 including indoor air
pollution)
Relies heavily on coal burning
16 of world’s 20 most polluted cities
are in China
62% of the cities suffer from
industrial smog
How Pollutants Are Formed from Burning Coal and
Oil, Leading to Industrial Smog
Sunlight Plus Cars Equal Photochemical Smog –
brown air smog
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Requires sunlight and cars
Morning traffic releases NOx and VOCs in the air
UV radiation produces a series of reactions that form as
many as 100 different compounds such as peroxyacyl
nitrates (PANs) and aldehydes.
Ozone is the most abundant. In sunlight, NO2
dissociates into O and NO. The O reacts with O2 to
produce ozone
Levels off pollutants peak around noon and drop during
the late afternoon, then starts again the next morning.
But NO drops as the sun gets higher as secondary
pollutants form.
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Present in most cities – irritates eyes and
respiratory tracts. The heat island effect makes
the reactions worse.
SMOG…
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Is worse on hotter days
Increases as traffic increases
Is more common in cities with sunny,
warm and dry climates with lots of cars
like LA, Denver, Sydney (Australia),
Mexico City, Jakarta (Indonesia) and
Santiago (Chile)
Mexico City Smog
A Model of How Pollutants That Make Up
Photochemicals Are Formed
Several Factors Can Decrease or
Increase Outdoor Air Pollution
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Outdoor air pollution may be decreased by
 Settling of particles due to gravity
 Rain and snow
 Salty sea spray from the ocean
 Winds
 Chemical reactions
 ex.
SO2 reacts with O2 in atmosphere to form SO3
which reacts with water vapor to form H2SO4-falls
out as acid rain
Several Factors Can Decrease or Increase
Outdoor Air Pollution
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Outdoor air pollution may be increased by
 Urban buildings
 Hills and mountains
 High temperatures
 Emissions of VOCs from certain trees and
plants –oaks, sweet gums, kudzu
 Grasshopper effect-volatile pollutants
transported by evaporation and wind from
tropical and temp. areas
 Temperature inversions
 Precipitation, wind
A Temperature Inversion
Warm air sits on cooler air. Occurs when areas where the normal
decrease in air temperature with increasing altitude is reversed
and air above the ground is warmer than the air below it.
Inversion layers can occur anywhere from close to ground level
up to thousands of feet into the atmosphere.
18.3 Acid Disposition Is a Serious Regional Air
Pollution Problem
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Acid deposition, acid rain
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Formation
1) sulfur dioxide (SO2) - forms H2SO4 (sulfuric acid)
2) nitrogen oxides (NOx) - forms HNO3 (nitric acid)
In the U.S., ~ 2/3 of all SO2 and ~ 1/4 of all NOx
comes from electric power generation that relies
on burning fossil fuel
Local versus regional problems-tall smokestacks
Effects of prevailing winds: prevailing winds can
blow acidic compounds over hundreds of miles
a) wet deposition: acidic rain, fog, and snow
b) dry deposition: acidic gases and particles
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Soils with limestone/calcium carbonate neutralize
acid deposition
Where is the worst acid deposition? Asia!! China is
biggest emitter of SO2
Natural Capital Degradation: Acid
Deposition, Acid Rain
Current and Possible Future
Acid Rain Problem Areas
Acid Deposition Has a Number of Harmful Effects
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Human respiratory disorders
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Aquatic ecosystems affected: Leach metals such as Pb
and Hg into water and can accumulate in tissues of fish.
EX: Mercury (Hg) in fish
Most fish cannot survive in water with pH < 4.5
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Al+3 and Hg become more soluble
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Acid Shock - A sudden acidification of runoff waters from the
spring melting of accumulated snow in the middle latitudes
because of the winter deposition of acidic precipitation.
Many lakes in Norway and Sweden have no fish
Acid Deposition Has a Number of
Harmful Effects
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Harms crops by making soil too acidic
(< 5.1)
Damage waxy coat on leaves
Impair germination
Leaches nutrients
Synergistic effects
Acid Deposition Has a Number of Harmful Effects
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Affects forests by leaching plant nutrients
such as Ca, Mg and releasing ions of Al, Pb, Cd
and Hg which are toxic to trees)
promotes acid-loving mosses that kill trees.
Tree foliage damaged, making trees more
susceptible to cold temps, diseases, insects,
drought, fungi
Hubbard Brook Studies- found that trees do
not suffer directly from acid rain, but from
insufficient nutrients. In order for trees to
recover, nutrients need to be replenishedthis can take decades if left to nature.
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Damages exterior paint on cars and
houses, deteriorates roofincg, marble
stature, historic buildings, stain glass
windows- costs $5 billion/yr in US
Is a regional problem that affects
areas that are downwind from large
car-dominated cities and from
polluting coal-burning facilities
(acidic components remain in air for
a few days)
Acid Deposition Has a Number of Harmful
Effects
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Damage to buildings, statues, and
monuments
http://www.youtube.com/watch?v=MqHw1hMEkAQ
Natural Capital
Degradation: Air
Pollution Damage to
Trees
Emissions
SO2 NOx
Acid
HO
deposition 2 2 O3
PANs Others
Direct damage to
leaves and bark
Reduced
photosynthesis
and growth
Tree death
Soil acidification
Leaching
of soil
nutrients
Acids
Release
of toxic
metal ions
Increased
susceptibility to
drought, extreme
cold, insects,
mosses, and
disease organisms
Root
damage
Reduced nutrient
and water uptake
Lake
Groundwater
Fig. 18-14a, p. 481
We Know How to Reduce Acid Deposition
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Prevention approaches that reduce or
eliminate emissions from SO2, nitrous
oxide, and particulates. Remove S from
coal before it is burned, use low-S coal,
remove NOx from car exhaust
Reduce coal use? Expensive and cost
passed on to consumers. Alternative
energy sources? Areas affected are
often far from sources.
Clean up
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Add lime to neutralize acidified lakes and soil