Acid rain: A rapidly shifting scene Government policy in regard to acid rain seems to be in a state of rapidflux. The widening belief that emission controls are inevitable has promoted the formation of many new alliances and schisms among affected parties Only a few months ago, the official position of the Reagan administration was that years of additional research were needed before the EPA could begin to design an emission control strategy for acid rain. Kathleen Bennett, the former EPA assistant administrator for air, noise, and radiation, repeatedly insisted that there was little conclusive scientific evidence that a substantial reduction in SO2 emissions "would produce dramatic reductions in acid deposition or any amelioration of its effects." She also said we might already have the controls in place that would solve the problem eventually, even though an EPA analysis and industry studies predicted that SO2 emissions are likely to increase over the next two decades. Other government officials also frequently claimed that the cause of acid rain had not been conclusively established. In June, however, after the new EPA team under Administrator William Ruckelshaus was in place, three reports were issued. Two of these indicate a surprising shift in administration policy on acid rain. The third, the long-awaited National Academy of Sciences (NAS) report on acid deposition, comes to strong conclusions on some controversial aspects. In the second annual report of the National Acid Precipitation Assessment Program, a part of the Reagan administration acting under White House control publicly states for the first time that the major cause of destruction of lakes and streams by acid rain in the Northeast is probably man-made pollution. But in most other respects, this report does not represent a major departure from the administration's frequently stated position. The second report that indicates a 0013-936X/83/0916-0401A$01.50/0
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pending policy change was released June 28 by the acid rain review panel appointed by the White House Office of Science and Technology Policy (OSTP) chaired by William A. Nierenberg, director of the Scripp’s Institution of Oceanography. This was not a complete report but a summary of a report that is to be submitted to White House science adviser George A. Keyworth I1 later this fall. It begins by saying that emissions of sulfur dioxide (S02) and nitrogen oxides (NO,) have increased the acidity of natural rainfall and that “additional steps [beyond to those mandated by the Clean Air Act] should be taken now which will result in meaningful
North America has been on the rise in the past few decades. The report cautions, however, that the evidence linking acid deposition to forest damage is not as compelling as that for aquatic damage. The OSTP panel writes that results from current atmospheric transport models for acid rain analysis are not fully in agreement and that they cannot be tested against observations because of the absence of good field data. Therefore, with present modeling methods, source-receptor relationships cannot be determined on a scale smaller than eastern North America. I n IO years, but not five, the summary states, a model of source-receptor re-
“It is in the nature of the acid deposition problem that actions have to be taken despite incomplete knowledge.” reductions in the emissions of sulfur compounds into the atmosphere, beginning with those steps which are most cost effective in reducing total deposition.” It states categorically that reducing SO? emission levels would reduce total sulfur deposition levels and, as a consequence, lower the probability that major changes will occur in more acid-sensitive lakes and forests. The report goes on to say that although scientific knowledge is incomplete, many observations indicate that acid rain is a problem for which immediate solutions should be sought. The panel members list nine observations that have led them to this conclusion. Among these are the fact that emissions of SO2 and NO, are at least I O times greater from human activities than from natural processes and that a large portion of these emissions return to the earth as sulfate (SO:-) and nitrate (NO;) in wet and dry deposition. Another is that the areas receiving the highest deposition are within and downwind from the major source regions. A third is that some lakes in the major receptor areas have become more acidic in the past two decades, with accompanying major changes in biological activity. The final observation is that forest damage in eastern 402A
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lationships for eastern North America may be developed.
Irreversible effects The OSTP panel notes that some effects of acid deposition might be irreversible. It defines irreversible changes as those that take more than several decades to eliminate. The committee members are especially concerned about the effects of acid deposition on unmanaged (nonagricultural) soils. They explain that increasing the acidity of these soils could change their microorganism population. Because microorganisms recycle the carbon and nitrogen in the food chain, the entire biosphere depends on them. If the population were to change, such a n effect might take many years to detect and would likely be long-term or irreversible. “The evidence that increased acidity is perturbing populations of microorganisms is scanty,” the committee notes, “but the prospect of such an occurrence is grave.” The OSTP summary stresses that some of the important information about acid rain may take I O to 20 years of data collection to obtain. Therefore, any recommendations made now must be based on imperfect data. But because of its concerns about irreversible effects, “it is in the nature
of the acid deposition problem that actions have to be taken despite incomplete knowledge.. . . Recommendations based upon imperfect data run the risk of being in error; recommendations for inaction pending the collection of all of the desirable data entail even greater risk of damage,” the OSTP panel states.
Third report The third report about acid rain was prepared by the National Research Council, the report-writing arm of the NAS. It was written by a committee chaired by Jack Calvert, director ofthe National Center for Atmospheric Research (Boulder, Cola.). Although this report cannot be construed as an expression of official administration policy, it will likely be read with care by the new EPA management team. It may also exert substantial influence on those members of Congress now considering whether or not to support the enactment of acid rain control legislation. For the most part, the NAS study is a very detailed discussion of certain aspects of the science of acid rain. Some of its conclusions are in precise agreement with those of the OSTP panel. Some of them relate to areas not discussed in the OSTP summarv. The NAS report agrees wiih the O S T P summary in saying that on a regional scale, natural sources cannot account for current ambient concentrations of pollutants such as SO*, NO,, SO:-, and NOT. Like the OSTP summary, it also states that a reduction in emissions of SOzwill reduce the average acidity of precipitation. It goes into great detail on this point, and in the process refutes one of the major arguments of those who do not favor emission controls. Little evidence for nonlinearity Opponents of controls have been saying for some time that the relationship between emissions of acidforming precursor gases and acid deposition may be nonlinear. If that is the case, lowering sulfur dioxide emissions might not produce a proportionate reduction in the average sulfate content of rainfall. In the worst case, they argue, a substantial reduction in emissions might not produce any reduction in acidity. Nonlinearity might conceivably result from competition between NO, and SO2 for oxidizing species or a saturation of the oxidizing ability of the atmosphere. According to this hypothesis, if there were only a limited amount of oxidizing material, as long as the amount of NO, re-
mained constant, only a limited amount of SO2 could be oxidized to SO:-, no matter how much SO2 was emitted. In consequence, the amount of SO:- produced would not be proportional to SO2emissions but would instead reflect the amount of oxidizing material available in the atmosphere. The NAS report, however, examines the relevant information on this point and concludes that there is no evidence “for a strong nonlinearity in the relationship between long-term average emissions and deposition.” The committee members base their conclusion on three major types of evidence: analvsis of historical trends (primarily in analysis of emissions data and 18 years of sulfate deposition at the Hubbard Brook Experimental Forest in New Hampshire), a comparison between the historical molar ratio of SOz:NO, in emissions to the molar ratio of SO$-:NOT in deposition, and theoretical calculations based on laboratory studies of the chemical reactions involved in conversion of SO2 and NO, to SO$- and NO; (see Calvert, p. 428 A, this issue). The extensive data collected in Europe over the past 25 years give the strongest indication of nonlinearity, the N A S report notes. This evidence is shaky, however, because sampling and analytical techniques in Europe changed throughout this period. Even if the relationship is nonlinear in Europe, it may be linear in the US., NAS argues, because in Europe the weather conditions, distribution of sources, and latitudes are different from those in the
that from deposited SO:-. The only substantial difference that a strong nonlinearity might make is that the SO2 that is converted to SO$- is perhaps transported farther on the average than the unoxidized SO2 and therefore, in the gaseous form, sulfur would be more likely to be deposited closer to the source.
lnadequate models Like the OSTP panel, the NAS committee does not have very much confidence in current mathematical models describing the movement of acid-forming pollutants over long distances and believes that reliable models will take years to develop. It
Models are not yet precise enough to analyze quantitatively the effects of certain geographical groupings of SO2 sources on specific receptor areas.
says that the results of these models are “qualitatively consistent with observations,” but that they are not yet precise enough to analyze quantitatively the effects of certain geographical erounines of SO? sources on soecific sensitive receptor areas. As a result, the committee concludes that current models cannot help us to us. Some scientists argue that the lin- choose among possible emission conearity question is not very important. trol strategies. The panel members They say that most of the SO2 that believe that we can say with confidence goes up comes down in the form of only that lowering emissions uniformly SO:- or SO2 somewhere over land over all of eastern North America (two-thirds to three-quarters over the would produce a proportional reducNorth American continent). The total tion in the acidity of precipitation over SOz), not the whole area, but that we cannot sulfur deposition (SO:the amount converted to SO:-, is what predict what the reduction would be in matters because most of the SO2 that specific areas. NAS gives several reasons for conis dry deposited as SO2 on land is converted to SO:- soon after it comes sidering current models inadequate. into contact with water. (The conver- One primary deficiency is that not sion rate in water is often about enough meterological data are avail100%/h.) There are many sources of able to reliably predict the movement water to react with deposited SO>, and mixing of air masses. “Upper air such as subsequent rainfall, dew, fog, soundings are made only twice daily at frost, and water expired by plants, widely separated stations in the US.” adsorbed on plant surfaces or within A second reason is that no model inplant structures. Therefore, much of cludes the sources and distributions of all the important ions in precipitation. the SO2 that is not converted to SO:in the air is converted on the ground. Another is that dry deposition meaMoreover, damage from SO2 reacting surements are sparse and highly unwithin and underneath material sur- certain, so that dry deposition prefaces is believed to be even greater than dicted by the models cannot be tested
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against observational data. A fourth reason is that most of the models incorporate little real chemistry, “but include instead only a fixed transformation rate [for SO21 (usually 1 -4%/h).” Two types of models, the STEM series and air shed model, “incorporate a significant number of gas phase reactions and cloud processes into an Eulerian grid calculation.” But these models have not been compared with each other or with simpler schemes. One basic practical problem with models is that if they incorporate many of the known atmospheric processes, they become very complicated and require a good deal of money and
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computer time to run. Not all the scientists who have worked with models would agree with the N A S conclusion. They argue that current models are far from perfect, but orovide more information than can be dbtained without them. They consider acid rain models analogous to atmospheric models used for weather prediction. Atmospheric models supply imprecise information, but it is valuable information that cannot be learned in any other way. Scientists point out that the eight models used in phase 111 of Work Group 2 established under the Memorandum of Intent (a bilateral agreement between the U.S. and Canada that set up the framework by which acid rain negotiations were to proceed) have been tested with field data from only one year-1978. If these models were tested further, using data from subsequent years, confidence in the reliability of one or more of them might he enhanced. Also, these superior models, if they do exist, might provide more insight about control strategies than can be obtained without them, even though the bestof models will always be simplified and imperfect. The detailed discussion of models in the NAS report indicates that two of the models that sound promising, because they incorporate Environ. Sci. Technol.. Vol. 17, NO.9,1983
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cloud processes and other aspects of precipitation chemistry, have not been tested against observational data. (If a model adequately predicts ambient SO:- concentrations and the sulfate content of rainfall for a series of years, it is considered a possible “good” one.) Some modeling experts would also argue that although thecurrent models do not accurately predict SO$- deposition in a quantitative sense, they do predict relative rates of deposition that agree well with current measurements. Therefore, the effects on a certain re-
those phenomena that should be 10 million tons of SO2 emissions and studied in the field include dry depo- four million tons of NO, emissions. sition; cloud processes, especially in Utilities, smelters, and light and heavy storm systems; the chemical reactions duty trucks all would be affected. The in clouds leading to H N 0 3 and bill would require that scrubbers be HzS04; the trajectories of air masses- installed on the 50 largest SOzemitters with the use of tracers, especially in(50 power plants), the bulk of which soluble and chemically inert gaseous are in the Ohio Valley. In this way, the high-sulfur coal intracers; and meteorological studies to establish a quantitative relationship dustry would largely be protected bebetween storm type and acid deposi- cause those 50 large power plants that tion and to measure air flow in the vi- now burn high-sulfur coal would have cinity of clouds. N A S considers that no incentive to switch to low-sulfur laboratory studies and the develop- fuel; high-sulfur coal is cheaper for them and they would have to install scrubbers regardless. The nationwide fee on electricity generation would spread the cost of scrubbers, the most expensive part of the program, over the country and eliminate the possibility that consumers in anv sinele state or region would experience large increases in electricity bills. This legislation is expected to have broad support in the House because it takes away two major objections to acid rain bills introduced orevious~v-disoroportionate increases in electric bills, and fuel switching, which would be disruptive to the coal market. Also, gion of reducing emissions from a ment of detailed models are important, some members of Congress who are group of sources in another region can but that these will not provide the not really in favor of acid rain legislabe compared qualitatively with the fastest path to a near-term strategy for tion believe that legislation is inevitable effects of reducing emissions in an al- dealing with acid rain. and favor this bill because it eliminates ternate region. a number of the objections they have The N A S report states that ana- New schisms to other bills. lyzing the trajectories of rainfall sysThe NAS and OSTP reports about The major acid rain bill in the Sentems a t three locations in the North- acid rain have contributed to the for- ate is the one introduced by Sen. east (Whiteface Mountain, N.Y.; mation of new alliances and schisms Robert Stafford (R-Vt.). Basically, it Ithaca, N.Y.; and south-central On- that would have been unthinkable a calls for an 8-million-ton reduction in tario) has shown that much of the year ago. Pro-control advocates in SO2 emissions in the 31-state region acidity in the precipitation is carried by Congress say that these reports will east of and bordering the Mississippi air masses from the South and South- make it possible for them to get an River. It does not specify how these west. But it cautions that current data emissions reduction program passed reductions are to be achievedand models do not allow us to deter- this year. Even some of those con- whether through coal switching, coal mine the relative importance of local gressional members who do not really washing, scrubbers, or least-emissions and distant sources in acid deposition favor control now believe that it is in- dispatch. Consequently, if a utility even though much evidence exists for evitable. Because the OSTP report is could achieve low enough emissions by long-range transport. radically different from former ad- switching to low-sulfur coal, it would ministration policy, it has led many be motivated to do so rather than inResearch needs members of the coal industry to the stalling scrubbers that cost $100 milSince the NAS committee members same conclusion. lion to $300 million for a large power have limited confidence in current To understand the new alliances and plant. But if a utility could not achieve models and believe that reliable models schisms, it is necessary to know some low enough emissions by changing to will take many years to develop, they of the provisions in the major bills now low-sulfur coal, it would have to install advise that direct empirical observa- before Congress. The important leg- scrubbers. tion in the field should be emphasized islation in the House, introduced by The net result of the Stafford bill now. They state that field studies will Reps. Gerry Sikorski (D-Minn.), would be that consumers in those provide information more quickly Henry Waxman (D-Calif.), and Judd states with the highest current SO2 about the delivery of acids to ecologi- Gregg (R-N.H.), calls for a 14-mil- emissions, such as Ohio and other cally sensitive areas and help in “im- lion-ton reduction in acid rain prestates in the Ohio Valley, would exproving the near-term strategy for cursors over a 48-state region by 1993. perience substantial increases in their dealing with the problem of acid de- A one-mill-per-kilowatt-hour fee on electric bills. States with the lowest position in eastern North America.” nonnuclear electricity generation emissions would experience minimal These studies will not provide a de- would pay 90% of the capital cost of rate hikes or none a t all. The electric tailed description of all the processes the control technologies needed for the rates in the Midwest are now considbut will supply “basic phenomenolog- reduction. The 14-million-ton reducerably lower than they are in the ical evidence.” According to NAS, tion would be achieved by controlling Northeast. Many environmentalists
It is plausible that a key part of the research program could be a mandated emGsions reduction of modest scale over the next four to eight years.
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and other observers argue that the Stafford bill would be fair because it would cause electric rates to become more equal throughout the country. They also maintain that the “polluter pays” principle has always been used in the past and should be applied to control of acid rain. Other observers argue that the Midwest is now in economic difficulty and cannot afford substantial rate hikes even if the net result is more equity. They also say that because the solution to the acidrain problem involves a great many uncertainties and because acid rain is a national and international problem, the major cost of solving the problem should be borne nationally.
Shock to industry Last year the utility and coal and mining industries stood behind the Reagan administration in staunchly opposing acid rain control legislation. These factions formed a powerful alliance that seemed in total agreement. During the past few months, in part because of the release of the OSTP and NAS reports, the alliance has fallen apart and the industries themselves have begun to form different factions. The initial reaction of the coal industry to the OSTP report was shock and dismay. Mining and Reclamation Council President Daniel Gerkin wrote a letter to presidential adviser Ed Meese, complaining about the OSTP report: “We find it inconceivable that such a previously unexpected study, carrying a White House-label, could be released to the public . . . to suddenly be blindsided by a White-Housesponsored report that totally departs from existing administration positions and to have no warning or indication that such a damaging report was forthcoming is tremendously disappointing.” The result is that the coal industry has broken up into several factionsthe United Mine Workers are against any acid rain controls; some of the high-sulfur coal producers privately favor a bill such as the SikorskiWaxman bill because it prevents fuel switching; and the low-sulfur coal producers favor moderate acid rain reductions achieved largely through coal switching. The low-sulfur producers have formed a low-sulfur coal coalition called the “Alliance for Clean Energy.” They do not favor any specific legislation, but want SO2 reductions to be limited initially and followed by greater reductions after scientific evaluation. They also favor a control plan that encourages fuel
switching. Schisms also have formed within the Edison Electric Institute (EEI). In July, the executive board made a recommendation that EEI consider endorsing a control approach. One such approach, originally proposed by New Hampshire Governor John Sununu, was a plan for an immediate five-million-ton SO2 reduction in 31 states, based largely on coal cleaning and switching. EEI’s midwestern members opposed the action by the executive board and the recommendation was withdrawn only two hours before EEI met with EPA Administrator Ruckelshaus. Yet the inevitability of congressional action is reflected in the recent comment of EEI’s director of environmental legislation, William Megonnell: “Minds have been made up [in Congress]. The politics outran the science years ago.” Publicly owned utilities once were allied with private utilities in advocating a research-only approach to acid rain. Now the American Public Power Association (AAPA) has split from the privately owned utilities, who still for the most part publicly oppose controls, and’have stated that the Sikorski-Waxman bill “is a move toward a more equitable financing scheme.’’ However, APPA believes that the utility tax levied to pay the cost of emission controls should be applied to SO2 emissions or Btus rather than electricity generation. Also, it believes that in addition to utilities, other industrial sectors ought to be considered for controls. At press time, no one was quite sure what the administration’s new approach to acid rain would be. Industry and members of Congress were anxiously or eagerly awaiting, as the case might be, a report by an EPA acid-rain task force to Administrator Ruckelshaus. This report was expected to be very influential in determining what the administration’s new acid rain policy will be. Research will likely continue to be a pivotal part of any program. It is plausible that a key part of the research program could be a mandated emissions reduction of modest scale over the next four to eight years to test what effect a larger emissions reduction would have in the future. For such a policy to be politically acceptable, Ruckelshaus would have to balance the amount of emissions reduction expected to give an observable change in deposition against the cost of such an emissions reduction. How he would accomplish this balance is not yet discernible. -Bette Hileman
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