108 Chapter 4

4.3 Water, Air, and Land Resources

Reading StrategyBuilding Vocabulary Copy the table below.As you read, add definitions and examples tocomplete the table.

Key ConceptsWhy is fresh water a vitalresource?

Why is the chemicalcomposition of theatmosphere important?

What are Earth’simportant land resources?

Vocabulary◆ point source

pollution◆ nonpoint source

pollution◆ runoff◆ acid precipitation◆ global warming

Water, air, and land resources are essential for life. You need cleanair and water every day. What’s more, soil provides nutrients that allowplants—the basis of our own food supply—to grow. How do peopleuse—and sometimes misuse—these vital resources?

The Water PlanetFigure 16 shows Earth’s most prominent feature—water. Water coversnearly 71 percent of Earth’s surface. However, most of this water is salt-water, not fresh water. Oceans have important functions. Their currentshelp regulate and moderate Earth’s climate. They are also a vital part ofthe water cycle, and a habitat for marine organisms. Fresh water, how-ever, is what people need in order to live. Each day, people use freshwater for drinking, cooking, bathing, and growing food. While freshwater is extremely important, Earth’s reserves are relatively small. Lessthan one percent of the water on the planet is usable fresh water.

Freshwater Pollution Pollution has contaminated many fresh-water supplies. In general, there are two types of water pollutionsources—point sources and nonpoint sources. Point source pollutionis pollution that comes from a known and specific location, such asthe factory pipes in Figure 17. Other examples include a leaking land-fill or storage tank.

Figure 16 Oceans cover almostthree fourths of Earth surface,making Earth a unique planet.

Definitions Examples

point source pollution: Pollution that factory pipes,can be traced to a location sewer pipes

nonpoint source pollution: a. b.

runoff: c. d.

greenhouse gas: e. f. ??

??

??

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FOCUS

Section Objectives4.10 Explain why fresh water is a

vital resource.4.11 Recognize why the chemical

composition of the atmosphereis important.

4.12 Identify Earth’s important landresources.

Build VocabularyParaphrase Before students read thesection, have them explain what theythink point source and nonpoint sourcemean. After they have read the section,ask students to explain the meanings ofthe terms in their own words, notinghow their definitions have changed, ifat all.

Reading Strategya. pollution that does not have a specificpoint of originb. runoff, water filtering through piles ofwaste rockc. water that flows over the land ratherthan seeping into the groundd. waste oil from streets, pesticides offfarm fieldse. gases that help maintain a warmtemperature near Earth’s surfacef. carbon dioxide, methane, water vapor

INSTRUCT

The Water PlanetUse CommunityResourcesHave students research the water supplyin their community. They should findout where their water comes from andhow it is treated to make it safe forhuman use. The Department of PublicWorks or the water department will havethis information. Students may be ableto tour the municipal water treatmentplant.Verbal, Interpersonal

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Reading Focus

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Section 4.3

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Nonpoint source pollution is pollution that does not have a specificpoint of origin. Runoff, the water that flows over the land rather thanseeping into the ground, often carries nonpoint source pollution. Runoffcan carry waste oil from streets. It can wash sediment from constructionsites or pesticides off farm fields and lawns. Water filtering through pilesof waste rock from coal mines can carry sulfuric acid into rivers or lakes.This contaminated water can kill fish and other aquatic life.

As you can see in Table 2, water pollution has adverse health effects.Pollutants can damage the body’s major organs and systems, cause birthdefects, lead to infectious diseases, and cause certain types of cancers.Contaminated fresh water can sicken or kill aquatic organisms and dis-rupt ecosystems. What’s more, fish and other aquatic life that live incontaminated waters often concentrate poisons in their flesh. As a result,it is dangerous to eat fish taken from some polluted waters.

What is the difference between a point and non-point water pollution source?

Table 2 Major Types of Water Pollution

Type Examples Sources Effects

Disease organisms Bacteria, viruses Wastes from people Typhoid, cholera, dysentery, and animals infectious hepatitis

Wastes that remove Animal manure and plant Sewage, animal feedlots Great amounts of bacteria oxygen from water debris that bacteria can remove oxygen from

decompose water, killing fish

Inorganic chemicals Acids, toxic metals Industrial effluent, Poisons fresh water and urban runoff, household can sicken those who cleaners drink it

Organic chemicals Oil, gasoline, plastic, Farm and yard runoff, Some cancers, disorders of pesticides, detergent industrial waste, nervous and

household cleaners reproductive systems

Plant fertilizer Water soluble compounds Sewage, manure, farm Spurs rapid growth of with nitrate, and garden runoff algae that decay and phosphorus ions deplete water’s oxygen;

fish die

Sediment Soil Erosion Disrupts aquatic food webs, clogs lakes and reservoirs, reduces photosynthesis of aquatic plants

Radioactive Radon, uranium, Nuclear power plants, Some cancers, birth substances radioactive iodine uranium ore mining defects, genetic mutations

and processing

Figure 17 Pollution from pointsources, such as these factorypipes, is easy to locate andcontrol.

Use VisualsTable 2 Have students study the table.Ask: Why is fertilizer considered apollutant if it is needed by plants? (Itcauses rapid growth of algae that decayand deplete water’s oxygen.) What aresome sources of water pollution fromorganic chemicals? (farm and yardrunoff, industrial waste, and householdcleaners) Where do disease organismsthat pollute water come from? (wastesfrom people and animals) What twotypes of water pollution can causecancers in humans? (organic chemicalsand radioactive substances)Visual

Build Science SkillsApplying Concepts Have studentsexplain how fish and other aquaticlife that live in polluted water canconcentrate poisons in their flesh.(Fish and other aquatic organisms passlarge amounts of water through theirbodies as they extract oxygen from thewater. If pollutants are also extractedfrom the water, they will accumulate inthe fish’s flesh in increasing concentration.This process is similar to that of a strainerconcentrating material from the waterthat is poured through it.)Verbal

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Answer to . . .

Point source pollution ispollution that comes

from a known and specific location.Nonpoint source pollution is pollutionthat does not have a specific point oforigin.

Customize for English Language Learners

Have students use a dictionary to look up themeaning of acid precipitation. Ask them to listthe different forms that acid precipitation cantake. (acid snow, rain, fog) Ask students whyacid precipitation can take many forms.

(Precipitation occurs when water vapor condensesin the atmosphere. The form of precipitationdepends on temperature, altitude, and otherphysical conditions.)

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Earth’s Blanket of AirEarth’s atmosphere is a blanket of nitrogen, oxygen, water vaporand other gases. The chemical composition of the atmos-phere helps maintain life on Earth. First and foremost, peopleand other animals could not live without the oxygen in Earth’satmosphere. But the atmosphere is also part of several othercycles, such as the carbon cycle, that make vital nutrients avail-able to living things.

The atmosphere also makes life on land possible by shield-ing Earth from harmful solar radiation. There is a layer ofprotective ozone high in the air. Ozone is a three-atom form ofoxygen that protects Earth from 95 percent of the sun’s harm-ful ultraviolet (UV) radiation.

Certain greenhouse gases in the atmosphere—such as carbon diox-ide, methane, and water vapor—help maintain a warm temperaturenear Earth’s surface. When solar energy hits Earth, the Earth gives offsome of this energy as heat. The gases absorb the heat Earth emits,keeping the atmosphere warm enough for life as we know it.

Pollution in the Air Pollution can change the chemical com-position of the atmosphere and disrupt its natural cycles andfunctions. Fossil-fuel combustion is the major source of air pollution.Most of this pollution comes from motor vehicles and coal or oil-burning power plants. Motor vehicles, like those in Figure 18, releasecarbon monoxide, nitrogen oxide, soot, and other pollutants. Some ofthe pollutants react to form smog. Power plants release sulfur dioxideand nitrogen oxides. These pollutants combine with water vapor inthe air to create acid precipitation. Figure 19 shows the primary airpollutants and the sources of those pollutants.

The burning of fossil fuels also produces carbon dioxide, an impor-tant greenhouse gas. The amount of carbon dioxide in the atmospherehas increased since industrialization began in the nineteenth century.This increase has altered the carbon cycle and contributed to the unnat-ural warming of the lower atmosphere, known as global warming.Global warming could lead to enormous changes in Earth’s environ-ment. These changes could include the melting of glaciers, which wouldcontribute to a rise in sea level and in the flooding of coastal areas.

Chlorofluorocarbons (CFCs) once used in air conditioners and plas-tic foam production destroy ozone in the stratosphere layer of theatmosphere. Researchers say that a significant loss of ozone could resultin an increased incidence of health problems like cataracts and skin can-cers because more of the sun’s UV radiation would reach Earth’s surface.

What is the role of ozone in the atmosphere?Primary Pollutants

What They Are

VolatileOrganics13.6%

Particulates6.0%Sulfur

Oxides16.4%Nitrogen

Oxides14.8%

Carbon Monoxide49.1%

StationarySource FuelCombustion

27.3%

Where They Come From

IndustrialProcesses

15.0%

Solid Waste Disposal2.5%

Miscellaneous9.0%

Transportation46.2%

Figure 19 Major PrimaryPollutants and Their SourcesPercentages are calculated on thebasis of weight. Using Graphs What are thethree major primary pollutants?What is the major source of airpollution?

Figure 18 Cars, trucks, and busesare the biggest source of airpollution. Laws that controlmotor vehicle emissions havehelped make the air cleaner inmany areas.

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Earth’s Blanketof AirUse VisualsFigure 19 Have students examine thegraphs. Ask: What makes up almosthalf of all air pollution? (carbonmonoxide) What fraction of pollutionsources are industrial processes?(about 15 percent) What do you think isthe source of most carbon monoxidepollution? (vehicle exhaust and fuelcombustion)Visual, Logical

Ask students if there is a hole in theozone layer high above Earth. If theysay yes, they may hold the misconceptionthat there is an actual hole in the skythat lets UV radiation through. Showstudents NASA satellite photos of ozonedistribution so they can read the ozoneconcentration in the “hole.” Explain thatozone is being depleted around theglobe but is particularly severe in certainareas, notably above Antarctica. Thisdepletion is actually a temporarydepletion of ozone in September andOctober of each year. In December andJanuary, the “hole” is repaired. The reasonfor concern is the fact that each year,more ozone is being depleted and lessis being repaired. Ask: What happensduring periods of ozone depletion?(More UV radiation reaches Earth’ssurface.) Why are scientists concernedif the “hole” is repaired each year?(The hole is not completely repaired, andincreasing amounts of ozone are beingdestroyed.)Logical

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Section 4.3 (continued)

Primary pollutants are those emitted byidentifiable sources. They immediatelypollute the air when they are emitted.Primary pollutants are also dangerousbecause they form secondary pollutantswhen chemical reactions take place among

the primary pollutants. The mixture of gasesand particles that make up urban smog is agood example of a secondary pollutant. Smogforms when unstable organic compounds andnitrogen oxides from vehicle exhaust react inthe presence of sunlight.

Facts and Figures

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Figure 20 Surface mining destroysvegetation, soil, and the contours ofEarth’s surface. However, laws nowrequire mine owners to restore thesurface after mining operationscease.

Air pollution is a major public health problem. It can cause cough-ing, wheezing, headaches, as well as lung, eye, and throat irritation.Long-term health effects include asthma, bronchitis, emphysema, andlung cancer. The U.S. Environmental Protection Agency estimates thatas many as 200,000 deaths each year are associated with outdoor airpollution.

Land ResourcesEarth’s land provides soil and forests, as well as mineral and energy

resources. How do land resources impact your daily life? Soil is neededto grow the food you eat. Forests provide lumber for your home, woodfor furniture, and pulp for paper. Petroleum provides energy and is in theplastic of your computer and CD boxes. Minerals such as zinc, copper,and nickel make up the coins in your pocket. Removing and usingresources from Earth’s crust can take a heavy environmental toll.

Damage to Land Resources There are an estimated 500,000mines in the United States. Mines are essential because they producemany of the mineral resources we need. But mining tears up Earth’ssurface and destroys vegetation, as you can see in Figure 20. It can alsocause soil erosion and create pollution that contaminates surroundingsoil and water and destroys ecosystems.

Agriculture has many impacts on the land as well. Today, farmerscan produce more food per hectare from their land. Extensive irrigationalso has allowed many dry areas to be farmed for the first time. But heavypumping for irrigation of dry areas is depleting the groundwater. Andover time, irrigation causes salinization, or the build-up of salts in soil.When irrigation water on the soil evaporates, it leaves behind a saltycrust. Eventually, the soil becomes useless for plant growth.

For: Links on environmental toxins

Visit: www.SciLinks.org

Web Code: cjn-1043

Land Resources

Motion AcceleratesErosionPurpose Students demonstrate howthe motion of water increases the long-term effects of erosion.

Materials 2 identical clean 1-L jarswith lids, marking pen, water, 2 identicalpieces of hard candy, measuring cup

Procedure Label the jars A and B.Place a piece of candy in each jar. Pour500 mL of water into each jar. Coverboth jars. Place them in a location whereboth can be seen. Shake jar A once ortwice a day. Do not disturb jar B.

Expected Outcome After only 2 days,students should be able to see that thedisturbed candy has dissolved muchmore than the undisturbed candy.Kinesthetic, Visual

Build Reading LiteracyRefer to p. 246D in Chapter 9, whichprovides the guidelines for relatingcause and effect.

Relate Cause and Effect Havestudents think about the build-up ofsalts in soil. Ask: Why can salts build upin soil used for intensive farming? (Inorder to grow large amounts of crops in anarea, farmers add heavy applications offertilizers to support the additional plants.Salts from the fertilizer eventually build upin the soil.)Logical

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Answer to . . .

Figure 19 The major primarypollutants are carbon monoxide,sulfur and nitrogen oxides, andvolatile organics. The major sourceof air pollution is fossil-fuel combustion.

Ozone absorbs harmfulultraviolet radiation

from the sun, thus protecting life.

Download a worksheet on environ-mental toxins for students tocomplete, and find additionalteacher support from NSTASciLinks.

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Section 4.3 Assessment

Reviewing Concepts1. Why is fresh water a vital resource?

2. Why is the chemical composition ofEarth’s atmosphere important?

3. What is the difference between point sourcepollution and nonpoint source pollution?

4. What do Earth’s land resources provide?

Critical Thinking5. Applying Concepts How would Earth be

different if there were no greenhouse gases?

6. Classifying Which of the following is anonpoint source pollution of water: rainwaterpouring from an eroded bank into a river, a

boat emptying a waste tank into a lake, or asewage plant sending sewage into a riverthrough a pipe?

7. Relating Cause and Effect How would theremoval of sulfur from coal affect the type of airpollution in a local area? Explain your answer.

Trees must be cut to supply our need forpaper and lumber. But the removal of forests,especially through clear-cutting, can damage land.Clear-cutting is the removal of all trees in an areaof forest. Cleared areas are susceptible to soil ero-sion. Forest removal also destroys ecosystems andwildlife habitat. The United States actually hasmore hectares of forest today than it did a centuryago. That’s because much of the virgin forest(forest that had never been cut down) that was cutlong ago has regrown as second-growth forest.The forest is not as diverse as the virgin forest—itdoes not contain as much variety of plant species.Some forestland has also become tree plantations,with even fewer species. As you see in Figure 21,the United States has lost most of its virgin forestduring the last few centuries.

Finally, land serves as a disposal site. You mayhave seen landfills and other waste facilities. Whendisposal is done correctly, there is minimal impacton land. But many old landfills leak harmfulwastes that get into soil and underground water.The same is true of buried drums of chemicals,which were often disposed of illegally. Waste isinevitable. But there is a need for ways to reduceit and make the disposal safer.

Write a brief paragraph that connects thefollowing: waste of paper, loss of speciesdiversity of forests, and the increase insecond-growth forest area.

Virgin Forests 1620–1998

Virgin forests, 1620

Virgin forests, 1998

Figure 21

Location These maps compare the location ofvirgin forests in the contiguous 48 states of theU.S. in 1620 and in 1998. Identifying EffectsHow has the amount of virgin forest changed?How has the location of virgin forest changed?

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AnswersIdentifying Effects The amount ofvirgin forest was much greater in 1620.The eastern half of the United Stateshas lost almost all of its virgin forest.There are now more virgin forests inthe western half of the country thanin the eastern half.

ASSESSEvaluateUnderstandingTo assess students’ knowledge ofsection content, have them write ashort paragraph explaining howozone can be essential to life whenit is in the upper stratosphere, yet aserious pollutant when it is closer toEarth’s surface.

ReteachHave students summarize theirknowledge of water, land, and airresources by making an outline ofthe section. They can use the headsas a guide and add information undereach head.

Student paragraphs should suggest thatwasting paper causes more trees to becut down, resulting in a loss of speciesdue to elimination of their habitat. Whentrees are clear-cut, the forest eventuallywill be replaced by a second-growthforest that has greater area but lessdiversity than the original forest.

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Section 4.3 (continued)

5. Earth would be too cold to sustain life.6. rainwater pouring from an eroded bankinto a river7. Removing sulfur from coal would decreasethe amount of sulfur oxides in the air. Sulfuroxides combine with water vapor to form acidprecipitation, so the acidity of the precipita-tion both locally and in more distant areaswould decrease.

Section 4.3 Assessment

1. People need fresh water for drinking, cook-ing, bathing, and growing food.2. The chemical composition of Earth’s atmos-phere helps to maintain life on Earth.3. Point source pollution has a known andspecific location. Nonpoint source pollutiondoes not have a specific point of origin.4. soil, forests, mineral and energy resources

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