In 1985, a hole in the ozone layer the size of the continental United States was discovered over Antarctica. This hole has appeared each subsequent spring and the amount of ozone depletion over this continent is up to 40%. Ozone in the stratosphere blocks out harmful ultraviolet rays from the sun and if such protection did not exist, there could not be life on Earth as we know it. As a matter of fact, until the atmosphere could build up the ozone layer around the Earth, life did not exist, The Environmental Protection Agency predicts there will be an increase of 20,000 skin cancer cases for every 1% decrease in ozone. (Environmental Defense Fund, 1990)
Ozone is a molecule consisting of three atoms of oxygen and is found in a layer where the concentration is only a few parts per million. This layer occurs in the atmosphere at altitudes of between 12-and 25 kilometers. In the spring of 1987, the mean ozone concentration over Antarctica was down 50%. (Shea, 1988)
Why are these reductions happening? During the long, sunless Antarctic winter (March-August) air over the continent becomes isolated in a swirling polar vortex that causes temperatures to drop below -90C. This is enough for the little water vapor present in the upper atmosphere to freeze and form polar stratospheric clouds. Chemical reactions on the surface of the cloud ice crystals convert chlorine from nonreactive forms such as hydrogen chloride and chlorine nitrate into active chlorine atoms (that are very sensitive to sunlight) . Furthermore, gaseous nitric oxide ordinarily able to inactivate chlorine is transformed into frozen and nonreactive nitric acid. (Shea, 1988)
A history and overview of ozone formation and subsequent problems can be found in the appendix pages 1-3. (Earthquest, 1991)
Spring sunlight releases the chlorine, starting a virulent ozone-destroying chain reaction that proceeds unimpeded for five to six weeks. Molecules of ozone are transformed into ordinary oxygen. The chlorine keeps attacking more ozone in this chain reaction. Global warming—a problem that will be presented in the last part of this unit encourages the ozone destroying process by increasing the formation of stratospheric clouds over Antarctica. (Shea, 1988)
What is causing the breakup of all this ozone? The answer is Chloroflourocarbons (CFC’s), Halons, carbon tetrachloride, nitric oxides, and methyl bromide-are the main culprits. (Environmental Protection Agency(EPA),1992)
CFC’s have gotten the most media attention and are the main ozone-destroying chemicals. CFC’s are very stable molecules and are not destroyed in the lower atmosphere. Hence, once released, CFC’s go upward and in six to eight years reach the stratosphere. Once in the stratosphere, they can survive for up to 100 years.
Each chlorine atom from a broken down CFC molecule is capable of destroying tens of thousands of ozone molecules due to the aforementioned chain reaction. (Shea, 1988)
CFC’s were developed in 1928 and their usage became widespread in the 1950’s-1980’s. In certain countries their usage is still growing. Worldwide CFC’s are used in the following ways; Aerosols (banned in the U.S.)—25%, rigid foam insulation—19%, solvents—19%, air conditioning—12%, refrigerants—8%, flexible foam—7%, and other uses total 10%. (Shea, 1988)
Scientists and finally politicians eventually realized the danger from CFC’s and in 1987 the Montreal Protocol was signed which states that the United States and other countries will cease CFC production by the year 2000. The U.S. will actually cease production earlier—in 1995. The Montreal Protocol has set aside a special $240 million fund to help developing nations switch to CFC- free technology. (NOAA & OIES, 1992)
The Hughes Corporation now uses a chemical derived from lemon juice in place of CFC’s to assist in its weapons manufacturing process. Northern Telecom has also ceased to rely on CFC’s. Unfortunately, countries like China are not ceasing their production of CFC’s. (Flavin, 1989)
Interestingly enough, scientists from the U.S. Geological Survey have discovered bacteria that eat CFC’s. The bacteria can only live in the absence of oxygen (anaerobic environments) such as in wetlands and soil where some CFC does penetrate. (Popwatch, 1992)
Halon, another problem, contains bromine—a more effective destroyer of ozone than chlorine (found in CFC). Halon was developed by the U.S. Army Core of Engineers at the end of World War II and is used extensively in fire fighting and fire extinguishers because it does not cause damage or leave a residue. Most Halon though, is kept for emergency purposes and stored. (Shea, 1988)
The EPA is concerned with Methyl Bromide, a soil fumigant developed as a pesticide in 1932. Estimates say that this chemical could be the cause of up to 15% of the total predicted global ozone depletion by the year 2000. Methyl Bromide is a new target of ozone protection efforts. (EPA, 1993)
Even if we stopped production of all ozone depletion chemicals today, the problem would go on for years. CFC’s once released into the atmosphere have a lifetime of 75-400 years. This means that they could break up ozone molecules through chain reactions that would go on for centuries. As another example, Nitrous oxide has a lifetime of 100-175 years in the atmosphere. (Gawell, 1989)
An interesting note, the 1991 Mount Pinatubo volcanic eruption spewed ozone—unfriendly chlorine compounds (eg. HC1) into the air and researchers believe that these were partly responsible for the record-breaking ozone hole over Antarctica in 1992. (Time Magazine, 1993)
In addition, there has been a decrease in the amount of ozone over the northern hemisphere at a rate of 1.7—3% in the past 25 years. This depletion happens mostly during the winter and at higher altitudes. (U.S.D.C. & NOAA, 1989)
Addition problems due to the decrease in stratospheric ozone aside from the increased risk in skin cancer include; a decrease in soybean crop yield and a decrease in phytoplankton productivity of oxygen (phytoplankton produce most of the world’s oxygen). (Shea, 1988)
Ozone (Tropospheric) Background Information.
While we can’t live without ozone in the stratosphere, it is very difficult to live with it in the troposphere. We live our lives in the troposphere or bottom layer of the atmosphere, yet this ground level ozone is the major constituent of photochemical smog. (EPA, 1992)
Ozone, a colorless gas, forms in the lower atmosphere as a result of chemical reactions between oxygen, volatile organic compounds and nitrous oxide, in the presence of sunlight, especially during hot weather. (EPA, 1992)
Sources of ground level ozone include; vehicles, factories, industrial solvents, gas stations, and farm equipment, to name a few. (EPA, 1992)
According to Connecticut’s Department of Environmental Protection (DEP), tropospheric ozone is Connecticut’s worst air pollution problem and we’re not alone. See appendix page 4-5. In 1992, Connecticut exceeded the federal ozone standard on 8 days—mainly in the summer when winds blow from the southwest. (DEP, 1993)
In 1989, the ozone level was above the health standard for 13 days. In the past 10 years, ozone levels exceeded the standard for 33 days in Connecticut—21 of those days occurring in the last 5 years. Ozone gas has a faint blue color and is monitored in 10 sites around Connecticut between April 1-October 31. (DEP, 1990)
To make air pollution reporting uniform throughout the country, a national “Pollution Standards Index” has been developed. See appendix pages 6-7. (DEP, 1990)
For additional information on the history of Connecticut’s air quality see appendix pages 8-11. (DEP, 1990)
Tropospheric ozone, aside from playing a key role in air pollution, also contributes to the greenhouse effect and is one of the six pollutants used by the EPA to set the national ambient Air Quality Standard. Ozone causes foliar plant damage, affects the human respiratory system and damages materials such as rubber and paint. (EPA, 1989)
Ozone is also an oxidant and through chemical reactions contributes to other pollutants such as sulfuric and nitric acids. In reality, it controls the chemical processing of all global emissions. (EPA, 1989)
Ground level ozone damage is estimated to reduce crop yields from 2-5%. (NAPAP, 1991)
During the July heat wave of 1993, unhealthy ozone (smog) levels were front page stories due to health risks, especially for people with respiratory problems. (Katz, 1993)
Acid Rain—Background Information
Acid Rain is another atmospheric problem that is worth investigating. Some of the same pollutants that are involved with ozone affect this problem too. Discussion of acid rain can be enhanced by the use of the SEPUP kits that will become part of the 8th grade curriculum starting in 1993.
In order to understand acid rain, one must first learn about pH. pH is the measure of the chemical activity of the acid and alkali dissolved in water and is measured on a negative logarithmic scale numbered 0-14. A number less than 7 is acidic, 7 = neutral and a number greater than 7 is alkaline (basic). The lower the number, the more acidic and the higher the number, the more basic. Another way to look at pH is; the lower the pH the greater the concentration of hydrogen ions. (American Chemical Society, 1991)
Acids and bases(alkaline substances) are two extremes that describe chemicals- just like hot and cold describe temperature. A substance that is neither acidic nor basic is considered neutral. Pure water is neutral. Vinegar and lemon juice, for instance, are acidic and laundry detergents and ammonia are basic. Chemicals that are very basic or very acidic are reactive and dangerous. A dangerous acid is automobile battery acid (contains acid similar to that causing acid rain). Household drain cleaner often contains lye which is very alkaline. (EPA, 1990)
Some common pH values are; human gastric juice 1.3-3.0, lemon juice 2.1, orange juice 3.0, black coffee 5.0, milk 6.9, egg white 7.6-9.5, baking soda in water 8.4 and household ammonia 11.9. (Barber, 1991)
Part of this curriculum will contain lesson plans that will enable a student to have a good understanding of the concepts of pH, acids, bases and reactions of and between both.
Acid rain affects the climate and the environment we live in. Fish are affected if water is pH 6 or lower. Buildings and paint are affected at a pH of 5.5 or lower. Trees and plants are affected if acid rain is pH 3.5 or lower. (EPA, 1990)
If acidity is increased, nutrients are leached from the soil and nitrogen-fixing bacteria are killed, and toxic metals are released. (EPA, 1988) Also, acid rain creates a cation imbalance in the soil which effects tree growth because the trees don’t get the minerals they need. (Leaf, 1990) These are some of the problems caused by acid rain and acid deposition—more will be discussed later.
Acid rain is rain that is more acidic than normal due to pollution put into the air by man. Sulfur dioxide and nitrogen dioxide are the main pollutants that cause acid rain. Acid rain forms high in the clouds where sulfur and nitrogen dioxides react with water, oxygen and oxidants. Here a mild solution of sulfuric and nitric acids are formed. Sunlight increases the rate of most of these reactions. Rainwater, fog and other types of precipitation contain sulfuric and nitric acids. (EPA, 1990)
Interaction between water droplets and carbon dioxide in the atmosphere gives rain a pH of 5.6, so clean, pure rain is normally acidic. (EPA, 1990)
About one half of the acidity in the atmosphere falls back to earth through dry deposition as gases and dry particles, with wind scattering them about. If acidic enough, these gases and particles can eat away the things they settle on. Also, these gases and particles get into runoff water. The combination of acid rain and dry deposition is called acid deposition and it has the potential to be even a larger problem than acid rain by itself. (EPA, 1990)
Wind carries pollutants for hundreds of miles before they become joined with water droplets to form rain and thus acid rain can be a problem in areas hundreds of miles away from polluting smokestacks. Dry deposition though is usually greater near the source of the pollutants. (EPA, 1990)
Natural sources of acids are volcanic gases and hot springs usually recycled in nature by absorption and breakdown to different substances which contribute to a small portion of acid rain. Actually, in these normal, natural amounts help to dissolve minerals and nutrients from the soil for plants to use as food. Pollution overloads this natural system. (EPA, 1990)
Sources of the two major acid rain pollutants are as follows; sulfur dioxide comes primarily from coal burning power plants and nitrogen dioxide comes primarily from motor vehicles and coal burning power plants. (EPA, 1988)
Over 80% of the sulfur dioxide emissions in the United States originate in the 31 states east of or bordering the Mississippi River and these pollutants are transported elsewhere by prevailing winds. (EPA, 1988)
Between 1940 and 1970, annual sulfur dioxide emissions had increased by more than 55% and nitrogen dioxide emissions had almost tripled. Ten percent of the lakes in the Adirondacks of New York and in the Upper Peninsula of Michigan were found to be acidic. Also, 2.7% of total stream reaches in the Mid-Atlantic and southwest were found to be acidic. The National Acid Precipitation Assessment Program (NAPAP) found also through a ten year federal research program that though some waters were affected, there was no measurable consistent effects on crop yields. (EPA, 1988)
In the late 1960’s and 1970’s scientists made the connection between acid deposition and acidification of certain lakes and sports fisheries (eg. the Adirondack Lakes). The extent of damage depends on the total acidity deposited and the sensitivity of the area on which it falls. Areas with acid-neutralizing compounds (eg. calcium carbonate) in their soil have a buffer against acid damage, but thin soils do not. (EPA, 1989) A buffer is a substance that has the ability to (partially) neutralize acid precipitation in soils and waters. (National Wildlife Federation, 1983)
Nitrogen dioxide is a light brown gas at lower concentrations, in high concentrations, it becomes an important component of unpleasant-looking brown urban haze. As stated previously, it results from the burning of fuels and motor vehicle emissions. Nitrogen dioxide is a major component of smog and acid rain, and can impair human health (eg. for asthmatics, it can increase breathing difficulty). (EPA, 1992)
Note—nitrogen dioxide is an oxidant and helps to speed up chemical reactions in both the troposphere and stratosphere. It is not only involved in the acid rain dilemma, but contributes to the ozone hole and ground level ozone pollution. In addition, this gas contributes to global warming. (EPA, 1992)
Sulfur dioxide is a colorless gas, odorless at low concentrations, pungent at high. It’s sources include; industrial, utility, and apartment house furnaces, boilers, petroleum refineries, smelters, paper mills and chemical plants. It is a major contributor to smog. Also, sulfur dioxide contributes to low visibility and can harm vegetables and metals. Like nitrogen dioxide, it causes human pulmonary problems. (EPA, 1992)
Acid rain is speeding up the weathering process by dissolving the mineral cement that glued sediments into rocks. As a result, brownstone buildings throughout the United States are slowly crumbling and many brownstone tombstones are becoming faceless monuments—their epitaphs erased by erosion due to acid rain. (Bell,1986)
The statue of Liberty, the Gettysburg Battlefield, and maple trees in New England, all feel the effects of acid rain. (Bell, 1986)
Acid rain and its effects also contribute to politics. One half of Canada’s acid rain originates in the United States and this has led to politics between the two countries and an agreement to lower the pollutants causing acid rain. (American Chemical Society, 1991)
In order to reduce acid rain in the U.S. and Canada, Title IV of the Clean Air Act amendment of 1990 establishes the Acid Rain Program. The goal of this program is to cut sulfur dioxide emissions in half and to substantially reduce nitrogen oxide emissions from electric utility plants. Sulfur dioxide is to be reduced by 10 million tons below the 1980 levels and nitrogen oxide by 2 million by the year 2000. Phase I begins in 1995. Also, starting in 1995, there will be a pollution allowance transaction and trading system set up. (EPA, 1992)
In addition to the above, other principles of the Acid Rain Program are as follows:
Free trading of emission allowance.
Permits and compliance plans.
Energy efficiency/pollution prevention incentives.
Reduction of acid deposition. (EPA, 1991)
For a history of government responses to acid rain see appendix pages 12-15. (EPA, 1989)
A chart that shows estimates on just how much sulfur dioxide can be found in the air can be found in the appendix on page 16. (EPA, 1992)
Acid rain seems to be one environmental problem that the government, politics or not , is taking seriously.