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 Ben- nett, the former EPA assistant ad- ministrator for air, noise, and radia- tion, repeatedly insisted that there was little conclusive scientific evidence that a substantial reduction in SO2 emis- sions "would produce dramatic re- ductions in acid deposition or any amelioration of its effects." She also said we might already have the con- trols 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 dec- ades.

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 adminis- tration policy on acid rain. The third, the long-awaited National Academy of Sciences (NAS) report on acid de- position, comes to strong conclusions on some controversial aspects.

In the second annual report of the National Acid Precipitation Assess- ment Program, a part of the Reagan administration acting under White House control publicly states for the first time that the major cause of de- struction 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 adminis- tration's frequently stated position.

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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 cau- tions, however, that the evidence linking acid deposition to forest dam- age 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 can- not be tested against observations be- cause 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.”

of the acid deposition problem that actions have to be taken despite in- complete knowledge.. . . Recommen- dations based upon imperfect data run the risk of being in error; recommen- dations for inaction pending the col- lection of all of the desirable data en- tail 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 con- sidering whether or not to support the enactment of acid rain control legis- lation.

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.

reductions in the emissions of sulfur compounds into the atmosphere, be- ginning 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 al- though scientific knowledge is incom- plete, many observations indicate that acid rain is a problem for which im- mediate solutions should be sought. The panel members list nine observa- tions that have led them to this con- clusion. Among these are the fact that emissions of SO2 and NO, are a t least I O times greater from human activities than from natural processes and that a large portion of these emissions re- turn to the earth as sulfate (SO:-) and nitrate (NO;) in wet and dry deposi- tion. Another is that the areas receiv- ing 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 observa- tion is that forest damage in eastern

402A Environ. Sci. Technol., VoI. 17. NO. 9. 1983

lationships for eastern North America may be developed.

Irreversible effects The OSTP panel notes that some

effects of acid deposition might be ir- reversible. 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 (nonagri- cultural) soils. They explain that in- creasing the acidity of these soils could change their microorganism popula- tion. Because microorganisms recycle the carbon and nitrogen in the food chain, the entire biosphere depends on them. If the population were to change, such an effect might take many years to detect and would likely be long-term or irreversible. “The evidence that in- creased acidity is perturbing popula- tions 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

The NAS report agrees wiih the OSTP summary in saying that on a regional scale, natural sources cannot account for current ambient concen- trations of pollutants such as SO*, NO,, SO:-, and NOT. Like the OSTP summary, it also states that a reduc- tion in emissions of SOz will 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 rela- tionship between emissions of acid- forming precursor gases and acid de- position may be nonlinear. If that is the case, lowering sulfur dioxide emissions might not produce a proportionate reduction in the average sulfate con- tent of rainfall. In the worst case, they argue, a substantial reduction in emissions might not produce any re- duction 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 pro- portional to SO2 emissions but would instead reflect the amount of oxidizing material available in the atmo- sphere.

The NAS report, however, exam- ines 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 ev- idence: analvsis of historical trends

that from deposited SO:-. The only substantial difference that a strong nonlinearity might make is that the SO2 that is converted to SO$- is per- haps transported farther on the aver- age 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

against observational data. A fourth reason is that most of the models in- corporate little real chemistry, “but include instead only a fixed trans- formation 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 re- actions 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

(primarily in analysis of emissions data and 18 years of sulfate deposition at the Hubbard Brook Experimental Forest in New Hampshire), a com- parison between the historical molar ratio of SOz:NO, in emissions to the molar ratio of SO$-:NOT in deposi- tion, and theoretical calculations based on laboratory studies of the chemical reactions involved in conversion of SO2 and NO, to SO$- and NO; (see Cal- vert, p. 428 A, this issue). The exten- sive data collected in Europe over the past 25 years give the strongest indi- cation 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 condi- tions, distribution of sources, and lat- itudes are different from those in the u s .

Some scientists argue that the lin- earity question is not very important. They say that most of the SO2 that goes up comes down in the form of SO:- or SO2 somewhere over land (two-thirds to three-quarters over the North American continent). The total sulfur deposition (SO:- + SOz), not the amount converted to SO:-, is what matters because most of the SO2 that is dry deposited as SO2 on land is converted to SO:- soon after it comes into contact with water. (The conver- sion rate in water is often about 100%/h.) There are many sources of water to react with deposited SO>, such as subsequent rainfall, dew, fog, frost, and water expired by plants, adsorbed on plant surfaces or within plant structures. Therefore, much of the SO2 that is not converted to SO:- in the air is converted on the ground. Moreover, damage from SO2 reacting within and underneath material sur- faces is believed to be even greater than

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 obser- vations,” but that they are not yet precise enough to analyze quantita- tively the effects of certain geograph- ical erounines of SO? sources on soe-

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

L . I

cific sensitive receptor areas. As a re- sult, the committee concludes that current models cannot help us to choose among possible emission con- trol strategies. The panel members believe that we can say with confidence only that lowering emissions uniformly over all of eastern North America would produce a proportional reduc- tion in the acidity of precipitation over the whole area, but that we cannot predict what the reduction would be in specific areas.

NAS gives several reasons for con- sidering current models inadequate. One primary deficiency is that not enough meterological data are avail- able to reliably predict the movement and mixing of air masses. “Upper air soundings are made only twice daily a t widely separated stations in the US.” A second reason is that no model in- cludes the sources and distributions of all the important ions in precipitation. Another is that dry deposition mea- surements are sparse and highly un- certain, so that dry deposition pre- dicted by the models cannot be tested

be dbtained without them. They con- sider acid rain models analogous to atmospheric models used for weather prediction. Atmospheric models supply imprecise information, but it is valu- able 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.

I f 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 0031

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$- depo- sition 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 studied in the field include dry depo- sition; cloud processes, especially in storm systems; the chemical reactions in clouds leading to H N 0 3 and HzS04; the trajectories of air masses- with the use of tracers, especially in- soluble and chemically inert gaseous tracers; and meteorological studies to establish a quantitative relationship between storm type and acid deposi- tion and to measure air flow in the vi- cinity of clouds. NAS considers that laboratory studies and the develop-

10 million tons of SO2 emissions and four million tons of NO, emissions. Utilities, smelters, and light and heavy duty trucks all would be affected. The bill would require that scrubbers be installed on the 50 largest SOz emitters (50 power plants), the bulk of which are in the Ohio Valley.

In this way, the high-sulfur coal in- dustry would largely be protected be- cause those 50 large power plants that now burn high-sulfur coal would have no incentive to switch to low-sulfur 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

It is plausible that a key part of the research program

region would experience large in- creases in electricity bills. This legis- lation is expected to have broad sup- port in the House because it takes away two major objections to acid rain bills introduced orevious~v-disoro-

could be a mandated emGsions reduction of modest scale over the next four to eight years.

portionate increases in electric bills, and fuel switching, which would be

gion of reducing emissions from a group of sources in another region can be compared qualitatively with the effects of reducing emissions in an al- ternate region.

The NAS report states that ana- lyzing the trajectories of rainfall sys- tems a t three locations in the North- east (Whiteface Mountain, N.Y.; Ithaca, N.Y.; and south-central On- tario) has shown that much of the acidity in the precipitation is carried by air masses from the South and South- west. But it cautions that current data and models do not allow us to deter- mine the relative importance of local and distant sources in acid deposition even though much evidence exists for long-range transport.

Research needs Since the NAS committee members

have limited confidence in current models and believe that reliable models will take many years to develop, they advise that direct empirical observa- tion in the field should be emphasized now. They state that field studies will provide information more quickly about the delivery of acids to ecologi- cally sensitive areas and help in “im- proving the near-term strategy for dealing with the problem of acid de- position in eastern North America.” These studies will not provide a de- tailed description of all the processes but will supply “basic phenomenolog- ical evidence.” According to NAS,

ment of detailed models are important, but that these will not provide the fastest path to a near-term strategy for dealing with acid rain.

New schisms The NAS and OSTP reports about

acid rain have contributed to the for- mation of new alliances and schisms that would have been unthinkable a year ago. Pro-control advocates in Congress say that these reports will make it possible for them to get an emissions reduction program passed this year. Even some of those con- gressional members who do not really favor control now believe that it is in- evitable. Because the OSTP report is radically different from former ad- ministration policy, it has led many members of the coal industry to the same conclusion.

To understand the new alliances and schisms, it is necessary to know some of the provisions in the major bills now before Congress. The important leg- islation in the House, introduced by Reps. Gerry Sikorski (D-Minn.), Henry Waxman (D-Calif.), and Judd Gregg (R-N.H.), calls for a 14-mil- lion-ton reduction in acid rain pre- cursors over a 48-state region by 1993. A one-mill-per-kilowatt-hour fee on nonnuclear electricity generation would pay 90% of the capital cost of the control technologies needed for the reduction. The 14-million-ton reduc- tion would be achieved by controlling

disruptive to the coal market. Also, some members of Congress who are not really in favor of acid rain legisla- tion believe that legislation is inevitable and favor this bill because it eliminates a number of the objections they have to other bills.

The major acid rain bill in the Sen- ate is the one introduced by Sen. Robert Stafford (R-Vt.). Basically, it calls for an 8-million-ton reduction in SO2 emissions in the 31-state region east of and bordering the Mississippi River. It does not specify how these reductions are to be achieved- whether through coal switching, coal washing, scrubbers, or least-emissions dispatch. Consequently, if a utility could achieve low enough emissions by switching to low-sulfur coal, it would be motivated to do so rather than in- stalling scrubbers that cost $100 mil- lion to $300 million for a large power plant. But if a utility could not achieve low enough emissions by changing to low-sulfur coal, it would have to install scrubbers.

The net result of the Stafford bill would be that consumers in those states with the highest current SO2 emissions, such as Ohio and other states in the Ohio Valley, would ex- perience substantial increases in their electric bills. States with the lowest emissions would experience minimal rate hikes or none a t all. The electric rates in the Midwest are now consid- erably lower than they are in the Northeast. Many environmentalists

404A Environ. Sci. Technol.. VoI. 17, NO. 9, 1983

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 eco- nomic difficulty and cannot afford substantial rate hikes even if the net result is more equity. They also say that because the solution to the acid- rain 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 al- liance 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 fac- tions.

The initial reaction of the coal in- dustry 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 sud- denly be blindsided by a White-House- sponsored report that totally departs from existing administration positions and to have no warning or indication that such a damaging report was forthcoming is tremendously disap- pointing.”

The result is that the coal industry has broken up into several factions- the United Mine Workers are against any acid rain controls; some of the high-sulfur coal producers privately favor a bill such as the Sikorski- Waxman 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 pro- ducers have formed a low-sulfur coal coalition called the “Alliance for Clean Energy.” They do not favor any spe- cific legislation, but want SO2 reduc- tions to be limited initially and fol- lowed by greater reductions after sci- entific 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 rec- ommendation that EEI consider en- dorsing a control approach. One such approach, originally proposed by New Hampshire Governor John Sununu, was a plan for an immediate five-mil- lion-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 Ruck- elshaus. Yet the inevitability of con- gressional 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 advo- cating 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 Si- korski-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 in- dustrial sectors ought to be considered for controls.

At press time, no one was quite sure what the administration’s new ap- proach to acid rain would be. Industry and members of Congress were anx- iously or eagerly awaiting, as the case might be, a report by an EPA acid-rain task force to Administrator Ruckel- shaus. 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 politi- cally acceptable, Ruckelshaus would have to balance the amount of emis- sions 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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