Khoa học môi trường

Khoa học môi trường

HO CHI MINH UNIVERSITY OF INDUSTRY INSTITUTE FOR ENVIRONMENTAL ENGINEERING & MANAGEMENT

Compiled by VO DINH LONG

ENVIRONMENTAL SCIENCES

(Specialized English course for Environmental Students)

HO CHI MINH CITY - 2006

CONTENTS

CHAPTER 1: BASIC UNITS OF ECOLOGY

After studying this chapter, you should be able to:

1 Define environment.

2 Define an ecosystem.

3 Identify the components of the biosphere.

4 Describe the living and nonliving components of the environment.

5 Explain that bacteria and fungi are agents of decay.

6 Discuss the process of photosynthesis.

7 Enumerate the important factors that affect the growth of plants and the survival of animals.

Part of the world where life operates is known as the biosphere

The biosphere consists of the air (atmosphere), water (hydrosphere), and earth (lithosphere) where living things interact with their environment

Figure 1.1: The biosphereWhen you study the interaction or relationship between organisms and their environment, you are studying an ecosystem The term ecosystem refers to all the living things and the nonliving things in a given area It includes all the plants and animals together with their surroundings The ecosystem of an aquarium, for example, consists of the hydrilla and others plants, fish, snails, and other aquatic animals,

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some of which can only be seen under a microscope It also includes sand and pebbles at the bottom We can also include the owner who takes care of the aquarium.

A grassland, too, is an ecosystem This ecosystem consists of the grass, earthworms, insects, bacteria, soil, water, sunlight, and other plants and animals that live on it The pond is another example of an ecosystem

The forest is a more complex ecosystem Can you identify some of the components of this ecosystem?

The entire earth can be thought of as an ecosystem It has an abundance of different kinds of species of living things which, although separate by great distances, still react with one another and with the nonliving world

In a forest ecosystem, interrelationships among its living and nonliving components occur The branches and leaves of trees help break the force of the rain Layers of dead leaves and twins and branches on the forest floor soak up water and prevent rain from washing soil away Little water runs off the land The roots of trees hold the soil and water on which they depend Moreover, when the leaves and branches decay, they become part of the rich topsoil

The soil is made up of minerals like silica and clay They come from the breakdown of rocks There are spaces between the mineral particles which are filled with air and water Roots of plants penetrate deeper into the soil causing physical change They loosen the tightly packed particle Chemical change also occurs The roots absorb the minerals present

Figure 1.2: Plant-soil relationshipThere are thousands of organisms that live in the soil, like earthworms, that decompose the dead plants and animals Some are too small to be seen, but they all help maintain the ecological balance in the soil

Figure 1.3: Organisms in the soil

Guide questions

1 What is an ecosystem?

2 How do the living components of an ecosystem affect the nonliving components? Give example

3 Can a fallen log be considered as an ecosystem? Explain your answer.

1.2 COMPONENTS OF AN ECOSYSTEM

In the preceding section you learned what an ecosystem is The living component is known as the biotic and the nonliving component is known as abiotic The biotic component consists of plants, animals, and bacteria The abiotic component includes all the factors of the nonliving environment such as the substratum, light, rainfall, nutrients, soil, and others Both the biotic and abiotic components are equally important in the ecosystem because without one of them the ecosystem would not function

Insightfulness

The ecosystem consists of the biotic and abiotic components The biotic components are the plants, animals, and decomposers The abiotic components are the non living factors, such as temperature, water, and others The abiotic affect the biotic components and vice versa

1.2.1 Green plants

Green plants are known as the producers They capture the energy from the sun and together with carbon dioxide (CO2) in the air and water (H2O) convert together those into food energy Since plants are able to manufacture their own food, they are also known as autotrophs (or self-nourishing) These plants are able

to manufacture food though the process of photosynthesis, which will be explained in the next section

Green plants also take substances, such as nitrogen and sulfur from the environment and convert those into plant materials that can be used by other organisms as food These green plants further provide oxygen which is taken in by humans and animals in the process of respiration For these reasons, all life, whether in the pond, forest, or grassland, depend on green plants

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You might think that green plants consist only of the trees or big plants that you see around The other producers are invisible to your eyes These are the microscopic drifting plants which are greater sources of food than the big plants that you can see We call these microscopic plants phytoplankton When they become too abundant, they can give a pond or a body of water a green color

Have you ever seen a pond or a lake with green surface?

Guide questions

1 What are producers?

2 What do producers perform in an ecosystem?

3 What are phytoplanktons?

1.2.2 Animals

Animals, or the consumers, obtain their food from plants or other animals Because of this, they are also known as heterotrophs, which means that they feed on others and cannot manufacture their own food, unlike the green plants

There are three different types of consumers, namely, the herbivores, the carnivores, and the omnivores

Figure 1.4: There are three different types of consumers

The herbivores are those that eat plants only For example, the caterpillar that feeds on leaves is an herbivore while the snake that eats the caterpillar is a carnivore Omnivores eat both plants and animals A human being is a good example of an omnivore

Through the process of respiration, animals combine the food they eat with oxygen to produce CO2 and

H2O which are used by plants in the photosynthesis process Animals also convert the materials of the plant bodies into the materials that make-up their own bodies All the energy produced and used by animals comes from the plants

Guide questions

1 What are consumers?

2 What are the three types of consumers? and give one example for each type

1.2.3 Bacteria and fungi as agents of decay

Have you ever observed what happen to leaves that fall on the ground?

After some time, the leaves wither, break down into smaller pieces, decay, and finally become part of the soil What do you think is responsible for this change?

Have you heard of the word decomposer? What do you think does a decomposer do?

Decomposers make-up the third biotic component of the ecosystem They use the bodies of dead animals and plants for their food The materials contained in these dead bodies are broken down by the decomposers, thus they get the energy they need and release the minerals and other nutrients back into the environment for use again by other organisms Bacteria are among the most abundant decomposers while fungi are known to be the fast-acting decomposers

Decomposers are found everywhere In the pond, they are abundant at the bottom where the remains of the dead organisms (plants and animals) settle On land, they abound on the surface of the soil where the dead bodies of plants and animals are found

Each of the three groups of the biotic component of the ecosystem - producers (plants), consumers (animals), and decomposers (bacteria and fungi) - has its own specific function or task to perform

Figure 1.5: Relationship among biotic component of the ecosystem

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The work performed by an organism is known as its ecological niche, while the place where the organism lives in the ecosystem is known as its ecological habitat.

Guide questions

1 What are producers?

2 Give examples of producers?

3 What do decomposers perform in the ecosystem?

1.2.4 Nonliving factors

The nonliving factors of the environment make-up abiotic component of the ecosystem These include the chemical and physical factors in the environment, such as light, temperature, water, pH (acidity), wind, chemical nutrients, salinity (saltiness), soil, and others Organisms are affected by the biotic factors simultaneously but, of course, different species of organisms are affected differently For example, lichens may not survive when temperature gets very high but cactus may

Different organisms thrive in different conditions There are animals, like the earthworms, which favor wet condition, while others, like ants, prefer drier conditions Some plants, such as cactus, grow best in sandy soil while tomatoes grow best in loamy soil

As a whole, these environmental factors not only provide essential energy and materials but also determine the kind of organisms that will inhabit the area Hence, they provide the conditions necessary for the survival of the organisms

Guide questions

1 What are the components of an ecosystem?

2 Give examples for each component of the ecosystem.

3 In general, what are the functions of these components?

4 Can an ecosystem exists without one of its components? Justify your answer

Vocabulary

Autotroph: Organism that is self-nourishing; one that can produce its own food

Hetertrop: Organisms that feeds on others and cannot manufacture its own food

Biological magnification: Accumulation or increase of chemical substances on organisms in succeeding higher trophic levels.

Biomass: Amount of organic materials in plants or animals from which energy can be derived

Energy: Capacity to do work

Energy content: The amount of energy available for doing work For example, the amount of energy in fuel available for powering a motor vehicle.

Food chain: Energy pathway which proceeds from the producers to the consumers

Food web: Series of interrelated food chains in an ecosystem

Pyramid of energy: Representation of the organic content in each trophic level.

Biosphere: Portion of the earth and its environment within which life in any of its form is manifested Photosynthesis: Process of manufacturing food by green plants in the presence of sunlight.

Atmosphere: Layer of air surrounding the earth

Hydrosphere: The part of the Earth composed of water including clouds, oceans, seas, ice caps, glaciers, lakes, rivers, underground water supplies, and atmospheric water vapor.

Lithosphere: The outer, rigid shell of the Earth, situated above the atmosphere and containing the crust, continents and plates or the solid part of the earth’s surface

Grassland biome: Community where grass is abundant while trees are scarce and where mostly herbivores and rodents dwell.

Carnivore: Animals that get food from killing and eating other animals.

Herbivore: Organisms that eat plants only

Omnivore: Organisms that consume both plants and animals

Biotic factor: Living component of the ecosystem which includes plants, animals, and bacteria

Biotic potential: Reproductive capacity of the living components of the ecosystem.

Producer (autotroph): Green plant or organism that, performs photosynthesis

Consumer: Organism that feeds on other organisms

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Decomposer (also known as microconsumer): Organism which breaks down nonliving organic material; example are bacteria and fungi.

Environment: Sum of all external forces and conditions acting on an organism or a community of organisms.

CHAPTER 2 MATERIALS AND NUTRIENT CYCLES

The energy that flows into an ecosystem cannot be recycled Once the energy is used, it is lost But it much be constantly repeatedly replenished if the ecosystem is to continuously function

The important chemical nutrients, however, are used repeatedly They are cycled between the living and nonliving components of the ecosystem Generally, they begin in the abiotic part of the ecosystem (water, land, and air) Then, they enter to the bodies of plants and animals and return into the abiotic environment

The movement of these materials and nutrients between the living and nonliving environment clearly shows the interrelatedness of the abiotic and biotic components in an ecosystem Among these recycled materials and nutrients are carbon, oxygen, water, nitrogen, and phosphorus

After studying this chapter, you should be able to

1 Identify different nutrients that can be recycled.

2 Explain the water, carbon and oxygen, nitrogen, and phosphorus cycles.

3 Discuss the importance of each of these cycles.

4 Discuss how people affect these cycles.

5 Differentiate micronutrients from macronutrients

2.1 IMPORTANCE OF THE NUTRIENT CYCLES

The energy from the sun flows to the plant goes to the herbivore that eats the plant, to the carnivore, and

to the last consumer until the energy is lost into the ecosystem The energy does not go back to the source

It cannot be used over and over again

In contrast, when the bodies of dead plants and animals decompose, they are changed into nutrients through the action of bacteria and fungi The nutrients are stored in the abiotic environment like the soil The nutrients can be used again by the plants The plants are eaten by the animals and when the animals die, they decompose into nutrients These nutrients can be used over and over again In this way, a cycle

of nutrients is formed

The cycle of nutrients is an important process that takes place in the ecosystem Through the cycle of nutrients, the organic compounds found in the bodies of organisms are converted into inorganic compounds which serve as nutrients to the other organisms In both processes of energy flow and nutrient cycles, the plants provide the link by which the biotic and abiotic components interact with one another

Insightfulness

Energy cannot be recycled When using, it is lost into the ecosystem.

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The nutrients in an ecosystem can be used over and over again They are cycled beginning from the nonliving environment: air, water, and soil Then, these substances are taken in by the producers and are passed on through several consumers They are returned to the nonliving environment by decomposers.

Nutrients may be classified into two types, namely, the macronutrients and the micronutrients The macronutrients are those that are required by the organisms in large quantities Examples are carbon, hydrogen, oxygen, and nitrogen Sulfur, phosphorus, and potassium are also macronutrients but are needed by organisms in smaller quantities The micronutrients are needed in very small amounts They are also essential to life Examples are copper, zinc, iron, and boron

The macronutrients are the major components of fats and carbohydrates They make-up the cell structures

of plants and animals The cell walls of plants, for example, are made up of a very rigid substance called the cellulose Cellulose is made up of these three elements with a ratio of 7.2 carbons, 1 hydrogen and 8 oxygen This substance makes the cell walls very firm and rigid It adds strength to the plant

Nitrogen, carbon, hydrogen, and oxygen are the building blocks of proteins Phosphorus makes up many nucleic acids and is also essential for the transformation of energy in the cells

The micronutrients are as important as the macronutrients Magnesium, for example, is necessary in the production of chlorophyll

Guide questions

1 What happens to the energy from the sun when it enters to an ecosystem?

2 What happens to the dead bodies of plants and animals in an ecosystem?

3 Define macronutrients and micronutrients.

4 Make a listing of micronutrients and macronutrients, and give their functions?

5 What are the components of cellulose?

2.2 THE WATER CYCLE

As with any cycle, the water cycle has neither beginning nor end However, it is useful to choose a starting point Let us begin with water vapor in the atmosphere

a)

Figure 2.1: The water cycle

When water in the atmosphere reaches saturation (the highest amount of moisture that the air can hold), it falls as rain This falls directly to the land and bodies of water like the oceans and seas Some runs off the surface of the land into rivers The rain that falls on the land is absorbed by plants through the roots and drank by animals Some penetrates the soil and becomes part of the underground water, which eventually empties into the oceans The processes of condensation and precipitation are responsible for the return of water from the atmosphere into the land and other bodies of water

The water from the land and other bodies of water returns to the atmosphere through the process of evaporation Plants return the water by the process known as transpiration, while animals do this through respiration Water accumulates again in the atmosphere as clouds and falls as rain

Guide questions

1 What is saturation?

2 What is evaporation?

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3 What is respiration?

4 Trace the pathway of the water cycle

2.3 THE CARBON AND OXYGEN CYCLE

Much of the carbon in the environment exists in the form of carbon dioxide Plants absorb this gas though the leaves and use in the process of photosynthesis Oxygen is given off during this process Animals and other consumers obtain their food as well as their oxygen needs from plants In the process of respiration, the food is broken down into CO2 and water which are returned into the atmosphere

Figure 2.2: The carbon and oxygen cyclesWhen the animals and plants die, their bodies and waters are broken down by the decomposers In this process, CO2 is produced and returned to the atmosphere Sometimes dead organisms fail to decompose quickly When this happens, the dead bodies change to coal, oil, and gas which become fossil fuels after a long time When burned, fossil fuels release carbon dioxide into the atmosphere

Insightfulness

Carbon dioxide is present in the atmosphere from wastes, dead bodies of organisms, and fossil fuels

Plants use CO 2 in the process of photosynthesis Animals obtain their food from the plants and release

CO 2 though the process of respiration Decomposers and burning also release CO 2 into the environment

Erupting volcanoes emit carbon dioxide The eruption of the volcano supplies fresh carbon to the atmosphere from the deeper part of the interior of the earth

Carbon dioxide combines with water and forms calcium carbonate (CaCO3) This compound is used in the production of shells of animals like clams and oysters When shelled organisms die, the calcium carbonate may dissolve or form part of carbonate rocks serve as an buffer environment and storing carbon for many years During the process of weathering, carbon dioxide is again released into the environment

Guide questions

1 What are the sources of carbon dioxide?

2 What are the sources of oxygen?

3 How is carbon released from carbonate rocks into the atmosphere?

4 How are fossil fuels formed?

5 What two important processes are involved in the cycle of carbon and oxygen? Discuss these processes

2.4 THE NITROGEN CYCLE

Nitrogen is an element crucial to life It is an important component of proteins and nucleic acids The nitrogen gas constitutes about 78 percent of the air in the atmosphere However, it cannot be used directly

by plants and animals Plants use it in the form of nitrates

You inhale large quantities of nitrogen but it remains in your body unchanged

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Figure 2.3: The Nitrogen Cycle

Nitrogen in the atmosphere is converted into nitrates in two ways: (1) by the action of lightning and (2) by action of specialized organisms Electrical activity (lightning) during thunderstorms converts nitrogen into nitrates but only a small amount The nitrates produced by this process fall to the earth with the rain

The organisms that convert nitrogen are bacteria, algae, and fungi, of which bacteria is the most important Nitrogen-fixing bacteria directly convert nitrogen into nitrates though the process called nitrogen fixation Examples of nitrogen-fixing bacteria are the Rhizobium, which live in the roots of legumes like beans, peas, and peanuts The association between Rhizobium and legumes forms swollen areas within the roots called nodules Nitrates are formed within the nodules The compounds are then used by the plants to build proteins, or remain in the soil as fertilizers Because of this, legumes are important crop rotation as they help maintain soil fertility This explains why farmers plant legumes in soil before they plant new crops

Decomposers break down the protein in the bodies of plants, animals, and their wastes In this process, ammonia is produced Ammonia may be used directly by some plants but others cannot They have to transform this into nitrates through the nitrogen-fixing bacteria This process converting ammonia to nitrates is known as nitrification The plants are then able to obtain nitrates to synthesize amino acids and proteins

The nitrates produced by the nitrogen-fixing bacteria are converted into nitrites by another group of bacteria called nitrite bacteria Nitrites are converted into nitrogen by the denitrifying the bacteria in a process called denitration Denitration completes the cycle of nitrogen

Insightfulness

- The most complex of the nutrient cycles is the nitrogen cycle It involves many microorganisms

- Nitrogen cannot be used directly by the plants It has to be transformed into nitrates

- Lightning, nitrogen-fixing bacteria, and decomposers convert nitrogen into nitrates

- Denitrifying bacteria convert nitrites into nitrogen, thus completing the nitrogen cycle

- Plants use nitrogen for the synthesis of amino acids and proteins

What will happen if the nitrates are not absorbed by plants? Is this beneficial to the soil?

If nitrates are not absorbed by plants, they are washed away by heavy rains This process is called leaching Leaching drains the soil of its nutrients which are ultimately lost into the rivers and shallow marine sediments These nitrates enter the marine food chain and are returned to land by the droppings of seabirds These droppings are known as guano, which were once a major world supply of fertilizer

Guide questions

1 What is the important of nitrogen?

2 What is the useful form of nitrogen?

3 How is nitrogen converted into nitrates?

4 What is nitrogen fixation?

5 Differentiate between nitrification and denitrification

6 Explain leaching What is its role in the nitrogen cycle?

2.5 THE PHOSPHORUS CYCLE

Phosphorus is essential to life It is a component of the cell membranes, nucleic acids, and adenosine triphosphate – the energy currency of the cell

Figure 2.4: The phosphorus cycle

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Phosphorus is found naturally in the environment in the form of phosphates Phosphates in the soil come from phosphate rocks Though the process of weathering, the phosphates are incorporated into the soil in soluble or insoluble forms The plants absorb the phosphate and use it for protein synthesis The animals obtain phosphate from the plants they eat When the plants and animals die, decomposition brings back the phosphate into the soil

Phosphate in the soil may be washed away into shallow marine sediments by means of leaching It may also reach the deep ocean sediments From the shallow marine sediments, the phosphates are returned to the soil in the form of guano deposits of marine fish and sediments Phosphates in the deep ocean sediments are recycled back to the soil by means of upwelling If upwelling does not take place, the phosphate becomes incorporated into the phosphate rocks

Phosphate rocks are mined to be used in the manufacture of phosphate fertilizers Though leaching, the phosphorus in these fertilizers is lost from the soil Human therefore hasten the rate of loss of available phosphate This can have serious effects on the supply of phosphorus for agriculture in the future

- Guano deposits are good sources of phosphates

Human activities have altered the cycle of materials in the environment When people cut down trees or destroy forest in one area, rainwater continues to flow until it finally reaches the sea instead of rising to the atmosphere and falling again on the forests The massive destruction of the forests changes the environmental conditions, so that forests may never recover at all

As the plants age and die, decomposition takes place and use up so much oxygen causing the death of fish and other animals

Guide questions

1 What is the importance of phosphorus?

2 What processes are involved in the cycle of phosphorus?

3 In what ways have people altered the cycle of nutrients in the environments?

4 Define algae bloom How does it lead to eutrophication?

5 What are the effects of eutrophication?

Denitrifying bacteria: Bacteria that convert nitrates into nitrogen gas.

Denitrification: Process that convert nitrates into nitrogen gas

Eutrophication: Accumulation of nutrients in a lake or pond due to human intervention or nature causes Evaporation: The process of the change in the state of a liquid or solid to a gas or vapor Vanishing of the surface of a liquid to the atmosphere.

Leaching: The process by which nutrient chemicals or contaminants are dissolved and carried away by water, or are moved into a lower layer of soil

Nitrate: Inorganic anion containing three oxygen atoms and one nitrogen atom.

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Nitrogen fixation: A process whereby nitrogen fixing bacteria living in mutualistic associations with plants convert atmospheric nitrogen to nitrogen compounds that plants can utilize directly.

Bacteria: Group of single - celled organisms responsible for functions like that decay of organic materials and nutrient recycling

Nutrient: Substance taken by a cell from its environment and used in catabolic or anabolic reactions.

CHAPTER 3 HUMANKIND’S INVENTION WITH NATURE

After studying this chapter, you should be able to

1 Discuss how ancient people affected the environment.

2 Explain the progress made in the field of agriculture.

3 Identify the advances in the area of medicine.

4 Enumerate the new technologies brought about by advances in engineering.

5 Get a glimpse of the bad side of human beings impact on the environment.

6 Enumerate some bad effects of modern technologies.

3.1 BALANCE OF NATURE

Scientists estimated that the earth is already around three billion years old, and it will exists for another three billion years The life of the earth depends mainly on the sun If the gravitational pull of the sun remains constant, the earth will continue to revolve around the sun in its present speed There is a delicate balance between the centrifugal force of the earth as is goes around the sun

If the sun continue to shine the way it is now, then the earth will continue to receive radiant energy needed

by the living creatures Again, there is a delicate balance here Too much sunshine will make the earth too hot for most living beings to survive In short, the balance of nature is so delicate that any action that might upset such balance could have catastrophic results

For millions of years, this balance of nature has been maintained The animals that antedated humans for thousands of year did not really disturb the environment The effect they made on the environment was minimal and Mother Nature easily recovered

During the dawn of civilization, humans and the predators lived in very similar ways Both hunted for food and dwelt in natural habitats, like caves With this kind of life, they did not alter the environment But, since humans were more intelligent and more cunning, plus the fact that they walked erect and made use of their hands, they were able to invent weapons to help them Axe from stones and spears from sharp object made them better hunters than the animals And when they learned the use of fire, they cooked their food with it, warmed their bodies by it, and heated a lot of things to help them survive That was when humans proved their superiority over animals

When they learned to eat green leafy vegetables and learned how to cultivate them, they started to alter the environment They made clearings in the forests and planted vegetables When the land was no longer that fertile, they abandoned the place and cleared other lands That was the beginning of forest destruction Then they learned how to domesticate animals and lived in a permanent dwelling which was made of the products of the environment, like wood for the structure and leaves for roofing They had to

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change the environment some more Fortunately, there were not so many people at that time, so the environment was able to recover The balance of nature remained

As the population increased and the needs of people became more complex, they put greater and greater pressure on the environment Larger houses were constructed from different materials, strong fences to protect them from enemies, irrigation canals for agriculture, and large enclosures for animals, all these required more change in the environment But even then, there was no serious damage to the environment from which nature was unable to recover It could be said then that by and large, humans lives for many, many years in harmony with the environment

The rise in civilization of the Sumerians, the Babylonians, the Egyptians, the Greeks, and the Romans placed additional burden on Mother Earth, especially in the terms of land used for public buildings, monuments, and, of course, houses With more lands used for agriculture and the upkeep of animals, especially those used in war, changes in the environment became more permanent But even then, they were not causes for worry

It was only during the rapid progress in knowledge about the world, followed by the so-called industrial revolution, when humans made greater impact on the environment

Guide questions

1 Explain in details the meaning of balance of nature

2 Name some ways by which humans upset the balance of nature

3.2 PROGRESS IN AGRICULTURE, ENGINEERING, AND MEDICINE

Because of their superior intelligence, aided by the virtues of curiosity, imagination, and creativity, humans were able to discover the many laws of nature, and they used this knowledge to control parts of nature mostly for the benefit of humankind, in general

In the field of agriculture, the knowledge of genetics produced larger and better varieties of fruits and vegetables These varieties gave better yields per area planted and were more resistant to diseases Some examples will be enumerated to highlight the point

Better yielding varieties of rice, wheat, and potatoes have resulted in bumper harvest in many parts of the world As the direct consequence, the problem of feeding the growing populations was partly solves by these discoveries

Scientists were able to breed seedless grapes and seedless papayas Mangoes are now harvested all year round And perhaps, the other fruits may soon be grown seedless, like melons, and watermelons Large varieties of guavas and Santo are now in abundance

In the field of medicine, doctor and the scientists were able to discover the cure for many diseases, thus prolonging and preserving producing healthier babies The end result of all these are a much faster rate of population increase

In the field of animal science, researchers were able to improve the breed of animals used for food Faster- growing chickens and pigs and cultured fish are some good examples Artificial hatching of eggs was invented All these resulted in more food for the fast-growing population of the world

In the field of engineering, scientists invented better means of transportation on land, at sea, and in the air The more recent inventions include the bullet train that can run up to 500 kilometers (km) per hour, airplanes that can carry up to 700 passengers, and large ships powered by nuclear fuel

Landscapes have been altered to improve services to the people For instance, dams were built to produce electricity for homes and factories Oil, coal, and other fossil fuels were mined to power these new inventions

For more comfort at home, scientists invented artificial lighting, air-conditioning systems, refrigerator to preserve food better, radio and television for faster and better dissemination of information and for entertainment, and all those electric gadgets in the kitchen to the delight of many housewives

In the field of food technology, we can choose from a very wide variety of food available in the market, caned goods of all kinds, powered milk, packed lunches, preserved fruits and vegetables, and many others

All there may be considered as the good impact humans have made on the environment As a result of these inventions and new technology, people are living better food, live in more comfortable homes, enjoy their vacations more, get better health services, travel faster, and dress better In short, they can do a lot better than their ancestors

3.3 ADVERSE EFFECTS OF PEOPLE’S ACTIVITIES

Humankind’s intervention with nature has its adverse effects too These include the pollution produced by modern technology and its ill effects on the environment (disruption of the atmosphere which causes greenhouse effect, ozone depletion and acid rain); among others; pollution of the water system, deforestation, improper disposal of solid wastes, as well as nuclear wastes; and noise pollution

3.3.1 The greenhouse effect

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Figure 3.1: The greenhouse effectToo much carbon dioxide and other gases emitted by factories are accumulating in the atmosphere These gases allow sunlight to penetrate the earth’s atmosphere but unfortunately, they also trap radiant heat and revert its escape into outer space

The immediate consequence is global warming, which is better known as the green-house effect The rise

in the average temperature of the earth could have serious consequences Among them is the melting of ice and glaciers in the North and South poles This will raise the water level in many areas of the world, resulting in the submersion of the low-lying coastal towns and cities

3.3.2 Ozone depletion

High above the earth’s atmosphere, between 15 and 59 km above the earth, is a layer of ozone (O3) It is formed when ultraviolet radiation (UV) splits a molecule of oxygen (O2), and the free oxygen atoms (O) combine with other oxygen molecules Ozone acts as a filter in the upper atmosphere, preventing the harmful ultraviolet radiation of the sun from reaching the earth Scientists discovered that compounds of carbon such as carbon dioxide (CO2) and chloroflofuorocarbons (CFCs), nitrogen oxides (NO) and methane break up ozone molecules, thereby gradually depleting it

Figure 3.2: Ozone depletion

In fact a large ozone hole was discovered above the tip of South America The people directly below it may experience skin irritations and soreness in their eyes This may be due to the higher intensity of harmful ultraviolet radiations hitting them

Ozone levels, on the average, have declined by around 2 percent between 1969 and 1988 But in some parts of the world, the decrease in much higher For example, in Melbourne of Australia, ozone levels dropped by as much as 10 percent in 1987, causing a 20 percent increase in ultraviolet radiation reaching the ground

3.3.3 Acid rain

Sulfur and nitrogen oxides are released from industrial factories, electrical power plants, smelting plants, and motor vehicles

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Figure 3.3: Acid rain

When these gases combine with the moisture in the atmosphere, they return to the ground as sulfuric acids and nitric acids These are popularly known as acids rain Acid rain brings damage to lakes, the soil, forest, and buildings

Acid rain and limestone Trees affected by acid rain

Figure 3.4: Effects of acid rain

Many lakes in the Scandinavian countries are seriously affected by acid rain Acid rain has brought extensive damage to the trees of Europe and the eastern part of the United States Famous buildings like the Taj Mahal in India are now being damaged by acids from local oil refineries

3.3.4 Water pollution

Industrial wastes disposed of in streams and rivers have polluted these bodies of water, making them unfit for fish and other aquatic animals to inhabit When the water from these streams and rivers flows into lakes and oceans, then these bodies of water also become polluted Wastes from industrial factories along the riverbanks polluted the river so much that for all practical purposes, the river is dead

Most of the industrial factories that dump their wastes into around rivers make water pollution The immediate consequence is the large reduction in fish catch

Drainage water pollution Solid wastes disposed to water

Severe water pollution Oil pollution

Figure 3.5: Water pollution

There are many rivers and lakes in our country suffering from pollution, perhaps to a lesser extent but nevertheless a serious threat to the environment If you add the bodies of water in other countries that are also polluted, then you will feel how serious this threat is to the earth’s environment

3.3.5 Deforestation

Deforestation occurs at an alarming rate Twenty-three percent of the Earth's land surface is covered by tropical rainforest; however, these forests disappear at a rate of 4.6 million hectares a year Forests are an integral part for the well being of life on Earth

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3.3.6 Solid waste disposal

Progress produces a large amount of garbage Much of these are nonbiodegradable (do not decay into useful fertilizer) or hazardous materials

Figure 3.7: Solid waste disposal

How to dispose of them is a big problem in many countries The most efficient way is landfills In Vietnam, garbage collection is not efficient With an indifferent population, garbage is one of the main sources of pollution especially in large population centers like Ho Chi Minh City When garbage is not collected on time, people tend to dump them almost everywhere, resulting in very unsanitary surroundings, clogged waterways, and polluted creeks and rivers Improper garbage disposal is known to have triggered the spread of diseases, epidemics, and other adverse effects on people’s health

3.3.7 Nuclear waste

Nuclear power is among the most efficient and relatively cheap sources of energy But the technology is highly sophisticated and the possibility of nuclear disaster is not remoted

Figure 3.8: Nuclear waste

The resulting nuclear radiations are very harmful to human beings and heavy dozes are fatal The thousands of deaths due to the atomic bombings of Hiroshima and Nagasaki during the Second World war and the hundreds of fatalities in the Chernobyl accident in the former Soviet Union are grim reminders of what could happen in the case of nuclear accidents

Figure 3.9: Hiroshima and Nagasaki disasters

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Figure 3.10: the Bombing of Hiroshima and Nagasaki

3.3.8 Noise pollution

Figure 3.11: Noise pollution from speaking-trumpet

Figure 3.12: Air and noise pollution

Noise pollution is a direct result of industrial revolution Noisy engines in factories, the noise produced by motor vehicles, the irritating noise produced by the jackhammer, and the most unbearable noise from jet engines are some example Perhaps noise pollution is the least paid attention to but the ill effects it has

one people are well documented Psychological effects including irritability, mental stress, and short temperedness are quite common Temporary or permanent loss of hearing is a more serious physical effect

of noise pollution

The impact of the different kinds of pollution on the people and environment is serious Permanent and irreparable damages on the ecosystem could make the earth no longer a pleasant place to live in and could even make it uninhabitable That is why pollution and its effects on the environment should be the concern of everybody

Guide questions

1 Which of the types of pollution briefly described above is the most dangerous?

2 As a student, how can you help in the proper disposal of garbage?

3 Do you know of steps taken by the government and/or other agencies to protect the environment from harmful pollution?

VOCABULARY

Acid precipitation: Rain or snow that has lower pH than precipitation from unpolluted skies

Acid rain: Moisture in the atmosphere which has been contaminated by oxides of sulfur and nitrogen Deforestation: Destruction of forest

Greenhouse effect: Rising of the average global temperature caused by the accumulation of the carbon dioxide and other gases in the atmosphere These gases trap radiant heat and prevent its escape into space

Nuclear fission: Splitting of an atomic nucleus when struck by neutrons.

Nuclear fusion: Joining of two small atomic nuclei to form a new and large nucleus.

Nuclear power: Energy derived from nuclear fission or fusion.

Ozone: Molecule that contains three molecules of oxygen found in the atmosphere and which screens ultraviolet rays.

Ozone layer (or the ozonosphere): Thin layer of ozone in the upper atmosphere which absorbs ultraviolet light and converts it into infrared radiation.

Pollution: That which occurs when there is a change in the physical, chemical, or biological conditions in the environment which harmfully effects the quality of life, including effects on other animals and plants.

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CHAPTER 4

THE POLLUTION PROBLEMS

After studying this chapter, you will be able to:

1 Trace the history of pollution in the world.

2 Identify the major sources of worldwide pollution.

3 Distinguish between toxic pollutants and those that are harmful only to the environment.

4 Describe the main causes of air, water, and land pollution.

5 Enumerate the efforts exerted by some people to help reduce pollution.

4.1 MEANING OF POLLUTION

When there is a change in the physical, chemical, or biological condition in the environment which harmfully affects the quality of life, including effects on other animals and plants, then we say that there is pollution in environment

The change is generally brought about by introduction of hazardous substance into the environment A hazardous substance includes any substance that poses a threat to human health or to the environment Substances that are poisonous to human beings and animals are called toxicants Those that harm to the environment may be corrosive, flammable, or explosive Examples of toxic materials are carbon monoxide (CO), sulfur dioxide (SO2), and the oxides of lead and mercury

Examples of substances that harm the environment include wastes disposed of improperly by industries, nonbiodegradable materials, like plastic, thrown just anywhere; and excessive carbon dioxide (CO2) introduced into the atmosphere

Problems caused by hazardous substances are twofold: first, they cause a wide range of harmful effects on human health such as cancer, damage to the brain, liver, kidney, bone marrow, embryo, skin, gastrointestinal organs, and to the central nervous system; second, these substances can cause long-term or permanent damages to ecosystem For instance, toxic substances dumped into the water system can cause long-term damage to most of our rivers and lakes

We classify pollution into four types: air pollution, water pollution, land and soil pollution, and noise pollution

Guide questions

Name some hazardous substances emitted by vehicles that run on gasoline or diesel fuel What possible damage can they cause to humans?

4.2 AIR POLLUTION

Substances that pollute the air are generally of two types The first types of air pollutants are those that are directly harmful to humans They include toxic materials emitted by factories and motor vehicles The second types of pollutants are those that damage the environment and possibly alter the earth’s climate

Figure 4.1: Environmental pollution

4.2.1 Toxic air pollutants

Toxic air pollutants include oxides of sulfur and nitrogen, carbon monoxide, volatile and organic compounds, lead oxide, and benzene

The main source of toxic pollutants is the burning of fossil fuels like gasoline, diesel, and petroleum in power plants, factories, and motor vehicles Burning of trash also produces toxic pollutants

Figure 4.2: Burning tyres harm to air environment

These pollutants are considered toxicants because the human body absorbs these gases together with fine particles into the bloodstream, causing adverse health effects The most obvious effects are:

1 Breathing difficulties

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2 Increased susceptibility to respiratory infection

3 Development of chronic lung disease

4 Worsening of existing heart and lung diseases

5 Fetal defects and various kinds of cancer

Figure 4.3: Health effects by environmental pollutants

4.2.2 Contributors of common air pollutants

The urban and industrialized areas in the world are the greatest contributors of air pollution Knowing that pollutants are the causes of many bad effects on human health, these should be main causes for alarm by the people in general and by the government in particular As experienced by the United States, Japan, and the European countries, emission control costs are high, but still, control measures must be undertaken

Otherwise, the cost of man-hours, health care, unproductively, and shorter life span will be more staggering UNEP and WHO suggested a gradual introduction, and proper maintenance of factories and power plants

Guide questions

1 Explain the two types of air pollution

2 Is air pollution in your area serious? If it is, do you known if you or some of your neighbors have suffered from of it? What suggestions can you give?

3 Do you know of some steps that the government has taken to reduce air pollution, especially in the

Ho Chi Minh City? How effective are they?

4 What are the forms of air pollution that can easily be avoided?

5 Enumerate some general effects of acid rain on the environment

6 Explain the greenhouse effect

7 Cite some possible consequences of an increase in global temperature

4.3 LAND AND SOIL POLLUTION

There are two principal sources of wastes responsible for the land and soil pollution The first one is the solid waste which comes from mining operations It includes direct waste from the mining of minerals and fossil fuels and those associated with the mining and processing industries Strip mining not only produces mineral waste that pollutes the soil and streams but also leaves huge scars on the land The loosening of the soil leads to erosion during heavy rains, causing sediments to settle at the bottom of rivers and lakes Erosion also adds to the deterioration of the land, making it unfit for agriculture It also makes the water turbid-cloudy, thick, and dense.

Figure 4.4: Pollutants harm to the environment

Another type of solid waste is the by-products of agriculture It includes animal manure and wastes from slaughtered horses and from all forms of crop harvesting These wastes are generally less polluted because they are spread over wide areas Also, they are biodegradable, meaning, they return to the soil as nutrients of plants In excessive amounts, they emit bad odor, which is almost intolerable to human beings

4.4 RADIATION AND ITS HARMFUL EFFECTS

Radiation is the general term used to refer to a variety of rays to which life on earth is exposed to These include visible light, infrared and ultraviolet rays, X rays, cosmic rays, and rays from radioactive materials

In a wide sense, any result of radiation energy to a living organism is a biological effect of radiation This includes normal effects like photosynthesis on plants and vision in animals and also the injurious effect burns, anemia, and cancer on humans and animals

4.4.1 Historical background

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When X rays were discovered by the German physicist Wilhelm Conrad Roentgen in 1895, the focus of attention was its possible applications, especially in the field of medicine The harmful effects were observed one year later In 1896, Elihu Thomas exposed one of his fingers to X rays and observed the burns caused by these

In the same year, the famous American inventor, Thomas Alva Edition, observed the effects of X rays exposure on one of his assistants, Clarence Dally Dally hair fell out and his scalp became inflamed Eight years later, he developed severe ulcers on both hands and arms They became cancerous and eventually caused his death

The harmful effects of radioactivity were also observed by Pierre Curie, a French chemist and one of the great scientists, in 1906 Burns were produced on the parts of the body exposed to radiation In 1925, a number of women exposed to paint containing radium became ill with anemia and had lesions in the jawbone and mouth Some of them developed bone cancer later

Ernest Lawrence - an American physicist who invented the cyclotron, a rich source of neutron - exposed rats to this deadly radiation He found that fast neutrons are 21/2 times more effective in killing them then slow neutrons

Neutron radiation harmed and killed many people in Hiroshima, Japan, when an atomic bomb was dropped there in 1945 A study was conducted on several hundred pregnant women who survived the Hiroshima and Nagasaki bomb blasts Their children were medically observed for more than 20 years Many of them had heads smaller than the normal size, and there was a significant increase in the number

of mentally retarded children

4.4.2 Specific harmful effects of radiation

There are many sources of radiation that may cause injury to human beings The natural sources, like cosmic rays and natural products like granite and monazite sands (an important source of the element thorium), give dosage that are very safe to humans

The artificial sources like medical X rays, high - voltage power supplies, television sets, and luminous dial watches give significant dosage but the effects do not show until after many years These effects may include lower blood counts, temporary sterility, skin irritations, and on rare occasions, cancer

Figure 4.5: Harmful effect of radiation

The very serious health effects come from very massive dozes of radiation from nuclear reactor leaks and explosions of nuclear weapons; such as:

The effects of the Hiroshima and Nagasaki explosions and lately, the Chernobyl disaster attested to the veracity of these estimates Although less damaging, the effects of the nuclear tests in the Nevada desert were also well documented

The bomb that was dropped in Hiroshima killed more than 140.000 of its 255.000 inhabitants, and more deaths occurred later from radioactive radiation The effects of the Nagasaki blast were similar to that of Hiroshima

In Chernobyl, Ukraine, four nuclear reactors used in generating electricity exploded in April of 1986 The explosion released between 50 and 100 million curies of radioactive material into environment Within a few months, 29 people died of radiation poisoning and 200 other were estimated to develop cancer in later life The eventual toll of the nuclear accident has been estimated to be as high as 135000 cancer cases and

35000 deaths

From 1951 to 1962, the United States exploded 126 atomic bomb into the atmosphere at the Nevada test sites Some civilians and military personnel working at the test sites developed disorders like cancer, heart disease, thyroid dysfunction, and diabetes The same thing happened to people in southern Utah where winds from the test sites carried radioactive material that affected a lot of people Tests were subsequently underground to minimize radiation effects and recently, testing of atomic weapons was altogether halter

Guide question

1 What types of radiation are useful to human? What types are harmful?

2 What type of radiation may be useful and harmful at the same time?

3 What events in the past resulted in many deaths due to massive exposure to radioactive materials?

4.7 POLLUTION REDUCTION

There is a universal concern for doing something about the production and disposal of hazardous substances Leading industrialized countries and some leading industrial companies have initiated serious efforts to reduce pollution

4.7.1 Recycling

How to handle society’s toxic chemical waste now ranks among the top environmental issues in most industrial countries Without concerned efforts to reduce, recycle, and reuse more industrial wastes, the quantities produced will overwhelm even the best treatment and disposal systems [Thảo Nguyên]

The process of converting materials into new products that may or may not resemble the original material

is known as recycling

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Figure 4.6: The conception of Recycle

For example, old newspapers may be recycled into newsprint paper, board for packing, and construction materials for roofing and insulation

The benefits of recycling include the following:

1 It reduces waste

2 It lowers energy, water, and primary raw material requirements

3 It reduces both air and water pollution

Imagine the number of trees that would be saved by recycling newspapers And imagine the amount of trash that would have to be disposed of if plastics, glass, and cans were not recycled

Japan is the leading country that undertakes recycling The country recycles or reuses about 50 percent of its solid wastes, compared with only 11 percent of the United States and 15 percent of Germany

Moreover, after burning 23 percent of Japan’s trash in waste-to-energy facilities, only 27 percent remains

to be disposed of in landfills and by other means In contrast, 83 percent of solid waste in the United Stated and 55 percent of solid waste in Germany are disposed of by similar means [Hồng Yến]

Table 4.1: Solid waste management in the United Stated, Japan and West Germany

States Japan

West Germany

Landfilled or others 83 27 55

Furthermore, Time magazine, in its January 2, 1989, issue, reported that Japan, in 1988, recycled 50

percent of its waste paper, 55 percent of its glass bottles, 66 percent of its beverage and food cans, and converted much of the remaining trash into fertilizers, fuel gases, and recycled metals

Part of the success of Japan’s recycling program is the whole-hearted cooperation of the citizens The Japanese separate their trash into six classifications to simplify recycling In contrast, the United Stated in

1986 recovered only 23 percent of its paper products, 9 percent of its glass, and 25 percent of its aluminum

Several countries have followed the Japanese Glass recycling is fast growing in Europe The cities of Rome, Vienna, and Madrid have put up recovery plants producing metals, glass, paper, plastics, fibers, and other products

Some third world countries, although on a limited scale, have similarly ventured into recycling In India, more than a third of urban waste is being composted to produce methane gas, fuel pellets, fertilizers, and animal feeds China, specifically the city of Shanghai, processes and sells more than 10 percent of its waste for biogas production, fertilizers, and brick and cement manufacture The city also reprocesses many materials like metals, rubber, plastics, paper, glass, and waste oil

4.7.2 What you can do

The following are things that you can do at home, in school, or in the community to help in the reduction

of pollution:

1 Help keeping your school free from unwanted garbage through proper disposal

2 Help organize or join campaigns in your community to inform the public of the hazards posed by pollution For example, tricycle drivers may not know that the noise produced by their engines could permanently impair their sense of hearing

3 Minimize the use of pesticides at home If you must use them, minimize the potential hazards by (a) making sure people and pets are out of the area during the application and (b) not applying near streams and ponds

4 Find out what companies are major contributors to pollution Do not patronize their products and convince others to do the same

5 Separate wastes that can be recycled Sell them to local dealers or give them to garbage collectors for their extra income

6 Help minimize the amount of waste produced in your home For example, use less plastic wrappers and sell or give old newspapers to dealers who in turn sell them for recycling

7 Volunteer to help in the information campaign to minimize pollution through proper waste disposal

8 Generate enthusiasm about programs that would minimize air, water, land, and noise pollution

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9 Eat fewer animal products and consume more grains, vegetables, and fruits that require less energy to produce and therefore create less pollution

10.Urge your parents to buy household items and appliances that contain no, or less, pollutants Read the labels carefully before buying.

11 Plant fast-growing trees especially around your house They provide shade during sunny days and absorb carbon dioxide in the air They therefore help counteract the greenhouse effect

12 By reducing energy consumption, you will help lessen environmental damage The energy you use may come from burning fossil fuels like gas, oil, or, coal Less energy used means less burning of these fossil fuels

13 Economize in the use of materials that contribute to the depletion of natural resources For example, by using less paper, which is a wood product, you help reduce the need for cutting trees

Guide question

1 Cite government efforts to reduce pollution

2 Explain the good side and the bad side of burning dry leaves under fruit-bearing trees, like mango

3 What materials are being recycled in Vietnam?

4 How is garbage (solid waste) disposed of in your community? Is it the good way?

VOCABULARY

Recycling: Processing of material into new products that may or may not resemble the original material Toxic substance: substance poisonous to human beings and animals.