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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON D.C. 20460

OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD June 22, 2010

EPA-CASAC-10-014

The Honorable Lisa P. Jackson

Administrator U.S. Environmental Protection Agency 1200 Pennsylvania Avenue, N.W. Washington, D.C. 20460

Subject: Review of the Policy Assessment for the Review of the Secondary National Ambient Air Quality Standards for NO

x and SO

x : First Draft (March 2010)

Dear Administrator Jackson:

The Clean Air Scientific Advisory Committee (CASAC or Committee) NO

x -SO

x Secondary NAAQS Review Panel met on April 1-2, 2010, to review EPA’s Policy Assessment for the Review of the Secondary National Ambient Air Quality Standards for NO

x and SO

x : First Draft . The chartered CASAC held a public teleconference on May 3, 2010, to re view and approve the report. This letter provides CASAC’s overall comments and evaluation. We highli ght the most important issues which need to be addressed as the first draft Policy Assessment (PA) is revised. The CASAC and Panel membership is listed in Enclosure A. The consensus responses to EPA ’s charge questions are presented in Enclosure B. Finally, Enclosure C is a compilation of individual panel member comments.

Overall, the CASAC NO

x -SO

x Secondary Panel found that the first draft of the PA has begun to provide a framework for developing a secondary standard that integrates two criteria pollutants in a valid, scientifically based approach and that also accounts for the presence of chemically reduced forms of nitrogen (NH

x ). EPA staff continues to innovate in the face of many complexities. We realize that this complexity has led to some portions of the PA th at are incomplete and others that need further refinement, and we look forward to reviewing subse quent and more complete drafts. The Panel is supportive of the approach that EPA staff has fo llowed in their development of an Atmospheric Acidification Potential Index (AAPI), which integrates the effects of NO

x and SO

x deposition on aquatic

acidification. This index can be the basis of a sta ndard that protects sensitive ecosystems while allowing for the actuality that in most locations in the U.S. NO

x and SO

x deposition may not be causing substantial

harm.

In addition to finishing the sections of the PA that EPA has identified as being incomplete, a specific need identified by CASAC is more compre hensive sensitivity and uncer tainty analyses of the proposed approach, and we recommend that a separat e chapter be devoted to such analyses. We recognize that a probabilistic uncertainty analysis is likely not practical given the time constraints to complete the PA and development of a secondary standard. The reasoning that supports EPA’s

assessment of the relative values of the uncertainties should be provided. At present, the reasoning behind the rankings of the uncertainties are not clearly articulated. Sensitivity analyses of the various terms included in the AAPI equation should be performed. The sensitivity analyses should be guided by estimates of the potential range of the terms in the AAPI. For example, the two approaches forcalculating N

eco can be used, and results from multiple CMAQ (and other air quality models and data analysis efforts) can be used to define potential ranges for L(NH 3 ), Q, VNO y and VNO

x . The Panel recommends the “V” terms be changed for clarity. The Panel also recommends that the “g(.)” term of the AAPI equation be expanded to s how the nitrogen cycling and b ackground cation weathering terms explicitly.

The approach laid out by EPA staff relies heavily on results of Community Multiscale Air Quality (CMAQ) modeling. Given this dependence, the PA should provide a more thorough evaluation of the ability of CMAQ to simulate the ambient con centrations and wet and dry deposition fluxes of the

SO

x , NO

x and NH

x species used in determining the AAPI. While details of this evaluation can be contained in an appendix, summary results should be br ought into Chapter 4. Additionally, the separate, recommended chapter on uncertainty should use this information in the overall assessment of uncertainty.

The Panel acknowledges that the current focu s of the PA is on adverse impacts of NO

x and SO

x deposition in acid sensitive ecosystems. However, th e PA should also include a succinct discussion of other potential impacts of NO

x deposition to N-limited ecosystems. For example, increased N deposition to N-limited ecosystems can lead to production increases that may be either beneficial or adverse depending on the system and management goals.

In revising the PA, the Panel asks that EPA use a c onsistent set of units in its presentation of data, results and equations. Given the focus of the docum ent on depositional effects that depend largely on the number of moles of reactive N or oxidized S, use of SI units (International System of Units) is likely the best approach. It may be most facile in some cases to just provide the necessary arithmetic conversion necessary to produce the results in SI units to avoid the problems associated with extensively redoing tables and figures. The units in every equation variable should be stated.

In closing, the Panel was pleased with the devel opment of the PA and trusts that our comments

are useful in the PA’s revision. We look forw ard to seeing the revised PA, along with the Agency’s response to how our comments have been addressed.

Sincerely,

/Signed/ /Signed/

Dr. Armistead (Ted) Russell, Chair Dr. Jonathan M. Samet, Chair CASAC NOx-SOx Secondary Panel Clean Air Scientific Advisory Committee

Enclosures

2NOTICE

This report has been written as part of the activ ities of the EPA’s Clean Air Scientific Advisory Committee (CASAC), a federal advisory committee independently chartered to provide

extramural scientific information and advice to th e Administrator and other officials of the EPA. CASAC provides balanced, expert assessment of scientific matters related to issues and problems facing the Agency. This report has not b een reviewed for approval by the Agency and, hence, the contents of this report do not necessa rily represent the views and policies of the EPA, nor of other agencies within the Executive Br anch of the federal government. In addition, any mention of trade names of commercial products does not constitute a recommendation for use. CASAC reports are posted on the EPA website at http://www.epa.gov/CASAC.

3Enclosure A

Rosters of the CASC NO

x -SO

x Secondary Review Panel and CASAC



### U.S. Environmental Protection Agency Clean Air Scientific Advisory Committee

NO

x 

### and SO

x 

### Secondary Review Panel

CHAIR Dr. Armistead (Ted) Russell , Professor, Department of Civ il and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA

MEMBERS

Dr. Praveen Amar , Director, Science And Policy, NESCAUM, Boston, MA

Dr. Andrzej Bytnerowicz , Senior Scientist, Pacific Southw est Research Station, USDA Forest Service, Riverside, CA

Ms. Lauraine Chestnut , Managing Economist, Stratus Consulting Inc., Boulder, CO

Dr. Ellis B. Cowling , University Distinguished Professo r At-Large Emeritus, Colleges of Natural Resources and Agricultur e and Life Sciences, North Caro lina State University, Raleigh,

NC

Dr. Charles T. Driscoll, Jr. , Professor, Department of Civ il and Environmental Engineering, College of Engineering and Computer Scie nce, Syracuse University, Syracuse, NY

Dr. H. Christopher Frey , Professor, Department of Civ il, Construction and Environmental Engineering, College of Engineering, No rth Carolina State University, Raleigh, NC

Dr. Paul J. Hanson , Distinguished R&D Sta ff Member, Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN

Dr. Rudolf Husar , Professor, Mechanical Engineeri ng, Engineering and Applied Science, Washington University, St. Louis, MO

Dr Dale Johnson , Professor, Nat. Res. Env. Sci., Co llege of Agriculture, Biotechnology, and Natural Resources, University of Nevada, Reno, Reno, NV

Dr. Donna Kenski , Data Analysis Director, Lake Mi chigan Air Directors Consortium, Rosemont, IL

Dr. Naresh Kumar , Senior Program Manager, Environm ent Division, Electric Power Research Institute, Palo Alto, CA

4Dr. Myron Mitchell , Distinguished Professor and Direct or of Council on Hydrologic Systems Science, College of Environmental Science a nd Forestry, State University of New York, Syracuse, NY

Mr. Richard L. Poirot , Environmental Analyst, Air Pollutio n Control Division, Department of Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT

Mr. David J. Shaw , Director, Division of Air Resour ces, Department of Environmental Conservation - New York State, New York State, Albany, NY, United States of America

Dr. Kathleen Weathers , Senior Scientist, Cary Institute of Ecosystem Studies, Millbrook, NY

SCIENCE ADVISORY BOARD STAFF Ms. Kyndall Barry , Designated Federal O fficer, Washington, DC

5

### U.S. Environmental Protection Agency Clean Air Scientific Advisory Committee

CHAIR

Dr. Jonathan M. Samet , Professor and Flora L. Thornton Chair, Department of Preventive Medicine, University of Southern California, Los Angeles, CA

MEMBERS Dr. Joseph Brain , Cecil K. and Philip Drinker Profe ssor of Environmental Physiology, Department of Environmental Health, Harvard School of Public Healt h, Harvard University, Boston, MA

Dr. H. Christopher Frey , Professor, Department of Civ il, Construction and Environmental Engineering, College of Engineering, No rth Carolina State University, Raleigh, NC

Dr. Donna Kenski , Data Analysis Director, Lake Mi chigan Air Directors Consortium, Rosemont, IL

Dr. Armistead (Ted) Russell , Professor, Department of Civ il and Environmental Engineering, Georgia Institute of Technology, Atlanta, GA

Dr. Helen Suh , Associate Professor, Department of Environmental Health, School of Public Health, Harvard University, Boston, MA

Dr. Kathleen Weathers , Senior Scientist, Cary Institute of Ecosystem Studies, Millbrook, NY

SCIENCE ADVISORY BOARD STAFF Dr. Holly Stallworth , Designated Federal Officer, Washington, DC

6Enclosure B

CASAC’s Consensus Responses to EPA’s Charge Questions

Executive Summary

The Panel finds that the draft Executive Summ ary is well written and is an appropriate representation of the main Po licy Assessment document. For the most part, the technical language, figures and the AAPI formulae convey the essence of each chapter. Clearly, future versions would need to incorporate the change s in the evolving main policy document. The fourteen-page Executive Summary is somewh at long. The summary of Chapter 5, the Conceptual Design of an Ecologi cal Standard, should be improve d to effectively communicate the significant new concepts such as SO

x -NO y deposition tradeoff and deposition load function. In particular, the equation for th e proposed standard (AAPI) needs to be explained more clearly, maybe with the aid of a conceptual diagram speci fically representing the underlying rationale of each of the terms in the proposed AAPI equation.

Chapter 2: Known or Anticipated Ecological Effects

1. What are the views of the Panel on the appropriateness of staff’ s weight-of-evidence approach which assesses information from across the various ecological research areas described in the NOx/SOx Secondary Standards Integrated Science Assessment (ISA), including studies of acidifi cation and nutrient-enrichment in aquatic and terrestrial ecosystems, and laboratory research on res ponses of plant and animal species to acidification and nutrient enrichment? To what extent is the presenta tion of evidence drawn from the ecological effects studies assessed in the ISA technically sound, appropriately focused and balanced, and clearly communicated?

The current document provides a good review based upon the ISA. There needs to be clarification, however, with respect to some of the details including how the document provides results with respect to the actual years of the an alysis. Some of the di scussion is repetitive and additional editing is needed to decrease the redu ndancy. The Panel asks that the referencing to

the scientific literature and prior review documen ts be consistent throughout the PA. Statements

of fact need to be refe renced to the literature.

The text is often written to sugge st that acidification or nutrient enrichment have the potential to affect all ecosystems in a similar manner. The do cument needs to clarify that many effects being discussed are applicable only to the most sensitive compone nts of ecosystems. These ecosystems may warrant special protection, but theydo not represent a response that is universal for all ecosystems and their respective components.

2. To what extent are the in terpretation and presentation of the results of the exposure and risk assessment technically sound, appropria tely balanced, and clearly communicated?

The staff has adequately summarized the informa tion contained in the REA, but some further clarification of the major points is warranted. Most of the asse ssments presented use steady state

7models; ecosystems, however, are never in stead y state. A summary of the assumptions and limitations of the steady-state models used in th e ecological effects studies should be included in

the document.

3. What are the views of the Panel on the criti cal uncertainties associated with the risk and exposure analysis and the evide nce from ecological effects studies that need to be characterized in terms of their potentia l implications for the secondary standards?

The discussion on critical uncertainties (Pages 35 -37) requires a more rigorous treatment than

that included in the curr ent draft. The rankings of uncertainty (high, fairly high, intermediate or low confidence) are based on EP A Staff judgment w ithout any explanation of how the Staff arrived at those rankings. For example, have the models and input parame ters been adequately evaluated to assign high confidence in them? If so, it is essential to provide justification for the assigned rankings. In addition, it is recommended that sensitivity analyses be conducted for the different models used for aquatic acidification an d terrestrial acidification and presented in the document (please note our earlier comment on the need for a separate chapter on uncertainty).

Chapter 3: Considerations of Adversity to Public Welfare

4. What are the views of the panel regarding the characterization of adversity to public welfare presented in this docum ent? What are the views of th e panel regarding the use of the ecosystem service framework as an additional metric to inform questions of adversity? What are the views of the panel regarding the usefulne ss of including economic valuation of some of these ecosystem services in the policy assessment document?

In Chapter 3, EPA needs to describe for th e Administrator and the public how and why the

current effects of SO

x /NO y deposition on sensitive ecosystems matter in terms of services and functions of ecosystems that are im portant to people. This is the motivation for this review. The ecosystem services framework and the availabl e economic valuation resu lts can help, but the Chapter does not yet provide sufficient informati on on the ecosystem servi ces and the resultant impacts of SO

x /NO y deposition. Throughout th e chapter it is important to re-iterate that ecosystem effects of concern as a result of SO

x /NO y deposition are currently occurring only in

certain sensitive areas.

The economic valuation estimates are useful when they are tied to the change or loss in value of ecosystem services that can be reasonably attributed to SO

x /NO y deposition. It is true that neither the economics nor the science can define pr ecisely the exact threshol d at which an effect becomes adverse, but the relative values of availa ble estimates still provide useful information to assess the question of adversity when they are put in the proper context. The monetary values that are presented in the chapte r need more explanation as to their policy implications. A table summarizing the monetary valuation associated w ith various ecosystem services estimates would be helpful.

85. To what extent is the pres entation of ecosystem services in this document scientifically sound and clearly communicated?

The basic concepts of ecosystem services and ho w they relate to ecosystem function and to the

idea of welfare effects as defined in the Cl ean Air Act are clearly communicated and well presented. The description and summary of how th ese services are specifi cally being affected by

SO

x /NO

x deposition need to be improved. The basic concepts of ecosystems services are useful to explain why the health of these systems matters, but more discussion is needed beyond providing the conceptual framework. This framework needs to be us ed to describe the effects for which the science provides reasonable confidence on the deleterious impacts that are affecting sensitive ecosystems under current conditions, and not just describing the effects that could happen. The description of deleterious ecosystem effects needs to be placed in the context of their geographical distribution. More can be don e to characterize the im portance of the current observed effects even though most changes in ecosystem services cannot be completely quantified.

The presentation lacks a clear communication of the potentially beneficial effects of nitrogen inputs to nutrient limited ecosystems. Due to their inherent capacities for N retention, the majority of US ecosystems will not experien ce significant negative impacts from N-induced

acidification or nutrient enrichme nt. Such a reality doesn’t elim inate the benefits of protecting more sensitive and valuable but less common ecosy stems, but EPA will be open to criticism if this is not explicitly acknowledged. Finally, timbe r products should be added to Table 3-1.

6. What are the views of the panel on the criti cal uncertainties associated with articulating adversity to public welfare that need to be characterized in terms of their potential implications for th e secondary standards?

It is quite clear that current levels of acidi fication are causing adverse effects on aquatic

resources in some locations. It seems there is su fficient evidence to support that these effects are adverse to public welfare with respect to a substantial proportion of lakes and streams in sensitive regions. These regions cannot support several species of fish and other aquatic biota due to anthropogenic induced acidification. Key un certainties include how much of the adversity would be reduced with a standard based on a gi ven level of acid neutralizing capacity (ANC). The economic valuation estimates show additional value for incremental improvements in ANC,

but do not reflect all the benefits of decreased deposition or point to a specific ANC level that should be required. Related to th is is the question of what per centage of acidified lakes and

streams need to achieve these ANC levels to elimin ate or at least reduce the adverse effect to an acceptable level. The evidence may not provide definitive answers to these questions, but the implications of available evidence can be more e xplicitly stated with regard to these questions and will be important considerations to inform the Administrator’s policy decisions on this NAAQS.

9Chapter 4: Addressing the Adequacy of the Current Standards

7. What are the views of the Panel on staff’ s assessment of the adequacy of the form of the existing NOx and SOx secondary standards? To what extent does the Panel agree with staff’s assessment of the protection provided by exis ting standards, given the cu rrent levels, forms, averaging times, and indicators?

In Chapter 4 clear and convincing arguments ar e presented questioning the ecological relevance

of the current SO 2 and NO 2 secondary standards (and many of their individual components), and

concludes that current standards do not adequately protect agains t adverse environmental effects

from SO

x and NO

x . Well-documented observations of chem ical and ecological effects of S + N acidification in monitoring programs like TIME, LTM and EMEP, combined with the

observations of no exceedances of current NO 2 or SO 2 standards in areas e xperiencing effects of aquatic or terrestrial acidificati on or nutrient enrichment provide a direct indication that current standards are not adequate. As the environmental effects from SO X and NO X occur primarily through the long-term cumulative deposition of mu ltiple S and N compounds, combined together rather than individually, the Chapter persuasive ly shows how the components of the current secondary standards are inappropriate in terms of indicators, averaging times, levels and forms, as well as in their single pollutant approaches to multi-pollutant problems.

8. What are the views of the Panel on the ti me frame of ecological response related to current deposition? The adequacy evaluation re lies on recent NOx, SOx, deposition, and on long-term steady state ANC. Does the panel agr ee that long-term ste ady state ANC is the most appropriate representation of ANC fo r evaluating the adequacy of the current

standards?

Use of long-term ANC derived from steady stat e modeling and recent deposition rates of SO

x and NO

x (and NH

x ) to evaluate the adequacy of current standards is a reasonable approach. This approach could be enhanced by also applyi ng dynamic acidification modeling techniques to “hindcast”changes for comparison with recent measurement or pa leo-limnological data, as well as to forecast chemical and ecological responses if current deposition rates remain unchanged. A parallel dynamic modeling effect would greatly inform the appropriateness of the assumptions invoked in steady-state calculations . Current levels of acidificati on and associated effects result

from a combination of current and historical deposition of SO

x and NO

x compounds, and their cumulative effects on the chemical and biological environment. As curre nt deposition rates are lower in most locations than they were several decades ago, it’s likely th at some aquatic and/or terrestrial ecosystems have shown some signs of recovery. An assessmen t of the adequacy of

current standards should consider the extent to which and rates at which some less sensitive systems may continue to recover at current S + N deposition, while other more sensitive systems will not recover or may experience further deteri oration if current “non-sustainable” rates of deposition remain unchanged.

109. To what extent are the characterizati ons of ambient air quality and deposition appropriately characterized, relevant to th e review of the secondary NOx and SOx NAAQS, and clearly communicated?

The characterizations of air quali ty and deposition presented in Ch apter 4 are, for the most part, appropriate and relevant to the review of secondary NO

x and SO

x standards. While the Chapter is nominally focused on evaluating the adequacy of current standards, it also includes considerations of the potential to use current monitoring networks (supplemented by additional measurements and/or by CMAQ mo del results) for the development of potential new standards and/or determining compliance with them. While most of the geographical distribution information included in maps is useful and clear ly presented, several of the figures appear to have inaccurate legends or capti ons (Figures 4-8 through 4-11). It would also be useful to include additional figures showing the geographical distribution of total NH

x N deposition, as

well as the fraction of total N deposition contributed by chemical ly reduced (or oxidized) N.

There are some important figures showing the re lationships between atmospheric concentrations and total deposition of S and N (V S/N ) that are not well developed in Chapter 5 (e.g., Figure 5-5). These types of depictions and the relationships they demonstrate are important. The importance of these relationships needs to be emphasized and their importan ce expanded upon in Chapter 4. Presumably, it could be clearly shown, through use of CMAQ ratio maps and scatter plots based on grid point comparisons, that NO Y is a much better predictor or indicator of total oxidized N (NO

x ) deposition than is NO 2 , and hence this result would dire ctly support the evaluation of adequacy of the various approaches for estimating S and N deposition inputs. This chapter should also include a summary of the performance assessment of CMAQ, as discussed in response to charge question 18.

Chapter 5: Conceptual Design of an Ec ologically Relevant Multi-pollutant Standard

10. What are the views of th e Panel on staff’s proposed c onceptual framework for the structure of a multi pollutant, ecologically relevant standard for NOx and SOx? To what extent does the Panel agree that this suggested structure adequately repr esents the scientific linkages between ecological responses, wate r chemistry, atmospheric deposition, and

ambient NOx and SOx?

The proposed conceptual framework for the stru cture of the proposed st andard is very wellthought out and quite innovative in its design for addressing comp lex linkages between various components (ecological effects, aquatic chemistry, atmospheri c wet and dry deposition, and atmospheric concentrations of NO y and SO

x ). However, as currently proposed, calculation of AAPI assumes deposition of reduced forms of reactive nitrogen to be constant in the future which is unlikely to be true considering the upward trajectory of U.S. ammonia emissions. A more realistic approach would be to treat ammonia as a variable component of the AAPI standard that can be updated. Additionally, the underlying assu mption of steady state behavior should be evaluated with a parallel effort using sensitivity analysis and dynamic modeling. The chapter should be improved to effectively comm unicate the important new concepts such as SO

x NO y deposition tradeoff and deposition load func tion. The AAPI equation for the proposed standard should include the ge ographical extent and numerical range of its applicability.

1111. What are the views of the P anel on the relevance of the conceptual design for developing standards to protect against aquat ic acidification effects?

a) What are the views of the Panel on staff’s proposed options for the ecosystem acidification model to represen t the ecological response function?

The Panel agrees with EPA staff that steady-st ate models are probably the best approach to develop a combined NO

x and SO

x secondary standard to protect surface waters against the effects of acidic deposition at this time. Th e Panel recommends, however, that the EPA take advantage of on-going efforts in dynamic modeling. Dynamic model calculations coupled with long-term measurements would greatly inform the regional and nationa l steady state modeling effort by helping to evaluate the assumptions in voked in the application of steady-state models, in evaluating the relative sensitivity of aquatic and forest ecosystems from acidification by acidic deposition, and building experience in the use of dyna mic models in critical load calculations for

future assessments.

b) What are the views of th e Panel on the relative merits of the two techniques for calculating Neco, the parameter representing the amount of deposited nitrogen that is available for acidification due to up take, denitrification, and immobilization.

In principal, Equation 3 (page 159) captures many of the major la ndscape and ecological factors that influence the processing of atmospherically deposited N within an ecosystem, including biological and abiotic retention of N (immobili zation, uptake and sedimentation), and gaseous loss (denitrification) after N has been deposited and/or transpor ted. This approach opens the “black box” and attempts to estimate some of the component parts of N processing and loss. It is best modeled as a dynamic process because such factors as age and stage of vegetation, soil moisture, moisture regime, and nutrient demand will affect various components of N cycling. For many ecosystems, complete suppor ting data may not be available.

Equation 4 is basically a mass bala nce approach that keeps track of inputs and outputs. It does not include the detailed biogeochemical processes id entified in Equation 3. Data for this latter approach may be much more readily available th an the approach using Equation 3. Watershed N retention can be estimated using this approach (e.g., Lovett et al. 2000, an d many others), but the processes involved in the retention are not detailed. This approach is most effectively used when hydrologic boundaries (e.g., watershe d) are defined. Hence, the Panel recommends that the mass balance (i.e., Equation 4) approach should be used.

c) what are the views of the panel on staff’s proposed options for developing acidsensitivity classes to categor ize the national landscape? Is it appropriate to base this classification on bedrock geology? Should mu ltiple criteria be us ed to inform the sensitivity categories.

Maps of bedrock geology are likely to be most effective in indicating the sensitivity of acidsensitive ecosystems in unglaciated parts of the country. Where glacial till or other forms of surficial materials have a major influence on soil characteristics, the direction contribution of the

12bedrock geology may be decreased. Ideally, a co mbination of topographic and landscape criteria

could be used that includes such factors as el evation and landuse/landcov er as well as bedrock and surficial geology. For example, highly N-defici ent, young forests are far more likely to take up large amounts of deposited N than older forests and/or those nearing N saturation (the latter being mostly at higher elevations). In the case of S, deficiencies are very unlikely and thus soil chemical adsorption is the most likely cause of rete ntion of atmospheric inputs (if it occurs). In any event, sensitivity to acidifica tion is a function not only of th e ability of the soils to buffer incoming acids but also the ability of both soils and living biota to reta in incoming S and N.

d) What are the views of th e Panel on staff’s proposed options for how to aggregate acidification modeling from the catchmen t-scale to represent acid-sensitivity categories at the national-scale?

It is difficult to evaluate these options in the abstract, without s eeing comparative example results from applying alternative approaches. Th e approach of specifying a percentage of water bodies to be protected within a given area appears reas onable, but would be critically dependent on how the areas were selected. Selecting a spec ific percent of lakes or stream segments to protect seems somewhat arbitrary, especially when combined with the range of approaches for selecting the size, variability a nd distribution of lake and stream characteristics within a region. It might be useful to consider approaches by which the water bodies within any specified area could be first stratified to include only those which were considered potentially susceptible to acidification, based on estimates of preindustrial ANC, or acid sensit ivity class. Then a decision to protect a specific fraction of the potentially susceptible surface waters within that area would be more objective.

e) What are the views of the Panel on staf f’s suggested method to account for reduced nitrogen in the deposition metric?

As we note in response to Charge Question 10, even though the framework and the structure of proposed approach “takes into account” the re duced ambient nitrogen and its deposition in designing AAPI (atmospheric acidi fication potential index), it does so by including current ammonia/um levels. This approach would lead to over or under-prediction for an area depending upon whether the actual concentrations of NHx incr ease or decrease over time (see also response to charge question 10).

12. What are the views of the Panel on the relevan ce of the conceptual design for developing standards to protect against terres trial acidification effects? terre strial nutrient enrichment effects? aquatic nutrient enrichment effect s? Does the Panel have suggestions on additional data or methods that might enable EPA to ex pand the current aquatic acidification approach to cover additional effects?

Useful standards for protecting against adverse acidification or nutrien t enrichment response need to be tailored for the biological a nd physicochemical characteristics of sensitive ecosystems. Recognition that a more complete data set is available to support the development of an aquatic effects standard, and that such a standard would likely demand lower levels of

13nitrogen and sulfur inputs to ecosystem, EPA st aff is advised to focus on an AAPI standard driven by aquatic effects concerns.

The proposed conceptual design approach for terrest rial acidification effect s is along the lines of the approach for aquatic acidification and seem s reasonable and consiste nt with state-of-thescience. The “BC/Al” ratio appears to have the same level of robus tness as a terrestrial ecological indicator (directly measurable and pr edictable via models) as ANC has for lakes and streams. It meets the important criterion that it is di rectly responsive to deposition changes as well as being a good and direct pred ictor of ecological effects. The range currently considered (0.6 to 10 B C /Al) seems rather broad compared to ANC range of 50 to 100 μ eq/L and, ideally, might be narrowed in future assessments. If appropriate, the indicator for the more sensitive ecosystem could be used to provide protection for the less sensitive ecosystem. However, this would require further evaluation.

For nitrogen nutrient enrichment of both aquatic and terrestrial ecosystems, we recognize it will take additional effort before one can establish appropriate ecological indicators for aquatic and terrestrial systems and associated secondary standards. One appr oach worth investigating for its applicability to the current effort is the important effort that is currently taking place in EPA’s total maximum daily load (TMDL) process of deriving and apportioning pollutant loading limits for impaired surface waters. EPA should look into combining the TMDLs and secondary NAAQS for both acidification and nutr ient enrichment effects.

For the case of nutrient enrichment of coastal estuar ies, it would be useful to increase the level of confidence (through additional modeling and measurements) in the estimates of the fraction of reactive N (including reduced nitrogen, NH

x ) loading that is attributable to atmospheric deposition.

13. What are the views of th e Panel on the critica l uncertainties asso ciated with the conceptual design of an ecologically relevant multi-pollutant standard that need to be characterized in terms of their potentia l implications for the secondary standards?

This is an important question a nd it correctly focuses on the implications of uncertainties for setting the secondary standards rather than the uncertainties by themselves. However, the

discussion of “uncertainties” in this draft (in this chapter and throughout the report) is generally descriptive in nature, which is not helpful in providing a quantitative e ffect of uncertainties on the potential effectiveness of the secondary standard s. It will be helpful if all the uncertainties and their implications are described in one pl ace under a separate chapte r (please note our earlier comments above). It is recommended that EPA conduct a sensitivity study to characterize uncertainty associated with different component s of the conceptual framework and propagate that uncertainty at every step to arrive at an ensemble of SO

x and NO y response surfaces to meet a given standard. This would in turn provide a range for SO

x and NO

x concentrations that might satisfy a given standard.

14As an example, the calculations for Adirond acks could be repeated by using the following approach:

• Calculate Neco using different proposed approaches,

• Use a probable range of estimates for [B C ] 0 ,

• Use an estimate of Q based on diffe rent years (dry vs. wet year),

• Calculate L(NH

x ), V NOy and V SOx using different air quality model simulations that may already be available,

o Use CMAQ, CAMx, or other model simulati ons for different y ears (with different meteorological conditions and different emissions),

o Use different chemical mechanisms, if available.

14. To what extent do the figur es and examples aid in clarify ing the text? Should more or less information of this type be included in the second draft?

The Panel notes that figures, tables, maps, and examples were very useful in understanding the text material, especially when subjects discu ssed are complex. If anything, we would have preferred more tables, figures, and examples as a ppropriate. In particular , a separate conceptual diagram should be added which shows the importa nt contributing factors for each term in the AAPI equation.

Chapter 6: Options for Elements of a Standa rd to Protect Against Effects from Aquatic

Acidification

15. To what extent does the Panel agree th at the proposal to develop an Atmospheric Acidification Potential Ind ex (AAPI) linked to key determ inants of aquatic ANC is a reasonable approach to developing an ecologica lly relevant standard? Does the Panel generally agree that the secondary standard options identified by staff (including indicator, averaging time, form, and level) are generally consistent with the avai lable scientific and technical information and ar e appropriate for considerati on by the Administrator?

The CASAC Panel supports the Atmospheric Ac idification Potential Index (AAPI) as a reasonable approach to developing a NO

x and SO

x Secondary Standard to protect against aquatic (and potentially terrestrial) acidif ication. This or something simila r to this steady-state approach is the only practical method that could be us ed for a national assessment within the current timeframe of policy recommendations and developm ent. We agree that the indicators (SO

x concentrations, NO y concentrations, ANC) selected are appr opriate. A multi-year averaging time should be considered given the year-to year c limatic influence on atmospheric deposition. The Panel agrees that the multi-pollutant approach is appropriate for the NO

x and SO

x secondary standard to protect ecosystems fr om acidic deposition. It would be useful to conduct a parallel effort to apply/use dynamic models and surface wa ter time-series data to evaluate the limitations in steady-state approaches and assumptions in developing the acidificati on secondary standard.

1516. What are the views of the Panel on the degree of uncerta inty associated with each element of the suggested standard, e.g. the eco logical indicator; th e concentration to deposition ratios, reduced nitrogen, the natur al background ANC, and the ambient indicator and averaging time for NOx and SO

x , and its relationship to the degree of protection that could be expected from the standard? What ar e the views of the Pane l on how to fairly characterize the uncertainty associated with the degree of protection that such a standard would provide from aquatic acidification?

The Panel clearly recognizes the challenges in the development of the AAPI. There are

considerable uncertainties associated with all steps of developing an AAPI and the implementation of the various modeling processes involved in each step of the analysis, from ecological effects to deposition to ambient NO

x /SO

x concentrations. Information on levels of ANC protective to fish and other aquatic biota has been well developed and presents probably the lowest level of uncertainty in the enti re methodology. However, there is still high uncertainty regarding pre-industr ial levels of ANC. In addition, estimates of ANC could be flawed by the application of steady-state models that assume that the soil exchangeable base cations remain consistent over time. In reality, the base saturation of soil decreases with acidic deposition, natural leaching processes, and plan t base cation uptake and therefore the use of dynamic models should be considered to reduce this source of uncertainty. The modeled concentration to deposition ratios (or “atmospheric deposition transformation ratios”) may present a high level of uncertainty, which should be evaluated in more detail with comparison to

observations. Various individua l components behi nd the total V N or V S are not very well defined and could be quite variable especially in complex mountain terrain and non-uniform canopies. Deposition velocities of reac tive N species, such as NH 3 and organic N, both for the aquatic and terrestrial ecosystems, have high levels of uncertainty. Information on ambient levels and distribution of the reduced N forms, NH 3 and NH 4 are scarce which increases the uncertainty of the modeled ambient concentrations and depositi on of these pollutants, especially in remote areas. Strong reliance on using the CMAQ mode l would be greatly improved by more specific comparisons between CMAQ estimates and measured values. This is especially true for the

modeled values of NH 3 levels and distribution. Therefor e more emphasis should be placed on improvement of the model performance evaluation. In that regard recent efforts of EPA and National Park Service (NPS) CASTNET network on adding NH 3 measurements with passive samplers are applauded and should be supported.

The Panel recommends that EPA pay close attention to an issue of matching temporal and spatial scales in various components of the AAPI.

Generally, a higher level of uncertainty is expect ed for the terrestrial ecosystems versus aquatic ecosystems due to their more complex structure and diversity throughout the US, especially for

the nutritional effects of de position of the total reactive N transformed into the NO

x concentration-based standards. Because uncertainties associated with various elements of the standard have not been clearly delineated, it is difficult to state with any degree of confidence what degree of protection could be expected from a given standar d. One possible approach is to characterize uncertainty by conducting a sensitivity analysis for each chemical form of the standard and propagate these uncerta inties to arrive at a range of protection that a given standard would provide from a quatic acidification.

1617. What are the views of the P anel on aggregating the terms (Q, N

eco and BC 0 * ) used in estimating natural background ANC, denoted by th e function g(·), into 5 bins based on the geologic classification scheme?

The Panel believes strongly that there are few adva ntages associated with aggregating the g term in the AAPI equation. The Panel suggests that BC 0 * and Neco be separated and addressed separately. This separation makes the role and uncertainty of these processes in regulating the AAPI equation more transparent. The Panel also suggests that the EPA consider and possibly include a term within g which accounts the supply of naturally occurring organic acids to the natural background ANC value. Some considera tion of chronically acid ic or highly acid

sensitive surface waters that would not be rec overable at a given ANC limit should be given in

the next draft of the PA.

18. What are the views of the Panel on the use of regional air quality modeling (e.g., CMAQ)

results to establish the concentration-to-d eposition ratio (VNOy, VSOx) and reduced nitrogen deposition (NHx) in the AAPI calculat ion? What are the view s of the Panel on the

critical uncertainties associated with the use of CMAQ to gene rate these parameters, and the potential implications of these unc ertainties for the secondary standards?

There are a variety of problems with the use of regional air quality modeling to establish VNO y , VSO

x and NH

x . Although CMAQ is a regional air quality model that has been under development for many years, it has limitations in the prediction of the concentrations and deposition of different chemical species within the NO y , SO

x , and NH

x categories. Another issue is that there is an inherent, unvalida ted assumption in establishing fixed VNO y and VSO

x , namely that these ratios don’t vary with changes in emissions.

There are many sources of uncertainties that can a ffect the final values derived from the model. These include, but are not limited to:

• uncertainties in emissions (particularly NH

x emissions, but also NO

x emissions);

• inability of models to correc tly predict deposition from clouds and fog (both with respect to spatial distribution and liquid wate r content) and precipitation; and

• incomplete representation of chemistry (particularly cloud chemistry, nighttime chemistry and reactions with terrestrial components).

A comparison of CMAQ derived values with meas urements is needed before any confidence can be placed on the use of the model to generate the desired parameters. Although the model cannot be evaluated for dry deposition because of lack of measurements, evaluation of the ability of the model to represent ambient levels can serve as a proxy for its ability to represent dry deposition. It is recommended that following evaluations (using daily or week ly averaged quantities) be performed to assess the uncertainty in the model:

1. Model performance for nitric oxide, nitrogen dioxide, sulfur dioxide, nitrate, ammonium and aerosol nitrate, ammonium, and sulfate fo r different networks for which the data are routinely available,

172. Model performance for wet deposition of su lfate, nitrate, and ammonium using the National Atmospheric Depositi on Program (NADP) network,

3. A regional model evaluation using the continuo us measurements of nitric oxide, nitrogen dioxide, nitric acid and NO Y from the SEARCH network in the southeastern U.S.

In addition, the CMAQ model should be run with different anthropogenic emissions scenarios (keeping the other parameters and inputs c onstant) to quantify the sensitivity of VNO y and VSO

x to emissions change.

19. What are the views of th e Panel regarding presentation of the standards as a set of trade-off curves for NOx and SOx associated with specific le vels of AAPI, and specific values of the g, V NOx , V SOx , and NHx terms?

The Panel supports the conceptual model of the of the trade-off curves for different deposition

and concentration values of NO

x and SO

x for different levels of AAPI. The Panel notes that similar curves have been developed using dynamic models. An example is shown below developed for the response of Watershed 6 at the Hubbard Brook Experimental Forest, NH to different scenarios of sulfate and nitrate depos ition using the model PnET-BGC (Figure 1). The Panel urges the EPA to consider expanding this a pproach to also address tradeoffs associated with ammonium deposition.

Figure 1. Response surfaces calculated for different conditions of stream ANC under different combinations of atmospheric nitrate and sulf ate deposition for Watershed 6 at the Hubbard Brook Experimental Forest, NH for two periods at steady-state (~2150) (left) and at 2030 (right). The lines represent different values of predicted ANC (C.T. Driscoll unpublished). Isopleth of ANC - Target Load (2030)

-3

1

1

1

1 0

0

0

0 -1

-1

-1

-1 -2 -2 -2

2

2

2

2

3

3

3 4

4

SO 4 (eq/ha-yr)NO3(eq/ha-yr)

ANC (μeq/L) 35.8 48.4 64.0 83.9 104.5 125.2 9.7 16.9 24.9 34.5 44.7 54.9 Isopleth of ANC - Critical Load

0

0 5

5

5

5 10

10

10

10 15

15

15

SO 4 (eq/ha-yr) 35.8 48.4 64.0 83.9 104.5 125.2 9.7 16.9 24.9 34.5 44.7 54.9NO3(eq/ha-yr)

ANC (μeq/L)

1820. What are the views of the Panel on using a single year or a three-year average of recent year CMAQ modeling results to estimate the AAPI terms?

The Panel supports using multi-year averages of CMAQ modeling results to estimate terms in the AAPI equation. A three-year average would help smooth out the year-to-year climatic

variation in air concentration and deposition estimates. The Pane l would also support four or five years.

21. What are the views of th e panel on the ambient monito ring requirements? Are the proposed three ambient air measurements – NOy, SO2 and particulate sulfa te – sufficient to judge compliance with and AAPI?

The proposed measurements of ambient concentrations of SO 2 , particulate sulfate and NO Y would constitute a minimally adequate suite of measurements for determining compliance with the AAPI. To provide continuing feedback to su pport refinement of, and to evaluate the efficacy of strategies to attain the AAPI, it will also be important to assure continuation of existing wet and dry deposition networks like NADP and CASTNET, to enhance those networks to add better measurements of gaseous ammonia concentration and deposition, and to assure the continuation of aquatic chemistry and effects monitoring e fforts like the LTM and TIME programs. The Panel also recommends an expansion of existi ng programs to include some soil (especially evaluating changes in base cation status) and biological monitoring.

22. What are the views of th e Panel on using existing NOy and PM2.5 sulfate measurement techniques as the basis for defining a Federa l Reference Method to judge compliance with

and standard?

PM 2.5 sulfate measurement techniqu es are well established, consistently produce similar results

across several different national networks, and should provide a re asonable basis for defining an FRM for compliance determination. Currently available NO Y measurement techniques should also provide a sound basis for defining a FRM method. NO Y measurements have been conducted successfully for many years by the research comm unity, and are currently experiencing more widespread deployment in routine state-operated monitoring networks. The methods are robust and standardized and it’s likely that early feedback from current monitoring efforts will identify any common problems with the methods and lead quickly to refined operational procedures. EPA is encouraged to consult with the CA SAC AAMM Subcommittee to review options for developing standard methods for measuring SO

x and NO y species for compliance determination, as well as for measuring other key species such as gaseous ammonia and organic nitrates which are currently not measured in routine monitoring networks.

19Chapter 7: Co-protection

23. What are the views of th e panel on the approach taken to compare the protection provided by a potential aquatic acidification st andard to the protection needed for terrestrial acidification?

The panel found it appropriate for EPA Staff to c onsider the potential interrelationships between aquatic acidification standards and protection of adjacent or closely related terrestrial ecosystems. Recognition that (1) various species of nitrogen (e.g., NH 4 or NO 3 ) and sulfur may cycle within or move out of ecosystems differen tly from each other based on their chemical and physical properties; and (2) aqua tic and terrestrial systems behave quite differently in the biogeochemical, temporal, and sp atial processing of nitrogen and ,sulfur should be clearly reiterated in this discussion. Chapter 7 shoul d be expanded to better explain the potential interrelationships between aqua tic and related terrestrial re sponses to acidification.

24. What are the views of the panel on a future comparison of the protection provided by a potential aquatic acidification standard to nut rient enrichment benchmarks? What are the views of the panel regarding usi ng a nutrient enrichment benchmark to be a limiting factor on the nitrogen in the aquatic acidification standard, instead of having a separate standard?

Dynamic models of ecological response shoul d be considered as the primary means of addressing a continuum of respons es linking terrestrial and aquatic system following nitrogen or sulfur inputs. The search for simple relationshi ps between aquatic and te rrestrial responses to regional nitrogen and sulfur atmospheric input s is a simplification of complex processes operating on divergent spatial and temporal scales . Where sulfur is the primary acidifying agent in a given region, one should not expect to find a related response to nitrogen enrichment. It is important to recognize that the re tention or lack of retention of nitrogen is controlled almost entirely by biological processes whereas the reten tion of sulfur is cont rolled by both abiotic (e.g., chemical adsorption) and biological processes (e .g., net immobilization or mineralization); thus, a combined standard in sites dominated by su lfur deposition may or may not protect from excessive nitrogen and vice-versa. The Panel is concerned that a single standard addressing both acidification and nutrient enrichment is pr obably not practical at this point.

Chapter 9: Conclusions

25. What are the views of th e Panel on the preliminary st aff conclusions regarding the adequacy of the current standards, the need for an integrated multi-pollutant structure for revised standards, and the propos ed form of the joint NO

x SO

x standards for aquatic acidification?

The review of current standards and the docum entation of the need for an integrated multipollutant structure for revised standards are we ll done. This chapter summarizes the importance of developing new secondary joint standards for NO

x and SO

x . The panel supports the current focus on aquatic acidification us ing ANC as a key parameter. The use of the AAPI for evaluating freshwater acidification is a new and creative approach for helping the development of the joint secondary standard for NO

x and SO

x . The use of the BC/Al ratio in evaluating

20acidification of terrestrial ecosystems appears to be an appropriate tool. Further development of a method that evaluates the impact of nitrogen as a nutrient for terrestrial and aquatic ecosystems will help expand the spatial scope of the second ary standard with respect to the effects of nitrogen deposition.

26. What are the views of th e Panel on the overall characte rization of uncertainty as it relates to the determination of an ecologi cally-relevant multi-pol lutant standard for NO

x and

SO

x ?

As we note a number of times, the treatment of un certainty is yet to be fully developed and the Panel recommends that this categorization be prov ided as a separate chapter in the next version of the report. This chapter wi ll need to discuss the major sour ces of uncertainty including: 1) the estimates of the atmospheric deposition of n itrogen and sulfur; and 2) the resultant ecosystem effects caused by acidification and addition of nitrogen as a nutr ient. The major sources of uncertainty will need to be highli ghted in the conclusions. The listing of future research needs to be reconsidered with respect to the comments provided by the Panel so that there is a clear priority with respect to the most critical n eeds for further developm ent and evaluation of secondary standards for NO

x and SO

x . Linking these needs to the most important aspects of uncertainty will strengthen the argu ments for these research efforts.

21Enclosure C

Review Comments from the NOx- SOx Secondary Panel on the Policy Assessment for the Review of the Secondary National Ambient Air Quality Standard for NO

x and SO

x : First Draft

Comments received:

Dr. Praveen K. Amar .................................................................................................................... 23 Dr. Andrzej Bytnerowicz .............................................................................................................. 29

Ms. Lauraine Chestnut .................................................................................................................. 33 Dr. Ellis Cowling .......................................................................................................................... 39

Dr. Charles T. Driscoll .................................................................................................................. 45

Dr. Paul J. Hanson ........................................................................................................................ 63

Dr. Dale W. Johnson ..................................................................................................................... 69

Dr. Naresh Kumar ......................................................................................................................... 73 Dr. Myron J. Mitchell ................................................................................................................... 77
Mr. Rich Poirot ........................................................................................................................... 105

Mr. Dave Shaw ........................................................................................................................... 117

Dr. Kathleen Weathers ................................................................................................................ 122

22

### Dr. Praveen K. Amar

Chapter 3: Considerations of Adversity to Public Welfare

Charge Question 4. What are the views of th e Panel regarding the characterizations of adversity to public welfare presented in the document? What are the views of the Panel regarding the use of the ecosystem services fr amework as an additional metric to inform questions of adversity? What are the views of the Panel regarding the usefulness of including economic valuation of some of thes e ecosystem services in the policy assessment

document?

Chapter 3 covers three areas of :a) adversity to public welfare, b) application of ecosystem services framework as a way/metric to address adve rsity to public welfare, and , c) usefulness of economic valuation approaches to “value” ecosys tem services, when doable. I think that the overall effort is quite good. My main and gene ral comment and concern is that of the three attributes of the adversity, “type , intensity, and scale,” (page 62, line 9), Chapter 3 needs to be improved with respect to explaining the scale of adversity to public we lfare driven by “delta” or changes to ecosystem services as a function of changes in atmospheric deposition of SOx, NOy, and potentially no changes (potentially increases) in atmospheric deposit ion of reduced NHx. The Chapter presents many quantitative numbers in dollars without the proper context (at least for me) when economic valuation data are presented. I would note that the “purpose of numbers is not numbers at all but insights.” And, insigh ts for policy makers are missing here. Also, see my response to Charge Question 5 below.

Charge Question 5. To what extent is the pr esentation of the ecos ystem services in the document scientifically so und and clearly communicated?

The concept of ecosystem services and its rela tionship to adversity and public welfare is reasonably clear to me. However, as I note abov e, the communication of quantitative information can be and should be improved. One suggestion is that many “ changes” in dollar values for ecosystem services caused by increased or decreased SOx and NOy deposition should be presented in Figures and Tables (or both) for be tter communication with the reader. It would also be helpful to write and comparatively explain these numbers so that the audience knows that “$0.69 million, or only $690,000” (value of “public welfare gains related to U.S. sugar maple and red spruce forest markets by eliminating cr itical load exceedances,” page 84) is quite “different” (in fact, different by four orders of magnitude or, by a ratio of 10,000 to 1) than $11.59 billion or $11,590,000,000 (annual bene fit for California residents from trail hiking, page 88). Do these two numbers make sense in a co mparative economic valuation mode? I do not know, but I am puzzled. Please present all dollar nu mbers with comparative insights. Otherwise, they are just numbers and not insights.

Charge Question 6. What are the views of the Panel on the critical un certainties associated with articulating adversity to public welfare that need to be characterized in terms of their potential implications for the secondary standards?

23It seems to me that the valuation (monetized or not) of all types of ecosystem services (provisioning, regulating, cultural, and supporting) needs to be addressed with the recognition

that different levels of uncertain ty are associated with valuati on (monetized or not) of the four important services ecosystems provi de towards public welfare.

I commend EPA for asking the question on uncertain ty “correctly” in that it focuses not on the

uncertainties associated with ar ticulating adversity to public we lfare themselves (“there will always be uncertainties,” what else is new ?), but on the effect of uncertainties on the “implications for the secondary standards.” My understanding is that th e second draft of Policy Assessment will be more descriptive and more quantitative than this draft on how overall uncertainties across the whole sp ectrum of this approach (atmospheric and ecological models, measurements of atmospheric and ecological data, valuation of eco system services, etc.) will be addressed. It will be a good idea if all the uncerta inties and their implications be described in one place under one chapter in some integrated and relative manner (in an Appendix?).

Chapter 5: Conceptual Design of an Ecol ogically Relevant Multi-Pollutant Standard

Charge Question 10. What are the views of the Panel on staff’s proposed conceptual framework for the structure of a multi polluta nt, ecologically relevant standard for NOx and SOx? To what extent does the Panel agree that this suggested structure adequately represents the scientific lin kages between ecological responses, water chemistry, atmospheric deposition, and ambient NOx and SOx?

The proposed framework and structure of the propos ed standard (s) is very well-thought out for addressing various components and connections be tween these components (ecological effects, atmospheric wet and dry deposit ion, atmospheric concentrations of NOy and SOx, and surface water chemistry), with one major exception noted below.

Even though the framework and the structure “t akes into account” the reduced ambient NHx and its deposition in design ing AAPI (atmospheric acidification pot ential index) , it does so in a manner such that future control strategies and policy options most probably will not allow EPA to address and require reductions in national ammonia emissions under proposed standard setting structure. Ammonia emissions are currently at ab out 4 to 5 million tons per year, and are rising. As the Executive Summary notes on Page ES-7, this approach assumes that “the reduced forms of nitrogen deposition are relative ly constant over time. This assumption could lead to over or under protection for an area depending on whether th e actual concentrations of reduced forms of nitrogen increase or decrease over time.” For th e case of unregulated ammonia as a criteria pollutant at the present time, emissions (and resulting ammonia and ammonium concentrations and reduced nitrogen deposition le vels) are only expected to increase by as much as ten percent over the next few decades because of increased food production and increased CAFO sources (confined animal feeding operations) in the U.S.

24Notwithstanding my concern about not addressi ng reduced nitrogen directly, the proposed structure more than adequately represents the scientific linkages betw een ecological effects, surface water chemistry, atmospheric deposition, and ambient levels of NOy and SOx.

Charge Question 11. What are the views of the Panel on the relevance of the conceptual design for developing standards to protect against aquatic acid ification effects?

Charge Question 11. a. What are the views of the Panel on staff’s proposed options for the ecosystem acidification model (s) to rep resent the ecological response function?

I do not have background or expertise in the de sign and application of ecosystem acidification models (MAGIC, FAB, SSWC, etc.) used in th is Policy Assessment and I found it difficult to follow the general flow of discussion. A general comment that can be made about these models is that they need to be “validated/verified/calib rated” to increase confidence in their results. This Chapter notes that model such as MAGIC, “becau se of their aggregated nature, need to be

calibrated to observational data fr om a system before it can be used to examine potential system response.” A large set of observational data on st ream water quality, soil chemical and physical characteristics, etc., are needed. My general ques tion is on the degree and ex tent of evaluation of ecological acidification models compared to, say, the evaluation/calibration of atmospheric models such as CMAQ. For example, recognizi ng that these models do involve different physical, chemical, and biological systems, is the level of confidence in these models at a “comparable” level?

Charge Question 11. b. What are the views of the Panel on the relative merits of the two techniques for calculating Neco, the parame ter representing the amount of deposited nitrogen that is available for acidificat ion due to uptake, denitrification and

immobilization?

As in above question, this is not my area of expe rtise and I am not sure which approach is more reliable. It appears to me, however, that the second approach (equation (4)), based on measured N leaching in a catchment, and may be more accurate. Is it? Is it also more protective? The text (page 160) briefly (but, no t clearly) describes a third approach where SSWC results on critical load are constrained by Neco (how and by how mu ch?). Which of the three approaches provide the optimum balance between accuracy/reliabil ity and ease of use? I assume our ecology colleagues will shed more light on this question.

Charge Question 11. c. What are the views of the Panel on staff’s proposed options for developing acid sensitivity cla sses to categorize the national landscape? Is it appropriate to base this classification on bedrock geology? Shoul d multiple criteria be used to inform the sensitivity categories?

The literature and published research in the field indicates that bedrock geology is an acceptable basis for developing acid-sensitivity classes on the larger scale of the U.S. One way to answer the question whether other multiple features/mu ltiple criteria, in addition to bedrock geology, may/should be used as the basis for national ca tegories of acid-sensitiv ity would be to do a “sensitivity analysis.” This c ould involve other variables to which acid-sensitivity has been

25shown to be correlated with (for example, elevation, watershed ar ea, percent forested watershed, etc.). However, this type of investigation needs to be well-designed and focused, taking into

account co-variables and would need to be valida ted with actual field data (for example, with surface water chemistry data) before multiple crite ria are selected to redefine acid-sensitivity categories on the national scale,

Charge Question 11. d. What are the views of the Panel on staff’s proposed options for how to aggregate acidification modeling from the ca tchment-scale to represent acid-sensitivity categories at the national-scale?

Of course, this question is on how to “add up” results of acidificati on modeling at catchmentscale to represent acid-sensitivity categories at the national scale. As the Policy Assessment notes, the proposed standard woul d be designed such that “a speci fied percentage of a population

of water bodies does not exceed a critical load fo r the specified value of ANC.” What is not clear is how this percen t of lakes/streams would be chosen. For example, would one choose, say,

50% of lakes or 95% of all lakes to be protected? I assume it is a policy call of EPA. This also implies that this percent number will be chosen fo r a certain area of certain spatial extent/size (all of Adirondack? Adirondack subdivided by geologic characteristics? by elevation?). The issue here is the difficulty of deciding an acceptable de gree of representativeness of a small sample of measured lakes to represent the whole population of lakes/streams with a large acid-sensitivity distribution. One potential and, may be better, appr oach would be to only include those lakes in the sample and in the total population that, ba sed on current and/or hi storic conditions, are considered to have high level of sensitivity to acidification in the first place. This is analogous to establishing primary (public health) NAQQS, base d on protecting the most sensitive fraction of human population.

Charge Question 11e. What are the views of the Panel on staff’s suggested method to account for reduced nitrogen in the deposition metric? As I note in response to Charge Question 10, ev en though the framework and the structure of proposed approach “takes into account” the re duced ambient NHx and its deposition in designing AAPI (atmospheric acidification potential index) , it does so in a manner such that it most probably will not allow EPA to address and re quire reductions in national ammonia emissions under the proposed standard structure. Ammonia em issions are currently at about 4 to 5 million tons per year and, unlike SOx and NOx emissions , are rising. As the Executive Summary notes on Page ES-7, this approach assumes that “t he reduced forms of nitrogen deposition are relatively constant over time. This assumption coul d lead to over or under protection for an area depending on whether the actual concentrations of reduced forms of nitrogen increase or decrease over time.” For the case of unregul ated ammonia, emissions (and resulting ammonia and ammonium concentrations and deposition of re duced nitrogen) are only expected to increase by as much as ten percent over the next fe w decades because of higher human population, increased food production and increased CAFO ac tivity (confined animal feeding operations) in

the U.S.

Charge Question 12. What are the views of the Panel on the relevance of the conceptual design for developing standards to protect against terrestrial acidification effects?

terrestrial nutrient enrichment effects? aquatic nutrient enrich ment effects? Does the Panel

26have suggestions on additional data or methods that might enable EPA to expand the current aquatic acidification approac h to cover additional effects?

The design approach developed here for aquatic acidification should be relevant to developing

future standards for terrestrial acidification effects. The “BC/Al” ratio appears to have the same level of robustness as an ecologi cal indicator as ANC is for la kes and streams. It meets the important criterion that it can be correlated with ecological effect s on forests and soils, and also through models, to acid deposition levels. As th e Assessment notes, in general, the aquatic critical loads offer greater protection to the wate rsheds than do the terrestrial critical loads. However, this relationship changes depending upon whether lakes are of “ low sensitivity”, “not sensitive”, “highly sensitive” or “moderately sens itive” etc. Therefore, it would be useful for EPA to allow sufficient flexibility into the pro cess of expanding the approach outlined here to terrestrial acidification, as well as to other ecological effects. For the case of nutrient enrichment of coastal estuaries, it would be extremely us eful to increase the le vel of confidence (through additional modeling and measurements) in dete rmining the fraction of reactive N (including reduced nitrogen, NHx) loading that is attributable to atmosphe ric deposition.

Charge Question 13. What are the views of the Panel on the critical uncertainties associated with the conceptual design of an ecologically relevant mu lti-pollutant standard

that need to be characterized in terms of their potential implications for the secondary

standards?

This is important question and, equally important, is asked “correctly” in that it focuses not on the uncertainties themselves (“there will always be uncertainties”) but on the effect of uncertainties on the implications for setting the secondary standards. My understanding is that the second draft of Policy Assessment will be more descriptive and more quantitative than this draft on how uncertainties across the whole sp ectrum of this approach (atmospheric and ecological models, measurements of atmospheri c and ecological data, ecosystem services) will be addressed. It will be a good id ea if all the uncer tainties and their implications be described in one place under one chapter in some integrated and relative manner (in an Appendix?).

The discussion of “uncertainties” in this draft (in this Chapter and throughout the report) is generally descriptive in nature. It is, however, not helpful in pr oviding a quantitative and relative sense of uncertainties in various components (e missions, wet and dry deposition predictions and measurements, ecological models versus CMAQ, etc. ). For example, it woul d be useful to state

that NH 3 emissions are much more uncertain than NOx emissions that in turn are less certain

than SO 2 emissions. It may also be useful to state th at dry deposition is simply not measured but

inferred from model calculations. For variables that have uncertainties of unknown magnitude, sensitivity studies could be usef ul to put bounds on the results.

14. To what extent do the figures and examples aid in clarifying the text? Should more or less information of this type be included in the second draft?

The Figures, Tables, and examples were very useful in understanding the text material, especially when subject discussed was not in my area of expertise (ecological models). If anything, I would have preferred mo re Tables, Figures, and examples to explain abstract ideas in

the text.

27General Editorial Comments :

Page 147, Line 10: I think you need to say not a DESIRED level but a “SPECIFIC or GIVEN”

level.

Page 147, Lines 21, 23, please avoid “Let us now.”” Or “ you could calculate..”

Page 148, Figure 5-2 Title: It is too long, a nd needs to be shortened and clarified.

Page 148, Line 7-8: Please restate, “it is not pr actical to evaluate each catchment individually since it is not the appropriate appr oach for a national standard.” Page 148, Line 11; “.. as far as the relati onship of total deposited N and S to ANC IS

CONCERNED.”

Page 148, Line 18: Please explain here what is meant by DL %ECO ?

Page 149, Line 28: please explain here what is meant by “recently developed base cation surplus.....”

Page 151, Line 2-4: Please write clearly to say “.. show long- term trends in RELATIONSHIP between anthro N and S dep and ANC .....”

Page 151: Table should be labe led Table 5.2-1. Also, the accompa nying text needs to explain how “single value” is different from critical load function.

Page 151, Line 16: Please describe and compar e and contrast the two approaches mentioned here: time series analysis and critical load approach

Page 151: Line 12-13 The Title 5.2.3 needs to say ““... indicator AND amount of N and S deposition.”

Page 152, Line 30: “.. the relations hip BETWEEN ANC and deposition.”

P 154, Line 10: “Consideration of the e ffects.... is REQUIRED extensively......”

P 154: Lines 20 and 29; please be parallel and use the term “surface water quality data”

P 155, Line 28: The technique does not DETERMINE the number of streams, it simply estimates

the number of streams.

P 156, Line 15: ‘the relations hip BETWEEN ANC and deposition

Page 161, Line 17: “...this technique is SHOWN...”

28

### Dr. Andrzej Bytnerowicz

Chapter 6: Options for Elements of a Standard to Protect Against Effects from Aquatic Acidification

15. To what extent does the Panel agree that the proposal to develop an Atmospheric Acidification Potential Index (AAPI) linked to key determinants of aquatic ANC is a reasonable approach to developing an ecologi cally relevant standard? Does the Panel generally agree that the secondary standard option s identified by staff (including indicator, averaging time, form, and level) are generally consistent with the available scientific and technical information and are appropriate for consideration by the Administrator?

In a general sense this is a r easonable approach that links eco logical responses (ANC as an ecological indicator), acidifying deposition of N and S (resulting from most important forms of atmospheric sulfur and reactive nitrogen), a nd ambient NOx and SOx concentrations. Science and logic behind this concept are good and base d on the current understandi ng of the effects of atmospheric deposition on aquatic ecosystems. I would like to complement the EPA authors for developing a concept that logically links the concentration-based standards for NOx and SOx with ecological effects of total N and S deposition that at the same time includes reduced form of N as part of the background chemical environment of the evaluated watersheds. Potential problems related to the proposed approach are mainly related to conversion of deposition to

concentrations and to the unknown levels of unc ertainty of various stages of the proposed methodology. While an averaging time of a single ye ar for acidification of aquatic ecosystems could be probably justified, a similar approach fo r the terrestrial ecosystems is too coarse and

therefore is not recommended. For te rrestrial ecosystems the annual averages should be based on aggregated values of the individual phases of physiological activ ity of vegetation specific for various ecological zones.

16. What are the views of the Panel on the de gree of uncertainty associated with each element of the suggested standard, e.g. the ecological indicator; the concentration to deposition ratios, reduced nitrogen, the natural background ANC, and the ambient indicator and averaging time for NOx and SO x , and its relationship to the degree of protection that could be expected from the st andard? What are the views of the Panel on how to fairly characterize the uncertainty as sociated with the degree of protection that such a standard would provide for aquatic acidification?

Scientific information on levels of acid neut ralizing capacity (ANC) pr otective to fish and aquatic biota has been well developed and therefore present the lo west level of uncertainty. On the other hand, the concentrations to deposition ratios present a very high level of uncertainty. Various individual components behind the total V N or V S are not very well defined and could be quite variable. According to my understanding of the problem, a level of uncertainty for water surfaces is lower than for the terrestrial ecosys tems. Deposition velocities of reactive N species,

such as NH 3 and organic N, both for the aquatic and terrestrial ecosystems have high level of uncertainty. Information on ambient levels a nd distribution of the reduced N forms, NH 3 and

29NH 4 + , are scarce and therefore there is very high level of uncertainty on distribution of these pollutants, especially in remote areas, and specifically in the mount ainous complex terrain. Ammonia concentration values from the CMAQ m odel are not reliable and have not matched the ground-level measurements (Fenn et al., 2009). In summary, the expected level of uncertainty of the proposed methodology for protection against acidification of the aquatic ecosystems is high.

17. What are the views of the Panel on aggregating the terms (Q, N eco and BC 0* ) used in estimating natural background ANC, denoted by th e function g(·), into 5 bins based on the geologic classification scheme?

Introduction of function g(

. ) aggregating Q, N

eco and BC

o seems to be appropriate. Using the geologic classification scheme is a good idea si nce chemistry and weathering of geologic

material are the main factors affecting abilities of the aqua tic ecosystems to cope with acidification caused by the atmospheri cally deposited S and N compounds.

18. What are the views of the Panel on th e use of regional ai r quality modeling (e.g., CMAQ) results to establish the concentration-to-deposition ratio (V NOy , V SOx ) and reduced nitrogen deposition (NHx) in the AAPI calculat ion? What are the views of the Panel on

the critical uncertainties associat ed with the use of CMAQ to generate these parameters, and the potential implications of these uncertainties for the secondary standards?

First, I would like to suggest changing sym bol “V” describing “concentration-to-deposition ratios” to a different one. Sy mbol “V”, at least in my understanding, has been used for description of deposition velocity (calculated by dividing deposition, or flux, of a given pollutant by its ambient concentration). As I stated a bove (point No. 16), the CMAQ model outputs often do not agree with the ground-level measurements, especially for the reduced N compounds (Fenn et al., 2009). Therefore I strongl y support the recent EPA’s efforts to enhance a national network

of NH 3 monitoring using passive samp lers. This effort should con tinue especially in remote areas. Implementation of passive sampling methodol ogy is needed and various passive samplers (such as Alpha, Ogawa or Radiello) could be used. It would make se nse to include such measurements as a permanent feature of the na tional monitoring networks such as CASTNET or

NADP.

19. What are the views of the Panel regarding presentation of the standards as a set of

tradeoff curves for NOx and SOx associated with specific levels of AAPI, and specific values of the g, V NOx , V SOx , and NHx terms?

It is a reasonable way of dea ling with two elements which si multaneously are responsible for acidification of the aquatic and terrestrial ecosystems. As I have stated above, the V values for specific components of deposition generally will have a high level of unc ertainty. Therefore

final calculations of the NOx or SOx con centrations might be problematic.

20. What are the views of the Panel on using a single year or a three year average of recent year CMAQ modeling results to estimate the AAPI terms?

30A single year or an average of three years of measurements based on the CMAQ model is not adequate. There will be large differences in co ncentrations of the pollutants responsible for acidification as well as significant spatial and temporal differences in N and S fluxes due to changing weather, distribution of emission sources, and levels of emissi ons. With an increasing use of green energy and unpredic table climate changes, year-t o-year information on annual values (possibly also presented as a running mean of three years) would gr eatly help in reliable

estimates of the AAPI values and reduction of their uncertainties.

21. What are the views of the panel on the ambient monitoring requirements? Is for the proposed three ambient air measurements – NOy, SO 2 and particulate sulfate – sufficient to judge compliance with and AAPI?

Some of the major components of NOy are measur ed on national air quality monitoring networks (NO, NO 2 and SO 2 ). Fine particulate sulfate has been extensively measured within the

IMPROVE and CASTNET networks in remote ar eas of the US. Among the NOy species, HNO 3 and particulate NO 3 are measured in the CASTNET ne twork. However, organic N is not routinely measured although it may provide substa ntial levels of reactive N (Zhang et al, 2008). In summary – for a successful national program designed for a long-term understanding of acidifying effects of atmospheric deposition, a nd information on relevant N and S species, a thorough evaluation of the national air quality mon itoring efforts in remote areas is needed. Some techniques, such as the already mentione d passive sampling, should be considered. They can be successfully used for m onitoring concentrations of NO, NO 2 , NH 3 , HONO and HNO 3 and

SO 2 . Such efforts are already underway in Europe on the ICP Forests Level II plots and have also

been conducted in selected areas of the United States and Canada.

22. What are the views of the Panel on usin g existing NOy and PM2.5 sulfate measurement techniques as the basis for defining a Fed eral Reference Method to judge compliance with

and

standard?

Use of chemiluminescence for total NOy measurements seems to be an accepted methodology although uncertainties exist related to reducti on of the organically bound and mineralized N (page 208 of the reviewed document and Navas et al., 1997). Extensive sulfate measurements

have been conducted nationwide within the CA STNET, IMPROVE and EPA CNS networks. It seems that these methodologies could be used for defining the Federal Reference Method, although an opinion of experienced atmospheri c chemists is recommended.

31References: Fenn, M.E., Sickman, J. O., Bytnerowicz, A., Cl ow, D. W., Molotch, N. P., Pleim, J. E., Tonnesen, G. S., Weathers, K. C., Padgett, P. E ., Campbell, D. H. 2009. Methods for Measuring Atmospheric Nitrogen Deposition Inputs in Arid and Montane Ecosystems of Western North America. Developments in Environmental Sc ience, Vol. 9, Allan H. Legge (Ed.), l77-225.

Navas, M. J., Jimenez, A. M., Galan, G. 1997. Air analysis: determinations of nitrogen compounds by chemiluminescence. Atmospheric Environment, 31, 3603-3608. Zhang, Y., Zheng, L., Liu, X.,Jickells, T., Cape, J. N., Goulding, K., Fangmeier, A., Zhang, F. 2008. Evidence for organic N deposition and its an thropogenic sources in China. Atmospheric Environment, 42, 1035–1041.

32

### Ms. Lauraine Chestnut

Chapter 3: Considerations of Adversity to Public Welfare

Charge Question 4: What are the views of the panel regarding the characterization of adversity to public welfare presented in this document? What are the views of the panel regarding the use of the ecosystem service fram ework as an additional metric to inform questions of adversity? What are the views of the panel regarding the usefulness of including economic valuation of some of thes e ecosystem services in the policy assessment

document?

Chapter 3 does a nice job at the beginning in bri nging in language from ot her agencies and other regulatory assessments to articulate why protec tion and preservation of natural environmental resources are important and motivate legislation and regulation in many areas. I especially like the words from the FWS about wildlife refuge systems being managed to “ensure that the biological integrity, diversit y, and environmental health of the Systems are maintained for the benefit of present and future generati ons of Americans.” (underline added)

The focus in the text is on federal protections, but it is important to r ecognize that the public

cares about all kinds of natural ar eas including state and local parks as well as the federal Class I areas. This distinction is important for the mana gement authorities, but not so much for the public. While Figures 3-4 and 3-5 have the right idea in terms of concept, the focus on NPS Class I areas is too limited. There are many areas throughout the country that are largely natural where people drive, fish, hike, sight see and enjoy the natural flora and fauna, including state and local parks, national and state forests, and all th e lakes and streams therein. Even though these do not have the protection levels of the national parks and wild erness areas, and there may be multiple uses such as timber harvesting and grazi ng, the value of these areas stems largely from

their natural characteristics and the public cares about the “integ rity, diversity and environmental

health” of these areas.

The basic concepts of ecosystems services are us eful to explain why the health of these systems matters. To aid this process of providing informa tion to help the Administ rator assess adversity with regard to determining an a ppropriate level for the secondary standard, more is needed than just a conceptual framework. The framewor k needs to be used to characterize the change or loss in services that currently ex ists as a result SOx/NOx depositi on. Chapter 3 does a reasonable job with this for the aquatic acidificati on case, but not as well for the ot hers. It is ideal if this change or loss can be defined quantitatively, but this is not necessary. The change or loss can be described based on causal linkages that are well do cumented even if they cannot be quantified with specific dose-response relationships.

The economic valuation estimates included in Chapter 3 are useful when they are tied to the change or loss in value of ecosystem services that can be reasonably attr ibuted to SOx/NOx deposition. Total values of serv ices that flow from the eff ected ecosystems are less useful because they convey little about what share of this value is being lost. In fact, if they are based

33on current service levels then th ey are already missing the value of what has been lost due to harmful effects of SOx/NOx deposition.

Page 76: The discussion here unnecessarily unde rcuts the usefulness of economic valuation estimates. It is true that just because there is some quantifiable economic welfare loss does not mean that the loss is necessarily significant e nough to be adverse. However, demonstrating a substantial loss in economic valuation terms would provide strong support for a determination

that there is an adverse eff ect, even though the numbers alon e are not enough to specify the specific threshold at which a loss become substantial rather than trivial.

Pages 77-78: The comments here about the assu mptions in economics that “public preference are paramount” are misleading. Economic valuati on takes expressed preferences to be a valid measure of welfare when they are based on accu rate information. If people do not express a value to protect ecosystems from the effects of pollution because th ey do not understand the implications of these effects, then such lack of value should not guide policy decisions.

Page 80: I think the Banzhaf et al. (2006) st udy should be given more mention than only in footnote 11. It provides strong ev idence that the public cares a bout water quality in Adirondack lakes being sufficient to support nati ve species, even if they do not participate in fishing. It is important to emphasize that these results are only for residents of NY state. Residents in other states could also be expected to value water quality in the Adirondack area. EPA may not have a great deal of confidence in the specific quantitati ve estimates based on extrapolations from the Banzhaf et al. study, but the fact that the resu lts exceed by a large amount the estimates of the

value of lost recreational fishi ng services is a very important finding that should be emphasized.

Page 82: The estimates of economic value of lost recreational fishing serv ices in the Adirondack region are not very well explained. The $4 million is the annualized value of reaching an ANC level of only 20. At ANC of 50 or 100, the annuali zed value is $8 to $9 million. This seems like the most relevant range. The $300 million num ber is a present value through 2100. (REA, Appendix 8, Table 2.2-6) When the fishing losses are extrapolated to all th e comparable lakes in NY state, the estimate of annual value of ga ining ANC of 50 is $25 to $28 million, and of gaining ANC of 100 is $110 to $130 million, and pr esent values are in the billions (REA, Appendix 8, Table 2.2-7). It is not enough to just say that the range is $4 million to $300 million. The numbers need a bit more explanation. It is al so not clear what point is being made in lines 11-15. In contrast to these numbers, the estimates of annual value to all NY state households of reducing acidification in the Adirondacks regi on to an ANC of 50 is $300 million to $800 million based on extrapolations from the Banz haf et al. study (REA, Appendix 8, Table 2.2-9). These estimates are worth mentioning in Chapte r 3. They reflect use and nonuse values held by the public for protecting the area and the underlyi ng study specifically described the effects of acidification in the region.

The discussion of the terrestrial effects of acidification would benef it from a descriptive

statement about how the terres trial ecosystem services are affected by SOx/NOx deposition

related acidification at current le vels. Can something be said about forest decline? Mortality rates of trees in sensitive species in affected areas? Ge ographic areas affected? Visual aesthetic effects

for visitors? Habitat lo sses or quality degradation? Th e statements should not be that

34acidification could cause these ki nds of effects, but rather, th at such and such effects are documented in specific locations at current conditions.

Page 83, lines 20-28: These seem like important studies. How do the descriptions of the effects on the forests that are being valued in these st udies compare to current documented effects of

acidification?

Page 84: I think these are estimates of loss in commercial value of timber harvested for red spruce and sugar maple trees. It appears to be re latively small compared to the total market (of these species alone or of all timber in the region?) , but this is not entire ly clear. These numbers need a bit more explanation and context. They appear to show that the commercial value of timber losses for these species is relatively inconsequential.

This section is challenging because the economic valuation estimates are limited and cover only a portion of the ecosystem services affected by deposition. The bottom line is therefore irrelevant, so it is insufficient to just list vari ous dollar amounts. It is important to include

discussion of what the available estimates cove r and why they are relevant—what do they say about the significance of the welfare effect? It is also important to re mind the reader of the lost or impaired services that are not included in these estimates.

Charge Question 5: To what extent is the presentation of ecosystem services in this document scientifically so und and clearly communicated?

The basic concepts of ecosystem services and ho w they relate to ecosystem function and to the

idea of welfare effects as defined in the C AA are clearly communicated and well presented. Description and summarization of how these se rvices are being affected by the effects of SOx/NOx deposition need to be improved. The RE A and ISA provide support for descriptions of these effects on services even though sp ecific quantification is not feasible.

Charge Question 6: What are the views of th e panel on the critical uncertainties associated with articulating adversity to public welfare that need to be characterized in terms of their potential implications for the secondary standards?

It is pretty clear that current levels of aci dification are causing adverse effects on aquatic

resources in some locations. It seems there is plenty of support to argue that it is adverse to public welfare to have a significant share of lake s and streams that cannot support several species

of fish that would have lived there bu t for the effects of manmade pollution. Important uncertainties include how much of th e adversity would be reduced with a standard

based on ANC 50 versus ANC 100. The economic valuation estimates show additional value in going from 50 to 100, but they cannot give a specif ic estimate of how much is enough to protect public welfare. Related to this is the question of what percentage of lakes and streams need to achieve these levels to eliminate an adverse effect. The evidence may not give a definitive answer to this question, but it needs to be addressed.

Chapter 9: Conclusions

35Charge Question 25: What are the views of th e panel on the preliminary staff conclusions regarding the adequacy of the current sta ndards, the need for an integrated multipollutant structure for the revised standards, and the proposed form of the joint NOx SOx standards for aquatic acidification?

The case has been well established that the cu rrent standards are not adequate to protect ecosystems from harmful effects of NOx and SO x deposition. The only aspect not addressed is that current exceedences of PM and ozone standards will require further reductions in NOx and/or SOx precursors as these also contribute to formation of PM and ozone. How far meeting these standards will go toward protecting ecosys tem resources from effects of NOx and SOx deposition has not been addressed, a nd it may be quite difficult to do so. The proposed form of the joint NOx and SOx st andard makes sense conceptually. The execution of the specifics still seems pr oblematic in several regards.

Charge Question 26: What are the views of th e panel on the overall characterization of uncertainty as it relates to the determinatio n of an ecologically-relevant multi-pollutant

standard for NOx and SOx?

Page 220, bullet (3): The conclusions stated abou t limited confidence in relating natural habitat provision and biological control se rvices to ANC levels are too cautious. A clear quantitative relationship between ANC concentrations and loss in fish species has been established. This means there is a loss in these services even if there is not a specific metric to quantify the total

welfare value of this loss.

Page 220, bullet (4): Please note that the dollar va lues for recreational fishing losses are in the Adirondack region (or for all of NY state, depending on the numbers presented) and are for NY residents only. Lines 24-25 seem to imply they are for the whole Northeast. Note the comment on Chapter 3 about the problem with lumping a nnualized and present va lue numbers into the same “range.”

Page 221, lines 12-14. It seems appropriate to also list the recreation and aesth etic value of forest health as a type of cultura l service that is harmed by the effects of acidification.

Other important uncertainties

Extrapolations from catchment or watershed specif ic analyses to regional areas are necessary to implement the proposed standards. Are these extra polations sufficiently accurate or reliable for use in a standard setting and enforcem ent process? (Chapter 5, section 5.2.1.7)

Selecting a method to estimate the amount of N that will be taken up by the ecosystem seems like an important unresolved i ssue. (Chapter 5, page 160).

Is there any information to help guide the Admi nistrator about what percent of an ecosystem would be appropriate for achievi ng a selected ANC? Are there pract ical constraints on what can be reasonably achieved? Is there a tradeoff, in practice, between the sele cted ANC target and the percentage of the area expected to meet that target?

36The exclusion of reduced forms of N from the st andard still seems problematic. It assumes that

the contribution of these to the ecosystem effects remains the same over time. (Chapter 5, page 165).

The benchmarks for terrestria l acidification effects of 0.6, 1.2, and 10 are mentioned several times. Do these relate to lower and higher levels of effect or are these a range of estimates for a “no effects” or safe level? How far will protec tion of aquatic resources go toward protecting

terrestrial resources and how doe s uncertainty about the benchmark make it difficult to answer this question?

The analysis for the acidification effects reveal s a tradeoff between SOx and NOx to achieve the same target (ANC level), but th is does not account for the fact that NOx contributes more to nutrient enrichment than does SOx. Thus, a comp rehensive standard would take account of both types of effects. This may not be feasible at this time, but it is a drawback of focusing only on acidification in setting a sta ndard that should be acknowledged.

Executive Summary

The executive summary does a good job of summar izing the main document, but suffers from the same limitations as are in the main document. It is generally well written and easy to

understand for a non-technical audience. In re viewing the ES I was looking for succinct descriptions of what the harmful effects of depos ition are and to what ex tent are these occurring now in the US. Pages ES-3 to ES-5 are close to accomplishing this, especially for acidification effects on aquatic ecosystems. Things that still ne ed to be explained are: (1) What does it mean

in terms of the health of the tr ees, forest, habitat, etc. if suga r maple or red spruce growth is reduced by 20%? (2) What is the evidence and exte nt of observed harm to forests (or specific species) at current deposition leve ls? Making the link between the Bc /Al ratio and the percentage reduction in growth is very helpful for the policy analyst, but it doe sn’t go far enough in explaining why this matters.

At the top of page ES-5: Is there a better word than “complicated”? The point is that there are multiple sources so there is difficulty in spec ifying or quantifying the amount of harm done by the one source of interest here, which is atmospheric deposition.

Page ES-6: Be careful to use the term “critical load” in a consistent manner. The PA document

has defined critical load as th e amount of deposition that the system can tolerate and still maintain a given level of functioning, as indicat ed by a measure such as ANC. Thus, there is a

critical load for ANC = 50 and a different cri tical load for ANC = 100. This means there is not one single “critical load” that determines what the policy objectives are.

Pages ES-8 and ES-9: The AAPI equation need s more explanation, term by term, for a nontechnical audience to comprehend. What is here is a good start.

Page ES-12, paragraph 4 that starts “ANC levels in the range...” This is an excellent summary of the effects on aquatic ecosystems at various ANC levels. This discussion needs to take the next step to describe what the welfar e implications of these effects are.

37Page ES-14: Bullets 3 and 4 are too limited on use type welfare e ffects. Recreational fishing and timber production are important services, but they are not the main reasons why people care about protecting these ecosystems.

38

### Dr. Ellis Cowling

My individual comments on the March 2010 Fi rst External Review Draft of the Policy Assessment for the Secondary National Ambient Ai r Quality Standards for Oxides of Nitrogen and Oxides of Sulfur are organized below in re sponse to each of the several Charge Questions posed in Lydia Wegman’s memoranda to Kyndall Barry dated March 4, 2010 in preparation for the April 1-2, 2010 CASAC meeting. As requested by Chairman Ted Russell, my attention has been given primarily to the three Charge Qu estions on Chapter 2 a nd the several Charge Questions on Chapter 6.

Overview Comments on the Whole of this First Draft Policy Assessment Document

Before plunging directly into my assigned chapters (Chapters 2 and 6), perm it me to suggest that a very constructive and useful addition to the Second Draft Policy Assessment document would be a short but very frank desc ription of the reasons why identifying ammonia and ammonium ion (NHx) as a seventh Criteria Pollut ant would not be a desirable alte rnative to the clever way that chemically reduced forms of nitrogen have been built into the “as given” characteristics of the various regions of our country where NHx deposition is a very significant contributing cause of both acidification and nitrogen enrichment of terrestrial and aquatic ecosystems.

This suggestion is especially relevant in view of the very thorough attention that was given to chemically reduced forms (NHx) of acidifying deposition in both:

 The ISA and the REA for the present Inte grated Review of the NOx/SOx NAAQS Secondary Standards, and

 The thorough exploration of th e importance of NHx as well as NOx and NOy in the soon to be completed Final Report of the Inte grated Nitrogen Committee of EPA’s Science Advisory Board.

Chapter 2: Known or Anticipated Ecological Effects

1. What are the views of the Panel on the appropriateness of staff’s weight-of-evidence approach which assesses information from ac ross the various ecological research areas described in the NOx SOx Secondary Standa rds Integrated Science Assessment (ISA), including studies of acidification and nutri ent-enrichment in aquatic and terrestrial ecosystems, and laboratory research on responses of plant and animal species to

acidification and nutrient enrichment? To what extent is the presentation of evidence drawn from the ecological effects studies assessed in the ISA technically sound, appropriately focused and balanced, and clearly communicated?

The summary of “known” effects of atmospheri c-deposition induced acidification and nitrogen enrichments effects presented in Chapter 2 is outstanding well done and faithful to the findings of causality and other atmospheric-ecosystem linkage relationships that are presented in the ISA

and the REA reviewed earlier by the CASAC Integrated NOx/S Ox Secondary NAAQS Review Panel. By contrast, “anticipated” effects are given very short shrift in Chapter 2.

39I was especially delighted to see for the first time in my career -- the extraordinarily useful overview figures shown in Figures 2.8 and 2.9 on pages 42 and 43. There is no general reference as to the source of either of these two figures. Thus, I presume that they were assembled by one

or more EPA staff or consultants whom I reco mmend develop and publish these two figures in one or more of the peer-reviewed journals of both ecology and atmospheric science. In doing so, however, it would be essential to include each of the original arti cles that are cited in Figure 2.8

but 17 of which are not included in the refere nce list on pages 52-61 at the end of Chapter 2.

My principal suggestions for improvement of th is otherwise excellently well written Chapter 2 are the following: a) Add to the list of references on pages 51-61 all those references that are included in the body of Figure 2.8 on page 42 but are not included in the references listed at the end of the chapter. b) Add literature citations to the various (1-20) geographical areas where effects of acidification have been observed in Figure 2-9. c) Revise the caption for Figure 2.8 so it is more fully descriptive of the information contained in this figure. d) Revise the wording of various paragraphs within Chapter 2 to include the phrase “total reactive nitrogen,” “total reactive N,” or at least “total N” in place of just “N” as used in many places in Chapter 2 so th ere is no question about whether the term “N” in this chapter includes both chemica lly reduced as well as chemically oxidized

forms of total reactive N.

This very same point is explained very thorough ly in Chapter 8 and also very well on lines 21 through 25 on page 37. But the just “N” terminology is adopted in most parts of Chapter 2. Examples of places where this suggested revisi on would increase the cl arity of communication throughout Chapter 2 include: lines 4 and 19 on page 35, line 17 on page 37, lines 8 and 23 on page 38, lines 13 and 20 on page 39, among many others.

I also recommend that this recommended revisi on of wording -- including the phrase “total reactive nitrogen,” “total reactive N, ” or at least “total N” in place of just “N” -- be examined not only in my two assigned chapters (2 and 6) but also in all the other chapters of this First Draft Policy Assessment document -- Chapters 3, 4, 5, 7, 8, and 9.

2. To what extent are the interp retation and presentation of the results of the exposure and risk assessment technically sound, appropri ately balanced, and clearly communicated?

As indicated in the first paragr aph of my comments to Charge Question 1, above: “The summary of “known” effects of atmospheric-deposition induced acidification and nitrogen enrichments effects presented in Chapter 2 is outstanding we ll done and faithful to the findings of causality and other atmospheric-ecosystem linkage relations hips that are presented in the ISA and the

REA.

40What are the views of the Panel on the critical uncertainties associated with the risk and exposure analysis and the evidence from ecological effects studies that need to be characterized in terms of their potential implications for the secondary standards?

Critical uncertainties are hardly to uched on at all in Chapter 2 but seem to have been dealt with more thoroughly (and I think approp riately) in Chapters 4 and 6. Thus I refer this question also

to the attention of the other CASAC Review Pa nel members Chairman Russell has identified in his message transmitted in Kyndall Barry’s E-mail message dated March 15, 2010.

Chapter 6: Options for Elements of a Standa rd to Protect Against Effects from Aquatic

Acidification

15. To what extent does the Panel agree that the proposal to develop an Atmospheric Acidification Potential Index (AAPI) linked to key determinants of aquatic ANC is a reasonable approach to developing an ecologi cally relevant standard? Does the Panel generally agree that the secondary standard option s identified by staff (including indicator, averaging time, form, and level) are generally consistent with the available scientific and technical information and are appropriate for consideration by the Administrator?

I believe that the structured plan outlined in Ch apters 5 and 6 for an Atmospheric Acidification Potential Index (AAPI) linked to key determinants of aquatic ANC is a reasonable approach to developing an ecologically-relevan t two-pollutant standard. A very complicated series of adjustments in thought processes by air quality managers will obviously have to be borne in mind. This will take a good deal of edu cational as well as technical thought.

But the logic and rationale behind the various part s of the AAPI as outlined in chapters 5 and 6 appear to be reasonably well thought out. Thus, I have so far discovered no serious omission from the various location-specifi c and ecosystem-specific factors as well as the mathematical calculations and modeling estimates that will have to be brought together when these kinds of integrated ecologically-relevant standards are implemented for two Criteria Pollutants at the

same time.

Also, the attention given in Chapter 6 to each part of the definition of a NAAQS standard (indicator, level, statistical form, and averaging time) seem appropriate to me.

16. What are the views of the Panel on the de gree of uncertainty associated with each element of the suggested standard, e.g. the ecological indicator; the concentration to deposition ratios, reduced nitrogen, the natural background ANC, and the ambient indicator and averaging time for NOx and SOx, and its relationship to the degree of protection that could be expected from the standard? What are the views of the Panel on how to fairly characterize the uncertainty as sociated with the degree of protection that such a standard would provide from aquatic acidification?

I am impressed with the extent to which the language used in Chapter 6 has embraced the concept of location-specific and ecosystem-specifi c Critical Loads which have been used widely in Europe and to a more limited extent in Cana da. But finally, the USEPA seems to be coming

41around to the idea that protection of ecosystems from adverse effects requires an approach that is very different from its traditional notions of national standards that are applied rather uniformly across our country for protection agai nst adverse effects on human health.

Once again in Chapter 6, the issue of how to c ope with the uncertainties associated with the degree of protection that any integrated NOx/S Ox secondary standard would provide has not been dealt with very explicitly – except with regard to spatial va riability. I hope that others in our panel, such as Rich Poirot, wi ll have more to suggest than I ha ve so far been able to suggest.

17. What are the views of the Panel on aggregating the terms (Q, N eco and BC 0 * ) used in estimating natural background ANC, denoted by the function g(·),into 5 bins based on the geologic classification scheme?

Use of a series of “5 (or more?) bins” for aggregati ng the terms (Q, N eco and BC 0 * ) used in estimating natural background ANC, denoted by the function g(·), seems reasonable to me, but I confess to having no direct experience from wh ich to offer a well-informed professional judgment in response to this question.

18. What are the views of the Panel on th e use of regional air quality modeling (e.g., CMAQ) results to establish the concentration-to-deposition ratio (V NOy , V SOx ) and reduced nitrogen deposition (NHx) in the AAPI calculatio n? What are the views of the Panel on the

critical uncertainties associated with the use of CMAQ to generate these parameters, and the potential implications of these un certainties for the secondary standards?

Although I am not a very mathematical-modeling-sa vvy kind of scientist, I have come to have great respect for the usefulness of both the CMAQ and the MAGIC models, and thus offer a largely-second-hand assurance of professional confidence in the us efulness of these two specific models for atmospheric processes in the cas e of CMAQ and acidifica tion effects on aquatic ecosystem in the case of MAGIC.

19. What are the views of the Panel regarding presentation of the standards as a set of

tradeoff curves for NOx and SOx associated wi th specific levels of AAPI, and specific values of the g, V NOx , V SOx , and NHx terms?

Using a series of tradeoff curves for compar ative evaluation of alternative NOx and SOx secondary standards associated with specific le vels of AAPI, and specific values of the g, V NOx , V SOx , and NHx terms seems intuitively promising to me. But, once again, I must confess to having no direct professional experience from which to offer a well-informed professional judgment in response to this question.

20. What are the views of the Panel on using a single year or a three year average of recent year CMAQ modeling results to estimate the AAPI terms?

I agree with the suggestion in this draft Po licy Assessment document that both one-year and three-year-long modeling results should be done for several different acidification sensitive and

42potential nitrogen-enrichment sens itive geographical areas and compar ed in the next draft of this CASAC Policy Assessment NAAQS Secondary NOx/SOx Review Panel process.

21. What are the views of the panel on the ambient monitoring requirements? Is for the proposed three ambient air measurements – NOy, SO 2 and particulate sulfate – sufficient to judge compliance with and AAPI?

No, I believe these three ambient air measurements – NOy, SO 2 and particulate sulfate – would not be sufficient to judge compliance with an AAPI unless NHx is also included in the

evaluation. It is the amount of total reactive nitr ogen (NOy + NHx), and not just the chemically oxidized forms of nitrogen and sulfur that cause adverse effects on both terrestrial and aquatic
ecosystems.

22. What are the views of the Panel on usin g existing NOy and PM2.5 sulfate measurement techniques as the basis for defining a Fed eral Reference Method to judge compliance with

and standard?

I believe that consideration should be given to using the existing meas urements of NOy and PM2.5 sulfate measurement techniques for defi ning a possible Federal Reference Method to judge compliance with a possible NOx/SOx Integr ated Secondary Standard. But I also know that we will need a substantially increased num ber of remote, rural, suburban, and urban sites and must examine critically the frequency with which these techniques would be used and the results compiled in useful ways.

Below please find a simplified diagram developed by Ted Russell for a presentation he made to the Integrated Nitrogen Committee of the EP A Science Advisory Board in October 2009.

43

# Integrating Across Species Contribution to

Acidification: A Proposed EPA Approach...

ANC Deposition

Load Atmospheric
Concentrations What is regulated

Total acidifying deposition Indicator Physical

Regulatory

Acceptable depositional rate

Deposition from reduced N

Dep NOx 

### – C NOx 

### Dep NOx



### – C SOx 

### Allowed NOx+SOx deposition Current

Allowed

44

### Dr. Charles T. Driscoll

General Comments

Modify the wording of the document by refraini ng from stating that inanimate objects like figures or chapters on documents state or do things.

Need to define acronyms that are not defined.

The referencing of the document is very uneven. Some references are provided. However in

some sentences detailed information is provided without proper citation.

Please refrain from using the word reduce. Th e word reduce can mean to decrease, but it can also mean to chemically reduce. Confusion w ill be less if the word reduced was only used to

indicate chemical reduction.

Also the word level is not a very specific term . Using it in the document leads to confusion.

Does level refer to concentration or deposition? It is best to use the actual term of interest.

Deposition units should be kg (indicate mass basis) /ha-yr not kg/ha/yr.

P67. TMDLs. In addition to Chesapeake Bay, th ere are TMDLs for surface water pH in at least

two states NY and TN. Shoul dn’t these be mentioned?

P157 (Section 5.2.2.2). The models used are steady-st ate models. I think some discussion of the advantages and disadvantages of steady-state vs. dynamic models is critical here. I think this

would be an essential foundation to this and ot her sections. Without such a discussion, the section is lacking.

P164. I think it is a great idea to ev aluate additional landscape feat ures in categorizing landscape sensitivity. Elevation is a logi cal one. Others might include forest cover and watershed area.

P164, line 25 This statement is not entirely true and should be re-written . Reduced nitrogen can be converted to nitrate but not always. It can be assimilated into soil and biomass. In fact most studies show it largely goes into soil. It can be deni trified. Also I don’t believe that nitrate deposition has the same effect as ammonium de position. Generally it would not. It depends on the associated cation and anion respectively.

P167, line 20. I like the anal ysis of terrestrial and aquatic aci dification. However, I suspect the analysis would be flawed by the application of steady-state models . Steady-state models assume that the soil exchange remains consistent over time. In reality, the base saturation of soil decreases with acidic deposition. So the sensitiv ity of terrestrial ecosystems to acidic deposition likely decreases with time. This aspect of acidification should be addressed in the text.

45P178, equation 2. Is this equation (2) correct? It does not seem possibl e. Doesn’t the lake retention term need to be prorated by its area? Does this equation assume some land cover other

than forest and lake? Some desc ription of this equation is essen tial to inform the reader of the

intent behind it.

P193. This line of reasoning of short-term atmo spheric events having important implications for episodic acidification is flawed. Episodic acidification largely resu lts from shifts in hydrologic flow paths (Chen et al. 1984). Inputs of nitroge n and sulfur from snowpack and atmospheric deposition largely cycle through so il. Short-term direct inputs from atmospheric deposition are not important in episodic acidification.

P197, line 4 and elsewhere. I am concerned th at the Neco term does not include organic nitrogen. This could be probl ematic. Some discussion of or ganic nitrogen should be given.

P214, line 2. Again, I question th e validity of comparing terres trial and aquatic ecosystem sensitivity given the steady-state modeling ap proach used. In some systems soil loss of exchangeable basic cations will continue over ti me. It would be more appropriate to use a dynamic model to evaluate this point.

Specific Comments P2, line 19 Change to: A summary of ecological... from the ISA and REA is provided in Chapter 2.

P2, line 21 Change to: Those ecological effects are placed within the context of “public welfare” in Chapter 3...

P2, line 23 Change to: The adequacy of the ... ecological effects is discussed in Chapter 4.

P2, line 24 Change to: The conceptual design ... multi-pollutant standards is developed in Chapter 5.

P2, line 25 Change to: Options for developing ... conceptual design are presented in Chapter 6.

P2, line 27 Change to: How seconda ry ... other ecological endpoints is described in Chapter 7.

P2, line 28 Change to: A consideration ... and oxidized forms of nitrogen is provided in Chapter 8.

P3, line 1 Change to: Preliminary st aff conclusions are summarized in Chapter 9, regarding ...

P3, line 10 ... NO

x and/or SO

x , but ...

P4, line 2 ... including total reactive ...

46P5, line 6 Change to: In the ISA the ecological ... to ecosystems are highlighted other ...

P5, line 7 Change to: In this assessment information on gas-phase ... on vegetation is evaluated, but effects of gas-phase NO

x ... on multiple ecological receptors are emphasized.

P7, line 28 Change to: framework, in the next section, we provide ...

P8, line5 draft Air Quality Cr iteria Document (AQCD) ...

P8, line 6 Change to: In this draft document a comprehensive assessment was provided ...

P12, line 1 Change to: In the petition ot her adverse ... criter ia pollutants were

also listed ...

P13, line 3 Change to: NO

x and SO

x for a combined secondary standard at this

time

P13, line 6 Change to: The conceptual framework was introduced in the REA

for ...

P13, line 14 Change to: The framework we are considering for the structure ... standard is depicted in Figure 1-1.

P13, line 24 What is meant by levels? C oncentrations? Levels is not a very specific word. Please clarify.

P13, line 25 Change to: a particular ex tent of ecosystem protection are those

concentrations that ...

P14, line 5 Change to: As more info rmation is available on effects ... NO

x and

SO

x , this approach ...

P14, line 9 Change to: such as atmo spheric characteristics and ecosystem sensitivity.

P14, line 20 Change to: effects

P15, line 18 Change to: ... humans fo llowing inhalation of air pollutants ...

P15, line 26 Change to: ... discussed in the ISA, the REA and ...

P19, line 3 Change to: ... variables c ontrolling the relationships of the ecological response to deposition.

47P19, line 7 Change to: ... weathering rate s, elevation, climatic factors or biological factors that ...

P19, line 9 What is meant by high na tural background acidification? Do you mean high internal supply of natu rally occurring organic acids? Please clarify.

P20, line 23 Change to: ... nitrog en deposition diminished when NO

x related deposition is decreased?

P22, line 2 Change to: In this chapter we address ...

P22, line 17 Change to: Those effects ar e evaluated in Chap ter 3 within the ...

P23, line 19 Change to: base saturatio n of soil decreases. Continued ... can deplete the available base cation pool in soil.

P23, line 22 Change to: The ability of a watershed to neutralize acidic deposition ... factors including weathering rates, bedrock composition, vegetation and microbi al processes, physical and

chemical characteristics of so il and hydrologic flowpaths (REA 2.1).

P24, line1 Change to: increases in i nputs of N and S to ecosystems and the

associated ...

P24, line 2 These sentences are confusing. The first phrase refers to shortterm deposition. The second part of the sentence and the following sentence refers to episodic acidification. I am confused. It appears that some text is missing.

P24, line 5 Change to: Episodic acidification refers ...

P24, line 20 Delete the last phras e in the sentence after the comma.

P24, line 24 Define surplus of base cations. Change to: ... in surface waters, the sum of base cations, ANC, di ssolved inorganic aluminum and pH (Note that calcium is a base cation).

P25, lines 1 and 2 Change to: dissolved inorganic Al

P25, line 9 Change to: Similarly, decreases in prey ...

P25, line 19 Change to: about 15 to 20%, exchange

P25, line 21 Change to: dissolved inorganic Al. The effect ...

P25, line 28 Change to: Acidic deposition and soil acidification has ...

P26, line 3 Change to: S ugar maple

48P26, lines 10, 11, 19 & 20 Forests are the only terrest rial ecosystem type that is sensitive to acidic deposition. Should the word “terrestrial” be changed to

“forest” in these sections and elsewhere to be more specific?

P27, line 4 Change to: deposition in this region is less clear

P27, line 23 Change to: integrity occur because the energy ...

P28, line 12 Figure 2-1 Change to: Ecological effects associated with alternative levels of acid neutralizing capacity (ANC)

P29, line 1 17 - and 5 - fold higher than what? Please clarify.

P29, line 4 This is a mistake and needs to be corrected. Virtually all watersheds experience episodic aci dification. Are you referring to acidic episodes (i.e., short-term decreases in ANC to low values that would cause biological effects)? Please clarify.

P31, line 7 Change to: are less sensitive sites

P31, line 8 Change to: Note that studies ...

P31, line 15 Change to: commonly consumed by sport fish

P31, line 7 Again as in the earlier Ad irondack section 10 – and 32 – fold higher than what? Please clarify.

P31, line 10 Again virtually all waters heds experience episodic acidification. Do you mean acidic episodes?

P31, line 17 Change to: a decrease in the condition ...

P 34, line 8 Change to: are less sensitive sites.

P34, line 9 Would it be good to refer to “forest acidification” rather than

“terrestrial acidification”?

P34, para. starting at line 10 It is necessary to clar ify the basis of the ratios. I believe these are

molar ratios. If I am correct, they should be clarified as such (e.g.,

line 10 Bc/Al soil saturation molar ratios. Line 14 Critical soil

Bc/Al molar ratio ... and throughout the remainder of the

document.

P35, line 16 Change to : ... can be decreased by 20% ... growth can be

decreased

...

P35, line 21 Change to: For r ed s pruce

P36, line 17 (i.e., ANC)

P36, line 28 Change to: Terrest rial (Forest?) Acidification

49P36, line 30 Change to: USFS – Kane E xperimental F orest

P37, line 2 Change to: was decreased by 20%.

P37, line 4 Change to: by soil available Ca 2+ depletion ...

P37, line 21 Change to : nitrogen (e.g., NH

x )

P38, line 8 Change to: chronic additions of N

P38, lines 13, 14, 15

P39, lines 7, 8

P41, line 2

P38, line 13 Change to: NO 3 - leaching, soil C:N ratio, rates of N mineralization, nitrification, and denitrification ...

P38, line 29 & throughout doc. Units of fl ux should be kg/ha-yr, not kg/ha/yr.

P39, line 28 Change to: directly deposite d to the water surf ace can pollute the

surface water. P41, line 15 Change to: Figure 2-8.

P42, Figure 2-8 Define MCF – Mixed Coni fer Forest; CSS – Coastal Sage Scrub.

P43, Figure 2-9 Can these locations be reor ganized so they are easier to follow,

either west to east or east to west or terrestrial vs. aquatic. The numbers do not seem to appear in any logical order. Also change #

10 to elevated NO 3 - leaching.

P45, line 29 Change to: NO 3 -

P46, line 21 Change to: DO, decreases in biodiversity ...

P46, line 21 Change to: desired decrease in load

P46, line 23 Change to: must be controlled

P46, line 24 Change to: decrease of total nitrogen

P46, line 25 Change to: indicated decreases in atmospheric ... could not

eliminate coastal ...

P46, line 27 Change to: by decreasing atmospheric

P49, line 5 Acronym correct? Define please.

P50, line 11 Change to: At sufficient concentration

P51, line 5 Change to: decreases in photosynthesis

P51, line 6 Change to: fixation, decreased k +

P63, line 9 Change to: to decrease or impair

50P65, lines 4-8 This sentence is confusing. Can it be re-written?

P65, line 8 Change to: W hile the

P66, line 11 alkalinity is equi valent (not roughly, it is).

P67, line 27 There are also TMDLs for su rface water pH. At least for the states

of NY and TN. Shouldn’t these be mentioned?

P72, line 1 delete etc. in paranthesis

P73, line 11 Change to: The spatial re lationships ... deposition levels are illustrated in Figures 3-4 and 3-5.

P74, 75; Figures 3-4 and 3-5 Give th e units of deposition in figures.

Figure 3-4 Change to: ... deposit ion of nitrogen and sulfur ...

Figure 3-5 Change to: ... deposit ion of nitrogen and sulfur ...

P77, line 21 Change to: (e.g. b ald e agle – should be lower case)

P77, line 22 Change to: willingness to pay (WTP)

P78, line 16 In brief for each region expe riencing ecological e ffects, ecological

indicators ...

The wording of this sentence is c onfusing. It should be re-written. P78, line 22 Change to: f igure

P79, line 4 Change to: In the next four sections, we summarize ...

P79, line 17 Change to: northeastern United States

P80, line 21 Change to: In the previous section, we describe the ecosystem ..., and summarize evidence ... existing NO

x /SO

x levels has not been quantified.

P81, line 9 Change to: In this case st udy, estimates of changes ... services are determined, as well ...

P81, line 15 What is meant by “zero -out” emissions? Please clarify.

P82, line 20 Bc:Al molar (?) to decreased tree ...

P82, line 27 Change to: northeastern United States

P83, lines 3, 10, 29 Change to: northeastern United States

P83, line 11 space after 2006

P85, lines 20, 28 decreases not reduction

P86, line 13 Change to: $2 billion (add space between $2 and billion)

P87, line 4 Change to: nitrogen decreases the ...

51P88, line 30 Change to: nitrogen deposition

P101, line 11 Change to: In this chapter, we address ...

P101, line 12 Change to: In the chapter, we begin

P102, line 9 Change to: as indicators, the current

P102, line 11 Should inputs of reduced N be mentioned here?

P102, line 16 Change to: acid inputs is decreased as natural buffers are depleted

more rapidly than they ...

P103, line 11 Change to: In addition, in this chapter we qualitatively address ...

SO

x and set up arguments ...

P104, line 25 Change to: This information suggests...

P105, line 6 Change to: ... jo int impact of the multiple pollutants ...

P105, line 8 Change to: This information suggests

P105, line 23-24 Change to: deposition falling on base-rich soils underlying

calcareous deposits have a ... falling on shallow acidic soils ...

P105, line 25-26 Change to: detriment to elevated acidic deposition while ... may

experience a marked loss in fish communities to a similar input

. P106, line 18 Change to: plus ammonium, NH 4
P108, line 11 Change to: 4-8 sites in the S outheast ...

P110, line 9 Change to: and IMPROVE networks. In addition

P111, line 1 Change to: primary complia nce purposes capture (delete “do”)

P111, line 4 S outheast, there are...

P111, line 22 Change to: of nitrate, ammonium, sulfate and other

P111, line 29 Change to: The o rganic nitrogen is ...

P112, line 8 Change to: deposition through m onitoring and m odels?

P113, line 19 define FAB

P114, line 114 define PAD

P115, line 10 Change to: reactive nitrogen and sulfur,

P115, line 25 Change to: throughout the e astern United States

P115, line 29 Change to: (NH 3 and NH 4 ),

P115, line 30 Change to: are provided in f igures 4-5

P116, line 3 Change to: In addition, f igures 4-12

52P116, line12 Change to: associated with the formation of

P116, line 16 Change to: Ambient conditions include ...

P116, line 18 Change to: This information is consistent

P120, Figure 4-8 Change to: ammonia, NH 4
P125, Figure 4-14 Change to: ... from re porting stations in Air Quality System (AQS).

P126, Figure 4-15 Change to: ... CMAQ m odeled oxidized nitrogen deposition (kgN/ha-yr).

P127, Figure 4-16 Change to: ... CMAQ mode led oxidized sulfur deposition (kgS/hayr). P130, line 11 Change to: In the previous sections we have

P130, line 13 Change to: This pattern suggest that

P131, line 1 Change to: In this section we focus on ...

P131, line 7 Change to: (N deposition in the e astern U.S. includes ...

P131, line 8 Change to: locations with greater than 9 kg N/ha-yr

, P131, line 12 Add reference

P131 and throughout Change from ha/yr to ha-yr

P132, line 1 Change to: flux of methane (CH 4 ), and ...

P132, line 8 Change to: In Chapter 3 of the REA a thorough assessment is

provided ...

P132, line 15 Change to: As discu ssed throughout the REA document, ...

P133, line 12 Change to: fully overlap . The locations of the case studies evaluated in the REA are shown on Figure 4-20.

P133, Figure 4-20 Change to: ...map highlighting the nine case study ...

P134, line 8 Change to: measuring the acid neutralizing capacity...

P134, line 16 Change to: and SO

x and loss of ANC in sensitive ecosystems , and

P134, line 23 Change to: ... case study area is 62.1 μeq/L (moderate ...

P134, line 25 Change to: ANC of 50 μeq/L , and ...

P134, line 26 Change to: This information indicates ...

P134, line 28 Change to: ... with greatly diminished fish species ....

P135, line 10 Change to: 57.9 μeq/L , indicating ...

53P135, line 12 Change to: ... area, this information suggests ...

P135, line 18 Change to: In the ISA it is not ed that large portio ns of the eastern

U.S. ...

P135, line 21 Should also note that the deposition is much lower.

P135, line 26 A reference should be provided for this report.

P136, line 1 Change to: ... could be classified as acid-impacted based on ...

P136, line 2 Change to: ... lakes classified as acid-impacted based on chronic

P136, line 5 Change to: ... in the e astern U.S. ...

P136, line 9 Change to: ... services such as recreational fishing.

P136, line 24 Change to: ... w ith significant effects on

... P137, line 1 Change to: ... sugar maple growth can be decreased by 20 percent.

P137, line 10 Change to: ... for a Bc/Al ratio ...

P137, line 13 Change to: ... range for sugar maple ( e.g. Arkansas, Illinois) no plots ... P137, line 16 Change to: ... loads for a BC/Al ratio of ...

P137, line 18 and 19 Need a reference

P137, line 22 Do you mean concentr ations rather than levels?

P138, line 23 and 24 Change to: 150 kg/ha-yr and 300 kg/ha-yr .... 0 to 5.5 kg/ha-yr

P138, line 30 Change to: In the ISA it is noted that ...

P138 & 139, line 31 & 1 Change to: In addition, forest management practices can significantly affect the nitrogen cycling, and ...

P139, line 17 Change to: in those locations decreases

... P139, line 30 Change to: ... deposition are limited,

P140-141 Change all ha/yr to ha-yr

P142, line 26 Many watersheds throughout North America may be conducive to methyl mercury production (e .g. Everglades, Southeast).

P145, line 11 Change to: There are now sufficient data ...

P145, line 14 Change to: (e.g. elevation, groundcover)

P145, line 19 Change to: ... are presented in C hapter 6.

P146, Figure 5-1 Change to: ... conceptual design of the NO

x and SO

x secondary

standard.

P146, line 20 Change to: In the following section, we describe ...

54P147, line 9 Change to: ... NH

x is often a large component of the ...

P147, line 13 Change to: ... applicat ion to aquatic acidification are presented ...

P147, line 20 Need to define ANC limit.

P147, line 23 Change to: ... is known, one could calculate ...

P148, line 17 Define tradeoff curve.

P149, line 11 Change to: In this section we present the ecological components ...

P149, line 20 Change to: ... acidification is one that is measurable

P149, line 26 Change to: ... indicators that could be used ...

P150, line 15 Change to: ... input of strong acid anions (e.g. NO 3 -

, SO 4 2- ).

P150, line 16 Change to: ... indirectly via drainage from terrestrial ecosystems. ... when the strong acid anions are ...

P151, line 1 Define F-factor

P151, line 3 & 4 Change to: ... N and S depos ition on predicted pre-industrial ANC

value . N ote that acidification ...

P151, line 15 Change to: ... sulfur de position, although this relationship is altered by landscape factors (e.g. geology, soils, land cover).

P151, line 22 Change to: ... two case study areas. These data were used to

compare ...

P151, line 23 Change to: ... (i.e. preacidification, 1860).

P152, line 1 Change to: ... marked increase in the number of acid-impacted lakes, characterized ... P152, line 14 Change to: ... corre spond to important conditions along the ANC response surface that are ... P152, line 19 Define critical limit of deposition.

P152, line 23 Change to: ... (REA 4.2). Note that a given level of ANC ...

P152, line 25 Change to: ... c oncludes that a quantitative relationship ...

P153, line 8 Change to: that will result in adequate biogeochemical conditions to sustain ecosystem health. Ad equate biogeochemical conditions is a subjective term ... (e.g. ANC = 20, 50, 100 μeq/L) representing different degrees of protection of aquatic ecosystems against acidic deposition.

P153, line 13 Change to: base cation supply to an ecosystem

P153, line 14 Change to: response to acidic deposition

55P153, line20 Change to: models are rather extensive

P154, line 3 Change to: modify the surface water ANC

P154, line 25 Change to: A ppendix 4

P154, line 27 Why the New England EMAP probability survey and not the Adirondack EMAP survey?

P155, line 12 Change to: include:

P155, line 13 Change to: model;

P155, line 14 Change to: concern;

P155, line 25 Change to: data are

P156, line 2 Change to: parameters are

P156, line 4 Change to: that are

P156, line5 Change to: scale are not

P156, line 26 Change to: include: (1) ... model; (2)

P156, line 27 Change to: concern;

P156, line 29 Change to: chemistry are not

P157, line 17 Change to: steady-state SSWC

P157, line 21 font shift ????

P157, line 24 Change to: is incorrect because in many ecosystems nitrate

P157, line 25 Change to: If nitrate is leaching

P157, line 25 “Nitrate leaching is dete rmined from the sum of measured

concentrations of nitrate a nd ammonium in the runoff”. This sentence makes no sense. Admittedly in many systems concentrations of nitrate are low, but really. What about organic nitrogen? Why is this ignored? It should be at least addressed in

the text.

P158, line 1 Change to: calculation are

P158, line 9 Change to: ; 2

P158, line 10 Change to: ; and 3)

P158, line 16 This figure title is not ve ry detailed or descriptive. A more detailed figure title should be given.

P159, line 3 Change to: μeq/L

P159, line 4 Change to: μeq/L

56P160, line 15 Change to: model are less certain

. P160, line 26 Change to: indication to be utilized is ANC.

P160, line 28 Change to: is known, the

P161, line 2 I Change to: In the following discussion, we

P161, line 4 Change to: loads is

P162, line 12 Change to: (Figure 5-4)

P162, line 13 Change to: Sullivan et al. (2007)

P162, line 17 Change to: Sullivan et al. (2007)

P163, line 9 Change to: have greater soil depth receive

P164, line 25 This statement is not entir ely true and should be re-written. Reduced nitrogen can be converted to nitrate but not always. It

can be assimilated into soil and biom ass. In fact most studies show it largely goes into soil. It can be denitrified. Also I don’t believe that nitrate deposition has th e same effect as ammonium deposition. Generally it would not. It depends on the associated cation and anion respectively.

P165, line 21 Change to: f rom

P170, line 20 Change to: A relationship for ... concentrations is provided in Equation 5. P171, line 2 Change to: aggregated deposition (space)

P172, line 25 Change to: T he oxidized sulfur ... values are listed in Table 1.

P173, line 1 Change to: simulations of (space)

P173, line 5 Change to: A nnual inverse ... simulations are shown in Figure 5-5.

P173, line 8 Change to: SO

x concentrations

P173, line 9 Change to: An example ... ratios is shown in Figure 5-6.

P173, line 10 Change to: Section 6 for (space)

P173, lines 11, 15 Are these figure num bers correct? Figure 1, Figure 3

P173, line 15 Change to: CV values ... areas (Figure 5-7)

P174, Figure 5-5 It is difficult to read the scale of this figure.

P175, line 2 Change to: schematic d iagram

P177, line 3 Change to: A proposed ... app lication is described in Section 5.2.

P177, line 5 Change to: strong acid anions

P177, line 9 Change to: aquatic biota.

57P177, line 12 Change to: strong acid anions

P177, line 16 Change to: In this section, we summarize and provide ... the

approach to calculate: (1) ... level; (2) ... level; and (3) ...

P178, line 3 Change to: μ eq/L

P178, line 4 Change to: μ eq/L

P178, line 25 Change to: can contribute to acidification

P178, line 28 (NO

x + S)

P179, line 12 Change to: evaluated

P179, lines 18, 19 50 μeq/L

P180, Table 5-4 Change to: Example c alculations from d etermining the p ercent of

w ater b odies a chieving t arget ANC l evels ... and conduct analysis right hand column ANC ≥ 50 μeq/L

P180, line 2 Change to: 50 μeq/L

P182, line 9 Change to: 50 μeq/L

P182, line 11 Change to: Neco is eliminated

P182, Table 5-6 Change to: 50 μeq/L ... units are in meq/m L -yr

P183, Figure 5-10 Change to: NO

x P184, line 1 Change to: m 2

P184, Figure 5-12 Change to: NO

x P185, Figure 5-13 Change to: NO

x P186, line 1 Change to: that neutralize the acidifying

P186, line 5 Change to: will vary in Equations 1 and 5

P186, line 19 Change to: is separated into

P190, line 3 What is by “mixture of the criteria pollutant(s). Please clarify.

P190, line 4 Change to: whether an area is in attainment of the

P190, line 7 Change to: (e.g. annual average).

P190, line 7 The term level is not cl ear. Please clarify. Do you mean

concentration?

P190, line 8 Change to: specific concentration (?) to ...

P190, line 22 Change to: A conceptual framework ... standard was described in Chapter 5.

58P190, line 27 Change to: Chapter 5, a set of potential ...

P191, line 13 Change to: In Section 6.2, we discuss

P191, line 14 Change to: In Section 6.3, we suggest

P191, line 15 Change to: In Section 6.4, we provide

P191, line 17 Change to: In Section 6.5, we discuss

P191, line 18 Change to: In Section 6.6, we address

P191, line 19 Change to: Finally in Section 6.7, we conclude

P192, line 9 Change to: S 2 O

P192, line 25 Define IMPROVE, if not previously defined.

P193, line 7 Change to: Note that chemical

P193 This line of reasoning of short-term atmospheric events having important implications for episodi c acidification is flawed. Episodic acidification largely results from shifts in hydrologic flow paths (Chen et al. 1984). Inputs of nitrogen and sulfur from snowpack and atmospheric deposit ion largely cycl e through soil. Short-term direct inputs are not important in epis odic acidification.

P194, line 17 Change to: (See 75 FR 2938, 2999; January 19, 2010)

P195, line 11 Change to: ecosystem, can potentially consume the acid neutralizing capacity of the ... to additional loading from acidic deposition. P195, line 20 Change to: to re- evaluate

P196, line 6 Change to: are atmospheric concentrations

P196, line 12 Change to: E quation (1)

P196, line 18 Change to: As such, the

P197, line 4 and elsewhere I am concerned that the Neco term does not include organic nitrogen. This could be problematic.

P197, line 7 Change to: C hapter 4

P197, line 23 Change to: variable

P197, line 28 Change to: m easured

P198, line 1 Change to: (e.g., to develop ... and N

x )

P198, line 14 Change to: sensit ive

P198, line 19 Change to: Note for this form

P198, line 20 Change to: different combinations (space)

59P198, lines 21, 22 Change to: E quation (1)

P198, line 23 Do you mean g?

P200, lines 7, 8, 10, 12 total nitrogen retention (?) The term nitrog en buffering doesn’t make much sense. Do you mean something else like retention? P200, line 13 Change to: to watershed nitrate leaching and associated

acidification.

P200, line 16 Change to: 50 μeq/L

P200, lines 18, 22 Do you mean wate rshed rather than water body?

P200, line 25 Do you mean g?

P201, line 2 Change to: areas (e.g. sensitive... Figure 6-1; reproducing ...

P201, line 9 Change to: (e.g. the 75 th or 95 th ... aquatic ecosystems),

P201, line 9 Do you mean g?

P201, line 16 Change to: from decreases

P201, line 25 Change to: naturally acidic

P201, line 26 Change to: naturally acidic areas, decreasing deposition

P203, line 21 Change to: The rational ... is discussed in Chapter 5

P204, line 2 Change to: natural acid neutralizing capacity

P204, line 24 Change to: also reaches a maximum at ... This pattern suggests

P205, lines 1, 17, 18, 23, 24, 25, 26, 28, 30

Give unit 50 μeq/L

P205, line 4 Change to: lead to decreases

P205, line 17 Change to: show a marked

P205, line 18 Change to: This pattern

P205, line 20 Change to: to decrease the

P206, lines 1,2 Change to: 100 μeq/L (give units)

P207, lines 9, 10, 19, 20 Change to: 50 μeq/L (give units)

P208, line 7 Change to: (Section 3.2)

P208, line 12 What is NCore? Please clarify.

P208, line 15 Define EPA CSN, if not done previously.

P209, line 28 Change to: largely or iented towards populated areas

P210, line 1 Change to: every watershed would not be feasible and may not ...

P210, line 11 Change to: the NO

x and SO

x S econdary S tandard

60P210, line 27 Change to: (e.g. ANC may be naturally low )

P210, line 9 Change to: assessment.]

P211, lines 10, 24, 26, 28 μeq/L (give units)

P211, line 20 Change to: large decreases

P212, line 5 Change to: 100 μeq/L

P213, line 4 Change to: In this chapter, we focus

P213, line 11 Change to: NO

x and SO

x Secondary Standard

P213, line 14 Change to: 50 μeq/L , soil Bc:Al molar ratio

P213, line 21 Change to: 50 μeq/L

P213, lines 22, 23, 24, 26 Change to: soil Bc:Al molar ratio

P213, line 26 Change to: T able 7.1

P214, Table 7.1 Change to: ANC 50 μeq/L ... soil Bc:Al molar ratios ... lakes or

streams

P214, line 2 Again I question the validity of comparing terrestrial and aquatic ecosystem sensitivity given the approach used. In some systems soil loss of exchangeable basic cations will continue over time. It would be more appropriate to use a dynamic model to evaluate this point.

P214, line 11 Change to: soil Bc:Al

P217, line 31 Change to: aquatic eco systems;

P218, line 2 Change to: impacts;

P219, line 18 Change to: in the REA

P220, line 19 Change to: by decreases in ANC

P220, line 22 Change to: 50 μeq/L

P221, lines 4, 7, 10, 14, 15 Change to: soil Bc:Al

P221, line 22 Change to: SO

x . P222, line 9 Change to: S 2 O

P222, line 24 Change to: standard (e.g. the target ANC)

P224, line 1 Change to: NO

x and SO

x Secondary Standard

61References :

Chen, C. W., S. A. Gherini, N. E. Peters, P. S. Murdoch, R. M. Newton, and R. A. Goldstein.

1984. Hydrological analysis of acidic and al kaline lakes. Water Resources Research

20 :1875-1882.

62

### Dr. Paul J. Hanson

General Comment:

The Policy Assessment for NOx and SOx welfar e effects represents a good beginning. I agree with EPA staff that a useful NAAQS for NOy and SOx welfare eff ects requires a unique indicator, averaging time; form and level separa te from the primary standards for NOx and SOx. I also agree that the data for te rrestrial effects are not as well established as those for aquatic impacts. The proposed focus on the devel opment of a standard focusing on aquatic considerations is an ap propriate path forward. The following comments are provided for EPA st aff’s consideration in the preparation of a second draft Policy Assessment (PA). I’m commenting on what I didn’t like or what I would like EPA to change. In general, I found the document to be an appropriate discussion of the policy needs for the NAAQS process for secondary effects of NOx and SOx.

Front Matter – Key Terms

The term or concept of “Adverse Effects” needs an overarching definition. I realize that Chapter

3 is set aside to discuss this issue, but a brief introduction to someone that might not read the entire report is advised.

In the definition of “Acid Neutralizing Capacity ” I wondered if the word “water” shouldn’t be replaced by precipitation. Pure wate r is not what falls from the sky.

Is base saturation really a measure of soil acidific ation (a process), or ju st an indication of the state of acidity of a given soil?

Add a definition of “Reduced N” to the list of key terms.

Should the definition of Eutrophication highlight its special significance to aquatic systems?

The definition of Semi-arid regions still contains a lower level of precipita tion than the definition of arid regions. I’ve pointed this out previous ly and it hasn’t been addressed. Someone needs to explain to me why the desert is n’t as dry as the semi-desert.

Page xiii line 28: Super and subscripts need attention.

Chapter 1:

Page 5 lines 6 to 11: Something isn’t quite righ t in this section. The wording implies a heavy emphasis on direct effects of gaseous forms of NOx and SOx, but I was left with the impression that the intention might have been something else.

63Page 12 lines 2 and 3: The inclusion of gl obal warming in this lis t seems unnecessary and perhaps a bit of a stretch. Connections between NOx and SOx and climate change do not show up elsewhere in the PA document.

Page 13 line 26: Isn’t the concept of “excessive degradation” a policy rather than a science question. Levels of change that represent exce ssive degradation are a judgment not a fact.

Page 14 line 9: The term “ecosystem sensitivities” might be replaced by ‘location-specific

characteristics’ to better inform the new reader of the intent.

Page 17 lines 12 and 13: I don’t think the PA does a very good job of addressing this question.

Page 20: On this page and in some other locat ions within the document the concept of reduced N (meaning chemically-reduced forms of N) ma y be confused with discussions of reduced deposition of N forms (see lines 23 and 24). I kn ow what the authors intended, but I did stumble over the presentation.

Page 21 line 18: Does the Agency or the Admini strator alone actively consider the appropriate

levels?

Chapter 2:

Page 23 line 8: Deposition of acidic compounds does lead to exposures , but not necessarily effects. The relationship between deposition (t he exposure) and the effects depends on the characteristics of the ecosystem.

Page 23 line 11: The wording might be changed to “magnitude and rate ”.

Page 23 line 26: The phrase “small spatial scales ” is not defined. Do the authors mean meters, kilometers, watersheds, counties, states or something else?

A common critique that I have within the PA document is th at sentences are often written to suggest that acidificati on or nutrient enrichment effects have the potential to effect all ecosystems, vegetation or aquatic systems th e same. The authors should be careful to reemphasize that many effects being discussed are applicable only to the most sensitive components of ecosystems. They may still warra nt special protection, bu t they do not represent a response that is univer sal for all organisms.

Page 24 lines 21 and 22: Later on in the docum ent confounding effects are mentioned, but this statement makes it appear that th e results of acidifica tion are absolute. In many cases I think it is likely that the evidence is based on inference drawn from strong correlations rather than a controlled study designed to isolate the specific effects of NOx and SOx additions to natural
systems.

Page 25 line 17: Should the C: N ratio really be in this list. It is not emphasized in the

document.

64Top of page 26: The statements in this section do not suggest lots of c onfidence in the certainty of the relationship between acidification a nd observed phenomenon. The text describes a correlation, a response that “may be contributing” a nd a “likely” response. If appropriate, please change this text to indicate what we do know versus what continues to be hypothesized pending

better data.

Page 26 line10: Not all terrestrial ecosystems ar e sensitive. The wording needs to be changed.

Throughout the document I believe it is important to characterize all pre- acidification resultsderived from MAGIC or CMAQ as simulations. Don’t pretend that we know what preacidification levels really are.

Page 32 line 6: I would change the wording here to “above simulated pr e-acidification (1860)

conditions”.

Page 38 line 4: The wording “terrestrial ecosystems” should be “sensitive terrestrial ecosystems”.

Page 38 lines 25 and 26: This is not true for al l species, organisms, or ecosystems. Make sure

that the reader is reminded that this documen t is taking the approach of protecting sensitive organisms and ecosystems.

Page 39 line 20: Add a reference for this statement.

Page 39 line 22 and line 24: The phrases “may resu lt” and “may lead to” do not make a believer out of me. I would hope that we would be ma king suggestions for NAAQS based on data that can be fully supported by the published literature.

Page 40 lines 6 to 8: This statement is too str ong. I don’t believe that “almost all” ecosystems will be altered by the addition of anthropogenic nitrogen. I actually expect the opposite. In most ecosystems (judged by % area of the US) we will be unable to detect the influence anthropogenic N additions. This is another case where the focus on sensitive ecosystems needs emphasis.

Page 40 line 13: I would add plant grow th rate to the list of factors.

Page 43 line 11: “Hardwood forests” probably need s to be changed to sugar maple species. I doubt seriously that the vast majority of upland oak hardwood forests located throughout the eastern United States are very sensitive.

Figure 2-8 is pretty, but it applicat ion to the analysis isn’t obvious.

Within Figure 2-9: Are the conclusions cited un der #13 the result of natu ral deposition or those derived from the manipulation studies conduc ted on the Fernow Experimental Forest?

65Section 2.3.3: I was surprised that this section did not conclude with the strong statement from the ISA report that few direct effects from gaseous NOx or SOx are anticipated throughout most

of the US.

Page 52 line 7: What does “significant numbers” imply?

Chapter 3:

General comment: The PA document doesn’t addr ess natural rates of change versus change induced by anthropogenic N and S inputs. Change happens anyway. How are natural rates of change viewed in the context of other changes driven by N and S inputs or various other confounding factors?

Page 68 lines 23 to 29: I found this section of text to be very important. The realization that the establishment of critical load demands a judgment call of what is or is not an important adverse effect makes subsequent di scussion of the use of critical loads in the characterizati on of risk to be a bit of a circular argument. This is an in teresting conundrum. Does the EPA staff have a

solution?

Page 72 lines 10 and 11: What is the policy rele vant background level of ecosystem change or biodiversity alterations against which anthropogenic N and S induced effects might be judged?

Page 83 line 2: Provide the re ference for this statistic.

Page 84 lines 7 to 23: I don’t believe this pa ragraph is a strong argument for broad national controls. The available data are representative of only a few key species. Furthermore, if the net annual effect is only $690,000 thousand dollars of production per year one might ask why we are concerned – certainly not for financial reason s. Conducting expensive research to understand responses, or setting standards to combat a problem that only sums to a $690K per year phenomenon are not good justifications. The arguments based on endangered species are
stronger.

Page 88 lines 9 to 15: These statements do not se em to consider that N and S deposition effects are fractional. For example, they are probably not likely to remove the entire ecosystem service for recreation. How does EPA judge the impact on aes thetic use if only a portion of an ecosystem is impacted by N and S inputs?

Chapter 4:

Page 103 lines 3 and 4: I thi nk this sentence should emphasi ze sensitive ecosystems not all
ecosystems.

Page 131 line 28: Add the word ‘sensitive’ to qua lify terrestrial and aquatic in this statement.

Page 131 line 31: Should carbon really be in this list? Convince me.

66Page 132 lines 1 to 5: These items seem to come out-of-the-blue. Are they needed?

Page 134 line21: Who defines the benchmark levels?

Page 135 line 18: The phrase “large portions” needs to be quantifie d. The authors should provide the area of the US involved to c onvince me that this is a big deal.

Page 136 line 16: There is not a significant risk to all terrestrial ecosystems. Only the sensitive systems are being highlighted in the case study analyses.

Page 136 line 28: Provide a quantitative statement fo r the land cover that defines “many” in this

sentence.

Page 137 line 19 and 20: What criteria were used to define the critical load that forms the basis for this conclusion? Change the word “bel ieves” to something else if you can. I’m not

interested in what EPA staff believes. I want to know what they can justify from the science.

Please conduct a search for the word believe a nd make appropriate subs titutes throughout the

document.

Page 138 lines 30 and 31: This may be true for some ecosystems, but othe r forests sequester all of the annual N inputs into aboveground wood production.

Page 139 line 8: Please be specifi c about the tree species to which this conclusion applies. It is not true for all species.

Section 4.5.2 seems to be missing a strong conclusion statement.

Section 4.5.4 seems a bit at odds w ith the statements in Section 4.5.2.

Page 141 line 5: “Large areas” is too vague. Please provide a quantitative statement about the amount of land area impacted.

Chapter 5:

Page 145 line14: You might add wi nd to the list of factors.

Section 5.3.1: This section reads as if the relationships are univer sal to all tree sp ecies. I don’t

believe that EPA would be able to support that concept. Ma ke this discussion reflect the sensitive species that it targets.

Section 5.4.1: In an attempt to ma ke the equations simple and easy to follow the authors have not appropriately reflected what is really being attempted. Equa tions 1 through 4 should include components for gaseous, particle and occult deposition that depend on concentrations and deposition velocities plus an independent compon ent of wet deposition that is a function of rainfall. The processes are not the same. Please make the equations reflect the true processes being calculated within the m odel (e.g., page 172 lines 8 to 11.

67Chapter 6:

No comment at this time.

Chapter 7:

This section is underdeveloped. There is not much to comment on.

Chapter 9:

Throughout this section make sure that the focus on sensitive aquatic and terrestrial ecosystems comes through loud and clear. Don’t lead the reader to conclude that all ecosystems are uniformly at risk from N and S inputs.

In the research needs list a better precipitat ion model or emphasis on direct measures of wet deposition inputs should be further emphasized.

68

### Dr. Dale W. Johnson

Comments on the Executive Summary:

P. ES-3, paragraph 5: I do not agree that geology is the principal factor governing sensitivity to N: decades of biogeochemical research have show n that plant uptake is a major factor (often THE major factor) deciding whether atmospheri cally-deposited N passes through the terrestrial ecosystem to the aquatic one.

p. ES-4, paragraph 3: Again, as th e authors are so often loathe to admit, I would assert that N deposition to N-limited commercial forests coul d be beneficial. After many such comments, however, I do not, expect to see this fact re flected in any executive summary and this is unfortunate because I can assure you that my coll eagues, at least, will take note of that and possibly dismiss this entire endeavor.

p. ES-5, last paragraph: The statement about the Sierra Nevada is an over generalization – the eastern and more remote portions of that range do not receive N deposition levels above 5.

p. ES-7, last paragraph: The statement that reduced forms of nitrogen are converted to nitrate is

incorrect as a blanket statemen t: ammonium can be taken up by pl ants or microbes before being nitrified and, in N-limited ecosystems (that is, in 90% of all terrestrial ecosystems), this is the rule not the exception. Also, in the same para graph, I simply do not understand the wording of

the last sentence.

p. ES-8, paragraph 1: The treatment of NH4 is very cursory and no doubt will invoke much

criticism.

p. ES-8, last paragraph: You shoul d mention that this applies to aquatic ecosystems – there is no

measure of ANC in terrestr ial ecosystems as such.

p. ES-9, paragraph 2: give units. Also, what kind of term converts deposition to fluxes? I thought deposition WAS a flux?

p. ES-11, paragraph 1: Give units. Is so mething missing in the equation as per “( . )”?

Comments on the overall document:

I reviewed the entire document, with special attention to those portions where I have some expertise. Specific suggestions and comments are given below.

p. 23, line 9: replace ”in some instances” with “unless buffered by high base soils”

p. 23, lines 15-28: Good summary, but you should also mention the effects of NH4+

69p. 24, line 16: replace “leads to the acidification of” with “leads to varying degrees of acifification” . It is all a question of amount: small background levels of SOx, NOx and NHx will not lead to any significant acidification nor will th is take place in limestone bedrock systems. As a generic statement, this does not stand.

p. 24, line 24: what is a su rplus of base cations?

p. 34, line 12: Replace “Tree species” with “Some tr ee species”. Some tree species tolerate Al very well and in fact seem to thrive in acidic environments.

p. 35, line 4: Replace “exceeds” with “exceed”

p. 37, lines 8-12: Having worked with many models of acidification over the years, I definitely do not share your high confidence in this one. I am not sure what change is needed, but I want to go on the record as a skeptic.

p. 39, line 24: insert “deemed desirable in commerc ial forests but may also” in front of “may”. Bias toward negative is showing through here again and I believe it is important to express both sides of the nitrogen issue.

p. 70, Table 3-1: Where are forest produc ts? Fiber, timber, furniture wood?

p. 72, lines 1-15: Important ecosystem services from forests should certa inly include timber, furniture wood, pulp stock from commercial forests.

p. 82, lines 27-28: A very true statement – but where is this shown in Table 3-1?

p. 84, line 11: What about loblolly pine? It is fa r more commercially impo rtant than sugar maple or red spruce.

p. 84, lines 21-23: This is a gross overstatement: these estimates are based on two species and do

not include the far more commercia lly important southern pines!

p. 84, lines 25-29: Why on earth have you decided to overlook any benefi cial effects in your economic assessment? I cannot imagine this being defensible and certainly do not agree with it in any way.

p. 88, line 30: change “depos itio” to “deposition”

p. 89, lines 1-2: If you select two case studies based on the presumed negative effects of atmospheric deposition, how can this possi bly be any kind of regional assessment?

p. 102, line 11: Add “or NH4+” after “SOx

p. 136, line 20: BC:Al in soils, presumably?

70p. 136, line 26: first mention I see of timber – again, loblolly pine is king of that.

p. 137, lines 1-8: This could us e some references cited.

p. 138, lines 10-15: This section is biased. Nitrog en limitation is common, not only in limited situations and N inputs will probably cause long -term benefits in most managed systems. I recognize from past experience that th e authors are very loathe to ad mit this, so I will continue to point it out. Your statements fly in the face of many decades of forest nutrition research.

p.138, lines 30-31 and on to page 139: As I have noted in the past, the statement that most atmospherically deposited N is retained by soils is disputed. The sentences after this try to

minimize N benefits to commercial forests, as the authors have done in the past. We have agreed to disagree on this matter, it seems.

p. 153, lines 7-18: This is where I have real troub le with the model used: no ecosystem or soil is ever in steady-state; Were this the case, no soils would ever acidify in the absence of atmospheric acid inputs, and they certainly have done so as evid ence by many studies in pristine

areas such as Alaska.

p. 155, lines 18-20: This seems like an overly confident statement – what is there to back it up? For example, here in the Sierra Nevada, we have chronically hydrophobic soils which can profoundly affect surface hydrology in ways very different from eastern soils which are not hydrophobic. This is a gross over generalization.

p. 158, line 21 through p. 159 line 17: Please provide units for DL ANClim (N+S) – it would seem from the other units given that th e units for this would be meq m -2 after some conversion?

p. 177, line 26 through p. 178, line 11: Same comment

Comments on Chapter 7 Charge Questions:

23. What are the views of the panel on the approach taken to compare the protection provided by a potential aquatic acidificatio n standard to the protection needed for

terrestrial acidification?

While I do not share the authors’ faith in the vali dity of the models used , I see no other viable approach for answering this question. Thus, I can offer no criticism for the approach taken.

24. What are the views of the panel on a future comparison of the protection provided by a potential aquatic acidification standard to nutrient enrichment benchmarks? What are the views of the panel regarding using a nutrient en richment benchmark to be a limiting factor on the nitrogen in the aquatic acidificatio n standard, instead of having a separate

standard?

Acidification and nutrient enrichment could be very much discoupled, especially if the major cause of acidification is S and not N. Also, there will be little aquatic eff ect of N deposition until

71the terrestrial ecosystem is N-saturated unless deposited N circumvents the terrestrial ecosystem (for example, but surface runoff). So on the face it it, it does not seem like a wise idea conceptually to try to use a st andard for one ecosystem and appl y it to the other. On the other hand, it could be argued that, in the absence of significant surface runoff, a linked standard is called for rather than a separate one in that aq uatic ecosystems will not receive much effect of N deposition until the terrestrial system is nitrogen saturated. When it comes to S, retention in the terrestrial ecosystem will be dominated by soil chemical processes (since S limitations in terrestrial ecosystems are exceedingly rare) and negative aquatic effects will not occur until and unless 1) sulfate is mobile in sufficient amounts in soils to become a majo r anion in solution, and 2) soils are either naturally acidic or become acidified by atmos pheric deposition. In cases where sulfate is complete mobile and soils are already ac idic (for example, Spod osols in the northeast), negative aquatic effects can be expected to o ccur immediately (and disapp ear immediately as S deposition declines). These are complicated questions that will probably need to be resolved with simulations of many different scenarios and linked standards would, on the face of it, seem to be

necessary.

72

### Dr. Naresh Kumar

Chapter 2: Known or Anticipated Ecological Effects

1. What are the views of the Panel on the a ppropriateness of staff’s weight-of-evidence approach which assesses information from ac ross the various ecological research areas described in the NOx/SOx Secondary Standa rds Integrated Science Assessment (ISA), including studies of acidification and nutri ent-enrichment in aquatic and terrestrial ecosystems, and laboratory research on responses of plant and animal species to

acidification and nutrient enrichment? To what extent is the presentation of evidence drawn from the ecological effects studies assessed in the ISA technically sound, appropriately focused and balanced, and clearly communicated?

The staff has adequately summarized the information contained the ISA.

2. To what extent are the interp retation and presentation of the results of the exposure and risk assessment technically sound, appropri ately balanced, and clearly communicated?

The staff has adequately summarized the info rmation contained in the REA, but their communication could be improved for clarity.

Additional discussion should be pr ovided on the assumptions and lim itations of the models used in the ecological effects studies.

3. What are the views of the Panel on the criti cal uncertainties associated with the risk and exposure analysis and the evidence from eco logical effects studies that need to be characterized in terms of their potential implications for the secondary standards?

The discussion on critical uncertainties (Pages 35 -37) requires a more rigorous treatment than

what is included in the current draft. The ranki ng of uncertainty (high, fairly high, intermediate or low confidence) is based on staff judgment wit hout any explanation of how the staff arrived at those rankings.

For example, have the models and input parame ters been adequately evaluated to assign high confidence in them? If so, it is essential to provide justification fo r the assigned rankings.

Chapter 5: Conceptual Design of an Ec ologically Relevant Multi-pollutant Standard

10. What are the views of the Panel on staff’s proposed conceptu al framework for the structure of a multipollutant, ecologically relevant standard for NOx and SOx? To what extent does the Panel agree that this sugge sted structure adequately represents the scientific linkages between ecological response s, water chemistry, atmospheric deposition,

and ambient NOx and SOx?

73Figure 5-1 correctly depicts the linkages between ecological indicators, atmospheric deposition

and ambient NOx and SOx concentrations. Howeve r, the uncertainties in the transformation functions between ecological re sponse and deposition and betw een atmospheric deposition and air quality indicators have not been clearly explained.

For example, the Agency plans to use CMAQ mo del to develop relati onship between SOx and NOx concentrations and the atmospheric deposition. However, CMAQ model was not adequately evaluated (either for its prediction cap ability for different species concentrations or for wet deposition, as a test of overall model capab ility) for the 2005 applica tion that was used in

the REA.

Although the data for evaluation may be spar se, it would still be useful to know how relationships between deposition and ambient con centrations obtained using the data compare against those usi ng the model.

Given the uncertainties in the models (both atmo spheric and aquatic) and the data bases, the Policy Assessment provides no indication on what ambient concentrations of SOx and NOx would meet a particular ANC. Simply stated, the Policy Assessment document does not provide

information on what the confidence interval fo r the ambient concentrations may be (For example, is it a factor of 2, 5 or even 10).

The agency should conduct a thor ough analysis of the sensitivity to different assumptions at every stage of the linkages depicted in Figure 5-1 to provide quantitative estimates of the uncertainty range in the final ambient concentrati on numbers needed to meet a particular level of

ANC.

11. What are the views of the Panel on th e relevance of the conceptual design for developing standards to protect agai nst aquatic acidification effects?

a) What are the views of the Panel on st aff’s proposed options for the ecosystem acidification model to represent the ecological response function?

The modeling approach suggested by the staff to represent the ecological response function seems reasonable; however, the key question is how the different terms in the equation are

estimated.

For example, the two approaches suggested by st aff for estimating Neco give very different results and (as noted by the staff) it is not clear which approach is better. The approach to calculate [BC] is not clearl y articulated in the Policy Assessment or its appendices. Furthermore, there is a lack of any discussion about the quantitative impact of uncertainties in estimating [BC].

b) What are the views of the Panel on th e relative merits of the two techniques for calculating Neco, the paramet er representing the amount of deposited nitrogen that is available for acidification due to uptake, denitrification and immobilization?

74The staff should attempt to reconcile the differen ce in the two approaches as they give very different results. In addition, the staff should indicate how data for use in these calculations will be collected and with what frequency.

As noted earlier, both methodologies should be used as part of a sensitiv ity study to explore the impact of all input parameters and assu mptions on final concentration values.

c) What are the views of the Panel on staf f’s proposed options for developing acid sensitivity classes to categorize the national landscape? Is it appropriate to base this classification on bedrock geology? Should multiple criteria be used to inform the sensitivity categories?

As noted in the Policy Assessment, bedrock geol ogy is a key factor influencing acid sensitivity,

but there are additional factors. Other fact ors include topography, elevation, soil depth, soil composition/pH, meteorology, and land use. Th e assessment should explain how additional factors may influence the classification process.

d) What are the views of the Panel on st aff’s proposed options for how to aggregate acidification modeling from the catchment-scale to represent acid-sensitivity categories at

the national-scale?

The example provided in the Policy Assessment document used the 169 catchments within the Adirondacks. However, the impact of extendi ng this methodology to the national scale is unclear. In doing so, is there not the potential for developing a standard that is more than requisite in many regions of the country?

Given that there are multiple judgments (appropria te ANC level, percentage of catchments) and multiple uncertainties in the calculations leadi ng to the index (Neco calculation, BC calculation) and multiple uncertainties in the back-calculation to atmospheric concentrations, the Policy Assessment has a major omission in not explaining how all these factors in fluence the range of potential values for a secondary NAAQS (as also noted earlier).

e) What are the views of the Panel on staf f’s suggested method to account for reduced nitrogen in the deposition metric?

The approach to account for redu ced nitrogen is problematic. First, it puts the onus of impr oving acidification on NOx and SO x alone when reduced nitrogen (NHx, both inorganic and organic) can be quite a considerable part of acidification in many

cases.

Second, the assumption that NHx deposition is co nstant over time is definitely wrong. Third, uncertainties associated with ammonia emissions and using CMAQ to calculate NHx deposition—as well as wet and dry deposition of SOx and NOy are high and have not been clearly explained or quantified. Although measurem ent data will be “blende d” with model data, the overall capability of the model to represent am bient concentrations and loss terms is essential to informing judgment on the model’s overall role in back-calculating a secondary NAAQS.

75Chapter 6: Options for Elements of a Standa rd to Protect Against Effects from Aquatic

Acidification

16. What are the views of the Panel on the de gree of uncertainty associated with each element of the suggested standard, e.g. the ecological indicator; the concentration to deposition ratios, reduced nitrogen, the natural background ANC, and the ambient indicator and averaging time for NOx and SO x , and its relationship to the degree of protection that could be expected from the st andard? What are the views of the Panel on how to fairly characterize the uncertainty as sociated with the degree of protection that such a standard would provide from aquatic acidification?

The uncertainties associated with various elemen ts of the standard have not been clearly delineated. As a result, it is di fficult to state with any degr ee of confidence on the degree of protection that could be expected from a given standard. As men tioned earlier, the best way to characterize uncertainty associated with the propo sed approach would be to conduct a sensitivity study for each element of the standard and propagate these uncertainties to arrive at a range of protection that a given standard woul d provide from aquatic acidification.

18. What are the views of the Panel on th e use of regional ai r quality modeling (e.g., CMAQ) results to establish the concentrat ion-to-deposition ratio (VNOy, VSOx) and reduced nitrogen deposition (NHx) in the AAP I calculation? What are the views of the

Panel on the critical uncertaint ies associated with the use of CMAQ to generate these parameters, and the potential implications of these uncertainties for the secondary

standards?

There are a variety of problems with the use of regional air quality modeling to establish VNOy, VSOx and NHx. Although CMAQ is a regional ai r quality model that has been under development for many years, it lacks in its capabi lity to correctly predict the concentrations of different species within NOy, SOx, NHx and th e wet deposition of these species. Although the model cannot be evaluated for dry deposition because of lack of measurements, evaluation of the ability of the model to represen t ambient levels can serve as a proxy for its ability to represent dry deposition.

A comparison of CMAQ derived values with measur ements is needed before any confidence can be derived on the use of the model to generate the desired parameters. There are many sources of uncertainties that can affect the final numbers derived from the model. These include, but are not limited to:

• large uncertainty in emissions (particularly NHx emissions, but also NOx emissions);

• inability of models to correctly predict clouds (both in cloud cover and liquid water content) and precipitation; and

• incomplete representation of chemistry (particularly cloud chemistry, nighttime chemistry and reactions with soil components).

76

### Dr. Myron J. Mitchell

Responses to “Charge Questions” are provided in italics.

LIST OF ACRONYMS AND ABBREVIATIONS

Detailed Comments

Page Line Comment

x 4 LTER should be defined as “Long Term Ecological Research”–delete monitoring.

x 29-30 Delete “reduced”.

xii 30-31 The definition for dry deposition implies that dry deposition only occurs when there is not wet deposition–this is confusing. Delete “in the absence of precipitation (e.g., rain, snow) or occult deposition (e.g., fog)”.

xii 37-40 The definition of ecosystem is too broad. The earth is not an ecosystem. Delete “Ecosystems cover a hierarchy of spatial scales and can comprise the entire globe, biomes at the continental sc ale, or small, well-circumscribed systems such as a small pond”.

xii 7 The definition of eutrophication is no t correct. Other elements (e.g., P) can result in eutrophication. Subs titute “nutrients” for “nitrogen”.

xiv 4 Change to “other forms of precipitation”.

Introduction

Detailed Comments

Page Line Comment

2 6 Replace “elements” with “components”.

5 7 Why are “commercially managed forests and agricultural lands” excluded? Does this mean that those porti ons of the Adirondacks that are used for commercial forestry are not to be considered?

7 1 Replace “components” for elements. I would suggest the term “element”

should be avoided in this document to avoid any confusion with chemical

elements.

778 22 “m3" needs to have the 3 superscripted.

9 6 Change to “that SO

x air concentrations have”.

9 19-20 This statement is not true and s hould be changed to “since dry deposition

was believed to account for a substantia l portion of the to tal acid deposition problem”.

13 4 Delete “past”.

15 28-29 It is not evident that emphasis ha s been added. Do the quotations indicate emphasis?

17 3-5 I agree that this review should not include those managed systems that are subject to N fertilization, but there are la rge areas of forest land that are managed (e.g., timber harvest) and not fertilized. These forests maybe highly susceptible to the effects of acidic deposition due to the combined deleterious effects of cation nutrient depletion due to bioma ss removal and leaching from the forest

soil.

18 11 Modify this statement to be more comprehensive: “acidification, nutrient depletion and the mobilization of toxic meta ls in sensitive aquatic and terrestrial ecosystems”.

19 1 This beginning sentence shows how the term “element” or in this case

“elements” can lead to confusion as indicated in my previous comments.

19 23 Change to “deposition decreased”.

19 24 Change to “deposition is decrease d”. There may be confusion in terms when discussing nitrogen in the use of the term “reduced” since it also has a chemical meaning.

Chapter 2: Known or Anticipated Ecological Effects

1. What are the views of the Panel on the appropri ateness of staff’s weight-of-evidence approach

which assesses information from across the vari ous ecological research areas described in the NOx SOx Secondary Standards Integrated Sc ience Assessment (ISA), including studies of acidification and nutrient-enrichment in aqua tic and terrestrial ecosystems, and laboratory research on responses of plant and animal species to acidification and nu trient enrichment? To what extent is the presentation of evidence draw n from the ecological eff ects studies assessed in the ISA technically sound, appropriately focu sed and balanced, and clearly communicated?

78The current document provides a good review based upon the ISA. There needs to be clarification, however, with respect to some of the details including how the document provides results with respect to specific yea rs. The document needs to be m ade more explicit with respect to the actual year(s) of the analyses. Some of the discussion is repetitive and some additional editing should be used to d ecrease the redundancy. Specific sugge sted changes are provided in my detailed comments.

2. To what extent are the interpretation and pres entation of the results of the exposure and risk assessment technically sound, appropriatel y balanced, and clear ly communicated?

The presentation and summarization of results related to exposure and risk assessment are generally good.

3. What are the views of the Panel on the critical uncertainties associated with the risk and exposure analysis and the evidence from ecological effects studies that need to be characterized in terms of their potent ial implications for the secondary standards?

More attention needs to be pla ced on the issues related to the uncertainties of the deposition estimates provided and used by va rious models. This is especi ally important with respect to estimates of dry deposition and deposition via clouds and fog. The descriptions of other issues of uncertainty are sound and include c onsiderations of the degree of uncertainty related to different ecosystems and their respective components.

Detailed Comments

Page Line Comment

22 26 Replace “significance” with “importance”. Reserve the use of the term “significance” here and elsewhere for indicating statistical significance.

23 5 Delete “and thermodynamic processe s”. This is not needed since thermodynamics is a function of the chemical reactions. 23 7 Not sure what is meant by “ecosystem exposure”.

23 13-14 Change to “and reduced chemical species”.

23 23 Replace “host” with “variety”.

23 26 Change to “but others, like geol ogy, vary over larger spatial scales”.

24 9 Change to “episodes with deleteriou s consequences to sensitive biota”.

24 17 Change to “biogeochemical components”.

24 20 Change to “water bodies; moreover, deposition”. Also change “effects” to

“affects”.

7925 2 Change to “in inorganic Al concen tration. These changes contribute to

declines”.

25 4 Change to “animal species in various ecosystems. These fish may also

serve as a source of food and recreation”.

25 15 Replace “communities” with “taxa”.

25 17 Change to “multiple studies are: ”.

25 19 Change to “20%, exchange chemistry”.

25 20 Change to “Under these conditions”.

25 23 Change to “The Ca 2+ and Al concentrations in soil water”.

26 3 Delete “episodic”.

26 3 Do not capitalize “sugar”.

26 4 Change to “cations from soil w ith low levels of available Ca”.

26 5 Change to “forests due to grassla nd soils being generally rich in base

cations”.

26 9-10 This is not a very useful senten ce. A more specific delineation of sensitive ecosystems is needed beyond freshwat er and terrestrial. Either delete or

revise.

26 16 Change to “flowpaths”.

26 16 Delete “at relatively high elevation”.

26 18 I would suggest that the term “magn itude” is not a very useful term. How about “range”? Also, line 21.

27 2 Delete “since the 1980s”.

27 7 I would be careful here with respect to how to phrase this description since

within the western U.S. there are acidic waters associated with various factors including acid mine drainage. Maybe so mething like: There the acidification of surface waters by acidic deposition is uncommon in the western U.S.

27 22 Replace “classes” with “taxa”.

8027 22 Change to “whereas other taxa ar e reduced to only acidophilic species”.

27 23-24 Change to “changes in taxa compos ition is associated with the high energy

cost”.

28 1 Delete “In the literature,”.

28 7 Delete “from the EPA-administered”.

28 Figure 2-1 Replace “forms” with “taxa”.

29 1-4 In this section be more explicit of the actual date(s) related to these results.

29 6 Change to “there would be no improvement in water quality”.

29 7-8 Change to “same from 2020 to 2050".

30 Figure 2-3 Figure caption. Ch ange from “and current (2006)

conditions” to “and 2006 conditions”.

31 5 Provide the actual year versus indica ting “current”. Also (line 7) give the actual year instead of indicating “today”. Such changes should be made for the

entire document.

32 12 Change to “emission levels from 2010 to 2050".

32 15 Change to “are predicted to increase by 5%”.

32 17 Change to “blacknose dace”.

33 Figure 2-6 This figure needs a scale indicator of size. Such scales are needed in all figures showing spatial location.

34 11 Change to “Tree health has been linked to the availability of base cations”.

34 12 Change to “Tree species show a range of sensitivities to”.

34 13 Clarify if thes e ratios are “molar” or “mass” based.

35 15 Change to “studied tree species”.

35 19 Delete “in 2002".

37 1 Change to “data sets”.

37 4 Change to “Ca 2+ ”.

8137 18-19 Change to “Nitrogen deposition is a major source of anthropogenic nitrogen”. For many terrestrial and fres hwater systems other sources of nitrogen including fertilizer a nd waste treatment are gr eater than deposition.

37 18-21 The statement associated with estuar ies is confusing. This needs to be

reworded to indicate that fo r estuaries that other sources of N input greatly exceed N deposition.

37 29 Change to “biogeochemical”.

38 27 Change to “The most sensitive terrestrial taxa to N deposition”.

39 27 Change to “sensitive terres trial ecosystems to N deposition”.

42 Figure 2-8 Delete in caption “with the inclusion of the diatom changes in the Rocky Mountain Lakes”.

45 22 Change to “0.7 kg N/ha/yr”.

46 7-8 As stated in a previ ous comment that the wording here with respect to the effect of N loads on estuaries is confusing.

46 20 Change to “eutrophication; however,”.

50 28 Change to “such as wate r availability, humidity”.

Chapter 3: Considerations of Adversity to Public Welfare

4. What are the views of the pane l regarding the characterizations of adversity to public welfare presented in this document? What are the views of the panel regarding the use of the ecosystem

services framework as an additional metric to in form questions of adversity? What are the views of the panel regarding the us efulness of including economic va luation of some of these ecosystem services in the po licy assessment document?

The inclusion of public welfare seems to be appropriate for this document. Clearly understanding the role of ecosystem services is central to setti ng these standards. Hence, a description of the importance of these services needs to be a fo cal point of the document. The use of economic valuation also needs to be included so that the public will be aware of the issues as they relate to economic issues and other ways to evaluate how the standards affect the public welfare. Clearly a major challenge in developin g the secondary standards will be to provide to the public information on ecosystem services and how maintaining th ese services is critical for the welfare of both individuals as well as the Nation. The more the importance that ecosystem services can be articulated, the better this document will serve in educating the public.

825. To what extent is the presenta tion of ecosystem services in th is document scientifically sound and clearly communicated?

The overall description is adequate, but further editing will be needed to sharpen the focus and to be sure to avoid confusion among the various issues relating to publ ic welfare and setting secondary standards for SO

x and NO

x . In some places it is not clear on the relative concerns associated with procedures to make evaluat ions on ecosystem services versus having the necessary information for making these evaluations. There is also an issue related to whether there should be an attempt to make an evaluation with respect to any positive aspects related to nitrogen deposition. If there is an exclusion of the determinations of the positive benefits, this might be construed as a major bias by EPA in this evaluation.

6. What are the views of the Pane l on the critical uncertainties associated with articulating adversity to public welfare that n eed to be characterized in terms of their potential implications for the secondary standards?

Some further elaboration of how the types of unc ertainties may affect th e setting of secondary standards and how these uncertainties vary with ty pe of effect on public welfare is needed.

Detailed Comments

Page Line Comment

63 2 Is this statement on limiting welfare e ffects of ozone to ve getation correct? Ozone can have major impacts on human h ealth and deterioration of materials?

65 4-11 This text is very difficult to follow and needs to be rewritten.

66 4 Change to “20 mg/L” and “CaCO 3 ". (See also line 7 and throughout this section where similar changes are needed) No te that the proper symbol for liters is

“L”.

70 7-8 Change to something like “Especi ally important is the acknowledgment

that it is difficult to measure and/or m onetize the goods and services supplied by ecosystems”.

74 Figure 3-4 legend. Do not capitalize nitrogen and sulfur. Also the source of these data needs to be provided. Units need to be given.

75 Figure 3-5 legend. Do not capitalize n itrogen and sulfur. Also the source of these data needs to be pr ovided. Units need to be given.

75-76 Change the ending and beginning se ntence of each of these pages to something like: “The difficulty in the monetization for ecosystems services has

83been previously emphasized hence necessitating using a subset of services in

economic valuation.

76 14 Delete “colloquially”.

76 14 Change to “However, the amount an individual is willing to pay”.

77 21 Do not capitalize “bald eagle”.

78 2 Including the term “costly” confuses issues related to evaluation of public welfare and monetary evaluation of ecosystem services. A major challenge in this document and for moving secondary standards forward will be to provide to the public information on the importance of ecosystem services and how the secondary standards help to protect these services.

79 4 Replace “certain” with “specific”.

79 10-11 Is it really true th at food is generally the mo st important provisioning service provided by inland service waters? Isn’t the availability of potable water by far the most important service?

80 9-10 This statement is confusing with respect to whether surface waters are affecting versus being affected by hydrological regimes and climates.

80 28 Change to “resulting from the d ecrease of anthropoge nic”. Isn’t it impossible to actually eliminate the anthropogenic emissions of NO

x and SO

x ?

81 2 See previous statement with re spect to issue of emissions being

eliminated.

81 14-16 Change to: These model runs assumed a 2010 implementation of “zeroout” emissions with a projected lag time to improvement of 10 years and thus results were calculated for the year 2020.

82 6-7 Change to “indicate that impaired lakes would decrease from 22 to 31% using background conditions”.

82 11-15 This sentence is very conf using and needs to be reworded.

82 16-17 Change to “This analysis provides results on only a subset of the impacts of acidification on public services and s uggests that the overall impact on these services is likely to be substantial”.

82 22 Clarify whether the issue is that there is no known procedure to make

these determinations or whether we do not have the necessary information.

8482 29 Do not start new paragraph.

82 30 Change to “producing timb er and maple syrup that”.

83 6 Give the names of these two listed species.

83 16 Replace “roughly” with “approximately” here and throughout document.

84 3 Replace “regulate that quantity a nd flows” with “help regulate the quantities and temporal discharge patterns”.

84 3-4 Delete the sentence starting with “F inally” and replace with “Forests also play an important role in carbon sequestrati on at both regional a nd global scales”.

84 24-29 This paragraph might be interp reted that EPA is not making a full evaluation and is biasing the analyses with consideration of only deleterious effects. Better justification is needed on why the beneficial effects are not to be

considered in the evaluation. Is there a problem with availabili ty of data or is there some other important issue that prevents this analysis?

85 2-3 Change to “Estuaries in the easte rn United States are important for fish and shellfish food production”.

85 20 Change to “Mistiaen et al. (2003)”.

86 13 Change to “$2 billion”.

86 13 Change to “Almost seven million people”.

86 17 Indent starting new paragraph.

87 1 Change “air” to “atmospheric”.

87 3-10 Clarify if these amounts are based upon an apportionment of the relative role of atmospheric deposition to tota l nitrogen inputs to the Chesapeake Bay.

88 21-22 Provide the names of these species.

88 30 Correct to “deposition”.

89 19-20 As indicated previousl y, clarify if the issue is th e lack of methods to make

the assessment or the absence of data needed for making evaluations of the impacts on services.

100 Here and elsewhere in the document th ere is specific reference to “staff”. This suggests that there is a subcompone nt of EPA that supports the narrative

85within this document. I would avoid th e use of this designation to avoid any

confusion.

100 13 Change to “Chapter”.

Chapter 4: Addressing the Adequacy of the Current Standards

7. What are the views of the Panel on staff’s as sessment of the adequacy of the form of the existing NOx and SOx secondary st andards? To what extent does the Panel agree with staff’s assessment of the protection provided by existing standards, given the current levels, forms, averaging times, and indicators?

The document provides a good review of existin g secondary standards and shows that they are not adequate for ecosystem protection.

8. What are the views of the Panel on the time frame of ecological response related to current deposition? The adequacy evaluation relies on recent NOx, SOx, deposition, and on long-term steady state ANC. Does the panel agree that long -term steady state ANC is the most appropriate representation of ANC for evaluating the adequacy of the current standards?

The use of long-term ANC has merits with resp ect to setting standards, but may not adequately capture some of the temporal changes that wi ll likely occur in conjunction with changes in surface water chemistry. Clarification is needed on the specific time to be used as targets for recovery and the actual rates of these recoveries.

9. To what extent are the characterizations of ambient air quality a nd deposition appropriately characterized, relevant to the review of the secondary NOx and SOx NAAQS, and clearly

communicated?

A more balanced approach is needed in which it is more clearly delineated what information the current networks currently provide and what in formation is lacking. Fo r example the network distribution may be completely adequate for estimating wet only sulfate deposition, but the estimates for NH

x , including both wet and dry, are lacking. Maybe the inclusion of a figure or table that provides a descri ption of the both spatial and temporal coverage of the major chemical species atmospheric concentrations w ould be useful. Some of the discussion implies that the CMAQ model will be used to overcome some of the problems with respect to spatial coverage of atmospheric pollutants and depositio n of sulfur and nitroge n compounds. Within the document the limitations of CM AQ need to be provided with respect to how well the model outputs have been validated both with respect to temporal and spatial patterns.

Detailed Comments

Page Line Comment

86101 15-17 Change to “Acidification occurs ove r extended periods and the ability of both terrestrial and aquatic ecosystems to recover is dependent upon not only the decrease in acidic depositi on, but the ability of these ecosystems to generate

cations that are needed for nut rients and base cation supply”.

101 24 Change to “This type of structure does not take into account the spatial and temporal variability of deposition and ecosystem processes with respect to the

effects of NO

x and SO

x on public welfare”.

102 2 Change to “including geological an d soil characteristic s related to the sensitivity to acidification as well as at mospheric and landscape characteristics that govern rates of deposition”.

104 10 Change to “of secondary standards”.

104 11 Change to “impact both n itrogen and sulfur acting”.

104 22 Change to “relevant chemical species”.

104 24 Change to “total nitrogen and total sulfur deposition”.

105 26-27 This general phrase has been used elsewhere in the document and does not adequately describe the issues. There ar e three major factors that all need to be considered: 1) Atmospheric concentrati ons 2) Deposition velocities of various chemical species and 3) the processing with in ecosystems. It is not clear what are “atmospheric factors” and what are “ecologi cal factors”. Is the type of vegetation (that affects deposition veloci ties) an atmospheric or ecological factor? Is surface wetness an atmospheric factor”? Are hydrological pathways ecological factors?

106 23-25 This statement is too pessimis tic and suggests that the monitoring networks are completely inadequate. It would be better to state that certain components (including NH

x ) are not adequately measured within the current networks. Figures 4-1, 4-2 and 4-3 suggest that the network coverage is quite

extensive.

107 2-3 In Figure 4-1 legend give the ac tual chemical N species for which

concentrations are monitored.

108-111 This section provides a narrative on what chemical species the various networks monitor, but it is not easy to use this in formation to evaluate the adequacy of the monitoring. Some summary figures or possibly a tabl e showing what actual chemical species are monitored and the number of sites doing this monitoring would be more helpful in evaluating the ad equacy of at least the spatial coverage of the networks for specific chemical species.

87108 2-3 In Figure 4-2 legend give the ac tual chemical S species for which

concentrations are monitored.

111 16-17 This statement suggests the CMAQ model will satisfy the needs with respect to providing data on atmospheric concentration and deposition of S and N chemical species. The limitations of the CMAQ need to be acknowledged.

111 29 Do not capitalize “organic”.

111-114 The discussion on the rationale with re spect to the use of CMAQ is useful, but little quantitative results are provided w ith respect to clearly indicating what CMAQ does well and where are the problems.

114 18-22 The focus of CMAQ on relatively short time (e.g., hourly values) may

result is a mismatch to the needs for a secondary standard that would more likely result in values needed for longer periods (e.g., yearly values).

115-123 These various figures show the mo deled results from CMAQ for various atmospheric chemical species and show the spatial detail available from the CMAQ output. There is discussion on how these modeled values show the spatial

distribution of these chemi cal species for the single year of simulation (2005). However, this is not very helpful in as certaining the accuracy and precision of the CMAQ simulations.

116 6-7 The assertion that the modeled and ob served values are similar needs to be backed up with quantitative evaluations.

116 16-17 In discussing these conditions provide the actual year of comparison. Also, the wording may be confusing w ith respect to the current secondary standards and the approach being develope d within the current document that is trying to develop secondary standards showing broader ecological effects.

125 Showing the results from CASTNET in Figures 4-12 and 4-13 is helpful,

but it would be more instru ctive is there were direct comparisons between the CMAQ and CASTNET results.

126-127 For Figure legends, correct the capitalization of units.

132 4-5 I don’t believe that there is su fficient evidence between S deposition and Hg methylation. There is known relati onship between sulfate reduction and Hg methylation, but there is no di rect linkage with S deposition.

132 23 It would be helpful to add a thir d category: nutrient depletion. This category is related to acidification, but focuses on the importance of the loss of nutrient cations from ecosystems.

88134 5 The MAGIC model certainly provides information, but there other sources of information that also indicate the importance of aquatic acidification in the

Adirondacks and Shenandoah National Park.

134 24 Change to “concern); however”.

135 4 change to “ results based upon the EMAP”.

135 9 Here and elsewhere instead of using the term “recent”, give the actual year or period of coverage.

135 12-13 Change to “As for the Adirondacks, these results suggest that a substantial proportion of streams”.

135 28 Change “kilometers” to “lengths”.

136 2 Change to “two to three times greater than the number of lakes classified

as”.

137 2 Change to “The REA did not evalua te all possible sensitive regions, but focused on specific case studies”.

137 2 Change to “For example, in the sugar maple case”.

137 14 Change to “For red spruce, 5% of all plots”.

137 15-16 Change to “In those states where red spruce is an important tree species (Maine”.

138 10 The statement “In certain limited situ ations” is not true. For many if not most terrestrial ecosystems N additions results in increased plant growth. This

includes both natural an d managed ecosystems.

138 14 I have commented previously on the importance of considering both “managed” and “unmanaged” systems especially with respect to forests.

138 20 Note that this statement is correct and conflicts with line 10.

138 23 Be careful in providing these numbers for nitrogen uptake by crops. Are these actual uptake values for N or th e amount of N applied as fertilizer?

138 26 This statement is not true. There is a substantial b ody of information on the effects of atmospheric deposition of N to forests and other ecosystems.

139 21 Change to “capacity of each county’s”.

89140 12 Change “were” to “was”.

140 26-31 This paragraph suggests that the st andard needs to focus on these systems which are most sensitive to increases in N deposition.

141 4 Delete “scientifically”.

141 5 Change “country” to “U.S.

141 13 Change to “received”.

141 21 Delete “, the authors estimated that”.

141 28 Shouldn’t this be “systems where N is limiting”?

142 13-16 Is this really a link with S depos ition or is this a function of sulfate concentration which can be affected by other factors in addition to S deposition?

142 29 Change to “Assessment document”.

Chapter 5: Conceptual Design of an Ecol ogically Relevant Multi-pollutant Standard

10. What are the views of the Panel on staff’s pr oposed conceptual framework for the structure of a multipollutant, ecologically relevant standard for NOx and SOx? To what extent does the Panel agree that this suggested structure adequa tely represents the scientific linkages between ecological responses, water chemistry, atmos pheric deposition, and ambient NOx and SOx?

Some of the discussion with resp ect to ecological responses and various watershed attributes were confusing in the d ifferent treatments of nitrogen and sulf ur. A treatment that shows more clearly the biogeochemical similarities and diff erences would strengthen the overall approach.

11. What are the views of the Pa nel on the relevance of the c onceptual design for developing standards to protect against aquatic acidification effects?

The overall conceptual design is adequate.

a) What are the views of the Panel on staff’s proposed options for the ecosystem acidification model to represent the eco logical response function?

There are some concerns related to the applicati on of this model with respect to accurately capturing the critical biogeochemical processes. There will be important tradeoffs between keeping the model relatively simple and capturi ng important spatial and temporal patterns affecting acidification.

90b) What are the views of the Panel on the relati ve merits of the two techniques for calculating

N
eco , the parameter representing the amount of deposited nitrogen that is available for acidification due to uptake, denitrification and immobilization?

The use of N

eco formulation that needs estimations of N retention, immobilization and denitrification may be very problematic since th e parameter estimates (e specially immobilization and denitrification) are very difficult to obtain. It would be better to focus on the actual N losses via leaching. This latter value is easi er to obtain, but may re quire a more empirical approach. An issue that needs consideration is the time units used in these ca lculations. It will probably be important to include some seasonal effects since there are marked changes in nitrate losses during different periods of the year.

c) What are the views of the Panel on staff’s proposed options for de veloping acid sensitivity classes to categorize the nationa l landscape? Is it appropriate to base this classification on bedrock geology? Should multiple criteria be us ed to inform the sensitivity categories?

It is not appropriate to only use bedrock geol ogy for assessing the poten tial for acidification and/or recovery from acidificati on. The surficial geology in cluding the parent material and hydrological flow paths can be extremely impor tant and catchments w ith the same parent material can show very different responses to acid ification. Yes, multiple criteria are needed to provide sufficient information for sensitivity cate gories. There has been discussion related to the use of elevation as a predicting variable. Clea rly elevation is a proxy for the more direct controls such as soil depth, vegetation type, etc. and it would be preferable to actually include the controlling variable in developing the model. At a minimum the issue of elevation being a proxy for controlling physical, chemical and biological components needs to be provided.

d) What are the views of the Panel on staff’s pr oposed options for how to aggregate acidification modeling from the catchment-scale to represent acid-sensitivity categories at the national-scale?

The aggregation needs to be done in a meaningful manner that takes into account the controlling factors of acidification of surface waters. Th ere is an over dependence on the use of bedrock geology that does not consider the importance of other critical factors, especially superficial geology including soil depth and soil chemistry, in affecting sensitiv ity to acidification.

e) What are the views of the Panel on staff’s suggested method to account for reduced nitrogen in the deposition metric?

The assumption that the proportion of reduced N is constant over time, may cause a number of problems both for forecasting and also for any attempt to examine model performance using hindcasting.

12. What are the views of the Pa nel on the relevance of the c onceptual design for developing standards to protect agai nst terrestrial acidification effects? Terrestrial nutrient enrichment effects? Aquatic nutrient enrich ment effects? Does the panel have suggestions on additional data or methods that might enable EPA to expand the current aquatic acidifica tion approach to cover

additional effects?

91Developing a single standard for either aquatic or terrestrial ecosystems is highly problematic due to the major differences in acidification and nutrient response among and within the regions. The standard needs to vary to account for differences in the biogeochemical processes among different responses. For terrestrial systems it will be particularly important to look at different biological species including trees that have ve ry different requireme nts for base status and nutrients (e.g., red spruce versus sugar maple) . There are importan ce differences in the landscape features across the nation and the historical inputs of S and N that influence ecosystem responses including ac idification and nut rient effects.

13. What are the views of the Pane l on the critical uncertainties a ssociated with the conceptual design of an ecologically relevant multi-pollutant st andard that need to be characterized in terms of their potential implications for the secondary standards?

The development of some careful analyses rela ted to the precision and accuracy of the CMAQ

simulations needs to be include d. It would be helpful to also show any other regional approaches that have estimated N and S depos ition and how these compare with CMAQ

simulations.

14. To what extent do the figures and examples ai d in clarifying the text? Should more or less information of this type be in cluded in the second draft?

The figures and examples need to be modified to capture the major processes that control ecosystem response to acidification and nutrien ts. See specific comments for more details.

Detailed Comments

Page Line Comment

147 9 Change “big” to “major”.

148 9 The term “landscape features” is rather vague. Does this include physical, chemical and biotic attributes? Isn’t there an important issue related to the history of deposition for given areas with the most sensitive areas to N deposition in the west which have been subject to relatively low atmospheric N inputs?

148 11 How is the country being subdivi ded? Are these states, biomes, ecosystem types, or something else?

149 19 Delete “scientific evidence”.

149 20-22 Change to “aquatic acidification shou ld be measurable and causally linked to the deposition of N and S. The indicat or should have ecological effects that adversely affect public welfare”.

92150 `6 Change to “impairment, incl uding the number of fish species”.

150 15 Change “acid anions” to “mobile anions”.

150 16 Change to “when these anions are mobilized in”.

150 22 Change to “deposition. These acidi fication models simulate a variety”.

150 26 Change to “ANC= 50 : eq/L”.

151 22 Change to “These data were”. Change “current” to “recent”.

152 3 Delete “time”.

152 15 Change to “with different levels”.

152 24 Change to “due to variation in biogeochemical processes among

watersheds”.

152 25 Change to “that quantifia ble relationships exist”.

152 26-27 Change to “These relationships are shown by long-term”

152 28-29 Change to “Models are impor tant tools in evaluating how”.

153 3 Change to “There are va rious factors that modify”.

153 4 Change to “of these factors are described”. Delete “that parameterize ecosystems to simulate the process”.

153 6 Change to “input data for 17 to 20 environmental”.

153 9 Change to “specific resp onses of aquatic ecosystems”.

153 12-13 Change to “The weathering of so il minerals is a major source of base cations to ecosystems”. (Note this it ma y not be the main source in all cases.)

153 15 Change to “Landscape factors that affect the acid sensitive of forest ecosystems”.

153 19-20 Delete from “Numerous ..... example,”.

153 22 Change to “Water discharge values for the catchment”.

153 27 Replace “quality” with “chemistry”.

93154 8 Replace “correlated” with “linked”.

154 8-9 Delete the sentence “Consideration....models”.

154 10-11 Change to “The calibration of th e models stream water chemistry, soil characteristics and atmospheric deposition estimates”.

154 15 Change to “will vary among catchments”.

154 16-17 Delete the sentence “However.... simulations”.

154 20 Replace “quality” with “chemistry”.

154 24 Give the units for the ANC values.

155 8 Delete “mountain”.

155 14-16 Change to: “With these data the atmospheric deposition loads that will

cause streams to exceed the critical limit of ANC can be calculated”.

155 18 Delete the sentence “The relationship....nationally”.

155 19 Change to “similar hydrology and mi neral weathering rates should show

similar”. Need to be careful in these stat ements since the amount of base minerals generated is a function not only the weathering rates of so il minerals, but also the hydrological relationships including flow paths.

155 21 Is there an implicit assumption of what maximum area constitutes a

“catchment”?

155 24-26 This statement is confusing in that critical load is highly dependent on the

characteristics of a catchment. How can aggregation be used to develop a national standard? Isn’t it more likely th at different standards will be needed for

different catchments or that standards will be set to protect a certain subset of

catchments?

156 3-7 It is not clear if developing a single standard is the goal of this process. See my previous comment.

156 14-15 Change to “Models are important tool for evaluating how multiple”.

156 17 Change to “Mineral weathering is a major source of base cations and is therefore considered an important fa ctor in determining critical loads”.

156 19 Replace “correlated” with “linked”. Here and elsewhere the use of the

term correlated is somewhat weak since this infers there is a statistical correlation

94and not necessarily a causal relationshi p. Using factors that have casual relationships is a stronger approach than using statistic al correlations.

156 21 Delete sentence “Modeling every...requirements”.

156-157 These summary statements should clarify that having a single secondary standard may not be warranted to take into ac count the substantia l variation in the sensitivity among regions with respec t to surface wate r acidification.

157 4 Replace “to” with “for”.

157 7 Change to “to protect different areas”.

157 13 Delete the phrase “sci entific literatur e”. Here and elsewhere in the document it is implicit that the overall pro cedure will be scientific and this phrase

is not needed.

157 20-23 This dichotomy is not valid since S can certainly be retained in ecosystems especially those with high potential for sulfate adsorption. Both the leaching of

nitrate and sulfate as well as the retention of N and S need to be part of the overall

evaluation.

157 26 This is confusing since there is gene rally little ammonium lost in runoff in systems sensitive to acidification. Maybe this should be restated with respect to N solute leaching and hence the inclusi on of DON would also be warranted.

157 16 The legend for Figure 5-3 needs more information including the meaning

of the various abbreviations.

159 1-23 The use of these models and the different treatment of S and N is confusing. It would be clearer if the models mo re accurately captured the biogeochemistry of each of these elements. One issue that could be important in

some of the areas is that th ere is a net loss of sulfate from soil that is greater than atmospheric inputs and this will delay the recovery of these systems from

acidification.

160 8-10 The use of N

eco formulation that needs estimations of N retention, immobilization and denitrification may be very problematic since the parameter estimates (especially immobilization and de nitrification) are very difficult to

obtain. It would be better to focus on the actual N losses via leaching. This

value is easier to obtain. An issue that needs consideration is the time units used in these calculations. It will probably be important to include some seasonal effects since there are marked changes in nitrate losses during different periods of the year.

95160 12 As indicated previously the assumpti on that all S deposit ion is leached is

not valid.

161 9 The goal of “obtaining a represen tative deposition value” is very problematic due to the high variation in acid base chemistry response among catchments is very high (e.g., even adjacent catchments may have very different responses).

161 12-23 There may be merit in the identi fication of specific population of surface waters that have substantial representa tion among all water bodies of a region, but are most susceptible to acidification.

162 3-10 The use of bedrock geology for the classification of acid sensitive catchments is problematic. The surficia l geology needs to be used in this classification. In the early days of “acid rain” research the use of bedrock geology was used in classifying wate rsheds, but as the understanding of acidification processes increases it became apparent that surficial geology including soil depth is very important in evaluating spatial variability of sensitivity to acidification. For example us ing Figure 5-4 it is indicated that the

central Adirondacks would be most sensit ive to acidification , but we know that the highest proportion of acidic surface wate rs in the Adirondacks are found in the southwest portion of this region.

163 6-15 Here and elsewhere in the document the use of elevation as a parameter is suggested in the analyses. Elevation is not the casual factor associated with sensitivity to acidification, but it is rela ted to factors that are correlated with elevation including precipita tion amount, soil depth, changes in vegetation, etc. It

would be better to use the act ual causal factor in these determinations or at least

indicate that elevation is li nked to these causal factors.

164 25-27 The statement that “reduced forms of nitrogen deposition” are quickly

converted to nitrate is not correct. Some reduced forms of N can be assimilated by both the vegetation and the soil microflora without being convert ed to nitrate. If nitrification rates are low N deposite d in reduced forms may also not be

converted to nitrate. It should be emphasized that the total amount of N deposited

is the factor that determines the N a tmospheric loading. This is why total N deposition needs to be considered in making these evaluations.

165 2-3 Isn’t the most important assump tions associated with any temporal changes in N deposition versus the relative importance of oxidized versus reduced forms of N deposition.

165 7-29 Within this “summary” a number of statements related to the use of bedrock geology, deposition calculations, etc. for which concerns have been provided in comments above.

96166 Table 5-2 (this is actually a figure ve rsus a table). The descriptors should be changed to more clearly reflect th e factors that infl uence acidification.

167 21 “This leads to the question, are a quatic or terrestrial ecosystem more sensitive?”–aquatic and terrest rial ecosystem responses to acidification differ with the effect of limiting nutrients (e.g., calcium) more important for terrestrial versus aquatic ecosystems. This actually is imp licit in the use of different indicators (e.g., Bc:Al for terrestrial and ANC fo r aquatic systems, respectively).

168 11 It is really feasible “one indicator that can be applied across the nation”. This may not be possible with differe nt conditions among regions (e.g., west having lower historical rate s of atmospheric N inputs).

169 2 Change to “first draft PA; however, a”

169 1-19 Concerns related to these summa ry statements are provided in my previous comments.

169 22-24 Clarification is needed on how cloud/fog deposition fits into these two

mechanisms.

169 25 Change to “and chemical species-specific”.

169 10 See above comment associated with incorporation of fog/cloud deposition

into this formulation.

171 1-2 The rationale for using V S/N is not evident due the great variation in deposition velocities among various atmospheric chemical species.

171 2 Change to “aggregated deposition”.

171 4 Change to “the chemical species specific”.

171 8 Clarify what is meant by “annual aver age”–isn’t the relativ e value the total annual deposition?

171 13-15 It is not clear what is be ing suggested by this statement.

171 25-27 The development of uncertainti es in the CMAQ predictions will be extremely important in understanding the accuracy and precision of these

estimates.

171-172 The procedure for calculating VS/N seem s very convoluted and it is not evident how this is better than calculating separately annual deposition of N and S.

178 3-4 Correct units.

97179 2-3 As stated previously, the calcula tion of a depositional load for a specific

ANC that does not account for variation in catchment responses to acidification will not result in accurate predictions of how these systems are responding. At least some classification of catchment types is needed. Such classifications have been used extensively in some of the regions such as the Adirondacks (e.g., (1) mounded seepage lakes with low levels of DOC; (2) mounded seepage lakes with high DOC; (3) drainage lakes in watersheds with thin till and with low DOC; and (4) drainage lakes in thin-ti lled watersheds with high DOC.

180-188 Before developing further details on thes e calculations, agreement is needed with respect to the overall appro ach. Many of these calculations are based on the need to develop a single standard. Are th ere other approaches that should be

considered?

Chapter 6: Options for Elements of a Standa rd to Protect Against Effects from Aquatic

Acidification

15. To what extent does the Panel agree th at the proposal to develop an Atmospheric Acidification Potential Index (AAPI) linked to ke y determinants of aquatic ANC is a reasonable approach to developing an ecologi cally relevant standard? Does the Panel generally agree that the secondary standard options identified by sta ff (including indicator, av eraging time, form, and level) are generally consistent with the available scientific an d technical information and are appropriate for considera tion by the Administrator?

The Atmospheric Acidification Potential Index ( AAPI) is an interesting approach that integrates aquatic ANC as affected by acidic deposition. The use of this inde x needs to be considered with respect to issues associated with temporal and spatial variability. A lthough the current approach allows for the development of unified national sta ndards, it does not account for the high level of biogeochemical variation in the processing of nitr ogen and sulfur in catchments. Especially for those catchments which have major differences in seasonal drainage ra tes (including snowmelt and droughts) time scales are needed that will refl ect episodic conditions. There is a large body of evidence of the importance of the spatial and temporal varia tion in reflecting acidification and nutrient enrichment processes among ecosystems. Some specifi c examples showing how these standards would account for episodic responses w ould be very helpful in showing that the standard would protect those systems for which epis odic acidification is the major issue. This would help link this to climat e change effects on hydrology and bi ogeochemistry. The sensitivity to episodic components could also be related to watershed type distributions including the presence of wetlands that would be especially important for episodes associated with rewetting after droughts.

16. What are the views of the Pane l on the degree of uncertainty a ssociated with each element of the suggested standard, e.g. the ecological indicator; the concentration to deposition ratios, reduced nitrogen, the natural background ANC, and the ambient indicator and averaging time for

98NOx and sox, and its relationship to the degree of protection that could be expected from the

standard? What are the views of the Panel on how to fairly characterize the uncertainty associated with the degree of protection that such a standard woul d provide from aquatic

acidification?

More attention is needed on other factors that will affect the biogeochemi cal processing of N and S within watersheds. Also, the strong reliance in using the CMAQ model would be greatly improved by more specific comparisons related to actual comparisons between CMAQ estimates and measured values. Consistency is needed be tween the temporal and s patial resolution of the depositional predictions and the ac tual measurements within terrestrial and aquatic ecosystems regarding nutrient enrich ment and acidification.

17. What are the views of the Pane l on aggregating the terms (Q, N

eco and BC0 * ) used in estimating natural background ANC , denoted by the function g( Α ), into 5 bins based on the geologic classification scheme?

I don’t believe the use of the ge ologic classification scheme is adequate to capture the spatial and temporal patterns needed for setting these sta ndards. This can be shown by looking at the modeled outputs in the Adirondacks that do not appear to show w hat is known about the spatial patterns of surface water acidific ation in this region. At a mi nimum more attention is needed with respect to surficial geology and soil propert ies both with respect to physical aspects (e.g., soil depth) and chemistry (e.g., base cation concentrations).

18. What are the views of the Panel on the us e of regional air quality modeling (e.g., CMAQ)

results to establish the concentration-to-de position ratio (VNOy, VSOx) and reduced nitrogen deposition (NHx) in the AAPI calculation? What are the views of the Panel on the critical uncertainties associated with the use of CMAQ to generate these parameters, and the potential implications of these uncertainties for the secondary standards?

As indicated in previous comment s there are a number of issues related to the use of the CMAQ results. A critical component of this analysis is the determin ation of the precision and accuracy associated with the calculation/estimates of depos ition velocities of the chemical species of sulfur and nitrogen.

19. What are the views of the Pane l regarding presentation of the standards as a set of tradeoff

curves for NOx and SOx associated with specific levels of AAPI, and specific values of the g, VNOx, VSOx, and NHx terms?

To make valid assessments of the effects of N and S deposition on ecosystem processes the various components that provide the deposition a nd the actual chemical species (especially for nitrogen compounds) need to be delineated separately.

20. What are the views of the Pane l on using a single year or a thre e year average of recent year CMAQ modeling results to es timate the AAPI terms?

99The use of such a short time frame for developing terms should be reconsidered especially in the context of ecosystem level responses that o ccur over much longer periods (e.g., decades and longer), but having multiple years for compar ison would be helpful in showing how meteorological conditions affect or do not affect the AAPI calculations. Is there an issue with respect to the limitations of results from the CMAQ model in determini ng what information is available with respect to atmospheric deposition?

21. What are the views of the pa nel on the ambient monitoring requirements? Is for the proposed three ambient air measurements – NOy, SO2 an d particulate sulfate – sufficient to judge compliance with and AAPI?

It is not completely clear whether this approach (especially aggregating information on watershed responses) will result in the development of useful results for predicting the spatial and temporal patterns of acidification and most importantly how these sy stems will respond to changes in loads of atmospheric deposition. This is also important with respect to the watershed response monitoring components bot h biological and chemical.

22. What are the views of the Panel on using existing NOy and PM2.5 sulfate measurement techniques as the basis for defining a Federal Reference Method to judge compliance with and

standard?

There are important issues with respect to whethe r NOy captures the major N chemical species. For PM2.5 the amount of S is relatively high in this atmospheric fraction, but its overall contribution to S loading is relati vely small; hence this is not the major issue. For S the major problem is associated with maki ng accurate and precise estimates of S in dry deposition and also for some sites deposition from fog and/or clouds.

Detailed Comments

Page Line Comment

190 15-16 I agree that the previous methods for defining indicator, averaging time, form and level are not appropriate with respect to ecosystem level effects associated with N and S deposition.

190 The statement that: “Moreover, th e inherently complex and variable linkages between ambient concentrations of NOx and SOx, their deposited forms of nitrogen and sulfur, and th e ecological responses that are associated with public

welfare effects call for cons ideration of a more comple x and ecologically relevant design of the standard that reflects these linkages” need s to be reflected in the procedures used to deve lop these standards.

191-192 Section 6.1 seems to be highly redundant with respect to information provided in previous chapters.

100193-194 Section 6.2--I agree that future efforts will need to consider how to incorporate results associated with episodic versus chr onic responses. This will be especially important in those areas in which snow melt is a dominant component of the hydrologic cycle.

194-195 The development an Atmospheric Acidif ication Potential Index (AAPI) has some potential, but this formulation must be sufficiently robust to account for differences in biogeochemical responses among watersheds.

195 15 I agree of the importance of in cluding “including landscape and atmospheric factors” in de veloping these formulations.

196 As stated previously, much of th is discussion and formulation is based upon the development of an aggregated va lue. This approach may result in erroneous recommendations if spatial va riability in watershed components and historical differences in deposition are not included.

198 6 The other ecosystem variables will be very important with respect to predicting sensitivit y to acidification.

200-201 The selection of the populations of ar eas to be considered with respect to sensitivity parameters will be important in developing these predictions. Clearly defining which subset of the overall populati on is sensitive to acidification and the relative importance of thes e sensitive populations should be a focal point of the analyses.

201 15-16 The need to exclude “water bodies that are naturally acidic” is a clear example of the need to account for the differences within and among regions with respect to biogeochemical re sponses of acidification.

201 20-27 The next draft should explore in a ddition to alternate combinations of the target ANC, but also the known variation in watershed processing of N and S.

203-207 Section 6.5 provides further elaboration (See also Chapter 5) of the rationale for using ANC as an ecological indicator for th e acidification of aquatic ecosystems.

207 12-13 The time issue with respect to r ecovery from acidification needs further elaboration and how the identified appro ach will address this issue. The time

issue needs to be included in earlier discus sion related to the application of critical

loads.

208 Section 6.6 covers some of the i ssues related to the more complete evaluation of the various atmospheric chemical species of N and S compounds. With the exception for the need for bette r quantification of ammonia, the most pressing issues relate to the estimates of dry deposition especially the utilization of deposition velocities.

101208-209 Section 6.6.2 considers the issues aro und sampling frequency. For looking at ecosystem level effects it will be important to have extended periods of measurement. In addition to monitoring current and future concentrations, there is a strong need to have historical meas urements of concentration. Having this

historical information is critical for looking at long term watershed responses including modeling efforts.

209 27-28 Clarify what is meant by “largely population oriented”.

210 1 Not sure of the point indicated by “Ambient monitoring at every watershed may be required due to the nature of the ambient air quality in acid

sensitive areas”.

210 4 I would not agree that using annual averages dampens “much of the spatial variability”. Do you mean variab ility of deposition estimates only?

210 6 How will CMAQ concentration values “provide insight into the likely spatial representativeness of monitors ” without clear docum entation that CMAQ is providing accurate and precise values of atmospheric concentration within region at various spatial scales.

210 8 How was this spatial variation of oxidized nitrogen in the Adirondacks

derived? The value of 1.46% for a coeffi cient of variation seems very small in reflecting changes in oxidized nitr ate values across this region.

210 Section 6.7 focuses mostly on the ju stification of the use of ANC and AAPI. It is not clear whether other parame ters need to be considered such as the effect of N addition in sensitive aquatic and terrestrial ecosystems.

Chapter 7: Co-protection

23. What are the views of the panel on the appro ach taken to compare the protection provided by a potential aquatic acidification st andard to the protection needed for terrestrial acidification?

The results presented that show differences in protection between aquatic and terrestrial systems are interesting and shows both the linkages, but al so some of the problems. There are issues beyond acidification with respect to terrestrial ecosyste ms recognizing that so il acidification is a natural process especially in forested ecosyst ems and hence the major concern is related to nutrient imbalances some of which is captured by the use of the Bc: Al ratio, but for this to be meaningful this ratio needs to address th e spatial variability of soil chemistry.

24. What are the views of the panel on a futu re comparison of the protection provided by a potential aquatic acidification standard to nutrie nt enrichment benchmarks? What are the views

102of the panel regarding using a nutrient enrichment benchmark to be a limiting factor on the nitrogen in the aquatic acidification standa rd, instead of having a separate standard?

The section on nutrient enrichment benchmarks is not yet developed fully in the document and hence comments would be premature.

Detailed Comments

Page Line Comment

213 Section 7.1--In further development of this comparison between terrestrial and aquatic systems a clarification of the relative importance of base cation generation and hence improvement of the Bc :Al ratio in terrestrial ecosystems is linked to ANC recovery in surface waters.

214 Section 7.2–As the role of nutrien t enrichment becomes more developed in this analysis this could have a mark ed effect on the overall approach in developing these standards especially w ith respect to difference among regions associated with the history of N deposition.

215 Section 7.3–The aquatic nutrient enrichment is not only associated with N effects on estuary eutrophi cation, but also on changes in the biota in surface

waters in the western U.S.

Chapter 9: Conclusions

25. What are the views of the Panel on the prelim inary staff conclusions regarding the adequacy of the current standards, the need for an integrat ed multi-pollutant structure for revised standards, and the proposed form of the joint NOx SOx standards for aquatic acidification?

The review of current standards and the need fo r an integrated multi-pollutant structure for
revised standards is well done and summarizes the importance of this effo rt for developing new secondary standards.

26. What are the views of the Pane l on the overall characterization of uncertainty as it relates to the determination of an ecologically-relevant multi-pollutant standard for NOx and SOx?

The section on uncertainty is yet to be fully d eveloped and this will likely be separate chapter. The determination and the discussion of uncertain ty in all aspects of the development of the secondary standards including atmospheric i nputs and ecosystem effects should be a predominate component of this document.

Detailed Comments

103Page Line Comment

218 19-20 The current focus on aci dification is well justified.

219-222 The conclusions indicate the major findings of this review esp ecially the rationale for focusing on acidification in the current version.

222 20 A brief summary that defines AAPI should be provided in the summary.

223 The section yet to be written on ke y uncertainties will be an important component of this report and associated recommendation. It will likely be necessary to include the effects associated with nutrient alterations that is a critical issue for both the east (Ca depleti on in terrestrial ecosystems) and west (N deposition affects on ecosystem struct ure in both aquatic and terrestrial ecosystems).

223 13-14 It will be impossible to develop “nationwide weatheri ng rates”–since these rates show a high amount of spatial vari ation as a function of surficial geology

and other factors such as climate.

224 8-12 The development of more comp arisons with model results with observational data would greatly strengt hen this overall approach by clearly showing what the models do well and where there are problems that will limit the ability to set secondary standards.

104

### Mr. Rich Poirot

Chapter 4: Addressing the Adequacy of the Current Standards

7. What are the views of the Panel on staff’s as sessment of the adequacy of the form of the existing NOx and SOx secondary standards? To what extent does the Panel agree with staff’s assessment of the protec tion provided by existing standards, given the current levels, forms, averaging times, and indicators?

Chapter 4 presents clear and convincing argumen ts questioning the ecological relevance the

current SO 2 and NO 2 secondary standards (and many of their individual components) and

concludes that current standards do not adequately protect agains t adverse environmental effects

from SO X and NO X pollutants. Well-documented observations of chemical and ecological effects of S + N acidification in aquatic chemis try and effects monitoring programs like TIME, LTM and EMEP, combined with the observations that there are no exceedances of current NO 2 or SO 2 standards in areas experiencing effects of a quatic or terrestrial ac idification or nutrient enrichment provide a general indication that current standa rds are not adequate. As the

environmental effects from SO X and NO X occur primarily through the long-term cumulative deposition of multiple S and N compounds, combined together rather than individually, the chapter persuasively shows how the elements of the current secondary standards are inappropriate in terms of indicato rs, averaging times, levels and fo rms, as well as in their single pollutant approaches to multi-pollutant problems.

8. What are the views of the Panel on the ti me frame of ecological response related to current deposition? The adequacy evaluation relies on recent NOx, SOx, deposition, and on long-term steady state ANC. Does the panel ag ree that long-term steady state ANC is the most appropriate representation of ANC for evaluating the adequacy of the current

standards?

Other panel members will have more informed opinions on this question. Of necessity, a NAAQS needs to be based on current air quality (and in this case asso ciated deposition), but

current effects reflect the cumulative influences of both current and historical deposition, just as

future chemical indicators like ANC and ecolo gical effects may show a substantial lag time before “recovery”, and may never recover to pr e-industrial conditions. I don’t know of a better or more responsive indicator than steady state ANC, and think it is a reasonably strong indicator of aquatic effects which has also been observed to be responsive to increasing and decreasing S and N emissions, air quality and deposition over time.

It seems possible that some aquatic systems ma y be especially susceptible to effects from episodic acidification in ways that may not be di rectly reflected by long- term steady state ANC. I’m not sure how these kinds of systems could be better protected, but again think that other panelists can offer better advice – if this is even a significant concern.

9. To what extent are the characterizati ons of ambient air quality and deposition

105appropriately characterized, relevant to the review of the secondary NOx and SOx NAAQS, and clearly communicated?

The characterizations of air quali ty and deposition presented in Ch apter 4 are, for the most part, appropriately characterized and releva nt to the review of secondary NO X and SO X standards. While the chapter is nominally focused on evaluati ng the adequacy of current standards, it also includes considerations of the potential to us e current monitoring networks (supplemented by additional measurements and/or by CMAQ model re sults) for the development of potential new standards and/or determining co mpliance with them. While most of the map information is useful and clearly presented, seve ral of the maps appear to have inaccurate legends or captions (Figures 4-8 through 4-11; see more detailed co mments below). It would also be useful to include maps of total NH X N deposition, as well as the fraction of total N deposition contributed by reduced (or oxidized) N.

There are some important maps showing the rela tionships between atmospheric concentrations and total deposition of S and N (V S/N ) presented with poor clarity in Chapter 5 (Figure 5-5). These kind of maps and the rela tionships they display are impor tant and could be introduced (much more clearly), and expanded upon in Ch apter 4. Presumably, it could be clearly demonstrated, through use of CMAQ ratio ma ps and scatter plots based on grid point comparisons, that NO Y is a much better pr edictor or indicator of total oxidized N (N OX ) deposition than NO 2 is, and this would directly suppor t your evaluation of adequacy. If time/resources allow, it could also be informative to consider if (NO Y minus NO) might actually

be a better indicator than total NO Y of total N OX deposition, since NO (is measured along with

NO Y but) does not deposit efficiently and may not be as good an indicator of local N deposition

as are other NO Y components). At some point it may also be useful to ask if NO Y is a substantially better indicator of N OX deposition (in rural/remote areas affected by acid deposition) than is the sum of HNO 3 + PNO 3 . The reason I suggest aski ng this is that if HNO 3 +
PNO 3 is an adequate indicator, then m onitoring for new standards (including SO 2 + PSO 4 ) could be accomplished by relatively modest enhancements to existing filter pack networks – less interesting but much less costly than adding new continuous SO 2 and NO Y monitors at many

rural/remote locations.

Other Comments on Chapter 4

P 101, line 7: Change “sensitivity” to “sensitive”.

P 104, lines 1 & 5: You refer to “t he last review” of secondary SO 2 NAAQS, and then cite an

EPA 1982 reference. Wasn’t there a review – or at least a decision not to revise – made in1988?

P 105, line 12: You could add “direc tly” between “not” and “address”

P 105, line 19: Change “grouping” to “groupings” or “groups”.

P 106, lines 1-4: this seems like somewhat of an odd question since it is really more the effectsbased monitoring programs like TIME and LTM that clearly show adverse effects occurring despite widespread attainment of the obviously inadequate cu rrent NAAQS. The subsequent

106review of existing air qu ality and deposition networks, while he lpful, seems to relate more to how well those networks could support the new st andards under considera tion. Toward that end, I think it might be useful to consider the extent to which existing networks might be adequate/inadequate or enhanced – both at minima l and at more scientifically ideal levels to support new standards. For exampl e, CASTNET already measures SO 2 & SO 4 = and IMPROVE could be similarly enhanced by adding back-up treated filters to catch SO 2. CASTNET already

measures HNO 3 and PNO3 - (& PNH 4 + ) by filter pack. Similar filter-based measurements might be added to IMPROVE, and possibly NH 3 by analyzing denuder extracts. If the sum of HNO 3 and PNO 3 - could be related to total N OX deposition nearly as well as NO Y can, it (combined with the use of filter pack SO 2 ) could save a lot of $ compared to the alternative of adding new

continuous NO Y and SO 2 monitors in rural areas.

P 106, line 13: Does this mean that when you refer to NO Y , you mean “all oxidized N expressed as if it were NO” or do you mean “expressed as total N”. Similarly on lines 19, 20, I assume you mean that TS refers only to the sulf ur from and not the actual sum of SO 2 & SO 4 =

.

P 108, line 6: Capital V in Visual.

P 109, line 6: Change “longe term” to “long-term”

P 111, lines 12-15: I don’t get your poi nt. You could have all the new SO X and NO Y monitors in the world and it would tell you absolutely nothing about whether S+N deposition occurring despite attaining the current SO 2 and NO 2 standards is causing advers e effects. Your existing

SO 2 and NO 2 network is adequate to tell whether sta ndards are attained (t hey are) and your existing aquatic effects networks (TIME, LTM, etc.) are adequate to tell you if sensitive aquatic
resources are protec ted (they’re not).

P 111, lines 28-29: I don’t disput e that NADP + CASTN ET are valuable networks and might be useful starting points for new measurements to assess a new standard (or evaluate its effectiveness). However, it should be noted that relatively few NADP sites and no CASTNET sites are operated by state or local air agenci es – whose jurisdictions might fall into nonattainment as a result as measurements made by EPA contractors (or academic research groups in the case of NADP) using funds that would othe rwise be allocated to th e states. Could make the states cranky...

P 111, line 30 & continuing: It’s also likely that th e current configuration of NADP sites is more suitable for evaluating acidification effects than is the current configur ation of (predominantly urban) air monitoring sites. So its more likely that air quality measurements might be added to NADP. However, as a practical matter, you w on’t actually need NADP data to evaluate compliance with a new NAAQS, though it will be useful to evaluate whether your assumed deposition to air quality ratios are, and are remaining, reasonable.

P 112 lines 9-16: This whole paragraph needs a re-w rite. Also (lines 11-12) it seems a bit harsh and certainly premature to conde mn CASTNET as a flimsy resear ch effort that will never attempt to develop better operationa l methods. Meanwhile in other sections of the PA (like the

107preceding page) you propose CASTNET as the l ogical starting point for a new compliance

network.

P 113, line10: You could add NH 3 to this list of important gasses not measured by CASTNET.

P 114, line 15: Delete either “treating” or “simulating”.

P 115, line19: the semicolon should be a comma (or be consistent and also use “;” in the next

line after NO

x .

P 115, lines 26 & 27: Change to either “... where the more aged air masse s consist...” or “with the more aged air masses consisting...”

P 115, lines 29-30: Try to be more careful and consistent with s ubscripts, superscripts, charge signs for ions, etc. – lest the reader waste time trying to figure out if you mean something different when you use ST and S T

.

P 116, lines 10-12: Just curious, but I wonder if these runs incorporate a recently developed CMAQ bi-directional flux algorithm for NH 3 (seen in recent talk by Robin Dennis) that roughly doubled the effective transport distance for NH 3 ?

p. 116, lines 18-21: I don’t really buy this logic. If the (annual) NO 2 standard were set low enough (and attained), the depos ition of oxidized N and its effects would certainly be

diminished. There are better indicators than NO 2 , but if you used NO Y , set the level appropriately and attained it, levels of NO 2 will be much lower than they are now and much,

much lower than the level of the current NO 2 secondary standard. Further, efforts to reduce NO 2 concentrations have not uni quely focused on reducing “NO 2 emissions”, but more typically emissions reductions (or permit conditions ) are based on reductions of NO or NO X emissions. I like the inclusion of the Figure 4-19 NO 2 /NO Y ratios (inversed), but this alone isn’t really sufficient to show the inadequacy of NO 2 . What you would really n eed for that would be a comparison of the superior effectiveness of NO Y as a surrogate for N OX (oxidized N) deposition. You could do this by showing CMAQ Ndep/ NO 2 ratio maps, similar to the Ndep/NO Y maps in Figure 5-5 (but make them legible) . A test of the strength of the predictors could be shown as a scatter plot & correlation of the deposition vs. atmospheric predictors, where each point would be a CMAQ grid cell location. In theory, NO Y should be a better predic tor – and especially if you constrained the comparison to rural locations where acidi fication may be a problem.

P 117, Figure 4-5: would it make any sense to express this in μg/m 3 of N, for a more direct comparison with its S counterpa rt (Figure 4-9), and to pr ovide more common units and comparability in deposition/air quality (V S/N ) ratio maps (Figure 5-5)?

P 120: In figure caption, “amm onia” should be “ammonium”.

PP 120-123: I think there’s a problem (probably with the units) in some of these, as the scale for

total SO X or ST, expressed “as μg/m 3 S” in Figure 4-9 goes from 0 to 10, but the scale for SO 2 - only in Figure 4-10, also indica ted as being expressed “as μg/m 3 S”, goes from 0 to 20. The SO 4

108plotted in Figure 4-11 also looks too high to be in the indicated units of μg/m 3 S, and so I suspect that 4-10 and 4-11 are probably showing μg/m 3 of SO 2 and SO 4 respectively (not just the S).

P 124: The VIEWS figures are useful, but you might include a footnot e explaining that the “plume” in the central US is an artifactual erro r from the interpolation & plotting routine, and not

“real”.

P 130: The scale indicates “ppbv” but the indicat ed ratio that’s plotted should be unitless.

P 131, line 5: Another good example of the confusi ng use of terms. In this case, I assume, but don’t really know, that you’re using “NO X ” to mean “the nitrogen from the total wet and dry deposition of all oxidized nitrogen compounds”, and that by “ total atmospheric deposition” you mean the “total wet and dry depos ition of all reactive nitrogen”. This reminds me that it would have been useful to include maps of total NHx N deposition, and of the ratio of total N deposited by oxidized N compounds.

p. 131, line 24: It’s not clear wh ere “summarized above” is pointi ng to. If you mean way back in section 1.4, why not say so, and save th e reader a lot of unn ecessary page flipping.

P 134, lines 21-26: Could you also include % of la kes exceeding CL for ANC of 100 μeq/l, since

that threshold is still on the table as a possible indicator level. Isn’t it?

P 135 lines 2, 3 and elsewhere: Y ou frequently invoke “brook trout ” as a “sensitiv e species”, but

I tend to think it as one of the more acid-tolerant species (Charlie or My ron can clarify this). Also, it’s not clear in this sentence whether an ANC of 20 is a base level which could dip even lower during an extreme event, or the level to which some baseline higher ANC might drop during an extreme event. I think this is an im portant concept that coul d be addressed in more detail. Finally, do you really mean to indicate a population decline during an event (fish kill)?

P 136, line 28 and lots of other places: Us e either BC/Al or Bc/Al but not both.

P 141, line 28: Am I thinking backwards or shouldn’t “sensitive ecosystems” in this context be ones where “N is limiting”, such that excess N would cause shifts in species?

Chapter 5: Conceptual Design of an Ec ologically Relevant Multi-pollutant Standard

10. What are the views of the Panel on staff’s proposed conceptu al framework for the structure of a multipollutant, ecologically relevant standard for NOx and SOx? To what extent does the Panel agree that this sugge sted structure adequately represents the scientific linkages between ecological response s, water chemistry, atmospheric deposition,

and ambient NOx and SOx?

The proposed conceptual framework and the struct ure of the proposed standard do an excellent job (under very challenging Clean Air Act cons traints) of representing the complex linkages between ecological effects, aquatic chemistry, a tmospheric deposition and air quality. It is

inconvenient that a direct measure of ANC in su rface waters, or measurements of deposition of S

109and (total reactive) N couldn’t be used as a more direct basis for a NAAQS. However, given the limitations of the current CAA, the proposed st ructure employs some clever and innovative

mechanisms to link air concentra tions to ecological effects, rec ognize the combined influence of S and N, accommodate the varying inherent sensitiv ities of different ecosystems, and incorporate – without directly regulating - the additional influence of reduced N.

11. What are the views of the Panel on th e relevance of the conceptual design for developing standards to protect agai nst aquatic acidification effects?

a) What are the views of the Panel on st aff’s proposed options for the ecosystem acidification model to represent the ecological response function?

Others on the panel will have much more informed opini ons on this than I could offer. On a related topic, I’m not sure that the concept of episodic acidification is adequately addressed in the acidification model(s) presented chapter – or elsewhere. It seems to be assumed that selection of a specific ANC limit – of say 50 μeq /l – would be intended to protect against both chronic and episodic effects. If th is is the case, it should be stated explicitly. If there might be exceptions, for certain types of catchments or ecosystems, these should also be presented along

with indications of how selecti on of alternative ANC limits might guard against these effects.

b) What are the views of the Panel on th e relative merits of the two techniques for calculating Neco, the paramet er representing the amount of deposited nitrogen that is available for acidification due to uptake, denitrification and immobilization?

Others on the panel will have much more informed opinions on this than I could offer. From the text explanation on p. 178, it would seem like e quation 3 is both simpler and more readily accessible or “testable” through direct methods than equation 2. I would think it would be applicable, however, only in s ituations where (or when) “N br eakthrough” has al ready occurred and is directly measurable, and therefore would only reflect current rete ntion rates, which well may decline further with continuing deposition. Equation 2 may be a better, more protective approach to guard against longer-t erm future effects and assure th at current rates of N deposition

are “sustainable”.

c) What are the views of the Panel on staf f’s proposed options for developing acid sensitivity classes to categorize the national landscape? Is it appropriate to base this classification on bedrock geology? Should mu ltiple criteria be used to inform the sensitivity categories?

This sounds like a reasonable approach, and po ssibly other variables (surface soil composition and depth, weathering rate, slope, elev ation, etc. could also be useful . It’s difficult to judge this without seeing an example, but in general, I think it coul d be an extremely valuable exercise to go through in some detail, regardless of what the eventual end use(s) is (are). Conceivably multiple approaches to developing sensitivity clas ses could be considered and then evaluated – by comparing measured vs. predic ted ANC using the different sens itivity classes. Would it be possible to use relatively abundant surface water chemistry data to guide this process?

110d) What are the views of the Panel on st aff’s proposed options for how to aggregate acidification modeling from the catchmen t-scale to represent acid-sensitivity categories at the national-scale?

It’s difficult to evaluate these options in the abstract, without seeing comparative examples. The approach of specifying a percentage of water bodies within a given ar ea sounds reasonable, but would be critically dependent on ho w the areas were selected. Sele cting a critical % of lakes to protect seems like a somewhat arbitrary decision in the first place, and when combined with optional methods of selecting the (size of, and distribution of lake characteristics within) spatial areas, the decision process could be extremely arbitrary. Within a small area at high elevation on the western slopes of the Adirondacks, 100% of lake s will exceed their critical loads to maintain a protective ANC, but as the area is expanded in si ze, the % of acidified la kes will eventually fall to single digits if aggregated at the stat ewide level, so where do you draw the line?

I wonder if it would be possible to modify th e geographical area concept to include only the population of surface waters within that area to include only those considered “potentially susceptible” to acidification – ba sed on characteristics of their underlying bedrock, soils, etc. This would minimize the importance of the specific areal selection, since the % affected metric would apply only to the lakes considered susceptibl e in the first place. Or maybe model estimates of preindustrial ANC levels could be used as an index of inherent sensitivity and a decision of

adverse affects could be based on shifts in ANC categories over time, or based on a limit to the % change in ANC from preindustrial conditions within the p opulation of potentially susceptible lakes in a given area.

In areas where acidified streams are at issue, it would be necessary to have some metrics for selecting the appropriate sections of streams to be evaluated, and this doesn’t seem to be discussed in much detail in the Policy Assessment. As with the affected lakes, some metric that reflects past ANC changes over time might be a useful way to judge adversity of current conditions. Conversely, in might be useful to consider a prog ress-based metric (% increase in ANC, or % shift between ANC categories over time) to determine future compliance with the NAAQS. I think there are other examples where one test is applied to get an area into nonattainment, but a different test is re quired to get out of non-attainment.

e) What are the views of the Panel on staff’s suggested method to account for reduced nitrogen in the deposition metric?

It’s unfortunate that reduced N can’t be more directly recognized as an important, unregulated pollutant and steps taken to reduce its emissions to the atmosphere and surface waters. However, given the constraints in the C AA definition of nitrogen oxides, staff have devised a rather ingenious method of accommodating its influenc e without regulating it directly. I would assume, however, that if NH X deposition rates were reduced in an acid sensitive area, then proportionately higher levels of S + N OX deposition could be accommodated.

12. What are the views of the Panel on th e relevance of the conceptual design for developing standards to protect against te rrestrial acidification effects? Terrestrial nutrient enrichment effects? Aquatic nutrient enrichment effects? Does the panel have

111suggestions on additional data or methods that might enable EPA to expand the current aquatic acidification approach to cover additional effects?

The conceptual design for protection against terr estrial acidification eff ects seems reasonable and

consistent with recent advances in the science and assessment methods. The BC/Al ratio seems like an excellent “chemical indicator” (directly me asurable and predictable via models), which is directly responsive to deposition ch anges on one end and directly pr edictive of ecological effects on the other end. The currently considered range of levels (0 .6 to 10) seems rather broad (relative to ANC ranges of 50 to 100, although from the comparisons of aquatic and terrestrial sensitivities provided, would seem to suggest th at a BC/Al of 10 at the most protective upper limit considered is most similar (similarly protect ive) to ANC at 50 μeq/l (least protective) lower limit. In a general way, it would seem logical to expect that if chroni c long-term deposition of acids, passing through soils support ing terrestrial ecosystems ente r aquatic systems sufficiently un-buffered by associated cations or enriched in t oxic Al to cause adverse aquatic effects, then

we should expect that there would also be long-term terrestrial effects in those upstream watershed areas. That is, we s hould expect that ideal aquatic and terrestr ial effects indicators might show simila r sensitivities.

Your approach for aquatic effects is more comp letely developed, and you could probably justify a position that it is logical to start simply w ith a single indicator to protect against aquatic acidification – which would in many cases also afford added protecti on against terrestrial acidification effects. However, I think you c ould also make a good argument that an approach using both ANC and BC/Al indica tors (& associated depositi on & AQ limits) would provide better protection and over somewhat broader area s as there may be sensitive soils within

catchments that have more well-bu ffered soils in other areas such th at there are terrestrial effects upland of lakes or streams whic h are relatively insensitive.

Confidence is lower for setting specific standard s for terrestrial and aquatic nutrient enrichment in the present review cycle, and a focus on acidifi cation could be justified. I think however that

the consideration of the carefu lly derived loading limits – and approaches to apportioning and reducing them – that have been / are being de veloped through EPA’s TMDL process might be given more consideration in the future. There might be some innovati ve ways of combining TMDLs and NAAQS (for both acidification and fo r nutrient enrichment effects). In seeking reductions from point source or direct runoff discharges, some TMDL exercises (CT River discharge to Long Island Sound, for example) ar e assuming specific future CAA reductions in atmospheric N deposition loadings as part of th eir basis to specify and allocate reductions in direct N discharges. Conceivably a N depositi on-related NAAQS could be considered exceeded throughout a watershed where downstream TMDLs are exceeded, and in the implementation phase, costs & ancillary benefits of decreasing N emissions from various source categories could be considered jointly. It should also be noted that TMDLs for crit ically acidified lakes have been developed in some states (VT & NH – based I think on ANC limits of 50 & 60 μeq/l respectively) and there may be so me logic to combining the NAAQS & TMDL processes – as if there were a single EPA...

13. What are the views of the Panel on the critical uncertainties associated with the conceptual design of an ecologically relevant multi-pollutant standard that need to be

112characterized in terms of their potential implications for the secondary standards?

Others on the panel will have much more informed opinions on this than I could offer. I think

each of the acidification models and the CM AQ model have been subjected to periodic performance evaluations and sensitivity analyses , and that some of th e most critical (most uncertain) model inputs, processes and parameters have been identi fied. Associated efforts are also periodically undertaken to id entify and strengthen th e weakest links in these models (or to develop better new ones) such that we can expe ct model-associated uncertainties to improve in the future. A strength of the proposed approach is that the AAPI is in effect a estimate derived from atmospheric measurements which has an approximate, measureable aquatic counterpart (ANC) indicator (and there are also various intermediate modeled deposition metrics that can be evaluated with measurements). As such, the net effect of the cumulative uncertainties and biases of the proposed regulatory metrics can be continually evaluated and refined.

14. To what extent do the figures and examples aid in clarifying the text? Should more or less information of this type be included in the second draft?

Given the complexity of the subject matter, the many associated equations and difficulty (for me at least) of “seeing” many of th ese concepts in the abstract, I found all of the illustrations and example calculations (from actual data) very help ful and would like to see more of the same. One figure in particular that seems important and could be presented more clearly is the display of modeled VS/N ratios (barely le gible) in Figure 5-5. Larger-scale versions of these plots would help, along with scales select ed to better show the ranges of values. Possibly use of the

same scales for both the S and N ra tios could be informative. It could also help to show zoomedin versions the cover identified sensitive areas in the Adirondacks, Shenandoah, etc. It strikes me also that the accuracy of these CMAQ estimates could be tested (easily for S, not so easily for N) by comparing the modeled ratios to t hose from CASTNET & NADP measurements. You presented some CMAQ model performance evalua tion information previously, but when model results are ratio-ed, there’s a potential for errors/biases to get compounded (or offset)

I had a difficult time making it th rough this chapter with confid ence that I was understanding the details of all the points being pres ented (in the 23 separate equations ). I think this was due partly to it being outside my expertise, partly to th e introduction of many new unfamiliar variables, and partly due to the inherent comp lexity of the subject (further confounded by the CAA constraints). However, I also think that the information coul d be presented more clearly, and here are some suggested approaches toward making this no more confusing than it needs to be:

• Be precise and consistent in your terminology (and triple check for typos especially in the equations). I see no useful reason whatsoever to use the terms NO X and NO Y to mean the same thing. NO X has inherent meaning (sum of NO and NO 2 , including the oxygen) to the air quality community and you can’t revise this meaning with a disclaimer up front that “when we say night we really mean day”. This gets further confused by the

occasional use of the term N OX to mean oxidized n itrogen”. I actually like this term (we can pronounce it “ennox”) and think it could be used nearly interchangeably with NO Y , with the possible distinction that the former re lates to the concept and the latter relates to our attempts to measure it. But I also see an occasional N OY – which I assume is a typo (pronounced as “annoy”), but then that makes me wonder if/when N OX is used as

113intended. Is g(·) the same as g the same as G? If you mean SO4 = , write it that way and don’t use Cl when you mean Cl - . Use BC/Al or Bc/Al, but not both, etc.

• Number the equations sequentially from the be ginning of the document – or at least from the beginning of each chapter (ra ther than anew each subchapt er) so that there won’t be 3 different equations #4 in a single chapter.

• For each chapter, or at least for chapter 5, or maybe as a stand-alone appendix applying to all chapters: develop a glossary -like list or table of all te rms used in your equations, along with definitions and other pertinent inform ation – possibly includi ng things like how the term would be measured or estimated, its units , etc. The Table A-3 list of variables used in the SSWC model presented in Appendi x A is a good example of what I mean.

Other comments on Chapter 5

P 145 & 6: The text describing Figu re 5-1 refers to squares, tria ngles and circles, but the figure contains only rectangles, diamonds and ovals.

P 148, lines 9-12: Its difficult to grasp this concept in the abstra ct. Could you give an example? Are you thinking about 5 bins or 25?

P 148, lines 16-18: It might help to have a diagram to illustrate this concept.

P 150, line 21: Add “of” after “deposition”.

P 153, lines 29, 30: Try to be consistent with use of charge signs for ions.

P 167, line 10 (& elsewhere): Be consistent in your use of terms: BC/Al or Bc/ Al? P 167, lines 26-30: This summary of aquatic vs. terre strial CL sensitivity seems inconsistent with the similar summary on p ES-13 of the executive summary.

P 168, lines 1 & 2: Is this observation that fo r the Shenandoah, the aquatic CLs provided much greater protection than te rrestrial true for BC/Al ratios of both 10 and 1.2?

P 169, line 3: Add something like “addre ssing” between “for ” and “these”.

P 171 line 2: aggregated deposition.

P 172, line 25 “Table 1” should be changed to “Table 5-3”.

P 172, line 28: The importance of large partic le S & N deposition may be overstated here – especially with respect to acidification effect s, which will tend to occur at higher elevation locations remote from coarse particle sources (w hich don’t transport very far). Also, S or N in coarse particles is often in associa tion with crustal material (containing Ca ++ , MG ++ K + ) or Na +
from sea salt – hence carrying its own buffers. At CASTNet sites (where open-faced particle samplers presumably include coarse particles), al l particles contribute less than 6 % of total S deposition at sites with S dep > 5 Kg/Ha/yr. For CASTNet nitrate depo sition, total particle nitrate deposition averages < 2% of total nitrate deposition across the whole network. So its not

114likely that coarse particle deposition accounts for much of the total S + N deposition load at any sites where aquatic acidification is a problem.

P 173, line 1 simulations of.

P 173, line 5: text refers to “inverse” V S/N but Figure 5-5 caption doe s not indicate “inverse”.

P 173, line 10: “6 for”. Also this seems like an example of something I’ve noted on several occasions of referring to something “deposition lo ad tradeoff curves” that hasn’t been explained yet. Makes it harder to understand...

P 173, line 11: “Figure 1” should be “Figure 5.5”, I think.

P 173 line 15: “Figure 3” should be Figure 5.7.

P 174, Figure 5-5: I would like to see these at larg er sizes with scales th at better show the range of values. These ratios seem very important (s ee response to Q 14). On a somewhat related topic, I would think that of all the NO Y components, NO is likely to have the lowest deposition velocity, and otherwise be least reflective of N deposition at a ny specific location. I believe that in making NO Y measurements the sampling is typically switched through a nd then bypassing the converter, such that concurrent NO and NO Y data are available. Possibly then [NO Y minus NO] might actually be a better AQ indicator of N OX deposition than total NO Y – both in reality and in CMAQ output. I would imagine this could be tested relatively easily with CMAQ.

P 178, line 28: Is this basically the equation for “deposition lo ad tradeoff curves” referred to previously and later in this section? If so, why not describe it as such here.

P 179, line 19: Is it really the “high variability in the data set” per se that results in “only 32%” of water bodies not exceeding their criti cal loads, or is it more that the selected population of lakes includes many which are relatively well buffered? Or are you making a point that use of “mean

DL %ECO ” can be problematic for areas with high va riability? This isn’t clear to me, but I’m

concerned that use of a metric based on % lakes in “an area” becomes an important, but arbitrary factor (based entirely on how the areas are spatially defined).

P 180, 2 nd line of Table 5-4 caption note: Delete either “across” or “on”.

P 180, Table 5-4: From the descriptions of e quations 2 and 3 on p 178, I would have assumed that for a given catchment either one equation or the other would apply (# 2 projecting the longterm additional N a system could handle before leaching – or # 3 based on measurements where saturation has already been reached). So I’m surprised to see in Table 5-4 that there are summary statistics for N

eco presented using both equations. I’m al so surprised that the results for

both N

eco and DL %ECO are so different depending on which equation was used. Can this be explained more clearly?

P 184, lines 1, 2: Eight significant digits for th ese “aggregate effective deposition velocities” seems a bit much. I also agree with your plans to change the term to something like “deposition

115ratio” for clarity. Why not do it the other way ar ound and call it a deposition ratio in the text and use your footnote to explain that you used to use another, less appropriate term.

p. 187, line 9: You indicate here that equati on 5 describes the “atmospheric concentration

tradeoff curves”. Is this corre ct or should it be equation 6?

P 187, line 2 & elsewhere: I think the term N OX is a logical way to describe “oxidized nitrogen”, but think it might be helpful to add a footnote ca ution that this should not be confused with NO X (which you have already confused with NO Y sometimes but not always). Also, I note that in equation 11, p 186 you use the new term N OY which I assume is the same as NO Y ?

P 187, lines 11, 22: The tern “g(·)” in equation 11 has become just “g” in equation 12 (then back to “g(·)” in equation 13). Do these changes have a meaning (that I don’t understand because I don’t know what (·) means)? And are either of th ese the same thing as “G” referred to on p 198,

line 23 and elsewhere in the PA?

116

### Mr. Dave Shaw

General Comments

I believe a strong case has been made throughout th e REA, ISA and this policy assessment (PA)

that the current SO

x and NO

x NAAQS are not adequate or appropr iately protective of welfare. A multi-pollutant strategy is appropriate and feas ible to propose at this time with some considerations. As I have mentioned in prev ious comments, there ar e not enough monitors in most areas of the country to adequately charac terize the sensitivities of regional ecosystems. While I do feel it is appropriate to use the existing data, and depend heavily on modeling at this time, it is necessary to commit to building the existing monitoring network throughout the country to better develop this NAAQS. Also, the m odels will be most useful if they are shared with all states which may wish to assist with refining them.

On that same note, I suggest a commitment of so me kind be developed within a year which is specific about providing adequate data to quantif y inputs and results. A plan should be outlined so that at the very least we can identify wher e monitoring is needed and perhaps prioritize to

make the best use of limited resources. This multi-pollutant approach will help in decreasing resource needs by having, for example, one mon itoring location for severa l pollutants. This proposed NAAQS is innovative but complicated and very model dependent, and because of that,

it calls for these other commitments. As I have previously indicated, we should be aiming to significantly improve our ability to make modifications to the next NAAQS (which hopefully will be quicker than the last) based on significan tly improved data and model outcomes. The best

scenario would be that these monitors would al ready be in place. Our atmospheric conditions and pollutant loads are changing; we don’t have any extra time for delaying.

Multi-Pollutant Approach

Multi-pollutant air quality planning is currently be ing evaluated in New York State. This may be a more efficient way to run and plan a State Air Quality program [than one pollutant at a time]. The ability to plan and regulate multi pollutants with one policy should be less resource intensive as well as give us a better understanding of co-b enefits between pollutants. So far, we have found that multi-pollutant planning tools and a pproaches lend themselves well to supporting implementation and enforcement of multi-pollutant secondary standards such as NO

x and SO

x . Since our endpoints, such as surface water Acid Neutralizing Capacity (ANC), are far removed from the emissions point sources, a multi-pollutant planning approach can be used to model the policy drivers and the resulting wide range and variety of benefits.

I believe that a multi-pollutant planning approach that integrates air quality and climate goals may prove to be the best action to take to meet the forthcoming multitude of federal and state environmental requirements. NYSDEC is in th e process of developing a comprehensive air quality management plan (AQMP) that is multi-pollutant in nature with the intent that it provide for a more efficient and proact ive pollution control process.

117Flexibility

The PA indicates that future drafts will be ex panded to include effects other than aquatic acidification which I support as we ll as future actions in this di rection. This assessment is based on available data and modeling and at this time, there is adequate data from New York’s Adirondack Region as well as the Shenandoah Re gion concerning surface water acidification. Other regions in the country th at currently do not have suffici ent monitoring data or modeling efforts to characterize their own sensitive ecosystem s may find that they must be more concerned with terrestrial acidification, ni trification or fresh water/coas tal eutrophication. Therefore, I suggest that sufficient flexibility be built into the policy to allow for these future monitoring/modeling effort s and characterization.

Models & Data

Appendix A provides a good overview of the mode ls, but could be improved by including an assessment of reliability and a description of wh at range of error is acceptable. It would be helpful to know what data exis ts for how many watersheds for what range of time. Page 28 mentions that there is a lot of variability from year to year; it would be helpful to know what is considered “a lot.” Also, it would be helpful to state how many years of data or monitoring sites would raise the reliability of this data by 2 times, 10 times, etc.

I am concerned about the availability of accurate weathering data since this is such a critical variable in the models. Have the lacking weathering rates been developed for the sensitive regions?

Appendix A also discusses the supporting datase ts for the MAGIC model. Datasets and the models should be made available to not only the EPA, but also the States which are responsible for implementing the NAAQS which are being propose d. I want to be certain that whatever models will be utilized, that the States have access to make refinements. This should help advance EPA’s progress on the same.

Reliance on ANC

ANC is an available, good indicator; however, it might be misleading to call it an “excellent” indicator (p. 134, line 16). There are other indicators that could be discussed and utilized, for example, when toxic inorga nic monomeric aluminum (Al im ) is not present, but ANC is low, then organically derived low pH and AN C might be more of a driver th an mineral acidity from an air quality problem.

While ANC levels may be current (lines 28-29), the biological data associat ed with them are not. The ANC and fish diversity relationship is based on a 1469 lake data set from 1984-1987, and the losses in health and reproductive capacity from other sources ma y be just as old or older. While evaluating monitoring data, it would be he lpful to include updated surveys in the modeled

lakes.

118Bedrock geology as an indicator

On pages 162 – 164, the discussion of acid sensitiv ity based on bedrock and multiple landscape features should also include a discussion of gl aciated versus non-glacia ted landscapes. In the glaciated Adirondack region, there are many ar eas where soils do not reflect the underlying bedrock. Surficial geology and depth of soil would be useful to discuss in this section.

Critical loads

I would like to see more discussion on critical loads data and models. While I understand that we would like to use landscape and effects data which are specific to the United States, I believe Canada and Europe have a w ealth of experience in the use of critical load s models and their

successes and limitations. From a policy perspective, it would be worthwhile to analyze their

use of critical loads and what they have learned from vari ous model approaches. Those experiences could inform the US NAAQS review and process.

Charge Questions

Chapter 9

25. What are the views of the Panel on the preliminary staff conclusions regarding the adequacy of the current standards, the need fo r an integrated multi-pollutant structure for revised standards, and the proposed form of the joint NO

x and SO

x standards for aquatic

acidification?

26. What are the views of the Panel on the ove rall characterization of uncertainty as it relates to the determination of an ecologica lly-relevant multi-pollutant standard for NO

x and SO

x ?

The document clearly demonstrates evidence that th e current standard is not adequate due to the fact that ecosystems are still impacted. The short term average NO

x and SO

x concentrations are not protective or appropri ate so there is a need to consider a new strategy. The evidence in the documents show that this is a multi-pollutant problem so a multi-pollutant approach is appropriate.

The current approach is acceptable because it is the most commonly used and understood. Knowing this, it would be best to stay mindful of the limitations of ANC as an aquatic endpoint and develop the policy to be open to refinement including other measures for aquatic endpoints

such as Al im and Base Cation Surplus (BCS).

That being said, I must re-state that we must make additional m onitoring available for locations which currently have no monitoring available. Wh ile this approach is the best with what is available, we may find with additional data coll ection, that different ecosy stems require different kinds of protection.

119Specific

Draft Executive Summary (ES)

ES-3 para 4. Line 4 delete’, acid’. “ para 4, line 6 substitute ‘salmonids’ or ‘trout ” for ‘Atlantic salmon’ if this is based on Adirondack evidence [Atlantic salmon are not common, found in only 13 out of 1469 lakes sampled during the ALS as opposed to brook trout found in 579 lakes].

ES-4 para 1. Since this is the first discussion of this topic it would be the best place to discuss the connection with springmelt (this occurs somewh ere later in the ES). Also the ANC levels

discussed are annual averages levels. Need to convey this clearly because, for instance, a springmelt ANC of 50 would not be associated with death or loss of biota, the effects description is associated with a baseflow or an annual average.

ES-5 full para 2 starting w ith Current acidification. Line 3 Add the year associated with 78% Adk lakes, and ‘basef low (summer) or annual (it’s one or the other, not both)’ before ANC. Line 4 Delete bluegill, since they are uncommon in the Adirondacks (occur ring in only 4 out of 1469 lakes surveyed during the Adir ondack lakes survey in 1984-87) and not raised to the level of recreationally signifi cant in this region.

“ para 3 line 2 add after ‘recent’ the year of the study.

ES-7 para 3. Bedrock geology may not be the best predictor of aci d-sensitivity in the Adirondacks due to glaciation (see comment in main PA document).

ES-9 on use of equations. It would be more us eful to describe the AAPI that use an equation (not recommended for an exec sum). ‘” First para under Options. Delete entire.

ES-10 para 1. An important paragra ph, it should stay in bu t be modified to be more clear and less wordy/redundant. It might also be moved up to the first paragraph in that section. “ para 3 line 1. Delete ‘using equation 1 above’. “ para 3 line 7 “an AAPI level” repeated. “ para 3 last line. Run on sentence. “ Para 4,5,6 Suggest better to explain in text than to use model terms.

ES-12 full para 2. Important point. How to treat naturally organic ecosystems is a key aspect. How does this overall approach (including how well does MAGIC treat this?) come close to adequately addressing this? “ full para 4. Suggest delete, sin ce all was stated ear lier in the ES.

120ES-13 last para first line af ter last review, include date. last para sentence beginning with “In addition..” delete “substan tial” and ‘information, based on” and “rigorous” because this could unintentionally mislead to belief that data and modeling are

abundant.

ES-14 bullet 1 line 1 Some language is missing. “ bullet 3 end of sentence, add “among others.” “ bullet 6 Clarify replacing the current forms of what?

Policy Assessment

Pg 219 lines 9-10. Add afte r studies “since 1991-93”.

Pg 221 line 6. Is it “s trongly” supported?

121

### Dr. Kathleen Weathers

Overarching comments:

I think this first Policy Assessment for the Re view of the Secondary National Ambient Air Quality Standards for NOx and SOx is an excellent start. The EPA staff should be commended.

Some general comments

Make sure to label all figures with scal e and direction, and provide cl ear figure legends. Also be careful not to report too many (i.e., not significant) figures (e.g. Figure 2-9, deposition of 66.507??).

References are uneven and inconsistent.

For all the analyses, especially the components of the AAPI equa tion a spatial scale must be decided upon. While watersheds ar e ecologically useful for mass ba lance calculations, it may be that geology, or even more likely, the spatial resolution of the deposition estimates may control the scale at which analyses can be performe d. I suggest laying out th e logic, issues and constraints of choosing spa tial units for analysis.

Relevant to Chapter 2 and 3, especially: I have articulated the concern in the past, and it was brought up again during the meeting, that interpre ting the relationship between fish presence and

abundance and ANC in the absence of info rmation about stocking for the region under consideration (which may be the primary cont rol on presence and abundance for many species) is difficult to defend. At a minimum I suggest not including in the analys is (whether ecological or economic) sportfish whose abundance and pres ence is largely contro lled by stocking.

As has been pointed out, there are “enhancing” effects of nitrogen deposition for some forest species and systems that have been documented, often in combination with a changing climate (temp, CO2) (e.g., Thomas et al. 2010 and references therein). This information should be included, perhaps as a preamble to documenting the detrimental effects of deposition/NOx and SOx (which is the focus of this document).

Please use common units throughout the document for displaying data in fi gures and in tables, whenever possible (e.g., kg/ha-yr vs meq/m2-yr).

Responses to Charge Questions:

CHAPTER 6 15: Developing an AAPI linked to key determinan ts of aquatic ANC is an interesting and defensible approach to developing an ecological ly relevant standard. And, yes, I think the secondary standard options identified by the sta ff can draw upon existing scientific and technical

122information. Of course, the devil is in the detail s (including uncertainties), which is no surprise, but will require significant work (see 16).

16: There are, in fact, considerable uncertainties associated with all steps of developing an APPI, and, of course all of the mode ling processes involved in ever y step of the analysis, from emissions to deposition to effects. It is importa nt to identify where the major uncertainties are and how they affect bottom lines. For example, ma tching temporal and spatial scales in various components of the AAPI remains an issue. Ho w should uncertainty be characterized with integrity? I note that there is much ongoing resear ch focused on uncertainty, how to characterize it, how to communicate it (witne ss efforts surrounding the IPCC).

I had actually expected, after suggestions and concerns that arose out of our last CASAC meeting, and because of their importance to the po licy process, that the section on uncertainties would have been developed further in th is document. It will be crucial.

However, that there are many uncertainties should not make scientists or policy makers reel (or at least reel away from making deci sions). It is the state of the scie nce (it is the state of life, in fact), and what is known should not be discoun ted. For example, what we do know about annual wet+dry deposition of S and N across the US ba sed on monitoring data and models is vastly more than we knew a decade ago, and it is important not to obscure that fact. That there may be 100% uncertainty is better than not having any es timate whatsoever; it is at times important to contrast uncertainty with no knowledge at all!

17: Aggregation has some similari ties with using ratios (e.g. stoich iometric ratios). It collapses all kinds of complex variables into a number. It’s simpler to unders tand (at least at first pass), but can obscure important patterns and processes, es pecially when aggregates change in value, sometimes as a result of component variables changing in different directions. It is therefore important to understand the sensitiv ity of the various components.

18: CMAQ modeling is a work in progress and hi ghly uncertain, as has been noted before, but perhaps no more uncertain than, say, the MAGIC model. As has also been pointed out before, there is a pressing need to compare CMAQ to other ground-based estimates of deposition, such as NADP + CASTNet sites (e.g., Weathers and Lynch 2008). For example, in a preliminary analysis, while CMAQ and CASTNeT dry deposition estimates compared well, the concentrations did not, suggesting that both de position velocities and concentrations vary between the two approaches, in oppos ite ways (Weathers and Lynch 2008).

It is critically important to recognize the scale over which deposition estimates can be produced and how they may, or may not, be useful in di stinguishing deposition estimates for watersheds, for example, that are geographically close toge ther. CMAQ’s spatial resolution for this document is 12-36 km (page 114). That said, I think that th e CMAQ model is the best model to use for the AAPI calculation for comparisons on a regional or national scale. One of its strengths is that wet+dry deposition can be estimated, using a common method, across the country, and that urban areas are included (see Par do et al. 2010). The weaknesses in clude an inability to scale down to watersheds, or areas where the most intensive ecosystem response variables are measured (e.g., lakes, watersheds that span < 12-36 kms in area). All of these concerns

123notwithstanding, use of CMAQ and NADP + CASTNeT (including using them to model deposition at finer spatial scales and across heterogeneous terrai n, e.g. Weathers et al. 2006) are state-of-the-art, currently.

19: It has parallels with the cri tical loads approach used for the EU and elsewhere; that approach

has been in use for awhile.

20. It depends upon the use/goal, of course. In gene ral, I think that annual (or, in some cases, multi-year) averages are more reasonable than short-term (weeks, months, even quarters) estimates for CMAQ, as well as other modeli ng results if the goal is to examine annual ecological responses that have se asonal responses or shortish la g times. Experience with P-Net and many other models suggests that “getting it right” for shorter time steps is extremely difficult, and perhaps not a reasonable goal. Howe ver, interannual variat ion can be high, based on weather patterns and emissions, especially for wet:dry ratios; it would be useful to discuss further the rationale for 3-year averages.

21: Expansion of biological (soi l, vegetation), hydrological/che mical as well as atmospheric (chemical species, such as NHx, and spatial extent over which measurements are made)monitoring needs to be significantly enhanced.

22: Other panelists are better suited to answer ing (technically) this que stion. I found the section confusing.

Overarching note: I think it essential to identify and remove from the AAPI analysis “naturally” acidified aquatic ecosystems (as a result of organic acidity vs strong mineral acidity), as was suggested in a few places throughout the document.

CHAPTER 7:

23: I am intrigued by the approach, and appreciated the first-pass comparison. Aquatic and terrestrial systems behave quite differently in the biogoechemical, temporal, and spatial processing of N and S, of course. And, S and N as ions or elements have different chemical (e.g., valence state) and physical prop erties that influence their (c ontrasting) behavior within ecosystems. The standards set for aquatic protec tion are likely to be more conservative (i.e., stringent) than terrestrial protection because, in part, the ecological responses to deposition ramify through the terrestrial eco system and, to a certain extent , are expressed in the aquatic system, as pointed to in this document.

Should a terrestrial acidification standard be pr oposed, a key component will be how to discern natural acidification (e .g. as a result of such processes such as respiration, etc.) from anthropogenic acidification.

24: I need more clarification on the question here.

References:

124125 Thomas, R.Q., C.D. Canham, K.C. Weathers and C.L. Goodale. 2010. Nitrogen deposition increases regional carbon storage and sh ifts competitive balance among trees. Nature

Geoscience 3: 13-17. Weathers, K.C., S.M. Simkin, G.M. Lovett, and S.E. Lindberg. 2006

. Empirical modeling of atmospheric deposition in mountainous landscapes. Ecological Applications 16:1590-

1607. Weathers, K.C. and J.A. Lynch. 2008. How Much Atmospheric Deposition Across the US: Comparison of N and S Deposition Estimates. Eos Trans. AGU, 89 (53), Fall Meet. Suppl., Abstract: B42A-01.