Chapter 15: Air Pollution
What’s in the air we breathe?
Ozone
• Stratospheric ozone absorbs 95% of UV
radiation
• 3O2 + UV  2 O3
• Tropospheric ozone is harmful to plants,
animals, and humans.
• Tropospheric ozone is made when air pollutants
undergo chemical reactions because of UV
exposure.
Air pollution
• The presence of one or more chemicals in the
atmosphere in sufficient quantities and
duration to cause harm to humans, other
forms of life, and materials.
Classifying Pollutants
•
•
•
•
•
Sulfur dioxide (SO2)
Nitrogen oxides (NOx)
Carbon Oxides (CO, CO2)
Particulate matter (PM)
Photochemical oxidants (formed as a result of
sunlight acting on chemical compounds in the air)
• Lead & Other Metals
• Volatile Organic Compounds (VOCs)
*See table 46.1 pg. 521 in book
Sulfur dioxide (SO2)
Description: colorless corrosive gas
Major Human Sources: combustion of coal
Health Effects: respiratory irritant
Environmental Effects: harms stomata and
other plant tissue, changes soil and water pH
Property Damage: converts to sulfuric acid in
atmosphere – eats away at metals, paints, etc.
Nitrogen dioxide (NO2)
Description: reddish brown irritating gas
Major Human Sources: combustion of fossil fuels,
wood and biomass
Health Effects: respiratory irritant
Environmental Effects: precursor to ozone, leads to
formation of photochemical smog, converts to nitric
acid in atmosphere – changes soil & water pH
Property Damage: Nitric acid eats away at stone,
metals, paints, etc.
Carbon Monoxide
Description: colorless, odorless gas
Major Human Sources: incomplete combustion
of most matter, including fossil fuels and
biomass (77% from car exhaust)
Health Effects: interferes with oxygen transport
in the blood – causes headaches at low
concentrations, death at high concentrations
Carbon dioxide
Description: colorless odorless gas
Major Human Sources: formed from complete
combustion of most matter including fossil fuels
and biomass
Environmental Effects: greenhouse gas that
affects climate and alters ecosystems
Suspended Particulate Matter
Description: solid or liquid particles suspended in air
Major Human Sources: combustion of fuels, unpaved
roads, construction, agriculture
Health Effects: exacerbates respiratory and
cardiovascular disease, reduce lung function, premature
death, toxic particulates such as lead (former gasoline
additive, old paint) and mercury (burning of coal) could
lead to mutations, reproductive problems and cancers
Environmental Effects: reduce visibility, contributes to
haze and smog, scatters and absorbs sunlight leading to
cooler temperatures
Photochemical Oxidants
Description: formed from sunlight reacting with
chemical compounds such as nitrogen oxides
and sulfur oxides in the air, Ex. ozone
Health Effects: respiratory irritant
Environmental Effects: harmful to plant tissues,
leads to smog creation
Volatile Organic Compounds
Description: hydrocarbons (contain hydrogencarbon bonds) such as gasoline, lighter fluid,
perfumes, paints, etc. Typically give off a strong
aroma.
Health Effects: some can be harmful, some not
Environmental Effects: play a role in the
formation of photochemical oxidants such as
ozone
Air pollution has both natural and
human sources
• Natural Emissions: volcanoes, lightning, forest
fires , and even plants!
– Volcanoes: SO2, CO, particulate matter, NOx
– Lightning: create NOx
– Fires: particulate matter, CO, NOx
– Plants: VOCs such as ethylene and terpenes
(precursors to photochemical smog)
• Anthropogenic (human caused) emissions
Practice Questions
1.
A.
B.
C.
D.
E.
A secondary pollutant
Forms in the stratosphere.
Is transformed by sunlight or water.
Cannot be directly tracked
Does not directly harm humans.
Forms primarily from incomplete
combustion.
Practice Questions
1.
A.
B.
C.
D.
E.
A secondary pollutant
Forms in the stratosphere.
Is transformed by sunlight or water.
Cannot be directly tracked
Does not directly harm humans.
Forms primarily from incomplete
combustion.
2. Carbon monoxide
A. increases lung cancer rates.
B. leads to the formation of photochemical
smog.
C. is most problematic in rural areas.
D. does not directly cause deaths.
E. is produced by incomplete combustion.
2. Carbon monoxide
A. increases lung cancer rates.
B. leads to the formation of photochemical
smog.
C. is most problematic in rural areas.
D. does not directly cause deaths.
E. is produced by incomplete combustion.
SMOG
• Photochemical: aka “brown air smog” Caused
by UV reacting with chemicals (NOx, VOCs in
the atmosphere) Found in modern cities,
especially in warm, sunny areas.
• Industrial smog: aka “gray air smog” Caused
by burning of fossil fuels, adds sulfur to air.
Rare in developed countries now.
Smog over LA
Factors in smog formation
Factors Decreasing Smog:
• Precipitation
• Salty sea spray
• Wind
• Reduce factory/car
emissions
Factors increasing Smog
• Urban buildings
• Hills and mountains
• High temperatures
Temperature Inversion
Issues with Air Pollution – Acid
Deposition
•
•
•
•
Coal & oil release sulfur when burned
S + O2  SO2
2SO2 + O2  2SO3
SO3 + H2O  H2SO4
Acid Deposition
Effects of Acid Deposition
• Decrease soil pH (more acidic)  Nutrient
leaching
• Decrease pH of rivers, lakes, ponds, etc
• Kills fish
• Lung/respiratory problems
• Degrade metal pipes, leading to water pollution
• Plants become more susceptible to disease,
parasites, etc
Practice Questions
1. High levels of photochemical smog are due to
I. nitrogen dioxide
II. Sulfur dioxide
III. VOCs
A. I only
B. I and II only
C. II and III only
D. I and III only
E. I, II, and III
Practice Questions
1. High levels of photochemical smog are due to
I. nitrogen dioxide
II. Sulfur dioxide
III. VOCs
A. I only
B. I and II only
C. II and III only
D. I and III only
E. I, II, and III
2. Thermal inversions
A. increase the rate of smog formation.
B. trap high concentrations of pollution at
ground level.
C. result in increased levels of acid deposition
D. are caused by high levels of precipitation.
E. reduce the negative effects of VOCs.
2. Thermal inversions
A. increase the rate of smog formation.
B. trap high concentrations of pollution at
ground level.
C. result in increased levels of acid deposition
D. are caused by high levels of precipitation.
E. reduce the negative effects of VOCs.
Solutions???
• What are some ways we can cut down on air
pollution? Brainstorm some ideas at your
table.
Electrostatic Precipitator
• Static electricity is used to give the smoke an
electric charge.
• When it passes by electrodes of the opposite
charge, most of the smoke particles cling to
the electrodes.
Wet scrubbers
• Gas forced through scrubbing liquid 
Calcium hydroxide (limewater) or Mg(OH)2
SO2 + Ca(OH)2 → CaSO3 + H2 O
• SO2 + Mg(OH)2 → MgSO3 + H2 O
• MgSO3 → SO2 + MgO
• Technique removes up to 95%
Baghouse Filter
• Much like a vacuum
Clean Air Acts
• US Congress in 1970, 1977, 1990
• EPA regulation of emissions that contribute to
global warming, ozone depletion and air
pollution
Marketplace to reduce pollution
• Clean Air Act of 1990 allows an “emissions
trading policy”
• Given a certain number of pollution credits a
plant can use
• Can buy or sell extra credits
Practice Questions
1. Which pollution control method was proposed
by an amendment to the Clean Air Act?
A. allowing tolls to limit the use of
automobiles.
B. a market for sulfur emissions
C. the regulation of radon emissions
D. the use of catalytic converters
E. chemicals developed to prevent the
formation of ozone.
Practice Questions
1. Which pollution control method was proposed
by an amendment to the Clean Air Act?
A. allowing tolls to limit the use of
automobiles.
B. a market for sulfur emissions
C. the regulation of radon emissions
D. the use of catalytic converters
E. chemicals developed to prevent the
formation of ozone.
Practice Questions
2. If carbon monoxide emissions decreased
from 145 million tons annually to 80 million
tons annually, by what percentage have
emissions been reduced?
A.
B.
C.
D.
E.
41%
45%
47%
52%
55%
Practice Questions
2. If carbon monoxide emissions decreased
from 145 million tons annually to 80 million
tons annually, by what percentage have
emissions been reduced?
A.
B.
C.
D.
E.
41%
45%
47%
52%
55%
Emissions Trading Game
• The colors blue and black are now considered
pollutants. For each item of visible clothing that has
ANY of these colors on it, you must pay 1 ticket.
• Each student is allowed 2 tickets and a packet of
Smarties.
• If you do not have enough tickets to cover your
“pollution,” you will LOSE THE GAME! (and be charged a
fine)
• You may attempt to “buy” (with Smarties), trade, etc. to
gain tickets if you need.
• Person with most Smarties is the WINNER – they are
the “cleanest” factory