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AIR POLLUTION
CHAPTER 15
Structure and Science of the Atmosphere
• The atmosphere consists of
several layers with different
temperatures, pressures, and
compositions.
• The atmosphere’s innermost
layer (troposphere) is made up
mostly of nitrogen and oxygen,
with smaller amounts of water
vapor and CO2.
• The ozone layer (stratosphere)
filters out most of the sun’s UV
radiation that is harmful to us and
most other species.
Structure and Science of the Atmosphere
The density of air molecules decreases as altitude increases.
(hence the term thin air high up in the mountains)
So… air pollution is more a concern at the earth’s surface.
Air contents:
Air Pollution
Air pollution - the
introduction of chemicals,
particulate matter, or
microorganisms into the
atmosphere at
concentrations high
enough to harm plants,
animals, and materials
such as buildings, or to
alter ecosystems.
Natural Sources of Air Pollution
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Volcanoes
Lightning
Forest fires
Plants
Anthropogenic Sources of Air Pollution
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On-road vehicles
Power plants
Industrial processes
Waste disposal
Primary Pollutants
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Primary pollutantspolluting compounds
that come directly out
of the smoke-stack,
exhaust pip, or
natural emission
source.
Examples: CO, CO2, SO2,
NOx, and most suspended
particulate matter.
Secondary Pollutants
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Secondary pollutants- pollutants that have undergone
transformation in the presence of sunlight, water,
oxygen, or other compounds.
Examples: ozone, sulfate and nitrate
Air Quality Indicator - Lichens
• Lichens can warn us of bad air
because they absorb it as a source of
nourishment.
• Some lichen species are sensitive to
specific air-polluting chemicals.
• After Chernobyl, more than 70,000
reindeer had to be killed because
they ate highly radioactive lichens.
• Because lichens are widespread,
long-lived, and anchored in place,
they can help track pollution to its
source.
Major Air Pollutants
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Sulfur Dioxide
Nitrogen Oxides
Carbon Oxides
Lead
Mercury
Particulate Matter
Volatiles Organic
Compounds
Ozone
Major Air Pollutants
• Sulfur dioxide (SO2) and Sulfuric acid:
• About one-third of SO2 in the troposphere occurs
naturally through the sulfur cycle.
• Two-thirds come from human sources, mostly
combustion of sulfur-containing coal and from oil
refining and smelting of sulfide ores.
Primary Air Pollutant
Secondary Air Pollutant
Acid Rain
Major Air Pollutants
• Nitrogen Oxides and Nitric Acid:
• Nitrogen oxide (NO) forms when nitrogen and oxygen gases
in air react at the high-combustion temperatures in
automobile engines and coal-burning plants.
• NO can also form from lightening and certain soil bacteria.
• NO reacts with oxygen to create NO2 with is a major
component in…
• Smog
• Acid Rain
• PANS (Peroxyacyl nitrates)
(respiratory & eye irritants in smog)
Major Air Pollutants
• Carbon Oxides:
• Carbon monoxide (CO) is a highly toxic gas that
forms during the incomplete combustion of
carbon-containing materials.
• Carbon dioxide (CO2)
• 93% of carbon dioxide in the troposphere occurs
as a result of the carbon cycle. (cellular respiration)
• 7% of CO2 in the troposphere occurs as a result
of human activities (mostly burning fossil fuels).
Major Air Pollutants
• Lead & Mercury
• Lead is a powerful neurotoxin.
• Was removed from gasoline over
three decades ago
• Concentrations in the air have
declined precipitously
• Mercury from coal fired power plants is
now of greater concern than lead
• Lead & Mercury are heavy metals. They
cause human health concerns – they
cause brain damage in infants and
children.
Major Air Pollutants
• Suspended Particulate Matter (SPM):
• Consists of a variety of solid particles and liquid
droplets small and light enough to remain suspended
in the air.
• The most harmful forms of SPM:
• Fine particles (PM-10)
• meaning the average diameter < 10 micrometers
• Ultrafine particles (PM-2.5)
• According to the EPA, SPM is responsible for about
60,000 premature deaths a year in the U.S.
Particulate Matter
Major Air Pollutants
Volatile Organic Compounds (VOCs):
• These organic compounds have a high vapor pressure, which
allows them to evaporate into atmosphere at room
temperature. Most VOCs are…
• Hydrocarbons
• emitted by the leaves of many plants as scents and odors
• Methane
• About two thirds of global methane emissions comes from human
sources (leakage from natural gas sources & livestock manure)
• Atmospheric methane concentrations are of interest due to methane's
impact on climate change, as it is one of the most potent greenhouse
gases in Earth's atmosphere.
Major Air Pollutants
Volatile Organic Compounds (VOCs):
• Some other VOCs include industrial solvents such as acetone,
trichloroethylene (TCE), benzene, paints, vinyl chloride and fuels
like gasoline.
• Long-term exposure to benzene can cause cancer, blood disorders, and
immune system damage.
Major Air Pollutants
Ozone (O3):
• Is a highly reactive gas that is a major component of
photochemical smog.
• It is a secondary air pollutant… it is created from
sunlight & VOCs, NOx, CO
• It can…
• Damage plants, rubber in tires, fabrics, and paints.
• Cause and aggravate respiratory illness.
• Can aggravate heart disease.
Major Air Pollutants
Ozone (O3):
SMOG
Air Pollution– Chapter 15
What is smog?
• Mexico City is one of the many
cities in sunny, warm, dry
climates with many motor
vehicles that suffer from
photochemical smog.
• The primary component of
smog is ozone. Secondary
components are VOCs and
sunlight.
• Smog is also impacted by
thermal inversions.
Photochemical Smog
Thermal Inversions
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Thermal Inversionwhen a relatively
warm layer of air at
mid-altitude covers a
layer of cold, dense
air below.
The warm inversion
layer traps emissions
that then accumulate
beneath it.
Thermal Inversions
Las Vegas NV
Los Angeles CA
• Cold, cloudy weather in a valley surrounded by mountains can
trap air pollutants (left).
• Areas with sunny climate, light winds, mountains on three sides
and an ocean on the other (right) are susceptible to inversions.
Smog & Thermal Inversions
• During severe inversions that last over long periods, smog
can cover entire metropolitan areas and cause respiratory
problems for the inhabitants of those areas.
London, England
2013
Factors Influencing Levels of
Outdoor Air Pollution
• Outdoor air pollution can be reduced by:
• settling out
• precipitation
• sea spray
• winds
• chemical reactions
• Outdoor air pollution can be increased by:
• urban buildings (slow wind dispersal of pollutants)
• mountains (promote temperature inversions)
• high temperatures (promote photochemical reactions)
ACID DEPOSITION
Air Pollution – Chapter 15
Acid Deposition
• Acid deposition consists of rain, snow, dust, or gas with a pH
lower than 5.6. It exists in two forms: dry acid deposition and
wet acid deposition (acid rain).
Acid Deposition
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Acid deposition- occurs when nitrogen oxides and
sulfur oxides are released into the atmosphere and
combine with atmospheric oxygen and water. These
form the secondary pollutants nitric acid and
sulfuric acid.
These secondary pollutants further break down into
nitrate and sulfate which cause the acid in acid
deposition.
Effects of Acid Deposition
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Lowering the pH of lake water
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Decreasing species diversity of aquatic organisms
Mobilizing metals that are found in soils and releasing
these into surface waters
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During the 1970’s and 1980’s, many lakes in Canada and the
Northeastern U.S. lost all of their fish due to lowered pH levels
Acid Deposition can release aluminum from lake sediments which, in
turn, adversely affects the gills of fish
Damaging statues, monuments, and buildings
Emissions
SO2
Acid H O
2 2
deposition
PANs
NOx
O3
Others
Reduced
photosynthesis
and growth
Direct damage to
leaves & bark
Tree death
Soil acidification
Leaching
of soil
nutrients
Acids
Lake
Groundwater
Release of
toxic metal
ions
Susceptibility
to drought,
extreme cold,
insects,
mosses, &
disease
organisms
Root
damage
Reduced nutrient
& water uptake
Where is Acid Rain a problem?
• In the US, the Appalachian forests from Maine to Georgia are particularly
affected by acid rain. Trees usually don't die outright but are weakened and
more susceptible to pathogens, insects, drought or extreme cold.
• In Europe, acid rain was first found in Scandinavia in the late 1950's and at
first it was thought to be a local problem, however, later it was discovered
that the pollution was actually coming from Britain and Northern Europe.
• Acid rain is an international problem because it is dispersed by winds.
Solutions
Acid Deposition
Prevention
Reduce air pollution
by improving energy
efficiency
Cleanup
Add lime to
neutralize
acidified lakes
Reduce coal use
Increase natural
gas use
Increase use of
renewable energy
resources
Burn low-sulfur coal
Remove SO2
particulates & NOx
from smokestack
gases
Remove NOx from
motor vehicular
exhaust
Tax emissions of SO2
Add phosphate
fertilizer to
neutralize
acidified lakes
OZONE LAYER DEPLETION
Air Pollution – Chapter 15
Stratospheric Ozone
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Good Ozone
Bad Ozone
The stratospheric ozone layer exists roughly 45-60
kilometers above the Earth.
Ozone has the ability to absorb ultraviolet radiation
and protect life on Earth.
Formation of Ozone - Stratosphere
Breakdown of Ozone - Stratosphere
Anthropogenic Contributions to Ozone Destruction
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Certain chemicals can break down ozone, particularly
chlorine.
The major source of chlorine in the stratosphere is a
compound known as chlorofluorocarbons (CFCs)
CFCs are used in refrigeration and air conditioning, as
propellants in aerosol cans and as “blowing agents” to
inject air into foam products like Styrofoam.
Anthropogenic Contributions to Ozone
Destruction
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When CFCs are released into the troposphere they make their way to
the stratosphere.
The ultraviolet radiation present has enough energy to break the bond
connecting chlorine to the CFC molecule. Creating a chlorine atom,
which then breaks apart the ozone molecules.
One chlorine atom can catalyze the breakdown of as many as 100,000
ozone molecules before it leaves the stratosphere.
Depletion of the Ozone Layer
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Global Ozone concentrations had decreased by more than
10%.
Depletion was greatest at the poles
Decreased stratospheric ozone has increased the amount of
UV-B radiation that reaches the surface of Earth.
Effects of Ozone Depletion
• Eye cataracts
• Sunburn and cancer
• Weaker immune systems
• Interference with photosynthesis which leads to lower crop
yields as growth is reduced
• Plants suffer as they become more susceptible to disease
• Plankton near the surface dies which disrupts food chains
INDOOR AIR POLLUTION
Air Pollution – Chapter 15
Indoor Air Pollution
Indoor air pollution usually is a greater threat to human health
than outdoor air pollution.
•According to the EPA, the four most dangerous indoor air
pollutants in developed countries are:
• Tobacco smoke (second-hand smoke can cause lung cancer… especially in children)
• Formaldehyde (wrinkle free shirts, particle board, carpets, nail polish)
• Radioactive radon-222 gas (in rocks & soil… penetrates building materials… created from
breakdown of uranium ore)
• VOCs in home products (wood flooring and products)
Indoor Air Pollution
Other indoor air pollutants are:
• Wood, animal manure or coal used for cooking and heating in developing
countries.
• Asbestos (heat resistant fiber in home insulation… used for fire-proofing)
• Carbon Monoxide (from auto exhausts, central heating furnaces, space heaters)
• Living things such as dust mites (mites feed on human skin.. Can cause asthma & allergies…
they live in bedding and furniture fabrics)
Structures with high levels of indoor air
pollutants that make people ill are said to suffer
from Sick Building Syndrome
WAYS TO PREVENT AIR
POLLUTION
Air Pollution – Chapter 15
The Clean Air Acts of 1970 and 1990 greatly
improved air quality in the United States
Air Quality Index (AQI)
The AQI is an index for reporting daily
air quality. It tells you how clean or
polluted your air is, and what associated
health effects might be a concern for
you.
The AQI focuses on health effects you
may experience within a few hours or
days after breathing polluted air.
EPA calculates the AQI for five major air
pollutants regulated by the Clean Air
Act:
1.ground-level ozone
2.particulate matter
3.carbon monoxide
4.sulfur dioxide
5.nitrogen dioxide
Ways to Prevent Air Pollution
Three techniques control particulate matter:
1.Scrubbers on smoke stacks – uses water
2.Electrostatic precipitators – uses an electric charge (+) and
they stick to (-) charged plates
3.Baghouse filters – uses fabric filters
*Drawback… All three types use electricity (additional energy) with require
the use of more fuel and result in increased carbon dioxide emissions
Preventing other types of air pollution:
4.Fluidized Bed Combustion - granulated coal is burned near
calcium carbonate - (reduces sulfur dioxide emissions from coal)
5.Catalytic Converters on cars (controls particulate matter and
nitrogen oxides)
1. Wet Scrubber
• Can remove 98% of SO2 and
particulate matter.
• Not very effective in removing
hazardous fine and ultrafine
particles.
2. Electrostatic Precipitator
• Can remove 99% of particulate
matter
• Does not remove hazardous
ultrafine particles.
• Produces toxic dust that must
be safely disposed of.
• Uses large amounts of
electricity
3. Baghouse Filters
Fabric filter are used to separate particulates from clean air.
4. Fluidized Bed Combustion
Coal is burned with limestone (contains calcium carbonate)
to help reduce acid-forming air pollutants
5. Catalytic Converters
The job of the catalytic converter is to convert harmful pollutants into less
harmful emissions before they ever leave the car's exhaust system. It uses a
honeycomb like mesh coated with metals (platinum or palladium) that will react
with the pollutants and produce cleaner gases (NO is reduced to O2 and N2)
SOLUTIONS TO POLLUTION
Air Pollution – Chapter 15
Solutions
Air Pollution
Outdoor
Improve energy efficiency to
reduce fossil fuel use
Rely more on lower-polluting
natural gas
Rely more on renewable energy
(especially solar cells, wind, &
solar-produced hydrogen)
Transfer technologies for latest
energy efficiency, renewable
energy, & pollution prevention
to developing countries
Indoor
Reduce poverty
Distribute cheap &
efficient cookstoves or
solar cookers to poor
families in developing
countries
Reduce or ban indoor
smoking
Develop simple and cheap
tests for indoor pollutants
such as particulates, radon,
and formaldehyde
Solutions
Indoor Air Pollution
Prevention
Cover ceiling tiles & lining of AC
ducts to prevent release of mineral
fibers
Ban smoking or limit it to well
ventilated areas
Set stricter formaldehyde
emissions standards for carpet,
furniture, and building materials
Prevent radon infiltration
Use office machines in well
ventilated areas
Use less polluting substitutes for
harmful cleaning agents, paints,
and other products
Cleanup or
Dilution
Use adjustable fresh air
vents for work spaces
Increase intake of outside air
Change air more frequently
Circulate a building’s air
through rooftop green houses
Use exhaust hoods for stoves
and appliances burning
natural gas
Install efficient chimneys for woodburning stoves
What Can You Do?
Indoor Air Pollution
• Test for radon and formaldehyde inside your home and take
corrective measures as needed.
• Do not buy furniture and other products containing formaldehyde.
• Remove your shoes before entering your house to reduce inputs
of dust, lead, and pesticides.
• Test your house or workplace for asbestos fiber levels and for
any crumbling asbestos materials if it was built before 1980.
• Don't live in a pre-1980 house without having its indoor air
tested for asbestos and lead.
• Do not store gasoline, solvents, or other volatile hazardous
chemicals inside a home or attached garage.
• If you smoke, do it outside or in a closed room vented to the outside.
• Make sure that wood-burning stoves, fireplaces, and kerosene- and
gas-burning heaters are properly installed, vented, and maintained.
• Install carbon monoxide detectors in all sleeping areas.
Solutions
Stationary Source Air Pollution
Prevention
Burn low-sulfur
coal
Remove sulfur
from coal
Convert coal to a
liquid or gaseous
fuel
Shift to less
polluting fuels
Dispersion or
Cleanup
Disperse emissions
above thermal
inversion layer with
tall smokestacks
Remove pollutants
after combustion
Tax each unit of
pollution produced
Solutions
Motor Vehicle Air Pollution
Prevention
Cleanup
Mass transit
Emission
control devices
Bicycles and
walking
Produce hybrid
and electric cars
Less polluting fuels
Improve fuel efficiency
Car exhaust
inspections
twice a year
Get older, polluting
cars off the road
Give buyers large tax
write-offs or rebates for
buying low-polluting,
energy efficient vehicles
Stricter
emission
standards