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17
Atmospheric Science and Air Pollution
Chapter Objectives
This chapter will help you:
Describe the composition, structure, and function of Earth’s atmosphere
Relate weather and climate to atmospheric conditions
Identify major pollutants, outline the scope of outdoor air pollution, and assess
potential solutions
Explain stratospheric ozone depletion and identify steps taken to address it
Define acidic deposition and illustrate its consequences
Characterize the scope of indoor air pollution and assess potential solutions
Lecture Outline
I.
Central Case: L.A. and its Sister Cities Struggle for A Breath of Clean Air
A. Today, L.A. still suffers the nation’s worst smog, but its skies are clearer than
in some of its ―sister cities‖ elsewhere in the world.
B. One of L.A.’s sister cities is Tehran, the capital of Iran. Both cities have a lot
of smog.
C. Health authorities blame several thousand premature deaths per year in Tehran
on lung and respiratory diseases resulting from air pollution. In 2006, fully
3,600 people succumbed in just a month.
D. As in Los Angeles, traffic generates most of the pollution in Tehran.
E. As with Los Angeles, topography worsens the problem.
F. And as with Los Angeles in recent decades, people are streaming Tehran from
elsewhere. As a result, the government’s efforts to rein in pollution are being
overwhelmed by population growth.
G. Cities like Tehran are taking steps to improve their air quality, just as
American cities like Los Angeles have done before them.
II.
The Atmosphere
1. The _____________________ is a thin layer of gases that surrounds Earth.
2. Earth’s atmosphere consists of 78% nitrogen (N2) and 21% oxygen (O2).
The remaining 1% is composed of argon (Ar) and minute concentrations
of several other gases.
3. Over our planet’s long history, the atmosphere’s composition has changed.
A. The atmosphere is layered.
1. The bottommost layer is the ____________________, which blanket’s
Earth surface and gives us the air we need to live.
2. The _______________________ extends from 11-50 km above sea level,
its temperature rising gradually with altitude.
3. A portion of the stratosphere between 17 km and 30 km above sea level
contains most of the atmosphere’s ozone and is called the
_________________. This layer greatly reduces the amount of UV
radiation that reaches Earth’s surface. The protection of the ozone layer is
vital for life on Earth.
4. Above the stratosphere lies the _____________________, which extends
from 50-80 km above sea level.
5. From the outer mesosphere, the ______________________
extends upward to an altitude of 500 km.
B. Atmospheric properties include temperature, pressure, and humidity.
1. ___________________________________ measures the force per
unit area produced by a column of air, and decreases with altitude.
2. ______________________________ is the ratio of water vapor a given
volume of air contains to the maximum amount it could contain at a
given temperature.
3. The temperature of air varies with location and time.
C. Solar energy heats the atmosphere, helps create seasons, and causes air to
circulate.
1. Energy from the sun heats air in the atmosphere, drives air movement,
helps create seasons, and influences weather and climate.
2. The spatial relationship between Earth and the sun determines how much
solar radiation strikes each point on Earth’s surface.
3. Because Earth is tilted on its axis (an imaginary line connecting the poles,
running perpendicular to the equator) by about 23.5°, the Northern and
Southern Hemispheres each tilt toward the sun for half the year, resulting
in the seasons.
4. Land and surface water absorb solar energy and then radiate heat, causing
some water to evaporate.
5. The difference in air temperatures at different altitudes sets into motion
_______________________________ as warm air rises, cools,
expands, and descends past other warm air that is rising.
D. The atmosphere drives weather and climate.
1. _______________________ specifies atmospheric conditions over
short time periods, typically hours or days, and within relatively
small geographic areas.
2. _______________________, in contrast, describes the pattern of
atmospheric conditions found across large geographic regions over long
periods of time, typically seasons, years, or millennia.
E. Air masses interact to produce weather.
1. The boundary between air masses that differ in temperature and moisture
(and therefore density) is called a ________________.
a. A mass of warmer, moister air replacing a mass of colder, drier air is a
____________________.
b. A mass of colder, drier air displacing a warmer, moister air mass is a
_____________________.
2. Adjacent air masses may also differ in atmospheric pressure.
a. A __________________________ contains air that descends because
it is cool and then spreads outward as it nears the ground. Highpressure systems typically bring fair weather.
b. In a ____________________________, warmer air rises, drawing air
inward toward the center of low atmospheric pressure. The rising air
expands and cools, and clouds and precipitation often result.
3. One type of weather event has implications for environmental health.
a. If a layer of cool air occurs beneath a layer of warmer air, this is known
as a _________________________, or ________________________.
b. The band of air in which temperature rises with altitude is called an
______________________________.
F. Large-scale circulation systems produce global climate patterns.
1. Near the equator, solar radiation sets in motion a pair of convective cells
known as ________________________.
2. Two pairs of similar but less intense convective cells, called
__________________ and ___________________, lift air and create
precipitation around 60° latitude north and south and cause air to
descend at around 30° latitude and in the polar regions.
3. These three pairs of cells account for the latitudinal distribution of
moisture across Earth’s surface.
4. As Earth rotates on its axis, north–south air currents of convective cells
appear to be deflected from a straight path; this is called the
__________________________.
G. Storms pose hazards.
1. _______________________ form when winds rush into areas of low
pressure where warm moisture-laden air over tropical oceans is rising.
2. _______________________ form when a mass of warm air meets a
mass of cold air and the warm air rises quickly, setting a powerful
convective current in motion.
III.
Outdoor Air Pollution
1. Whether from primitive wood fires or modern coal-burning power plants,
people have generated _______________________, gases and particulate
material added to the atmosphere that can affect climate or harm people or
other organisms.
2. _______________________ refers to the release of air pollutants.
3. In recent decades, government policy and improved technologies have
helped us reduce most types of ___________________ (often called
____________________________) in industrialized nations.
A. Natural sources can pollute.
1. Natural processes produce a great deal of air pollution. Some of these
natural impacts are made worse by human activity and land-use policies.
2. Volcanic eruptions release large quantities of particulate matter, as well as
sulfur dioxide and other gases, into the troposphere.
3. Sulfur dioxide reacts with water and oxygen and condenses into fine
particles called ________________________.
4. Fires from burning vegetation also pollute the atmosphere with soot and
gases.
5. Winds sweeping over arid terrain can send huge amounts of dust aloft.
B. We create outdoor air pollution.
1. Since the onset of industrialization, human activity has introduced a
variety of sources of air pollution. Air pollution can emanate from mobile
or stationary sources, and from _________________________ or
________________________.
2. Once in the air, a pollutant may do harm directly or may induce chemical
reactions that produce harmful compounds.
a. ___________________________, such as soot and carbon monoxide,
are pollutants emitted into the troposphere in a form that can be
directly harmful or that can react to form harmful substances.
b. ____________________________ are harmful substances produced
when primary pollutants interact or react with constituents of the
atmosphere.
3. Pollutants differ in the amount of time they spend in the atmosphere—
called their ________________________—because substances differ in
how readily they react in air and in how quickly they settle to the ground.
C. Clean Air Act legislation addresses pollution in the United States.
1. Congress has passed a number of laws dealing with pollution.
a. The ___________________________ set strict standards for air
quality, imposed limits on emissions, provided funds for research, and
allowed citizens to sue parties violating the standards.
b. The __________________________ sought to strengthen regulations
pertaining to air quality standards, auto emissions, toxic air pollution,
acidic deposition, and ozone depletion, while introducing an emissions
trading program.
c. In 1995, businesses and industry were allocated permits to release
sulfur dioxide that they could buy, sell, or trade among one another.
This market-based incentive program reduced sulfur dioxide levels.
D. The EPA sets standards for ―criteria pollutants.‖
1. The EPA and the states focus on six ____________________________,
pollutants judged to pose especially great threats to human health.
a. ___________________________ is a colorless, odorless gas
produced primarily by the incomplete combustion of fuels.
b. __________________________ is a colorless gas with a pungent
odor that is released when coal is burned. It contributes to acid
deposition.
c. __________________________ is a highly reactive, foul-smelling
reddish gas that contributes to smog and acid deposition.
d. __________________________ results from the interaction of
sunlight, heat, nitrogen oxides, and volatile organic compounds.
e. _________________________ is any solid or liquid particle small
enough to be carried aloft; it may cause damage to respiratory tissues
when inhaled.
f. ______________ is a metal that enters the atmosphere as a
particulate pollutant, released by industrial processes and fuel
combustion.
E. Agencies monitor emissions.
1. ______________________________________ are carbon-containing
chemicals used in and emitted by vehicle engines and a wide variety of
solvents and industrial processes, as well as by many household
chemicals and consumer items.
2. In the United States in 2008, human activity polluted the air with 123
million tons of the six monitored pollutants.
F. We have reduced U.S. air pollution.
1. Reduction in air pollutants have occurred despite population increases.
2. New technologies such as catalytic converters, electrostatic precipitators,
and ______________________ helped to reduce pollutants.
G. Toxic pollutants pose health risks.
1. _________________________________ are substances known to cause
cancer, reproductive defects, or neurological, developmental, immune
system, and respiratory problems in people and other organisms.
H. Industrializing nations are suffering increasing air pollution.
1. Chinese cities suffer the worst air pollution as they industrialize rapidly.
I. Air quality is a rural issue, too.
J. Smog is our most common air quality problem.
1. Since the onset of the industrial revolution, cities have suffered a type of
smog we call ________________________, or gray-air smog.
K. Photochemical smog results from a series of reactions.
1. ___________________________________, or brown-air smog, is formed
when sunlight drives chemical reactions between primary pollutants and
normal atmospheric compounds, producing a mix of over 100 different
chemicals, tropospheric ozone often being the most abundant.
L. We can take steps to reduce smog.
M. Synthetic chemicals deplete stratospheric ozone.
1. Ozone molecules are considered a pollutant at low altitudes, but at
altitudes of 25 km (15 mi) they are highly effective at absorbing incoming
ultraviolet radiation from the sun, thus protecting life on Earth’s surface.
2. Years of dynamic research by hundreds of scientists revealed that certain
airborne chemicals can destroy ozone by splitting its molecules apart, and
that most of these _____________________________ are human-made.
3. In particular, researchers pinpointed ______________________—humanmade compounds derived from simple hydrocarbons such as ethane and
methane in which hydrogen atoms are replaced by halogen atoms such as
chlorine, bromine, or fluorine.
a. Industry was mass-producing one class of halocarbon,
____________________________________, at a rate of a million
tons per year in the early 1970s, and this rate was growing by 20%
a year.
4. CFCs reach the stratosphere unchanged and can linger there for a century
or more.
N. The Antarctic ozone hole appears each spring.
1. In 1985, researchers shocked the world by announcing that stratospheric
ozone levels over Antarctica in springtime had declined by half in just the
previous decade, leaving a thinned ozone concentration that was soon
dubbed the _______________________.
2. In the Antarctic spring (starting in September), sunshine returns and UV
radiation dissipates the clouds, releasing chlorine atoms, which begin
destroying ozone.
3. The ozone hole vanishes until the following spring, and the globe as a
whole loses a bit more of its ozone layer.
O. The Montreal Protocol addressed ozone depletion.
1. The world community came together in 1987 to design the
_____________________________, which has been signed by 196
nations.
2. As a result, we have evidently stopped the Antarctic ozone hole from
growing worse. However, the ozone layer is not expected to recover
completely until 2060–2075.
3. Environmental scientists have attributed the success of the Montreal
Protocol to several factors.
a. Informative scientific research developed rapidly, facilitated by new
and evolving technologies.
b. Policymakers engaged industry in helping to solve the problem.
Industry became willing to develop replacement chemicals in part
because patents on CFCs were running out and firms wanted to
position themselves to profit from next-generation chemicals.
c. Implementation of the Montreal Protocol after 1987 followed an
adaptive management approach, adjusting strategies midstream in
response to new scientific data, technological advances, or economic
figures.
P. Acidic deposition is another transboundary pollution problem.
1. _____________________________ refers to the deposition of
acidic or acid-forming pollutants from the atmosphere onto Earth’s
surface.
2. Acidic deposition is one type of _____________________________,
which is the wet or dry deposition on land of a wide variety of pollutants.
Q. Acidic deposition has many impacts.
1. Acid deposition can also mobilize toxic metal ions from the soil and
convert them from insoluble to soluble molecules where they hinder
nutrient uptake by plants.
2. Acid water running off the land is toxic to many aquatic and terrestrial life
forms and has led to the death of ecosystems.
3. Other than altering natural ecosystems, acid precipitation also damages
crops.
4. Because the pollutants leading to acid rain may travel long distances,
their effects can be felt far from their points of origin.
R. We have begun to address acid deposition.
IV.
Indoor Air Pollution
1. Indoor air generally contains higher concentrations of pollutants than
does outdoor air. As a result, the health effects from
_________________________ in workplaces, schools, and homes
outweigh those from outdoor air pollution.
A. Indoor air pollution in the developing world arises from burning wood.
B. _______________________ and ______________________ are
the most dangerous indoor pollutants in developed nations.
1. Secondhand smoke has been found to cause many of the same
problems as directly inhaled cigarette smoke.
2. After cigarette smoke, radon gas is the second-leading cause of
lung cancer for Americans.
C. Many VOCs pollute indoor air.
1. Products that emit VOCs surround us; VOCs are emitted in very
small amounts.
2. The implications for human health of chronic exposure to VOCs are
far from clear. There are so many, at such low levels, that it is
difficult to study their effects.
D. Living organisms can pollute.
1. Dust mites, animal dander, fungi, mold, mildew, and bacteria can all
cause health problems.
2. Microbes that induce allergic responses are thought to be one
frequent cause of building-related illness.
3. When the cause of such an illness is a mystery, and when symptoms
are general and nonspecific, the illness is often called
____________________________________.
E. We can reduce indoor air pollution.
1. Using low-toxicity materials, monitoring air quality, keeping rooms
clean, and providing adequate ventilation are the keys to alleviating
indoor air pollution in most situations.
2. In the developed world, we can try to limit our use of plastics and
treated wood when possible and to limit our exposure to pesticides,
cleaning fluids, and other known toxicants by keeping them in a
garage or outdoor shed.
V.
Conclusion
A. Indoor air pollution is a potentially serious health threat but one that we
can do a great deal to minimize for ourselves and our families.
B. Outdoor air pollution has been addressed more effectively by
government legislation and regulation.
C. Much room for improvement remains, particularly in reducing
acidic deposition and photochemical smog.
Key Terms for Chapter 17
acidic deposition
acid rain
aerosols
air pollutant
air pollution
ambient air pollution
atmosphere
atmospheric deposition
atmospheric pressure
carbon monoxide
chlorofluorocarbons (CFCs)
Clean Air Act of 1970
Clean Air Act of 1990
climate
cold front
convective circulation
Coriolis effect
criteria pollutant
Ferrel cell
front
ground-level ozone
Hadley cell
halocarbons
high-pressure system
hurricanes
indoor air pollution
industrial smog
inversion layer
lead
low-pressure system
Montreal Protocol
nitrogen dioxide
nitrogen oxides
outdoor air pollution
ozone-depleting substances
ozone hole
ozone layer
particulate matter
photochemical smog
polar cell
primary pollutant
relative humidity
residence time
scrubbers
secondary pollutant
sick-building syndrome
stratosphere
sulfur dioxide
temperature inversion
thermal inversion
tornadoes
toxic air pollutant
troposphere
tropospheric ozone
volatile organic compounds (VOCs)
warm front
weather