Acid Rain - Problem in the Making

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Spring '98 Period 2 Mr. Congelli Overly Acidified Precipitation - A Major Problem in the Making? Overly acidified precipitation and its ramifications are, according to the vast majority of experts, a very important environmental issue facing the world today. The effects of overly acidified precipitation (commonly known as acid rain) are slowly and insidiously wearing down the environment, affecting places in almost every continent. Nevertheless, very few people know what acid rain is. Nor do many people know what its causes are, the history of our awareness of it, its effects, or what we can do to stop it. When the general populace comprehends the facts about acid rain, perhaps they will be able to make a better, more informed decision about the acid rain dilemma. To understand the acid rain issue, one must first know what acid rain is. Acid rain is dilute acids that are given off naturally and by man's constructs. Rain is, naturally, slightly acid. Carbon dioxide (CO2) which is naturally occurring in our air dissolves in rain water, resulting in the production of a slight acid. This slight acid is not harmful - it is actually useful because it aids in the dissolving of minerals, allowing plants, and consequentially animals, to absorb the minerals with greater ease. (McCormick, 11) But when the precipitation becomes overly acidic, problems can occur. Humankind has to burn fuel to keep its machines running. When this fuel is burned, be it coal or a petroleum based fuel, smoke is given off. In this smoke there are agents which increase the acidity of the water it comes into contact with in the air. (McCormick, 4) Acid rain can be defined as rain which is harmfully acidic. A key part of understanding the acid rain issue is understanding what an acid is. An acid is, generally speaking, a chemical compound that breaks into smaller pieces. These pieces react with and break apart chemical compounds known as bases. For example, if you mix vinegar (an acid) with baking soda (a base) the vinegar reacts with the baking soda and breaks it down into smaller pieces and breaks down itself into smaller pieces which cannot react with each other. This breaking down quality of acid can be quite derogatory, as we shall see later. Two acids make up most of acid rain. These acids are SO2 (sulfur dioxide) and NOx (nitrogen oxides) (Ostmann, 39-40). The acidity of a substance is expressed as its pH. pH comes from the French "povoir hydrogene", which is French for "hydrogen power". (Microsoft Corp., 1) "The term... can be defined as the negative logarithm of the concentration of H+ ions (protons): pH=-log10[H+] where [H+] is the concentration of H+ ions in moles per liter." (Microsoft Corp., 1) These H+ ions often join together with water molecules to form hydronium (H3O+) ions. Because of this, oftentimes pH is expressed in terms of the concentration of hydronium ions. (Microsoft Corp., 1) "In pure water at 22 degrees Celsius (72 degrees Fahrenheit) H30+ and hydroxyl (OH-) ions exist in equal quantities; the concentration of each is 0.10 (to the seventh power) moles/liter. Consequently, the pH of pure water is -log (0.10(seventh), which equals log(7) or y. If an acid is added to water, however, an excess of H30+ ions is formed; their concentration can range between 0.10(sixth) and 0.10 moles/liter, depending on the strength and amount of the acid. Therefore, acid solutions have a pH between 6 (weak acid) and 1 (strong acid). Inversely, a basic solution has a low concentration of H30+ ions and an excess of OH- ions, and the pH ranges from 8 (weak base) to 14 (strong base)." (Microsoft Corp., 1) Because the pH scale is logarithmic, a difference of one digit is really a difference of ten times. A substance with a pH of 2.0 is 10 times as acidic as a substance with a pH of 3.0. A substance with a pH of 1.0 is 100 times as acidic as a substance with a pH of 3.0. This means that a difference of just a few tenths in pH, which might not look too important when seen by the untrained eye is actually a large and potentially important change in acid concentration. (Ostmann, 25) There are a few ways in which the pH of a substance can be measured. One of these ways is called titration. Titration is neutralizing the test acid (or base) with a base (or acid) with a given known pH, with an indicator present. An indicator is a compound whose color changes with it's pH. The pH of a solution can also be measured directly by taking two special electrodes, immersing them in the solution, and measuring their electric potential. (Microsoft Corp., 1) Being able to determine the pH of a substance is a vital element in the study of acid rain. The causes of acid rain are many. Both man and nature produce the gases which are the catalyst for the creation of overly acidic precipitation. About half of the sulfur dioxide that is in the atmosphere today is natural, the rest being man-made. In industrial regions, only about 10 percent of the sulfur dioxide in the air is natural. (McCormick, 6) Nature creates about half of the SO2 and NOx in the air. Volcanoes, swamps, and rotting organic material create sulfur dioxide. (McCormick, 6) Lightning may also constitute part of the natural NOx in the atmosphere. "Two strokes of lightning over one square kilometer, or two-fifths of a square mile, produce enough nitric acid to make four-fifths of an inch of rain with a pH of 3.5." (Ray, Dixy lee, 57) Nature is an important constituent of our acid rain problem, but it is not the one over which we have control. The human race creates the other half of the SO2 and NOx in the atmosphere. This is caused by man's burning of fossil fuels. To keep our factories and vehicles running, we must burn oil and coal (unless we utilize alternative energy sources such as wind or solar power). When these fuels are burned, they give off fumes which contain large quantities of SO2 and NOx.. In the UK, a typical highly industrialized country, 5% of the SO2 and 4% of the NOx came from domestic heating, 28% of the SO2 and 21% of the NOx came from commerce and industry, 1% of the SO2 and 29% of the NOx came from vehicles, and 66% of the SO2 and 46% of the NOx came from power stations. (McCormick, 6-7) In one year, the US adds about 30 million metric tons of SO2 and about 26 million metric tons of NOx to our atmosphere. Yearly, mankind adds about 100 million metric tons of SO2 and about 35 million tons of NOx to the atmosphere. (Ostmann, 11) Although mankind contributes a considerable amount of SO2 and NOx to the atmosphere, thankfully it is the source over which we have real control. There are ways of reducing man-made acid emissions. We can do things to make our fossil fuels themselves cleaner, things we can do to make the smoke from industry cleaner, and we can do things to make the emissions from cars cleaner and/or use less fossil fuels in cars. Another important thing we can do to reduce the acid rain problem is conserve energy. Every time we use a kilowatt-hour, some SO2 and NOx has to be released into the atmosphere (assuming that your power comes from a fossil fuel-fired power plant). There are many ways we can make our industries run cleaner. We can actually clean coal before it is burned. It can be crushed and washed in water or go through an electrostatic process to take out the sulfur. We can remove much of the sulfur in oil by refining or distilling it and then reacting it with hydrogen. (McCormick, 21) "Because nitrogen oxides are formed by burning fuels reacting with nitrogen in the air, they can be reduced by lowering the combustion temperature and reducing the time air stays in the combustion chamber." (McCormick, 22) Even after the fossil fuel is burned, things can be done with the smoke to make it cleaner by filtering it. In cars, exhaust gases can be put through a catalytic converter attached to the exhaust. The gases react with the chemicals in the filter, reducing hydrocarbon and NOx emissions by up to 90% (McCormick, 23) Many processes are used to clean coal smoke before it is released into the atmosphere. In wet scrubbing, "Coal is burned in [the] furnace or boiler. Fans pull resultant gases through [a] precipitator where fly ash is removed. [A] Damper directs gases to scrubber spray tower where [the slurry of water and chemicals is sprayed to remove SO2 and remaining ash. Clean gases then go up [the] stack. Liquid chemicals [which were] used to absorb SO2 drains into reaction tank where sulfur is removed through a chemical process. Bleed pump routes it to clarifier from which it drains to sludge disposal pond." (Ostmann, 161) (look at Coal Scrubber diagram for visual representation) This is the oldest and most common way of cleaning out coal smoke. Used in conjunction with washing the coal before burning it, these methods can be quite effective. The structure used for this process is huge, being about 600 feet long and 10 stories high. Between 1 and 3 percent of the energy produced in burning 10,000 tons of coal daily in a typical 900 megawatt power plant is taken up by running the scrubber. Better forms of scrubbing coal smoke have been developed in the last few decades. "Dry scrubbing" is much more water and energy efficient and is not as expensive as wet scrubbing is. Regenerative scrubbing is also a process used to clean coal smoke. Dry and wet scrubbing create great amounts of sludge though, and regenerative scrubbing avoids this problem by converting the SO2 into pure sulfur. This pure sulfur can be put to good use to replace part of the asphalt needed for road resurfacing. The Canadians are already researching uses for this waste sulfur. Unfortunately, in 1982 no full-size US power plants were equipped with dry or regenerative scrubbing. (Ostmann, 160-162) A large reason we have an acid rain problem is that not too many power plants use sulfur control measures. In 1982 (the year my source was copyrighted), only about 15 percent of the US's coal fired power plants were equipped with SO2 scrubbers. Scrubbers are very expensive - about 15% of the cost of a new, coal-fired, power plant is the scrubber. A new plant cost about $800 million in 1980. A new coal power plant emits about 33 million pounds of SO2 and about 28 million pounds of NOx annually. It cost more to install scrubbers in an old plant than it is to build them with a new power plant and the greater expense must be paid for in a shorter amount of time, so there are very few old power plants with scrubbers. (Ostmann, 162-163) The emissions from these dirty power plants and other sources of toxic emissions can have great consequences. Much of the SO2 and NOx in these fumes doesn't rise very far and returns to earth quickly in the form of dry deposition, or acid dust. The lion's share of the remaining SO2 and NOx is carried far from its source, maybe 620 miles (1000 km) from the source, bonds with water suspended in the air, and falls to earth in the rain as wet deposition such as acid rain, hail, or snow. Acid rain can help make ozone, which is a very harmful pollutant when found in the lower atmosphere. This acid deposition, whether dry or wet, can be extremely bad for the environment. (McCormick, 6-9) This acid rain can chew up and spit out the very processes of life which allow us and other plants and animals to survive on this good green earth. If you dipped your hand in hydrochloric acid, the tissues of your hand would be damaged severely. Just like how some acids can hurt humans by direct contact, many organisms are vulnerable to other types of acid contact. "Scientists already know a great deal about how acidification can disrupt the natural order from the level of the molecule to the scale of whole populations: - Enzymes, which catalyze vital reactions inside cells, are dependent on the acidity of the surrounding environment and are rendered less effective or totally inactive by increases in acid levels. - Proteins, which comprise a significant part of the matter in all cells, undergo changes in geometry and function when altered. - Organisms generally cannot reproduce and maintain themselves in optimal fashion unless their environment stays within a fixed range of acidity. - Acidification of an environment frees up toxic metals such as aluminum, mercury, and lead that would otherwise stay safely bound. - Acidification limits the diversity of an ecosystem by preventing the establishment or flourishing of acid-sensitive species." (Ostmann, 21) These effects can be quite devastating on many systems of organisms. Perhaps the life system most easily effected by acid rain is the freshwater lake or stream. "Acid and most water creatures, large and small, just do not mix." (Ostmann, 21) Acidified water seeps insidiously into lakes from under the ground, washes in from the surface of the earth, flows in from rivers, or falls into lakes as acid dust or acid rain. When the pH of a freshwater body reaches a certain threshold, fry (young fish) begin to die. In an hypothetically recently acidified lake, there are 1, 2, 3 year old fish. Then the 3yr old fish eventually die of natural causes (but speeded to their deaths by the effects of acidification). None of the eggs laid by the young fish hatch due to the acidification of the lake. Then we have 2 and 3 year old fish. The 3 year olds die. The eggs laid by the 2 year old fish don't hatch. Then there are only 3 year olds. These old fish don't lay eggs, so when they die there are no more fish left in the lake. The animals that eat the fish, like bears and herons, run out of food at that lake and have to go somewhere else for food. When acid rain falls into a lake, some of the acid is neutralized by alkaline substances in the lake and in the underlying rock. An example of this neutralization is when you drop a teaspoon of vinegar into a bowl full of baking soda. The vinegar will react with an amount of baking soda and both will be turned into a neutral substance. There will still be baking soda left over though. Many lakes which rest on limestone, a basic substance, have a large neutralizing capacity. Those lakes which have little of this "buffer" are extremely vulnerable to acidification, though. Much of the Northeast, Eastern Canada, the area just south of the Great Lakes, and the Appalachians fall into this category of buffer-deficiant geography (Ostmann, 40-41) (see diagram). When acid comes into contact with the rock on the bottom of a lake, toxic metals such as aluminum and mercury are leached out of the rock and permeate everything in the lake. "You are glumping the pond where the Humming-Fish hum. They can no longer hum for their gills are all gummed." - Dr. Seuss, "The Lorax" The above quote is from "The Lorax", a film by Dr. Seuss. It is usually considered a film for children, but indirectly it deals with the problem of acid rain. The acid is "glumped" into ponds via the rain, and liberates toxic metals from the local rock. These toxic metals are bad for the fishes' gills, and the fish produce a white gummy substance to avoid contact with excessive amounts of the toxic metals. The fishes' gills get all gummed and they can't survive for want of oxygen. The aluminum and mercury build up inside the fish from what they eat in the acidified pond, and sometimes these fish can be so permeated with the toxic metals that they are poisonous to man. You probably have seen notices near lakes warning fishermen of the mercury content of the fish of that pond and telling them not to eat more than a certain number of fish from that body of water each week or month. The toxic metals are also poisonous to the fish and kill the fish directly. The liberation of toxic metals is a great concern within the acid rain dilemma. Strangely enough, many acidified lakes look beautiful and pristine. That is because much of the life in them has been wiped out by acid rain. Also, dust and other kinds of sediment are often trapped on the lake bed by sphagnum moss, which is extremely acid tolerant. A acidified lake is as barren as a desert though, and this beauty is only skin deep. (McCormick, 16) Many lakes that you and I visit, and many that you and I don't have been affected by acid rain. Many lakes in the Adirondacks have been affected greatly, as this quote demonstrates: "In the 1930s almost all high Adirondack lakes - those over 2000 feet in elevation - contained fish and were popular fishing spots. About 1950, however, visitors and park officials began to see fewer and fewer fish. A number of causes were suggested, such as excessive beaver activity or windstorm damage to the lake watersheds.... Finally, in 1975, a Cornell University scientist discovered why the fish were disappearing. Carl Schofield's survey of the Adirondack lakes revealed that more than half were devoid of fish and most other forms of aquatic life. The explanation, according to Schofield, was acid rain and snow." (Ostmann, 38-39) Lakes have also been affected in the following parts of the world: Ontario, the Boundary Waters region of northeastern Minnesota, the Great Lakes, New England, areas of Nova Scotia, the Rocky Mountains, the Sierra Nevadas, the Appalachians, Florida, southern Sweden, southern Norway, and even Venezuela. (Ostmann, 39) In Sweden, over 18,000 lakes have been acidified. (McCormick, 31) It is quite distressing to see so many lakes rendered devoid of most of their aquatic life. Acid rain also affects plants. When acid rain falls onto soil which is rich in certain minerals crops, plants, and trees need to prosper, the soil can often neutralize the acid rain. This neutralization interferes with the minerals and seems to reduce the prosperity of plants. Barley, for example, grows 25 to 40 percent less in a sulfuric atmosphere. Tobacco can be affected by ozone damage. This ozone damage shows first on the leaves. Until the 1950s this damage was called weather fleck. It is now known to be ozone damage. (McCormick, 15) Trees are also something very important to our planet being affected by acid rain. Trees in the Black Forest and in southern Sweden have been affected greatly by acid rain. (McCormick, 12) "When acid rain falls onto its leaves, a tree will absorb alkalines from the soil, to counter the effect of the acid. As a result, the soil becomes more acid. Rain falling directly onto the soil also increases its acidity. Acid water moves through the soil, washing out nutrients and releasing poisonous metals, some of which are absorbed by the tree roots. It can be many years before the damage begins to show, and by then a whole forest may be affect." (McCormick, 14) The death of trees is a very important consideration when looking at the acid rain problem. The health of humans is also compromised by the existence of the acid rain problem. In big cities, acid smogs are common. Dry acid deposition creates these acid smogs. Los Angeles, Athens, and Mexico City have very bad smogs. London used to have very serious smogs - in 1952 a winter smog speeded the deaths of 4000 people, most of whom were sick or elderly. This shocked the government into placing air pollution controls on London, and now London has cleaner air than many other cities. (McCormick, 9) In some parts of Sweden, the local drinking water is so polluted that it is not potable for children. (McCormick, 31) Acid rain also is harmful to the constructs of humankind. Architecture, monuments, paint, cars, and even steel bridges are corroded by acid rain. It has been estimated that between 1961 and 1986 the Parthenon has taken more damage from corrosion than in the past 2400 years from natural forces. The Statue of Liberty, the Taj Mahal, and St. Paul's Cathedral have all been corroded greatly by air pollution. It is quite sad to see a regal statue corroded in a matter of decades instead of millennia. (McCormick, 18) Since the Middle Ages, people have realized that things were going wrong with the rain, especially in highly industrialized areas. The English exemplify this early acid rain awareness best. As early as 1257, Queen Elanor of Aquitane, wife of Henry III, complained of evil-smelling British air. This bad smelling air was actually a result of coal being burned in London and other places around Britain, although that was not completely understood at the time. By the late 1280's, the air problem was so bad that two commissions were appointed to deal with the problem. They did nothing, although coal burning was banned during Parliament sessions for a time. By the 1600's people began to realize the dangers of coal smoke. In 1620 King James I "was moved with compassion for the decayed fabric [of Saint Paul's Cathedral]... near approaching ruin approaching ruin by the corroding quality of the coal smoke... where unto it had long been subject." (Ostmann, 24) In 1661 John Evelyn wrote in his work, "Fumifugium", that because of "Clouds arising from those great Fires, the Aer is so distemper'd and such unreasonable and unnatural storms are engendered." According to Peter Brimblecombe (an English acid rain researcher), the English no really feasible alterna

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