&EPA
United States Clean Air Markets Division
Environmental Protection Office of Atmospheric Programs
Agency (6204N)
June 2001
EPA430-R-01-005
How to Measure the Effects of Acid
Deposition:
A Framework for Ecological Assessments
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Acknowledgements
Special thanks are extended to Noreen Clancy, Paillette Middleton, and Allan Auclair at RAND Environmental Science and Policy Center for
their valuable assistance.
Front cover photos clockwise from top left: Loren Hutchinson Calvin Coolidge State Park, Plymouth, VT, NOAA Photo Gallery, trout,
VTvjsb.comMetawlee River, VT', NOAA Photo Gallery, Cormorant.
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Table of Contents
Section I. Overview 1
Tribal Nations Have Unique Situations 1
Using Section 105 Funds for Assessment Purposes 2
Section II. Assessment Process 3
Value of Assessments 3
Assessing the Acid Rain Program 4
Section III. Scope of Assessment 11
What Distinguishes Core and Ultimate Assessments? 11
What Are Key Criteria for Determining the Scope? 13
Section IV. Key Questions 15
Section V. Identifying and Using Available Data Sources 17
CMAP 17
Emission Databases 21
National Air and Deposition Monitoring Networks 21
Ecological Monitoring 23
General Steps for Conducting Data Quality Assurance 26
Section VI. Identifying Appropriate Analytical Tools 27
Air Quality 27
Ecological Impacts 30
General Steps for Conducting Model Quality Assurance 30
Section VII. Integrating Information to Assess Response 33
Limitations of Using Web Databases 35
Section VIII. Communicating Results 37
Section IX. Examples of State-level Ecological Assessments 39
Section X. References 41
Appendix A. Frequently-Raised Issues and Questions 43
Emissions, Concentration, and Deposition Analysis Considerations 43
Ecosystem Analysis Issues 44
Appendix B. Sample Integrated Assessment 47
Background 47
Results 48
Acid Deposition Analysis 49
Visibility Analysis 53
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List of Tables and Figures
Table 1. Air, Deposition, and Ecological Network Descriptions and Pollutants Monitored 18
Table 2. Representative Models and Required Data Sources 28
Figure 1. Ecological Assessment Process with Feedback Loops 3
Figure 2. Electric Generating Units Affected By Phases 1 and 2 of Title IV 5
Figure 3. National Emissions of Sulfur Dioxide 6
Figure 4. National Emissions of Nitrogen Oxide 6
Figure 5. Average pH of Precipitation at Monitoring Sites in 1994 (pre-Phase I of
Title IV) and 1997 (after Phase I) 7
Figure 6. Sulfate Deposition at Monitoring Sites in 1994 (pre-Phase I of Title IV)
and 1997 (after Phase I) 8
Figure 7. Various Response Times to Changes in Emissions 9
Figure 8. Comparison of Core and Ultimate Assessments 12
Figure 9. Assessment Strategy 12
Figure 10. Examples of Endpoints Associated with Pollutant Impacts 16
Figure 11. Sulfate Deposition at Two NADP Sites from 1978 to 1997 33
Figure 12. Relationship Between Sulfur Deposition and Precipitation at Two NADP
Sites Over the 1978-1997 Interval 34
Figure 13. A Comparison of Ambient Air Quality, Deposition and Streamwater Data
from 1977-1997 at Selected Sites in Pennsylvania 35
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Acronyms
AIRMoN Atmospheric Integrated Research Monitoring Network
CASTNet Clean Air Status and Trends Network
ELS Eastern Lake Survey
EMAP Ecological Monitoring and Assessment Program
EPA U.S. Environmental Protection Agency
FHM Forest Health Monitoring Program
GIS Geographic Information Systems maps
IMPROVE Interagency Monitoring of Protected Visual Environments
ISEM Intensive Site Ecosystem Monitoring
LTER Long Term Ecological Research Program
LRM Long Term Monitoring Project
MAGIC Model of Acidification of Groundwater in Catchments
MAHA Mid-Atlantic Highlands Assessment
N, NOX, NC>3 Nitrogen, Nitrogen Oxides, Nitrate
NADP/NTN National Atmospheric Deposition Program/National Trends Network
NAMS National Air Monitoring Stations
NAPAP National Acid Precipitation Assessment Program
NAWQA National Water Quality Assessment Program
NH^ Ammonium
NOAA National Oceanic and Atmospheric Administration
NSS National Stream Survey
NSWS National Surface Water Survey
PAMS Photochemical Assessment Monitoring Stations
PM2 5 PMjQ Particulate Matter (2.5 microns in size or less, 10 microns in size or less)
RADM Regional Acid Deposition Model
S, SO2, SO4 Sulfur, Sulfur Dioxide, Sulfate
SENIOR Southeastern Network for Intensive Oxidant Research
SCION Southeastern Consortium Intermediate Oxidant Network
SLAMS State and Local Air Monitoring Stations
SON Spatial Ozone Network
SOS Southern Oxidant Study
TIME Temporally Integrated Monitoring of Ecosystems project
USDA U.S. Department of Agriculture
VOC Volatile Organic Compounds
WLS Western Lakes Survey
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section i. Overview
In an effort to reduce the adverse effects of acid
deposition on human health and the environment,
Congress established the Acid Deposition Control
Program, which was passed in 1990 as Title IV of the
Clean Air Act Amendments (hereafter "Title IV"). Title
IV requires reductions in annual emissions of sulfur
dioxide (SO2) and nitrogen oxides (NOx), the precur-
sors of acid rain, from electric utilities.
EPA hopes to facilitate the use of localized monitoring
where available in conjunction with national networks
and promote ecological assessment initiatives at the
state and tribal nation levels in order to better under-
stand which regions of the country show signs of
improvement and if any are continuing to degrade. This
combination of local, regional and national ecosystem
assessments will improve the decision-making and
evaluation process regarding current air pollution con-
trol strategies.
Phase I of the Acid Rain Program achieved substantial
emission reductions, resulting in significant environ-
mental and health benefits. As even greater emission
reductions occur under Phase II of the Acid Rain
Program (2000 forward), the ability to describe the eco-
logical response to these reductions becomes increas-
ingly important. This type of assessment is key to
determining whether current control levels provide ade-
quate protection to human health and the environment,
and whether further pollution control steps may be nec-
essary. Given the trans-boundary nature of air pollu-
tion, mitigating the problem on a regional or national
scale will usually prove much more effective than con-
trolling emissions in a single state. One of the key roles
states and tribal nations can fill is long-term monitoring
of acid deposition or water quality and biological
parameters. States and tribal nations have a lot to gain
from measuring whether there have been improvements
in the health of their ecological resources since imple-
mentation of Title IV (1995).
For purposes of this handbook, an ecological assess-
ment is defined as:
a process in which a clear understanding of
baseline conditions and ensuing changes to
ecosystems are monitored and documented
over time with the goal of establishing long-
term environmental trends.
An ecological assessment can be "integrated" and cap-
ture the full range of processes and responses from
emissions to atmospheric transport to deposition to eco-
logical and human health impacts. Most assessments,
however, examine just a piece of that larger picture.
Integrated assessments are useful to synthesize existing
knowledge, but smaller, more focused assessments are
extremely important and valuable as well. For many
states and tribes these smaller assessments are more
practical and will make up the large majority of the
analyses conducted.
This Handbook describes a process and provides gener-
al guidelines that states and tribal nations can follow in
beginning to assess ecological benefits resulting from
the emission reductions achieved under Title IV.
Information on basic assessment approaches, relevant
national monitoring programs, as well as the availabili-
ty of modeling data are discussed in the remainder of
this handbook. EPA assumes that local monitoring data
availability is known foremost by individual states and
tribal nations, so that information is not included here.
The goal of EPA's Clean Air Markets Division (former-
ly the Acid Rain Division) in developing this Handbook
is to encourage ecological assessment initiatives at the
state and tribal nation level, especially by those that are
not currently monitoring ecosystem effects or perform-
ing ecological assessment studies. Title IV is a national
program resulting in significant emission reductions
nationwide, so the Acid Rain Program focuses primari-
ly on national and regional monitoring programs to dis-
cern national trends.
EPA recognizes that the level and extent of environ-
mental protection measures are directly dictated by the
availability of resources. The resource base of states
and tribes can vary greatly from those who have few
methods to pay for assessments to those who are confi-
dent assessments are a valuable investment for the
future. All states do receive grants, called section 105
funds, that may be used for Acid Rain assessments.
EPA can assist states in designing assessment projects
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and provide other technical assistance as needed. Tribes
also have access to EPA funds that can be used for
assessments.
While the information in this handbook focuses on the
needs of states and tribal nations it will also be of use to
university researchers, other federal scientists, foreign
researchers and other related organizations, although
they are not explicitly addressed.
Tribal Nations Have Unique Situations
Although one handbook will not address all needs of
states and tribes alike, this handbook attempts to pro-
vide information that may be helpful to both groups.
EPA recognizes that tribes have treaty and trust rela-
tionships with the U.S. government as well as relation-
ships with states. Tribes and states often have different
values and motivations for conducting ecological
assessments and may have unclear boundaries of man-
agement responsibility.
A tribe may have many reasons for asserting environ-
mental decision-making authority over its reservation.
The environmental values and ideals that a tribe holds
may differ from those addressed by state agencies but
tribes are nevertheless often affected by decisions made
by states. The process by which a tribe makes environ-
mental decisions may also differ from the public partic-
ipation process conducted by state agencies. The reser-
vation is the home of the tribe, with historic, cultural,
and religious significance which may not be understood
or appreciated by non-tribal agencies. This often makes
the protection of the environmental quality of the reser-
vation a high priority to tribal members.
Many tribes have not been systematically monitoring
and documenting key ecological parameters over the
past few decades to assess change. This should not keep
these tribes from beginning the assessment process
now. In addition, tribes have their own unique ways of
establishing historical or baseline ecological informa-
tion based on their culture of oral history. Often it pro-
vides a greater level of detail in assessing long-term
change than documented monitoring alone. Although it
does pose challenges to comparing the historically-
derived information to actual field measurements col-
lected in the present day, traditional ecological knowl-
edge should be considered a starting point in providing
valuable information different from what current scien-
tific knowledge can provide. This knowledge, used in
conjunction with scientific methods is invaluable to the
understanding of ecological resources on tribal lands.
Using Section 105 Funds for Assessment Purposes
States receive block grants from EPA in order to do work on air issues. These funds are called "section 105
funds" after the section of the Clean Air Act that authorizes them. They can be used for a wide variety of pur-
poses, one of which is assessing the impacts of emissions reduction programs. EPA encourages states with an
interest in conducting assessments to use section 105 funds for that purpose. Some potential uses include:
• setting up atmospheric deposition or ecological monitoring site(s)
• conducting simple trends analyses on existing data sets that have not yet been "mined"
• integrated analyses of some combination of emissions, atmospheric transport, deposition, and ecological
effects
• communicating existing assessment data or data being collected under another program to the public
and/or policymakers
• other assessment projects relating to acid deposition
EPA Regional and Headquarters staff can provide technical assistance to states designing and evaluating these
assessments if requested.
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Section II.
Assessment Process
The primary purpose of lowering emissions is to
reduce the adverse effects to human health and
the environment. Resource managers need to
determine if the environment is reaping the intended
benefits, over what timeframe, and what additional
actions might need to be taken. In other words, assess-
ments are the basis for any course-corrections or
improvements made during the now-popular adaptive
management process. In general, environmental assess-
ments can help determine how successful current and
past policies are in protecting natural resources and how
much further the policies may need to go. An assess-
ment uses science to answer policy-relevant questions
such as, "Are our forests healthier since we reduced
emissions?" or "Do we have fewer acidic lakes and
streams than 10 years ago?" Assessments can also be
useful in identifying gaps in knowledge, identifying a
research strategy, prioritizing needs, and allocating
resources needed to achieve environmental goals
(Bernabo, 1993).
Value of Assessments
Assessments assist in this effort by providing the vehi-
cle for organizing and focusing information on environ-
mental policies. They are the link between the best data
Figure 1. Ecological Assessment Process with Feedback Loops.
Assessment Process
Determine
Key
Questions
New Views
Select Level of
Assessment
Detail Using
Criteria
Stakeholder/Reviewer Feedback
ASSESSME
Depict
Impacts
over
Geographic
Area
Perform
Analysis
(I.e.,source/
receptor
relationship)
Obtain Models
And Data
Synthesize
Results
COMMUNICATION
Tailor Materials
Involve Stakeholders/Reviewers in Planning
Ongoing Review
Recommendations
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and knowledge available (both monitoring and scientif-
ic experiments on mechanisms) and any actions taken
such as analyzing, interpreting, and using the informa-
tion to make decisions. For the purposes of this
Handbook, an assessment is considered an iterative pro-
cess of analyzing and synthesizing various pieces of
information in order to evaluate and communicate their
significance for decisionmaking. This includes deci-
sion-making as it relates to a resource manager's devel-
opment of a research strategy, or decision-making as it
relates to a policy-maker's evaluation of an emission
reduction policy.
When conducting an assessment, structured frame-
works, methodologies, and guidelines are usually fol-
lowed. Figure 1 shows a pictorial representation of the
assessment process. In an ideal world, these individual
assessments are repeated over time to continually eval-
uate changes and improve understanding of why the
changes are occurring. Therefore, the assessment pro-
cess (the act of repeating individual assessments) is
considered an iterative one of refining our understand-
ing of environmental change as science and societal
values evolve. An individual assessment hopefully will
not be a complete replication of a previous assessment
but an evolution based on greater understanding. The
iterative process is an important function because the
credibility of assessments for policy applications
requires a process of open review with wide participa-
tion to avoid the perception or reality of policy biases.
However, in cases where an iterative assessment pro-
cess is impossible, a single assessment for a given geo-
graphic area or ecosystem still provides a wealth of
information.
Ecological assessments as a process are imperfect. It
should not be expected that the process is easy, or even
well formulated. It requires some willingness to exper-
iment as the process is undertaken. Experts acknowl-
edge that it is not known how all the various natural
communities or species within ecosystems will respond
to pollution reductions. However, acknowledging the
uncertainty does not prevent decisions from being made
on a daily basis regarding managing resources.
Therefore the pertinent question becomes: "how do I
manage those resources most effectively in the face of
uncertainty?" Assessments provide a solid framework
from which to answer this question.
This Handbook identifies a set of ground rules that can
be helpful in establishing boundaries and providing
structure to the process. It also provides guidance on
performing the five basic steps to conducting an eco-
logical assessment. Each of these steps will be dis-
cussed in more detail in the following sections:
Section IV: Identify the key policy-relevant questions
to be addressed (e.g., Is recovery occur-
ring in those lakes and streams known to
have been impacted by acid deposition?
Are fish populations healthier?).
Section V: Collect and synthesize environmental
monitoring data and information relevant
to the policy questions (e.g., surface water
chemistry data, tree health data).
Section VI: Identify available and appropriate analyti-
cal tools for collective data analysis (e.g.,
models, statistical analyses).
Section VII: Integrate and assess the environmental
monitoring data and information in a for-
mat that addresses the policy questions.
Section VIII: Communicate the results to the policy,
scientific, environmental, and industrial
communities as well as to the general
public.
Assessing the Acid Rain Program
EPA's Acid Rain Program, established under Title IV
(Acid Deposition Control) of the 1990 Clean Air Act
Amendments, calls for major reductions of sulfur diox-
ide and nitrogen oxides, the pollutants that cause acid
rain. The program uses market-based incentives to
achieve a nationwide limit on SC>2 emissions more cost
effectively than traditional regulatory methods. The
Acid Rain Program requires a two-phased tightening of
restrictions on fossil fuel-fired power plants, resulting
in a permanent cap on SC>2 of 8.95 million tons nation-
wide, half the amount emitted in 1980. Phase I began in
1995, affecting roughly 440 of the larger, higher emit-
ting electric utility units in the eastern United States.
NOX emission reductions are also phased, with Phase I
beginning in 1996. Rather than setting an absolute limit
on emissions, Title IV controls how much NOX is emit-
ted for each unit of fuel consumed (Ib/mm Btu). (Total
NOX emissions are not capped). The limits on emission
rates per unit of fuel consumed will maintain annual
NOx emissions 2 million tons below what emissions
would have been without the Acid Rain Program
(beginning in 2000). Phase II for both SC>2 and NOX
began in 2000 and requires reductions in both pollutants
from more than 2000 units across the country. Figure 2
displays the geographical distribution of those sources
affected by Title IV.
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Figure 2: Electric Generating Units Affected By Phases 1 and 2 of Title IV.
. Gr-T^
s^Ste, % %Sl^s*-\,?x «1K
~
« Phase I;
Substitution/Compensating Units
s Phase II
Phase I of Title IV has led to greater than expected
reductions in emissions. National emissions of SO 2 and
NOX are shown in Figures 3 and 4. The even more sub-
stantial reductions that will occur during Phase II make
the ability to describe the ecological response increas-
ingly important in determining whether current control
levels provide adequate environmental protection.
A reduction in sulfur and nitrogen oxides emitted into
the atmosphere will result in a reduction of pollutant
concentrations in the air and a reduction of acidic depo-
sition to the Earth's surface. Even so, it is important to
have realistic expectations. Atmospheric transport and
deposition is a complex process and there is almost
never a 1:1 or linear relationship between the tons of
emissions reduced and tons of deposition avoided.
Seasonal variability can mask ecosystem changes due
to reductions in deposition. Only after several years of
monitoring data will it be possible to separate the sea-
sonal variability from an overall change.
Assessments must continue long after emissions reduc-
tions take place because of the time lag before ecologi-
cal responses are seen. Even after reductions occur,
ecosystems may take many years or even require
human intervention (such as restocking fish) before
recovering to a condition comparable those known his-
torically. Decades of leaching valuable minerals from
soils, the removal of sensitive fish species, or changes
in ecosystem structure cannot be reversed quickly and it
can take decades or longer to rebuild mineral stores,
reintroduce missing links in aquatic ecosystems, and
reach other necessary milestones to recovery.
A preliminary interpretation of regional monitoring
data from EPA (CASTNet) and NOAA (AIRMoN)
indicates that Title IV emission reductions are having a
positive effect on reducing air concentration levels of
SO2 (NAPAP, 1998). An analysis of wet deposition
monitoring data (NADP) demonstrates that Phase I
emission reductions resulted in a decrease in the acidi-
ty of precipitation and sulfate deposition in the
Midwestern and northeastern U.S. (see Figures 5 and
6). The spatial and temporal trends of these reductions
are important components in assessing the ecosystem
effects.
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SJOOO
A full range of ecosystem
responses are expected over
time, based on various char-
acteristics of the ecosystem.
Ecosystems are complex
and are constantly respond-
ing to multiple inputs and
stressors, such as other pol-
lutants, climate, and land-
use patterns. These inputs
and stressors cause chemi-
cal changes within ecosys-
tems, which can exhibit
long lag times before mani-
festing a response. This lag
time between pollutant
loadings and ecosystem
response underscores the
need for continuous long-
term monitoring, which
helps in our understanding
of what changes are occur-
ring and when they are
occurring. Figure 7 displays
the timeframe of environ-
mental responses to these
reduced emissions, which
can range from hours in the
case of changes in air con-
centrations of SC>2 and
decades to centuries in the
case of forest health and soil
nutrient reserves.
It is also important to
remember that within this
assessment process some
relationships are better
understood than others. For
example, emissions, air
concentrations, and deposi-
tion data are fairly well
understood in comparison
to the ecosystem, and especially to the biological
cell/tissue/population effects. There are some good case
studies of causal mechanisms, but the great majority of
ecological sensitivities and effects or responses are not
well understood. The process is to then infer that the
ecosystem or specific biological organisms will be
under less stress from the reduced pollutants and health
will improve. It might be helpful to think of the efforts
to determine causal relationships as a series of hypothe-
ses that are being tested and then constantly revised.
Figure 3. National Emissions of Sulfur Dioxide (in thousand tons).
1970
1990
1995
1997
• Fuel combustion nTr.uisport.ilion nliulustrfeil Pro cesses mid Other j
Source: National Air Pollutant Emissions Trends Update, 1970-1997. U.S. Environmental Protection
Agency, Research Triangle Park, NC.
Figure 4. National Emissions of Nitrogen Oxide (in thousand tons).
19SO
1970
19SO
199S
19P7
iFuelamibiutun • TnnqtoTtatiDn D Industrial Pn and Other
Source: National Air Pollutant Emissions Trends Update, 1970-1997. U.S. Environmental Protection
Agency, Research Triangle Park, NC.
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Figure 5. Average pH of Precipitation at Monitoring Sites in 1994 (pre-Phase I of Title IV) and 2000
(post-Phase I).
Sites not pictured:
AK01 52
AKD3 5.1
PR20 5.2
Sites not pictured:
AK01 5.2
AK03 5.2
VI01 5.0
Source: National Atmospheric Deposition Program (NADP)
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Figure 6. Sulfate Deposition at Monitoring Sites in 1994 (pre-Phase I of Title IV) and 2000
(post-Phase I).
Sites not pictured:
AK01 1 kg/ha
AK03 1 kg/ha
PR20 17 kg/ha
Sulfate as SO/'
Sites not pictured:
AK01 1 kg/ha
AK03 1 kg/ha
VICH 6 kg/ha
Source: National Atmospheric Deposition Program (NADP)
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Figure 7. Various Response Times to Changes in Emissions.
Hours
Days/
Weeks
Months
Years
Decades
Centuries
Air Concentration
Deposition
Aquatic(episodic)
Soil andPlantProcesses
Aquatic (chronic)
ForestHeilth
Soil
Note: The time it takes for various environmental impact areas (soils, aquatic, and forest ecosystems) to
respond to changes in emissions varies tremendously. Episodic aquatic ecosystems may be affected in
days/weeks, whereas forest health and soil nutrient reserves may take decades to centuries.
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Section
Scope of Assessment
This section outlines the scope of an assessment.
The different characteristics of assessments are
discussed in terms of the level of complexity
that can be considered. At one end is what is referred to
as a "Core Assessment," or the simplest analysis that
can be done to provide meaningful information for the
questions being posed by the state or tribal nation. The
other extreme is referred to as an "Ultimate
Assessment." An Ultimate Assessment attempts to take
into account all of the relevant interrelated issues asso-
ciated with the questions being posed and in order to
provide a detailed quantitative analysis of the relation-
ships among issues, causes, and effects. In this section,
we provide guidelines for determining the level of data
detail and model sophistication that might be appropri-
ate for the Core, the Ultimate and, as is likely to be the
more typical case, an assessment that falls somewhere
in between.
What Distinguishes Core and Ultimate
Assessments?
The scope of an assessment is characterized in terms of
the issues of concern and the key questions asked along
with the level of detail of the analysis (e.g., data and
models) used to address the issues. This Handbook
concentrates on ecological assessments related to acid
deposition. However, the same framework can be used
to design assessments to answer all sorts of environ-
mental questions. For acid deposition, the questions
center around the effectiveness of emission reduction
strategies in improving ecosystem environments.
Considering the relationships of ecological effects to
other impacts and multiple driving factors (such as
meteorology or climate change in addition to emission
reductions) broadens the scope of the assessment.
A Core Assessment considers changes in key sources as
well as key ecological receptor areas. The emphasis is
on using existing analyses and data, and non-key but
related factors and issues are not explicitly addressed.
Data and modeling analysis requirements are well
focused and minimal.
In an Ultimate Assessment, multiple consequences of
emission changes throughout the region surrounding
the receptor sites of concern are taken into account.
Related issues and influences such as changes in ozone,
particulate matter and haze are also explicitly consid-
ered. Social, economic, and political influences may
also be included in the analysis. Data and modeling
analysis requirements are more complex since more
sources, processes, and environmental impacts are
explicitly taken into account.
The differences between the Core and the Ultimate
Assessment scope, tools, and resource requirements are
summarized in Figure 8. The Core is limited to quanti-
tative analysis of one or two key or representative
impacts associated with one or two receptor areas (e.g.,
a lake or terrestrial ecosystem) associated with a small
well-defined set of sources (e.g., nearby major station-
ary source). The data used in the analysis are available
and well characterized. Similarly, models used are easy
to access and apply. Analyzed and fully developed ref-
erence tables and/or graphics indicating source and
receptor region relationships derived from the Regional
Acid Deposition Model, can also be used to help in the
assessment at the Core level. In general, a basic Core
Assessment could be initiated as a screening or scoping
study with costs in the range of ten to fifteen thousand
dollars whereas the more complex assessments require
resources up to a hundred thousand dollars or beyond.
Often a scoping or Core Assessment can provide the
information needed to help the decision maker decide
on next steps, which might include a more extensive
assessment.
Each step of the Assessment Strategy outlined in Figure
9 implies a range of possible questions, analyses, mod-
els, data and resource requirements. Core questions
about key impacts and major sources (e.g., has the key
regional ecosystem changed as a result of emission
changes?) differ from questions that consider a broader
range of factors (e.g., other economic and social factors
as well as emission trends) in ultimately determining
answers to the "why" question. The complexity of the
question determine the elements to be considered. Basic
ecosystem and emissions data are needed for Core
11
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Figure 8. Comparison of Core and Ultimate Assessments.
Tools
Full
Data
Models
Li mited
Data
Ivtodels
Ultimate
Core
Ultimate
Scope
Ultimate
$10k Key Receptors
Key Sources
Key Impacts
hAjltiple Receptors
Multiple Sources
Multiple Impacts
Resources
Needed
A Core assessment is limited in the number of receptors, sources and impacts as
well as analytic tools used and resource requirements. As you move from a Core
assessment toward an Ultimate assessment all of these requirements increase.
Figure 9. Assessment Strategy
Evaluate tools and analysis:
-Revise and modify framework
if tools and data inadequate
or other findings suggest new
questions
Models/Data:
-acquire tools
-proceed with first
round analysis
Refine Needs Based on
Limitations:
-Substitute data and model
requirements with existing
analysis results and/or
strategies
Formulate Key Questions
-Has the key regional
ecosystem changed?
-Why?
ASSESSMENT ELEMENTS
Receptors and Imparts
Sectors and Sources
Single/Multiple Sectors
Near Source/Long Range
Episodes/Long Term Averages
Other Air Quality/Climate Issues
Other Land/Water Use Factors
Socioeconornic Considerations
Regulations and Source Controls
Policies and Management Options
Set Up Analysis Framework:
-Examine trends in
ecosystems and emissions
from sources in the region.
•Examine issues and factors
affecting ecosystems
Required Elements:
-ecosystem data
-emissions data
-other factors affecting
ecosystems
Resource
Constraints:
-agency resources
-ability to acquire
data and tools
Set Information and
Resource Needs:
-Desired databases, models,
and previous analyses for
the area
-Analysis time estimates
12
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Assessments while additional information is needed to
answer broader questions.
It should be kept in mind that resource constraints will
become more significant as the assessment becomes
more complex. A state or tribe may have relatively easy
access to information required for the Core Assessment,
but may have complex questions that require something
close to an Ultimate Analysis to answer. However, for
more complex analyses approaching the Ultimate, the
resource requirements (time, expertise and cost)
become higher. After evaluating the questions, frame-
work and resource requirements, the assessment can be
scaled up or down to meet the needs of the tribal nation
or state within the available resources.
What are Key Criteria for Determining
the Scope?
The scope of the assessment is determined, to a large
extent, by the specific policy questions being addressed
(these questions will be discussed in detail in the fol-
lowing section). The range of receptors, impacts,
sources and other factors to be considered in establish-
ing causes and effects sets the bounds for the level of
analysis required. In-depth questions dealing with mul-
tiple relationships and scales can be posed. However, if
the data and/or modeling support is not readily avail-
able or cannot be obtained within budget, then less rig-
orous approaches must be taken, which rely on previous
Key criteria for determining
the scope of an assessment
key questions
data quality/quantity
model availability
local analysis expertise
computer constraints
time limitations
funding considerations
analyses or data not explicitly related to the question
being posed.
Several criteria then determine the needed and/or feasi-
ble level of detail for the assessment. The level of detail
that can actually be addressed depends on the data and
model availability and quality; staff, computer and
other resource requirements and availability; assess-
ment deadlines or other time constraints; and basic
funding considerations.
13
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Section IV.
Key Questions
Those conducting assessments, such as resource
managers, should seek the input of relevant
stakeholders such as scientists, policymakers,
industries, environmental groups, and community
groups in formulating the assessment questions.
Involving stakeholders at the outset will help to ensure
that an ecological assessment is both relevant and cred-
ible. Such inclusion will also increase an assessment's
chance of being perceived as a useful and successful
exercise upon its completion. The stakeholder process
is also important because it brings to the table the soci-
etal values, preferences, and priorities, as well as scien-
tific knowledge and agency priorities. It is also impor-
tant to keep in mind that societal values can be very dif-
ferent for different groups. For example, the value that
a tribal society places on natural resources and their
stewardship can vary greatly from that of a non-tribal
society, just as such values can drastically vary from
one geographic location to another. Assessments
involving more than one community should make sure
as many voices as possible have a chance to participate
in the process.
Below is a sample list of the types of policy-relevant
questions likely to be identified for the purpose of
assessing ecological change from Title IV emission
reductions. It might be helpful to categorize the ques-
tions as either "feasible" or "not feasible at the present
time" based on the scope of the assessment you nar-
rowed in on in Section III.
• Have sensitive ecosystems in this state or tribal
nation been identified?
• What are the current physical, chemical, or biolog-
ical characteristics or states of these ecosystems?
• Have baseline measurements been established?
• How have these characteristics changed over time
and what are the trends in these changes?
• How are emissions spatially distributed in relation
to sensitive ecosystems and/or existing ecological
problems?
• Does this state or tribal nation have (or have access
to) adequate monitoring and spatial coverage to
detect changes in deposition and ecosystem
effects?
• What are the dose-response relationships of atmo-
spheric deposition (specifically sulfur, nitrogen,
and base cations) on aquatic and terrestrial
resources?
• What evidence do we have of ecosystem changes
due to increases in atmospheric deposition?
• What evidence do we have documenting ecosys-
tem recovery due to reductions in atmospheric
deposition or reductions in sulfur concentrations?
• Are there baseline ecological (biological) data
available in order to measure a change in a certain
sensitive ecosystem?
• What are the best parameters to measure ecosys-
tem level changes (e.g., water chemistry changes,
population changes, etc.)?
• Are there uncertainties that affect the understand-
ing of the links and cause/effect relationships
between emission decreases, deposition changes,
and ecological effects (e.g., responses influenced
by other factors such as climate change, ozone,
land-use changes and the carbon cycle)?
• What are the environmental/human health end-
points?
These questions can be further expressed in terms of
particular impacts or endpoints. Some key endpoint
examples are summarized in Figure 10. Endpoints for
human health effects have been extensively studied and
are directly related to criteria pollutant standards.
Endpoints associated with ecosystem and other welfare
parameters such as visibility and materials damage also
have been studied in detail. Assessments of ecological
impacts are critical to our ability to improve the state -
of-the-science and incorporate ecological effects into
future policies.
Once the relevant questions are developed, it can then
be determined how useful current research or monitor-
ing data will be in providing answers, and what meth-
ods of research and assessment should be applied. In
developing the key questions to assess the impacts of
acid deposition for a particular area, it is important to
keep in mind that Title IV of the Clean Air Act took
effect in 1995. This date represents that point at which
decreases in emission rates can be referenced and com-
pared to earlier and/or later periods. Some reduction in
emissions may even have occurred prior to 1995 as util-
15
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Figure 10. Examples of Endpoints Associated with Pollutant Impacts
Pollutants
ind
HEALTH
Mortality
Chronic Bronchitis
Hypertension
Hospital Admissions
Respiratory Related
Symptoms
Endpoints
VISIBILITY
Deciview Changes
(decreased visibility)
MATERIALS
Soiling Damages
ECOSYSTEMS
Agricultural
Productivity
Forest Aesthetics
Forest Health
Recreational Fishing
Biodiversity
Lake Acidification
Timber Productivity
ity companies adjusted emission levels in anticipation
of pending regulations.
The key questions are likely to differ from one state or
tribal nation to another and are apt to change over time
as new concerns arise and/or as new perceptions
emerge from ongoing research into the effects of acid
deposition on ecosystems. It is likely, therefore, that the
data required to address decision needs will vary with
location and over time. It is also likely that, as our
understanding of the ecological effects of sulfate and
nitrate deposition improves, different data and tools
may be needed than what were needed in 1990 or 1995.
Where information is not available from nearby moni-
toring sites designed to measure deposition and other
effects of changes in pollutant emissions (e.g., ambient
air and surface water quality), data from other monitor-
ing programs and/or model results will need to be used.
Data from unrelated programs should be used with the
guidance of experts who understand the assumptions
and other technical issues that may impact the strength
of the assessment.
16
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sectionv. Identifying and Using Available
Data Sources
In order to answer your policy-relevant questions,
you need scientific data and information. This sec-
tion outlines the data on acid deposition and its
ecological effects that are available for use by states and
tribal nations from national networks.
National air quality and deposition monitoring net-
works are used to answer questions about trends on
national and regional scales. Using national monitoring
emissions and deposition data will provide overall
trends, however, there are no comparable national mon-
itoring networks for surface water/soil chemistry or
ecological data designed to provide a national picture of
ecological effects. To get an idea of what is happening
with the local ecology it will most likely be necessary
to look at intensive monitoring projects on specific
ecosystems or research projects conducted by universi-
ties, state or federal scientists, etc. A vast amount of
high-quality science was conducted in the 1980s and
early 1990s by the scientific community for the purpose
of attaining the state of science and technology on the
issue of acidic deposition. This science was sponsored
by the U.S. National Acid Precipitation Assessment
Program (NAPAP) and fed into a NAPAP Integrated
Assessment Report (NAPAP 1991). Much of the bench-
mark science that is summarized in those reports, along
with the methods employed, should prove to be a good
foundation for most types of ecological assessments
conducted today.
Descriptions of many ongoing national air monitoring
networks and ecological monitoring networks are listed
in Table 1 with some additional detail in the paragraphs
that follow the table. This list is not comprehensive.
Again, national coverage is the focus of those networks
cited in Table 1. States, universities, and other groups
have databases that could be accessed and of direct rel-
evance since many of them will focus on smaller spatial
scales or specific ecosystems. It is strongly recom-
mended that such databases be explored in addition to
the national datasets. For example, if you were con-
ducting an assessment within the state of Minnesota
you would contact the MN Department of Natural
Resources for ecological and water databases, the MN
Pollution Control Agency for emissions and water
databases, and the University of MN for ecological and
water databases.
EPA has combined many of its databases into the
Envirofacts Warehouse, which can be accessed at
http: //www. epa. gov/enviro/index_i ava.html. Data sets
are also available from monitoring networks that are no
NEWHC-MAP NOW AVAILABLE!!
C-MAP is the Clean Air Mapping and Analysis Program, a website designed and maintained by
EPA Clean Air Markets Division. This Web site is designed to take advantage of new geograph-
ic mapping techniques to assess the environmental benefits of sulfur dioxide and nitrogen oxide
emission reduction programs, such as the Acid Rain Program. Using a Geographic Information
System (GIS), C-MAP allows users to view a series of national and regional maps in the "Map
Gallery" section, and then download the data used to generate the maps in the "GIS Data
Download" section. The maps display information showing how changes in emissions result in
changes in air quality indicators, acid deposition, and sensitive ecosystems. The GIS database
provides an extensive inventory of national/regional level emissions, environmental effects, and
demographic data available for download, including air quality, surface water quality, acid depo-
sition, forest health, and sensitive ecosystem data. Many of the datasets described in this
Handbook can be accessed or linked to from C-MAP.
See: httD;//www.eDa.gov/airmarkets/cmaD/
17
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longer active (not included in Table 1). This informa-
tion can be helpful in assessing trends but locating these
data sets may require a bit of investigation.
Considerations for using databases to address ecologi-
cal assessment questions and general approaches to
assuring the quality of data, which is not part of a
national network, also are provided.
Emissions Databases
EPA is the primary source of emissions data for all of
the United States, at both national and state levels.
These data are available at http://www.epa.gov/ttn/
chief. Complete documentation of emissions inventory
development for the U.S. can be found in the EPA
National Air Quality and Emissions Trends Report,
1998 (http://www.epa.gov/oar/aqtrnd98/'). That report
is a good starting point for obtaining total emissions
data for assessments. Emissions are summarized by
pollutant, category, and state. Emissions associated
with a particular source will need to be accessed from
local state agencies. Development of inventories can be
done specially for a regional assessment by supple-
menting the EPA inventories with updated and source
specific information and by implementing a variety of
emissions models. However, this is a resource intensive
process. At the very least, any inventory used for an
assessment, particularly a local assessment, should be
spot-checked to see if it appears reasonable.
Under Title IV each regulated unit (e.g. boiler at a
power generating facility) is required to account for
every ton of emissions. In order to ensure compliance
each unit was required to install a continuous emission
monitoring system (CEM) to record various parameters
on an hourly basis such as heat input and total mass
emissions. The data are electronically transferred to
EPA's Emissions Tracking System (ETS) each quarter
and compared against the number of allowances held by
each unit at the end of each year. (Allowances are allo-
cated by EPA each year and each allowance allows the
holder to emit one ton of SO 2. Allowances can be
bought and sold or banked for future use.) Emissions
data from non-affected sources are estimated using
models and representative emission measurements.
Emissions data from sources in the Acid Rain Program
can be accessed on the web at http://www. epa. gov/air-
markets/emissions/.
The Emissions & Generation Resource Integrated
Database (E-GRID) is a comprehensive source of data
on the environmental characteristics of all electric
power generated in the United States. An integration of
18 different federal data sources, E-GRID2000 pro-
vides information on air pollutant emissions and
resource mix for 4600 individual power plants, more
than 2000 generating companies, states, and regions of
the power grid. The data are expressed in terms that
allow direct comparison of the environmental attributes
of electricity generation at any level. The latest version,
E-GRID2000, includes data from 1996 through 1998.
The new 1998 data have been reconfigured to reflect
the industry's current structure, including company
mergers, power plant divestiture to non-utility compa-
nies, and grid reconfigurations through December 31,
2000. E-GRID is accessible through a user-friendly
data browser or by viewing Microsoft Excel spread-
sheets, both downloadable from the EPA Clean Air
Markets web site at (http://www.epa.gov/airmarkets/
e grid/index).
The EPA Office of Enforcement and Compliance oper-
ates the American Indian Lands Environmental Support
Project (AILESP). AILESP integrates and assesses
recent multi-media point-source releases, the potential
impacts of contaminants, and recent compliance and
enforcement histories for facilities located on and with-
in five kilometers of Tribal areas. This project uniquely
assimilates and synthesizes disparate data sources to
create a better understanding of the nature and extent of
permitted point sources on and near Tribal areas. AILE-
SP can be found on EPA's website at
http://es.epa.gov/oeca/ailesp/index.html. Emissions at
the tribal level can be deduced from the emissions
inventories by examining the emissions for states and
counties that overlap tribal lands. Emissions for specif-
ic sources or source categories in a particular area may
be available from local, state or tribal agencies.
Information also is readily available for counties.
National Air and Deposition Monitoring
Networks
The two pollutants controlled under Title IV are sulfur
dioxide (SC^) and nitrogen oxides (NOX) because of
their recognized contributions to adverse health and
ecosystem effects. There are many national networks
that monitor SC>2 and NOX as part of their design and are
therefore an available source of air quality data (see
Table 1). Detailed descriptions of national monitoring
and analysis of these and other key pollutants (e.g.,
those for which standards have been set) at the
21
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metropolitan level are also available in the EPA
National Air Quality and Emissions Trends Report
1998 mentioned earlier. In addition, both maps and
time series are available for one or more sites on a large
selection of (wet) deposition parameters at the National
Atmospheric Deposition Program:
http: //nadp. sws.uiuc.edu/.
Ambient monitoring for SO 2 and NOx has been done at
urban monitoring stations as well as some rural stations
for up to 25 years. The IMPROVE visibility network
has almost 10 years of aerosol speciation data (e.g., sul-
fates, nitrates, organic and elemental carbon, and
ammonium) for PM2.5 and PMio (particles 2.5 microns
or less in size and 10 microns or less in size).
Precipitation chemistry in some networks goes back
almost two decades. All monitoring data generally are
available to the public upon request to the network
manager responsible, but may require persistence in
obtaining the specific information you need.
NADP/NTN: The National Atmospheric Deposition
Program (NADP) was established in 1978 to provide
information on geographical patterns and temporal
trends in U.S. precipitation chemistry. A major objec-
tive of the program is to characterize geographical pat-
terns and temporal trends in acid deposition of the
United States through development and maintenance of
a deposition monitoring network called the National
Trends Network (NTN). Long-term monitoring stations
are sponsored by cooperating agencies and organiza-
tions that volunteer personnel, equipment, analytical
costs, and other resources and agree to follow the
Network's standard established procedures. The net-
work currently consists of over 200 monitoring sites
across the nation with 5 of those stations located on
tribal lands (ME, SC, MI, MN, NY). NADP/NTN crite-
ria and protocols ensure uniformity in siting, sampling
methods, analytical techniques, data handling, and
overall network operation.
CASTNet/ AIRMoN: The EPA Clean Air Status and
Trends Network (CASTNet) and the National Oceanic
and Atmospheric Administration (NOAA) Atmo-
spheric Integrated Research and Monitoring Network
(AIRMoN) both provide information on site-specific
deposition that can be interpolated in some instances to
a regional scale. Dry deposition measurements in these
networks are a product of ambient air concentrations
and modeled deposition velocities. CASTNet measures
ambient 03, SO2, HNOs, particulate nitrate, and sulfate
and ammonium species. CASTNet is a primary source
for data to estimate dry acidic deposition and to provide
data on rural ozone levels. Used in conjunction with
other national monitoring networks, CASTNet deter-
mines the effectiveness of national emission control
programs. CASTNet data has been collected since 1987
and is available on the web at http://www.epa.gov/cast-
net.
AIRMoN brings together wet and dry deposition com-
ponents to reveal the causes of observed trends. The
AIRMoN-wet program relies on common field equip-
ment, a single analytical laboratory, and centralized
quality assurance. Daily samples are collected, and
samples are analyzed for nitrate, sulfate, and ammoni-
um. The AIRMoN-dry program relies on a two-tiered
approach that infers dry deposition from air quality,
meteorology, and surface observations and directly
applies eddy flux and/or gradient techniques. These
methods yield average dry deposition rates to areas,
typically many hundred meters in radius, surrounding
observation points. Observation sites are located within
areas that are both spatially homogeneous and repre-
sentative of the larger region. Sites selected for wet
deposition measurement may not be representative sites
for dry deposition measurement.
SLAMS/NAMS: State or Local Air Monitoring
Stations (SLAMS) and National Air Monitoring
Stations (NAMS) are federally mandated air quality
monitoring networks. They are designed to measure cri-
teria pollutants (characterizing maximum concentra-
tions, population exposure, source impacts, attainment
and non-attainment areas. The NAMS network, a sub-
network of SLAMS, is designed to track air quality in
urban, multi-source-impacted areas with high popu-
lation density. These surface air quality measurements
will generally be impacted by local and regional
sources. The current generation of O^, NO/NOx, SO2
and CO instrumentation used in these networks can
deliver virtually continuous data.
PAMS: Photochemical Assessment Monitoring
Stations (PAMS) is a small and newer network designed
to improve understanding of ozone (O^y PAMS is
intended to provide information for control strategy
development and evaluation, emissions tracking, trend
analysis, and exposure. It measures 03, speciated VOC,
and NOX. Speciated VOC and carbonyl compounds cur-
rently being measured have minimum sampling times
of one hour and three hours respectively. The methods
used to measure speciated hydrocarbons and carbonyls
in PAMS are still evolving, and quality assurance pro-
cedures and standards are still being developed. For
example, the NO 2 channel of the NOX analyzers (like all
22
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present generation commercial chemiluminescent NOX
analyzers) suffers from interference by more oxidized
forms of NOX such as HNO3 and PAN.
SOS: Like PAMS, the Southern Oxidant Study (SOS)
provides information primarily on Q and its precur-
sors. However, unlike the routine monitoring of the
PAMS, SLAMS, and NAMS networks, SOS provides
detailed information on interaction between regional
and urban Q pollution in the southern United States.
SOS has included simultaneous and interacting region-
al- and urban-scale air quality field experiments embed-
ded in a three-tiered network of sub-networks having
different levels of spatial and temporal resolution and
instrumental and technological sophistication. The net-
work includes:
• Spatial Ozone Network (SON) for continuously
monitoring surface O3 concentrations at some sites
• Southeastern Consortium Intermediate Oxidant
Network (SCION) for monitoring Q, NO, NOy,
HNOs, CO, SO2 and speciated hydrocarbon con-
centrations at a smaller number of sites
• Southeastern Network for Intensive Oxidant
Research (SENIOR), which uses state-of-the-sci-
ence instrumentation to characterize detailed
chemistry and chemical processes at a variable
number of rural sites in the region during intensive
measurement campaigns.
Ecological Monitoring
The response of ecosystems to changes in emissions is
still the most elusive piece of the assessment puzzle.
Ecosystems rarely show linear changes to management
decisions, and as was mentioned earlier, the lags in eco-
logical responses resulting from emission reductions is
primarily on the order of decades to centuries (see
Figure 7). National ecological monitoring networks are
limited, although state-level or regional networks exist
in many parts of the country.
Therefore, one of the key roles states and tribal nations
can fill is long-term monitoring of water quality and
biological parameters. These data are critical in the
actual documentation of recovery. Monitoring ecologi-
cal changes requires a commitment to consistent, long-
term monitoring to receive the full benefits of the net-
work. Decision-makers often have difficulty supporting
efforts with payoffs 20 years in the future, but without
good long-term monitoring data it is impossible to doc-
ument ecosystem recovery and to verify models. For
ecological networks that have been established, it is
often a recurring battle to simply maintain the existing
network. During budget cuts networks are vulnerable
targets often resulting in the loss of monitoring stations,
the funds to analyze what data is collected, or other
functions of the network. Such changes often compro-
mise the integrity of the entire network. This may
explain some of the variability encountered in ecologi-
cal data sets.
A partial list of parameters which could be measured to
document changes due to reductions in deposition
include: water chemistry changes; phytoplankton/zoo-
plankton population changes or species
presence/absence changes; fish species changes; fish
survival in formerly fishless waters; coastal eutrophica-
tion; red spruce recovery; decreases in the severity of
acidic episodes; decreases in the mercury levels in fish;
changes in diatom species found in the surface sedi-
ments of lakes. The National Research Council has
recently published a book titled Ecological Indicators
for the Nation (http://books.nap.edu/books/0309
068452/html/index.html). The book identifies national
level indicators needed for decision making and also
shows how the recommended methods can be useful at
regional and local scales.
Below is a brief description of those networks refer-
enced in Table 1 including a more complete list of the
parameters measured.
Forest Health Monitoring (FHM): Founded in 1990,
the multi-agency FHM serves as both the scientific
foundation and the administrative framework for col-
lecting, managing, assessing, and reporting forest
health information. The goals of the program are to
monitor, assess, and report on the long-term status,
changes, and trends in forest ecosystem health and sus-
tainability in the U.S. The USDA Forest Service in
cooperation manages FHM with other program part-
ners. All measurements are taken annually (June 15-
Sept. 15) on a systematic grid of about 4,000 forested
ground plots across the nation. A quarter of the plots are
measured each year on a four-year cycle.
In addition to the ground plot measurements, detection
surveys are conducted. These include aerial and
ground-based survey data on forest insects, diseases,
and other forest stressors collected by FHM partici-
pants, and data from other programs on factors such as
climate, weather, air pollution, management practices,
and forest growth.
23
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A special aspect of FHM is a network of intensive site
ecosystem monitoring sites (ISEM). These are on bio-
logically representative sites such as the Long Term
Ecosystem Research (LTER) sites, and are designed to
(i) correlate stressors with forest condition, (ii) improve
monitoring and evaluation techniques, (iii) identify
causal agents, and (iv) improve the estimation of future
forest condition.
The FHM measures the following parameters:
plant species diversity
bioindicator plants
lichen communities
tree mortality
lichen chemistry
wildlife habitat
tree damage
root condition
dendrochemistry
branch evaluation
leaf area index
tree regeneration
vegetation structure
air pollution
tree growth
foliar chemistry
scenic beauty
tree crown condition
dendrochronology
soils
scales into assessments of ecological condition and
forecasts of the future risks. EMAP will develop and
demonstrate indicators to monitor the condition of eco-
logical resources, and investigate multi-tier designs that
address the acquisition and analysis of multi-scale data
including aggregation across tiers and natural
resources. Measurements are taken annually at 12,600
sites in the eastern portion of the United States, which
include areas of Maryland, Virginia, West Virginia,
North Carolina and Pennsylvania. EPA recently
announced the initiation of the Western Environmental
Monitoring and Assessment Program that began in the
summer of 1999 and will run for five years.
EMAP measures the following parameters:
Water:
• discharge
• aquatic biota
• sediment chemistry
• habitat
sediment load
inorganic chemistry
trace metals
Long-Term Monitoring Project (LTM): As part of the
EPA's ongoing Long-Term Monitoring project, changes
in surface water chemistry have been monitored since
the early 1980's. Sampling occurs at 45 lakes in the
Northeast and Upper Midwest and at 12 streams main-
ly in the Mid-Atlantic region (lakes in Maine and
Vermont; Adirondack and Catskill regions of New
York; Michigan, Wisconsin, and Minnesota [MI, WI,
MN monitored until 1995]; Virginia streams in the Mid
Appalachians; and streams in the Catskill Mountains,
New York). Among the factors being monitored are
acidity, sulfate concentration and nitrate concentration.
Note that LTM data is not available via the internet but
can be obtained upon request to EPA (see Table 1).
The Temporally Integrated Monitoring of Ecosystems
(TIME) project is a related EPA program to measure
water quality in acid-sensitive environments. Sampling
occurs at 60 lakes in the Northeast and 60 streams in
Mid-Atlantic region. It formed part of the Mid-Atlantic
Highlands Assessment (MAHA) to provide a suite of
environmental assessment tools.(http://www.epa.gov/
emfiulte/html/remap/three/index.html).
Environmental Monitoring and Assessment
Program (EMAP): EMAP is an EPA research program
designed to develop the tools necessary to monitor and
assess the status and trends of the nation's ecological
resources. EMAP's goal is to develop the scientific
understanding necessary to translate environmental
monitoring data from multiple spatial and temporal
Marine/coastal:
• salinity/freshwater flux
• zooplankton
• nutrients/contaminants
• submerged/coastal habitats
Soils:
• texture
• toxicity
• structure
• strength
• erodability
Animals
• species/range/population
Miscellaneous
• landscape pattern
Vegetation
• growth rate
• above-ground biomass
• disease intensity
chlorophyll
animals
sediment
chemistry
mineralogy
climate
faunal biomass
recruitment
species/cover/range
nutrient availability
Long-Term Ecological Research (LTER): The
National Science Foundation established the LTER pro-
gram in 1980 to support research on long-term ecolog-
ical phenomena in the United States. The Network now
consists of 21 sites representing diverse ecosystems and
research emphases. A network office coordinates com-
munication, network publications, and planning activi-
24
-------
ties. The LTER involves more than 1,100 scientists and
students investigating ecological processes operating at
long time scales (e.g., decades) and over broad spatial
scales. The LTER Network is committed to long-term
ecological research on the following core areas:
• Pattern and control of primary production
• Spatial and temporal distribution of populations
selected to represent trophic structures
• Pattern and control of organic matter accumulation
and decomposition in surface layers and sediments
• Patterns of inorganic inputs and movements of
nutrients through soils, groundwater and surface
waters
LTER measurement increments vary from hourly to
annually, based on indicator of interest. Some of the
indicators included are listed below:
Climate:
• meteorology
Precipitation/deposition:
• wet deposition
Water:
• discharge
• organic contaminants
• inorganic chemistry
• trace metals
snow
dry deposition
sediment load
aquatic biota
sediment chemistry
habitat
National Water-Quality Assessment Program
(NAWQA): NAWQA, which is managed by USGS,
provides information on water resources in 60 river
basins and aquifers which together account for 60 to 70
percent of the nation's water use and population served
by public water supplies. The NAWQA goal is to iden-
tify the common environmental characteristics associat-
ed with the occurrence of key water-quality constituents
and to explain their differences. To make the program
cost effective and manageable, intensive assessment
activities in each of the study units are conducted on a
rotational basis, with one-third of the study units being
studied intensively at any given time. For each study
unit, 3- to 5-year periods of intensive data collection
and analysis are alternated with 5- to 6-year periods of
less intensive study and monitoring. Coinciding with
the study-unit investigations are national synthesis
assessments. Generally, two to four national synthesis
topics are studied at a given time. Two issues of nation-
al priority—the occurrence of nutrients and pesticides
in rivers and ground water—were selected as the first
issues, followed by the occurrence and distribution of
volatile organic compounds (VOCs). Collectively,
NAWQA measures:
Water:
• discharge
• organic contaminants
• inorganic chemistry
• trace metals
sediment load
aquatic biota
sediment chemistry
habitat
Marine/coastal:
• salinity/freshwater flux
• zooplankton
• nutrients/contaminants
• submerged/coastal habitats
Soils:
• texture
• mineralogy
• structure
Vegetation:
• growth rate
• above-ground biomass
• nutrient availability
Animals:
• food source/quality
• species/range/population
Miscellaneous:
• fire
chlorophyll
animals
sediment
chemistry
climate
faunal biomass
recruitment
species/cover/range
recruitment
Marine/coastal:
• salinity/freshwater flux
• nutrients/contaminants
National Surface Water Survey (NSWS): The
National Surface Water Survey (NSWS) sampled the
chemistry of 2,311 lakes and 433 streams nation-wide
between 1984 and 1986. The objective was to charac-
terize and classify these aquatic systems in terms of
their acidic sensitivity, chemistry, biological and bathy-
metric features. The Survey was divided into the
National Lake Survey and the National Stream Survey.
Closely related studies included the Long-Term
Monitoring Project (1982-present) and the Episodic
Response Project (1988-1990). These data are particu-
larly useful as a baseline to compare with more recent
data to assess whether any significant changes have
taken place since the implementation of the Acid Rain
Program.
National Lake Survey. The Eastern Lake Survey - Phase
I (ELS-I), conducted in the fall of 1984, was the first
25
-------
part of a long-term effort by the U.S. Environmental
Protection Agency National Surface Water Survey. It
was designed to quantify the acid-base status of surface
waters in the United States in areas expected to exhibit
low buffering capacity at a single point in time. The
effort was in support of the National Acid Precipitation
Assessment Program. The survey involved a three-
month field effort in which 1,612 probability sample
lakes and 186 special interest lakes in the Northeast,
Southeast, and Upper Midwest regions of the United
States were sampled.
The Eastern Lake Survey - Phase II (ELS-II), conduct-
ed in the spring, summer and fall of 1986, focused on
the northeastern United States. ELS-II involved the re-
sampling of a subset of lakes in the northeastern United
States sampled in ELS-I to determine chemical vari-
ability and biological status. Furthermore, within-index
period variability was examined in the fall of 1986 to
provide insight concerning the ability to detect chemi-
cal changes over time, and the precision of the estimates
of the number of acidic lakes from Phase I.
The Western Lake Survey-Phase I (WLS-I), conducted
in the fall of 1985, involved 719 lakes in the western
states (CA, OR, WA, Rocky Mountain states).
The parameters measured in Phase I included: alu-
minum, alkalinity, acid neutralizing capacity, calcium,
dissolved inorganic carbon, dissolved organic carbon,
chloride, color, specific conductance, iron, potassium,
magnesium, manganese, ammonium, sodium, sulfate,
nitrate, pH, total phosphorus, silica, turbidity, water
chemistry. The parameters measured in Phase II includ-
ed: selected re-survey of chemistry survey of Phase I,
lake bathymetry, spring, summer, and fall seasonal
chemistry, summer chlorophyll, and summer zooplank-
ton species / abundance.
National Stream Survey. The National Stream Survey
(NSS-I) primary goals were (1) to determine the per-
centage, extent (number, length, and drainage area),
location, and chemical characteristics of streams in the
United States that are presently acidic, or that have low
acid neutralizing capacity (ANC) and thus might
become acidic in the future, and (2) to identify streams
representative of important classes in each region that
might be selected for more intensive study or long-term
monitoring. The parameters measured included: alu-
minum, alkalinity, acid neutralizing capacity, calcium,
carbonate, color, specific conductance, dissolved inor-
ganic carbon, dissolved organic carbon, bicarbonate,
potassium, magnesium, ammonium, sodium, nitrate,
total nitrogen, pH, total phosphorus, silica, total sus-
pended solids, and turbidity. NSS datasets can be
accessed through the following website:
http://www.epa.gov/emfiulte/html/otherdata/napap/nss/
index.html
General Steps for Conducting
Quality Assurance (QA)
Data
Quality assuring data is necessary in order to provide
some level of confidence that the data are representing
what is actually occurring in the environment. Use of
data that has not been formally quality-assured may be
necessary when quality-assured data is not adequate or
when non-quality-assured data sets useful to the assess-
ment are available. Data that has not been quality-
assured should be indicated as such when used and
treated cautiously.
Several quality checks can be applied to increase confi-
dence in the data.
• Check with data managers for documentation and
informal evaluation of the data base
• Examine the data base for prominent anomalies
(e.g. missing data, negatives, spikes)
• Seek explanation for anomalies from data man-
agers
• Fill data gaps or omit periods without reliable
information
• Obtain additional formal or informal expert evalu-
ation of the data patterns
• Derive a rough estimate of data uncertainty (e.g.
range of error/accuracy/reliability) for the data set
Application of all of these steps would constitute a
thorough evaluation of the data set.
The extent to which a data base can be evaluated
depends on the assessment needs and the resources
available. For scoping assessments, a detailed evalua-
tion of the data as noted above may not be needed.
Bringing in additional expert evaluation and develop-
ment of well-defined uncertainty bounds is less critical.
Similarly if resources are very limited, the last two steps
may not be feasible. At a minimum, it is important to
scan the data for prominent anomalies and omit them to
avoid obvious errors in the analysis.
26
-------
section vi. Identifying Appropriate Analytical
Tools
Relationships between emission changes, pollu-
tant concentrations in the atmosphere, deposi-
tion of pollutants and the impact on ecological
and other resources can be quantified and predicted
through the use of computer models and associated
databases. Models range from those that describe links
between one receptor area and one source to others that
describe the complex regional scale relationships, con-
sidering the influence of all major sources and project-
ing a wide variety of receptor impacts throughout the
region. Some models address changes over short time
periods such as episodes, others focus on longer time
periods, and some attempt to do both. Usually, models
focus on one part of the overall assessment. Emission
models develop emissions data for input into air quali-
ty models. The output of the air quality models are then
translated into impacts using a variety of models char-
acterizing human health and ecological welfare and
other effects. Selection of the best model framework or
best set of models depends on the question being asked.
Resources and availability of the models also are fac-
tors.
It is important to keep in mind the limitations of mod-
eling. Models are valuable tools that can be used to pre-
dict future scenarios or to better understand changing
parameters, but they cannot replace actual field mea-
surements that monitor the current status of the envi-
ronment. Models must be verified and tested against
observational data to ensure that they accurately reflect
what is measured in the "real world" (this will be dis-
cussed in more detail later in this section). This
becomes complicated when working with complex
models that rely upon outputs from other models.
Combining models also multiplies the uncertainty of
the final results and can make them less reliable.
A range of models for drawing links between emis-
sions, air concentrations, deposition and impacts are
summarized in Table 2. Input data requirements, model
outputs, capabilities and limitations, and references for
the models are included. This set is not inclusive; rather,
it provides models representative of the full range of
outputs from emissions to effects.
Air Quality
As described in the previous section, air quality data is
available from various national networks. Similarly,
deposition data is available from large-scale networks.
Trend analysis—examining emission changes and air
quality and deposition changes over a period of time—
provides a way of exploring how impacts are affected
by changes in emissions. When observations are not
adequate, either because of the locations of monitors or
when the samples were collected, modeling can provide
data for the trend analysis. Air quality models are most
useful for examining future conditions. A number of
models have been evaluated by EPA and are available
on the EPA web site. These models range in applica-
tions from individual emissions sources to multiple
sources and to larger regional scale analysis.
The most comprehensive, extensively evaluated and
applied acid deposition model is the Regional Acid
Deposition Model (RADM). The model was developed
during the 1980s and is used in the NAPAP assess-
ments. RADM continues to be one of the primary mod-
eling systems used to characterize and address acid
deposition and related air quality issues in the Eastern
US. RADM is also used to predict or project the effec-
tiveness of proposed pollutant reduction legislation on
acid deposition and visibility.
One of the applications of RADM has been to develop
what are called "principle airsheds." Principle airsheds
are conceptual boundaries that separate areas contain-
ing sources that deposit efficiently to a particular recep-
tor region from those that do not. Airsheds are different
from watersheds, which have actual physical bound-
aries. Any given source is in a single watershed, but a
single source can be in many airsheds depending on
how many receptor regions it significantly influences.
In addition, sources that are not in a particular receptor
region's airshed can still contribute small amounts of
deposition to that receptor. Airsheds can be developed
for waterbodies, such as the Chesapeake Bay or
Albemarle Sound, or for terrestrial ecosystems such as
the Adirondack region of New York or Shenandoah
National Park. These airsheds do not represent the only
27
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source areas for emissions that impact these receptor
regions; rather they represent the area from which emis-
sions are frequently and easily transported to the recep-
tor region.Airsheds are useful conceptual and commu-
nications tools but they must be used carefully with a
clear understanding of their underlying assumptions.
A selection of RADM results from a recent assessment
is provided in the Appendix. The results illustrate how
acid deposition, aerosol concentrations and visibility
are expected to change as a result of reductions in emis-
sions. The results also provide information that can be
used in individual state and tribal assessments of the
impacts of proposed legislation on human health and
the well-being of ecosystems in their particular regions.
The RADM results are described in more detail in the
Appendix. Additional information on RADM-derived
regional acid deposition impacts for the Eastern US is
located at http://www.sph.unc.edu/ies/airpoll.htm.
For those doing assessments west of the Mississippi
River, there are two models that can be used: Models-
3/CMAQ and REMSAD. Until recently, air quality
models typically addressed only single pollutant issues.
Models-3/CMAQ (Community Multiscale Air Quality)
was developed by EPA's National Exposure Research
Laboratory to address the broad scope of the 1990
Amendments and the complex interaction among pollu-
tants. CMAQ is still undergoing evaluation but is
expected to be available shortly.
The Models-3 framework provides tools to prepare
emissions and meteorological inputs, define emissions
control strategies, project future emissions inventories,
execute meteorological models, delineate a geographic
domain, select alternative atmospheric chemical reac-
tion mechanisms, set vertical and horizontal grid reso-
lutions, and manage a series of air quality model runs.
CMAQ is applied through the Models-3 system.
CMAQ contains state-of-the-science simulations of
atmospheric transport processes, atmospheric chem-
istry, aerosol dynamics and chemistry, cloud chemistry
and dynamics, and deposition processes. A key aspect
of the Model-3/CMAQ system's structure is its flexibil-
ity to incorporate scientific and modeling advances, to
test alternative modeling approaches, and to link with
human and ecosystem exposure models. Models-3 is
available at http://www.epa.gov/asmdnerl/models/.
REMSAD was developed by ICF Consulting for the US
EPA. It is based on an Eulerian (grid) approach and may
be applied at scales ranging from a single metropolitan
region to a continent containing multiple urban areas. It
was designed to be capable of simulating the complex
long-range transport and deposition of atmospheric pol-
lutants to aquatic environments, and to assess the rela-
tive impacts of alternative control strategies. Although
initially developed to study the transport and removal of
airborne toxics, the interdependence of the processes
which also control the formation and removal of parti-
cles was recognized, and therefore the model was
designed for both toxics and particulate matter applica-
tions. REMSAD is non-proprietary and can be run on a
desktop computer. More information about REMSAD
is at http://www.epa.gov/ttn/scram/ under "alternative
models."
Ecological Impacts
The endpoints of assessments—stream pH, visibility,
human health, etc.—are often known as "receptors."
Relating changes in emissions to resulting changes in
key receptors can be challenging, given the complexity
of the environment and the slow pace of changes in eco-
logical systems. Whereas comparisons of emissions and
air quality should be made using data from consistent
time periods/years; ecological impact models translate
concentration and deposition changes into future esti-
mates of ecological changes. Since many ecological
changes occur over many years, information from air
quality models has to be adapted for use in these longer-
term time frames. Make sure that the model you choose
to use can provide the correct outputs (e.g. does it pro-
vide the streamwater chemistry parameters you need?)
and that it can be applied to the correct spatial scale.
Many ecological models are designed for small areas,
and changes or additional runs may be necessary to
extrapolate to the area in question.
MAGIC is one of the models developed to estimate
acidification of lakes and streams in response to sulfur
deposition is MAGIC (Model of Acidification of
Groundwater in Catchments). It was the principal
model used by NAPAP to estimate future damage to
lakes and streams in the eastern United States. MAGIC
is a lumped-parameter model of intermediate complex-
ity, developed to predict the long-term effects of acidic
deposition on surface water chemistry. The model sim-
ulates soil solution chemistry and surface water chem-
istry to predict the monthly and annual average concen-
trations of the major ions in waterbodies. At the heart of
MAGIC is the size of the pool of exchangeable base
cations in the soil. As the fluxes to and from the pool
change over time due to changes in atmospheric depo -
30
-------
sition, the chemical equilibria between soil and soil
solution shift to give changes in surface water chem-
istry. Although there are some uncertainties with regard
to the model, particularly concerning watershed nitro-
gen dynamics, MAGIC provides a generally accurate,
well-tested, and widely accepted tool for modeling the
response of surface water chemistry to sulfur deposi-
tion.
PnET-BGC is an integrated model that simulates the
concentrations and transport of major elements, includ-
ing nitrogen, in forest vegetation, soil, and water. The
model was formulated by linking two submodels to
allow for the simultaneous simulation of major element
cycles in forest and interconnected aquatic ecosystems.
These submodels include 1) PnET, a simple generalized
model of monthly carbon, water, and nitrogen balances
which provides estimates of net primary productivity,
nitrogen uptake, and water balances (Aber et al 1997;
Aber and Driscoll 1997); and 2) BGC, a new submodel
which expands PnET to include vegetation and organic
matter interactions of other elements (including calci-
um, magnesium, potassium, sodium, silica, sulfur,
phosphorous, aluminum, and chloride), abiotic soil pro-
cesses, solution speciation, and surface water process.
PnET-BGC uses measured and estimated data on mete-
orology and atmospheric deposition. The model is run
for several hundred model years prior to the advent of
anthropogenic deposition to allow the forest, soil, and
water to come to steady-state conditions. The model
simulates estimates of changes in atmospheric deposi-
tion from 1850 to the present day. Future scenarios of
changes in atmospheric deposition are simulated using
projections provided from simulations with the
Regional Acid Deposition Model (RADM) based on
model runs of air emission control scenarios.
General Steps for Conducting Model
Quality Assurance
Many standard models have been documented and eval-
uated for use in various applications. Models that have
not been thoroughly tested but are considered appropri -
ate for the assessment can be evaluated using a hierar-
chy of methods. The most familiar approach is direct
comparison with observational data. This approach,
however, is often not adequate for evaluating models
because the necessary observational data may not be
available or may not be strict enough for testing the
model for a specific application. Often the observation-
al data itself may already be earmarked for use with the
model in doing the assessment.
Several steps can be applied to gain further confidence
in the model:
• Compare model results with observational data if
the observational data is available.
• Examine the extent to which models and observa-
tions produce the same associations among key
variables.
• Check how appropriately the model responds to
changes in key input parameters such as emissions.
• Examine documentation to see how the model is
behaving in simulating key variables compared to
simulations of other model studies.
• Check scientific and technical reviews if available
to see how well the model integrates current scien-
tific knowledge for the current application purpos-
es.
• Seek expert reviews of the models.
All of these steps performed together would constitute
a thorough review of the model. In cases where this
level of evaluation is not needed, as in a scoping study
or where resources are not available for an in-depth
evaluation, then a limited evaluation should be done. At
a minimum, the model should be executed for a variety
of conditions to check how robust it is under a range of
parameter values, such as emissions, that are relevant to
the assessment questions.
31
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-------
section vii Integrating Information to Assess
Response
at
3
cm
Assessing the effectiveness of the Acid
Rain Program requires the ability to
relate changes in emissions to
changes in deposition and to changes in sensi-
tive receptors. An assessment can focus on any
one of these steps, or it can be integrated and
look at all of them. The end-goal of the techni-
cal analysis is to evaluate how well current
emission control efforts work in reducing
human and environmental impacts and to facil-
itate and assess the potential need for further
actions. These assessments will almost certain-
ly receive public scrutiny, and must be able to
withstand the normal processes of evaluating
financial and other costs associated with pro-
posed management actions. In addition, it will
be important to establish the level of certainty
that can be placed on the finding. This section
illustrates possible methods of analyzing spatial
and temporal patterns and then relating these
patterns and changes to ecological impacts
using statistical and other assessment tech-
niques.
Analyzing Spatial and Temporal Patterns. Changes
in spatial patterns, often illustrated using GIS
(Geographic Information System) maps and time series
trends, expressed in graphical formats, provide a useful
indicator of the effects and of the effectiveness of the
Title IV. Ideally, pre-regulatory concentrations, emis-
sions and deposition data will be obtained and used for
comparison and quantification of the magnitude of
changes. At the national scale there was a large
decrease in sulfur dioxide emissions during the 1970's
and early 1980's, with additional decreases in the
1990s. About a 30% reduction occurred in the eastern
U.S. between 1980 and 1995. This is due in part to the
fact that utility companies had already started to reduce
their emissions of sulfur dioxide. If the site is located
in the eastern U.S., data may show a dramatic decrease
in SC>2 emissions in 1995, which is consistent with the
first year of compliance under Title IV.
Trend analysis should be done over several years; year-
to-year trends are often "noise" and not reliable in the
long-term. However, a comparison of national deposi-
Figure 11. Sulfate Deposition at Two NADP Sites from
1978 to 1997.
40.0
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0
36.0 -
32.0 -
28'° 1
24.0 J
20.0 H
16. OH
12.0 -
8.0
ding RidgVf PA
HubbaniBraaltJM
1977 1982 1987 1992 1997
Source: NADP website (http://nadp.sws.uiuc.edu/)
tion maps from 1994 versus 1995 displays the expected
drop in overall SC>2 concentration and sulfate deposi-
tion expected from the large reductions in sulfur diox-
ide emissions that took place in 1995.
This relationship is even more apparent when compar-
ing the longer-term trend in deposition between 1980
and 2000. The 1994-1995 drop in total annual sulfate
deposition in response to Title IV regulations stands out
in Figure 11 above. Monitoring data from Leading
Ridge, PA showed an especially marked drop in 1995.
In addition to temporal variability, there is spatial vari-
ability in the response as well. The response of deposi-
tion to emissions followed a somewhat different pattern
at Hubbard Brook, NH, but a sharp reduction after Title
IV took effect is still apparent.
Bivariate Relationships. Bivariate plots are often used
to examine the relationship between emissions (e.g.,
SC>2 emissions on the x-axis) and the concentrations
and/or total deposition of the acid derivative sulfate
(SO/f ) in precipitation (on the y-axis). In the example
above, Driscoll et al. (1998a) found a linear relationship
33
-------
accounting for half of the variation (where r = 0.48 to
0.62) at the Hubbard Brook Watershed in New
Hampshire. This implies that cutting emissions will,
with a 48-62% certainty, result in a proportional
decrease in rain and stream concentrations of sulfate.
To further illustrate these analysis techniques, dNADP
sulfur and precipitation data was downloaded from the
NADP website http://nadp.sws.uiuc.edu/). The data
was plotted using maps, time series, and bivariate
graphs to facilitate the analysis.
There is a known positive relation between the annual
total precipitation and the total deposition. At the PA
and NH locations cited above, however, the relationship
for the 1978 to 1997 period is not a particularly strong
one, or at least highly variable as you can see (Figure
12).
The precipitation/SC>4 deposition relationship has sev-
eral implications: (i) the significantly higher precipita-
tion at the PA station in 1996 (32% increase, or a total
of 152.4 mm ppt) compared to 1995 (115.8 mm ppt) can
explain much of the increased total annual SO 4 deposi-
tion in 1996 relative to the year earlier; (ii) the total
annual 864 deposition dropped in 1997 compared to
1996 and was similar to that of 1995; this was consis-
Figure 12. Relationship Between Sulfur Deposition
and Precipitation at Two NADP Sites Over the
1978-1997 Interval.
40.0
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32.0 -
28.0 -
g 20.0 1
£ 16. OH
13
l/J
12.0 H
8.0
ding ttidnv, P4
Hubbard Brook. NH
38 58 78 98 118 138 158
Precipitation
(cm, annual total)
Source: NADP website (http://nadp.sws.uiuc.edu/)
Essential Steps for Integrating Data
Define the key questions and the needs of the
manager/decision maker. The key questions
identified in Section IV form the focus of the anal-
ysis of the scientific data and related information.
The assessment is designed to support the evalua-
tion and decision-making processes.
Acquire and analyze necessary emissions, con-
centration, and deposition data. This is the vital
first step in analyzing the impact of changes in
emissions in response to Title IV. Establishing
these relationships is important since there is gen-
erally good supporting evidence (NAPAP, 1990)
that reductions in emissions are reflected "down-
stream" (e.g., decreased air concentrations and
deposition rates of acidic compounds).
Acquire and analyze ecosystem data.
Acquisition and analysis of ecosystem data is the
next, and perhaps more challenging, step. Data on
explicit ecosystem indicators are limited and link-
ing impacts to deposition requires integration of
information on different temporal scales possibly
covering large source areas.
tent with the total precipitation in 1997 (107.2 mm
ppt) being similar to that in 1995; and (iii) the total
annual precipitation in 1994 (106.0 mm ppt) was
similar to that of 1995, discounting the likelihood
that the 1994 -1995 drop in SO4 deposition was due
to a difference in rainfall between those years.
Integrated Analysis. Another common analysis
technique involves plotting the emissions over a one
to three-decade interval simultaneously with ambi-
ent air concentrations, total deposition rates, and
typically, a response such as change in water chem-
istry or soil cation base capacity. Likens et al (1996),
Driscoll et al (1993, 1995, 1998a), Lawrence et al
(1995), and Shortle et al. (1997) provide examples
of this approach.
In Figure 13, annual average levels of the ambient
air SO 2 concentration (Allegheny County, PA), the
SC>4 deposition rate (Leading Ridge, PA), and the
streamwater 864 concentration (Young Woman's
Creek at Renovo, PA) are plotted simultaneously
over the 1977 to 1997 interval.
This integrated analysis example shows a direct
34
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Figure 13. A Comparison of Ambient Air Quality,
Deposition, and Streamwater Data from 1977-1997
at Selected Sites in Pennsylvania.
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Year
1997
Sources:
Ambient air SC>2- http://www.epa.gov/aqspubll/annual summarv.html
Deposition Rate 804:
http://nadp.sws. uiuc.edu/nadpdata/siteinfo. asp?id=PA42&net=NADP
Streamwater 804 Concentration:
http://wwwrvares.er.usgs.gov/wqn96cd/wqn/wq/formats/wq.fmt
Monitoring locations. The location of sample
sites and/or summary area (as in the case of the
county average used for ambient air quality)
were not spatially consistent, e.g., data were
not necessarily available for any one geo-
graphical location of interest.
Years for which data is available. The select-
ed starting and ending dates limited the num-
ber of sites for which the analysis could be
done; not all stations selected started in our
year of choice (1997). The data on Streamwater
values for 1996 and 1997 were not on the Web
and were accessed by calling the USGS
database manager.
Annual averages. The number of samples
and/or the months of observations to represent
an annual average varied in all cases, suggest-
ing that a robust analysis would require con-
siderable commitment of time and access to
appropriate statistical expertise.
Locating the correct database. A consider-
able fraction of the time (e.g., half to two-
thirds) to complete the analysis and construct
the graphs was spent in locating and accessing
the appropriate databases. Although a large
potential choice exists, the number of suitable
databases were narrowed to a smaller number
in practice.
comparison between changes that occurred along the
sequence of emission to air quality to deposition to
stream response. It also illustrated the relative ease of
access to websites with acid rain data, and of the limi-
tations and difficulties likely to be encountered.
Limitations of Using Web Databases
Some of the limitations and difficulty in using the Web
databases, such as those used in these analyses, are as
follows:
Changing analysis methods. In the case of some
parameters, the laboratory methods changed over the
two-decade interval so that values were not strictly
comparable, and strict continuity was lost. Contact with
the database manager proved valuable / necessary
where choices had to be made and/or where questions
arose as to the significance of sampling or laboratory
methods changes.
Confidence intervals. Statistical confidence
(e.g., sd, se, range) of each sample point was not explic-
it / immediately available, but could probably be
obtained by accessing the original sample data.
These and other analytical challenges have been dis-
cussed for this kind of integration by Clow et al (1999:
ftp://bqsnt.cr.usgs.gov/manilles/Clowfact3.pdf). Their
results are encouraging since they were able to observe
clear responses to emissions reductions when long time
series were used and where the data had been rigorous-
ly screened and appropriately transformed to achieve
methods consistency.
Even with the very rudimentary analysis in the "test"
illustration of Figure 13, some consistency in the depo-
sition and Streamwater response to decreasing ambient
SC>2 levels can be discerned. The sharp changes in 1995
in response to Title IV regulations are unambiguous in
all cases. Note that the vertical scales differ between the
three parameters and can influence the apparent degree
35
-------
of change. To achieve simplicity of scale, the ambient
air quality was multiplied by 3,000. This has the effect
that the marked air quality response may be somewhat
exaggerated relative to the deposition and streamwater
trends. Microsoft Excel (and other graphics routines)
enable the user considerable flexibility in scaling final
presentations. Trend lines can be added; those shown
are second order polynomials. Correlations and other
statistics are easily achieved. The correlations between
air quality and deposition, for example, was r =0.65;
between air quality and streamwater response, r = 0.51.
Although the correlation between deposition and
streamwater was significant (also r = 0.51), the soils in
the watershed are likely to strongly influence the degree
of response depending on the extent to which sulfur
oxides are retained in soil and vegetation.
36
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section VIM. Communicating Results
Effective communication with key people and
organizations is a critical element in the suc-
cess of ecological assessments. A communica-
tion strategy is necessary to make sure the important
information gets to diverse audiences and to integrate
varied approaches and formats for effective communi-
cation. A highly effective method for designing a com-
munication strategy is based on two steps: (1) assess-
ing communication needs and potential responses, and
(2) developing detailed guidelines for implementing the
most effective responses.
The needs assessment and guidelines for responses are
based on the answers to four questions:
• WHO do the assessment managers need to com-
municate with?
• WHY do the assessment managers need to com-
municate with them?
• WHAT information must be communicated?
• HOW can it be communicated most effectively?
The answers to the "who, why, and what" questions are
developed through discussions with scientists, man-
agers, policy makers and other key people. Those
answers provide a starting point for developing the
"how" answers. These questions and answers provide
an analytical matrix for defining the assessment man-
agers' communication goals and the most effective
ways to accomplish them.
The "WHO" answers enable the assessment managers
to target the most relevant audiences instead of dissi-
pating their resources in communication efforts that are
too broad or diffuse. In most situations where state and
tribal agencies are assessing ecological responses to
emission reductions achieved under the Acid Rain
Control Program, the most important audiences will be
policy makers, such as members of state legislatures,
Congress, and the general public. However, it is impor-
tant not to overlook other key groups such as environ-
mental advocacy organizations and industry trade
groups.
The "WHY" answers must provide precise definitions
of the various and sometimes diverse goals of the dis-
semination effort in order to determine what informa-
tion must be communicated. For example, one goal may
be to increase the general public's awareness of the
broad problems involved in an environmental policy
issue, while another may be to inform legislators about
assessment results related to a bill that is being consid-
ered.
The "WHAT" answers must propose various types and
levels of information that are needed to achieve the
goals that have been defined. For example, broad expla-
nations of ecological problems and general policy
options may be presented to the general public, while
detailed scientific conclusions related to specific provi-
sions of a particular bill may be more useful to legisla-
tors.
The "HOW" answers will provide detailed guidelines
for implementing the communication strategy. Once the
"WHO", "WHY" and "WHAT" have been defined, the
services of an experienced communication professional
can be very valuable in selecting the most effective
communication media and methods to reach precisely
targeted audiences with carefully selected information.
For example, the best ways to communicate with the
citizens of a densely populated eastern state may be
quite different from those that will most effectively
reach the members of a tribe scattered across a western
tribal nation.
A well-designed strategy will define the assessment
managers' communication needs and provide a priori-
tized list of specific responses to those needs. It also
will specify the professional skills and experience need-
ed to implement the responses effectively. It will pro-
vide managers and those who have been assigned day-
to-day responsibility for communication with the nec-
essary information and resources to organize, oversee,
and carry out communication activities knowledgeably
and effectively.
37
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-------
section ix. Examples of State-level
Ecological Assessments
Minnesota
The Minnesota Department of Natural Resources
(DNR) has developed tools (e.g., Geographic
Information Systems, Ecological Classification
Systems, environmental indicators, and biological sur-
veys) that describe and predict how resources interact
within ecosystems, and how they respond to human
uses. The DNR is applying these tools over large geo-
graphic areas over long time frames. One program that
has emerged from this is the Minnesota Environmental
Indicators Initiative (EII). This project will create the
framework for an integrated, statewide network for
selecting and monitoring environmental indicators. The
EII will provide the first statewide network for (1)
understanding and forecasting ecosystem health status
and trends, (2) assessing the ability of ecological sys-
tems to provide resource benefits, (3) anticipating
emerging environmental problems, and (4) monitoring
progress in maintaining and restoring ecosystems.
(http://www.dnr. state.mn.us/eii/)
Vermont
The Vermont Forest Ecosystem Monitoring (VForEM)
is a network of cooperators from government, academ -
ic and private sectors who gather and pool information
on Vermont's forest ecosystem. Using a multi-disci-
plinary approach to understanding forest ecosystems,
over 40 cooperators from various disciplines work
together at two sites, Mount Mansfield and the Lye
Brook Wilderness Area, to integrate research and mon-
itoring programs. This includes the integration of data
from multiple data sets maintained in the VForEM Data
Library, and results in a holistic view of ecosystems.
VForEM projects fall into six general categories:
Terrestrial Flora
Surface Water
Geology and Soils
Terrestrial Fauna
Atmosphere
Human Impact
(http ://www.uvm. edu/~snrdept/VMC/index.html)
Maryland
In 1987, the Maryland Department of Natural
Resources designed the Maryland Biological Stream
Survey (MBSS) to provide information on the ecologi-
cal consequences of acid deposition and other human-
related impacts. MBSS is a long-term monitoring pro-
gram designed to describe the current status of aquatic
biota, physical habitat and water quality in first, second,
and third order non-tidal streams. MBSS data will also
be used to identify probable causes of ecological degra-
dation, investigate relationships between human activi-
ties and ecological response, and identify areas in need
of protection or restoration. Approximately 1,000 sites
were sampled between 1995 and 1997. Monitoring
parameters include the following:
pH
Nitrate
Temperature
Sulfate
Conductivity
Dissolved Oxygen
• Dissolved Organic Carbon
• Acid Neutralizing Capacity
(http://www.dnr.state.md.us/streams/acid/index.html')
Maine
Maine's Department of Environmental Protection is in
the last stages of an assessment done in collaboration
with the Northeast States for Coordinated Air Use
Management (NESCAUM) and EPA's Clean Aire
Markets Division. The assessment used the RADM
model to correlate sulfate and nitrate deposition in New
England with upwind emissions. Due to the variability
in data of one or a few deposition monitoring sites, this
assessment chose a regional analysis of sulfate and
nitrate deposition of the New England area. Total pre-
cipitation and total deposition data sets were combined
and normalized to a mean of 1 (Shannon, 1999).
Analyses indicate a correlation between emissions and
a drop in sulfate deposition, but there was no change in
nitrate deposition. Further analysis indicates a positive
correlation between the decrease in sulfate deposition in
New England and a change in lake chemistry in Maine.
(http: //www. state. me. us/dep)
39
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Section X.
References
Clow, D.W and M.A. Mast. 1999. Trends in precipitation and stream-water chemistry in the northeastern United
States, water years 1984-1996. United States Geological Survey Fact Sheet 117-1999, July 1999.
Driscoll, C.T., K.M. Postek, D. Mateti, K. Sequeira, J.D. Aber, W.J. Kretser, M.J. Mitchell, and D.J. Raynal.
1998a. The response of lake water in the Adirondack region of New York to changes in acidic deposition.
Environmental Science and Policy 1: 185-198.
Driscoll, C.T., G.E. Likens, and M.R. Church 1998b. Recovery of surface waters in the northeastern U.S. from
decreases in atmospheric deposition of sulfur. Water, Air, and Soil Pollution 105: 319-329.
Driscoll, C.T, K.M. Postek, W. Kretser, and D.J. Raynal. 1995. Long-term trends in the chemistry of precipitation
and lake water in the Adirondack region of New York, USA. Water, Air, and Soil Pollution 85: 583-588.
Driscoll, C.T., and R. Van Dreason. 1993. Seasonal and long-term temporal patterns in the chemistry of
Adirondack Lakes. Water, Air, and Soil Pollution 67: 319-344.
Heggem, D., S.A. Alexander, and J.E. Barnard 1993. Forest Health Monitoring 1992 Activities Plan. Report
EPA/620/R-93/002. U.S. Environmental Protection Agency, Office of Research and Development, Washington,
DC.
Lackey, R.T. 1997. If Ecological Risk Assessment is the Answer, What is the Question? Human and Ecological
Risk Assessment 3(6): 921-928.
Lawrence, G.B., M.B. David, and W.C. Shortle. 1995. A new mechanism for calcium loss in forest-floor soils.
Nature 378:162-165.
Likens, G.E., C.T. Driscoll, and D.C. Buso. 1996. Long-term effects of acid rain: Response and recovery of a for-
est ecosystem. Science 272:244-246.
Middleton, P. 1997. Background Document on Air Quality Data Compatibility. Prepared for the Commission on
Environmental Cooperation. RAND Environmental Science & Policy Center, Washington, D.C.
NAPAP. 1998. NAPAP Biennial Report to Congress: An Integrated Assessment. U.S. National Acid Precipitation
Assessment Program, Silver Spring, MD. http://www.nnic.noaa.gov/CENR/NAPAP/NAPAP_96.htm
NAPAP. 1990. Acidic Deposition: State of Science and Technology, Volumes I-IV. National Acid Precipitation
Assessment Program, Washington, DC.
National Research Council. 1999. Ecological Indicators for the Nation. National Academy Press, Washington, DC.
Shannon, J. 1999. Regional trends in wet deposition of sulfate in the United States and SC>2 emissions from 1980
through 1995. Atmospheric Environment 33(5):807-816.
Shortle, W.C. and E.A. Bondietti. 1992. Timing, magnitude, and impact of acidic deposition on sensitive forest
sites. Water, Air, and Soil Pollution 61: 253-267.
41
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Shortle, W.C., K.T. Smith, R. Minocha, G.B. Lawrence, and M.B. David. 1997. Acidic deposition, cation mobiliza-
tion, and biochemical indicators of stress in healthy red spruce. Journal of Environmental Quality 26:871-876.
Stoddard, J.L., C.T. Driscoll, J.S. Kahl, and J.H. Kellogg. 1998. Can site-specific trends be extrapolated to a
region? An acidification example for the Northeast. Ecological Applications 8(2):288-299.
Stoddard, J.L., C.T. Driscoll, J.S. Kahl, and J.H. Kellogg. 1998. A regional analysis of lake acidification trends for
the Northeastern U.S., 1982-1994. Environmental Monitoring and Assessment 51:399-413.
U.S. Environmental Protection Agency. 200. Analysis of the Acid Deposition and Ozone Control Act (S.172).
Prepared for the Senate subcommittee on Clean Air, Wetlands, Private Property and Nuclear Safety.
http://www.epa.gov/airmarkets/articles/
U.S. Environmental Protection Agency. 1999. The Benefits and Costs of the Clean Air Act, 1990-2010. EPA
Report to Congress EPA-410-R-00-001
U.S. Environmental Protection Agency. 1998. Regulatory Impact Analysis for the NO^ SIP Call, FIP, and Section
126 Petitions, EPA, ARD, September 1998 volume 1 chapter 4. http://www.epa.gov/capi/ipm/npr.htm
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Appendix A. Frequently-Raised Issues and
Questions
This section discusses some of the questions that are
frequently raised when conducting assessments of acid
deposition. It is useful to be aware of these issue from
the beginning, so as to take them into account when
designing and conducting the assessment as well as
communicating the results.
Emissions, Concentration, and
Deposition Analysis Considerations
The following notable issues, complications, and data
limitations and other constraints have implications on
how the data can be interpreted.
Only a portion of acid deposition precursors are cur-
rently being controlled. Although the largest emitting
power plants were controlled under Phase I in 1995, a
larger number of utilities did not come into compliance
until 2000 when Phase II began and controls on Phase I
sources were tightened further. However, other chemi-
cal species such as NQc are not as aggressively con-
trolled under Title IV and still others such as ammoni-
um (NH/i) not at all. The result is that only a portion of
total acidity is being reduced by Title IV, therefore, any
analysis is unlikely to document a complete ecosystem
response.
Methods of measurement of S and N deposition are
variable, and some nitrogen deposition data is
thought to be underestimated. The difficulty in accu-
rately measuring and modeling deposition, particularly
of nitrogen compounds, remains a large obstacle to
accurately quantifying actual acidity impacts. Wet
deposition sites are located away from local emissions
sources (e.g., major highways, chemical factories, cat-
tle, hog and chicken farms, and fertilizer applications)
in order to be as regionally representative as possible.
Evaluations of nitric acid based on ozone behavior as a
surrogate indicate that dry deposition measurements of
nitrogen may underestimate actual rates by as much as
30% during the summer, depending on the site. In addi-
tion, nitrogen deposition measurements do not include
ammonia and organic nitrogen, which may further
underestimate total nitrogen deposition loads. In addi-
tion, NADP measures NH4 somewhat inaccurately; val-
ues may be underestimated by as much as 15%.
Both of these inaccuracies tend to underestimate nitro -
gen depositon, so current nitrogen deposition estimates
can be considered conservative. Since any underestima-
tions apply universally across the entire data record,
they should not affect the trends in deposition but could
affect analyses of environmental response (NAPAP,
1990).
Dry deposition is very condition and site specific, and
models do not currently exist that can accurately quan-
tify the variations. Therefore, some modelers make the
assumption that total deposition is twice that of wet
deposition. If wet deposition of S or N is 20 kg/ha/yr,
for example, the total deposition is estimated to be 40
kg/ha/yr. By deduction, the dry deposition component is
assumed to be 20 kg/ha/yr. Studies show, however, that
numerous factors influence the dry deposition rate and
a uniform assumption is unwarranted. For example over
the extent of the Chesapeake Bay, it is typically
assumed that dry deposition is uniform, but the reality
is that it is dependent on precipitation, wind, tempera-
ture, and water currents; these all vary greatly from
north to south over the length of the Bay.
Experimental work on throughfall deposition (includ-
ing gaseous, aerosol, particulate fractions of dry depo-
sition) under a tree canopy shows that a significant
amount of sulfur is deposited in the forest stand (e.g., a
dramatic increase in sulfur relative to samples obtained
above the canopy). There are also large differences in
deposition rates between conifer and hardwood forest
types. Both wet and dry deposition increase as the ele-
vation increases.
There is a significant unknown source of sulfur at
most sites in the Northeast U.S. Driscoll et al. have
found a discrepancy in the S budget at most intensively
sampled locations in the Northeast U.S. The quantities
of output of sulfur in streamwater are larger than the
measured inputs of sulfur in precipitation, suggesting a
significant unknown S source. Three possible sources
of the "unknown sulfur" were hypothesized: sulfur
43
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stored on S-absorbing sites in soils and sediments at the
time of high S deposition are being "bled out" or
leached; underestimates of dry S deposition; and miner-
alization of S from naturally occurring minerals.
Investigations to date indicate that the first hypothesis is
not supported by data. The error in dry deposition
would have to be on the order of 2-3 fold. While possi-
ble, this appears to be unlikely. Mineralization of sulfur
from naturally occurring minerals was tested using iso-
topes and papers to be the likely source. The prepon-
derance of 150 sites sampled by EPA in 1990 show this
phenomenon. Among 50 sites examined in the
Adirondacks all (except for a few with large wetlands)
show a sulfur surplus.
Climate is a major factor influencing deposition
rates and can explain a significant part of the
observed pattern over the last three years. Climate,
notably the year-to-year changes in temperature and
precipitation, is a significant factor affecting deposition
rates. Title IV changes alone do not explain all of the
variation in measured deposition and concentration. In
Ohio, the total precipitation in 1995, 1996, and 1997
has been higher than the 15-year average and this can
explain the higher than expected S and N deposition
rates observed. Not only is concentration affected; total
S and N deposition is a function of the amount of rain-
fall. The total precipitation has been going up at many
eastern U.S. stations. Moreover, the high precipitation
levels typical of high elevation mountain sites has
meant that there has been little change so far in the total
S deposition in response to Title IV. The higher temper-
atures at many stations in the eastern U.S. is also a fac-
tor since temperature influences the oxidation rate of
SC>2 in the atmosphere. As was noted earlier SC>2 con-
centrations have come down by about 20%.
The time-scale and integration interval of the analy-
sis is very important. Currently, recovery in response
to Title IV, as measured by increased acid neutralizing
capacity, is not being observed in most lakes and
streams (Driscoll et al. 1998a, 1998b). The exception is
New England lakes where signs of recovery are being
observed. Soils and sediments have been sinks of S and
N over several decades and it will be some time before
the S and N leach out. The process of replacing the lost
Ca, Mg, and cation base capacity is a geological process
on the scale of decades and centuries. There is a need to
recognize that different ecosystems and different pro-
cesses may respond to deposition changes on various
time scales, some more easily measured than others. In
addition, sublethal, but persistent (chronic) effects of
acidity stresses are now recognized to be as important
as the direct, lethal, short-term or acute effects.
A long integration interval (e.g., one year) needs to be
used when samples of N are being averaged from dif-
ferent monitoring networks. The problem is that
although laboratory procedures are identical, the field
monitoring procedures for N are not, so that values dif-
fer and cannot be averaged across multiple stations.
While S is not affected in this way, nitrate levels cannot
be simply averaged without correction factors. A long
integration time helps somewhat to modulate any bias
of different sampling procedures.
The spatial scale is very important; responses may
not be uniform. There is not a uniform response or uni-
form recovery associated with Title IV or other pro-
grams. Some parts of New England., for example, are
exhibiting signs of recovery, yet other parts of the east-
ern U.S. show no signs of recovery or even continue to
degrade.
NADP was established to show region to region differ-
ences in the acidity of wet deposition. State or tribal
nation scales will require much more detail than the
NADP data are designed to provide. The appropriate
unit of ecological analysis is the watershed, again on a
much smaller scale than called for by the NADP sam-
pling design. A model developed at Pennsylvania State
University estimates the deposition on a 100 meter
scale by including the National Weather Service and
other meteorological data from the National Oceanic
and Atmospheric Administration, high resolution
topography data, vegetation cover, etc. The result is a
highly detailed map that shows the considerable varia-
tion in deposition rates from one location to another. If
a relatively small area is being studied, national moni-
toring data such as NADP may have limited utility.
Sensitivity of the ecosystem versus resolution of the
data is important. The degree of sensitivity of ecosys-
tem parameters and processes makes a difference in the
scale of precision required in the deposition data.
Ecosystem Analysis Issues
The following notable issues, complications, and data
limitations and other constraints have implications on
how the data can be interpreted.
Typical Ecosystem Indicators. Some ecosystem com-
ponents or processes are being monitored that are
44
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directly sensitive to acidic deposition. The following
parameters, among others, are being monitored as indi-
cators of acidic deposition effects: lichen communities,
air quality bioindicators, soil base cations, acid neutral-
izing capacity, soil aluminum/calcium ratio, streamwa-
ter or lake chemistry (pH, sum of base cations, Ca, Mg,
SO/i, NOs), benthic macro-invertebrates, and fish popu-
lations.
Another source of data on indicators is a wide spectrum
of biological data collected outside the acid rain moni-
toring network but of potential interest and utility in
addressing certain policy questions, such as data col-
lected as part of the Long Term Ecological Research
Program (see Table 1).
Statistical Analyses. The kinds of statistical analyses
and tests applied to the data will depend on the nature
and complexity of the air quality-response links being
explored. Bivariate graphs and time series frequently
appear in the assessment literature. Shortle and
Bondietti (1992) and Likens et al (1996) are examples
of recent studies that examined the relationship between
acid deposition rates and flux of base cations in soil,
and in streamwater, respectively. Multivariate analyses
(e.g., factor analysis, multiple regression) are less com-
monly reported in the literature, but present an effective
option when examining several environmental param -
eters simultaneously.
There are some problems and outstanding questions
about the methods and the databases that may have
significant impacts on the interpretation of results.
Among those noted in discussions with scientists are:
• the potential impacts of repeated re-sampling
• the importance of the timing of (re-)measurements
• high spatial variation and need for comparison
across spatial gradients
• the difficulty in establishing true controls (e.g.,
before or after acid rain impacts; or acid rain ver-
sus non-acid rain regimes for comparison of iden-
tical sites)
• the need to define recovery
• the presence of unknown manmade or natural
sources of sulfur and nitrogen
Ecological Models. Models offer an opportunity to
examine some kinds of deposition responses that are
difficult to measure or observe in the field such as long
response times, subtle or transient effects, and spatial
and temporal patterns that are difficult to monitor and
map with sufficient resolution. They also offer the
opportunity for experimentation by internal modeling
exercises using constructs in the place of real world
data. Some models already developed and available for
analyzing acid rain effects are enumerated in Section
VI. It will be important to determine what models are
available and which may be of use in your assessment.
Most models need specific kinds of input data, and gen-
erate specific kinds of output (e.g., ecosystem respons-
es) based on a set of assumptions about how the exter-
nal influences affect key processes within the ecosys-
tem. Assuming a model exists that can address the pol-
icy questions, it will be important to obtain documenta-
tion of the model, and articles describing its application
to specific problems or issues.
The following key issues should also be kept in mind
when conducting an ecological assessment.
Ecological changes may be due to many factors, and
attributing the cause to decreasing atmospheric
deposition will require good scientific monitoring
data. There is a growing awareness that other factors
may be playing a role in ecosystem effects. Organic
pollutants such as trizene and atrazene, widely used in
agriculture, are suspected by some scientists to be a fac-
tor in amphibian declines in the Northeast, for example.
The skin of frogs is highly absorbent of these chemi-
cals.
A suite of indicators is necessary to capture the full
effects of changing acidic deposition on ecosystems.
There is definitely a move away from single-factor
evaluations (e.g., stream water chemical quality)
toward indicators based on a multiplicity of interac-
tions. Several experts from different disciplines may be
involved. Managers need a broad integration of many
component responses in order to make robust decisions.
It is true that the broader analysis is perhaps less "rig-
orous" and precise scientifically than a narrowly taken
approach on one or more parameters. However, a broad
analysis can often describe the full range of ecosystem
responses more accurately and lead to better-informed
management decisions.
How many and what indicators should be used?
There is no precise answer to this question. It varies
depending on the data and resources available, and gen-
erally all desired indicators cannot be included. In dis-
cussions developing this Handbook, one scientist indi-
cated "I am not suggesting hundreds but a selection of
6-12. The problem is that if you put a team of review-
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ers in a room, there would be a range of different per-
ceptions on what the 6-12 indicators should be, and no
consensus." Ecological assessments are still an evolv-
ing process.
In developing a comprehensive assessment, would
the aquatic system be a good place to start? The
development of an effective protocol to do an assess-
ment is a huge and extremely difficult problem to tack-
le. A few key mechanisms can be identified; however,
this is not the whole picture. There is the most informa-
tion available on the aquatic side, so that is usually a
good place to start. There is a sense that aquatic scien-
tists are getting close to agreeing on a set of indicator
species.
It is true that the data and the models for quantifying
links between deposition and stream chemistry, and
especially those between stream chemistry and the bio-
logical responses (invertebrates, fish) are good. These
links are much better resolved than the terrestrial soil
chemistry-tree responses.
Given that it is possible to develop a good assessment
procedure and model for the aquatic ecosystem, the
rhetorical question is how much confidence do you, the
manager, and the end-users need in the assessment?
Despite the fact that these questions remain, managers
cannot wait for perfect assessment designs or complete
scientific consensus before taking action.
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Appendix B. Sample Integrated Assessment
The modeling results presented here include analysis of total annual deposition, total annual mean aerosol concen-
trations and visibility for emission scenarios related to new and existing legislation. The Regional Acid Deposition
Model (RADM) was used to model sulfur and nitrogen deposition and the Regional Particulate Model (RPM) was
used to model particulates in order to calculate visibility. The results illustrate possible acid deposition and visibili-
ty changes in the future throughout the Eastern US. Results are presented on the standard 80 by 80-kilometer
RADM gnd.
Inspection of these maps provides a way to estimate potential changes in impacts related to deposition, aerosol
concentrations and visibility within the individual grids. For example, a change in sulfate deposition within a grid
can be translated into anticipated ecosystem responses in the grid some time in the future.
Background
This analysis was requested when legislation was proposed during the 106th Congress called Senate Bill S. 172.
This legislation focuses on utility emissions because they account for about two-thirds of the total SO 2 emissions
and one-third of the NOx emissions in the United States. In addition, available control options and the costs associ-
ated with particular control scenarios are well understood (U.S. EPA 1998).
Emission inventories were developed for each scenario. EPA analyzed impacts of the full S. 172 bill and its com-
ponents on acid deposition and visibility in the Eastern U.S. in 2010. Results of the major deposition, aerosol con-
centrations and visibility parameters for the East are presented here.
Scenarios. The following three scenarios were chosen for air quality and deposition modeling:
• 1990 Base. The base case reflects emission conditions as they were in 1990. The emissions profile was derived
from the EPA section 812 prospective study, The Benefits and Costs of the Clean Air Act, 1990-2010 which
examines the costs and benefits for air quality legislation for the next 10 years. More detail on how this inven-
tory was developed is available in the study itself.
• 2010 Base (S-172) or Existing Clean Air Act (Title IV) Only. The 2010 Base assumes full implementation of
Title IV controls, and no additional controls from other emissions reduction programs affecting electric utility
units.
• 2010 Full (S-172) or Existing Clean Air Act (Title IV) Plus Additional S(>2 and NOx. This scenario assumes
the same conditions as in the 2010 Base plus addition controls on SOX and NOx as outlined in S172.
47
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Results
The results are presented in graphical format and are grouped into acid deposition and visibility analyses.
The acid deposition analysis includes:
• Deposition: Sulfate and nitrate deposition for the three scenarios.
• Percent Change in Deposition: Percent changes in the base 1990 year and the two 2010 scenarios for sulfate and
nitrate total deposition.
The visibility analysis includes:
• Aerosol Concentrations: Total aerosol concentration expressed by sum of sulfate, nitrate and ammonium
aerosols for the three scenario years.
• Percent Change in Concentrations: Percent changes in total aerosol concentration for the three scenarios.
• Percent Change in Visibility: Percent changes in visibility calculated from the aerosol concentrations for the
three scenarios.
Analysis of the information is provided. Guidance on how to interpret the information and use it in an assessment
also is noted.
This air quality and deposition modeling was done using RADM, the aerosol and visibility modeling also included
a component called RPM. When this is the case, the headers include the term RPM.
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Acid Deposition Analysis
The first six maps represent the annual total deposi-
tion (wet and dry) for the three scenarios for nitrogen
and for sulfur. The three graphs on this page depict
nitrogen deposition in 1990, in 2010 with Title IV
only, and in 2010 with Title IV and S-172.
Deposition is expressed in kilograms nitrogen per
hectare per year.
The highest nitrogen deposition levels are in the
Ohio River Valley and areas to the east. Nitrogen
deposition would decrease from over 10 kg-N/ha/yr
in the Ohio River Valley in 1990 to 6-8 kg-N/ha/yr
in 2010 if S-172 were implemented.
Annual Oxidized Nitrogen (NOx) Deposition in
1990 (kg-N/ha/yr)
Source: Regional Acid Deposition Model (RADM)
Annual Oxidized Nitrogen (NOx) Deposition in
2010 with Implementation of Title IV only (kg-
N/ha/yr)
Source: Regional Acid Deposition Model (RADM)
Annual Oxidized Nitrogen (NOx) Deposition in
2010 with Implementation of Title IV and S-
172 (kg-N/ha/yr)
Source: Regional Acid Deposition Model (RADM)
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The following three maps show sulfur deposition in
1990, in 2010 with Title IV only, and in 2010 with
S-172. Deposition is expressed in kilograms sulfur
per hectare per year.
As illustrated, sulfate deposition is generally highest
in the Ohio river valley and to the east of this area.
The sulfate deposition load would decrease in those
mid-west areas of highest deposition from more than
20 kg-S/ha/yr in 1990 to 12-16 kg-S/ha/yr in 2010 if
S-172 were implemented. Title IV provides an inter-
mediate level of reduction in deposition.
Annual Total Sulfur (S) Deposition in 1990 (kg-
S/ha/yr)
Source: Regional Acid Deposition Model (RADM)
Annual Total Sulfur (S) Deposition in 2010
with Implementation of Title IV only (kg-
S/ha/yr) (base)
Source: Regional Acid Deposition Model (RADM)
Annual Total Sulfur (S) Deposition in 2010 with
Implementation of Title IV and S-172 (kg-
S/ha/yr)
Source: Regional Acid Deposition Model (RADM)
50
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The following two sets of maps present the percent change in deposition. The first set on this page is for nitrogen
deposition under 2010 conditions with Title IV only and for 2010 conditions with Title IV and S-172. Changes for
both scenarios are in comparison to the 1990 Base conditions. As illustrated in the Title IV/S172 graphic, the areas
of greatest improvement in nitrogen deposition levels are in the Ohio river valley area. There are also significant
improvements in the south and in southern New England. Nitrate deposition shows a much greater level of improve-
ment with implementation of the full S-172 emissions reductions than with only Title IV. Environmental impacts
and/or benefits are expected to be highest in these areas of greatest reduction in deposition load.
Percent Reduction in Annual Oxidized
Nitrogen (NOx) Deposition between 1990
Conditions and Implementation of Title IV
only in 2010 (kg-N/ha/yr)
Source: Regional Acid Deposition Model (RADM)
Percent Reduction in Annual Oxidized
Nitrogen (NOx) Deposition between 1990
Conditions and Implementation of Title IV
and S-172 in 2010 (kg-N/ha/yr)
Source: Regional Acid Deposition Model (RADM)
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The two maps on this page present the percent change in sulfur deposition. The first is for 2010 conditions with
Title IV only and the second is for 2010 conditions with Title IV and S-172. Changes for both scenarios are in
comparison to the 1990 conditions. As illustrated in the Title IV/S172 graphic, the areas of greatest improvement
in sulfur deposition levels are in the Ohio river valley area. There are also significant improvements in the south
and in southern New England. Sulfate deposition shows a much greater level of improvement with implementation
of the full S-172 emissions reductions than with only Title IV. Environmental impacts and/or benefits are expected
to be highest in these areas of greatest reduction in deposition load.
Percent Reduction in Annual Total Sulfur
Deposition Between 1990 Conditions and
Implementation of Title IV only in 2010 (kg-
S/ha/yr)
0—5
5—10
10 -15
15 -20
20 —25
25 —30
> 30
Source: Regional Acid Deposition Model (RADM)
Percent Reduction in Annual Total Sulfur
Deposition Between 1990 Conditions and
Implementation of Title IV and S-172 in
2010 (kg-S/ha/yr)
Source: Regional Acid Deposition Model (RADM)
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Fine Participate and Visibility
Analyses
The first three maps present the annual mean total
aerosol concentrations for 1990 and for the two 2010
scenarios. The concentrations are expressed as
micrograms per cubic meter. The totals include con-
tributions from sulfate, nitrate and ammonium
aerosols. Contributions from other aerosols are
assumed to be much lower than other components in
the East and do not need to be included in the analy -
ses. High concentrations occur mainly in the same
regions as the high deposition levels.
Annual Mean Total Aerosol Concentrations
(SO4, NO3, and NH4) in 1990 (ug/m3)
0 — 2
2-4
4—6
6 — 8
8—10
10 —12
12 —14
> 14
Source: Regional Acid Deposition Model (RADM) and RPM
Annual Mean Total Aerosol Concentrations
(SO4, NO3, and NH4) with Implementation
of Title IV only in 2010 (ug/m3)
Source: Regional Acid Deposition Model (RADM) and RPM
Annual Mean Total Aerosol Concentrations
(SO4, NO3, and NH4) with Implementation
of Title IV and S-172 in 2010 (ug/m3)
LEGEND:
0 — 2
2 — 4
4—8
6 — 8
8—10
10 -12
12 —14
> 14
Source: Regional Acid Deposition Model (RADM) and RPM
53
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The next two maps show the percent reduction in total annual mean aerosol concentrations for both 2010 scenar-
ios. Improvement is greatest mainly in the regions of the highest initial concentrations.
Percent Reduction in Aerosol
Concentrations (SO4, NO3, and NH4)
between 1990 Conditions and 2010
Conditions with Title IV (ug/m3)
LEGEND:
% Increase
0—5
5—15
> 15
% Reduction
0—5
5—15
15 —25
25 —35
i > 35
Source: Regional Acid Deposition Model (RADM)
Percent Reduction in Aerosol Concentrations
(SO4, NO3, and NH4) Between
Implementation of Title IV only and
Implementation of Title IV and S-172 in 2010
(ug/m3)
Source: Regional Acid Deposition Model (RADM) and RPM
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The last two maps present the visibility changes for the two 2010 cases. In both cases, the absolute change in visi-
bility at the 90th percentile is presented. Deciview is a unit for visibility and is related to aerosol light extinction
(light scattering and absorption of sunlight by the aerosols). Total light extinction is the sum of the concentrations
of each visibility-reducing aerosol weighted by the light extinction efficiency of that aerosol. Sulfate and nitrate
aerosols have similar light extinction efficiencies. The lower deciviews are related to better visibility and higher
ones are associated with poorer visibility.
Annual Change in Visibility between 1990
Conditions and Implementation of Title IV
only in 2010 (90th percentile change in
deciviews)
Source: Regional Acid Deposition Model (RADM)
Annual Change in Visibility Between 1990
Conditions and Implementation of Title IV
and S-172 in 2010 (90th percentile change in
deciviews)
Source: Regional Acid Deposition Model (RADM), RPM
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