Preparing visuals

For this it is better to practice the presentation with the help of audio- and video-taped recording to control the manner of speaking and body language reducing the script to notes of the most important points. Fluency and confidence come with practice. A speaker should explore a wide range of demonstration materials, their advantages and disadvantages in order to choose the ones that are most helpful to put over the subject of your talk, the ones that suit your style and fit in best. Here the importance of visual aids to concentrate the attention of the audience, to lay special emphasis on basic features, to reinforce salient ideas and thus contribute to a presentation should be mentioned.

Information presented visually is better retained, but there are some rules to be remembered. Rule number one is: if you are going to use demonstration materials, use them well. Ensure that you know how to handle them, make sure that they are all usable, in the right place and in the right order. Never write or talk with your back to the audience. What you write on the board write clearly and distinctly.

Appendix 5

Supplementary reading

Actual ecological problems of the biosphere

Acid rain's effect on plants and wildlife

Acid rain (or more accurately acid precipitation) occurs when sulfur dioxide and nitrogen oxides are emitted into the atmosphere, undergo chemical transformations and are absorbed by water droplets in clouds. The droplets then fall to earth as rain, snow, mist, dry dust, hail, or sleet. This can increase the acidity of the soil, and affect the chemical balance of lakes and streams. The term "acid rain" is sometimes used more generally to include all forms of acid deposition - both wet deposition, where acidic gases and particles are removed by rain or other precipitation, and dry deposition removal of gases and particles to the Earth's surface in the absence of precipitation.

Acid rain is measured using a scale called "pH." The lower a substance's pH, the more acidic it is. Pure water has a pH of 7.0. Normal rain is slightly acidic because carbon dioxide dissolves into it, so it has a pH of about 5.5. As of the year 2000, the most acidic rain has a pH of about 4.3.

Acid rain is defined as any type of precipitation with a pH that is unusually low. Dissolved carbon dioxide dissociates to form weak carbonic acid giving a pH of approximately 5.6 at typical atmospheric concentrations of CO₂. Therefore a pH of less than 5.6 has sometimes been used as a definition of acid rain. However, natural sources of acidity mean that in remote areas, rain has a pH which is between 4.5 and 5.6 with an average value of 5.0 and so rain with a pH of less than 5 is a more appropriate definition. Acid rain accelerates weathering in carbonate rocks and accelerates building weathering. It also contributes to acidification of rivers, streams, and forest damage at high elevations. When the acid builds up in rivers and streams it can kill fish.

Almost everybody has heard about acid rain and knows that it is something bad. But what exactly is it? What are its effects on plants, animals, human beings, and what can be done to solve this problem?

The term acid rain does not convey the true nature of the problem and therefore scientists use the term "acid depositions". This is because the acid which has formed due to pollution may return to the earth as a solid or a gas and not just as rain. Depending upon the climatic conditions it could also come down as rain, fog, or snow, and in the wet form it is known as "acid precipitation".

Sources

Certain industries, as well as emissions from vehicles give rise to increase of sulphur dioxide and nitrogen oxides in the air. These emissions change into sulphates and nitrates under the influence of sunlight and moisture, and get converted into sulphuric acid and nitric acid, which come down as acid rain.

Coal generally contains between 2 - 3 % sulphur, and when it is burned, this sulphur is released into the atmosphere. Electric companies and other industries which burn coal cause a lot of emission of sulphur dioxide. Other industries which process raw ore containing sulphides in order to obtain copper, zinc, or nickel also cause an increase in sulphur dioxide levels in the atmosphere.

The major source of emissions of nitrogen oxides into the air is from vehicles and other places where fossil fuels are burned. Forest fires, often caused by man, either deliberately or accidentally, are another source of pollution.

Naturally occurring phenomena like volcanic activity, lightning, or organic decay, also gives rise to an increase in atmospheric pollutants but not much can be done about these causes. However over 90% of sulphur dioxide emissions and around 95% of nitrogen oxides released into the air are from man made sources.

The problem of acid rain is not new. It was first noticed during the 17th. century, when people observed the effects of industrialisation on plants and animals. As far back as in 1872, the Scottish chemist, Angus Robert Smith wrote a book "Air and Rain: The Beginnings of Chemical Climatology", in which he used the term "Acid Rain", and the name has stuck. The problem has become severe since the 1960s when fishermen noticed a sharp reduction in the quantity of fish in lakes of North America and Europe.

The havoc done by acid rain is not localised in the place where it is caused. The atmospheric emissions may travel for several days and over long distances depending upon wind and climatic conditions, before coming down as acid rain. The problem caused in an industrialised area may therefore result in acid rain in the surrounding forests or lakes, or even further away. It is believed that around 50% of the acid rain that occurs in Canada is due to pollution caused in the United States of America, and the effect of polluting industries in England can be felt in Norway.

If there were no pollution, the rain would still be acidic. Natural rainfall has a pH of around 6.0. This is because of the effect of Carbon dioxide in the air which combines with water to form carbonic acid. The effect of this is however negligible, as it is neutralised in the soil by alkaline material like limestone. However the other emissions cause the pH of the rain water to drop below 5.5 and at this level it is considered to be acid rain. The soil cannot now neutralise the acidity of the rain water. In some places the acidification is so severe that the pH drops to around 4.0. Rare cases have been reported of acid rain having pH of around 2 - 2.5.

Effects of acid rain on plant life.

Both natural vegetation and crops are affected by acid rain. The roots are damaged by acidic rainfall, causing the growth of the plant to be stunted, or even in its death. Nutrients present in the soil, are destroyed by the acidity. Useful micro organisms which release nutrients from decaying organic matter, into the soil are killed off, resulting in less nutrients being available for the plants. The acid rain, falling on the plants damages the waxy layer on the leaves and makes the plant vulnerable to diseases. The cumulative effect means that even if the plant survives it will be very weak and unable to survive climatic conditions like strong winds, heavy rainfall, or a short dry period. Plant germination and reproduction is also inhibited by the effects of acid rain.

Effects of acid rain on aquatic life

The action of acid rain causes harmful elements like mercury and aluminium to be leached from the soil and rocks and it is then carried into the lakes where aquatic life may be affected. Warning signs have been posted at several lakes, telling about the dangers of eating fish which may have been poisoned by mercury. Just as the soil has a natural ability to neutralise the acidity of rain water, within a certain limit, so also lakes and other water bodies can to a certain extent nullify the effects of acid rain. However as the acidity increases, the natural mechanisms are no longer able to cope. As the water gets more acidic its pH goes down. As the pH reaches 5.5, plankton, certain insects and crustaceans begin to die. At a pH of around 5.0, the fish population begin to die. When the pH drops below 5.0, all the fish have died, and the bottom of the lake lies covered with undecayed material. Every year during the spring thaw, there is a sudden increase in the acidity of the lakes as frozen acid is suddenly deposited in them. This "Acid Shock" prevents the reproduction of aquatic species, or results in the deaths of the hatchlings.

Effects on animals and birds.

All living organisms are interdependent on each other. If a lower life form is killed, other species that depended on it will also be affected. Every animal up the food chain will be affected. Animals and birds, like waterfowl or beavers, which depended on the water for food sources or as a habitat, also begin to die. Due to the effects of acid rain, animals which depended on plants for their food also begin to suffer. Tree dwelling birds and animals also begin to languish due to loss of habitat.

Effects on human beings

Mankind depends upon plants and animals for food. Due to acid rain the entire fish stocks in certain lakes have been wiped out. The economic livelihood of people who depended on fish and other aquatic life suffers as a result. Eating fish which may have been contaminated by mercury can cause serious health problems. In addition to loss of plant and animal life as food sources, acid rain gets into the food we eat, the water we drink, as well as the air we breathe. Due to this asthmatic people and children are directly affected. Urban drinking water supplies are generally treated to neutralize some of the effects of acid rain and therefore city dwellers may not directly suffer due to acidified drinking water. But out in the rural areas, those depending upon lakes, rivers, and wells will feel the effects of acid rain on their health. The acidic water moving through pipes causes harmful elements like lead and copper to be leached into the water. Aluminum which dissolves more easily in acid rain as compared to pure rainfall has been linked to Alzheimer disease. The treatment of urban water supplies may not include removal of elements like aluminum, and so is a serious problem in cities too.

Other effects

All living things, whether plants or animals, whether living on land or in the water or trees, are affected either directly or indirectly by acid rain. Even buildings, bridges and other structures are affected. In cities, paint from buildings have peeled off and colours of cars have faded due to the effects of acid rain. From the Taj Mahal in India to the Washington Monument great buildings all over the world have been affected by the acid rainfall which causes corrosion, fracturing, and discoloration in the structures. In Europe, structures like The Acropolis in Greece and Renaissance buildings in Italy, as well as several churches and cathedrals have suffered visible damage. In the Yucatan peninsula in Mexico, and in places in South America, ancient Mayan Pyramids are being destroyed by the acid rain. Temples, murals, and ancient inscriptions which had previously survived for centuries are now showing severe signs of corrosion. Even books, manuscripts, paintings, and sculpture are being affected in museums and libraries, where the ventilation system cannot eliminate the acid particles from the air which circulates in the building. In some parts of Poland, trains are required to run slowly, as the tracks are badly damaged due to corrosion caused by acid rainfall.

What Society Can Do About Acid Deposition 

There are several ways to reduce acid deposition, more properly called acid deposition, ranging from societal changes to individual action.

Understand acid deposition's causes and effects

To understand acid deposition's causes and effects and track changes in the environment, scientists, state governments, and academic study acidification processes. They collect air and water samples and measure them for various characteristics like pH and chemical composition, and they research the effects of acid deposition on human-made materials such as marble and bronze. Finally, scientists work to understand the effects of sulfur dioxide (SO₂) and nitrogen oxides (NO_x) - the pollutants that cause acid deposition and fine particles - on human health.

To solve the acid rain problem, people need to understand how acid rain causes damage to the environment. They also need to understand what changes could be made to the air pollution sources that cause the problem. The answers to these questions help leaders make better decisions about how to control air pollution and therefore how to reduce - or even eliminate - acid rain. Since there are many solutions to the acid rain problem, leaders have a choice of which options or combination of options are best. The next section describes some of the steps that can be taken to reduce, or even eliminate, the acid deposition problem.

Clean up smokestacks and exhaust pipes

Almost all of the electricity that powers modern life comes from burning fossil fuels like coal, natural gas, and oil. Acid deposition is caused by two pollutants that are released into the atmosphere, or emitted, when these fuels are burned: sulfur dioxide (SO₂) and nitrogen oxides (NO_x).

Coal accounts for most sulfur dioxide (SO₂) emissions and a large portion of NO_x emissions. Sulfur is present in coal as an impurity, and it reacts with air when the coal is burned to form SO₂. In contrast, NO_x is formed when any fossil fuel is burned.

There are several options for reducing SO₂ emissions, including using coal containing less sulfur, washing the coal, and using devices called scrubbers to chemically remove the SO₂ from the gases leaving the smokestack. Power plants can also switch fuels; for example burning natural gas creates much less SO₂ than burning coal. Certain approaches will also have additional benefits of reducing other pollutants such as mercury and carbon dioxide. Understanding these "co-benefits" has become important in seeking cost-effective air pollution reduction strategies. Finally, power plants can use technologies that don't burn fossil fuels. Each of these options has its own costs and benefits, however; there is no single universal solution.

Similar to scrubbers on power plants, catalytic converters reduce NO_x emissions from cars. These devices have been required for over twenty years in the US, and it is important to keep them working properly and tailpipe restrictions have been tightened recently. EPA has also made, and continues to make, changes to gasoline that allows it to burn cleaner.

Use alternative energy sources

There are other sources of electricity besides fossil fuels. They include: nuclear power, hydropower, wind energy, geothermal energy, and solar energy. Of these, nuclear and hydropower are used most widely; wind, solar, and geothermal energy have not yet been harnessed on a large scale in this country.

There are also alternative energies available to power automobiles, including natural gas powered vehicles, battery-powered cars, fuel cells, and combinations of alternative and gasoline powered vehicles.

All sources of energy have environmental costs as well as benefits. Some types of energy are more expensive to produce than others, which means that not all Americans can afford all types of energy. Nuclear power, hydropower, and coal are the cheapest forms today, but changes in technologies and environmental regulations may shift that in the future. All of these factors must be weighed when deciding which energy source to use today and which to invest in for tomorrow.

Restore a damaged environment

Acid deposition penetrates deeply into the fabric of an ecosystem, changing the chemistry of the soil as well as the chemistry of the streams and narrowing, sometimes to nothing, the space where certain plants and animals can survive. Because there are so many changes, it takes many years for ecosystems to recover from acid deposition, even after emissions are reduced and the rain becomes normal again. For example, while the visibility might improve within days, and small or episodic chemical changes in streams improve within months, chronically acidified lakes, streams, forests, and soils can take years to decades or even centuries (in the case of soils) to heal.

However, there are some things that people do to bring back lakes and streams more quickly. Limestone or lime (a naturally-occurring basic compound) can be added to acidic lakes to "cancel out" the acidity. This process, called liming, has been used extensively in Norway and Sweden but is not used very often in the United States. Liming tends to be expensive, has to be done repeatedly to keep the water from returning to its acidic condition, and is considered a short-term remedy in only specific areas rather than an effort to reduce or prevent pollution. Furthermore, it does not solve the broader problems of changes in soil chemistry and forest health in the watershed, and does nothing to address visibility reductions, materials damage, and risk to human health. However, liming does often permit fish to remain in a lake, so it allows the native population to survive in place until emissions reductions reduce the amount of acid deposition in the area.

Look to the future

As emissions from the largest known sources of acid deposition - power plants and automobiles-are reduced, scientists and their colleagues must assess the reductions to make sure they are achieving the results Congress anticipated. If these assessments show that acid deposition is still harming the environment, Congress may begin to consider additional ways to reduce emissions that cause acid deposition. They may consider additional emissions reductions from sources that have already been controlled, or methods to reduce emissions from other sources. They may also invest in energy efficiency and alternative energy. The cutting edge of protecting the environment from acid deposition will continue to develop and implement cost-effective mechanisms to cut emissions and reduce their impact on the environment.

What Is The Ozone Hole?

The Ozone Hole often gets confused in the popular press and by the general public with the problem of global warming. Whilst there is a connection because ozone contributes to the greenhouse effect, the Ozone Hole is a separate issue. However it is another stark reminder of the effect of man's activities on the environment.

Over Antarctica (and recently over the Arctic), stratospheric ozone has been depleted over the last 15 years at certain times of the year. This is mainly due to the release of manmade chemicals containing chlorine such as CFC's (ChloroFluoroCarbons), but also compounds containing bromine, other related halogen compounds and also nitrogen oxides (NO_x). CFC's are a common industrial product, used in refrigeration systems, air conditioners, aerosols, solvents and in the production of some types of packaging. Nitrogen oxides are a by-product of combustion processes, eg aircraft emissions.

The current levels of depletion have served to highlight a surprising degree of instability of the atmosphere, and the amount of ozone loss is still increasing. GreenPeace have documented many of the concerns that this raises.