REPORT OF THE

                          ACID  RAIN PEER REVIEW PANEL

                                    JULY 1984
                        WILLIAM A.  NIERENBERG,  CHAIRMAN

                           DR.  GEORGE A. KEYWORTH,  II

                        SCIENCE ADVISOR TO THE PRESIDENT




                            WASHINGTON, D.C.  20500
                           U.$. Environmental Protection Agency

                           fleeioii V. Library
                           230 South Dearborn Stroet
                           Chicago, Illinois  60604

U'S' Env'ronmenta( Protection  Agency

                         ACID RAIN PANEL REPORT
                            TABLE OF CONTENTS

   Executive Summary 	     ii

   Acknowledgments 	     vi

   I - Introduction	    1-1

  II - General Comments on the MO I Reports	   II-l

 III - General Comments on Acid Rain	III-l

  IV - Research Recommendations	   IV-1

   V - Review of Work Group 1 Report - Impact Assessment . .  .    V-l

  VI - Review of Work Group 2 Reports - Atmospheric
       Sciences and Analysis	   VI-1

 VII - Review of Work Group 3B Report - Emissions,
       Costs and Engineering Assessment  	  VII-1

Appendix 1 - Panelists' Institutional Affiliations and
             Scientific Disciplines  	   Al-1

Appendix 2 - Charges of the Panel Charter	   A2-1

Appendix 3 - Work Group Structure for Negotiation of a
             Transboundary Air Pollution Agreement 	   A3-1

Appendix 4 - Materials Provided to the Panel	   A4-1

Appendix 5 - Benefit-Cost Analysis Applied to the Acid Rain
             Problem	   A5-1

                         ACID RAIN PANEL REPORT

                           EXECUTIVE SUMMARY

     In January 1982,  the Office of Science and Technology Policy asked

Professor William A. Nierenberg, the Director of Scripps Institution of

Oceanography, to assemble and chair a scientific panel on acid rain.  He

agreed and a panel of  nine scientists was formed shortly thereafter.  They

were chartered to perform three tasks.
     The first was to complete a peer review of the scientific  basis

relating to acid deposition in Eastern North America performed  by three

U.S.-Canadian scientific work groups.  These bi-lateral studies were

called for by the August 1980 Memorandum of Intent between the  U.S.

and Canada on transboundary air pollution.   The peer review of  each  of

these three studies is the subject of a separate chapter in this report.

     The peer review finds the bilateral reports to be basically sound

and thorough.  The scientists reviewed a large amount of material, both

published and unpublished, but there is a tendency toward recitation

rather than synthesis and integration.  The reports often depend too

much on unpublished data, but this may reflect the growing but  still

incomplete state of knowledge.

     Work Group I reviewed a huge amount of data, which was often in-

complete or conflicting, in its long report.  But its message was weakened

considerably because it did not comply with its fundamental charge to

examine squarely the strength of  the  link between  acid  deposition  and

chemical and biological ecological changes.   Work  Group 2  produced a

comprehensive series of reports but greatly  overemphasized  the  present

role of computer models for understanding long-range transport.  Work

Group 3B presented & large amount of  data on emissions,  control techniques

and costs, but enclosed it in a report which is  difficult  to read  and

harder still to interpret.

     The biggest failing of these reports was that the  two  parties of

Work Group 1 were unable to agree on  a preliminary acceptable deposition

rate.  In view of the importance  of this subject and the feasibility

of establishing a value (deductible from the MOI reports themselves), we

recommend that Work Group 1 reconvene for this express  purpose.
     The second task the Panel was asked to perform was to provide further

research and monitoring recommendations to reduce uncertainties in the

scientific and technical knowledge regarding acid deposition.   The panel

finds that current scientific understanding of acid deposition is still

highly incomplete.  In order to begin to eliminate the major gaps most

efficiently, it is recommended that highest priority be given to research

on quantifying the effects of acid deposition (both wet and dry) on the

total ecological system, distinguishing between the ecological effects of

dry and wet deposition of sulfur and nitrogen, differentiating the en-

vironmental effects of acid deposition from those of natural stresses,

measuring dry deposition ac selected representative sites in eastern North

America,  and applying tracer techniques on a broad scale to improve our

knowledge of the source-receptor relationship.   At lower-priority, research

should include determining quantitatively the detailed mechanisms for the

atmospheric oxidation of SC^ and the oxides of  nitrogen (NOX),  improved

refinement of computer models of long-range transport, better  data on

emission of SC^ and NOX, evaluating new or improved control technologies

for SC>2 and NO , and economic analyses of costs and benefits.

     Up to 1984, the way in which the Federal Government conducted its

research program on acid rain was disappointing.   A greater portion of the

funds should be allocated outside the Federal laboratories to  attract new

research groups, disciplines and approaches.   Particular emphasis needs

to be placed upon supportive research to understand the ecological con-

sequences of both wet and dry acid deposition.
     Finally,  the panel was asked to provide an independent assessment  of

the uncertainties in available scientific and technical information on

which recommendations of the U.S.-Canadian Work Groups are based.   In

response to this charge, general comments, findings,  and recommendations

concerning acid deposition that  encompass policy matters as well as science

were developed.  Chapter III of  this report contains  these general comments.

In summary, the panel views the  acid rain problem as  follows:

     Acid deposition belongs to  a socially very important class of problems

that only appear to be precisely soluble by a straightforward sum of ex-

isting technological and legislative fixes.  This is  deceptive.   Rather,


this class of problems is not permanently solved in a closed fashion,  but

must be treated progressively.   As knowledge steadily increases,  actions

are taken which appear most effective and economical in the light of  in-

creasing understanding.

     Large portions of eastern North America are currently being  stressed

by wet deposition of acids, by dry deposition of acid-forming substances,

and by other air pollutants such as ozone, metals,  and organics.   Annual

wet deposition of acidity in the northeastern United States and portions of

Canada is at lease 10 times that of remote areas.   Acid deposition has

altered the chemistry and biology of aquatic and terrestrial ecosystems of

eastern North America.  The principal agent altering the biosphere acidity

is traceable to man-made sulfur dioxide (802) emission.  The Clean Air Act

of 1970 has reduced the emission of SO? considerably, and may continue to

do so.  Nevertheless, the ecological problems that clearly result from

man-made acid emissions are sufficiently well substantiated that  ad-

ditional reductions are required to prevent even more consequential

environmental effects.  The panel recommends that cost effective  steps

to reduce emissions begin now even though the resulting ecological

benefits cannot yet be quantified.

     There exist large uncertainties in every aspect of acid deposition —

emission, transport,  transformation, and eventual deposition, interaction

with the biosphere, and economic consequences.  Nevertheless, when all

the converging partial indicators are considered, it becomes clear that

acid deposition is a  problem for which solutions should be sought now,

and further remedial  steps  taken.

                          ACID RAIN PANEL REPORT

     The panel wishes to express its appreciation to Mrs.  Julie Rahn, a

consultant to the panel, for her efforts in improving the  readability and

clarity of this document.  Her many hours of work have made this report a

cohesive whole, rather than the many separate pieces she started with.

     Typing of the report and its many drafts, as well as  logistics support

for the October 1983 meeting, was provided by Mrs. Shirley Bonsell and her

staff—Mrs. Judi Dubaldi, Mrs. Gail Rainey and Ms. Susan Romano—of the

Science Research Laboratory at West Point.

     Lastly, we thank Major John K. Robertson, Executive Secretary, for his

time and work on behalf of the panel.  His efforts in supervising

production of drafts of this report, collating comments, proofreading,

negotiating word changes, and attempting in vain to enforce deadlines are


                          ACID RAIN PANEL REPORT

                             I - INTRODUCTION

     In January 1982, in anticipation of the March 1982 publication of the

Work Group reports produced under the United States-Canadian Memorandum of

Intent (MOI) on Transboundary Air Pollution, Dr. George A. Keyworth, II,

Science Advisor to the President, asked Dr. William A. Nierenberg, Director

of Che Scripps Institution of Oceanography, to chair a panel to review the

final MOI reports.  After consulting members of the National Academy of

Science and the National Academy of Engineering, Dr. Nierenberg nominated a

panel of scientists and engineers to the task.  In May 1982, Dr. Nierenberg

approached the nominees and asked them to serve.  The panelists, their

institutional affiliations, and scientific disciplines are listed in

Appendix 1.

     In August 1982, formation of the Acid Rain Peer Review Panel was

announced in the Federal Register.  The charges in the charter given to the

panel by the Office of Science and Technology Policy in that announcement

are reproduced in Appendix 2.

     Prior to its first meeting, the panel received the only MOI report in

final form, that of Work Group 33; the table of contents for each of Che

draft Work Group reports (1, 2 and 3B); the table of contents for any

supplementary materials produced by the Work Groups; and the United SCates

and Canadian membership lists for the Work Groups.  (The organization and

terms of reference of the MOI Work Groups are given in Appendix 3.)

     The panel's first meeting in Washington, D.C. on 7 and 8 October 1982

consisted of background briefings by the United States co-chairmen and some

American members of the three Work Groups.  Dr. Keyworth addressed the


                          ACID RAIN PANEL REPORT

panel, reaffirming its Charter.  Officials from EPA and the State

Department also addressed the panel regarding coordination of the United

States Work Groups and negotiation of the transboundary treaty.  The

Executive Director of the Interagency Task Force on Acid Precipitation

briefed the panel on the task force's organization and mission.  Because

agreement seemed imminent on the Work Group 1 and 2 reports, the panel

agreed to start reviewing the current draft reports of these groups.

     Between the October meeting and a second meeting scheduled for 1 and 2

December 1982, draft final documents were obtained from the American

co-chairmen of the Work Groups, copied and disseminated.  The Work Group 1

report was marked by the Work Group to indicate which sections were still

in question.  A list of materials provided to panelists for review and

background reading is furnished in Appendix 4.

     Further meetings of the panel were held on 1 and 2 December 1982 in

Washington, D.C., 27-29 January 1983 in La Jolla, California, and 2-4 June

1983 in Washington, B.C.  These meetings were held to discuss the MOI

reports, to plan the structure and content of the panel's report, and to

begin writing drafts.  In March 1983 the panel was provided with the final

versions of the Work Group 1 and 2 reports, along with a list of

differences between the final versions and the drafts they had been working

with since November 1982.  A final meeting was held in West Point, New York

on 26-28 October 1983 to complete the rough draft of  the panel's report.

Successive drafts were mailed to panel members for revision from November

1983 to March 1984.

                          ACID RAIN PANEL REPORT


     The panel is impressed with the efforts of the United States-Canadian

Work Groups.  They faced a monumental task in reviewing and integrating the

vast amount of written material available on acid rain.  Much of this

material has not yet been published in the scientific literature and is

available only as unreviewed monographs and technical reports by agencies

of both federal governments and by industrial special-interest groups.

Generally, the Work Groups have reviewed the material well, but in some

areas we feel there has been overdependence on "soft" literature (writings

which are not formally published, not peer-reviewed and not available to

the general public, such as in-house reports, personal communications, and


     We are disappointed that the two parties of Work Group 1 were unable

                                                         _ 2
to agree on a preliminary target loading for sulfate (804  ).  The Work

Group agreed that no ecological or chemical effects in sensitive

fresh-water lakes and streams are observed when the sulfate loading

(deposition) is less than 17 kilograms per hectare per year (kg/ha/yr).

They also agreed that chemical and biological effects begin to be observed

in these bodies at loadings of 20 and 30 kg/ha/yr respectively.

     We know that it is not possible at this time to establish a precise

loading below which the average sensitive aquatic system will be protected.

The present loading, however, is at least 10 times greater in the Northeast

than in remote areas of the world.  We believe that this present loading is

too high and that a target loading should be set.

                          ACID RAIN PANEL REPORT

     If the figures Chat Work Group I agreed on are used, it would follow

that a decrease to 30 kg/ha/yr would serve to eliminate damage to all but

the most delicate of the fresh-water biological ecosystems.  This is

equivalent to a 25% reduction in deposition.  We recommend that,  given the

degree of agreement to date, the two sides reconvene to develop an agreed

preliminary target loading which can be used until better target  loading

values are available.  We expect that the reassessment will recognize the

large annual variability of the loadings as a normal effect.

     The panel feels there was an overdependence on modeling, particularly

by Work Group 2.  This dependence on modeling is questionable in that the

science behind the models is still not definitive, and proper data for

verifying the models are not yet available.  The extensive use of models

may not be the responsibility of the Work Groups, but of those who defined

the terms of reference for the Work Groups in the MOI.

     The reports say little of dry deposition or of pollutants other than

S02«  The reports describe sulfur pollution in wet deposition as  the

predominant factor in acid deposition and acidification of our ecosystems.

Little mention is given to co-pollutants, or the combined effects of

multiple pollutants.  Natural pollutants are ignored or mentioned in

passing (granted, little is known about their amount or role).  The reports

are not well-rounded scientific documents (e.g., they do not assess

conflicting data, gaps in knowledge, strengths or weaknesses in their

conclusions, or alternate theories or explanations).  Again, this may

stem from the terms of reference given to the MOI Work Groups.

                          ACID RAIN PANEL REPORT

     In the assessment of control strategies, material is presented which

will allow workers to begin to assess the costs of controlling emissions

and their effects (unit costs are presented, but no attempt is made at

integration).  On the other hand, the panel notes a complete lack of

framework or any attempt at assessing the benefits of emission control,

perhaps because of problems in assessing the value of natural ecosystems.

The models for benefit-cost analysis presented in the MOI reports require

data for both costs and benefits.

                          ACID RAIN PANEL REPORT


     The United States and Canada together annually emit approximately

25,000,000 tons of sulfur dioxide and a comparable amount of nitrogen

oxides.  These oxides can be converted by atmospheric chemical processes

into sulfuric and nitric acids (112804 and HN03, respectively).  The

emissions are large enough to increase appreciably the acidity of natural

rainfall.  Rain in most of eastern North America is considerably more acid

than expected from natural processes alone.  The Clean Air Act of 1970

marked the formal recognition by the United States government of the

importance of reducing emissions of sulfur and nitrogen oxides to the

atmosphere.  New power plants constructed since 1970 do control such

emissions to lower levels.  Such controls were a prudent first step, but

have not accomplished all that was initially intended.  We recommend that

additional steps should be taken now which will result in meaningful

reductions in the emissions of sulfur and nitrogen compounds into the

atmosphere, beginning with those _steps_ which are most cost-effective

in reducing total deposition.  Emission reductions are meaningful when they

produce a detectable decrease in both acidic deposition and degradation of

the biosphere.

     An incomplete data base and sometimes contradictory interpretation of

these data prevent the kinds of certainty which scientists would prefer.

There are, however, many indicators which, taken collectively, lead us

to conclude that acid deposition is a problem for which solutions should be

sought.  These indicators are as follows:

     (1) In eastern North America, emissions of S02 and NOX from human

activities appear to be at least ten times larger than emissions from

natural processes.

                           ACID RAIN PANEL REPORT

     (2) A substantial fraction of such emissions returns as sulfate and

nitrate (NC>3~) in rainfall;  a comparable amount returns as "dry" deposition

through surface-interaction processes which are more difficult to monitor

than "wet" deposition.

     (3) In eastern North America the areas receiving the most-acid rain

are found within and close to the major source regions.

     (4) Acidity (sulfate and nitrate) in wet deposition is substantially

greater in eastern North America than in areas without industrial


     (5) Acid precipitation contributes to the greater-than-natural

hydrogen-ion levels in some lakes and streams in eastern North America.

     (6) Although some kinds of lakes have been acid throughout their known

history, others in areas subjected to acid deposition have become

appreciably more acid during the past few decades.

     (7) These changes in lake acidity have been accompanied by major

changes in the biological activity within them, often including the

disappearance of various aquatic biota, most visibly fish.

     (8) The largest of such aquatic effects have occurred in "sensitive"

regions, in which acidity is not "buffered" by the presence of alkaline


     (9) Large areas of eastern North America have been identified whose

geologic composition is characterized by the absence of any important

buffering capacity.

     (10) Forest damage has been increasing in eastern North America during

the past few decades; acid deposition may be a contributor.

     The overall scientific understanding of the various aspects of acidic

precipitation is incomplete at  the present time, and will continue  to


                          ACID RAIN PANEL REPORT

have major uncertainties well into the future.  Some of these gaps in our

knowledge are permanent because the necessary measurements were not made

ten, twenty, or fifty years ago; the potential future utility of such

information was not yet recognized.  Other gaps exist because the needed

scientific techniques have not yet been perfected or have not been adapted

to the scale required for measurements covering much of the entire Western

Hemisphere.  Some of the important information will require at least ten or

twenty years of additional data collection to take full cognizance of

atmospheric variability and atmospheric cycles.  Biological systems are

extremely complex and variable.  Response and recovery of many of these

systems to external stress will require long-term (decades) detailed study

for full evaluation.  For these reasons, any current scientifically derived

recommendations must be based on an imperfect, but always increasing, body

of pertinent data whose quality and completeness can be expected to improve

for decades.  Recommendations based on imperfect data run the risk of

being in error; recommendations for inaction pending collection of all the

desirable data entail the even greater risk of ecological damage.

     The chemical processing of SC>2 and NOX into acids in the atmosphere

potentially involves a very large number of chemical reactions, whose

relative importances change drastically with time and location, often in

response to varying meteorological conditions.  Sulfur and nitrogen can be

removed from the atmosphere in various chemical forms, and by both dry

processes at the surface and wet processes in rainfall.  Measurements of

804"  and NC>3~ in rainfall are now widespread, but do not have a long

historical base.  Measurements of dry deposition are so scattered (and of

questionable validity) that quantitative assessment is essentially not

possible even now.


                          ACID RAIN PANEL REPORT

     Modeling of atmospheric emissions, transport and deposition has been

confined almost entirely to the sulfur cycle, leaving nitrogen and other

pollutants to the future.  The existing models do not agree with one

another, and cannot be verified by good field data because such data are

scarce.  The models do not even reproduce well the observations on gaseous

SC>2 that are available.  Models cannot be relied on to estimate how much

material emitted at one place will be deposited in another, or how much SC>2

will be'converted to H2S04 before deposition,,

     There exists now no acceptable method for determining source-receptor

relationships on a scale much smaller than "eastern North America".  With a

very large effort in laboratory atmospheric chemistry, field measurements,

and atmospheric modeling, it might be possible within ten years (but

certainly more than five years) to produce a verified source-receptor model

for eastern North America.  We have great hope that methodology based on

natural tracers in fossil fuels may bypass some of these difficulties and

perhaps reduce the time needed to elucidate this complex of problems.  Even

if a verified model is developed in the future, the source-receptor

relationship may be found to be sufficiently complex and variable that

emission controls would still need to be assigned over large areas rather

than locally.

     Reducing present SC>2 emissions would reduce deposition of total

sulfur, and, consequently, both reduce the probability of major degradation

of additional acid-sensitive lakes or forests and allow anthropogenically

acidified areas to begin to return to their original biological condition.

                          ACID RAIN PANEL REPORT

     The effects of acid deposition on biological systems in North America

range from certain to speculative.  There is no question that fresh water

bodies in sensitive areas have been altered.  At high concentrations,

acidity can release, or "mobilize", aluminum from solid minerals;  this may

lead to toxic effects on biota in both lakes and forest soils.  While there

is strong evidence for damage to limestone monuments, bridges, buildings,

and other structures from SC>2 anc* other corrosive gases, there is no good

estimate of the economic magnitude of these effects or of the contribution

from acid deposition.  The effects of air pollutants and acid deposition on

agriculture may be important but quantitative evidence is scanty.

     Lakes and streams may require years or decades to recover from

anthropogenic acidification once the acidic inputs are removed, with the

recovery time depending on local geochemical factors, flushing rates, rates

of species colonization, extent of alteration of trace-element composition,

and other factors.  In contrast, recovery times for stressed terrestrial

ecosystems are decades to centuries.  At its simplest level, this

difference in recovery times arises because the major photosynthetic

organisms in aquatic environments are relatively short-lived compared to

trees.  There are, however, many other complex differences between the two

types of systems.

     We are especially concerned about real and potential changes in the

chemistry and biology of soils in nonagricultural areas (i.e., unmanaged

soils).  Because soils need hundreds to thousands of years to develop, they

will recover very slowly from anthropogenically induced changes unless

artificial amendments such as lime are used.

                          ACID RAIN PANEL REPORT

     Soil microorganisms may be particularly sensitive to changes in

acidity; this fundamental part of the biological cycle is responsible for

cycling nitrogen, carbon, phosphorus and other essential nutrients through

the food web.  For example, the entire biosphere depends on proper

functioning of denitrifying microbes.  Although evidence that increased

acidity is perturbing populations of microorganisms is scanty, the prospect

of such an occurrence is grave.  Biogeochemical changes in soils appear to

be particularly long-term.  It may take years or even decades of

accumulation of acidity and other toxic airborne pollutants before

consequences can be observed.  It may take at least that long for the soils

to revert to their original condition.  It is this aspect which gives us

the greatest concern.

     Acid deposition belongs to a socially very important class of problems

that appear to be precisely soluble by a straightforward sum of existing

technological and legislative fixes.  This is deceptive.  Rather, this

class of problems is not permanently solved in a closed fashion, but is

treated progressively.  As knowledge and understanding steadily increase,

actions are taken which appear most effective and economical at each


     Actions to reduce acid deposition will have to be taken despite

incomplete knowledge.  We have earlier estimated how long it may take to

understand "wet" atmospheric chemistry or the biological response to

acidity.  Reasonably accurate models incorporating relevant meteorology,

chemistry, mineralogy and biology will take even longer.  Yet, if we wait

until scientific knowledge is definitive, recovery times may have increased

to decades or a century or more  (for mature forests and soils).


                          ACID RAIN PANEL REPORT

     We feel that the proper initial approach is to begin immediately with

the most economically effective steps for reducing acid deposition.

Control costs appear to range widely, especially for sulfur removal;  some

steps can be much more cost-effective than others.  Some of the most

economically efficient means for lessening sulfur emissions in eastern

North America and other sensitive areas are intensifying coal washing and

placing initial controls on nonferrous smelters; switching to fuel of lower

sulfur content during summer (when most sulfuric acid is deposited) might

lessen the overall deposition in distant regions without necessarily

changing annual emissions.  Other control technologies are often more

expensive, but research is steadily decreasing their cost.

                          ACID RAIN PANEL REPORT

                      IV - RESEARCH RECOMMENDATIONS

     It is critical that new funds be made available both to initiate

additional studies and to continue and expand present studies.

     There are four general areas of uncertainty for quantitatively

understanding how and to what extent anthropogenic emissions of S02 (and

NOX) may damage ecosystems:

     A.  Magnitude of anthropogenic emissions and their relation to natural


     B.  Chemistry of conversion of S02 (NOX) to sulfuric (nitric)  acid in

         the atmosphere, in precipitation, and after dry deposition.

     C.  Transport of acid and its precursors from sources to points  of


     D.  Present and potential ecological consequences of the deposition.

     By far the largest quantitative and even qualitative uncertainties

exist in the fourth category, (D), which is the most complex because  of the

large number of components and their variabilities.  It also has been the

least adequately supported with research funds, especially in the area of

effects on unmanaged soils, wetlands, and forests.  This fourth category is

the most important to the acid rain problem, because ecological

consequences are the raison d'etre of the problem.  At present, the need

for quantitative description or precision in the other three areas  is much

less urgent.  Unfortunately, acquiring quantitative and decisive

information in this fourth category will take at least a decade of  careful

field and laboratory study.

                          ACID RAIN PANEL REPORT

     For these reasons, we suggest the following order of  priorities  for

research support:

     1.  We give highest priority to quantifying the effects of  acid

deposition, both wet and dry, on the total ecological system,  including

natural and managed vegetation, soil, and ground water.  Of  special

importance may be effects on microbial activity in soil and  wetlands  and,

through that, on the nitrogen cycle.

     These investigations should include laboratory and field studies as

appropriate on:

         1) Detailed ecosystem analyses on a variety of terrestrial
         watersheds, including associated lakes and streams.  These studies
         should determine the relative inputs of H+, 804"  ,  and  N03~  from
         direct deposition and from biological and chemical  activities
         within soils, lakes and lake sediments.  The studies should
         include landscapes containing clear-water lakes,  brown-water
         lakes, and streams.  Although the studies should  concentrate on
         eastern and north central states, they should include sensitive
         areas in other parts of the country.  These ecosystem studies
         should also emphasize:

             a) Effects on vegetation and soils.  Detailed studies are
         urgently needed on direct and indirect effects of acid  precipi-
         tation on vegetation and soils of managed (i.e.,  agricultural) and
         unmanaged (i.e., forest) systems.  These studies should be
         long-term, so they can include the natural variability  in climate
         and biological response.

             b) Biogeochemical processes, including effects  of acidity and
         metals released by acidity on microorganisms which process
         nutrients and organic material in soils, lake sediments, rivers
         and, most importantly, fresh—water wetlands; the effects of
         acidity on geochemistry of the soil; and mechanisms controlling
         the chemistry of drainage waters.

            c) The relative effects of natural and anthropogenic sources of

         2) Physiological bases of toxicity from acid and dissolved
         aluminum.  We are approaching an understanding of the mechanisms
         of acid toxicity on fish, but relatively little is known about the
         physiology of acid toxicity on other aquatic and terrestrial
         organisms, plants in particular.  Moreover, at least in field
         studies, it is clear that acid and aluminum may act


                          ACID RAIN PANEL REPORT

         synergistically.  Their individual physiological effects should be
         distinguished by laboratory studies.  Effects of calcium, humate
         and fulvates on the uptake of metals should be an important part
         of such research.  Liming may actually increase the toxicity of
         aluminum dissolved by the acidified water and then complexed by
         dissolved organic carbon.  Liming precipitates the dissolved
         organic carbon and leaves the aluminum in a more toxic ionic form.
         The generality of this occurrence should be investigated because
         it affects the utility of liming as a countermeasure to lake

         3) Study of historical trends in lakes and bogs.  To evaluate the
         temporal trends of acidity in lakes from various parts of the
         country, cores taken from the bottom of lakes should be analyzed
         for shifts in species in the watershed (by pollen analysis),
         shifts in chemistry of the water and sediments, and shifts in
         organisms in the lake (diatoms, desmids, chironomids, cladocerans,
         fish).  Bogs and lakes should be selected from the entire East,
         the upper Midwest, and various parts of Canada.  As part of these
         studies, the identities of the species must be verified and
         voucher specimens must be kept.  Long-term experimental studies in
         natural ecosystems should be initiated to provide a basis for
         interpreting existing sediment profiles.

         4) Extended data bases.  Lakes and streams in the northeastern
         United States are clearly being affected by acid rain.  Before
         such effects become severe in other parts of the country (e.g.,
         southeastern United States), the extent and severity of the
         problem should be surveyed. Teams of scientists should examine the
         condition of sensitive surface waters throughout the United
         States, including clear, poorly buffered waters at relatively high
         altitudes.  These studies should include analyses for pH, Ca+ ,
         Mg+ , 304" , NC>3~, dissolved metals and alkalinity, and should
         continue for at least a decade.

         5) The effects of reduced emissions should be quantified by
         carefully designed ecological studies and monitoring programs.

     2.   Quantifying the relative effects of dry deposition of acid

precursors (SO?, NOV) vs. wet deposition of acid onto a given ecological

system.   Because dry deposition should dominate over wet deposition in many

regions, it is important to know how relevant the form of deposition is to

ecological systems.  For example, how much difference does it make whether

sulfur is adsorbed as 862 by a soil (whose surface is often wet) or

deposited as sulfuric acid in precipitation?  This question can probably be

answered before the full effects of acidification are understood.


                          ACID RAIN PANEL REPORT

     3.  Natural vegetation is stressed by a  variety of  agents  acting

separately or together.   Some, such as droughts, are independent  of  S02  and

NOX emissions.  Others are associated with these emissions  and  acid

deposition.  It is important to have laboratory data and particularly  field

observations directed toward disentangling the effects of acid  deposition

from those of other anthropogenic atmospheric insults (especially 0^,

SO? and toxic trace elements), drought, pests, and plant diseases.

     4.  Next, but much less important, would be a reliable relation

between emission of S02  and NOX in one region and deposition of these  gases

or the acids derived from them in another region.  Models do not  yet give

such information and are unlikely to do so before a sufficient  data  base is

acquired with respect to which models can be tested.  For dry deposition,

which may be as important as wet deposition (only one-fifth of  the S02

emitted in eastern North America comes down "wet"), there is not  even  a

full year's data for any natural ecosystem.  Therefore,  developing and

implementing methods for carefully measuring dry deposition at  a  limited

number of regionally representative sites in eastern North America is

particularly important for verifying models and predicting ecological

effects.  As a complement, more monitoring data on SO? and NOX  in rural

areas are needed.  These data should also lead to improved sulfur and

nitrogen budgets for eastern North America.

     5.  Understanding of transport also may profit greatly from network

measurements of tracers (elements, compounds, stable isotopes)  presently

emitted continuously (or perhaps artificially inserted tracers),  because

relative abundances of certain tracers can uniquely characterize area  and

point  sources of S09 and NOX.  Both of the above measurement programs


                          ACID RAIN PANEL REPORT

(4 and 5) appear to us more urgent at this time than expanded efforts in

constructing mathematical models, which can be verified only by comparing

them with data which do not yet exist.

     6.  Next in importance is understanding the atmospheric chemistry by

which SO? and M0y are acidified before they are deposited by precipitation.

The importance of such information depends upon the answers to priorities 2

and 4.  Thus, if the ecological consequences and transport ranges were

shown to be insensitive to degree of conversion to acid, it would not be

particularly important to determine the details of atmospheric oxidation.

But if, for example, sulfuric acid deposited in precipitation were found to

be potentially harmful, the atmospheric chemistry of SC>2 conversion would

become very important for verifying models and (more significantly) for

selecting the best control strategies.  (For example, would it be easier to

control oxidants or S02 to reduce wet deposition of sulfuric acid?)

Necessary to understand quantitatively the atmospheric transformation to

acid would be field programs in cloud chemistry (especially on the surface

of and within droplets) and oxidant measurement (especially R2®2> an<^

probably 03 and oxidant precursors) at droplet altitudes.  Laboratory

experiments should include mechanisms of oxidizing SC>2 and NOX, as well as

isotopic f ractionation of *°0 in sulfate as a function of S02 oxidation

mechanisms and isotopic composition of reactants (for comparison with field

data on *°0 in rainwater, sulfate, and cloud-droplet oxidizers such as
     7.  The information resulting from priorities 4 through 6 should then

be incorporated into improved computer models.  (One purpose will be to

decide whether the improved models perform significantly better than the


                          ACID RAIN PANEL REPORT

original ones did.)  A key question involving both chemistry and

meteorology is the degree of linearity between SC>2 emission and eventual

wet and dry deposition, but a precise answer is not achievable now because

of insufficient data.

     8.  Although emission data for SO? and N0y can be improved, their

accuracy is already much better than for deposition;  however, better

emission data on alkaline particles and oxidant precursors may be useful.

Natural sources of many species still need to be characterized more


     9.  Engineering research on ways to remove sulfur at the source should

still be supported by federal and industrial agencies.

    10.  The main applied purpose of the scientific understanding which

could be advanced by these programs is to inform those who decide upon

control strategies.  To a great extent, optimal strategies must await

such understanding.  Some important relevant information, however, may be

obtained now from improved economic analyses on:

         a) Cost of material damage from 302 emission.

         b) Cost of altered yields of agricultural crops from S02 and 03.

         c) Future S02 and NOX emissions with more realistic projections of
            electric-power use, retirement of old generators, steel
            production, coal vs. oil, etc.

         d) Costs of using low-sulfur fuels when season (e.g. , summer) or
            frequency of precipitation favors wet deposition of acid.

         e) For each S02 source, one should determine the lowest-cost
            approach for removing increasing amounts of sulfur.

         f) What kind of legislation would result in least cost
            to society for a given total emission reduction? For example,
            if one assumes that sulfur emitted from one source is
            ecologically equal to that from any other, what would be

                          ACID RAIN PANEL REPORT
            the consequence of allowing a free-market sale of limited
            pollution rights for SC>2?
     We are disappointed at the way in which the Federal Government has

been conducting its research program on acid rain.  A much larger share of

the research should be given to non-Federal laboratories.  In addition, we

feel strongly that highest priority be given to the most creative ideas

and innovative approaches.

     We realize that the Federal Government and other agencies are

supporting important ongoing research on acid deposition.  At the same

time, however, imbalances exist, with some areas seriously underfunded.

One example is ecological effects, where a relatively modest increase in

support (several million dollars annually) would have disproportionately

great results.  Although current funding of acid rain studies is  much

higher than in the past and increasing, carefully chosen priorities in

fields and investigators can markedly accelerate progress in this difficult


                          ACID RAIN PANEL REPORT



     Large areas of eastern North America are currently being stressed by

wet deposition of acids, by dry deposition of acid-forming substances, and

by various other air pollutants such as ozone.  The panel has concluded

that acid deposition has altered aquatic and terrestrial ecosystems of

eastern North America both qualitatively and quantitatively.  Perhaps the

best known of these changes is that numerous recently acidified lakes in

the northeastern United States and southeastern Canada no longer contain

viable populations of some species of fish.

     Work Group 1 was charged with reviewing the past, present, and

projected impacts of transboundary transport of air pollutants into

sensitive receptor areas in the United States and Canada.  In addition,

Work Group 1 was to estimate the number of years remaining until the

sensitive areas were affected significantly, and to propose the amount of

reductions in deposition of the pollutants on various time scales that

would be required to protect these areas.

     Work Group 1 produced a final report which was very long—626 pages

of text.  Most of this length was due to the large amount of evidence

reviewed.  But part of the length came about because the Canadians and

Americans could not agree on certain sections and issued them separately,

and because the Work Group went well beyond its charter by including extra

chapters on damage to man-made structures, methods to estimate benefits

from controlling transboundary transport, an inventory of natural

resources, and liming.


                          ACID RAIN PANEL REPORT

     In the seccions below, we first offer general remarks on the

report as a whole, and then deal with each chapter individually.

General Remarks

     Perhaps the greatest strength of this report is the amount of evidence

presented for relatively recent chemical and biological changes in natural

ecosystems in parts of North America remote from urban or industrial

centers.  The evidence is convincing—something is happening.  Some of

these changes may be natural, because ecosystems are not always static.

But the report offers massive evidence that air pollutants are associated

with many of these changes.  The report documents clearly that high levels

of acidic deposition are linked with ecological changes in parts of eastern

North America.  In areas with less deposition, similar changes are weaker

or absent altogether.

     But is the link to air pollution causal or coincidental?  In some

cases, such as ozone and vegetation or sulfur dioxide and man-made

structures, it is definitely causal, and the report says so.  In the case

of acid deposition and ecosystems (the major concern of the entire

Memorandum of Intent), however, the degree of causality is drawn much less

clearly.  To be sure, whole-lake and stream acidification experiments in

Canada and the United States have shown that systematic, widespread, and

reproducible chemical and biological changes occur as pH drops below about

5.5.  Similar changes are observed in numerous lakes and streams which have

been acidified recently.

     This is not  direct evidence of causality, however; it is only

circumstantial evidence.  In our view, the crux of the acid precipitation


                          ACID RAIN PANEL REPORT

debate is the strength of the link between acid deposition in a given

region and ecological changes in that region.  The fundamental charge of

Work Group 1 was to address this point in detail, by documenting the past,

present, and future adverse effects of transported and deposited air


     Work Group 1 did not meet this charge fully.  Commendable as its

Final Report is, it dwells too much on data rather than on ideas, and on

individual relations rather than on the big picture.  Too much of the

material is not digested; critical issues are hedged or obfuscated rather

than met squarely.  The terras of reference demand clear statements;  the

Work Group often neither offered them nor noted their absence.  This

failure to deal directly with some of the most important questions is the

greatest weakness of the Final Report.

     We recognize fully that the environmental effects of acid deposition

(and of ozone and other transported pollutants) are exceedingly complicated

and not amenable to any simple description.  Nevertheless, brief statements

of the current understanding are required by decision-makers, and are

extremely important to the concerned public as well.  We feel that Work

Group 1 could and should have summarized its findings much more succinctly

than it did.

     Consider aquatic effects, for example.  Although it is presently not

possible to prove that acid deposition has changed the chemistry or biology

of aquatic systems in eastern North America (absolute proof of causality is

usually impossible in science), an extremely convincing argument can be

made.  Recently acidified lakes and streams are found only where there is

                          ACID RAIN PANEL REPORT

acid rain (not in the Sierra or Cascade Mountains, the Boundary Lakes Area

of northern Minnesota, or northern Scandinavia, for example, even though

these areas are environmentally sensitive).  In recently acidified lakes,

the dominant anion is sulfate, as it is in acid raia.  Elevated sulfate is

found in most surface waters throughout eastern North America and southern

Scandanavia, even in those not yet acidified.  In non-acidified lakes the

dominate anion is usually bicarbonate.  In lakes near very strong sources of

sulfur dioxide, such as the smelters of Sudbury, Ontario, ecological effects

have been severe.  Thus, there can be no doubt that high loadings of acid

can destroy the normal biology of a lake.

     But what about the majority of the lakes, which are subject to more

typical rates of acid deposition?  At present, the percentage of these

lakes affected chemically or biologically is not known.  (In fact, the

total number of lakes in eastern North America is not known.)  Of the known

lakes, only a tiny percentage has ever been studied, and only a tiny

percentage of these studies has systematically surveyed the ecological

changes.  Thus, we are dealing with an enormous deficit of data relative to

the potential importance of the problem.

     One point is certain—it is very difficult to generalize about lakes

and their response to acid deposition because the response of a lake depends

on factors such as its underlying geology, nearby vegetation, size and depth

of the lake, nature and depth of surrounding soils, relative area of lake

and watershed, and other factors, all of which vary over large ranges.

Thus, a population of lakes should respond in a great variety of ways to a

given amount of acid deposition, and that is exactly what is seen in eastern

North America.


                          ACID RAIN PANEL REPORT

     At high elevations in the Adirondack Mountains, where soils are thin,

minerals are resistant to weathering, and lakes are poorly buffered and

receive heavy loadings of acid, a large fraction of the lakes is already

acidified.  At lower altitudes, some lakes are acidified, some are being

titrated, and others show no effects of acidification.  Some large lakes,

such as Erie and Cayuga, are basic and will remain so indefinitely because

of their size and buffering.  Other large lakes, however, such as Honnedaga

in the Adirondacks, are already quite acidic (pH < 5.0) because of the

small size of the watershed relative to the lake (only 4:1); thus, the

water in the lake is largely rainfall, with minimal alteration by soils in

the watershed.  A "typical" nonacidified New England lake may have a pH

above 6 because it contains small amounts of bicarbonate, but sulfate has

become the dominant anion.  And so it goes throughout the spectrum of lake

response to acid deposition.

     As a lake receives acidity, its alkalinity first decreases (the

titration phase), then disappears altogether, after which the lake

acidifies rapidly.  It is now known that biological effects occur

throughout the titration phase, not solely after the lake is acidified.

(By acidified, we mean having reached a pH of lower than about 5.5).

     In summary, then, lakes do not have to be acidified to be acidifying,

and may show biological effects well before they are acidified.  For the

reasons given above, lakes in a given area will follow highly

individualized pathways toward acidification.  Some may never become

acidified, some may already be acidified, and many will be somewhere in

between.  Others, the so-called "brown-water" lakes, are naturally acid

from organic acids, and hence are not as directly affected by contemporary


                          ACID RAIN PANEL REPORT

acid deposition.  (All lakes in the eastern United States have  some  amount

of humate.)  With such variety available in the lakes of  a given region,

exceptions can be found for any statement.  These exceptions  are expected,

however, and should not be overemphasized in developing the total picture.

     Our last general remark on the Final Report of Work  Group  1 concerns

our mixed feelings regarding the extra chapters on additional topics.   On

the one hand, the effort and concern behind them were commendable.  On the

other hand, we regret any time they took away from dealing with the  central


Remarks on individual chapters

     Aouatic Impacts

     The chapter on aquatic impacts takes up nearly half  the  Final Report,

and rightly so, because this aspect of acid deposition is one of the most

important and complex.  In our view, the huge mass of material  on aquatic

effects was covered well by Work Group 1.  As noted above, there was a

certain lack of synthesis throughout, which greatly weakened  the force of

their message.

     One very important aspect of aquatic effects which could have been

treated more fully in this chapter is the general confusion between the

various types of naturally acid surface waters.  There are three distinct

types. The first type has high concentrations of organic  acids, is often

yellow or brown in color, usually contains growths of Sphagnum, and  normally

has a pH below 5. The second type results from volcanic activity: these

waters are high in mineral acids and can have pHs below 4.  (This second

                          ACID RAIM PANEL REPORT

type does not occur in eastern North Airerica and will not he discussed

further.)  The third type contains clear water and is found over granite or

sand; these waters have very low conductivity, poor buffering,  and pHs of

5 .6 to 7.0 .

     The first type, the brown-water lakes and streams, have been naturally

acid for thousands of years, yet much of the literature on these lakes and

streams was not considered.  In these waters, dissolved aluminum and other

toxic metals are low in concentration and are conplexed hy the  dissolved

organic matter and thereby rendered nontoxic to organisms.  As  a result,

brown-water lakes and streams may support thriving communities  of plants,

animals, and microbes.  In contrast, the recently acidified waters are

normally derived from the third type listed above.  Their major acids are

mineral (e.g., J^SC^ and UNO}), and their concentrations of dissolved

organic matter are low.  At low pH, dissolved metals such as aluninun exist

in inorganic forms which may be quite toxic to organisms.  These acidified

lakes and streams have depleted populations of plants, animals, and

microbes.  It is these acidified waters and aquatic effects that are of

concern relative to acid rain.

     Much of this aquatic chapter was devoted to reviewing effects of acid

deposition under controlled or laboratory conditions.  A clearer

demarcation between laboratory results and symptoms noted in real

ecosystems would have been desirable.  It is easy for the reader to confuse

potential effects with actual ones.

     The different fates of hydrogen and sulfate ions in watersheds was

properly stressed in this chapter.  While more than 80% of the  acidity is

                          ACID RAIN PANEL REPORT

absorbed, even by the less-buffered granitic soils, this is not the case

with sulfate which reaches the lakes and streams in much higher proportion.

    Perhaps the most important aspect of the aquatic chapter needing

comment is the failure of the American and Canadian members to agree on a

value for target loading, or rate of deposition of sulfate necessary to

protect sensitive ecosystems in eastern North America.  Separate summaries

issued by the United States and Canada for the aquatic chapter represented

the only area of the entire MOI process in which the two countries

officially disagreed.  Careful reading of these summaries convinces us,

however, that the the American and Canadian delegates were actually quite

close on target loadings, but had many other differences of opinion about

aquatic effects.  The American summary consistently stressed the gaps and

uncertainties in the data and the consequent difficulties in drawing

conclusions from them, whereas the Canadian summary consistently stressed

that much of importance could be concluded from the available data.  The

present data document large-scale chemical and biological effects of acid

deposition on non-brown-water lakes in eastern North America.  These

effects are numerous and severe enough to warrant mitigation of SC>2 and NOX

from anthropogenic sources.

     Terrestrial Impacts

     This chapter is not as comprehensive as the one on aquatic impacts.

The literature is not covered as well, especially in the sections on

forests and soils.  This is unfortunate, because terrestrial effects of

acid precipitation may be extremely important, and may rival or exceed

those in surface waters. Laboratory experiments have shown that acid

                          ACID RAIN PANEL REPORT

deposition adversely affects both plant growth and foliage.  In the natural

environment, however, the effects are not so clear because acid rain is

only one of several stresses on plants, some others being ozone, SC>2,

metals, and droughts.  Also, it is often difficult or impossible to

distinguish effects of direct deposition to the exposed plant from effects

of increased ground-water acidity or leaching of essential micronutrients

on root systems.

     Another important terrestrial effect of acid deposition may be on

cycling of nutrients by bacteria, blue-green algae, and fungi.  For

instance, pHs of 3.2 inhibit mineralization of glucose in soils, pHs of 3.0

to 4.0 reduce decomposition of plant litter, and pHs below 6.5 decrease

sulfur reduction in soils.  Because cycling of nutrients is such a critical

function of the biosphere, any adverse effect could be significant. More

research in this area is needed, particularly in wetlands, lake and river

sediments, and terrestrial soils.

     Lichens are apparently quite sensitive to S02«  In some areas, they

have merely been depleted; in others, the species have changed.

Agricultural plants are sensitive to acid deposition in the laboratory, but

effects on actual crops are much less clear, possibly because most crops

are annuals and are fertilized routinely.  Some recent field experiments,

however, have shown large decreases in yield.  Forests might be expected to

show more clear-cut effects of acid deposition, because trees are

perennials, are usually not fertilized, and often grow in soils whose

levels of nutrients are low.  Although forests in numerous areas receiving

heavy loadings of acid are growing less rapidly now than earlier, it is

very difficult to ascribe these changes uniquely to acid deposition.  More


                          ACID RAIN PANEL REPORT

recent data from Germany (not reviewed in the Final Report)  have suggested

that acid deposition affects forest growth significantly and support the

conclusion that the major effect is on roots, not foliage.

     Acid deposition probably does not affect terrestrial wildlife

directly, but may influence it indirectly via decreased plant growth or

contamination by metals.  Soil bacteria and fungal microrhizae may also be

affected by acidified soils; because both are important in cycling

nutrients through terrestrial ecosystems, affecting them would affect the

entire ecosystem.

     It is still difficult to estimate economic effects of acid deposition

on the terrestrial biosphere.  It is also not yet possible to map forest

sensitivity to acid deposition.  Nevertheless, it appears that acid

deposition has increased rates of podzolization in forests of eastern North

America.  Such changes are extremely rapid in the context of historic soil

development and thus represent an important alteration of the biosphere.

     Human health and visibility

     In general, this chapter is done well.  We accept the assertion that

acidic deposition does not directly affect human health.  Even indirect

effects such as increases in aluminum or lead in water supplies appear to

have no immediate health effect, although they should be monitored.

     On the other hand, degradation of visibility by fine-particle acidic

aerosol is real and widespread.  While it is true that its effects show up

most clearly in the West, where virtually unlimited visibility surrounding

scenic vistas is expected, we differ from Work Group 1 on the relative

                          ACID RAIN PANEL REPORT

importance of visibility there.  Preoccupation with the West is largely

cultural.  Eastern North America has many regions with great vistas which

are widely valued when seen.  When weighted for the larger number of people

in the East, we believe that maintaining visibility there is at least as

important as in the West.  Once one becomes attuned to atmospheric optics,

reduced visibility can be just as annoying over distances of 5 miles as

over 150 miles.

     Man-made structures

     In our view, this chapter is not required by the terms of reference

of Work Group 1.  It is interesting, however, and possibly important,

because cultural relics as well as modern structures are being corroded by

atmospheric chemicals.  This chapter points out, however, that most of the

damage to materials is probably caused by corrosive gases generated locally

rather than by regional pollutants or deposited acidity.  S02 (in

combination with adsorbed water) is the most important corroding agent,

followed by NOX and ozone.

     Methodologies for estimating economic benefits of controls

     We consider this chapter to be of limited value.  Its basic problem

lies in the first sentence of the summary:  "Traditionally, the

decision-making process has required an appreciation of the costs and

benefits associated with following a prescribed set of actions."  The

benefits of a properly functioning ecosystem are much more than matters of

dollars and cents, and are often not appreciated by people unfamiliar with

ecology.  To a large extent, our clean air and clean water depend on

                          ACID RAIN PANEL REPORT

ecological cycles.  Unfortunately, the inherent worth of an ecosystem, its

components, or the benefits associated with their maintenance can not

yet be expressed in terms of pure economics, nor are they liable to be in

the foreseeable future.

     Thus, we feel that this chapter is not helpful at the present time.

We also feel that its statement that current benefit-cost analyses must

"either omit real but intangible benefits or include a wide uncertainty

range" is overly bland and fails to deal with the real point of the

relevance of economics to ecological protection.

     Resource inventory

     In our view, the major result of this chapter is that it is presently

impossible to evaluate our natural resources accurately.  In the words of

Section 1.7.1, "The completion of this inventory has served to underline

the considerable weakness which exists in our ability to adequately

quantify the extent of the resource at risk."  We agree.


     We share with Work Group 1's mixed feelings about liming.  It is a

temporary solution which should be applied as sparingly as possible in as

few locations as possible.  Before wholesale liming is undertaken, careful

field studies of its aquatic effects are needed.

Did Work Group 1 meet its terms of reference?

     Work Group 1 was given eight specific terras of reference.  We now

review each of them.

                          ACID RAIN PANEL REPORT

     "identify and assess physical and biological consequences possibly

related to transboundary air pollution"  This was met well, for both

pollutants such as ozone and deposition of acidity.

     "determine the present status of physical and biological indicators

which characterize the ecological stability of each sensitive area

identified"  We are not sure whether the intent of this term of reference

was to evaluate the inherent stability of sensitive areas of eastern North

America (ecological stability is currently a controversial topic) or the

actual extent of changes in the various areas.  Work Group 1 seems to have

addressed the latter reasonably, but not the former.  Sensitive organisms

and their disappearance were treated in some detail.

     "review available data bases to establish more accurately historic

adverse environmental impacts"  Work Group 1 evaluated historic trends in

ecosystems at least as well as had been done previously, if not better.

Brown-water, hutnate-rich lakes and streams, however, which would have

rounded out their analysis, were ignored.

     "determine the current adverse environmental impact within identified

sensitive areas-annual, seasonal, and episodic"  This represents an

enormous undertaking.  This term of reference embodies the ultimate goal of

all studies about effects of acidic deposition.  Were the answer known, a

precise program of controls could be begun with full confidence. Work

Group 1 tried, but the two countries diverged concerning the dose-response

curve for deposited acidity.  In actuality, there are as many dose-response

curves as there are water bodies and ecosystems.  Some cases are known

accurately, but many more cases are completely unknown, and will remain so

for many years.


                            ACID RAIN PANEL REPORT

     "determine the release of residues potentially related to

transboundary air pollution, including possible episodic release from

snowpack melt in sensitive areas"  Work Group 1 dealt satisfactorily with

melting of snowpacks, but did not consider any other residues in detail.

     "assess the years remaining before significant ecological changes are

sustained within identified sensitive areas" Work Group 1 did this only

poorly, but it is exceedingly difficult to do at all.  It demands the

history of every ecosystem of interest from which to develop models for

testing.  Considering that every lake in eastern North America responds

individually to acid deposition, and even though helpful groupings can be

made, to perform this task quantitatively presents a formidable challenge

even for the next hundred years.

     "propose redactions in the air pollutant deposition rates-annual,

seasonal, and episodic-which would be necessary to protect identified

sensitive areas"  Work Group 1 tried this only for annual rates, and could

not agree on the value.

     "prepare proposals for the "Research, Modelling and Monitoring"

element of an agreement"  This was done satisfactorily.

     In summary, Work Group 1 met three of the eight terms of reference

well, two partially, and three poorly.  It seems to us, though, that the

failure to meet certain terms of reference was mostly a consequence of the

difficulty of the terms of reference.

                          ACID RAIN PANEL REPORT


     Work Group 2 produced a Final Report (2F) and four supporting

technical papers:

     2F-A  Atmospheric Sciences Subgroup Report

     2F-M  Regional Modeling Subgroup Report

     2F-I  Monitoring and Interpretation Subgroup Report

     2F-L  Local and Mesoscale Analysis Subgroup Report

     The first section below discusses some of the major topics dealt with

in these reports.  The next section offers remarks on the individual

reports themselves.  The last section considers whether Work Group 2 met

its terms of reference.

Remarks on Specific Topics

     Items of Concern

     In general, the reports of Work Group 2 are carefully done and

credible, and give a fair and balanced account of the state of current

knowledge of many meteorological and chemical aspects of acid deposition as

of 1982.  A great deal of effort was obviously put into them.

     Nevertheless, we have reservations about certain portions of these

reports.  The specific topics in question are the emphasis on modeling, the

modeling of sulfur only, the lack of data on dry deposition, and the

treatment of the linearity question.

     Our greatest concern is the emphasis placed on modeling—at the

expense of traditional scientific approaches—to deduce the relative

                          ACID RAIN PANEL REPORT

importances of local and distant sources of sulfur in air and in

deposition.  When Work Group 2 was formed, it was widely expected that

transport models could be developed to derive such source-receptor

relationships.  The reports make it abundantly clear, however, that the

models failed to furnish reliable source-receptor relationships.  The

creation of the Subgroup on Monitoring and Interpretation partway through

the work was an attempt to restore a balance between models and the more

traditional approaches, but it seems to have been too little and too late.

     We feel that Work Group 2 concentrated too heavily on sulfur.

According to the MOI terms of reference, Work Group 2 was to deal with "the

transport of air pollutants between source regions and sensitive areas" and

calculate how to "achieve proposed reductions in air pollutant

concentration and deposition rates which would be necessary in order to

protect sensitive areas."  The terms of reference do not mention any

specific pollutant.  But Work Group 2 modeled the transport and deposition

of sulfur only.  The nitrogen system, the other major contributor to

acidity in deposition, was not included.  Other gaseous and particulate

pollutants which are proven to be or are potentially injurious (ozone,

organics, metals, etc.) were relegated to a single chapter in the Final

Report.  In so doing, any relations between these pollutants and sulfate or

acidity were never clarified.  By delving deeply into the transport of

these other substances, much could have been learned about transport of

acidic materials.  Instead, the "other pollutants" were used merely as

additional examples of materials which can be transported across political

borders.  An interesting class of problems not considered by Work Group 2

is how pollutants interact to produce a given effect.

                          ACID RAIN PANEL REPORT

     In great contrast to wet deposition of sulfur and nitrogen, which is

now being measured routinely and accurately at many sites in North America,

dry deposition is far behind.  Reliable techniques are still being

developed; very little quantitative information is available.  From

quantitative measurements in a few calibrated watersheds (Hubbard Brook in

New Hampshire, for example), it is clear that dry deposition of sulfur is

important, because more sulfur arrives at the surface than can be accounted

for by precipitation alone.  But measurements of this type are

time-consuming, and hence too scattered to have provided any general

picture of dry deposition.  Without accurate dry-deposition velocities,

transport models are hardly more than educated guesses.

     Confusion about the definition of "linearity" is common in discussions

of acid deposition.  To its credit, Work Group 2 adopted a strict

definition and used it consistently.  Unfortunately, though, the difference

between this definition and the more common colloquial use of "linearity"

was not given.  As a result, Work Group 2's discussion on linearity can be

quite hard to follow.

     Long-range transport models

     Earlier in this chapter we stated that Work Group 2 placed far too

much emphasis on long-range transport models as the primary source of

information on transboundary transport of acidity.  To a large extent, the

terms of reference of Work Group 2 forced this emphasis upon its members.

The terms of reference of Work Group 2 (reproduced in Appendix 3 of this

report) indicate clearly that in August 1980 it was widely held that

transport models would soon be the most reliable way to understand

                          ACID RAIN PANEL REPORT

long-range transport.  The very first sentence of the Work Group's specific

terms of reference shows how central the models were to be:  "The Group

will provide information based on cooperative atmospheric modeling

activities leading to an understanding of the transport of air pollutants

between source regions and sensitive areas . . ."  Work Group 2 was also to

"provide initial guidance on suitable atmospheric transport models to be

used in preliminary assessment activities."  Only near the end of the terms

of reference were traditional scientific methods mentioned, and then in a

subordinate way:  "assess historic trends of emissions, ambient

concentrations and atmospheric deposition to gain further insights into

source-receptor relationships for air quality, including deposition."  Not

only do these terms of reference assign the responsibility strongly to

models, they also indicate no doubts that models would succeed.  This

orientation was even incorporated into the original title of Work Group 2,

"Atmospheric Modeling Work Group."

     The fraraers of Work Group 2 were not alone in their optimistic view of

models.  A similar opinion was elaborated somewhat in the recent OTA

(Office of Technology Assessment) report, "The Regional Implications of

Transported Air Pollutants:  An Assessment of Acidic Deposition and Ozone",

Interim Draft, July 1982:  "Transport models are the only practical

procedure available to estimate the relationship between areas of origin

and areas of deposition of long-range transport pollutants.  Large-scale

regional transport cannot now be measured directly for the large number of

sources of emissions and deposition regions of interest, and under the

variety of meteorological conditions needed to perform the analysis.

Models describing long-range transport of sulfur oxides have been available

                          ACID RAIN PANEL REPORT

for several years; preliminary models of nitrogen oxides transport are just

now being developed."

     The dominance of transport models was built into the structure of Work

Group 2.  Although meteorologists and measurement specialists were

originally included in the Group, their presence was intended primarily to

provide data for the modelers and only secondarily to allow independent

assessments of the source-receptor relationship.  Subsequently, Work Group

2 was restructured to give a larger role to scientific approaches other

than modeling.  It was then given a new title, "Atmospheric Sciences and

Analysis", which better reflected its new composition.  Separate reports on

atmospheric sciences and monitoring were issued.

     Work Group 2 treated its long-range transport models thoroughly and

fairly.  Assumptions of the models are well articulated, characteristics of

the models are displayed in detail in an extensive table and elaborated in

the text, and results are presented both as raw output and in partially

digested form.  We would have preferred, hoxrever, to see the results of the

models summarized more fully than they were, and their implications

explored more deeply.  The Final Reports of Work Group 2 spent too much

time comparing the models and not enough time evaluating the meaning of

their results.

     Final Report 2F comments on the diversity of approaches and parameters

in the eight models.  We wish to stress again just how different the models

can be; the differences have significant consequences.  For example,

consider the transformation rate of S02 to sulfate.  While values in all

the models average about 1% per hour, some models assume a constant 1% per

                          ACID RAIN PANEL REPORT

hour, others have different rates for winter and summer, and others have

diurnally varying rates which can range from 0.1 to 5.5% per hour.  Winds

are also handled very differently by the models.  Some use long-term means

or statistics, others calculate them every 3-6 hours; some average through

a mixed layer, others use discrete levels.  Mean trajectories from Sudbury,

Ontario and St. Louis, Missouri during January and July 1978 (Report 2F-M)

reflect these differences by showing surprisingly wide divergence between

the models.  Even the monthly-mean trajectories spread over angles of

30-60°.  In one case, the angle was well over 90°, as the trajectory of one

model went westward while the others went eastward.

     The strengths of transport models are well known and need no further

comment here.  The important result to be recognized by all who seek to use

models as an aid in understanding or as part of decision-making is that

their overall performance is still marginal and their value is still

limited.  In most discussions of models to date, this point has not been

stressed.  To its great credit, Work Group 2 pointed this out clearly (with

the one exception discussed below).  The more dominant the role given to

models, the more important it is to be fully cognizant of their


     The following limitations of the long-range transport models used by

Work Group 2 need to be kept in mind:

     (1) With one exception, they consider only sulfur.  The roles of

nitrogen, ozone and the hydrocarbons, all of which are intimately involved

in the atmospheric processing of sulfur compounds, are not considered


                          ACID RAIN PANEL REPORT

     (2) Only linear chemistry is included.  In the real atmosphere,

rates of chemical reactions may be highly nonlinear, at least on the small

scale.  On larger scales of distance and time, however, fluctuations in

rate may average to a pseudo-linear behavior.  In Chapter 4 of Report 2F,

the performance of the transport models relative to the nonlinear ambient

system is acknowledged as follows:  "The reaction rates are nonlinear with

regard to S02 because the free radical concentrations are not constant over

time and space.  The LRT models, therefore, may not correctly predict the

quantity and the deposition patterns of H2S04 formed through the gas-phase


     (3) Cloud chemistry, which is now emerging as an extremely important

part of the sulfur cycle, is not considered by any of the eight transport

models.  Work Group 2 has, though, attempted to assess the implications of

this new information (the most important of which is that the majority of

the oxidation of S02 fflay take place in the aqueous phase in clouds) to

control strategies in Chapter 4 of Report 2F.  Among other things, they

concluded that, "Since the LRT models do not employ the 1^02 and Oj

concentration fields, which have important spatial-temporal variations, it

is unlikely that they can correctly predict the present quantity and

deposition patterns of H2S04 formed through aqueous-phase reactions."

Thus, the models cannot handle either gas-phase or aqueous-phase oxidation


     (4) Because dry deposition of S02 and sulfate cannot be measured at

present, their simulation by the transport models cannot be verified.  The

absence of dry deposition of S02 and sulfate, which is now considered

comparable to wet deposition of sulfate, is particularly important.


                          ACID RAIN PANEL REPORT

Ultimately, variable dry-deposition velocities will probably be required to

simulate long trajectories in eastern North America which pass over areas

with different surface characteristics.  Only one MOI model incorporated

surface-dependent rates of dry deposition (UMACID), and that model was not

among the most "successful" ones.

     (5) Background deposition is not handled adequately.  According to

the Executive Summary of Final Report 2F (Chapter II), "The role of natural

or very distant anthropogenic sources of acidity in eastern North America,

although likely to be small, remains to be clarified in order to determine

what 'background' deposition to use in constructing atmospheric models of

source-receptor relationships."

     (6) There are meteorological limitations as well.  For example,

the Executive Summary recognizes one of the well-known problems with

air-mass trajectories:  "Back air-trajectories analyses are unable to

distinguish between near and more distant sources within the same

directional sector and cannot be used to trace an air-inass trajectory

during periods of weak, variable air flows or over very long distances."

     Another meteorological problem is concerned with simulation of air

movement at the top of the mixed layer.  The eight transport models

evaluated by Work Group 2 assumed that emissions were dispersed into the

mixed layer, whose top is typically one kilometer, and remained there.  In

summer, when wet deposition of sulfate is greatest in the Northeast,

cumulus clouds commonly draw air out of the turbulent mixed layer and into

the more laminar air above.  The time required to process a given parcel of

air in this way is typically 0.5 to 1 day.  Thus, there can be a sink for

                          ACID RAIN PANEL REPORT

SC>2 at the top of the mixed layer which is comparable to or greater than

dry deposition at the surface.  This upper sink is not included in any of

the eight transport models.

     Linearity and nonlinearity

     The question of "linearity" was given a somewhat confused treatment by

Work Group 2.  This is unfortunate, because the concept of linearity is

extremely important to formulating a strategy to reduce deposition of

sulfate.  Linearity is used and understood differently in different

branches of science, and has colloquial usages which differ from the

scientific definitions.  To its credit, Work Group 2 chose a single usage

and stuck to it.  They could have eliminated a great deal of confusion,

however, by stressing their definition more and explicitly describing how

it differed from other current usages.

     Work Group 2 never defined linearity directly.  The closest they came

was in Appendix 3 of Final Report 2F, where a linear model is defined as

one "where all the interrelationships among the quantities involved are

expressed by linear equations which may be algebraic, differential, or

integral."  This is essentially the definition of a linear system as one

whose variables are related only by linear equations.  To this should have

been added the definitions of the three types of linear equations, for

there are differences among them.  For example, a linear algebraic

equation is one whose variables appear to the first power only and have

constant coefficients, i.e., cannot involve other variables.  In linear

differential equations, however, the coefficients of the dependent variable

and its derivatives may be functions of the independent variable.

                          ACID RAIN PANEL REPORT

     Work Group 2 used linearity in a  restrictive fashion.   While  they

allowed the coefficients in a rate equation to contain other variables (see

pages 4-1 and 4-2 of Final Report 2F,  for example),  they required  these

variables to reaain constant.  If they did not, the  systea was considered

nonlinear.  According to Work Group 2's definition,  the sulfur system in

the atmosphere will be linear when the rates of its  reactions and

depositions are first-order in SC>2 or  sulfate and have constant

coefficients.  If, for example, the rate of oxidation of SC>2 is found to

involve any other atmospheric species  whose concentration can vary (such as

the hydroxyl radical) or any meteorological variable such as sunlight or

humidity, the sulfur system must be considered nonlinear.  By this

definition, it is in fact nonlinear, because the oxidation of S02  is known

to be a complex function of sunlight,  moisture and co-pollutants.

Alternatively, if the concentration of any sulfur species, in either the

atmosphere or deposition, is found to  depend on the  abundance of any

chemical variable, the sulfur system in the atmosphere is nonlinear.

(Again, it is clearly nonlinear.)

     The problem with this use of linearity is that  it corresponds to

neither the standard algebraic nor differential definitions given above.

It is rather like the algebraic form applied to a differential equation.

Work Group 2 should have pointed this  out.

     Work Group 2's definition of linearity for atmospheric sulfur

corresponds to the common, or colloquial, use in which a given change

in S02 emissions produces the same percentage change in sulfate or sulfate

deposition.  The recent National Research Council (NRC) report on acidic

deposition in eastern North America examined whether the sulfur system


                          ACID RAIN PANEL REPORT

there was linear in this sense.  Linearity in the colloquial sense is a

critical issue in deciding whether to bear the heavy expense of reducing

sulfur emissions nationally.  Everybody agrees that the sulfur system is

nonlinear in Work Group 2's sense.  'The important sense is to determine how

much one can reduce deposition by reducing emission, i.e., how nearly

linear the sulfur system is on the temporal and spatial scales of eastern

North America.

     An expanded discussion of the effect of scale on (colloquial)

linearity would have been useful at this point.  On the global scale, the

sulfur system is clearly linear, for all the sulfur emitted is deposited

(sulfur does not accumulate in the atmosphere the way longer-lived

constituents such as carbon dioxide and the Freons do).  On the smallest

scale, sulfur is highly nonlinear (again colloquially), for it is easily

transported away from the point of emission.  On intermediate scales, such

as the size of eastern North America, the degree of linearity must be

intermediate.  In this sense, we find the report of the NRG committee most

interesting, for it judged the most probable value in the northeast to be

80% linearity, with the range of possible values being 50 to 100%.

     The source-receptor relationship

     The source-receptor relationship (discussed explicitly in the Regional

Modeling Subgroup Report 2F-M) is implicit throughout all the material on

modeling.  Work Group 2 recognized that this relationship forms the basis

of all control strategies for acid deposition, and that the present

uncertainties in our knowledge of this relationship may strongly affect

recommended courses of action.  Thus, Work Group 2's conclusion that the

                          ACID RAIN PANEL REPORT

source-receptor relationship is poorly known beyond the simple

demonstration of long-range transport is potent and must be reckoned with.

Essentially all the MOI modeling was an attempt to define the

source-receptor relationship as well as possible with current tools.

     Local vs. distant sources

     This important topic is treated fairly in both the Local and Mesoscale

Analysis Subgroup Report (2F-L) and the Final Report (2F).  The potential

importance of local and regional sources, as well as distant sources, is

clearly recognized and stated.  At the same time, the relative scarcity of

data on nearer sources is noted, and more research is called for.

     More could have been done, however.  Inspection of the transfer

matrices of the eight models shows clearly that six of them predict broadly

equal contributions from regional and distant sources to suspended and

deposited sulfate in the sensitive regions of New York and New England.

Even though it is presently impossible to verify these predictions, the

similarities from such different models when entire source regions are

considered is an important property.  This is an example of the kind of

result from models which will eventually guide policy.

     Effect of uncertainties in emissions on transport models

     Chapter 2 of Final Report 2F summarizes the emission data used by Work

Group 2 in its regional transport models.  The treatment for this topic is

brief and straightforward, presumably because emission data for S02 is the

least controversial aspect of  transport modeling.  We agree.

                          ACID RAIN PANEL REPORT

     Nevertheless, we find the passing reference to uncertainties in

emissions — a single sentence near the end of Chapter 2 — a bit too casual.

Work Group 2 took Work Group 3B's emission uncertainties at face value.

We feel that they should have at least commented on them.

     In the Final Report of Work Group 33, the uncertainties in total

United States emissions of S02 and NOX are claimed to be less than 3%.  For

Canada, the figures are estimated at 6 and 10%, respectively.  Relative

uncertainties in S02 emissions from single states range from 10% for the

larger emitters to 20% for the smaller emitters.  Within a state or

province, the uncertainty in emission of S02 from a given class of source

varies from roughly 15 to 100%, with the largest sources generally having

the smallest percentage uncertainties.  Uncertainties of individual sources

appear to be in the same range.  Uncertainties in NOX emission are

generally larger than those for
     While it is difficult to find any particular flaw in the method used

by Work Group 3B to evaluate uncertainties, we feel that the results are

generally optimistic.  For example, we are extremely reluctant to believe

that total United States emission of SC>2 is known to 3%.  We also feel that

very few point-source emissions are known to 15%.

     Nevertheless, uncertainties in emissions are surely much lower than

those in other aspects of acid deposition and associated transport models.

For example, the best natural emission estimates for S02 in eastern North

America are at least an order of magnitude smaller than currently estimated

anthropogenic emissions.  Dry deposition of SC>2 , which is commonly believed

to be comparable to wet deposition of sulfate, is hardly more than guessed

                          ACID RAIN PANEL REPORT

at for natural ecosystems.  Thus, outflow of sulfur to the Atlantic Ocean,

which is the difference between total emission in eastern North America and

total deposition there, is also not well known.  Limitations like this led

Work Group 2 to state in its Executive Summary (Chapter 11 of Final Report

2F) that wet deposition, dry deposition, and outflow of sulfur to the

Atlantic are all "roughly equal."  Considering the large differences in

assumptions and parameters of the various transport models, the differences

in their results, and the unknown absolute accuracy of any of them, we

conclude that uncertainties in regional emissions are not likely to be the

limiting factor in developing and evaluating transport models for many

years to come.

Remarks on individual reports

     Final Report (2F)

     The Final Report (2F) of Work Group 2 is a fair and accurate summary

of the several supporting documents.  It is written well.  Many of the

remarks of the previous section refer to this report.

     The Final Report discusses the various transport models evenhandedly.

Their limitations are stated directly.  The strengths and weaknesses of

transfer matrices are discussed clearly at the outset.  Where the report is

not intended to justify exhaustively certain aspects of the models (e.g.,

the discussion of deposition in Chapter 5), it says so.

     We recommend that serious evaluation of the results of Work Group 2 be

based on its entire product, i.e., the four subgroup reports as well as

the Final Report.

                          ACID RAIN PANEL REPORT

     Final Report - Atmospheric Sciences Subgroup (2F-A)

     The report of the Atmospheric Sciences Subgroup does not pretend to be

comprehensive, and should not be judged as such.  Rather, it was intended

to provide "some information to Memorandum of Intent modelers in areas of

particular concern."  It consists of four articles.  The first two are

detailed, thorough and accurate, and were written expressly for the MOI

work.  The last two, on dry deposition and precipitation scavenging, are

executive summaries from the EPA Critical Assessment Review Papers, and

were added later.  Brief summaries of each are given below.

          Paper 1 -"Sulfur and Nitrogen Chemistry in Long-range Transport

          Models" by J. L. Durham et al.

     This paper contains a detailed and accurate summary of homogeneous

(gas-phase) and heterogeneous (in water or on solid particles) chemistry of

nitrogen and sulfur.  Nitrogen chemistry in the presence of hydrocarbons is

summarized as follows:  "the major observed phenomenon in the system is

conversion of NO to N02 • • • accompanied by accumulation of 03."  This

section contains considerable discussion of various reaction rates, but

with no conclusion that any particular values can be applied generally.

     The complexities of oxidation of S02 are also covered in detail.

After concluding that gas-phase oxidation of 302 maY ^e dominated by the OH

radical in both the clean and polluted troposphere, the writers note that

the maximum rates of oxidation of S02 observed repeatedly in polluted

atmospheres cannot be accounted for even by summed gas-phase reaction

rates.  Except for organics, the rates of oxidation of S02 in droplets are

                          ACID RAIN PANEL REPORT
fairly well understood.  Oxidation by 1^2 is the only reaction fast enough

to produce potentially important amounts of H2S04 in the troposphere.  The

role of metallic catalysts in aqueous oxidation is still poorly understood.

The only important heterogeneous reaction on the surfaces of solid aerosol

particles involves soot.

     Do field and laboratory studies agree?  The paper states that

"uncritical acceptance of all of the rates (in a sample calculation) . . .

would lead to the S02 conversion rate exceeding 40% per hour.  However, if

only the well-established rates are considered, the S02 conversion rate

becomes < 1.1% hour"*-." The uncertainty in this calculation can be

contrasted with other statements from this paper:  "Field measurements on

the rates of S02 oxidation indicate that maximum S02 oxidation rates of the

order of 10% per hour are typical of many atmospheric pollution scenarios,"

and "the average diurnal rate is 1% per hour."  In other words, this paper

amply confirms that great uncertainties still exist in the measurements and

even in the mechanisms for oxidizing S02 to H2S04 , and implies that it will

be a long time before these uncertainties are removed.

          Paper 2 -"The Seasonal Dependence of Atmospheric Deposition and

          Chemical Transformation Rates for Sulfur and Nitrogen Compounds"

          by M. Lusis and L. Shenfeld.

     A one-sentence summary of  this comprehensive collection of seasonal

data is given on their page 2-31:  "It must be concluded that at present

the available plume data is too conflicting to draw any firm conclusions

about the seasonal dependence of the 302 oxidation rate in plumes."

                          ACID RAIN PANEL REPORT

           Paper 3 -"Dry Deposition of Acid Substances" by B. Hicks.

     Its opening sentence describes the situation succinctly:  "Recent

workshops and committee deliberations have agreed that is is not possible

to monitor the dry deposition of acidic atmospheric materials directly."

The paper also outlines the difficulties and problems in any other


           Paper 4 -"Precipitation Scavenging Processes" by J. Hales.

     This paper is not actually a product of the United States-Canadian

Work Groups, but rather the Executive Summary from the EPA Critical

Assessment Review Paper on Acid Deposition.

     We note that this review of atmospheric science material (2F-A) was

"prepared and compiled for the purposes of providing some background and

support for the modeling work" (emphasis added).

     Final Report - Regional Modeling Subgroup (2F-M)

     This report is well-written and makes its points clearly.  Assumptions

in techniques and limitations of results are given adequately.  The

performance of each of the eight models is reviewed in detail.  The

conclusions drawn are reasonable.  The writers were wise to include as much

raw data as they did, particularly in light of the critical role that

models were expected to play at the outset of the MOI process.

     More specific remarks on modeling are given above.

                          ACID RAIN PANEL REPORT

     Final Report - Monitoring and Interpretation Subgroup (2F-I)

     This is a very good treatise, which generally meets its terms of

reference.  It is an excellent introduction to the deposition program  and

its interpretation.

     In spite of its length, we have the distinct impression that  much of

the literature surveyed here is still under-interpreted.  (We have the same

feeling about much of the other MOI material, as well.)   Apparently, the

field of acid precipitation is growing so rapidly and its practitioners ara

so active that it is difficult to find qualified people  who have enough

time to synthesize it into a coherent whole.  This is one of the great

needs at present.

     The section on "Preliminary data interpretation" seems a bit  forced.

We would have preferred a briefer treatment of the ways  to interpret data,

followed by a deeper interpretation of available data.  The Monitoring and

Interpretation Subgroup had a golden opportunity to illustrate the role

that innovative scientific thought can play in the acid-deposition question

and should have been given more resources to do so.  Considering that  this

subgroup almost did not exist, though, the product is quite acceptable.

     Proper interpretation of monitoring data, however,  requires critical

attention at each step.  For example, the use of single-station sector

analysis as an independent way to derive source-receptor relationships has

several limitations which may temper one's conclusions:   (1) Because many

air-mass trajectories are curvilinear, they may originate in a different

sector than indicated by their final direction.  (2) The method is

inherently episodic—conclusions may be influenced greatly by the


                          ACID RAIN PANEL REPORT

selection of incidents.  (3) Wet deposition is a function of volume of

precipitation, as well as trajectory.  (4) Local and distant sources cannot

be distinguished by sector analysis alone.  It is not clear that the

Monitoring and Interpretation Subgroup considered these factors fully.

     The section on temporal trends of deposition and its relation to

trends in emission could have been expanded and refined.  This critical

topic needs a great deal more attention and more data.  The record is very


     The treatment of "other substances" was superficial, as it was in the

Summary Report.  Organic materials were treated better than ozone and


     The report offers seven recommendations concerning deposition

monitoring.  Because a solid data base is so important to understanding

deposition, we endorse these recommendations strongly.

     Final Report - Local and Mesoscale Subgroup (2F-L)

     This report is excellent.  Its literature review is thorough and

digested.  The relevant models and their characteristics are documented in

detail.  Scientific knowledge and models derived from this evidence are

presented in a balanced fashion.  The potential weight of local and

uiesoscale effects relative to long-range effects is shown carefully.  The

present limitations of local and mesoscale analysis are given, together

with recommendations for future work.  This fine report should serve as the

basis for renewed interest in local and mesoscale effects.

                          ACID RAIN PANEL REPORT

Did Work Group 2 satisfy its terms of reference?

     The seven (six originally plus one added later) terms of reference for

Work Group 2 are given in Appendix 3 of this report.  Three were related

directly to transport models.  Ironically, we believe that Work Group 2

satisfied the other terras of reference, but not those associated with

transport models.  In the paragraphs below, we discuss each term of


     "identify source regions and applicable emission, data bases"  This was

done satisfactorily, with data supplied by Work Group 3B.

     "evaluate and employ available field measurements, monitoring data and

other information"  This term of reference was met, both by using field

studies to help understand transport (Monitoring and Interpretation

Subgroup Px.eport) and by using the monitoring data to help evaluate the

transport models.

     "assess historic trends of emissions, ambient  concentrations and

atmospheric deposition trends to gain further insights into source-

receptor relationships for quality, including deposition"  This was done,

primarily by the Monitoring and Interpretation Subgroup; however, much

more could have been done.

     "prepare proposals for  the "Research, Modelling and Monitoring"

element of an agreement"  Thirteen proposals appear in Chapter  11 of Final

Report 2F.

     "evaluate and select atmospheric transport models and data bases  to be

used"  This term of reference was met in  the sense  that eight available


                          ACID RAIN PANEL REPORT

transport models were selected for further consideration.  To the extent

that the performances of the eight models were to be evaluated and at least

one selected with confidence for further use, this goal was not met.  As

stated in the preface to the Regional Modeling Subgroup Report (2F-J1), "In

view of significant uncertainties in the model input and validation data,

which could not be quantified within the time allotted for preparation of

this report, no recommendations on the absolute performance of the regional

models can be made at this time."  In other words, all eight models were

considered unverified and unverifiable.

     "relate emissions from the source regions to loadings in each

identified sensitive area"  This task was fulfilled in the narrow sense

that calculations were run with each model.  Work Group 2 made it quite

clear, however, that the results of this exercise were not considered

reliable.  Thus, this term of reference was not met.  For example, the

Executive Summary (Chapter 11 of Final Report 2F) states:  "The transfer

matrices of the different models exhibit variations among the magnitudes of

the transfer matrix elements.  This variability could lead to substantial

differences in the selection of optimum emission reduction scenarios

depending upon the particular model applied and the level of detail

required. ...  It has not been possible to date to choose a 'best model1

among the eight or to produce with confidence a 'best estimate'  single

transfer matrix for each variable based upon a valid statistical analysis

of all model results."

     "calculate emission reductions required from source regions to achieve

proposed reductions in air pollutant concentration and deposition rates

which would be necessary in order to protect sensitive areas"  Work Group 2


                          ACID RAIN PANEL REPORT

stated that it had not met this term of reference.  According to Chapter 4

of Final Report 2F, "it is unlikely that they (the models) will correctly

predict the resulting changes in dry and wet deposition patterns due to

reductions in concentrations of SC>2, H-2^2» or both."  From the Executive

Summary:  "The adequacy of available models to predict the results of

alternative emission patterns is uncertain."

     In this context, we are puzzled by a statement in the Executive

Summary which is both self-contradictory and in opposition to other

conclusions of Work Group 2:  "Work Group 2 has provided the kind of

'operational tools' required for calculating emission reductions required

to achieve concentrations and deposition rates necessary to protect

sensitive areas; however, the Work Group has not been able to provide

definitive guidance concerning a preferred model or the quantitative degree

of confidence that can be placed in any of the individual models."  How can

a model be an "operational tool" if its accuracy is unknown?  Work Group 2

has not provided the kind of operational tools which can be used to select

control strategies for 862•  Work Group 2 has evaluated eight preliminary

models, some of which may, with considerable refinement, someday become

true operational tools.

     Similar conclusions about models have been drawn by others.  The OTA.

report cited above quotes a report by the Utility Air Regulatory Group

(UARG) on five  transport models to the effect that they "cannot, at the

present time, provide adequate information that would assist in

distinguishing between policy options."  On the other hand, the UARG review

also concluded  that "the best available methodology currently available for

                          ACID RAIN PANEL REPORT

investigating the transport, transformation, and deposition of atmospheric

pollutants on a regional scale involves the use of long-range transport


     In our opinion, the inadequate performance of the eight transport

models should not be considered the fault of the modelers or of the models.

The models were the state-of-the-art for that time.  Their failure meant

merely that they were asked to do too much too soon in their development.

This result supported those members of Work Group 2 who maintained from the

beginning that decisions for reducing acidic deposition should not be based

solely on information which had been processed through models.  It now

appears that it will be a good many years before transport models will be

ready to assume the responsibility accorded them in August 1980 in the MOI

terras of reference.

     Information from tracers
     The outlook for understanding the source-receptor relationship, even

when distant sources are involved, may not be as bleak as it would appear

from transport models alone.  Tracers may provide an independent way to

derive such information.  To date, the accuracy of transport models has

been impossible to verify because sulfate from one region cannot be

discriminated from sulfate from another region.  But additional substances

which can be linked with one or another region offer ways to deduce the

regional origins of sulfate in air or in deposition.

     Tracers may be pollutants already present (referred to as "natural"

tracers in Chapter 8 of Final Report 2F) or substances introduced

deliberately.  Both types of tracers may be of great value, as acknowledged


                          ACID RAIN PANEL REPORT

in Chapter 8, and are being developed intensively at present.  Deliberate

tracers, such as SFg, heavy methanes, or perfluorocarbons,  have been

exploited longer than the other type, but may be more limited in the long

term because they are usually long-lived gases whose atmospheric behavior

does not mimic that of the sulfur system.  The principal usefulness of

these tracers is to study large-scale trajectories and diffusion.

     Pre-existing tracers, especially those involving minor elements in the

aerosol, may offer more direct information on sources and transport of

atmospheric sulfur.  Trace elements have been used successfully to

determine the relative importances of various sources of urban aerosol.

This approach is generally referred to as "urban receptor modeling" or the

"chemical element balance" method.  Curiously, receptor modeling was not

mentioned by Work Group 2.  One possible reason is that urban receptor

modeling is not directly applicable to acid precipitation,  whose scale is

hundreds or thousands of kilometers and where regions rather than

individual stacks are the relevant sources.

     Regional-scale source apportionment for aerosols is developing

rapidly.  It is now known that aerosols from several source regions in

eastern North America have characteristic elemental signatures that can be

followed and discriminated hundreds of kilometers downwind.  With proper

care, the major source areas for secondary constituents such as sulfate can

also be determined with reasonable confidence.

     It would thus appear that tracer techniques, singly or in combination,

offer an alternative way  to deduce the source-receptor relationship, and

that transport models need no longer be relied upon exclusively.

                           ACID RAIN PANEL REPORT
                         AND ENGINEERING ASSESSMENT
Organization of report

    Work Group 3B was given three major charges:  to identify control

technologies (pollutants unspecified) and determine their costs, to

evaluate emissions (present emissions, better estimates of past trends, and

most probable future emissions), and to prepare proposals for research and

development projects aimed at improved control of emissions.  Accordingly,

the report is built around these three principal topics.  Emissions receive

nearly 200 pages of text, control technologies just over 100 pages, and

research and development nearly 50 pages.  Most attention goes to S02, with

NOX second, and all other pollutants a distant third.  "Other pollutants"

as a group are given less than 30 pages.

General remarks

    This report contains a huge amount of information.  Clearly, a great

deal of work has gone into preparing it.  It will be of much use to many

persons and agencies.

    Unfortunately, however, it contains major flaws which limit its value

significantly.  The quality of writing and organization is very poor,

certainly the worst of the three reports this panel reviewed.  This is not

just an academic matter, for the report is very difficult to read,

understand, and deal with.

For example, the Table of Contents is very difficult to use.  The

headings are often insufficiently descriptive, if not misleading or wrong.

                          ACID RAIN PANEL REPORT

The organization and titling of the chapters and sections make the report

very difficult to use.  For example, as Chapter A is currently

organized, it is nearly impossible for the reader to sense the true

organization of the report as a whole.  Chapcer 3 is nisleadingly entitled

"Trends in Emissions", when its most important section, current emissions,

is not a trend.  Chapter C, on control technology and costs, should have

been so labeled instead of the inappropriate "Emission Source Sectors."

     The report has not been carefully edited; it is full of misspellings,

poor grammar, and cumbersome expressions.  In Appendix A, the reader is

referred to Chapter C for the 1980 emissions, when they are actually in

Chapter B.  A problem with incorrect word-processing technique following

subscripts occurs throughout.  Again we stress that the net effect of all

these errors is to make Report 3B much less readable than it should be.

     The report is more a compendium of facts than a digestion of them.

Perhaps this resulted from the size of the task relative to the

resources and deadlines.  If so, it would be regrettable.   We note that

this report appeared several months before those of Work Groups 1 and 2

(June 1982 vs. January 1983 and November 1982, respectively).

     It is true that matters of emission and control tend to be more

cut-and-dried than those of atmospheric transport, transformation,

deposition, and interaction with the biosphere, but this is no reason to

subjugate critical thought and reasoning to the extent that the writers of

report 3B have.  For example, we are offered the emission inventory for

1980, together with a detailed discussion on how it and its uncertainties

were calculated.  For the United States, the probable errors in both S02


                          ACID RAIN PANEL REPORT

and NOX are given as about 3%.  These figures are not discussed further,

even though they are almost certainly far too low.  The projected emissions

are not seriously questioned, as they should be.  The recommendations for

research and development are merely listed, without any attempt to rank

them in terms of inherent value, promise, etc.  It is widely assumed that

emissions are the best-known component of the entire acid-rain phenomenon.

The writers of report 3B had an opportunity to comment on this topic, but

missed it.

     Most importantly, the writers have offered us no statement on what

their report means.  Decision-makers in both the United States and Canadian

governments, who often do not have technical backgrounds, need such a

section.  As a result of its absence, intermediaries less familiar with the

original data will have to try to determine the meaning of this report for


Remarks on specific topics

     Identifying control technologies and costs

     In our view, report 3B identifies all relevant control technologies

and assesses their costs reasonably.  In this sense, the report is a very

useful handbook, although perhaps unduly pessimistic about prospects for

improvements in control technologies.  Unit control costs (per kilogram of

sulfur) vary by nearly a factor of 100, but the report does not develop the

implications of this important finding.

                          ACID RAIN PANEL REPORT


     Methods of calculating past emissions appear to be reasonable,

although little detail is given.  We note that the report does not say

whether its historical trends are considered superior to other published

trends, or even different from them.  Recall that one of the terms of

reference was to generate "improved" historical trends.

     The estimates of current emissions also seem reasonable, as do' the

methods used to arrive at them.  As noted above, the uncertainties seen

quite low, especially for the United States as a whole.  Here the

methodology may be questionable.  The technique used for combining

uncertainties requires errors to be random and nonsystematic; probably

neither condition is satisfied in practice.  Consequently, we believe that

the actual uncertainties may be several times greater than those given in

the report.

     Concerning projected emissions of S0£ and NOX, we note that report 3B

offers a single way of calculating each, without documenting that this

scenario is indeed the most probable, as specified in the terras of

reference.  We fully realize the large effort involved in making

projections, but feel that their results are insufficiently supported.

Reasons for choosing one scenario or model over another should be given.

In addition, the effect of variations of several key parameters should be

considered, such as the rate of increase in generating electricity, the

degree of switching from oil to coal, the extent of replacing older power

plants by newer ones with tighter emission controls, and the mix of NOX

                           ACID RAIN PANEL REPORT

emission characteristics for new vehicles.  To the extent that projections

are intended to help plan for the future, the effects of reasonable

variations in these parameters would be useful.

     Concerning research and development, we found it interesting that Work

Group 33 spent considerably more effort in identifying and tabulating

current projects than it did in proposing new ones or areas of

concentration for the future.  The list of areas for future research cited

here is too long to be regarded neutrally; the projects must be ranked or

rated in some way.

     The report indicates that per capita emissions of S02 are twice as

large in Canada as in the U.S., but the implications are not developed.

Did Work Group 3B meet its terms of reference?

     Work Group 3B was given six terms of reference, on three topics; one

was deleted by the Work Group.  We feel that three of the five remaining

terms of reference were met.  We now list each term of reference and

whether it was met:

     "identify control technologies, which are available presently or in

the near future, and their associated costs"  This was met partially.  The

report lists unit costs, but does not project costs for any abatement


     "review available data bases in order to establish improved jiistorical

emission trends for defined source regions"  Some data bases were reviewed;

the report does not say whether all were.  Historical emission trends

                          ACID RAIN PANEL REPORT

for source regions were produced, but the report does not specify whether

they are considered better than earlier trends.  Consequently, this term of

reference was not met.

     "determine current emission rates fron defined source regions"  This

was met satisfactorily.

     "project future emission rates from defined source regions for most

probable economic growth and pollution control conditions"  Emissions were

projected from specific source regions under a certain growth pattern and

for the present degree of pollution controls.  It was not stated whether

the conditions for economic growth or pollution control were the most

probable ones.  Therefore, this term of reference has not been met.

     "prepare proposals for the "Applied Research and Development"

element of an agreement"  This was met satisfactorily, but without any

ranking of proposals.

                          ACID RAIN PANEL REPORT
                                APPENDIX 1
                        AND SCIENTIFIC DISCIPLINES
                       ACID RAIN PEER REVIEW PANEL

    William A. Nierenberg                             Physicist-
    Director                                            Oceanographer
    Scripps Institution of Oceanography
    La Jolla, California

Vice Chairman

    William C. Ackermann                              Civil Engineer
    Department of Civil Engineering
    University of Illinois
    Urbana, Illinois


    David H. Evans                                    Fish Physiologist
    Department of Zoology
    University of Florida
    Gainesville, Florida

    Gene E. Likens                                    Ecologist
    Section of Ecology and Systematics
    Cornell University
    Ithaca, New York

    Ruth Patrick                                      Limnologist
    Department of Limnology
    Academy of Natural Sciences
    Philadelphia, Pennsylvania

    Kenneth A. Rahn                                   Atmospheric Chemist
    Center for Atmospheric Chemistry Studies
    Graduate School of Oceanography
    University of Rhode Island
    Narragansett, Rhode Island

    F. Sherwood Rowland                               Atmospheric Chemist
    Department of Chemistry
    University of California
    Irvine, California

                          ACID RAIN PANEL REPORT
                           APPENDIX 1. CONTINUED
Members, continued

    Malvin A. Ruderraan                                Physicist
    Department of Physics
    Columbia University
    New York, New York

    S. Fred Singer                                    Environmental
    Department of Environmental Sciences                Scientist
    University of Virginia
    Charlottesville, Virginia

Executive Secretary

    John K. Robertson                                 Geochemist
    Science Research Laboratory
    U. S. Military Academy
    West Point, New York

Office of Science and Technology Policy

    Tom Pestorius                                     Mechanical Engineer
    Senior Policy Analyst
    Office of Science and Technology Policy
    Washington, DC

                          ACID RAIX PANEL REPORT
                                APPENDIX 2
                       CHARGES OF THE PANEL CHARTER
                       ACIO PAIN' PEER REVI,-:w PA:.:EL
1 .  Conmittee's Official Designation:

    Acid Rain Peer Review Panel

2.  Objectives and Scope of Activities and Duties:

    0 Review the reports of the Working Groups directed hy the 5 August
      1980 f'er.orandun of Intent (MOI) on Transboundary Air Pollution
      between the U.S. and Canada talcing into account currently available
      scientific and technical knowledge on the production, transport,
      transformation, and deposition of pollutants; the effect of these
      pollutants on our surroundings, and the economics and engineering
      estimates of control technology performance.

    0  Provide an assessnent of:

       (a) whether the Working Groups have fulfilled their charters under
           the Menorandun of Intent;

       (b) whether the Working Groups have utilized all significant
           research and data impacting on their topics in for^.ulatinp
           their reports;

       (c) whether the Working Groups' reports:

           (1)  clearly identify their assunptions,

           (2)  present and discuss alternate theories and explanations,

           (3)  provide support of conclusions and recommendations by the
                data and other evidence considered, and

           (4)  address the uncertainties in the available knowledge and
                its impact on their recommendations.

    0  Provide an independent assessment of the uncertainties in available
       scientific and technical information on which recommendations of the
       working groups are based.

    0  Recommend further research and monitoring  tasks which will reduce
       uncertainties in the scientific and technical knowledge.

    0  Provide a written report, with executive surnary addressing the
       above charter.


                           ACID RAIN PANEL REPORT

                                APPENDIX 3


I.  Purpose

To establish technical and scientific work groups to assist in preparations
for and the conduct of negotiations on a bilateral transboundary air
pollution agreement.  These groups shall include:

1.   Impact Assessment Work Group

2.   Atmospheric Modelling Work Group

3A.  Strategies Development and Implementation Work Group

33.  Emissions, Costs and Engineering Assessment Subgroup

4.   Legal, Institutional Arrangements and Drafting Work Group

II.  Terras of Reference

                                A.  General
1.  The Work Groups shall function under the general direction and policy
guidance of a Canada/United States Coordinating Committee co-chaired by the
Department of External Affairs and the Department of State.

2.  The Work Groups shall provide reports assembling and analyzing
information and identifying measures as outlined in Part B below, which
will provide the basis of proposals for inclusion in a transboundary air
pollution agreement.  These reports shall be provided by January 1982 and
shall be based on available information.

3.  Within one month of the establishment of the Work Groups, they shall
submit to the Canada/United States Coordinating Committee a work plan to
accomplish the specific tasks outlined in Part 8, below.  Additionally,
each Work Group shall submit an interim report by January 15, 1981.

4.  During the course of negotiations and under the general direction and
policy guidance of the Coordinating Committee, the Work Groups shall assist
the Coordinating Committee as required.

5.  Nothing in the foregoing shall preclude subsequent alteration of the
tasks of the Work Groups or the establishment of additional Work Groups as
may be agreed upon by the Governments.
 This is the Annex of the "Memorandum of Intent between the Government of
 Canada and the Government of the United States of America concerning
 Transboundary Air Pollution."


                          ACID RAIN PANEL REPORT

                           APPENDIX 3, CONTINUED

                               B.  Specific

    The specific tasks of the Work Groups are set forth below.

1.  Impact Assessment Work Group

The Group will provide information on the current and projected impact of
air pollutants on sensitive receptor areas, and prepare proposals for the
"Research, Modelling and Monitoring" element of an agreement.

In carrying out this work, the Group will:

-identify and assess physical and biological consequences possibly related
 to transboundary air pollution;

-determine the present status of physical and biological indicators which
 characterize the ecological stability of each sensitive area  identified;

-review available data bases to establish more accurately historic adverse
 environmental impacts;

-determine the current adverse environmental impact within identified
 sensitive areas-annual, seasonal and episodic;

-determine the release of residues potentially related to transboundary air
 pollution, including possible episodic release from snowpack melt in
 sensitive areas;

-assess the years remaining before significant ecological changes are
 sustained within identified sensitive areas;

-propose reductions in the air pollutant deposition rates-annual, seasonal
 and episodic-which would be necessary to protect identified sensitive
 areas; and

-prepare proposals for the "Research, Modelling and Monitoring" element of
 an agreement.

2.  Atmospheric Modelling Work Group

The Group will provide information based on cooperative atmospheric
modelling activities leading to an understanding of the transport of air
pollutants between source regions and sensitive areas, and prepare
proposals for the "Research, Modelling and Monitoring" element of an
agreement.  As a first priority the Group will by October 1, 1980 provide
initial guidance on suitable atmospheric transport models to be used in
preliminary assessment activities.

                           ACID RAIN PANEL REPORT
                           APPENDIX 3, CONTINUED
In carrying out its work, the Group will :

-identify source regions and applicable emission data bases;

-evaluate and select atmospheric transport models and data bases to be used;

-relate emissions from the source regions to loadings in each identified
 sensitive area;

-calculate emission reductions required from source regions to achieve
 proposed reductions in air pollutant concentration and deposition rates
 which would be necessary in order to protect sensitive areas;

-assess historic trends of emissions, ambient concentrations and atmospheric
 deposition trends to gain further insights into source receptor
 relationships for air quality, including deposition; and

-prepare proposals for the "Research, Modelling and Monitoring" element of an

3A.  Strategies Development and Implementation Work Group

The Group will identify, assess and propose options for the "Control" element
of an agreement.  Subject to the overall direction of the Coordinating
Committee, it will be responsible also for coordination of the activities of
Work Groups I and II.  It will have one subgroup.

In carrying out its work, the Group will:

- prepare various strategy packages for the Coordinating Committee designed
  to achieve proposed emission reductions;

-coordinate with other Work Groups to increase the effectiveness of these

-identify monitoring requirements for the implementation of any tentatively
 agreed-upon emission-reduction strategy for each country;

-propose additional means to further coordinate the air quality programs of
 the two countries; and

-prepare proposals relating to the actions each Government would need to
 take to implement the various strategy options.
 work Group 2 added another specific term of reference to its work and
 inserted it between the fourth and fifth terms of reference given here.  It
 reads (Work Group 2 Final Report, Appendix 1, pg. Al-2):  "evaluate and
 employ available field measurements, monitoring data and other
 Work Group 3A did not publish a final report.


                           ACID RAIN PANEL REPORT
                           APPENDIX 3. CONTINUED
3B.  Emissions, Costs and Engineering Assessment Subgroup

This Subgroup will provide support to the development of the "Control"
element of an agreement.  It will also prepare proposals for the "Applied
Research and Development" element of an agreement.

In carrying out its work, the Subgroup will:

-identify control technologies, which are available presently or in the near
 future, and their associated costs;

-review available data bases in order to establish improved historical
 emission trends for defined source regions;

-determine current emission rates from defined source regions;

-project future emission rates from defined source regions for most probable
 economic growth and pollution control conditions;
-project  future emission rates resulting from the implementation of
 proposed strategy packages, and associated costs of implementing the
 proposed strategy packages; and

-prepare proposals for the "Applied Research and Development" element of an

4.  Legal, Institutional and Drafting Uork Group

The Group will:

-develop the legal elements of an agreement such as notification and
 consultation, equal access, non-discrimination, liability and

-propose institutional arrangements needed to give effect to an agreement
 and monitor its implementation; and

-review proposals of the Work Groups and refine language of draft
 provisions of an agreement.
 Work Group 3B deleted this specific term of reference from its work (Work
 Group 3B Final Report, Appendix 1, pg. A-2).
 Work Group 4 did not publish a final report.

                            ACID RAIN PANEL REPORT
                                 APPENDIX 4
                       MATERIALS PROVIDED TO THE PANEL
September 1982  - Work Group 3B Final Report, dated June 1982.
                - Outlines of each Work Group's report and lists of the United
                  States and Canadian members in each Work Group.  Prepared
                  by the Executive Secretary.
October -       - Interim Draft of "The Regional Implications of Transported
 November 1982    Air Pollutants: An Assessment of Acidic Deposition and
                  Ozone", Office of Technology Assessment, dated July 1982.
                - Work Group Reports as follows:

                  Work Group 1

                     •  Phase I Interim Report, dated February 1981.

                     o  Phase II Interim Working  Paper, dated October 1981.

                     «  Phase III Draft Report, marked by the United States
                        Co-chairman to indicate sections not yet agreed to by
                        the Work Group, not dated.

                  Work Group 2

                     9  Phase I Interim Report, dated January 1981.

                     «  Addendum to Appendix 8 -  transfer matrices of the
                        Phase I Report on Atmospheric Modeling, dated
                        6 February 1981, revised  10 July 1981.

                     »  Atmospheric Transport and Deposition Modeling:
                        Inventory, Analysis and Recommendations, dated
                        December 1980, revised June 1981.

                     •»  Phase II Working Report (2-15), dated 10 July 1981.

                     •»  Atmospheric Sciences Review (2-14), dated 10 July

                     3  Modeling Subgroup Report  (2-13), dated 10 July 1981.



   « Model Profiles

      o  Documentation  of  the Atmospheric Environment
        Service Long-Range Transport  of  Air  Pollutants
        Model AES-LRT  (2-5), dated 15 May 1981.

      o  Documentation  of  the Advanced Statistical
        Trajectory Regional Air Pollution Model  ASTRAP
        (2-6), dated 12 May 1981.

      o  Documentation  of  the Eastern  North American
        Model for Air  Pollution ENAMAP (2-7),  dated
        30 June 1981.

      o  Documentation  of  the Ontario  Ministry  of the
        Environment Statistical LRT Model OME-LRT (2-8),
        dated 31 March 1981.

      «  Documentation  of  the University of Michigan
        Atmospheric Contribution to Inter-Regional
        Deposition Model  UMACID (2-10),  dated
        24 June 1981.

      o  Documentation  of  the Transport of Regional
        Anthropogenic  Nitrogen and Sulfur Model  MEP-TRANS
        (2-11), dated  30  June 1981.

      o  Documentation  of  The Capita Monte Carlo  Model
        MCARLO (2-12), dated 30 June  1981.

   9 Phase III Draft Report 2F, dated 15 October 1982.

   » Atmospheric Science  Review Sub-group Report, 2F-A,
     dated 15 October  1982.

   • Local and Mesoscale  Analysis Subgroup Report, 2F-L,
     dated 15 October  1982.

   « Monitoring and Interpretation Subgroup  Report, 2F-I,
     dated 15 October  1982.

   » Regional Modeling Subgroup Report, 2F-M,  dated
     15  October 1982.

   » Replacement pages for the four subgroup reports,
     dated 11 November 1982.

Work Group 3A

   9 Interim Report, dated January 1981.

                            ACID RAIN PANEL REPORT
                            APPENDIX 4, CONTINUED
                  Work Group 3B

                     9 Interim Report, dated 15 January 1981.

                - Draft copy of "High-Leverage Investment in the
                  Atmospheric Sciences and Related Disciplines", paper by
                  the Committee on Science, Engineering and Public
                  Policy, National Academy of Science, dated 22 October

                - Draft of EPA Critical Assessment Document, Volumes 1 and
                  2, dated October 1982.

2 February 1983 - Drafts of "Modeling Uncertainty About Carbon
                  Dioxide" and "A Review of Estimates of Future
                  Carbon Dioxide Emissions", papers for review by the
                  Carbon Dioxide Assessment Committee, National Academy
                  of Science.

2 March 1983    - Work Group 2 Final Report, dated 15 November 1982.

                - List of differences between the above report and the
                  draft given to the panel in November 1982.  Prepared
                  by the Executive Secretary.

                - Model Profile

                     9 Documentation of the Regional Clitnatological
                       Dispersion Model RCDM-2 (2-9), dated September 1982.

29 March 1983   - Work Group 1 Final Report, dated January 1983.

                - List of differences between the above report and the
                  draft given to the panel in November 1982.  Prepared
                  by the Executive Secretary.

April 1983      - Executive Summaries - Work Group Reports, dated
                  February 1983.

May 1983        - Public Comments:

                     9 American Petroleum Institute: "Role of Organic Litter
                       in Lake Acidification and Buffering"; "Using
                       Historical Data to Ascertain Lake Water pH Trends";
                       "Comments on the MOI Emission Inventory"; "Total
                       Primary Sulfate Emissions"; "Emissions Projections for
                       Industrial Boilers"; "Comments on the MOI Emission
                       Inventory Uncertainty Estimates".

                     » Everett and Associates: "Comments on Section 3, Aquatic


                            ACID RAIN PANEL REPORT
                            APPENDIX 4,  CONTINUED

                     9 Hunton and Williams,  on behalf  of  the  Utility Air
                       Regulatory Group:  "Review and Critique of  the Work
                       Group 1 Phase II  and  Phase III  Impact  Assessment of  the
                       U.S.-Canadian Transboundary Treaty Negotiations";
                       "Review and Critique  of the Work Group 2  Phase II  and
                       Phase III Modeling Activities of the U.S.-Canadian
                       Transboundary Treaty  Negotiations";  "Comments on the
                       Final Report of Workgroup 33".

July 1983       - "Acid Deposition in North  America -  A Review of the
                  Documents  Prepared under the Memorandum of  Intent
                  between Canada and the United States of America,  1980,
                  on Transboundary Air Pollution - II  Technical
                  Report", prepared by  the Royal Society of Canada  for
                  the Government of Canada,  dated May  1983.

October 1983    - "The Ups and Downs of  Acid Rain". Preprint  by
                  Fred Singer.

                - "Observations in German Forests during the  Late
                  Summer of  1983", memorandum from Dr. Ellis  Cowling,
                  dated 7 October 1983.

                - The following papers,  most translated from  German,
                  were offered to the panel:

                     « "Devastating effect of acid rain on forests  described."
                       Stern, 28 October 1982, pp. 35, 36, 38.

                     * "The  Disease Picture—Different Species of Trees,  but
                       Identical Symptoms,"  by Peter  Schuett.  Bild der
                       Wissenschaft 12:  86-101, 1982.

                     » "Air Pollution—A Danger to Trees for  over 100 years
                       now," by Karl Friedrich Wentzel.  Bild der Wissenschaft
                       ^2: 103-106, 1982.

                     • "Die  Versauerung  - Giftstoffe  Reichern Sich An,"  by
                       Bernhard Ulrich.   Bild der Wissenschaft 12:  108-119,

                     « "Production and Consumption of  Hydrogen Ions in the
                       Ecosphere," by B. Ulrich.  In  Effects  of  Acid
                       Precipitation on  Terrestrial Ecosystems,  pp. 255-281.
                       Edited by T. C.  Hutchinson and  M. Havas.  New York:
                       Plenum Press, 1978.

                     • "Theoretical Consideration of  the Ion  Cycle in Forest
                       Ecosystems," by B. Ulrich.  Z.  Pflanzenernaehr. Bodnek.
                       144 (6): 647-659, 1981.


a The Destabilization of Forest Ecosystems by the
  Accumulation of Air Contaminants," by B. Ulrich.   Per
  Forst und Holzwirt 36 (21):  525-532,  1981.

3 "Balances of Annual Element  Fluxes Within Forest
  Ecosystems in the Soiling Region," by E. Matzner  and
  B.  Ulrich.  Z. Pflanzenernaehr.  Bodenk.  144 (6):
  660-681, 1981.

* "Dangers for the  Forest Ecosystem Due to Acid
  Precipitation - Necessary Countermeasures:   Soil  Liming
  and Exhaust Gas Purification," by B.  Ulrich. Preprint.

* "Appendix 3 - Explanations for Filling Out  the Form
  'Recording Forest Damage1."   Preprint.

» "Chemical Changes Due to Acid Precipitation in a
  Loess-Derived Soil in Central Europe," by B. Ulrich,  R.
  Mayer, and P. K.  Khanna.  Soil Science 130  (4): 193-
  199, 1980.

                           ACID RAIN PANEL REPORT

                                APPENDIX 5


                              S. FRED SINGER

     Before making any decisions or taking actions, it is natural to inquire

about the benefits following from these actions and the cost involved.   This

kind of reasoning applies to both public and private decision-making.  But

public decision-making, in addition, involves the concept of equity, the

consideration of whether those who are paying the cost of certain actions

are also receiving all or most of the benefits.

     Equity considerations aside, one needs some estimate of costs and

benefits, expressed in similar units, so that one can make a comparison.  It

is most convenient, but not always easy, to express the benefits and costs

in monetary units.  Much progress is being made in quantifying benefits in

areas which are usually considered to be unquantifiable—not only health

effects but also improvement in visibility, aesthetic effects, and the
     When weighing benefits against costs, it is not sufficient to have the

benefits large enough to be commensurate with the costs, i.e., to have the

benefits approximately equal to the costs.  All this means is that the net

benefits, that is, the difference between benefits and costs, are zero.  But

that same result can always be obtained by doing nothing, in which case

assuredly the benefits as well as the costs would be zero; hence, the net

benefits would also be zero.

     What we would like to do, in principle at least, is to make the net

benefits as large as possible.  A simple theoretical discussion tells us


                           ACID RAIN PANEL REPORT

                           APPENDIX 5,  CONTINUED

that this is equivalent to a situation  where the incremental benefits

resulting from a particular action are  equal to the incremental cost.  This

can be seen as follows.  If incremental benefits were greater than

incremental costs, then it would pay to continue with our actions and

thereby increase the net benefits.  On  the other hand, if incremental

benefits are less than incremental costs, then we have gone too far.   Figure

1 demonstrates this principle of marginal benefit-cost analysis.

     Most of the costs are usually incurred as capital coses in the initial

period, while the benefits may extend over a longer period of time.  It is

necessary, therefore, to "discount" both the costs and benefits to the same

year, say to the present, with the use  of an appropriate interest rate, in

order to carry out our analysis.  This  is a detail perhaps, but it can be


     More generally, "dynamic" benefit-cost analysis deals with the problem

of optimization in the presence of many sources of pollution, with only some

of them—usually the new ones—subject  to stringent controls.  Under those

conditions, large sums can be invested  without any immediate benefits.

(See, e.g., Fig. 2).  The classic example is automobile pollution where

great pollution control costs may be incurred for new cars initially, but               ^

where there can be no substantial improvements in air quality until almost

all of the old cars have disappeared from the fleet.  This is a general                 -/

problem where one has facilities that are "grandfathered," for example,

grandfathered electric utilities and grandfathered industries, which are not

required to control their pollution to  the same degree as new plants.  Thus,

                           ACID RAIN PANEL REPORT
                           APPENDIX 5, CONTINUED
                            25       50       75      100
FIGURE 1.  Typical costs and benefits associated with increasing reductions
in emissions.  Note that zero net benefits , i.e.  E-C occur both if nothing
is done (i.e., zero reduction) and for large reductions (where the
benefit-cost ratio B/C is 1).  Maximum net benefits occur somewhere between
these two cases.
FIGURE 2.  Emissions of S02 as a function of time.  Curve A:  without
emission controls.  Curve B:  with controls, emissions gradually declining.
However, the imposition of extreme new source performance standards (NSPS)
can produce a perverse effect (Curve C) by encouraging the continued
operation of older power plants that do not have to comply with NSPS.  Curve
D shows the effects of the 1977 Clean Air Act Amendments which actually
encouraged the use o£ higher sulfur coal.  (All curves are drawn

                           ACID RAIN PANEL REPORT

                           APPENDIX 5, CONTINUED

there is an incentive to make old plants last longer, because if  they are

not required to have pollution control equipment they are cheaper to

operate.  Dynamic benefit-cost analysis also takes into account that

there may be other sources of emissions, including natural sources,  so that

working on only one industrial pollution source, like electric utilities,

may not be optimal.


     When we apply this analysis to the acid rain problem, we can identify a

number of benefits which would result if acid deposition were to  diminish.

Many of these benefits have been described in the Work Group 3B Report, but

they have not been evaluated or even estimated.  They could include

recreational fisheries, commercial fisheries, the aquatic ecosystem

generally, agriculture, forestry, the general preservation of the ecosystem,

x^ater supply for various human uses, effects on buildings and structures,

atmospheric visibility, and, finally, human health (morbidity and


     Benefit analysis proceeds in two steps:  (1) one estimates how much

reduction in damage would result if acid deposition were to be decreased by

a certain percentage, say ten percent; and (2) one judges what an emission

reduction of, say, one million tons of sulfur dioxide per year implies in

terms of reduced acid deposition—at a particular S02 emission level.

Step 1 is within the province of Work Group 1.  Step 2 belongs to Work Group

2, and involves the well-known scientific complications having to do with

(a) the degree of mixing as  opposed to advection; (b) the degree of

conversion of S02 into sulfuric acid, including questions of nonlinearity

                                      ACID RAIN PANEL REPORT

                                      APPENDIX 5.  CONTINUED

           and saturation effects;  and (c) the presence of other pollutants,  whether

           man-made or natural,  which produce similar final effects.


                It is important  to  make some rough, even order-of-magnitude estimates.

*          One should at least be able to decide which effects (or benefits)  are more

           important and which are  of lesser importance.  The methodologies for making

           such determinations are  available but the work has not been done.   For

           example, one methodology which is useful in many situations is  to  estimate

           benefits by measuring "willingness to pay."  Into this category falls the

           topic of "liming," whereby lime is applied to lakes or water supplies in

           order to reduce the acidity of the water.  From the cost of the liming

           effort, one can at least derive a lower limit to the benefits which come

           about with reduced acidity.


                Estimating the control costs of emissions which are thought to be the

           precursors of acid deposition is also a difficult subject,  but  perhaps not

           as difficult as estimating benefits.  Cost estimates require knowledge in

           areas of technology and  atmospheric science.

 *"              First of all, it is important to know what technologies can be brought

 .          to bear for the removal  of, say, sulfur at different stages in  the

           combustion process, ranging from cleaning coal and removing sulfur during

           burning, to removing  S02 from flue gases.  Because of the rapid evolution in

           technology and because of uncertainties about reliability and costs of

           different technologies,  such knowledge is often hard to come by.


                           ACID RAIN PANEL REPORT

                           APPENDIX 5, CONTINUED

     The Work Group 3B Report addresses this matter, but Is not altogether

hopeful about the efficacy and reliability of control devices.  It is our

view, after reviewing research in progress and consulting industry experts,

that the technical problems can and will be solved.  According to this view,

the unit cost of pollution control should stabilize or even decrease in the


     The other quantitative input relates to dispersion of emissions, their

conversion into acids, and eventual deposition.  Here, however, one may

proceed in steps, starting with the simplest model and proceeding to more

complicated ones.  Certainly the simplest model is that of a "single box" in

which emissions from the eastern United States and Canada are received.  In

this box nodel, reduction of emissions from a source anywhere has the same

value as reduction of emissions from another source.  The problem then

simply becomes that of reducing S02 emissions from all present sources and

future sources as well.

     A more realistic approximation, yet still quite simple, could divide

the transport problem into two parts:  (1) local, i.e., less than 300 miles

from the source; and (2) distant, i.e., greater than 300 miles.  One would

then argue that all sources in one "box" contribute a certain fraction of

their emissions to distant pollution, with the fraction being the same for

all sources.
 There may, however, exist a serious pollution problem in the disposal of

 the slurry-like waste material from flue gas desulfurization.

                           ACID RAIN PANEL REPORT

                           APPENDIX 5, CONTINUED

Least-Cost Approach

     Borrowing the concept of the "bubble," which is now widely used to

allow emissions trading within any given plant, it may be possible to apply

emissions trading to the whole region so that a least-cost approach to the

reduction of emissions can be put into effect.  It is interesting that many

people are coming to this conclusion.   Setting aside for a moment the

question of who pays for the control of pollution—ultimately always, of

course, the consumer—pollution control can then be achieved by the

least-cost method.  This means that, initially, sulfur will be removed by

simple washing of coal (thereby removing the inorganic sulfur in pyrites)

and by pollution control in presently uncontrolled smelters.  As noted by

Work Group 3B, these techniques cost (per kilogram of sulfur removed) only a

few percent of the cost of flue-gas scrubbing in a power plant burning

low-sulfur coal, yet a kilogram of sulfur removed by any method should have

an equivalent effect on air quality, according to the simple box model.

     The approach just described is in strong contrast to the following

scenario which is economically quite inefficient.  The argument is often

made that since pollution control is expensive, it is best to apply it to

industries that can afford it or that can easily pass along the costs.  It

is argued that pollution control on smelters would make them noncompetitive
 For example, David Hawkins, former EPA Assistant Administrator for Air

Quality in the Carter Administration, writing in AMICUS, proposes a wider

bubble approach.

                           ACID RAIN PANEL REPORT

                           APPENDIX 5, CONTINUED

and put them out of business, but that control on utilities might add only a

few percent to the electricity bill of their customers.  But if it costs the

utility 100 times more to remove a kilogram of sulfur as it does the

smelter, wouldn't it make more sense to ask the utility customers to pay the

smelters to remove the sulfur?

     A practical way of achieving the least-cost approach to pollution

control is to introduce what are called transferable emission rights.  This

would guarantee that the market will work in such a way as to achieve the

lowest-cost methods of removing pollution.   A central authority,

presumably the government, would have to decide how much sulfur may be

admitted into the atmosphere, based on some benefit-cost considerations.  By

limiting the number of rights sold or made available by other means, one can

control exactly the amount of sulfur emitted.  The rights can either be

given away, for example to existing polluters who would be grandfathered, or

they could be auctioned off so as to create greater equity as well as a

source of money for the Treasury.  The only important matter for the

least-cost approach is that rights be issued and that they be transferable.
 The present approach of prescribing ultrastrict performance standards for

new sources is extremely costly and wasteful to society.  A recent report by

the Congressional Budget Office shows that emission trading would lower

considerably the cost of S02 abatement (The Clean Air Act, The Electric

Utilities, and The Coal Market, April 1982).

                           ACID RAIN PANEL  REPORT
                           APPENDIX 5,  CONTINUED
                       KILOGRAMS OF SULFUR REMOVED
FIGURE 3.  Control costs  vs.  increasing  reduction in SC>2 emissions.  The
slope of the curves gives the cost  per pound of  sulfur removed.  Curve A
illustrates the approach  mandated by  present legislation, focussing on BACT
(best available control  technology),  such as flue gas desulfurization.
Curve B illustrates schematically a "least-cost" approach which starts with
lowest-cost methods,  such as  low-sulfur  coal or  coal washing, before
proceeding to higher-cost approaches.

                           ACID RAIN PANEL REPORT

                           APPENDIX 5, CONTINUED

     To take an actual example, smelters would be inclined to sell their

rights to the utilities and use the money to control their pollution.

Smelters might even make some money because they can remove their pollution

at very little cost and they can sell their rights at a higher price.  The

overall result would be to achieve the desired reduction of emissions at the

lowest cost to society as a whole or a much higher degree of pollution

control with no more money spent overall.


     In the absence of even order-of-magnitude estimates of economic damage

attributable to acid deposition, and with emission control costs certainly

in the multibillion dollar range, one must question whether we are attacking

a million-dollar problem with a billion-dollar solution.

     An additional caveat derives from the present scientific uncertainties:

Will a reduction in emissions produce proportionate reductions in deposition

and in the environmental impacts believed to be associated with acid

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