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 plants, animals,
and materials such as buildings, or to alter ecosystems.
Why is air pollution considered a global system?
Earth’s atmosphere is a global commons or
worldwide public resource.
Major Air Pollutants
•
Sulfur Dioxide
•
Nitrogen Oxides
•
Carbon Monoxide
•
Particulate Matter
•
Lead
•
Volatiles Organic Compounds
•
Ozone
•
Mercury
•
Carbon Dioxide
Of the pollutants above what are the criteria
pollutants? What does criteria stand for?
Criteria Pollutants vs Primary Pollutants
Criteria Pollutants are controlled by the Clean Air
Act. The EPA is required to set National Ambient Air
Quality Standards (NAAQS) for the six common air
pollutants. These commonly found air pollutants (also
known as "criteria pollutants") are found all over the
United States.

Primary pollutants are direct products of
combustion and evaporation and can lead to
secondary pollutants.

On your chart notes mark the primary
pollutants.
Compound
Criteria Air Pollutants
Sulfur Dioxide
Primary
Nitrogen Oxide
Primary
Carbon Monoxide
Primary
Particulate Matter
Primary
Lead
Primary
Ozone
Other Air Pollutants
Volatile Organic Compounds
Primary
Mercury
Carbon Dioxide
Primary
Symbol
Anthropogenic Cause
Effects/ Impacts
Examples of Sources for the Six Criteria
Pollutants
1
3
2
O3 – Ozone
NO2 – Nitrogen Dioxide
CO – Carbon Monoxide
Ozone: Formed by the
interaction of sunlight with other
other pollutants: NO, CO, and
Volatile Organic Compounds
(VOCs)
Car exhaust and Electricity
Generation produce NO during
combustion, which gets
converted into NO2 in the
atmosphere
All combustion processes such
as car exhaust and Electricity
Generation
O3, NO2, and CO will be discussed further in Lesson 2
Lesson 1: Air Pollution Basics
Examples of Sources for the Six Criteria
Pollutants
4
5
PM2.5,10 – Particulate
Matter
Car Exhaust, Electricity
Generation, Fires, and Road
dust
6
Pb – Lead
SO2 – Sulfur Dioxide
Iron smelters and other
industrial processes.
Before it was banned, leaded
gasoline was a major contributor
to lead in the atmosphere.
Electricity Generation from
burning of coal.
O3, NO2, and CO will be discussed further in Lesson 2
Lesson 1: Air Pollution Basics
**Page 412
Primary and Secondary Pollutants
•
Primary Pollutants are emitted
directly from various sources and
cause harm in their emitted state.
•
•
Examples of Primary Pollutants:
NO, SO2, CO, CO2
Secondary Pollutants result from
chemical transformations in the
atmosphere.
•
Examples of Secondary
Pollutants: O3, H2O2, HNO3,
H2SO4, Nitrate and Sulfate
Particles
Lesson 1: Air Pollution Basics
What is the difference between a
primary and a secondary pollutant?
• Primary causes secondary.
• If society controls primary
then secondary pollution
will reduce.
Natural Sources of Air Pollution
Volcanoes
Lightning
Forest fires
Plants
Anthropogenic Sources of Air Pollution
On-road vehicles
Airplanes
Power plants
Industrial processes
Waste disposal
How does the Clean Air Act regulate
anthropogenic emissions?
•
•
In developing the Clean Air Act of 1970 and
subsequent amendments:
The Clean Air Act (CAA) is the
comprehensive federal law that regulates air
emissions from stationary and mobile
sources. Among other things, this law
authorizes EPA to establish National
Ambient Air Quality Standards (NAAQS) to
protect public health and public welfare and
to regulate emissions of hazardous air
pollutants.
Air Quality Index
Levels of Health Concern
A daily measure of the quality of the air generally published along with weather
reports based on the amount of the six criteria pollutants in the air.
What is photochemical smog and
how does it form?
• Key Components:
• Sunlight
• NO
• Oxygen
• VOC’s
• Ozone
2
Photochemical smog in
Denver!
Photochemical Smog
Thermal Inversions:
How does an inversion layer influence air
pollution events?
Thermal Inversion
when 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.
Acid Deposition
What is acid deposition?
What are the 2 primary pollutants?
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.
How does acid deposition have a
negative effect on Earth’s surface?

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
Acid Deposition
Ways to Prevent Air Pollution
Pollution control methods for SO2, NOx, and
particulates.
Removing sulfur dioxide from coal by
fluidized bed combustion
Better combustion of fuels to reduce NOx
Catalytic converters on cars (NOx )
Scrubbers on smoke stacks
Baghouse filters
Electrostatic precipitators
Baghouse filters- most efficient
Electrostatic precipitators
Scrubbers on smoke stacks
Catalytic Converter
an automobile exhaust-system component
containing a catalyst that causes
conversion of harmful gases (as carbon
monoxide and uncombusted
hydrocarbons) into mostly harmless
products (as water and carbon dioxide)
Good vs Bad Ozone
Even # Tables: Good ozone (blue poster)
pages 52-55, 424-427
Odd # Tables: Bad ozone (orange poster)
pages 415, 417-418
Good Ozone:
Formation and Breakdown of Ozone
How does the stratospheric ozone layer
form and why is it beneficial?
First, UV-C radiation breaks the bonds holding together the
oxygen molecule, leaving two free oxygen atoms:
1) O2 + UV-C -> 2O
Sometimes the free oxygen atoms result in ozone:
2) O2 + O -> O3
Ozone is broken down into O2 and free oxygen atoms when it
absorbs both UV-C and UV-B ultraviolet light:
3) O3 + UV-B or UV-C -> O2 + O
Breakdown of the Good Ozone
How does the stratospheric ozone layer
deteriorates?
Reducing our Good Ozone
4) O3 + Cl -> ClO + O2
5) ClO + O -> Cl + O2
6) O3 + O -> 2O2
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 = good up high, bad near by!!!
Anthropogenic
Contributions to Ozone
Destruction
What causes the depletion
of the ozone layer?
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 present 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
Steps taken to reduce ozone?
Montreal Protocol on Substances That Deplete the Ozone Layer in
1987: reduce CFCs by 50% by the year 2000.

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.
Indoor Air Pollutants
Main sources of indoor pollution for developing countries?
Wood, animal manure or coal used for cooking and heating in
developing countries.
Main sources of indoor pollution for developed world?
Asbestos
Carbon Monoxide
Radon
VOCs in home products
Sick building syndrome?
The buildup of toxic compounds and pollutants in an airtight space;
seen in newer buildings with good insulation and tight seals against
air leaks.