&EPA United States Environmental Protection Agency Office of Public Affairs (A-107) Washington DC 20460 OPA-86-009 September 1986 ACID RAIN An EPA Journal Special Supplement ------- Dark i /ctulh i usf shadun.s mvr flte Adirondack Mnuntuins nrm L PJdrii/. \V. .As part of the A'ationoJ Surlui i' \\'d(er Survey, sciend i.dll(j( ted samples from kikes in this area to study the impact of acid rain ------- Acid rain . . . Few environmental problems have caused so much controversy— and so much confusion . . . People have been worrying about acid rain for decades . . . Now countries in several parts of the world are working together to control it ... Research into many different aspects of acid rain is advancing . . . And so is the technology to reduce it. In this special supplement, the EPA JOURNAL takes a look at what we know about acid rain—-and what we don't know: • The Acid Rain Phenomenon • An Acid Rain Chronology • An International Perspective • Acid Rain Research • Control Technologies • Implementation Issues ------- The Acid Rain Phenomenon All rainfall is by nature somewhat acidic. Decomposing organic matter, the movement of the sea, and volcanic eruptions all contribute to the accumulation of acidic chemicals in the atmosphere, but the principal factor is atmospheric carbon dioxide, which causes a slightly acidic rainfall (pH of 5.6) even in the most pristine of environments. (See box for an explanation of pH.) In some parts of the world, the acidity of rainfall has fallen well below 5.6. In the northeastern United States, for example, the average pH of rainfall is 4.6, and it is not unusual to have rainfall with a pH of 4.0—which is 1000 times more acidic than distilled water. Although precipitation in the western United States tends to be less acidic than in the East, incidents of fog with a pH of less than 3.0 have been documented in southern California. There is no doubt that man-made pollutants accelerate the acidification of rainfall. We know that man-made emissions of sulfur dioxide SO2 and nitrogen oxides (NOJ transformed into acids in the atmosphere, where they often travel hundreds of miles before falling as acidic rain, snow, dust, or gas. All these wet and dry forms of acid deposition are known loosely as "acid rain," which is now recognized as a potentially serious long-term air pollution problem for many industrialized nations. Emissions and Deposition Before the Clean Air Act was passed in 1970, U.S. SO2 and NOX emissions were increasing dramatically. (See Table 1.) Between 1940 and 1970, annual SO2 emissions had increased by more than 55 percent. Over the same period, NOX emissions had almost tripled. TABLE 1 Historic U.S. SO2 and NOX Emissions (In Millions of Tons) 1940 1950 1960 1970 1980 1984 S02 19.8 22.4 22.0 31.1 25.6 23.6 NOX 7.5 10.3 14.1 20.0 22.5 21.7 The Clean Air Act helped to curb the growth of these emissions. By 1984, annual SO2 emissions had declined by 24 percent, and NOX emissions had increased by only 9 percent. These reductions in historical growth rates took place despite the fact that the U.S. economy and the combustion of fossil fuels grew substantially over the same period. Acid-forming emissions are not spread evenly over the United States. Ten states in the central and upper Midwest—Missouri, Illinois, Indiana, Tennessee, Kentucky, Michigan, Ohio, Pennsylvania, New York, and West Virginia—produce 53 percent of total U.S. SO2 and 30 percent of total U.S. NO*. Table 2 lists the top ten SO2 and NOX emitting states. SO2 emissions are concentrated along the Ohio River Valley in Ohio, Indiana, Pennsylvania, Illinois, and West Virginia. These five states, along with Missouri and Tennessee, produce 44 percent of all SO2 in the United States. U.S. NOX emissions tend to be more evenly distributed, but again, states along the Ohio River are especially high producers. Four of the five highest SO2-producing states—Ohio, Indiana, Pennsylvania, and Illinois—are also among the top ten NOx-producing states. Thus, the Ohio River Valley and the states immediately adjacent to it lead the U.S. in emissions of both major components of acid rain. TABLE 2 Top Ten SO2 and NOx Producing States in 1984 (In Millions of Tons) S02 NOX 1. 2. 3. 4. 5, 6. 7. 8. 0. 10, Ohio 2.58 Indiana 1.67 Pennsylvania 1.60 Illinois 1.38 Texas 1.24 Missouri 1.18 West Virginia 1.02 Florida 0.99 Georgia 0.93 Tennessee 0.92 Texas 3.25 California 1.17 Ohio 1.14 Illinois 0.99 Pennsylvania 0.92 Indiana 0.83 Florida 0.70 Michigan 0.69 Louisiana 0.68 New York 0.62 How "Acid" Is Acid Rain? Lemon V Vinegar / \ / / "Pure" Rain (5.6] Distilled Water / ^Baking Soda 1 1 1 1 ACID RAIN 1 1 1 1 1 2 3 4 5 6 7 8 9 10 11 12 13 14 ACIDIC NEUTRAL BASIC The pH scale ranges from 0 to 14. A value of 7.0 is neutral. Readings below 7.0 are acidic; readings above 7.0 are alkaline. The more pH decreases bolow 7.0, the more acidity increases. Because the pH scale is logarithmic, there is a tenfold difference between one number and the one next to it. Therefore, a drop in pH from 6.0 to 5.0 represents a tenfold increase in acidity, while a drop from 6.0 to 4.0 represents a hundredfold increase. All rain is slightly acidic. Only rain with a pH below 5.6 is considered "acid rain." Acid Rain Precursors 44% 34% Transportation Electrical Utilities NITROGEN OXIDES [NOX) 19.7 million metric tons.NO,, 18% 1% Industrial Processes and Fuel Combustion Commercial/ Industrial/ Residential Other EPA JOURNAL ------- Although we can't be certain of long-term trends in acid deposition, it is possible to draw conclusions about current patterns. A comparison of the pH of U.S. rainfall with the states producing the greatest SO2 and NOX emissions clearly shows the solid link between acidic emissions and acidic deposition. Data collected by several different monitoring networks show that the areas of the U.S. receiving the most acid rainfall are downwind and northeast of those states with the highest SO2 and NOX emissions. Effects of Acid Rain The environmental effects of acid rain are usually classified into four general categories: aquatic, terrestrial, materials, and human health. Although there is evidence that acid rain can cause certain effects in each category, the extent of those effects is very uncertain. The risks these effects may pose to public health and welfare are also unclear and very difficult to quantify. The extent of damage caused by acid rain depends on the total acidity deposited in a particular area and the sensitivity of the area receiving it. Areas with acid-neutralizing compounds in the soil, for example, can experience years of acid deposition without problems. Soils like this are common throughout the midwestern United States. On the other hand, the thin soils of the mountainous Northeast have very little acid-buffering capacity, making them vulnerable to damage from acid rain. Aquatic Effects The adverse effects of acid rain are seen most clearly in aquatic ecosystems. The most common impact appears to be on reproductive cycles. When exposed to acidic water, female fish, frogs, salamanders, etc., may fail to produce eggs or produce eggs that fail to develop normally. Low pH levels also impair the health of fully developed organisms. Some scientists believe that acidic water can kill fish and amphibian reptiles by altering their metabolism, but we have little evidence that this is happening now. We do know, however, that acid rain plays a role in what scientists call the "mobilization" of toxic metals. These metals remain inert in the soil until acid rain moves through the ground. The acidity of this precipitation is capable of dissolving and "mobilizing" metals such as aluminum, manganese, and mercury. Transported by acid rain, these toxic metals can then accumulate in lakes and streams, where they may threaten aquatic organisms. Some lakes in areas of high acid deposition and low buffering capacity have been found to be both highly acidic and lifeless. Yet other lakes in similarly sensitive areas have not. Different lakes vary in the time it takes to reach an acidic condition, and rates of recovery from acidification also seem to vary. Scientists are using field studies, long-term water quality data, studies of fish population declines, and lake sediment studies to analyze the acidification of various lakes. However, both the data and the theoretical models currently available are unproven in their ability to make an accurate prediction of the effects of continued acidic emissions. Terrestrial Effects We know less about acid rain's effects on forests and crops than we do about effects on aquatic systems. The most extreme form of damage some have attributed to acid rain is the phenomenon known as "dieback." Dieback is a term applied to the unexplained death of whole sections of a once-thriving forest. At this time, however, we have little direct evidence linking acid rain to forest dieback. Scientists do agree that acid rain can lead to other, less extreme effects on soil and forest systems. It can leach nutrients from soil and foliage while inhibiting photosynthesis. Acid rain can also kill certain essential microogranisms. The toxic metals it mobilizes when passing through soil can be harmful not just to aquatic life but to trees and crops as well. But, again, we have little evidence that such damage is occurring now because of acid rain. Some experts even point to data indicating that acid deposition may actually benefit certain trees and crops. For example, some pitch pine seedlings SULFUR DIOXIDE (SO2) 21.4 million metric tons SO2 Transportation Electrical Utilities Industrial Processes and Fuel Combustion Commercial/ Industrial/ Residential ------- have grown better when treated with increasingly acidic water, and exposure to combinations of acid rain and mist has stimulated red spruce growth. It is possible that nitrates derived from the nitrogen oxides in acid rain confer some nutritional benefits on trees and plants. Materials Effects Acid rain can also damage man-made materials, such as those used in construction and sculpture. We are all familiar with photographs of statues that are losing their features and shape, with acid rain often cited as the culprit. The problem is far more than aesthetic. Building materials, too, can be degraded by acidity. For example, limestone, marble, carbonate-based paints, and galvanized steel all can be eroded and weakened by the kind of dilute acids found in acid deposition. Since materials naturally deteriorate with time, it is difficult to differentiate the effects of acid rain from damage caused by normal weathering. It is also hard to identify the specific damage caused by specific pollutants or combinations of pollutants. As a result, the particular role played by acid rain in the deterioration of materials is still a major unknown. Human Health Effects So far, we don't know of any human health problems resulting from direct contact with acid rain. Inhaling acidic particles in acid fog may possibly carry some health risk, but more research is needed to confirm whether this constitutes a real risk. Acid rain may also indirectly affect human health when it mobilizes toxic trace metals such as aluminum and mercury. When dissolved in acidic water, these metals can be ingested by fish and animals, building up in the human food chain. Acidic water could also leach lead out of pipe solder and into drinking water supplies. But these are only possibilities. No one has established that current emissions of SC>2 and NOX are actually causing such damage, or that such damage will continue or increase in the future if SC>2 and NOX emissions are not reduced. An Acid Rain Chronology A lead chamber constructed by 19th century English scientist Robert Angus Smith as part of his experimental research into air quality. 1661-2: English investigators John Evelyn and John Graunt publish separate studies speculating on the adverse influence of industrial emissions on the health of plants and people. They mention the problem of transboundary exchange of pollutants between England and France. They also recommend remedial measures such as locating industry outside of towns and using taller chimneys to spread "smoke" into "distant parts." 1734: Swedish scientist C.V. Linne describes a 500-year-old smelter at Falun, Sweden: ". . . we felt a strong smell of sulphur . . . rising to the west of the city ... a poisonous, pungent sulphur smoke, poisoning the air wide around . . . corroding the earth so that no herbs can grow around it." 1872: English scientist Robert Angus Smith coins the term "acid rain" in a book called Air and Rain: The Beginnings of a Chemical Climatology. Smith is the first to note acid rain damage to plants and materials. He proposes detailed procedures for the collection and chemical analysis of precipitation. 1911: English scientists C. Crowther and H.G. Ruston demonstrate that acidity of precipitation decreases the further one moves from the center of Leeds, England. They associate these levels of acidity with coal combustion at Leeds factories. 1923: American scientists W.H. Maclntyre and I.E. Young conduct the first detailed study of precipitation chemistry in the United States. The focus of their work is the importance of airborne nutrients to crop growth. 1948: Swedish scientist Hans Egner, working in the same vein of agricultural science as Maclntyre and Young, sets up the first large-scale precipitation chemistry network in Europe. Acidity of precipitation is one of the parameters tested. EPA JOURNAL ------- An In :tive 1954 : Swedish scientists Carl Gustav Rossby and Erik Eriksson help to expand Egner's regional network into the continent-wide European Air Chemistry Network. Their pioneering work in atmospheric chemistry generates new insights into the long-distance dispersal of air pollutants. 1972: Two Canadian scientists, R.J. Beamish and H.H. Harvey, report declines in fish populations due to acidification of Canadian lake waters. 1975: Scientists gather at Ohio State University for the First International Symposium on Acid Precipitation and the Forest Ecosystem. 1977: The U.N. Economic Commission for Europe (ECE) sets up a Cooperative Programme for Monitoring and Evaluating the Long-Range Transmission of Air Pollutants in Europe. 1979: The U.N.'s World Health Organization establishes acceptable ambient levels for SO2 and NOX. Thirty-one industrialized nations sign the Convention on Long-Range Transboundary Air Pollution under the aegis of the ECE. 1980: The U.S. Congress passes an Acid Deposition Act providing for a 10-year acid rain research program under the direction of the National Acid Precipitation Assessment Program. 1980: The U.S. and Canada sign a Memorandum of Intent to develop a bilateral agreement on transboundary air pollution, including "the already serious problem of acid rain." 1985: The ECE sets 1993 as the target date to reduce SO2 emissions or their transboundary fluxes by at least 30 percent from 1980 levels. 1986: On January 8, the Canadian and U.S. Special Envoys on Acid Rain present a joint report to their respective governments calling for a $5 billion control technology demonstration program. 1986: In March, President Ronald Reagan and Prime Minister Brian Mulroney of Canada endorse the Report of the Special Envoys and agree to continue to work together to solve the acid rain problem. Principal source: Ellis B. Cowling, "Acid Precipitation in Historical Perspective," Environmental Science and Technology, Volume 16, Number 2, 1982. Aid rain is not considered a threat to the global environment. Large parts of the earth are not now, and probably never will be, at risk from the effects of man-made acidity. But concern about acid rain is definitely growing. Although acid rain comes from the burning of fossil fuels in industrial areas, its effects can be felt on rural ecosystems hundreds of miles downwind. And, if the affected area is in a different country, the economic interests of different nations can come into conflict. Such international disputes can be especially difficult to resolve because we do not yet know how to pinpoint the sources in one country that are contributing to environmental damage in another. Concerns about acid rain tend to be raised whenever large-scale sources of acidic emissions are located upwind of international borders. Japan, for example, has not yet suffered any environmental damage due to acid rain, but the Japanese are worried about the potential downwind effects of China's rapidly increasing industrialization. A similar problem has risen on the U.S.-Mexican border, where some people are worried that Mexico's new copper smelter at Nacozari could cause acid rain on the pristine peaks of the Rocky Mountains. Besides scattered instances such as these, acid rain has emerged as a serious international issue only in two places: western Europe and northeastern North America. Europe Diplomatic problems related to cross-boundary air pollution first surfaced in Europe in the l!)50s, when the Scandinavian countries began to complain about industrial emissions traveling across the North Sea from Great Britain. Since then, acid deposition has been linked to ecological damage in Norway, Sweden, and West Germany, and low-pH rainfall has been measured in a number of other European countries. (See map on this page for the average pH of rainfall over Europe in 1980.) The political and scientific controversies over acid rain an: multiplied in Europe because so many countries are involved. Table 3 lists the SO2 emissions of 21 European nations in 1980. A comparison of the pH map with Table 3 reveals that some countries producing very low amounts of S()2 are nevertheless experiencing low-pH rainfall and high rates of acid deposition. Norway, for example. produced approximately 137,000 metric tons of SO2 in 1980. yet receded depositions of about 300,000 metric: tons. Clearly, Norway, like a number of other European nations, is being subjected to acid deposition that originates outside its borders. Sweden pioneered the development of extensive and consistent monitoring for acid precipitation in the late 1940s. In 1954, the Swedish monitoring program TABLE 3 European S().; Emissions in 1980 (In Thousands of Metric Tons) Austria Belgium Bulgaria Czechoslovakia Denmark Finland France Federal Republic of Germany Greece Hungary Italy Netherlands Norway Poland Portugal Romania Sweden Switzerland United Kingdom USSR Yugoslavia 441) 809 1 .000 3,100 399 600 3,270 3,580 700 1.663 3.HOO 487 137 2,755 149 200 450 119 4,680 25,500 ;t.ooo (Figures from U.S. Department of State) ------- was expanded to include other European countries. The results of this monitoring revealed the high acidity of rainfall over much of western Europe. Prompted by these findings, the U.N. Conference on the Human Environment recommended a study of the impact of acid rain, and in July 1972, the U.N. Organization for Economic Cooperation and Development (OECD) began an inquiry into "the question of acidity in atmospheric precipitation." In 1979, a U.N. Economic Commission for Europe (ECE) conference in Stockholm approved a multi-national "Convention" for addressing the problem of long-range transboundary air pollution. Both the United States and Canada joined the European signatories. Since then, a number of European countries, including France, West Germany, Czechoslovakia, and all the Scandinavian countries, have agreed to reduce their 1993 SO2 emissions by at least 30 percent from 1980 levels. More recently, ECE members decided in 1985 to broaden their goals to include the control of nitrogen oxides, which have been gaining recognition as important acid rain precursors. Workshops are now underway to determine the nature and extent of NOX pollution in various countries, as well as possible approaches for controlling it. North America The United States and Canada share the longest undefended border in the world and billions of dollars in trade every year. We also share a number of environmental problems, foremost among them the problem of acid rain. In both countries, acidic emissions are concentrated relatively close to our mutual border. Canadian emissions originate primarily in southern Ontario and Quebec, while a majority of U.S. emissions originate along the Ohio River Valley. Each country is contributing to acid rain in the other. But because of prevailing wind patterns and the greater quantities of U.S. emissions, the United States sends much more acidity to Canada than Canada sends to us. In 1980, for example, the U.S. produced over 23 million metric tons of SO', and over 20 million metric tons of NOX; Canada produced 4.6 million metric tons of SO2 and 1.7 million tons of NOX. In the early 1970s, Canadian scientists began to report on the adverse environmental effects of acidity in lake water, and to link fish kills in acidic lakes and streams in eastern Canada to U.S. emissions. By the late 1970s, acid rain had become a serious diplomatic issue affecting the relationship of the two countries. In 1980, we took our first joint step towards resolving the issue with a Memorandum of Intent that called for shared research and other bilateral efforts to analyze and control acid rain. One of the most spectacular projects was a high-altitude experiment called "CAPTEX." Trace elements of various chemicals were inserted into SO2 plumes from coal-fired power plants in the Midwest. Their dispersion was monitored along a path extending across the northeastern United States to Canada. These and other experiments have helped scientists gain new data on the formation and distribution of acid rain. When Brian Mulroney became Prime Minister of Canada in 1984, he pressed for more than research; he wanted bilateral action to control acid rain. At the first "Shamrock Summit" in March 1985, Mulroney and President Reagan agreed that Canada and the United States would each appoint a high-level Special Envoy to study acid rain. The Special Envoys would be charged with recommending a plan to alleviate both the environmental and the political damage caused by acid rain. William Davis, former Premier of Ontario, and Drew Lewis, former U.S. Secretary of Transportation, were named Special Envoys. In January 1986, the two men presented their joint recommendations for U.S.-Canadian action. They proposed a $5 billion U.S. technology demonstration program, ongoing bilateral consultations at the highest diplomatic levels, and cooperative research projects. Western Europe and North America are highly industrialized, and it is likely that acid rain will continue to be a serious concern in both areas for the foreseeable future. But the nations involved are coming to terms with their common problem. In Europe, several nations have already taken steps to reduce transboundary air pollution. In North America, the President of the United States has endorsed the proposal to invest $5 billion to demonstrate innovative technologies that can be used to reduce transboundary air pollution. And in both Europe and North America, the diplomatic groundwork for long-term cooperative activities has been established. EPA JOURNAL ------- Acid Rain Research Despite intensive research into most aspects of acid rain, scientists still have many areas of uncertainty and disagreement. That is why the United States emphasizes the importance of further research into acid rain. Scientific research into acid rain has accelerated significantly in the 1980s. In 1982, the federal agencies (see box) involved in the National Acid Precipitation Assessment Program (NAPAP) budgeted $14.4 million for acid rain research. For 1987, the President is requesting $85 million for acid rain research: a more than fivefold increase in as many years. The increased funding has shown results. Scientists today have a much greater understanding of the chemistry of acid rain than they did in 1980. But they are still seeking a better grasp of the effects of acid rain on lakes, streams, forests, and construction materials. National Surface Water Survey The National Surface Water Survey is EPA's primary source of data on the impact of acid rain on America's lakes and streams. Plans for the project began in 1983, with the first of three planned phases completed by the fall of 1984. The goal of Phase I was to measure the acidity of U.S. lakes and streams. It was not feasible to sample all the lakes and streams in potentially susceptible areas, so methods of statistical sampling The National Acid Precipitation Assessment Program With a dozen federal agencies involved, acid rain research can be complicated organizationally as well as scientifically. To prevent duplication of effort and foster creative cooperation among the agencies, the National Acid Precipitation Assessment Program (NAPAP) was set up in 1980. NAPAP is chaired jointly by EPA, the President's Council on Environmental Quality, the National Oceanic and Atmospheric Administration, and the Departments of Agriculture, Energy, and Interior. EPA plays a major role in several of NAPAP's key research initiatives: • Expansion of the National Trends Network, which gathers definitive acid rain data at monitoring stations throughout the nation. This network currently monitors wet deposition at 150 locations around the country, and it is being extended to include 100 dry deposition monitoring stations. • Investigations into "source-receptor relationships," the relation between changes in emissions and changes in deposition levels at distant locations. EPA's Atmospheric Processes Program is developing an ambitious Regional Acid Deposition Model that will enable scientists to predict the amounts of acid rain resulting from given levels of emissions. With the model's predictive powers, policy-makers will be able to weigh the benefits and drawbacks of different regulatory scenarios. • The Delayed/Direct Response Project, which is working to determine the rate at which lakes acidify and to identify factors that hasten or retard that process, such as the acid-neutralizing capacity of surrounding soil. A "delayed" response is one that takes 10 years or longer. A "direct" response is acidification occurring in fewer than 10 years. Under this program, EPA has sampled 145 watersheds in New England with the help of the Soil Conservation Service. as li. rent' brought ; were used to make the final selection. Phase I data collection was divided into three components: Eastern Lakes, Western Lakes, and Eastern Streams. Preliminary findings from the Eastern Lakes Survey were made public in August 1985. Many people expected that more acidic lakes would be found in the Northeast than in other parts of the United States. They based this expectation on the fact that Northeast states are downwind of the major generators of acid rain precursors in the Ohio River Valley. Eastern Lake Survey teams took samples at 763 northeast lakes. On the basis of those samples, EPA scientists estimated that only 3.4 percent of the lakes sampled in the Northeast had pH values of 5.0 or less. The comparable figure for the Upper Midwest was also low: 1.5 percent. Surprisingly, Florida—far to the south of industrial sources of acid rain—had a much higher percentage of acidic lakes than the Northeast and the Upper Midwest. Over 12 percent of lakes sampled in Florida had pH levels of 5.0 or less. EPA believes that it is too early to attribute this high Florida figure to the impact of acid rain. Natural processes or land use practices may also contribute substantially to the acidity of many Florida lakes. ------- It took a lot of hard work to gather the data that formed the basis of these findings. Scientists on the helicopter sampling crews had to cope with the pressure of weeks of constant travel as well as the hazards posed by erratic weather conditions. At all times and under all conditions, scientists had to observe rigid test procedures to protect the validity of their data. Nature didn't help, either. Survey work had to be completed in the fall, because chemical variations within lakes were lowest then. But during the Western Lake Survey, premature winter weather froze many lakes in the Rockies and the Sierra Nevada, and snow and high winds whipped Wyoming and Colorado. Helicopter teams had to curtail their flying schedules to avoid treacherous afternoon wind storms. And some ground teams were trapped in blizzards and had to be rescued. Ground teams were needed for the Western Lake Survey because many of the 757 lakes sampled in that part of the country were in areas protected by the Wilderness Act. Because the Act forbids any mechanized means of transport in wilderness areas, the U.S. Forest Service would not permit EPA's flotation helicopters to land there. Instead, Forest Service teams had to hike to remote lakes to complete their sampling. The Forest Service did permit EPA to sample 50 wilderness lakes with both helicopter and ground-access crews, enabling the Agency to check samples obtained by ground crews against those obtained by helicopter teams. Expertise gained during Phase I of the National Surface Water Survey is already proving useful in Phase II, which was initiated in the Northeast at the end of 1985. Phase II researchers are looking for variations in surface water chemistry from region to region and from season to season. They are also planning to calculate the fish population at selected lakes and streams surveyed in Phase I. This data will be valuable as scientists try to evaluate the impact of acid rain on aquatic life. For Phase III, EPA plans to modify a long-term monitoring project already in progress. The goal of Phase III will be to identify trends in surface water chemistry using long-term monitoring data. The work, which is planned to continue indefinitely, is being designed to be adaptable to other surface water pollution problems as well as acid rain. Materials Effects Research Scientists who specialize in the materials effects of acid rain still don't know how wet and dry acid deposition affects the natural processes of decay. One way to answer this question is to measure tombstones. EPA recently sponsored research into the rates of deterioration of headstones at 18 A Day in the Life of a National Surface Water Survey Helicopter Team Helicopter teams involved in Phase I of the National Surface Water Survey faced demanding schedules. With nearly 1600 lakes to sample within a few weeks in the fall of 1984, they had to stay on the go constantly. When flying conditions were good, the teams had daily itineraries that could include as many as six lakes within a hundred-mile radius. Poor weather conditions, on the other hand, could force cancellation of an entire day of sampling. Just verifying the identities of the lakes to be sampled was a big job. Map coordinates used by the helicopter's navigation system had to be double-checked against U.S. Geological Survey maps, and the lakes had to be photographed to further verify their identities. Once landed on the lake surface, the helicopters had to maintain stable positions in the water while the scientists took samples and measured lake waters for depth. pH, conductivity, temperature, and transparency. The completed samples were then rushed back to mobile field laboratories, usually by 6 or 7 p.m. The helicopter teams could then relax for the evening, although their usually isolated base stations rarely offered much in the way of recreational activities. But for the chemists in the field lab trailer, the night was just beginning. Procedures for the survey required that the samples be processed and filtered immediately after their delivery to the base station. Work in the lab trailer often stretched long past midnight. Chemists had to put in extra hours to make sure the samples were ready by daybreak for the flight to a cooperating laboratory, where they were further analyzed for 20 chemical variables. By morning, yesterday's samples were on their way to the lab. Meanwhile, at another set of lakes, the helicopter teams were gathering additional samples. And so the process was repeated until 1592 lakes in four areas east of the Mississippi had been sampled. The thousands of samples collected during Phase I of the Surface Water Survey will help scientists understand much more clearly the effects of acid rain on aquatic ecosystems. EPA JOURNAL ------- Veterans Administration cemeteries. Two of the cemeteries provided particularly valuable data. One was located in an industrial area close to New York City, while the other was in a semi-rural area of Long Island. New York University had previously traced changes in the thickness of tombstones at both cemeteries, as well as the depth of their emblem inscriptions. Using these data to calculate weathering rates at the two cemeteries, scientists compared them with estimates of rates of increase in SO2 in New York City from 1880 to 1980. They found what is known as a "linear" relation between the two rates. In other words, increased SO2 concentrations were directly proportional to increased weathering rates. This correlation enabled scientists to develop a formula for calculating the damage caused to materials in the New York area by SO2: 10 millimeters of fine grain marble will be worn away every century for every part per million of SO2 in the air. This study was the first statistically significant proof of damage to stone from an acid rain precursor. It would be difficult to carry out other experiments of this kind, because historical data on air pollution levels are extremely rare. But it is clear that decay accelerated by acid deposition has ramifications far beyond the graveyard. Some acid rain concerns are primarily cultural. For example, the rapid deterioration of the Acropolis in modern times prompted EPA to join a recently completed NATO pilot study on the conservation and restoration of monuments. Scientists from 10 countries monitored acid rain damage to monuments, developed formats and procedures for documenting acid rain damage, and evaluated various means of conserving and restoring damaged monuments. But acid rain threatens more than cultural artifacts. Though experts cannot yet fix an exact dollar value to the materials damage caused by acid rain, they agree that it damages homes, commercial buildings, highways, bridges, and other structures vital to our everyday lives. EPA is now working with the U.S. Army Corps of Engineers to develop a list of materials subject to acid rain damage. This inventory will draw together the data needed to assess the magnitude of acid rain-induced materials damage. Estimates should be ready by 1990, Forest Response Program In the early 1980s, experts began to see unexplained growth reductions and foliage damage in U.S. forests. The evidence was first spotted in New York and New England, but similar problems have now been detected in the Appalachians and the Carolinas. Even worse forest deterioration has occurred in Europe, where whole stands of European trees, especially on mountain peaks, have gone into an unprecedented decline. Scientists are still uncertain of acid rain's role in such instances. Many factors other than acid rain could be responsible for forest damage. Changes in soil or climate could play a role, as could changes in insect or pathogen activity. For these reasons, among others, the evidence for acid rain damage to forests is thought to be weaker than corresponding evidence of damage to aquatic systems. To clarify the effects of acid rain on trees and other vegetation, EPA began the Forest Response Project (FRP) in 1985. FRP scientists are studying the role of acid rain and other pollutants in causing or contributing to forest damage in the United States, They are also trying to determine the mechanisms causing the damage, and the relationship between various "doses" of acid deposition and the "responses" they are suspected of causing, Initial research is studying two types of U.S. forests that have experienced damage or decline. The first type of forest, common to New England and New York, contains spruce and fir. The second, known as "Southern commercial," includes several species of pines valuable to the economy of the southeastern United States. At two sites in New England and three sites in the Southeast, tree's are being classified and checked for height and radial growth. Scientists are also conducting field experiments to compare the growth of trees in open-top chambers with those in rain-exclusion chambers. Control chambers in laboratories permit comparable experiments with seedlings, although it is still difficult to extrapolate from seedlings to mature trees. EPA is also setting up a "Mountain Cloud" data-gathering network to study the effects of various acid rain patterns on forests at differing elevations. "Mountain Cloud" sites will be co-located with biological stations that measure plant growth and productivity, as well as soil chemistry. This work and other studies planned for eastern hardwood forests and western conifers should begin to give us a clearer idea of the kind of threat acid rain poses to the $38.5 billion forest products industry. The Future Many challenges confront acid rain scientists. There is still a need to increase scientific understanding of the effects of acid rain, and the rate at which those effects occur. As yet, scientists lack reliable methods of extrapolating on a regional level what is known about the effects of acid rain in small-scale environments. They also need to determine the level of acid deposition that is realistically compatible with protecting our valuable resources. As these and other questions are answered, we will have a much clearer understanding of the type of control program needed to protect all the resources at risk from acid rain. A videotape documentary entitled "The National Lake Survey" is available for loan from the Audio-Visual Division of the EPA Office of Public Affairs (A-107), Room 2435, 401 M Street SW, Washington DC 20460. Phone (202J 382-2044. This 15-minute overview of the lakes portion of the National Surface Water Survey offers a first-hand look at acid rain sampling in action. ------- Control Technologies Over the last few years, the U.S. Gongress has considered several pieces of legislation proposing acid rain control programs. Most of them have called for SO2 and NOX reductions of 8 to 10 million tons a year. To achieve that level of control, many existing sources of SO2 and NOX—especially utility and industrial coal-fired boilers—would have to be retrofitted with control equipment. But the availability, cost, and technical complexity of existing retrofit controls leave much to be desired. Existing Control Options A number of different methods of equipping new boilers with NOX controls have been developed and tested. But, overall, NOX control technologies have not been commercially retrofitted on existing boilers as extensively as SO2 controls. At present, there are three techniques available for reducing the amount of SO2 emitted from existing coal-fired boilers: coal-switching, coal-cleaning, and flue gas desulfurization. Unfortunately, each of these techniques Ohio ; ivhf ' u LIMB ui'r pollution has drawbacks that limit their ability to reduce SO2 emissions by 8 to 10 million tons per year. A coal-burning facility could cut down on SO2 emissions by switching from a high-sulfur to a low-sulfur coal. However, this fuel shift could damage some kinds of boiler equipment. It could also generate regional hostility by causing shifts in existing coal markets. A second option is for sulfur to be cleaned from coal before it is burned. Physical coal-cleaning technologies are available commercially today. A substantial amount of coal already is being cleaned because of the savings that result from lower shipping costs, lower boiler-maintenance costs, and the higher energy content of the cleaned coal. However, coal is cleaned primarily to rid it of ash and other non-combustibles. Not enough SO2 could be cleaned from coal to hit the emissions reduction target of a large-scale acid rain control program. Currently, there is only one technology available that could reduce SO2 emissions to the extent required by an ambitious acid rain control program: flue gas desulfurization (FGD), a process better known as "scrubbing." FGD uses "sorbents" such as limestone to soak up (or "scrub") SO2 from exhaust gases. This technology, which is capable of reducing SO2 emissions by up to 95 percent, can be added to existing coal-fired boilers. FGD does have several drawbacks. The control equipment is very expensive and very bulky. Smaller facilities do not always have the capital or the space needed for FGD equipment. Even some larger power plants would find it technically very difficult to retrofit FGD systems on older cramped facilities. Expanding Our Control Options The Report of the Special Envoys on Acid Rain, presented to President Reagan on January 8, 1986, recognized the political and economic problems that stem from having only a limited menu of pollution control options. The report stated: "The availability of cheaper, more efficient control technologies would improve our ability to formulate a national response that is politically and economically acceptable." The Special Envoys went on to recommend a $5 billion U.S. program to fund the commercial demonstration of control technologies that promise greater emissions reductions, lower costs, or applicability to a wider range of existing sources. They also recommended that special consideration be given to projects that have the potential to reduce SO2 emissions from existing facilities that burn high-sulfur coal. Over the past several years, millions of dollars have been spent researching a variety of innovative approaches to the control of SO2 and NOX emissions from existing coal-fired utility and industrial boilers. Major federal research programs are being funded by the Environmental Protection Agency, the Department of Energy, the national laboratories (Argonne, Brookhaven, Lawrence Berkeley, and Oak Ridge) and the Tennessee Valley Authority. In addition, the Electric Power Research Institute is cooperating with different electric utilities to improve the control of utility boilers. This research and testing have already generated a number of attractive candidates for the kind of commercial demonstrations recommended in the Report of the Special Envoys. The four technologies described here represent just a few of the wide range of potential candidates for funding as commercial demonstration projects. The EPA JOURNAL ------- purpose of these projects will be to determine whether technologies such as these can be proven to work in existing commercial facilities. LIMB The Limestone Injection Multistage Burner (LIMB) is an emerging control technology that can be retrofitted on a large portion of existing coal-fired boilers, both utility and industrial. Its broad applicability makes it an attractive candidate for funding under the proposed commercial demonstration program. In a LIMB system, an SO2 sorbent (e.g., limestone) is injected into a boiler equipped with low NOX burners. The sorbent absorbs the SO2, and the low NOX burners limit the amount of NOX formed. Thus, LIMB is capable of reducing both SO2 and NOX by about 50 to 60 percent. LIMB technology will not be applied widely until a number of technical problems are solved. The sorbent injected into the boiler tends to increase slagging and fouling, which in turn increase operation and maintenance costs. Because boilers retrofitted with LIMB tend to produce more particulates of smaller sizes, particulate control becomes more difficult. Furthermore, technical questions remain as to what sorbents are most effective in a LIMB system, and how and where to inject the sorbents. EPA has a major research and development program in progress to improve LIMB technology. A full-scale demonstration of LIMB is underway on a utility boiler in Lorain, OH. The retrofitted boiler will be started up in the spring of 1987, and the results of early tests will help determine whether LIMB technology is a suitable candidate for funding under the proposed commercial demonstration program. In-Duct Spraying LIMB controls SO2 and NOX emissions during the combustion process itself. It is also possible to control SO2 after combustion by cleaning it out of the exhaust gases. The scrubbers now in use apply this kind of post-combustion technology. If ways could be found to reduce the technical complexity and economic costs of scrubbing, post-combustion controls would become a more attractive method of reducing SO2 emissions. EPA, DOE, and private industry are involved in efforts to improve flue gas desulfurization (FGD) technology. Much of the research focuses on the development of more effective sorbent materials. In addition, the possibility of injecting a sorbent directly into existing exhaust ductwork is being investigated. An in-duct spray drying FGD system would improve on traditional scrubbers in several ways. Current scrubbers require the construction of very large reaction vessels where the exhaust gases and sorbent can mix to extract the SO2. These vessels are very expensive, and sometimes the space they demand simply isn't available at existing facilities. If, however, the sorbent could be injected into existing ductwork, the cost of the reaction vessel could be eliminated, and it would be much easier to retrofit controls on a wider range of sources. Space constraints would no longer be a limiting factor. In order to test and improve in-duct scrubbing techniques, a demonstration control system is in the process of being tested at a utility in Beverly, OH. The Department of Energy plans to fund another demonstration project in the near future. Even if this research is successful, it is unlikely that in-duct FGD systems will achieve an SO2 control rate of much more than 50 to 60 percent. But if they can be retrofitted widely and at relatively low cost, in-duct FBC systems could join LIMB as an attractive candidate for a commercial demonstration program. Reburning Another relatively new technology known as reburning, or fuel staging, is capable of reducing NOX emissions in existing boilers. In a coal-fired boiler, reburning is accomplished by substituting 15 to 20 percent of the coal with natural gas or low sulfur oil and burning it at a location downstream of the primary combustion zone of the boiler. Oxides of nitrogen formed in the primary zone are reduced to nitrogen and water vapor as they pass through the reburn zone. Additional air is injected downstream of the reburn zone to complete the combustion process at a lower temperature. In general, NOX reductions of 50 percent or more are achievable by reburning. When combined with other low NOX technologies, such as low NOX burners, NOX reductions of up to 90 percent may be achievable. Reburning tests have been performed by EPA on gas-, oil-, and coal-fired research combustion systems. EPA and the Gas Research Institute are preparing to co-sponsor reburning tests at a large industrial or utility coal- or oil-fired boiler. Fluidized Bed Combustion Fluidized bed combustion (FBC) is an innovative approach to SO2 and NOX control in both utility and industrial boilers. In an FBC boiler, pulverized coal is burned while suspended over a turbulent cushion of injected air. This technique is promising from an economic perspective, because FBC boilers allow improved combustion efficiencies and reduced boiler fouling and corrosion. Such boilers also are capable of burning different kinds of low-grade fuels like refuse, wood bark, and sewage sludge. In addition, FBC offers a number of environmental advantages. If the coal is mixed with limestone or some other sorbent material during combustion, the SO2 is captured and retained in the ash. FBC boilers have another environmental advantage over typical coal-fired boilers: they have the potential to control NOX as well as SO2. FBC boilers must operate within a narrow temperature range (1500-1600 degrees Fahrenheit) that is substantially lower than typical boiler temperatures. Lower combustion temperatures inherently limit the formation of NOX. Thus, FBC boilers may be able to control NOX by 50 to 75 percent at the same time as they control SO2 by up to 90 percent. An FBC system does have one major drawback: it requires the construction of a new boiler. Thus, it is more of a replacement technology than a retrofit. The number of existing boilers that could be replaced with FBC boilers at reasonable cost is limited, and its promise is more likely to be realized on new sources. A Less Limited Future Limestone injection multistage burners, in-duct sprayers, reburners, and fluidized bed combustion systems: these and several other technologies are capable of expanding the current rather limited "menu" of acid rain control options. If they can be proven to work on existing commercial facilities, state and federal lawmakers will have much more latitude as they frame legislation for controlling acid rain. Clearly, it would be inefficient and ineffective to try to implement a major acid rain control program before technically viable and economically affordable technologies are available. Thus, the proposed five-year, $5 billion program for commercial demonstration of acid rain control technologies fills a very real need. ------- Implementation Issues Solving problems can sometimes create problems. Take, for example, the implementation of a major new regulatory program. Enacted to control one problem, it can generate many problems of its own. If the undertaking is complicated, expensive, and time-consuming, it can catch state governments unprepared. What would happen if the U.S. Congress passed a law controlling acid rain? Under several bills now being considered, experts foresee the following difficulties: • New reductions would probably be required in a shorter time—and at greater marginal cost—than those already achieved under the Clean Air Act. • Requirements for control of acid rain precursors (SO2 and NOX) could generate conflict and confusion as to which sources should be controlled. Who would make these choices, and on what grounds? • It would be hard to develop a convincing rationale, in terms of local costs incurred, for an acid rain control program because most of the environmental benefits would accrue in another state. Existing air pollution programs did not face this problem, because they tended to impose costs in the same areas where environmental quality was improved. Acid rain controls, on the other hand, would be intended to protect whole regions, but the costs would not be spread evenly over the region. However, some of the cost of controlling acid rain would be felt on a regional scale. Controls imposed on a utility in one state would, to varying degrees, affect utility rates in neighboring states, because electric power is often generated in one state and sold in another. There would also be shifts in the cost of high- and low-sulfur coal, in the cost of manufactured goods, and in employment. These shifts would be felt in the economies of whole regions, not just states. Policy-makers must consider all these factors as they design a major acid rain control program. They must also recognize that a control effort will have significant impacts on many sectors: electric utilities as well as other industries, public utility commissions as well as state executive and legislative offices. Therefore, the concerns of these and other parties must be incorporated into the decision-making process. State Acid Rain Programs To help prepare for the complexity of implementing a major acid rain control program, EPA has committed to work with the states on these kinds of issues. With a special Congressional appropriation EPA established the State Acid Rain (STAR) program to identify and resolve potential problems. It is now funding studies in 36 states on such implementation questions as: • How should control obligations be allocated to individual pollution sources so that statewide emissions reduction targets can be met? • What techniques are available to control each source, and what are their economic and social costs? • How can the gains secured for the environment be maintained in the future without impeding economic growth? Projects in Progress Different states and regions are using their STAR grants in different ways. Wisconsin, for example, has substantial SO2 emissions in excess of the quantitative limitation incorporated in many acid rain control proposals. Therefore, Wisconsin is faced with the possibility of a very substantial emissions reduction requirement. To prepare for whatever may come, the state's air pollution control officials decided to develop complete model programs for hypothetical statewide emissions reductions of 30, 50, and 70 percent. The broad issues of data base, available control techniques, control strategy, and maintenance of achieved emissions reductions are all being studied. Wisconsin's air officials, together with those of Minnesota and Michigan, are also studying possible tri-state emissions reduction plans. In recognition of the crucial role that existing regulation of utility rates will play in acid rain control, they are also bringing together environmental officials and utility regulatory officials of the midwestern states to pool their knowledge and coordinate their planning. A group of eight northeastern states decided to look in greater depth at the technologies available for controlling their specific acid rain sources. They wanted to be ready in case they needed to prepare state or regional strategies for controlling acid rain. They are also beginning the essential task of coordinating the ideas, plans, and policies of their environmental agencies with those of their public utility commissions. These northeastern states are also studying various ways of maintaining environmental goals while permitting economic growth. One approach recommends an initial period of over-control to build up a margin of compliance that permits later economic growth. Another suggests offsetting emissions from new sources with new controls on older sources. Another noteworthy STAR program is being conducted by the states of Tennessee, Kentucky, and Alabama, in conjunction with the Tennessee Valley Authority. This project is examining alternative emission reduction strategies for a multistate utility system. State Acid Rain (or STAR) projects are enabling environmental professionals to study the interrelated problems that an acid rain control program is likely to raise, and to search for equitable and efficient solutions. The states involved in the STAR program have very different views of the policy questions raised by acid rain. Their citizens have very different, and very large, interests at stake. Nevertheless, the air pollution professionals in the states and at EPA have agreed to put any policy disagreements to one side while they seek answers to the questions that will have to be resolved if any acid rain control program is to be successfully implemented, n If you have any further questions about acid rain, contact the Department of Environment in your state or EPA's Office of Air and Radiation, either in Washington DC (202/382-7407) or in the EPA regional office that serves your community (Show map of EPA regions). EPA JOURNAL ------- This small pilot scale LIMB combuster, designed to reduce both sulfur dioxide and nitrogen oxides emissions from coaJ-burning facilities, is being tested with funds from EPA's Air and Energy Engineering Research Laboratory. ------- The Environment. 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