Jekyll Island meeting report Plenary lectures on acid deposition
Courtney Riordan
George Hidy
In May 1985, the 15th Annual S y m p sium on the Analytical Chemistry of Pollutants convened in Jekyll Island, Ga. In even-numbered years the symposium meets overseas; next year’s meeting will be in Lausanne, Switzerland, and Joseph Tardellas of the Technical University of Lausanne will be the chairman. One highlight of these symposia is a series of plenary lectures invited each year by William Donaldson of the EPA laboratory in Athens, Ga. This year, the plenary speakers gave an overview of how scientists look at the progress in and problems of air quality measurement and acid deposition.
was airing the scientific understanding of the problem and offering options for control. This year’s lectures gave an unexpectedly candid evaluation of the scientific aspects of the problem of acid deposition.
The speakers Courtney Riordan of EPA in Washington, D.C., commented on his involvement with the acid deposition problem. Formerly the assistant administrator for research and development, Riordan is now head of the Office of Acid Deposition and Quality Assurance. George Hidy, president of the Desert Research Institute (Reno, Nev.), discussed the formalism of measurement processes with application to air quality. James Galloway of the University of Virginia at Charlottesville presented a comprehensive review of current understanding of acid deposition. He was one of five scientists to advise the White House staff in 1983 on acid deposition, at a time when EPA Administrator William Ruckelshaus 904 Environ. Sci. Technol..\Fol. 19, NO.10, 1985
The EPA view Courtney Riordan has been involved in the acid deposition imbroglio since early 1983, when he stepped down as assistant administrator for research and development. He had been offered a choice of projects and elected to work on the problems of acid deposition. He believed that this area offered challenges not only in environmental monitoring and chemistry but in science across the board. The disciplines represented in EPKs acid rain research program include biogeochemistry, hydrology, soil chemistry, engineering, economics, and biology. Riordan highlighted the conflicts that exist between carrying on a research program and fulfilling the mandate of the policy maker. “Today, we have instant everything,” he said. “There is a demand on the part of policy makers that we have instant answers. The success of science and technology is that they have spoiled decision makers, who become frustrated and bored if you cannot come up with answers in two years. “At EPA we are trying to structure a research program that will give staged outputs and data that will raise our level of understanding incrementally. At the
same time, the output of the program will raise the level of debate and discussion that goes on on acid deposition,” Riordan said. Everyone agrees that acid deposition is a complex problem. It involves the transport and transformation of pollutants over large areas; a single source can cause problems as much as 2000 km away. In the main, SO.,, NO.,, and hydrocarbons from stationary and mobile sources are emitted into the atmosphere. They are then transformed by heterogeneous chemistry in the gas phase and the wet phase and are scrubbed out of the atmosphere to fall on different surfaces. This causes problems in forests and on agricultural land, for example. The pollutants also enter water directly or through subsurface systems, ultimately causing acidification of surface waters. For operational purposes, Riordan said, EPA defines acid deposition as wet deposition with a pH below 5.0. This definition is contrary to the earlier accepted value of 5.6-the pH of water equilibrated with CO? in the atmosphere. Because of natural background material in the atmosphere, EPA researchers believe that natural rain cannot have a pH above 5.1 or 5.2. Dry deposition is the material that is removed by deposition, atisorption, and impaction in the form of gaseous and particulate matter. The federal research program in which EPA participates now operates
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about 140 stations across the country that measure wet deposition weekly; there also is a Canadian network. The full network has been in place only since 1984. The U.S. did not begin to increase the number of deposition monitoring sites until 1980. Because trends in data have not developed, existing information is not terribly useful. Riordan expects that 1985-86 data will help EPA to determine what trends have been developing. EPAs current monitoring system works well, but the agency is considering adding eventssampling sites to provide information about the conditions that contribute to the acidity of rainfall. “The unfortunate part of the atmospheric chemistry problem is that we do not know how to measure dry deposition,” said Riordan. The wet deposition component has been measured using gross mass balances. It is estimated that 20% of what goes up in the northeastern part of the US.comes down as wet deposition, that 50% comes down as dry deposition, and that as much as 30% is transported off the North Anierican continent. These estimates are based on gross assumptions from budget studies and from mass balance calculations that have been carried out as a result of field studies. “We do not have a good quantitative estimate of these distributions, and in particular we do not know how they are spatially distributed in terms of the dry deposition component,” Riordan said. Natural sources of sulfur are not a factor in contributing to acid deposition of sulfate concentrations in the Northeast. Emissions of SO2 from large utilities create most of the problem. The most acid regions of the US.. such as the Adirondack Mountains and the New England states. receive about
30 kg/ha-y of sulfate. This is considerably above the level that has been suggested as appropriate to prevent acidification of surface waters. For example, the Canadian government has maintained that a wet-deposition loading of about 20 kg/ha-y is the maximum that Canada can absorb and still protect its surface waters. The Swedish government has suggested that levels may need to be as low as 9 kg/ha-y. The problem of acid deposition in the Adirondack lakes was discovered in the mid-1960s. There are about 3000 lakes in the Adirondack mountains, and the current estimate is that 200 of them with pH below 5.0 have documented histories of reduced fisheries. The chemistry of these lakes further suggests that they have been acidified by deposition. In the early 1970s, independent researchers began to study the problem, but EPAs aquatic research program did not begin until 1982, at a time when a number of questions were being asked. Riordan said that because the program had a long-term focus it was spread thinly over a number of issues.
Agency mandate Riordan said, “When Bill Ruckelshaus came into the agency, in May 1983, we were running the acid deposition research program at a fairly low level of intensity. It was a IO-year federal research program, authorized by Congress at $5 million each year. In my view, the funding was a great underestimation of what would be necessary to research adequately the scientific issues associated with acid deposition.” By the middle of 1983, total funding for the national program amounted to about $18 million. but this was spread among many agencies.
When Ruckelshaus came to the agency, discussion on the issue of acid deposition tended to be heated. Congress was calling for 8-12-million-ton reductions in annual SO2 emissions in the eastern 31 states of the US. Riordan said that Ruckelshaus “put a large amount of his reputation behind doing the best job possible to make decisions on acid deposition that were scientifically correct and socially acceptable. He accepted this as a reasonable risk to take as a decision maker. . . . “The total emissions in the 31 eastern states of the U.S. are about 26 million tons. You talk about reducing from 26 to 12 million tons and you are dealing with sources other than utilities. The cost of achieving such levels of control would be substantial,” Riordan said. He also said that depending on which estimates you believe, the program would cost anywhere from $2 billion to $6 billion a year for IO years. “A total bill of $20 billion to $60 billion was something that was not looked upon lightly.” The question was whether we knew to what extent US. lakes were acidified. Although EPA did have a research program at that point, the answers were not available. In fact, EPA was able to provide data only for the lakes that had been studied-a relatively small number, owing to the program’s limited funding. Riordan said, “You tend to look where the problem is and try to understand the mechanism of the problem and then worry about extrapolation to the universe. We were not able to come up with a representative picture of what the acidification status of surface waters in the US. really was. “At the time we were able to document only 200 acid lakes in the Adirondacks, New England, and the Environ. Sci. Technot.. Vol. 19. NO. 10. 1985 605
upper Midwest-about 200 lakes that had pHs less than 5.0.” Documented reductions in fisheries and the surface water chemistry suggest that strong inorganic acids, rather than organic acids, were the source of the low pH in those waters. As a result of the researchers’ inability to say how many lakes currently were acidic, and because of their inability to determine whether more lakes were going to become acidified, Ruckelshaus became concerned about the status of the research program in the aquatic effects area. He decided that a major infusion of new money for a spectrum of research projects was needed to obtain more data. These projects would aim primarily at gathering data on the status of acidified lakes, on collecting data on comparability, and on starting laboratory and field studies. “As a result of looking at the surface water question, we did undertake certain surveys to determine the chemical status of the nation’s waters,” Riordan said. Another EPA study is on direct vs. delayed responses to acidification; it is being undertaken in conjunction with a soil survey. “Basically, we are attempting to push the limit of our understanding in carrying out these projects. They all involve some significant risk that we have attempted to quantify before presenting the research projects to the administrator, ” he said.
The lake survey EPA researchers looked at data that were being used to describe the problem of acid deposition. Much of it was “snapshot” data, the form and substance of which will certainly change as more information becomes available. There was not much understanding of the temporal experience of any watershed. Riordan said, “The decision makers and ourselves were faced with data which were cross sectional from a m a l l number of watersheds, in terms of the total number of watersheds in the eastern U.S.” A number of workshops and special groups examined the situation, and a proposal was adopted to carry out a surface water survey, first in the East and then in the West. The question of whether it is possible to rely on a single sample had to be resolved in designing the survey. The researchers decided finally that if they were to take single samples from a large number of lakes during fall turnover they could expect to get a reasonable picture of the status of lakes in the northeastern U.S. This would require using a representative sample of watersheds in sensitive areas. There are certain parts of the country that do not experience the problems of 906 Environ. Sci. Technol., Vol. 19, No. 10, 1985
acidification. In places where there is a good deal of limestone and in calcerous areas acid deposition is not a concern. Said Riordan, “You are able to eliminate parts of the country that just are not going to be a problem. But the Northeast, the Adirondacks, the Berkshires, the Appalachians, and the southern East Coast, including Florida’s ponds and sand and gravel lakes, are the areas that are potentially susceptible to acid deposition.” The researchers divided the eastern U.S. into three regions and developed a sampling plan involving 2000 lakes. The chemistry of this area was complicated because of low-ionic-strength waters. The researchers were concerned
about speciation, particularly of aluminum, as a measure of the potential for biological effects. When inorganic aluminum is released at low pH, there is concern about its ultimate precipitation on the gills of fish, for example. Riordan said, “We had to go through a developmental program to come up with a protocol that was acceptable to the people working in the area.” Quality assurance was another major issue in the program. About 30% of research funding went to make sure that accurate measurements were made. There are many reasons that a single sample taken from a lake may not be representative. But when one is faced with the need for data, compromises
must be made. Riordan said, “We went through an elaborate design of the survey and had it peer reviewed twice during the period of its development. We finally designed a survey that was reasonable to carry out. The data are now coming in and are very illuminating .” The report on the eastern lakes, extrapolated to the total population of lakes in the eastern U.S., was to be published in September of this year. The surface water survey cost about $3000 per lake. The data should radically change the way in which acidification of surface waters in the U.S. is perceived.
Prediction How do we predict what happens to a watershed under acid deposition? One issue that came up during the policy review was the result of looking over the literature in the middle of 1983. The researchers wanted to know what is happening in northeastern lakes. When the data for these lakes are examined, some surprising interpretations are possible. After compensating for evaporation and transpiration, evaluating the deposition of sulfate ion into the watershed, and then calculating loadings, sulfate appeared to be mobile in these systems. Riordan said, “What came down in rain was coming out in surface waters. Admittedly, it was crude; we didn’t have budget studies to confirm that sulfate is coming down and going out in water. Nevertheless, one could surmise that the sulfate was not being absorbed in the soils or being taken up in the vegetation.” Lysimeter and laboratory soil column studies indicated that some soil systems were saturated with sulfate. Scientists at Oak Ridge National Laboratory and other places had been working with static systems and coming to the conclusion-based on a static equilibrium model-that sulfate is likely to be mobile in these systems. There also were other characteristics that might be critical in determining whether a watershed could be damaged by acid deposition. Exchange of base cations and weathering rates that would be the source for leaching those base cations, and the sulfate absorption capacity that was in the soil system itself, were suggested as possible determining factors. The researchers also asked whether it is possible to characterize watersheds, including their soil hydrology, in a way that makes it possible to predict whether northeastern watersheds generally fall into the category of direct response systems. Direct response systems are those in which the soil is already saturated with sulfate. Riordan
said, “As a result, weathering rate and I the exchange capacities alone would determine whether these systems were either acidic or not because they were in dynamic equilibrium.” Was the supply of base cations sufficient to compensate for the infusion of hydrogen ion and therefore to prevent acidification of surface waters? Would sufficient weathering rates and the supply of base cations offset acid input and therefore prevent further degradation? A conceptual model was developed incorporating two basic characteristics: the ability to retain sulfate and the ability to supply base cations. If a lake system has a very low ability to supply base cations and a very low absorption capacity, then it could be expected to respond very quickly to input of acids. If the soil is saturated rapidly, its ability to supply base cations would be overcome, and acidic waters would result. On the other hand, if lake systems have high sulfate absorption capacity and high base cation exchange capacity, then they would be fully protected against the effects of acid deposition. It is the lake systems that fall within these extremes that are of major concern to the research program. EPA has adopted this model with some modifications and has used it to develop the direct-delayed research program. The purpose is to select, on the basis of a lake survey, a representative sample of watersheds and soil and to characterize it for sulfate adsorption capacity and exchange capacity. By 1987 EPA researchers hope to have devised a method for predicting acidification of northeastern lakes. Riordan said, “It’s a big gamble. It is impossible to put the probability on such a program. But I would say that the probability of being able to complete it with success is only 50%.” The direct-delayed response study was scheduled to begin this past summer. Researchers were expected to begin sampling certain watersheds in the Northeast and to start gathering soil samples for sulfate absorption capacity analysis, base cation exchange capacity, and weathering rates. The next step will be an attempt to classify watersheds as direct responding or delayed responding. In the latter case, researchers will try to determine the amount of time it is likely to take a delayed response to manifest itself. It is a highrisk program because it may already be too late to correct the damage done.
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This is the first part of a three-part article. In the next two issues, we will report on lectures given by George Hidy of the Desert Research Institute and James Galloway of the University of Virginia at Charlottesville.
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