Air Pollution
Atmospheric pressure (millibars)
Temperature
Pressure
Thermosphere
Heating via ozone
Mesosphere
Stratopause
Stratosphere
Altitude (miles)
Altitude (kilometers)
Mesopause
Tropopause
Ozone “layer”
Heating from the earth
Troposphere
(Sea
level)
Temperature (˚C)
Pressure = 1,000
millibars at ground
level
Fig. 19-2, p. 440
Layers of the Atmophere
• Thermosphere: Closest to the surface of the
Earth. This is where all weather and air travel
occurs. Most pollutants affect this layer. Has the
highest concentration of molecules
• Stratosphere: Contains the ozone layer which
absorbs incoming UV radiation
• Mesosphere: temperature decreases with
altitude
• Thermosphere: Warmed by the sun, lowest air
pressure of the layers
Major Air Pollutants
•
•
•
•
•
•
•
•
Nitrogen Oxides
Carbon Oxides
Sulfur Oxides
Particulates
Ozone
PANS
Volatile Organic Compounds (VOCs)
Radon (Indoor air pollutant)
Primary Pollutants
• Pollutants that retain the same chemical
formula from the source to the atmosphere
• methane, SO2, CO, CO2, NO, dust particles,
microorganisms, and chlorofluorocarbons
(CFC’s)
• Causes of Primary Pollutants – factories, cars,
wind and soil, volcanoes, forest fires, pollen,
decaying plants, salt particles from the sea, and
refrigerants.
Primary Pollutants
CO CO2
SO2 NO NO2
Most hydrocarbons
Most suspended particles
Sources
Natural
Secondary Pollutants
SO3
HNO3 H3SO4
H2O2 O3 PANs
Most NO3– and SO42– salts
Stationary
Mobile
Fig. 19-3, p. 442
URBAN OUTDOOR AIR POLLUTION
• Industrial smog is a mixture of sulfur
dioxide, droplets of sulfuric acid, and a
variety of suspended solid particles emitted
mostly by burning coal.
– In most developed countries where coal and
heavy oil is burned, industrial smog is not a
problem due to reasonably good pollution
control or with tall smokestacks that transfer
the pollutant to rural areas.
Sunlight plus Cars Equals
Photochemical Smog
• Photochemical smog is a mixture of air pollutants
formed by the reaction of nitrogen oxides and
volatile organic hydrocarbons under the influence
of sunlight.
Sunlight plus Cars Equals
Photochemical Smog
• Mexico City is one
of the many cities
in sunny, warm, dry
climates with many
motor vehicles that
suffer from
photochemical
smog.
Figure 19-4
Temperature Inversions
• 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.
Figure 19-5
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 are fine particles
(PM-10, with an average diameter < 10
micrometers) and ultrafine particles (PM-2.5).
– According to the EPA, SPM is responsible for about
60,000 premature deaths a year in the U.S.
Major Air Pollutants
• Volatile organic compounds (VOCs):
– Most are hydorcarbons emitted by the leaves of
many plants and methane.
– About two thirds of global methane emissions
comes from human sources.
– Other VOCs include industrial solvents such as
trichlorethylene (TCE), benzene, and vinyl
chloride.
• Long-term exposure to benzene can cause cancer,
blood disorders, and immune system damage.
Major Air Pollutants
• Radon (Rn):
– Is a naturally occurring radioactive gas found in
some types of soil and rock.
– It can seep into homes and buildings sitting above
such deposits.
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.
– Formaldehyde.
– Radioactive radon-222 gas.
– Very small fine and ultrafine particles.
Chloroform
Para-dichlorobenzene
Tetrachloroethylene
Formaldehyde
1, 1, 1Trichloroethane
Styrene
Nitrogen
Oxides
Benzo-a-pyrene
Particulates
Tobacco
Smoke
Asbestos
Carbon Monoxide
Radon-222
Methylene Chloride
Fig. 19-11, p. 453
INDOOR AIR POLLUTION
• Household dust mites
that feed on human skin
and dust, live in
materials such as
bedding and furniture
fabrics.
– Can cause asthma attacks
and allergic reactions in
some people.
Figure 19-12
Case Study: Radioactive Radon
• Radon-222, a
radioactive gas
found in some
soils and rocks,
can seep into
some houses and
increase the risk
of lung cancer.
Sources and paths of entry
for indoor radon-222 gas.
Figure 19-13
Radon Mitigation
• Vent air
Mitigation Techniques
• Wet Scrubbers – removes particulates & Sulfur
oxides
Mitigation Techniques
• Electrostatic Precipitators
http://www.bbc.co.uk/schools/gcsebitesize/science/images/ph_elect28.gif
Mitigation Techniques
• Mechanical Filters
• Air filters like your furnace filter, car filter
• Remove particulates from the air. Particulates
removes depends on the quality of the filter.
Mitigation Techniques
• After-burners – used for VOCs and particlute
pollution control
• Breaks down the molecular structure into CO2
and Water Vapor
• Used often for Methane (CH4)
• May be used for energy
http://depts.washington.edu
/centc/research_methane.ht
m
Acid Deposition
• Acid Rain caused by sulfur dioxide emissions
• Sulfur dioxide in the atmosphere reacts with
water vapor to form sulfuric acid:
SO2 + H2O -> H2SO4
ACID DEPOSITION
• Acid deposition consists of rain, snow, dust,
or gas with a pH lower than 5.6.
Figure 19-6
ACID DEPOSITION
• pH measurements in relation to major coalburning and industrial plants.
Figure 19-7
ACID DEPOSITION
• Environmental Effects:
• Erosion
• Leaching of toxic metals (such as lead and
mercury) from soils and rocks into acidic lakes
used as sources for drinking water
• Disruption of aquatic ecosystems
ACID DEPOSITION
• Health effects:
• Acid deposition contributes to chronic
respiratory disease and
ACID DEPOSITION
Figure 19-8
ACID DEPOSITION
Figure 19-9
Mitigation Techniques
• Add neutralizing base to acidic water – Lime is
a good base to use
• Add phosphate fertilizer which raises the pH
level of the water
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
Add phosphate
fertilizer to
neutralize
acidified lakes
Burn low-sulfur coal
Remove SO2
particulates & NOx
from smokestack
gases
Remove NOx from
motor vehicular
exhaust
Tax emissions of SO2
Fig. 19-10, p. 452
Seasons
OZONE DEPLETION IN THE
STRATOSPHERE
• Less ozone in the stratosphere allows for more
harmful UV radiation to reach the earth’s
surface.
– The ozone layer keeps about 95% of the sun’s
harmful UV radiation from reaching the earth’s
surface.
– Chlorofluorocarbon (CFCs) have lowered the
average concentrations of ozone in the
stratosphere.
– In 1988 CFCs were no longer manufactured.
Ultraviolet light hits a chlorofluorocarbon
(CFC) molecule, such as CFCl3, breaking
off a chlorine atom and
leaving CFCl2.
Sun
Cl
UV radiation
The chlorine atom attacks
an ozone (O3) molecule,
pulling an oxygen atom off
it and leaving an oxygen
molecule (O2).
Summary of Reactions
CCl3F + UV Cl + CCl2F
Cl + O3 ClO + O2
Repeated
Cl + O Cl + O2
many times
Once free, the chlorine atom is off
to attack another ozone molecule
and begin the cycle again.
A free oxygen atom pulls
the oxygen atom off
the chlorine monoxide
molecule to form O2.
The chlorine atom
and the oxygen atom
join to form a chlorine
monoxide molecule
(ClO).
Fig. 20-18, p. 486
OZONE DEPLETION IN THE
STRATOSPHERE
• During four
months of each
year up to half of
the ozone in the
stratosphere over
Antarctica and a
smaller amount
over the Artic is
depleted.
Figure 20-19
OZONE DEPLETION IN THE
STRATOSPHERE
• Since 1976, in Antarctica, ozone levels have markedly
decreased during October and November.
Figure 20-20
OZONE DEPLETION IN THE
STRATOSPHERE
• Ozone thinning: caused by CFCs and other
ozone depleting chemicals (ODCs).
– Increased UV radiation reaching the earth’s
surface from ozone depletion in the
stratosphere is harmful to human health,
crops, forests, animals, and materials such as
plastic and paints.
Natural Capital Degradation
Effects of Ozone Depletion
Human Health
• Worse sunburn
• More eye cataracts
• More skin cancers
• Immune system suppression
Food and Forests
• Reduced yields for some crops
• Reduced seafood supplies from reduced phytoplankton
• Decreased forest productivity for UV-sensitive tree species
Wildlife
• Increased eye cataracts in some species
• Decreased population of aquatic species sensitive to UV radiation
• Reduced population of surface phytoplankton
• Disrupted aquatic food webs from reduced phytoplankton
Air Pollution and Materials
• Increased acid deposition
• Increased photochemical smog
• Degradation of outdoor paints and plastics
Fig. 20-21, p. 488
Global Warming
• Accelerated warming because of decreased ocean uptake of CO2 from
atmosphere by phytoplankton and CFCs acting as greenhouse gases
Case Study: Skin Cancer
• Structure of
the human
skin and
relationship
between
radiation
and skin
cancer.
Figure 20-22
Law – Clean Air Act
•
•
•
•
1963 - first passage
1970, 1977 and 1990 - amended
Involves EPA
Sets standards for acceptable levels of sulfur
oxides, nitrogen oxides, ozone, carbon
monoxide, hydrocarbons, lead, & more
• Provides pollution credits for industries that
utilize pollution-control devices
• It established NAAQS and AQI
• Clean Air Act: EPA
National Ambient Air Quality
Standards (NAAQS)
• Sets acceptable concentrations for 6 “criteria”
pollutants that:
– Threaten public health/the environment
over broad areas (non-point)
– Are emitted in large quantities
– CO, Pb, Nitrogen Oxides, Ozone, Particulate
Matter and Sulfur Dioxides
Air Quality Index (AQI)
• Measures levels of 5 criteria pollutants
• Forecast of daily air pollution levels
• Purpose to educate and protect publicfocuses on health effects
• Categories: green= good, yellow=
moderate, orange= unhealthy for sensitiv
groups, red= unhealthy, purple= very
unhealthy
National Emissions Standards for
Hazardous Air Pollutants
• Regulates emissions (from point
sources)
• For specific substances (air toxics w/
known or suspected serious health
effects (mutagens, carcinogens,
neurotoxins)
• Tend to be localized, from point sources
• Examples: Ammonia, chlorine, asbestos,
arsenic, mercury, benzene