Chapter 15
Air Pollution and Stratospheric Ozone
Depletion
Air Pollution
• Air pollution: the
introduction of
chemicals, particulate
matter, or
microorganisms into the
atmosphere at
concentrations high
enough to harm living
things and materials, or
alter ecosystems
Major Air Pollutants
•
•
•
•
•
•
•
•
Sulfur dioxide (SO2)
Nitrogen oxides (NOx)
Carbon oxides
Particulate matter (PM)
Volatile Organic Compounds (VOCs)
Ozone (O3)
Lead
Mercury
Particulate Matter (PM)
Smog
• Portmanteau of smoke + fog
– Ex: “Brangelina”
– Ex: “Tomkat”
– Ex: “Strogiana Lima”
Photochemical (Brown) Smog
• NOx + VOCs + sunlight = photochemical smog
• Found in areas with a lot of cars (Los Angeles,
New York, Sydney, etc.)
Sulfurous (Gray) Smog
• SOx + PM + fog = sulfurous smog
• Found in areas with a lot of coal burning
(Victorian London)
Primary Pollutants
• Primary pollutants:
polluting compounds
that come directly out
of the smokestack,
exhaust pipe, or
natural emission
source
– Ex: CO, CO2, SO2, NOx,
and most suspended
particulate matter
Secondary Pollutants
• Secondary pollutants:
pollutants that have
undergone transformation
in the presence of
sunlight, water, oxygen, or
other compounds
– Ex: ozone (O3), sulfate
(SO42-), and nitrate (NO3-)
Natural Sources of Air Pollution
•
•
•
•
Volcanoes
Lightning
Forest fires
Plants
Anthropogenic Sources of Air Pollution
•
•
•
•
Vehicles
Power plants
Industrial processes
Waste disposal
History of Air Pollution in the U.S.
• www.youtube.com/watch?v=3PO_3exwN-I
What are some examples of
standards?
• Every student must achieve a minimum score in
the Keystone Exams before graduating high
school in Pennsylvania
• There may not be more than 2 rodent hairs per
100 grams of peanut butter
• Adriana Lima refuses to date Mr. Strogen because
she has “standards”
Clean Air Act
• Since 1970, the goal of the Clean Air Act has been to
reduce the amount of pollution in America’s air
• The Act created the National Ambient Air Quality
Standards (NAAQS), which sets a maximum level of
pollution allowed per pollutant
• Six major “criteria” pollutants are regulated:
– NO2
– SO2
– Ozone
– CO
– Lead
– Particulate Matter (PM)
Regulation
• The Environmental Protection Agency (EPA) has
regulatory authority over the air standards
• Each state is obligated by law to meet the
NAAQS
• Areas that do not meet the standards are called
“non-attainment”
Percent Change in Air Quality
Pollutant
1990 vs. 2008
Carbon Monoxide
-68%
Ozone
-14%
Lead
-78%
Nitrogen Dioxide
-35%
PM10
-31%
Sulfur Dioxide
-59%
Comparison of Growth Areas and
Emissions, 1980-2008
Number of People Living in Counties with Air Quality
Concentrations Above the Level of the NAAQS in 2008
Photochemical Smog
Fig. 17-6 p.
424
Photochemical Smog
• http://teachers.redclay.k12.de.us/william.bak
er/Environmental%20Science%20Files/06%20
Air%20PollutionSolid%20Waste/photochemical_anim.swf
Photochemical Smog
40
Ozone
VOCs
Parts per million
30
Nitric oxides
20
10
0
6
7
A.M.
8
9
10
11
12
1
Noon
Time
2
3
4
5
6
7
8
P.M.
Photochemical Smog
www.airinfonow.org/html/makingozone/o3play.htm
www.airinfonow.org/html/lungattack/lungplay.htm
Thermal Inversions
• Thermal Inversion:
when a relatively warm
layer of air at midaltitude covers a layer of
cold, dense air below
• The warm inversion layer
traps emissions that
then accumulate
beneath it
Acid Deposition
Acid Deposition
• Acid deposition: occurs when nitrogen oxides
and sulfur oxides are released into the
atmosphere and combine with atmospheric
oxygen and water, forming 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
• Lowering the pH of lake
water
• Decreasing species diversity
of aquatic organisms
• Mobilizing metals that are
found in soils and releasing
these into surface waters
• Damaging statues,
monuments, and buildings
Effects of Acid Deposition
• http://news.discovery.com/videos/earth-acidrain-eating-washington-dc.html
Ways to Prevent Air Pollution
• Catalytic converters on cars
• Removing sulfur dioxide from coal by fluidized
bed combustion
• Scrubbers on smoke stacks
• Baghouse filters
• Electrostatic precipitators
Catalytic Converter
• http://www.youtube.com/watch?v=rmtFpSV0tY
Wet
Scrubber
Baghouse Filter
Electrostatic
Precipator
Stratospheric 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
Ozone
Formation & Breakdown of Ozone
• First, UV-C radiation breaks the bonds holding
together the oxygen molecule O2, leaving two
free oxygen atoms: O2 + UV-C
2O
• Sometimes the free oxygen atoms result in
ozone:
O2 + O
O3
• Ozone is broken down into O2 and free oxygen
atoms when it absorbs both UV-C and UV-B
ultraviolet light:
O3 + UV-B or UV-C
O2 + O
Anthropogenic Contributions to Ozone
Destruction
• 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
• When CFCs are released into the troposphere
they make their way to the stratosphere
• The ultraviolet radiation has enough energy to
break the bond connecting chlorine to the CFC
molecule
• Which can then break apart the ozone
molecules
Anthropogenic Contributions to Ozone
Destruction
• First, chlorine breaks ozone’s bonds and pulls off one
atom of oxygen, forming a chlorine monoxide
molecule and O2:
O3 + Cl
ClO + O2
• Next, a free oxygen atoms pulls the oxygen atom
from ClO, liberating the chlorine and creating one
oxygen molecule:
ClO + O
Cl + O2
• 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
• 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
Depletion of the Ozone Layer
• Destruction is seasonal:
• Mid-spring at poles is low
O3 concentration point
• During winter ice clouds
concentrate Cl atoms
• They are released during
spring, destroying ozone
• By summer production is
greater than depletion
Indoor Air Pollutants
SOURCE
Indoor cooking fuel
Asbestos
Carbon Monoxide
Radon
VOCs in home
products
RISK
REMEDIATION
Sick Building Syndrome
• Due to insulation and
prevention of drafts
• Caused by high concentrations
of VOCs, hydrocarbons,
allergens
• Present if symptoms start upon
entry and are relieved 20
minutes after exiting
• EPA - four reasons: faulty
ventilation, chemical
contamination from inside or
outside, and biological
contamination