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-08-012

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

. Washington, DC 20460

Subject: Clean Air S c ientific Advisory Comm ittee’s (C ASAC) Peer Review of EPA’s Integrated Science Assessment (I SA) for Oxides of Nitrogen and Sulfur – Env i ronmental Criteria ( First External Revi ew Draft, Decem ber 2007)

Dear Adm i nistrator Johnson:

The Clean Air Scientific Advisory Co mm ittee (CASAC) NO x & SO x Secondary National Am bient Air Quality Standards (NAAQS) Review Panel m e t on April 2-3, 2008 to review EPA’s Integrated Science Assessment (I SA) for Oxides of Nitrogen and Sulfur – Environmental Criteria (First Extern al Review Draft, December 2007) (see Appendix A for th e Panel roster). This letter has been reviewed and approved by the chartere d CASAC at the public co nference call on May 5, 2008 (see Appendix B for the CASAC Roster). W h ile the P a nel views that the first draft ISA was inform a tive, it also found that the first draft did not fully m eet its objec tive. The ISA should be an informative, succin c t, and usefu l summ ary of the eviden ce for consideration in the NAAQS review process. The Panel recognizes that this is a significant undert aking, particularly noting th at this is the f i r s t ef f o rt to c onsider developing standards that m i ght integrate across multiple criteria po llu tan t s as has b e en recomm ended by a number of advisory bodies, includ ing National Ac adem y comm ittees. In this le tte r, th e CASAC Panel f i rs t of f e rs gene ral c o mm ents and recommendations followed by responses to the Agency’s charge questions. Comm ents from the individual Panel m e mbers are provided in A ppendix C.

1. An Executive Summ ary would be valuable. It should bring f o rward the key points and findings from the individual chapters, with em phasis on the summary and conclusions. In addition to highlighting the findings a nd “take hom e” points from the ISA, an Executive S u mm ary would also provide vari ous linkages between the pollutants under consideratio n, their atm o spheric dynam ics, and their environm ental effec t s. Further, the Panel recomm ends that the introductory chap ter also include a ta ble and associated discussion of which effe cts are or are not being addressed in th is NAAQS review and

1why. This table and discussion should also identify where the associ ated inform ation can be found in the ISA and in what other docum ents the effects that are not included are discussed (s uch as the P M ISA). Addition a ll y, a summary of the data and studies tha t would reasonably be used to inform th e setting of the secondary NAAQS should be presented in a second table (or tables). The Pa nel recomm ends that the critical data needs be included both here and in the Con c lusions cha p ter.

2. An issue per tinen t to a ll of the chapters is an im balance in how the various species of total reactive nitrogen 1 (Nr) (which includes oxidized, reduced and organic for m s of nitrog en) a r e tre a ted. A t presen t, th ere is significantly m o re em phasis and inform ation for oxides of nitrogen than for reduced and organic nitrogen com pounds. Greater consideration should be given to the em issi ons, dynam i cs, effects and linkages of reduced and organic nitrogen based on the current and growing reco gnition of the im portance of these form s of Nr in the biogeochem i cal N cy cle with respect to nitrogen enrichm e nt and acidification.

3. The effects of Nr should also be con s ider ed in th e contex t of multi-po llutant, m u ltief

f ects scen arios. Euro pe has been dea ling with sim ilar m u lti-pollutan t , multi-ef f ects challenges. While their approach to policy developm ent differs from the US, m u ch c a n be learned specifically from how the scienc e has supported the developm ent of European policies. F o r exam ple, European as sessm en ts of potential C sequestration in forests include probable enhancem ent of growth as a result of Nr deposition in N-lim ited ecosystem s, which are q u ite comm on. Special at tention should be given to the scientific foundations that led to adopti on of multiple-pollutan t/m ultipl e effects p e rspectives and the concep ts of Critica l Loads and Target Load s in m a nagement of NO x , NH x , VOC, ozone, and PM within the European Uni on. The Panel has provided a number of references for your considera tion in Attachm e nt C.

4. A wide range of “indicators” – including am bient air concen trat ions (gaseous and aerosol), deposition (wet and dry), and environm ental (bi ogeochem i cal) – are discussed in the ISA and will later be ut ilized in the enviro nm ental risk and exposure assessm ents (REA). It would be usef ul to prov ide som e relevant inf o rm ation in the ISA to illus t r a te how som e of these indicators are related to or distinct from others. Application of these indicators and their relationships should be a focus throughout the docum ent. For

exam ple, how do spatial and tem poral patter ns of gaseous S and N com p ounds in the

am bient air com p are to em issions, aeros ol concentrations, or deposition?

Responses to EPA’s Charge Questions :

Atmospheric Sciences and Ecological Exposures

1. To w h at extent is the ev idence on atmo spheric chemis try a nd physics, air quality, and deposition and exposure sufficiently and correctly des cribed, clea rly

1 The term total reactive nitr ogen includes all b i ologically, ph otochem i cally and rad i atively active com p ounds.

2communicated, and relevant to the review of the secondary NAAQS f o r NO 2 and SO 2 ?

2. How w e ll characteriz e d are the rele vant prop erties of the ambient air concentrations and deposition of NO x and SO x , including policy-relevant backgroun d concentrations, spatial and te mporal patterns, and the relationships betw een ambient air co ncentration s and ecolo gical expos u res?

3. How sufficient is the in form ation on atmospheric scien ces and exposures for the purposes of evaluating and interpreting th e ecologica l effects presen ted in Chapter 4 of the draft ISA?

In general, these questions align with Chapters 2 and 3. EPA staff has done a good job identifying the key considerations included in these two chapters and necessary to respond to these charge questions. However, more atte ntion to identifying and quantifying linkages is needed. EPA should also consider com b ining Chap ters 2 and 3 into a single, m o re integrated chapter. This would effe ctively present the in form ation in a “source to exposure” form at which is m o re in line with the organiz a tion of the Draf t ISAs f o r the Prim ary NO x and SO x standards.

The atm o spheric chem istry and physics secti on was sufficient in coverage and clearly communicated, with the exception of the role of ammonia in gas a nd particle phase reactions of the NO x -SO x -NH x system. The air quality discussion wa s hindered by inadequate depictions of the m onitoring networks: m i xing less relevant networks like ozone with SO 2 and NO 2 networks obscured im portant inform ation about SO 2 /NO 2 monitor location and density. The docum e nt concludes th at the exis tin g networks are sufficient, but various networks that could contribute data to asses s concentrations and dep o siti on each have sign ificant shortco m ings. The SO 2 /NO 2 monitors are sparse, prim arily urban, and absent from large parts of the country. Sim ilar problem s plague the particulate m a tter (PM) sp eciation netw ork, which is also prim arily urban and thus poorly suited to char acterize rural and remote areas. Monitoring networks like NADP and CASTNET are cr itic a lly im portant f o r the qu antif ica tion of depositio n and tra c king spatial and tem poral patterns, b u t suffer from gaps in co verage as well, and cann o t accu rately characterize exposure for the broad h e terog e ne ity in sensitiv e ecosystem s. Additional monitoring data exist that ought to be incorporated in this docum e nt and used in the risk

exposure assessm ent (e.g., SEARCH)

. The dearth of a m m onia

, ammonium and organic Nr data is a significant shortcom ing that, while not imm e diate l y re solv able, could be addressed by including a summ ary of data from research studies.

Spatial and tem poral trends in em issions and con centr ation s need to be b e tte r rep r ese n ted in figures and/or tabl es. Em issions of SO x , NO x , N 2 O and NH x need to be better quantified, not only at the national level, but also at the regional level. P r ojecti ons of future em issions should be included in the ISA to put in to p e rsp ectiv e th e future im portance of sulfur oxide and reduced, organic and oxidized nitrogen em issions. Explicit linkages between em issions, am bient concentrations, and deposition should be m a de. EPA should c onsider showing m a ps of SO 2 (and NO x ) em issions adjacent to SO 2 concentrations and SO 4 deposition. The Panel recognizes that this com p arison m a y still be insufficient to p r ovid e the quan titative linkag e s that should ultim ately b e m a de.

3Air quality modeling appears to be essentia l to providing quantita tive linkages between

source em issions and deposition fluxes. The cu rrent treatm e nt of m odel capabilities and

accom p anying uncertain ties in their application shoul d be bolstered. A particular need is to expand discussions of model evaluation and the integration of m odel re sults and observations, which are ve ry lim ited sp atia lly and in term s of s p ecies m onitored.

Acidif icatio n

4. How w e ll are the ma jo r effects o f NO x and SO x on ecological acidification identified and characteriz e d? To what extent do th e discussions and integration of evidence across scales (e.g. species, commun i ties, ecosy stems, and regions) correctly represent and clearly communica te the s t ate of the scien ce?

5. How w e ll has the ISA characteriz e d the relat ionship betw een acidifying deposition levels of NO x and SO x and environmental effects?

6. How w e ll character i z e d is the re la tive im portance of the oxidiz e d and the reduced forms of nitrogen on ecosystem acidification?

The effects of SO x and NO x on ecological acid i fication we re adequate ly identif ied, characterized, and integ r ated across s cales ; howev er, the Panel has identified m odi fications or additions for EPA’s consideration. A conceptual figure illustrating the highlighted processes could be introduced at the begi nning of the docum ent to guide the reader through the entire docum ent. The Agency m a y cons ider identifying direct and i ndirect effects of deposition on acidification . For exam ple, figures s howing the direct links – e.g., depos iti on levels on the x-ax is and acidification response(s) on th e y-axis – would be helpf u l. The im portance of the SO 4 2- and NO 3 - m obile anions needs to be highlighted. Th e Panel would also like the EPA to consider further use of ecosystem functions (production, nu trient cycling, etc.) as response variables to acidifying deposition. T h e discussion of th e natural and anthropoge nic processes of soil acidification should be moved to the beginning of the docum ent. Where possible, point out the likely proportions that are due to natural versus anthropogenic causes. Further consideration

m i ght also be given to adding a discussion on the effects of capacity (ch a nge in soil acidity) and intensity (ch a nges in so il soluti on, natural water). The for m er m i ght take decades whereas th e latter changes m o re rapidly in response to the in puts, outputs and cycling of m i neral acid anions such as including NO 3 - , SO 4 2- and Cl -

.

Under indirect effects, the docum ent should not e that som e important linkages have been

m a de betwe e n acidifying deposition and the inter action of other pollutants (e.g., ozone) and other stressors (drought, pests, or pat hogens), as well as other processe s (fire). Relationships between

em ission and deposition (or lack of such) should be reiterated here. Reduced and oxidized form s of nitrogen were characterized well; though as previously noted, the influence of all f o rm s of reactive nitrogen on acidifi cation (in addition to NO x ) should be balanced.

4Nitrogen Enrichment

7. How w e ll are the ma jo r effects o f NO x as it co ntributes to nitrogen en richment o f the ecosys t ems appropriately identified and characteriz e d? To w h at extent do the discussions and integration of eviden ce across scales (e.g. various species, communities, ecosystems, and reg ions) correctly represen t and clear l y communicate the state of the science?

8. How w e ll characteriz e d are the relationship s betw een ambient atmo s pheric nitro g en concentrations, nitrogen deposition and total nitrogen lo ads, and environmental effe cts?

9. To w h at extent has the draft ISA adequa tely characteriz e d the contribution of oxidiz e d and reduced forms of nitrogen to ecological effects related to nutrient enrichment?

The im pact of nutrient enrichm e nt on terrestr ial and aquatic ecosystem s is a m a jor focus of this first draft ISA. Alt hough adequate attention is given to nutrient enrichm e nt effects of oxidized form s of reactive nitrogen (Nr), m a inly NO x and N 2 O, the tre a tm ent of the environm ental effects of reduced and organic fo rm s of reactive nitrogen (Nr) is in adequate. Increased emphasis on the wet and dry atm o spheric deposition of a m m oni um ion (NH 4 + ), gaseous ammonia (NH 3 ) and inorganic Nr is needed in the S econd Draft ISA.

The Panel also recomm e nds the further deve lopment of the quantitative relationships between atm o spheric con centratio ns of Nr, deposition rates and th e resu lting effects. To the extent practical, linkages between source(s) and effect(s) should be dem o nstrated. As noted previously, additional potential environm ental impacts from Nr-deposition and the resulting nutrient enrichm e nt should be further discussed, in cluding such effects as increased plant growth leading to carbon sequestration (including enhancem ent of pro duction in com b ination with increasing C O 2 ), enhanced fire danger and increased pot ential of windthrow. A further indirect effect is that nutrient en richm e nt will m odif y the nitrog en cycling: includ ed in this modification is the alteration of N inputs and outputs to/from the system as a result of biotic and abiotic factors such as N fixa tion by plants and fires.

Additional case studies should be also a dded to better represent the various U.S. ecosystem s and deposition scenarios. Exam ples for inclus ion in the ISA are the m i xed conifer forests of the San Bernardino Mountains, coasta l sage and desert ecosystem s of southern Calif ornia, which exper i ence h i gh g r adien t s of N depositio n.

Other Welfa r e Effects

10. Several additional effects are dis c ussed, includ ing mercur y methyla t ion, direct g a sphase effects on foliage, and N 2 O as a greenhouse gas. How well does the draft IS A characterize the eviden ce on these topics?

Section 4.4 of the report appropriately described av ailable inform ation and discussion of additional N O x and SO x deposition-related welfare e ffects including the link between

5atm o spheric am bient sulfate and m e rcury m e thyla tion; the direct phytotoxic effects of gaseous nitrogen and sulfur oxides on vegetation (including HNO 3 ); enhanced production of N 2 O fro m N saturation ; and the elevation of nitrate in surface water. The EP A should expand this section to include succinct discussions of the contribution of NO x and SO x to the production of particulate

m a tter and tropospheric ozone. Addition a lly, the Pa nel reco mmends that new sectio ns be added on the relationship betw een nitrogen deposit ion and carbon sequestra tion within natural ecosystem s and im pacts on fires and other poten tial feedbacks. The discussion should include reasoning as to why certain effects are not m o re f u lly consid ered with in the ISA in re gards to evaluating as secondary NAAQS for NO x and SO x . This m i ght sim p ly be recognition that they are fully con s idered els e where in do cum e nts related to other NAAQS. The discussion of

m e thylation should be addressed in the context of the local, regional and global geochem i cal cycling of both Hg and SO x and that the two share comm on s ources. Further, to the extent practical, the ISA should indicate the relative NO x and SO x contribution s to each of the welfare effects listed above (e.g., what fraction of global N 2 O e m ission are attributable to anthropogenic N-enrichm e nt).

Conclusions

11. What are the view s of the Panel o n the appropriateness a nd comprehensiveness of the conclusions drawn in Chapter 5?

12. How adequate is the dr aft ISA for providi ng information and guidance to future exposure, risk and policy assessments that may be prepared in support of this NAAQS re view?

Generally the Panel found that the conclusions, presented in Chapter 5 of the ISA, were logically an d appropriately drawn from the inform ation presented in the preced ing chapters and annexes. In som e cases the concluding m a terial c ould be m o re efficiently organized so that there is better con g ruence between the co nclusions an d the information p r esen ted in the ch apters. Th e Panel noted that the language em ployed is occa sionally m o re subjective or speculative than necessary. It would be more rigorous to em ploy a m o re consistent and liberal use of references to docum ent the concluding statem ents. The Panel al so suggests that a condensed version of the conclusions section be brought forward to the beginning of the ISA doc ument as an executive

summary.

While brevity is desirable throughout this ISA docum e nt, some of the concluding sections were so pared down that they failed to convey m u ch useful inform ation. For exam ple, the summ arization of case studies in Chapter 5 is inadequate to convey much detail about the characteristics of the case study locations, the reasons for their selection, the im plications and signif i can ce of the enviro nm ental ef f ects of S and N depositio n on ecosystem resources and functions in these locations, or the intended future analyses in the environ m ental risk and

exposure assessm ents. Related effects of S a nd N pollutants – such as on m a terials dam a ge, visibility and clim ate forcing – which are not the intended focus of this assessm ent, need to be briefly sum m a rized here, with pointers to loca tions where the relevant infor m ation can be

access e d in other docum ents.

6A key basis for policy decisions is a clear dem ons tration th at introduction of a control strategy (e.g. decreasing Nr a nd S emissions) will produce the desired d ecreases in adv e rse effects. This calls for a dem onstration that the existing evid ence shows links between em issions,

atm o spheric concentration, deposition, water and/ or soil concentration, and harmful effects on ecosystem resources, services and fu nctions. Th is chapte r sh ould be the place at which this crucial set of causal connections are summa rized and judged as to their strength.

The draft IS A provides an appropriate review and summary of the science regarding the effects of S and N deposition on ecos y stem che m is try and b i ology and this will be very helpful for the future risk and policy assessm e nts. However, as noted above, the ISA docum ent would be m o re helpf u l if the implications of all e ffects on ecosystem functions were m o re clearly articula ted. This will p r ovide an ess e ntia l link to the policy a ssessm ent re garding the adversity of these effects.

The degree to which this ISA is going to address econom ic valuation and ecosystem services needs to be clarified. The ISA should sp ecifically note that linkages between ecosystem functions, changes in ecosystem services and ultim a tely to ar ticu l ation of the welfare effects and potential econom i c valuation will be developed in the subsequent risk and policy assessm ents. Econom ic valuation is m e ntioned in the intr oduction to the ISA as a potential m eans to determ ining what constitutes an adv e rse effect , but is not m e ntioned again in the m a in ISA docum ent, except for a lone table in the conclusi ons chapter that lists some econom ic valuation study results and in the Appe ndix (as a review of the current literat ure). It is im portant to clarify that economic valuation is not necessary for an assessm ent of the adversity of an effec t , although if available it would be useful. Further, there was som e discussion as to how far this IS A should go in rega rd s to ecosys t e m f unction-ecosystem servic e link a ges, versus how m u ch will be covered in later docum e nts (e.g., the REA docum en ts). To the degree the ISA does cover those linkages, it should explore m a pping relevant ecosy stem functions (e.g., nutrient cycles, system acidification, productivity) that are affected by Nr and SOx onto specific ecosystem services (ecosys t em services as d e fined by th e Millenni um Ecosystem Assess m e nt for exam ple). The resulting organizational sequence—from e m ission to deposition to effect s on ecological function to iden tifyin g where the affected eco system func tions fit into ecosystem services—m a y provide the sc ientif ic f r am ework f o r th e developm ent, description and valuation of changes in ecosystem services.

In summ ary, the inf o rm ation prov ide d in this first draft ISA needs to be further developed to provide the range of infor m ation desi red to review the secondary NAAQS for NO x and SO x . The need f o r the quantita tive li nkages between ambient air qualit y, depositional fluxes, and the resulting ef f ects to the e x tent practical cannot be overs ta ted. This applies to not only nitrogen and sulfur oxides, but reduced and or ganic form s of nitrogen as well.

7The CASAC NO x & SO x Secondary NAAQS Review Pane l was pleased to review the f i rst draf t of the ISA for Oxides of Nitrogen and Sulfur – Environmental Criteria . W e look forward to review of the second draf t and wish you well in this im portant endeavor.

Sincerely,

/Signed/ /Signed/

Dr. Ar m i stead (Ted) Russell, Chai r Dr. Rogene Henderson, Chair CASAC NO x & SO x Secondary Clean Air S c ientific Advisory Comm ittee NAAQS Re view Panel

Enclosures

8Appendix A: Roster of CASAC NO x & SO x Secondary NAAQS Revie w Panel



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

### & S O x 

### Secondary NAAQS Review Panel

CAS AC M E MBERS

Dr. Armiste a d (Ted) Russell (Chair) , Professor, Departm e nt of Civil and Environmental Engineering

, Georgia In stitu te of Technology, Atlan t a, GA

Dr. Ellis B. Cow ling , University Distinguished Professo r At-Large Em eritus, Colleges of Natural Resources and Agricultur e and Life Sciences, North Caro lina S t ate University, Raleigh, NC

Dr. Douglas Cra w ford-Bro wn , Professor Em eritus and Director Em eritus, Departm e nt of Environm ental Sc iences and Enginee r ing and UNC Institu te f o r the Envir o nm ent, University of North Carolina at Chapel Hill, Chape l Hill, NC

Dr. Donna Kenski, Data Analysis Director, Lake Mi chigan Air Directors Consortium, Rose m ont, IL

PANEL M E MBERS

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

Dr. Andrz e j Bytnerow i cz , Senior Scientist, Pacific Southw est Research Station, US DA Forest Service, Riv e rside, CA

Ms. Lauraine Chestnut , Managing Econom ist, Stratus Cons ulting Inc., Boulder, CO

Dr. Charles T. Driscoll, Jr. , Professor, Environm ental System s Engine ering, College of Engineering and Com p uter Science, Syracuse Un ivers ity, Syracuse, NY

Dr. Paul J. Hanson , Distinguished R&D Sta ff Mem b er, Environm ental 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 & T r end Analysis (CAPITA), Washington University, St. Louis, MO

Dr. Dale Johnson , Professor, Departm e nt of Environm en tal and Resource Sciences, College of Agriculture, University of Nevada, Reno, NV

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

9Dr. Myron Mitchell , Distinguished Professor and Direct or of Council on Hydrologic System s Science, College of Environm ental and Forestr y, State University of New York, Syracuse, NY

Mr. Richard L. Poirot , Environm e n tal Analyst, Air Pollutio n Control Division, Departm e nt of Environm ental Conservation, Verm ont Agency of Natural Resources, W a terbury, VT

Mr. David J. Shaw , Di rector, Division of Air Resources , New York State Departm e nt of Environm ental Conservation, Albany, NY

Dr. Kathleen Weathers , Senior Scientist, Institu te of Ecosystem Studies, Millb rook, NY

SCIENCE ADVISORY BOARD STAFF Ms. Kyndall Barry , Designated Federal Officer, 1200 Pennsylvania Avenue, NW 1400F, W a s h ington, DC, Phone: 202-343-9868, Fax: 202-233-0643, (barry.kyndall@epa.gov)

10Appendix B: Roster of the chartered CASAC



### U.S. Environmental Protection Agency Science Advisory Board (SAB) Staff Office Clean Air Scientific Advi sory Committee ( CASAC)

CAS AC M E MBERS

Dr. Rogene Henderson (Chair ) , Scientis t Em eritus, Lovela c e Respira t or y Research I n stitu te, Albuquerque, NM

Dr. Ellis B. Cow ling , University Distinguished Professo r At-Large Em eritus, Colleges of Natural Resources and Agricultur e and Life Sciences, North Caro lina S t ate University, Raleigh, NC

Dr. James D. Crapo , Professor, Departm e nt of Medi cine, National Jewish Medical and Research Center, Denver, CO

Dr. Douglas Cra w ford-Bro wn , Professor Em eritus and Director Em eritus, Departm e nt of Environm ental Sc iences and Enginee r ing and UNC Institu te f o r the Envir o nm ent, University of North Carolina at Chapel Hill, Chape l Hill, NC

Dr. Donna Kenski, Data Analysis Director, Lake Mi chigan Air Directors Consortium, Rose m ont, IL

Dr. Armiste a d (Ted) Russell , Professor, Departm e nt of Civ il and Environm ental Engineering, Georgia Institute of Technology, Atlanta, GA

Dr. Jonathan Samet , Professor and Chairm an, Departm e nt of Epide m iology, Bloom b erg School of Public Health, Johns Hopkins University, Baltim ore, MD

SCIENCE ADVISORY BOARD STAFF Mr. Fred Butterfield, CASAC De signated Federal Officer , 1200 Pennsylvania Avenue, N.W

., Washington, DC, 20460, Phone : 202-343-9994, Fax: 202-233-0643, ( butterfield.fred@epa.gov )

11Appendix C: Com p ilation of Indivi dual Panel Mem b er Comments on EPA’s Integrated Science Assessment (ISA) for Ox ides of Nitrogen and Sulfur – Environmental Criteria (Decem ber 2007)

Comments receiv e d:

Dr. Praveen Amar

............................................................................................................... ........ 13 Dr. Andr z e j Bytnerow i c z ........................................................................................................ .... 18 Ms. Lauraine Chestnut

.......................................................................................................... ..... 24 Dr. Ellis B. Cow ling

........................................................................................................... ......... 26 Dr. Douglas Craw ford-Brow n ................................................................................................... 31 Dr. Charles T. Driscoll, Jr.

................................................................................................... ...... 35 Dr. Paul J. Hanson

............................................................................................................. ......... 57 Dr. Dale Johnson

............................................................................................................... .......... 65 Dr. Donna Kenski...............................................................................................................

......... 71 Dr. Naresh Kumar

............................................................................................................... ....... 75 Dr. Myron Mitchell

............................................................................................................. ........ 78 Mr. Richard Poirot

............................................................................................................. ........ 87 Dr. Armistead Russell

.......................................................................................................... ....... 95 Mr. David Shaw

................................................................................................................. ....... 101 Dr. Kathleen Weathers

.......................................................................................................... ... 107

12

### Dr. Praveen Amar

This write u p addresses the first three charge questions from NCEA. The Charge Questions are reproduced below:

1. To what extent is the evidence on atmos pheric chemistry and physics, air quality, and deposition and exposure suffi ciently and correctly descri bed, clearly com m unicated, and relevant to the review of the secondary NAAQS for NO 2 and SO 2 ?

2. How well characterized are the relevant prope rties of the ambient air concentrations and deposition of NOx and SOx, including policy-re levant background concentrations, spatial and temporal patterns, and the rela tionships between ambient air concentrations and ecological exposure?

3. How sufficient is the informa tion on atmospheric sciences and ex posures for the purposes of evaluating and interpreting the ecolo gical effects presente d in Chapter Four of the draft ISA?

Response:

Chapter 2 ( The Atm o spheric Chem istry and Phy s ic s of Nitrogen and Sulfur Oxides, as well as Annex AX1 with the same Title), and Chapter 3 ( Ecological Exposure to Oxides of Nitrogen and Sulf ur, and to Ammonia and am monium , as well as Ann e x AX2 with the sam e Title ) provide a reasonably detailed de scription of the atmospheric sc ience, air quality, deposition, and exposure. H o wever, the Chapters can and shoul d be im proved for m o re clear communication. It is understandable that various se ctions have different authorship s. These Chapters and other chapters in the ISA would therefore benefit from t h e services of an expe rt technical/sc i entif ic edito r resu lting in a m o re readab le IS A that m o re clearly com m unicates th e im portant findings of these Chapters (as well as other chapters ).

Specific Comments to improve th e ISA are provided below:

Page 2-2: Line 8: It is importa nt to state the m o re im portant point first, followed by a m i nor point. Ammonia is included in this ISA, first because of its role in NOx and SO 2 chem istry, and its role in ni trification, and, second (and a distant second!), because its oxidation can be a m i nor source of NOx. There are other parts of this ISA th at do suffer from the sam e issue. That is, first order issues should be mentioned first.

A General comm ent about tim e scales of various chem icals/reactions: The ISA does a very good job of providing tim e scales of various reactions a nd species. However, it woul d be very useful if

m a ny of these im portant reactions’ tim e scales are presen ted in a single Table, where readers can

com p are them in one place and dr aw m eaningful conclusions.

Page 2-4: Line 17: P (O 3 ): Ozone Production Efficiency: It is an im portant concept. However, I do not think it is clearly define d in the docum ent (as num ber of m o lecules of ozone produced per

13molecule of NOx over a certain tim e period and over a spatial extent, etc.). I suggest it should be explicitly defined first tim e it appears.

Page 2-7 (Lines 22-23): Awkward and an out-o f-contex t reference to the fact that NO 3 deposition is a “com p lex function of wind speed.” W h at does this m ean? Needs an explanation.

General Comment about Section 2.2 .2: Halogen Che m istry in the Ma rine Layer: This section is written rather poorly and seem s to be out of context with the m a in the m e of SO 2 and NOx chem istry. I found it hard to follow. If it has im portant im plications for the deposition of nitrogen and sulfur com pounds on coastal and non-coasta l/regional scales, they should be stated.

Page 2-9, General Sulfur Chem istry: Besides SO 2 , SO 3 though sm all in amount com p ared to SO 2 (about 1 to 3 percen t of total em itted SOx in stack s) has been known to cause visib i lity degradation (“Blue plum e” downwind of large power plants burning high sulfur coal, and equipped with pollution controls of SCR and FGDs). It needs to be addressed here or in the PM docum ent.

Page 2-10: Line 1: It is stated that aque ous-phase oxidation of SO 2 is responsible for about 80% of

the tota l o x idation (im p lying th at the re m a ining 20 percent is by hom ogeneous gas phase oxidation or by m e tal-catalyzed reac tions). However, the ISA should note that the s ituation is lot

more com p l e x than that. For exam ple, which of the various oxidation pathways dom i nates depends on the details of the local accum u lation of the co-pollutants such as ozone, hydrogen peroxide, hy drocarbons, ammonia, a nd catalytic m e tals ( Fe, Mn, and oth e rs). This will h a ve an im pact on final deposition levels of sulfur.

Page 2-14: A clear explanation of S (IV) and S (VI) would be helpful.

Page 2-21: S ection on Satellites: A comment sim i l a r to the comment on Halogen Chem istry above. This section appears to have been written out-of-context and needs to be integrated with the larger context of estim ating ecological exposures to S and N deposition and how satellite data

m a y be helpful in providing total loadings of S and N on larger scales th at only satellites can provide. Sam e comment on Table 2.6-1. Ma y be, the Table needs to be removed.

Page 3.2: SOx Em issions: Lines 14-18: The statem ent that sources other than electric utilities “m ake only a very m i nor contribution” to overall SO 2 e m issions is quite inaccurate and needs to be corrected. In 2003, the non-EGU sources in the US contributed 31% of the total SO 2

em issions (at 5 mm tpy com p ared to about 11 mm tpy for EGUs). For exam ple, industrial, commercial, and institutional (IC I) boilers burning coal and oil produce about one mm tpy of SO 2 in the US. Sa m e text appears in the Annex and needs to be correct ed. Also, the Summ ary (page 3-59 ) needs to be corrected.

Page 3.9 NH 3 Em issions, Lines 23-28: Very awkward de scription of ammonia em issions. ThreeWay catalysts and amm o nia em ission from the m are NOT the prim ary source of ammonia, and therefore, a description of a m m onia em issions must start with known large sources of a m m onia (liv estock and agricu ltu ral operation s). Pleas e rewrite for m o re effective communication and drop the words “for these reasons.. .”

14A potentially im portant point a bout ammonia em issions is the geographic shift in ammonia

em issions th at seem s to have taken p l ace in the U S between 1980s and late 1990s and m a y still be accelerating. The attached slid e, courtesy of Dr. Bruce Hicks, NOAA, shows that the “center of a m m onia em issions” m a y be shift i ng from Mi dw est to th e Southeast an d the Carolinas. That is, amm onia em issions (in N kg/ha) have increased by about 2 to 3 Kg/ha in the Southeast and gone down by 1 to 2 kg/ha in the Midwest. This shift in density of ammonia em issions has obvious im plications on the regional atm o spheri c chem istry of SOx, NOx, and ammonia and the resulting regional wet and dry deposition patterns for both sulf ate and nitrates. ISA should address the impact of this potential trend in geographic change in amm oni a em issions.

Page 3-10: S ection 3.4: E v aluating E m ission Invent ories: The ISA should note that the first step to evaluate em ission inventories is not by looking at the am bient c oncentrations. The first step in evaluating reliab i lity an d accuracy o f e m ission inventories n eeds to ta ke into account the

m e thods and procedures that are used to pr oduce em ission inventories them selves (use of

em ission factors, use of CEMs, QA/ QC m e thods , un certainty in determ ining spatial and tem poral profiles, speciation factors for VOCs and prim ary PM em issions, etc.).

Page 3-11, Section 3.5.2 NO2: Say “NO 2 interac t ion with veg e tation is M O RE DIFFICULT TO UNDE RST AND than ....”

Page 3-16 Line 10: Not clear a bout the distinction between “aer osol-phase” and “solid-phase”. Are they not the sam e in the context of atm o sphe ric chem istry of aerosols?

Page 3-16, Line 7: “Title IV Reductions in NOX and SO 2 ” and not N and S.

Page 3-17, Figure 3.6-3 : The Title n e eds to be m odified to ind i cate that the Figure also shows trends, if any (2002 to 2006).

Page 3-19, Lines 8-10: Pleas e rewrite for clarity.

Page 3-21: S a tellites: sam e comment as above . P l ease note the larger context of S and N deposition.

Page 3-34: S ection 3-9: Harvar d Forest: I have a comment sim ilar to the comment on Halogen Che m istry above. It reads as an independent pie ce without being integrated into the ISA. It is too long and not clear. Pleas e shorten it and rewrite.

Page 3.12 PRB Concentrations of NOx and SOx: This is well-written se ction and does a very good job of responding to the Charge Ques tion 2 on the subject of PRBs of NO 2 , SO 2 , and nitrate and sulfate deposition over various regions in the US and at different tim e scales.

Page 3-43 Regional-Scale CTMs, Also Annex AX-2 (AX2.10.1.1, Page AX2-62): The text notes that the capabilities of a num b er of CTMs designed to study local and regional-scale air pollution problem s were summ arized by Russell and Denn is (2000) and by othe rs, including Arnold (2003), etc. What is m i ssing is the reference to recent peer reviews of the CMAQ system itself.

15The ISA needs to recogn ize th at CM AQ m odeling system has been extensively peer-reviewed. The ISA docum ent should refer in Chapter 3 and in Annex AX-2 to the three detailed written reports of the external peer review panels. It w ould also be useful to in clude a short summary of the m a jor findings of the peer review reports that were published by the CMAS in years 2003, 2005, and 2007. They are available on CMAS we bsite ( www.cm ascenter. o rg ). The th ree references (they should be included bo th in Chapter 3 and Annex AX-2) are:

1. Am ar, P., R. Bornstein, H. Feldm a n, H. Jeffr ies, D Steyn, R. Ya m a rtino and Y. Zhang, 2004: Final report: December 2003 Peer Review of the CMAQ Model . Report su bm itted to C M AS Center, University of North Caro lin a at Chapel Hill, July, 2 4 pp.

2. Am ar, P., D. Chock, A. Hansen, M. Moran, A. Russell, D. Steyn and W. Stockwe ll, 2005: Final Report: Second Peer Review of the CMAQ Model . Rep o rt subm itte d to CMAS Center, University of North Carolina at Chapel Hill, July, 33 pp.

3. Aiyyer, A., D. Cohan, A. Russell, W. Stockwe ll, S. Tanrikulu, W

. Vizuete and J. W ilczak, 2007: Final report: Third Peer R eview of the CMAQ Model . Report sub m itted to CMAS Center, University of North Carolina at Chapel Hill, February, 25 pp.

A General Comm ent on Dry Deposition: The IS A need s to be m o re clear and explicit that we only ESTIMATE dry deposition and therefore co mme nts about total depo sition (wet and dry) and about th e relativ e co ntribu tion of each pathw a y have a level of uncertain ty that is hard to determ ine.

In summ ary, Chapters 2 and 3 and annexes a ddress the firs t three charge questions on

atm o spheric science and ecological exposure in a satisfactory m a nner. However, the whole docum ent needs a thorough technical and scientific editing job as we ll as a better integration of

som e of the sections (Halogen Chemistry, Harvard Forest, sa tellites u s e) into the ove r a ll ISA.

Chapter 5: Findings and Conclusions

General Comment: This Chapter does a good j ob of summ arizing the ISA with m a jor “take hom e” m e ssages. As noted above for Chapte r 2 and 3, this Chapter does need a thorough scien tif ic ed iting job f o r it to communicat e com p lex concep ts in a clear m a nner.

Specific Comments follow:

Page 5-2 Section 5.2.2: The conclusion drawn here that current routine monitoring is “adequate” or ‘f ully ad e quate” af te r listi ng m a jor problem s with m easurem ent of gase ous and particulate species does not seem to be ju stif ied. I think it is a m a tter of tone and the revised language should indicate W H Y the current network is adequate.

16Page 5-3 Line 30: Please see th e co mments for Chapter 2 ab out SO 2 em i ssions from sources other than p o wer plants. They are no t “very li ttle, ” since they are a bout 1/3 of the total SO 2

em issions.

Page 5-11: Lines 20-31: Not cl ea r why there is n o rela tions hip between recent trend in N deposition and trends in nitrate con c entrations in surface waters. Have th e recen t red u ctions in NOx e m issions in the eastern US because of the “NOx SIP Ca ll” taken into account?

Page 5-36: Line 20: Please s ee m y comm ent above on “adequate m onitoring.” Here, it says that the m onitoring networks are “inadequ ate.” Need to be consistent.

Geographic Shift in Ammonia Em issions

(courtesy of Bruce Hicks, NOAA)

17

### Dr. Andrz e j Bytnerow i cz

General Co mments :

Chapter 4 is well written and com p rehensive and presents state of the scientific knowledge on ecological effects of acidification, nitrogen nutrient additions and other welfare effects of N and S. The chapter is very in for m ative an d is ba sed on the relevant and current peer-reviewed literature from North America and Europe.

Having said this, I would like to sugg est th at N effects are p r esented in a context of m u ltipollutant, multi-effects scenarios. Exam ple of suc h an approach is the 1999 Gothenburg protocol of the UN Convention of Long-range Transport of Air Pollutants recommending evaluation of the com b ined effects of NOx, SOx, NH 3 , and VOCs on acidificati on, eutrophication and ground levels ozone im pacts (Working Group on Effects, 2004).

Specific co mments :

Page 4-4, Figure 4.1.-1. should be changed to Table 4.1.-1. Why eutrophication is not shown as a possible disturbance if forests? In row 7 (atmospheric pollutant), the end products of deposition are show n, but not the pollutants causing biological effects (e.g., NO 2 , SO 2 , HNO 3 , NH 3 , particulate NO 3 , particulate N H 4 ).

Page 4-5, point 7 – ammonia (NH 3 ) should be listed as well.

Page 4-9, Figure 4.2-1 m i xed up wi th Fig. 4.2-2.

Page 4-13, lines 12-27. E l evated levels of tropos pheric ozone and land disturbances such as

catas troph ic f i res or with dthrows should be m e ntioned as factors affecting water resources of ecosystem s and their leaching potential.

Page 4-22, lines 25-27. T h is could be a good r ecommendation for future research needs.

Page 4-29, lines 27-28. Reduced cold tolera nce is also caused by euthrophication.

Page 4-35, line 14. These effects on epiphytes , if I recall, were also caused by NO 2 and SO 2

. Page 4-35, section 4.2.2.2.3. The described effects ar e to a large extent no t caused by acidity but direct tox i c effects of SO 2 on plants.

Pages 4-38 through 4-44. Change SO 4 + to SO 4 2-

. Page 4-66, lines 26-28. Reference is needed.

18Page 4-73, lines 28-32. It is a very important statem ent – clearly no single “definitive” critical load for US ecosystem s is possible. The eco-reg ional approach to the CL issue seem s to m a ke

most sense.

Page 4-98, lines 15-17. Is it contribution of gaseous HNO 3 or of total dissolved NO 3 - ?

Page 4-121, lines 18 -20. In regard to changes in lichen species com position, there are differences in responses to reduced vs. oxidized N. It ha s been proposed that elevated levels of HNO 3 have negativ e effects on sen s itive lichen s such as Ramalina menziesii in the San Bernardino Mountains of southern California (Riddell et al., 2008). Such effects are attributed m o re to the direct HNO 3 toxic ity th a n NO 3 - deposition. There is also a hi gh probability that the reduced N resulting from high NH 3 and particulate NH 4 + could affect lichens downwind of the Los Angeles pollution sources area (Prof. Eva Barreno, persona l comm unication). H o wever, it has to be

rem e m b ered that the dis a ppearance o f lichens in southern California c ould also be caused by high levels of a m bient ozone in the area (N ash and Sigal, 1998; Sigal and Nash, 1983).

Page 4-122, lines 20 -26. It should b e added that increas ed m o rtality of the high elev ation trees in areas of elev ated N depo sition c ould be partially caused by their in creased sensitivity to frost.

Page 4-129, section 4.3.3.1.4. This se ction should be incorporated into the forests section (4.3.3.1.1) (see m y re m a rks below).

Page 4-131, section 4.3.3.1.6. This sec tion should be divided and m oved i n to “forests” and “arid & sem i -arid ” ecosystems (see m y rem a rks below).

Page 4-147, lines 28-30. Transiti onal ecosystem s (as m e ntioned in the previous sentences) should also be added.

Page 4-152, lines 15-18. I do not s ee a logical link here. If es tuaries and coastal water are inherently sensitive to increased N loading, this is not because of the high releases of N inputs back to the atm o sphere (high m i crobial activity). Increased release of N into the atm o s phere can be considered as an avoidance m echanism in the presence of excessiv e N loads.

Page 4-154, lines 21-24. Ranges of de position that m a y be affecting sensitive species seem to be

m i xed up – levels in alpine ecosystem s should be lo wer than in othe r terrestrial ecosystem s cited in this ISA docum ent (see Baron et al. 2000; Bowm an et al., 2006).

Page 4-162, line 8. S deficiency level at <80 μg/g seem s to be very low. In Scots pine f o liage in the pristine area of Europe the lowest recorded level of S was ~400 μg/g (Molski et al., 1981).

Page 4-176. Section on the direct effects of HNO 3 on plants should be considered and possibly added.

Page 4-180, Table 4.2-2. Add “of” after “Exam p le”.

Page 4-186, Table 4.2-9. Change “eith” to “with” in the second line.

19Page 4-189. Table 4.3-2. in the column “Factors that govern vulnerability”, add a sentence “Interactions with other contributin g stres s ors su ch as elevated le vels of ozone or drought”.

Replies to the assigned questions:

7A. How well are the m a jor effects of NOx as it contributes to nitrogen enrichm e nt of the ecosystem s appropriately identified and characterized ?

Generally the effects of NOx c ontribution to the N enrichm e nt of various ecosystem s are well describ e d. T h ese effects are div i ded into the terr e s trial, trans i tional, aqu a tic (f resh water and

estuar ine an d coasta l wa ter) ecosys t e m s. Two case studies (a lpine and sub

- alp i ne communities in Colorado an d in Chesap eake Bay) are describe d. Som e other case stud ies could be possibly added – such as the m i xed conifer forest of the S a n Bernardino Mountains (Fenn and Poth, 1999; 2001; Fenn et al., 2003) and grassland ecosystem s in the San Francisco B a y area (W eiss, 1999).

7B. To what extent do the discussions and inte gration of evidence acro ss scales (e.g.. various species, communities, e c o system s, and regions ) c o rrec tly repr esent and clearly communicate the state of science?

Generally the effects (biogeochem i cal processes and biological eff ects) have been described (as in point 1 ) f o r the ter r estria l, tr ansitio nal and a quatic ecosystem s from a pe rspec tive o f the ef f e cts indicators. S o m e confusion is caused by placing herbaceou s and plants and shrubs (4 .3.3.1.4) and mycorrhizal and m i crobial activity (4.3.3.1.6) into separate sections. Inform ation contained in those sections should be incorporated into the forests (4.3.3.1.1) a nd arid and sem i -arid ecosystem s (4.3.3.1.3). Lichens could stay alone si nce their evaluation surveys have been done mostly for larger geog rap h ic areas en com p assing various ecosystem s (often including agricu ltu ral or the urb a n

- wildland in terf ace ). W h at is m i ssing are the desert ecosystem s – effects of N deposition in these N-lim ited sy stem s, especially in the vicin ity of strong N sources areas, should be mentioned. A good exam ple is the Moja ve Desert in California which is strongly af

f ected by N depositio n f r om the Los Angeles a r ea. Ther e ar e only a f e w ref e rence s r e f e rring to those problem s , however, research is ongoing at the University of California in Riverside (Allen et al., 2008).

8. How well characterized are th e relationsh i ps b e tween am bient atm o spheric n i trogen concentrations, nitrogen depos ition and total nitrogen loads, and environm ental effec t s?

These relationships are not well described. This is m a inly ca used by a lack of sufficient understand ing of these relationship s

. Understand ing respons es of ecosystem s to N addition are often based on fertilization e xperim e nts, using m a inly NH 4 NO 3 or (NH 4 ) 2 SO 4 additions and

assum i ng that these additions would sim u late wide spectra of atm o spheric N deposition scenarios. More experim e nts on natural N depos ition g r adien t s, with th e a d equate ly id entif ied N

com ponents (gases, aeros o ls and solu ble ions ), sh ould be con ducted. Dep o sition of N to forest ecosystem s is calculated mostly from throughfa ll data with an assum p tion that wet and dry deposition com ponents are included. Th is approach has been used at large scales in Europe and helped in calculating critical lo ads for N and S deposition and acidity (ICP Forests and ICP Maps

20and Modelin g products ). However, the N dry depos ition component, especially when there is not sufficient precipitation to rem ove N deposited on foliage and other surf aces to throughfall solution, m a y be grossly m i scalculated. The in ferential m e thod (using inform ation on ambient concentratio ns of m a jor N depositio n drivers, th eir depos itio n velocity as well as can opy characteristics, such as leaf area index, LAI) m a y be helpful in such cases. This m e thod could also be applied in such ecosystem s (grasslands, deserts, alpine and sub-alpine ecosystem s ) where throughfall cannot be used at all or is very difficult to be app lied. The inferential m e thod has

num e rous lim itations and uncertainties; however, it can b e us ed for larg e geographic areas. This

m e thod is the basis for the CASTNET estim ates of N dry deposition at th e nation a l scale. It has to be rem e mbered, however, that ther e is not enough data for ambient NH 3 , which is one of the

m a in drivers of N dry deposition. In additi on, un derstand ing of N deposition in com p lex (m ountain) terrains is still poor.

9. To what extent has the draft ISA adequately ch aracterized the cont ribution of oxidized and reduced form s of nitrogen to ecological effects related to nutrien t enrich m e nt?

Contribution of reduced vs. oxidi zed for m s of at mospheric nitrog en to nutrient enrichm e nt effects are not well understood and subsequently not well described in the ISA. The main reason for that is an inadequate unders tanding of the chem ical environm ent of ecosystem s for which the effects of N deposition are be ing described. As I m e ntioned above, m o st of knowledge on the ecosystem responses com e s from the fertilizer studies. Such experim e nt s are well suited for understanding biological effects of N in the wet deposition dom i nated ecosystem s , such forests in the eastern United States. However, in the ar id and sem i -arid ecosystem s, where large portion of N deposition m a y result from gaseous HNO 3 , NH 3 or particulate NO 3 - or NH 4 + , f e rtiliza tion experim e nts m a y quite poorly m i m i c the real-wor ld interactions between the atm o sphere and ecosystem s (vegetation, soils a nd surface water com ponents).

Recommen d ations :

1. W h ile SO 2 and NOx concentrations should be m o nitored for health reason (prim a ry standards), they have very lim ited app lication for evaluation of environmental (ecolog i cal) effects. Therefor e there is a need for monito ring concentrations of m a jor drivers of N & S deposition. For S, this is m o stly SO 4 in wet precipitation m e asured nationally (e.g. NADP network). Ho wever, for N, not only wet NO 3 and NH 4 deposition (also m easured nationally), but al so dry deposition of gaseous HNO 3 , NH 3 and particulate NO 3 and NH 4 as well as the organic com pounds s hould be included. Activities of the national m o nitoring networks, especially CASTNet should be continued and expanded, especially in the underrepresented Western US. 2. For prelim inary determ ination of HNO 3 and NH 3 “hot spots”, use of passive sam p lers should be considered. Passive sam p lers ha ve already been successfully used in monitoring networks in California: Sequoia National Park (Bytnerowicz et al., 2003), Lake Tahoe (Gertler et al., 2006), or Jos hua Tree National Park (Allen et al., 2008). 3. National ef forts in ecolo gical m onitoring of N & S deposition effects are needed. Suc h efforts could be sim ilar to those in E u r ope under the auspices of the UN Econom ical Comm ission for Europe, nam e ly the ICP Fo rests Level and ICP Modelling and Mapping efforts. Monitoring results from the ICP Forests Level II plots have allowed for

21determ inatio n of CL and their exceed ances. The n e wly develo ped network for CL estim ates on 17 US Forest Service E xperim e nt al Forests and additi onal 4 sites across the US will help to dete rm ine if the CL approach cou l d be applie d and be pra c tic al in the US. Research co llabo ration within th e US and with the Canadian and European partners is planned. If successful, the m onitoring efforts in the US FS could be expanded into a denser national network. It is envis i o n ed that US FS Forest Inventory and Analysis (F IA) Phase 3 (Forest Health Monitori ng) sites could be utilized. The Intens iv e Site Mon i toring (ISM) s ite th at would in tegrate the FIA Phas e 3 and the ICP Forests Level II-type plots will be estab lished in the San Bernardino M ountains of south e rn Californ i a in summ e r 2008. 4. Effective collabo ration b e tween EPA, vari ous national m onitoring networks, and land

m a nage m e nt agencies such as US Forest Serv ice or National Park Se rvice, in developing a national program for mon itoring an d evaluation of N & S effects on eco system s, including CL calculations, should be encouraged.

References :

Allen, E.B., L. E. Rao, R.J. Steers, A. Bytnerowicz, and M.E. Fenn. 2008. Im pacts of

atm o spheric nitrogen deposition on vegetation and soils in Joshua Tree National Park. In R.H. Webb, L.F. Fensterm aker, J.S. Heato n, D.L. Hughson, E.V. McDonald, and D.M. Miller, eds. The Mojave Desert: Eco s ystem Processes and Sust ainability. University of Nevada Press, Las Vegas. In press. Báez, S., Fargione, J., M oore, D.I., Collins, S.L., and Gosz, J.R. 2007. Atmospheric n itrog en deposition in the northern Chihuahuan desert: Te mporal trends and poten tial consequences. J. Arid Environ. 68, 640-651. Bytnerowicz, A., Tausz, M., Alonso, R., Jone s, D., Johnson, R., and Grulke, N. 2002. Summ ertim e distribution of air pollutants in Sequoi a National Park, Califor nia. Environm ental Pollution, 118, 187-203 Fenn, M.E., Haeuber, R., Tonnesen, G.S., Baron, J.S., Grossm an-Clarke, S., Hope, D., Jaffe, D.A., Copel a nd, S., Geiser, L., Rueth, H.M ., and Sickm a n, J.O. 2003. Nitrogen em issions, deposition, and m onitoring in the wester n United States. BioScience 53, 391-403. Fenn, M. E ., and Poth, M. A. 1999. Tem por al a nd spatial trends in stream water nitrate concentrations in the san Bernardino Mountains , southern California. J. Environ. Qual., 28, 822-836. Fenn, M. E., and Poth, M. A. 2001. A case study of nitrogen saturation in westen U.S. forests. Sci. W o rld J., 1, 433-439. Gertler, A., Bytnerowicz, A., Cah ill, T. A., Arbaugh, M ., Cliff, S., Kahyao ğ lu-Kora č in, J., Tarnay, L., Alonso, R., and Fraczek, W

. 2006. Local air quality thre atens L a ke Tahoe’s clarity. California Agriculture, 60, 53-58. Molski, B., B y tnerow i cz, A

. , and Dm uchow s ki, W

. 1981. Conte n t of sulphur and fluorine compounds i n Sc ots pi ne needles as a n indicat or of air pollution in P o land. S ilva F e nnica, 15

, 4, 419-421. Nash, III, T. H., and Si ga l, L. L. 1998. Epiphyti c lichens i n the Sa n Be rnardiono Mountains in relation to oxidant gradients. In: Miller, P. R ., McBride, J. R. (eds.) Air Pollution in the Montane Forest of Southern Californi a. A Ca se St udy of the San Bernardi no Mountai ns. Ecol. Stud., vol. 134, Springer , Ne w Yor k, 223-234.

22Riddell, J., Nash III, T. H., and Padg ett, P. 2008. Th e effect of HNO 3 ga s on the lichen Ramalina menzie sii . Flora, 203, 47- 54. Sigal, L. L., and Nash, III, T. H. 1983. Lichen co mmunities o n conifers in southern California: an ecological survey relative to oxidant air pollution. Ecology, 64, 1343-1354. Working Group on Effe cts. 2004. Review and Assessm ent of Pollution Effects and Their Recorded Trends. UNECE Convention on Long Range Transboundary Air Pollution, Brussels, Be lgium

. Weiss SB. 1999. Cars, cows, and checkerspo t bu tterflies : Nitrogen depos ition and m a nagem e nt of nutrient-poor grasslands for a threat ened species. Conservation Biology 13, 1476-1486.

Some literature citations supporting evid ence of increased w i ndthrow in forests experiencing elevated N depositio n :

Braun, S., Schindler, C., Vilz, R., Fluckiger, W

. 2003. Forest dam a ges by the storm " L othar" in

perm anent observation plots in Switzerland: the significance of soil acid i fication and nitrogen deposition. W a ter, Air and S o il Pollution, 142, 327-340.

Nilsson, C., Stjernsquist, I., Barring, L., Schl yter, P., Jonsson, A. M., Sa muelsson, H. 2004. Recorded storm da m a ge in Swedish fore sts 1901-2000. Forest Ecology and Management, 1999, 165-173.

United Nations Economic Comm isiion for Europe, The Condition of Forests in Europ e , 2005 Executive S u mm ary, ENECE Geneva, 32 pp. ISSN 1020-587X.

23

### Ms. Lauraine Chestnut

Charge question 11 (appropr iateness and com p rehensiv eness of conclusions?)

The review of relevant econom ic valuation studies is included only as an appendix and is not incorporated into the conclusi ons. T a ble 5.5-2 lists som e results of water quality valuation studies in the Chesapeake Bay, but I don' t see discu ssion of this table in th e text. As a result of both of these factors, th e treatm ent of the econo m i c valuatio n literature s eem s disconnected from the rev i ew o f the science. It is no t clear how the review of the econom ics literatu re con t ribu tes and fits into this ISA. Ther e was m e ntion in the introduction that econom ic valuation m a y be helpful in assessing what effects are adverse, but I don' t see any discussion of specifically how the cur r ent litera ture m a y be usef ul in this regard in the appendix or in the findings and conclusions. If the ISA is not going to m a ke the link between harmful effe cts on ecosystem functions to the question of how these trans l ate into welfare effects and ass o ciated econ om ic values, then this should be explained in the in troduction. This link needs to be m a de at som e point in this process, but it m a y be better addressed in the risk and policy a ssessm ents. If this is EPA’s intention, it needs to be stated in the introduction. The ongoing work of the SAB Comm ittee on Valuing the Protection of Ecol ogical System s and Services (C-VPESS) and EPA’s Ecological Benef its Assess ment Strategic Plan should also be cited here as important background m a terials for econom ic valuation m e thods.

It is also importan t to s t r e ss tha t a de term inati on of there being an advers e welfare effect does no t necessarily require that it be quantified in m onetary value terms. Econom ic valuation studies

m a y be helpful in assessing when an affect is ad v e rse, esp ecially for direct use values. However, for total value (including nonuse, bequest, and even som e indirect use values) the public can only assess these values when they are fully inform ed a bout what the changes to the ecosystem resources and functions are, including an unders tanding of the im plications of these changes on the quality of the m a ny e c osystem services that these resources provide. This information and understanding has to have its found ations in the science. The c onclusions in the ISA would be more usef ul if they ar ticu l ated the im plica tions of the changes observed in the various ecosystem s affected by N and S deposition in term s of changes or losses in ecosystem functions.

Charge question 12 (adequate inform ation and guidance for the exposure, risk and policy

assessm ents?)

In reviewing the ISA I kept looking f o r two types of infor m ation that seem to be key to this process of considering secondary standards: 1. What inform ation is th ere th at tells us when a change in an ecosystem m i ght be considered adverse?

2. What levels of depositio n/exposure can a system tolerate with out incu rrin g adverse ch anges ?

Perhaps these questions are to be addressed m o re explicitly in the risk assessm ent phase. I didn' t see them explic itly addr essed in the ISA. A f e w observations rela ted to th e question o f what exposures can be tolerated include:

241. Exposures that can be tolerate d vary for different resources and different locations according to several known characteristics.

2. It will be very hard to say what levels of N deposition can be to le rated wh en ther e are significan t o t her sou r ces in aquatic sy stem s (especially for estu aries )

.

3. The answer m a y be different fo r reco very of currently injure d resources than for prevention of future degradation.

4. The question is com p licated by episodic events (e.g. spring runoff) that cause tem porary but dam a ging increases in exposures.

The ISA notes that the current secon d ary stand a rds for SO 2 and NO 2 were not set to address the effects of deposition, but has the case been m a de that these standards are not sufficiently protective? Perhaps this is obvious , but if current sta ndards are being m e t a nd adverse affects are still occu rr in g, then the standard s are not adequate. Related to this issue is the question of whether adv e rse ef f ects of depositio n will con tinue once the prim ary NAAQS f o r PM and ozone

are m e t. These standards are going to require furth e r redu ction s in SO 2 and NO x e m issions from current levels. At what point in this process does it need to be assessed whether the reductions in deposition that will result will be suf f icient to protect ecosyst em resources, or is this not relev a nt?

25

### Dr. Ellis B. Co w ling

Individual Comments on the First External Review Draft of the Integrated Science Assessment for the Secondary National Air Quality Stan dards for Nitrogen Dio x ide and Sulfur Dioxide

These Individual Comments are developed in the form of responses to most of th e 12 Charge Questions received from Kyndall Barry together w i th the final agenda for our CASAC Pe er Review on April 2, 2008.

Chairm an Ted Russell asked Andrzej Bytnerowicz a nd m e to give special attention to Charge Questions 7-9 in the attached list. T hus I am very m u ch looking forward to com p aring notes with Andrej during our P eer review on April 2, 2008. My responses to m o st of the Charge Questi on are presented below in ordinary type after presentation of the Charge Questions in Bold Type

. 1. To w h at extent is the ev idence on atmos pheric chemis try a nd physics, air quality, and deposition and exposure sufficiently and co rrectly des cribed, clearly communicated, and relevant to the review of the secondary NAAQS for NO 2 and SO 2 ? Chapter 2 of this ISA giv e s a very tho r ough accou n t of the m a jor sources, and the chem ical and physical transport, transfor m a tion, and atm o spheric deposition processes for oxides of nitrogen and sulfur. The sc hem a tic diagram of the cycle of reactive nitrogen in Figure 2.2.1 gives a reasonably fi rm foundation for understanding those parts of the nitrogen cycle that involve oxidized form s of nitrogen.

But this s c h e m a tic diagr a m includes no m e ntion or pictorial illustrations of the huge (m ostly agricultural) sources of reduced and organic for m s of reactive nitrogen that are critical to understandin g bot h the nit r ogen enrich ment and aci dification effects of atm o spherically deposited nitrogen an d sulfur on terr estrial and aquatic ecosy stems.

If EPA is serious about dealing with bot h nutri ent enr i ch m e nt and acidification of ecosy stems induced b y atm o spheric deposition of to tal reactiv e ni trogen, the A g ency needs to include in Chapter 2 of t h e Second Review Draft of this ISA for “NOx” and “”SOx,” a sim i lar schematic diagram for the major sources, transfor mation, transport and atm o spheric deposition processes for reduced and organic form s of reactive nitrogen.

2. How w e ll characteriz e d are the relevant pr op erties of the ambient air concentra t ions and deposition of NOx and SO x, including policy-relevant backgroun d concentrations, spatial and temporal p a tterns, and th e rela t io nships between ambien t air concentrations and ecologica l expo sures?

3. How sufficient is the in formation o n a tmospheric sciences a nd exposures for the purposes of evaluating and interpreting the ecologica l effects presen ted in Chapter 4 of the draft IS A?

264. How w e ll are the ma jor effects o f NOx and SO x on ecological acidification identified and characterized? To w h a t extent do the di scussions and integration of evidence across scales (e.g. communities, eco systems, and regions) correctly represen t and clearly communica te the s t ate of the scien ce? The presentation of current sc ientific knowledge about the e ffects of NOx, SOx, and total reactive nitrogen in Chapter 4 of this First Dr aft ISA is very thorough and com p rehensive. The discuss i on and integ r ation of evidence ac ross scales (com munities, e c o system s, and regions is also reasonably com p lete.

5. How w e ll has the ISA characteriz e d the relatio nship betw een acidifying deposition levels of NOx and SOx and environmental effects?

6. How w e ll characterized is the relative impo rtance of the oxidiz e d and the reduced forms of nitrogen on ecosystem acidification? Although Chapter 4of this First Draft ISA gives a very thorough and wide ranging account of the huge increase in scie ntific understanding of ni trogen enrichm e nt and acidification effects of atm o sphe rically deposited nitrogen and sulf ur on the structure, specific com ponents, functions, and ecosystem services provided by m a ny different ecosystem s in m a ny different parts of this country, the atte ntion given to com p arison of the extent to which these m a ny adverse effects are caus e d by atm o spheric d e position of oxidized and organic form s of nitrogen vs oxidized form s of nitrogen is vanishingly sm all. The truth is that although there are short-term differences in th e rapidity and specific species effects of nitrogen enrich m e nt effects induced by reduced vs oxidized form s of nitrogen, the long-term effects are essen tially indistinguishable. Thus, the most im portant policy relevant decision that needs to be m a de with regard to the Second Draft ISA is to set the stage more adeq uately for consideration of a “Total Reactive Nitrogen” a pproach in a i r qua lity m a nagem e nt in this coun try and to ref r a i n f r om trying to deal only with oxidized form s of nitrogen rather than the sum of oxidized, plus reduced, plus organic form s of reactive nitrogen.

7. How w e ll are the major effects of NOx as it contributes to nitrogen enrichment of the ecosystems appropriately identified and ch aracteriz e d? To what extent do the discussions and integration of evidence acro ss scales (e.g. various species, communities, ecosystems, and regions) correctly represent a nd clearly communicate the sta t e o f the science? The adverse effects of atmospherically depos ited nitrogen and sulfur on terrestrial and aquatic ecos y stem s f a ll into two m a jor categorie s that are reasonably we ll describ e d in this First Draf t I n tegra t ed Sc ience Asses s m ent f o r Oxides of Nitrogen and Sulfur – “Nutrient Enrichm e nt” and “Acidif i cation.” To tal reactive nitrog en dep o sition is the principal cause of

27nutrient enrichm e nt whe r eas both nitrogen and su lfur deposition are th e principal caus e s of acidification in both terrestria l and aquatic ecosystem s.

Notably, however, in the contex t of this CASAC Peer Review of the secondary standards for nitrogen and sulfur oxides, this First Draf t ISA f a ils to d e m o nstra t e th at it is not ju st o x idized for m s of nitrogen and sulfur that induce m a jor a dverse ecosystem effects, but also chem ically reduced and organic form s of nitrogen, and to a lesser extent, also reduced and organic for m s of sulfur. In som e very important parts of the US, atm o spheric deposition of reduced and organic form s of nitrogen are larger in total load of reactiv e nitrog en tha n the to tal lo ad of oxidized form s of nitrogen. The principal sources of oxidized airborne nitrogen and sulfur are com b ustion of fossil fuels used in production of electricity, industrial pr ocesses of m a ny sorts, transportation vehicles, and both commercial and dom e stic hom e and wa ter heating system s. These m a tters are adequate ly c overed in this First Dr af t ISA. But this is NOT tru e f o r the ver y im portant reduced and organic form s of nitrogen. The principal sources of air em issions of reduced and organic for m s of nitrogen are agricultural operations that in clude fertilization of crops and forests, but even m o re im portantly include anim al rearing operati ons (principally chicken, turkey, and egg production units, swine f a rm s, and both beef and dairy cattle far m s) but also including other dom e stic anim als such as horses, goats, shee p, and even com p anion anim als. Municip a l waste handling and processing faci lities and septic tank system s are also important sources of air em issions of a m m oni a and amm o nium ion.

Please see the comm ent written in response to the first Charge Question listed above with regard to the need for a schem a tic diagram si m ilar to Figure 2.1.1, but developed for reduced and oxidized for m s of nitrogen rather th an just for oxidized form s of nitrogen.

8. How w e ll characterized are the relationsh ips betw een ambient atmospheric nitrogen concentrations, nitrogen deposition and total nitrogen loads, and environmental effects? My im pression is that the contributions of i norganic form s of nitrogen (principally nitrate ions and am monium ion concentrations to total n i trogen loads in wet depo sition are reasonab l y well characterized. On the other h a nd, the contribution of organic form s of nitrog en to total reac tive nitrog en loa d s in wet deposition are not very well characterized. Also the contributions of gaseous ammonia, volatile organic acids and am ines, and various nitrog en and sulf ur aeros ols to to ta l n itrog en a nd sulfur loads are not ve ry well characterized.

At the sam e tim e, despite som e of these uncer tainties about specific air concentration, total loads, and ecosystem responses, however, th e general quantitative re lationships between regional decreases and increas es in total em issi ons of nitrogen and sulf ur relationships and several different nutrient enrichm e nt a nd acidification effects are reasonably well characterized.

9. To w h at extent has the draft IS A adequate ly characteriz e d the contribution of oxidiz e d and reduced forms of nitrogen to ecologica l effects related to nutrien t enrichment?

28The presen t Draft ISA does a pretty adequate job of characterizi ng the contribution of oxidized form s of nitrogen to nitrogen enrichm e nt but has a long way to go with regard to the contribution of reduced form s of nitrogen to nutrient enrichment.

10. Several additional effects are d i scussed, including mercury methylation, direct gasphase effects on foliage, and N 2 O as a greenhouse gas. How w e ll does the draft IS A characterize the eviden ce on these topics? My im pression is that the present draft ISA doe s a reason ably adequate job of describing the available ev idence on these other topics. I gath er from som e of the Charge Questions in the Draft Scope and Methods paper, how ever, that E P A is still trying to m a ke up its m i nd about how m u ch a ttention to give to these other eff ects that go beyond the gene ral issues of nutrient enrichm e nt and acid i fication effects in both terrestrial and aquatic ecosy stem s.

11. What are the view s of the Panel on the appropriateness and comprehensiveness of the conclusions drawn in Chapter 5?

I could not be m o re delighted with the decisi on to provide this kind of bulletized presentation of m a jor Findings and Conclusions f r om the various chapters of this draft ISA! It appears that a consid erable and well-foc used effort has been m a de to develop this series of very caref ully cra f ted brief su mmary state m ents that: 1) Contain the distilled essence of the most im por tant topics covered in each chapter, and 2) Are as directly relevant as possible to the overarching Key Policy Questions that should be the principal focus of all aspect s of these NAAQS review processes:.

“What scien tific evidence and/or scientific insig h ts 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 alternat ive indicator s , levels, s t atistical forms

, or averaging times of these standards are needed to protect public health with an adequate margin of safety and to protect public welfare?

“What scien tific evidence and/or scientific insig h ts have been developed since the last review to indicate whether, and if so, what particular ecosystem components or other airquality-related public welfare values, are more or less sensitive than the populations of humans for which primary standards are esta blished and for this reason may require a different indicator, level, statistical fo rm, or averaging time of a secondary standard in order to protect public w e lfare.”

12. How adequate is th e draft ISA for providi ng information and guidance to future exposure, risk and policy assessments that may be prepared in support of this NAAQS review ?

29I am a bit confused b y this question. At fi rst, I thought the question related to needs for inf o rm ation and guidance for future NAAQS reviews, but then the question e nds with ”policy assessments that m a y be prepared in support of this NAAQS r e view ? In any event, I do not recall that very much atte ntion has been given in this First Draf t I S A to providing infor m ation and guidance with regard to either future or the present reviews for secondary N AAQS standards fo r nitrogen and/or sulfur.

30

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

This review focuses prim arily on Chapter 5: Findings and Conclusions, although it draws on inf o rm ation in the e a rlier chapte rs f r o m which the Findings were drawn. My first very general comment is that the Findings did, I believe, com p ort with the m a jor conclusions one m i ght draw from the earlier chapters. At least, they summ ari zed what I took to be most of the main points in these earlier chapters, although I caution that I am not an ecologist and so there m a y have been significan t p o ints m a de earlier that d i d not m a ke their way into Chapter 5.

It was a bit hard (perhaps too hard) to get th e subsections of Chapter 5 to m a tch the way the earlier chapters were o r g a nized. Th is is due largely to the fact th at Chapter 5 itself does not have any system atic approach to presenting the finding s and conclusions concerning effects (which is really the focus of the NAAQS process). The effect s are divided between Ac idification; Nitrogen Nutrien t Enrichm e nt; and Other W e lfare Effects. Then these three m a jor classes of effects are subdivided in various ways (such as Aquatic; Terrestrial; etc). Ho wever, the subdivisions are not consistent across th e classes of effect. I suppose this m i ght be because so m e of the subdivision s are relevant for one class of ef fects and not others, but I can’t see any reason why this should be the case. It would have been m u ch more helpful to have the three m a jor classe s subd ivided into the sam e set of subsections so the reader can quickly go through and find, for exam ple, the Biochem i cal Effects for all three clas ses. The need ed inf o rm ation is all th ere, I just w a nted a more consistent structure to the presentation of it.

I also didn’t understand the case studies. I coul d find no consistency in the way they were approached, or any conclusions that could be drawn from the m . There was no explanation of what they are doing within the docum ent (i.e. what the reader is to take from them ). They struck

m e as an arbitrary set of rather poorly detailed cases – I’m sure the authors had som e reasons for selec ting the m , but this was not evid ent.

My final general quibble is w ith the highly qua litative n a tur e of m a ny of the conclusions on ecological effects, and the general presum ption that an effect is the s a m e as an advers e effect. The chapter is littered with phrases such as “could cause”, “are thought to”, etc. There is an im plicit assumption throughout that ecosystem s ar e in their optim al states before NAAQSrelevant sources are added to the world, and that all these sou r ces can do is weaken ec osystem health. Perhaps the authors don’ t intend this im plicit assum p t i on, or the impression that the phrases I m e ntion count as strong evidence for any sort of belief, but I was left uneasy with m a ny of the conclusions for the reasons above.

I now have som e specific comments on parts of Chapter 5:

1. On Page 5-2 at the bottom

, the authors conclu de that m easurem ents below the dete ction lim it cause “irresolvable uncertainty in the s e data ”. I a g ree with th e sentim ent here, but there are policy and regulatory decisi ons that can be m a de that don’t ha ve this “irresolvab l e un certainty ”. For exam ple, if the regulatory lim it is well above the detection lim it, and all the positive results are be low th e regulatory lim it, th en a large num ber of results be low the de tection lim it does not

31prevent a decision as to whether a s i te is in com p lianc e to be m a de with high levels of certainty. Whether the “irresolv a ble uncertain ty” has any imp lications for decision s depends entirely on the kind of decision being taken.

2. On Page 5-4, first bullet, the authors state that “annual NOx has decreased < 35% over the years”. It was not clear w h ether th is is to m ean it has decreased by less than 35% of the baseline year (1990) or has decreased TO LESS THAN 35% of the value in the baseline year.

3. On Page 5-6, the authors correc tly state that it is possible th at sm all amounts of SO2 m a y be beneficial. It would be useful to indicate how this am ount compares to the levels considered under a NAAQS and the levels currently found in the environ m ent. If the am ounts that are beneficial overlap the amounts foun d in the environm ent, this has significant im plic ations for the NAAQS. And it also would be useful to characterize the ev idence for beneficial effects, sin ce it indicates that the expo sure-response curve m a y be U-shaped. Focusing only on the “bad” effects leaves the d o cum e nt open to charges of bias and presum es there is som e sort of m onotonic increase of bad effects with exposure, or a thre shold below which effects don’t occur (but also are not b e neficial).

4. In that sam e paragraph, the authors state that lack of observation of a change doesn’t m ean that no ch an ge is taking place (it m a y have been belo w the ab ility to detect such a ch ange). I ju st want to be sure it is also understood that this statem ent cannot be used to therefore justify regulatory action ; the ev idence s i m p ly becom e s ne utra l with r e spect to decisions being taken.

5. On Page 5-11, the second bullet, the authors conc lude that a lack of relationship may indicate that the trends are on a tim e s cale longer than is being m easure d. W e ll, yes, this could be the case. Or it could just be that there IS no relationship. I find th is pattern throughout the docum ent: a tendency to explain away a lack of relationship as being due to som e limita tion in the data, rather than the sim p ler, and m o re truthful, clai m that there h a s been no trend observed to date.

6. On Page 5-12, first bullet, line 16, the term “ likelihood” is used. I couldn’t figure out the sense in which it is being used here. I assu m e it is not in the statistical sense.

7. On Page 5-15, last full paragr aph, the final sentence doesn’t seem to m e to follow from the evidence p r esented, un less one assu m e s that ANC values are the sole determ inant of acidic episodes. I won’t comment further on this, because it is not m y area of ex pertise, but this im plicit

assum p tion must be m a de and so I w a s left w ondering where the evidence was given to support it.

8. Throughout the d i scus sion on NOx and SOx depositi on, I could not fin d any recog n ition, o r at leas t explicit consideration, of deposition on to la nd that then enters a waterbody thro ugh run-off. I am assum i ng it is b e in g considered even if not called out direct ly in the text. ( ?)

9. On Page 5-17, last bullet, the issue of Hg increasing in fish is brought up. I realize that the authors are suggesting here that this increase above “safe” levels is due in part to the effects of acidic deposition, but this section is f o cused on effects and no specific effect is m e ntioned (unless on e takes the increased Hg its elf as an effect, which is what I pres um e the authors

32intend ). But there shou ld at le ast be s o m e m e nti on of the exte nt to which this inc r eas e in Hg is due to the ef f ects of acid i c depos itio n and not ju st to lo ading of the original Hg into the waters.

10. On Page 5-18, first paragraph under 5.5, we find another instance in which a change is

autom a tically considered adverse. The argum ent is that excess N creates “unnatural rates in som e species and change in th e com p etitiv e inte rac tio n s ...”. This is then f o llow e d by the c l a i m that this will decrease ecosystem health and biodi versity. Again, I am not an ecologist, but my reading of the literature suggests it is far from evident that all such changes weaken ecosystem health (unless one assum e s a priori that ecosystem s are in their op tim al state of health absent increased N). Or the key m a y be in the term “ex cess”. Perhaps the autho r s have som e idea as to what level o f N constitutes an “exces s ” and are re ferring only to this condition, in which case we have a tau t ology (the lev e l of N that is “excess ” b e ing by definition the level of N that causes weakened ecosystem health). W ithout addressing th is issue, the reader is likely to assum e that “excess ” is the sam e as “increas ed”, which would not be true.

11. On Page 5-19 at the top, it seem s to m e that th ere is an assum p tion bei ng m a de here that all N in the system is bioavailable. I m a y be wrong in this, but it does seem to m e that assumption is inherent in the paragraph. At the bottom of that s a m e page, the authors ref e r to the “av ailab i lity of NO3-. I wonder if they m ean “bioavailabil ity” or if the two term s are interchangeable.

12. On Page 5-21, line 13, it is noted that a change in shoot-to-root ratio ca n be adverse. I would guess it is adverse primarily if the ratio increases, not decreases.

13. On Page 5-26, line 12, it is m e ntioned that the function is not linear , but no indication is given of the kind of non-lineari ty it represents. S o m e clarit y here would be good (threshold, positiv e second derivative, negative second deriv a tive, U-sh aped, etc).

14. The Regional Trends sections struck m e as unsatisfactory throughout the chapter. I was never clear, in any of them , what im portant conclusions, related to a NAAQS decision, I was to take away. It was n ’t even m a de clear w hy a regional trend is of interest.

15. On Page 5-31, a list of biol ogical m easurem e n ts to as sess eutroph ic condition is p r ovided. But I don’t see why this list is here. I can find no way in which it inform s the later discussion or conclusions.

16. The discussion of Greenhouse Gases beginning on Pa ge 5-35 is conf using, or at least given in

too m u ch of a sketch. I haven’t any idea wh at the reader is take away from this.

17. On Page 5-36, the first sentence states that in the chapter data were “integrated and collectively considered in for m ulating conclusions”. I don’t thi nk the chapter accom p lished this,

or m a de it evident. I am not saying the conclusi ons are wrong, or that the authors didn’t have good reasons for giving them . I a m s i m p ly saying th at the chapter doesn’t lay out all clearly how the data were “integrated and collectively con s id er ed”. I would be m o re inclined to say that the data were co llec t ed tog e ther, the auth ors consid ered them , and conclusions were formulated (in ways that are not transparent to the reader).

3318. On Page 5-37, line 11, there is an instance of som e thing that a ppears in other places in the chapter. Som e N and S deposition rates are m e n tioned, but there is no indication given as to whether these are large or sm all compared to deposition rates one w ould expect under NAAQS levels. The reader is left, therefore, w ondering wh ether these deposition rates are significant with respect to any decisions that m u st be taken under NAAQS.

19. The final sentence of the chapter is that “The Chesapeake Bay is an exam ple of a l a rge wellstudied estu ary that receives 21 – 30% of its total N load from the atm o sphere”. This seem s a very odd way to end the chapter, as this sentence is essentially a non sequitur and certainly doesn’t sum m a rize any of the im por tant conclusions.

34

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

I have a few general co mments that I will relay to you in th is letter and the enclos ed file has m y detailed comments. I was disappoin ted in the ISA. The scope is ge ne r a lly f i ne bu t the tex t is n o t polished. It does not appear that the docum ent was particularly we ll ed ite d. As a resu lt, I h a ve considerable comments.

I have a few concerns with the docu m ent. Secti ons are high ly redundan t . W ith a bit of editing, I would guess that the length could be decrease d 25%. The ref e rencing of the docum ent is uneven. There are m a ny instan ces where facts ar e stated th at are not common knowledge and no citation is provided. I w ould think that this approach would not be acceptable. Other sections of the docum ent are referenced adequately.

There are several s t atements th at are m a de whic h are incorrect. I have either noted these or corrected th e text.

I do not like the approach as on 1-6, line 26 “Cha pter 2 highlights”. This is gramm a tically incorrect. A chapter is an inanim ate object a nd cannot highlight anything. This is done throughout the docum ent. It should be corrected.

The section on sam p ling and analysis for NO x and SO x (2.6) while interesting, is long and could easily be put in an Appendix.

I understand that I really don’t have much say in the m a tter, but interests would be best served if the scope of the ISA was expande d to include base cation and Cl - depositio n. Cl - is probably largely derived from coal com bustion or industrial processes at least away from the coast. Both base cations are Cl - deposition can in fluence the acid-bas e chem istry of ecosystem s.

• In Chapter 3 (3-28), shouldn’t som e m e ntion be m a de of cloud deposition?

• In this section (3-28, 15), it is m e ntioned that NH 3 is not included in deposition estim a tes. Another problem that isn’t m e ntioned is DON de position. This should be added to the text.

• The docum e n t is m a de confusing by m i xed units and sym bols

. Mass and molar, English and

m e tric. It seem s that there is no unit or scale that is not used in this docum ent.

• Also different ways of expressing units are used (e.g., kg/ha-yr vs. kg ha -1 yr -1 ). A con s isten t for m at should be used throughout the docum ent.

35Specific Comments on Integr ated Science Ass e ssment for Oxides of Nitrogen and Sul fur in Environmental Criteria

Chapter 2

Page 2-2, line 5 Reference needed.

Page 2-3 Figure title: Define M, PAH, P AN

Page 2-4, line 6 Change to: ... (e.g. nitrosam ines, nitro-PAHs)

Page 2-5, line 23 Change to: ... eff ectively no chem ical or physical rem oval

m echanism in the ....

Page 2-10, line 24 Make italics: in situ

Page 2-11, line 4 H +

Page 2-11, line 12 Change to: ... com pounds affect

Page 2-14, line 6 Change to: ... acidity, at adequate concentrations it affects...

Page 2-14, line 19 Change to: For any [NH x ] in the system ... condensed phase (Reaction 2. 4-4).

Page 2-16, line 17 Change to: ... Earth’s surface...

Page 2-19, line 27 Change to: .... oversaturated with ....

Page 2-21, line 22 Make italics: in situ

Page 2-21, line 25 Change to: An overvie w of the three satell ite... backscatter is contained in Table 2.6-1.

Page 2-21, line 27 Change to: Total column [NO 2 ]... s a tellite is shown on Figure 2.6-1.

Page 2-23, line 9 Change to: ...; s ee the more com p l e te description ...

Page 2-28, line 12 Change to: Excess NH 3 alone or together with NO x can enhance

to terres t rial and aquatic ecosystem s.

Page 2-29, line 7 Change to: ... networks is sparse over...

36Chapter 3

Page 3-1, line 11 Change to: In this sec tio n brief summ aries...(NH 4 + ) are provided.

Page 3-2 Section 3.1.2.1 Soils. T h is section needs som e citations.

Page 3-2, line 20 Isn’t N 2 the dom i nant soil gas?

Page 3-2, line 30 Is there a ty po here? D o you m ean “Although N 2 O is not reactive... ?

Page 3-3, line 4 Do you m e a n...oxidation of NH 3 released .... ?

Page 3-3, line 24 Is there a w o rd or som e thing m i ssing? This sentence doesn’t m a ke

sense.

Page 3-3, line 28 What is m e a n t by fuel N loadings? Clarify.

Page 3-3, line 31 What section?

Page 3-4, Line 3 & 4 Need a reference

Page 3-4, line 23 Change to: ... and this pattern rem a ins...

Page 3-5, line 5 This sentence doe sn’t m a ke sense, please clarify.

Page 3-5, line 9 What is m e a n t by “stim u lated through soil m a nagem e nt”?

Page 3-5, line 12 You don’t really want the brackets here do you?

Page 3-5, lin e 29 Cultiva tion of soil with hi gh organ i c s conten t is not an addition of N as indicated in the sen t ence that fo llows.

Page 3-6, line 1 Change to: ... of which a sm all portion

Page 3-6, line 30 Change to: Data for SO 2 em issions...state leve l tota ls ar e depicted in Figure 3.2-1.

Page 3-7, line 6 Change to: The m a gn itude and spatial distribution... in the A R P is depicted in Figure 3.2-2 for the CONUS.

Page 3-7, line 7 Change to: .... continuing elevated density of SO 2 em ission sources in th e ... com p ared to the W e st, par ticu l ar ly in th e Centra l Ohio River Valley.

Page 3-9, line 2 Change to: ... incr e a ses with inc r eas ing f i re in te nsity.

37Page 3-9, line 12 Change to: ... em i ssions are lower. Reduced light levels...

Page 3-9, line 16 Change to : However, note that ...

Page 3-9, line 30 Need a citation

Page 3-12, line 23,24 Need citations

Page 3-14, line 7 Change to: The networ ks, sponsoring agencies... are listed in Annex Table AX2.5-1.

Page 3-20, line 1 Does CASTNET really have cation data? I never knew that.

Page 3-20, line 19 Change to: ... of ~ 90 s ites. In addition the seven At m o spheric

... Also doesn’t AIRMon provide ga s and particle chem istry and estim ates of dry deposition?

Page 3-22, line 31 Change to: Contributio ns from several... than 30 years are summarized in Annex Table AX2.5-5.

Page 3-23, line 9 Change to: Am bient [NO 2 ] ... through 2005 is shown in Figure 3.7-1.

Page 3-24, Para. 1 Need citations

Page 3-25, line 6 Change to: ... evident along the O h io ...

Page 3-25, line 7 Change to: ... have been decreasing throughout...

Page 3-25, line 9,10 Define CMSAs and LOD

Page 3-26 Figure title: Lower case c in concen tration

Page 3-26, line 3 Change to: The com pos ite diel... database is shown in Figure 3.7- 4.

Page 3-27 Figure title: Clarify what is m eant b y “in focus”.

Page 3-27, line 1 Change to: ... by s ources som e distance above the Earth’s surface.

Page 3-33, line 3 Change to: Note, however, ...

38Page 3-33, line 26 Change to: ... are problem a tic because ....

Page 3-34, line 4 Change to: ... a sim ilar re lative decrease

Page 3-35 Figure title: Clarify what is m eant b y O 3 /10

Page 3-36, line 26 Change to: ... observed fluxes described here are com p ared in Figure 3.9-5.

Page 3-44, line 28 Change to: Results of a ..., respectively ar e shown in Figures 3.10-1 and 3.10-2.

Page 3-44 In the com p arison of m e asured and modeled deposition (e.g. Figure 3.10-1) som e discussion s hould be given on testing dry deposition fluxes. Also in Figure 3.10-1 the fluxes are given on an annual basis. W h at about patterns for other tim e intervals such as monthly or weekly? Th e scatter should be m u ch greater. Should other predicted values for shorter time intervals be discussed?

Page 3-45, line 4 Why is this a critical load ? Th is definition s eem s inconsis ten t with the rem a inder of the docum ent. Please clarify.

Page 3-48 The statem e n t in the first pa ragraph that atm o spheric load is equal or exceed s riverine load (line 8 ) is inconsisten t with the statem ent in the 4 th paragraph that atm o spheric deposition is 10-40% of the

tota l load. T h is needs to be cla r ified. Also a reference for the 10- 40% contribution value needs to be referenced (Castro and Driscoll 2002?).

Page 3-50, line 4 Change to: Several wate rbodies ... to total N loads are listed in Table 3.11-1.

Page 3-50, line 15 I do not believe the statem ent that 30-70% of the volum e of a n im al waste is em itted a s NH 3 . This is not possible. T h e statem ent needs to be fixed.

Page 3-50, line 21 Change to: Several im po rtant watersheds ... airsheds are listed in Table 3.11-3 and 3.11-4.

Page 3-50, line 23 Reference is needed to ju stify the statem ent on larger airsheds for oxidized N.

Page 3-51, line 1 Change title: 3.12 Background (PBR) concentrations and deposition of NO x and SO x

39Page 3-51, line 20 Change to: The annual m ean [NO 2 ] ...[NO 2 ] (bottom panel) are shown in Figure 3.2-1.

Page 3-53 Give com p l e te fi gure title. Don’t be lazy.

Page 3-54, line 8 Change to: The highest values are ... Ohio River Valley (Figure 3.12-3 (upper panel)).

Page 3-54, line 23 Change to: Results from ... (Bey et al., 2001) is shown in Figure 3.12-5.

Page 3-55 Again, give com p lete figure title

Page 3-56 Again, give com p lete figure title

Page 3-59, line 7, 16 In addition to givi ng background concentrations, the summ ar y should provide deposition values.

Page 3-59, line 12 Give the reader the speci fic percentage that EGUs contribute to SO 2 e m issio n s.

Page 3-59, line 29 Again, that statem ent about the NH 3 contribution from ani m al waste is incorrect and needs to be fixed.

Page 3-60, line 21,26 Again, the inconsiste nt statem ent about the atm o spheric

contr i bution to the tota l estuar ine input needs to be m a de consistent. The 10-40% value is the correct s t atem ent (Castro and Driscoll 2002).

Page 3-62 Is this the original refe rence? It is difficult to believe.

Chapter 4

** There needs to be a global search on th is chapter on sulfate. It should be SO 4 2- . The entire chapter needs to be fixed. Also throughout the docum e nt, the authors refer to “inorganic Al”. There needs to be a glob al search on this. This needs to be refe rred to as “dissolved inorganic Al” or “m onom eric inorganic Al”. Much of pa rticulate m a tter or soil is inorganic Al. The authors want to refer to dissolved inorganic Al. **

Page 4-1, line 8 Change to: A discussion of acidifica tion is presented in Section 4.2. Nitrogen (N) enrichm e nt is discussed in Section 4.3.

Page 4-1, line 19 Change to: ... , info rmation is pre s ented in this Integr ated Science Ass e ssm ent (ISA) that was collected...

40Page 4-3, line 1 Change to: Critical loads as a ... quantif ying disturbance is discussed in the following section.

Page 4-7 Paragraph 1: There is no di scussion of target loads here. Should the text be expanded to address th e concept of target load s ?

Page 4-7, line 24 Change to: ... is the accum u lation of hydrogen ion (H + ) ...

Page 4-7 Section 4.2.1.1: This sec tion on soil acidification is woefully inadequa te. Soil ac idif ic ation is re ally the loss of base ca tions plus the accum u lation of acid i c anion s . The authors should refer to van Breem en et al. (1983) or Bi nkley and Richter (1987).

Page 4-9 The incorrect figure is with this figure title.

Page 4-10, line 1 The statem e n t of m obility of sulfate governing m o st aspects o f soil and water acidification is sim p ly not true and dem onstrates a

com p lete lack of understanding of th e process. T h is needs to be corrected.

Page 4-10, line 6 Change to: ... depos ited S is transpor ted to the soil ...

Page 4-10, line 7 Change to: ... acts as a mobile anion at ...

Page 4-10 Paragraph 2: References are ne eded to docum ent sta t em ents m a de in the paragraph.

Page 4-10, line 11 Change to: ... leach ing of cations, and ...

Page 4-10, line 13 Change to: ... W h en S is transported from

.... Page 4-10 Last paragraph: You need to clarify why accu m u lated sulfate is slowly released from soi l

. Page 4-11, line 2 Change to: ... the accu mulation of the historic legacy of

atm o spheric S deposition in soil was ...

Page 4-11, line 9 Change to: ... and the difficulty in discerning the effects of net SO 4 2- description and net S m i neralization m a ke it difficult...

Page 4-12 Paragraph 1: Virtually a ll m a ss balance studies show N retention. See Cam pbe ll et al. (2004) for example.

Page 4-12 Paragraphs 1 and 2: Re ferences are needed to do cum e nt the

statem ents m a de.

41Page 4-12, line 9 Change to: ... betw een atm o spheric N depositio n and the C:N...

Page 4-13, line 3 Add ...leach ing to surface waters in the eastern U n ited States (Aber et al. 2003)

Page 4-13, line 8 Change to: ... Although concentrations of NO 3 - are typ i ca lly less than SO 4 2- in drainage waters...

Page 4-13, line 12 Change to: ... leach ing from forest ecosystem s...

Page 4-13 Paragraph 3 – References are needed

... Page 4-13, line 14 Clarify sentence

Page 4-13, line 20 Change to: ... m o st noteworthy effect of ....

Page 4-14, line 1 Change to: ... This pattern was likely due ...

Page 4-14 Paragraph 2: References needed ....

Page 4-14, line 21 Change to: ... S and N in acidic deposition enhance inputs of strong acid anions that can accelerate ...

Page 4-14, line 25 Change to: ... plant nu trien t s from soil; and...

Page 4-15 Paragraph 1: Reference needed....

Page 4-15, line 10 Change to: ... docum en ted decreases in base saturation of ...

Page 4-15, line 16 This statem ent is not co rrect. Likens et al . (1996) and Kirchner and Lydersen (1995) docum ented decreases in stream concentratio ns of base cations du e to decreased leaching fro m the soil exchange com p lex. They document decreases in soil exchangeable pools of base cations due to elevated acidic deposition.

Page 4-15, line 27 Should cite Cronan and Schofield (1990)

Page 4-15, line 29 Change to: ... de position because inorganic m onom e ric ... Page 4-16 Paragraph 2: References needed....

Page 4-16, line 30 Change to: ... depos ition tends to rem a in in solution ...

Page 4-17, line 1 Need to clarify this senten ce. Changes in concentrations of base cation s do n o t necess a rily result in in creas es in d i ssolved ino r ganic alum inum

.

42Page 4-17, line 8,9 Change to: ... as chron i c condition or episod ic condition. Chronic condition refers to annual ...

Page 4-17, line 11 Change to: ... Episodic condition refers to ...

Page 4-17, line 12 Change to: ... provide less neutralization of ....

Page 4-17, line 18 Change to: ... acidic deposition lik ely has subs tantially in creased

... Page 4-17, line 20 Change to: ... Many st ream s that exhibit chem ical conditions during ...

Page 4-17, line 24 Need to define ANC

Page 4-17, line 25 Change to: in the central Appalachian Mountain region ... (a reference is also need ed to docum ent this s t atem ent)

Page 4-18 Figure title. The f i gure is incor r ec t f o r the f i gur e title and tex t citation. Also in situ should be in italics.

Page 4-19, line 19 The statem e n t here is no t exactly correct. The difference between summer and spring ANC during baseflow conditions was on average 30 μ eq/L. This m eans that acidic episo d es would occur on average when summer ANC values reached 30 μ eq/L.

Page 4-19, line 23 Define: episodic ANC

Page 4-19, line 28 Change to: ... c ontact with ANC s upplying m a terials ...

Page 4-20, line 2 Change to: ... this pattern can be ...

Page 4-20, line 6 Reference needed ...

Page 4-21, line 1 Make italics: in situ

Page 4-21, line 4 Change to: ... during lo w flow, there is a shift to conditions of moderate to severe episo d ic ac idification during high flow that showed higher ...

Page 4-22, line 28 Change to: ... 2002), larger-term trends in ...

Page 4-22, line 28,29 Sentence not clear, please clarify

Page 4-23, line 12 Should the title be Terrest rial Ecosystem s or Forest Ecosystem s ?

43Page 4-23 4.2.2. Terrestrial Ecosystem s . Shoul d enhanced leaching of nutrient cations from the canopy due to acid i c dep o sition b e

m e ntioned in this section?

Page 4-24 Paragraph 1: Reference needed

Page 4-24 Paragraph 2 and elsewhere: Throughout the docum ent the authors discuss soil horizons as though they are always and only Spodosols. I don’t believe that the only sensitive soils are Spodosols. Aren’t other soil type s important? When the authors refer to O and B horizons, they need to clarify the geographic context they are discussing, and if they are re ferring to all Spodosols.

Page 4-24, line 10 Why is the Bs horizon more sensitive than the Oa horizon in the forest floor? I believe th at the fo rest floor is m o re susceptible to cation change from acidic depositi on than the m i neral so il. M o st of the roots are in the forest floor. Is a 20% loss of Ca 2+ in the forest floor less im portant than a 50% loss of Ca 2+ in the m i ner a l soil?

Page 4-25, line 2 Do we actually know th at Al only becom e s m obi lized after C a 2+ becom e s depleted ? If th is is tr ue (I don’t believe it) how about a reference docum e nting it?

Page 4-26, line 10 Need a reference

Page 4-26, line 17 Change to: ... nitrificat ion rates are difficult to m easure directly

... Page 4-28, line 2 Do you m e a n terrestrial or forest?

Page 4-29, line 4 Has there been red spruce d ecline in the Southeast? Please provide a referenc e.

Page 4-29, line 14 Need a reference

Page 4-31, line 25,26 Change to: ... A concep tual view...m aple dec line is provided in Figure 4.2-2.

Page 4-33, line 6,7 Clarify sentence

Page 4-33 I think Ju ice et al. (2006) shows som e com p elling data on sugar

m a ple response to Ca ad dition. The authors shou ld consid er

m e ntioning this work.

44Page 4-34, line 2,3 This section is on tree he alth. W hy m e ntion soil cation depletion here? W ouldn’t it be more appropri ate in the so il effects section ?

Page 4-40 Note that w h ile tem poral patterns in surface wate r NO 3 - loss are confusing and variable. Aber et al. (2003) shows that there are spatial patterns acro ss th e region which are con s istent with

atm o spheric N depositio n contr i buting to elev ate d NO 3 - leaching.

Page 4-41, line 18 Change to: ... Effort s to explain the com p lex patterns in ...

Page 4-43, 14-16 Likens et al. ( 1998) showed increased losses of Ca 2+ with flow during the 1960s and a declining pattern in later years.

Page 4-44, line 18 How do She n andoah stream s show c h anges in soil sulfate adsorption ? Please clarify. On e i m portant observation that is ignored in th is repo rt is that although surface water ANC appears to be increasing, soil losses of ex changeable cations are continuing despite reductions in acidic deposition. This observation should

m e mentioned som e whe r e in the docum ent.

Page 4-46, line 8-10 How large is large?

Page 4-46 Do you really believe this st atem ent is true? Virtually all studies that m easure m a jor ion c h em istry m e asure pH. I believe that ANC is m o re commonly focused on becau se it is m o re straight forward. pH is a non-linear m easurem ent a nd its changes are difficult to inte rpre t as trends.

Page 4-47 The statem e n t that waters with ANC < 0 μ eq/L have “no capacity to neutralize acid inputs” is not true. An ANC value below 0

μ eq/L sim p ly m eans that H + values are elevated (the solution pH is below the equivalence point). Th is statem ent needs to be corrected.

Page 4-48, line 7,8 Change to: acidifi cation (a decrease in ANC observed...)

Page 4-48, line 15 Where is Table 4.2-4?

Page 4-49, line 1 The units should be μ eq/L-yr.

Page 4-49, line 2 Change to: ... re present significant trends towards...

Page 4-49, line 11 Change to: ... ANC bel o w zero μ eq/L.

Page 4-49, line 20 Add Driscoll et al. (1988)

45Page 4-51, line 9,10 These conditions can also resu lt in direct m o rtality as results f r om in situ bioassays show (Van Sickle et al. 1996).

Page 4-51, line 12 Add reference

Page 4-51, line 15 Change to: ... vigor, an d reproductive success; and

Page 4-57, line 8 Table 4.2-6 – is m i ssing

Page 4-57, line 15 Change to: ... relationships are complex, however, ...

Page 4-57, line 22 Change to: ... However, note that effects...

Page 4-60, line 16 Change to: Note that the absence ...

Page 4-61 Figure: It would be helpful if a comment was m a de on the consistency of Figure 4.2-11 with 4.2-10. Although the line 4.2-10 is different. The values on the two f i g u res ac tually seem quite sim ilar. Is fish diversity respons e to acidification sim ilar in the Adirondacks and Virginia?

Page 4-66, line 6 What does this m ean eva porative concentration? Please clarify.

Page 4-69, line 1 Change to: ... conditions in the Park for ...

Page 4-69, line 14 Elsewhere in the documen t Al concentrations are expressed in

μ m o l/L.

4-70, line 22 Aren’t the USDA Forest Inve ntory D a ta (FIA) available? Please clarify.

Page 4-71, line 9 Change to: Note that the McNulty...

Page 4-72, line 1 Red spruce are gene rally found at higher elevations.

Page 4-72, line 5 Change to: ... sugar maple which are ....

Page 4-72, line 7 Change to: ... areas where sugar m a ples appear to be ...

Page 4-73, line 28 Change to: Note that critical loads...

Page 4-74 4.2.4.3.2: The text in this section is redundant with the previous

m a terial presented.

Page 4-74, line 20 Give the specific %.

46Page 4-76, line 11 Change to: ... 1991 levels of stream area th at was suitable for brook trout survival

Page 4-76, line 18 Change to: ... re quired to restore w a tershed soils... (Note throughout the docum e nt, th e authors use the term buffering capacity incorrectly. Please co rrect this.)

Page 4-76, line 25 Change to: ... was partly because SO 4 2- adsorption Also throughout the docum ent, the authors refer to sulfur adsorption. I believe it is m o re appropriate to refer to sulfate adsorption.

Page 4-77, line 30 Change to: ... For aquatic ecosystem s , .... Page 4-79, line 30,31 Change to: ... ANC ha ve been increased through lim ing...

Page 4-80, line 14 Change to: ... (e.g., pH, Al, Ca, ANC, DOC, dissolved OC)... Why do the authors use the term dissolved OC? Why not use DOC? Most reade r s will be f a m iliar with this te r m

. Page 4-81, line 4 Change to: ... increased with lake pH and ....

Page 4-81, line 20 Change to: ...low weat hering rates (Driscoll et al. 1991, Sullivan et al. 2006a)

Page 4-82, line 2,3 Need a reference

Page 4-82, line 25,26 Need a reference

Page 4-84 Figure 4.2-14: W hy not upda te this figure and show the m o s t

com p lete tim e series of precip ita tion chem istry ?

Page 4-84, line 23 Change to: ... The hydrogen ion deposited ....

Page 4-87, line 6 Change to: ... m odel simulations coupled with population-level extrapolations suggest that ...

Page 4-87, line 23 Change to: ... cations, hydrogen ion and ....

Page 4-89, line 15 This statem ent is not exac tly true and needs to be qualified. T h ese authors provided an upper lim it of organic acid content and as a result greatly understated the num be r of fishless lakes due to acidic deposition. This is a very im portant m i stake and needs to be clarified.

47Page 4-89, line 22 Change to: ... pH and ANC decreased substantially...

Page 4-89, line 26 Note that Van Sickle et al. (1996) was part of the ERP and not subsequent to it.

Page 4-90, line 14 Change to: ... from 1982-2000 in the original 16 ALTM ...

Page 4-90, line 15,16 Change to: ... from 1992 to 2000 in the com p lete set of 48 ALTM lakes. (Note that 32 additional lakes were added to the

program in 1992). They found ...

Page 4-92 Figure 4.2-18. You have the in correct citation for this figure. It should be Driscoll et al. (2003a).

Page 4-92, line 4 The population-base estim a tes need to be m e ntioned earlier in the text where this study is first m e ntioned.

Page 4-93 Figure title: Change to: ... ANC at three dates f o r the population.

Page 4-94, line7 Note this citation is not correct. Chen and Driscoll (2004) applied the m odel to the DDRP lakes.

Page 4-94 Paragraph 2: W hy not add a sentence or two on the m odeled changes in zooplankton and fish species diversity that are discussed in Sullivan et al. (2006b)?

Page 4-94, line 30-32 No! W a ters heds that are sensitive to m e rcury deposition are forested, have an abundance of wetlands, shallow hydrologic flow paths, are un productive and im pacted by acidic deposition (Driscoll et al. 2007).

Page 4-95, line 27 Change to: ... stream s in the Park is linked ...

Page 4-95, line 28 Change to: ... soils to adsorb SO 4 2- is decreasing due to the longterm accumulation of SO 4 2- on soil adsorption sites associated with a legacy of elevated acid i c deposition.

Page 4-97, line 14 Change to: ... At the low-ANC (~0 μ eq/L) ...

Page 4-97, line 16 Change to: ... Increase s in base cations tended to com p ensate...

Page 4-97, line 26 Change to: ... NO 3 - concentr ation s usually incr eased...

Page 4-97, line 29 Change to: ... to th e changes in ANC of Paine Run...River, and contributed to decreases in ANC in Pi ney River.

48Page 4-98, line 3,4 Note that base flow ANC is controlled by bedrock geology.

Page 4-98, line 6 Note during high flow, the shallow flow paths dim i nishes contact between ...

Page 4-98, line 5 Change to: ..., probably because S O 4 2- adsorption ...

Page 4-99, line 1 Change to: ... m o re vulnerable to adverse effects of episodic acidification ...

Page 4-101 Paragraph 1: Isn’t th is m a terial redundant with p. 76?

Page 4-101, line 8,9 These categor ies should have been define d previously in the text when they are first m e ntioned.

Page 4-101, line 31 What are sensitiv e Si -b ased watersh e ds ? Pleas e clarify. Som e where the def i nitio n of sensitiv e southeas te rn watersh e ds needs to be defined: silicicl astic, granitic, and basaltic

Page 4-101, line 32 Is the loading kg S/ha-yr or as SO 4 2- ? Clarify.

Page 4-102, line 1 Change to: ... Prio r to the Industrial Revolution, m o st ....

Page 4-102, line 3 Again, define Southeast wa tershed sensitivity and be consistent using it throughout the text.

Page 4-102, line 10 Clarify what is m eant by sm all areas

Page 4-104, line 7,8 Here you finally define the watershed sensitivity classes. Use these term s throughout the text.

Page 4-104, line 25 Change to: ... N is transported between air ...

Page 4-104, line 27 Change to: ... because it is transported from the ....

Page 4-104, line 31 Change to: ... Leachin g from soil, ....

Page 4-104, line 32 I don’t believe that n i trate leach ing from atm o spheric d e position results in a violation of drinki ng water standards (>10 m g N/L). Where? I defy you to provide a reference(s).

Page 4-105 Also m e ntion causes of dec lines in subm erged aquatic vegetation (SAV) and causes of increases in nu is ance alg ae s p ecies.

Page 4-105, line 3,4 see P. 112

49Page 4-105 Note that nitrogen is also part of proteins, not only enzym e s.

Page 4-106, line 29 Change to: ... N leaches from soils to ....

Page 4-109, line 21,24 Delete parenthesis from NO 3 - plus NH 4 + on both lines

Page 4-111, line 5-7 Redundant. Denitrifi cation has been defined previously.

Page 4-112, line 11,12 See below in consistent with plot on p. 105

Page 4-112, line 19 Change to: ... are generally thought to reduce ...

Page 4-112, line 22,23 The m e thane response to nitrog en addition is co nfusing and inconsistent. This section should be rewritten.

Page 4-113, line 5 Change to: Note that the N enrichm e nt...

Page 4-114, line 2 Change to: ... in the easte rn United States (Driscoll et al. 2003a).

Page 4-114, line 21 Change to: ... fr esh surface waters are: (1) elev ated...

Page 4-114, line 22 Change to : ... water; and (2) ....

Page 4-114, line 24,25 Need reference

Page 4-114, line 26 Change to: ... in the A d irondacks (Aber et al. 2003)

Page 4-116, line 22 Change to: ... This pattern suggests that N ...

Page 4-116, line Should you m e ntion increases in populations of nuisance algae?

Page 4-119, line 15 Change to: ... not generally accoun t for all wastewater inputs

Page 4-119, line 16-23 Should also c ite Castro and Driscoll (2002).

Page 4-120 Change to: ... Source: (Driscoll et al. 2003b).

Page 4-126, line 15 These units do not m a ke se nse. W h a t is the areal basis of the applic ation ?

Page 4-129, line 16 4.3.3.1.4 Herbaceous Plants a nd Shru bs – Move to forest section

Page 4-132, line 3 Change to: ... This pattern suggests selective ...

Page 4-132, line 14 Change to: ... In the reference plots, five species...

50Page 4-132, line 14-16 I do not understa nd this sentence. Please clarify.

Page 4-135, line 1 This would be m u ch more useful if expressed as a loading rate. The units shown here do not m a ke sense m g /L-yr?

Page 4-135, line 32 Make italics: in situ

Page 4-138, line 17, 18 Make italics: in situ

Page 4-145, line 12 Make italics: in situ

Page 4-145, line 18 Change to: ... (e.g., cyanobacteria, dinoflagellates)

Page 4-146, line 1 Note Driscoll et al. (2003) is not the origin al citation. It should be (Valiela et al. 1990).

Page 4-147, line 27,28 Change to: An overvie w of the sensitiv e ecosy s t em s is given in Table 4.3-2.

Page 4-152, line 9 Make italics: in situ

Page 4-152, line 28 Change to: ... future outlook of the U.S. estuaries based ...

Page 4-154, line 2 Change to: ... lim ited, though note that m a ny ....

Page 4-160, line 26 Define very low. Is n’t it generally defined as <2 m g /L?

Page 4-163, line 27 Change to: ... oxygen c ontent, supply of la bile organic carbon,

tem p erature, pH ...

Page 4-165, line 2 Please clarify the m a ss ba sis of the loading Kg S/ha or Kg SO 4 /ha ?

Page 4-166, line 3,4 This statem ent is inco rrect and m i sleading. High production of sulfide will lim it m e thyl m e rcur y production (Benoit et al. 2003). This sentence needs to be rewritten.

Page 4-166, line 30 Change to: ... waters hed soils and the transport of naturally...

Page 4-168 Section 4.4.1.2.2: There is no reference to effects of m e rcury on song birds and terrestrial food ch ains (see (Rimmer et al. 2005).

Page 4-169 No reference is m a de of Drevnick et al. (2007) w h ich suggests a link between declines in atm o spheric S deposition and fish Hg.

51Page 4-170, line 28 What is SO 4 2- deficit? I never heard of such a thing. Please clarify.

Page 4-171, line 26 Change to: ... Pollu tants m u st be transported from the ....

Page 4-171, line 27 Change to: ... Although the transport of pollutants...

Page 4-172, line 23-25 Change to: ... concentrations of SO 2 . The effect of SO 2 on vegetation are summ arized including som e discussion of the lim ited rec e n t liter a tur e

. Page 4-176, line 27,28 Change to: ... In Annex 7, a short list of GHGs and the environm ental factors.... of clim ate change are provided in Table 7-1. A comprehensive...

Page 4-177, line 22 Change to: ... The additional la boratory study ...

Page 4-177, line 25 Change to: ... 145 yr old beech tree ...

Page 4-179, line 4 Change to: ... tem p erature, precipitation, and forest soil ...

Page 4-179, line 10 Change to: ... s how increasing tem p erature increases ...

Page 4-179, line 21 Change to: ... ground water NO 3 - concentratio n is elevated

... Page 4-179 Again, I can’t believe that atm o spheric N deposition results in surface water concen trations th at app r oach drinking water standards. Please provide a reference.

Chapter 5

Page 5-3, line 11 Change to: ... ne tworks is greatly lim ited over large ...

Page 5-5, line 23,24 As indicated before, this statem ent is not correct and inconsistent with lines 25 and 30 imm e diately below. Please fix.

Page 5-6, line 1 What ecological effect s does S deposition have on Chesapeake Bay?

Page 5-6, line 14 Change to: ... includ ing topography vegetation, soil chem istry ...

Page 5-8, line 9 Change to: ... Th ere are several ind i cators of stress...

Page 5-9 Paragraph 1: Need reference.

52Page 5-9 Bullet: A num b er of studies show ongoing soil acidification (i.e., net Ca 2+ loss) despite decreases in ac idic deposition (Bailey et al. 1996, Likens et al. 1998, H untington et al. 2000).

Page 5-9, line 24 Change to: ... as the pH decreases below 6.0

Page 5-10, line 14 Change to: ... whic h tend to provide less neutralizing of ...

Page 5-12, line 12 The sentence as written does not m a ke sense. Please change. Change to: ... Decreases in pH below values of 6.0 typically

Page 5-14, line 19 Change to: ... in the pH range 5.0 to 6.0

Page 5-14 Fourth bullet – Change to: ... decrease in ANC below ___ μ eq/L. Again, this sentence needs to be clarified. There is som e threshold ANC below which effects are evident. My guess is that it is about 100 μ eq/L.

Page 5-15, line 20 Change to: ... that where chronically acidic during summer in the

... Page 5-16 Last bullet: The authors should clarify that stream surveys were not conducted in the Adirondacks or New England.

Page 5-16, line 28 Delete space before Maxim u m past ...

Page 5-17 Fourth bullet: Again, this is a best case scenario because the study overstated the level of acidity associ ated with o r ganic acids. This needs to be clarified. Page 5-17, line 30 Change to: ... with siliciclastic geology and ...

Page 5-19, line 19 Change to: ... el evatio n, clim ate, s p ecies, composition ...

Page 5-19, line 26,27, 28 Change to: : comm un ities. The ecological effects...studied in

recen t years are summ arized in Table 4.3-1.

Page 5-19, line 32 Change to: ... ecosystem s. Note that N saturation...

Page 5-20, line 16 Delete first sentence. S t art paragraph with ... In general forest ...

Page 5-23, line 1 Change to: ... More than 30 kg N/ha-yr of ...

Page 5-28 Last bullet. N fluxes ... to the total N budgets are com p ared in Table 5.5-1.

53Page 5-28, line 10 Change to: ... N to total phosphorus was ... (Note, also c l ar if y if this ra tio is on a molar or m a ss basis.)

Page 5-31, line 1 Change to: ... Si:N ratio decreases below....

Page 5-31, line 6,7 Change to: ... in community com position, reduces hypolim netic DO, decreases biodiversity, and cau ses declines in subm erge d ...

Page 5-32, line 26 Need a reference. Should the units here be m e tric?

Page 5-33, line 30 Change to: ... influe nced by oxygen content, supply of labil organic carbon, tem p erature ...

Page 5-36, line 11 Change to: ... av erage of 0.053 ppm. (space after 0.053)

Page 5-36, line 19 Change to: ... Note that the regulatory....

Page 5-37, line 13 Change to: ... for m s of reactive nitrogen loading...

Page 5-38, line 2 Change to: ... hypoxic zones, loss of habitat and harmful ...

Page 5-39 Third section. Base Cations. Add references (Bailey et al. 1996, Huntington et al. 2000).

54References :

Aber, J. D., C. L. Gooda le, S. V. Ollinger, M. -L. Sm ith, A. H. Magill, M. E. Martin, R. A. Hallett, and J. L. Stoddard. 2003. Is n itrog en depo sition alterin g the nitrogen status of northeas tern forests ? Bio S cience 53 :375-389. Bailey, S. W., J. W

. Hor nbeck, C. T. Drisco ll, and H. E. Gaudette. 1996. Calcium inputs and transpo r t in a base-poo r forest ecosy stem as interpreted by Sr isotopes (Paper 95W R 03642). W a ter Resources Research 32 :14. Benoit, J. M., C. Gil m our, A. Heyes, R. P. Mason, and C. Miller. 2003. Geochem i cal and biological controls over m e thyl m e rcur y production and degradation in aquatic ecosystem s. Pages 262-297 in Y. Chai and O. C. Braids, editors. Biogeochem i stry of Environm entally Im portant Trace Elem ents , ACS Sym posium Series #835. Am erican Che m ical Society, W a shington, DC. Binkley, D., and D. Richter. 1987. N u trient Cycl es and H+ Budgets of Forest Ecosystem s

. Advances in Ecological Research 16 :1-51. Ca m pbell, J. L., J. W

. Hornbeck, M. J. Mitchell, M. B. Ada m s, M. S. Castro, C. T. Driscoll, J. S. Kahl, J. N. Kochenderfer, G. E. Likens, J. A. Lynch, P. S. Murdoch, S. J. Nelson, and J. B. Shanley. 2004. Input-output budgets of inorga nic nitrogen for 24 forest watersheds in the Northeas tern United States : A re view. W a ter, Air, and Soil Pollution 151 :24. Castro, M. S ., and C. T. Driscoll. 2002. At m o sphe ric nitrogen deposition to estuaries in the m i dAtlantic and Northeastern United States. Environm ental Science and Technology 36 :8. Cronan, C. S., and C. L. Schofield. 1990. Relatio nships betw een aqueous alum inum a nd acidic deposition in forested watersheds of North Am erica and Northern Europe. Environm e n tal Science and Technology 24 :1100-1105. Drevnick, P. E., D. E. Ca nfield, P. R. Gorski, A. L. C. Shinnem a n, D. R. Engstrom , D. C. G. Muir, G. R. Sm ith, P. J. Garrison, L. B. Cleckner, J. P. Hurley, R. B. Nobl e, R. R. Otter, and J. T. Oris. 2007. Deposition and cycling of sulfur controls m e rcury accum u lation in isle Royale fish. Environm ental Science and Technology 41 :7266-7272. Driscoll, C. T., K. M. Driscoll, K. M. Roy, a nd M. J. Mitchell. 2003a. Chem ical response of lakes in the Adirondack region of New Yo rk to declines in acidic deposition. Environm ental Science and Technology 37 :2036-2042. Driscoll, C. T., Y.-J. Han, C. Y. Che n, D. C. Eve r s, K. F. Lambert, T. M. Holsen, N. C. Ka mm an, and R. K. Munson. 2007. Mercury cont am ination in forest and freshwater ecosystem s in the Northeastern United States. Bio S cience 57 :17-28. Driscoll, C. T., N. M. Johnson, G. E. Likens, and M. C. Feller. 1988. The effects of acidic deposition on stream water chem istry: a com p arison between Hubbard Brook, New Ha m p shire and Jam i eson Creek, British Colum b ia. W a ter Res ources Research 24 :195- 200. Driscoll, C. T., R. M. Ne wton, C. P. Gubala , J. P. Baker, and S. W

. Christensen. 1991. Adirondack Mountains. Pages 133-202 in D. F. Charles, editor. Acidic D e position and Aquatic Ecosystem s : Regional Case Studies. Springer-Verlag, New York. Driscoll, C. T., D. W h itall, J. Aber, E

. Boyer, M. Castro, C. Cronan, C. L. Goodale, P. Groffman, C. Hopkinson, K. La m b e r t, G. Lawrence, and S. Ollinger. 20 03b. Nitrogen pollution in the northeas tern United States : Sources, eff ects, and m a nage m e nt options. BioScience 53 :357-374.

55Huntington, T. G., R. P. Hooper, C. E. Johns on, B. T. Aulenbach, R. Cappellato, and A. E. Blum . 2000. Calcium depletion in a southeaste rn United States forest ecosystem

. Soil Science Society of Am er ica Journ a l 64 :1845-1858. Juice, S. M., T. J. Fahey, T. G. Siccam a, C. T. Dr iscoll, E. G. Denny, C. Eager, N. L. Cleavitt, R. Minocha, an d A. D. Richardson. 200 6. Response of sugar m a ple to calciu m addition to northern hardwood forest. Ecology 87 :1267-1280. Kirchner, J. W., and E. Lydersen. 1995. Base Cation Depletion and Potential Long-Term Acidification of Norwegian Catchm ents . Environm ental Science and Technology 29 :1953-1960. Likens, G. E., C. T. Driscoll, and D. C. Bus o. 1996. Long-term effects of acid rain: Response and recovery of a forest eco s y stem . Science 272 :244-246. Likens, G. E., C. T. Driscoll, D. C. Buso, T. G. Siccam a, C. E. Johnson, G. M. Lovett, T. J. Fahey, W

. A. Reiners, D. F. Ryan, C. W. Martin, and S. W

. Ba iley. 1998. T h e biogeochem i stry of calcium at Hubbard Brook. Biogeochemistry 41 :85. Ri mm er, C. C., K. P. Mc Farland, D. C. Evers, E. K. Miller, Y. Aubry, D. Busby, and R. J. Taylor. 2005. Mercury concentrations in Bi cknell' s Thrush and other insectivorous passerines in m ontane forest of north eastern North Am erica. Ecotoxicology 14 :223-240. Sullivan, T. J., C. T. Driscoll, B. J. C o sby, I. J. Fernandez, A. T. Herlihy, J

. Zhai, R. S. Stem berger, K. U. Snyde r, J. W

. Sutherland, S. A. Nierzwicki-Bauer, C. W. Boylen, T. C. McDonnell, and N. A. Nowicki. 2006a . Assessm ent of the Extent to Which Intensively-Studied Lakes are Representativ e of the Adirondack Mountain Region. Final Report 06-17. New Yor k State Energy Resear ch and Developm ent Authority, Albany, NY. Sullivan, T. J., I. J. Fern andez, A. T. Herlihy, C. T. Driscoll, T. C. McDo nnell, K. U. Snyder, and J. W

. Sutherland. 2006b. Acid-base characterist ics of soils in the Adirondack Mountains, New York. Soil Scien c e Society of Am erica Jou r nal 70 :141-152. Valiela, I., J. Costa, K. Forem a n, J. M. Teal , B. Howes, and D. Aubrey. 1990. Transport of groundwater-borne nutrients from watershe ds and their effect s on coastal waters. Biogeochemistry 10 :177-197. van Breem e n, N., J. Mulder, and C. T. Driscoll . 1983. Acidification and alkalinization of soils. Plant and So il 75 :283-308. Van Sickle, J., J. P. Baker, H. A. Simonin, B. P. Baldigo, W

. A. Kretser, and W

. F. Sharpe. 1996. Episodic a c idif ication of sm all strea m s in the northeas te rn United States : Fish m o rtality in field bioassays. Ecological Applications 6 :408-421.

56

### Dr. Paul J. Hanson

My comm ents include general thoughts on the or ganization and content of the ISA, comments on specific chapters and item s w ithin the text, and summ ary t houghts on the charge question to which I was assigned.

General Comments: The Integ r ated Science Assessm ent (ISA) pr ovides a concise, but occasionally cursory overview of the key sc ie ntif ic issues f o r nitr ogen and sulfur oxides related to atm o spheric chem istry and physics (Section 2), ecological expos ures (Section 3), and e ffects (Section 4). The section on effects is m i ssing a brief discussion of the im portance of NO x as an ozone precursor. NOx-induced tropospheric ozone effects need no t be covered in detail sin ce they hav e recen tly been rev i ewed as a part of the recen t CASAC evaluation of photochem i cal oxidan t s. Nevertheless, the key role that NOx plays as a precursor to ozone in the troposphere must be highlighted in the ISA. The ISA would benefit f r om the addition of a section on the com p lexity of N and S biogeochem i cal cycles and the need to understa nd all natural and anth ropogenic inputs and outputs to these cycles. The m o st readable and b e st prep ared sect ion of the ISA was Section 5 on Findings and Conclusions. In fact, I recommend that Section 5 be brought forwar d (at least in part) to be presented as a summ ary of the docum ents key c onclusions. Section 5 stri kes the right balance between the beneficial and adve rse effects of N deposition th at was largely m i ssing within Section 4. In a lead-off positi on within the ISA, the Findings and Summ ar y m a terial would provide the key conclus i ons f r om which an in ter e sted re ader m i ght then search f o r ad dition a l details and support within the document and it s A nnexes. All key conclusions within the Findings and Summ ary section m u st include parenthetical references to the pages within the ISA or appropriate Annex that the r eader could look to find justifi cations for the conclusions. For continu i ty with th e p r evious Air Quality Cr iteria Docum e nts (AQCD) f o r nitrog e n and sulfur oxides, summary m a terials from those docum ents that have not been changed by new research m i ght be brought forward and used with in the ISA. For exam ple, little n e w inf o rm ation has becom e available on the direct effects of NOx and SOx on plant response, but the quantitative understanding of the ge nerally high am bient concentratio ns needed to illicit adverse responses to direct NOx or SOx exposures shou ld be reiterated with in the ISA. Section 5 provides the general statem ents of lim ited direct effects at cu rrent am bi ent concentrations, but Section 4 should include an overview of the key data from previous AQCDs in support of those

statem ents. When adverse effects are discussed within Section 4 of the ISA they should (where possible) be referenced to the st ate o f current exp o sures presente d within Section 3. F o r exam ple, the autho r s need to sho w the reader how to inte rpret a m u lti-year experim e ntal exposure to 20 to >100 kg N ha -1 y -1 in the context of ambient levels that typically are m a xed out near 10 kg N ha 1 y -1

. The authors have not taken full advantage of the Annexes. By m y count Annexes 1 and 2 were cited 7 and 11 tim es, respectively, but Annexes 3 through 10 were cited only 2,1,1,0, 1,0,0, and 1 tim es, respectively. The Annex m a terial sh ould serve as a source of expanded inform ation

57for the reader to highlight key poi n t s m a de within the ISA. In thei r current for m and level-of-use the Annexes are not helpful to the reader. References to prim ary research articles and cr oss-references to key discussions within the ISA and Annexes are often left out or ignored. T h is deficiency m u st be corrected. I offer som e suggestions in the specif i c comm ents listed below

. A lim ited literature search for nitrogen depos ition and im pacts research conducted from 1991 through 2008 produced a num ber of research arti cles that are not m e ntioned or evaluated within th e I S A. As m u ch as possible the aut hors need to lim it the use of subjective statements like ‘m aybe’, ‘if’, ‘probably’, ‘po ssibly....etc’. Rewriting such st atem ents to indicate the true quantitative nature of the prim ary research conclusions would be a better approach.

Specific Comments: Chapter 1 Page 1-2 lines 5 to 22: A dd a bullet asking if the f o rm of the current secon d ary stand a rd is appropriate for the evaluation of a nd protection against adverse effects.

Page 1-5 lines 12 to 15: Even though no subs tantive research has been generated on the topic of gas phase responses to NOx and SOx since the publication of their m o st recent AQCDs, respectively, the ISA should include a brief overview and quantification of the air concentrations of gaseous form s of N and S necessary to generate adverse responses.

Chapter 2 Page 2-16 line 10: The term sensitiv e ecosystem is used he re prior to it be ing def i ned in the context of the ISA.

Chapter 3 Page 3-11: S ection 3.5.1 is inadequately re ferenced. The authors should either add references or point to a more detailed discussion within an A nnex or to pages within a previous A Q CD where such a discussion can be found. The following references m i ght be quoted as a dem onstration of how HNO 3 is incorporated in to f o liage : Hanson PJ, Garten CT (1992) Depo sition of H 15 NO 3 vapor to white oak, red m a ple and loblo l ly -pine foliage -experim e ntal-ob s ervat i ons and a gene ralized- m odel. New Phy t ologist 122:329-337. Garten CT, Schwab AB, Shirsh ac TL (1998) F o liar retention of N-15 tracers: im pli cation s for net

canopy exchan ge in low-and high-elevation fo rest eco sy ste m s. FOREST ECOLOGY AN D MAN A GE MENT 103: 211-216. Vose JM, Swan k W T (1990) Preli m i n ary esti m a tes of foliar absorption of N-15 labeled nitric-acid vapor (HNO 3 ) by m a ture ea ster n white-pine (Pinus-strobu s) CANADIA N JO URN A L OF FOREST RESEARCH 20:857- 860.

Page 3-11: A num b er of usef ul references could have b een a dded/cited within th is section. For exam ple:

A m m a nn M, Siegwolf R, Pichlm ay er F, et al. (1999) Esti m a tin g the uptake of traffic-derived NO2 fro m N-15 abundan c e in Norway spruce needle s. Oe cologia 118: 12 4-131. Boy ce RL, Friedland AJ, Cha m b e rlain CP, et al. (1996) Dire ct canopy nitrogen uptake from N-15- labeled wet dep o sition by m a tu re red spruce. CANADIA N JO URN A L OF FOREST RESEARCH 26: 1539-1547 Nussbau m S, V onball m o o s P, Gfeller H, et al. (1993) Incorporation of at m o spheric (NO 2 )-N-15- nitrogen into free a m ino-acid s by Norway spruce picea-abi e s (l) karst. Oecologia 94:408-414.

58Qiao Z, Murray F (1998) Im pro v e m ent of the N-15 dilution m e thod for esti mation of absorpt i on of NOx by plants supplie d with N

- 15-labelled fertilizer. New Phy t ologist 138:13-18. Segsc hneider H J , Hutzen H, Forstel H, et al. (1 993) Uptake of (NO2)-N-15 and m e ta bolic tra n sfer of the (NO2)-N-15 nitrogen to various nitrogen fr actions of sunf lowers. ISOTOPENPRAXIS 2 9 :51- 57. Vallano D M , Sparks JP (2008) Quantify ing fol i ar uptake of gaseou s nitrogen dioxide usin g enriched foliar delta N-15 values . New Phytologis t 177: 946- ??? Vonball m o os P, Nussb au m S, Brunold C (1993) The relationshi p of nitrate reductase-a ctivity to uptake and assi milatio n of at m o spheri c (NO2)-N-15-nitr ogen in nee d les of norway spruce (Picea-a b ies [ l ] Karst). Isoto p enpraxi s 29: 59-70.

Page 3-11 lines 24 to 25: A reference is needed f

o r this sta t e m ent. Perhaps the f o llo wing: Hanson PJ, Rot t K, Ta y l or GE, et al. (1989) N O 2 depo sition to ele m ents repre s entativ e of a forest landsc a pe. At mospheric Enviro n m ent 23:1783- 1794.

Page 3-12 line 21: A reference is needed fo r the 1 ppb com p ensation point quoted here.

Figure 3.6-1: W hy is this figure used? S houldn’t it be a summ ary of NOx and SOx issues?

Figure 3.6-2. The caption should read ‘Aggregate m a p of the m a jority of routin e U.S. m onitoring stations.’

The Figure and brief paragraphs on page 3-17 seem unnecessary.

Section 3.7.1 would be improved with the inclus ion of the graph dem onstrating the nature of NOx concentrations through tim e (i.e., over de cades). Is this data not available? The graphics provided for SOX and nitrogen and sulfur deposition in subsequent sections nicely dem o nstrate the declining nature of N and S inputs to most regions from the late 1980s early 1990s in when com p ared to 2004 to 2006 data.

For places w h ere a com p lete continu ous record ex ists it would be appropriate to inclu d e a graphic showing the full trajectory of N and S de position through m e asured tim e.

Captions for the Figure 3.8-x series need to in clude a description of the source of the data within th e f i gures.

Statem ents m a de at the top of page 3-41 need to be referenced to th e i r s ource lite rature. In general, S ection 3 suffers from inadequate attribution of the prim ary source data.

The total and background axes with the figures on pages 3-52, 3-53, 3-55, and 356 should be m a de the sam e . As dr awn, the figures m a ke it difficult to judge the level of background N or S levels against current tota ls. I would also reco mm end t h at the bottom graph in each of these figures be cha nged from a percentage of background to a quantitative am ount of the indicated exposure m easure above background. Low background levels near zero m a ke the calculation of percent changes of little value. That is, a large percentage of a really sm all va lue is of ten still a rea lly sm all value.

59Page 3-58 lines 28: This is a key point. W h ere are the data or references to back it up? A citation to a publication, or another E P A report needs to be included here. Additional references are also needed on page 3-59.

Please consider bringing the following Annex fi gures forward to this section of the ISA: AX4.1-1, AX4.1-2, AX4.1-3.

Chapter 4 I would prefer to see this sect ion organized along the lines of di rect versus indirect effects of NOx and SOx. That approach has serv ed th e c o mm unity well in the p r e ceding AQCDs, and it be tte r re f l ects th at nature of the current N and S standards (gaseous exposures). Specifically Section 4.4.2 shoul d be moved ahead of the discussion of acidification and nitrogen nutrient additions . This recomm endation is not offered to perpetuate the use of a gaseous form of the welfare standard, but ra ther to recognize the history of NOx and SOx regulations. Delega ting the prim ary eff ects of NOx and SOx exposures to a hidden corner at the b ack of the report seem s inappropriate.

Page 4-2 line 1: The term biosynt hesis m a y need further def i nition.

Section 4.1.3: The discussion of critical lo ads m i ght be better located following the discussion of all direct and i ndirect effects. Redundant sec tions could all be com b ined togethe r in to a single sec tion on th e c r itica l lo ads relev a nt to the com b ined and inte ra cting effects of the full range of adverse effects of N a nd S inputs. Such a section should describe the need for a com p rehensive bioge ochem i cal cycling-based assessm ent of the N and S cycles in support of the concept of critical loads.

Page 4-6 lines 10 and 11: W h ere ar e the dose-response relationships?

Page 4-7 line 28: A reference is needed for this statem ent.

Page 4-8 line 1: A reference is needed for this statem ent.

Figure 4.2-1 contains the wrong im age. It has been inadverten tly swapped with the figure for the im age in Figure 4.2-2.

Top of page 4-12: References to these statem ents are needed.

Page 4-12 lines 20 and 21: A reference is needed for the C:N statem ent.

Page 4-12 line 28: N m a y also be retained for long periods within plant biom ass.

Page 4-12 line 29: A reference is needed for this statem ent.

At som e poi nt within Section 4 it would be useful to summ arize the percent of US land area (perhap s within regions) anticip a ted to be impacted by direct effects of N and S for m s, acidification, N deposition, etc. A table w ould suit this purpose nicely.

60References are needed in Sec tion 4.2.1.4 on base cation leaching.

Page 4-26 line 22: OC needs to be defined.

Section 4.2.2.2 is a good discussion (needing re ferences) that m i ght serve the reader bette r if it o ccurr ed ear lier in the doc um ent.

Page 4-28 line 25: W oul d it be appropriat e to change the word “gradual” to ‘accelerated ’ ?

Page 4-29 lines 14 to 22: References for these statem ents are needed.

Page 4-31 line 10 and 11: The authors should be careful when using as phrase like “contributed to”. In m a ny cases the data pr obably showed only a correlation with an observed effect rather than proof of a sp ecific m echanism responsible for the effect. Sim ilarly, o n Page 4-31 line 26, sho u ld or co u l d the word “in d icated” be replaced with ‘hypothesized’?

Page 4-33 lines 19 and 20: Can this stat em ent be m a de more quantitative?

Section 4.2.4.1 is an excellent se ction that is well referenced . Use it as an exam ple when modifying other portions of Section 4.

Page 4-64 line 23: An “in review” paper is no t an acceptable inclusion in the ISA.

Page 4-65 line 8: W e re discussed regions acid naturally or have they developed acidity as a result of anthropogen i c N and S additions ? Can such a dis t inction be m a de?

Page 4-66 lines 26 to 28: Add the litera tu re c ita tion f o r this statem ent.

Page 4-70 line 21: I think this headin g should be num b ered. Perhaps 4.2.4.2.2.

Bottom of page 4-70 and top of page 4-71. The text should be expanded to show the

com ponents of the analysis of McNulty et al . (2007). The reader doe sn’t have sufficient inform ation. Is such inform ation present in an Annex? If so, please direct the reader to the text. How are variable rates of plan t productivity used in this analysis?

Page 4-71 line 30: A reference for this statem ent is needed.

Page 4-104 lines 14 to 24: This m a terial is unnecessarily redundant with m a terial in Sections 2 and 3.

Page 4-121 line13: Is a change in pro ductiv ity or biodiversity n ecessarily an adverse effect? This question should be discussed in the context of N and S deposition or loading.

61W ithin section 4.4, the discussion on direct phytotoxic effects shoul d be moved to the front of Section 4. The discussion of di rect phytotoxic effects should include a description of the key expos ure response relationships know to drive adverse direct effects. Such inform ation could easily be lif ted and reused from prior AQCDs since little new infor m ation is available on this topic. The following references pub lished since the last N and S AQCDs and should be considered for inclusion in the ISA discussion:

A m m a nn M, vonBall m oo s P, Stalder M, et al. (1995) Uptake a nd assi m i lation of at m o spheric NO2-N by spruce needl e s (Picea abie s) : A field study

. W A TER AIR AND SOIL POLLUTION 85:1497- 1502. Desa ntis F, Allegrini I (1992) Heterogen e ou s r eactions of SO 2 and NO2 on c a rbonaceo us su rfaces. ATMOSP HERI C ENVIRO NMENT PA RT A-GENERAL 26: 3061-3064. GunthardtGo e rg MS, Sch m utz P, Maty ssek R, et al. (1996) Le af and ste m stru cture of poplar (Populus

x eura m e ricana ) as influenced by O-3, NO2, t h eir co m b i n atio n, and different soil N suppli e s. CAN A DIAN JOURNAL OF FO REST RESEARCH 26:649- 657. Kainulain e n P, Holopain en JK, Oksane n J (1995) Eff ects of so2 on the conce n trations of carbohy drates and sec ondary co m p ound s in sc ots pine (pinus- s y l vestris l) and norway spruce (picea-abie s (l) karst) seedli ngs. New Phy t ologist 130: 231-23 8. Manni nen S, Huttunen S (2000 ) Respon se of needle sulp hur and nitrogen con centration s of Scots pine

versu s Norway spruce to SO2 a nd NO2. ENVIRON M ENTAL POLLUTION 107:421-436. MENG FR, CO X RM, ARP P A (1994) Fu m i gating m a ture spruce branche s with so2 effects on net photosy n the s is and sto m at al co nductanc e. CA NADIAN JOU R NAL OF FO REST RESEARCH 24:1464-1471. Qiao Z, Murray F (1997) The e ffects of root ni troge n supplie s on the absorptio n of at m o spheri c NO2 by

soy b ean leave s

. NEW PHYTO L OGIST 136: 239-243. Qiao Z, Murray F (1998) The e ffects of NO2 on the uptake an d assi m i l a tion o f nitrate by soybean plants. ENVIRONME N TAL AND EXPERI MENTAL BOT A NY 39:33-40. Thoene B, Schroder P, Papen H, et al. (1991) Ab sorption of a t m o sph e ric no2 by spruce (picea-abies l karst) trees .1. no2 influx and its correlation wi th nitrate reduction. New Phy t ologist 117:575- 585. Vassilako s C, Katsa nos N A , Niotis A (1992) Phy s icoc he m i c a l da m a ge para m e t e rs for the action of so2 and no2 on sing le pieces of m a r b le. At m o spheri c Environ m e n t 26: 219-223. W o l f enden J, Pearson M, Francis BJ (1991) effects of over-winter fu m i gation with sulfur and nitrogen dioxide s on bioche m i cal para meters and spring growth in red spruce (Picea-rubens Sarg) Plan t Cell and Enviro n m ent 14:35-45

. W u l ff A, Karenla m pi L (1996) Effects of long-ter m open-air e xposure to fluoride, nitrogen com p o und s and SO2 on visi ble sy m p to ms, pollutant accu mulation and ultrastructure of Sc ots pine and Norway spruce seedlin gs. Trees 10:157-171

.

A brief section on the role of NOx as an ozone precursor should be added to Section 4.4. This need not be very long, but it should pr ovide sufficient infor m ation to inform the reader that NOx pollution is often indirec tly responsible for known adverse effects of photochem i cal oxidants on vegetation (and m a te rials too for that m a tter). The reader could sim p ly be pointed to the recen t AQCD for ozone and other photoch e m i cal oxidants.

Som e m e ntion should be m a de of the potential for anthropogenic N additions to fertilize

natura l ecos y stem s leading to the s e q u estra tion of CO 2 fr o m the atm o sphere. This could be added as a counter point to the discussion of N 2 O em issions to be expected from N saturated sy stem s. If the author s don’t provide this discussion and show that the issue was considered others will dem a nd that it be added later.

The Tables attached at the back of Section 4 should be em bedded with the text to which they apply or m oved to their corresponding Annex.

62Chapter 5 I really enjoyed read ing Section 5. I found it to be c oncise, infor m ative and easy to follow. As I’ve already s t ated I believe it (or a portion of it) could be presented at the front of the docum ent. I does, however, n eed to be populated with references to appropriate portions of the ISA, ISA-Annexe s or other published wo rk that support each

statem ent.

Page 5-2 line 13: Should “nitri fication” be ‘e utrophication’?

Page 5-4 lines 16 to 18: Although this stat em ent m a y be true, I don’t believe it is supported w ithin the curren t draft of the ISA.

Section 5 m i ght be rearranged to include: 5.4 Direct P hototoxic Effects of NOx and SOx 5.5 Indirect effects of acidification and nitrogen nutrient enrichm e nt 5.6 Other effects

Page 5-7 line 29: Should this read ‘Inorganic alum inum....’?

Page 5-18 lines 19 and 20: Reword as “...ecosystem s causes fertilization of trees and grass l an ds accelerating growth in som e species.... The words “inadvertent” and “unnatura l” seem ed inappropriate to m e

. Page 5-19 line 9: Change to “W hen N increases to....”

Page 5-20 lines 24 and 25: N is also retained in biom ass.

Page 5-37 lines 27 and 28: I would change “m any forest ecos y stem s” to ‘sensitive forest ecosystem s’. There are m a ny forest ecosystem s that not show any adverse effects from this level of N depositio n for a long tim e (if ever).

Most of the Tables should be used in thei r resp ective Sections a nd associated with

som e descriptive text. T a ble 5.7-1 is a ppropriate to the Summary and Findings section, and I would retain it. It would be helpful, however, to add a column to Table 5.7-1 to show how the experimental le vels of N&S exposure actually relate to current N or S deposition rates. In m a ny cases the experim e nts use N deposition rates that are an order of m a gnitude above current levels.

63Draft Text for an Ans w er to ISA Charge Question #10:

Several additional effects are dis c ussed, in clud ing mercur y methyla t ion, direct g a s-phase effects on foliage, and N 2 O as a greenhouse gas. How w e ll does the draft ISA characteriz e the evidence on these topics?

Designating the direct ef fects of gas p h ase NO x and SO x as an additional ef fect is in con s isten t with prio r AQCDs that appropria te ly deline a ted d i rect versus indirect effects of the defined criteria pollutants. I would argue that the ISA should re turn to this form at and characterize gas phase effects of nitrogen and sulfur oxides as direct effects that are seldom expressed under

current atm o spheric conditions. Th at discussion could be logically followed by a discussion of the indirect effects of acidi fication, nitrogen nutrient addi tions, sulfur-induced m e rcury

m e thylation, the producti on of the greenhouse gas N 2 O, the production of tropospheric ozone, the contributions of NOx and SOx to visibility issues, and the interactive influence of global anthropogenic N additions on carbon sequestration within natural ecosystem s . The last item on the stim ulation of ecosystem carbon sequestration is not currently discusse d within the ISA, but should be considered as an addition.

Som e references related to N de position and carbon sequestration: Grace J (2004) Understa ndi ng and m a naging t h e globa l carbon cyc l e. Journa l of Ec ol ogy 92:189-202. H y vonen R, A g ren G I , L i n d e r S, et al. (20 07) T h e lik ely im pact of e l e v at ed [CO 2 ], nitro g e n dep o si tio n, in creased tem p erature an d m a nag e m e nt on c a rbo n se ques t rati on in tem p erate a n d borea l fores t e c osy s tem s : a litera ture re vi e w . New Phy t o l og ist 17 3: 46 3

- 480. K o rner C (2 00 0) Bi osp h ere r e spo n ses to C O 2 enri chm e nt. Ec ol og ica l A ppli cat io ns 10: 15 90- 16 19

. Mak i pa a R

, K a rjala i n e n T, Pussine n A

, e t al. ( 1 9 99) Eff ects of cl im ate cha n g e a n d ni troge n de posi t i on

o n th e car b o n seq u estration o f a fo rest ecosyste m in the b o r eal zo ne. CANAD IA N JOURNAL O F FO REST RESEA RCH 29: 14 90- 15 01

. N a del hoffer K J , Em m e tt BA , G u n d ersen P, et al. (19 99) N itroge n de po siti on m a kes a m i nor

con t rib u t i o n t o car bo n se qu estrati o n i n t e m p erate forest s. N a ture 3 98: 14 5-14 8. N o rby RJ (19 88) N itr oge n dep o si tio n: a c o m pone nt of g l ob al ch an ge a n aly s es. N e w Phy t olo g is t 13 9:1 89- 20 0. Oren R, E llsw o rth DS, J o h n s en KH, et al

. (200 1) Soi l fe rtili ty lim its carbo n sequ estrat io n by forest e c os y s tem s in a C O 2-enric h ed a t m o sphere. N a ture 41 1: 46 9-47 2. Schin d l e r D W , Bay l ey SE (1 99 3) The b i os phere as a n in creasin g s i n k f

o r atm o spheri c carb o n - estim ates from increased n i troge n de posi t i on . G l o b a l B i oge oc hem i cal Cy cles 7 : 7 17- 73 3.

64

### Dr. Dale Johnson

The quality of the review is very m i xed, especia lly in Section 4. The first part is fraught with inaccu racies , m i sconceptions, and bias, the last pa rt is even handed and co mplete. Indeed, there

seem s to be a real dichotom y between two diffe rent authors who seem to have written this section, and the second one has a m u ch m o re comp lete and balanced view of the situation. Again, I stress the need f o r looking at all points of view – which in total this docum ent does, but only in certain parts and these parts do not adequa tely m a ke their way in to the summ ary sections. The focus is on the negative effects, which leaves this docum ent open for severe criticism once it is released. There are se veral peer-reviewed publi cations that discuss a nd even dem o nstrate the possibility that increased N deposition has or wi ll increase terrestrial ecosystem C se questration. Below I cite som e examples:

LeBauer, D.S., and K.K. Treseder. 2008. Nitroge n lim itation of net prim ary productivity in terrestrial ecosystem s is globa lly distributed. Ecology 89: 317-379.

This is a m e ta ana l ysis o f f

e rtiliz er s t udies th at in vestig ated la titud i nal tre nds in respo n se to N. They note th at m o st fertilizer applications differ from atm o spheric deposition in that they are greater in quantity (at least over the short term ) and pulse-like in tim e . They also fully recognize the potentially negative effects of too much N. The las t senten ce of th eir C onclusions reads: "Incr easing N depositio n, particula r ly in the m o st rap i dly dev e loping regions, is likely to f u rther stim ulate global NPP and slow the accum u lation of atm o spheric CO2."

Magnini, F., Mencuccini, M., Borghetti, M., Berb ig ier, P, Beringer, P., Delzon, S., Grelle, A., Hari, P., Jarvis, P.G., Kolari, P., Kowalski, A. S., Lankreijer, H. Law. B.E., Lindroth, A., Loustau, D., Giovanni, M., Moncreiff, J.B., Raym ent, M., Tedeschi, V., Valentini, R. and Grace, J. 20 07. The human footprint in the carb o n cycle of temperate and boreal forests. Nature 447: 848-850.

A quote from their abstract: "After the confounding effects of disturbance have been factored out, however, forest net carbon sequ estration is found to be overwh elm i ngly driven by nitrogen deposition, largely the resu lt of hum a n activities."

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

. 2008. Sim u lated chronic nitrogen deposition increases carbon stor age in Northern Tem p erate forests. Global Change Biology 14: 142-153.

This is a field study where applicatio ns of N at 30 kg ha-1yr-1 over two d ecades p r od uced greater C sequestration in surface soils and live w oody tissues in north ern hardwood forests in Michig an.

65For the com b ined effects of CO2 and N:

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

The authors point out that m odel estim a tes of C s e questration due to el evated CO2 are probably greatly inflated becau se they do not account fo r N lim itation. They calcu late som e projected incre a ses in N depositio n and estim a te how m u ch th is cou l d f a cilitate the m odeled estim a tes of CO2-enhanced C sequestration and it falls far short. So the point is that m odels that do not incorpor ate N overestim ate C seques t ra tion and a l so im plies that m o re N will lead to more C sequestration.

Again, I m u st em phasize that this is m eant to provi de the other side of the N deposition issue and in no way negates the w e ll-docum ented negative e ffects of excessive N deposition on terrestrial ecosystem s. The problem with nitrogen in terrest rial eco system s is that there is a very short plate a u betw een def i cien cy, where in creas ed gro w th with inc r eased N inp u ts will o ccu r, and excess, where m a ny negative effects s u ch as so il and water acidification and water pollution

commence.

Specific co mments:

p. 1-2, lines 5-22: Here I ask m y recurring question: why the com p lete focus on adverse effects? 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. Agai n, I do not advocate excusing air polluters on this basis, but I think a fair and com p lete assessm ent re quires that this side be discussed. T o fail to do so risks losing credib ility f o r the entire ef f o rt.

p. 4-2, Title: The very title of this section clearly shows an bias toward ad verse effects and such a bias is com p lete ly unacc eptable in a docum ent th at purports to be scientif ically objective.

p. 4-3, lines 7-8: It is very hard to imagin e th at in creas ing N deposition will f a il to cau se “change” in any ecosystem, whether it be beneficial or harm ful change. I think there is a need to be m o re specific here.

p. 4-7, line 24: Acid cations th at build up during soil acidific ation include, im portantly, Al 3+ as well as H +

. p. 4-7 line 25: Soil acidification IS a natural proc ess. There is no doubt of this. Extremely acidic soils can be found in pristine pa rts of the world. Y ou should elaborate on such processes here – carbonic acid, organic acids, plant cation uptake.

p. 4-7, line 28: W h ere have decreases in pH attr ibutable to acidic de position been found in the US? You should cite ref e rences here.

66p. 4-8, line 6: The B horizon lies below the Oa hor izon? S i nce when? This can happen in som e cases, but is the excep tio n rather than the ru le . What happened to the A and E horizons? Does this author know anything about soils and soil genesis?

p. 4-8, lines 15-17: Actually, the si tuation with hardwoods is much m o re com p licated than that and this statem ent is m i sleading. Hardwoods, by taking up larger am ounts of Ca, actually acidify sub surface soil horizon s m o re than conifers to even though they m a y enrich surface h o rizons with Ca by litterfall recycling. Th ere is a classic paper by Alban ( 1982) that clearly show this and should be cited here. Also, an excellent source of inform ation is the review paper by Stone (1975).

p. 4-8, line 28 and throughout: “SO 4 + ”?? Since w h en is sulfate a catio n ? This is an embarrassing

m i stake. Sulfate is an an ion: SO 4 2-

p. 4-10, lines 5-6: Som e oil crops have S de m a nds that are in line with S deposition.

p. 4-10, lines 25-31: There are MANY other refere nces besides Sullivan et al 2004 that show this.

p. 4-11, line 30: Add this to the list: “3) greater growth causing m o re cation uptake and therefore more soil acidification”

p. 4-12, lines 2-9: Ammonium is also acidifying: it is either taken up by plants or m i crobes, thereby releasing H + , or is nitrified, cr eating nitric acid.

p. 4-14, lines 17-31: This is a good description of the leaching and acidification processes.

p. 4-15, lines 1-13: There are som e significant probl em s with this section. First of all, it is stoich iom e trically im possible f o r the soil ch anges described by Bailey et al to have been caused by any known level of acidic depos ition – I wro t e a le tter to the editor ab out this and felt that their reply was inadequate (Johnson, 2006). I insist that this be included in the discussion. Secondly, there are several exam pl es in the literature – even an entire book – written about studies where plant catio n uptake as well as atm o spheric deposition has caused substantial soil acidification (Johnson and Todd, 1990; Richter and Markewitz, 2001; Trettin et al., 1999). This review of the soil acidification literature for the US is tota lly inadequate and m i sleading.

p. 4-16, lin es 17-26: In n a ture, the rate of soil we athering seld om exceeds the rate of acidification – that is why soil na tura lly ac idif y. So it is no t r ealistic to as sum e that soil weath e rin g will a i d in the recovery of acidified soils.

p. 4-18, Figure 4.2-2: It a ppears that you have the wrong figure he re. I see a soil profile, not an in situ bioassay.

p. 4-23, line 16: “lowered or IN CREASED plant productivity”

p. 4-24, lines 2-3: why spell out potassium and sodium but not Ca and Mg?

67p. 4-24, line 30: Al is not toxic to all tree roots. Som e plants tolerate it and like acidic soils.

p. 4-26, line 12: Do you m ean Nitrogen to Carbon ra tio? If so, the usual expression is carbon to nitrogen ratio.

p. 4-31, lines 10-13: I thought that the red spruce declin e was largely attributed to clim atic factors. W h a t about Art Johnson’s work?

p. 4-37, lines 5-10: How about som e of the N-lovi ng invasive grasses in the southwestern US like Brom us species ? Ed ie Allen h a s shown that N depositio n clea rly f a c ilitates th is in southern California.

p. 4-43, line 22: Do you m ean cation here?

p. 4-43, lines 25-26: In the st udy of Lawrence et al, did H + and Al 3+ decrease to m a ke up the difference b e tween base cation d ecreases and m i neral acid an ion decrease s? Som e thin g surely had to, otherwise charge ba lance was not m a intained.

p. 4-44, lines 4-5: How were strongly acidic organic anions estim ated?

p. 4-63: A discussion of capacity/inte n sity and ani on m obility concepts f o r

water ac idif ication is needed here. Na m e ly, that a strong acid anion su ch as sulfate or nitrat e passing through an acid soil c a n m o bilized H + and Al 3+ with no delay because these acid cations are m o st available on exchange sites to balance the anions. This reac tion does not require soil ch ange and is instantly reversible if strong acid anion inputs cease. This is quite a different m a tter from the case where soils acidify. An already acidic soil, whether by natural acid production or by acid rain, is a necessary but not sufficient condition for the acidi fication of soil water – strong acid anions are also need ed.

p. 4-84, lines 13-23: This is very interesting – we did not expect that soils of the northeast would have such buffering with respect to sulfate. Very im portant point.

p. 4-91, Figure 4.2-17: The y-axis le gends on this figure are m e ssed up.

p. 4-104, line 30: “unnatural growth rates?” Again, this reflects th e negative bias that seriously detracts from this entire docum ent. Just say incr e a sed growth rates and le t the re ader d ecide if it is good or bad.

p. 4-105, lines 16-17: O n ce again, this statem ent refl ects the negative bias th at seriously detracts from this entire docum ent. I suspect that you would also be looking for negative effects if N lim itations were inc r eas ed rath er th a n decrea sed in the end l es s search for negativ e con s equences. Please let us sim p ly state what we think will happ en and leav e out thes e value judgem e nts.

p. 4-106, lines 9-10: At LAST! W e s ee the m e nt ion of potential beneficial effects.

68p. 4-111, lines 3-17: O n ce again, there is too much negative bias here. I raise once again the issue of global C and the potential for N pollu tion to m a ke the terr estria l C balance b e tter (Kauppi et al., 1992; Ma gnini et al., 2007).

p. 4-121, lines 12-32: This is as close to a balanc ed presentation as I have yet seen in this docum ent. It needs to be up front along w ith all the potential negativ e effects.

p. 4-122, lin es 15-16: Of course add i ng the lim iting nutrient causes the n e xt m o st lim iting nutrient to becom e li m iting – ev eryone who has ever worked w ith fertilization knows this. W hy is this a bad thing ? Is it h ealth ier f o r a f

o rest to be N lim ited than Ca, K, or Mg lim ited ? Once again, an unnecessary value judgem e nt here.

p. 4-123-124: At last we see the new article by Magnini and a balanced discussion about it. I think this kind of alternative view ne eds to be m o re up front as well.

p. 4-126: Good discussion of potential effects on gr asslands and invasive species problem s in rela tion to N.

p. 4-127-128: Again, a very good disc ussion of potential N effects on arid and sem i -arid lands. N inputs in these areas could be a real problem and there is not much to be seen in the way of benefits.

p. 4-161-162: Good discussion of the non-acidifyi ng effects and biological role of sulfur.

p. 5-6, lines 19-31: Some of that good discussion and balanced tr eatm ent seen on the last pages of section 4 need to m a ke their way into this summ ary.

p. 5-7, line 29: Alum inum is t oxic to SOME tree roots.

p. 5-8: Again, Som e of t h at good discussion and balanced treatm en t seen on the last pages of section 4 need to m a ke their way into this summary.

p. 5-12, lines 2-4: This is a very im portant yet seldom recognized point about surface water vs soil acidification.

p. 5-18, lines 19-20: Once again, why m u st we say unnatural? W hy not just INCREASED growth rates? And then go on to elaborate about how you do not want this to happen in certain places (if in deed you do want to m a intain N deficiencies).

p. 5-21: Good summary about N effects on growth, both positive and negative.

References:

Bailey, S. W., S. B. Horsley, and R. P. Long. 2005. Thirty years of change in forest soils of the Allegheny P l ateau, Pennsylvania. Soil Sci. Soc. Am . J. 69:681-690.

69Johnson, D.W. 2006. Comments on “Thirty years of ch ange in forest soils of the Allegheny Plateau, Pennsylvania.” Soil Sci. Soc. Am er. J. 69: 2077.

Johnson, D.W., and D.E. Todd. 1990. Nutrient cycli ng in forests of W a lker Branch Watershed: Roles of uptake and leachi ng in causing soil change. J. Environ. Qual. 19: 97-104.

Kauppi, P.E., Mielikäinen, K. and Kuusela, K ., 1992. Biom as s and carbon budget of European Forests, 1971 to 1990. Science, 256: 70-74. Magnini, F., Mencuccini, M., Borghetti, M., Berb ig ier, P, Beringer, P., Delzon, S., Grelle, A., Hari, P., Jarvis, P.G., Kolari, P., Kowalski, A. S., Lankreijer, H. Law. B.E., Lindroth, A., Loustau, D., Giovanni, M., Moncreiff, J.B., Raym ent, M., Tedeschi, V., Valentini, R. and Grace, J. 20 07. The human footprint in the carb o n cycle of temperate and boreal forests. Nature 447: 848-850.

Richter, D.D., and D. Markew itz. 2001. Understanding soil cha nge. Soil sustainability over

m illennia, c e nturies, and decades. Ca mbridge University Press

. Stone, E.L. 1975. Effects of species on nutrient cycl es and soil change. Philos. Trans. R. Soc. Lond. Ser. B Biol. Sci., 721: 149-162.

Trettin, C.A., D.W

. Johnson, and D.E. Todd, Jr. 1999. Forest nutrient and carbon pools: a 21-

year assessm e nt. Soil Sci. Soc. Amer. J. 63: 1436-1448.

70

### Dr. Donna Kens k i

Overall, this was a fine job summa rizing a lot of data. The quality varied from section to section, but m o st of t h e relevant infor m ation was here . Nevertheless there were som e significant shortcom ings that should be addressed in futu re drafts. Most of m y comments address the presentation of air quality and em issi ons data, per Charge Questions 1-3.

The chem istry discussion is adequate. Most of the air quality issues were covered in Chapter 3, and I found them lacking in several ways, especia lly with respect to th e nitrogen species. Section 3.1 needs a m a p of NO x e m i ssions density (all sources) and a com p arison, at least nationally b u t preferab ly regionally

, of the relative im portance of each o f the anthrop ogenic and biogenic sources to total NO x e m issions. W e ’re told that soil contribut es 10% of NO x em issions globally, and 26% of NO in Illinois, but no estim ates are given for soil NO x contribution to US

em issions either nationally or regionally. Sim ilarly for biom as s burning. T h e statem ent that increased wildfires will m a ke e m issions from th is sector increasingly important should be substantia te d with quantita tive da ta . This information is too impor tant to releg a te to the Annex, and Table 3.11-2 puts sources in pr io rity o r der bu t is not qu an titativ e. Tab l e AX2-1 contains the relevant inform ation, and a shortened version of it, edited to elim inate the m a ny s m all sources and include only m a jor categories wo uld add significantly to this section. The section also needs a description of NO x e m ission trends, parallel to the discussion of SO x e m ission trends in Sec. 3.2. W h ile changes in NO x have not been as dram atic as those for SO x , they are docum ented an d the data are readily available. In addition, som e infor m ati on about future-year em issions projections would be nice, along with a brief summary of recent and exp ected con t ro ls on NO x and SO x sources. These analyses have been done by EPA already. Anothe r significant hole in the em issions discussion was NH 3 . Although we’re told that the NEI underestim ated NH 3

em issions by a factor of 2 or 3, we’re never gi v e n an estim a te of what those em issions are (underestim ate or not).

Section 3.6.1, and especially p. 3-15, lines 9-15 is som e what m i sleading in its description of the monitoring networks. S u re we have lots of oz one m onitors, but ozone monitors don’t tell us much about NO x or SO x or NH 3 . I don’t understand why the author s of this section decided to show us plots of ozone and PM2.5 air quality but not plots of SO 2 , NO x or NH 3 concentrations . W h ile it is tr ue as sta t ed in lin es 11-1 3 that NO x and SO x are o f ten m onitored at th e sa m e sites, the num ber of NO x and SO x m onitors is far less than for oz one or PM25. More relevant would be a plot of just NO 2 and SO 2 m onitors, which would m a ke imme diately apparent the significant gaps in spatial coverage of m easurem ents for these gases. F i gures 3.6-1 and 3.6-2 leave the reader with the im pression that the network of NO x /SO x m onitors is m u ch more dense than it really is. Including NATTS, HA PS, CO, and lead sites in Fi g. 3.6-2 only obscures the m a tter further. It m a y also be wort h noting that m onitors for both NO x and SO x have been cut from the networks in recen t years because their m a in purpose is perceived to be for com p aring to the prim ary NAAQS. As ambient concentrations for both NO x and SO x have fallen well below the standard throughout the US, the m o n itors are seen as a lower prio rity and unnecessary expense. At the sam e tim e, m onitoring budgets have been cut, leading to m onitor shut downs.

71Another shortcom ing of this section is that it does not address urban-ru ral differences. Figure 3.6-3, for exam ple, is of lim ited usefulness in as s e ssing th e com position of aerosol th at im pacts the sens itive

, m o stly rur a l reg i ons ide n tif ied late r; differences in urban a n d r u r a l a e r os ol s ha ve been noted by m a ny. A s i m ilar plot, but based on IMPROVE data, would be an im provem e nt, or a plot that shows both urban and rural com positi on. The m a j o rity of m o nitors, both gas and particle, are in urban areas; rural NO x and SO x monitors are rare. How does the lack of rural NO x and SO x m o nitors af f ect estim ates of N depositio n?

Figures 3.7-2 and 3.7-3, which com p ares am bient SO 2 and SO 4 concentrations in the early 1990s with m o re recent data, are very effective, but the text or captio n should note whether Fig. 3.7-3 is showing SO 4 concentrations in particulates or in rain f a ll – its not cle a r wh ich. A sim ilar set of plots should be shown for NO x and NH 3

. I didn’t like Fig. 3.7-4 when it showed up in the S O x prim ary ISA (as I recall from discussions, none of the panel did) and I still don’t like it. It is not effectively comm unicating inform ation about SO 2 concentrations; replotting on a log scale would m a ke it m u ch more informative. Especially in this con t ex t, the ex trem e valu es are less inf o rm ative than the rest of the distribution.

Figures 3.8-1 thru 3.8-4 are also inef fective. It is difficult to distinguis h m eaningful differences by com p aring the size of the pies in the upper and lowe r plots, and also to tell if there have been changes in the geographic distribution of th e various for m s of S and N deposition. N ADP produces a much m o re effective set of plots, at least for wet deposition, sim ilar to Fig. 3.7-2; perhaps tho s e could be s ubstitu ted h e re (s ee http ://n adp.sws.uiuc.edu/iso p leths / annualm aps.asp ) or these could be reworked to show the data in a sim ilar fashion. At least change the pies to bar charts as in Fig. 3.2-1.

Section 3.6.4 on satellite observati ons was too brief to be useful . It seem s clear that the technology holds great prom ise; it would be helpful to see som e support of that notion, rather than just have a laundry list of satellites without any indication of their st rengths and weaknesses. Is there usef ul data for o u r purposes (N and S deposition ) being produced by the satellites now ? If so report it here.

Section 3.6.5 could be rem oved to Annex 2.

This chapter should have left us with an understanding of the relative im portance of NO x , NH 3 , and organic nitr ate depo sition n a tion ally and regi onally, bu t a t the end I still f e lt unable to asse ss those except in a qualitative way.

Ultim ately, the question we want to answer is , wh at kind of secondary stan dard would be adequately protective of our sensi tiv e ecosystem s. Here I th in k th e ISA was not very helpful. I was search ing f o r inf o rm ation that explic itly li nked am bient concentrations or em issions with deposition and m o re im portantly with acidifica tion effects. How are ambient con cen trations rela ted to d e position ? Are thes e ess e ntia lly equ i v a lent? Can we com p are (using GIS tools or other quan t itative techn i ques) the d i s t ribu tion of c oncentratio ns (or depos ition ) to the distr i bution of

sensitiv e ecosystem s?

72Som e other general comm ents:

The various chapters and subsections m a ke occasi onal m e ntion of shortco m ings in the data and areas that are poorly understood, bu t these shortcom ings aren’t co llectively addressed anywhere. These data g a ps and res e arch need s s hould be ex plicitly d i scussed and su mmarized in the conclusions. Doing so would help us better understand som e of the lim its to our knowledge and also hopefully help EPA target research efforts and support future review s.

Another concern I have is that NH x isn’t addressed com p rehensivel y h e re because the focus is NO x and SO x , and it m a y not be comprehensively discu ssed in the PM ISA, because the focus there is PM. W h en or where does N H x get its due? If we always c onsider it as a sm aller part of

som e thing else, it m a y never get dealt with adequ a tely. I appreciate that NH x ’s contributions to deposition and acidification were discussed here at som e lengt h, but we seem in danger of

m a rginalizin g its ve ry im portan t role in nitr ogen and sulfur deposition because it is a lesser player, without doing the re search to adequately ch aracterize its ro le.

More specific comm ents:

p. 2-29 line 6-7 The concluding sentence, that covera ge of monitoring networ ks is thin over large expanses of the US, is true, but not a conclusion that follows from the previous discussion, which is only about the adequacy of th e m o nitoring techniques. It is a statem ent more approp riate for Sec. 3.6.1.

p.3-7 line 7-9 overrepresentation is a poor word choice. Perhaps hi gher density would be better.

p. 3-13, eqn 3.5-4 Isn’t the sec ond = sign supposed to be a + ?

p. 3-16, caption to Fig. 3.6-2 should be ..m ajority of routine...

p. 3-35, caption to Fig. 3.9-1 should read ...25 th and 75 th quartiles...

p. 4-7 Throughout this Section (4.2) the concept of base saturation is discussed and a few benchm ark figures (base saturation less than 20%, for exam ple ) are m e ntioned, but it does not explain how base satu ration is quan t ified until p. 4- 24. A brief definition at the b e gin n ing of this section would be a usef ul addition sin ce it m a y not be f a m iliar to the m a ny in the a t m o spheric community.

pp. 4-7 - 4-191 Som e how in this entire chapter, SO4 2- m o rphed into SO4 + . Search and replace gone awry? Very disconcerting.

pp. 4-9, 4-18 Figures 4.2-1 and 4.2-2 have been switched. T h e captions are correct but the figures them selves are reversed.

p. 4-24 Later in the docum ent there are m a ps of sensitive area s (although not enough—m u ch more of the data could/should have been summ a r ized graphically). Any available to show soil base saturation, or Ca:Al ratios, which m i ght be helpful here?

73p. 4-24 Change in term s soil water -> soil soluti on is confusing. Are these the synonym s or is there som e subtle difference?

p. 4-26 line 12 Calcium should be Carbon

p. 4-64, section 4.2.4.2 This section suffers from a l ack of integration. It’s difficult to assess the extent and distribution of these sensitive areas without som e gra phical help. Figure 4.2-12 is a start, but only tells part of the story; Figure AX4.3-2 does a much better job showing the location and extent of acidification. Also, acidified stream s and lakes are som e tim e s m e ntioned

separa tely a nd som e times toge ther ; it is no t clear whether regions w ith a c idif ied s t re am s

necessa rily also have ac idif ie d lakes, and vice versa.

p. 5-16, lines 5-14 Although this se ction is supposed to be about recent trends in acidification recovery, this last bullet doesn’t say anything about recovery and s eem s out of place. The parent section 4.2.4.2.1 em phasizes that this WSA surve y is summ er data and therefore biased low, but that caveat is not repeated here, as it should be. These results al so don’t jive with later data (i.e., on p. 5-17, 66% of Adirondack stream s currently have high Al). It would be useful to have a graphical assessm ent of the geographic extent of acidification eith er here or as suggested earlier, in section 4.2.4.2. Figure AX4.3-2 is very helpf u l in this regard.

p. 5-36 lines 19-23 Absolutely true that regula tory networks cannot ad equately characterize regiona l heterogene ity ( on a scale th at m a tches that of the se nsitiv e ecos y stem s) and hotspots. But the statem ent about hotspots identified at res earch sites was not discu ssed in the text, except in reference to Hg. If this is docum ented it should be discussed in the body of the ISA, not

m e ntioned first in the summary.

p. 5-36, line 25 lead should be led

p. 5-38 This section comes to an abrupt end; is som e thing m i ssing?

74

### Dr. Nares h Kumar

Inform ation provided in the Integrated Scien ce A ssessm ent docum ent on atm o spheric chem istry and physics, air quality, and deposition and exposur e is concise, but sufficiently comprehensive. Specific co mments are:

Page 2-2, Lines 6 & 7: N itric acid doesn’t contribute to the ac idity of par t icles, so ther e is a ne ed to reword th e senten ce.

Page 2-2, Lines 23 & 24: It woul d be m eaningful to m e ntion the contribution to NOx em issions from m obile sources and electric utilities (e .g., According to NEI 2003, 55% of NOx e m issions were from mobile sources and 22% were from e l ectric utilities).

Page 2-5, Line 7: The following reactions should be added before Equation 2.2-2

O 3 + NO 2 Æ NO 3 + O 2 NO 3 + NO 2 Æ N 2 O 5

Page 2-5, Line 15: The nitrate radical, NO 3 should be included as part of the photolysis.

Page 2-6, Lines 7 thru’ 16: The paragraph should also m e ntion the negati ve radiative forcing caused by nitrate particles.

Page 2-6, Line 28: Add “from the free tr oposphere” at the end of the sentence.

Page 2-7, Line 9: Add “except at low e r te m p eratu r es” at the end of the sentence.

Page 2-8, Line 13: There is no SO 4 2- in Equation 2.2-15.

Page 2-8, Line 22: “diatoni c” shou ld be “diatom i c”.

Page 2-9, Line 31: Change “high” to “m oderate”

Page 2-9, Line 32: After “in the aqueous phase in cloud droplets”, a dd “by reaction w ith H 2 O 2 , O 3 or O 2 through catalysis by Fe and Mn.

Page 2-10, Line 7: After “highly sol uble”, add “as well as hygroscopic”.

Page 2-11, Line 3: “Methane sulfuric acid” should be “m ethanesulfonic acid”.

Page 2-12, Figure 2.3-1: Include Fe, Mn and O 2 where reaction from S(IV) to S(VI) is shown.

Page 2-13, Line 18: Add m a nganese (Mn) to the list of m e t a ls that can catalyze oxidation by O 2

.

75Page 2-17, Line 17: Include E dgerton et al., 2006 and Edgerton et al., 2007 in the list of references on newer m e thods for m easuri ng nitrate, amm onia and ammonium . SEARCH network has been in place sin ce 1999 and has been widely used by the community, but there is

no m e ntion of this netw ork anywhere in the ISA docum ent.

Page 2-21, Line 12: H 2 SO 4 should be changed to SO 2

. Page 2-24, Line 22: Ad d “for IMPROVE and ther m a l-optical transm ittan ce (TOT) for STN” at the end of th e senten ce.

Page 2-25, Line 2: Change “well correla ted” to “m oderately well correlated”.

Page 2-26, Line 1: Remove NH 4 NO 3 f r om the list.

Page 2-26, Line 6: After “PM 10 ”, ad d “, partly b ecause NO 3 - contributes sm aller fraction to PM 10 and partly b ecause NO 3 - is present in a non-volatile form , suc h as NaNO 3 , in the coarse m ode.”.

Page 3-1, Lines 23 & 24 : Electrical u tilities and v a rious industries accoun t for about one-th i rd of anthropogenic NOx e m issions (not roughly half).

Page 3-20, Line 13: Add descrip tion of the SEARCH network. Here is the suggested description to choose from :

Southern Company and E PRI funded SEARCH program has provided a highly instrume nted eightstation network since 1998 ( and continuing till at least 2010 ) in the states of AL, FL, GA and MS ( H ansen et al., 2003 )

. At present, the suite of measu r ements mad e at all sites includes:

1. 24-hr PM 2. 5 filter samples, analyzed for mass, ions ( s ulfate, nitr ate, ammonium )

, organic carbon( OC)

, elemental ( b lack) carbon (EC or BC)

, and elements as mea s ure d by X-ray fluorescence (XRF ) ;

2. 24-hr PM Coa rse mass, ions, and XRF elements;

3. 24-hr g a seou s ammonia a s collected with an annula r denuder;

4. continuous (minute to ho urly) PM 2. 5 mass, OC, E C , ammoniu m , nitrate, a nd sulfate; light scattering an d light absorption;

5. continuous g a seous ozone , nitric oxide, nitrogen dio x ide, total oxidized nitrog en ( N

O y )

, nitric acid, carbon monoxide, a nd sulfur dio x ide; and

6. continuous 1 0 -m meteoro l ogical para m eters: win d speed, wind direction, temperatu r e, relative humidity, solar ra diation, baro m etric pressure and p r ec ipitation.

Page 3-23, Line 22: SE ARCH sites have also m eas ured nitric acid (Zhang et al., 2006; Blanchard and Hidy, 2003) since 1998 and the m easured hourly concentrations range from less than 1 ppb

to m o re than 10 ppb.

76Page 3-42, Line 14: Add “interna tional transport” as one of the issues addressed by global CTMs.

Page 3-43, Line 17: I suggest ad ding Arnold and Dennis (2006) re ference, as they went beyond just testing the operational m odel perfor m a nce.

Page 3-47, Line 27: I suggest adding appropriate references to the SEARCH sites here.

References :

• Arn o l d

, J.R. and Denn is, Rob i n L. (20 06). Tes tin g CM AQ ch em istry sen s itiv ities in b a se case an d

e m issions c ont rol runs at SE ARCH a n d SO S99 s u rface sit e s in t h e s out heastern US. A t m o s. En v i ro n

. 40 ( 2 6 ) 502 7-5 040

.

• Blanchard, C.L

. and Hidy, GM. (2003 ). E f fects of cha n ges in s u lfat e, am m onia, and nitric acid on particulate nitrate conc entrati ons in the s o utheastern Unite d States. J. Air Waste Mange. Assoc. 53 2 83- 29 0.

• Edg e r t on , E.S

. , H a r t sell, B. E. , S a ylo r , R.D

. , Jan s en , J. J. , Han s en , D

. A

. , and H i d y , G

. M. (2 006 ). Th e S o u t h e a s te rn Ae r o so l Re s e ar ch an d Ch ar a c t er iz a tio n Stud y: Par t I I I

. C o n tin uou s Measu r emen ts o f PM 2.5 Mass and C o mp o s ition

. J. A i r Waste M a nge. Ass o c. 56 , 13 25- 134 1.

• Ed gert o n , Say l or , H a rt sel l

, Ja nse n , Ha nsen ( 2 0 0 7 ) Am m oni a an d Am m onium M easurem ent s f r o m t h e Southeastern U. S.

, At mos

. E n viron. , 41, 33 39 -33 5 1

.

• H a n s en, D. A.

, Edg e r t on , E.S

. , H a r t sell, B. E. , Jan s en , J.J

., K a nda sam y , N., Hidy, G.M. , a n d Blanc h ar d, C

. L. (2003). T h e Sout heastern Ae ros o l Resea r ch an d C h aracteri zation St udy: Part 1 – Overvie w

. J. Air W a ste Mange . Ass o c. 53 146 0-1 471

.

• Zha n g, Y., Liu, P.

, Quee n, A

. , Misenis, C. , P u n, B. , Sei gne ur, C. , a n d Wu, S.- Y

. ( 2 006). A c o m p rehe nsive

p e rf or m a n ce ev alu a tion o f MM5

- C MAQ f o r th e Su mm er 1 9 9 9 Sou t h e rn O x i d an ts Study ep isod e—Part I I : Gas a n d aer os o l pre d i c t i o n s

. A t mos. E n viron. 40 (26 ) 48 39- 48 55

.

77

### Dr. Myron Mitchell

General Co mments

The December 2007 version of the “Integrated S c ie nce Assessm ent for Oxides of Nitrog en and Sulfur – Environm ental Criteria” has done a very good job in summarizing a substantial am ount of infor m ation. Included within th is analysis is discussion on the relevance of this infor m ation to policy decisions. There is som e reference and disc ussion to results from European analyses. It would be interesting to m a ke som e further explicit com p arisons of the success or lack of success of the European analy s es includ ing th e relevan ce of these analyses to both interpretations and policy im plication s in th e United Sta t es.

In the various sections, however, there is som e tim es substantial repetition and overlap. Som e of this is likely inevitable, but having addition a l cro ss referencin g am ong cha p ters would also be helpful. Removing some of this overlap will m a ke the docu m ent m o re readable and reduce the overall length. In Chapter 3 (ECOL OGICAL E X POS U RE S TO OXIDE S OF NITR OGEN AND SULF UR, AND T O AMMONI A AND AMMONIUM) som e fur t her discussion of the issues related to m odel param e terization, assum p tions and differences in the predictions of concentrations and deposition would be helpful in placing results in the context of the overall confidence levels of predicted values both across tem poral and spatial scales.

In Chapter 4 (EFFECTS OF ACIDIFIC ATION AND NITR OGEN E N RI CHMENT ON ECOS YSTE MS AND OTHER WEL F ARE E F F E CTS) m o re attention should be given to the potential importance in at least so m e watersheds of other sources of sulfate th at will affect the recovery from acidification. These sources can include organic sulfur m i neralization and the weathering of sulfur bearing m i nerals.

In Chapter 5 (FINDINGS AND CO NCLUSIONS), this inform ation should be converted to an Executive S u mm ary in which the salien t features of the docum ent are articu l ated.

Inclusion in the assessment of the im pact of tota l reac tive n itrogen would help strengthen the im portance of all reactive nitrogen chem ical speci es including ammonium to the tota l nitrogen loading of ecosystem

.

More Detailed Comments

Page Comment

xx Change to: Dr. Myron Mitchell, Distingui shed Professor and Director of Council on Hydrologic System s Science, College of Environm ental and Forestry, State University of New York, Syracuse, NY

xxxv Change to: The rem oval of gases and part icles from the atm o sphere to surfaces by rain or other for m s of pr ecipitation

782-2 Change to: contributing to the acidity of cloud, fog, and rain water and ambient particles in the atm o sphere.

2-3 Change to: few hours during summ er days of high photon flux to roughly 24 h during winter with less

2-4 Change to: 2002). The m echanism s for transporting the NO X precursors, the factors controlling the

2-6 Change to: on the conventional 100- year tim e horizon of ~296 – i.e., N 2 O is nearly 300 tim e s more effective on a per m o lecule basis for trapping heat in the

atm o sphere than carbon dioxide (CO 2 )(IPCC,

2-13 Indicate location of “Mace Head” in line 3.

2-18 Be m o re explic it in wha t is the inte rf erence by NO Z com pounds in line 1.

2-20 Reword to clar if y the iss u e related to : also lead to artifact volatilization and associa t ed p o sitiv e bia s in [ H NO 3 ] measured dow nstream

2-20 Would this be an appropriate place to discuss issues related to differences between CASTNET and the Canadian (CAP MoN) dry deposition com p arisons. I believe m o st of the differences are as sociated with the dry deposition m odeling versus the actual m easurem ents of ga seous chem ical species.

2-22 Figure 2.6-1 needs to provided with be tter resolution of th e contour lines.

2-24 Should Teflon be indicated to be a registered nam e ? ®

3-1 Delete: (The category label for NH 3 and NH 4 + is NH X .)

3-1 Substitu te “ a pproxim a tely” f o r “rou ghly” her e a nd elsewher e in the do c u m e nt.

3-2 Change to: Where N is in excess of bi otic dem a nd, gaseous N e m issions increase by m i crobial transform a tion.

3-2 The issue related to “Although N 2 is not reactive in the troposphere, N 2 O is a greenhouse gas (GHG) with a significan t global warm ing potential (GW P ) from its direct radiative forcing and from its...” m a ybe should be linked to the discussion in Chapter 2.

3-3 Change to: Em ission ra tes of NO f r om cultiva t ed soils dep e n d chief l y on N f e rtiliza tion levels

3-3 Change to: can have wide variation around this value

793-3 Change to: N in plants is present m o stly as am ine (NH2) groups in am ino acids.

3-3 Change to: will m a ke em issions f r om this source increasingly im portant

3-8 This statem ent needs clarification: E m issions of SO 2 from burning vegetation are generally in the range of 1 to 2% of th e biom ass burned (e.g., Levine et al., 1999).

This would suggest that 1 to 2% of biom ass gets converted to SO 2 . This seem s to high with respect to the av erage S concentration in ve getation. Does this study suggest that 1 to 2% of the S in biomass is converted to SO 2 ?

3-9 Be m o re explicit about which pattern in the s t atement: Anth rop ogenic em issions of NH 3 show a strikingly different pattern from t hose of NO X or SO 2

.

3-10 Does the statem ent “Results from som e more recent em issions evaluation studies have been mixed, with som e studies s howing agreem ent to within ±50%” im ply that som e of these studies show th at agreem ent is greater th an 50%?

3-21 Figure 3.6-7

. Routinely operating North Am erican precipitation and surf ace water networks: U pper left, Canadian Air and Precipitation Monitoring Network (CAPMoN); upper righ t, Integrated At m o spheric Monito rin g Depositio n Network (IADN); bottom

, National Atm o spheric Deposition Monitoring Program (NADP) with TIME/LTM surface chem istry sites.

This figure shows a symbol of N-saturated forests. W h at is the source of this designation? W h at is the coverage associ ated with the sym b ol? Other Ecological Resources are also noted, but the source of these designations is not included in the figure legend.

3-22 3-23 Som e further discussion of differences of these E u ropean m o nitoring efforts

com p ared to those in the U.S. m a y be helpful. Also, som e discussion on differences with the Canadian m onitoring efforts should be included.

3-47 Change to: param e terizations of a tmospheric chem ical and physical processes in models

.

3-48 Change to: In a watershed, everything that is dep o sited in its area

4-1 Change: Structure refers to the sp ecies richness, abundance, and community

com position that u ltim ately re late to ecosystem biodive rsity.

To som e thin g like : Struc t ure m a y ref e r to a v a riety of m easurem ents inclu d ing the species rich ness, abundance, comm unity com position as well as landscap e attributes. T h e biotic components comose the biodiversity of an ecosystem.

804-1 Change to: Com p etition am ong and within species and to lerance to env i ronm ental stresses are key elem ents of survivorship

4-1 Change to: Function refers to the suit e of processes and interactions am ong the ecosystem com ponents and their environm ent that such as nutrient and energy flow as well as other attributes inclu d i ng water d ynam i cs and the flux of trace

gases

.

4-2 Change to: related to functions of energy flow and nutrient cycling

4-2 Change to: Energy m o ves from one organism to another through food we bs , until it is u l tim a tely re leased a s heat. Nutr ie nts and water can be recycled. Air pollution alters the function of ecosystem s when elem ental cycles or the energy flow is altered. This alteration can also be m a nife sted in changes in the biotic

com position of the ecosystem

.

4-6 The use of “we” seem s awkward in this type of discussion. I would suggest rewording.

4-8 It m a y also be useful to include th e term “forest floor” when discussing the O horizon of forest soils.

4-8 For the docum entation of soil acidific ation the following reference should be included : Su lliv an, T.J., I.J. Fernandez, A.T. Herlihy, C.T. Driscoll, T.C. McDonnell, N.A. Nowicki, K.U. Snyder , and J.W. Sutherland. 2006. Acid-base characteristics of soils in the Adir ondack Mountains, New York. Soil Science Society of Am erica Journal 70: 141-152.

4-11 Not only is the fate of carbon-bonded sulfur an issue, but also the fate of ester sulfate need s to be cons idered.

4-11 This m i ght the be place to at least m e n tion th at su lf ate iso t opi c have indicated the potential for the net m i neralization of orga nic S contributing to sulfur im balances for watersheds. This has been found in studi es both the United States and Europe. Som e relevant references would include:

Novák, M. M. J. Mitchell, I. Jacková, F. Buzek, J. Schweigstillová, L. Erbanová, R. Prikryl and D. Fottová. 2007. Proce sses affecting oxygen isotope ratios of

atm o spheric and ecosystem sulfate in two contrasting forest catchm e nts in Central Europe. ES&T 41(3): 703-709. DOI: 10.1021/es0610028

Likens, G.E., C.T. Driscoll, D.C. Buso, M.J. Mitchell, G.M. Lovett, S.W

. Bailey, T.G. Siccama, W

. A. Rei n ers, C. Alewell. 2002. The biogeochem i stry of sulfur at Hubbard Brook. Biogeochem i stry 60:235-316.

81Gbondo-Tugbawa, S.S., C.T. Driscoll, M.J. Mitchell, J.D. Aber and G.E. Likens. 2002. A m o del to sim u late the response of a northern hardwood forest ecosystem to changes in S deposition. Ec ological Applications 12:8-23.

In addition, som e m e nti oned should be in cluded about the po tential role of weathering reactions for contributing to sulfate in som e watersheds. A good

exam ple is:

Shanley, J.B., B. Mayer, M.J. Mitchell, R.L. Michel, S. Bailey and C. Kendall. 2005. Tracing sources of stream water su lfate during snowm e lt using S and O isotope ratios of sulfate and 35 S activity. Biogeochem i stry 76:161–185

4-14 The is also strong evidence of the im portance of winter tim e processes and the possible link a ge to c lim ate in af f ectin g nitrate loss es. See for exam ple:

Eim e rs, M.C., Buttle, J. M., W a tm ough, S. A., 2007. The contribution of rain-onsnow events to annual N O 3 -N export at a forested catchm e nt in central O n tario, Canada. Applied Geochem i stry, 22: 1105-1110.

Ca m pbell, J.L., M. J. Mitchell, P. M. Groffman, L. M. Christenson. 2005. W i nter in northeastern North A m erica: An of ten overlooked but critical period f o r ecological processes. Fron tiers in Ecology 3(6):314-322.

Park, J, M.J. Mitchell, P.J. McHale, S. F. Christopher and T.P. Myers. 2003. Interactive effects of ch anging clim ate and atm o spheric deposition on N and S biogeochem i stry in a forested watershe d of the Adirondack Mountains, New York State. Global Change Biology 9:1602–1619.

4-20 to 4-22 There is evidence that episodic acidi fication associated with droughts and the mobiliza tion of sulf ate is also im portant. This ha s been shown f o r studies in Canada and the northeast U.S. See for exam ple:

Eim e rs, M.C., W a t m ough, S.A., Buttle, J.M., Dillon, P.J., 2007. Drought-induced sulphate release from a wetland in south-central Ontario. Environm ental Monitoring and Assessm e nt, 127: 399-407.

Eim e rs M.C. and Dillon P.J. 2002. Clim ate effects on sulphate flux from forested catchm e nts in south-central Ontario. Biogeochem. 61: 337–355.

Mitchell, M.J. K.B. Piatek, S. Christophe r, B. Mayer, C. Kendall and P. McHale. 2006. Solute sources in stream water duri ng consecutive fall storm s in a northern hardwood forest watershed: a com b ined hydrological, chem ical and isotopic approach. B i ogeochem i stry 78: 217-246.

824-26 Should this heading be Changed to: 4.2.2.1.3 Soil Nitrogen: Carbon to Nitrog en Ratio

Not sure if the em phasis is on Ca and if the ra tio indica tion is appropriate.

4-33 & Elsewhere Change SO 4 + to: SO 4 2-

4-39 Change to: The increasing trend in Virg inia stre am s is presum ably the result of decreased soil solu tion s u lf ate conce n tra tion and net desorption in the soil in response to decreased S deposition.

4-41 As indicated above (see comments for 4-14) that th ere is other evidence that changes in winter tim e conditions can affect nitrate export.

4-42 Other studies in the Adirondacks have also identif ied the im portanc e of within lake pro cess e s in affecting nitrate lo sses from lake/watersheds. See for exam ple:

Ito, M., M. J. Mitchell, C

. T. Driscoll, R. M. Newton, C.E. Johnson, and K.M. Roy. 2007.Controls on surface water chem istr y in two lake-watersheds in the Adirondack region of New York: differences in nitrogen solute sources and sinks. Hydrological Processes 21:1249-1264.

Ito, M., M.J. Mitchell, C.T. Driscoll and K.M. Roy. 2005. Nitrogen input-output budgets for lake-watersheds in th e Adirondack region of New York. Biogeochemistry. 72:283-314.

4-44 Change to: with the exception of str eam s in Shenandoah National Park, Virginia, which appear to exhibit decreases in adsorbed su lfate in soils.

4-62 to 4-63 The discussion in this section needs to differentiate between bedrock geology and surficial geology. Surficial geology is a m u ch m o re im portant predictor of the sensitivity to acidification than bedrock geology. Differences in surficial geology can be especially im portant for predicti ng sensitivity to acidification within a region.

4-73 Som e of this discussion on critica l lo ads is r e petiti ous from pr evious sections although this previous s ection is referenced.

4-82 I don’t believe the followi ng statement is true for th e Adirondacks: However,

recen t research suggests that N has ac cum u lated in soils over tim e in the Adirondacks and that som e forests have e xhibited declining retention of N inputs. The result h a s been in creased leaching of NO3 t o surface waters.

83See for example:

Mitchell, M.J., C.T. Driscoll, S. Inamdar, G. McGee, M. Mbila, and D. Raynal. 2003. Nitrogen biogeochem i stry in the Adirondack m ountains of New York: hardwood ecosystem s and associated surface waters. Env i ro nm ental Pollution 123:355-364.

Mitch e ll, M. J., C.T. Driscoll, J. Ow e n, D. Schaefer, R. Michener, and D.J. Raynal. 2001 Nitrogen biogeochem i stry of three hardwood forest ecosystem s in the Adirondack Mountains. Biogeochem i stry 56: 93-133.

4-112 Wetlands after droughts can also serve as nitrate sources when rewetted. See for

exam ple:

Wat m ough S.A., Ei m e rs M.C., Aherne J. and Dillon P.J. 2004. Clim ate effects on nitrate export from forested catchm e nts in south-central Ontario. Environ. Sci. Technol. 38(33): 2383–2388.

Also, som e m e ntion of t h e role of N-fixati on should be included for wetlands; see: Hurd, T. M., D. J. Raynal, and C. Sc hwintzer. 2001. Sym b iotic N-fixation of Alnus incana spp. rugosa in shrub w e tla nds of the Adirondack Mountains, New York. Oecologia 126: 94-103.

4-129 The following paper co uld be referenced showin g the effect on N additio ns on understo ry comm unities in the Adiro ndacks:

Hurd, T.M., A.R. Brach, and D.J. Raynal. 1998. Responses of understory vegetation of Adirondack forests to nitrog en additions. Can J. For. Res. 28: 799- 807.

4-162 There is fairly good evidence that for fo rest ecosystem s with closed canopies that throughfall sulfate is a good estim ate of total sulfur deposition. See: Lovett G.M., Thompson A.W ., Anderson J.B. and Bowser J.J. 1999. Elevational patterns of sulfur deposition at a s ite in the Ca tskill Moun ta ins, New York. Atm o sp heric Environm ent 33: 617–624.

4-162

to 4-170 The discussion on the form ation of MeHg needs to em phasize the inte rre lation ship with su lf ate concentrat ions and the role of sulfate reducing bacte r ia l. Such f o cus will he lp em phasis th at the m e of this re port re la tes nitrog en and sulfur. The extensive discussion on Hg biogeochem i stry and environm ental effects can be condensed.

4-179 An evaluation of nitrate sources to wate rs with respect to atmospheric deposition needs to separate how nitrogen depositi on load in g leading to more nitr ate loss

84versus atm o spherically deposit ed N being found directly in drinking water. Forest watershed level work using stable isotopes shows predom inantly that alm o st all of the nitrate in surface and ground waters ha s been biotically derived. See f o r

exam ple:

Burns, D. A. and Kendall, C.: 2002, Analysis of δ 15 N and δ 18 O to dif f e rentia te NO 3 sources in runoff at two watersheds in th e Catskill Moun tains of New York’, Water Res. Res. 38(9), 1–11.

Piatek, K.B., M.J. Mitchell, S.R. Silva and C. Kendall. 2005. Sources of nitrate in Adirondack surface water during d i ss im ilar snowm e lt events. W a ter, Air and Soil Pollution 165:13-35.

Kendall, C.: 1998, ‘Tracing nitrogen sources and cycling in catchm ents’, in C. Kendall and J. J. McDonnell (eds), Is otope Tracers in catchm e n t hydrology, Elsevier Science, BV, pp. 519–576.

5-36

to 5-37 The conclusion section should then be shorted and include inform ation on the overall approach of the study including im portant resources to be used and potential lim ita tions.

5-3 Not sure we have good estim ates for so m e pollutants such as ammonia. This

statem ent seem s contradicto r y:

Despite the af orem entioned lim itatio n s, for the purposes of identifying and quantifying the atm o spheric concentrat ions and deposition totals causing ecological effects, these m easurem ent techniques and sam p ling frequencies are fully adequate. Nevertheless, the coverage of the networks is ve ry th in ov er la rge expanses of the interior United States.

5-6 As stated previously the im portan ce of superficial geology needs to be

em phasized.

5-36

to 5-42

to 5-44 TABLE 5.7- 1. SUMMARY OF NITR OGEN DEPOSITION LEVELS AND THE COR R ESP ONDING E FFECTS OF ACIDIFIC ATION AND NUT RIE N T ENRICHM E NT ON ECOSYSTEMS.

To this table could be added the resu lts from the Adirondack Manipulation and Modeling Program (AM M P): Mitchell, M.J., C.T. Driscoll, J. Owen, D. Schaefer, R. Michener, and D.J. Raynal. 2001. Nitrogen biogeochem i stry of three hardwood

85forest ecosystem s in the Adirondack Mountains. Biogeochemistry 56: 93-133.)

This study included exp e rim e ntal ad ditions of ammonium sulfate and nitric acid (14 and 28 kg N ha -1 yr -1 ). The biogeochem i stry of nitrogen (N) was evaluated for three forest ecosystem s [Woods Lake (W L), Pancake-Hall Creek (PH C ) and Huntington Forest (HF)] in the Adirond ack region. Bulk N deposition was higher at sites in th e west than those in th e c e ntral and eastern Adirondacks. These higher

atm o spheric N inputs were reflected in higher bulk throughfall fluxes of N (WL and PHC, 10.1 and 12.0 kg N ha -1 yr -1 , respectively) in the western Adirondacks than at HF (4.6 kg N ha -1 yr -1 ) in the central Adirondacks. The greatest increas e in nitrate loss in response to the experi m e ntal treatm ents occurred at HF where th e HNO 3 additions resulted in the highest nitrate con centration s and lowest N retentions.

86

### Mr. Rich ard Poiro t

Generally, I think the docum e nt provides a t horough and useful summ ary of the state of knowledge relating to the ecological effect s of S & N deposition – prim arily through acidification and nitrogen enrichm e nt. Several other welfare effects of these pollutants are briefly discussed, although there is no m e ntion of m a terial s dam a ge. As indicated in previous comments, I think it m i ght have also been useful to consid er the im porta nt welf are ef fects of sulfate and nitrate aerosols under both this secondary SO x/NOx review, as well as in the PM review (copy/paste). Excluding aerosol e ffects here seem s to point to an advance decision that som e sort of depo sition, critical load s, or critical lo ads exceedance-type ind i cators are b e in g considered as a possibility for secondary S and N (hopefully including reduced N) NAAQS.

This f l exibility in consid ering a lte rna tive indica tors would be a welcom e change in the Agency’s approach to secondary (or prim ary) NAAQS, as I think previous reviews have been constrained to consideration of indica tors based on the nam e d gase ous criteria pollutants – SO 2 or NO 2 – even though I think the Clean Air Act provides ample encouragem en t to consider the effects of secondary transform a tion products and com b inati ons with other pollutants. Since this ISA represents a beginning of the new, stream lined NAAQS review process, its difficult to get a sense of just how far the inform ation and analysis should be taken or “set up” in this docum e nt, what belongs in the risk/exposure assessm ent, and what should be left to the ANPR. If there is really going to be consideration of several deposition-related indica tors in this r e view cycle, I think th ere s hould be ad dition a l discussion of the op tions – like critical lo ads - up fron t in th is ISA, since these are the kind of alternative lim its to be evaluate d in the risk/exposure assessm ent, and should definitely not be introduc ed for the first tim e in the ANPR.

Another general comm e n t is that I think the docum ent is unnecessarily silent on projected future reductions in S and N em issions tha t will resu lt f r om the CAIR rule. W e would like to have a better sense of what kinds of e ffects have occurred, are currently occurring, and are expected to occur as future “on the books” em ission reductions o ccur. At som e poi nt before this review is

com p leted, there will lik e ly be som e consider atio n of how NAAQS which rela te to lo cation

specific effects and m easurem ents may interact w ith the rec e ptor locatio n-insens itive em issions cap & trade approach th at has beco m e the prefe rred regulatory approach fo r further reductions in S and N e m issions.

Chapter 2 The 1 st half of the chapter’s discussion of at m o s pheric chemistry seem s reasonably thorough, although it m i ght m o re logically fo llow the discussion of emissions at the beginning of Chapter 3. Its not clear whether this leve l of detail on atmospheric chem istr y is needed in th is new-sty l e “Integ rated Science Ass e ssm ent” (as com p ared to a criteria docum e nt or an annex to this ISA). Any excess infor m ation here is harm less, but every attem p t should be m a de to m a ke the discussion relevant to those aspects of atm o sphe ri c ch em istry that m a y be especially critical to understanding the sources exposures and environm ental effec t s of these S & N pollutants (or other pollutants like Hg the e ffects of which em issions of thes e pollu tants m a y af f ect).

87By contrast, the very brief 2-paragraph secti on 2.5 on At m o spheric T r ansport conveys alm o st no useful inform ation (and there’s not all that m u ch more detail on transport provided in the Annex). I think this section needs work and m i ght m o re logically be either tightly focused on those aspects of atm o spheric chem istry which in turn affect th e transpo r t and ultim ate deposition, or expanded and com b ined with the section on ch em ical trans port m odels (CTM) at the end of chapter 3.

The 2 nd half of chapter 2 seem s unnecessar ily lim ite d to m easurem ents of the “nam ed” NOx and SOx criteria pollutants, with addi tional tangential discussion of artif actual gain s an d losses of S & N species in PM m a ss m easurem ents (which is som e what beside the point). At the sam e ti m e , this discussion of m easurem ents, networks, & li m itations seem s unnecessarily disconnected from discussion of the sam e topics for m e asurem ents , networks & lim itations of gaseous & aerosol concentrations, and wet and dry deposition which are included in the first half of Chapter 3 (which actually has relatively little direct discussion of “Ecol ogical Exposures” until the section on Harvard Forest Flux m easure m ents on p. 3-34). I think it would be bette r to com b ine all these discussion of m easurements of the relevant gase ous, aerosol, wet and dry deposition networks in a single section. Em issions to chem istry & tr ansport to concentrati ons to deposition and

exposures seem s like a more logical way to present this inform ation.

Specific Comments p. 2-1, lines 13-27 (& footnote 1) : P o ssibly you could also include a m e ntion here of the CAA definition of “welfare effects” m odified in Section 302 (h) of the 1990 CAA to include the phrase: “...whether caused by tr ansform a tion, conversion, or co m b ination with other air pollutants”. All gaseous, aerosol and deposition oxidation products of (traditionally defined) SOx & NOx em issions should be clearly on the ta ble for consideration, and “com bination with other pollutants” m a y help open the door to c onsidering effects resulting from both oxidized & reduced N em issions.

p. 2-2, line 7: If you changed “p articles” to “aerosols ” (which includes the suspending gaseous

m e dium ), you could leave (gaseous) HNO 3 on the lis t.

p. 2-3, Figure 2.2-1: Som e i norganic nitrates – like NH 4 NO 3 – can also be transported to rem o te regions under low tem p eratures. Genera lly th is s ection s eems overly brief.

p. pages 2-7 to 2-98: This is an interesting and thorough discussion, but there needs to be a clearer connection m a de between this halogen chem istry and either the em issions, transport or deposition of S & N compounds. You m i ght also add som e where here that free Cl & Br released by these reactions can also cont ribute to the conversion of Hg 0 to Hg 2+ , enhancing the potential for wet & dry Hg deposition to the environm ent.

p. 2-9 line 29: Add “gaseous” before “species”.

p. 2-16, line 29: Form ation of aerosol NH 4 NO 3 can also subs tantially enh a nce the atmospheric lif etim e(s) a nd transpo r t distan ce (for both oxidized & reduced N). At som e point (not sure where) you should also add som e discussion of both current and projected future aerosol

88sulfate/n i trate/amm onium /acidity relationsh i ps, as lower levels of acidic sulfate m a y lead to increased levels (& longer trans port distances) of aerosol nitrate.

p. 2-16, lines 26-29: This discussion seem s overly sim p lified. Yes, NO a nd NO 2 are less solub l e than SO 2 , but they are also m u ch m o re reactive an d, with their “longer-lived reservoir species HNNO 3 ” do not necessarily tran sport over longer distan ces th an SO 2 and its transformation products.

p. 2-17, lines 7, 9, 13, 14: Here it looks like you use “NOx” with several different m e anings, and while you claim (line 14) to lim it the chapter to F R M/FEM, the chapter quickly m oves beyond FRMs for NO/NO 2 to more exotic species & m e thods.

p. 2-21, lines 15-19: I think this is stated backward. There is more likely to be volatilization loss of NO 3 - from (relatively acidic) P M 2. 5 f ilters ( i f Tef l on – not nylon) a nd m o re like l y to be positiv e nitr ate a r tif ac ts on alkaline PM 10 (or PM 10- 2. 5 filters), unles s preceded by H N O 3 denuders.

p. 2-21, line 22 – p. 2-22, line 8: This is a lim ite d discussion and wi m py illustration of current

sate llite sen s ing poten tia l f o r NO 2 . See for example : http://datafedwiki.wustl.edu/i ndex.php/2007-07-18_ESIP_Dem o _OMI_NO2 f o r a bette r illustra tion o f & links to OMI NO 2 data and im ages.

p. 2-24, lin e 22: Traditio nally the STN networ k has em ployed therm a l-optical tran sm ittance (TOT), while the IMPR OVE network has used T O R. Currently, STN sites are transitioning to TOR in a phased process – over several years.

p. 2-24, line 23: IMPROVE sa m p le frequency changed from t w ice a week (W ed & Sat) to 1 in 3 day (sam e as STN) in Sept. 2000.

p. 2-24, lines 27-31: IMPROVE denuders are co ated with a com b ination of carbonate and glycerin.

p. 2-25, lines 13-22: Its not clear what kind of sampling you’re refe rring to here. Glass fiber f ilter s with b a sic co arse p a rticle s on the f ilte rs would be ind i c a tive of TSP sam p lers currently used prim arily for sam p ling for Pb NAAQS. These are v e ry rarely analyzed for SO 4 , NO 3 , Cl, or PM m a ss (which is irrelevant for TSP). Quartz filters can also have (sm a ller than glass but signif i can t) positiv e ar tif acts f r om SO 2 or HNO 3 . Denuders are not really m u ch of a n option for hi-vol PM 10 sam p lers – on which quartz filters are t ypically run, but yes, denuders on lo-vol Tef l on f ilter PM 10 or PM 10- 2. 5 (by dichot) sam p ling would help elim inate artifacts.

p. 2-26, lines 6-7: Actually, the loss of pNO 3 from FRM PM 2. 5 sam p les is like l y to b e grea ter than for the “other s i m p le collection system s described above”. Also, the discussion in the f o llowing se veral p a rag r aphs is in te r e sting & inf o rm ative, but re late s prim arily to how nitra t e

sam p ling losses affect PM 2. 5 m a ss measurem ents (not nitrate m easure m ents, which are usually not conducted on these Teflon filters). This reminds m e to lam e nt again that its too b a d aeroso l

89nitrate is “off the table” in this NAAQS revi ew – since it is not fully included in our

m easure m ent-based definition of PM.

p. 2-27, lines 4,5: I would add “nitrate” after “a mmonium ” (amm onium sulfat e is very stable). Also, chang e s in th e equ ilib rium between aeroso l and gaseou s precur s ors can be due to f actors other than T

, RH and acidity – such as changes in the precursor gas concentrations - for exam ple rapid loss of (sticky) HNO 3 & NH 3 concentrations in the indoor environm ent.

p. 2-27, lines 3-21: W h y not m ove the discussion of negative pNH 4 artif acts ad jacen t to th e discuss i on o f positive p N H 4 artifacts beginning line 21, p. 2-25. Also I question your im plication that neg a tiv e artifacts generally exceed positive artifacts for NH 4 . Can you provide a reference f o r this ? NH 4 is not m easured in IMPROVE and NH 3 denuders are not used in STN – which does

attem p t to q u antif y NH 4 . W h at is the intended m eaning of the occasional [ ] in this paragraph?

Chapter 5 This chapter provides a concise sum m a ry of the in form ation presented in the preceding chapters. It was generally well-written, but as with the o t h e r chap ters, there we re s ection s tha t were choppy (m ultiple autho r s ? ) or where the language w ould benefit from som e m o re carefu l editing for clarity. In som e cases, the brevity (highl y desirable) seem s too brief to convey useful inform ation and would benefit from a bit m o re deta il. The use of references is not consistent from section to section and I suggest using m o re rather than fewer (they don’t take m u c h room and inspire confidence). In som e sections the language is unnecessarily vague (“very large”, “higher than m i ght be expected”, etc.) or speculative (“m a y occu r”, “is probably ongoing”, etc.). In m a ny cases, a good point is being introduced that could easily be restated m o re objectively.

It should be clear that this is a “sum m a ry” (whi ch is fine), but not in tended as an integrative synthesis or winnowing down of crucial inform a tion. There are no new insights provided here, and the chap ter doesn ’t lead in a ny obvious directions toward sele ction of alternative or specific indicators. For the m o st part, the m o re detail ed and useful inform ation is presented in the preced ing chapters. A strong point o f Chapter 5 is a series of excellent su mmary tables at th e end (especially Table 5.7.1 on N deposition & effects). These tables star t to provide a sense of what kinds of effe cts are occurring in what regions at what loading rate s. I would have liked to see this inform ation taken a bit further to m o re dire ctly address th e concept of critical loads (and exceedances of critical loads), in ways that m i ght provid e m o re advanc e insights into possible elem ents (indicators, averaging tim es, leve ls & form s) of new secondary N AAQS.

Specific Comments p. 5-1, line 32: You could add pSO4 as parallel to pNO3 in line 29.

p. 5-2, line 7” “controlling SO 2 oxidation” isn’t really the righ t term here. Could reword as

som e thing like “...altering the chem istry of SO 2 oxidation products by neutralizing...”

p. 5-2, line 23: “adequate” (a questionable judgm en t here), could be im proved by adding “for determ ining com p liance with curr ent NAAQS”.

90p. 5-3, line 3: “regulatory” doesn’t seem quite right here (& in seve ral other instances). W e have no “regulations” for required m onitoring of NH 3

. p. 5-3, line 7: You could add a bullet or 2 here describing routine m e thods/networks and lim itations f o r m onitoring of wet (&/o r dry) deposition of S & N com p ounds.

p. 5-3, line 31: Can you be m o re qua ntitative than “very little...”

p. 5-4, line 5: Sam e as previous com m e nt. What % does “su b stantially s m aller” m e an?

p. 5-4, line 19: You could add “atm o spheric” before “N”.

p. 5-4, lin e 2 3 : Do you mean “...em itted to the atmosphere...”?

p. 5-4, line 26: There are not “regulatory” m onitoring networks for deposition (although m a ybe there should be).

p. 5-5, lin es 23-26: Its n o t clear what you m ean by “riverine flow in the absence of deposition ” (som e of the riverine flo w N is from deposition to upland surface waters or catchm e nts, som e is from non-atmospheric sources, and then there’s som e directly deposited to the surface waters of the coastal estuary). Also, its not clear what the 11, 5.6 & 5.6 kg N ha-1 refer to here.

p. 5-6, line 21: You could replace “understood” (speculative) with “described in detail”.

p. 5-7, line 23: Can you use a m o re object ive phrase than “thought to be”?

p. 5-8, line 30: Can you use a m o re objective phrase than “may occur”? For exam ple, have such effects been observed anywhere? If not, you m i ght express these as logical expected outcom es which have not been observed to date...

p. 5-9, line 27: “Consequently” doesn’t seem qui te right. Organic m a tter build-up isn’t necessarily a consequence of “fungi that feed on organic debris ...” unless they are less efficient than the b acterial consu m ers they replace, in which case say so..

p. 5-10, line 1: You could repl ace “expanded” with som e thing like “reflected a substantial increase in...” The CD didn’t expand knowledge; it just docum e nted it.

p. 5-11, line 16 (& also 5-12, lines 2 and 29 & elsewhere): There are several different indications of a uniquely different situation in the Mid-Appa lachian region. It would be useful to provide

som e explanation of reasons for this differen ce. Maybe you could do th is in the case studies (m ake it clear there why Shenandoah is different fr om the Adirondacks) and have pointers to that discussion whenever you indicate a ‘Shena ndoah exception’ elsewhere in the document.

p. 5-12, line 28: Add “in” after “decreased”.

p. 5-13, line 2 “Al generally becom e s the gr eater health risk” Greater than what?

91p. 5-13, line 19: I assum e that by “the m o st se rious effects” you m ean som e thing like “m ore serious than long term ”, which I find very count er-intuitive – and would need m o re convincing to accep t as absolute tru t h. I don’t see any need to play off the severity of chronic vs. acute acidification against each other, nor do I lik e the policy im plication that its only the ep isodes th at

m a tter.

p. 5-15, line 9: This is a good ex am ple of overly speculative phras ing (“acidification that has occurred to date has likely b een very lim ited”). You could say roughly the sam e thing m o re objectively by indicating th at “acid i fication that has been observed to date has been very lim ited”).

p. 5-15, line 9,10: Not clear what “E pisodic acidification does occu r” m eans here. In the W e st?

p. 5-15, lines 29-30: I’m surprised that the absolute concentrations of SO4 2- (as well as its % of

tota l ion con centr ation ) d i d not a l so decrease. If they did, why not say this as well, as a decrease in the % could be due to an increase in som e thing else.

p. 5-16, lin e 18 (& nex t few pages): These case s t udies s e em like they need som e additional detail. I’m not quite sure what’s the intended poi nt. Maybe you could put som e e m phasis on the sim ilarities & differences between the focus regions . For ex am ple what were the pa s t & cu rren t deposition levels in the Adirondacks – to co m p are with those reported subsequently for Shenandoah? Possibly an additional ‘case study’ for an acid-sensitive alpine W e stern ecosystem would round out the regional covera ge, and would also help em phasize the extrem e s e nsitivity in these f r ag ile ecosystem s which will n o t benef it f r o m CAIR em issions reductions.

p. 5-16, lines 30-32: This is awkwardly worded. I assum e you m ean that the num ber of lakes with ANC < 50 has m o r e than doubled from pre-indus trial tim e s (it’s not th e estim ate of the # of pre-industrial low ANC lakes pre-in d u strial lakes that’s chang e d).

p. 5-17, lin es 8-10: It seem s like these future pr o j ections are out of pl ace here. I would m ove them to after line 23.

p. 5-18, line 32: Add “assessm ents of” before “the im pacts”.

p. 5-21, lines 10, 12-17, 23 & elsewhere: At som e poi nt, it w ould be useful to add som e direct discuss i on o f N-f e rtiliz e d “growth” enhancem ents vs. othe r c onsequences of this f e rtilization & growth. In som e places an im pressio n is give n th at “growth ” is always go od, or good up to a point beyond which other adverse consequences can result. Possibly also add som e discussion of

com b ined effects of N fert ilization + clim ate chan ge.

p. 5-23, line 4: Can you give a quantitative ex ample of what you m ean by “very high”?

p. 5-24, lines 3-4: Can you use a m o re objective term than “are thought to include”? Could you

say som e thing like “Observed effects... have included...”

92p 5-24, line 5: Sam e comment as above. “woul d be considered relatively low” by whom ? Com p ared to what?

p. 5-27, line 1: This is an in teresting observation. I wonder w hy? Also, “disproportionately high” com p ared to what?

P 5-27, lines 7-10: It m i ght be helpful to provi de som e com p arative in fo on N dep rates in Netherlands vs. US.

p. 5-30, line 25 and following paragr aph. I think this section s hould extend beyond the current discussion - focused largely on primary productivity – and describe some of the biogeochem ical effects of excess growth and deco m p osition on dissolved oxygen, etc.

p. 5-30, line 31: Could you say “N-lim ited”, rather than “N-deficient”?

p. 5-31, lines 18-30: You m i ght add “turbidity” to this list. Its not a “biological” m e a s urem ent, but neither is DO.

p. 5-33, line 10: Can you state this more objectively than “probably ongoing”?

p. 5-33, line 14: Aren’t current inputs in this region m u ch lower than 10 kg N ha -1 yr -1 ?

p. 5-34, line 3: You could add “SO4 depos ition and” before “Hg m e thylation”.

p. 5-34, line 10: W hy ar e DIC & DOC in ( )?

p. 5-36, lin e 19: There are no “regu l atory networks” for S or N depositio n.

p. 5-36, line 20: You could add “, elevational gr adients and” before “ hotspots” to emphasize a particularly im portant inadequacy of existing deposition netw orks.

p. 5-36, line 22: Add a (cite) where indicated.

p. 5-37, lines 2-4: Is it possible you m eant “hi gh elevation areas of the West” in line 4? Otherwise including both the Appalachians and high elevation seem s redundant. And if you did

m ean the “West” (which would be true) you m i ght describe the first region as “New York / New England” to include the Adirondacks & Catskills. Possibly a l so add a m e ntion of sens itiv e are a s in Canada which m i ght benefit from future reductions in US S and or N emissions.

p. 5-37, line 11: I hesitate to criticize this presentation of qua ntitative “lim its” here, since I think more such num b ers would be usef ul in this sec tio n, but in th is case, I think N depositio n rates are already below this 9-15 kg N ha -1 yr -1 lim it, while the low bou nd lim it of 0 kg S ha -1 yr -1 suggests that no am ount of S reduction would prevent re-aci dification (which doesn’t m a ke sense). It

m i ght also be useful here to provide som e i ndications of how these ranges com p are to both current deposition levels and fu ture projections under of CAIR and contrast these with the estim ated dam a ge thresholds in both Adirondacks and Shenandoah.

93p. 5-37, line 14: As in a previous comment, you are im plying here that “growth” in som e ecosystem s is a beneficial outcom e – to be contrast ed with “adverse effects” in others. I think this cou l d be fixed by changing “eco system s” to som e thing like “ecosystem com pone nts”.

p. 5-37, line 19: Insert “Adding” before “excess” or change “to” to “in”.

p. 5-37, line 26: Should be “W est” coast.

p. 5-39, end of 1 st line under Nitrate: Add s to 1980. And 2 nd to last line: Could you add exam ple parenthetical “X ueq/L)” to indi cate what is m eant by “Very High”.

p. 5-42: Table 5.7.1 pro v ides a very useful qua ntitative sum m a ry of effects of N deposition on acidification and nutrient enrichm e nt that have been identified in recent studies. W ould it be possible to provide a similar summ ar y table providing quantitative of S deposition (or S+N deposition where applicable) on acidification? It is curious that th ese concluding summary tables include som e international observations but seem to have no Canadian references.

94

### Dr. Armistead Russell

W h ile I th in k the cur r ent ISA f o r Oxides of Nitro g en and Sulf ur-Environ m ental Crite ria prov ides much of the needed inform ation for the pro cess of reviewing the secondary NAAQS for NOx and SOx, at present the docum e nt is in need of significant m odification to provide such inform ation efficiently and effectively. The docum ent should be read and edited for relevancy of the inf o rm ation being p r ovided, and how it is pro v id ed, to the ultim ate go al of the rev i ew of , and providing the scientific basis for possibly ch anging, the associated secondary NAAQS

. One step in this process would be to look at Chapter 5 and edit what is presented there to specifically provide a summary of what inform ation is needed to provide a scientific f oundation for a review of the standard. Having edited the summary chapte r, then go back and write the chapters to b r ing forth th e specific po ints needed to provide the basis for w h at is in Chapter 5.

Unlike the ISA’s for the two associated prim ar y NAAQS, this docum ent begins in Chapter 2 with the m o re trad itional Crite ria Doc u m e nt appr oach of reviewing the atmospheric physics and chem istry of NOx and SOx, as opposed to a “Sour ce to Dose” presentation, which here would be source to exposure or load. The latter appro ach led to a m u ch m o re efficient p r esen tation of the key concepts, data and science. As it curren tly reads, aspects of Chapter 3 seem ed to be

som e what re petitive of in f o rm ation in Chapter 2, and the flow is awkward. Taking a source to exposure/load also leads back to the key idea that th e increased environm ental exposures can be linked to a source, which is what is controlled. Maybe it is due, in part, to lack of scientific investigatio n, but it is th is type of inf o rm ation that is required for this review. In revising the current Draft ISA, it m i ght be good to have som e one read Chapter 5, the Conclusions, first, and then identify what are the m a jor points, and what is needed to support the key findings as to the environm ental im plications of anthropogenically-influenced incr eased exposures and loads. Then, the degree to which those key findings are supported in Chapters 1-4 can be assessed, and the discussion of tangential inform ation can be stream lined.

Chapter 2:

As noted above, I think the ISA would benefit from a Chapter 2 that goes from Sources to Environm ental Exposu r e/Load. Chapter 3 shou ld be integ r ated in. In ad dition to hav i ng atm o spheric chem istry and physics, aquatic a nd soil chem istry and physics should be added. This would save m u ch repetition later on in the report (e.g., about what leads to acidif ication, its affect, m obilization of alum inum , etc.). Fig. 2.2-1 could have a twin(s) showing what is happening in surface water and the s o il-water m a trix.

On page 2-3, line 16, one should note they are refe rring to U S e m issions. Lines 19-23 are a bit confusing at present. W h at is im portant, here, is that virtually all of the f u el-bound sulfur gets oxidized to a volatile component (S O2 or SO3), and that there is very little natural, oxidized sulf ur in a i r over the US, so the sulf u r

em itted f r om burning a f u el is quantita tive l y re la ted to that in the f u el.

95The section on Measurem ent Methods needs to be refocused. The m a jor question to be addressed here is if the current m e thods em ploye d in the field provide reliable m easurem ents of NOx, NH3, NH 4 + , NO 3 - , SO2 and SO 4 = for levels of interest, and this should be answered quantitatively. At present, there is discussion of th e various m easurem ent approaches (s om e is needed) and lots of discussion on possible interferences, but neve r does one get the answer to what is th e typical un certain ty in th e m easurem en ts at a typica l m onitor in the US and how that im pacts our ability to accurately quantify environm ental exposures. I suspect that the m e thods

em ployed for m o st of the species, while subject to som e interferences, provides fine data, and that the lev e l of uncerta inty is such that we need not concern our selves with possib l e interferences and biases. The m a jor exception, of course, is ammonia, which is not even discussed. What really lim its our ab ility to qua n t ify depositio n accurately (e.g., do we need m o re accurate m easurem ents, different kin d s?). Quantify the problem s, let the reader asses s if they are of concern.

More specific comm ents:

2-1:24-27: What about pSO4? Rxn 2.2-2: Balance the reaction. 2-5:13: Reactions 2.2-1 and 2.2-2. Section 2.2.2 It is not apparent the need for so much on Cl chem istry. Also, this section should be preced ed by a m o re com p rehensive discuss i o n of N2O5. I would be v e ry tem p ted to

m i ni m i ze this discussion.

2-9:25: Not sure why you use m onom e ric. W h a t polym ers do you have in m i nd? 2-10: 28: In both cases, NO3 and H are radicals, not ions. 2-11:2 Ravishankara. 2-13:28: A second reaction for comparison s hould be added (i.e., the ozone reaction). 2-14:10: W h at chem istry of NO3- form ation is being discussed? 2-15:1: Ammonium nitrate form ation as well. 2-17:30 Remove “all”. 2-21: Sectio n 2.6.2.2 needs to a ddress accuracy more directly. 2-22...: Section 2.6.3 should be m o re quantitative.

A section on NH3 m easurem ent is needed.

2-27: Section 2.7.1: It is weird that pNO3 is included here, pS O4 is not. 2-28:28: There is a summ ary pa ragraph for NH3 that is about as long as those for the other species, bu t where is th is drawn from?

At present, the summ ary is a bit sparse.

96Chapter 3

The Chapter beings with a discussion of sour ces, which as noted above, should go in a more integrated C h apter 2. It seem s a bit unnatural to not start “the story” w ith sources. Also, while this chapter starts with sources, one does not ge t a quantification of such. One should not have to go to the Annexes to get a r easonably quantitative overview. A single table showing the contributions of, say, m o bile, non -m obile, utility, bioge nic an d agricu ltu ral sources to oxidized NOx, N2O, reduced N and SOx is required. This m i ght be done on a tons of S and N basis for ready com p arison between the oxidized and reduced f o rm s. Som e estimate of the tra n sport to North Am erica m i ght also be provided. (A sister Table showing the fate of the above is also suggested.)

A Table of fate of reduced N, oxidized N and SOx is suggested, showing the m a sses dry and wet deposited by species, as well as the amount transported away from the continent and associated

estuar ies. H a ving th is ta ble in tegra t e d with the table of sources m i ght be of interest from a m a ss balance p e rs pectiv e.

Figure 3.7-4 As discussed during the SOx-Prim ar y ISA review, this figure is not very effective. First it r e f e r s to “... in f o cus” in f o c u s of what ? Further, m o st of the data is very m u ch at the bottom end, so it is difficult to see what is really happening, and it n eeds to include m o re inform ation (what years...). I would have it provide the m ean, m e dian, 5 & 95%iles, and the

extrem e value. Further, it m i ght be given on a log scale as most of the lower level infor m ation is now lost.

There is a bit of a contradiction in C h apter 3. O n page 3-8, line 11, it says the ratio of N-to-S is 14, close to that in the tissue. The prior line says that approxim ately half of the S is in the ash. Please exp l ain further.

In considering em issions, it would be good to also provide som e infor m at ion as to future

em issions for perspective. CAIR is going to si g n ificantly lo wer em issions in areas where they are currently high. This is im portant for our fu rther consideration as to how a standard m i ght im pact air q u ality.

Section 3.13 Summ ary.

This section starts out very roughly. 3.13.1 reads more like a se t of bullet points in sentence for m . The last paragraph (3-161, l4-6): Is this w h at you really m ean to say, and from what part of the report is it distilled? Ta ble 3.11.1 is rather m o re concrete at 21%, but does not indicate the reduced N fraction. Also, the first sentence of 3. 12.2 is not really taken f r om som e thing in the text (I m i ght add this to the prior text).

3-60:26 change to “...su rface of some coastal...”

What this chapter (or what should becom e a section of Chapter 2) needs is to focus on what one wants to know, as this section currently has som e stuff I like to know, and som e of what is not needed to assess a NAAQS. W h at is really needed ? I would say a best es tim ate (m ap ) of total N

97and S deposition, a list of estuar ies suffering eutrophication with estim a tes (and uncertainties) of what is con t ributing. Th ere was too little on ammonia(um ) deposition.

Specific co mments:

3-2:30: This sentence contains a non-sequiter. 3-3:2: Reactions, not reactivities. 3-4:16: I would rem ove “sm a ll” 3-4:24: “... for exam ple, is estima te d to have decreas ed...” 3-9:16: Remove “However” 3-13:13 “is a sm aller loss process th an its n e t th e r m a l decomposition ” 3-13:28 Remove “which” 3-14: Section 3.5.5. the source stre ngth given is not a source strength unless one knows the volum e. Further, m o re infor m ation on how robus t this value m i ght be nationally is needed. 3-23: Section 3.7 is somewhat repetitive of pr ior sections. 3-23:23-29: W h at is this paragraph trying to say? 3-23:28: Higher than w h at? 3-24:1-8: Much m o re quantitative inf o rm ation is available, e.g., annual average concentrations of the various individual oxidized nitrogen species. Figure 3.7-2: Put Figure 3.7-3 righ t below this figure for comparis on. Also, can you provide the

sam e figures for oxidized nitr og en sp ecies of in terest? 3-26:2 “for more com p l e te descriptions” 3-26:7: This is not seen in Fig. 3.7-4. 3-28:6: “correlative”? 3-28:29 “...m ean oxidi zed N...” 3-36:6: Units on deposition velocity? 3-36:7-7: Is this a m a jor extrapolation. Please clarify. Fig. 3.9-3: How significant is “a”, and the units for concentration are no n-standard. 3-41:3-5: Further explanati on as to “why” is needed. 3-43:26-27: Sa m e should be added for regional scale. 3-47:19-17: I would note all of the evaluation work and m easurem ents done by/for the state, RPO’s and EPA. It m a y not get published in the open literature, but these groups probably do most of the model evaluations done. 3-48:12 “This”? 3-50: W h at is needed here are the best estim a tes of N deposition using C M AQ. Figure 3.12-3: How about adding N H 3?

Chapter 4:

Chapter 4 reads m o re like the old Criteria Docu ments, being rather exhaustive and sometim es appearing to lose the point.

Also, m a ybe I m i ssed this, but this chapter seem s to have ad hoc decided to use SO 4 + instead of using SO 4 = (or SO 4 2- ). Why?

There is significant repetition in this chapter. Much of what is in 4.2.1.4 is in pages 4.10-12.

984-1:22: interacti ng 4-2:6: “...when the nutrient...” Figure .1-1 : For the forest critical ch em ical lim it, what are th e units of 1.0? For the Lake, is “0” sensible? 4-7:13 Mig h t you add surface water acidificatio n ? 4-8:4: Define Oa 4-8-29: W h at about NH x ? Fig. 4.2-1: W r ong figure. (Switch with 4.2-2) 4-11:25: Replace “Th i s” with “The” 4-13:22: “... forested areas , it is ...” 4-15:27 Define “%” of what. 4-16: “...acidic deposition m oblizes...” no comm a. 4-16:14-16: Repetitive. 4-19:11-12: Sa m e paragraph. 4-19:16: “...general... generally...” 4-19:28 “or neutralizing” Fig. 4.2-3 Probably should define ANC in the caption and also add the 0 lines. 4-22:30 All the “in summ ary” statem ents get a bit old. 4-24:3: [K] Section 4.2.22: Repetiti ve of prior m a terial. Fig. 4.2-6: “Bad death”? As opposed to “Good death”? 4-39:25-26: Sentence needs a bit m o re explanation. 4-43::19: “linear ly ” 4-44:31: Context needed for 5.0, 5.5 and 6.0. Reference to w h at effects. 4-49: Should not ANC m easure m ent be up front in m easurem ent m e thods? 4-49:9: Repetitive. 4-49:14: S m all is not defined, and why is this v i ewed as small? 4-49:23-24: Unclear clause at the en d. 4-50: Lines 21-22 and 25-26 a ppear to be contradictory. 4-54:20: Be specific as to at what level. 4-64:23: Lawrence no longer in review, I think. 4-123:L24...: Again, seem s repetitive. 4-129:17 Reviewing only the negati ve effects appears one-sided. 4-130:2: “Results of these studies...” 4-132:30: C onfirm e d? Support? 4-135:1: W h at would this equate to in term s of deposition? 4-148:29: define stges. 4-150:26: “probably”? Cite. 4-152.19-27: Largely repetitive. 4-154:5-9 T h e term significant here must be purely definitional. W h at is m eant by, or determ ines, significant? 4-156:4...: Repetitive. 4-157:14 “N iwot Ridge wh ere...” remove comma. Section 4.4.1.2 can be shortened. 4-168:19-21. This need not be stated. It has to be.

994-174:3-14. Be quantitative... at wh at levels are the im pacts found? 4-177:12-31 Use sam e units as before. 4-177:3-: Provide units on coefficients. 4-178:9-14: Discuss exactly what wa s m easured, provide uncertainties. 4-179:24-25: Is this likely an issue? 4-179: Provide a summ a r y.

Chapter 5:

This chapter is still a bit choppy, but prim arily sh ould be revised by asking the question: W h at inform ation specifically is needed to provide the scientific basis for reviewing the NAAQS secondary N O x and SOx standards.

Specifics:

5-3:8-12: What about ammonia? 5-12:28: “... decreased in som e ...” 5-12:31: be a bit m o re specific as to how. 5-13:29-30: Could just be m y me mory, but I don’t recall this. 5-16-28: Remove extra “.” 5-16:30 Try not to use “m any” as op posed to giving a specific fraction. 5-18:5: rearrange sen t en ce” “con t rib u tions of CA...acidity ) from som e ...” 5-20:16: “...section discusses...” 5-20:31: “is it “of” or “by”? 5-26:8-28: These are important poin ts, but they did not seem to com e out very distinctly in the chapters. (sam e with 5-27:15-20). 5-28:22: “AQCD , further studies s u ggest productivity...” 5-31:6: awkward sentence. 5-37:16 rem ove “in”

Overall: Probably the single bi ggest lim itation in this docum ent is acknowledged early on: It does not try to establish critical loads, without w h ich it becom e s di fficult to know what levels of environm ental exposures are accep table or not. Decision m a ke rs and advisors need such inform ation, even if it is fraught with “uncertainties.” (I put uncertainties in quotation m a rks as it seem s as though we use that as a reason to not go forward, which is not the case.) The second real need of this ISA is to dig m o re in to the reduced nitrogen deposition issue.

10 0

### Mr. David Shaw

Chapter 1 Comments

Message of the document This chapter drives the whole docum ent and as su ch it should say up front that a m a jor part of this as sessm ent is exam ining. A prim ary unit of m easure is shown throu ghout as dep o sition, so it must state th e streng th of a deposition approach to both of these cont am inants. I also feel th at the purpose and consequences of evaluating N a nd S in tandem should be addressed. While the chapte r ope ns with a sta t em ent of elim inating par tic ulates in the scope of this scientific analysis, I do not f eel that this is not an appropriate m e ssage.

Framing Questions Som e of the fra m ing questions (pg 1-2) are awkward (e.g. bullet 3 line 13) and don’t focus the work as well as the m o re succinct language below (proposed by E.Cowling). Individual Comm ents on the September 2007 Draft Plan for Review of the Secondary National Air Quality Standards for Nitrogen D i oxide and S u lfur Dioxide October 26, 2007. I suggest substituting the fra m ing questions for these:

“W hat scien tif ic ev idenc e and/or s c ie ntif ic insights have been developed since the last review to indicate if the current public-health based and/ or the current public-welfare based NAAQS need to be revised or if alternat ive levels, indicators, statistical form s, or averag ing tim e s of these standard s are needed to protect public health with an adequate

m a rgin of sa fety and to protect public welfare? ”

“W hat scien tif ic ev idenc e and/or s c ie ntif ic insights have been developed since the last review to in dicate wheth e r, and if so, what particular ecosystem co mponents or other airquality-related public welfare va lues, are m o re or less sensit ive than the populations of hum a ns for which prim ary standards are esta blished and for this reason m a y require a different level, indicator, stat istical form , or averaging tim e of a secondary standard in order to protect public w e lfare? ”

Format The for m at calls for a su mmary of findings at the end of each m a jor segment of each chapter which the authors do, but they should also, as m u ch as possible, discuss the relevance of each of those findings with the two questions above. Th is should be expressed in Section 1.3. The for m at should also require that the conclusions in Chapter 5 rest ate these original questions and summarize a ll f i ndings w ithin the two reworded fram i ng questions. The summaries would serve the docum ent best by ensuring that all th e m a terial is summ arized in a clear and conc ise m a nner.

The deposition m onitoring network m a ps are t oo sm all to show adequacy of the network.

10 1Gaps in legislative background and history of the current review CAIR should be m e ntioned in the re gulation portion of this discussion.

Major s c ien t if ic, m u lti-state and na tio nal survey s and summ ary reports of the per i od ( i .e., since SO 2 NAAQS 1982) need to be m e ntioned, included but not lim ited to the EPA Eastern and W e stern La ke Surveys, the Nation a l Acid Precip ita tion Asse ssm ent Program (NAPAP), the NAPAP Integrated Assessm e nt in 1991, and the EPA Acid Deposition Standard Feasibility Study Report to Congress in 1995. Significant state su rveys like the Adirondack Lakes Survey in 1984-1987 and the ongoing Adirondack Long Term Monito ring of lakes and stream s should also be included.

The recen t p r ogression o f the im portance of N in acidificatio n should be given m o re atten tion. For exam ple, the recent chem ical recovery si gnal in Adirondack lakes appears closely linked with N deposition. Recent data show stream acidification is also highly correlated.

Section 1.1.3 SO x . Include the primary standard for SO x . Fill in the history gap between 1988 and 2006.

Section 1.1. 4. Include w h at led to th e developm en t of a deposition appro ach to th is s econdary standard as opposed to an am bient air standar d. Add what other states m a y have done with respect to 1) m o re stringent pr im ary standards or 2) proposals of secondary standards or other regulations to protect the environm ent from NO x and SO x .

Current levels of am bient and depos ition N and S are im proved because of all efforts to attain clean air, w h ich should include m a jor state e fforts such as N e w York State’s NYS Sulfur Dioxide Control Prog ram in 1985 that evolv e d into its Acid Deposition Control Pro g ram

. Several no rtheast s t ates (NH,VT, CT and ME) have discuss e d or proposed S and N deposition standards to protect forests.

Particula t e of NO x and SO x omission

The first paragraph states “The scope of the joint NO x and SO x ISA is lim ited to welf are topic s that do not duplicate those addressed by the forthcom ing particulat e m a tte r (PM) sc ienc e

assessm ent. The welfare effects of visibility im pa irm e nt and clim ate inte ra ctions assoc i ated with particulate NO x and SO x will be addressed within the sec ondary PM NAAQS.” The om ission of particulate p h ase NO x and SO x lim its the poten tia l f o r setting standard s in the f u ture us ing both PM and oxides of Nitrogen and Sulfur standards. Furtherm ore, PM plays a significant role in nitrogen and sulfur deposition. I feel that separating out the ef fect s of gas- versus aerosol-phase S/N will be dif f i cult, sin ce wet and d r y depositio n can inc l ud e both phase s, and atm o spheric chem istry and transport affect both phases. The ISA clearly s t ates that “p articulate N O x and SO x will be add r essed with the secondary PM NAAQS review,” and it theref ore becom e s crucial th at these two review process track s are highly consistent with each other. O n e cannot p r oceed independently of the other track.

10 2Implementation of a secondary sta ndard(s) It is im portant to state that th is docum ent covers the setting of a secondary standard(s) but not, at this point, the im ple m entation of a secondary NAAQS. They would need to be developed or ......This would be very difficult because at pres ent, there are no adequate source-receptor models to provide the level of control that would be required to m eet the secondary N AAQS, if the deposition standards were excee ded in any particular area.

Charge Questions

Question #1 To w h at extent is the ev idence on atmos pheric chemis try a nd phy sics, air quality, and deposition and exposure sufficiently and corr ectly des cribed, clearly communicated, and relevant to the review of the secon d ary NAAQS for NO 2 and SO 2 ?

· The inform a tion on gas-phase chem istry and phy sics is sufficient and well-pre sented in Chapters 2 and 3.

· Since both gas-phase and pa rticulate S/N are involved in deposition, the ISA would benefit from inclusion of m o re chem i s try a nd physics on the particulate side in these chapters as well.

· Clearly communicated – see “Form a t” s ection. S u mm aries are graded as poor.

Question #2 How w e ll characteriz e d are the relevant prop ert ies of the ambient air concentra t ions and deposition of NO x and SO x , including policy-relevant background concentrations, spatial and temporal patterns, and the relationships betw een ambient air concentrations a nd ecological exposures?

· There is enough inform a tion on urban NO 2 and SO 2 to characterize am bient levels, bu t not enough infor m ation in rural areas and sensitive ecosystems.

· In general, em ission inventories for SO 2 , whose sources are well-characterized, are m o re reliable than estim ates for em issions of NO x, and certainly far more reliable than NH 3

em issions.

· There is m o re inform ation, in term s of spatial coverage, on wet deposition of SO 4 , NO 3 , and NH 4 than am bient SO 2 , NO 2 , or NH 3

Question #3 How sufficient is the in formation o n atmosphe ric sciences and exposu res for the purposes of evaluating and interpreting the ecological e ffec t s prese n ted in Chapter 4 of th e draft ISA?

There is an inherent danger here of assum i ng that all areas of ecologi cal effects are eq ually im portant or equally developed in th e litera ture, which in m y vi ew, they are not. The danger is

10 3the inev itab l e conclus i on that the suf f i cien cy of the inf o rm ation will not b e adequate f o r all of them

.

A better use of tim e woul d be to go to the bigger questions fram ed above that have to do with the interaction between the prim ary and the seconda ry standards, and the value and need for establishing deposition standards.

General Co mments

Deposition-based Standard The draft IS A de m onstrates a strong interrelati onship between deposition data and effects to ecosystem s as shown in Table 5.7-1. Concentration- based standards are not biologically relevant

to m o st resources at risk from air pollution (s urface waters, groundwater , soils, etc). It is im portant that other EPA program s (i.e. CAMD) are reviewing or part ic ipating in this ISA. All

program s should be aware of the pro posed m ove forward to a m u lti-po llutant appro a ch and this new pathway.

One or multiple s econdary standard One secondary standard for the US or several accor ding to various sensitive receptor areas in the country? Prim ary standards protect only one organism , people, and they are distributed throughout the country, so generally one size does fit all. Seconda ry standards protect sensitive ecological recepto r are a s (ER) whic h are not ev enly dis t ribu ted and have m u ltiple se nsitiv e

com ponents within them . Are we setting one secondary standard for the country? Have we identified all of the sensitive environm ents that we wish to track and to protect?

W ithin each sensitive en vironm ent, have the ec ological asses s m e nts identified a sing le or multiple d e p o sition targets ? Shouldn’t each ecolo g i cal area h a ve one targeted ? Have the m a jor eutroph ication-str e ssed estuar ies p i c k ed a lim it f o r NO x and NH x ?

Critical load s m a y be an area of interest. I feel th ere is a need for di scussion on the state of knowledge of critical loads. W h ile there m a y not be a high resolution understanding (sm a ll blocks) areas can be defined by forest or eas t vs west. The EU has critical loads in place.

Emphasis on Certainty While there is uncertainty surrounding som e data or m odeling, I feel that it is im portant to

em phasize that solid and certain data does exis t wh ich the scientific community has accepted.

Climate change There m a y be a need for analys is of the effects of the SO x and NO x deposition on climate change. In addition, the eff ects of clim ate change on SO x and NO x pollution.

Adequacy o f existing air monitoring netw ork

· The density of SO 2 and NO 2 m onitors is adequate to track the prim ary standard, but is not adequate for the secondary standard.

· The bulk of the am bient SO 2 and NO 2 m onitors, as well as the Speciation Trend Network for fine particulate SO 4 and NO 3 , are located in urban and suburban areas.

10 4· There is no national NH 3 m onitoring program , and what little inf o rm ation is ava ilab l e for am bient concentratio ns is re searc h -orien ted.

· There is inform ation on fine particulate SO 4 and NO 3 at >100 Class I areas through the IMPROVE program, but this is probably no t adequate to characterize all s e nsitive ecosystem s across the nation.

· The m a jor deposition networks (CASTNet , NADP/NTN) were generally established to track the effects of em issions reducti ons from the energy generation sector.

· In term s of data coverage, there are more wet deposition m onitors m e asuring SO 4 , NO 3 , and NH 4 than there are am bient NO 2 m onitors, however these netw orks are not generally capable of characterizing deposit ion in urban areas or m a ny rural areas (especially in the western US).

· Dry deposition of S/N is inferred rather th an m easured directly by routine networks like CASTNet, but ev en so there are far fe wer dry deposition sites com p a r ed to wet.

Transformation Products Clarify which N pollutants are being discusse d. Research w h ich oxi dized N com pounds are relev a nt and f

easible to monitor. W h ile NO y m a y be m o re appropriate, th ere is a need to discuss the difficulty of m easuring individual com pound s. Chapter 2 does describe som e of the heterog e neo u s chem istry between NO y and halogens, but does not really cover ammonium nitr ate / sulf ate f o rm ation. Hal ogen chem istry plays an im portant role in urban coastal settings, but amm oni um nitrate/s u lfate chem istry is im portant over vast regions of the continent.

NO x as a precursor NOx should be discussed as a precursor to the following: Ozone Am bient nitrates N depositio n Fine particulates

Inclusion of N 2 O N 2 O is certainly a greenhouse gas, but is not a component of NO y , nor is it relevant to O 3 /PM/haze for m ation or N deposition (and subseque nt acidification or nu trient enrichm e nt). More inform ation on particulat e N would be favored over N 2 O analysis.

Dry deposition There are different m oni toring networks for sulfur and nitrogen. Monitoring network not adequate for dry deposition

Emissions inventories Are em ission inventories adequate for each, SO x , NO x and NH x ? For the prim ary and secondary standard? In general, em ission inventories for SO 2 , whose sources are pretty well-characterized,

are m o re reliable th an estim a tes for em issions of NO x, and certain ly f a r more re liab l e than NH 3

em issions.

10 5Multiple in dicators an d multiple s e nsitiv e are a s. States m a y contain s e veral sens itive regions. Sen s itiv e reg i on s like the Ad irondack M ountains will have m u ltip le na tur a l resou r ce s with dif f e re nt indicato r s and/or c r itic al th reshold s (see Figure 4.1.-1, page 4.4). Have all th e sensitive a r eas with in the US been identified (Alaska and Hawaii have none?)? Will each s t ate be respons ible for verifying thes e areas ? Is there is enough data to do that in each area? Or whether there will be a blanket single ind i cator f o r e a c h sensitive region? W h at is the m o re quantifia b l e indicator o f ecological health ? Has the ef f e cts lite ratu re (for the case study areas where th e literature is more com p lete) id entified the m o st representative indicator to protec t the whole area?

Other ed ito r ial co mme nts: 1. Figure 4.2-2 wrong diagram for the caption. 2. pg 4-41, line 6 Figure 4.2- 2 should be Figure 4.2-8. 3. pg 5-10 line 12. Sprin g chem istry is not bas e flow conditio n for stream s in the Eastern US. 4. Glossary. Add base cati on surplus, chronic acidifi cation, episodic acidification...

10 6

### Dr. Kathleen Weathers

This chapter was rather unbalanced in writing s t y l e as well as analys is and synthesis. It was of

ten dif f i cult to identif y the sa lien t p o ints (b o tto m lines) in much of the f i rst par t of the docum ent (until 4.3 ). Th ere were inaccuracies an d often unqualified (under referen ced ), valueladen language was used (see specific comments, below). Consider reor ganizing and rewriting the chapter, using one voice, and organizing the chapter aroun d a conceptu al m odel. The integ r ative tables that are at the end of the docum ent could be used to guide a discussion on the overarching effects of acidification and nitr ogen enrichm e nt on ecosystem s . Supporting inform ation could then be revised, condensed and used to underpin this synthesis.

4a How wel l are the major effects of SOx and NOx on ecological acidif ication identified and characterized? 4b To what extent do the discus sion and the integration of evidence across scales (e.g., species, communities and ecosystems and regions) correctly r e presen t and clear l y communicate the s t ate of the science?

The m a jor acidification effects, which have been indirectly or direc tly like d to the (wet,

som e ti m e s wet + dry) deposition of sulfur and ni trogen, have been identified and characterized in this ch apte r. The rela tiv e im portance and cer tain ty of various effects was less well characterized.

Categorization of biological and chem ical effects is a useful way to partition.

Again, I sug g est add i ng a conceptu al m odel to the beginning of this section. The table (identified as Fig. 4.1-1) and its a ssociated description is a start. However, I do think that it is more logical to consider deposition as a driv ing variable and various ecosystem (i.e., export rates, nutrient or pollutant cycl ing, acidification process, produc tivity) or ecological properties as response to variables rather than the other wa y around, despite the suggestion that working from top to bottom is inherent in th e cr itic a l load appr oach.

Much of the text details studies that have explored the effects of acidification on the various foci of ecological studies (as listed above). The coverage of the literature is not as broad as it m i ght be; it relies heavily on a lim ited se t of research/researchers’ work. There is also m u ch supporting literature in this ch apter from pa st decades. It is very useful to cite these f oundational studies, but also im portant to note what the relevant (to this tim e period) bottom lines ar e, esp ecia lly in situations w h ere the environm ental conditions ha ve changed significantly in the inte rim. One suggestion is to identify what is new (recent results, or synthe sis efforts) and what has been known for som e tim e. I am concerned that studi es whose results, for exam ple, point to how ecosystem s responded to the depositional regim e in the 1980s and 1990s m a y be dis m issed, or questioned as relevant in 2008. However, there ha ve been a num b er of integrated studies over the past several years, both m odeling efforts and synthesis whose results are cited. Thus, it would be usef ul to iden tif y which cla ss of resu lts is tim eless, i.e., where th e f i ndings still ho ld despite significant changes in em issions and/or de position over tim e . Integration and synthesis is a challenging task.

10 75. How well has the IS I character i zed the relatio n s hip between acidifying deposition levels o f NOx and SOx and ecological effects.

The characterization could be m a de m o re direct . As one example, studies that highlight deposition, whether estim a ted acro ss the landscape or to a site (e.g., Lovett and Reuth 1999), or controlled through experim e ntal a dditions (Harvard Forest, Catski lls, Bear Brook additions, for

exam ple), were not highlighted or cited well throughout the text.

The ecosystem approach was underscored in the firs t part of the chapter. Thus fra m ing the relationsh i ps of depositio n and ecolog i cal respons es using a m a ss balan ce approach w ould be an other logical way to organize the discussion. In this way, it would be possible to m ove from the influence of S and N on watersheds, to comm uni tie s and spec ies with in wa tersheds. Consider including a table or a secti on th at su mmarizes th e relation s hips between deposition and ecological effects toward the be ginning of the chapter.

I appre c ia te d the in trodu ction of cr itical lo ads as a way that the EU and others have considered successf ully the re lation ship betwee n atm o spheric depos itio n and enviro nm ental ef f ects; it is an im portant approach to explor e in this docum ent.

The word/concept “thresholds” is used in num erous cases. It should be (re) defined in this section. A summ ary section or table identifying ecological th resholds that have been docum ented (the response variable and the ac tual threshold) w ould be very useful. Even if it turns out that few have been defined, it would be useful exercise.

An introductory paragraph about the (legitim ate/de fensible) use of m odels and a brief characterization (i.e., table about the nature and utility of the various models , and their results, that are cite d throughou t this chapter) would be a useful addition. Also, wher ever th ere are m u ltiple m odel results for an ecosystem or region, a summary of the sim ilarities (e.g., page 4-87 for the Adiriondacks) as well as the differences in m odel results and whether there has been any independent validation or verifica tion of the m odel s should accom pany the com p arison. It is also critical to point out which m ode ls co nsider b i olo g ical inte rac tions (the bio part of biogeochem istry) and which do not. Since N is very bi ologically active, and tree species can have a considerable effect on N loss from ec osystem s (e.g, Lovett et al. 2000, 2002, 2004), use of any models that do not consider the influence of bi ology on geochem i cal cycles should be very well justified. And, the details, strengths and weaknesse s of m o dels that do include biological process ing should likewise be revealed.

6. How well characterized are the oxidized and reduced forms of nitrogen on acidification

The N cascade section was good. Consider including the first part of the N cascade section and a parallel sulfur section at beginning of this chapter.

Make clear that in addition to HNO3 wet and dry deposition, som e areas of the country are exper iencing a rise in NH3 em issions and NH4 wet de position (NADP data show this increase). Although there are fundamental differences in ecol ogical processing when reduced vs oxidized

10 8nitrogen is added to an ecosystem

, it would be us eful to point out that there m a y be downstream acidification /eutrophication effects if nitrog en dem a nd is exceeded and nitrogen is leached as a result of NH4-N deposition (in addition to the brief m e ntion on page 4-145).

A few overarching com m e nts:

Total deposition, wet+snow+d ry+fog, in places where it m a tters, is still poorly characterized for most places on the plan et, especially in non-hom ogeneous terrain (e.g., see W eathers et. al. 2000, 2006). Getting reasonab l e estim a tes of total de po sition, especially acro ss space, and relating

em issions to deposition are still activ e areas of research. These facts can be problem atic when deposition is used as the indepe ndent variable or treatm e nt for any of a suite of ecological responses. I do not think that this challenge — obtaining and using re asonable estim ates of deposition — renders specific studi es either inadequate or wrong. However, it does underscore the need f o r multiple lin e s of evidenc e to iden tif y, with som e conf idence, the ef f ects of N and S on loading e c osystem s , species, and communitie s. These m u ltip le lines o f evidence o f ten com e through the use of experim e ntation (especially loading studies), m odeli ng, theory, long-term analyses, and use of deposition grad ients (where there are su rely la rge dif f erences in deposition even if the a b solute num bers have lar g e uncer tain tie s associated with them ). I think that pointing out the im portance and power of m u l tiple lines of evidence in supporti ng current understanding about the effects of NOx and SOx on ecological sy stem s woul d be a useful thing to do at the beginning of this section.

I like the case studies, but they could be used m o r e effectively, perhaps to highlight parts of a co nceptual m o del. Make clear why par ticu l ar case studies are being used.

Som e details:

The charge on sulfate is incorr ectly identified throughout the text : sulfate is an anion, not a cation, and it’s divalent, not m onova lent. I note, however, that th ere is correct inference for sulfate’s behavior throughout the text (i.e. it is listed/included in discussions about m o bile anions).

Decom position should be added as an im portant process in section 4.1.1 and food webs vs food chains are more realistic descrip tion s of energy movem e nt within ecosystem s.

There are many places in the text where referen ces are m i ssing, but necessary. The references also seem quite biased toward speci fic researchers or research groups.

Correct the text for reduction/ox idation reactions and products (the transform a tion from ammonium to nitrate is oxid a tio n, f o r exam ple).

Figures 4.2-1 and 4.2-2 are transposed.

Y axis on Fig. 4.2-6: “B ad?” death?

Do the colors m ean anything on Fig. 4.2-12?

10 9It seem s to m e that m u c h of the fish data th at include abundance, biodi versity, and total num bers of species present as response variables are potentially confounde d by freshwater stocking activit ies. Perhaps stocking did not influence the resu lts or was not practiced in m a ny of the focal surface waters. If that is true, it would help to s a y so, if it is no t, it m a y still be worth mention i ng this confounding point.

I believe that the original refe rence to N saturation was Agren and Bosatta (1988) (page 4-106).

Equating throughfall N flux with atmospheric N de position is not warranted in m a ny locations in the US because of variable uptak e and leach i ng in the canop y (page 41 10). Throug hfall deposition or flux is often considered to be a goo d indicator of what is deposited to the forest floor, but no t necessarily what is dep o sited from the atm o sphere to canopies when the nutrient, ion or elem ent of interest is biolog ically react ive/activ e. Sulfur, however, has often been considered an exception. In regard to su lfur in throughfall, research th at has suggested its utility as an indicator of total deposition should be included as well as the one on page 4-162 (Cape) that questions it. For exam ple, m a ny papers, includi ng Garten and Lindberg; L i ndberg and Johnson; Lovett; W eathers e t a l .; a nd m o re have pointed to its utility.

Words such as “harm f ul” or “negative effects” w ithout qualification should be avoided; if used they should be qualified with sp ecific environm ental term s (e.g., harmful physiological effects of acidity on fish biota ) . Also “ecosys t e m or ecologi cal hea lth” is ill d e fined and often a lightning rod-word. I suggest defining it, or better yet, don’t use it.

Consider doing a publication coun t by year on the topic of acid ification/critic al loads.

Listed below are so me relevant articles whose results should be co nsidered when revising the ISA:

Butler, T. J., G. E. Likens, F. M. Verm ey len, and B. J

. B. Stun der. 200 5. T h e im p act of changing nitrogen oxide e m is sions on wet a nd dry nitrogen deposition in the northeastern USA. At m o s. Environ

. 3 9 : 4851- 486 2. Burgin, A.J. and S. K. Hamilton. 20 07 . Have we ove rem phasi zed the role of de nitrification i n aquatic

ecosy stem s? A review of nitrate rem oval pathway s . Fr ont. Ecol. E n viron. 5:89- 9 6 [ i ndirect effects of S on N biogeochem i stry ] Caraco, N.F. 1993. Distur bance of the phosphorous cy cle: a case of indirect effects of human activit y

. Trends in Evolutio n an d E c ology 8:5 1 -5 5. [ i ndirect effects of S on P biogeoche mistry ] Caraco, N.F., J.J. Cole, G.E. Likens, G. M. Lovett, an d K.C. Weathers. 2003. Variation in NO 3 export

from flowing waters of vast ly different sizes: Does on e m odel fit all? Ecosystems 6:344- 352. [ N deposition and what influences nitrate in aquatic sy stem s draining various source areas] Groffm an, P.M., J.S. Baron, T. Blett, A. J. Gold, I. Go odm an, L.H. Gunderson, B

. Levinson, M. Palm er, H.W. Paerl, G.D. Peterso n , N.L. Poff, D.W. Rejeski, J.F. Reynol ds, M.G. Tur n er, K.C. Weathers and J. Wiens. 200 6. Ecolo g i cal thresholds: An im por tant concept with no practical application, or the ke y to suc cessful environmental m a n a ge m e nt? Ec osystem s 9:113

. [a very cursory examinati on of t h e concept and diffi culties surrounding thr esholds; acid deposition used as an exam ple] Kelly , V.R., G.M. Lovett, K.C. Weathers, and G.E. Li kens. 200 5

. T r ends in atmospheric amm oniu m concentrations in relation to atm o spheri c sulfate and local agriculture. Environmental Pollut i on 135:3 63-3 69.

11 0Kelly , V.R., G.M. Lovett, K.C. Weather s , and G.E. Li kens. 200 2. T r ends in at m o spheric concentration and deposition com p ar ed to regional and local polluta nt em issions at a rural site in southeastern New York, U S A. Atmospheric Environment 36:15 69 -1575. Likens, G. E., D. C. Buso, and T. J. Butl er. 200 5. L ong-term relationships bet w een SO2 an d NOx

em issions and SO42- and NO3-concentration in bulk deposition at the Hubbard Brook Experimental Forest, New Ham p shire. J. Enviro n. Monitor. 7( 10):96 4 -96 8

. Lovett, G.M., K.C. Weathers, and M.A. Arthur. 20 02

. Control of ni trogen loss fr om forested watersheds by soil C:N ratio and tree species co m p o s ition. Ecosystems 5:712-7 18. Lovett, G.M., K.C. Weathers, and M.A. Arthur. 20 04. The influenc e of tree species on nitroge n cy cli ng in the Catskill Mountains, N e w York. Biogeochemistry 67:28 9-30 8. Lovett, G.M., K.C. Weathers, and M.A. Arthur. 20 01. Is nitrate in strea m water a n indicator of forest

ecosy stem health in the Catskills. Pp. 23-30. In : M.S. Adam s (ed.). Catskill Ecosy s tem Healt h

. Purple Mountain Press, Fle i sch m a nns, N e w York. Lovett, G.M. 1994. Atm o spheric deposition of nutrie n ts and pol lut a nts to north Am erica: an ecological perspective. Ecol. Apps. 4 : 629-6 50. Lovett, G.M. and H. Reuth. 1999. Soil nitrogen trans f ormations in beech and maple stands al ong a nitrogen depo sition gradien t

. Ecol. Apps . 9:13 30-1 3 3 4

. McNeil, B.E., J.M. Read and C.T. Driscoll. 2007. Foliar nitrogen responses to elevated at m o s pheric nitrogen depo sition in nine tem p erate forest canopy sp ecies. Environ. Sci. and Te chnol 4 1 :51 9 1

- 5197

. Sim k in, S.M., D.N. Lewis, K.C. Weathers, G.M. Lov e tt, and K. Schwarz. 2004

. Determination of sulfate, nit r ate and chloride in thro ug hfall using i o n-exchange resins. Water, Air and Soil Poll ution 153: 3433 5 4

. Tem p ler, P.H., M.A. Arthu r , G.M. Lovet t and K.C. W eathers. 2007. Plant and So il Natural Abundance 15N: Indicators of relative rates of nitrogen cy cling in tem p er ate f o rest ecosy stems. Oecologia . 1 53: 3 99-4 06. Tem p ler, P.H., G.M. Lovet t , K.C. Weathers, S.E.G. Findla y , and T. E. Dawson. 2005

. I n fluenc e of tree species on 15 N sinks and forest N retention in the Catskill Mountai ns, New York, USA. Ecosyste m s 8 : 1-16. Weathers, K.C., G.E. Likens, and T.J. B u tle r. 200 6. A c id rain. Pp. p p . 15 07-1 522

. In: W. Rom (ed.). Environm ental and Occupational Medicine, 4t h editi o n . Lippi ncott- Raven and Wilkins Publishers, Philadelphia

. Weathers, K.C., S.M. Simkin, G.M. L o vett, and S.E. Lindberg. 20 06

. Em pirical m odeling of atm o spheric deposition i n m ountainous landscapes. Ecological A pplicatio ns 1 6 :159 0-16 07. [ R eview of deposition i n heterogeneous terrain , use of throughfall sulfate as an indicator of t o tal deposition; quantification of hotsp ots o f S and N de position, in g e neral and Acadia and Great Sm oky M o un tain National Parks, in parti c ular] Weathers, K. C., G.M. Lovett, G.E. Likens, and R. Lathrop. 2000. The effect of la ndscape featu r es on deposition t o Hunter Mountain, Catskill Mountains, N e w York. Ecological Ap pli c ations 10: 52 8- 540. [ quantifi cation of hots pots of S and N deposition] Weathers, K. C., G.E. Likens, F.H. Bormann, J.S. Eaton, W.B. Bo wden, J.L. Anderson, D. A. Cass, J. N. Ga lloway

, W.C. Keene, K.D. Ki m b all, P. Huth, and D. S m iley

. 1986. A regional acidic cloud/fog e v ent in t h e eastern United States. Nature 319:6 57-6 5 8

. [i m portanc e of fog or clouds in delivering acidify ing substances to ecosy ste m s ]

.

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