UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON D.C. 20460
OFFICE OF THE ADMINISTRATOR
SCIENCE ADVISORY BOARD
December 23, 2008
EPA-CASAC-09-004
The Honorable Stephen L. Johnson
Administrator
U.S. Environmental Protection Agency
1200 Pennsylvania Avenue, N.W.
Washington, DC 20460
Subj ect: Peer Review of EPA's Risk and Exposure Assessment to Support the Review of
the Secondary National Ambient Air Quality Standard for Oxides of Nitrogen
and Sulfur: First Draft
Dear Administrator Johnson:
The Clean Air Scientific Advisory Committee (CASAC) NOX & SOX Secondary
National Ambient Air Quality Standards (NAAQS) Review Panel held a public meeting on
October 1 -2, 2008 to review EPA's Risk and Exposure Assessment to Support the Review of the
Secondary National Ambient Air Quality Standard for Oxides of Nitrogen and Sulfur: First
Draft (see Enclosure A for the Panel roster). The Panel discussed its draft report on November
19, 2008 at a public teleconference. The Panel's draft report was reviewed and approved by the
chartered CASAC at the public teleconference on December 19, 2008 (see Enclosure B for the
CASAC roster).
Overall, the Panel found the first draft of the Risk and Exposure Assessment (REA)
document to be a credible beginning in the development of the assessments needed to support
future rule-making. The Panel recognizes the time constraints under which the present first draft
REA was prepared and that much of the analyses and the subsequent interpretation have yet to be
completed (e.g., Chapter 7 is focused primarily on acidifying deposition and Chapter 8 only
begins to explore how a secondary NAAQS might be structured). The Panel has many
suggestions for strengthening the document in response to the Agency's charge questions.
Individual comments from the Panel members are provided in Enclosure C.
The Panel strongly supports the up-front inclusion of a policy-focused interpretation of
each of the key scientific findings in the Integrated Science Assessment (ISA). These policy
interpretations should be included in an Executive Summary, as well as in the applicable sections
of the REA. As discussed in prior reviews of the ISA and Scope and Methods documents, it is
critical that the REA give attention to all forms of reactive nitrogen (Nr, which includes
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oxidized, chemically-reduced and organic nitrogen forms) deposition because all forms can
contribute to both acidification and nutrient enrichment of ecosystems. Moreover, the science
indicates that ecological effects could be ameliorated by decreasing deposition of any of those
forms. From a scientific standpoint, this intricate relationship indicates that the applicable
NAAQS standard(s) should address total reactive nitrogen deposition. Thus, the Panel affirms
that science-based secondary NAAQS standards for nitrogen and sulfur should consider the
ecological consequences of total Nr deposition. However, it is noted that the present
interpretation of the regulatory authority of EPA recognizes only oxidized forms of nitrogen and
sulfur as Criteria Pollutants. The Panel recommends that the EPA move forward with
establishing scientifically-based standards that effectively protect the environment, while
recognizing the current regulatory constraints.
Scope of the Review
1. Chapters 1 and 2 provide the background, history, and framework for this review,
including a discussion of our focus on the four key ecological effect areas (aquatic
acidification, terrestrial acidification, aquatic nutrient enrichment, terrestrial nutrient
enrichment). Is this review appropriately focused in terms of characterizing the important
atmospheric and ecologic variables that influence the deposition and, ultimately, the
ecologic impacts of nitrogen and sulfur? Does the Panel have any further suggested
refinements at this time?
Chapters 1 and 2 of the REA begin to satisfy the goals of providing a clear and correct
framing of the issues, providing a coherent method for reaching conclusions required in the
NAAQS review process, summarizing the relevant policy questions and building on the ISA.
The appropriate effects are considered in the REA and the potential relationships between
atmospheric deposition and ecological effects are outlined.
The Panel commends EPA on its use of figures and diagrams throughout Chapters 1 and
2: such illustrations help orient the reader and provide a framework for discussion. It would be
helpful if Figure 1.4-1 was accompanied by descriptions in the text that explain how well each of
the steps can be executed, what the major uncertainties are, and where each component is
addressed in the later parts of the REA. Such modifications would assist in guiding the reader
through the material in the document. It would also be beneficial for the Agency to include a
paragraph on the central concept of N and S "loading" because this concept is pivotal to the
document. Similarly, the concept of "N saturation" needs to be introduced earlier in the
document with a clear delineation of how this concept is, or should be, used in evaluating the
effects of N loadings. There should be greater coherence between the text, figures and policy
statements with respect to reduced and organic forms of N: both forms of N are mentioned here
and in the ISA, and are important contributors to the effects being exhibited by ecosystems in
response to N deposition. In the present version of the REA, the chemistry figures and the policy
questions essentially address only the oxidized form. The material should be modified to address
chemically-reduced and organic nitrogen.
Discussions of uncertainty in Section 2.4 are generic and qualitative: it is unclear when
uncertainty is being discussed and when variability is the real issue. The document needs to be
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explicit that variability and uncertainty are two important but different concepts, with different
impacts on establishing secondary NAAQS. The issue of uncertainty needs to be paramount in
the discussion of monitoring networks. The sparse data from the existing network, the
relationship between ambient concentrations and dry deposition and our understanding of cloud
water deposition introduce significant uncertainty in estimates of total deposition. The Panel
recommends that Chapters 1 or 2 address uncertainty with a discussion of the implications on
EPA's ability to perform the assessments outlined in Chapters 7 and 8. Additionally, the
uncertainty issue should extend to the discussion of climate change, for which there are both
beneficial and adverse effects of atmospheric Nr in ambient air and deposition. The REA is
unclear on how a change in the secondary NAAQS will affect climate change and in what
direction. If the science is uncertain on the level and direction of effects on climate, it should be
clearly stated in the REA.
Exclusion of non-ecological public welfare effects of NOxand SOx(e.g., effects of N- and
S-containing particulate matter on visibility degradation and climate change, materials damage)
continues to be an area of concern for the Panel. To ensure that the current REA meaningfully
represents an assessment of environmental criteria, EPA should state clearly in which Agency
documents the omitted NOX/SOX welfare effects will be treated and provide a short synopsis of
the key non-deposition effects in appropriate locations in the REA.
The Panel recognizes that including a discussion of the potential primary NAAQS (i.e.,
based on public health) for NOX and SOX, and the current PM NAAQS, is premature at present.
However, future drafts of the REA should include an analysis of how the estimates of ecological
exposure and risk are impacted by the range of primary standards under consideration and if the
respective primary NAAQS would (or would not) be adequately protective of the full range of
environmental risks. Of particular concern is that in the past, the secondary NAAQS for a
number of pollutants has been set identical to the primary NAAQS. As noted later in this letter,
the Panel finds the proposed approach for a secondary NOX-SOX NAAQS to be innovative, but
has concerns about its feasibility. Given the challenges the Agency may face with rulemaking
and implementation, a policy decision could be to once again set the secondary NOX and SOX
NAAQS to be identical to their respective primary NAAQS. We recommend a full assessment of
the implications of making such a decision.
Air Quality Analyses
1. To what extent are air quality characterizations and analyses presented in Chapter 3
technically sound, clearly communicated, appropriately characterized, and relevant to
the review of the secondary NAAQS for NOX and SOx?
2. Section 3.2.1 describes an approach for evaluating the spatial and temporal patterns for
nitrogen and sulfur deposition and associated ambient concentrations in the case study
locations. This draft document includes the analysis for the Adirondacks case study.
Does the Panel agree with this approach and should it be applied to the other Case Study
Areas?
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3. Section 3.2.2 describes the relative contributions of ambient emissions of nitrogen and
ammonia to nitrogen deposition for the case study areas. To what extent is the approach
taken technically sound, clearly communicated, and appropriately characterized?
The general nature of Question 1 leads the Panel to both address the question and also to
provide general comments on the current air quality analyses. Assuming the many and important
missing "placeholder" sections are satisfactorily completed, the air quality characterizations and
analyses presented in Chapter 3 should provide a reasonably sound and clearly communicated
characterization of estimates of deposition of total reactive nitrogen and acidifying species to the
specific case study areas. The Chapter, when completed, should also provide information that is
relevant to potential revisions to the current secondary NAAQS for NOX and SOX.
Given that most of Chapter 3 is devoted to the presentation of model results from the
Community Multiscale Air Quality (CMAQ) model and Response-Surface Model (RSM), a
major limitation of the current chapter is the absence of any evaluation of model performance on
simulated levels and atmospheric deposition rates of the various forms and phases of sulfur- and
Nr-containing chemical species. It is critical that EPA complete the placeholders that relate to
model/measurement comparisons and the characterizations of uncertainty in model results. For
example, plots of spatial and temporal variability with measurements would convey how well the
model captures the spatial and temporal patterns. Per the panel's previous recommendations on
the ISA, much of the needed evaluation of the CMAQ model should be included in the ISA.
There is also a need - either in the ISA or here in the REA - for a more detailed description of
the RSM and an evaluation of its performance for the S and N species. With the relatively
extensive sets of air quality, atmospheric deposition and environmental measurements available
for the Adirondacks, this may be a good case study area in which to evaluate model performance
prior to extending this approach to other case study areas.
The complex terrain in sections of the Adirondacks also raises concerns. It is not
appropriate to compare the 12-km spatial resolution of the modeled deposition with the spatial
patterns in actual deposition (including orographic precipitation increases and cloud water
deposition) or the spatial patterns in sensitive species and ecosystems. A sensitivity analysis of
variations within selected Adirondack model grid cells could help evaluate the importance of
spatial variability, scale and resultant effects on deposition estimates.
The Panel was pleased to note the efforts of the Agency to link the atmospheric models
(relating emissions to deposition) with watershed or landscape models (relating deposition to
environmental effects). The disparity in the time scales between atmospheric (i.e., CMAQ) and
watershed models is a major issue. Atmospheric models typically provide predictions at
relatively fine time scales (e.g., hourly) over a single year, while the watershed models often
provide results on scales ranging from decades to centuries. To the extent possible, it would be
helpful if CMAQ could be run for a number of recent years (2002-2006), varying both
meteorology and emissions, to provide a better understanding of inter-annual variability and
longer-term spatial patterns. This would provide a more robust basis for model-to-measurement
and model-to-model comparisons.
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Assuming the model evaluations indicate reasonable performance for most of the
chemical species of concern, the Panel recommends that the model results (for both sulfur and
reactive nitrogen species) be used to generate a number of maps that illustrate the spatial
distributions of:
• emissions (preferably interpolated to better illustrate high-emitting regions),
• atmospheric concentrations (gaseous and aerosol and combined species),
• deposition (wet, dry, total S, total N, oxidized N, chemically-reduced N, etc.), and
• ratios of deposition to atmospheric concentrations and deposition to emissions.
The Panel recommends that the maps have a consistent spatial resolution (e.g., 36 km) over the
contiguous United States and a finer resolution over the case study areas. Such maps would
provide the reader a more direct understanding of the spatial relationships that exist between
emission location, ambient concentrations and the resulting deposition. The maps would also be
useful in proposing a structure for a secondary NAAQS.
In addition to these maps, the Panel recommends the EPA use scatter plots of gridded
model results to further illustrate the key relationships between the deposition metrics most
relevant to environmental effects and alternative air quality metrics upon which the secondary
NAAQS might be based. The scatter plots could also be used to provide information relevant to
uncertainty analysis.
Case Study Analyses
Before dealing with the specific charge questions with regard to the Case Study Analyses,
the Panel offers the following general comments. The proposed use of ecological indicators that
can be linked to varying severity or magnitudes of effects (and related losses in ecosystem
services) goes beyond the concept of estimating critical loads at which ecosystems experience no
effects according to present knowledge. An important consideration as these indicators are
selected and further developed is how to describe effect indicators of varying severity rather than
just providing a "no-effects" threshold. A continuum of effect indicators will provide important
information on the range of adverse responses, and quantifying the response indicators to various
emissions and deposition levels will be important for the eventual assessment of what ecological
effects are considered to be adverse. A separate section may be needed to discuss the ecological
implications of various levels of acid neutralizing capacity (ANC) and associated effects, and its
application to evaluating effects of acidifying deposition. This discussion should include a
consideration of the implications for moving beyond single critical load "no-effects threshold"
approaches to more comprehensive approaches that offer varying degrees of ecosystem
protection within specified levels of statistical probability.
The modeling approaches used to develop critical loads for these case studies are very
different. Evaluating these different approaches could be very instructive. In particular, a
discussion of the relative merits of dynamic models vs. steady state models in these specific
applications is needed. For example, MAGIC does not effectively simulate watershed nitrogen
dynamics, so if watershed nitrogen dynamics is an important component of the critical load there
will undoubtedly be some errors. Most forest ecosystems currently are losing exchangeable
cations and accumulating S and N, so by definition they are not steady-state systems. Applying a
steady-state model to such systems is problematic as a critical loads assessment tool.
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In the case study Attachments, the discussions of varying amounts of ANC and their
associated effects on ecosystem function differ from what is presented in the main chapters of
the REA document. A more consistent approach is needed for setting the ANC limits of concern
with respect to ecosystem sensitivity to acidification and recovery from acidification. The panel
suggests that full protection offish species (set at 100 ueq/L) should be considered in the case
study scenarios.
It would be useful and instructive to include an N-limited site among the case studies.
Possible systems would be the rapidly-growing and N-demanding Douglas-fir forest ecosystem
in the Pacific Northwest or a loblolly pine dominated forest stands in the Southeastern US. For
better understanding of the regional effects of N deposition in the southern Sierra Nevada, EPA
should consider a comparison of responses in mixed conifer forests (e.g., the Kings River Project
area) as compared to ANC changes in the nearby lakes of the sub-alpine and alpine zone (e.g.,
such as leaching of nitrate to streams, lichen species composition, and invasion of invasive
grasses).
Additionally, it may be useful to include an up-front discussion of how the acidity of the
solid phase of the soil affects soil solution acidity which can in turn affect surface water acidity.
In an already acid soil (whether acidic due to natural or anthropogenic processes), soil solution
acidity can increase or decrease instantaneously with the introduction or removal of mineral acid
anions (such as sulfate, nitrate, or chloride) without any change in the soil solid phase. This is
sometimes referred to as the "intensity effect" and is described in Reuss and Johnson (1986)1.
In contrast, acidification of the solid phase of the soil can take a long time and is usually not
reversible without liming.
1. Attachment 2 presents a GIS analysis to define geographical areas that are sensitive to
acidification and nutrient enrichment. Are the national geospatial datasets chosen
adequate to identify sensitive areas? Are there other data sets that have not been
identified by this analysis that we should consider? Does the panel agree with this
approach or can they suggest alternatives?
The selected datasets and the general GIS approach are appropriate for this analysis, and
the Panel has no recommendation for additional datasets to consider. The period of coverage and
spatial representativeness (e.g., the lichen database) are possibly important limitations that
should be noted.
2. Attachment 3 presents our current progress on evaluating the effect of aquatic
acidification in the Adirondacks. It describes the use of the MAGIC model to evaluate
ANC levels in selected streams and lakes in Adirondacks and Shenandoahs. To what
extent is the approach taken technically sound, clearly communicated, and appropriately
characterized?
Reuss J.O., and D.W. Johnson. 1986. Acid Deposition and the Acidification of Soil and Water. Chapter 7.5:
Capacity versus Intensity. Ecological Studies No. 59. Springer-Verlag, New York, Pages 71-72.)
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The selection of the Adirondacks and the Shenandoah Park as case study areas and the
use of MAGIC as the modeling tool are appropriate; however, this section needs to be edited for
clarity. At present, it is generally confusing, especially the modeling approach and descriptions
of MAGIC and ASTRAP models. Numerous errors make it difficult to fully assess technical
merits of the discussion in Attachment 3.
ANC has been selected as a metric to quantify the current acidic conditions and
biological impacts because, in many studies, it was found to be the most appropriate single
indicator of the biological response of aquatic communities in the acid-sensitive ecosystems and
it is relatively easy to simulate using watershed biogeochemical models. Based on the ANC
values and fish populations responses, five classes of biological responses (acute, severe,
elevated, moderate and low concerns) have been developed and can by used for evaluation of
risk assessment using the critical loads concept. As suggested above, for a higher level of
protection offish species EPA should consider using a more conservative value of 100 ueq/L
instead of 50 [j,eq/L.
Some comparisons of these case study results with other efforts to evaluate acid
deposit!on/biogeochemical responses in each of these sites (especially the Adirondacks) would
be useful to indicate either differences from or support for these modeling efforts.
3. Attachment 4 presents our current progress on evaluating the effect of terrestrial
acidification. It outlines apian to use the Simple Mass Balance Model to evaluate current
deposition on forest soil ANC for sugar maple in Kane Experimental Forest and red
spruce in Hubbard Brook Experimental Forest. To what extent is the approach taken
technically sound, clearly communicated, and appropriately characterized?
The selection of the study area is reasonable. Attachment 4 is highly uneven. Substantial
detail has been provided in some cases, while broad generalizations are made in others. It is
difficult for the reader to ascertain the salient points in this chapter.
4. Attachment 5 presents our current progress on evaluating the effect of aquatic nutrient
enrichment. It outlines apian to evaluate how changes in nitrogen deposition affect the
eutrophication index in two estuaries: Chesapeake Bay andPamlico Sound. The analysis
will model one steam reach (Potomac River andNeuse River) to determine the impact on
the eutrophication index for the estuary. To what extent is the approach taken technically
sound, clearly communicated, and appropriately characterized?
The approach is appropriately characterized. The Chesapeake Bay has been the focus of
considerable efforts relating to the effects of nitrogen loading on eutrophication. Extensive
investigations have been made to identify Nr sources within both the very large airshed and the
much smaller watershed areas of the Chesapeake region. However, a potential drawback of the
choice of both the Chesapeake Bay and Pamlico Sound areas is that for both areas atmospheric
nitrogen deposition is not likely to be the dominant component of the total nitrogen loading, and
thus may not be as sensitive to atmospheric deposition changes as other ecosystems where
deposition is the major source of nitrogen loading. Future assessments should consider including
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case studies of watersheds where atmospheric deposition provides a greater proportion of the
total N loading.
5. Attachment 6 presents our current progress on evaluating the effects of terrestrial
nutrient enrichment. It describes an approach to evaluate the effects of N deposition on
the Coastal Sage Scrub community in California and mixed conifer forests in San
Bernardino and Sierra Nevada Mountains. To what extent is the approach taken
technically sound, clearly communicated, and appropriately characterized?
The selection of coastal sage scrub (CSS) and mixed conifer forest ecosystems is
appropriate. Attachment 6 provides a comprehensive review of existing scientific knowledge for
these two ecosystems and the findings have been clearly communicated. For development of
critical loads for CSS, accumulation of biomass of invasive grasses (critical level for occurrence
of catastrophic fires) could be considered. For the mixed conifer forests, change in lichen
communities is a good indicator for ecosystem effects at the low end and nitrate leaching to
surface water is a good indicator at the high end of total Nr deposition loads.
Additional Effects
1. In this chapter, we have presented results from some initial qualitative analyses for
additional effects including the impact of sulfur deposition on mercury methylation, the
impact of nitrous oxide on climate change, and the impact of nitrogen deposition on
carbon sequestration. Are these effects sufficiently addressed in light of the focus of this
review on the other targeted effects in terms of available date to analyze them?
These descriptions and level of detail in Chapter 6 seem adequate, but the relevant issues
go beyond those associated with carbon sequestration, mercury methylation and nitrous oxide
emission changes. The chapter would be much improved by providing a short summary that
describes additional welfare effects of SOX and NOX for which deleterious impacts are expected
(e.g., effects on visibility, climate and materials; as well as the deposition-related terrestrial and
aquatic effects on which the REA currently focuses). Additional information is needed as to the
effect of changes in pH on mercury concentrations in fish and other organisms. This summary
should indicate both the importance of these ecosystems to individual regions and, in the context
of the entire United States, the overall adverse ecological impacts. In considering the impacts of
nitrogen deposition on carbon sequestration, the positive (e.g., increased forest growth and
harvestable timber production) and the negative relationships need to be considered and
presented in a balanced fashion.
Synthesis and Integration of the Case Study Results into the Standard Setting Process
1. The purpose of Chapter 7 is to summarize the Case Study results and characterize the
relationship between levels of an ecological indicator and the associated degree of
ecologically adverse effects. To what extent is this approach characterized at this point of
the review? Does the Panel have any further suggested refinements at this time?
Chapter 7 remains in a very early stage of development; thus it is difficult to provide
summary comments on the overall content and direction of this chapter. The Chapter ends
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abruptly and seems incomplete. Section 7.3 should be completed and a discussion of linkages
between ecological indicators and adverse effects in terrestrial ecosystems is needed (similar to
section 7.3.1 focusing on ANC in freshwater systems).
In general terms, the outline and material included in the Chapter are appropriate to the
intended summary. Table 7.1 will be very important in its final form in future drafts of the REA
and thus EPA should carefully consider its contents. The initial statement at the beginning of
Section 7.2 strikes the right balance between important effects while recognizing their variable
and localized nature. As appropriate throughout Chapter 7 (and the entire REA), the wording
should be scrutinized so that the reader is clear when NOX and SOX versus total S or N deposition
are the real drivers for the effects being considered. In the summarized cases, the key metric is
total deposition irrespective of the original chemical forms of the airborne S and N inputs.
Considerations in the Structure of the NOx/SOx Secondary Standard
1. Chapter 8 begins to explore how a secondary NAAQS might be structured to address the
targeted ecological effects discussed in the risk assessment. The next draft of this
document will include one or more examples of how this structure might be used to relate
specific levels of air quality indicators with a corresponding ecological indicator for a
given location and/or scenario. To what extent is the described approach technically
sound, clearly communicated and appropriately characterized at this point of the review?
Does the Panel have any further suggested refinements at this time?
As noted previously, the Panel views that, scientifically, a NAAQS standard developed to
protect ecological systems should focus on total acidifying deposition and excess nutrient
enrichment, both of which include chemically-reduced, organic and oxidized forms of total
reactive nitrogen. The current constraints have led EPA to focus on developing a combined
ambient standard that is limited to sulfur and nitrogen oxides, but which may accommodate
indirect consideration of contributions from other forms of reactive nitrogen as well. The
proposed approach is scientifically well-founded: it is designed to lead to atmospheric
deposition rates that will protect at least some (and perhaps many) of the target ecosystems as
measured by specific ecosystem-based indicators of adverse ecological effects (e.g., ANC).
While the approach does not directly include targeted decreases in atmospheric deposition of
reduced or organic forms of nitrogen, the approach does include consideration of chemically
reduced and organic nitrogen loadings as part of the already existing conditions that contribute to
acidification and nutrient enrichment of sensitive ecosystems. As such, the approach could
provide for a substantial decrease in some of the adverse ecological effects of acidification and
nutrient enrichment in various part of the United States.
The Panel concludes that the approach presented is novel and environmentally relevant.
The description should be clarified and more detail should be provided, specifically with regard
to how the approach could be implemented in some of the proposed Case Study Areas. EPA
should clarify how the approach would promote controlling chemically-reduced and oxidized
nitrogen loadings as a means to decreasing ecological acidification and nutrient enrichment.
Currently, the discussion in Chapter 8 on establishing an appropriate linkage between
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ambient air concentrations and ecosystem effects, and the importance of spatial and temporal
scales, is limited. The Chapter should show how the proposed approach directly addresses the
Panel's concerns that, from a scientific perspective, the resulting environmentally-focused
standard would include all reactive N deposition. Further, the Panel has concerns about the
feasibility of implementing a standard based on this approach. There are a number of
complications that need to be addressed so as to fully inform policy-makers, particularly in
preparation for the development of an appropriate Advanced Notice of Proposed Rule Making
(ANPR). Critical issues that need to be elaborated upon include:
1. whether (or how) a standard will integrate the multiple indicators identified in the case
studies,
2. what are the appropriate spatial scales for each indicator and sensitive ecosystem,
3. how varying levels of protection required by different ecosystems can be accommodated,
and
4. what level of protection is being provided to various ecosystems under alternative levels
and forms of the standards.
The REA as a whole needs to show how the results of the case studies (specifically, the
relationships between the observed chemical and biological changes and N and S atmospheric
deposition) can be linked to the traditional NOX, SOX and PM standards that are based on ambient
concentrations. It is imperative that this additional linkage information is incorporated in the next
draft of Chapter 8.
In summary, the CAS AC Panel was pleased to review this first draft of the Risk and
Exposure Assessment to Support the Review of the Secondary National Ambient Air Quality
Standard for Oxides of Nitrogen and Sulfur. The Agency's venture into new territory in the
consideration of multi-pollutant standards is laudable. Shifting to standards that focus on
ecological effects and employ metrics that are specifically relevant to ecosystems will have some
inherent complexities and difficulties, and the Panel looks forward to following and contributing
to the evolution of suggested approaches.
Sincerely,
/Signed/
Dr. Armistead (Ted) Russell, Chair
CASAC NOX & SOX Secondary
NAAQS Review Panel
/Signed/
Dr. Jonathan M. Samet, Chair
Clean Air Scientific Advisory Committee
Enclosures
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Enclosure A
U.S. Environmental Protection Agency
Clean Air Scientific Advisory Committee
NOX& SOX Secondary NAAQS Review Panel
CHAIR
Dr. Armistead (Ted) Russell, Professor, Department of Civil and Environmental Engineering,
Georgia Institute of Technology, Atlanta, GA
PANEL MEMBERS
Dr. Praveen Amar, Director, Science and Policy, NESCAUM, Boston, MA
Dr. Andrzej Bytnerowicz, Senior Scientist, Pacific Southwest Research Station, USDA Forest
Service, Riverside, CA
Ms. Lauraine Chestnut, Managing Economist, Stratus Consulting Inc., Boulder, CO
Dr. Douglas Crawford-Brown, Professor Emeritus, Department of Environmental Sciences and
Engineering, University of North Carolina at Chapel Hill, Chapel Hill, NC
Dr. Charles T. Driscoll, Jr., Professor, Environmental Systems Engineering, College of
Engineering and Computer Science, Syracuse University, Syracuse, NY
Dr. Paul J. Hanson, Distinguished R&D Staff Member, Environmental Sciences Division, Oak
Ridge National Laboratory, Oak Ridge, TN
Dr. Rudolf Husar, Professor and Director, Mechanical Engineering, Engineering and Applied
Science, Center for Air Pollution Impact & Trend Analysis (CAPITA), Washington University,
St. Louis, MO
Dr. Dale Johnson, Professor, Department of Environmental and Resource Sciences, College of
Agriculture, University of Nevada, Reno, NV
Dr. Donna Kenski, Data Analysis Director, Lake Michigan Air Directors Consortium,
Rosemont, IL
Dr. Naresh Kumar, Senior Program Manager, Environment Division, Electric Power Research
Institute, Palo Alto, CA
Dr. Myron Mitchell, Distinguished Professor and Director, College of Environmental and
Forestry, Council on Hydrologic Systems Science, State University of New York, Syracuse, NY
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Mr. Richard L. Poirot, Environmental Analyst, Air Pollution Control Division, Department of
Environmental Conservation, Vermont Agency of Natural Resources, Waterbury, VT
Mr. David J. Shaw, Director, Division of Air Resources, New York State Department of
Environmental Conservation, Albany, NY
Dr. Kathleen Weathers, Senior Scientist, Institute of Ecosystem Studies, Millbrook, NY
SCIENCE ADVISORY BOARD STAFF
Ms. Kyndall Barry, Designated Federal Officer, 1200 Pennsylvania Avenue, NW
1400F, Washington, DC, Phone: 202-343-9868, Fax: 202-233-0643, (barry.kyndall@epa.gov)
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Enclosure B
U.S. Environmental Protection Agency
Clean Air Scientific Advisory Committee
CHAIR
Dr. Jonathan M. Samet, Professor and Chair, Department of Preventive Medicine, University
of Southern California, Los Angeles, CA
MEMBERS
Dr. Joseph Brain, Philip Drinker Professor of Environmental Physiology, Department of
Environmental Health, Harvard School of Public Health, Harvard University, Boston, MA
Dr. Ellis B. Cowling, University Distinguished Professor At-Large Emeritus, Colleges of
Natural Resources and Agriculture and Life Sciences, North Carolina State University, Raleigh,
NC
Dr. James Crapo, Professor of Medicine, Department of Medicine, National Jewish Medical
and Research Center, Denver, CO
Dr. H. Christopher Frey, Professor, Department of Civil, Construction and Environmental
Engineering, College of Engineering, North Carolina State University, Raleigh, NC, USA
Dr. Donna Kenski, Data Analysis Director, Lake Michigan Air Directors Consortium,
Rosemont, IL
Dr. Armistead (Ted) Russell, Professor, Department of Civil and Environmental Engineering,
Georgia Institute of Technology, Atlanta, GA
SCIENCE ADVISORY BOARD STAFF
Dr. Holly Stallworth, Designated Federal Officer, 1200 Pennsylvania Avenue, NW,
Washington, DC, Phone: 202-343-9867, Fax: 202-233-0643, (stallworth.holly@epa.gov)
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Enclosure C
Comments received:
Dr. Praveen Amar 15
Dr. Andrzej Bytnerowicz 17
Ms. Lauraine Chestnut 20
Dr. Ellis B. Cowling 22
Dr. Douglas Crawford-Brown 30
Dr.Charles T. Driscoll 33
Dr. Paul J. Hanson 43
Dr. Rudolf Husar 49
Dr. Dale W. Johnson 52
Dr. Donna Kenski 55
Dr. Naresh Kumar 62
Dr. Myron J. Mitchell 65
Mr. Richard Poirot 84
Mr. David Shaw 89
Dr. Kathleen C.Weathers 93
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Dr. Praveen Amar
The charge is to respond to Questions #2 and 3 related to air quality analyses. Specifically, the
two questions are reproduced here:
Question # 2 : Section 3.2.1 describes an approach for evaluating the spatial and temporal
patterns for nitrogen and sulfur deposition and associated ambient concentrations in the case
study locations. This draft document includes the analysis for the Adirondacks Case Study. Does
the Panel agree with this approach and should it be applied to the other Case- Study Areas?
Question # 3 : Section 3.2.2 describes the relative contributions of ambient emissions of nitrogen
and ammonia to nitrogen deposition for the case-study areas. To what extent is the approach
taken technically sound, clearly communicated, and appropriately characterized?
Question # 2 Response:
The approach outlined in Section 3.2.1 should prove to be useful in that it does propose to do a
complete analysis of spatial and temporal patterns of concentrations and deposition of sulfur and
nitrogen compounds (dry oxidized nitrogen, dry reduced nitrogen, wet oxidized nitrogen, wet
reduced nitrogen, dry sulfur deposition and wet sulfur deposition). However, the analyses at the
present time are based only on CMAQ predictions (text says "CMAQ data"; "CMAQ
predictions" is more appropriate) are only for one year (2002), and for just one case-study
location (Adirondacks).
1. At a minimum, before one can answer the question "Does the Panel agree with this approach
and should it be applied to other case-study areas?" with a reasonable level of confidence,
the proposed approach needs to include an independent as well as corroborative (by
comparing it to model-predicted results) analysis that is based on measured data for this
case-study region (as well as the remaining case-study regions). It appears that modeled
CMAQ results are reasonable, but it will increase the confidence in this approach if the
measured data from NADP and CASTNet (and other networks in the Adirondacks region
and other regions) corroborate the modeled predictions.
2. It is also important that before this approach is applied to other case-study areas, that the
placeholders on Page 3-53 and 3-54 be completed. I would recommend that the analysis of
inter-annual variation in N and S (for the years 2002-2006) deposition as well as uncertainty
analysis (Section 3.2.1.5) be first completed for Adirondacks region before similar analyses
are done for the other four case-study regions.
3. Once the measured deposition data analyses are completed, Section 3.2.1 should include a
brief evaluation/comparison of CMAQ predictions for the four nitrogen and two sulfur
components. As a part of this evaluation, the measured precipitation data and modeled
(from MM5?) precipitation data (amounts and spatial patterns) should be compared. This
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is important since the modeled results in Section 3.2.1 indicate strong correlations between
amount of precipitation and wet deposition.
4. A general comment on presentation of results on dry deposition of N and S: This section
needs to be more clear and explicit that we only estimate dry deposition (whereas we
measure wet deposition) and therefore conclusions on total deposition (wet and dry) and on
the relative contribution of each pathway have a level of uncertainty that is hard to
determine, but needs to be acknowledged (for example, in Section 3.2.1.5 on Uncertainty).
Question # 3 Response:
This question involves the description of relative contributions of ambient emissions of NOx
and ammonia to deposition of nitrogen (total nitrogen deposition (TND), oxidized nitrogen
deposition (OND), and reduced nitrogen deposition (RND)) for the eight case-study regions. It
asks if the approach used is technically sound, clearly communicated, and appropriately
characterized. Here are some comments:
1. The "model of the model" or the RSM (Response-Surface Model) applied to CMAQ
needs a more friendly description on how it works. On Page 3-55, the text makes an
effort but does not succeed in explaining what (and how) exactly RSM does. It appears
that RSM is like an "instrumented CMAQ" model in that it "represents the outputs of the
CMAQ model using statistical predictions." It is not clear to me what exactly these
statistical predictions are. It might be useful to compare the "workings" of RSM with,
say, Direct Decoupled Method (DDM) or other "process" models (that evaluate the
relative contribution of various processes embedded in the model on model predictions).
Has the RSM approach been applied by the general scientific and policy/regulatory
communities outside the US EPA?
2. To the extent RSM is essentially based on the "brute-force" approach of "zeroing out"
NOx or ammonia emissions (recognizing there are some residual emissions for NOx that
include international sources and lightning, and, for NH3, they include international,
non-anthropogenic and point source emissions), I am not sure this is the right approach to
accurately answer Question # 3. Are there more appropriate approaches that do not
"unduly stress" the CMAQ model that can better address this question of relative
contributions?
3. It is not clear to me how the twelve "emission control factors" on Page 3-56 were actually
applied in the model. Were the emissions zeroed out only for the case-study region or for
the whole modeling domain?
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Dr. Andrzej Bytnerowicz
Question 2 - Current progress on evaluation the effects of aquatic acidification in the
Adirondacks and Shenandoah. To what extent is the approach taken technically sound, clearly
communicated, and appropriately characterized?
Selection of the Adirondack Mountains and Shenandoah National Park for estimation of
ecological effects and risks caused by acidifying deposition of N and S is well justified. The two
areas experience high levels of deposition, are characterized by a high density of
anthropogenically acidified lakes and streams, and there is a well documented record of chemical
and biological changes from many studies with their results published in peer-reviewed
literature.
The proposed approach is logical and technically sound. The wet deposition data comes from the
NADP/NTN networks operational in the Adirondacks since 1978 and in the Shenandoah since
1980. Current conditions were evaluated by a 3 step process that assessed trends in surface water
SC>42", NOs" and ANC concentrations; the percent of watershed bodies that have different degree
of acidity; and the percent of water bodies receiving N & S deposition above the harmful levels
(exceedance of critical loads). Biological effects of acidity caused by atmospheric N & S
deposition are measured at the individual level as fitness and at the community level as species
richness and community structure. ANC has been selected as a metric to quantify the current
acidic conditions and biological impacts because in many studies it was found to be the best
single indicator of the biological response of aquatic communities in the acid-sensitive
ecosystems. Relationship between ANC and number offish species showed that at the ANC
values of 50-100 |j,eq/L, species richness begins to decline. Based on the ANC values and fish
populations responses, five classes of biological responses (acute, severe, elevated, moderate and
low concerns) have been developed and can by used for evaluation of risk assessment using the
critical loads concept.
It will be interesting to see complete results of the planned evaluations.
Specific comments:
Page 32, Figure 5.1-2 - why there is such a high difference in the "severe" category between the
observed and MAGIC modeled outputs?
Page 33, Figure 5.1-3 - change ANC units to |j,eq/L. In the same figure - why not to use more
conservative value of 100 |j,eq/L instead of 50 |j,eq/L as the threshold of protection?
Question 5 - Current progress on evaluating the effects of terrestrial nutrient enrichment for
coastal sage scrub and mixed conifer forests of California. To what extent is the approach taken
technically sound, clearly communicated, and appropriately characterized?
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Selection of coastal sage scrub (CSS) and mixed conifer forest ecosystems is appropriate
because: (a) these ecosystems have high geographic coverage and are located in the important
wildland-urban interface I highly populated areas, (b) they encompass a strong gradient of N
deposition from the low, background levels up to the highest levels recorded in the US, (c) these
ecosystems have been investigated for a long time from a perspective of interactive effects of
atmospheric deposition, climate change fire and other stressors, (d) results of these
investigations are well documented in the peer-reviewed literature.
If the goal of this chapter was to review the current state of science for these two case studies,
than the approach taken was technically sound and findings have been clearly communicated.
However, if results of these two case studies were supposed to show how the relationships
between the observed chemical and biological changes and N atmospheric deposition (possibly
expressed as critical loads) could be linked to the concentration-based NOx/SOx standards, then
the used approach was not inadequate and should be revised.
The chapter provides a comprehensive review of the existing scientific knowledge for these two
case studies. GIS maps show modeled N deposition in portion of California encompassing the
two selected ecosystems, CSS threat from fire, and the presence of acidophyte lichens.
Three-dimensional maps illustrating loss of CSS in relation to different levels of fire threats or N
deposition could greatly help in developing a probabilistic approach to the evaluation of N
deposition risks to important California ecosystems.
For development of CL for CSS, in addition to biodiversity changes or changes in lichen
communities, accumulation of biomass of invasive grasses (critical level for occurrence of
catastrophic fires) could be considered (Anderson, 1982; Scifres and Hamilton, 1993; Gimeno et
al., 2009; Minnich and Franco-Vizcaino, 2009). For more information on this subject please
contact Drs. Richard Minnich and Edith Allen, UC Riverside. For the mixed conifer forests, on
the low end of N deposition changes in lichen communities, and on its high end, nitrate leaching
to surface water, are good end points for CL estimates. Other, such as possible changes in
understory biodiversity changes could also be considered and explored.
Data on N deposition levels was obtained from the NADP and CASTNET networks and modeled
N deposition distribution from the CMAQ model runs for 2002, which were based on the 12 km
grids. As the authors of this analysis suggest, results from the 4 km grid would greatly improve
accuracy of predicted relationships between N deposition and the biological effects.
Some data for the main drivers of N dry deposition in the San Bernardino Mountains, gaseous
HNOs and NH? from passive samplers have already been published (Bytnerowicz et al, 2007).
More results on distribution of N nitrogenous gases monitored with passive samplers in southern
California and southern Sierra Nevada are currently being prepared for publication (Andrzej
Bytnerowicz, unpublished).
Suggestion: For better understanding of regional (southern Sierra Nevada) effects ofN
deposition, comparison of responses in mixed conifer forests (Kings River Project) such as
leaching of nitrate to streams, lichen species composition, and invasion of invasive grasses, could
be compared to ANC changes in the nearby lakes of the sub-alpine and alpine zone.
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Specific comments:
Page 13, 1st paragraph - also high levels of NHa and NH4+ are deposited to CSS of southern
California.
Page 29, Figure 3.1-1. Scale for N deposition is too coarse - a bracket 6.83-70.04 kg N/ha/yr is
not acceptable.
Page 33, 1st paragraph - bark beetle should be added as important stressor in the mixed conifer
forest ecosystem.
Page 44 and 45, section 5.2 - for the mixed conifer forest also changes of species composition of
the under story vascular plants should be considered.
Page 45, list of questions - in regard to responses of lichens to N deposition, effects of oxidized
vs. reduced N should be considered. This may be of interest because there is a potential shift
towards less reduced N due to the movement of dairy farms from the Los Angeles Basin to
California Central Valley.
References:
Anderson, H. E. 1982. Aids to determining fuel models for estimating fire behavior. USDA
Forest Service Intermountain Forest and Range Experiment Station, General Technical Report
INT-122, Ogden, Utah. http://www.fs.fed.us/rm/pubs_int/int_gtr!22.pdf
Bytnerowicz, A., M. Arbaugh, S. Schilling, W. Fraczek, D. Alexander, P. Dawson (2007) Air
pollution distribution patterns in the San Bernardino Mountains of southern California: a 40-year
perspective. TheScientificWorldJOURNAL 7(S1), 98-109. DOI 10.1100/tsw.2007.57.
Gimeno, B. S., Yuan, F., Fenn, M. E., Meixner, T. 2009. Management options for mitigating
nitrogen (N) losses from N-saturated mixed-conifer forests in California. In: A. Bytnerowicz, M.
Arbaugh, A. Riebau and C. Andersen (eds). Wildland Fires and Air Pollution, Developments in
Environmental Sciences, Vol 8, Elsevier, Amsterdam, pp. 425-455.
Minnich, R. A., Franco-Viscaino, E. 2009. A probabilistic view of chaparral and
forest fire regimes in southern California and northern Baja California. In: A. Bytnerowicz, M.
Arbaugh, A. Riebau and C. Andersen (eds). Wildland Fires and Air Pollution, Developments in
Environmental Sciences, Vol 8, Elsevier, Amsterdam, pp. 339-364.
Scifres, C.F., Hamilton, WT. 1993. Prescribed Burning for Brushland Management: The South
Texas Example. Texas A & M University Press, College Station.
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Ms. Lauraine Chestnut
Charge question 1: Scope of the review
There seems to be some ambiguity regarding use of the term "sensitive." It sometimes seems to
mean an ecosystem that is vulnerable but not necessarily harmed at current or historic deposition
rates, and other times it seems to mean that harm is occurring at current exposures. To me, the
word sensitive fits better for the former than for the latter. For there to be harmful effects it
would seem to require both sensitivity and exposure. Thus, the selected case studies are
appropriately selected as not just sensitive, but currently being affected by N and/or S deposition.
Pages 2-7 to 2.8
Descriptions of ecosystem services reduced or degraded as a result of harmful effects on
ecosystem functions are not only important inputs into economic valuation and cost-benefit
analysis, they are important in helping policy makers and the public understand the significance
of the effects on the ecosystems.
It is important to recognize that economic valuation is best considered relative to an alternative.
In figure 2.3-2 it is unclear what an economic value to "maintain" an ecosystem would be
without specifying what would happen if some action were not taken. There may be a value to
prevent a specified amount of degradation or a value to obtain a specified improvement, but the
value to simply "maintain" is probably ambiguous.
Page 2-13
This discussion of uncertainty is pretty weak. One important note is that variability is not the
same thing as uncertainty. There may be a lot of variability in how different ecosystems respond
to the same amount of N/S deposition but it may be able to specify this variability with a great
deal of certainty.
It is important to acknowledge uncertainty, but a critical thing here is how to determine when
there is enough known to be able to set reasonable standards. The uncertainty issue will need to
be taken up again when the analysis is further along. A key question is whether there is enough
confidence in the results that they are useful to assist policy decision-making. This requires more
than just listing sources of uncertainty, but necessitates an assessment of the significance of the
uncertainty and how it affects the results.
Case studies
The proposed use of ecological indicators that can be linked to varying levels of effects (and
related losses in ecosystem services) goes beyond the idea of estimating critical loads at which
ecosystems experience no effects. This does not come through in the current draft until Chapter
7, and is a missing perspective in the various case study appendices. An important consideration
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that has to be made as these indicators are selected is their ability to be linked to effects of
varying severity rather than defining simply a "no effects" threshold, because this will be
important information for the eventual assessment what effects are adverse.
The REA ultimately needs to describe the significance of the effects on ecosystem function and
services at current levels of exposure and at alternative levels of exposure that might be achieved
with alternative standards in the case study areas. Selecting any secondary standard probably
requires more than a determination of a "safe" level because the standard needs to protect against
adverse effects, not just any effects. The case study analyses seem to be headed in this direction
and I look forward to seeing this further fleshed out in the second draft.
Chapter 8
An important issue is that is not yet addressed is how the analysis will deal with spatial scale in
defining a potential standard. This is complicated by expected variability in ecological response
to deposition in different locations even within a case study ecosystem. It is unlikely to be
reasonable or even feasible to set a standard to protect the most sensitive ecosystems (or
components of an ecosystem). The scale decisions can be somewhat analysis driven in that the
results may show reasonable categories or groupings, such as X% of lakes in the Adirondacks
that would have an ANC of 50 or 100 at various ambient co
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Dr. Ellis B. Cowling
My individual comments on the August 2008 First External Review Draft of the Risk and
Exposure Assessment (REA) for the Secondary National Ambient Air Quality Standards for
Oxides of Nitrogen and Oxides of Sulfur are organized below in response to each of the several
Charge Questions posed the Panel in preparation for the October 1-2, 2008 CAS AC meeting.
As you will see, somewhat more detailed attention has been given to the five Charge Questions
on Case Study Analyses and the recently received Chapters 7 and 8 than to other parts of this
Risk and Exposure Assessment as requested by the Chair.
Scope of the Review
2. Chapters 1 and 2 provide the background, history, and framework for this review,
including a discussion of our focus on the four key ecological effect areas (aquatic
acidification, terrestrial acidification, aquatic nutrient enrichment, terrestrial nutrient
enrichment). Is this review appropriately focused in terms of characterizing the important
atmospheric and ecologic variables that influence the deposition and, ultimately, the
ecologic impacts of nitrogen and sulfur? Does the Panel have any further suggested
refinements at this time?
My most serious reservation about the analysis framework for Chapters 1 and 2 is that chemically
reduced forms of nitrogen (NHx), organic forms of nitrogen (NCx), and total reactive nitrogen
(Nr) all are not included in the specific wording of any of the 20 policy-relevant questions that
are said to constitute the framework for this review on the effects of nitrogen and sulfur pollution
on acidification and nutrient enrichment of aquatic and terrestrial ecosystems in the US.
This reservation is surprising in view of the very comprehensive analysis regarding the
importance of chemically reduced forms of reactive nitrogen contained in the Integrated Science
Assessment (ISA) document and also in view of the October 31, 2007 Resolution from the
Science Advisory Board's Integrated Nitrogen Committee (INC) which makes the following
strong assertion from the INCs Committee's examination of much of the same body of evidence
reviewed in the ISA:
"The current air pollution indicator for oxides of nitrogen, NOx, is an inadequate measure
of reactive nitrogen in the atmospheric environment. The SAB's Integrated Nitrogen
Committee recommends that inorganic reduced nitrogen (ammonia plus ammonium) and
total oxidized nitrogen, NOy, be monitored as indicators of total chemically reactive
nitrogen."
Please note the roster of current members of the SAB's Integrated Nitrogen Committee whose collective
competence with regard the public welfare and public health effects of reactive nitrogen is very similar to
the collective competence of the CASAC Panel selected to review Secondary NAAQSfor Oxides of
Nitrogen and Oxides of Sulfur as can be seen in the Determination Memo at
http://vosemite.epa.gov/sab/sabproduct.nsf/02ad90bl36fc21ef85256eba00436459/c83c30afa465
6bea85256ealQ047elel!QpenDocument&TableRow=2.1#2.
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The conclusionary statements written in bold-type in Chapter 4 of the ISA indicate that:
"The evidence is sufficient to infer a causal relationship between "acidifying deposition"
(which includes NHx, and NCx, as well as NOx) and the following adverse acidification
effects:
a) "changes in biogeochemistry related to terrestrial ecosystems,"
b) "changes in terrestrial biota,"
c) "changes in biogeochemistry related to aquatic ecosysytems,"
d) "changes in aquatic biota."
Also, "The evidence is sufficient to infer a causal relationship between Nr (reactive nitrogen)
deposition (which also includes NHx, NCx, and NOx) and the following additional ecologically
adverse nutrient- enrichment effects:
e) "alteration of biogeochemical cycling of N in terrestrial ecosystems,"
f) "alteration of biogeochemical cycling of C in terrestrial ecosystems,"
g) "alteration of biogeochemical flux of N2O in terrestrial ecosystems,"
h) "alteration of biogeochemical flux of CH4 in terrestrial ecosystems,"
i) "alteration of species richness, species composition and biodiversity in terrestrial
ecosystems,"
j) "alteration of the biogeochemical cycling of N,"
k) "alteration of the biogeochemical cycling of C,"
1) "alteration of N2O flux in wetland ecosystems,"
m) "alteration of CH4 flux in wetland ecosystems,"
n) "alteration of species richness, species composition and biodiversity in wetland
ecosystems,"
o) "alteration of biogeochemical cycling of C in freshwater aquatic ecosystems,"
p) "alteration of species richness, species composition and biodiversity in freshwater
aquatic ecosystems,"
q) "alteration of the biogeochemical cycling of N in estuarine aquatic ecosystems,"
r) "alteration of the biogeochemical cycling of C in estuarine aquatic ecosystems,"
s) "alteration of species richness, species composition and biodiversity in estuarine
aquatic ecosystems,"
"The evidence is sufficient to infer a causal relationship between:
t) "exposure to NO, NO2, and PAN and injury to vegetation" and
s) "exposure to HNOs and changes to vegetation."
On the basis of this substantial body of accumulated evidence, I recommend that a schematic
diagram similar to Figure 1.3-1 be included in Chapter 1 of the Second Draft REA document to
illustrate the "cycle of reactive, chemically reduced nitrogen species." I also recommend that:
a) Chemically reduced (NHx) and also organic forms (NCx) of total reactive nitrogen also
be included among the nitrogen pollutants of concern in many of the 20 policy-relevant
questions listed in Section 1.4 on pages 1-17 through 1-20 in Chapter 1 of this First Draft
REA, and
b) Appropriate answers about both chemically reduced (NHx) forms of total reactive
nitrogen, and, if possible also organic forms (NCx) of total reactive Nitrogen (Nr), be
presented in Chapters 2, 3, and 4 of the Second Draft REA when it is completed.
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Air Quality Analyses
4. To what extent are air quality characterizations and analyses presented in Chapter 3
technically sound, clearly communicated, appropriately characterized, and relevant to the
review of the secondary NAAQS for NOx and SOx?
With the exception of the major reservations stated in answer to the Charge Questions about
the Scope of the Review, I believe that the analyses presented in Chapter 3 are technically
sound, clearly communicated, and appropriately characterized.
5. Section 3.2.1 describes an approach for evaluating the spatial and temporal patterns for
nitrogen and sulfur deposition and associated ambient concentrations in the case study
locations. This draft document includes the analysis for the Adirondacks case study. Does
the Panel agree with this approach and should it be applied to the other Case Study Areas?
The approach used for evaluating the spatial and temporal patters for of N and S deposition and
associated ambient concentration seems very reasonable to me. This approach proved to be useful in
the Adirondacks Case study and I expect it to be reasonable for other case studies as well.
6. Section 3.2.2 describes the relative contributions of ambient emissions of nitrogen and
ammonia to nitrogen deposition for the case study areas. To what extent is the approach
taken technically sound, clearly communicated, and appropriately characterized?
I presume from examining the figures and associated text for the data presented on pages 3-63
through 3-112 that this question should have read:
" Section 3.2.2 described the relative contributions of chemically oxidized and chemically
reduced forms to total reactive nitrogen for the Case Study areas. To what extent is the
approach taken technically sound, ...etc."
On the assumption that my presumption is correct, I consider this combination of modeling and
measurement approaches to be reasonable. But I must confess that it took me a very long time to
finally understand the rationale behind the statement on lines 10-12 on page 3-13 that "In order to
calculate total nitrogen (by which I suppose the author meant deposition of total reactive
nitrogen) the two chemical species from the National Atmospheric Deposition Program (NADP)
(i.e., NO3- and NH4+) were added together and then added to the total dry deposition values
estimated from the Community Multiscale Air Quality model (CMAQ).
It also took me a very long time to understand what was meant by the term "zero-out of NOx
emissions" as used in most of the figure captions on pages 3-63 through 3-112) and periodically in the
associated text.
With regard to the questions of "clearly communicated and appropriately characterized" I offer the
following comments:
1) What a delight it was to find the following firm statement on lines 15-20 on page 3-70:
"Figures 3.2-42 examines the relative impact of emissions on NH3 of the deposition of total
reactive nitrogen. Figure 3.2-42 shows that NH3 emissions represent a significant contribution to
total reactive nitrogen in most case study areas, although the impact varies by season and by area.
The smallest impact of NH3, 10% occurs in the Potomac case study area in February. The
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largest impact of NH3, 73% occurs in the Neuse Case study in July. The Neuse case study has
the largest overall impact of from NH3 of any of the case study areas, across all four seasons."
2) On lines 6 and 7 also on page 3-63 (and another case on lines 9 and 10 on page 3-71) we find
three very confusing sentences that reveal clearly why EPA's constant use of the terms "reduce,"
"reducing" and "reduction" is so often confusing and ambiguous:
"One possibility is that reducing NOx reduces HNO3, which limits ammonium nitrate
formation (and for existing aerosol, a reduction in HNO3 shifts the equilibrium towards the gas
phase), thereby increasing the lifetime of NH3. A net increase in NH3/NH4 results. Because the
deposit velocity of NH3 is much higher than the deposition of NH4+ aerosol, dry deposition of
NHX increases.
The terms "reduce," "reducing" and "reduction" have both chemical and numerical meanings.
Fortunately we have the unambiguous terms "decrease" and "decreasing" which have only a
single (always numerical) meaning. So why not use the unambiguous term "decrease" instead of
the word "reduce" when our intended meaning is numerical and thus reserve the term "reduce"
for its chemical meaning?
Is this what was meant by the sentence quoted above?
"One possibility is that decreasing emissions of NOx decreases air concentrations of HNO3,
which limits ammonium nitrate (NFLtNOs) formation (and for existing aerosol, a decrease in
HNO3 emissions shifts the equilibrium towards the gas phase), thereby increasing the
atmospheric lifetime of gaseous NH3. A net increase in the ratio of gaseous NH3 to NH4+ aerosol
in the atmosphere results. Because the deposit velocity of gaseous NH3 is much larger than the
deposition velocity of NH4+ aerosol, dry deposition of NHX increases.
Case Study Analyses
1. Attachment 2 presents a GIS analysis to define geographical areas that are sensitive to
acidification and nutrient enrichment. Are the national geospatial data sets chosen
adequate to identify sensitive areas? Are there other data sets that have not identified by
this analysis that we should consider? Does the Panel agree with approach or can they
suggest alternatives?
I have only limited experience with the several data bases that were used in the GIS analysis used in
an attempt to define geographic areas that are sensitive to acidification. Thus I have only limited
professional experience on which to base a detailed judgment in response to this question.
Nevertheless, my general impression derived from study of the summary map on page 18 of
Attachment 2, and my general awareness of soil, vegetation, surface and ground waters, and the
topographical, meteorological, and climatic factors that are relevant to acidification and nutrient
enrichment, lead me to conclude that the GIS approach used is generally sound. I know of no
additional data sets that should be included in this analysis.
2. Attachment 3 presents our current progress on evaluating the effect of aquatic acidification
in the Adirondacks. It describes the use of the MAGIC model to evaluate ANC levels in
selected lakes and streams in the Adirondacks and Shenandoah. To what extent is the
approach taken technically sound, clearly communicated, and appropriately characterized?
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I have no direct experience on which to base an informed judgment in response to this question.
However, several of my colleagues tell me that the MAGIC model is very appropriate for these kinds
of analyses.
3. Attachment 4 presents our current progress on evaluating the effect of terrestrial
acidification. It outlines a plan to use the Simple Mass Balance Model to evaluate current
deposition levels on forest soil ANC for sugar maple in the Kane Experimental Forest and
red spruce in the Hubbard Brook Experimental Forest. To what extent is the approach
taken technically sound, clearly communicated, and appropriately characterized?
I have studied Attachment 4 with considerable care and consider that the approach taken so far (since
this is still a work in progress) is technically sound, clearly communicated, and appropriately
characterized.
4. Attachment 5 presents our current progress on evaluating the effect of aquatic nutrient
enrichment. It outlines a plan to evaluate how changes in nitrogen deposition affect the
eutrophication index in two estuaries: the Chesapeake Bay and Pamlico Sound. The
analysis will model one stream reach (Potomac River and Neuse River) to determine the
impact on the eutrophication index for the estuary. To what extent is the approach taken
technically sound, clearly communicated, and appropriately characterized?
I have studied attachment 5 with reasonable care and conclude that the approach taken in this case
also is technically sound, clearly communicated, and appropriately characterized.
5. Attachment 6 presents our current progress on evaluating the effects of terrestrial nutrient
enrichment. It describes an approach to evaluate the effects of nitrogen deposition on the
Coast Sage Scrub community in California and in mixed conifer forests in the San
Bernardino and Sierra Nevada Mountains. To what extent is the approach taken
technically sound, clearly communicated, and appropriately characterized?
I have no experience with any of the western state ecosystems that are discussed in Attachment 6.
Thus I have no professional experience on which to base an informed response to this question.
Additional Effects
1. In this chapter, we have presented results from some initial qualitative analyses for
additional effects including the impact of sulfur deposition on mercury methylation, the
impact of nitrous oxide on climate change, and the impact of nitrogen deposition on carbon
sequestration. Are these effects sufficiently addressed in light of the focus of this review on
the other targeted effects in terms of available date to analyze them?
Chapter 6 provides a useful overview of the impact of sulfur deposition on methylation of mercury
which seems to me to be very worthy of consideration with regard to setting appropriate limits on the
amount of air emission of sulfur oxides that should be permitted in various regions of the US. I see
little reason for worry about nutrient enrichment or acidification effects of carbon sequestration. I do
believe, however, that nitrous oxide emissions should be incorporated in EPA's review of the
NAAQS for nitrogen pollution and its effects on terrestrial and aquatic ecosystems.
Synthesis and Integration of Case Study Results into the Standard Setting Process (Chapter 7)
1. The purpose of Chapter 7 is to summarize the Case Study results and characterize the
relationship between levels of an ecological indicator and the associated degree of
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ecologically adverse effects. To what extent is this approach technically sound, clearly
communicated and appropriately characterized at this point of the review? Does the Panel
have any further suggested refinements at this time?
I believe that the attempt being made in Chapter 7 to building a scientifically sound linkage between
carefully selected ecological indicators and the extent and magnitude of ecologically adverse effects
is a very complicated but very desirable goal.
During my initial readings of Chapter 7, and even more Chapter 8 during the few days between their
availability to CASAC on September 23 and the CASAC meeting on October 1 and 2, it appeared to
me that EPA was deliberately trying to build a case for making a modest decrease in emissions of
nitrogen oxides (NOx ~ which is already recognized as a Criteria Pollutant) -and of course would
help decrease the adverse acidification and nutrient enrichment effects of total acidifying deposition
and of total reactive nitrogen ~ without also having to develop the very challenging regulatory case
for "listing" ammonia and ammonium ions" as Criteria Pollutants.
At that time, my "seat-of-the-pants" inclination was to believe that the extent of decrease in reactive
nitrogen pollution loads that are needed to protect sensitive terrestrial and aquatic ecosystems of this
country probably cannot be achieved without taking steps to also include significant decreases in the
amounts of chemically reduced and perhaps also organic forms of total reactive nitrogen.
During the CASAC meeting in the Research Triangle Park on October 1 and 2, 2000, however, and
also during the EPA Science Advisory Board's Integrated Nitrogen Committee (INC) Workshop held
in Washington DC on October 29 and 30, 2008,1 began to see several things much more clearly:
1) EPA already has full regulatory authority to limit air concentrations of oxides of nitrogen in order
to protect sensitive ecological systems from adverse effects,
2) The regulatory and political obstacles that would have to be overcome in order to "list" ammonia
and ammonium ion as Criteria Pollutants are extraordinarily large,
3) It would not be possible to meet the court-ordered regulatory deadlines for completion of the
current NOx and SOx Secondary NAAQS Standard reviews if an attempt were made to overcome
these very imposing regulatory and political obstacles,
4) It would be possible to consider the amounts of NHx and NCx as part of the "already existing
conditions that lead to acidification and nutrient enrichment of sensitive aquatic and terrestrial
ecosystems,"
5) It should be possible to determine what technically achievable extent of decrease in emissions of
NOx might be sufficient to protect some if not all sensitive ecosystems in various parts of the US
from the adverse ecological effects caused by reactive-nitrogen-induced acidification and nutrient
enrichment of aquatic and terrestrial ecosystems, and
The present drafts of Chapters 7 and 8 indicate that OAQPS is seeking first to determine, within
EPA's present regulatory structure, if decreases in emissions of nitrogen oxides (NOx) — which
are already recognized as a Criteria Pollutant - could achieve an adequate decrease in the
adverse acidification and nutrient enrichment effects of N pollution that are now occurring in
various parts of the United States.
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During our CASAC discussions with OAQPS on October 2, 2008, we were assured that Chapters
7 and 8 of the Second Draft REA will deal much more completely with the combined causal
effects of both chemically reduced (NHx) and chemically oxidized forms of reactive nitrogen
(NOx).
Considerations in the Structure of the NOx/SOx Secondary Standard (Chapter 8)
1. Chapter 8 begins to explore how a secondary NAAQS might be structured to address the
targeted ecological effects discussed in the assessment. The next draft of this document will
include one or more examples of how this structure might be used to relate specific levels of
air quality indicators with a corresponding ecological indicator for a given location and/or
scenario. To What extent is the described approach technically sound, clearly
communicated and appropriately characterized at this point of the review? Does the Panel
have any further suggested refinements at this time?
In Section 8.1 - Possible Structure of a Secondary Standard - the diagram in Figure 8.1-1 was especially
informative of the approach that is currently being considered by OAQPS. The example given was based
on the ecological indicator ANC (acid neutralizing capacity) and assumed that the pollutants of concern
were not only the chemically oxides form of reactive nitrogen (NOx) and sulfur (SOx), but also the
chemically reduced forms of reactive nitrogen (NHx).
The attached diagrams were developed by Ted Russell in his role as Chair of the CASAC NOx/SOx
Secondary Standards Review Panel for presentation to the SAB's INC Committee during the INC
Workshop in Washington DC on October 30, 2008. These two diagrams were designed to show how
OAQPS might include an estimate of chemically reduced nitrogen as one of the "already existing
conditions" that lead to acidification and/or nutrient enrichment of aquatic and terrestrial ecosystems, and
thus to provide a basis for calculating the amount by which nitrogen oxide deposition would need to be
decreased in order to achieve an appropriate critical load for acidification effects and a similarly
appropriate critical load for nutrient enrichment.
Integrating Across Species Contribution to
Acidification:
A Proposed EPA Approach...
Indicator
What is regulated
Physical
Total acidifying
deposition
Acceptable depositional rate
Deposition from reduced N
Allowed NOx+SOx deposition
DepNOx -
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Applied to Nutrient Enrichment
Indicator
What is regulated
?
(your thoughts?)
Deposition
Load
Atmospheric
Concentrations
Total Nutrient Load
Allowable RJoad-
Non-atmospheric load
Allowed NOx
deposition
Deposition from
reduced N
cF
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Dr. Douglas Crawford-Brown
I am charged primarily with Scope of the Review, and so my comments are primarily on that
issue. The specific Charge Question addressed is:
"Scope of the Review: Chapters 1 and 2 provide the background, history and framework for this
review, including a discussion of our focus on the four ecological effect areas (aquatic
acidification, terrestrial acidification, aquatic nutrient enrichment, terrestrial nutrient
enrichment). Is this review appropriately focused in terms of characterizing the important
atmospheric and ecologic variables that influence the deposition and ultimately the ecologic
impacts of nitrogen and sulphur? Does the panel have any further suggested refinements at this
time?"
This review also considers Chapters 7 and 8, as these are the core of the document in regards to
an eventual regulatory decision.
As with my review of the ISA, my conclusion here is that the REA does in fact satisfy the goal in
the Charge Question, subject to the comments below. The correct effects are considered (there
may be more effects one could note, but the ones considered here are the most significant and are
likely to bound the areas of concern adequately), and the correct relationships to atmospheric and
ecologic variables are considered (again to the extent these are needed to draw the primary
conclusions). The document is well written, being easy to follow and nicely organized, although
the wheels fall off a bit - or are not even present - in Chapters 7 and 8). The authors have culled
the most important conclusions from an immense literature, focusing the reader properly onto the
key findings. A theme that will emerge below, however, is my feeling that the available data and
analyses may support the need for considering a reduced NAAQS for NOx and SOx, but is
insufficient to suggest the actual ambient levels needed to avoid demonstrably adverse effects
(which I contrast with effects alone, which may or may not be sufficient to deem adverse).
This document would benefit greatly from an Executive Summary similar to the one in the ISA.
There is a large amount of information here, but it can be boiled down to a few key conclusions.
My fear is that failing to do that, the authors may find specific parts of the document picked in
the policy process because they support a desired conclusion and policy solution. There needs to
be a concise and unambiguous statement of the key scientific conclusions, and an Executive
Summary is exactly the place to put these.
I found Chapter 1 very well written. The document lays out the relevant policy questions and
even relates these (in contrast to past documents) clearly to the task of deciding whether the
NAAQS needs to be revised and, if so, how the information would be used to do that.
Figure 1.4-1 is quite interesting, but it also lays clear the one glaring problem with a secondary
NAAQS, since the key element is the Ecological Effect Function. I don't see where such a
function is sufficiently well established to allow use in setting a secondary standard, other than
perhaps as an analogue to an effects threshold in non-cancer human health risk assessment,
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probably with some margin of safety inherent in it due to the inability to draw a proper line
between effect and adverse effect.
Chapter 2 begins by listing the appropriate effects, and I agree with the selection of these based
on the information in the ISA. Table 2.1-1 is particularly useful in providing a road map to the
material in the entire document. In the previous draft, I was unclear as to the purpose of the case
studies. In the present draft, this point is clearer, and I agree with the idea that given the very
large inhomogeneity in both exposure conditions and species across different geographic areas,
the best that can be done is to select a few representative but sensitive regions and determine
where the ambient levels would need to be to protect these. The one thing missing is a clear
statement as to how unique these case study areas are. One can't set national standards based on
a few outliers in the national distribution, and I believe a better case can be made in the
document as to why these particular areas studied are not in the extremes of the tail of inter-site
distributions of sensitivity.
I particularly like the structure of the assessment outlined in the seven steps. While the
committee may have disagreements over specific methodological issues, these seem to me the
appropriate steps and an innovative way to get at the issue of a secondary NAAQS that relies
maximally on available data. I fully support the EPA staff in this choice of framework, even if in
the end they must execute it somewhat more qualitatively than might be desired. The point is that
it is the right way to be thinking about the NAAQS.
The ecosystem services discussion in Chapter 2 was interesting to read. It presented the subject
well, and it is evident to me that ecosystem services is one lens through which to view a
secondary NAAQS (although it doesn't capture issues such as inherent rights of other species).
My problem lies in a disconnect between the detailed discussion of ecosystem services and the
specific Ecological Effect Functions in Figure 1.4-1.1 don't believe the document, or even the
current state of the science, allows for development of such a Function needed to determine how
much a specific ecosystem service is impacted by a given N or S loading, or how adverse is a
given decline in ecosystem service. I wouldn't be inclined to support a position that says any
decline is automatically adverse; the same applies to my position on human health imapcts. Due
to this methodological and computational gap, the Ecosystem Services discussion in Chapter 2
comes off as more interesting than truly informative - a good idea that can't quite be pulled off
when the data are analyzed.
The uncertainty discussion, as in almost all of the REAs we have reviewed, is quite generic and
qualitative. But given the nature of this exercise, I am not sure a more quantitative approach to
uncertainty would inform the final decision. This is because, while there are quantitative
uncertainties having to do with the data and modelling, an equally important uncertainty is the
conceptual relationship between the case studies and any sort of statement about the impact of a
national standard.
As Chapters 3, 4 and 5 are outside my area of expertise, especially with respect to specifying
where the staff should look for representative but sensitive case study areas, I don't provide
comments here, other than to note that Chapters 4 and 5 are of little use given their sketchy
nature.
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The heart of the REA is found in Chapters 7 and 8. Table 7.1-1 agrees with the information
provided in Chapter 1, so at least the methodology is consistent on this point. The framework of
thinking laid out in this Chapter is appropriate, although provided here in much too sketchy a
form for me to agree or disagree with how it is being executed. There remain two areas in which
substantial disagreement can arise between individuals reviewing the document: (1) the
methodological steps in calculating impacts on a given case study site and (2) drawing summary
conclusions across sites. At the moment, the document does not fully clarify the first, and the
second issue is dealt with more through aspirations than any clear approach. But I must withhold
judgment until the final report is prepared. The staff is at least headed in the right direction, have
a proper roadmap in front of them and have the expertise on hand to carry out these tasks.
In Chapter 8, the phrase "uniform level of ecosystem protection" occurs, and seems to become a
key idea in how a NAAQS might be considered. This idea really needs more of an explanation.
Given the high levels of inhomogeneity, and the fact that the conclusions rest ultimately on case
studies of sensitive areas, and the quite diverse kinds of effects being considered, I don't
understand what is meant by a "uniform level of ecosystem protection". It surely doesn't mean
that the level of effect will be the same across all ecosystems in the country, or even that the
same ambient level will produce the same level of effect everywhere, or that the effects will be
equally adverse in some deeper sense. And there is no common metric to which all these diverse
effects can be reduced. So, just what does it mean?
Again, Figure 8.1-1 is the right kind of structure, but I don't see how the Ecological Effect
Function will be developed as anything other than a threshold model. And I don't see where a
margin of safety is recognized or introduced. But it is still the right conceptual approach if it can
be pulled off methodologically.
Much of the discussion in Section 8.2 seems to me of a policy nature, belonging in a much
earlier chapter. It almost comes across as being filler here while the staff tries to figure out
exactly how they will execute the ambitious steps in Figure 8.1-1.1 recommend moving it to the
front of the REA in either Chapter 1 or 2.
The rest of the Chapter 8 strikes me as a lot of scientific detail with little to connect it all to the
final calculations. I can't comment on many of the equations proposed, because they relate more
to environmental transport and fate than to effects. But it is evident to me that there is still a large
gap between methodologies to estimate deposition and methodologies to relate these loadings to
any specific effect that will drive a NAAQS.
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Dr. Charles T. Driscoll
The document "Risk and Exposure Assessment for Review of Secondary National Ambient Air
Quality Standards for Oxides of Nitrogen and Oxides of Sulfur" is an effort by U.S. EPA staff to
provide and discuss a framework for establishing secondary standards of nitrogen oxides (NOX)
and sulfur dioxide (SO2). Overall, I found the framework thought provoking and an interesting
path forward in the establishment of secondary standards. While I enjoyed reviewing the
document, there were several general technical issues that I am concerned about. There are
several wording and grammatical problems in the text that should be addressed before the
document is more widely circulated. Finally, there are numerous small technical and wording
problems in the document. I have organized my comments around these three issues.
Unfortunately, the document is not complete. Major sections are missing or partially complete.
It is really a waste of time to conduct a review of such a large and complex document when the
document is incomplete.
Technical Issues:
1. Case studies and modeling approach. I think the approach of using case studies to
address the framework for secondary standards is a good and appropriate one. I also
generally think the specific case studies that are advanced in the REA are appropriate and
helpful. I generally endorse the approach used. There are a few general
comments/issues I would like to address.
The case studies for aquatic effects in the Adirondacks and the Shenandoah Park regions,
terrestrial effects on red spruce and sugar maple in the East and terrestrial effects on
coastal sage scrub and conifer forests in California seem appropriate. I also like the two
estuarine sites to evaluate coastal effects. I do have some concerns with the estuarine
studies. First, it appears that the entire estuary watershed will not be evaluated (i.e.,
Chesapeake-Potomac; Pamlico; Neuse). Will this be a problem or is the scope of doing
the entire watershed just too great for this assessment? More problematic is conducting
analysis for two watersheds that are in fairly close proximity? Although there is
considerable information for Chesapeake Bay and Pamlico Sound, wouldn't it make more
sense to conduct one of these case studies at a site with more contrasting features, with
different land cover, climatic or N sources? I would think interest's would be best
served by either selecting a northern estuary (e.g., Gulf of Maine, Long Island Sound) or
a Gulf estuary as a second site.
The other general technical comment is that the approaches used to develop critical loads
for these case studies are very different. Evaluating these different approaches could be
very instructive but also problematic. I like the approach proposed of using a dynamic
acidification model for the Adirondack and Shenandoah case studies. Note, however,
that MAGIC does not effectively simulate watershed nitrogen dynamics. So if this is an
33
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important component of the critical load, there will undoubtedly be some errors. I find it
disconcerting that for the terrestrial acidification assessment a steady-state model is being
used. First, is it a good idea to use a dynamic model for the aquatic assessment and a
steady-state model for the terrestrial assessment? While I agree with the authors that
critical loads are a steady-state phenomenon, ecosystems are not. Forest ecosystems are
losing exchangeable cations and presumably accumulating sulfur and nitrogen. This
makes these systems by definition not a steady-state and increasingly sensitive to inputs
of acidic deposition. While the application of a steady-state model is easy, it would
seem to be problematic as an assessment tool. There are clear limitations in using a
steady-state model for critical loads assessments. Finally, I don't understand how the
critical loads will be determined for the coastal and terrestrial nutrient case studies.
SPARROW is a statistical model and it is not clear how this can be used to evaluate
greater and lower N loads.
2. Nitrogen saturation. Throughout the text, N saturation is referred to. However, I could
not find any discussion of this phenomenon in the introductory sections. It is discussed
in the ISA but not (that I could find) in the REA. A brief summary of N saturation might
be helpful.
3. Time scale disconnect. There appears to be a disconnect between the time scales used
for the atmospheric modeling and the effects assessments. Ecosystem effects of air
pollutants are largely manifested over decades to multiple decades. Certainly the
simulations conducted by MAGIC are conducted with what I believe to be the
appropriate temporal perspective. I believe the time-scale for nutrient effects on
ecosystems similarly have a long-term perspective. In contrast, the deposition/CMAQ
analysis seems to be largely focused on a short-term or seasonal perspective. Why?
There seems to be a complete disconnect in the atmospheric and effects modeling
concerning time-scale of analysis. Isn't the primary concern here ecological effects?
Do seasonal or monthly patterns in air concentration or deposition have any relevance for
this long-term analysis of ecosystem effects?
4. Climate. I am a bit surprised that no discussion is given to changing climate. The
framework to be developed is examining effects that will play out over the next decades.
It is projected that climate will also change substantially over the same period. Climate
change will affect hydrology and ecosystem response to air pollution. Climate change
should be mentioned and needs to be addressed in future assessments.
5. Establishing standards around ambient air concentrations. In Chapter 8, limited
discussion was advanced in establishing ecosystem effects around ambient air
concentrations. While I can see that this might be a desirable objective, as we currently
have primary standards and some quasi secondary standards based on ambient air
concentrations. However, for ecosystem effects, I do not see this approach as workable.
I think the standard needs to be based ultimately on total sulfur and total nitrogen
deposition. There are many species of sulfur and nitrogen all which contribute to
ecological effects but having different residence times in the atmosphere. These
residence times vary in time and space. The key driver of ecological effects is long-term
34
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total deposition. Establishing standards around ambient air concentrations would seem
to be intractable.
6. Spatial variability in sensitivity. I'm not sure if this consideration is relevant for the
nutrient case studies, however, the acidification case studies will exhibit considerable
spatial variability in sensitivity to acidic deposition. There is a range of ecosystem
sensitivity to acidification from highly sensitive to highly insensitive. How will this
range of ecosystem response to acidic deposition be addressed when establishing the
critical load? Will all ecosystems be protected? 90%, 50%. Some discussion of this
consideration would be helpful.
Written Document Considerations:
1. Written perspective. The document is written from the "we" perspective (i.e., we did
this..., we analyzed that...). I find this approach somewhat disconcerting. The reason
being it is not clear who owns the document. Is this EPA's document or the contractor's
document? Who are we? I would like to see the document altered.
2. Typos, errors, writing mistakes. As with the last draft of the ISA, the REA (and the 2nd
draft of the ISA) is filled with mistakes and typos. I point out many of these in my
specific comments (see below). However, these are by no means all the mistakes. This
document needs to be carefully read, proofread and edited for consistency and to
eliminate the mistakes.
3. Redundancy. There are many redundant sections in the document. This makes a very
long document, longer than it needs to be. The document should be edited to eliminate
the redundant text.
4. Tense. The REA switches back and forth from the past to present tenses. I can see
writing in either tense. However, the document should be edited so it is written in a
consistent tense.
Specific comments:
Page 1-2, line 16 Units of ANC jieq/L?
Page 1-11, line 24 I don't agree with the statement. Most published studies
document inputs of oxidized and reduced N. A few don't, but
most do.
Page 1-12, line 10 Space missing.
Page 1-12, line 13 I would change the wording. Acidification is an environmental
effect due primarily to sulfur and secondarily nitrogen in most
environments.
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Page 1-13, line 12 As above, need to define N saturation.
Page 1-13, line 19 Change air to atmosphere.
Page 1-15, line 22 alpine
Page 1-16, line 12 It is incorrect to state that watersheds conducive to methylation are
found in the northeastern U.S. and southeastern Canada. They are
found all over. See Figure 6.1-3.
Page 2-2, table 2.1-2 Under aquatic acidification also include hydrologic flow paths
under sensitivity variable.
Page 2-4, line 15 Eliminate comma
Page 3-7 I would like to see this section expanded to include a section of
background (pre Industrial Revolution) deposition, including
sulfate, nitrate, ammonium and basic cation deposition.
Page 3-8 I would like to see a brief description of organic N deposition,
including sources.
Page 3-9, thru 12 There is a summary of spatial deposition patterns. The discussion
of how these maps are produced is in the section that follows
(3-12). The methods section should be moved in front of the
maps. Also, the maps are generated for 2002. Some discussion
should be given as how representative this year is, given
year-to-year variability in deposition. Moreover, it is critical to
clarify on the deposition maps the units of mass (e.g., Kg N/ha-yr
or kg NOs/ha-yr).
Page 3-12, line 10 data are ...
Page 3-13, line 1 data were...
Page 3-13, line 6 Change to... kg/ha-yr.
Page 3 -13, line 7 data were...
Page 3-16, line 5 Need to clarify the time interval kg/ha-yr?
Page 3-16, table 3.2-2 It is not clear what this table is. Some additional text is necessary.
Page 3-19 It would be helpful to put the Adirondack Park and the
Shenandoah National Park boundaries and the Chesapeake and
36
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Pamlico watershed areas on the map so the reader can understand
the scope of the analysis relative to the total resource.
Page 3-25, line 7,8 Change to... kg N-ha/yr.
Page 3-35, line 12 Change to... fairly uniform.
Page 3-36, figure 3.2-14 Why show figures of both monthly and seasonal deposition? Isn't
this redundant?
Page 3-38, figure 3.2-16, 17, 18, 19
These figures are difficult to read and are they really helpful?
Page 3-40, line 4 Change to... generally uniform...
Page 3-50, lines 3, 17 and Page 3-51, line 6
Change...drop to decrease
Page 3-50, figure 3.2-28 and elsewhere
Aren't the monthly patterns in wet deposition strongly driven by
the quantity of precipitation? Wouldn't patterns for a different
year with different precipitation patterns be different? As a result,
this temporal section is misleading because it is strongly affected
by the meteorology for that year. If true, why include all this
analysis? As a minimum, this fact should be clarified and some
data provided on 2002 as a reference year.
Page 6-1, line 3-4 Rephrase. Every wetland has sulfate. The production of methyl
mercury is largely mediated by sulfate reducing bacteria.
Page 6-1, line 22 Also phosphorus (or N) can be important as it regulates aquatic
productivity and therefore mercury concentrations in aquatic
organisms (Driscoll et al. 2007).
Page 6-2, line 4 Change to...Industrial Revolution.
Page 6-2, line 28 This sentence needs to be clarified. Ionic mercury can be reduced
and evaded and separately methylated. Methyl mercury is not
reduced. Where does this 1-2% come from? The extent of
methylation is highly variable from ecosystem to ecosystem.
Page 6-4, line 14-16 Why is methane needed? Why do you need HgS in the equation?
Define MeHg+.
Page 6-4, line 20 Also anoxic conditions.
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Page 6-4, last paragraph
Page 6-5, line 12
Page 6-5, figure 6.1-2
Page 6-6, line 3
Page 6-6, line 5
Page 6-10, line 4
Page 6-12, line 5
There are other studies that probably should be cited (Branfireun et
al. 1999), (Jeremiason et al. 2006).
Change to.. .methylation can occur within.
Hg can also be supplied from sediments.
Change to... anoxia, sulfate).
Change to... response, hydrology, nutrient loading, limnology).
Is this really true? I do not believe it. % methyl mercury is
highly variable. Need to correct.
Change to... oxidizing NH4+.
Page A3
Page A3
Page A3
-l,line 15
-1, line 20
Subscript 2.
hydrogen ion, and Aln+.
1, line 20 and throughout the document
I don't think the writers of this document understand the concept
of buffering capacity. Buffering capacity is the resistance of a
system to changes in pH. I would recommend eliminate using the
term here and elsewhere or change the phrasing to use it correctly.
An alternative could be acid neutralizing capacity or acid-base
status.
Page A3-2, 1st paragraph
Page A3
Page A3
Page A3
Page A3
Page A3
Page A3
-2, line 10
-2, line 12
-2, line 12
-2, line 27
-2, Iine3 0
-3, line 5
I suggest adding a sentence or two about
immobilization/mobilization of SC>42" and NCV by plants/soil
organic matter.
There are numerous chemical indicators.
NCV, Aln+
Change to... of base cations; and ANC.
Change to... precipitation enters the soil and soil water to
emerge...
K+ + Na+ + NH4+) - (SO42" + N
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Page A3-3, line 6 Change to... This is the acid neutralizing capacity (ANC), or the
Page A3-5, line 4 acidic surface waters (14%; ANCXO jieq/L).
Page A3-5, line 26 United States
Page A3-6, line 24 Need to define the time and mass basis of deposition (e.g., kg
S(Vha-yr or kg S/ha-yr).
Page A3-7, line 12 Change to... weathering rates and limited neutralizing of acid
inputs.
Page A3-8, line 5 Again need to define the time and mass basis of deposition.
Page A3-9, line 19 Aln+
Page A3-9, line 21 with limited leaching
Page A3-9, line 23 EPA-administered Long-Term Monitoring (LTM) program.
PageA3-15, line 12 SO42"
Page A3-16, line 9 comma
Page A3-16, line 19 it's the acid neutralizing capacity of a ...
Page A3-16, line 21 The acid neutralizing capacity of a ...
Page A3-17, line 3 20 |ieq/L (limited protection)
Page A3-16, line 12 This sentence makes no sense. At ANC = 0 jieq/L a water is
chronically acidic.
Page A3-17, line 8 Sub and super script
Page A3-20, line 5 Units should be eq/ha-yr.
Page A3-20, line 7,8 I would eliminate the term occult deposition simply call it cloud
and fog deposition.
Page A3-20, line 10 Units meq/m2-yr
Page A3-22, line 24 This description needs to be expanded or clarified. There are
more than 200 NADP sites.
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Page A3-28. line 25 in the catchment
Page A3-29, line 19 400 meq/m3
Page A3-29, line 24 The titles used for these classes should be consistent with the titles
established in table 4.1-1 on A-14.
Page A3-33 There needs to be some discussion on the time and nitrogen
retention assumptions used to obtain critical loads.
Page A4-1 I would change the title to Forest Acidification Case Study.
Page A4-1, line 17 hydrogen ions
Page A4-1, line 19 where strong acids
Page A4-4 Should also consider citing the recent paper by (Warby et al. (in
press)) attached), which shows widespread soil acidification in the
Northeast.
Page A4-5, line 14 This statement needs to be reworded. Al mobilization occurs
under low % base saturation and high concentrations of acid
anions. The statement as it stands is incorrect.
Page A4-9, line 18 Should be (Driscoll et al. 2001).
Page A4-10 It would be helpful to cite the study by (St. Clair et al. 2005) which
shows decreases in foliar antioxidant enzymes in sugar maple in
response to lower foliar and soil Ca2+ in Pennsylvania.
Page A4-19, line 1 Again need to specify the mass and time basis of deposition.
Page A4-28, line 10 acidity input neutralized by
Page A4-28, line 18 parties
Page A4-49 Need to indicate the units of the figure.
Page A4 References Should be BioScience.
Page A5-18, 1st paragraph Need to use metric units.
Page A5-26, line 6 Need to define Nr.
Page A5-30 SPARROW is a steady-state model. Will need to demonstrate
how you can use it.
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Page A5-55, line 7 were from
Page A5-58, line 6, 8 Does the SAV coverage really have this level of significant
figures?
Page A6-10, line 1 Change to... Mediterranean climate. This climate is.. A
Page A6-25, line 16 result of long-term elevated N deposition rather than pulses
Page A6-42, line 7 data are
Page 7-3, line 12 Change to... where strong acids are
Page 7-11, line 2 catchment to neutralized acid anion deposition is known as acid
neutralizing capacity.
Page 8-1, line 14 There cannot possibly be a uniform level of ecosystem protection
due to the inherent variability in ecosystem sensitivity.
Page 8-4, figure 8.1-1 Add climate as a variable/fixed factor.
Page 8-5, line 2 What is meant by the point of deposition?
Page 8-8, line 14 What about forest acidification?
Page 8-8, line 14 How can you say whether precipitation occurs or not. Is there a
location where precipitation does not occur? Rewrite sentence.
Page 8-10, line 24. Do you mean deposition is expressed or an equivalence basis?
Please clarify.
Page 8-11, line 4 This sentence makes no sense and should be rewritten.
Page 8-14, line 1 data are
Page 8-14, line 20 Do you mean equivalence ratio?
References:
Branfireun, B. A., N. T. Roulet, C. A. Kelly, and J. W. M. Rudd. 1999. In situ sulphate
stimulation of mercury methylation in a boreal peatland: Toward a link between acid rain
and methylmercury contamination in remote environments. Global Biogeochemical
Cycles 13:743-750.
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Driscoll, C. T., Y.-J. Han, C. Y. Chen, D. C. Evers, K. F. Lambert, T. M. Holsen, N. C.
Kamman, and R. K. Munson. 2007. Mercury contamination in forest and freshwater
ecosystems in the Northeastern United States. BioScience 57:17-28.
Driscoll, C. T., G. B. Lawrence, A. J. Bulger, T. J. Butler, C. S. Cronan, C. Eagar, K. F. Lambert,
G. E. Likens, J. L. Stoddard, and K. C. Weathers. 2001. Acidic deposition in the
northeastern United States: Sources and inputs, ecosystem effects, and management
strategies. BioScience 51:180-198.
Jeremiason, J. D., D. R. Engstrom, E. B. Swain, E. A. Nater, B. M. Johnson, J. E. Almendinger,
B. A. Monson, and R. K. Kolka. 2006. Sulfate addition increases methylmercury
production in an experimental wetland. Environmental Science and Technology
40:3800-3806.
St. Clair, S. B., J. E. Carlson, and J. P. Lynch. 2005. Evidence for oxidative stress in sugar maple
stands growing on acidic, nutrient imbalanced forest soils. Oecologia 145:258-269.
Warby, R. A. F., C. E. Johnson, and C. T. Driscoll. (in press). Continuing acidification of organic
soils across the northeastern USA: 1984 - 2001. Soil Science Society of America Journal.
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Dr. Paul J. Hanson
The Risk and Exposure Assessment (REA) ... represents a good beginning, but many sections are
not yet complete or only partially complete making it difficult to judge the full intent or appropriateness
of the document.
Specific comments and suggested edits:
Front matter:
Page xii: Should the definition of ecological dose be limited to toxicants that inhibit microbe-mediated
ecological processes! I would think that the term should apply to all biological organisms. It may be
that it is a term that dominates microbial studies.
Top of Page xiii: The most common example of an ecosystem benefit would probably be an increase in
productivity. Why isn't this an example?
Page xiii: The difference between elasticity and sensitivity (page xv) isn't clear. Is there a reference for
the use of the term elasticity that might be placed here?
Page xv: The precipitation range for semi-arid regions should probably be 250 to 500 mm. It certainly
shouldn't be the same as the definition for arid systems.
Chapter 1
Page 1-3 line 8: I recommend the following wording change ".. .both ambient air and surface deposited
species of NOx and SOx...
Page 1-10 line 23: N2O is nitrous oxide not nitrogen dioxide.
Page 1-12 line 9: For parallel structure I would add the spelled out version of sulfur dioxide.
Page 1-13 line 5: Remove the semicolon.
Page 1-13 line 13: I would change "direct effects" to 'direct adverse effects'. There is some evidence
for localized N uptake.
Page 1-14 line 11: The text must be changed to "..detail on how acidification affects sensitive
ecosystems " Don't leave the reader with the impression that acidification is having effects on all
ecosystems.
Page 1-14 line 17: I don't understand "re-acidification". This concept needs to be further developed.
Page 1-14 line 31: Add 'productivity' to the list of changes driven by N deposition.
Page 1-15 line 14: This threshold for N saturation is only relevant for some, but not all eastern forests.
Those levels of N deposition would be easily assimilated by much of the upland oak forests throughout
the eastern United States growing on deeps soils with ample base saturation. Page 3-186 of the ISA states
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"there is currently no published national assessment of empirical critical loads for N in the U.S "
Table 3-25 is a nice summary of what is known. The REA needs to reflect the limited amount of data
available for developing quantifiable thresholds, and appropriately characterize those ecosystems for
which it might appropriately be applied. Avoid inappropriate extrapolations. Lines 14 to 19 on page
4-16 of the ISA include good statements that should be used within the REA to qualify the nature of
ecosystem sensitivity.
Page 1-15 lines 21 and 22: Similarly, the wording may need to be changed here to suggest if these levels
represent an appropriate threshold for all or just some sensitive grasslands.
Page 1-15 line 30: Add a reference for the sentence ending on this line.
Figure 1.3-3 still doesn't show the productivity enhancement effect of N, which is clearly a dominant
process in the N cycle.
Bottom of page 1-17: Should some mention be made at this point to N standards for water pollution? It
isn't necessary, but might be a useful connection. Section 3.3.6 of the ISA and the associated annex might
be cited.
Figure 1.4-1 doesn't adequately capture the integrated nature of NOx and SOx pollution that is being
attempted in this document. Are they truly intertwined all along this process or do they only come
together after deposition takes place?
Chapter 2
In Table 2.1-1 ANC should be defined, productivity should be added as an ecosystem service where
appropriate, and N leaching might be added as an indicator of terrestrial nutrient enrichment. The
characteristics of sensitivity for terrestrial nutrient enrichment might be updated.
Sections of Table 2.3-1 still need to be filled in.
Chapter 3
Page 3-4 lines 6 and 7: Check the wording. 30 to 70% of the animal wastes can't be emitted as NH3.
Should it read 30 to 70% of the N losses from animal wastes?
Page 3-5 lines 10 to 15: Are there not any natural sulfur emissions in and around Yellowstone or in other
hot springs areas of the country? I realize they may be inconsequential....
Pages 3-10 to 3-11: Question: Have all of the emissions reductions resulting from past clean air
legislation been realized? Will new standards for ozone impact the likely deposition rates for N in the
future? Should such a discussion be included someplace in this document?
Chapter 3 doesn't include much on temporal changes in deference to the maps of recent conditions.
Those are fine, but I think some discussion of where we have been and where we are going should be
included in the REA. Figures 2-59 or 2-103 from the ISA might be considered.
Page 3-12: Super and subscripts for charge are missing for SO4"2, NO3", and NH4+.
Question: Do the QMAC estimates of deposition to terrestrial systems include foliar uptake of NO or NO2
near urban areas or along major roadways where air concentrations are high enough to drive this
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pathway?
Table 3.2-2 is not well defined. It needs references.
I was disappointed by how much information was still not added to the document (especially in this
Chapter). We are being asked to provide comment on a document that has a lot missing from it.
Captions to Figure 3.2-12, -13, and -14 need to be reworded to ".. .nitrogen deposition by source and
quarter.... The most interesting data in many cases has to do with the source of N forms rather than the
season of the year.
Figures 3.2-22, -23, -24, and -25 lack units (presumably kg/ha as for N).
Captions to Figure 3.2-27 and -28 need to be reworded to "...sulfur deposition by source and quarter....
Page 3-54: Again.. .we don't have much to review yet.
Page 3-54 line 14: Reword as... ."Public welfare effects associated with direct exposure to NOx and SOx
do not occur for current ambient concentrations."
Page 3-54 line 23: The discussion on pages 1-10 and 1-11 seems to disagree with this statement. The
REA has already been defined to deal with total reactive N.
The discussion of Data and Tools (Section 3.2.2.2) should probably be presented earlier within Chapter 3
(perhaps around page 3-17).
Figures 3.2-35 and -36: Adding pixels for actual forest cover within these maps would be useful to better
reflect the actual extent of the forest types. The coastal sage map (Figure 3.2-37) appears to be drawn
this way.
The text for Figures 3.2-39, -40, -41, -42, -43, and -44 is way too small and the figure captions are
inadequate. Please revise.
Page 3-70: At this point of the discussion it occurred to me that a case study for an area dominated by
NH3 deposition (i.e., Iowa, Minnesota, Illinois) should probably be added to the REA. It wouldn't
necessarily show adverse effects, but it would complete the picture of total reactive N deposition across
the US. Page 3-103 of the ISA provides some rationale for not including such a case study since
agricultural areas are overwhelmed by fertilizer additions. However, limited natural areas (forests,
prairies) are embedded within areas dominated by agriculture.
Chapter 4: Incomplete and not reviewed.
Chapter 5: Incomplete and not reviewed.
Chapter 6
Figure 6.1-4: SRB should be defined in the figure caption.
Page 6-16 line 13: Remove the word "often". Fungi should probably also be recognized as an important
contributor to decomposition.
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Increased nitrogen does affect the N content of green leaves. Is this pattern well established for litterfall
as well? Does the pattern differ by vegetation type (i.e., trees, grasses, crops...)?
Page 6-17: Some of this material might be better left to the ISA document. Lines 24 to 28 are not
needed here.
Page 6-19: How the contribution of atmospheric deposition to upland watersheds actually finds its way
into waterways isn't clear. The 'filtering' effect of upland vegetation will vary tremendously from
location-to-location. This concept needs to be made clear in the document.
Chapter 6 seems to lack summary conclusions:
What terrestrial systems are at risk? What percent of US land area?
What aquatic systems are at risk? What percent of US freshwater area?
Chapter 7
Page 7-5 line 4: Replace "ecosystem health" with another term. It isn't and perhaps can't be defined.
Page 7-5. Line 7: Change to "this is hypothesized to change...." Or provide the references that show
proof.
Page 7-5 line 21: Spell out CSS.
Page 7-7 Table 7.1-1: Replace "tree health" with a more meaningful term or terms such as rate of
growth, survival....
Page 7-8: The deposition levels proposed are appropriate for 'sensitive' ecosystem, but not all
ecosystems. A concept of one size does not fit all will need to be worked into the conclusions of the REA.
While protection of sensitive systems may be a justification for a new standard and level, it shouldn't be
interpreted as having the same effect on all areas of the US. That is, lowering inputs to areas currently
unaffected will not help them. Pages 3-78 and 3-79 of the ISA include text that might be useful in
clarifying this point.
Chapter 7 ends abruptly and seems incomplete.
Chapter 8
Page 8-1 lines 14 and 15: The concept of achieving a standard based on a "uniform level of ecosystem
protection" seems at odds with the REA document. The REA clearly states that the impacts of N and S
deposition are localized throughout the US and subject to the correct combinations of deposition and
susceptibility of the target terrestrial and aquatic ecosystems.
Page 8-4 Figure 8.1-1: An air quality based estimate of total N and S form deposition may not be
sufficient information to judge impacts on acid neutralizing capacity. A data layer on extant edaphic
conditions is needed. The deposition metric should probably also be enhanced to allow for the
estimation of biological immobilization (i.e., plant and microbial uptake of some fraction of the total
deposition).
Page 8-5 lines 1 to 3: Plant uptake needs to be included in this list.
Page 8-28 lines 2 to 9: I don't agree with the assumption that annual accumulation of N inputs into wood
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increment can be ignored in this analysis. Except for low or no productivity ecosystems this is a
significant sink for atmospheric N deposition that must be included in the calculation of N available for
other soil interactions.
Section 8. 4 is incomplete. More material is needed.
Attachment 3
Page 1 line 16: The phrase "a host of biogeochemical processes" is too vague. Please expand this
concept.
Attachment 4
Pages 2 and 3: Table 1.1-1 is not filled in. The term forest health should be replaced.
Pages 12 and 13: Table 1.2-2 is not complete.
Page 31: The authors conclude that the simple mass balance method would be used in the REA. What
caused the authors to exclude the dynamic model method? Lack of input data? Lack of validation?
Page 32: All evapotranspiration does not occur at the surface of the soil profile. Did the authors mean to
imply evaporation alone?
Page 42 line 17: Is the nitrogen immobilization mentioned here microbe and plant or just microbe?
Figure 3.1-2 is missing units.
Page 53: The conclusions need work. The imbalances for Ca, Mg, and Al suggested for forest soils are
for localized sensitive systems. As worded, the conclusions would be taken as a broad generalization for
all US ecosystems.
Attachment 5: No comment
Attachment 6
Page 6: Table 1.2-2 is missing too much information to be fully evaluated.
The studies cited and discussed for the CSS system should be closely evaluated to determine which were
based on manipulative studies capable of determining cause-and-effect relationships versus those that
represent correlation studies for which relationships between known variables and measured responses
were assumed to be viable explanations for adverse responses.
Studies highlighted in the ISA within Tables 3-15, 3-17, 3-18, and 3-19 might have a larger presence
within the REA.
Figure 5.1-1 and -2: In my opinion the change in CSS seen in Figure -1 doesn't correlate very well with
the dominant deposition patterns in -2. How well does N deposition really correlate with change? How
much does land use change through time get in the way of the interpretation of N deposition cause and
effects in this case study?
Page 46 lines 4 versus line 15: The conclusion of "compelling evidence" on line 4 does not seem to
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agree with the authors conclusion about the research still underway on line 15. A word change seems in
order.
Page 47 line 5: Is a modification of a valued ecosystem an ad
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Dr. Rudolf Husar
These comments are addressing primarily the 1st draft REA section: Additional Effects. It also
includes both general comments on the approach to the REA as well as comments on sections of the the
first REA draft document.
Comments on REA Chapter 6: Additional Effect
1. Charge: In this chapter, we have presented results from some initial qualitative analyses for
additional effects including the impact of sulfur deposition on mercury methylation, the impact of
nitrous oxide on climate change, and the impact of nitrogen deposition on carbon sequestration.
Are these effects sufficiently addressed in light of the focus of this review on the other targeted
effects in terms of available data to analyze them?
Overall, this chapter is a good effort to illustrate additional, non-ecological risks associated with
anthropogenic N and S. Indirect sulfur impacts are well captured by the problem of sulfur-induced
methylation of mercury, which then causes the effects in biota. The interaction of nitrogen and carbon
cycles is also properly illustrated in the section on nitrogen-induced changes in the carbon sequestration.
The utility of the section on N2O impact on climate is less obvious.
This chapter is clearly a first draft. In the introduction it would be helpful to provide more extensive
rationale and criteria on the general approach for selecting these Additional Effects. The rationale should
also include why some obvious additional effects on materials, visibility and soil are not being
considered. See further discussion regarding these effects in the general comments on REA below.
6.1 Sulfur and Mercury Methylation
Page 6-2 Line 10: Currently, i.e. since 1995, coal combustion was, indeed, the main cause of
anthropogenic mercury deposition. However, prior to the regulatory action, around 1990, the
anthropogenic mercury emissions were dominated by other sources. Since deposited mercury has
a long residence time in soil and biota, much of the mercury methylation occurs on the
accumulated mercury from solid waste and other agricultural, medical, residential usages.
Page 6-2 Line 13: Atmospheric mercury particles cannot possibly remain in the atmosphere for
more than two years. Even stratospheric particles, have atmospheric residence time of less than
two years. As with the rest of ambient aerosols their atmospheric residence time is less than a
week in the planetary boundary layer and less than 3-4 weeks in the mid-troposphere.
Page 6-3: Figure 6.1-1 represents the mercury cycle in the ecosystem. It has many compartments
and arrows representing the mercury flow and transport/transformation processes. It is
recognized that full quantification of the mercury cycle through air, water, land and biota is not
possible at this time. However, it would be helpful, at least in the text, to highlight the main
flows and processes that dominate the mercury cycle.
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6.2 Nitrous Oxide
Page 6-10:1 find little justification for this section on the climate impact due to anthropogenic
N2O. As stated in the REA, N2O contributes only about 6% of GHGs and the man-induced
sources of atmospheric N2O are only 10% of that, i.e. .6% of the GHGs.
Page 6-12 Line 31: The statement "that nitrogen addition increased N2O emission by 215%"
could benefit from a reference, compared to what?
6.3 Carbon Sequestration
Page 6-13: This section is an appropriate illustration of the interdependence of nitrogen (sulfur?)
and carbon cycles through air, land, water and biota. The meta-analysis of existing literature is an
appropriate method for illustrating the interdependences of the earth system components and
how changes in one set of environmental chemicals may have intended and unintended
consequences throughout the earth system.
General comments on the first draft REA
This REA focuses on ecosystem welfare effects that result from the deposition of total reactive
nitrogen and sulfur." I concur with D. Johnson that exclusive focus on "negative" effects of N
and S deposition is a flawed approach. It ignores the broader context and the full dynamics of
eco system responses to anthropogenic N and S deposition. The beneficial effects of
atmospheric S and N fertilization should also be considered. This would also require definitions
and/or conventions on what's harmful and what's beneficial.
The man-induced nitrogen and sulfur deposition should be compared quantitatively to the
naturally occurring N, S flows. This will allow estimating the significance of the man-induced
stress, compared to the naturally occurring values. By avoiding such broader context, the risk
assessment will be susceptible to criticisms of incompleteness and possibly irrelevance to actual
ecological risk estimation.
Page 1-2 Line 9: "In the Act (Section 109 B 2) the purpose of the secondary NAAQS is to
protect the public welfare from any known or anticipated adverse effects..." Clearly, a
secondary NAAQS includes all welfare effects, not only the effects on the ecosystem. This fact
is not followed through in the REA and ISA.
Page 1-2 Line 19: "Adverse public welfare effects are based on an assessment of how
ecologically adverse impacts translate into adverse impacts on public welfare" In this sentence
as well as throughout the REA welfare effects only include effects on ecosystem . As stated
above welfare effects include damage to materials, visibility, soils, climate.
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Specific comments on sections of the first draft REA
Page 1-13: Figure 1.3-2 representing the sulfur cycle should be made more quantitative. The
schematic Figure on the biogeochemical cycles of sulfur is good. However, such a general
Figure should be fortified by adding magnitudes to the flows represented by the arrows. The
transfer rates, say over the US, can be estimated from the model runs, or based on the empirical
evidence. There is ample literature on biogeochemical cycles that estimates the magnitude and
importance of the various flow rates.
Page3-5 Line 4: " ... .combustion of fossil fuels by electric utilities (-66%) " This percentage is
inconsistent with 71% EGU contribution shown in the pie diagram, Figure 3.1-5.
Page 3-8: The section layout for 3.1.4 on Deposition starts with the total deposition maps that
are obtained by combining the model and measured values. The description of the data and
tools is given after that. The customary approach is first to present the input data, tools and
methods and then the resulting computed values. Also, as discussed at the October CASAC
meeting, a separate section on CMAQ model comparison with the observations for the key N, S
species would be most desirable.
Page 3-8: Section 3.1.4.1 on Nitrogen Deposition has many useful quantitative numbers.
However, the source and estimation methods for these estimates are not well documented.
Page 3-10: The useful Figure 3.1-7 on oxidized N deposition should be augmented with
separate Figures for dry and wet deposition of N. The wet deposition Figure should also
compare the model and measured oxidized N deposition.
Page 3-11: Ditto for reduced N deposition.
Page 3-12: Ditto for reduced S deposition.
Page 3-12: Section 3.2. could be subdivided such that the procedures for model-observation
data fusion has a more extended separate sub-section.
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Dr. Dale W. Johnson
As has been noted in previous reviews, I feel that this document is unbalanced with respect to the
effects of nitrogen deposition. Some very simple facts need to be acknowledged and considered:
1) most terrestrial ecosystems in the USA are nitrogen-deficient; therefore 2) increased inputs of
N are likely to cause growth increases; 3) growth increases will almost certainly result in
increases in carbon (C ) sequestration, which in turn may have inadvertent benefits for the CO2 /
climate problem. This is not to diminish any statements about the negative effects of N
deposition, it is simply to add balance to this document. As scientific reviewers, we have the
responsibility to treat this and all other subjects in a completely objective manner.
Below are some specific comments, some editorial in nature, some technical in nature, and some
where I see this lack of objectivity and balance. Following that I will address the specific
questions assigned to me.
Specific comments:
p. 1-13, lines 4-7: This is a balanced statement - the review of effects should really flow from
this approach, considering both increased productivity (which may be beneficial in some cases,
detrimental in others) and increased soil acidity and eutrophication.
p. 1-15, line 14: 5.6 to 10 kg ha"1 yr"1? Can you really narrow this down to one decimal point?
p. 1-15, line 17: should include "and carbon sequestion" after "carbon cycling".
0. 1-17, line 13: From a soils point of view, the effects of NOx really cannot be readily
distinguished from the effects due to total reactive nitrogen - both are transformed in the soil
rather extensively.
p. 2-5, line 25: should add "timber production and carbon sequestration" after "water". I note that
timber production is mentioned page 2-7, lines 19-20, but only in the context of how soil
acidification might negatively affect it. Soil acidification may well negatively affect timber
production, and the latter statement should stay as it is, but increased N deposition will probably
also increase timber production and this needs to be acknowledged.
p. 2-9, line 27: should add "timber production and carbon sequestration" after "water quality"
Attachment 1, p. 3:1 see Carbon Sequestration is listed as a potential section 6.3 - this is a good
thing. Looking forward to seeing it.
Attachment 3, p. 1, lines 17-26: There needs to be a discussion of the effects of mineral acid
anions on soil solution (what Reuss calls intensity effects, which can happen very quickly) in
addition to the discussion of how they affect soils (capacity effects, which take a long time to
occur). Reuss points out in his 1983 paper (Reuss, 1983) and in our small book (Reuss and
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Johnson, 1985), both of which are cited later in the Terrestrial Case Study, that A13+ increases to
the 3/2 power of Ca2+, for example, as total mineral acid anion (e.g., nitrate and sulfate)
concentrations increase, and this happens even if there is NO CHANGE IN THE SOIL AT ALL.
Thus, if the soil is already acid, the introduction of mineral acid anions will cause the immediate
mobilization of Al and acidification of soil solutions and probably surface waters long before any
change in the soil takes place. Conversely, if the mineral acid anion concentrations are reduced,
one should see a very rapid recovery. In short, the soil solution can change very quickly and
almost independently of the soil, and this has major implications for the effects of N and S
deposition on aquatic ecosystems.
Attachment 4, p. 1. lines 16-29: Same exact comment above applies here and in this case, our
small book is cited as a source but only part of the story (the soil part, not the soil solution part)
is reviewed. This is an important point - please include it in the next draft.
Attachment 4, p. 5, lines 10-17: Same comment as above here. It is not necessarily true that
"inorganic Al does not become mobilized until after soil Ca is depleted" if the soil is already
acidic, as many unpolluted soils indeed are.
Question 4 Response: The revisions have improved the characterization of adverse ecological
effects, but I see no real consideration of the potential positive effects of N deposition as yet.
Timber production is mentioned, but only in a negative context and I see little or nothing on C
sequestration. The one pager for section 5 refers to case studies and gives no indication that this
approach will be changed.
Question 4b: I see no discussion on effects on carbon budgeting as yet - have I missed
something? I do see Carbon Sequestration is listed as a potential section 6.3 - this is a good
thing. Looking forward to seeing it.
Chapters 7 and 8 (Sent 19 Sept 2008)
Chapter 7: We are asked if the approach is technically sound to consider "ecologically adverse
effects". For the most part, yes, it is. However, once again, I note that this section focuses
entirely on negative effects of N. This document should also consider cases where increased
production could be a positive effect - such as on timber production and C sequestration.
p. 7-1, lines 21-27: This is a real mouthful. Can it be simplified and broken into at least two
sentences?
p. 7-3, line 12: Why "inorganic and mineral acids"? They are basically the same thing.
Section 7.1.4:
Chapter 8: Many questions are posed to the panel here and I will not repeat them. I had problems
with the conceptual framework for the calculations, as noted below.
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Section 8.3.3:1 had a very difficult time following this section and do feel like I ought to be able
to. It would help a great deal if units could be specified in the various equations and the
assumptions were clearly spelled out in the beginning. For example, is it assumed that base
cation concentrations will remain at pre-industrial levels? The equations would suggest so, as
would the statement on p. 8-29, lines 13-15.1 cannot really agree with the assumption state here
that "pre-industrial base cation concentrations effectively set the long-term capacity of the
catchment to neutralize acidic deposition because it represents the only source of base cation
input that is sustainable over the long-term". For one thing, soils in humid regions always
naturally acidify and therefore there is no long-term steady state base cation flux until soils
become extremely acidic- it is always slowly decreasing. I also think that the implicit
assumption here that base cation concentrations in streams will not increases over the long-term
in response to acidic inputs is flawed - some soils have a very large exchangeable base cation
pool and could buffer such inputs for a much longer term than the typical attention span of
scientists and policy makers, let alone the public.
p. 8-29, lines 18-19: This statement makes no sense. At steady state, the leaching rate of base
cations is, by definition, equal to weathering inputs, not "at lesser or greater rates".
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Dr. Donna Kenski
Overarching concerns: EPA staff have clearly made a great effort in pulling this document (and
its companion ISA) together, and should be commended for the high-quality (and quantity)
produced thus far. Nevertheless its current incomplete status and the pressing schedule make it
hard to see how all the remaining tasks can be completed, and reviewed, in sufficient time to
meet the predetermined deadlines. Staff and contractors to EPA need to be realistic in judging
how much can really be done in the remaining months. If it is time to set priorities, perhaps that
is something that can be discussed at this meeting.
The CAA requirement that the secondary standard be in the form of a concentration standard is
going to require us to tolerate a much higher level of uncertainty than usual in the standard
setting process, because of the need to employ multiple models to characterize the
concentration-deposition-ecological effect-ecological indicator linkage. Consequently, the REA
in general needs to be much more comprehensive and transparent in describing the levels of
uncertainty encountered at each of these steps and their impacts on overall uncertainty. For
example, so much hinges on the CMAQ estimates of deposition, and yet there is little
information given in the REA or the ISA on CMAQ performance. It seems from the ISA that
CMAQ has really only been evaluated in terms of its annual estimates of aerosol deposition, and
those are accurate to within a factor of 2. No CMAQ performance evaluation is given for
deposition to specific locations, particularly locations that share characteristics of the sensitive
areas focused on in this analysis. Likewise, none is given for measurements with a shorter time
frame than annually. A clear-eyed discussion of these uncertainties for CMAQ and for the other
models used to support the REA (MAGIC, ASTRAP, Sparrow) is a critical component that
needs to be incorporated.
Charge Questions: Scope of the Review
1. Is the review appropriately focused in terms of the targeted effect variables and in terms
of characterizing the important atmospheric and ecologic variables that influence
deposition and ultimately the ecologic impacts of nitrogen and sulfur? Does the Panel
have any further suggested refinements at this time?
Generally, the review seemed to focus on appropriate variables, although as noted above, the
complete scope may be too broad to accomplish before the court's deadline. The
policy-relevant questions posed in Sec. 1.4 weren't actually addressed directly (perhaps it's still
too soon, given the incomplete case studies) but I did note that questions 3 and 4 of that list (i.e.,
to what extent do receptor surfaces influence dry deposition, and can effects of NOx be
distinguished from effects due to total reactive nitrogen) did not seem to be discussed or
addressed by any of the case studies in Attachments 3-6, although Chap. 3 did present a nice
graphical characterization of the areas and their relative proportions of NOx vs total and other
forms of N nitrogen. However, most of that was modeled data and little comparison to
measured values was presented for comparison. Perhaps more of that is coming in the second
draft, since there were lots of missing sections to Chap. 3.
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Similarly, the list of issues on p. 1-20 should include evaluating the impacts of atmospheric
deposition relative to other paths (nitrogen runoff from agricultural lands, for example). This
might be what is meant by the last bullet, but it wasn't clear; perhaps it could be made more
explicit.
Air Quality Analyses (Chapter 3)
1. To what extent are the air quality characterizations and analyses presented in Chapter 3
technically sound, clearly communicated, appropriately characterized and relevant to the
review of the NAAQS?
The analyses in Chap. 3 could more accurately be described as modeled estimates of air quality,
rather than air quality characterizations, which I think of as based on measured data. While the
graphs were useful and logically presented, there was very little measured data given for
comparison, so it is not possible to judge their 'soundness'. Combined with the lack of CMAQ
validation discussion (mentioned above), it becomes more important to see these in the context
of measured data as well. But this may be premature if the next draft is meant to include such
comparisons.
I would have liked more discussion of the monthly patterns of deposition shown, for example, in
Figs 3.2-14 through 3.2-19. Clearly wet deposition is driven largely by precipitation, but what
drives the other components of deposition? Are these emission patterns or meteorological
patterns or biological activity patterns? Some discussion of the importance of these various
temporal scales for the ecological effects modeled is probably appropriate as well. A minor
complaint on the communication of the results: the color scheme for Figures like 3.2-6 etc. is
not intuitive. The scheme used was almost a rainbow-like scale, which is easy to interpret and
would have been fine, but instead green was sandwiched between yellow and orange, breaking
the natural progression of colors (red -> orange -> yellow) that most of us have internalized and
making it harder to visually establish a continuous gradient of concentration changes.
2. Section 3.2.1 describes an approach for evaluating the spatial and temporal patterns for
N and S deposition and associated ambient concentrations in the case study locations.
This document includes the analysis for the Adirondacks case study. Does the Panel
agree with this approach and should it be applied to the other case study areas?
It was a sound approach and a useful exercise that may give as clear a picture of deposition as
we're likely to get. With the additions/changes noted above, I would welcome this analysis for
the other areas.
3. Section 3.2.2 describes the relative contributions of ambient emissions of nitrogen and
ammonia to nitrogen deposition for the case study areas. To what extent is the approach
taken technically sound, clearly communicated, and appropriately characterized?
This was an interesting exercise that was very useful in establishing the relative importance of
NOx and NH3 emissions to overall N deposition and the relative responsiveness of deposition to
changes in emissions. It was very helpful to establish this kind of personal internal calibration
in a strong visual way. It is also a critical comparison to establish in making a strong case for the
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ability of a NOx-concentration based standard to be sufficiently protective, despite our
understanding that impacts are really driven by total nitrogen. Given the lack of spatial and
temporal variability in the contributions of NOx to oxidized N and NH3 to reduced N, those
maps probably don't need to be shown, just described instead. The results look perfectly logical
and convincing, although I resist accepting these results completely until seeing further
documentation of CMAQ's performance. The REA notes that the RSM has been validated for
PM and O3, but it's not clear whether that validation translates to deposition parameters as well.
Presumably the missing section 3.2.2.5 on uncertainty will address some of these issues. Again,
as above, the color scale on all these plots is counterintuitive. Using the color red to depict no
impact and green for 100% impact is contrary to general mapping conventions and at least in my
case, caused me to continually misinterpret the plots.
Case Study Analyses (Attachments 2-6)
6. Att. 2: Are the nationalgeospatial datasets chosen adequate to identify sensitive areas?
Are there other data sets that have not been identified by this analysis that we should
consider? Does the panel agree with this approach or can they suggest alternatives?
I have no knowledge of other datasets that could be useful to this effort. Some of the data were
quite old (1971 for the range of red spruce) and caused me to wonder whether the range could
have changed significantly in the intervening 37 years. Perhaps the authors could comment on
the issues that might be affected by such old observations. Similarly, the dataset on acidophytic
lichens was clearly not complete, or at least spatially representative, and impacts the results.
One can't protect lichens that haven't been identified as sensitive, and the current map, which
shows clusters of lichens within some states but none in neighboring states, strongly implies that
some species have not been identified in those neighboring states.
7. Att. 3: re MAGIC model to evaluate ANC levels in selected streams and lakes in
Adirondacks and Shenandoahs. To what extent is the approach taken technically sound,
clearly communicated, and appropriately characterized?
The selection of MAGIC is appropriate, but this section was poorly written and extremely
confusing, especially the modeling approach and description of MAGIC and ASTRAP. I think
the dates given for scaling the historic data to deposition are wrong in several places, but the text
was too convoluted to tell for sure. Also it would have been nice to see a map or at least a better
description of how the ASTRAP sites are connected to the MAGIC sites. The classes and
descriptions of ANC limits kept changing within the text and figures and should be made
consistent. The discussions of critical load frequently mixed up the concepts of greater than-less
than and above-below, adding to the confusion. It was very difficult to wade through the errors
and try to make sense of what was really being accomplished here. The approach may be
sound, but can't be assessed on the basis of what was presented. It was certainly not
communicated or characterized in a satisfactory way.
8. Att. 4: use of 8MB model to evaluate current deposition on forest soil ANC for sugar
maple in Kane Experimental Forest and red spruce in Hubbard Brook Experimental
Forest. To what extent is the approach taken technically sound, clearly communicated,
and appropriately characterized?
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The selection of the study area was reasonable and the description of the method was clear.
Without results it's not possible to say too much more. The Table 3.1-2 had some numbers that
need to be explained further, however. The range of critical N loads vary by a factor of 10 over
the 3 study periods shown, and each of the methods gives very different results. Why the big
difference? The text mentions biomass changes; is this the sole reason? Is this magnitude of
change in biomass typical? How comparable are the methods? The text in Section 1.1.1 was
unnecessarily repetitive and could be tightened up; no need to quote the ISA at such length.
9. Att. 5: Aquatic nutrient enrichment—evaluate how changes in N deposition affect the
eutrophication index in two estuaries: Chesapeake Bay andPamlico Sound. To what
extent is the approach taken technically sound, clearly communicated, and appropriately
characterized?
10. Att. 6: Terrestrial nutrient enrichment—evaluate effects of N deposition on CSS
community in California and mixed conifer forests in San Bernardino and Sierra Nevada
Mountains. To what extent is the approach taken technically sound, clearly
communicated, and appropriately characterized?
Additional Effects (Chap. 6)
1. Impacts ofS deposition on Hg methylation, impacts of NO on climate change, and impact
of N deposition on C sequestration. Are these effects sufficiently addressed in light of
the focus of this review on the other targeted effects and in terms of the data available to
analyze them?
This was an adequate review of these effects. The focus appropriately belongs on acidification
and enrichment effects.
Synthesis and Integration of Case Study Results into the Standard Setting Process (Chap 7)
1. Purpose is to summarize the case study results and characterize the relationship between
levels of an ecological indicator and the associated degree of ecologically adverse
effects. To what extent is the approach taken technically sound, clearly communicated,
and appropriately characterized? Does the Panel have suggested refinements?
I'm still uncertain about exactly how the case studies ultimately are used. Are they merely for
scientific support and justification, or do the model results from them get incorporated eventually
into a quantitative relationship that can be plugged into the framework presented in Chapter 8?
I think the confusion stems from the incomplete nature of this chapter. When it is fleshed out in
the next version with real data, the application of the case study results should be obvious.
Considerations in the Structure of the NOx/Sox Secondary Standard (Chap 8)
1. Is the suggested overall structural framework for a secondary standard technically sound
and logically presented?
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The recently added Chapter 8 was very lucid and well written, presenting a helpful blueprint for
how to move from ambient concentrations to possible secondary standard. I found no technical
or logical fault in it.
2. Is the description and development of the deposition transformation function (Fig 8.1.1)
between air quality indicators and the deposition metric clear and technically sound?
3. Is the description and development of the ecological effect function (Fig. 8.1.1) between
the deposition metric and the ecological indicator clear and technically sound?
4. Does the discussion adequately capture the potential use of categorical variables versus
continuous variables when accounting for the variability of atmospheric, landscape, and
ecological factors ?
These were all fine.
5. Are there any key elements missing from the framework?
There needs to be a more complete discussion of how a standard can accommodate geographic
variation; i.e., how to equitably control NOx and Sox to adequately protect sensitive areas
without overcontrolling in areas that are far less sensitive to acid deposition. Section 8.3.1 made
reference to varying factors within the transformation function by location, and the fact that
deposition loads will vary by location, but it was not clear from the text how this translates to
variation in the standard. It seems that the standard must account for different concentrations in
different regions, but how that is specified is still pretty fuzzy.
Another big piece that is missing is the discussion of CMAQ (or other model) uncertainties. It
was interesting that this is the first place in the REA (Sec. 8.3.2.1.2) where CMAQ performance
evaluation (or the lack thereof) is mentioned. Given the very heavy reliance of the REA
analyses on CMAQ (a necessary reliance, admittedly), it is critical to have its performance
characterized as thoroughly as possible so that the Administrator and others can assess a
proposed standard's potential for success.
Section 8.3.2.2.2 leaves aggregation methodology as an open research issue. Does this mean it
will be resolved in the next draft by work the staff is doing? If not what are the implications of
leaving this issue unresolved?
6. Does the framework need to be expanded or revised to accommodate the appropriate
consideration of ecological indicators besides ANC when developing a secondary
NAAQSfor NOx and Sox
Isn't that the point of the case studies? It seems premature to answer this question until those
results are complete. ANC seems adequate for acidification effects, but the other case studies
weren't really far enough along to evaluate. The chapter should include some discussion of how
the standard might account for multiple indicators.
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7. Does the panel have any further suggested refinements at this time ?
Section 8.3.2.4 needs additional attention. It mentions possible work on MCIP and CMAQ to
incorporate measurements, which would be great and I highly encourage. But is it really
possible to produce results and incorporate them into the next draft?
Section 8.3.3 on the deposition-indicator links could benefit from a discussion of how influential
the various parameters are on the outcome, at least in a qualitative sense. It would help the
reader (and presumably the Administrator) evaluate which are the critical parameters controlling
the relationship. There also needs to be some discussion or graphical analysis of the
geographic sphere of influence of NOx/SOx concentrations on each sensitive area. For
example, if the indicator were set at an ANC of 50 ueq/L in the Adirondacks, how much would
NOx and Sox need to be reduced to reach that ANC, and over what geographic area?
Somewhere the document needs to lay out that visual frame of reference for the geography of
influence on the sensitive areas. We know that deposition is some function of distance, and that
high concentrations close to a sensitive receptor will be more influential than the same
concentrations far way; how far away is far enough to have negligible impact?
Specific comments, typos, etc.:
p. 3-3, Fig 3.1.2 (also Fig 3.1-5) Avoid use of pie charts, as they make it difficult to make
quantitative comparisons. Bar charts are almost always preferable. The use of 3-D
unnecessarily complicates these figures and also makes it more difficult to visually compare
the slices of the pies.
p. 3-4, lines 12-13: Fig. 3.1-4 actually shows facilities, not annual emissions by state.
p. 3-6, lines 14-16: Is the NEI fire inventory error corrected here? If not, a statement about
the correct magnitude of fire emissions should be added.
p. 3-8, line 9: Figure 3.1-6 shows total N deposition in Ohio and Pennsylvania of >20
kg/ha/yr, definitely much more than the 9.2-9.6 kg/ha/yr cited here. Which is correct? This
and the following figs 3.1-7,8,and 9 are nice but the colors are difficult to distinguish in the
printed version.
p. 3-50, line 1: ARD-> ADR
p. 3-57, line 10: remove question mark
p. 6-7 caption to Fig. 6.1-3: watershed should be plural
p. 6-18, line 6: Not clear what 'further stabilizing soil carbon compounds' actually means.
Do they then have longer lifetimes?
p. 6-23, line 12: Onondagal ->Onondaga
p. 7-1, line 28: area should be plural
p. 8-14: Equation numbers don't follow the text
Attachment 2, p. 2, line 14: remove 'is'
Attachment 2, p. 3, line 19: is this really 51 inches, or should it be cm, as 4.1.11 says about
this same dataset?
Attachment 2, p. 7, line 17: remove 'Sulfur Containing'
Attachment 2, p. 7, line 26: remove 'Nitrogen Containing Chemical Species'
Attachment 2, p. 8, line 9: remove 'deposited'
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Attachment 2, p. 11, line 8: remove 'Nitrogen Containing Chemical Species'
Attachment 2, p. 11, line 18: Containing -> Including
Attachment 2, p. 16, line 4: remove meter
Attachment 3: fix the subscripts and superscripts throughout. Too many grammar errors
and typos to enumerate here - this whole section needs careful editing.
Attachment 3, p. 6, line 24: deposition is more like 17 and 13 kg/ha according to the Figure
3.1-1, not 15 and 10.
Attachment 3, p. 8, line 4: deposition is more like 18 and 11 kg/ha according to Fig. 3.2-1.
This makes me distrust the % declines in these species, here and on p. 6, but I didn't
recalculate them.
Attachment 3, p. 12, Fig. caption: 12 streams are shown, not 13. Lots of other typos in this
caption.
Attachment 3, p. 16, line 26: >50 should be <50
Attachment 3, p. 17, lines 6-8: Fig. 4.1-2 doesn't imply that biota are not often harmed
below and ANC of 100, only that the harm is less severe than for lower ANC
Attachment 3, p. 17, line 12: It doesn't make sense to say that an ANC of 0 protects surface
waters from becoming acidic, waterbody
Attachment 3, p. 17, line 17: change 'deposition - critical load' to 'deposition less than
critical load'
Attachment 4, p. 1, line 6: should be 'sulfur loads to and effects on a chosen...'
Attachment 4, p. 10, line 4: on -> at
Attachment 4, p. 11, line 16: not clear, reword
Attachment 4, p. 11, lines 21-22: not clear, reword
Attachment 4, p. 23, line 22: HBEF
Attachment 4, p. 25, line 8: litterfall
Attachment 4, p. 33, line 17: put weathering on its own line
Attachment 4, p. 38, line 13: Arrhenius
Attachment 4, p. 48 and 49: It would be helpful for these figures to include the HBEF as
well; its very hard to place it accurately given the map on p. 21
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Dr. Naresh Kumar
COMMENTS ON SECTION 6.1. SULFUR AND MERCURY METHYLATION
GENERAL COMMENTS
The section begins with a segment on the chemistry and physics of mercury atmospheric
transport, fate, and deposition, followed by a more detailed segment discussing the chemical
determinants of mercury methylation.
The two segments of the section differ greatly in their accuracy, completeness, and
understanding of mercury chemistry and environmental behavior. While the second part, on
mercury methylation specifically, is generally complete and accurate, the first, background,
segment has a number of factual errors, misinterpretations, and erroneous conclusions in it.
As two examples, the first segment presents an erroneous picture of the behavior of elemental
mercury (or Hg°) in the environment, and of "methylmercury" (dimethylmercuric salts) in
organisms. In the first case, Hg° is presented as being "reduced" in surface ecosystems to
become methylmercury; in reality, Hg° is the reduced form, and plays no part in methylation,
which occurs through bacterial action on the oxidized form, divalent mercury (or Hg+2 in the
text). In the second case, methylmercury is openly stated to be "lipophilic," or preferentially
attached to fatty tissues in fauna, when in fact methylmercury is lipophobic and associated with
protein sulfhydryl groups, in muscle tissue.
The entire section need to be thoroughly reviewed and rewritten from the beginning to more
accurately reflect our basic understanding of mercury chemistry, transport, and fate in the
environment. Specific comments on the text follow.
SPECIFIC COMMENTS
• To date, there has been no unequivocal demonstration of sulfate limitation in US or
global waterways such that natural sulfate addition or subtraction alone has produced a
change in methylation rates or mercury in fish. Such demonstrations have occurred only
in experimental manipulations of microcosm ecosystems. Since fish take up only a
fraction of the methylmercury in the water column and biota of lower trophic levels, there
is always an excess of MeHg in studied water bodies. And downtrends in sulfate addition
have always been matched by downtrends in divalent mercury deposition, so that it is not
possible to separate sulfate availability from divalent mercury burden.
• It is mentioned that "Mercury concentrations have increased approximately 2 to 5 times
since the onset of the industrial revolution and appear in even the most remote locations
on the Earth (Munthe et al, 2007; U.S. EPA, 2006). " The accepted global average ratio
of atmospheric mercury mass now compared to the period prior to the Industrial
Revolution is in the range of 2 to 3, not 2 to 5. Ratios higher than 3 can be found in local,
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single-instance measurements of concentrations in, e.g., an ice core, but these are
characteristic of individual locations and not the global balance of mercury.
It is stated in the text that "In the United States, the primary source of mercury to
ecosystems is atmospheric deposition due to coal combustion (e.g., coal-fired electric
utilities). Other sources include municipal waste combustion, medical waste incineration,
chlor'-alkali plants, and industrial boilers. " This sentence appears to propagate the
common misconception that mercury emissions (anywhere) are proportioned exactly the
same as mercury deposition (anywhere else). This is obviously incorrect, since both total
and wet deposition of mercury at any location on earth (or in the United States) is made
up of contributions from hundreds of sources at widely varying distances upwind, and is
not linearly proportional to the fraction of total emissions each source, or source type,
makes up. Therefore, it should be noted that a significant amount of mercury depositing
within the United States originates in other countries, primarily mainland Asia. The
sources of mercury depositing to U.S. ecosystems varies widely, both geographically and
by source, depending on the proximity of U.S. sources and the precipitation climatology
of the setting.
It is mentioned that, "Depending on the paniculate association and oxidation state,
atmospheric mercury particles can remain suspended in the atmosphere for more than 2
years (Evers et al, 2007; U.S. EPA, 2006)" This sentence should be rewritten or deleted.
There is no relation between "particulate association" (an unexplained term) and
oxidation state for mercury; most of the mercury bound to particles is divalent mercury
(or "Hg+2" as used in the report). But the statement that such particle-bound mercury has
an atmospheric lifetime of more than 2 years is not true; due to gravitational settling,
coagulation, etc., Hgp has an average lifetime in the atmosphere of several days to about
two weeks, no more. And no source of mercury emissions to the atmosphere issues more
than about 3% of mercury mass in the form of particle-bound mercury, in any case. It is
suggested inserting something like this: "There are three primary forms of mercury in
atmospheric sources of the substance: elemental mercury, reactive gaseous mercury, and
particle-bound mercury. Once emitted, the three forms behave very differently in the
atmosphere and deposit over very different geographic patterns. It generally takes
hundreds or thousands of miles for half of the emitted gaseous elemental mercury to
deposit to ground level, while half of the reactive gaseous mercury will deposit within
about 150 miles of the source. Particulate-bound mercury, generally 3 percent or less of
the emitted mercury mass, deposits in intermediate patterns (M. Cohen, 2004). "
The text states that, "When deposited into terrestrial and aquatic ecosystems, elemental
mercury is oxidized to reactive mercury (Hg+2) (Ambrose et al., 2005; U.S. EPA, 2006). "
A number of statements need to be corrected or nuanced in this passage. Any "deposition"
of elemental mercury occurs by gas-phase transfer at ground level from regions of higher
concentration (that is, the atmosphere) to regions of lower concentration (to plant stomata,
soil pores, interstitial spaces, etc.), basically a down-gradient mass transfer. There is nearly
no oxidation of elemental mercury to the divalent form occurring at the ground surface;
more likely is removal of elemental mercury back to the atmosphere by revolatilization, or
evasion. There may also be a net output of elemental mercury from the surface by
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insolation (solar radiation) producing photoreduction of divalent mercury, or demethylation
and photoreduction of monomethylmercuric halides.
• The entire sentence where methylmercury is stated to be "lipophilic" needs to be
corrected. First, mercury cannot be "reduced and methylated to methylmercury"; the
reduced form of mercury is the insoluble elemental mercury, Hg°; because of its
insolubility in water, it is unavailable to sulfate-reducing bacteria for the methylation
process. Of the "deposited mercury pool," typically half or more is (wet-deposited)
divalent mercury, most of the remainder dry-deposited elemental mercury; of the amount
of divalent mercury dissolving in water bodies, between 1% and 10% may be methylated
and dissolved in the water column. Of this 1% to 10% (depending on the particular water
chemistry; higher fractions for more anoxic waterways), perhaps 10% of that (or 0.1% to
1% of the dissolved divalent mercury) may be taken up into the food web. Second,
mercury is most certainly TVOriipophilic, but rather lipophobic. it attaches to
protein-based sulfhydryl groups and resides primarily in muscle and nerve tissue ("fish
flesh"). This distinction is important because it is the root of the finding that cooking fish
which may be mercury-laden will in fact not decrease, but increase, the concentration of
the mercury in the cooked product. Any fat that is cooked off is mercury-free, and the
lower weight cooked fish remaining has the same mass of mercury as prior to cooking,
but in a lower-weight portion offish (with some fat and water mass cooked off), hence
higher net mercury concentration.
• There seems to be a faulty reference in the sentence "The majority of U.S. waters are
sulfate-limited (Harmon et al, 2007); therefore, decreases in sulfate are likely to
promote decreases in methylmercury. " Harmon et al., 2007, "Using Sulfate-Amended
Sediment Slurry Batch Reactors to Evaluate Mercury Methylation," Arch. Environ.
Contam. Toxicol 52, 326-331 (2007); [DOT: 10.1007/s00244-006-0071-x] does not have
a single word to say about sulfate-limited waterways. The term "-limited," in fact, occurs
only once in the document, in the introduction, with no reference to the state of U.S.
waters.
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Dr. Myron J. Mitchell
General Comments (For these general comments my responses are in italics}
The document and associated attachments are extensive and it is a major challenge to provide a
cohesive approach to presenting this information. I recognize the difficulty and complexity of
pulling all of this together. The potential for providing clearer linkages in this document to the
"Integrated Science Assessment for Oxides of Nitrogen and Sulfur - Environmental Criteria "
may help maintain focus and reduce the size of the document. More consistency is needed in the
use of terms such as oxides of sulfur, oxides of nitrogen, sulfur oxides, nitrogen oxides, SOX, NOX,
etc. Also, in the document there are differences in criteria for sensitivity of various parameters
such as ANC. Careful editing would help focus the document and reduce redundant information.
The draft document has many noun trains such as "draft revised criteria document".
Responses to Charge to the CASAC NOX/SOX Secondary Review Panel
Scope of the review (Chapters 1 and 2):
1. Chapters 1 and 2 provide the background, history, and the framework for this review,
including a discussion of our focus on the four key ecological effect areas (aquatic acidification,
terrestrial acidification, aquatic nutrient enrichment, terrestrial nutrient enrichment). Is this
review appropriately focused in terms of the targeted effect areas and in terms of characterizing
the important atmospheric and ecological variables the influence the deposition and, ultimately,
the ecological impacts of nitrogen and sulfur? Does the Panel have any further suggested
refinements at this time?
Chapter 1 needs a more balanced introduction with respect to the impacts of S andNgaseous
constituents and deposition with greater attention earlier in each chapter on the effects ofN on
ecosystem structure and function including the alteration of species composition. In Chapter 2
(Section 2.4) the description of errors in the analyses needs a more rigorous approach that more
clearly identifies specific issues related to sources and amount of errors. In its current form
Chapter 2 provides very broad descriptions that do not clearly identify the major sources of
error that are important to the current assessment. Possibly reference to subsequent chapters
that more clearly delineate these errors would be helpful.
Air quality analyses (Chapter 3):
1. To what extent are the air quality characterizations and analyses presented in Chapter 3
technically sound, clearly communicated, appropriately characterized, and relevant to the review
of the secondary NAAQS for NOX and SOX ?
The terminology and analyses associated with "policy-relevant background concentrations" is
confusing. Some consideration is needed of the adequacy of the current monitoring network in
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evaluating air quality especially in relationship to measurements in urban settings.
2. Section 3.2.1 describes an approach for evaluating the spatial and temporal patterns for
nitrogen and sulfur deposition and associated ambient concentrations in the case study locations.
This draft document includes the analysis for the Adirondacks case study. Does the Panel agree
with this approach and should it be applied to the other Case Study Areas?
This can be a helpful approach. However, within each of these regions there have been other
measurements made of associated parameters including precipitation amount, atmospheric
deposition, etc. It does not appear that any substantial attempts are being made in this document
to compare these current results with previously published results? There is a major emphasis
on providing both spatial and temporal patterns using the CMAQ modeling results. Shouldn 't
these modeling results be compared with other results of deposition measurements for this
region? Having some comparisons with these other measurements would be helpful in evaluating
the CMAQ deposition estimates. The issues and problems associated with making measurements
of air pollution concentrations and converting them to deposition by various inferential
procedures needs to be clearly articulated.
3. Section 3.2.2 describes the relative contributions of ambient emissions of nitrogen and
ammonia to nitrogen deposition for the case study areas. To what extent is the approach taken
technically sound, clearly communicated, and appropriately characterized?
Clarification is needed on the relative importance of the emission sources including the accuracy
of these emission estimates, atmospheric chemical conversions and the estimates of deposition
velocities in evaluating the results of these model outputs. Too much of this section describes
model output with little supporting evidence of the relationships noted.
Case Study Analyses (Attachments 2-6):
These attachments are extensive and it would be most helpful if they were more targeted to the
issues and needs of the "Risk and Exposure Assessment to Support the joint Review of the NO 2
and SO 2 Secondary National Ambient Air Quality Standards".
1. Attachment 2 presents a GIS analysis to define geographical areas that are sensitive to
acidification and nutrient enrichment. Are the national geospatial datasets chosen adequate to
identify sensitive areas? Are there other data sets that have not been identified by this analysis
that we should consider? Does the Panel agree with this approach or can they suggest
alternatives?
In general, the selected regions and associated data sets appear to be appropriate for this
analysis.
2. Attachment 3 presents our current progress on evaluating the effect of aquatic
acidification in the Adirondacks. It describes the use of the MAGIC model to evaluation ANC
levels in selected lakes and streams in the Adirondacks and Shenandoahs. To what extent is the
approach taken technically sound, clearly communicated, and appropriately characterized?
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There is some differences in the deposition estimates being used for estimates using the MAGIC
versus other approaches in the document (e.g., ASTRAP versus CMAQ). Will this result in some
issues relating to congruity of analyses in the document? These analyses have a specific focus
on the Grimm and MAGIC models. There have been other efforts to evaluate acid
rain/biogeochemical responses in each of these sites (especially the Adirondacks) and hence it
would be useful to include some of these other results to indicate either differences or support of
these current modeling efforts. In these discussions different levels ofANC are suggested that
differ than for other sections in the document. A more consistent approach is needed on setting
the ANC limits of concern with respect to sensitivity to acidification and recovery from
acidification. Possibly a separate section is needed with respect to ANC and its application to
evaluating acidity and the various levels that are used. This would need to be included before
the case studies section.
3. Attachment 4 presents our current progress on evaluating the effect of terrestrial
acidification. It outlines a plan to use the Simple Mass Balance Model to evaluate current
deposition levels on forest soil ANC for sugar maple in the Kane Experimental Forest and red
spruce in the Hubbard Brook Experimental Forest. To what extent is the approach taken
technically sound, clearly communicated, and appropriately characterized?
This portion of the document is highly uneven with in some cases substantial detail provided and
in other places there are broad generalizations. This makes it difficult for the reader to
ascertain the salient points.
4. Attachment 5 presents our current progress on evaluating the effect of aquatic nutrient
enrichment. It outlines a plan to evaluate how changes in nitrogen deposition affect the
eutrophication index in two estuaries: the Chesapeake Bay and Pamlico Sound. The analysis will
model one stream reach (Potomac River and Neuse River) to determine the impact on the
eutrophi cation index for the estuary. To what extend is the approach taken technically sound,
clearly communicated, and appropriately characterized?
The Chesapeake Bay has been the focus of considerable efforts relating to the effects of nitrogen
loading on eutrophication. There have been extensive investigations on this site and there are
extensive data sets that can be used in the analyses. A major drawback of this site, however, is
that it is not likely that atmospheric nitrogen loading is a major component of the total nitrogen
loading. Hence, the Chesapeake Bay will not be very sensitive to changes in atmospheric
nitrogen inputs. Although the information on the Neuse River is less extensive, there are similar
problems with the overall importance of atmospheric N loading. In attachment 5, page 20 it is
indicated that "Previous studies have estimated that wet atmospheric deposition of nitrogen
(WAD-N), as deposition of dissolved inorganic nitrogen (DIN: NO''3 , NHs /NfT ) and dissolved
organic nitrogen, may contribute at least 15% of the total externally supplied or "new " nitrogen
flux to the coastal waters of North Carolina ".
5. Attachment 6 presents our current progress on evaluating the effect of terrestrial nutrient
enrichment. It describes an approach to evaluate the effects of nitrogen deposition on the Coastal
Sage Scrub community in California and in mixed conifer forests in the San Bernardino and
Sierra Nevada Mountains. To what extent is the approach taken technically sound, clearly
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communicated, and appropriately characterized?
The selection of the Coastal Sage Scrub community in California and in mixed conifer forests in
the San Bernardino and Sierra Nevada Mountains needs some further justification versus other
regions including the alpine andsubalpine communities of the eastern slope of the Rocky
Mountains in Colorado. These sites in California are certainly important and interesting sites,
but it may be difficult to separate the effects of nitrogen deposition versus other air pollution
components, especially ozone.
Additional Effects (Chapter 6):
1. In this chapter, we have presented results from some initial qualitative analyses for
additional effects including the impact of sulfur deposition on mercury methylation, the impact
of nitrous oxide on climate change, and the impact of nitrogen deposition on carbon
sequestration. Are these effects sufficiently addressed in light of the focus of this review on the
other targeted effects and in terms of the available data to analyze them?
These descriptions seem adequate, but certainly the issues go beyond those associated with
carbon sequestration. Some additional discussion of the importance of mercury being found in
other components of the ecosystems including song birds should be included.
The purpose of Chapter 7 is to summarize the Case Study results and characterize the
relationships between levels of an ecological indicator and the associated degree of ecologically
adverse effects. To what extent is this approach technically sound, clearly communicated and
appropriately characterized at this point of the review? Does the Panel have any further
suggested refinements at this time.
In its current form this Chapter is highly descriptive. Future revisions will need to include more
specific quantitative results that show a clear relationships to the assessment.
Chapter 8 begins to explore how a secondary NAAQS might be structured to address the targeted
ecological effects discussed in the risk assessment. The next draft of this document will include
one or more examples of how this structure might be used to related specific levels of air quality
indicators with a corresponding ecological indicator for a given location and/or scenario. To
what extent is the described approach technically sound, clearly communicated and appropriately
characterized at this point of the review? Specifically, we are asking:
• Is the suggested overall structural framework for a secondary standard technically sound
and logically presented?
• Is the description and development of the deposition transformation function (Figure
8.11) between air quality indicators and deposition metic clear and technically sound?
• Is the description and development of the ecological effect function (Figure 8.1-1)
between the deposition metric and ecological indicator clear and technically sound?
• Does the discussion adequately capture the use of categorical variables versus continuous
variables when accounting for the variability of atmospheric, landscape and ecological
factors?
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• Are any key elements missing from the framework?
• Does the framework need to be expanded or revised to accommodate the appropriate
consideration of ecological indicators besides ANC when developing a secondary
NAAQS forNOx and SOx?
• Does the panel have any further suggested refinements at this time?
Providing a clear scientific linkage that is policy relevant between concentrations ofSOx and
NOX and resultant S and N deposition and subsequent translation to ecosystem level effects is a
major challenge. There are good linkages between concentrations ofSOx andNOx and
deposition, but the linkage to ecosystem level effects is more complicated due to inherent
variability across the United States of the sensitivity of these systems. There are major problems
with respect to both having confidence in calculated deposition velocities and how to ascertain
"functional forms ". A clear delineation of which ecosystem types are most important with
respect to specific ecological effects (e.g., acidification in the northeast, N deposition affecting
biological community structure in the mountain west, etc.) is required. Such categorization will
be very important in setting secondary standard(s) that will be relevant to those effects which are
of greatest importance to various regions that have different relative representations of various
ecosystem types.
Specific Comments in which italics indicate specific changes.
Page(s) Lines(s) Comment
xv 3-5 Why should this definition only include terrestrial ecosystems?
1-1 8 Change to "The NAAQS have been established for pollutants".
1-2 8 Change to "complex interactions among relevant chemical species
of.
1-3 10 Clarify more specifically who is "we". Do you mean EPA?
1-3 19 "Chapter 2" should be in bold font.
1-4 1-5 This does not agree with provided definition on nitrogen
enrichment (page xv, lines3-5)
1-5 13 Change to "This draft".
1-5 15 Delete "held".
1-5 24 Change to "identified the critical components to be".
1-5 25 Specify the title of the "Administrator" here and elsewhere in the
document.
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1-6 5 Change "NAAQS for NO2 was set at 0.053 ppm".
1-6 10 Change to "secondary NAAQS values for 862 under".
1-6 13 Change to "of evidence from vegetation effects ".
1-6 19 Change to "EPA was aware that SOX has other".
1-6 25 Here and elsewhere be consistent in the use of terms SOX and
sulfur dioxides.
1-7 17 Change "completed by EPA at this time".
1-7 20-23 Change to "Administrator's conclusions that (1) based upon the
then-current scientific understanding of acid deposition, it would
be premature and unwise to prescribe any regulatory control
program, and (2) when the scientific uncertainties had been
substantially reduced through ongoing research efforts, EPA would
draft and support an appropriate set of control measures".
1-8 3 Change to "Due to the complexities and substantial remaining".
1-8 20-21 Change to "long-term".
1-9 28 Be more explicit with respect to this "Federal Register notice".
1-10 7 Why "beyond full implementation of Title IV...."?
1-10 7 Change "to presented in the 2005 NAPAP Report".
1-10 10 Be more specific with respect to which "recent reports".
1-10-11 It would preferable to start with a clearer definition of the different
forms of nitrogen oxides and then discuss some of the confusing
terminology.
1-11 6 Are another group of individuals using different terminology for
nitrogen oxides?
1-11 12 Change to "deposition of reactive nitrogen"
1-11 19 Change to "In many regions".
1-11 22 Change to "assessing the impacts of nitrogen deposition".
1-11 24-26 This is not true most research does consider separately the oxidized
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and reduced forms of nitrogen inputs especially for natural
ecosystems. In many cases the total input of reduced nitrogen is
less well known than that of oxidized nitrogen.
1-12 13-14 With reduction in S deposition the relative importance of N
deposition in contributing to acidification has increased. This
should be noted in this introductory information.
1-13 5 The statement "sometimes limiting" with respect to N is
misleading. Nitrogen is often a limiting nutrient with respect to
primary production in terrestrial ecosystems. Even though N may
be a limiting nutrient does not necessarily imply, however, that
there may not be substantial ecosystem damage. Changing N
inputs can alter ecosystem structure including altering the system
from a more desirable state. Such factors are especially important
with respect to the evaluation of N deposition in the western U.S.
Such secondary effects need to be considered in setting standards.
1-13 6 Change to "acidification, nutrient enrichment, eutrophication, and
changes in species composition".
1-14 7-9 Other effects including changes in species composition and
community structure need to be included for both terrestrial and
aquatic systems especially associated with N inputs.
1-14 10-24 Clearly there have been substantial studies of acidic deposition
effects in the eastern U.S., but some consideration is needed of
effects in the western U.S. where the effects appear to be
substantially different especially with respect to N deposition
influences.
1-14 26 Does the reference to "high elevation lakes" refer to the western
U.S.?
1-14 31 In this section the issue of changes in "community composition" is
mentioned and this needs to be included earlier in the document.
1-15 1-4 This statement on alteration of aquatic communities needs to be
made congruous with earlier statements on overall effects of S and
N deposition.
1-15 22 Change to "alpine".
1-16 5 Provide some information on what are these "other factors". Do
you mean periods of relatively high microbial activity?
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1-16 8 Be more explicit on the relationship (e.g., positive or negative)
between "oxygen content, temperature, pH, and supply of labile
organic carbon".
1-16 11 Be more explicit on what are these conditions. Do you mean for
conditions the amount of wetlands and linkages to drainage
waters?
1-16 Figure 1.3-3 should explicitly have a category for changes in species
composition that may differ from altered biodiversity.
2-1 9-12 This listing needs to explicitly include effects on community
structure and species composition.
2-1 16-18 This statement begins to raise the issue associated with different
effects depending on region in the U.S.
2-1-2 The absence of case studies in the Rocky Mountain west is
problematic.
2-4 This introduction can be improved with a more focused approach.
There is considerable repetition in this part of the document.
2-5 4-5 Change to "data were not sufficiently available to perform".
2-5 18 Clarify in scaling-up clarify how this will be done with respect to
sensitive areas (e.g., will this be done for all sensitive areas or will
the scaling be a function of other sensitive areas with similar
characteristics?
2-6 27 Change to "need for them".
2-6 28 A citation is needed for the "MEA" here. Later it is indicated that
MEA (2005).
2-7 3 Care should be made in the use of the term "regulating" since this
term has a different meaning in the context of environmental
regulations such as those associated with laws formulated by the
EPA. Maybe a clarifying phrase is needed to avoid any confusing
recognizing that the term regulation has a different meaning in an
ecological context.
2-6 14 Are there different references for the MEA? Here it is indicated:
MEA, 2005b. Also see Line 17 (MEA, 2005b).
2-7 This section needs some further articulation with respect to the
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description of ecosystem services. Is this description based solely
on what is provided in (U.S. EPA, 2006)? It would be helpful to
provide some further references that link these statements to other
informational sources.
2-7 16 Change to "interest in the risk assessment described in the current
document'.
2-7 20-22 A better description is needed that clarifies the association of NOX
deposition and eutrophication.
2-7 23-25 This statement is poorly worded.
2-7 26-31 The wording of this section needs much better clarification. It is
confusing whether a linkage or several linkages are being
evaluated.
2-8 Figure 2.2-2 Ecosystem Services: the ecological processes or functions having
monetary or non-monetary value to individuals or society.
2-9 1-2 Change to "We have begun identifying the primary ecosystem
service(s) affected by either acidification and/or enrichment and
for major ecosystem types and components (i.e., terrestrial
ecosystems, soils".
2-9 4 Change to "The impacts affecting various".
2-9 6-7 Change to "These impacts on ecosystem services will be".
2-9 10 Change to "tourism. Effec ts on fisheries (decreased".
2-9 21 Change to "tourism. Effects on fisheries".
2-9 27-28 Change to "hazard mitigation. Methods for evaluating linkages to
measurements and ecosystem services may include".
2-10 5 Clarification is needed on what is meant by "community".
2-10 7 Change to "changes in stand density, shifts in". Densification is
jargon. Change to "shifts in lichen community species
composition".
2-10 14 Delete "intake".
2-10 15-16 Why distinguish between "Native Americans and Alaska native
Villagers"?
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2-13 2-4 Change to "Our approach in evaluating risk assessment relies
upon various analytical tools and techniques, data sources, and
other forms of analyses each of which has inherent uncertainties ".
2-13 6 Change to "affect the level of its response".
2-13 10-11 This is not a very succinct or complete description of the errors
associated with modeling approaches.
2-13 12 Change to "involved with the transformation and fluxes of nitrogen
and sulfur constituents'".
2-13 14-15 It would be more helpful to be more explicit in describing the
sources of uncertainty. For example with respect to deposition,
wet deposition of S and N can be relatively well characterized
compared to dry deposition. The major issue associated with the
errors related to dry deposition are associated mostly with the
modeling of deposition velocities. Also, be more specific in what
is being implied with the use of the term "ecological modeling".
2-13 14-21 This section needs to include more specific information. It would
be most helpful to explicitly state the major sources of error in risk
estimates.
2-13 22-30 These statements are very general. At a minium specific examples
need to be supplied that show actual examples of these errors and
importance to the assessment.
2-14 2-3 It is anticipated that these discussions will provide sufficient detail
on these sources of error in risk assessment.
2-14-15 References should also include citations to the actual literature and
not rely solely on EPA documents.
3-1 10 Change to "The deposition results".
3-1 26 Change to "The total amount of NOX emitted in the USA in 2002".
3-2 3-4 Change to "primary emitters of NOX, mainly as NO and
3-2 5 Change to "utilities, with additional contributions".
3-2 9 Change to "remainder of anthropogenic emissions".
3-2 10 Delete "component".
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3-2 15-16 Delete "in the pie charts in".
3-2 16-17 Change to "Results are shown on both a national basis (contiguous
states only) as well as for the eastern".
3-2 18 Delete "For this display".
3-3 1-2 Delete "Note that emissions from Alaska and Hawaii are not
included in any of these charts".
3-3 5-6 (not shown) with the on-road sector being the largest contributor,
followed by emissions".
3-3 8 Change "overall" to " 'national' .
3-3 12 The figure caption needs more information (e.g. that Hawaii and
Alaska are excluded in these results).
3-3 15 Change to "contiguous states".
3-4 3 Change to "emissions^row fertilized".
3-4 5 Clarify what is meant by "30%-70%". Does up to 70% of the
waste mass be converted to emitted NH??
3-4 9 Change to "impact from the input of total reactive".
3-4 10 Explicitly state what is meant by "This".
3-4 12 Change to "Total USA emissions of.
3-5 9 Change to "utilities using coal" .
3-5 12 Change to "up to
3-5 13 This becomes a little confusing since the figure does not provide
emission data from Hawaii and Alaska. Why not include values
for these states in these figures.
3-5 13-14 Sulfur is found in other forms besides amino acids in vegetation so
change to "Sulfur is a macronutrient (typically being 1 to 2%) and
is released as SC>2 if vegetation is combusted (Levine and Pinto,
1998)". Also, there can be other forms of gaseous releases of
sulfur components from vegetation (as well as soil) including H2S,
COS, methyl mercaptan, etc. I am not sure where in the document
these biogenic sulfur sources should be included.
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3-6 1-2 Delete since information has been included in my suggested
modification.
3-6 3-6 Change to "Theproportion of SC>2 emissions from major sources
are shown in Figure 3.1-5 both on a national total basis well as for
the eastern and western United States".
3-6 6 Why not include Alaska and Hawaii for completeness?
3-6 14-16 The relative importance of this error needs to be stated explicitly.
3-7 2-5 Not sure the term "policy-relevant" is a useful term with respect to
defining background concentrations. What is the basis of the actual
value being used? Is it based on a specific time period or some
calculation that attempts to separate out natural versus
anthropogenic emissions? How can the general effects of N
fertilizers and N atmospheric deposition in affecting NC>2 flux be
evaluated? Is this 100 ppt based on some type of area weighted
basis or some other form of calculation?
3-7 4 Delete "policy-relevant"?
3-7 25 Change to "This source distinction and quantification will".
3-8 13-14 Further information should be provided on the source and methods
for estimating these deposition values. This information is
provided later on page 3-13. This information should be provided
earlier in the document.
3-8 19 Not sure what "Great Waters" means.
3-8 19-23 References are needed here.
3-9 Figure 3.1-6. Reduce the significant digits in the figure legend to nearest l/10th.
3-10 Figure 3.1-7. Reduce the significant digits in the figure legend to nearest l/10th.
3-11 Figure 3.1-8. Reduce the significant digits in the figure legend to nearest l/10th.
3-11 9-10 Further details on how these deposition estimates were derived
should be provided. This information is provided later on page 313.
This information should be provided earlier in the document.
3-12 Figure 3.1-9. Reduce the significant digits in the figure legend to nearest l/10th.
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3-12-13 See previous comments on the placement of this information
within the document.
3-12-16 Isn't much of this information relevant to the overall predictions of
N and S deposition. It was not clear why this more extended
discussion was focused on the case studies. Was there a different
type of analyses done for deposition for the case study regions than
for the overall U.S.?
3-16 Aren't all these abbreviations already provided and hence Table
3.2-1 can be deleted.
3-16 Are these formulas included to show the conversions from formula
compound mass to nitrogen or sulfur mass? If this is there only
use then Table 3.2-2 should be deleted.
3-17 11 Has the western case study been identified?
3-20 Within each of these regions there have been other measurements
made of associated parameters including precipitation amount,
atmospheric deposition. Is there any attempt being made in this
document to compare these current results with previously
published results?
3-23 There are well established geographic patterns in N and S
deposition across the Adirondacks. Shouldn't these be
acknowledged? There has also been substantial work on deposition
estimates in the Adirondacks using other approaches. For wet only
deposition for example see: Ito, M., MJ. Mitchell and C.T.
Driscoll. 2002. Spatial patterns of precipitation quantity and
chemistry and air temperature in the Adirondack Region of New
York. Atmospheric Environment 36:1051-1062. Also other
studies have evaluated the relative contribution of wet and dry
deposition. See for example: Mitchell, M.J., C.T. Driscoll, J.
Owen, D. Schaefer, R. Michener, and DJ. Raynal. 2001 Nitrogen
biogeochemistry of three hardwood forest ecosystems in the
Adirondack Mountains. Biogeochemistry 56: 93-133. Would
some comparisons with other investigations be warranted?
3-25 This repeats a previous comment with respect to the inclusion of
previous analyses of these regions in these cases studies.
3-26-53 There is considerable detailed treatment of the results provided by
the CMAQ modeling including temporal and spatial results. With
so much emphasis on these model results it would be useful to
provide some other confirmation of these deposition values.
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3-54 14-15 This is not entirely true. There can be instances were ambient
concentrations of NOX and SOX are directly deleterious. These
conditions, however, have not been generally found in the USA
during the period of concern associated with acidic deposition
effects. For Europe conditions in the "black-triangle" and other
centers of high pollutant concentration there were direct impacts
especially associated with SOX.
3-55-70 The format and output of the CMAQ modeling runs are provided
in some detail. Some further comparison of the CMAQ results,
especially, in the areas of test cases, would be helpful in providing
some objective measurements of the model results.
3-70-72 The model results need to be verified with actual data that show
these relationships. Clearly the model functional relationships and
parameterization will effect overall model output. It is important
that it be clearly identified when model outputs are producing
results that have been verified elsewhere or whether there are
currently no empirical and experimental results that provide data to
verify these results. Such arguments can also be made for the other
N gaseous constituents.
3-70 16 It is suggested that there is "statistical imprecision in the
modeling". There are other important sources of model error that
need to be considered including uncertainty in model formulations.
3-82 7-9 Statements such as "Figure 3.2-55 shows that NOX emissions
account for almost all oxidized nitrogen deposition in the
Adirondacks Case Study Area, while Figure 3.2-56 shows that
NHs emissions account for almost all reduced nitrogen deposition"
have important implications with respect to making
recommendations associated with NOX emission controls. Are
these results verifiable and can the emissions also be linked to
specific geographical areas?
3-87 How are these high emission locations ascertained? Is this a
function of the location of specific monitoring locations (e.g.,
CASTNET sites).
3-112 This section on uncertainty (3.2.2.5) that has yet to be completed
needs to include not only statistical issues, but also uncertainties in
the model formulations and associated parameters.
3-113-114 This is a relatively limited reference list with considerable reliance
on EPA documents. This section would be strengthened by
inclusion of results from the peer reviewed scientific literature that
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support the suggested findings.
4-1
5-1 The sections on "ACIDIFICATION" and "NUTRIENT
ENRICHMENT" include only outlines, but the suggestion of the
importance of providing uniform terminology is encouraging.
6-1-10 This section gives a useful review of recent findings linking the
cycling of S and Hg. This section also includes more references to
the referred literature related to this topic
6-10-13 The section on NITROUS OXIDE provides additional information
on this N gas and provides a clear indication of the importance of
this gas including its linkage with N deposition and is important
role as a "greenhouse" gas.
6-13-18 The synopsis on CARBON SEQUESTRATION provides a useful
overview of important interactions between N deposition, warming
and the carbon cycling in terrestrial ecosystems. This is a very
large and important subject area. As suggested a detailed analyses
is beyond the scope of this review. The term carbon sequestration
does not really capture the total content of this section.
6-19-22 More emphasis in the description of aquatic effects should be
placed on changes in the phytoplankton community structure that
has been most noted in the western U.S.
7-1
7-15 In its current version this "Synthesis and Integration of Case Study
Results" is highly descriptive. This will need to be improved with
specific quantitative results that show a clear relationships to the
assessment.
8-1
8-30 Clearly providing a clear scientific linkage that is policy relevant
between concentrations of SOX and NOX and resultant S and N
deposition and subsequent translation to ecosystem level effects is
a major challenge. Clearly there are good linkages between
concentrations of SOX and NOX and deposition, but the linkage to
ecosystem level effects is more complicated due to inherent
variability across the United States of the sensitivity of these
systems to acidification, eutrophication and changes in biotic
composition. It will be important to formulate an approach that
takes into account these geographical patterns of sensitivity.
8-4-5 Figure 8.1-1 needs to indicate in some format that these ecological
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indicators may not be constant over the United States (e.g., N
deposition levels with respect to changes biotic community
structure being more sensitive in the Mountain west than the
eastern U.S.). These issues are outline on lines 1-7, page 8-5.
8-5 22 The problem in not including reduced N chemical species in any
formulations associated with N deposition effects is highly
problematic. I am not sure it is feasible to focus solely on NOX.
8-9 There are major difficulties in setting national standards for SOX
and NOX concentrations without taking into account regional
effects.
8-13 As suggested the development of these "functional forms" will be
critical and may have both spatial as well as temporal components.
8-13 Clearly EPA is making heaving reliance on the CMAQ model
suggesting the importance of validating results using other
approaches and the linkages between gaseous concentrations and
specific deposition levels.
8-14-17 The issues of deposition velocities are not trivial. For example
look at the differences in deposition associated with the estimates
at the same site for CAPMoN and CASTNET. Although
CAPMoN and CASTNET provide similar concentrations of gases
the deposition velocities are higher for CAPMoN verus
CASTNET.
8-23 The discussion of uncertainties needs to include the various issues
associated with the calculation of deposition velocities.
Attachments
2, pg 2 5 Change "to reflect most recent conditions".
2, pg 2 14-15 Not sure that there is a relationship between steepness and base
cation leaching rates versus the role of slope in affecting the
contact of drainage waters to soils and the relative contributions of
ground waters to drainage with groundwaters generally being more
rich in base cations than waters derived from shallower soil
sources.
2, pg 3 30 Isn't a threshold of 400 [j,eq/L or less considered acid sensitive?
Would a threshold of 100 ueq/L better? Also, note that the correct
symbol for liter is "L" not "1". Change for entire document.
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2, pg. 5 Figure 3.2-1. Give a citation for the Acid Sensitive Waters
(USGS).
2, pg. 7 Why was there no selection of a threshold for sulfate deposition?
Is this awaiting the determination of critical load? At a minimum
the European critical load could be used.
2, pg 8 Same comment for total N and S deposition and the assignment of
a value as that provided by sulfate.
2, pg. 9 The inclusion of high elevation could also be justified by other
criteria such as the potential contribution of occult (fog)
deposition. If occult deposition accounted for in the CMAQ
estimates. This also relates to rationale provided with respect
topographic position (Attachment 2, page 17).
2, pg 9 25-28 This is confusing with respect S and N deposition since it was
suggested above that no criteria for S and N deposition were
defined. If these top quartiles are used the actual values need to be
supplied that make up these quartiles. Also, the year or years from
which these deposition data are derived needs to be given
explicitly.
2,pg 10 14 Why "Total nitrogen (Kjeldahl)". Do you mean total dissolved
nitrogen or total dissolved Kjeldahl nitrogen. Why exclude nitrate
in surface waters?
2,pg 11 Although there are weak linkages between N deposition and N
solute concentrations in surface waters, it would be preferable to
provide the data layer of actual N solute concentrations in surface
waters.
2, pg!2 18-19 Provide these nutrient concentrations available from the National
Nutrient Database. Provide a citation for this and the other data
bases.
2, pg 15 These N deposition data layers seem to be redundant from data
layers previously described.
2, pg 16 More clearly delineate the difference between "content" and
concentration". Content should be reserved for the total amount
(mass, molar value) of a an element on a per unit area while
concentration is the amount (mass, molar value) of an element per
unit of mass (sometimes) expressed as %.
2,pg 18 The delineation of the location of acidophilic lichens appears to
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have a strong boundary based upon state borders especially notable
in Arizona and an absence in New Mexico.
3, pg 10 Here and elsewhere "uM" is not a correct abbreviation. The
abbreviation for mole is "mol".
3, pg 12 Note that these ANC levels are lower than those suggested to be
considered to be of concern in Attachment 2.
3, pg 15 There have been other models (e.g,. PnET-BGC) that have been
applied particularly to the Adirondacks to evaluate especially
temporal patterns of acidification. Wouldn't it be helpful to at
least do some comparisons using other models besides MAGIC.
3, pg!8 8 Change to "SO4 2"".
3, pg 21 Clarify how the ratios of wet to dry deposition were derived.
3, pg 22 15 Are the total deposition values used in the MAGIC calculations
different from deposition estimates used elsewhere in the entire
document?
3, pg 22 27-29 Some elaboration on how ASTRAP derived deposition would be
helpful and how these estimates confirm or differ with the CMAQ
estimates.
3, pg 23-26 There is considerable discussion of the calibration of MAGIC in
this section. Some of this could be reduced and inclusion of other
ways of comparing model output with other published results
including other models (e.g. PnET-BGC) would provide additional
perspectives of these results.
3, pg 29 Similar to previous comments, although the discussion and
definition of the F-factor provides background information this is
not a novel approach, but rather one that could be cited. More
emphasis of the validation and comparisons with actual
measurements versus description of the model development would
be more helpful.
3, pg 31 Figure 5.1-1. Trends in LTM monitored lakes in the Adirondacks
of New York would be improved if specific lake classes were used.
It is not clear from these figures how a general trend for the LTM
monitored lakes were obtained.
3, pg 32 Figure 5.1-2. The modeled values appear to be substantially
different that those of the measured values. Doesn't this bring into
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question to validity of the predictions for 2010? I don't believe the
results of this figure are discussed within the document.
3, pg 35 Clearly the document is incomplete at this stage.
4, pg 1-2 This seems repetitious of information provided in the main
document.
4, pg 5 "M" is not the correct SI abbreviation for mole. The correct
abbreviation is "mol".
4, pg 4-9 Not sure that this much restating of what has previously been
found about Al and Ca relationships is needed.
4, pg 11 Would it be more efficient to cross reference the description of
ecosystem services as provided in the main document?
4, pg 18-20 Are the details of the history of the Kane Forest needed in this
document?
4, pg 21-25 Similarly to the previous comment, are all these details about
Hubbard Brook needed for this document?
4, pg 26-47 This is difficult to follow due to the level of detail. Perhaps a more
generalized format in which could be imbedded specific references
to the literature or the inclusion of appendices so that the major
theme of the discussion is not lost.
4, pg 50 Not sure of the importance of the inclusion of the section on
"Implications for other systems" in this document.
4, pg 51-52 The uncertainties issues need to be better integrated into the overall
document.
4, pg 53 The "Conclusions" summarize the important issues and these
issues should be the focal points of this entire section with a need
6, p 43 The figure on this page (Figures 5.1-1 5.1-2) appears to have an
inappropriate numbers. Shouldn't they be 6.1-1 and 6.1-2?
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Mr. Richard Poirot
These comments pertain primarily to REA Chapter 3 (Sources, Ambient Concentrations, and
Deposition), for which the following charge questions were provided.
Question 1: To What Extent are the air quality characterizations and analyses presented
in chapter 3 technically sound, clearly communicated, appropriately characterized, and
relevant to the secondary NAAQS for NOx and SOx?
Question 2: Section 3.2.1 describes an approach for evaluating the spatial and temporal
patterns for nitrogen and sulfur deposition and associated ambient concentrations in the
case study locations. This draft document includes the analysis for the Adirondacks Case
Study. Does the Panel agree with this approach and should it be applied to the other
Case- Study Areas?
Question 3: Section 3.2.2 describes the relative contributions of ambient emissions of
nitrogen and ammonia to nitrogen deposition for the case-study areas. To what extent is
the approach taken technically sound, clearly communicated, and appropriately
characterized?
Assuming the many and important missing "placeholder" sections are filled in, I think the air
quality characterizations and analyses presented in chapter 3 will provide a technically sound,
clearly communicated, appropriately characterized, and relevant to the secondary NAAQS for
NOx and SOx (although it still remains unclear to me what kind of 2ndary standards are being
contemplated). Many of these placeholders refer to evaluations of model performance, and
since the majority of the chapter consists of presentation of intensively graphical model results,
filling the placeholders will be key to providing confidence in the model results. The technical
approach appears to be reasonable, but without a better sense of model performance (including
both CMAQ and the RSM meta-model), the technical soundness and relevance to NAAQS can't
really be evaluated.
The presentation of the information is clear (even beautiful), but there is minimal discussion or
interpretation of the graphical results, which makes it difficult to maintain interest in looking so
many pictures. Conversely, it might be informative to poll the model results in ways that might
provide a better understanding of relationships among the various metrics of air quality,
deposition and environmental effects. For example: what would the maps look like that show
the ratios of S deposition to S emissions; N (oxidized) deposition to N (oxidized) emissions; N
(reduced) deposition to N (reduced) emissions. What would maps look like that show ratios of
S (or N) deposition to ambient SO2 (or NO2) concentrations? What if modeled S emissions were
rolled back to show alternate lower maximum levels of SO2 (and/or NO2) - what would be the
subsequent changes in S (and/or N) deposition in sensitive downwind areas? If sections of the
Adirondacks were considered to be experiencing adverse levels of acidifying deposition, how
could the models be used to determine the "significant contributing area" - or perhaps some
combination of emission size, and frequency upwind - such that a non-attainment area might be
defined to better include the contributing emissions? A possible approach for an improved
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secondary SOx or NOx NAAQS might consider (much) lower levels but averaged over larger
areas or longer averaging times.
With the caveat that the model performance needs to be more clearly examined and documented,
I think the more detailed approach applied here for the Adirondack case study is reasonable, and
could be applied to other case study areas. One possible concern - possibly more relevant to the
Adirondacks than to most of the other case study areas - is whether the 12 km gridding might be
coarse relative to the spatial variability in deposition, terrestrial & aquatic ecosystems and
associated effects. Potentially the larger grid cells may fail to adequately capture orographic
increases in precip volume & deposition and the additional increases from occult deposition at
highest elevations (or in certain coastal areas) - in comparison with variations in sensitive
terrestrial and aquatic biota within these grid cells . See for example: Miller, E.K. et al. 1993.
Atmospheric deposition to forests along an elevational gradient at Whiteface Mountain, NY
USA. Atmos. Environ. 27A:2121-2136.
140
120 "
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Elevation {meters}
Figure 1. Variation in wet, dry, cloud, and total sulfur deposition over -2km ground
distance as a function of elevation on Whiteface Mt., NY, 1986-1989 (from Miller etal.
1993).
Possibly this influence of occasionally large terrain, deposition and species variations within the
relatively large grid cells could be evaluated by conducting a higher resolution sensitivity
analyses within selected grid cells in the Adirondacks case study area. Alternatively, it might at
least be possible to disaggregate the coarser modeled dry dep. estimates to combine with the
higher resolution wet dep. estimates from the Grimm & Lynch approach. Arguably the dry dep
totals and variability may be less important than wet dep at more remote receptor locations.
Possibly also a terrain-based cloud deposition model could be added to provide added detail for
higher elevations or in coastal areas.
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Regarding the soundness of the technical modeling approach to estimate the relative
contributions of ambient emissions of oxidized and reduced nitrogen to nitrogen deposition for
the case-study areas - the approach seems sound but again there is a need to evaluate the
performance of the models (CMAQ + RSM). Trust but verify. This evaluation could/should
extend where possible to subcomponents of the models such as emissions inputs and space/time
patterns of modeled estimates of wet oxidized N and wet reduced N deposition.
That being said, I do like the approach of directly linking the estimates of changes in Nr
deposition to changes in specific emission sources. I would think a similar approach could also
be taken to zero out and otherwise reduce SOx emissions from different source categories. Down
the road, this may allow a bundling & comparing of projected "optional" future emission
controls (small, medium, large, etc.) to desired reductions in deposition in sensitive areas, in
comparison to the associated concentrations in atmospheric NOx & SOx concentrations (in the
event the layers say we have to stick with the traditional indicators). What new NAAQS limits of
these indicators (perhaps averaged over larger - or much larger - areas than single monitors)
would be necessary to achieve the desired reductions of Nr and/or S deposition in sensitive
areas?
In addition, if you were to add various levels of SOx (and NOx) emission reductions to your
modeled scenarios, it would be a snap to calculate and display the resulting changes in sulfate
and nitrate aerosols (and in their visibility effects) that would result from any changes in S & N
emissions or deposition or SO2 & NO2 concentrations. This would allow you to (a) consider a
more complete set of welfare benefits that would result from any revised NAAQS based on
deposition effects and/or (b) might lead to and help justify alternative ambient air indicators - for
example the sum of total atmospheric oxidized S and N compounds (sum in ug/m3 of S from
SO2 and pSO4 and N from NO, NO2, HNO3, and pNO3 or somesuch) - that might not be
considered if only deposition-related effects are considered, but which might, set at the right
levels, result in large deposition-related benefits.
Other Minor Comments:
p. 3-1 lines 16-23: This is a good example of what seems like an intentional sense of vagueness
regarding which pollutants and secondary transformation products are or are not the subject of
this review, and/or available as potential indicators for secondary NAAQS. Why are nitric acid
and PNO3 considered part of "NOx", while SOx includes only gaseous SO2?
p. 3-4, Figure 3.1-3: This figure just doesn't look right - and seems inconsistent with the
reduced nitrogen deposition map in Figure 3.1-8 on p. 3-11.
p. 3-4, lines 3-5: Does confined feeding really increase animal wastes, or does it just increase
atmospheric emissions from them?
p. 3-4, line 12: Figure 3.1-4 does not show annual 2002 SO2 emissions "by state".
p. 3-5, line 4: I would change "Industrial" to "Anthropogenic".
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p. 3-5, lines 10-15: Should marine DMS emissions be mentioned here?
p. 3-6, lines 14-16: Can you provide any quantitative indication of how large these fire SO2
emission underestimates are?
p. 3-8, lines 5-7: Does this increased deposition of reduced nitrogen also pertain over the
100-year period of the preceding sentence. Can you say something more precise about trends
over the past several decades?
p. 3-12, lines 10-14: This description relates to how NADP interpolates its wet deposition data.
However, later you indicate using the precip-volume-enhanced estimates from Grimm & Lynch
(2004). So which was it? One general concern is that the 12 km gridding may overly smooth
some of the more extreme orographic increases in precip - and you seem to exclude cloud water
deposition. Possibly this could be handled by conducting some sensitivity analyses for grid
cells containing higher elevation terrain - especially for the Adirondack and Shenandoah case
studies.
p. 3-16, line 11: Why not also describe CASTNet (& AIRMoN dry) data for HNO3, NO3, NH4,
SO4?
p. 3-23, lines 4&5 and lines 11&12: say roughly the same thing twice.
p. 3-23, line 7: "(25% wet vs. 6% dry)" and 69% what?
p. 3-23, line 12: Change "does" to "do".
p. 3-54, line 17: You could add "current and historical" before "atmospheric deposition".
p. 3-55, lines 20-21: Can you provide any indication of if and how well the RSM technique
(and for that matter the underlying CMAQ model) works for all the SOx, NOx and reduced N
species you will use it for?
p. 3-57, line 5: Am I missing something or did you only use a couple (zero-outs) of these 210
control runs? So what was the purpose of the other runs?
p. 3-71, line 8: Delete one "deposition" in "greater deposition of oxidized nitrogen deposition".
p. 3-71, lines 8-15: I would think formation of aerosol NILtNOs would tend to increase the
transport distance, but would not lead to any net decrease or increase in Nr deposition. It all
gets deposited eventually. An exception might be if aerosols persist long enough to transport
out of the (US or North American) domain.
p. 3-73: I must have blinked somewhere, because I didn't expect to see this large, international
"sugar maple case study" area discussed previously. Its not listed as a "Case Study Location" in
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Table 2.1-1 on page 2-2&3. It reminds me to ask for a clearer "up-front" description (& map)
of all the intended case study areas.
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Mr. David Shaw
General Comments
Thank you for addressing the outcome of this REA. I believe that this makes the document
more focused.
I still feel that a specific goal of this assessment should be to identify and report sensitive areas
which do not have adequate monitoring. Adopting this longer view in this analysis will enable
the next review process to start from a stronger point. In identifying areas without adequate
monitoring data, we may be able to start the process of getting a stronger data record of results
for future analysis. It is my hope that this will lead to better modeling due to better data.
While there are certainly areas that are deficient in monitoring data, there definitely are areas of
strong monitoring data with analysis. I still feel that the areas of certainty do not receive equal
treatment as uncertainty. I feel we must be clear that we do understand causes, effects and
variability in our ecosystem response.
On this note, the analyses presented in Chapter 3 of the REA rely heavily on modeling and don't
always reinforce where the measurements are the strongest. It is important to emphasize where
we have the most confidence (e.g. wet deposition, ANC measurements in case study areas) and
the least confidence (e.g. air concentrations and dry deposition of NOx/SOx, where
measurements are lacking). Much of the information on dry deposition will come from CMAQ,
and the measured data from CASTNet and other special studies could be used to assess the
model at selected locations.
Charge Questions
Scope of the Review
Question 1
Chapters 1 and 2 provide the background, history, and the framework for this review,
including a discussion of our focus on the four key ecological effect areas (aquatic
acidification, terrestrial acidification, aquatic nutrient enrichment, terrestrial nutrient
enrichment). Is this review appropriately focused in terms of the targeted areas and in terms
of characterizing the important atmospheric and ecologic variables that influence the
deposition and, ultimately, the ecologic impacts of nitrogen and sulfur? Does the Panel have
any further suggested refinements at this time?
Pages 1-1 to 1-10:
I feel that this gives good overall information on the Rational, Background and History. It
might also be a good place to address other pollutants associated with NOX and SOX analyzing
the whole set of problems associated with these pollutants.
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Page 1-8 lines 3-5:
Lines 3-5 state that 'in spite of the complexities and uncertainties....' it became clear that a
program to address acid rain was needed. In actuality, it was the evidence of a preponderance of
the scientific data of the NAPAP effort which made it clear that an acid rain program was
needed. This builds on one of my general comments regarding an emphasis on uncertainty
rather than giving equal treatment to those areas where certainty exists.
Page 1-16:
I would recommend adding a discussion on critical loads as the organizing principle of this RAE
assessment. Include the current understanding of ecological indicators and how levels of the
proposed standard will be integrated.
Page 1-20:
It would be helpful to explain how the existing monitoring data will be used to evaluate the
success of the proposed standard? How and when will the existing monitoring networks be
evaluated for adequacy of measuring ecosystem response?
Page 2-10:
I appreciate the effort in adding sulfur and mercury methylation. The fact that it will be
addressed will make this a stronger analysis.
Page 2-11, Table 2.3-1:
I feel that it would be beneficial to add to Cultural Services "chemical and biological degradation
of Constitutionally (federal and states) protected Wilderness areas". This would apply to
several if not all Targeted Effect Areas. The point being that the ADK case study area, for
example, represents a 6 million acre region, 43% of which is protected by the NYS Constitution
as 'forever wild' Forest Preserve. Here, tree cutting is not allowed, yet atmospheric deposition
damages forests and diminishes aquatic ecosystems within these forests. The remaining 57% is
devoted principally to forestry, agriculture, and open-space recreation, a portion of which is
sensitive to negative effects of atmospheric deposition. This landscape holds an additional
cultural value to New Yorkers especially, and to others from the US and around the world.
Pg2-12:
In the box where "provisioning services" and "cultural services" for Sulfur and Mercury
Methylation are provided, fish kills is listed as an ecological impact. From the literature that I
am familiar with, fish kills or declines in fish populations are not a good indicator of MeHg,
however, declines in the success of species higher in the food web such as loons and humans
occur because of MeHg neuron toxic effects and bio accumulation.
Air Quality Analysis
Question 1
To what extent are the air quality characterizations and analyses presented in Chapter 3
technically sound, clearly communicated, appropriately characterized, and relevant to the
review of the secondary NAAQSfor NOX and SOx?
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Sections 3.1.4 and 3.2:
It seems as if the dataset discussion (Section 3.2) would be more beneficial if it appeared before
the composite deposition maps (Section 3.1.4). These composite maps consist of modeled dry
and measured/interpolated wet deposition. For these maps, are the units actually kg ha"1 y"1, or
are they kg N ha"1 y"1 and kg S ha"1 y"1? Some mention should be made that the dry deposition
estimates are generally consistent with whatever measurements (e.g. CASTNet) are available,
that one year of modeling is adequate to capture the seasonal/spatial variability in the predictions
(i.e. this is not an atypical year), and that other photochemical models are capable of estimating
dry deposition and could be used to perform such an analysis.
Section 3.2.1.2:
I am interested to know why SC>2 and NC>2 from SLAMS/NAMS monitors are not included in the
measured database? While there may not be many NC>2 monitors in rural areas, there should
still be some measurements of SC>2 in the case study areas.
Page 3-21 ADK case study area:
There are several questions regarding the selection of this study that would be of interest to note
in the REA:
How were the 44 lakes and ponds selected?
How was the subset of 15 lake sites selected for geographic variation in deposition assessment?
How representative are these sites of the whole region?
Is there an elevational stratification?
Are any of the intensive study sites part of the current Adirondack monitoring programs (e.g.,
ALTM, TIME, AEAP)?
Have any or will any of the model results be compared with existing long term monitoring data?
Some important facts to point out regarding this region is that 22% of it is above 600 m were the
sensitive spruce fir forest community becomes dominant. Further up above 900 m are key
signature mountain peak ecosystems containing over 100,000 acres.
Monitors are not measuring any deposition data above 610 m in NYS, with the exception of the
top of Whiteface Mountain.
Pages 3-35 through 3-37, and 3-50 through 3-53:
It may not be necessary to include the additional information on a monthly basis. The form of
the annual NAAQS looks to be seasonal or annual, so presenting deposition on a seasonal basis
seems to be adequate to capture the variation over the course of a year.
Figures 3.2-29 through 3.2-44:
I would recommend that the metrics for these figures are clearly stated. Also, it would be
helpful to confirm that the "whiskers" are the minimum and maximum and that the boxes are
25th/75th percentiles.
Figures 3.2-45 onward:
It might help the reader to reverse the color scheme, that is display the smallest impacts in green
and the largest impacts in red.
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Misc.
In the introduction there are many references to "... noted below in Section 1 .x...." I would
recommend removing the word "below" in each of these references.
Page 1-3 line 19, "Chapter 2" should be
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Dr. Kathleen C.Weathers
Overarching comments on Chapters 7 and 8:
First, I think that the case study approach is useful and appropriate for this analysis. Next,
Chapter 8 provides some interesting ideas to ponder. Finally, the incompleteness of this
document makes it difficult to provide much in the way of pithy comments. In addition, there's
much editing that will need to be done on these chapters.
Case Studies: As we discussed during the first meeting of the Panel, the choice of case studies is
critical. My biggest concern about the case studies identified in this draft is whether they are
representative enough. That the there is sufficient data and information for a case study is, of
course, a major criterion. Further, their use should be supported and justified in regard to the
suite of impacts of air pollution they illustrate with regard to direct and indirect effects of
atmospheric N and S. I question the use of the Chesapeake Bay/Pamlico Sound in this regard,
mainly because atmospheric N deposition to the region is not a large proportion of N inputs to
the ecosystem. Thus, unless it is used as a contrasting example of a system in which the
atmospheric deposition of N is not a major component of N loading (I note that this contrast
could have utility), the Chesapeake Bay/Pamlico Sound regions may not be the most illustrative
case study to use. I do think that, if feasible, evaluating deposition impacts on a coastal
ecosystem(s) would be instructive.
I mentioned in my last review that I thought Day-Cent-Chem should be considered as a potential
model to be used for these case study analyses. It has some advantages over Magic, and some
parallels with other biogeochemical models (PNET-BGC, for example).
Would it be possible to consider in some creative way a "case study" that summarizes and
synthesizes experimental manipulations of N and S inputs (e.g., Harvard Forest, Catskill
Mountains, NY, Bear Brook, ME, Mt Ascutney)?
Conceptual pieces: I agree with using a "weight-of-evidence" approach, which I interpret to
mean that assessing effects using a suite of different tools (modeling, experiments, theory,
long-term monitoring) can be used to provide the most robust syntheses. The IPCC has used this
approach successfully.
As the authors of this document are no doubt well aware, ecosystems are affected by the amount
(and sometimes concentration) of a pollutant or nutrient that is actually makes its way to the
ecosystem — i.e., that is deposited. Working backwards from that fact suggests that what will be
necessary is a set of standards that consider actual loading — deposition — to ecosystems, rather
than atmospheric concentration-based standards that identify the role of "modifying factors." The
devil's in the details of Figure 8.1-1! As research has demonstrated, for some chemical species,
there may be little connection between emissions and total deposition downwind, much less all
of the biologic and geochemical transformations that happen from deposition to terrestrial
processing to surface water effects (or not).
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As noted in this REA, lining up the spatial and temporal scales of analysis and output are critical
issues, for example, high temporal resolution (air concentrations and deposition on an hourly
basis, for example) but low spatial resolution (across the country) may be exactly the opposite of
what would be most useful for assessing ecosystem effects.
The likelihood that current rates of deposition will show immediate effects on downstream
ecosystems for nutrients such as N is quite low. Rather, capturing the longer-term average loads
and patterns of deposition is likely to be more relevant.
The derivation of deposition metrics and transformation functions were at once described in
great detail and in not enough detail. Seeing the forest for the trees will be very important. See
comments about a deposition standard, above.
General comments on Chapters 7 and 8:
Note that I have not offered detailed editorial comments for this review.
I'm not sure that I agree (page 7-2, lines 15-16) with the statement that it is the increase in sulfur
and nitrogen content of soils that is the sole reason for alteration of major biogeochemical
processes. Also, just below, missing from the description of acidic deposition's effects on aquatic
system are the properties of the adjacent terrestrial watershed, including hydrologic pathways.
And, at the end of this paragraph, the reasons why the results from the case studies for the
Adirondacks and Blue Ridge Mountains might be applicable to the rest of the Appalachians and
the Northeast should be identified.
There appears to be some confusion about terrestrial acidification, or at least the beginning of the
terrestrial acidification should be rewritten for completeness (i.e., natural and anthropogenic
acidification occur in soils), accuracy, and clarity.
I appreciate the importance of the statements on pages 8-12, lines 9-13 in regard to a national
transformation function with local modifying factors within it. This is very important given the
importance of landscape (in its broadest sense) in influencing inputs.
I note the absence of cloud or fog deposition in Section 8.3.2.1.1 suggest mentioning in the text
that it will not be included directly here. This vector can be critically important, but only in
coastal and mountainous ecosystems.
Surely the intention in the Catchment parameter section is to use GIS databases (not actual
topographic maps)?
Be sure to label figures clearly as well as be clear when discussing total (wet + dry? or Nr, or?)
deposition. Note annual or seasonal as well in the text.
Organic nitrogen, in regard to both its atmospheric input (less known) and output (more known)
via surface waters should be at least mentioned as part of the N effects picture. While it is not
directly part of NOx/SOx emissions, it is nonetheless important and it is becoming especially
relevant in regard to climate change.
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Such terms as ecosystem services, and ecosystem health, should be explicitly, consistently, and
clearly defined among and within these NAAQS review documents.
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