MATH SKILLS READING SKILLS
Use the table below to answer questions 31–32. Read the passage below, and then answer
the questions that follow.
31. Analyzing Data Which of the types of
species in the table below are most accurately Excerpt from M. Reaka-Kudla, D. Wilson,
described? What do the numbers indicate and E. Wilson, eds., Biodiversity II, 1996.
about how well various species are studied?
Aside from the academic tradition of biodiver-
32. Applying Quantities Which of the types of sity, another powerful influence, related to
species may represent the greatest unknown biodiversity, brought our culture to its current
loss of biodiversity? Which type of species is level of technological development: the explo-
probably least important for further research ration of the New World. From the thirteenth
into biodiversity? to the nineteenth centuries, technological
developments in navigation allowed European
Estimates of Knowledge of Earth’s Species voyagers to embark on an unprecedented
exploration of the globe. These expeditions
Type of Number Described Number Accuracy revolutionized knowledge of the geography,
species of species species threatened of human culture, and biology of the world at
described as % of or extinct estimates the time. This ultimately led to a reevaluation
total of human society’s place in the world and an
understanding of the evolution of all living
Bacteria 4,000 0.40 (unknown) very poor things. But the exploration also allowed the
94.55 3,843 good acquisition of untold wealth in living and non-
Vertebrates 52,000 26.67 628 moderate living natural resources, which was brought
84.38 back from the New World and invested in the
Crustaceans 40,000 31,277 good culture of western Europe.
Plants 270,000 1. What do the authors probably mean by
the term influence?
WRITING SKILLS a. a force of cultural change
b. a new type of scientific discovery
33. Writing Persuasively Write a letter to the c. a source of geographic information
editor of a publication or to an elected repre- d. a form of navigation
sentative in which you express your opinion
regarding protections of endangered species 2. Which of the following are not mentioned
that might affect your local area. by the authors as factors in our current
level of technological development?
34. Outlining Topics Outline the major strat- a. geographical information
egies for protecting biodiversity that have b. knowledge of a variety of species
been described in this chapter. List pros and c. new forms of government
cons of each strategy. d. evolutionary theory
3. Which of the following did the authors
most likely discuss in the paragraph just
before this passage?
a. natural resources of the New World
b. religious beliefs of native peoples
c. academic tradition of European biology
d. history of European expeditions
Chapter 10 Review 279
10C H A P T E R Standardized Test Prep
Understanding Concepts Reading Skills
Directions (1–4): For each question, write on a Directions (7–10): Read the passage below. Then
separate sheet of paper the letter of the correct answer the questions.
answer.
Scientists are developing new methods of
1 Which of the following phrases describes conservation in an attempt to preserve species
on the verge of extinction. Captive-breeding
the term genetic biodiversity? programs try to restore the population of a
A. the variety of habitats found in an species. Another approach is to preserve germ
plasm. Germ plasm is any form of genetic
ecosystem material, such as that contained within the
B. the variety of species present in an reproductive, or germ, cells of plants or
animals. Germ-plasm banks store seeds,
ecosystem sperm, eggs, or pure DNA in special controlled
C. the differences between populations of environments. Farmers and gardeners also
preserve germ plasm when they save and
species share seeds.
D. the different genes contained within
7 One way that scientists are trying to preserve
members of a population
species on the verge of extinction is by
2 What species are critical to the survival of A. logging tropical rain forests
B. developing new methods of conservation
an ecosystem? C. removing species from the endangered list
F. bottleneck species H. exotic species D. abandoning new methods of conservation
G. endemic species I. keystone species
8 What is the aim of captive-breeding
3 Which of the following describes a species
programs?
that is likely to become endangered? F. to increase the population size of a
A. insects that have to adapt to an urban
species to double its former size
environment G. to restore the animal kingdom
B. small mammals that live in urban H. to restore germ plasm
I. to restore the population of a species
ecosystems
C. birds that can only survive in rural 9 What is stored at germ-plasm banks?
ecosystems A. seeds, sperm, eggs, or pure DNA
D. mammals that need an undeveloped B. seeds that are not used by farmers and
habitat to breed successfully gardeners
C. animals from captive-breeding programs
4 Why is international cooperation crucial to
that were not able to survive in the wild
securing future biodiversity? D. instructions about how to restore a
F. Wildlife protection laws vary from
species when it becomes extinct
country to country.
G. Poaching is the most important reason 0 Compare the genetic material in germ-
for a species population decline. plasm banks wih the seeds saved and
H. Habitat destruction and other causes of shared by farmers and gardeners.
extinction cross international borders.
I. Protecting species sometimes conflicts
with the interests of human populations.
Directions (5–6): For each question, write a short
response.
5 Why could private or non-governmental
agencies be more effective in protecting
species than government agencies?
6 Compare endangered species with
threatened species.
280 Chapter 10 Standardized Test Prep
Interpreting Graphics
Directions (11–14): For each question below, record the correct answer on
a separate sheet of paper.
The graph below shows the number of families of marine organisms that
existed millions of years ago. Use this graph to answer questions 11 and 12.
Number of marine families 1,200 Major Extinction Events
1,000
Major extinction events
800
600 500 400 300 200
400 Millions of years ago
200
0
100 0
q How has the biodiversity of marine families changed over the last
500 million years?
F. It has increased.
G. It has decreased slightly.
H. It has remained the same.
I. It has decreased significantly.
wWhat is the average number of families of marine organisms lost in a
major extinction event?
A. 25 C. 100
B. 75 D. 150
e If 90 families were lost in an extinction event that lasted 10 million
years, and each family contained 200 species, how many species were
lost every 100,000 years during that period?
F. 90 H. 200
G. 180 I. 360
r What do we know about the number of individual species currently Test
living on Earth? Converting the largest
A. There are no new species being found. numbers to scientific
B. All the species that exist on Earth have been cataloged. notation may help
C. About 1.7 million species are known to exist. you simplify your
D. There are more trees and mammals than there are insects. calculations.
Chapter 10 Standardized Test Prep 281
10C H A P T E R Exploration Lab: FIELD ACTIVITY
Objectives Differences In Diversity
̈ USING SCIENTIFIC METHODS Observe Biodiversity is most obvious and dramatic in tropical rain forests
and measure differences in species and coral reefs, but you do not have to travel that far to observe
diversity between two locations. differences in species diversity or to see the effects that humans
can have on biodiversity.
̈ USING SCIENTIFIC METHODS Graph and
analyze data collected to reflect Recall that biodiversity is most often defined as the number of
differences in species diversity. different species that are present in a given area. This measure
can be estimated by making a sample count of species within a
̈ Evaluate the possible reasons for representative area. It is often easiest and most effective to collect
observed differences in biodiversity. or observe small organisms, such as insects and soil dwellers, or
stationary organisms, such as plants and trees. In this activity,
̈ USING SCIENTIFIC METHODS Infer other you will investigate the differences in species diversity in two
human activities that may influence areas that are close to each other, but that are affected differently
local biodiversity. by humans. You may work in teams or groups.
Materials Procedure
graph paper 1. Choose two sites for your analysis. Site 1 should be an area
hand lens that has been greatly affected by humans, such as your
meterstick or tape measure school building and the surrounding sidewalks, parking area,
pen or pencil or groomed lawns. Site 2 should be an area within view of
string or chalk line site 1 but that is less affected by humans, such as a wooded
area or a vacant lot overgrown with weeds. If directed by
optional materials: local-area field your teacher, you may choose more than two sites. Also ask
guides for plants, animals, and your teacher about your sample square size.
soil organisms; shovel or trowel
2. At each site, measure a 5 m ҂ 5 m square area using the
meterstick or tape measure. You might use the edge of a
building as a side of your square, or you might use trees as
the corners. Mark the measurement of the area with string or
a chalk line, as shown in the photograph.
3. Observe each site carefully, and record a detailed description
of each site. Include as many features as possible, such as
location, soil condition, ways the area is used, amount of sun
or rain exposure, and other factors that might affect the
organisms that exist there.
4. For each site, create a table like the table below.
Species Counts Per Site
Species type Site number ___ Site number ___
̈ Step 2 Measure and mark off Animals DO NOT WRITE
sample areas for your observation Plants IN THIS BOOK
and counts of species diversity. Fungi and other
soil organisms
282 Chapter 10 Exploration Lab
5. Using your hand lens, find as many different species as pos- ̈ Step 5 Observe and record how
sible within the site. Record each new species by placing a many different types of organisms
slash or tick mark in the column for each different species you find within each sample area.
identified in each general category. You do not need to iden-
tify every organism by scientific name, but using field guides
may help you have an idea of what you are finding. You may
also make more specific categories (such as birds, insects,
grasses, and trees) if you are able. Be careful not to disturb
the area unnecessarily.
6. Repeat steps 2–5 for each site. If directed by your teacher,
compare your data with those of other groups.
7. After you have made and recorded all of your observations,
put away your materials and restore anything you disturbed
at the sites.
Analysis
1. Constructing Graphs Create a bar graph of the number of
species counted at each site. As directed by your teacher, you
may combine all species counts into one total per site or
graph each category of organisms separately.
2. Analyzing Results Based on your observations of the organ-
isms found at the sites, which area reflected a higher level of
biodiversity?
3. Interpreting Results What factors may have contributed to
the differences in biodiversity at the sites?
Conclusions
4. Drawing Conclusions What can you conclude about the
effect of human activities on biodiversity?
5. Applying Conclusions What other human activities, besides
those you observed directly, could have affected the biodiver-
sity present at your sites?
6. Evaluating Methods Do you feel that the method used in
this lab was an effective way to identify biodiversity in an
area? Why or why not? How could it have been improved?
Extension
1. Research and Communications If you were able to use
local field guides, what can you generalize about the
organisms that you were able to identify? Pay attention to
aspects such as how easily recognized each organism is,
how common it is in your local area, where it is found out-
side of your area, or what other unique facts are known
about the biology or habitat needs of the organism.
Chapter 10 Exploration Lab 283
DR. E. O. WILSON: CHAMPION OF BIODIVERSITY
Dr. Edward Osborne Wilson most influential scientists and citi- Alabama at the age of 20, Wilson
deserves some of the credit for the zens of our time. was well known as a promising
fact that this book includes a chap- entomologist—an expert on the
ter called “Biodiversity.” A few It All Started with Bugs insect world. His specialty is the
decades ago, the word biodiversity study of ants and their complex
was used by few scientists and was Even before his scientific career, social behaviors. So it makes sense
found in few dictionaries. Dr. Wilson developed a fascination that Wilson next went to study at
Wilson has helped make the con- with insects and the natural Harvard University, home to the
cept and value of biodiversity world. He always had high expec- world’s largest ant collection. While
widely recognized, through his tations of himself but made the at Harvard, he earned his Ph.D.,
extensive research, publishing, best of circumstances. Although conducted field research around the
organizing, and social advocacy. his parents were divorced and his world, collected more than 100 pre-
father’s government career viously undescribed species, and
Since his early career as a pio- required frequent moves, Wilson wrote several books on insect physi-
neer in the fields of entomology found companionship in the ology and social organization. He
and sociobiology, Dr. Wilson has woods of the southern United eventually became curator of the
gained recognition for many addi- States or the museums of Museum of Entomology at Harvard.
tional accomplishments. He has Washington, D.C. After injuries
written two Pulitzer Prize-winning damaged his vision and hearing, Clearly, Wilson has a passion
nonfiction books, and has Wilson focused his scientific skills for insects. “There is a very special
received the National Medal of on the smaller forms of life. pleasure in looking in a micro-
Science and dozens of other scien- scope and saying I am the first per-
tific awards and honors. Wilson is By the time he earned his mas- son to see a species that may be
widely recognized as one of the ter’s degree at the University of millions of years old,” he says.
Some of Wilson’s research has
̈ Dr. Wilson with one of his favorite subjects—ants. focused on the social behavior
of ants. Among other important
scientific findings, Wilson was
the first to demonstrate that ant
behavior and communication is
based mostly on chemical signals.
From Insects to Humans
In 1971, Wilson published The
Insect Societies, which surveyed the
evolution of social organization
among wasps, ants, bees, and ter-
mites. Wilson began to extend his
attempts to understand the relation-
ship of biology and social behavior
to other animals, including humans.
In 1975, Wilson published a con-
troversial book exploring these new
ideas, called Sociobiology. Now an
accepted branch of science, sociobi-
ology is the study of the biological
basis of social behavior in animals,
including humans.
During Wilson’s studies of the
behavior of ants and other social
insects, he became interested in the
284 Chapter 10 Making a Difference
insects’ role in the ecosystems where ̈ Dr. Wilson (center) speaks to politicians and the public about the need
he studied them. Some of his to conserve our planet’s biodiversity.
research involved camping for
months at a time in a remote wilder- The book showed both how such private meetings with scientists and
ness such as the Amazon basin, care- incredible biodiversity has evolved policy makers around the globe,
fully studying the activities of certain on the Earth and how this asset is urging them to support conserva-
species. His writings include amaz- being lost because of current human tion efforts based on sound science.
ing tales of watching huge colonies activities. The book clearly
of “driver” ants swarm out over an explained for the general public Dr. Wilson recently began pro-
area, capturing and killing a great many of the problems and potential moting the need for a global bio-
many other species in their path. solutions regarding biodiversity that diversity survey. This project
we have studied in this chapter. would involve an international
If you have ever played the scientific effort on par with the
popular computer game SimAntTM, Urgent Work Human Genome Project. Wilson
Dr. Wilson again deserves credit for states that “to describe and clas-
providing the inspiration. In 1990, Despite his fame, Wilson is a soft- sify all of the species of the world
Wilson received his second Pulitzer spoken fellow who would prefer to deserves to be one of the great sci-
Prize for co-authoring The Ants, an live a quiet life with his research and entific goals of the new century.”
enormous encyclopedia of the ant with his family in their home in the
world. In addition to describing woods of Massachusetts. But the What Do You Think?
8,800 known species of ants, the urgent problem of species loss makes
book details the great variations Wilson willing to face the public. Do you find insects interest-
among ant species in terms of “Humanity is entering a bottleneck ing? Could you imagine your-
anatomy, biochemistry, complex of overpopulation and environmen- self as an entomologist? Do
social behaviors, and especially their tal degradation unique in history. We you think that Dr. Wilson
critical role in many ecosystems. need to carry every species through made a goal early in his life to
Wilson reminds us that ants “are the bottleneck . . . Along with culture be an internationally famous
some of the most abundant and itself, they will be the most precious conservationist? What has led
diverse of the Earth’s 1.4 million gift we can give future generations.” him to take on this role?
species. They’re among the little
creatures that run the earth. If ants In 1986, Wilson served as one
and other small animals were to dis- of the leaders of the first National
appear, the Earth would rot. Fish, Forum on Biodiversity, and then as
reptiles, birds—and humans— editor of Biodiversity, the resulting
would crash to extinction.” collection of reports. Wilson
continues to engage in public and
Onward to Biodiversity
As with many great scientists, each
thing Dr. Wilson studies leads him
to new questions and new ideas.
During his research in remote lands,
Wilson spent time reflecting and
writing on the nature of ecosystems,
the importance of biodiversity, and
the role of humans in relation to
these. In 1992, he put many of these
ideas into another popular book
called The Diversity of Life. This
book combined Wilson’s engaging
writing style and personal expertise
with the latest ecological research.
Chapter 10 Making a Difference 285
WATER, AIR, AND LAND
286
4U N I T
CHAPTER 11
Water
CHAPTER 12
Air
CHAPTER 13
Atmosphere and
Climate Change
CHAPTER 14
Land
CHAPTER 15
Food and Agriculture
For thousands of years, humans
have altered the environment to
grow food. These rice paddies in
China are built to trap water from
the monsoon rains.
287
Water 11C H A P T E R
288 Chapter 11 Water 1 Water Resources
2 Water Use and Management
3 Water Pollution
PRE-READING ACTIVITY
Layered
Book
Before you
read this chap-
ter, create the FoldNote
entitled “Layered Book”
described in the Reading and
Study Skills section of the
Appendix. Label the tabs of
the layered book with “Water
Resources,” “Water Use,”
“Water Management,” and
“Water Pollution.” As you
read the chapter, write infor-
mation you learn about each
category
under the
appropri-
ate flap.
This composite photograph shows
what an iceberg might look like if
you could see the entire iceberg.
SECTION 1
Water Resources
EARTH SCIENCE CONNECTION
The next time you drink a glass of water, think about where the Objectives
water came from. Did you know that some of the water in your
glass may have been part of a rainstorm that pounded the Earth ̈ Describe the distribution of Earth’s
long before life existed? Or that water may have been part of a water resources.
dinosaur that lived millions of years ago. Some of the water we
drink today has been around since water formed on Earth bil- ̈ Explain why fresh water is one of
lions of years ago. Water is essential to life on Earth. Humans can Earth’s limited resources.
survive for more than a month without food, but we can live for
only a few days without water. ̈ Describe the distribution of Earth’s
surface water.
Two kinds of water are found on Earth. Fresh water—the
water that people can drink—contains little salt. Salt water—the ̈ Describe the relationship between
water in oceans—contains a higher concentration of dissolved groundwater and surface water in
salts. Most human uses for water, such as drinking and agricul- a watershed.
ture, require fresh water.
Key Terms
The Water Cycle
surface water
The Earth is often called “the Water Planet” because it has an river system
abundance of water in all forms: solid, liquid, and gas. Water is watershed
a renewable resource because it is circulated in the water cycle, groundwater
as shown in Figure 1. In the water cycle, water molecules travel aquifer
between the Earth’s surface and the atmosphere. Water evapo- porosity
rates at the Earth’s surface and leaves behind salts and other permeability
impurities. Water vapor, which is a gas, rises into the air. As recharge zone
water vapor rises through the atmosphere, the gas cools and con-
denses into drops of liquid water that form clouds. Eventually the Figure 1 ̈ The water cycle is the
water in clouds falls back to Earth and replenishes the Earth’s continuous movement of water
fresh water. The oceans are an important part of the water cycle between Earth and its atmosphere.
because almost all of Earth’s water is in the oceans.
Section 1 Water Resources 289
SALT WATER 97% Global Water Distribution
FRESH To understand why fresh water is such a limited resource, you
WATER 3% have to understand how little fresh water is found on Earth.
Although 71 percent of the Earth’s surface is covered with
Icecaps and Other fresh water, nearly 97 percent of Earth’s water is salt water in
glaciers 77% water 1% oceans and seas. Figure 2 illustrates this relationship. Of
the fresh water on Earth, about 77 percent is frozen in gla-
Groundwater 22% ciers and polar icecaps. Only a small percentage of the
water on Earth is liquid fresh water that humans can use.
Figure 2 ̈ This pie graph shows the The fresh water we use comes mainly from lakes and rivers
distribution of water on Earth. What and from a relatively narrow zone beneath the Earth’s surface.
percentage of the Earth’s fresh water
is in a form that humans can use? Surface Water
Surface water is fresh water on Earth’s land surface. Surface
water is found in lakes, rivers, streams, and wetlands. Throughout
history, people have built cities, towns, and farms near reliable
sources of surface water. Some of the oldest cities in the world
were built near rivers. Today, most large cities depend on surface
water for their water supplies. Rivers, lakes, and streams provide
drinking water, water to grow crops, food such as fish and shell-
fish, power for industry, and a means of transportation by boat.
■✓● Reading Check Why do most large cities depend on surface water?
(See the Appendix for answers to Reading Checks.)
Figure 3 ̈ Watersheds of the World
This map shows the Earth’s major water-
sheds. The highlighted area of the satellite
image below shows that the Mississippi
River watershed covers almost half of
the United States.
290 Chapter 11 Water
River Systems Have you ever wondered where all the water in a Connection to Biology
river comes from? Streams form as water from falling rain and
melting snow drains from mountains, hills, plateaus, and plains. Ganges River Dolphins The
As streams flow downhill, they combine with other streams and Ganges River dolphin is one of
form rivers. The more streams that run into a river, the larger the the world’s few freshwater
river becomes. As streams and rivers move across the land, they dolphin species. This dolphin is
form a flowing network of water called a river system. If a river almost completely blind, but it
system is viewed from above, it can look like the roots of a tree can easily navigate through silty
that are feeding into a trunk. The Mississippi, the Amazon, and river water by using sonar.
the Nile are enormous river systems because they collect the
water that flows from vast areas of land. The Amazon River sys- www.scilinks.org
tem is the largest river system in the world—it drains an area of
land that is nearly the size of Europe. Topic: Watersheds
Code: HE81636
Watersheds The area of land that is drained by a river is
known as a watershed. The watershed of the Mississippi River
is shown in the satellite image in Figure 3. Pollution anywhere
in a watershed may end up polluting a river. The amount of
water that enters a watershed varies throughout the year.
Rapidly melting snow as well as spring and summer rains can
dramatically increase the amount of water in a watershed.
Other times of the year, the river system that drains a water-
shed may be reduced to a trickle. Communities that depend on
rivers for water can be severely affected by these changes to the
river system.
Section 1 Water Resources 291
Geofact Groundwater
How Much Groundwater Is Most of the fresh water that is available for human use cannot be
There on Earth? There are about seen—it exists underground. When it rains, some of the water
50 million cubic kilometers of that falls onto the land flows into lakes and streams. But much of
groundwater on Earth. That means the water percolates through the soil and down into the rocks
there is about 20 times more water beneath. Water beneath the Earth’s surface in sediment and rock
underground than in all of the formations is called groundwater.
rivers and lakes on Earth!
As water travels beneath the Earth’s surface, it eventually
reaches a level where the rocks and soil are saturated with water.
This level is known as the water table. In wet regions, the water
table may be at the Earth’s surface and a spring of fresh water
may flow out onto the ground. But in deserts, the water table
may be hundreds of meters beneath the Earth’s surface. The
water table is actually not as level as its name implies. The water
table has peaks and valleys that match the shape of the land
above it. Just as surface water flows downhill, groundwater tends
to flow slowly from the peaks of the water table to the valleys.
■✓● Reading Check How can the location of the water table in wet
regions be different from its location in deserts?
The Ogallala Aquifer:
An Underground Treasure
Anyone who has eaten food pro- Ogallala Aquifer has started to ̈ The Ogallala Aquifer holds
duced in the United States has show its limits. Water is being about 4 quadrillion liters of water—
probably enjoyed the benefits of withdrawn from the aquifer 10 to enough to cover the United States
the Ogallala Aquifer, one of the 40 times faster than it is being to a depth of 0.5 m (1.5 ft).
largest known aquifers in the world. replaced. In some places, the water
This enormous underground water table has dropped more than 30 m
system formed from glaciers that (100 ft) since pumping began.
melted at the end of the last Ice
Age, 12,000 years ago. Today, the Humans are not the only living
Ogallala Aquifer supplies about one- things that depend on the Ogallala
third of all the groundwater used in Aquifer. In some areas, the aquifer
the United States. flows onto the surface and creates
wetlands, which are a vital habitat
People began to use the for many organisms, especially
Ogallala Aquifer extensively for irri- birds. These wetlands are often the
gation in the 1940s. With help first habitats to disappear when the
from this ancient water source, water table falls.
farmers turned the Great Plains
into one of the most productive Many people are working
farming regions in the world. For together to try to conserve the
many years, farmers seemed to Ogallala Aquifer. For example,
enjoy a limitless supply of fresh some farmers have begun to limit
water. But in recent years, the irrigation during bird migrations in
order to allow surface-water levels
292 Chapter 11 Water
Aquifers An underground formation that contains groundwater www.scilinks.org
is called an aquifer. The water table forms the upper boundary of
an aquifer. Most aquifers consist of materials such as rock, sand, Topic: Groundwater
and gravel that have a lot of spaces where water can accumulate. Code: HE80699
As well, groundwater can dissolve rock formations, such as those Topic: Aquifers
made of limestone, and fill vast caves with water, which creates Code: HE80089
underground lakes. Aquifers are an important water source for
many cities and for agriculture.
Porosity and Permeability Although most rocks appear solid,
many kinds of rocks contain small holes, or pore spaces. Porosity
is the percentage of the total volume of a rock that has spaces
(pores). Water in an aquifer is stored in the pore spaces and flows
from one pore space to another. The more porous a rock is, the
more water it can hold. The ability of rock or soil to allow water
to flow through it is called permeability. Materials such as gravel
that allow the flow of water are permeable. Materials such as clay
or granite that do not allow the flow of water are impermeable.
The most productive aquifers usually form in permeable materials,
such as sandstone, limestone, or layers of sand and gravel.
EARTH SCIENCE CONNECTION
̈ Sandhill cranes are among the
many kinds of birds that rely on
water from the Ogallala Aquifer.
to rise. Other farmers have the value of the Ogallala Aquifer CRITICAL THINKING
adopted water-saving irrigation and are fighting to preserve it.
systems and are planting crops They are pressuring politicians to 1. Applying Ideas Most of the
such as wheat or grain sorghum, replace policies that encourage water in the Ogallala Aquifer came
which require less water than corn wasting water with policies that from glaciers that melted thousands
or cotton. promote water conservation. These of years ago. What is the aquifer’s
efforts may help save this under- primary water source today?
Many farmers and other resi- ground treasure.
dents of the Great Plains recognize 2. Expressing Viewpoints Do
you think residents of the Great
Plains are the only people who
have an interest in conserving the
Ogallala Aquifer? Write an editorial
that expresses your viewpoint.
WRITING SKILLS
Section 1 Water Resources 293
Figure 4 ̈ Groundwater and the Water Table
Aquifers are underground formations
that hold water. Impermeable rock
can be porous or nonporous, but
only permeable rock allows water
to pass through it.
The Recharge Zone To reach an aquifer, surface water must
travel down through permeable layers of soil and rock. Notice
the permeable layers above the aquifer in Figure 4. An area of the
Earth’s surface from which water percolates down into an aquifer
is called a recharge zone. Recharge zones are environmentally
sensitive areas because any pollution in a recharge zone can also
enter the aquifer.
The size of an aquifer’s recharge zone is affected by the per-
meability of the surface above the aquifer. Structures such as
buildings and parking lots can act as impermeable layers to
reduce the amount of water entering an aquifer. Communities
should carefully manage recharge zones, because surface water
can take a very long time to refill an aquifer. In fact, aquifers can
take tens of thousands of years to recharge.
Wells If you go nearly anywhere on Earth and dig a hole deep
enough, you will eventually find water. A hole that is dug or
drilled to reach groundwater is called a well. For thousands of
years, humans have dug wells to reach groundwater. We dig wells
because groundwater may be a more reliable source of water
than surface water in some areas and because water is filtered
294 Chapter 11 Water
and purified as it travels underground. The height of the water
table changes seasonally, so wells are drilled to extend below the
water table. However, if the water table falls below the bottom of
the well during a drought, the well will dry up. In addition, if
groundwater is removed faster than it is recharged, the water table
may fall below the bottom of a well. To continue supplying water,
the well must be drilled deeper.
S E C T I O N 1 Review
1. Describe the distribution of water on Earth. Where is CRITICAL THINKING
most of the fresh water located? 5. Making Comparisons Read the description of
2. Explain why fresh water is considered a limited aquifers. Why is an underground lake an aquifer?
resource.
READING SKILLS
3. Explain why pollution in a watershed poses a poten-
tial threat to the river system that flows through it. 6. Analyzing Relationships Describe the relationship
between groundwater and surface water in a water-
4. Describe how water travels through rock. shed. What human activities in a recharge zone can
affect the groundwater?
Section 1 Water Resources 295
SECTION 2
Water Use and Management
EARTH SCIENCE CONNECTION
Objectives You may have heard the expression “We all live downstream.”
When a water supply is polluted or overused, everyone living
̈ Identify patterns of global downstream can be affected. The number of people who rely on
water use. the Earth’s limited freshwater reserves is increasing every day. In
fact, a shortage of clean, fresh water is one of the world’s most
̈ Explain how water is treated so pressing environmental problems. According to the World Health
that it can be used for drinking. Organization, more than 1 billion people lack access to a clean,
reliable source of fresh water.
̈ Identify how water is used in
homes, in industry, and in agricul- Global Water Use
ture.
To understand the factors that affect the world’s supply of fresh
̈ Describe how dams and water water, we must first explore how people use water. Figure 5
diversion projects are used to shows the three major uses for water—residential use, agricul-
manage freshwater resources. tural use, and industrial use.
̈ Identify five ways that water can Most of the fresh water used worldwide is used to irrigate
be conserved. crops. Patterns of water use are not the same everywhere, how-
ever. The availability of fresh water, population sizes, and eco-
Key Terms nomic conditions affect how people use water. In Asia,
agriculture accounts for more than 80 percent of water use,
potable whereas it accounts for only 38 percent of water use in Europe.
pathogen Industry accounts for about 19 percent of the water used in the
dam world. The highest percentage of industrial water use occurs in
reservoir Europe and North America. Globally, about 8 percent of water is
desalination used by households for activities such as drinking and washing.
Residential Water Use
There are striking differences in residential water use throughout
the world. For example, the average person in the United States
uses about 300 L (80 gal) of water every day. But in India, the
296 Chapter 11 Water
Percentage of water use 100 Figure 5 ̈ Europe is the only
90 Residential continent that uses more water
80 Industrial for industry than for agriculture.
70 Agricultural
60 Asia Africa Australia World
50
40
30
20
10
0
North South Europe
America America
Source: World Resources Institute.
average person uses only 41 L of water every day. In the United Table 1 ̄
States, only about half of residential water use is for activities
inside the home, such as drinking, cooking, washing, and toilet Daily Water Use in the
flushing. The remainder of the water used residentially is used United States (per Person)
outside the home for activities such as watering lawns and wash-
ing cars. Table 1 shows how the average person in the United Use Water (L)
States uses water.
Lawn watering 95
Water Treatment Most water must be treated to make it potable, and pools 90
or safe to drink. Water treatment removes elements such as mer- 70
cury, arsenic, and lead, which are poisonous to humans even in low Toilet flushing 10
concentrations. These elements are found in polluted water, but
they can also occur naturally in groundwater. Water treatment also Bathing 20
removes pathogens, which are organisms that cause illness or dis- 10
ease. Bacteria, viruses, protozoa, and parasitic worms are common Brushing teeth*
pathogens. Pathogens are found in water contaminated by sewage 5
or animal feces. There are several methods of treating water to Cleaning
make it potable. Figure 6 shows a common drinking water treat- (inside and outside)
ment method that includes both physical and chemical treatment.
Cooking and drinking
Other
*with water running
Source: U.S. Environmental Protection Agency.
Figure 6 ̈ Drinking-Water Treatment
Section 2 Water Use and Management 297
Industrial
water use
(world) 19%
Other water use
(world) 81%
Figure 7 ̈ Water is a very important Industrial Water Use
industrial resource. These nuclear
power plant cooling towers release Industry accounts for 19 percent of water used in the world. Water
the steam produced from water used is used to manufacture goods, to dispose of waste, and to generate
to cool a nuclear reactor. power. The amount of water needed to manufacture everyday items
can be astounding. For instance, nearly 1,000 L of water are needed
Comparison to produce 1 kg of aluminum, and almost 500,000 L of water are
Table needed to manufacture a car.
Create the Graphic Organizer
entitled “Comparison Table” Most of the water that is used in industry is used to cool power
described in the Appendix. Label plants, as shown in Figure 7. Power-plant cooling systems usually
the columns with “Residential pump water from a surface water source such as a river or lake,
Water Use,” “Industrial Water carry the water through pipes in a cooling tower, and then pump
Use,” and “Agricultural Water the water back into the source. The returned water is usually
Use.” Label the rows with warmer than the source, but it is generally clean and can be reused.
“Characteristics” and “Water
Conservation.” Then, fill in the Agricultural Water Use
table with details about the char-
acteristics and the ways Did you know that it can take nearly 300 L (80 gal) of water to
water can be con- produce one ear of corn? That’s as much water as an average per-
served in each type son in the United States uses in a day! Agriculture accounts for
of water use. 67 percent of the water used in the world. Plants require a lot of
water to grow, and as much as 80 percent of the water used in
agriculture evaporates and never reaches plant roots.
Irrigation Fertile soil is sometimes found in areas of the world
that do not have abundant rainfall. In regions where rainfall is
inadequate, extra water can be supplied by irrigation. Irrigation
is a method of providing plants with water from sources other
than direct precipitation. The earliest form of irrigation proba-
bly involved flooding fields with water from a nearby river.
■✓● Reading Check How does the amount of water used for industry
compare with the amount of water used for agriculture?
298 Chapter 11 Water
Other water
use (world)
33%
Many different irrigation techniques are
used today. For example, some crops, such as Agricultural water
cotton, are irrigated by shallow, water-filled use (world) 67%
ditches, as shown in Figure 8. In the United
States, high-pressure overhead sprinklers are the
most common form of irrigation. This method of
irrigation is inefficient because nearly half the water Figure 8 ̈ High-pressure overhead
sprinklers (left) are inefficient because
evaporates and never reaches the plant roots. Irrigation systems a lot of water is lost to evaporation.
Water-filled ditches (above) irrigate
that use water more efficiently are becoming more common. cotton seedlings.
Water Management Projects Figure 9 ̈ This aqueduct in Spain
was built almost two thousand years
For thousands of years, humans have altered streams and rivers ago by the Romans.
to make them more useful. Nearly two thousand years ago, the
Romans built aqueducts, huge canals that brought water from the
mountains to the dry areas of France and Spain. One such aque-
duct is shown in Figure 9. Some of these aqueducts are still used
today. Engineering skills have improved
since the time of the Romans, and water
projects have become more complex.
People often live in areas where the
natural distribution of surface water is
inadequate. Water management projects,
such as dams and water diversion canals,
are designed to meet their needs. Water
management projects can have various
goals, such as bringing in water to make
a dry area habitable, creating a reservoir
for recreation or drinking water, or gen-
erating electric power. Water manage-
ment projects have changed the American
Southwest and have proved that if water
can be piped in, people can live and grow
crops in desert areas.
Figure 10 ̈ This canal carries water Water Diversion Projects To supply dry regions with water, all or
more than 300 km across mountains part of a river can be diverted into canals that carry water across
and deserts to supply drinking water great distances. Figure 10 shows a canal that diverts the Owens
to Los Angeles, California. River in California to provide drinking water for Los Angeles.
Another river, the Colorado River, is diverted to provide water for
several states. The Colorado River begins as a glacial stream in the
Rocky Mountains and quickly grows larger as other streams feed
into it. As the river flows south, however, it is divided to meet the
needs of seven western states. So much of the Colorado River’s
water is diverted for irrigation and drinking water in states such as
Arizona, Utah, and California that the river often runs dry before
it reaches Mexico and flows into the Gulf of California. In fact, the
Colorado River reaches the Gulf only in the wettest years.
Dams and Reservoirs A dam is a structure built across a river to
control the river’s flow. When a river is dammed, an artificial
lake, or reservoir, is formed behind the dam. Water from a reser-
voir can be used for flood control, drinking water, irrigation,
recreation, and industry. Dams are also built to generate electrical
energy. Hydroelectric dams use the power of flowing water to
turn a turbine that generates electrical energy. About 20 percent
of the world’s electrical energy is generated by hydro-
electric dams, such as the one shown in Figure 11.
Although dams provide many benefits, interrupting
a river’s flow can also have far-reaching consequences.
When the land behind a dam is flooded, people are
often displaced and entire ecosystems can be destroyed.
It is estimated that 50 million people around the world
have been displaced by dam projects. Dams also affect
Figure 11 ̈ Dams, such as this
one in Zimbabwe, are built to
manage freshwater resources.
300 Chapter 11 Water
the land below them. As a river enters a reservoir, it slows down MATHPRACTICE
and deposits some of the sediment it carries. This fertile sediment
builds up behind a dam instead of enriching the land farther Israeli Agriculture
down the river. As a result, the farmland below a dam may From 1950 to 1980, Israel
become less productive. Dam failure can be another problem—if reduced the amount of water
a dam bursts, people living along the river below the dam can be loss in agriculture from 83 percent
killed. In the United States, the era of large dam construction is to 5 percent, mainly by switching
probably over. But in developing countries, such as Brazil, India, from overhead sprinklers to water-
and China, the construction of large dams continues. saving methods such as drip irriga-
tion. If a small farm uses 10,000 L
Water Conservation of water a day for overhead sprin-
kler irrigation, how much water
As water sources become depleted, water becomes more expensive. would be saved in one year by
This is because wells must be dug deeper, water must be piped using a drip irrigation system that
greater distances, and polluted water must be cleaned up before consumes 75 percent less water?
it can be used. Water conservation is one way that we can help
ensure that everyone will have enough water at a reasonable price. Figure 12 ̈ Drip irrigation systems
use perforated tubing to deliver
Water Conservation in Agriculture Most of the water loss in water directly to plant roots.
agriculture comes from evaporation, seepage, and runoff, so
technologies that reduce these problems help to conserve water.
Drip irrigation systems offer a promising step toward conserva-
tion. Shown in Figure 12, drip irrigation systems deliver small
amounts of water directly to plant roots by using perforated
tubing. Water is released to plants as needed and at a controlled
rate. These systems are sometimes managed by computer pro-
grams that coordinate watering times by using satellite data. A
well-designed drip irrigation system loses very little water.
Water Conservation in Industry As water resources have
become more expensive, many industries
have developed water conservation plans.
The most widely used water conservation
plans involve the recycling of cooling water
and wastewater. Instead of discharging used
water into a nearby river, businesses often
recycle water. Thus, the production of 1 kg of
paper now uses less than 30 percent of the
water it required 50 years ago. Small busi-
nesses are also helping conserve water.
Denver, Colorado, was one of the first cities
to realize the value of conserving water in
business. The city pays small businesses to
conserve water. This saves money for the city
and businesses, and also makes more water
available for other uses.
■✓● Reading Check What are two ways in which
water is conserved in industry?
Section 2 Water Use and Management 301
Figure 13 ̈ This xeriscaped
yard in Arizona features plants
that are native to the state.
What kinds of plants are
native to your region?
Table 2 ̄ Water Conservation at Home Although households use much
less water than agriculture or industry, a few changes to residen-
What You Can Do tial water use will make a significant contribution to water con-
to Conserve Water servation. People can conserve water by changing a few everyday
habits and by using only the water that they need. Some of these
• Take shorter showers, and conservation methods are shown in Table 2.
avoid taking baths unless you
keep the water level low. Water-saving technology, such as low-flow toilets and shower
heads, can also help reduce household water use. These devices
• Install a low-flow shower head are required in some new buildings. As well, many cities pay resi-
in your shower. dents to install water-saving equipment in older buildings.
• Install inexpensive, low-flow About one-third of the water used by the average household
aerators in your water faucets in the United States is used for landscaping. To conserve water,
at home. many people water their lawns at night to reduce the amount of
water lost to evaporation. Another way people save water used
• Purchase a modern, low-flow outside their home is a technique called xeriscaping (ZIR i SKAY
toilet, install a water-saving ping). Xeriscaping involves designing a landscape that requires
device in your toilet, or simply minimal water use. Figure 13 shows one example of xeriscaping
place a water-filled bottle inside in Arizona.
your toilet tank to reduce the
water used for each flush. Can one person make a difference? When you multiply one
by the millions of people who are trying to conserve water—in
• Do not let the water run while industry, on farms, and at home—you can make a big difference.
you are brushing your teeth.
Solutions for the Future
• Fill up the sink basin rather than
letting the water run when you In some places, conservation alone is not enough to prevent
are shaving, washing your hands water shortages. As populations grow, other sources of fresh
or face, or washing dishes. water need to be developed. Two possible solutions are desalina-
tion and transporting fresh water.
• Wash only full loads in your
dishwasher and washing
machine.
• Water your lawn sparingly.
302 Chapter 11 Water
Desalination Some coastal communities rely on the oceans to pro- www.scilinks.org
vide fresh water. Desalination (DEE SAL uh NAY shuhn) is the
process of removing salt from salt water. Some countries in drier Topic: Water
parts of the world, such as the Middle East, have built desalination Conservation
plants to provide fresh water. Most desalination plants heat salt
water and collect the fresh water that evaporates. Figure 14 shows Code: HE81625
one such plant in Kuwait. Because desalination consumes a lot of
energy, the process is too expensive for many nations to consider. Figure 14 ̈ Most desalination
plants, such as this one in Kuwait,
Transporting Water In some areas of the world where freshwa- use evaporation to separate salt
ter resources are not adequate, water can be transported from from ocean water.
other regions. For example, the increasing number of tourists
visiting some Greek islands in the Mediterranean Sea have taxed
the islands’ freshwater supply. As a result, ships travel regularly
from the mainland towing enor-
mous plastic bags full of fresh
water. The ships anchor in port,
and fresh water is then pumped
onto the islands. This solution is
also being considered in the United
States, where almost half of the
available fresh water is in Alaska.
Scientists are exploring the possi-
bility of filling huge bags with
water from Alaskan rivers and
then towing the bags down the
coast to California, where fresh
water is often in short supply.
Because 77 percent of the
Earth’s fresh water is frozen in
icecaps, icebergs are another
potential freshwater source. For
years, people have considered
towing icebergs to communities
that lack fresh water. But an effi-
cient way to tow icebergs is yet to
be discovered.
S E C T I O N 2 Review
1. Describe the patterns of global water use for each CRITICAL THINKING
continent shown in the bar graph in Figure 5. 5. Making Comparisons Write a description of the
2. Describe the drinking water treatment process in evaporative method of desalination using terms from
your own words. the water cycle. WRITING SKILLS
3. Describe the benefits and costs of dams and water 6. Identifying Alternatives Describe three ways that
diversion projects. communities can increase their freshwater resources.
4. List at least three things you can do to help conserve
the world’s water supply.
Section 2 Water Use and Management 303
SECTION 3 EARTH SCIENCE CONNECTION
Water Pollution You might think that you can tell if a body of water is polluted
by the way that the water looks or smells, but sometimes you
Objectives can’t. There are many different forms of water pollution. Water
pollution is the introduction of chemical, physical, or biological
̈ Compare point-source pollution agents into water that degrade water quality and adversely affect
and nonpoint-source pollution. the organisms that depend on the water. Almost all of the ways
that we use water contribute to water pollution. However, the
̈ Classify water pollutants by five two underlying causes of water pollution are industrialization
types. and rapid human population growth.
̈ Explain why groundwater pollu- In the last 30 years, developed countries have made great
tion is difficult to clean up. strides in cleaning up many polluted water supplies. Despite this
progress, some water is still dangerously polluted in the United
̈ Describe the major sources of States and in other countries. In developing parts of the world,
ocean pollution, and explain the water pollution is a big problem. Industry is usually not the
effects of pollution on ecosystems. major cause of water pollution in developing countries. Often,
the only water available for drinking in these countries is pol-
̈ Describe six major laws designed luted with sewage and agricultural runoff, which can spread
to improve water quality in the waterborne diseases. To prevent water pollution, people must
United States. understand where pollutants come from. As you will learn,
water pollution comes from two types of sources: point and
Key Terms nonpoint sources.
water pollution
point-source pollution
nonpoint-source pollution
wastewater
artificial eutrophication
thermal pollution
biomagnification
Figure 15 ̈ Point-source pollution
comes from a single, easily identifiable
source. In this photo, the waste from
an iron mine is being stored in a pond.
Table 3 ̄
Sources of Point Pollution
• leaking septic-tank systems
• leaking storage lagoons for
polluted waste
• unlined landfills
• leaking underground storage
tanks that contain chemicals or
fuels such as gasoline
• polluted water from
abandoned and active mines
• water discharged by industries
• public and industrial waste-
water treatment plants
304 Chapter 11 Water
Point-Source Pollution FIELD ACTIVITY
When you think of water pollution, you probably think of a single Identifying Sources of
source, such as a factory, a wastewater treatment plant, or a leaking Pollution Walk around your
oil tanker. These are all examples of point-source pollution, which neighborhood, and record poten-
is pollution discharged from a single source. Table 3 lists some addi- tial sources of nonpoint pollution.
tional examples of point-source pollution. Point-source pollution can See Table 4 for examples. Count
often be identified and traced to a source. But even when the source the number of potential sources
of the pollution is known, enforcing cleanup may be difficult. of nonpoint pollution, and sug-
gest ways to reduce each source
Nonpoint-Source Pollution of pollution in your EcoLog.
Nonpoint-source pollution comes from many different sources Table 4 ̄
that are often difficult to identify. For example, a river can be pol-
luted by runoff from any of the land in its watershed. If a farm, a Nonpoint Sources of Pollution
road, or any other land surface in a watershed is polluted, runoff
from a rainstorm can carry the pollution into a nearby river, • chemicals added to road
stream, or lake. Figure 16 shows common sources of nonpoint pol- surfaces (salt and other
lutants. Table 4 lists some additional causes of nonpoint pollution. de-icing agents)
Because nonpoint pollutants can enter bodies of water in • water runoff from city and
many different ways, they are extremely difficult to regulate and suburban streets that may
control. The accumulation of small amounts of water pollution contain oil, gasoline, animal
from many sources is a major pollution problem—96 percent of feces, and litter
the polluted bodies of water in the United States were contami-
nated by nonpoint sources. Controlling nonpoint-source pollution • pesticides, herbicides, and
depends to a great extent on public awareness of the effects of fertilizer from residential lawns,
activities such as spraying lawn chemicals and using storm drains golf courses, and farmland
to dispose of used motor oil.
• feces and agricultural chemicals
from livestock feedlots
• precipitation containing air
pollutants
• soil runoff from farms and
construction sites
• oil and gasoline from personal
watercraft
Figure 16 ̈ Sources of Nonpoint
Pollution Examples of nonpoint-
source pollution include livestock
polluting water holes that can flow
into streams and reservoirs, oil on
a street, which can wash into storm
sewers and then drain into water-
ways, and thousands of watercraft,
which can leak gasoline and oil.
Section 3 Water Pollution 305
Table 5 ̄ Pollutant Types and Sources
Type of pollutant
Pathogens Agent Major sources
Organic matter disease-causing organisms, such mostly nonpoint sources: sewage or animal
Organic chemicals as bacteria, viruses, protozoa, and feces, livestock feedlots, and poultry farms;
Inorganic chemicals parasitic worms sewage from overburdened wastewater
Heavy metals treatment plants
Physical agents animal and plant matter remains, mostly nonpoint sources
feces, food waste, and debris from
food-processing plants
pesticides, fertilizers, plastics, mostly nonpoint sources: farms, lawns, golf
detergents, gasoline and oil, and courses, roads, wastewater, unlined landfills,
other materials made from petroleum and leaking underground storage tanks
acids, bases, salts, and industrial point sources and nonpoint sources:
chemicals industrial waste, road surfaces, wastewater,
and polluted precipitation
lead, mercury, cadmium, and arsenic point sources and nonpoint sources:
industrial discharge, unlined landfills, some
household chemicals, and mining processes;
heavy metals also occur naturally in some
groundwater
heat and suspended solids point sources and nonpoint sources: heat
from industrial processes and suspended
solids from soil erosion
Principal Water Pollutants
There are many different kinds of water pollutants. Table 5 lists
some common types of pollutants and some of the possible
sources of each pollutant.
Wastewater
Do you know where water goes after it flows down the drain in a
sink? The water usually flows through a series of sewage pipes
that carry it—and all the other wastewater in your community—
to a wastewater treatment plant. Wastewater is water that con-
tains waste from homes or industry. At a wastewater treatment
plant, water is filtered and treated to make the water clean
enough to return to a river or lake.
Treating Wastewater A typical residential wastewater treatment
process is illustrated in Figure 17. Most of the wastewater from
homes contains biodegradable material that can be broken down by
living organisms. For example, wastewater from toilets and kitchen
sinks contains animal and plant wastes, paper, and soap, all of which
306 Chapter 11 Water
are biodegradable. But wastewater treatment plants may not remove Connection to History
all of the harmful substances in water. Some household and indus-
trial wastewater and some storm-water runoff contains toxic sub- Cryptosporidium Outbreak In
stances that cannot be removed by the standard treatment. 1993, a pathogen called
Cryptosporidium parvum contami-
Sewage Sludge One of the products of wastewater treatment is nated the municipal water supply
sewage sludge, the solid material that remains after treatment. of Milwaukee, Wisconsin. The
When sludge contains dangerous concentrations of toxic chemi- waterborne parasite caused more
cals, it must be disposed of as hazardous waste. The sludge is than 100 deaths, and 400,000
often incinerated, and then the ash is buried in a secure landfill. people experienced a flulike ill-
Sludge can be an expensive burden to towns and cities because ness. Cryptosporidium is found in
the volume of sludge that has to be disposed of every year is animal feces, but the parasite
enormous. usually occurs in low levels in
water supplies. The outbreak in
The problem of sludge disposal has led many communities to Milwaukee was probably caused
look for new uses for this waste. If the toxicity of sludge can be by an unusual combination of
reduced to safe levels, sludge can be used as a fertilizer. Sludge heavy rainfall and agricultural
can also be combined with clay to make bricks for buildings. runoff that overburdened the
city’s water treatment plants.
■✓● Reading Check Why is it so expensive to dispose of sewage sludge?
Figure 17 ̈ Wastewater Treatment Process
PRIMARY TREATMENT
Filtration Wastewater is passed through a large
screen to remove solid objects.
First Settling Tank Wastewater is sent into a large
tank, where smaller particles sink to the bottom and
form sewer sludge. The sludge is removed from the
water.
SECONDARY TREATMENT
Aeration Tank Wastewater is mixed with oxygen and
bacteria. The bacteria use the oxygen and feed on the wastes.
Second Settling Tank Bacteria grown in the aeration tank, as
well as other solid wastes, are removed in the form of sludge.
Chlorination Chlorine is added to
disinfect the water before it is released
into a stream, lake or ocean.
Section 3 Water Pollution 307
QuickLAB Artificial Eutrophication
Measuring Most nutrients in water come from organic matter, such as
Dissolved Oxygen leaves and animal waste, that is broken down into mineral
nutrients by decomposers such as bacteria and fungi. Nutrients
Procedure are an essential part of any aquatic ecosystem, but an overabun-
dance of nutrients can disrupt an ecosystem. When lakes and
1. Start with three water samples, slow-moving streams contain an abundance of nutrients, they
each in a plastic jar that is 3⁄4 are eutrophic (yoo TROH fik).
full. Two water samples should
be tap water from a faucet with- Eutrophication is a natural process. When organic matter
out an aerator. One sample builds up in a body of water, it will begin to decay and decom-
should be water that has been pose. The process of decomposition uses up oxygen. As oxygen
boiled and allowed to cool. levels decrease, the types of organisms that live in the water
change over time. For example, as a body of water becomes
2. Using a dissolved-oxygen test eutrophic, plants take root in the nutrient-rich sediment at the
kit, test the boiled water and bottom. As more plants grow, the shallow waters begin to fill in.
one other water sample. Eventually, the body of water becomes a swamp or marsh.
3. Tighten the lid on the third The natural process of eutrophication is accelerated when
sample, and then vigorously inorganic plant nutrients, such as phosphorus and nitrogen, enter
shake the sample for one the water from sewage and fertilizer runoff. Eutrophication
minute. Unscrew the lid, and caused by humans is called artificial eutrophication. Fertilizer
then recap the jar. from farms, lawns, and gardens is the largest source of nutrients
that cause artificial eutrophication. Phosphates in some laundry
4. Repeat step 3 twice. Then, and dishwashing detergents are another major cause of eutrophi-
uncap the jar quickly, and test cation. Phosphorus is a plant nutrient that can cause the excessive
the sample. growth of algae. In bodies of water polluted by phosphorus,
algae can form large floating mats, called algal blooms, as shown
Analysis in Figure 18. As the algae die and decompose, most of the dis-
solved oxygen is used and fish and other organisms suffocate in
1. Which sample had the highest the oxygen-depleted water.
dissolved oxygen level? Which
sample had the lowest level?
2. What effects do rapids and
waterfalls have on the levels of
dissolved oxygen in a stream?
What effect does thermal pollu-
tion have?
Figure 18 ̈ In an effort to limit
artificial eutrophication, some states
have either banned phosphate
detergents or limited the
amount of phosphates
in detergents.
308 Chapter 11 Water
Thermal Pollution Figure 19 ̈ Fish kills, such as this
one in Brazil, can result from thermal
If you look at Figure 19, you might assume that a toxic chemical pollution.
caused the massive fish kill in the photo. But the fish were not
killed by a chemical spill—they died because of thermal pollution. Connection to Chemistry
When the temperature of a body of water, such as a lake or stream,
increases, thermal pollution can result. Thermal pollution can occur Dissolved Oxygen One of the
when power plants and other industries use water in their cooling most important measures of the
systems and then discharge the warm water into a lake or river. health of a body of water is the
amount of dissolved oxygen in
Thermal pollution can cause large fish kills if the discharged the water. Gaseous oxygen enters
water is too warm for the fish to survive. But most thermal pollu- water by diffusion from the sur-
tion is more subtle. If the temperature of a body of water rises even rounding air, as a byproduct of
a few degrees, the amount of oxygen the water can hold decreases photosynthesis, and as a result of
significantly. As oxygen levels drop, aquatic organisms may suffo- the rapid movement (aeration) of
cate and die. If the flow of warm water into a lake or stream is water. The amount of oxygen that
constant, it may cause the total disruption of an aquatic ecosystem. water can hold is determined by
the water’s temperature, pressure,
Groundwater Pollution and salinity. Slow-moving water
tends to have low levels of dis-
Pollutants usually enter groundwater when polluted surface water solved oxygen, while rapidly flow-
percolates down from the Earth’s surface. Any pollution of the ing streams have higher levels.
surface water in an area can affect the groundwater. Pesticides, Artificial eutrophication and ther-
herbicides, chemical fertilizers, and petroleum products are com- mal pollution also reduce levels of
mon groundwater pollutants. Leaking underground storage tanks dissolved oxygen. When dissolved
are another major source of groundwater pollution. It is estimated oxygen levels remain below
that there are millions of underground storage tanks in the United 2 mg/L for several hours, fish and
States. Most of the tanks—located beneath gas stations, farms, other organisms suffocate, and
and homes—hold petroleum products, such as gasoline and heat- massive fish kills can result.
ing fuel. As underground storage tanks age, they may develop
leaks, which allow pollutants to seep into the groundwater. Section 3 Water Pollution 309
MATHPRACTICE The location of aging underground storage tanks is not
always known, so the tanks often cannot be repaired or replaced
Parts per Million Water until after they have leaked enough pollutants to be located.
contamination is often Modern underground storage tanks are contained in concrete and
measured in parts per million have many features to prevent leaks. Other sources of groundwa-
(ppm). If the concentration of ter pollution include septic tanks, unlined landfills, and industrial
a pollutant is 5 ppm, there are wastewater lagoons, as shown in Figure 20.
5 parts of the pollutant in 1 million
parts of water. If the concentration Cleaning Up Groundwater Pollution Groundwater pollution is one
of gasoline is 3 ppm in 650,000 L of the most challenging environmental problems that the world
of water, how many liters of gaso- faces. Even if groundwater pollution could be stopped tomorrow,
line are in the water? some groundwater would remain polluted for generations to come.
As you have learned, groundwater recharges very slowly. The
Figure 20 ̈ This diagram shows process for some aquifers to recycle water and purge contaminants
some of the major sources of can take hundreds or thousands of years. Groundwater is also dif-
groundwater pollution. Runoff and ficult to decontaminate because the water is dispersed throughout
percolation transport contaminants large areas of rock and sand. Pollution can cling to the materials
to the groundwater. that make up an aquifer, so even if all of the water in an aquifer
were pumped out and replaced with clean water, the groundwater
could still become polluted.
310 Chapter 11 Water
Figure 21 ̈ Major North American Oil Spills
1 1 Nantucket, 6 Prince William
2
3 Massachusetts, Sound, Alaska,
4
5 1976 1989
6
7 6 2 Puerto Rico, 7 Caribbean Sea,
8
Location of spill 9 8 1978 1975
0 1 3 Atlantic Ocean, 8 Nor th Atlantic
1988 Ocean, 1988
5 3 4 Tuxpan, Mexico, 9 Bay of
49 7 1996 Campeche,
2 5 Galveston Bay, 1979
Texas, 1979
500 1,000 1,500 2,000 2,500 3,000 3,500
Barrels of oil spilled (in thousands)
Ocean Pollution Ecofact
Pollutants are often dumped directly into the oceans. For exam- Cruise Ship Discharges In one
ple, ships can legally dump wastewater and garbage overboard in year, ships dump almost 7 billion
some parts of the ocean. But at least 85 percent of ocean pollu- kilograms of trash into the oceans.
tion—including pollutants such as oil, toxic wastes, and medical About 75 percent of all ship waste
wastes—comes from activities on land. If polluted runoff enters comes from cruise ships. According
rivers, for example, the rivers may carry the polluted water to the to most international law, cruise
ocean. Most activities that pollute oceans occur near the coasts, ships are allowed to dump nonplas-
where much of the world’s human population lives. As you might tic waste—including untreated
imagine, sensitive coastal ecosystems, such as coral reefs, estuar- sewage—into the oceans. Increasing
ies, and coastal marshes, are the most affected by pollution. public pressure has begun to cause
the cruise-ship industry to change
Oil Spills Ocean water is also polluted by accidental oil spills. this practice, however.
Disasters such as the 1989 Exxon Valdez oil spill in Prince
William Sound, Alaska, make front-page news around the world. www.scilinks.org
In 2001, a fuel-oil spill off the coast of the Galápagos Islands
captured public attention. Each year, approximately 37 million Topic: Water Pollution
gallons of oil from tanker accidents are spilled into the oceans. Code: HE81629
Figure 21 shows some of the major oil spills that have occurred
off the coast of North America in the last 30 years.
Oil spills have dramatic effects, but they account for only
about 5 percent of oil pollution in the oceans. Most of the oil
that pollutes the oceans comes from cities and towns. Every year,
as many as 200 million to 300 million gallons of oil enter the
oceans from nonpoint sources on land. That’s almost 10 times
the amount of oil spilled by tankers. Limiting these nonpoint
sources of oil pollution would go a long way toward keeping the
oceans clean.
■✓● Reading Check How can limiting nonpoint sources of oil pollution
help to keep the oceans clean?
Section 3 Water Pollution 311
Figure 22 ̈ The accumulation of Water Pollution and Ecosystems
pollutants at successive levels of the
food chain is called biomagnification. Water pollution can cause immediate damage to an ecosystem. For
Figure 23 ̈ The Cuyahoga River example, toxic chemicals spilled directly into a river can kill nearly
was so polluted with petroleum and all living things for miles downstream. But the effects of water pol-
petroleum byproducts that it caught lution can be even more far reaching. Many pollutants accumulate
on fire and burned in 1969. in the environment because they do not decompose quickly. As the
pollutant levels increase, they can threaten an entire ecosystem.
312 Chapter 11 Water
Consider a river ecosystem. Soil tainted with pesticides washes
into the river and settles to the bottom. Some of the pesticides
enter the bodies of tiny, bottom-dwelling organisms, such as insect
larvae and crustaceans. The pesticides are stored in their body
tissues. A hundred of these organisms are eaten by one small fish.
A hundred of these small fish are eaten by one big fish. A preda-
tory bird, such as an eagle, eats 10 big fish. Each organism stores
the pesticide in its tissues, so at each step along the food chain,
the concentration of the pesticide passed on to the next organism
increases. This buildup of pollutants at higher levels of the food
chain is called biomagnification. Biomagnification, which is
shown for the pesticide DDT in Figure 22, has alarming conse-
quences for organisms at the top of the food chain. Many U.S.
states limit the amount of fish that people can eat from certain
bodies of water because of biomagnification.
Cleaning Up Water Pollution
In 1969, the Cuyahoga River in Cleveland, Ohio, was so polluted
that the river caught on fire and burned for several days, as
shown in Figure 23. This shocking event was a major factor in
the passage of the Clean Water Act of 1972. The stated purpose
of the act was to “restore and maintain the chemical, physical,
and biological integrity of the nation’s waters.” The goal of the
act was to make all surface water clean enough for fishing and
swimming by 1983. This goal was not
achieved; however, much progress has been
made since the act was passed. The per-
centage of lakes and rivers that are fit for
swimming and fishing has increased by
about 30 percent, and many states have
passed stricter water-quality standards of
their own. Many toxic metals are now
removed from wastewater before the water
is discharged.
The Clean Water Act opened the door
for other water-quality legislation, some of
which is described in Table 6. For example,
the Marine Protection, Research, and
Sanctuaries Act of 1972 strengthened the
laws against ocean dumping.
The Oil Pollution Act of 1990 requires
all oil tankers traveling in U.S. waters to
Table 6 ̄ FIELD ACTIVITY
Federal Laws Designed to Improve Water Quality Coastal Cleanups You can be a
in the United States part of a coastal cleanup. Every
September, people from all over
1972 Clean Water Act (CWA) The CWA set a national goal of making the world set aside one day to
all natural surface water fit for fishing and swimming by 1983 and help clean up debris from
banned pollutant discharge into surface water after 1985. The act also beaches. You can join this interna-
required that metals be removed from wastewater. tional effort by writing to The
Center for Marine Conservation.
1972 Marine Protection, Research, and Sanctuaries Act, amended
1988 This act empowered the EPA to control the dumping of sewage If you do participate in a
wastes and toxic chemicals in U.S. waters. coastal cleanup, keep a record of
the types of trash you find in
1975 Safe Drinking Water Act (SDWA), amended 1996 This act your EcoLog.
introduced programs to protect groundwater and surface water from
pollution. The act emphasized sound science and risk-based standards
for water quality. The act also empowered communities in the protec-
tion of source water, strengthened public right-to-know laws, and pro-
vided water system infrastructure assistance.
1980 Comprehensive Environmental Response Compensation and
Liability Act (CERCLA) This act is also known as the Superfund Act.
The act makes owners, operators, and customers of hazardous waste
sites responsible for the cleanup of the sites. The act has reduced the
pollution of groundwater by toxic substances leached from hazardous
waste dumps.
1987 Water Quality Act This act was written to support state and
local efforts to clean polluted runoff. It also established loan funds to
pay for new wastewater treatment plants and created programs to
protect major estuaries.
1990 Oil Pollution Act This act attempts to protect U.S. waterways
from oil pollution by requiring that oil tankers in U.S. waters be
double-hulled by 2015.
have double hulls by 2015 as an added protection against oil
spills. Legislation has improved water quality in the United
States, but the cooperation of individuals, businesses, and the
government will be essential to maintaining a clean water supply
in the future.
S E C T I O N 3 Review
1. Explain why point-source pollution is easier to con- CRITICAL THINKING
trol than nonpoint-source pollution. 5. Interpreting Graphics Read the description of
2. List the major types of water pollutants. Suggest biomagnification. Draw a diagram that shows the
ways to reduce the levels of each type of pollutant in biomagnification of a pollutant in an ecosystem.
a water supply.
READING SKILLS
3. Describe the unique problems of cleaning up
groundwater pollution. 6. Applying Ideas What can individuals do to
decrease ocean pollution? Write and illustrate a
4. Describe the source of most ocean pollution. Is it guide that gives at least three examples.
point-source pollution or nonpoint-source pollution?
WRITING SKILLS
Section 3 Water Pollution 313
11C H A P T E R Highlights
1 Water Resources Key Terms Main Ideas
surface water, 290 ̈ Only a small fraction of Earth’s water supply
river system, 291 is fresh water. The two main sources of fresh
watershed, 291 water are surface water and groundwater.
groundwater, 292
aquifer, 293 ̈ River systems drain the land that makes up
porosity, 293 a watershed. The amount of water in a river
permeability, 293 system can vary in different seasons and from
recharge zone, 294 year to year.
̈ Groundwater accumulates in underground for-
mations called aquifers. Surface water enters an
aquifer through the aquifer’s recharge zone.
̈ If the water in an aquifer is pumped out
faster than it is replenished, the water table
drops, which can affect humans and animals
that depend on the groundwater.
2 Water Use and Management potable, 297 ̈ There are three main types of water use:
pathogen, 297 residential, industrial, and agricultural.
dam, 300 Worldwide, most water use is agricultural.
reservoir, 300
desalination, 303 ̈ Dams and water diversion projects are built
to manage surface-water resources. Damming
and diverting rivers can have environmental
and social consequences.
̈ Water conservation is necessary to maintain
an adequate supply of fresh water.
Desalination and transporting water are
options to supplement local water supplies.
3 Water Pollution water pollution, 304 ̈ Water can become polluted by chemical,
physical, or biological agents. Most water
314 Chapter 11 Highlights point-source pollution in the United States is caused by
pollution, 305 nonpoint-source pollutants.
nonpoint-source ̈ Groundwater pollution is difficult to clean
pollution, 305 up because aquifers recharge slowly and
because pollutants cling to the materials that
wastewater, 306 make up an aquifer.
artificial eutrophica- ̈ Ocean pollution is mainly caused by coastal,
tion, 308 nonpoint-source pollutants.
thermal pollution, ̈ Government legislation, such as the Clean
309 Water Act of 1972, has succeeded in reducing
surface-water pollution. Future challenges
biomagnification, include reducing nonpoint-source pollution and
312 groundwater pollution.
11C H A P T E R Review
Using Key Terms 12. Which of the following processes is not used
in a conventional method of water treatment?
Use each of the following terms in a separate a. filtration
sentence. b. coagulation
c. aeration
1. aquifer d. percolation
2. recharge zone
3. reservoir 13. Which of the following is not an example of
4. wastewater point-source pollution?
5. biomagnification a. oil that is escaping from a damaged tanker
For each pair of terms, explain how the meanings b. heavy metals that are leaching out of an
of the terms differ. underground mine
6. surface water and groundwater c. water runoff from residential lawns
7. porosity and permeability d. untreated sewage that is accidentally
8. watershed and river system released from a wastewater treatment plant
9. point-source pollution and nonpoint-source
14. Which of the following pollutants causes
pollution artificial eutrophication?
a. heavy metals from unlined landfills
STUDY TIP b. inorganic plant nutrients from wastewater
and fertilizer runoff
Root Words To practice vocabulary, write the c. toxic chemicals from factories
key terms and definitions on a piece of paper and d. radioactive waste from nuclear power
fold the paper lengthwise so that the definitions plants
are covered. First, see how many definitions you
already know. Then, write the definitions you do 15. Pumping large amounts of water from an
not know on another piece of paper, and practice aquifer may cause the
until you know all of the terms. a. water table to rise.
b. recharge zone to shrink.
Understanding Key Ideas c. wells in an area to run dry.
d. percolation of groundwater to stop.
10. Which of the following processes is not
a part of the water cycle? 16. Oil pollution in the ocean is mostly caused by
a. evaporation a. major oil spills, such as the 1989 Exxon
b. condensation Valdez oil spill.
c. biomagnification b. the cumulative effect of small oil spills and
d. precipitation leaks on land.
c. decomposed plastic materials.
11. Most of the fresh water on Earth is d. intentional dumping of excess oil.
a. located underground in aquifers.
b. frozen in the polar icecaps. 17. Thermal pollution has a harmful effect on
c. located in rivers, lakes, streams, aquatic environments because
and wetlands. a. water has been circulated around power-
d. found in Earth’s atmosphere. plant generators.
b. it increases the number of disease-causing
organisms in aquatic environments.
c. it reduces the amount of dissolved oxygen
in aquatic environments.
d. it decreases the nutrient levels in aquatic
environments.
Chapter 11 Review 315
11C H A P T E R Review
Short Answer Concept Mapping ?
??
18. What effect can buildings and parking lots
have on an aquifer’s recharge zone? 26. Use the following terms to create a concept
map: Earth’s surface, rivers, underground,
19. Why is the use of overhead sprinklers for fresh water, water table, 3 percent, and icecaps.
irrigation inefficient? What is a more efficient
method of irrigation? Critical Thinking
20. List three advantages and three disadvan- 27. Making Comparisons Read the description
tages of dams. of artificial eutrophication in this chapter.
Do you think artificial eutrophication is
21. What is the process of eutrophication, and more disturbing to the stability of a water
how do human activities accelerate it? ecosystem than natural eutrophication is?
22. Describe the steps that are involved in READING SKILLS
the primary and secondary treatment of
wastewater. 28. Analyzing Relationships Water resources are
often shared by several countries. A river, for
Interpreting Graphics example, might flow through five countries
before it reaches an ocean. When water
The graph below shows the annual flow, or dis- resources are shared, how should countries
charge, of the Yakima River in Washington. Use determine water rights and environmental
the graph to answer questions 23–25. responsibility?
23. In which months is the river’s discharge 29. Making Inferences Explain why it takes 36
highest? What might explain these dis- gallons of water to produce a single serving
charge rates? of rice, but it takes more than 2,000 gallons
of water to produce a single serving of steak.
24. What might cause the peaks in river discharge What do you think the water is used for in
between November and March? each case?
25. How might the data be different if the 30. Making Inferences Why is there so little
hydrograph readings were taken below a fresh water in the world? Do you think that
large dam on the Yakima River? there would have been more fresh water at a
different time in Earth’s history?
Hydrograph of the Yakima River
Mean daily discharge (ft3/s) 10,000 Cross-Disciplinary Connection
9,000
8,000 31. Social Studies Find out how freshwater
7,000 resources affected the development of one cul-
6,000 ture in history. Use at least five key terms from
5,000 this chapter to write a two-paragraph descrip-
4,000 tion of how the availability of fresh water
3,000 affected the culture you chose. WRITING SKILLS
2,000
1,000 Portfolio Project
ON D J F M A M J J AS 32. Investigation Find out about the source of
1988 1989 Months the tap water in your home. Where does the
tap water come from, and where does your
wastewater go? Does the water complete a
cycle? Make a poster to illustrate your find-
ings. You may want to work with several
classmates and visit the sites you discover.
316 Chapter 11 Review
Pumping rate (gal/min)MATH SKILLS READING SKILLS
The graph below illustrates the pumping rates for Read the passage below, and then answer
a set of wells that provide water to a small com- the questions that follow.
munity. Use the graph to answer question 33.
Water use is measured in two ways: by with-
10 drawal and by consumption. Withdrawal is the
removal and transfer of water from its source
8 to a point of use, such as a home, business, or
industry. Most of the water that is withdrawn
6 is eventually returned to its source. For exam-
ple, much of the water used in industries and
4 homes is treated and returned to the river or
lake it came from. When water is withdrawn
2 and is not returned to its source, the water is
consumed. For example, when a potted plant
0 is watered, almost all of the water eventually
Well A Well B Well C Well D Well E enters the atmosphere by evapotranspiration
through the leaves of the plant. The evapo-
33. Analyzing Data How many gallons does rated water was consumed because it was not
Well B pump per day? What is the average directly returned to its source.
pump rate for all of the wells? In one hour,
how many more gallons of water will Well A 1. According to the passage, which of the
pump than Well C? following statements is true?
a. Water that is consumed was never
34. Making Calculations If placing a container withdrawn.
of water in your toilet tank reduces the b. Water that is withdrawn cannot be
amount of water per flush by 2 L, how much consumed.
water would be saved each day if this were c. A fraction of the water withdrawn is
done in 80 million toilets? (Assume that each usually consumed.
toilet is flushed five times per day.) Convert d. All of the water withdrawn is consumed.
your answer into gallons (1 L = .26 Gal).
2. Which phrase best describes the meaning
WRITING SKILLS of the term evapotranspiration?
a. the absorption of water by plant leaves
35. Communicating Main Ideas Why is water b. the process by which potted plants
pollution a serious problem? transpire their leaves by evaporation
c. the process by which the atmosphere
36. Writing Persuasively Write a letter to a sena- maintains water levels in plant leaves
tor in which you voice your support or criti- d. the process by which water evaporates
cism of a hypothetical water diversion project. from plant leaves
3. Which of the following statements is an
example of consumption?
a. A river is diverted to irrigate crops.
b. A power plant takes in cool water from
a lake and returns the water to the lake.
c. A dam forms a reservoir on a river.
d. An aquifer is recharged by surface
water.
Chapter 11 Review 317
11C H A P T E R Standardized Test Prep
Understanding Concepts Reading Skills
Directions (1–4): For each question, write on a Directions (7–9): Read the passage below. Then
separate sheet of paper the letter of the correct answer the questions.
answer.
In 1969, the Cuyahoga River in Ohio was
1 Why are the oceans important to the water so polluted that the river caught fire and
burned for several days. This event was a
cycle? major factor in the passage of the Clean Water
A. Oceans contain saltwater. Act of 1972. The stated purpose of the act was
B. The four major oceans are all joined. to “restore and maintain the chemical, physi-
C. Most of Earth’s water is contained in the cal, and biological integrity of the nation’s
waters.” Although the goal of the act was not
oceans. achieved, much progress has been made since
D. Oceans cover more of Earth’s surface the act was passed. The percentage of lakes
and rivers that are fit for swimming and fish-
area. ing has increased by about 30 percent.
2 Where do we find most of the water that is Additional water-quality legislation has been
enacted, both by the federal government and
available for human use? individual states. Many toxic metals are now
F. groundwater removed from wastewater before the water is
G. the ocean discharged.
H. polar ice caps
I. rivers and streams 7 What was a major factor in passing the
3 Which of the following is an example of a Clean Water Act?
A. All the lakes in the United States were
nonpoint-source of pollution?
A. chemical factory heavily polluted.
B. livestock feedlot B. The Cuyahoga River was so polluted
C. oil spill
D. wastewater treatment plant that it caught fire and burned for
several days.
4 How does heat act as a water pollutant? C. People could not swim or fish in any
lakes or rivers.
F. It slows down the flow of water. D. Previous laws were never passed.
G. It speeds up chemical reactions.
H. It increases the nutrients in the water. 8 What was achieved through the Clean
I. It decreases oxygen in the water.
Water Act?
Directions (5–6): For each question, write a short F. About 30 percent more lakes and rivers
response.
are now fit for swimming and fishing.
5 Economic forces influence how people G. The chemical, physical, and biological
use natural resources. One rule of integrity of the nation’s waters has been
economics is the law of supply and restored.
demand. This law states that the greater H. All of Ohio’s bodies of fresh water are
demand for a resource, the more that now in good condition.
resource is worth. How do economic I. Wastewater with toxic metals is stored,
forces affect the use of water resources not dumped.
in developing countries?
9 Infer three reasons why the goal of the
6 People often live in areas where water
Clean Water Act was not achieved.
resources are inadequate. Justify the use of
water management projects, such as dams,
in these areas.
318 Chapter 11 Standardized Test Prep
Interpreting Graphics
Directions (10–12): For each question below, record the correct answer on
a separate sheet of paper.
The map below shows the water resources of Canada. Use this map to
answer questions 10 through 12.
Canada’s Water
0 What can be inferred about the human population of Canada? Test
A. Most people live in the southeast part of Canada. When analyzing rela-
B. The greatest number of people live along the west coast. tionships, look for the
C. The Hudson Bay area is the most populous part of Canada. answer that is not only
D. More people live around the Great Lakes than along the true but that also best
describes the relation-
Saskatchewan River. ship as a whole.
q Which of the following is the northernmost source of fresh water?
F. Baffin Bay
G. Great Bear Lake
H. Hudson Strait
I. MacKenzie River
w What is the relationship between cities and water resources?
A. Cities are always located near rivers.
B. Cities are always located near lakes.
C. Cities are never located near salt water.
D. Cities are usually located near water resources.
Chapter 11 Standardized Test Prep 319
11C H A P T E R Exploration Lab: MODELING
Objectives Groundwater Filters
̈ Construct a model of the Earth’s As surface water travels downward through rock and soil, the water
natural groundwater filtering system. is filtered and purified. As a result, the water in aquifers is generally
cleaner than surface water. In this investigation, you will work in
̈ USING SCIENTIFIC METHODS Test the small teams to explore how layers of the Earth act as a filter for
ability of your groundwater filters groundwater. You will make models of the Earth’s natural filtration
to filter contaminants out of differ- system and test them to see how well they filter various substances.
ent solutions.
Procedure
Materials
1. Label four beakers as follows: “Contaminant: glucose,”
beakers, 750 mL (5) “Contaminant: soil,” “Contaminant: food coloring,” and
glucose solution “Water (control).”
glucose test paper
graduated cylinder 2. Fill these beakers two-thirds full with clean tap water. Then
gravel add to each beaker the contaminant listed on its label. (The
metric ruler table on the next page shows how much of each contaminant
soda bottles, 2 to 3 L (4) you should use.) Stir each mixture thoroughly.
red food coloring
sand 3. Copy the data table into your notebook. Carefully observe
soil each beaker, and record your observations. Use some of the
stirring rod glucose test paper to test the glucose level in the glucose beaker.
wax pencil
4. Make four separate filtration systems similar to the one shown
optional contaminants: below. Your teacher will provide you with bottle caps that have
cooking oil, detergent, fertil- holes poked through them. Fasten each cap to a bottle. Cut the
izer, vinegar, soda bottom off of each soda bottle, and fill each bottle with layers
of gravel, sand, and soil. Consider using the optional filter
optional filter materials: materials, such as alum or charcoal, but be sure to make all
alum, charcoal four of your systems identical.
̈ Filter Apparatus Your ground
filtration models should be layered
as shown here.
320 Chapter 11 Exploration Lab
Observations of Substances in Surface Water
Contaminant Before filtration After filtration
Glucose (15 mL) DO NOT WRITE
Soil (15 mL) IN THIS BOOK
Food coloring (15 drops)
Water (control)
5. You are now going to pour each mixture through a filtration ̈ Step 6 Pour each sample of con-
system. But first predict how well the filters will clean each taminated surface water through
water sample. Write your predictions in your notebook. a filter.
6. Stir a contaminant mixture in its beaker, and immediately
pour the mixture through a filtration system into a clean
beaker. Observe the resulting “groundwater,” and record
your observations in the table you created. CAUTION:
Do not taste any of the substances you are testing.
7. Repeat step 6 for each mixture. Clean and relabel the
contaminant beakers as you go along.
Analysis
1. Analyzing Results Test the glucose-water mixture for
the presence of glucose. Can you see the glucose?
2. Analyzing Results Was the soil removed from the water
by filtering? Was the food coloring removed? How do
you know?
Conclusions
3. Drawing Conclusions How accurate were your predictions?
4. Drawing Conclusions What conclusions can you draw about
the filtration model and the materials you used?
Extension
1. Making Predictions Choose a substance from the materi-
als list that has not been tested. Predict what will happen if
you mix this substance in the water supply.
2. Evaluating Results Now test your prediction. Use the filter
that was the control in the earlier experiment. How did
your results compare with your prediction?
3. Analyzing Results Compare your results with the results
of other teams. What precautions do you recommend for
keeping groundwater clean?
Chapter 11 Exploration Lab 321
THE THREE GORGES DAM
China’s Yangtze River is the third- Yangtze River to prevent flooding. ̈ The Three Gorges Dam is named
longest river in the world after the About 1 million people died in the for the beautiful canyons it will flood.
Nile and the Amazon. The Yangtze last century from flooding along When completed, the dam may meet
River flows through the Three the river. The damage caused by a 20 percent of China’s energy needs
Gorges region of central China, severe flood in 1998 is estimated to with hydroelectric power.
which is famous for its natural have cost as much as the entire
beauty and historical sites. For dam project. The dam will also Almost 2 million people living in
thousands of years, the area’s sheer provide millions of people with the affected areas must be relo-
cliffs have inspired paintings and hydroelectric power. China now cated—there are 13 cities and hun-
poems. This idyllic region seems burns air-polluting coal to meet dreds of villages in the area of the
like the sort of place that would be 75 percent of the country’s energy proposed reservoir. As the reser-
protected as a park or reserve. But needs. Engineers project that when voir’s waters rise, they will also
in fact, it is the construction site the dam is completed, its turbines destroy fragile ecosystems and
for the Three Gorges Dam—the will provide enough electrical valuable archeological sites.
largest hydroelectric dam project energy to power a city that is
in the world. When the dam is 10 times the size of Los Angeles. Opponents of the project claim
fully operational, the Yangtze River When the Yangtze’s flow is con- that the dam has already increased
will rise to form a reservoir that is trolled, the river will be deep pollution levels in the Yangtze
595 km (370 mi) long—as long as enough for large ships to navigate River. Most of the cities and facto-
Lake Superior. In other words, the on it, so the dam will also increase ries along the river dump untreated
reservoir will be about as long as trade in a relatively poor region wastes directly into the water. Some
the distance between Los Angeles of China. people think the reservoir will
and San Francisco! become the world’s largest sewer
Some Disadvantages when 1 billion tons of sewage flow
Benefits of the Dam into the reservoir every year.
The project has many drawbacks,
The dam has several purposes. It however. The reservoir behind the
will control the water level of the dam will flood an enormous area.
̈ The reservoir that will form behind the Three Gorges Dam is shown
in yellow.
Long-Term Concerns
People have also raised long-term
concerns about the project. The dam
is being built over a fault line.
Scientists question whether the dam
would be able to withstand earth-
quakes that may occur along the
322 Chapter 11 Points of View
EARTH SCIENCE CONNECTION
fault. If the dam burst, towns and Hidden Costs?
cities downstream would be flooded.
Another concern is that the reservoir Supporters of the dam claim that
may quickly fill with sediment. The the project will cost $25 billion,
Yangtze picks up enormous amounts while opponents claim that the
of yellowish soil and sediment as it cost will be closer to $75 billion.
flows across China. When the river The true cost of the dam may
is slowed by the dam, much of the never be known because corrup-
silt will be deposited in the new tion and inefficiency have plagued
reservoir. As sediment builds up the project from the start.
behind the dam, the deposited Controversy over the dam has
sediment will reduce the size of the prompted the U.S. government
reservoir—limiting the flood- and the World Bank to withhold
prevention capacity of the dam. In money for the project. Public
addition, productive farming regions opposition to the project has been
below the dam will be deprived of silenced since the Tiananmen
the fertile sediment that is deposited Square crackdown. But with help
every year when the river floods. from private investment compa-
nies from the United States, the
The enormous reservoir may Chinese government is continuing
also cause disease among the local with the project, and the dam is
population. The potential heath slowly being built. The world’s
risks include an increase in third-longest river will soon swell
encephalitis and malaria. The most in the middle, and China will
deadly disease spread by the Three change along with it.
Gorges Dam could be a parasitic
disease called schistosomiasis.
̈ Engineers discuss plans at the dam construction site. The project created ̈ When the dam waters rise, these
more than 20,000 construction jobs. ancient temples will be flooded.
What Do You Think?
Hundreds of dams in the
western United States provide
electrical energy, drinking
water, and water for crops.
Unfortunately, these dams
flooded scenic canyons and
destroyed ecosystems. Now
that the environmental con-
sequences of large dams are
known, do you think that
China should reconsider the
Three Gorges Dam project?
Chapter 11 323
Air 12C H A P T E R
324 Chapter 12 Air 1 What Causes Air Pollution?
2 Air, Noise, and Light
Pollution
3 Acid Precipitation
PRE-READING ACTIVITY
Booklet
Before you
read this chap-
ter, create the
FoldNote entitled “Booklet”
described in the Reading and
Study Skills section of the
Appendix. Label each page of
the booklet with a main idea
from the chapter. As you
read the chapter, write what
you learn about
each main idea
on the appropri-
ate page of the
booklet.
Nagano, Japan, is just one of many
cities around the world that
suffers from unhealthy levels of
air pollution.
SECTION 1
What Causes Air Pollution?
EARTH SCIENCE CONNECTION
In Mexico City, children rarely use the color blue when they Objectives
make paintings of the sky. This metropolitan area of 20 million
people is known as the most dangerous city in the world for chil- ̈ Name five primary air pollutants,
dren because of its very polluted air. and give sources for each.
Clean air consists mostly of nitrogen and oxygen gas, as well ̈ Name the two major sources of air
as very small amounts of argon, carbon dioxide, and water vapor. pollution in urban areas.
When harmful substances build up in the air to unhealthy levels,
the result is air pollution. ̈ Describe the way in which smog
forms.
Most air pollution is the result of human activities, but pol-
lutants can also come from natural sources. A volcano, for ̈ Explain the way in which a ther-
example, can spew clouds of particles and sulfur dioxide, mal inversion traps air pollution.
SO2, into the atmosphere. Natural pollutants also include dust,
pollen, and spores. Key Terms
Primary and Secondary Pollutants air pollution
primary pollutant
A pollutant that is put directly into the air by human activity is secondary pollutant
called a primary pollutant. An example of a primary pollutant is smog
soot from smoke. Figure 1 shows some sources of primary air pol- temperature inversion
lutants. Secondary pollutants form when primary pollutants react
with other primary pollutants or with naturally occurring sub- Figure 1 ̈ Each day in the United
stances such as water vapor. An example of a secondary pollutant States, hundreds of thousands of
is ground-level ozone. Ground-level ozone forms when the ultra- tons of polluting emissions that result
violet rays of the sun cause emissions from cars, trucks, and natu- from human activity enter the air.
ral sources to react with oxygen in the atmosphere.
■✓● Reading Check Why is ground-level ozone an example of a second-
ary pollutant? (See the Appendix for answers to Reading Checks.)
Sources of Primary Air Pollutants in the U.S. (Per Day)
80
Emissions (in thousands of tons) 70 Carbon monoxide (CO)
Nitrogen oxides (NOx)
60 Particulate matter (PM)
50 Sulfur oxides (SOx)
Volatile organic compounds (VOCs)
40
30
20
10
0 Industry Transportation Other sources
Electricity production
Source: U.S. Environmental Protection Agency.
Section 1 What Causes Air Pollution? 325
Table 1 ̄ Primary Air Pollutants
Pollutant Description Primary Sources Effects
Carbon
monoxide CO is an odorless, Sources of CO are cars, CO interferes with the blood’s ability
(CO) colorless, poisonous gas. trucks, buses, small to carry oxygen, slowing reflexes and
It is produced by the engines, and some causing drowsiness. In high
Nitrogen incomplete burning of industrial processes. concentrations, CO can cause death.
oxides (NOx) fossil fuels.
NOx can make the body vulnerable to
Sulfur When combustion NOx comes from burning respiratory infections, lung diseases,
dioxide (SO2) (burning) temperatures fuels in vehicles, power and cancer. NOx contributes to the
exceed 538°C, nitrogen brownish haze seen over cities and to
Volatile and oxygen combine to plants, and industrial acid precipitation.
organic form nitrogen oxides.
compounds boilers. SO2 contributes to acid precipitation
(VOCs) as sulfuric acid. Secondary pollutants
Particulate SO2 is produced by SO2 comes mostly from that result from reactions with SO2
matter chemical interactions burning fossil fuels. can harm plant life and irritate the
(particulates respiratory systems of humans.
or PM) between sulfur and
VOCs contribute to smog formation
oxygen. and can cause serious health
problems, such as cancer. They may
VOCs are organic VOCs come from burning also harm plants.
chemicals that fuels. Vehicles are a major
vaporize readily and source of VOCs. Particulates can form clouds that
form toxic fumes. reduce visibility and cause a variety of
Most particulates come respiratory problems. Particulates have
Particulates are tiny from construction, also been linked to cancer. As well,
particles of liquid or agriculture, forestry, and they may corrode metals and erode
solid matter. fires. Vehicles and buildings and sculptures.
industrial processes also
contribute particulates.
www.scilinks.org Sources of Primary Air Pollutants As shown in Table 1 above,
household products, power plants, and motor vehicles are
Topic: Air Pollution sources of primary air pollutants such as carbon monoxide,
Code: HE80033 nitrogen oxide, sulfur dioxide, and chemicals called volatile
organic compounds (VOCs). Carbon monoxide gas is an
326 Chapter 12 Air important component of the exhaust from vehicles. Vehicles
are also a major source of emissions of nitrogen oxides. Coal-
burning power plants are another source of nitrogen oxides.
Sulfur dioxide gases are formed when coal and oil, which
contain sulfur, are burned. Power plants, refineries, and metal
smelters contribute much of the sulfur dioxide emissions to the
air. Vehicles and gas station spillage make up most of the
human-made emissions of volatile organic compounds. VOCs
are also found in many household products.
Particulate matter can also pollute the air and is usually
divided into fine and coarse particles. Fine particles enter the air
from fuel burned by vehicles and coal-burning power plants.
Sources of coarse particles are cement plants, mining operations,
incinerators, wood-burning fireplaces, fields, and roads.
The History of Air Pollution Geofact
Air pollution is not a new phenomenon. Whenever something Sea-Coal In 12th-century London,
burns, pollutants enter the air. Two thousand years ago, Seneca, a wood was becoming too scarce
Roman philosopher and writer, complained about the foul air in and too expensive to use as a fuel
Rome. In 1273, England’s King Edward I ordered that burning a source. Large deposits of coal
particularly dirty kind of coal called sea-coal was illegal. One man called sea-coal that are found off
was even hanged for disobeying this medieval “clean air act.” the northeast coast of England
provided a plentiful alternative.
The world air-quality problem is much worse today because However, this soft coal did not
modern industrial societies burn large amounts of fossil fuels. As burn efficiently. The sea-coal pro-
shown in Figure 2, most air pollution comes from motor vehicles duced mostly smoke and not
and industry. much heat. The smoke from the
coal emanated from London
Motor Vehicle Emissions homes and factories and combined
with fog to produce smog.
Almost one-third of our air pollution comes from gasoline
burned by vehicles. According to the U.S. Department of Connection to Law
Transportation, Americans drove their vehicles over 2.6 trillion
miles in 1998. Over 90 percent of that mileage was driven by Off with His Head! Around
passenger vehicles. The rest was driven by trucks and buses. 1300 CE, King Edward II of
England forbade the burning of
Controlling Vehicle Emissions The Clean Air Act, passed in 1970 coal while Parliament was in ses-
and strengthened in 1990, gives the Environmental Protection sion. “Be it known to all within
Agency (EPA) the authority to regulate vehicle emissions in the the sound of my voice,” King
United States. The EPA required the gradual elimination of lead in Edward II said, “whosoever shall
gasoline, and as a result, lead pollution has been reduced by more be found burning coal shall suffer
than 90 percent in the United States. In addition, catalytic con- the loss of his head.”
verters, which are required in automobiles, clean exhaust gases of
pollutants before the pollutants are able to exit the tailpipe. The
EPA estimates that cars and trucks today burn fuel 35 percent
more efficiently and with 95 percent fewer emissions of pollutants,
excluding carbon dioxide, than they did 30 years ago.
Figure 2 ̈ The refinery shown in
this photograph is a source of volatile
organic compounds. The tanker truck
in the foreground is emitting nitrous
oxide into the atmosphere.
Section 1 327
MATHPRACTICE California Zero-Emission Vehicle Program A catalytic converter,
as shown in Figure 3, is a device that is used to control emissions
Utility Incentives for from most American vehicles. In California, motor vehicles account
Zero-emission Vehicles for more than half of the ozone and particulate matter that pollutes
The Los Angeles Department the air. To improve air quality, the state’s Air Resources Board
of Water and Power provides established the Zero-Emission Vehicle (ZEV) program in 1990 to
discounts of $0.025 per kilowatt encourage the development of less-polluting vehicles. ZEV pro-
hour (kWh) for electricity used to grams have also been adopted in Maine, Massachusetts, New York,
recharge electric vehicles. If the and Vermont.
energy charge per kWh is $0.02949
and you use 150 kWh hours of Zero-emission vehicles have no tailpipe emissions, no
electricity per month to recharge emissions from gasoline, and no emission-control systems, which
your vehicle, how much money deteriorate over time. Battery-powered electric vehicles are the
would you save on your electric bill only true ZEVs at the moment, but there are two types of partial
each month? each year? How much ZEVs. One type is clean, fuel-efficient hybrid cars, which are
would you save if you had three powered by both batteries and gasoline engines. Hybrid cars are
electric cars? already in use today and are very popular. The other type is vehi-
cles powered by methanol fuel cells. Many automobile manufac-
Figure 3 ̈ The catalyst material in turers have built these vehicles, but they are still in the prototype
a catalytic converter (top) causes a stage of development.
chemical reaction that changes
exhaust emissions to less harmful
substances. The bottom illustration
shows a car’s contribution to
air pollution.
Interior Exhaust
̈ Car seats may be covered in plastic that contains ̈ Car exhaust is a major source of nitrogen oxides,
a volatile organic compound called vinyl chloride. carbon monoxide, and hydrocarbons.
Body and Frame ̈ In developing countries, car exhaust may
̈ Steel smelters send thousands of metric tons of contain over a thousand poisonous substances.
sulfur dioxide into the air each year.
̈ Each car on average
̈ Many auto factories in Mexico, Eastern Europe, releases 4.5 metric
and some Asian countries lack pollution-control tons (5 tons) of
devices. carbon dioxide
every year.
Fuel Tank
̈ When filling the car with
gasoline, VOCs escape into the
atmosphere.
328 Chapter 12 Air
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