ECOLOGY AND THE CONSERVATION OF NATURAL RESOURCES
|Pollution and Environmental Health
|Process of Science
To develop an understanding of the interdependence of all organisms and the need for conserving natural resources
A relatively unpolluted environment is essential to maintain the quality of life on earth.
Ecology N2.00 To understand that maintaining clean air is essential to the continued existence of life on earth
INSTRUCTIONAL OBJECTIVES: The learner will:
2.01 describe the basic composition of air.
OUTLINE OF CONTENT:
2.02 identify the major types of air pollutants and their sources.
2.03 identify current methods of controlling contamination of the atmosphere.
2.04 describe the chemical reactions necessary in the formation of acid rain.
2.05 identify the effects that acid rain has on both aquatic and terrestrial flora and fauna.
2.06 describe the greenhouse effect and identify various consequences and impacts associated with it.
2.07 describe the structure of the earth's ozone layer, its importance to the earth, and the destructive effects that fluorocarbons have on that layer.
I. Basic composition of air.
A. Layers of the atmosphere
II. Air pollutants and their sources.
B. Gases present in the atmosphere
III. Methods of controlling contamination of the atmosphere.
B. Point sources
2. Nitrogen oxides
3. Sulfur oxide
4. Evaporated hydrocarbons and solvents
5. Carbon monoxide
6. Photochemical smog
7. Metals and fluorides
1. Power plants
C. Non-point sources
4. Other industries
3. Household aerosol propellants
4. Junk yards (CFCs)
IV. Chemical reactions necessary in the formation of acid rain.
2. Electrostatic precipitators
4. Absorption (activated charcoal)
1. Catalytic converters
C. Increasing fuel use efficiency
2. High temperature incinerators
3. Fluidized bed combustion
A. H and the pH scale
V. Effects of acid rain on aquatic and terrestrial flora and fauna.
B. How acid rain forms
C. Sources of acid rain precursors
D. Measuring acid rain in your community
A. Historical awareness of the problem
VI. Greenhouse effect and the consequences associated with it
B. Acids, pH, and normal rainfall
C. The formation of acid rain
1. Sources of acid precursors
D. Impact on the abiotic elements of the environment
2. Photochemical conversion to acids
3. Long distance dispersals
1. Natural buffers
E. Impact on the biotic elements of the environment
2. Leaching effects on metals
a. Toxic heavy metals
b. Magnesium and the chlorophyll molecule
1. Direct effects of lower pH on:
2. Disturbances in ecosystems
b. plant nutrient absorption and foliage
a. soil carbon and nitrogen cycle interference
b. lakes collapse of the food pyramid
A. The gases involved and how long it takes for them to migrate to the upper atmosphere
VII. Ozone layer
B. The rate of increase of production of the greenhouse gases
C. How the heat is trapped
D. Human practices contributing to the effect
1. Burning fossil fuel
E. Consequences of global warming
2. Forest and tropical rain forest deforestation
1. Regional climatic changes and associated land use
2. Coastal flooding
A. The structure of the ozone layer
1. The difference between surface level ozone and upper atmospheric ozone
B. The importance of ozone to life on earth
2. Location of the upper layer and annual fluctuations
1. Ultraviolet shielding
C. Ozone and CFC reactions
2. Effects of UV radiation on living organisms
D. Antarctic and Arctic ozone layer damage
COMPONENT OF SCIENCE: Process of Science
To enable students to demonstrate the processes of science by posing questions and investigating phenomena through language, methods and instruments of science.
1.5 EXPLAINING - Phenomena and related information are made understandable through discussion that culminates in a higher level of learning.
STANDARD: The learner will understand that:
1.5a - Tables and graphs may be used to interpret the meaning and significance of data.
BENCHMARK: Things change in steady, repetitive, or irregular ways. Tables, charts, and graphs are effective ways to show quantitative values and relationships.
Pictures related to energy production and clean air
Troposphere, hydrocarbons, pH
This classroom connector addresses Instructional Objective 2.01, and 2.02.
Today we are going to talk about air and air pollution. Take a moment to think about the air we breathe. Now write down four adjectives that describe the qualities of unpolluted air and four adjectives that describe the qualities of polluted air. (List these on the board.)
Our atmosphere is a 25 to 35 mile thick blanket of gases that surrounds the earth. The composition and density of it varies with altitude. Due to gravitational forces, most of the gases are in the lower six to seven miles, the troposphere. Here the air is about 78.7% nitrogen, 21% oxygen and 1% a mixture of argon, carbon dioxide, neon, helium, methane, krypton and numerous trace gases. There is also water vapor present. In a humid tropical rain forest, the air might contain 5% water vapor. In a dry desert or cold polar region there may be practically none at all. The so called ozone layer lies between 10 and 30 miles out. We'll get into that subject later.
Air pollutants come from various sources. The vast majority are products of combustion. By far the greatest amount of air pollution comes from the burning of fossil fuels. Fossil fuels contain carbon, hydrogen, and oxygen. They are hydrocarbons. They also contain sulfur and nitrogen. Both of these elements, essential to life, were present in the tissues of the plants and animals that the coal and oil were formed from. When burned, these fuels release sulfur and nitrogen oxides. Carbon monoxide, a very toxic gas, is the result of incomplete combustion and of course there is plenty of carbon dioxide released.
Depending upon the type of fuel, various particulate pollutants like smoke, soot or ash are also released. Additives to gasoline like lead also make up some of the pollution. Other air pollutants include evaporated hydrocarbons, solvents, CFC, and various household propellants. Some are produced when incompletely burned or evaporated gasoline combines with nitrogen oxides in the presence of sunlight. These are called photochemical pollutants. The visible part of this pollution is called smog.
All of the pollutants come from a variety of sources: point sources like power plants, incinerators and smelters and non-point sources like cars, trucks, planes, trains, fires, service station, parking lots, and leaking discarded air conditioners and refrigerators.
It has become customary in urban areas to include a daily pollution index or count in the weather report. What do you suppose the weathermen mean when they say the air pollution index for the day was in the "good range?" How is this misleading? Why is it dangerous to talk this way?
Yesterday, we discussed the composition of the air, some types of pollutants and the sources of air pollution. We learned that burning fossil fuels to obtain energy is by for the greatest source of air pollution. (List transportation, heating and generating electricity on the board. Ask the students to copy them.) Now list the fuels that are burned to provide energy for these three categories of use.
These uses are indeed necessary in our modern society so we cannot just stop. We have to convert to nonpolluting, renewable energy sources. Sooner or later we are going to exhaust our fossil fuel resource. Today we are going to learn about several of the methods of controlling contamination of the air that are currently being used. These methods can be grouped into three categories: separation, conversion, and conservation.
Separation involves the mechanical or chemical separation of pollutants from the air. The cyclone separator utilized the fact that particulates are heavier than air and will settle out. Sooty or dusty air is blown into a circular chamber where it swirls and rises. The heavier dust falls to the bottom of the chamber and the cleaned air leaves through the top.
Electrostatic precipitators electrically charge dust particles which stick to the precipitator walls in much the same manner that a balloon sticks to a wall after you've rubbed it on your hair. (demonstrate) Most electrostatic precipitators are used in steel mills and power plants that burn fossil fuels. They are very efficient; 99% or higher.
However, pollutant gases are not so easily removed by mechanical means. Gas molecules will adhere to solid surfaces. Activated carbon is specially treated charcoal that can retain 10% or more of its weight of pollutants. The pollutants can then be recovered from the activated charcoal and, if valuable, recycled. The process is called adsorption.
Other gaseous pollutants are soluble in certain liquids. These may be removed by either bubbling the polluted air through or spraying a mist of the liquid on the air to dissolve the pollutant. The air molecules pass through the liquid unaffected. These types of devices are called scrubbers and are among the most popular means for cleaning sulfur and nitrogen oxides from the effluence of coal fired power plants.
Sometimes, it is easier and more efficient to convert pollutants into less harmful compounds without removing them. Catalytic converters in automobiles force exhaust through a chamber that contains heavy metals that catalyze, or speed up the oxidation of unburned fuel.
High temperature incineration is another means. Ideally, if kept at high enough temperatures for long enough periods of time, most compounds will be converted into simple harmless compounds. However, problems of expense arise; it takes a large amount of energy to maintain the incinerators at high temperatures. Also, in the real world of incineration they are often overloaded with an amalgam of materials which results in less than ideal operating temperatures. As the exhaust gases cool new, unknown compounds form, some of which are very toxic and are released into the air or retained in the ash. There is no way to adequately monitor what goes into the incinerator. Municipal trash incineration has been compared to someone going into a chemistry stock room, pulling bottles of reagents indiscriminately off the shelf, mixing them together and burning them. In addition to this, low or trace levels of toxins in the unburned trash are concentrated in the ash demanding that the ask be treated like toxic waste. These ashes are usually taken to a standard landfill however.
Fluidized bed combustion of coal is an old technology that has come into popularity again. TVA has a pilot plant in Paducah, Kentucky. In a conventional coal fired power plant, coal is burned to produce steam which turns generator turbines to generate electricity. The smoke from the furnace is high in sulfur dioxide, a chief cause of acid rain. The smoke must be "scrubbed," a complex and expensive process, before released into the environment. In the FBC plant, pulverized limestone, coal and air are blown into the combustion chamber and burned. The sulfur in the coal combines with the calcium in limestone (CaCO3) to form calcium sulfate, a solid, which is retained in the ash. This solid ash can be easily and safety introduced into the environment as road bedding or construction material. Electricity is generated in the same way as a conventional power plant. This method is very attractive because it can be adapted to conventional plant operations with little retraining of personnel, unlike scrubber technology which essentially requires a chemical plant to be built on the power plant sight. There is also great flexibility in the grades of coal that can be burned. It is particularly suited to the Tennessee and Ohio River Valleys where there is an abundance of natural limestone and high sulfur coal.
Finally, probably the most sensible means to control contamination of the air by fossil fuel combustion products is to use less and use it more efficiently. This can be accomplished by switching to alternative renewable fuel sources. Photovoltaic systems should be able to meet at least some of the electrical power requirements of the United States within four or five decades.
In the mean time, we can improve engine efficiency and put heat that would be wasted to some other use; heating buildings, apartments, or greenhouses. This is called co-generation. It makes use of heat that would otherwise go up the chimney.
Now we're going to divide into groups of five. (Have the students move their desks together) Each group is going to sketch the design of a power plant and air purification system that uses conservation, separation and conversion strategies. (Have each student in the group be responsible for a particular aspect of the plant i.e. 1. power generation, 2. separation, 3. conversion, 4. fuel selection 5. a compatible companion industry that will use the waste heat. You might have each student draw their sketch on a separate piece of paper in a fashion that fits with the others in a mosaic. Let them write descriptions of and justifications for their designs. Share class wide.)
Raise your hand if you've heard of acid rain. (pause) Almost everybody who has watched T.V., read a newspaper, or listened to the radio in the last few years has heard of it. What I want you to do now is to write down the year that you think the effects of acid rain were first observed and noted by a scientist. (pause, circulate, encourage guesses) It may surprise you to learn that in _____ an English naturalist wrote that something was damaging the vegetation in London. A few years later the first study was done and it was determined that something in the smoke from coal furnaces in homes and factories was harming the plants.
It was recommended that the smokestacks be built higher so as to disperse the pollutants to "lands afar." What's wrong with that solution?
(Must material has been produced about acid rain. The students need to be familiar with the concept of pH.)
Before we get into how acid rain is formed and what effect is has on the environment, we're going to learn about acid solutions and the pH scale. Acid solutions in water contain hydrogen ions attached to water molecules. They can be weak solutions like vinegar which is sour, or very strong like sulfuric acid which in its pure form would burn a hole in your skin. Acids are the opposite of bases, which contain hydronium ions. Acids are neutralized by bases. Limestone and marble contain calcium carbonate, baking soda is also basic or alkaline. Strong bases like lye and NaOH are dangerous, for they can burn your skin, too.
The acidity or alkalinity of liquids is measured on a pH scale which ranges from 0 - 14. Seven is neutral and ad the pH of pure distilled water. Readings above 7 are alkaline and readings below 7 are acidic. The lower the pH number, the stronger the acid. The scale is logarithmic which means that a solution with a pH of 3 is ten times as acidic as a solution with a pH of 4, 100 times as acidic as one with a pH of 5 and 1000 times as acidic as one with a pH of 6.
Yesterday we learned about acids, bases and the pH scale. Write down what you believe the pH of pure unpolluted rain water would be. (pause) You may be surprised to learn that pure rainwater has a pH of 5.7. Is that slightly acidic or slightly basic? (response)
Today we're going to learn how certain gases in the air can cause the rain to be extremely acidic. But first let's deal with normal pure rainfall.
Recall that carbon dioxide is present in the air. CO2 dissolves in atmospheric water vapor to form a weak acid, carbonic acid. The pH of pure unpolluted rain is therefore about 5.7.
Now for polluted air. When fossil fuels are burned, the carbon is oxidized to CO2 and the sulfur is oxidized to sulfur dioxide. Some nitrogen, the major component of air, is oxidized to nitrogen oxide at high combustion temperatures. These sulfur and nitrogen compounds, called acid rain precursors, are further oxidized in the atmosphere by sunlight energy. They may adhere to dust particles and fall to earth close to their source or combine with water vapor to form sulfuric and nitric acid. They may be carried great distances before falling to earth as either rain or snow, particularly if they're released from very tall smokestacks.
Sulfur dioxide emissions account for over half of the acid rain precursors. Sixty-five percent come from fossil fuel burning power plants, twenty-six percent from industrial sources and nine percent from non-ferrous smelters. Copper Basin in Tennessee is an infamous site of an abandoned copper mine. For years the smelting operations there polluted the air with sulfur dioxide killing all vegetation and causing erosion down to the subsurface rock. Finally it was realized that the sulfuric acid pollutants were worth more than the copper being mined and the smoke was treated and the acid recaptured.
Forty-two percent of the nitrogen oxide emissions come from transportation sources, thirty-two percent from power plants and twenty-six percent from other forms of combustion. In nature, lightning provides the energy to oxidize atmospheric nitrogen. The spark plugs in cars provided the energy for human made nitrogen oxides.
Draw two pie graphs on your paper that show the sources of the nitrogen and sulfur oxide precursors of acid rain. (check for accuracy in proportion)
This is the
time this file has been accessed since 11/04/02.
The University of Tennessee at Martin is not responsible for the information or views expressed here.
Ecology And The Conservation Of Natural Resources Home Page