UNITED ST ATES E N VI RON M E N T A L PR OTE C TION AGE NCY WASHING T O N D. C. 20460

OFFI CE OF THE A D M I N ISTR A T OR SCI E NCE A D VI SORY BO A RD May 19, 2008

EPA-CASAC-08-011

The Honorable Stephen L. Johnson Adm i nistra tor U.S. Environm ental Protection Agency 1200 Pennsylvania Avenue, N.W

. Washington, DC 20460

Subject: Consultation on EPA’s Draft Scope and Methods Plan for Risk/Exposure Assessment: Secondary NAAQS Rev i ew for Oxides of Nitrogen and Oxides of Sulfur (March 2008 Draft)

Dear Adm i nistrator Johnson:

The Clean Air Scientific Advisory Co mm ittee (CASAC) NO x & SO x Secondary NAAQS Review Panel m e t on April 3, 2008, and ha s completed its consultation on EPA’s Draft Scope and Methods P l an for Risk/E xposure Assessment: Secondary NAAQS Review for Oxides of Nitrogen and Oxides of Sulfur (March 2008 Draft). The C A SAC uses a consultation as a m echanism for individual technical experts to provide comm en ts on the Agency’s draft plan for developing technical assessm ents as the basis of the review of the secondary NAAQS for NO x and SO x . W r itten comm ents provided by the individual Pane lis ts in res ponse to th e Agency’s ch arge questions ar e enclos ed with this le tter.

As this is a consultation, we do not expect a formal response from the Age n cy. W e thank the Agency for the opportunity to provide advice early in the NAAQS re view process, and look forward to the review of th e First Draft Risk and Exposur e Assessm ent in October 2008.

Sincerely,

/Signed/

Ar m i stead (Ted) Russell, Ph.D. Chair, CASAC NO x & SO x Secondary Review Panel

EnclosuresAppendix A: Roster of CASAC NO x & SO x Secondary NAAQS Review Panel



### U.S. Environmental Protection Agency Clean Air Scientific Advisory Committee NO x 

### & SO x 

### Secondary NAAQS Review Panel

CASAC MEMBERS

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

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. Douglas Crawford-Brown , Professor Emeritus and Director Emeritus, Department of Environmental Sciences and Engineering and UNC Institute for the Environment, University of North Carolina at Chapel Hill, Chapel Hill, NC

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

PANEL 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. Charles T. Driscoll, Jr. , Professor, Environmental Systems Engineering, College of Engineering and Computer Science, Syracuse University, Syracuse, NY

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

Dr. Rudolf Husar , Professor and Director, Mechanical Engineering, Engineering and Applied Science, Center for Air Pollution Impact & Tr end Analysis (CAPITA), Washington University, St. Louis, MO

Dr. Dale Johnson , Professor, Department of Environmen tal and Resource Sciences, College of Agriculture, University of Nevada, Reno, NV

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

Dr. Myron J. Mitchell , Distinguished Professor and Direct or of Council on Hydrologic Systems Science, College of Environmental and Forestr y, State University of New York, Syracuse, NYMr. 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 Resources , New York State Department of Environmental Conservation, Albany, NY

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

SCIENCE ADVISORY BOARD STAFF Ms. Kyndall Barry , Designated Federal Officer, 1200 Pennsylvania Avenue, NW 1400F, Washington, DC, Phone: 202-343-9868, Fa x: 202-233-0643, (barry.kyndall@epa.gov)Appendix B: Agency Scope & Methods Plan Charge Questions

1. In outlining the scope of this risk/exposure ass essment, we have created a flow diagram that represents how nitrogen and sulfur compounds move from ‘source to dose’ in the environment (see Figure 2-1). How adequately does this conceptu al model for evaluating risks due to depositionrelated ecological effects characterize what should be covered in the scope of this assessment?

2. The main ecosystem effects areas we anticipate evaluating in this risk/exposure assessment are (1) risks to terrestrial ecosystems from nitrogen enrichment effects, (2) risks to aquatic ecosystems from nitrogen enrichment effects (eutrophication), (3) ri sks to terrestrial ecosystems from acidification effects (nitrogen and sulfur), and (4) risks to aquatic ecosystems from acidification effects (nitrogen and sulfur). We also plan to qualitatively discuss the role of sulfur enrichment on methylmercury production and the role of nitrous oxide in climate cha nge. What key effects areas, if any, have been overlooked by this approach? Should the assessment plan be modified to include other effects?

3. Due to the complexity of conducting a nationwide risk/exposure assessment for welfare effects due to NOx and SOx, we have outlined a strategy designe d to identify sensitive ecosystems and a range of harmful/adverse effects (see Figure 3-1). The seven steps are to (1) identify documented biological, chemical and ecological effects and potential ecosyst em services, (2) define sensitive areas using GIS mapping, (3) select risk/exposure case study assessment areas, (4) evaluate current loads and effects in case study assessment areas, (5) scale up the case study assessment areas to larger sensitive areas where feasible, (6) assess current ecological conditions in those areas, and (7) assess alternative levels of protection under different ambient scenarios. Does the Panel agree with this general approach? Should it be improved or modified?

4. In the seven-step approach to the current cond itions risk/exposure assessment, Step 1 (Section 3.1) describes an approach to identif y the documented effects, biological, chemical and ecological indicators, and potential ecosystem services related to acidification and nutrient enrichment. Does the Panel agree with this approach or can they suggest alternative approaches we should consider?

5. In the seven-step approach to the current cond itions risk/exposure assessment, Step 2 (Section 3.2) outlines a path to define areas sensitive to total reactive nitrogen and sulfur inputs. Do the Panel members agree with this approach or are there better alternatives that should be considered?

a. We are attempting to characterize the risks to ecosystems from sulfur and nitrogen deposition nationwide by clustering sensitive ecosystems where possible and by using the linkages between these areas at different scales. Please comment on the adequacy of this approach. b. How appropriate are the datasets and GIS maps listed in Table 3-4 for identifying ecosystems sensitive to nitrogen and sulfur and/or are there others that have been overlooked?

6. In the seven-step approach to the current cond itions risk/exposure assessment, Step 3 (Section 3.3) outlines a path to identifying risk/exposure case study assessment areas.

a. Table 3-5 provides an initial list of indicato rs, mapping layers and multimedia models that may be used to assess ecosystem risk and exposure. Please comment on the appropriateness of these and suggest alternatives that ma y be better suited for this analysis. b. Please comment on the list of potential case study assessment areas in Table 3-6 and Table 3- 7 and make recommendations or suggest any alternatives.7. In the seven-step approach to the current cond itions risk/exposure assessment, Step 4 (Section 3.4) outlines a path to assess current nitrogen and sulfur loads and their effects on case study assessment areas. Does the Panel agree with how we have descr ibed our approach to identifying datasets, gaps, and uncertainties?

a. We have initially identified the primary chemical indicator that is most suitable for assessing ecosystem acidification effects as acid neutralizing capacity (ANC), with alternatives depending on data availabilit y (see section 3.4.1 and Appendix B). Does the Panel agree with this selection, or can they suggest alternative/additional key indicators? b. We have described the models being consider ed for this analysis (see section 3.4.2 and Appendix C). Does the Panel agree with the choice of these models, and can they help prioritize them for modeling the responses of th e indicators recommended in Step 1 (Section 3.1)?

8. In the seven-step approach to the current cond itions risk/exposure assessment, Step 5 (Section 3.5) discusses how to scale up case study areas to more spatially extensive sensitive areas, where appropriate. Does the Panel agree with this a pproach or can they suggest alternatives?

9. In the seven-step approach to the current cond itions risk/exposure assessment, Step 6 (Section 3.6) outlines a path to assess the current conditions of sensitive ecosystems. How well does the Panel agree with the approach outlined for calcul ating response curves and utilizing mapping and ecosystem services to characterize current conditio ns or can the Panel recommend alternative approaches?

a. How well does the Panel agree with using ecosystem services to provide a common metric for comparing ecological risks due to nitrogen and sulfur deposition effects? b. How well does the Panel agree with collecting current valuation studies to understand the value of bundled ecosystem services? Can the Panel recommend additional or alternative approaches?

10. In the seven-step approach to the current cond itions risk/exposure assessment, Step 7 (Section 3.7) describes an approach to assess degrees of protecti on/levels of effects unde r alternative forms and levels of ambient NOx and SOx standards. This approach attempts to describe how the methods, models, and results of the current conditions risk /exposure assessment can inform our evaluation of the appropriate form(s) and level(s) of a national standard. How well does th e Panel agree with the approach outlined in this section, the issues pr esented, and the 9 steps outlined to assess potential forms and levels of the standard? Please suggest a ny additional or alternativ e steps we should take into consideration.

11. Additional ecological/welfare effects due to NOx and SOx emissions that we do not currently anticipate evaluating in detail in this review include the following:

• Nitrogen saturation,

• Maple decline,

• Ammonia air deposition and toxicity to native mussels,

• Relationships between acidity/nutrient enrichment and mercury methylation,

• Sensitive areas for acidity/nutrient enrichment impacts, identified from biogeochemical characteristics, and

• Climate change effects due to N 2 O. Does the Panel agree that these represent lower pr iority effects for the cu rrent assessment? If not, what does the Panel recommend?Appendix C: Com p ilation of Indiv i dual Panel Mem b er Comments on EPA’s Dr aft Scope a n d M e thods Plan for Risk/ Exposure Assessment: Secondary NAA Q S Review fo r Oxides of Nitrogen and Oxides of Sulfur (March 2008 Draft)

Comments receiv e d:

Dr. Praveen Amar

............................................................................................................... .......... 7 Dr. Andr z e j Bytnerow i c z ........................................................................................................ .... 10 Ms. Lauraine Chestnut

.......................................................................................................... ..... 17 Dr. Ellis B. Cow ling

........................................................................................................... ......... 19 Dr. Douglas Craw ford-Brow n
................................................................................................... 28 Dr. Charles T. Driscoll........................................................................................................

........ 31 Dr. Paul J. Hanson

............................................................................................................. ......... 33 Dr. Rudolf Husar

............................................................................................................... ......... 37 Dr. Dale Johnson

............................................................................................................... .......... 40 Dr. Donna Kenski...............................................................................................................

......... 44 Dr. Naresh Kumar

............................................................................................................... ....... 46 Dr. Myron J. Mitchell

.......................................................................................................... ....... 47 Mr. Richard L. Poirot

.......................................................................................................... ....... 58 Mr. David J. Shaw

.............................................................................................................. ........ 63 Dr. Kathleen Weathers

.......................................................................................................... ..... 66

6

### Dr. Praveen Amar

This write up provides comm ents in three area s, as requested by Dr. Ted Russell, the Panel Chair. These three areas relate to :

1. Adequacy of how well the REA (Risk/Expos ure Assessm ent) covers som e of the “additional” issues such as m a ple decline, ammonia air deposition, et c. The exact charge question #11 related to “additional e ffects” is reproduced here :

Additional ecological/welfare effects due to NOx and SOx emissions that we do not currently anticipate evaluating in detail in this re view inc l ude the fo llowin g :

• Nitrogen saturation,

• Maple decline,

• Ammonia air deposition and to xicity to native mussels,

• Relationship between acidity/nutrient enrichment and mercury methylation,

• Sensitive ar eas for ac idity/nu trien t enrichment impacts, identified from biogeochemical characteristics, and

• Climate cha nge effects d u e to N 2 O. Does the Panel agree that thes e represen t lowe r priority e f fects for the current assessment? If not, what does the Panel recommend?

2. Sections 2.3.2 (overview of nitrogen deposit ion) and Section 2.3.3 ( overview of sulfur oxides and sulfur deposition), and 3. Overall g e n e ral comm ents on the co mple te Scope and Methods Docum e nt

First, a general comm ent about the w hole document. I think it is generally written better than the ISA. Howe ver, various chapters can and should be im proved for m o re clear comm unication. It is understandable that various sections have diffe rent authorships. These sections and chapters would theref ore benefit f r om the services of an ex pert technic a l/s cien tif ic edito r resu lting in a more readab le docum ent that m o re clearly communicates what the proposed Risk/Exposure Assessm ent is expected to accom p lish.

Charge Question # 11

The Scope and Methods Docum e nt currently pro poses to assess the areas m e ntioned above under Charge question #11 in a qualitative m a nner (Page 15; Appendix A.2, etc.). My sense is that

som e of these areas are of gr eater importance than others. Fo r exam ple, understanding of the relationship between sulf ur de position and enhanced m e thyl m e rcury (MeHg) production in aquatic system s has serious policy implications as a num ber of m e rcury control program s from

m a ny industrial sources (coal-fired p o wer plan ts, m unicipal waste com b ustors, s t eel m ills, industrial boilers) ar e being put in place in the US at the sam e tim e m a jor SO 2 reduction

program s are being im plem ented (e.g., CAIR). To the extent sulfur depos ition levels would be

7changing in the US at the sam e tim e Hg depositi on levels would be changing, this “integrated”

assessm ent needs to be indeed “in t eg rated. ”

I do not have the expertise on the direct toxici ty of a m m onia on m u ssels, however, this Risk Assessm ent would benefit great ly from m o re e m phasis on all scienc e-r e la ted issues related to ammonia: better quantification of its em issions, its atm o spheric chem istry and physics, its fate and transport, wet and dry deposition of a m m oni a and its products, and ecological effects. As other m e m b ers of this C A SAC Panel have noted in the i r com m e nts, the ISA as well a s the S and M docum ent sim p ly seem to address the role of ammonia as an aftert hought and do not address the issu e of ammonia at a level it d e s e rves.

I suggest that the areas in Char ge Question #11 (at least som e of them ) be given m o re attention than what is being proposed. For example, instead of addressing them in any future Risk/Exposure Assessm ent docum ent in an Appe ndix, they be addressed in the body of the report itself as short and separate chapters. It is recognized that som e of treatm e nts m i ght be more qualitative or em pirical. That does not m a ke them less important.

Sections 2.3.2 and 2.33 (Nitrogen and Sulfur Deposition ):

Sections 2.32 and 2.3.4 are short. I do not think they provide true “overview” of nitrogen deposition, or for that m a tter, su lfur deposition. Section 2.3.2 m o s tly covers the history of how N 2 O was addressed in previous stan dards review and then notes that it will not be covered in a quantitative way in the current assessm ent. It is important, as I note abov e, that all th e “additional issues” in cl uding the role of N 2 O as a greenhouse gas be covered in this docum e nt in a clear and well-referen ced m a nner (for exam pl e, the recent 2007 IPCC reports). One suggestion is that a revised Scope and Methods docum ent rem ove these sections from their present location and integ r ate them m o re ef f

ectively with othe r s ection s

.

Overall General Comments on th e Document

Page 1, Line 7: “... deposition of am bient particles, GASES, AND AC IDS, that can..”

Page 3, Line 12 “THOUGH” is an awkw ard way to start this sentence.

Page 5, Second Para: “welfare effects identified should be PR OTECTED from adve rse effects .” Need to rew r ite.

Page 6, Section 2.2: Please be very careful when using the words uncer tainty and var i ability in the sam e sentence unless you explain their clear and very different m eanings. Many people take them to m e an the sam e thing and the y sim p ly ar e very different concepts , both in science and in policy

- settin g.

Page 8, Last paragraph: “this assessm e nt would focus on ecologi cal quality and its effects from acidification...” This is the fi rst and the only tim e this docum ent uses the words “ecological quality.” What exactly is m eant? Also, the sen t ence needs to be rewritten for clarity.

8Page 9, Line 8, Please change to “precurs ors NOx and volatile organic COMPOUNDS...”

A General Comm ent: I would very m u ch like to reinforce what Dr. Cowling noted in his comments on the September 2007 Draft Plan. These words speak m o re clearly than anything I have seen relative to what needs to be done in this assessm ent for the joint secondary standard(s) for revising/modifying/establ ishing a new/ standard(s):

i) “What scientific evidence and/or scientific insights have been developed since the last review to indicate if the cu rrent public-health based and/or the current public-welfare based NAAQS need to be revised or if altern a t ive lev e ls, in dicators, sta tistica l form s, or averaging times of these standards are n eeded to protect pub lic health with an adequate margin of safety and to protect public welfare?”

ii) “What scientific evidence and/or scientific insights have been developed since the last review to indicate whether, and if so, what particular ecosystem components or other air-quality-related public we lfare values, are more or less sensitive than the populations of humans for which primary standards are established and for this reason may require a different lev e l, indica tor, statistica l form, or averaging time of a secondary standard in order to protect public welfare?”

Page 11, Second Paragraph, “... Fram e w ork to analyze alternative air quality standards ...” W hy not also include deposition standa rd s as well as c r itica l loads he re? A quick review of this docum ent also m a kes it clear that critical load s as an organizing principle for establishing standards need to be paid m o re atten tion ( j ust lik e the ro le of ammonia needs to be paid m o re atten tion )

.
Page 24 (also other places): I s uggest that this docum e nt be cl earer about ecosystem services, valuation, valuation m e thods (both quantitative and non-quantitative). Since these areas are covered in the environm ental econom i cs and d ecision analysis areas, it would be a very good idea th at th ey are des c rib e d m o re clearly for the g e neral audience of this assessm ent.

Page 25: The “Seven-Step Process” to undertake REA: I do not claim expertise, but S t eps 5, 6, and 7 (“whe n f easible, s cale up c a se studies... ” , assess the cu rrent ecolog i cal cond itio ns, assess alternative levels of prot ection...”, etc.) do not seem as rigorous as they w ould need to be to lead to a defensible standard(s).

Page 28: I am not so certain that ‘organic ac ids are comm on NATURAL sources of acidity in surface waters.” I would note that m a ny VOCs do l ead to seco ndary organ i c aeroso ls (S OAs) and then to organic acids that are not “natural.”

9

### Dr. Andrz e j Bytnerow i cz

General Comments

The docum e n t describes Problem For m ulation, the fi rst phase of the Ecological Risk Assessm ent (ERA) for ambient NOx and SOx, and focuse s on the last component of the Problem Form ulation Phase - the Analysis Plan. The docum ent is logically structured and follows seven clearly described steps. The plan presents in teresting ideas for devel opm ent of the secondary standard for NOx and SOx. End points and conceptu al m odels are also discussed but with m u ch less detail.

In the beg i n n ing of the d o cum e nts a clear stat ement is m a de that for evaluating ecological ef

f

ects, tota l reac tive N ( both in th e o x idized and reduced f o r m s) will be consider ed. This is because red u ced N compounds m a y be responsib le for m a ny effects caused by oxidized N. This is obvious and clear from the point of view of t h e present scientif ic knowledge. However, this is a long stretch from NOx (NO and NO2) and SO x which are the criteria pollutants for which secondary standards are being considered. I beli eve that legal considerations of such an expansion of the NOx/SOx term should be disc ussed upfront. If not, it m a y be expected that problem s with various stakeholders d u ri ng public discussion could take p l ace.

Consideration for alternative s econdary standards to am bient c oncentrations of NOx and SOx should also be addressed. For N, all for m s of r eactive N cou l d be considered as part o f the secondary standard. NOx (NO and NO2) is onl y a sm all portion of the problem , however, theoretically it is possibl e to link the secondary pollutants (s uch as HNO3 or particulate NO3) to the prim ary pollutants (NO and NO2). Amm oni a is the key pollutant for which concentrations and spatial and tem poral distributi on should be better characterized.

Considering high probability that relationships between NO2 concentration s (or reactiv e N; Nr index) to N deposition, and between N depositio n and its eco logical effects m a y be weak, the deposition-based indices such as critical load s (C L), should be considered as a potential secondary standard. However, in order to consider such an approach a nation-wide monitoring of n deposition, sim ilar to the European ICP Forest s and ICP Vegetation, should be in place. Based on the existing m onitoring efforts in the U.S., secondary standard for NOx and SOx based on N deposition could be considered only for a sm all portion of the country.

Options such as “cap an d trade”, or em ission re d u ction goals for specific adm i nistrative areas (states, counties, air qu ality m a nagem e nt districts) should be addresses and considered. W h at

was accom p lished for th e reductions of the SO2 em issions in the Midwest and Northeast based on the requirem ents of Ti tle IV of the CAAA or what is presen tly being done in Europe under the auspices of the Conventi on on Long-range T r ansboundary Air Pollution (CLRTAP) could be used as examples of the alternative approaches and possibilities (although such m e as ures m a y be politically d i fficult to be accom p lished). However, a note of caution – su ccessful redu ction of the SO2 em issions was rela tively easy co nsider ing th at SO2 sour ces ar e m a inly la rge poin t em itters. For NOx such possibilities cou l d be difficult to accom p lish because of th e com p lexity of the N chem istry a nd m u ltiple sources of e m issions.

10Com p ared to the m a in ISA docum e n t, transitional ecosystem s are not m e ntioned. For consistency this docum ent should also treat them separately (especially since these ecosystem s are very sen s itiv e to the N inputs).

Diagram s used in the docum e nt greatly help a reader to v i sualize the plan ned risk assessm ent process envisioned by the authors. F i gur es 2-5, 3-1, or 3-5 are m o st useful.

A discussion of how the clim atic conditions, or c lim ate variability, could affect the proposed risk

assessm ent process is lacking. Mete orological variability is m e ntione d, but this is not sufficient.

More em phasis should b e placed on how the oth e r co-o ccurring stressors (troposph eric ozone, drought, pests, diseases or catas trophic fires) affect N cyclin g and biological effects of N deposition.

Are the CMAQ estim ates of N deposition updated? If I rec a ll the CMAQ sim u lation for the western US, the latest model runs we re done for 2002 (Gail Tonnessen, personal communication).

It would greatly help in review of th is docum ent if the lines w e re num bered!

Specific co mments

Page 1, first paragraph. A senten ce “As discussed in the Integrat ed Review Plan (U.S. EPA, 2007a), this was done in recogni tion of the im por tant linkages between ambient nitrogen and sulfur leading to deposition of a m bient pa rticles that can hav e significan t impacts on environm ent”. This is only partially true consider ing that particles have only very sm all effects on the total N or S deposition. Gases or dissolved ions are m u ch m o re i m portant. Therefore, I suggest deleting “of am bient particles”.

Pages 7 through 9, Section 2.3. I found this section confusing and I suppose that other readers

m i ght have a sim ilar experience. As I have st ated in the beginning of m y comments, this docum ent is supposed to represent the Problem Form ulation Phase. As such I would expect that the end points and conceptual m odels would get th e sam e level of detail as the Analysis Plan. Although the conceptual m odels are described in sect ion 2. “Background and Overview”, specifically in section 2.3.1, a discussion of endpoints is not easily found. Sections 2.3.2. “Overview of nitrogen deposition” and 2.3.3. “O verview su lfur oxides and sulfur deposition ” are too short to present a good discussion of th e problem . I suggest skipping them completely and referrin g a reader to the com p rehensive review of these problem s in the m a in ISA docum ent.

Page 19, Table 2.1. The proposed schedule of th e re viewing process is tight and very am bitious. The CASAC public review of the REA docum e n t in October is very early consider in g that the draft will b e released in August. In my particu l ar case, a very activ e sch e dule of con f erences in August, Septem ber and October and summer vacation, does n o t leav e eno ugh tim e for a thorough review. Therefore, I recomm end m oving the CASAC review to Nove m b er 2008.

11Page 27, Table 3-1. For alum inum mobilization, terre strial ecosystem s (T) should be added. In the sam e table, for N concentration s , al so terrestrial ecosys t em s are affected.

Page 31, 3.2, Step 2 (Define sensitive areas) and page 35, 3.3, Step 3 (Select risk/exposure cases study assess m e nt area within a se ns itive area) - u s e of natural gradien t s of N and S deposition should be considered.

Page 32, first two lines. I would argue that areas with good linkages to larger ecoregions should be also considered for new case studies. Results f r om such area could be extrapolated by m e ans of

geostatistics in to m u c h larger areas.

Page 35, last paragraph. I would like to suggest that “new N” could be called “reactive N species ”, su ch as amm o nia or n itric acid. “Old N ” would be N stored in ecosystem s as NO3-.

Page 38, first paragraph. Again – use of natura l gradients for selecti on of the appropriate

assessm ent areas should be considered.

Page 38, I would also suggest placing special empha sis on som e areas in California, such as the San Bernardino Mountains, coastal sage and dese rt ecosystem s that have been intensively studied and are sensitiv e to N additions.

Page 40, Table 3-6. W e stern states are under-re presented. P l ease see m y comm ent above.

Page 43, bullets. More appropriate w ould be using the term of “n itrate and ammonium deposition”. Ammonium would result from dry deposition of NH3, particulate NH4+ and water dissolved N H 4+ deposition.

Page 57, firs t parag r aph. After estab l ishm ent of the baseline conditions, more advanced modeling techniques (dynam i c m o dels) would have to be used. Such m o dels are able to take into account time effects and m a y be useful for ecologi cal risk assessm ent. During the last few years such m odels have been used by the ICP Modeling and Maps in Europe.

The sam e pa ragraph. W h ile particular loading “X ” can cause a certain negative effect “Y”, it would be very difficult to translate it to am bien t concentration of a pollu tant (esp ecially if NO and NO2 are concerned )

. That ef f

ect “Y” would re sult f r om deposition of multiple N s p ecies. Is CMAQ, or other m odels, able to specify what concentrations of i ndividual pollutants are responsible for the loading “X”? Maybe checking how the RAINS model used in Europe deals with such is sues is neces sary at th is step of the analysis planning?

Comm ents on bullets from Page 57

“ W hat adverse effects are we trying to protect ag ainst?” Best approach w ould be to look at multiple sen s itiv e ind i ca tors (lik e se nsitiv e liche n s, C/N ratio, N foliar le vels, m y corrhizae colonization). Use of single indicator could be m i sleading. However, for practical reasons and large-scale estim ates, a single, easy to determ in e indicator (such as NO3- in soil solution) should be considered as a good initial step.

12Next bullet – inform ation on contribution of N oxidized and reduced form s to total N pollution (reactive N) effects is still poor . More intensive field cam paigns and long term m onitoring using

som e new te chniques is urgently needed. A key problem is a need for better understanding of ammonia concentration s in the ev alu a ted eco system s.

Effects do occur due to different form s of N. Effects of gaseous N species (NO, NO2, NH3 or HNO3) are very different am ong each other, and quite different from the effects of particulate or water-dissolved NO3- or NH4+.

How should alternative levels be selected? Co m b ination of various m e thodologies is needed (controlled experim e nts, field exposures including natural gradients, others).

What are the correct temporal and sp atial scales f o r the am bient air i ndicator? Ideally hourly values should be available. However, consider ing a lack of proper m onitoring equipm e n t that could be used at large scales, the weekly, bi -weekly or even monthly averages of the key deposition drivers would greatly help our abilit ies to m odel deposition. In such cases, passive

sam p lers for gaseous pollutants could be use d. Infor m ation on particulate com ponent of dry deposition is poor, and its contribut ion to the total deposition m a y gr eatly vary in space and tim e.

Spatial coverage would depend on the chem ical and topographic com p lexity of the area of interest. There are new geostatistical m e thodologi es available that m a y help in optim izing monitoring networks and ad equate spatial coverage.

Large-scale monitoring of throughf all could be used for integrative m easure of wet and dry N deposition. However, use of the throughfall analysis m e thodology in arid and sem i -arid ecosystem s is question a b l e.

Comm ents on using 9 steps to determine the appropriate level and a form of a standard:

Generally this is a logica l and well defined plan.

Point 1 – portion of dry deposited N, both in gaseous and aerosol form s, is not well characterized.

Point 2 – OK.

Point 3 – here, contribution of the main contribu tors to dry deposition of N, a m m onia and nitric acid have to be better characterized.

Point 4 – the m o st sensitive indicators, and sets of various indicators, have to be considered. Although I generally agree with a need for determ ining ecosystem services and bundling them in order to find com p arisons between locations, I am not sure if that would not com p licate the establishm ent of a link between effects, depos ition, am bient concentrations and em issions.

Point 5 – OK.

13Point 6 – I suggest consideri ng collaboration with the Europe an scientists and m odelers experienced in using RAINS m odel. Im pacts of m e teorological ( c lim atic ) variability are of a very high importance.

Point 7 – cr itica l load s c on cept would be very useful.

Point 8 – in tuitiv ely I ag ree. However, I have to g e t acqua inte d bette r with the ava ilab l e litera ture to say m o re.

Point 9 – OK.

Responses to the assigned questions:

Question 8. In the sev e n

- step app r oach to the curr ent cond itio ns ri sk/exposure assessm e nt, Step 5 (Section 3.5 ) discus ses h o w to scale up case stud y areas to more spatia lly extens ive se nsitiv e areas, where appropriate. Does the Panel agree with this approach or can they suggest alternatives ?

The proposed approach seem s to m a ke sense as long as the extrapolati ons are done within the

sam e ecoregions. However, distribution of concentr ations of the key drivers of N dry deposition, specifically nitric acid vapor and am monia, m a y dram atically change between the urban and agricu ltu ral sources and the recepto r areas du e to their high r e activ ity and deposition to vegetation and other su rfaces. Therefore the on -g round determ inations of patterns of their distribution are recommended. Passive sam p lers offer a relatively sim p le and reliable m e thod for determ ining pollution co ncentr atio ns. Results of such m onitoring efforts aided by geostatistics

m a y be used for generation of concentration su rf aces of these pollutants. For estim ates of dry deposition of these gases inferential m e thods c ould be used at large geographic scales. In addition, complexity of soils char acteristics have to be also ta ken into account in proposed scaling-up exercises.

Question 9. In the sev e n

- step app r oach to the curr ent cond itio ns ri sk/exposure assessm e nt, Step 6 (Section 3.6 ) outlines a path to asses s the curr en t conditions of sensitiv e ecosystem s. How well does the Panel agree with the approach outline d for calculating response curves and utilizing

m a pping and ecosystem services to characterize current conditions or can the Panel recommend alternative approaches ?

This is a valid approach. Response curves from c ontrolled experim e nts or natural gradient studies encompassing wide ranges of deposition levels would provide databases needed for estim ates of current conditions and models sim u lating future changes. Critical loads (C L) calcu lations (perform ed with steady state, em piri cal or dynam ic m odels) have been used in the NE USA and Canada for m a ny years. In Europe, CL have also been successfully m easured on the ICP Forests and ICP Vegetation networks . T h e ICP Modeling and Maps converts that inform ation to m a ps representing ann u al lev e ls of CL and exceedances for N and S deposition and acidity. The European Regi onal Air Pollutio n Inf o rm ation and Sim u l a tion (RAINS), uses those results for controlling of the internati onally agreed quotas of e m issions for individual countries. A sim ilar approach could be tested and possibly used in the U.S. as well. Instead of

14individual countries (as in Europe ), states or air quality m a nagem e nt districts could be used as the adm i nistrative units of control.

a. How well does the Pane l agre e with using ecosy stem services to provide a common metric for com p aring ecological risks due to n itrogen and sulfur deposition effects?

This could be very useful approach for inte grating effects of deposition of N and S on ecosystem s. By presentin g exam ples of what serv ices are affected, potential stakehold e rs would be able to better com p rehend im p lications of the adverse effects of elevated N and S deposition. That could bring m o re attenti on and potential support from the general public, NGOs and other stakeholders which would help in developm ent of the second ary, welfare effe cts-based standard.

b. How well does the Panel agree w ith collecting current valuati on studies to understand the value of bundled ecosystem services? Can the Panel recommend additi onal or alternative approaches ?

I generally agree with this approach. A holistic ap proach to th e various ly affected services seem s to be logical. However, it should be evaluated if these new complex attributes of changes would

not com p licate the entire process of secondary st andards developm ent. Maybe as the first step towards developm ent of a new standard the we ll tested European approach (CL and RAINS

com b ined) should be initially considered. The idea of ecosystem s services (including their bundling) could be considered as the next step leading to further im pr ovem e nt of the standards.

Question 10. In the sev e n

- step app r oach to the cu rrent conditions risk/expo sure assessm e nt, Step 7 (Section 3.7) describes an appr oach to assess degrees of prot ection /lev e ls of eff e cts u nder alternative form s and levels of am bi ent NOx a nd SOx standards. This approach attempts to describe how the m e thods, m odels, and results of the current conditions risk/exposure assessm ent can inform our evaluation of the appropriate fo rm (s) and levels(s) of a national standard. How well does the Panel agree w ith the approach outlined in this se ction, the issues presented, and the 9 steps outlined to assess potential f o rm s and levels of the standard? Please suggest any additional o r alternative s t eps we sho u ld take into consideration?

The section presents an interes ting p l an for defining and describing eco log i cal changes caused by N and S deposition and an attem p t to associa t e the m with the NOx and SOx concentration-based standards. Although not easy to im pl em ent on a national scale, the critical loads (CL)

m e thodologies could be used for defining levels o f the acceptable deposition of N, S a nd acidity. Maps of CL exceedances, as it h a s been done for the NE United States, eastern Canada and Europe, can be very usef ul in showin g the areas where the u n acceptable deposition h a s taken place. Such inform ation aided by app r opriate m ode ls cou l d lead to recomm endations of where the N deposition reductions are needed in order to prevent deterioration of sensitive ecosystem s. While it m a y be possible to use such inform ati on for recomm ending e m ission reductions, as it is being done in Europe under the Convention on L ong-Range Transport of Air Pollution (please

see m y re m a rks above), a direct link to am bien t NOx or SO2 concentrations would be extrem ely difficult, if not im possible, to establish.

15Plan presented in Section 3.7 establishes a fram ew ork of the logically ali gned steps (activities) that theore tically could lead to developm ent of new, concentra tion-based standards for NOx and SOx.

16

### Ms. Lauraine Chestnut

One general comment: There will undoubtedly be lim itations in data for this assessm e n t. I want

to recomm e nd that there be an e ffort throughout the process to defi ne data that will improve this

assessm ent the next tim e around. Collection of som e of these data m a y be ongoing, but there

m a y not yet be enough to answer the quantitative questions: the need for these m onitoring and data collection efforts to have continued suppor t should be articulated. There m a y be further monitoring and data collection that would be helpful. These need to be defined and prioritized so that resources are put to their best use and support is generate d for m o re monitoring and data colle ction w ith f o cus on the spec if ic inf o rm ation needed to help answer the key policy questions.

Section 2.4 1. It seem s really im portant for this assessm ent to address the question of whether both S and N have to be reduced to obtain benefits, or are they causing sep a rate eff ects that are essen tially additive? Th is speaks to whether th e sta ndards for the two need to be linked.

2. On page 18, I don’t understand the question ab out whether long-term effects and cumulative loadings are relevant to the NAAQS review. If they are im por ta nt for understanding the effects on ecosystem s, why would they not be relevant?

Charge question 4: The need to define and describe the nature of the harm to the ecological resource that m i ght be considered an adverse effect needs to be consid ered right at the beginni ng when the indicators are reviewed and selected. It is im portan t tha t th e sele cted in dicato rs be a b le to be lin ked to changes in deposition, but also to changes in ec osystem services. There m a y be a threshold or a continuous relationship between levels of th e indicators and harmful effe cts on ecosystem services (o r even a nonlinear relation s hip that entails positive effects over som e ranges and negative effects over other ranges). E ither way, it is im portant to ask whether a given change in the se lected indica tor c a n be inte rpre ted as s howing a harm ful effect, the implications of which can be articulated for the policy m a ker. For example, do we know at what level for each indicator the ecosystem looses capacity to support som e species that would norm a lly be expected to liv e in th is system ? I t will be ve ry im portant to be able to e xplain why the change in the indicator m a tters and what the si gnificance of the change is in te rm s of ecosystem functions and services.

Charge question 9b: Once the losses or im pairm e nts in ecosystem fu nctions and services at current deposition rates

are quan tif ie d (or othe rwise cha r ac ter i zed) then it will be us ef ul to se arch f o r availab l e valuation studies that provide releva nt information. It does not seem useful to try to determ ine total values for all eco sy stem services even in the selected case study areas, becau se th e policy relevant valuation is s u e f o r these pollutants is probably not a total loss in services, but a m a rginal change in quality or quantity of som e services. To the extent that the literatur e supports valuation of bundled ecosystem services it m a kes sense to use th is approach, especially if these services are

17perce i ved as connected o rjoin t produ cts of the ec osystem f

u nctions, and if there ar e multip le services affected by the sam e change in pollution exposure.

Charge question 11: I think EPA has selected the right categories of ef fects to focu s the quan titative risk as sessm ent ef

f

o rts. This list of oth e r ef f

ects need s to be included and described. In som e cases the

assessm ent m i ght provide partial qu antitative inf o rm ation. For exam ple, will it be po ssible to say what the exp ected ch ang e s in am bient concen trations of N 2 O m i ght be expected as a result of alternative standards? I agree it is not appropriate to expend resources here to try to quantify the associated clim ate change effects.

18

### Dr. Ellis B. Co w ling

Individual Comments on the Draft Scope a nd Methods Plan for the Risk/Expos ure Assessment: Secondary NAAQS Review for Ox ides of Nitrogen and Oxides of Sulfur

Before plunging directly into m y specific as signm e nts to critically review the “Key Policy Relevant Questions” in Section2.4 and answ er Charge Questions 3-7 in preparation for the April 3, 2008 CASAC Consultation, let m e emphasi ze how pleased I was to see in this Draft Scope and Methods Plan how m u ch EPA appears to be prog ressing in its willingn ess to think in

a m o re holistic way about:

1) Multip le po llutan ts and multiple ef fects of ai rbo r ne pollutan t s that of ten occur in the

sam e air parcel and frequently act together to cause sim ilar, different, and/or som e tim e s more pronounced effects than single pollutants acting alone.

2) Broadening the “Indicator of Concern” for the secondary NAAQS for “Oxides of Nitrogen” to include chem ically reduced and organic form s as well as oxidized form s of “total reactive nitrogen,”

3) Recognizing that NAAQS designed to protect ecosystem s fro m adverse effects of air pollutants of ten require different pollutant indicators, levels, averaging tim es, and statistical form s than NAAQS designed to protect hum an health.

4) The m u ltiple sim ilarities and advantages rather than just the differences am ong “NAAQS,” “Critical Loads” and “Target Loads” for nitrogen and sulfur air pollutants.

5) How “the words we choose often reveal the quality ( a nd sometim es also the lim itation s) in our understanding” about various phenom ena in nature. Useful exam ples in the

curren t Draft Plan in clud e the s i gnificance of such words as “ecosystem services;” “acid i ficatio n,” “nutrient enrichm e nt,” “nitrogen saturation,” “NOx/SOx,” “NOx/NHx/ S Ox,” “total reactive n itrogen,” “acid precip itatio n,” “acid i fying depositio n,” “wet plus dry acidify ing deposition,” Etc.

Please no te a f e w additional comm ents below re garding som e of these important m a tters and especially the Resolution displayed on page 3 of these Individual Comme nts after it w a s passed by the Integrated Nitrogen Comm ittee of the EP A Science Advisory Board for Communication on October 31, 2007 to our CASAC NAAQS Re view Panel on the Secondary Standards for Oxides of Nitrogen and Oxides of Sulfur.

19My Specific Assignmen t s in this CASAC Consultation on the Draft S c ope and Methods Plan for the Risk/Exposure Assessme nt Secon d ary NAAQS Review for Nitrogen Dioxide and Sulfur Dioxide

My specific assignm ents in preparation fo r our April 3, 2008 CASAC Consultation on the Draft Scope and Methods Plan as outlined in Chairm an Ted Russell’s m e mo of 11 M a rch 2008

are:

1) Key Policy Relevant Issues. These topics are summarized in Sec tion 2.4 in the Draft Scope and Methods Plan, and

2) Charge questions 3-7 – Ecologi cal Effects Characterization. These Charge Question s are listed in Lydia W e gm an’ s m e mo to Kyndall Barry dated 5 March 2008.

Chairm an Russell also g a ve the f i r s t of th ese two assignm ents to six other CASAC pa nel colleagues – Douglas Crawford-Brown, Paul Hans on, Naresh Kum a r, Myron Mitchell, Kathleen Weathers and Lauraine Chestnut . He also gave the second assignm ent to three other CASAC Panel m e m b ers – Charles Driscoll, Myron Mitche ll, and David Shaw. Thus, I am ve ry m u ch looking forward to comparing notes with all of these other people during our Consultation on April 3 rd !

Assignment 1) -- Critical Review of sect ion 2.4:“Key Policy Relevant Questions”

Both the current Chair of CASAC, Dr. R ogene Henderson, and others am ong the Statutory Mem b ers of our Clean Air Science A dvisory Co mm ittee hav e written in recen t m ont hs about th e Need for Policy Relevancy as the Dom i nant Con cern in the New NA AQS Review Processes.

In these carefully stru ctu r ed rev i ew p r oce sses, the m o st critical and overarching policy question that needs to be answered is :

“What scien tific evidence and/or scientific ins i g h ts have been developed since the las t review to in dicate if the cu rrent public-health based and/or the current public-we l fa re based NAAQS need to be revised or if alternat ive indica tor s

, leve ls, s t atistical forms , or averaging times of these standards are needed to protect public hea lth with an adequate margin of safety and to protect public welfare?”

And sim ilarly, especially with rega rd to the p r esen t integra t ed [sim ultaneous] review of the Secondary S t andards for NOx and SOx, the m o s t critical and overarching Key Policy Question is:

“What scien tific evidence and/or scientific ins i g h ts have been developed since the las t review to in dicate whether, and if so, what particular ecosystem components or oth e r airquality -re l ated public we lfare va lues, are more or less sens itiv e than the p opulations o f humans for which primary standards are establ ished and for this reason may require a diffe rent indicator, leve l, statis tica l form, or averaging time of a secondary standard in order to protect public welfare.”

20W ith the latter overarching Key Policy Ques tion in m i nd, we now have the considerable advantage th at a m u ch more com p lete focus can be achiev e d on crit i cally important scient if ic findings that are as d i rectly relevan t as possible to this overarching Key Policy Question. To achieve this more com p l e te focus, it is desirab l e that each chapter of the Integrated S c ience Assessment , the Risk/E xposure Assessmen t , and the Policy Assessment/Rule Ma king docum ents for each criteria po llutant should contain a summ ar y section co mposed almost entirely of v ery carefully crafted summary s t atemen ts of conclusions and/or scientific findings . T h ese carefully crafted summary statem ents should:

1) Contain the distilled ess e nce of the most im portant topics covered in each chapter, and
2) Be as directly relevant as possible to th e overa rching Key Policy Ques tion w r itten above.

.
Section 2.4 of the present Draft Scope and Methods Plan co ntains a series of 17 policy relevant questions to which caref ully craf ted sc ien tif ic answe r s could be developed. But these mostly policy relevant questions need to be bett er organized and coordina ted so that the answers to these questions can be used to build a c oherent series of linkages betw een the m a jor acidificatio n and nutrient en rich ment effects of concern and the nitrogen and sulfur secondary NAAQS standards that will be ne ce ssary to a void these e c ological ef f

ects.

My m o st serious reservation about the 17 polic y relevant questions li sted on pages 17 and 18 of Section 2.4 is that chem ically reduced form s of nitrogen (NHx), organic for m s of nitrogen (NCx), and total reac tive nitrog en (T Nr) all are n o t inc l uded in eithe r the specif ic wor d ing or th e written context of any of these 17 questions. Only the first sub-part of the sixth question listed on page 17 deals exp licitly with ammonia, ammonium ion, and/or to tal reactive nitro g en as alternative “indicators ” of nitrogen pollution.

“Should the current standards for NO 2 (as an indicator for NOx) and SO 2 (as an in dicato r for SOx) be retained, revised, or revoked and/or replaced with alternative stan dard(s) having different indicators to provide the required protection from known or anticipated adverse welfare effects ? ”

I hope that these 17 policy relevant questions can be adjusted, revise d, reorganized, and/or

augm ented in order to further increase th eir valu e in optim izin g the quality of summary state m ents of scien t if ic findings tha t will b e as r e levan t as p o ssible to th e overa rchin g Key Policy Question printed a bove in bold italic type.

In this connection, please also note once again the attached

Resolution from the Integrated Nitrogen Co mmittee o f th e Science A d visory Board for Consideration by the CASAC S econdary NAAQS NOx and SOx Review Panel

During the ongoing m eeting of the EPA Scien ce Advisory Board’s Integrated Nitrogen Comm ittee (INC) -- m eeting at SAB Headquart ers in W a shington DC on October 29-31, 2007 -- the several m e mbers and Chair of th e INC, Dr. Jam e s Galloway of the University o f Virginia,

21asked m e (as the CASAC-designated liaison person to the S c ience Advisory Board’s Integ r ated Nitrogen Co mmittee) to present the f o llowing Re solution (which was developed and approved by the INC) for consideration during the CA SAC review of the NAAQS for NOx and SOx during our C A SAC Conference Call Consultation on October 30, 2007.



### Resolution

The current air poll u tion i ndi cator for oxides of nitrogen, NOx, is an inadequate measure of reactive ni trog en in the atmospheric environment. The SAB’s Integrated Nitrogen Commi ttee recommends that inorganic reduced nitrogen (ammonia plus ammoni um) and total oxidized nitrogen, NOy, be monitored as i ndicators of to tal chemically reactive nitrogen.

Assignment 2 – Charge Questions from OAQP S

My comm ents are o r gan i zed below in respons e to each of the several Charge Question s posed in Ly dia W e gm an’s m e m o to Kyndall Barry dated 8 March 2008. As you will see m u ch more detailed attention has been given to Char ge Questions 3-7, to which Chairm an Ted Russell asked m e to give special attention.

1. In outlining the scope of this risk/exposure as s ess ment, we have created a flow diagram that represents h o w nitrogen and sulfur compo unds move from ‘source to dose’ in the environment (see Figure 2-1). How adequately does this concep tual model for evaluating risks due to deposition-related ecological effect s c h aracteri z e what should be covered i n the scope of this assess ment? This conceptual m odel seem s very adequate as an initial fram e of reference for deposition-related ecological risks

2. The main ec osystem eff e cts areas w e anticipa te evaluating in this risk/exposure ass ess ment

are: (1) risks to terrest rial ecos y stems f r om nitrogen enrichment effec t s, (2) risks to aquatic ecosystems from n i tr ogen enric h ment eff ect s (eutrophic a tion),

(3) risks to terrest rial ecos y stems f r om acidif ication effect s (nitrogen and sulfur), and
(4) risks to aquatic ecosystems from a c id ification effects (nitrog e n and sulfur).
We also plan to qualitatively discuss t h e role of sulfur enrich me nt on methylmer c ury production and the role of nitrous oxi de in c lim ate change. What key effects areas, if any , have been overlooked by this approach? Should the asses sment plan be modified to include other effect s ? Especially considering the court ordered tim e constraints under which this Risk/Exposure Assessm ent must be completed, it seem s very r easonable to co ncentrate on these the four

m a jor aspects -- nutrien t enrichm e nt and acid i f i c a tion in te rre strial and aquatic ecosystem s but to also include som e assessm ent of the other two effects of sulfur enrichm e nt on m e thylme rcury production and N 2 0 influences on clim ate change.

223. Due to the complexity of conducting a na tionwide risk/exposure assessment for welfare effect s due t o NOx and SOx, we have outlined a strategy designed to identify sensitive ecosyste m s a nd a range of harmful/adverse eff ect s (see Figure 3

- 1). The seve n steps are t o (1) identify documented b i ological, chemical and ec ological effects and potential ecosystem service s , (2) define sensitive areas using GIS mapping,

(3) select ri s k /exposure c a se study assess ment area s, (4) evaluate current loads and effect s in case study assess ment areas, (5) scale up the case stud y assess ment areas to larger sen sitive areas whe re f e asible,

(6) assess cu rrent e c ological conditi ons in those areas, and
(7) assess alternative levels of prot ection under different ambi ent scenarios.
Does the Panel agree with this general approach? Should it be improved or modified?
Yes, I agree that this general approach is sound, But i t certainly can be im proved and m odified in its presentation and im ple m entation within the Ri sk/Exposure Asses s m ent for which this is a Draft Plan.
As indicated on page 2 of these Individual Co mme nts, m y m a jor res e rvation about the general approach outl i ned in t h is Draft Sc ope and Methods Pl an is that it re mains unclear if EPA is really willing and i n terested to include reduced (especi ally ammonia and amm oniu m ) and organic form s of nitrogen (amino acids and volatile am i n es) as well as oxidized for m s of nitrogen in the crucially im portant “indicators” being considered in t h is integrated (sim ultaneous) review of the present “NOx ” and “SOx” NAA QS seco ndary standards.

It was reassur i ng to read i n several parts of this Draft Scope and Methods Plan:(f o r exam ple) on page 22 that:
“The risk exposure assessment will focus on ecos y stem welfare ef fects that resu lt from the deposition of total reactive nitroge n “ and also on page 26 that:

“To asse ss the i m pacts of t o tal reactive nitroge n and sulfur loading we plan to identify adverse terre s t rial and aquatic effect s ... ”

But it was als o discouraging to see that the sche m atic diagra m chos en for inclusion on page 12 of this Draft Scope and Metho d s Plan deals onl y with oxi dized forms of nitrogen an d includes no mention or pictorial illustrations of the huge (m ostly agricultural) sources of reduced and organic forms of reactive nitrogen.

If EPA is seri ous about dealing with bot h “nutrient enrich m e nt” an d “acidificati on” of ecos y stem s induced by atm o spheric deposition of total reactive ni trogen, the agency will have to learn how to sustain its rec e nt succes s in learning to think m o re holistically (in part by learning how to write

m o r e holistically ) about a mmonia, a m m oniu m ion, NHx, and NCx, and TNr about “ecosy stem services” “cri tical loads,” and “m ultiple pollutant/m ultiple effects” approaches in air qualit y management.

What a different im pressio n this Draft Scope and Methods Plan wo uld have created if:

 the m o re incl usive abbreviation “NOx, NHx, and SOx) had been used instead of just “NOx and SOx,” or

 the words total reactive nit r ogen” and “total nitr ogen loading” were used m o re frequentl y and

m o re appropriately :

23• In form ulating the Key Po licy Relevant Questions listed on pages 1 7 and 1 8

,

• In the captions of the tables and figures on pages 12, 1 6 , 19 , 28 , and 29, as well as

• In preparing the major subheadings and topic sentences of paragra phs on pages 7, 15, 16, 19, 2 1 , 2 2 , 2 7

, 49, 55,5 6 , 5 9

, and A-3.

4. In the seven- s tep approach to the curr ent co nditions risk/expos ure asse ss me nt, Step 1 (Section 3.1) describe s an approac h to identify the do cumen t ed effect s, biological, chemical and ecological indicators, and potent ial ecosystem s erv ices r e lated to acidification and nutrient enrich ment. Does the Panel agree with this approach or can they suggest alternative approaches we should consider? I think you did very well in devising the seve n step approach presented in Figure 3.1 -- the first step of which is described m o re fully in the text in Section 3.1.1 on pages 26-30. Thus I encourage your continuing use of this first step approach so long as you keep in m i nd that reduced and organic form s of nitrogen m a y be e v en m o re i m portant than oxidized form s of nitrog en in m a ny of the sensitive a r e a s to wh ich this approach is intended to be applied.

5. In the seven- s tep approach to the curr ent co nditions risk/expos ure asse ss me nt, Step 2 (Section 3.2) outlines a path to define areas sen sitive to total reactive nitrogen and sul f ur inputs. Do the Panel me mbers agree wit h this approach or a re there bett er alt ernatives that should be considered?
Once again, I think your step 2 approach m a kes sense. I was especially pleased to see that your intention is t o use GIS m a p p ing as a tool to furthe r analy ze and inte rpret the strengths and lim itations of sim i l a rities and differences am ong these sel ected sensitive areas.

a. We are atte mpting to characteri ze the risk s to eco systems fro m sulfur and nitrogen deposition nationwide by clustering sensit ive ecosystems whe re possible and by using the linkages between the se a reas at differ e nt scal es. Pl ease comme n t on the ade quacy of this approach.
I have only very lim ited pers onal experience in using these kinds of cl usterting analy t ical tools, thus I

am not well qualified to assess the adequacy of t h ese methods of analy s is.
b. How appropriate are the datasets and GIS map s listed in Table 3-4 for identifying ecosystems sensitive to nitrogen and sulfur and/or are there oth ers that have been overlooked?
The array of general ty pes of ecosy stems listed in Table 3-4 see m s very adequate to me excep t for the lack of near-c oastal oceans waters.

6. In the seven- s tep approach to the curr ent co nditions risk/expos ure asse ss me nt, Step 3 (Section 3.3) outlines a path to identifying risk/expos ure cas e study asses sment ar eas. a. Table 3-5 provides an initial list of indicators, mapping lay ers and multimedia model s that may be used to

assess ecosys t em ri sk and exposure.
a. Please comment on the appropriateness of th es e and suggest alternatives that may be better suited for this analysis.
Over the past 20 y ears, I have had som e interacti ons with the pri n cipal investigators invol ved i n about half of these studies of ecosy stem eff ects, possible indi cators, and the m a pping lay e rs and m odules used in these kinds of terre strial and aquatic pr oblem areas. Fro m t h ese interacti ons, I have the general i m pre ssion that the se problem ar eas ar e appropriate for use in Step 3 and I have no suggestions o f other m e tho d s that would be m o re suitable for this kind of analy s is.

24b. Please comment on the list of potential case st udy asses sment ar eas in Table 3-6 and Table 3-7 and make reco mmen dations or suggest any alternatives.

As in m y response to the issues rai sed in Charge Question 6a, I ha ve had som e interactions with the principal inve stigators involved in about half of these studies and believe that the array of possible

case study areas listed in Tables 3-6 and 3-7 is reasonabl e and is like l y to be fr uitf ul for the pur poses of this Risk/E xposure Assessment and evaluation of benefits that ar e likely to oc cur from decr eases in

atm o spheric loading of tota l reactive nitrogen. M y experience is much m o re li mited with respect to sulfur and m e rcury l o ading

. 7. In the seven- s tep approach to the curr ent co nditions risk/expos ure asse ss me nt, Step 4 (Section 3.4) outlines a path to assess cu rrent n i trogen and sulfur loads and their effe cts on case st udy

assess ment a reas. Does th e Panel agree with how we have desc ribed our approach to identifying datasets, gaps, and uncertainties?
The task of identify i ng useful data sets is cha llenging but the associate tasks of identify i ng gaps and characterizing uncertainties is even m o re co m p licated and challeng ing The ap proach you hav e planned to use see ms very sensible. I am also pa rtic ularly pleased that y o u plan to stretch even further and at tem p t to characteriz e uncertainties in the context of cu rrent understanding of to tal reactive nitrogen im pact s on ecosy stem services rather than the m o re fam iliar measures of eco sy stem growth, stabil ity, and productivit y

. a. We have initially identified the pri m ary che m ic al indicator that is most s u itable for asses sing ecosyste m ac idification effects as acid neutrali z i ng capacity (ANC), with alternatives depending on data availability (see section 3.4.1 and Appendix B). Does the Panel agree with this selection, or can they suggest alternative/additional key indic a tors?

I presu m e tha t y ou m ean that at m o spheri c-depos ition induced losses in ANC” rat h er than just ANC itself is “the m o st suitable che m ic al indicator for asse ssing ecosy ste m a c idificati on effects. With this

sm all adjustment in the p h rasing of yo ur question, I agree that ANC is probably the in dicator of choice for assessing acidification effects in aquatic ecosy stem s. I know of no indicator that would be

m o re suitable althoug h m a ybe loss of cation exchange capacity m i g h t be worth s o me consideration. Charles Dri s coll will be bet t er able to answer this question m o re authoritativel y tha n I am able to do.

b. We have describ e d the models bein g considered for this analysis (see s ecti o n 3.4.2 and Appendix C). Does the Panel agree wit h the choice of these mod e ls, and can they help prioritize them for modeling the re sponses of the indica tors recommende d in Step 1 (Section 3.1)?
I have no experience on which to base an inform ed judgm ent about the com p ar at ive merits of these

m odels.

8. In the seven- s tep approach to the curr ent co nditions risk/expos ure asse ss me nt, Step 5 (Section 3.5) discusse s how to scale up case stu d y areas to more spatially extensiv e sensitive area s, where appropriate. Does the Panel agree wit h this approach or can they suggest alternatives? I have no experience on which to base an info rm e d judgm ent in response to this question.

9. In the seven- s tep approach to the curr ent co nditions risk/expos ure asse ss me nt, Step 6 (Section 3.6) outlines a path to assess the cu rr e n t conditi ons of sensitive ecosyste m s. How well do es the Panel agree with the approach outlined for ca lculating response curves and utiliz ing mapping and ecosyste m se rvices to characteri ze cu rrent con d itions or can the Panel recommend alternative approaches?
I agree that the approach outlined in Section 3. 6 is appropriate for your assessment of the cur r ent condition of e c osy s tems. As indicated in m y respon se to Charge Question 7 (above) I am very pleased

25that y ou are planning to ba se y our assessm ent on th e magnitude of at m o spheric deposition im pacts on
ecosy ste m ser vices.

a. How well do es the Panel agree with using ecosy ste m se rvices to provide a common metri c for compari n g ecological risks due to ni trogen and sulfur deposition effects?
Once again, I am very pleased that you a r e pla nning t o use ecosy stem services as the base for your assessment of com p ar ative risk due to total reactive nitrogen a nd sulfur deposition effects.

b. How well do es the Panel agree with collectin g current valuation studies to understand the value of bundled ecosyste m se rvices? Can th e Panel reco mmen d additional or alternative approaches?

I a m not sure what is m e ant by “bundled eco sy ste m ser vices” thus I have no basis on which to offer an infor m ed judgm en t in answer to this question

,

10. In the seven- s tep approach to the curr ent condi tions risk/expos ure asse ss me nt, Step 7 (Section 3.7) describe s an approac h to assess d e grees of pro t ection/levels of effects un der alternati v e forms and le vels of ambient NOx and SOx standa rds. This approach attempts to descri be how the methods, models, and results of th e curr ent co nditions risk/exposure assess ment can inform our evaluati on of the ap propriate form (s) and level(s) of a nati onal standar d . How well does the Panel agree with the approach outlined in this sec tion, the issues pre sented, and the 9 steps outlined to asses s potenti a l forms and levels of the standard? Please suggest any additional or alternative steps we shoul d take into c o nsideration.

I am very ple ased to see th at you plan to do what a ppe ars to m e to be a very thorough and effective analy s is of alternative for m s and levels of a m bi ent “NOx and SOx” standards ( by which I pre s u m e you also m e an alternative “NOx, NHx, NCx” or “total reactive nit r ogen” standards” ).
The nine step approach y o u have outli n e d seems very sensible to me although I could n o t fig u re out how step 1 an d 3 are different from each other, I was also puzzled about wh y yo u included t h e “levels and for m s” of altern ative standards and not also the associat ed “averaging time and stat istical form” of alter n ative standards. Maybe the latter tw o as pects are so m u ch less i m portant than the first two that the latter two are not essential for the purpos e of this analy s is.

11. Additional e c ological/welfare effec t s d u e to NOx and SOx emis sions that we do not currently anticipate evaluating in d e tail in this review includ e the following:

• Nitrogen saturation,

• Maple decl ine,

• Ammonia air deposition and toxicity to native mussels,

• Relationships betwe e n acidity/nutrient enrich me nt and merc ury methylation,

• Sensitive areas for acidity/nutrient enrichment impacts, iden tified from b i ogeochemic a l characteris t ics, and

• Climate ch ange effects due to N 2 O.
Does the Panel agree that these r e pre s e n t lower pr iority effects f o r the curr e n t assess men t ? If not, what does the Panel recommend?
I agree that al l of these effe cts are of les s e r i m porta nce than the four main topics that are planned for inclusion – n u trient enrich ment and acidification e ffects on both terrestrial and aquatic ecosy ste m s.

26But would en courage so m e reconsideration of both “n i t rogen saturation” -- which is hard to av oid since it is the “li m iting case” when you a r e already dealing with nit r ogen enrichment effects.

I feel sim i larly about keeping c lim ate ch ange effects caused by N 2 O e m issions in the present as sess ment plan --mainly because cli m ate change ef fects ar e so lik ely to become very m u c h m o re i m por tant in the future of o u r countr y ’s con cerns about h u man induced changes in t h e chem ical and p h y sical clim ates of our planet.

27

### Dr. Douglas Cra w ford-Bro wn

This review focuses prim arily on the Risk Assessm e nt Fra m ework presented, both in the Overview sections and in the step-by-step procedures described in Chapter 3 and in the appendices. The goal is to ensure both that the ri sk assessm ent goals are appropriate f o r standardsetting, and that the m e thods to be u s ed will p r o v ide the k i n d s of infor m ation, of sufficient quality, to meet those goals.

The authors have focused appropriately on acidif ication and nutrient enri chm e nt in the general fra m ework for deposition-related ef fects from both S and N oxides, as these are the ef fects for which the scientific database is sufficiently sound. The decision to include perturbations on

m e thyl m e rcury also appears sound. My prim ary c oncern on all of these m easures is w h ether loading, rath er than sub s equent concentrations, will be sufficient to accu ra tely determ ine effects levels. I realize th e data are prim arily in the form of loadings, and so this m a y be unavoidable. But is still s eem s to m e that the r e can be larg e var i ations in th e relatio nship between loading and concentration due to differences in hydrological characteristics and chem ical reaction rates (e.g. buffering) between water system s. But so long as the resulting vari ability and uncertainty can be characterized, this should not prove a large problem for establishing a NAAQS.

W ith respect to N2O as a greenhouse gas, I appr eciate the attempt to place oxides of nitrogen into a fram ework that includes consideration of clim ate change, but can f i nd little in the docum ent to support th e idea th at it will prov e p o ssible to relate em ission s to either H GH forcings or resulting changes in climate or ecosy stem m easures. Th is is a n inte resting idea th at probably is not yet ready for NAAQS . It was wise, therefore, to leav e the discuss i on q u alitative on this point.

I rem a in unclear as to the role of the case stud ies. The decis i o n to focus on especially sensitive ecosystem s is a good one so long as it can be assum e d that they are representative of a reasonably large class of such sensitive sites on the national scale (I don’t think it would be appropriate to base national sta ndards on situations at 1 or 2 outlier sites). So, the question that will naturally arise is wh at thes e cas e study sites are taken to repr es ent in a nation a l distribu tion. It would be good if some indicati on could be giv e n of the number of such places in the US that

m i ght be equally s e nsitive and equally exposed (or som e combination o f sensitiv ity and exposure that m a kes them experience im pacts at least as large as th e case studies).

I realize that m u ch of the work will d e pend on what is found in prelim inary assessm ents of the data, but I was not at all clear as to how the spa tial reso lution was to be treated. W h ere there is high spatial variability, the expos ure side of the exposure-respons e relationship can be greatly affected by choice of location. Th e authors do m e ntion that they will explore this issue with

exam ination of spatial g r adients, but don’t prov id e m u ch detail as to how these grad ien t s will b e quantified to determ ine the appr opriate grid size for atm o sphe ric concentration, loadings and ef

f

ects. Care will need to be taken in this asp ect o f the assess m e nt.

28The authors m e ntion at one point th at they will search for ways to “conso l idate effects” effects across acid ification and nutrient en richm e nt. It would be nice to have such a summ ar y m easure, but I doubt it will b e pos sible to acco mplish this goa l. Ins t ead , one will be left with a v a riety of what are essentially hazard quotients with no way to com b ine these into a summary hazard index. This won’t prevent setti ng a secondary N AAQS, however.

Figure 3-1 is a good summ ary of the steps to be taken. I don’t, however, know what Step 5

m eans (I understand it conceptua lly, but don’t k now how it will be acco mplished other than through pure judgm ent).

I am supportive of Step 1 in general, although the authors will need to th ink carefully about how they will ensure that decisions are based on adve rs e effects and not sim p ly effects. As written, the docum ent m a kes it sound as if any change in any indicator is adverse, an assum p tion with which I disagree. That can in part be dealt with by relating indicator ch anges to alterations in ecosystem services, alth ough (i) the data to supp ort such relationshi p s are lacking and (ii) it still will be im portan t to def i ne what is m eant by a s i g n if icant de cline (and no t sim p ly a change) in an ecosystem service).

While the us e of GIS to exam ine the issue of ecosystem sensitivity m a y prove useful, I see nothing here that convinces m e such a GIS-based study can provide fundam e ntal insights into the causes of sensitiv ity. An d I don’t fully understan d why the GIS studies are needed. I would

assum e the causes of sen s itiv ity are e l ucida t ed in the sc ientif ic litera ture, negating the need f o r a scientific study as part of the NAAQS process. The m a pping layers select ed appear appropriate, but again I can’t see how they will be overlain an d assessed to eithe r iden tif y sensitiv e area s tha t can be used as case studies or to elucidate condi tions that lead to sens itivity. But perhaps the authors will find a way to perform a useful assess m e nt once they data are collected, v i sualized and analyzed spatially.

At one point, on Page 38, the authors comment that one wants to select a region where

atm o spheric effects dominate (at l east, this is what I take them to m ean). That is good f o r a scientific study of the effects of deposition, but a region can be sensitive to deposition precisely because there are o t her s ources of nutrients that p u sh the sys t em close to s o m e natural lim its. So I am not sure that this cr iterion would be appropriate fo r s e lec ting ca se stu d ies.

The candidate assessm e n t areas starting on Page 39 represent a good cross-section of potential case study areas. They will need to be narrowed to m a ke the study feasib le.

I have little expertise on mode ling deposition, an d so will no t comment on that aspect. I note, however, that m a ny of t h e m odels go well be yond m odeling deposition, looking at speciation, concentration in water, etc. I was never sure whic h aspects of a particular model the authors were proposing to use, given the early parts of the docum ent suggested that loading would be the

exposure m easure in exposure-response relationships.

Step 5 rem a ins very “black box” to m e . I th ink the idea is good, but can’t see the m e thodology that is being proposed.

29Step 6 appears to be a form of hazard quotien t , or m a rgin of exposure approach. I supp ort th is in general as it is the be st that can be done.

The natural services valuation will be tricky. There are signifi cant conceptual problems with approaches that begin to m i m i c Costa n za-like valuations, in larg e part because th ere is no real

m a rket in which these services are traded. So th e values are hypothetical, in the sense of a kind of

revealed pref erence. I suspect ther e will be a lot of disagre e m e nt on this aspect of the

assessm ent.

If the fram e w ork in the first 6 steps can be work ed out, then Step 7 should be relatively straightforward and I support the approach defined here.

30

### Dr. Charl e s T. Dris coll

Comments on Draft Scope and Methods Pl an for Risk/Exposure Assessment: Secondary NAAQS for Oxides of Nitrogen and Oxides of Sulfur

General and specific com m e nts :

Page 10 Does figure 2-1 im ply that spec ies alterations, eutrophication and m e rcury

m e thylation are by-products of nutrient en richment or are they relevant to both disturb a nces ? Is there so m e significance to th e fact that these are sub-bu llets under nutrient enrichm e nt? Please clarify.

Page 14 2.3.4. Isn’t nutrient enrichm e nt (terrest rial) and eutrophication (aquatic) really the

sam e thing? W hy give these separate designations? This seem s to confuse the issue.

Page 15 Last paragraph. W hy are sulfur-m er cury interactions ex acerbated in coastal

waters m o re than other ecosytem s? Is there any scientific basis for this

statem ent?

Page 16 Figure 2-5. Would it be useful to sep a rate freshwater and coastal sy stem s for aquatic effects ? Thes e are very different sy stem s.

Page 16 There is lim ited sc ientif ic evidenc e that inc r eas e d NO 3 - leaching inhib its

m e thyl m e rcury production.

Page 17 Bullet 4. This bullet is very focused com p ared to the other bullets. Could it be modified to m a ke it m o re consistent w ith the o t h e r bullets ? Som e thing like “W hat is to tal sulf ur and nitrog en de position to ecosystem s and how do values vary across the landscap e?”

Page 17 Bullet 6, sub bullet 2. I’m not sure I understand the context of this question: Does it refer to whether the effects of atm o spheric nitrate deposition can be distinguished from effects a ssociated with other inputs of nitrogen? This is a strange question. Can it be m a de m o re explicit?

Page 27 Som e of the indicators on the table d on’t m a ke sense. W h at is alum inum or m e tal mobilization ? How do you quantify or char acterize forest health ? W hy are ANC and alkalinity both listed? Under nutrie nt enrichm e nt should SAV density or hypolim netic DO be listed? Should m e t hyl or total m e rcury be included?

Page 28 For acidification there should be a prim ary indicator of soil calcium status, m a ybe soil % BS, in addition to ANC whic h is indicative of surface water.

31Page 28 Why isn’t deposition an indicator fo r acidification like nutrient enrichm e nt?

Page 28 Third line. Should this be carbon to nitrogen ratio?

Page 28 Table 3-3. SAV area should be included.

Page 45 Again, it is critical to hav e both a so il and surface water ind i cator for acidification . For exam ple in the Nort heas t surface water ANC is increasing while soils are continuing to lose exchangeable C a 2+ even und er current decreasing d e position. Because so il a nd surface waters are no t com p letely coupled, tw o indicators should be used: m a ybe ANC and soil % BS.

Page 47 If CMAQ is to be used to m a ke depositi on projections, it is cri tica l tha t an ef f

o rt be m a de to validate simulations of tota l and dry deposition. Models like MAGIC or PnET-BGC require historical (dating back to 1850) a nd future values of total deposition. W ill CMAQ be able to d o th is ? A data fusion exercise will b e needed. It would be helpful to evaluate th e compatib ility of output data from CMAQ with the inpu t re quirem e nts f o r the wa tershed m odels. This is a critical issue th at will need to be addressed in a rigorous way.

Page 48 Paragraph 3. Define GUI.

Page 49 Is it possible to summ arize this text by developing a table wh ich lists the potential models, their char acte r is tics, po tentia l f o r application and lim itations? It w ould be good to indicate which of these models ha ve been used in exercises sim ilar to what is proposed. My sense is that m a ny of these models have never been applied to anything even close to what is proposed here. Also which of the m ode ls have been tested at any of the proposed study regions in a m a nner sim ilar to w h at is proposed here? Have any of these m odels been linked with CMAQ and how successful h a s this b een ? Also, analy s is of sulfate effects on m e rcury m e thylation

was m e ntioned in the introductory m a terial s. Are there any m odels available to assess this effect?

Page 50 Paragraph 1. Note PnET-BGC can be applied in a shorter than m onthly tim e -step, if that is desired. Most past sim u lations have been done in a monthly tim e-step to reduce com putative time in long-term si m u lations.

Generally, the draft S&M Plan seem s appropriate. That said, what is discussed is very general and not very specific. Also, what is p r oposed is v e ry am bitiou s . I would im agine it would take considerable tim e and resources to conduct the pr oposed analysis. Little text was focused on critica l lo ad s. How does the Draf t S & M Plan in corporate ex isting critical load efforts or is

com p atible with cr itical load ef f

o rts or plans ?

32

### Dr. Paul J. Hanson

The plan contains appropriate general prin cipals, but the presentation and term inology could be im proved as ou tlin ed in th e following co mments. Policy relevan t background levels of NOx and SOx exposures, acidification, and N & S de position should be discussed or planned to be discussed som e where in this docum e nt (see page A-8 for an exception). Adding line num bers to this docum e nt would ha ve facilitated its review.

Specific co mments :

I would add def i nition s f o r the f o llo wing term s used in th e d o cum e nts to the “Key Te rm s” pages:

• Adverse Effect/Change – See possible definitions in text on page E-1.

• Crite ria po llutant

• Dose – see use on page 10.

• Ecological quality – used on page 8

• Indicator – This term is used two ways in th is docum e nt. On the one hand it is used (I think correctly) in term s of the definition of a possible Secondary NAAQS . In other places it is u s ed to describe a m easure of change driven by N O x and SOx pollutants. The authors need to choose one for m of use and stick with it thro ughout the docum e nt.

• Multim edia Modeling – W hy isn’t th is jus t eco lo gical o r proc ess m odeling?

• Sensitiv e Ec osystem

Page vii: W i thin th e definition of Total Reactiv e Nitrogen the last line m i ght inc l ude the phrase ‘N-containing organic compounds’.

Page 2 (top of the page): I’m not convinced that the authors should concl ude that a more robust database will be available after another 5-year cycle. Does E P A have plans to fund significant new research? Are o t her agencies or organizations planning inve stm e nts in N and S deposition effects research ?

Page 2 (m iddle): The regulatory authority for ad dressing NO x and SOx as criteria pollutants is well described. More detail on how this author ity trans l ates to the subsequ e nt extended discussion on N and S deposition effects (acidi fication, N enrichm e nt) would be appropriate. A brief comm ent to th is iss u e is added at the top of page 3.

Page 6: The previous N O x AC QD published in 1995 was not lim ite d to a discussion of a m bient air effects of NO2 on ve getation. It included a la rge am ount of data summ arized from the acid rain literature on N deposition e ffects (or potential effects).

Page 8: The connection between NOx em issions, s ubsequent deposition and the direct generation of N2O sole ly from the anthropogenic N inputs is not strong. Should it rea lly be included here? References or direction to the ISA could also be used at the bottom of page 8.

33Page 9 second paragraph: The prim ary effect of NOx and SOx would be a direct effect on vegetation function / surv ival o r a direct im pact on a m a terial s u rface. I woul d classify all of the effects discussed in this plan as secondary. The N and S deposition effects are at leas t one step

rem oved from the for m of the prim ary pollutant . After rewording, however, I would retain this paragraph. For com p lete appreciation of the im pa cts of NOx and SOx on public welfare, their contribution to the generation of atm o spheri c particles and tropospheric ozone is worth

m e ntioning.

Figure 2-1 m a y reflect the proposed assessm ent pro cess, but it doesn’t illus trate the com p lexity of the problem in m y opinion. I recommend something like the followi ng alternate figure. In this

exam ple the bold arrows reflect the d o m i nant pro cesses to be focuse d on within th e REA.

Page 11 4 th line from the bottom : Should the word “reduced” be oxidized?

Top of page 12: The word “or” m i ght be changed to ‘and’.

Page 15: In the first bullet, Risks should probably be associated with ‘adverse nitrogen enrichm e nt effects’.

Figure 2-5: This is a m u ch better figure than F i gure 2-1. It might be m oved forward and used together with Figure 2-1. It m i ght also include other dashed ovals for additional known effects of

34NOx and SOx that are sim p ly not dealt with in this docum ent (e.g., tropospheric ozone and aerosols, visibility, particulate m a tter).

The bottom full paragraph on page 16 needs a reference.

Bullets on page 17: 1 Good 2 May not be enough inform ation 3 Good 4 Good 5 Critical 6 Current standards provide little protect ion nor do they inform the phenom e non of acidification or N enrichm e nt highlighted in this docum ent. 7 It isn’t clear how anthropogenic NOx from at mospheric pollutant sources can be distinguished from other for m s of N inputs (i.e., agricultu ral fertilizer).

Bottom of page 17: Ecosystem characteristics will be cr itica l . This is a k e y issue.

Page 18: The bullet questions and key issues ou tlined on this page are very good. At the bottom of the page it m a y not be clear what is intend ed in the discussion of long-term i m pacts (weeks, months, years, decad es??). A statement on the n eed to understand backg r ound levels of N and S deposition and natural processes of acidification in a regulat ory context should probably be included.

Page 22: In the third paragraph 2nd line, please el im inate the word advers e. Not all effects are adverse.

Section 3.1.1: To avoid confusion with the use of the word ‘indicat or’ as a term to describe the nature of the regulated pollutant (e.g., NOx and SOx atm o spheric concentrations), I w ould change the use of indicator throughout this section to som e thi ng like ‘m ea sures of response/change’.

Page 29: As a m easure of nutrient enrichm e nt, th roughfall N deposition (T able 3-3) will fail to

m easure the com ponent of rainfall N absorbed by the canopy. I favor the use of total N deposition as an indicator of pollutant exposure.

Page 30: A m easure of e c ologi cal or biological change resu lting from acidification or N enrichm e nt will be d i f f i cult to iso l ate f r om tr end s in othe r biogeochem i cal cyc ling dr ivers (tem perature, soil water status, herbivory outbreaks....).

Middle of page 35: The suggestions of the EES are well thought out and should be the basis for this evaluation. It will be critic al to show that the anthropogenic source of the driver for adverse ecological changes is the cause for any perc eived adverse effects. Can this be done?

Bottom of page 35: Can new and old N really be distinguished (or need to be distinguished) in the context of the N and S biogeochem i cal cycles ? Distinguishing anthropoge nic contributions to

35N & S deposition m i ght be accom p lished via the use of stable isotope s t ud ies or m easurem ents, but such observations will not be availa b l e f o r EPA’s analys is in this REA

.
Page 45: As an indicator of the pollutant I would favor com b i n ed wet and dry N deposition.

Using throu ghfall would underestimate to tal N a dditions (i. e

. , the canopy is a good filter for the

extra c tion of N f r om rainf a ll).

Page 47: Of the m onitoring networ ks m e ntioned on this page, severa l seem to be unrelated to air pollution (e.g., agricultural runoff modeling). Th ey m a y be needed to calculate total N enrichm e nt ef f

ects, but they will no t inf o rm air quality issu es them selves.

Page 47: Add a reference for the “N ational Atlas”.

Bottom of Page 55: The point m a de at the botto m of this page is really important. I don’t, however, know how one will define a nation a l s t andard specific to reg i on al areas.

Page 57: Application of modeling for the purpo ses proposed by EPA in this docum ent tends to

assum e that the m odels have validated m echanism s that ‘get it right’. This m a y not actually be the case. EPA should be careful not to apply m o de ls validated for one area /region to other areas without appropriate attention to their utility in those regions. The authors should provide a m o re detailed discussion of the m echanisms needed by ‘useful’ m o dels ahead of their description of the m odels chosen for th e REA analyses.

Page 58 Bullet #5: Are sufficient data actually available to support the developm ent of these relationships.

Page 58 Bullet #7: W h er e the effects from loadi ngs are anticipated to accum ulate over long tim e periods (i.e., years), it m a y be im portant to begin to also evalua te th e poten tia l im plications of clim ate change on such relationships.

36

### Dr. Rudolf Husar

Overall, the draft plan, Scope and Methods se ction is for the Secondary NAAQS for NOx an d SOx is thorough and executable. In particular, expanding the scope by com b ining NOx and SOx is comm endable. The c o m b ined rev i ew plan is consistent w ith th e in tertwined and multifaceted nature of welfare im pacts. However, there are se veral serious concerns re garding som e aspects of the Scope and Methods sections:

Question 1: Conceptual Mode l of th e W e lf are Risk

Consideration of other We lfare Effects of NOx/SOx.

The prim ary NAAQS is focused on protectin g hu m a n health, while NAAQ Standards are to protect and m i ni m i ze the w e lfare effects of pollutions. The planned scope of the NAAQS review docu m ent review is focused alm o st excl usively on the ecological effects of SOx & NOx. The known welfare effects such as perturbations to the atm o sphe re (weather, clim ate, optics), and the econ o m i c/esth etic effects on m a n- m a de m a terials are not covered.

Marginalizing these non-ecological welfare ef fects will om it a significant rationale for

m itigating S OX/NOx em issions. This om ission is a l so in co nsisten t with the recen t trend toward integ r ated a ssessm ent of interlinked pollutan t sy stem s: W h ile Sox and NOX are considered a s a

com b ined set of inter a cting pollutants, the i r com b ined effects are treated inco mpletely in piecem eal fashion. This lim its the ability of the docum ent to provide a full rationale for acting on welfare effects.

It is recog n ized that som e discussion of welfare effects of Sox/NOx have been incorporated in the NAAQS Criteria docum ent fo r PM . If deem ed desirable, this docum e nt could

m a ke references to the specific sub

- sections of the PM Docum e nt. Ho wever, the key findings relevant to the welfare effects s hould be present in this docum e nt, so as to provide a com p lete

37assessm ent. Also, as stated below, most other docum e nts do not treat the question of indicators adequately.

The discussion at the RTP m eeting has pa rtially resolved m y concern. A concise summary of the sulf ate and n itr ate – r e la ted vi sibility ef f

ects in th is docum ent still seem s appropriate.

Question 2: Seven-Step Methodology

Apply Abridged 7 Steps to N on-Ecological W e lfare Effects

The seven-step m e thodology proposed for the eco logical effects is s ound and executable. The sam e methodology, suitably abridged for each welf are effect should be applied to the other welfare effects. This would give consistency and scien tif ic ro bustness to the docum ent.

Elaborate versions of Steps 3, and 5 m a y not be necessary for som e effects. However, the developm ent of sensitiv e areas, ind i ces, current c onditions would be desirab l e for these welfar e effects.

382.3.2 Overview of Nitrogen Deposition This section gives appropriate general exposition of NOx chem istry

, con centrations and de position. In this overvi e w, (includin g in Fig 2.2) it would hav e been helpful to indicate that

• NOx deposit ion is prim arily throug h g a seous HNO3

• Total deposition is dom inated by d r y d e position

The addition of the NOx flow diagram discussed at t h e CASAC m eet ing will reduce m y concern. Such a diagram should indicate the relative magnitude s of the wet/dry deposition processes.

The inclusion of N2O in this sc oping docum ent discussion is puzzli ng. It is stated that N2O is a greenhouse gas but also that. “S ince that is outs i d e the scop e of this rev i ew, it will no t be a quantitative part of this assessm ent”. So, how wa s the scope defined? What is the r a tionale f o r

om ission?

2.3.3 Overview of Sulfur Oxides and Sulfur Deposition This section gives appropriate general exposition of SOx chem istry

, concentrations and de position. It is not clear what is m eant by “Due t o known acu te effects on plants, in pre v ious NAAQS reviews, SO 2 served a s the chem ical indicator for SO x species.” For the reviews ove r the past 30+ y ears, SO2 and SO4 hav e been clearly separated when p r esen ting their concentrations and depositi on. In what

context was SO2 a surro g a te ?

Pertaining sections 2.3.2 and 2.3.3, there is a gene ral comment regarding the use of the CMAQ model. The heavy reliance on CMAQ m odel for (c oncentration and) deposition estim a tion is of concern. The CMAQ m odel perfor m a nce for Sox is docum ented and for a m bient SO4 concentrations, it seem s adequate. However, th e m a rginal perform a nce of CMAQ for Sox we t deposition and for non-s u lfur species suggests c onsiderab le room for improvem e nt. Additional effort directed toward CMAQ validation should be included. The direct use of observational data in estim ating deposition (S tep 4) and for ex trapo l ating the case s t u dy areas (Step 5) shoul d be considered.

The discussion at the CASAC mee tin g regard ing CMAQ and its ca lib ratio n /evalu ation f o r use in this docum ent has not elim inated m y concern. Evidently, the CMAQ evaluation is s till som e one else’s problem...

3.2.2 GIS Mapping This activity is co mm end a ble. This section outline s a very am b itious plan t o generate many of ‘GIS la y e rs’ for use i n the assessm ent. In particular, Table 3-5 sum m a r i zes the current plan for GIS m a pping lay e rs and m odels to b e applied in the risk/exposure assessm e nt of targeted sensitive

ecosy stem s. These lay e rs originate from a variety o f sources and they represe n t very diverse content. The preparation of each lay e r and t h e integration of the la yers to support the seven steps is a technically and scientifically challenging task.

It would appear useful to prior i tize th e prepa r atio n of data lay e rs, te st the layer- integ r a tion

m e thodologies on sim p le data fusion analyses. F i na lly, the credibility of th is would be enhanced if the GIS data layers prepared for the Re view would be docum ented, cataloged, published and

m a de available for re -ev a luation and re-use by the regulatory and sc ien tif ic community.

The EPA presentation at the CASAC m eeting has addressed these issues adequately.

39

### Dr. Dale Johnson

General Comments

As in m y las t two reviews, I stress the need fo r looking at all points of view, especially with respect to nitrogen deposition. As in the other docum e nts, the focu s is on the negative effects, which leaves this docum ent open for severe criticis m once it is rele ased. T h is is e s pec i ally true for the potential effects of nitrogen deposition on carbon sequestration in US forests – this could in fact be a negative effect of reducing N e m issions! Once again, I do not advocate excusing air polluters on this basis, but I think a fair and co mplete assessm e nt require s that this side be discussed. T o f a il to do s o risks losin g credib ility f o r the entir e ef f

o rt.

Question 4. How well are the m a jor effects of NOx and SOx on ecological acidification identified an d characterized ? To what exten t do the discuss i o n s and integ r ation of evidence across scales (e.g., species, comm uni ties, ecosy stem s, and regions) co rrectly represent and clearly com m unicate th e state of the science?

The effects of NOx and SOx on ecological acid i ficati on are fairly well ch arac terized – that is not the problem

. The problem is the scope of this assessm ent – nam e ly, the focus on acidification. Nitrogen is the lim iting n u trient f o r most te rres t r i a l ecosys t em s and ther ef ore ther e is the distin ct possibility of beneficial effects as well. I believe that it is a b o th a sc ientif ic and str a tegic m i stake to ignore the potential benefits of N deposition to the national C budget while at the sam e ti m e considering only one part of th e greenhouse situation by including the negative effects of N2O. I daresay that clim ate chan ge is potentially a m u ch large r envir o nm ental is s u e than ac idic deposition o r N satura tio n is – at leas t it cer tain ly loom s much larger in the m e dia and the m i nd of the public these days. Nadelhoffer et al. (1999) dism iss the potential be nefits of N deposition on forest growth largely on the assumption that most deposited N is immobilized by m i crobial uptake in the forest floor and soil and only a sm all proportion (20% in their studies) is recovered by trees. This is in fact typical of previous fo rest f e rtilization studies which show that m i crobes typically out com p ete trees for N. However, th e argum ent is disputed by Jenkinson et al (1999) find their argum e nt unconvincing b ecause it ig n o res foliar u p take: m o st atm o spherically

deposited N first im pinges on the foliage, not the fo rest floor, as in fertil iz er stud ies an d in the studies cited by Nadelhoffer et al (1999), and m i crobial com p et ition in the f o rest cano py is considerably less than in the soil. At a m i ni m u m, the argum ents by Nadelhoffer et al (1999) im ply that greater rates of N deposition would lead to greater rates of forest C sequestration, an

argum ent also im plied by the analysis of Hunga te et al (2003). Fina lly, a recent study by Pregitzer et al (2008) has conclu sively dem onstrated that experi m e ntal inputs of N at relatively low levels (30 kg ha-1 yr-1) caused significant in creas es in C sequestratio n in liv e trees and forest floor in forests in Michigan.

Again, I emphasize that the point of delving into this issue in som e detail is not to justify incre a ses in N depositio n but to f u lly ventilate b o th sides of that issue. T h e potential contr i bution of N deposition, especially at highe r levels, to N deficient forest s has not unresolved and needs

som e experim e ntation and careful analysis. Th e current proposed m e thods include only those

40sites whe r e N depositio n has proven to have neg a tive e f f

ects or is like ly to have negative ef f

e cts, and these sites are sim p ly not typical of forest s in the United States which are m o stly N-lim ited rathe r than N saturated. Furtherm ore, the resu lt s from these arguably unusual N-saturated sites, which do not reflect the norm a l N lim ited condi tion of forests in the US, will th en be extrapolated, apparently to repres ent N effects over the entire countr y. This is bias in the extrem e – case stud ies need also to include ch ronically N deficient sites where gro w th and ind e ed even ecosystem health m i ght im prove with incre a sed N depositio n! I believe that such an analys is should be a part of the p l an for asses s ing the effects of atm o spheric d e pos ition in the d o cum e nt being reviewed. It m a kes no sense to partition out the a c idif ication ef f

ect s of air pollution from the poten tial effects of C sequestration.

5. How well has the ISA characterized the relatio n ship between acidifying deposition levels of NOx and SOx and environm ental effects?

All of the comments m a de above apply to this question as well. The ISO has som e technical problem s in the way acidification is handled, as no ted in m y review, but the m a jor problem is the

com p lete focus on acidification and the lack of perspective on the larger C budget and global clim ate issu es loom ing ahead.

6. How well charac ter i ze d is the relative im porta nce of the oxidized and th e reduced fo rm s of nitrog en on ecosystem acidification ?

There is so m e lack of clar ity on th is in the ISA docum ent, as noted in m y detailed review on p. 4- 12, lines 2-9. Ammonium is acidifying whether it nitrifies or is taken up by plants or m i crobes (in th e latter case, cau sin g the releas e of H + during uptake). T h e oxidized f o rm of N, nitr ate, is not in itself acidifying – in fact, uptake of nitrate should cause the release of OH - to mainta in charge balance in the plant or m i crobe.

Specific Comments:

p. 2. paragraph 2: Effects on clim ate are m e ntioned here – such effects must include the potential increases in C sequestration associated with N deposition from pollution in order to be a

com p lete picture.

p. 14, last p a ragraph : “can be characterized as a positiv e or n e gativ e effects...” Only negativ e effects are sought in the case stud ies proposed in this docum ent. No m e ntion is m a de of potential positiv e effects on th e bu llet list on p. 15.

p. 26, top: “we plan to identify adverse terres trial and aquatic effects..” Why only adverse ef

f

ects? Pos i tive ef f

ects were m e ntioned ear lie r – was this only lip se rvic e ? W h ere is the balance?

p. 26, bottom : “focused on what so il features should be tracke d, including how organic m a tter affects m i crobial processes.” I do not understand what is m eant here by how organic m a tter affects m i crobial processes nor how it relates to the problem at hand.

41p. 27, Table 3-1: Carbon budget, gro w th, etc are highligh t ed here – but th is will apparently be assessed only in sites specifically selected to show the m o st adverse effects in the case study

assessm ent. Furtherm ore, the resu lts from these arguably unusual N-saturated sites, w h ich do not ref l ect the n o rm al N limited cond itio n of f

o rests in the US, will th en be ex trapo l ated, a pparently to represent N effects over the entire country. This is bias in the extrem e – case studies need also to include chronically N deficient sites where gr owth and indeed even ecosystem health m i ght im prove with incre a sed N depositio n!

p. 30, paragraph 1: am ong ecosystem services, th e exam ple or prim ary production is given. See comments directly above. Assessm e n t of prim ary production appears to be lim ited to sites where N effects are known to be negative.

p. 31, paragraph 1: Most ecosystem s in the US ar e sensitive to N depositio n in the s e ns e that growth incr e a ses m i ght occur. In som e cases this will be “b ad ”, as in exo t ic species inv a sions, and in som e cases this will be “good” as in commercial forests.

p. 32, GIS m a pping: I firm ly believe that the GIS m a pping exercise should also include a thorough analysis of potentia l effects of increased N deposition on C sequestration.

p. 36, Table 3-5: Indicators shoul d include foliar N concentration and should be stratified by species. W e have reasonably good data on foliar N le vels for deficiency, and even toxicity levels for m a ny species. Foliar N should be included in the indicator list.

p. 38: The list of prospective sites here should include fast growing forests of the southeast (loblolly pine, for exam ple) where N inputs m a y well cause greater growth and C sequestration. Also should include the San Bern ardino sites in southern Calif ornia where N saturation is

extrem e. San Bernardin o ’s are bu ried in Table 3

- 7, but should be included here. This list is biased towar d sites with negativ e ef f

ects and inc o m p lete.

p. 44: Lake Tahoe should include forest effects, were forests are thought to be typically N lim ited. Lake Tahoe is also som e wha t unique in that m u ch of the pollution enters the la ke directly since ratio of land to wate r in the wate rsh e d is very lo w.

References:

Hungate, B.A., J.S. Dukes, M.R. Shaw, Y. Luo, and C.B. Field. 2003. Nitrogen and clim ate change. Science 302: 1512-1513.

Jenkinson, D.W

., K. Gouldi ng, and D.S. Powlson. 1999. N itrogen deposition and carbon sequestration. Nature

Nadelhoffer, K.J.,. B.A. Emm e tt, P. Gunderson, O. J. Kjønaas, C.J. Koopm ans, P. Schleppl, A. Tietem a and R.F. W r ight. 1999. Nitrogen depos ition m a kes a m i nor contribution to carbon sequestration in tem p erate forests. N a ture 398: 145-148.

42Pregitzer, K.S., A.J. Burton, D.R. Za k, and A. F. Talhelm

. 2009. Sim u lated chronic nitrogen deposition increases carbon stor age in Northern Tem p erate fo rests. Global Change Biology 14: 142-153.

43

### Dr. Donna Kens k i

I had 2 assignm e nts for this docum ent so I’ll address those first:

I was asked to comm ent specifically on Sec. 2.3.1. W h ile it m i ni m a lly fulfilled its stated purpos e (i.e., to provide an overview of the risk assessm ent fram ewor k), it was too abbreviated (4 paragraphs!) to be as effective as it co uld be. Section 3.7 actually did a much m o re

com p rehensive and coherent job explaining the risk assessm ent and its ap plication to the standard-setting process. In f act, Section 3.7 was the first tim e I felt like this docum ent actually pulled all th e pieces tog e ther and made a cas e for how the process should work. Consequently I

recomm end beefing up Sec. 2.3.1 with m u ch of the text from Sec. 3.7 (the bulleted lists especially, as well as the revi sed version of Fig. 2.1).

My second assignm ent was Charge q u estion 11 : “Additional ecological/welfare effects due to NOx and Sox em issions that we do not currently an tic ipate ev aluating in d e tail in this r e view include the following: Nitrogen saturation, Maple decline, Ammonia air deposition and t oxicity to native m u ssels, Relation s hip s between ac idity /nutrien t enrichm e nt and m e rcury m e thylation, Sensitiv e ar eas f o r acid i ty/nutrien t e n richm e nt impacts, iden tif ied f r om biogeochem i cal characteristics, and Clim ate change effects due to N2O. Does the Panel agree that thes e rep r esent lower p r iority effects for the current as sessm ent? If not, what do es the Panel recomm end?”

While I agree that these MAY be lower priority e ffects, I don’t think they necessarily should be neglected altogether. Although the plan says that N2O, for exam ple, will be includ ed in the scope of the review in a non- quantitative way (p. 13, Sec. 2.3.2), it never m e ntions how these lower priority effects will be included, even in a qualitative way. The rest of the plan seem s to focus solely on the m ode ling of the 4 defined risk s (p. 15, aquatic and terr estrial acidification and nitrogen enrichm e nt) and never circles back to pick up these other effects. At what point do they get inco rporated and ho w? It th is is part of step 5, it was not obvious. It should be ex plicitly stated.

Of these lower prio rity ef f

ects, the on ly one that s eem ed really tangential is the ammonia deposition and toxicity to m u ssels. It is well es ta blished that mussels are sensitive to ammonia in water, but I was unable to find any papers on am monia deposition and subsequent impact on surface water concen trations. These should be cite d, at least in Appendix A where the subject is briefly reviewed.

44Other general comm ents:

I found this docum ent very difficult to follow, but I’m not sure exactly why. Organizationally it

seem ed sound. There were som e term inology issu es that complicated th e presentation. For

exam ple, total re active n itrog en is de f i ned in the glossary as oxidized and reduced sp ecies as well as organic com pounds, but this is not the sta ndard term inology in at m o spheric chemistry, I believe (it may be in the deposition/ecol ogical w o rld). Seinfeld and Pandis (in A t mospheric Chemistry a nd Physics ) and m a ny ot hers define reactive nitr o g en as NOy (oxidized an d organic species), not including reduced nitrogen species. It seem ed like the docum ent was inconsistent, using reactive nitrogen to m ean NOy som e ti m e s and other tim e s to m ean NOy plus NHx. For

exam ple, p. 11, Sec. 2.3.2, 4 th line, def i nes total reac tive n itr ogen as NOy (or at lea s t I think that’s what it’s trying to do, w ith an unfortunate typo using redu ced for reactive). Th en again on page 23, end of 1 st paragraph, it says EPA plans to evalua te the contribution of NOx to total reactive nitrogen relative to redu ced for m s of nitrogen. So I’m left quite confused about how and when ammonia/um will or won’ t be inco rpor ated in to th is assessm ent. This lead s to a la rger concern when we get to the very end (p. 59), wh ere som e useful bullets item i ze questions about the levels and for m s of t h e standard that m i ght be considered. Som e what om inously, it sounds as if these questions m i ght not be discussed as part of the risk assessm ent but only as part of the policy assessm e nt (i.e., the ANPR). I hope that is not the case and that the com i ng risk/exposure

assessm ent will dis c uss these op tion s thoroughly

. Mo re im portan t , it is n o t clear fro m this short list whe t her the ind i cato r itse l f will b e evalua ted, and again w h ether it will include tota l nitrogen effects, versus total re active nitrogen (NOy + NHx or just NO y??).

The general approach, especi ally the reliance on GIS m a ppi ng, seem s sound, but the real question is how m u ch da ta exist to support this ef fort in a m eaningful way. Not possible to assess this from the Scope and Methods Plan.

Appendix B is too short to be useful. Rather than just describing the PnET-N-DNDC model and its input param e ters, it should ha ve incorporated model results.

45

### Dr. Nares h Kumar

Charge Question 1. In o u tlin ing the scope of this risk/exposu r e assessme n t, we have created a flow diagram that represents how nitrogen and su lfur compounds move from ‘source to dose’ in the environment (see Figure 2-1) . How adequately does this conceptual model for evaluating risks due to deposition-related ecological effects char acterize what should be covered in the scope for this assessment?

The conceptual m odel shown in Figure 2-1 is a simple, but efficient way to represent risk

assessm ent fram ework for deposi tion-related ecologica l effects. Various endpoints, such as “acid i ficatio n”, “nutrient enrichm e nt”, “clim ate cha nge”, etc. are listed ou tside the dotted line suggesting that these will be described in detail in the assessment docum ent. However, later it is

m e ntioned that the N 2 O ef f

ect (clim ate change ) is outside the scope of this assessm ent and will be included only quantitatively. It is fine to do so, but Figure 2- 1 should be m odified to m a ke it clear which endpoints w ill b e assess ed only quantit ativ ely (one suggestion is to italicize su ch endpoints).

In Section 2.3, Page 8, where the N 2 O effect is discussed the first tim e in the text, a discussion on the scope of assessm ent for N 2 O effec t should be included. For ex am ple, it should be made clear whether th e N 2 O ef f

ect will be pa rt of f

i nal deliberati ons f o r

review/revision of the NAAQS f o r NOx and SOx.

Also, carbon sequestration shoul d be added as an endpoint un der “Nutrient Enrichm e nt” in Figure 2-1 and a discussion should be included in the text describi ng this effect. Sim ilar to the N 2 O effect, it should be m a de clear whether the carbon seques tration effect will be part of final deliberations for review/revisi on of the NAAQS for NOx and SOx.

46

### Dr. Myron J. Mitchell

Final Comments on: Draft Scope and Methods P l an for Risk/Exposure Assessm ent: Secondary NAAQS Re view for Oxides of Nitrogen and Oxides of Sulfur

General Co mments

More consistency is needed throughout the docum ent on the different definitions and for m s of chem ical species includ ing the group ing of these ch em ical species into classes. The linkage of acidification with cation (e.g., Ca and Mg) nutri en t depletion and the m obilization of to xic cations (e.g., alum inum ) needs to occur earlier in the docum ent so that the total ram i fication of acidification is clearer. The docum ent needs con s iderab le wo rk with re sp ect to consistency and the use of precise descriptions. Some statem ents lack clarity. The criteria for selecting case studies are discussed, but an una m b iguous delineation of the importa nce of specific criteria in

m a king these selections is needed. T h roughout the docum ent there are statem ents about the needs for data. It would be be tter to state that “in f or m a tion” is what is required. Data availability without previous inte rpretation and analyses are less usef ul than those data sets that have been e v aluated. Those data s e ts that h a ve b een evalu a te d by m u ltiple approach e s would be especially useful. Som e reference to the Eu ropean experiences in developing m e thods for Risk/Exposure Assessm ent m i ght be insightful incl uding the relatively wide application of the MAGIC m o del at various European sites.

W ithin these proposed scope and m e thods in some instances the plan seem s very ambitious and I

am not certain that com p letion is possible within the tim e f r am e of the assessm ent and with the

resourc e s av ailab l e to do these tasks. This issue m a y be especially im portant in evaluating im pacts on ecosystem services. Th e docum ent need s to m o re clea rly a r tic u late p r io rities with respect to various approaches. I would suggest that it m a y be most facile to focus especially on the cas e stud ies to show most clearly the linka ges between sulfur and nitrogen deposition and adverse d a mage to eco sy stem s.

Specific Comments

Page Comment

2 It is not clear whether N 2 O is includ e d with the d e f i nition s of “oxides of nitrog en” and or “nitrogen oxides.” On page 11 it is stated that “th e family of nitrogen oxides includes any gaseous com b ination of nitrogen and oxygen, e.g., NO 2 , NO, N 2 O, N 2 O 3 , N 2 O 4 , and N 2 O 5 .”

6 Change to: in previous NAAQS reviews on nitrogen or sulf ur

4711 Change to: In an analytical approach unconstrained by data and other resource lim itations, one could envision a comprehensiv e risk assessm e n t covering all potentially affected ecos y stem s and all s c ien tif ic ally supported ef fects on those ecosystems in the United States.

11 The identification of the N chem ical sp ecies provided below needs to be better aligned with the definitions of N ch em ical species given on page 2: “ The sum of

m ono-nitrogen oxides, NO 2 and NO, t y picall y are referred to as nitrogen oxides (NO x ) in the atm o spheric science comm unity . More form ally , the fam ily of nitrogen oxides includes an y gase ous com b ination of nitrog en and ox y g e n, e.g., NO 2 , NO, N 2 O, N 2 O 3 , N 2 O 4 , and N 2 O 5. Total reduced nitrog en (NO y ) includes all nitrogen oxides as we ll as gaseous and particulate nitrate species such as HNO 3 , PAN, and aerosol phase amm oniu m nitrates. Reduced atm o spheric nitrogen species inc l ude

amm onia gas (NH 3 ) and a m m oniu m io n (NH 4+ ), the sum of whic h is referred to as NH x .”

13 The following statem ent is confusing with respect to how N 2 O is tr eated in this

assessm ent: “ S ince the de finition of “welfare effec t s” includes effects on clim ate [CAA Section 302(h)]

, we will include N 2 O within the scope of this review. Howeve r, it is m o st appropriate to analy ze the role of N 2 O in an thropogenic clim ate change in the context of all of the green house gase s. Since that is outside the scope of this review, i t will not be a quantitativ e part of this assessm e nt.”

13 I don ’ t believe that generally the SO 2 or SO x inclu d es particu l ate sulfate particles as stated: “ SO 2 is one of a group of substances k nown a s SO x , which include m u ltip le gaseous (e. g

. , SO 2 , SO, SO 3 , S 2 O 3 , S 2 O 7 ) and particulate (e.g., amm oniu m s u lfate) species ( Figure 2-4 ).”

21 Is this sta t e m ent really necessa ry: “ In addition to these four effects, we p l an to address, a s a ppropriate an d within our tim e constraints, im pacts associated with nitrous oxide (N 2 O) and t h e influence of sulfur en richm e nt on methy l m e rcury production.”

22 This statem e n t needs to be reworded t o clearly suggest the challenge associat ed with

m a king an assessm ent of im pacts on a diverse set of ecosy stem ty pe s over a range of

atm o spheric inputs: “The anticip ated spatial extent and diversity o f ecological effects due t o deposition of nitrogen and sulfur do not facilitate a nationwide analy s i s .”

24 Change to: case stud y are a s, data m a y not be suffici ent to perform a quantita t i ve

assessm e nt for each

28 In Table 3-2, why are K and Na not in cluded with Ca and Mg as base cations?

28 Change to: “ exchange capacity (CEC) are m o re widely availabl e at the present tim e than inform ation on biological indicators”

4828 The following statem ent im plies that CASTNET underestim ates dry depo sition of nitrogen. If this is the case, fu rther explanation is warranted: “ This creates

com p lica tion s in developi ng estim ates for total nitrogen deposition levels because dry

- deposition data source s will likely be underesti m a ted.”

29 The followin g statem ent is not true sin ce there is a linkage with Ca availability and tree species (e.g., sugar m a ple) that produce litter this has higher N m i neralization and nitrification rates: “ F or terrestri al ecosystems, low calcium to nitroge n ratios in soils are com m only related to increased n itrificatio n and potential increases in soil acidity and releases in NO 3 to receiving waters; however, these m easure m e n ts are not always widel y available.” Liter a tur e exam ples include:

Christopher, S.F., B.D. Page, J.L. Cam pbell and M.J. Mitchell. 2006. Contrasting

stream water NO 3 - and Ca 2+ in two nearly adjac e nt ca tchm ents: th e ro le of soil Ca and forest vegetation. G l obal Change Biology 12:364-381.

Page, B.D. and M.J. Mitchell. 2008. Infl uences of a calcium gradient on soil inorganic nitrogen in the Adirondack Mountains, New York. Ecological Applications. (In Press)

29 Change to: For aquatic ecosy stem s, the indicators for “ nutrient enrichm e nt” effects reflect a combination of inputs from various sou r ces

29 Not sure what “are enco urag ed” im plies in the f o llowing: “ are encouraged for inclusion in num eric crite ria as part of EPA-approved state water quality standards (U.S. E P A, 2 000)”.

29 Clarif ica tion is needed o n the “data-fusion approa ch.”

29 In table 3-3 c h ange to: “ R e flects a combination of i nputs from various sources (air, discharges to water, diffuse runoff, and groundwater inputs)”.

29 In tab l e 3-3, the followin g statem ent (Rep eated twice) is con f using: “Relative role of air deposition should ideally be compar ed with air deposi tion data and also with availab l e (pr e f e rably m u lti-m e dia) m odels.”

How can the m odels be separated from ai r deposition data since the m odels are needed to c a l cula te depo sition ?

30 Is it correct to include within eco system services “ cultural services including spiritual or religious values, aesthetic values? ”

30 What is m e ant by “t y p e o f environm ental system ?”

30 It is not clear how the foll owing approach will produce the needed outcom e :

“ Identify Da tabase s of Indicator Co nditions: The indicators selected will relate to

49available com p endiu m s of literature abstracts or actual database sy stem s (as stand alone files or accessed through Web portals) to provide readily available and transparent wa y s to d o cu m e nt the nature of the in dicators and the indicator conditions used to defin e the environm ental im pairm e nts.”

“Com pendiu m s” should be “com pendia.”

30 Change to: Identify a nd Addre ss Te mporal Issues: Differe nt ecoregions, landscapes , biological provinces will have differing degrees of susceptibility to im pair m e n t s or differing recovery pote n tial, depending on edaph i c characteristics

, past land use and/or pollu tion histories.

30 For the follo wing statem ent, be m o re explicit on the actual tim e s needed for re covery (fairly rapid and m u ch longer recovery tim es need som e approxim a te values): “Som e ecolo gical systems m a y be cap able of fairly rapid recove ry respon ses once pollutant loadings a r e significantly abated; ot her sy stem s, such as large r estuarine aquatic sy stem s, m a y require m u ch longer recovery times.”

31 Provide better description versus the fo llowing jargon: or at least define these term s “potential ne ar-field and f a r-field linkages.”

31 The term s in Figure 3-2 sh ould be refle c ted in the text.

31 Change to: Inland acid-sensitive waters in the eastern United States and nitrogensensitive ecosy stem s in the Rocky Mountains and other parts of the western United States m a y require large-scale, special-area assessm ents

.

31 Clarify wh y t h is area is sp ecial (Is this different fro m the sensitivity of other areas? ) :

“ E cosystem effects in spe c ial areas”

31 How c ould linkages not b e geographic a lly significa nt ? Note the statem ent: “If the linkages are geographically sig n ificant”

32 Why this spe c ific exam ple: (e.g., local research of MeHg form ation in Devil’ s Lake, WI).

If this exam ple is used, at least a citatio n is needed.

32 Change to: Of special interest will be the characterization of linkages that can be used for synthe sizing results fo r the entire U.S.

32 Why “ m ay ” in the followi ng statem ent: “ I nform a tio n that deals with special case stud y areas (e.g., the Adirondack Mo u n tains or spe c ial alpine an d sub-alpine ”

Previous statem ents have suggested the im portance of focusing on sensitive system s.

32 For heading “3.2.2 GIS Mapping” de lete m a pping; this is redundant.

5032 Reword for clarity and precision: “T o describe th e national picture, we pla n to m a p the locations of those sensitive ecosy st em s identified in Section 3.2.1 and ide n tify the characteristics of the biological and biogeochem i cal properties that create the sensitivity .”

32 By “unm apped areas” do es this im ply areas in whi c h an approp riate GIS is n o t available?

32 There are different issues associated with scale and defining the boundaries o f a GIS. Clarify the following statem ent : “ S ensitive areas can be identified at different spatial scales b y usi ng different approaches for defining t h e boundarie s of the m a pped units.”

32 The description under 3.2.2 needs consider able m o d i fication to clarify how GIS will be applied to this assessm e nt.

33 The linkages need to be m a de m o re explicit in som e co m ponents of: Figure 3-3. Docum e nted biological, biogeochem i cal, and ph y s i ographic linkages.

34 Provide further details on the source of the “ESRI 8.3 data disks.”

35 It is stated that “ Where case study or ecosy stem -specific data are available, a subset of m a ps for the case study assessm e nt area m a y be created.”

Are only “d ata” needed rather than info rm ation associa t ed w ith th e interp reta tion of these data?

35 It is suggested that “ Com p le m e ntary to these efforts, we m a y use a statistical cluster analy s i s to group ecosystem units into sim ilar sets. Clustering ecosy stem s m i ght reduce the num b er of locations that need to be m odeled to adequately characterize the variability in ecosy stem response to c h anges in nit r ogen and sulfur deposition.”

It would also be helpful to identify key eco syste m attribu t es that a r e m o st cr itical in the classification and grouping of these ec osystem s with respect to effects of N and S pollutants.

35 It is stated that “ In selecting areas to assess ecolo gical effects from air deposition, the SAB Ecologi cal Effects Subcomm ittee (EES) su gge sts considera tion of (1) cl ear quantifiable ecological effects due to a i r pollution, (2) the degree to which a significant com ponent of ecological effects are attributable to air pollution, (3) the responsivene ss of eco sy st em services to changes in air pollution, (4) the cum u lative im pacts of multiple air pollutants, (5) the abundanc e of ecological effects and

econom ic benefit cost analy s i s , and (6) the visibility to the public and value of resources at risk (U. S . EPA, 2005 ). W h ile these recomm endatio ns were m a de in the context of a prospective c o st-benefit analy s i s , m a ny of these re comm endations are sound in the context of ou r NAAQS risk analysis.”

51Having som e hierarchy in these selection crite ria would be useful since there could be distinct differences am ong ecosy stem s on the relative value of e ach of these criteria.

35-37 In addition specific recommendations are provided from the ESS regarding selection criteria. These factors need to be blended into a m o re cohesive set of criteria for selection.

36-37 The inform a tion provided in Table 3- 5 (Summ a r y of Indicators, Mapping Layers, and Models for Targeted Ecosystem s ) is very diverse with respect to types of inform ation, spatial scales, level of previous analy s es, etc. It will be very useful to cle a rly in dicate prio rities in the selection of attributes from this table. This selection should be based upon well-identified criteria.

45 The following statem ent is weak: “ Depending on the adequacy and abundan ce of data for areas, the evaluation m a y entail co m puter m odeling, statistical analysis, or qualitative a n aly s i s .”

Clearer criteria of the impor tance of the type and am ount of infor m ation available need to be provided in selecting case study sites.

45 I am not sure that the following i ndicator is useful due the role of canopy exchange processes in markedly affec ting the concentration and fluxes of N chem ical species in th ro ughfall: “Nitrate, ammonia, organ i c n itrog en thro ughfall deposition f o r ter r es tr ial ecosystem s.”

46 It is stated that: “W e plan to evalu a te the spa tia l a d equacy of availab l e m o nitor i ng data including GIS m a pping of docum ente d data to iden tif y any m eaningful spatial gaps.”

What will b e done if these spatial g a ps are found?

46 It is stated that: “Fo r each ecosystem eff ect, we plan to de te rm ine if there is a

tem poral dim e nsion to exposure.”

Isn’t there always a tem p oral dim e nsion to exposure? Aren’t more critical issue aspects associated with non-lin earities, thresholds, lag-tim es, etc.? Som e of this is discussed in the followin g sentences.

46-47 Each of these sources of loading inform ation has lim itations. Including som e details on the errors of thes e estim a tes would be helpful

47 In discus sin g the “CMAQ Depositio n Modeling ” the issu es r e lated to uncertainties associated with the calculat ion of deposition velocities as a function of surface ty pes needs so m e mention with re spect to the overall confidence in the predictions.

5248 In discussing acidification the im portan ce of the contribution of m obile anions (sulf a te and nitr ate ) to th e loss nutrie n t and toxic cations needs m o re e m phasis. The pH effe ct is only a sm all part of the im pacts.

50 An i m portan t criterion for selecting re gions to m odel should include availability of previous modeling efforts.

50-51 Further clarity is needed in the s ection on “Assess Uncertainty in Loading and Exposure Com putations.” For example doe s resolution include both tem poral and spatial cons iderations ? What is m e ant by “differing com p lexities? ” Does this

m ean landscape com p lexities, com p lex pro cesses, or som e thing else? If more invento r ies of reactiv e N species are needed for the m odeling, how will these inventories be done in the context of this effort?

51 Is it f eas ible to dete rm ine “the con t r i butions from air deposition sources can be analyzed relative to all other m a jor anth ropogenic or natural sources for sensitive ecosystem s across the country? ”

51 How will the assessm ent balan ce the need s of doing rigo rous analyses in one or possibly few regions with the greatest le vel of accuracy and precision versus a broader range of regions with lower accuracy and precis i on ?

52 Be m o re specific in which param e ters will be evaluated with respect to “response curves.”

52 More clearly differentiate how the C a lculate Desired Exposure Endpoint

com p ares with the de ter m ination of critica l lo ad includ ing th e criter ia use d in these de term inations.

53 The following approach is quite vague and am biguous: “The specific m e thods used to evaluate adversity will depen d on the availab ility of data and m e thods for the ind i cato r s of interes t rela ted to ac id ification and nutrient enrichm e nt and on an

assessm ent of the appro p riateness of each type o f quantification in com p aring different levels and forms of the standa rds. In our initial assessm e nt of the available data, given the tim efra m e for this NAAQS review, we have determ ined that the m o st useful approaches will be those focusing on quantifying the link between changes in ecosystem indicators and ecosystem services.”

Can som e priorities be suggested on wh ich indicators would have highest prior ity ?

53 Doing the following is certainly a da unting challenge: “Thus, when ecosystem servic es a r e quantif ied and their ecological response functions to NO x and SO x are modeled, it is im perative that the entire bundl e of services be evaluated, and that the linkages and tradeoffs am ong ecosyst em services are included in the quantification (i.e., ecological tradeoff functions [ETFs]).”

5354 Is it f eas ible to do the f o llowing within the tim e f r am e of this assessm ent? “Theref o re, at th is tim e , data m i ning will be c e ntr a l to dev e lo ping at leas t a prelim inary assessm ent of potential impacts of NO x /SO x deposition and acidity on ecosystem services. In the current pl an, process-based m odels are being considered to be used to (1) synthesi ze/link the suite of ERFs and ETFs and (2) generate m a ps and summ aries of ecosystem services and tradeoffs in response to

curren t and future am bient air indicators for NO x and SO x . The collection of response and tradeoff functions will aid in th e valuation of the services at risk to these criteria pollu tants where possible.”

55 To accom p lish the tasks that are s t ated m i ght requ ire a v e ry selective cho i ce of a region or a f e w regions where the av ailab l e inf o r m ation is suf f i cient to d o this work within a relativ ely s hort tim e :

1. Identify areas/regions of the c ountry receiving high levels of NOx/SOx deposition and acidity impacts. 2. In those r e gions, id entif y ecosyste m s sensitive to elev ated levels of nitr ogen and sulfur, using som e comm on selection criteria. 3. In those s e nsitive eco system s, ask what ecosys t em services are expected to be prevalent and “valued” (i.e., som e s ubset of all potential services). 4. In those areas, identify what data ar e available to develop ERFs and ETFs, at least to a qualitative degree that would enable production of spatial and tem poral

m a ps to identify different degrees of pr otection that would ex ist under alternative secondary N AAQS. Cha n et al., (200 6) produced such m a ps for several ecosystem services in th e Central Coast ecoregion of California. The linkage and

com p arison of m u ltiple e c osystem services in th e region would provide inform ation for consideration of tradeoff value of one service versus another.

58 The following evaluation approach is extrem ely am bitious:

A 1. Identify the relative cont ribution of loadings associated w ith atm o spheric deposition of nitrogen and sulfur. 2. Identify the m o st critical im pacts fr om nitrogen and/or sulfur loadings (i.e., acidification, nutrient enrich m e nt, or eutrophication). 3. Identify the contribution to atm o sphe ric loadings f r om total re active n itrog en, NOx, and SOx. 4. Identify the biogeochem i cal indicators /resources of concern in the assessm ent area and the ecosystem services asso ciated with those indicators. a. Determ ine the eco system service e ffects associated with th e m o st-critical im pacts. b. Bundle ecosystem services to fi nd common metrics for comparison across locations. 5. Define the exposure-response (loadi ng-response) functions (ERFs) for the ecological indicators of concern.

546. Estim ate the loadings/exposures associat ed with current and alternative levels of the NOx and SOx standard s (using CMAQ modeling). a. Analyze the relation s hips betw een NOx, SOx, and ot her reactive forms of nitrogen. b. Assess th e im pacts of m e teorological variability on thes e relationships. 7. Estim ate the ecosystem i m pacts associated with estim a ted loadings. 8. Convert estim ates of individual ec osystem risks to comm on units using

a. econom ic valuation based on benefits transfer f r om existing literature estim ates b. biogeochem i cal equivalents using ecological tradeoff funct i ons (ETFs). 9. Com b ine individual risk estim ates to produce overall im pact estim a tes @

Would it be more feasible to determ ine a hie r arc h al appro a c h with respe c t to the selection of case study areas wh ere the entire suite of appr oaches is utilized while f

o r others a more lim ited assessm ent will b e m a de?

59 The questio ns posed are valid and in teres ting, bu t addres sing them will be a m a jor task:

A How do alternative levels and forms of th e standards relate to a given exposure

m e tric? What are the appropriate averag ing tim e s f o r alter n ative leve ls and f o rm s of the standards? What alternative levels of th e standards should be considered? Should there be alternative levels of the standards (i.e., individual NOx and SOx standards or a com b ined NOx/SOx standard)? Do the am bi ent air ind i cator form s allow for site-specific p r otection while

m a intaining nationa l con s isten c y ? Does the ambient air indicator adequately account for the eff ects of total reactive nitrog en ? Does the form of the standard have an im pact on the risk?

As I have said previously with resp ect to the overall approach, should som e of these questions have greater priority?

A-1 In determ ining A Sensitiv e Ecosystem s @ having som e criteria related to inf o rm ation availability would facil itate the assessm e nt of A Targeted Eco s ystem Effects. @

A-1 The susceptibility of the ecosystem s to the depletion of nutrient cations should also be an important factor with resp ect to eval uating sensitivity.

A-1 In grouping ecosystem s A statistical cluster an alys is @ should be supplem ented with consider atio n of the m a jor f actors th at ar e m o st critica l in de term ining the im pacts of N and S deposition. Can the cluster an alysis include weig hting of the most critical facto r s ?

55A-2 In addres sin g the issu es of N enrich m e nt the importance of the generation of the mobile nitra t e anion with respec t to mob iliza tion of toxic Al and H ions a nd loss of nutrient cations (especially Ca and Mg) needs to be included.

A-2 The quantification and analyses of ec osystem services in the context of this

assessm ent will be a m a jor cha lleng e.

A-3

to A-5 A m a jor tas k will be the separa tion o f atm o spheric deriv e d f i xed N versus other N sources especially fertilizer and was t e treatm ent in m a king evaluations for the large r coas ta l watersh e ds

.

A-5 The heading A A.1.3 Aquatic Sulfur Enrichm e nt @ is likely not appropriate since much of the discussion focuses on the generation of MeHg which m o st likely is predom inantly generated in wetlands. Maybe a separate section on wetlands would be helpful.

A-6 The following statem ent is not corre ct in the con t ext of sulfate/MeHg rela tionsh i ps : A The A cause-and-effect relationship @ between sulfur and m e rcury deposition from the atm o sphere has been dem onstrated in the lab and in

sm all-scale f i eld exp e rim e nts @

.

A-6

to A-7 The section on A Terres t rial Acidif ic ation Due to Nitrogen an d Sulf ur @ with respe c t to the discussion on nutrient cation de pletion should briefly indicate the im portance of specific tree species s u ch as sugar m a ple in th is assessm ent.

A-7 In discussing episodic acidification, som e m e nti on of clim ate linkages would be appropriate. This is relevant not only to snowm e lt ep isodes b u t also the s u mm er storm events, especially those following droughts.

A-8 It would be better to indicate that this is A Sugar Maple Decline @ . Som e m a ple species are v e ry res i lient to atm o sphe ric pollutants and nutrient depletion.

A-9 Data suggests that sugar m a ple has hi gher Ca requirem ents than other dom i nant species in th e northeastern forests of th e U.S. m a king it m o re sensitive to Ca depletion. S ee for example: Page, B.D ., T.D. Bul l en and M.J. Mitchell. 2008. Influences o f calcium availab i lity an d tr ee species on the cycling of Ca isotopes in soil, vegetation, and stream wate r. Biogeochem i stry. DOI 10.1007/s10533-008- 9188-

56B-1

to B-2 The im portance of N 2 O em issions is due to its role as a green house gas. It m a y not be f easib le to add r ess f u lly the im portanc e of this f actor in this as sessm ent without spending considerable effort in tegrating green house gas discussion into the docum ent.

C-1

to C-4 Som e consideration is n eeded on the accuracy an d precis i on of the estim ates associa t ed w ith th e use o f the CMAQ MODELING. How will the unc erta inties associated w ith the m ode ling of the atmo spheric deposition of sulfur and nitrogen af

f

ect the ab ility of the a ssessm ent to predic t the ef f

ects of spatia l and te mporal patte rns ?

57

### Mr. Rich ard L. Poi r ot

Supplemental Post Meeting (4/2-3/08) Indi vidual CASAC Comments on Secondary SOx & NOx Integrated Science Assessment and Ec ological Risk/ Exposure Assessment Draft Scope and Methods Document

Shortly after the 4/2-3/08 CASAC Re view of the Secondary S O x & NOx Integrated Science Assessm ent and Ecological Risk/ Exposure Assessm en t Plan, it has com e to m y attention that EPA funding for several critical long -term atm o spheric d e pos ition -related m onitoring and research program s , whic h have been invaluable to understanding the continuing effects of sulfur and nitrogen deposition, are sche duled to be substantially re duced or elim inated in the Adm i nistration’s proposed 2009 budget. Specifically, the Clean Air Status and Trends Network (CASTNET) air quality and dry deposition netw or k is scheduled for a 25% funding reduction in 2009, and the Temporally-Integrated Monitoring of Ecosystems and the Long-Term Monitoring (TIME/LT M) programs (which had recen tly been saved from proposed cuts in 2008

, but) will be considered “com pleted” (i.e. term inat ed) in 2009. See attached letter from Assistant Adm i nistrator George Gray to Gary Lovett (chair of the Northeast Ecosystem Research Cooperativ e steering co mmittee).

The tim ing for reduction and/or term ination of th ese valuable long term program s is especially poor, since the Agency is currently considering secondary standards for SOx and NOx, which are being specifically focused on the environm ental e ffects of S a nd N deposition. At the sam e ti m e , large additional S and N em issi ons reductions are scheduled in the Eastern US under the Clean Air Interstate Rule (CAIR), while new sources of S and N e m issions are com i ng on line in m a ny western states, northern Mexico a nd western Canadian provinces.

The ISA and Ecological Risk/Exposure docum ents s hould be modified to reflect these planed changes in the Agency’s sulf ur and n itrog en depo sition

- r e la te d m onitorin g and rese ar ch

program s, clearly indicating:

- CASTNET, TIME & LTM are scheduled fo r large cuts or elim ination in 2009,

- why the Agency plans to reduce or elim inate these long-term program s,

- how the Agency plans to evaluate env i ronm enta l effects of fut u re em ission changes from CAIR, new SOx or NOx NAAQS, a nd/ or other em issions changes,

- how the Agency plans to consider secondary SO x, NOx or PM standards in this or future NAAQS review cycles without the infor m ati on on deposition and ecological effects that these program s provide.

5859Comments on SOx/NOx Eco- Risk Assessment Draft Scope & Methods Document

It was a pleasure to read th rough this planning docum e nt. It was clearly written and wellorganized, founded on a sound conceptual m odel and guided by an excellent series of key policyrelevant questions (on pages 17 & 18). B ecause of the new and unfa m iliar NAAQS review process, its difficult to judge how fa r the inform ation shou ld be developed in each stage of the review (what belongs in the dom ai ns of the ISA, the risk assessm e nt or the policy assessm e nt) but it appears like the planned eco logical risk/exposure assessm e nt should provide an adequate basis for consideration of policy options for secondary NOx and SOx NAAQS.

At the sam e tim e, I think the potential for effec tive secondary standards could be substantially enhanced or lim ited by how broadly or narrowly the pollutant effects of interest are defined (for

exam ple including or excluding aeroso l-phase effects), and by how m u ch f l exibility is allowed in consider ing the m easured indica tors by which co mpliance with the s econ d ary stand a r d s will be determ ined (for exam ple: SO2, total atm o spheric sulfur, sulfur deposition, exceedance of critical loads for S or S+N deposition, etc.). Statem en ts on page 56 and 57 of the plan im ply that deposition-b a sed ind i cators of ecolo gical risk ar e not at all the sam e as and will need to be rela ted to co mparable a m bient air c oncentr atio n indica tors - perhaps lim ited to the no m i nal gaseous criteria pollutants of sulfur dioxide and nitr ogen dioxide. If that is the case, I doubt very much that any useful secondary standards can be developed f o r th ese pollutants, and I think this critically important issue and should be discussed in som e de tail at this review m eeting.

Assum i ng this issu e can be satisfacto r ily reso lv ed , I also m u ch adm i re the carefully reasoned conceptual model as well as the very am bitious approach for conducting the assessment. I don’t personally h a ve enough fa m iliarity with the m a ny types of atm o spheric, geological, chem ical, biological and socio-econom ic data and m odel param e ters needed to conduct the proposed

assessm ent, but it strikes m e as a very challenging undertaking to first collect all these necessary layers of inf o rm ation and then and then m a ke them all f it together to pro duce the p r o posed quantitative assessm ents, especially since each step in the p r ocess depends upon successful previous steps. I note the phrases “we plan to ” or “we intend to” appea r 4 3 tim es in th e docum ent, but there are no “we have done”s. In m a ny cases, I assum e you have already gathered

som e of these data and tested th eir u s e in som e of the intended applications – i.e. have som e sense tha t th is approa ch will ac tually work. It would be help f u l f o r revie w ers to see s o m e

exam ple interm ediate dem onstration products to give a better sense that th is plan will actually work.

Charge Questions 8-10:

8. In the seven-step approach to the current cond itions risk/exposure asse ssment, Step 5 (Section 3.5) discusses how to scale up case study areas to more spatially extens ive sensitive a r eas, where appropriate. Does the Panel agree with this ap proach or can they suggest alternatives?

Its not entirely clear how geographically lim ite d your case study areas will be, but generally the process of scaling resu lts to larger spatial dom ains should be reasonable if your case studies identify the key biogeochem i cal param e ters associat ed with the effects, and if you have data with sufficient quality and resolution to identify sim ilar condi tions over larger regi ons. I imagine this

60will of ten in volve m oving f r om intensive lo cation s where deta iled on -site m easurem ents are available, to broader sp atial areas where surr ogate data estim ates will need to be em ployed. Presum ably it will be possible to test som e of yo ur projected scaled eff ects at oth e r s i tes where detailed data are available. Possibly you could also test scalability by pr ojecting site-specific results to h i gher or lower deposition rates from the recen t past. It should also be possible and desirable to include some bounding estim ates as you extrapolate results over space (& tim e).

9. In the seven-step approach to the current cond itions risk/exposure asse ssment, Step 6 (Section 3.6) outlines a path to as sess the curr ent conditio ns of sens itive ecosystems. How we ll does the Panel agree with the approach outlined for calcul ating response curves and utilizing m apping and ecosystem services to character i ze cu rren t conditions or can the Pan e l recommend alternative approaches? How well does the Panel agree with using ecosystem services to provide a common me tric for comparing ecological risks due to ni trogen and sulfur deposition effects? How well does the Panel agree with collecting curre nt valuation studies to understand the value of bundled ecosystem ser v ices? Can the Panel re commend additiona l or a lterna tive ap proaches?

I have only general comm ents here, as I really don’t know enough about the “ecosystem services” approach for assessing valuation. I th ink it should be possible to develop reasonable ecosystem response curves for a variety of endpoint s as well as to provid e a detailed descriptive summary of the various short and long-term conse quences th at are expected to resu lt if critical loads or o t h e r such effects lim its are exceeded. I would think this des c riptive inform ation of expected consequences could be carried through to future steps in the process, regardless of whether the “value of bundled ecosystem services” can be e ffectively communicated to your readers. I don’t think it’s abso lutely necessa ry to direc tly co mp are/contrast the risks of S vs. N pollution (its not like we can have a standard for only one or the other), but if you have a way to present the v e ry different effect s of acidification & nitrification in common units than yes, this could be very helpful.

10. In the seven-step app roach to th e current con d itions ris k /exposure as sessment, Step 7 (Section 3.7) describes an approach to assess degr ees of protection/leve ls of effects under alternative forms and levels of ambient NOx and SOx standards. This approach attempts to describe how the methods, models, and result s of the current condi tions risk/exposure assessment can inform our evalu ation of the appropriate form (s ) and lev e l(s) of a national standard. How well does the Panel agree with the appr oach outlin ed in this section, the issues presented, a nd the 9 step s outlin ed to assess poten tial forms a nd levels of the standard ? Please suggest any additiona l o r alterna t ive step s we sh ould take into considera t ion.

As indicated above, I have a m a jor problem with the im plied constraint on NOx/SOx indicators. If you are talking only S O 2 and NO2 as NAAQS indi cators, I think chances of useful secondary NAAQS are slim . A comparison of spatial & te mporal fields of S & N em issions, ambient concentrations of gaseous SO2, NO, NO2, H NO3, NH3, aerosol SO4, NO3, NH4 and wet & dry S and N (oxidized & red u ced) depos ition (recen t past , curren t, and projected [post CAIR] future) should be a relatively straight-forward m odeli ng exercise – w h ich we would want to see confirm e d to the extent possible with m easuremen ts. This kind of inform ation can and should be conducted in parallel with and independently from the eco-risk assessm ent, and results

61distributed as soon as feasible to this panel for review (if you can provide all of the above in gridded GIS data layers so m u ch the better). At the sam e time, I th ink it w ould also be useful to consider the possible benefits of a wide r range of indicators than SO2 and NO2.

In m a king this broader assessm ent, I would encour age you to continually consider what the best ecological indicators would be and then consider whether w e have in place adequate

m easurem ent program s to track them in the loca tions of concern. I would also encourage full consideration of the sources, eff ects and benefits of controlling reduced N

, regardless of whether anticipated policy -relev a nt “NOx” NAAQS indicat o r m e tric s are like ly to include it or not.

62

### Mr. David J. Shaw

General Co mments

Outcome of REA

Is this REA the sam e one that is described as due August 2008 (Table 2-1)? The REA Plan is difficult to assess in term s of what outcom e to expect because it has so m a ny uncertainties builtin, f o r instan ce “depend i ng on availa ble data”, or “if f

easible” is used a lot. Also, who will do the actual assessm ent work, over what tim e period ? W h at funds are available for the w o rk? Who is the audience?

Adopting a Longer View

From what I have looked at so far, I think it is saf e to say that most of the environm entally sensitive a r e a s do not ha ve adequate monitoring in place to track the ch an ges tha t we will need to quantify when the next review of the these pollutants becom e due in 5 -10 years. It seem s appropriate to m a ke it a requirem e nt that th is REA m a ke specific recomm endations on what needs to be in place to make the nex t assessm ent more adequ a tely qu antitative o r pop ulated with data. W e don’t want to see m o re sophisticated m odels with the sam e poor data. W e do want to see a strong er data reco rd of results on the ground.

This longer term view (5 to 10 year) is also an opportunity to exam ine in this REA what m e trics would be more useful that sim p ly going with th ose that are currently available, e.g. the base cation surplus is a be tte r indica tor th an ANC or pH where DOC is changing like in the Adirondacks.

Reliance on Modeling

A m odel like CMAQ certainly can produce estim a tes of dry deposit ion, but one of the drawbacks is that there is no way to asse ss if these estim a tes are reasonabl e. For this reason, it probably

m a kes m o re sense to em phasize thos e m easuremen ts and m odel predictions that we have the most confidence in, nam e ly wet deposition. (Section 3.4.2, pages 46-47)

Using f i ve years of m o del resu lts cer tain ly is be tt er than relying on a single m odeling year. W e re these five years m odeled in a consistent fash ion – sam e version of MM5, consistent em ission invento r ies, consistent C M AQ features/param eters, etc. ? Hav e they been evaluated ag ainst all available am bient con cen tration and d e position measurem ents, both for individual years and for the entire five-year period? (Appendix C)

Data Certainty

Few, if any, of the references to existing data pr ovide the years of data availability. T h e length and current-ness of records are critical to any assessm ent especially becau se the last d ecade has

63been a tim e of significant em issions/depositi on changes and ecosystem response signals have been detected.

Missing from the docum ent is a discussion (with m a ps) of the docum ented areas of the US where sensitive ecosystem s and high deposition rates of N and S have been identified (e.g. NAPAP Biennial Report to Congress: An Integrated Assessm e nt, May 1998, Figure 19, page 55 ).

PM & Ozone

I feel it is important to addre ss particulate m a tter and ozone in this ISA as well as the P M and ozone ISAs.

The om ission of particulate phase NO x and SO x appears to lim it the pote n tia l f o r setting standards in the future using bot h PM and oxides of Nitrogen and Su lfur standards. Furtherm ore, PM plays a significant role in n itrogen and sulfur deposition.

Also, separa ting out the ef f

ects of gas- versu s aer osol-phas e S/N will be d i f f i cult, since wet and dry deposition can include both phases, and atm o spheric chem istry and transport affect both phases. The ISA clearly st ates that “particulate NO x and SO x will be add r essed with the secondary P M NAAQS review,” and it therefore b ecom e s crucial that thes e two review process tracks are h i ghly consistent with each other. On e cannot p r o ceed indep e ndently of th e other track.

Climate Change

Clim ate change discussion appears to be lim ited to N 2 O. I feel that the clim ate change issue m a y be addressed m o re appropriately by in clud ing f o lia r inju ry d a ta (USDA).

Section 2.3.1, Figure 2-1, page 10: Consider am e nding this figure. Climate change m a y a ffect the “Characterization of Exposur e” and “Characterization of Ecol ogical Effects,” so consider putting arrows from “Cl i m a te Change” to these boxes. Suggest changing “Clim ate Change (N 2 O)” slightly to “ C lim ate Change (N 2 O, etc.).”

Charge Que s tions

The 7 step approach seem s thorough, but I do not feel that the gaps and unce rtainties are properly described.

Identifying docum ented effects seem s appropriate, but I feel that not all indi cators are identified. Specif i cally, f o liar in jury (USDA) and base ca tio n surplus.

Specific Comments

Section 2.3, page 8: W h y is the do cu m e nt disregarding dam a ge to m a terials, in cludin g decay of buildings, statues, and sculptures that are pa rt of our national heritage this tim e around?

64Section 2.3.2, pages 11-13: Although N 2 O is inc l uded in this review process, it is not part of NO y . Nor does it play a role in N deposition, so wh ile it could be included elsewhere in this docum ent it does not really belong in this section.

Section 2.4, last bullet on page 17: Is it necessa ry to be able to distinguish NOx from total reactive N ? Isn’t the purpose of th is to exam ine all oxid e s of N?

Section 3.1.1, page 28: add ‘bas e cation surplus’ to Table 3- 2. Key indicators of nutrient enrichm e nt. This first paragraph is about depositi on and applies genericall y to both acidification and nutrient enrichm e nt issues.

Section 3.3, page 36-37: Table 3-5 More detail needed on the indicator data. Add dates of the

m a pping layers, whether point or polygon data, the num ber of data points or polygons in the study area (m aybe the whole US), and the resolution of the base data.

Section 3.3, page 38: I f eel th at in cluding the Catskills of New York will provide im portan t inform ation and data.

Section 3.4.1, page 45: Selection of ANC as an indicator. Have all sens itive regions and case study areas been evalu a ted independ ently for selec tion of best indicato r s? Just becau se ANC is most widely available, it m a y not necessarily be the best, e.g. see disc ussion on using base cation surplus for Adirondack stream s in th e ISA. Also th e th ree f i r s t bullets of i ndicators are not really indicators (see page A-4 paragraph for indicators).

Section 3.4.2, page 47: The m a ps are too sm all.

There are many acronym s throughout this docum e nt, and not all of them are commonly used. Please inclu d e a listing of these.

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### Dr. Kathleen Weathers

This is a useful docum ent for catalyzing discus sion and getting feedback from the comm ittee. The approach relies almost exclusively on pro cess-based and spatial m o deling analysis. A short discussion of what—if any—other ty pes of analytical and assessm ent tools are available would be useful.

Specific and general comments, questions and suggestions are listed below.

Section 2.3.1

I applaud th e use of a co ncep tual m o del and framework.

Explicitly m i ssing from the conceptual fram ewor k, however, is the key link (flow arrow) between concentrations and depos ition. Also, the signi ficance of the arrow s and boxes should be identified (e.g., what’s the distinction between the dotted and solid lines surrounding boxes. And the arrows ?

What’s the difference between ecosystem effect s and ecosystem responses, or services (in boxes), for that m a tter?

I think that it would be helpful to def i ne gene ral ecosystem functions (e .g., productivity, nutrient cycling, etc.) and then point to places where the deposition of S and N ha s been dem o nstrated to alte r them

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Page 1: Consider altering the sentence beginnin g with “Our plan...” to : “...and the levels of deposition,” and the environmental effects on ecosy stems of this deposited material .”

Page 1: “Along with these case studies, we plan to conduct statistical and spatial characterizations...” Are th ese analyses intended to be new work/research?

Section 2.1: The legislative m a ndate reads to m e as the request for de te rmination of cr itical loads, albeit within a narrow range.

Section 2.2, page 6 awkward phrase: ....im portance of acid neutralizing capaci ty in surface water acidification.

Page 8, 2 nd para: tropospheric ozone

Page 8, last para: “Against this broad bac kground...” awkward and, in places incorrect.

Page 9, “In this current review...a ppropriateness of NO2 as a n indica tor...” I’m not sure what this

m eans.

66Words such as harm ful (page 11) should be m odified by ecological or environm ental.

The consideration of critical load analysis as an ecosystem

- type specific risk m a y be more useful than considering it as a site-specific risk.

Page 11, the paragraph beginning with “Each co mponent of the fram ewor k...” isn’t clear.

Fig 2-2 m i ght note explicitly the form ation of a mmonium s u lfate, since both N and S are of inte rest h e re

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2.3.3. The first couple of sentences are awkward. Also, acidification of the environm ent should include lowering the natural pH of rain, wate r bodies and/or terrestrial ecosystem s

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2.3.4: are the deposition of NOx a nd SOx m eant to infer the deposit ion of nitric and sulfuric acids? If not the second se ntence is not right.

2.3.4: Be specific, for exam ple: “Nitrogen and su lfur enrichm e nt repres ents a continuum of effects...and it can b e characterized as positiv e (in c reas e in en vironm ental param e ter y with enrichm e nt, or additional N or S, or with increm ental additions of N or S) or negative (decrease in environmental param e ter y with increase in N or S, etc)

Say clearly why m e thylm e rcury is being cons idered here vs other linked biogeochem i cal interactions (the effect of su lfur on phosphorous release/availabi lity in aquatic system s, for

exam ple).

Figure 2.5: consider depicting f eedbacks and linked processes

Section 2.4:

Clarify...”rather than on the effects of aerosol NO x and SOx that rem a in in the atm o sphere.”

Page 17, second bullet: responses = effects? and vari ability is m eant to be spatial and tem poral, correct?

Page 18, second set of bullets: Identifying important ch em ical species in th e atm o sphere? Important m e ans rela tiv e to other species, b e cause they can cause env i ronm ental effects ? Over space and tim e ?

Page 18, last bullet: Changes in land use m i ght be added to the m e teorologic and climate considerations

Section 3: Seven-step approach

The 7-step approach is appeali ng. It uses both spatial and m echan istic m odels to explore inputs of N and S a c ross the US as well as the eff ects of N and S deposition. I rem a in concerned, however, th at (1) the data that ar e necessary for m a ny of the analys es do not exist or (2) available data are not at an appropriate sp atial or tem poral scale and/or cannot readily or reasonably be

67linked together or extrapolated using geostatistical or other tool s. (3) F i nally, I cannot tell whether or h o w experimental d a ta, f o r exam ple N or S or combined N and S additio ns would be used to inf o r m this analy s is.

Since both the use of biogeochem i cal process mode ls in new geographic lo cations as well as the creation of GIS-based models and an alys is are activ e areas of scien tif ic resea r ch, to what exten t is it n eces sary that these model analy s es and extr apolations appear in p e er reviewed p ublication before they can be effectively used in this assessm e nt? In addition, the steps that will be used to validate or verify m odel results should be identified.

Under Key Indicators of Nutrient Enrichment : W h at’s the bas i s of the sug g estion that wetdeposition monitoring stations can provide m o re... an extensive range of nitr ogen species than is possible for dry-depositi on m onitoring stations?

As m e ntioned in m y review of the scien ce assessm e nt, throughfall N m a y not reflect N deposition levels. Also, C:N in so ils have been related to nitr ate in surface waters draining watersheds.

Table 3-3 : Technically, there aren ’t “dry deposition m onitoring” ne twork s , rathe rth er e exis t air concentration m onitoring networks and those data are used to estim ate dry deposition.

See comm e n t above abo u t indicato r s and through fall. Sulfur h a s been used successfully as an index of wet+dry deposition in the eastern US.

Recovery should be defined cl early and carefully for the pur p o ses of this assessm ent.

W h at’s the o p erative def i nition of a multi-m e dia m odel?

Step 5 (Section 3.5) :

The spatial extrapo l ation of case stud y areas is an interesting approach; my answer to whether I agree with the approach depends upo n answers to several que stions. It is not clear to m e the basis upon which case study areas could be scaled, or whether the interpol ation techniques alluded to

are app r opriate spa tia l e x trapo l ation tools. Pr esum ably deposition output from the CMAQ m odel will be m a pped on to th e sensitive a r eas, f o r in s t ance. Are th e spatial s cales com p arable ?

Step 6 (Section 3.6) :

The goal of creating response curves needs m o re explanation. Is the goal to identify thresholds, or iden tif y inf l ection po ints ? W h at’s a desir e d ex posure endp oint? How will, or how could, published loading experim e nts be used to help id entif y respo n se curves ?

An exa m ple of “quantifying the link between ch anges in ecosystem indicators and ecosystem services” w ould m a ke easier a discussi on on the utility of this approach.

68I concur with the idea of using the Millennium Ecosystem As sessm ent’s definition of ecosystem services. I think that parts of the m a pping steps identified on page 55 are a good start:

It m a kes sense to m e that the firs t data layer should be a total (wet + dry) S and N deposition

m a p, apparently generated from CM AQ.

The acidity impact datalayer is p r esu m ably de rived, but from which data or datalayers? And, from here on out w ith the m a pping exercises, the devil is in the details. For exam ple, what are th e common selectio n criter ia ? H o w will the pr evalent ec osystem services be ide n tif ied ? A highlighted exam ple from the Chan et al. 2006 paper would aid this discussion.

The valuatio n of ecosystem services is out of the realm of m y direct expertise, but it seem s to m e that there is always the danger of undervaluing ecosystem services , especially when considering biogeochem i cal cycling of m u ltiple, inte racting e l em ents.

Step 7 (Section 3.7) :

Based on th e heterogeneity in S and N loading, ecosystem sensitiv ity and responses across th e United States, I think it very im portant to include as part of the seconda ry NAAQS a “for m that allows for consideration of regional heterogeneity.”

Resilience ( a nd recove r y ) will n eed to be def i ne d.

The need to rela te am bient concen tra tions with actual deposition loads app e ars ag ain in this section.

In the list of associated is sues, “If total nitrogen...” con centration, content in what?

I agre e tha t it will b e m o st f r uitf ul to do intens ive analyses on sm aller regions.

W ill the pro posed analy s es be done on watershe ds? Or on ecosystem s with som e other boundary and if so, what and why? It would be useful to define boundaries for these assessm e nt areas.

Many, if not all, of the 9 steps en tail s i gnifican t an alysis (which is evid ent to those who will be working on this docum ent, of course). Are all step s equally important to com e to policy relevant conclusions? Is it possible to id entify what the most “sens i tiv e” steps are, m eaning which ones have the greatest influence on th e policy-relevant conclu s i ons . W h at is the rela tive im portanc e of assessing the im pacts of m e teor ological variab ility on loadings and exposures across the US (presum a bly) vs analyzing the relationships be tw een NOx, SOx and other reactive form s of N (in the atm o sphere?)? My assessm ent of the appr oach depends, in part, on answers to these questions.

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