Impacts of Air Pollutants on Wilderness
Areas of Northern Minnesota
Gary Glass—EPA, Duluth
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IMPACTS OF AIR POLLUTANTS ON WILDERNESS AREAS OF NORTHERN MINNESOTA
Final Draft Copy
Project Coordinator
Gary E. Glass
Environmental Research Laboratory-Duluth
Duluth, Minnesota 55804
ENVIRONMENTAL RESEARCH LABORATORY-DULUTH
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
DULUTH, MINNESOTA 55804
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IMPACTS OF AIR POLLUTANTS ON WILDERNESS ARRAS OF NORTHERN MINNESOTA
Edited by
Gary E. Glass, Environmental Research Laboratory-Duluth and
Orie L. Loucks, The Institute of Ecology-Indianapolis,
Air Quality and Modeling
This section was written primarily by Dr. K. W. Ragland (University of
Wisconsin- Madison) and Dr. B. C. Scott (Battelle, Pacific Northwest
Laboratories). It does not indicate endorsement by EPA or Battelle. K.
Wllkening, C, Donovan, and H. Hall (University of Wisconsin-Madison) did much
of the computer work. The cooperation of J. Bowman (Minnesota Copper-Nickel
Study) was most helpful.
Terresterlal Impacts
Edited by S. S. Smith and 0. L. Loucks, University of Wisconsin-Madison,
and E. Preston, EPA Laboratory, Corvallis, from contributions provided by a
panel including J. Bromenshenk, University of Montana, Missoula; J, Chilgren,
EPA Laboratory, Corvallis; S. Eversman, Montana State University, Bozetnan; C.
C. Gordon, University of Montana, Missoula. Additional help was provided by
J. Lieberman and B. Patterson of the. Minnesota Copper Nickel Project and P.
Juneau, ERL-D.
Aquatic Impacts
Edited by J. Eaton, ERL-D and B. Coffin, MDNR from contributions provided
by a panel Including E, Corham, University of Minnesota, Minneapolis, H.
Harvey, University of Toronto, Toronto, Ontario, G. R. Hendery, Rrookhaven
National Laboratory, Upton, N.Y., D. W. Schindler, Freshwater Institute,
Winnipeg, Canada, C. L. Schofield, Cornell University, Ithsca, N.Y., G. E.
Glass, L. J. Keinis, L. Anderson, C. Sandberg, T. Roush, J. Use, and J.
Rogalla, Environmental Research Laboratory, Dulut'n, Minnesota, S. Eisenreich,
University of Minnesota, Minneapolis, and members of the Minnesota Regional
Copper-Nickel Study.
1978 Data Report (Appendix D) - and Manuscript
G. E. Glass, L. J. Heinis, L. Anderson, F. Boettcher, C. Sandberg, B.
Halligan and T. Roush, with acknowledgements of assistance from the staff of
the following organizations:
USEPA Environmental Research Laboratory-Corvallls, D. Krawczyk
USEPA Environmental Research Laboratory-Duluth, T. Highland, P. Gray and
B. Halligan
USDA Forest Service-Duluth, J. M. Ramquist, E. Marsolek, and B.
Dovenmuehl
Freshwater Institute Winnipeg
Minnesota Pollution Control Agency, J. Pegors and T. Mustek
University of Wisconsin-Madison, A. Andren
University of Mlnnesota-Duluth, Lake Superior Basin Study Center
Laboratory
USDC Voyagour's National Park Director
ill
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PREFACE
Many of the objectives that drive efforts to improve our environment are
local in nature and can be viewed as improvements in the quality of life. For
example, the opportunity to swim in rivers and lakes, to catch sport fish in a
beautiful lake or to camp in a wilderness area are certainly valuable. But
these objectives are certainly not necessary for our biological requirements.
Other efforts for environmental protection are driven by the necessity to
sustain the very existence of mankind. Such examples are the protection of the
ozone layer, preservation of our soil for food productivity, the maintenance of
our forest lands for production of wood products, and the protection of
terrestrial vegetation to assure gas balance in the atmosphere.
This report presents evidence to suggest that not only is atmospheric
pollutant deposition threatening a huge, beautiful wilderness area of the
continent, but adds another large geographical area where evidence is appearing
that the forests may be endangered for wood production and sustaining the
atmospheric life supporting systems.
Donald I. Mount, Director
Environmental Research Laboratory
Duluth, Minnesota
March 6, 1979
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ABSTRACT
The goal of this study was to examine previously unanswered questions of
potential effects from the proposed Atikokan power plant on ecosystems in the
Boundary Waters Canoe Area (BWCA) and Voyageurs National Park (VNP) of
Minnesota using the most relevant data and analytical methods. The principal
steps have been to focus on: 1) the ultimate deposition of emissions from the
plant (rather than only on pollutant concentratfons) , 2) the use a time-varying
grid model with provision for atmospheric transformations, and 3) a detailed
review of all available data from the region on atmospheric deposition of
pollutants, water quality, and effects. The results are considered in relation
to a review of responses by terrestrial and aquatic organisms to changes in the
chemistry of this environment.
The sensitive aquatic and terrestrial receptors in the BWCA-VNP region are
described quantitatively and this information is assessed in terms of what is
currently known about the impacts of atmospheric pollutants. Specific
conclusions based on factual information, probable consequences and possible
impacts of the proposed coal-fired power generating station at Atikokan,
Ontario are presented.
The study supports, in part, the conclusions reached previously concerning
the predicted air concentrations of sulfur dioxide but differs significantly
with the conclusions concerning the significance of future impacts. When the
total emissions from the proposed power plant are considered, the increased
loadings of sulfuric and nitric acids, fly ash and mercury as an addition over
and above other regional sources will, with high probability, have significant
consequences for the sensitive receptors in the BWCA-VNP region, especially for
the future of sport fisheries and other aquatic resources.
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DISCLAIMER
This report has been prepared and reviewed by the Environmental Research
Laboratory-Duluth, U.S. Environmental Protection Agency. The contents do not
necessarily reflect the views and policies of the U.S. Environmental Protection
Agency, nor does mention of trade names or commerical products constitute
endorsement.
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CONTENTS
Title, Authors and Acknowledgements iii
Preface iv
Abstract v
Tables x
Figures xi
1. Introduction ............. 1
Background ..... 1
Uniqueness of the BWCA 3
Structure of the study 5
2. Summary of Results and Conclusions 6
Air Quality Impacts 6
Conclusions of fact 6
Probable consequences .... 7
Terrestrial Impacts . . 7
Conclusions of fact 7
Probable impacts 8
Possible impacts 8
Aquatic Impacts 9
Conclusions of fact 9
Probable impacts 10
Possible impacts 11
3. Air Quality in the Boundary Waters Canoe Area (BWCA) 12
Introduction ¦ . . ¦ . . . . . . • . . • • • • . . « . • • • • 12
Background Air Quality Data Near the BWCA 14
Atikokan Emissions . 16
Atmospheric, Dispersion, Transformation and Deposition .... 18
Plume chemistry 18
Dry deposition 19
Wet deposition 20
Description of the Three-Dimensional Dispersion Model .... 27
Model formulation 27
Numerical solution of the plume model ..... 31
Meteorological data used in the model 33
Plume Model Results for Atikokan 55
Atmospheric loadings in the Quetico area ........ 44
Validation of the Model 45
Summary Discussion of the Atikokan Modeling Results 47
4. Potential Effects of Coal Combustion Emissions on the Terrestrial
Biota of the BWCA 49
Introduction and Goals . 49
Biological and Temporal Characteristics of the Boundary
Waters Canoe Area 50
Plant community types 51
Long-term stability of the BWCA landscape 54
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Biotic. Responses to Coal-Fired Power Plant Emissions 55
Residuals of concern 57
Impacted components: conifers (pines and aspen) 59
Impacted components: lichens and bryophytes (sphagnum) .... 65
Impacted components: arthropods (insects) 69
Impacted components: amphibians 73
Impacted components: soils . 73
Impacted components: nutrient cycling 79
Influence of affected trees on insect populations 82
Bioaccumulation 87
Application of Response Information to the Boundary Waters Canoe
Area 89
Significance for pines in the BWCA . 90
Significance for lichens in the BWCA 90
Significance for insects in the BWCA 91
The potential for the bioaccumulation of toxic materials in
the BWCA 91
Significance for nutrient cycles in the BWCA 92
Lake and watershed chemistry in relation to BWCA soils .... 92
5. Impacts of Acidification on Aquatic Ecosystems of the Boundary
Waters Canoe Area (BWCA) and Voyageurs National Park (VNP) 97
Introduction 97
Characteristics of Lakes Vulnerable to Acidification 98
Physical factors in the characterization of vulnerable
lakes 98
Chemical characteristics and responses of vulnerable
lakes 103
Atmospheric acidification of BWCA-VNP lakes ....... 105
Impacts Upon Aquatic Communities ...... 112
Effects on mierobiota 116
Effects on benthic plants 118
Effects on phytoplankton 120
Effects on invertebrates ....... 120
Effect on vertebrates-fish 122
Effects on other vertebrates 126
Summary 126
References 128
Appendices
A. Wet removal rates for SC>2 gas and SO4 aerosol 154
Simple model calculations applied to the proposed emissions at
Atikokan ............ 168
C. Representative analysis of coal and fly-ash for major and trace
components . . . . . . . . . « « « . . , . . « . » . . . . . . . • .173
D~1 Fishes known to be present in the BWCA and border lakes from
records of the Minnesota DNR area fisheries headquarters in Ely,
Finland and Grand Marals, Minn., Pers. Comm., and from Eddy and
Underhill (1974) 175
D-2 Lake benthic invertebrates collected from five large lakes in
Superior National Forest by the Minnesota Copper-Nickel Study Croup
(MCNSG) in 1976 1 76
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D~3 Zooplankton collected by the MCNSG in 1976 and 1977 ... 178
D-4 Phytoplankton collected by the MCNSG during the fall and summer on
1976 and 1977 1 79
D-5 Water quality of 85 BWCA-VNP area lakes, laboratory analysis,
November 1978 180
D-6 Water quality of 85 BWCA-VNP area lakes, field and descriptive
analysis. November 1978 182
D-7 Summary of snow data from the BWCA-VNP area, March 1978. Component
concentrations in melted snow and calculated loadings 184
D~8 Mercury concentrations in fish from selected Northern Minnesota
lakes (data from Minnesota DNR, 1978) 185
D-9 Relative sizes (inches) and mercury content (ppm) of walleye from
12 Northern Minnesota waters, 1977 186
D-10 Relative sizes (inches) and mercury content (ppm) of pike from
14 Northern Minnesota waters, 1977 187
D— 11 Distribution of lake surface areas for BWCA and fall 1978
sampling 188
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TABLES
Number Page
1 Summary of Available Data on Air Pollutants in the Boundary
Waters Canoe Area and Adjacent Ontario 15
2 Atikokan Power Plant Emissions 17
3 Wind and Diffusivity Profiles 29
4 Model Parameters Which are Species Dependent . 34
5 Average Meteorological Data, International Falls, MN., 1970-74 . . 36
6 Number of Periods Per Year When the SO2 Concentration in the
BWCA is in Given Range due to Atikokan Plume 43
7 The Virgin Upland Communities in the BWCA Showing Relative
Importance of Stands and Species 52
8 Summary of Results Available on Native Vegetation Responses to
SO2 in Combination with Other Pollutants 62
9 Summary of Results Available on Native Insect Responses to SO2
and Other Pollutants ........... ........... 83
10 Potentially Sensitive Headwater Lakes 96
11 The pH of Precipitation on the Laurentian Shield of Eastern North
America 106
12 Calcite Saturation Indices (CSI) for 85 BWCA-VNP Lakes, Calculated
According to Conroy et al. (1974) and Kramer (1976) 108
1.3 Snow-melt Enrichment of Dissolved Components; Percent of Total
Mass Found in Melted Snow as a Function of X Melted (Average
of Three Sites in BWCA-VNP) 113
14 Approximate pH at which fish in the LaCloche Mountain lakes,
Ontario, stopped reproduction (after Beamish, 1976) . 125
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FIGURES
Number Page
1 Map of the study area showing grid for computer model 13
2 Qualitative description of synoptic situations envisioned for
the model. The symbols represent: *, ice particles; , melting
ice particles; 0, liquid drops; o, cloud droplets; , trajectory
of air flowing into the storm (solid lines) - - , motion of
hydrometeors relative to the storm (dashed lines). The verticle
scale represents typical cloud depths 22
3 Washout ratio as a function of precipitation rate. Curve 1
represents predictions for intense convective storms or from
clouds where tops are warmer than 0°C; Curve 2 represents
predictions for storms where rain develops without the
assistance of an ice growth stage; Curve 3 is for storms where
the ice growth process is necessary for initiating precipitation . . 25
4 Sulfate concentrations in surface precipitation at Penn State
University, September 1976 through January, 1978. The curve is
an eyeball fit to individual data points 26
5 Schematic diagram of the parameters used in the grid model 28
6 Computed annual average concentrations due south of Atikokan
for SO2» SO4, fly-ash and mercury . 38
7 Computed 24-hour worst-case concentrations due south of Atikokan
for SC>2» SO4, fly-ash, and mercury 39
8 Computed 3-hour worst-case concentrations due south of Atikokan
for SO2 , SO4 , fly-ash and mercury 40
9 Computed annual and seasonal dry deposition flux due south of
Atikokan for SO21 SO4, fly-ash and mercury. There are only
two seasons - summer and winter. Summer is defined as when the
snow is not on the ground 41
10 Computed annual and seasonal wet deposition flux due south of
Atikokan for SO2> SO^, fly-ash and mercury. There are two
seasons - summer is rain and winter is snow 42
11 Results of the sensitivity tests of the grid model showing
the influence on SO2 concentration for a worst-case day 46
12 Distribution of vegetation types in the BWCA-VNP vicinity 53
13 Summary schematic of regional material exchange system and
biological response processes 56
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General exchange relationships between pH and cations. (From
Backman and Brady, 1969; in Birkeland, 1974) 78
Outline map of the areas of sensitive soils (shaded) within the
Kawishiwi Area Soils Map 93
Sample sheet of the soil map of the Kawishiwi Area showing
sensitive soil areas (shaded), and the location of six potentially
sensitive lakes (see arrows) .... 94
Regions of North America containing lakes that are sensitive
to acidification by acid precipitation, based on bedrock geology.
Calcareous overburden will modify this picture somewhat. (From
Galloway and Cowling, 1977) 99
Rainy Lake drainage basin emphasizing major watershed areas and
major river flow patterns toward U.S./Canadian border lakes.
Water flow direction toward Lake Superior, Hudson Bay, and Lake
of the Woods watersheds are indicated 100
Profile of waters along the international boundary, Lake Superior to
Rainy Lake Reservoir. (From Minnesota Pollution Control Agency,
1969.) 101
Park boundaries outlined on the Rainy Lake drainage basin. November
1978 EPA sampling sites 102
Percentage distribution of 85 BWCA-VNP lakes vs. observed lake water
alkalinity (November 1978) 104
The relationship between pH and alkalinity in 85 BWCA-VNP lakes. . . 107
Data from lakes in southern Sweden showing the relationship between
acid loading and pH change for very sensitive and somewhat less
sensitive surroundings. (From Dickson, 1978.) 109
Acid titration of selected BWCA-VNP lakes . . Ill
The relationship between size and mercury concentration of Walleye
and Northern Pike taken from selected BWCA-VNP area lakes 114
Regressions of log mercury concentration against total length for
brook trout sampled from acid drainage lakes and limed, seepage
and bog lakes in the Adirondacks. ( * , adjusted mean mercury
concentrations for the two classes, from covariance analysis.)
(After Schofield, 1978.) 115
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SECTION I
INTRODUCTION
The Boundary Waters Canoe Area (BWCA), located along 176 km (110 miles)
of the Minnesota-Ontario border, occupies 439,093 hectares (1,085,000 acres)
of characteristic northwoods terrain. Over nineteen-hundred km (1,200
miles) of streams, portages and foot-trails connect the hundreds of pristine,
is Inndstudded lakes that make up approximately 1/3 of Che total area. Few
wilderness areas have been the focus of as much persistent concern for
protection from human impacts as has the BWCA.
The 1976 proposal by Ontario Hydro to build and operate a major
coal-fired power plant north of the Quetico-BWCA wilderness complex has led
to concern that air quality and ecosystems in the area could be inadvertently
degraded, in spite of the years of effort and the legislation designed to
protect it. Given the important natural resources represented by the waters,
forests, and air of the BWCA, many Individuals, legislators and environmental
organizations have been concerned with possible deficiencies in the available
data, methodology, and scope, of the assessments carried out since the plant
was first proposed. These concerns have led to the decision by the U.S.
Environmental Protection Agency, in cooperation with state agencies,
universities, and other federal agencies to proceed with the present
comprehensive study of potential impacts on the biota, air and water quality.
Additional data and new analytical tools, including a grid model which
computes pollutant transformation and deposition, were available and
appropriate for a second-level analysis.
Background
Ontario Hydro, a crown corporation established by the Ontario govern-
ment, requested in 1976 and received in 1977, Provincial approval to build an
800-megawatt, coal-fired electrical generating station near Atikokan,
Ontario. The site is approximately 20 km (12 miles) from the northern
boundary of Quetico Provincial Park and about 55 km (38 miles) from that
portion of U.S.-Canadian border which forms the northern edge of the BWCA in
Minnesota.
Criticism of the project from Canadian and U.S. environmental
organizations and individual scientists has centered on the proposed plant's
proximity to the Quetico-BWCA wilderness complex, coupled with the omission
of any scrubber technology. Concern also has been addressed to the Ontario
Hydro Environmental Analysis document, which, critics noted failed either to
give-substantial evidence for its claim that no vegetation damage would
result from SO2 emissions, or it's failure to treat adequately the problems
of acid precipitation and deposition of pollutants in the Quetico-BWCA
environment.
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The Atikokan facility is to be staged in four 200 megawatt units, two of
which are to be in service during 1983. The boilers for these units would
burn either low sulfur subbituminous coal from Alberta or lignite from
Saskatchewan. The proposed facility would feature electrostatic
precipitators to control particulate emissions but no scrubbers would be used
to minimize SO2 emissions. Planning for the Atikokan generating station
began in 1974; in 1976 Ontario Hydro published an Environmental Analysis and
Supplementary Report dealing with the project. The regulations of the recent
Environmental Assessment Act of Ontario are not retroactive and thus do not
apply to the Atikokan generating station.
U.S.-Canadian international negotiations on the Atikokan plant began in
August, 1977. At that time the Canadian participants agreed to provide the
U.S. Department of State with additional information for a more precise
evaluation of the project's potential transboundary effects. Technical
studies were undertaken in each country of the SO2 concentrations expected
to originate from this plant. The results were exchanged in late December,
1977. Based on the additional Canadian information and in consultation with
the Department of State, the U.S. Environmental Protection Agency proceeded
with its initial review of the Atikokan proposal.
During this period, Minnesota congressional representatives and several
environmental organizations urged the Department of State to ask Canadian
officials (1) to refer the matter to the International Joint Commission
(IJC), with a moratorium on plant construction (to allow a comprehensive
study of the plant and its impacts), or (2) to ask for installation of the
best available scrubbers (90% efficient) similar to those already used
extensively in Minnesota.
The Department of State presented the results of the EPA initial review
at a second international negotiations meeting held January 11, 1978. The
EPA review included a literature survey on acid rain problems and projections
of SO2 dispersal using the standard Gaussian plume dispersion mode.
At this January meeting, the U.S. team noted that results of both
Canadian and U.S. modeling studies indicated the concentrations of SO2
entering the BWCA from the Atikokan plant occasionally may be in excess of
the Class I air quality standards permitted under the U.S. Prevention of
Significant Deterioration criteria. (Covering classified wilderness, Class I
is the most stringent standard.) Also using the studies from both countries,
the Canadians concluded at the January meeting that the predicted
transboundary impact of SO2 emissions from the Atikokan generating station
was below the threshold at which injurious environmental effects are known to
occur. Canadian officials confirmed that the plant would meet all Canadian
environmental requirements.
The U.S. negotiating team initially requested the installation of 50%
efficient scrubbers. The Canadian representatives indicated they could not,
at that time, accept such a requirement. The negotiators then focussed on
discussing a referral to the IJC that would not include a construction
moratorium, but would feature a program to monitor effects of the plant.
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The Department of State submitted proposed wording for such an IJC reference,
and the Canadian Office of Foreign Affairs agreed to consider the proposal.
The U.S. team, lead by officials of the Department of State, including
representatives from the State of Minnesota, the Environmental Protection
Agency, and the Forest Service, USDA, which manages the RWCA. The Canadian
team, headed by officials from the Bureau of USA Affairs of the Department of
External Affairs, included representatives of the Province of Ontario,
Environment Canada, the Canadian Embassy In Washington, and the Canadian
Consulate in Minneapolis.
On February 22, 1978, some members of the U.S. negotiating team met in
Chicago to discuss additional potential air quality impacts such as acid
fallout. Also present were staff of the EPA Office of International
Activities, EPA Region 5, scientists from the EPA Environmental Research
Laboratory-Duluth (MN), Environmental Research Laboratory-Corvallis (OR) , and
several universities, as well as representatives from conservation
organizations. At this meeting the data base, methodology, and scope of the
initial EPA study were reviewed In detail, especially the following: (1) the
lack, of realistic simulation of meteorological and chemical transport and
deposition processes by a Gaussian plume model over the distance involved In
the Quetico-BWCA study; (2) the omission of a data base on existing
conditions covering sensitive water quality, water flow direction, and high
mercury levels In fish; and (3) the necessity that contributions made by the
Atikokan plant be assessed against present background levels and all planned
future sources in the area. The consensus of those attending was that the
Atikokan generating station had the potential to be a significant addition to
the pollutants In the BWCA area for both air and water and that a much more
comprehensive study to assess its significance should be undertaken.
On March 20th, the Canadian Embassy issued a diplomatic note rejecting
any International Joint Commission reference, citing as its reason "the lack
of indiction of any potential injury" to the U.S. side, such injury potential
being "the traditional basis for considering transboundary pollution
questions" by the IJC. The Canadian team also concluded that since the
existing studies predicted that concentrations of the pollutant of major
concern in the U.S., sulphur dioxide, would be far below injurious levels,
there was no basis for considering the Installation of scrubbers.
Subsequently, the U.S. Environmental Protection Agency agreed to support
a limited additional study of potential Impacts of the proposed Atikokan
power plant, for which this report details results. This latest study was to
be supported also, in part by the Department of State, the Forest Service,
USDA, and the Minnesota Pollution Control Agency, and to be conducted under
coordination of EPA Environmental Research Laboratory-Duluth.
Uniqueness of the BWCA
The Boundary Waters Canoe Area has been recognized as a unique resource
for many decades. In 1930 the Shipstead-Hewton-Wewland Act was passed to
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protect its shorelines and water levels from dam building and drainage. In
1948, passage of the Thye-Blatnik Act allowed condemnation and purchase by
the federal government of private lands in the "roadless area", as it was
then called. President Truman issued an Air Ban in 1950, stopping the float
plane flights into the "roadless area" which allowed over-fishing of many
lakes. The 1964 Wilderness Act contained specific provisions allowing
certain logging and motorized activity within portions of the BWCA but
otherwise mandated specific wilderness protection. Recently passed legis-
lation in the 1977-78 Congress now further limits nonwilderness uses of the
BWCA.
It is difficult adequately to describe the BWCA's significance to the
American public as a conservation, scientific, and recreation resource for
the present and future. It is the only large lakeland unit of the United
States wilderness system and one of the system's largest units of any kind.
East of the Rockies it is presently larger than all other existing units
combined. Embracing the largest remaining virgin forest in the east, it
attracts more recreationists than any other wilderness area in the nation,
and lies within two days travel of nearly 50 million people. As the last
large, unmodified northern coniferous forest ecosystem in the eastern U.S.,
it has become the focus of much education and demonstration management in
wilderness ecology, animal behavior, vegetation history, nutrient cycling,
and aquatic ecosystems.
The attraction of the area appears to be not any single factor but a
combination of related ones: fishing and camping in a sought-for atmosphere
of wild, unpolluted landscape. However, the evergreen forests, clear water
and air, rock outcrops and shallow soils that are the conspicuous ingredients
of the BWCA landscape are all also unusually sensitive to regionally
transported pollutants. The expansive and relatively unspoiled terrestrial
and aquatic ecosystems In the BWCA are the major reasons for its recognition
as a unique resource in the United States; it is this recognition and
uniqueness that have led to a protective degree of legislative and citizen
vigilence, and, indirectly, to recent monitoring of air quality in
northeastern Minnesota. Since August 8, 1977, the BWCA has been protected by
U.S. Clean Air Act amendments that guarantee maximum "Class I" protection for
parks and wilderness areas. The intent of a Class I status is to assure
long-term maintenance of air quality over an area at essentially the 1974-75
levels. Class I applies to areas such as the BWCA in which practically any
change in air quality would be regarded as signficant.
Complementing the BWCA is Ontario's adjacent Quetico Provincial Park,
453,258 ha (1,120,000 acres) where logging and snowmobiles are banned, and
motorboats are banned except on the periphery. In 1973 the Ontario
Provincial Government determined that Quetico did not fit into any of the
usual classifications for provincial parks and declared it a "primitive
wilderness". The importance of the BWCA to the United States has been
greatly augmented by the forward- looking decisions made by Canadians in
regard to the Quetico Park, established simultaneously in 1909, with the
Superior National Forest to create an international sanctuary. Approximately
902 of the people who visit and enjoy the resources of Quetico are U.S.
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citizens, and, over the years the Quetico-Superior (BWCA) area has come to be
viewed as a single air, water, biological, and recreational resource.
Structure of the Study
This study has been structured to capitalize on, rather than duplicate,
any of the previous assessments of the Atikokan power plant. New data and
modeling approaches were available from two major energy-impact studies
sponsored by the EPA, and results of an intensive study in the northern
Minnesota area by the State of Minnesota also were becoming available. These
results, together with the previously available literature could be used in
conjunction with the issues identified during reviews of the previous
assessments to set a new standard of analysis and evaluation.
Thus, the analysis and assessment process incorporated In this report is
divided into three areas: (1) air quality modeling (using multiple modeling
approaches for predicting air pollutant concentrations and deposition); (2)
terrestrial effects (emphasizing transformation products of the SO2 and the
receptors within the BWCA); and (3) aquatic effects (considering acid inputs,
due to all substances leaving the stacks at Atikokan, as well as existing
conditions including high levels of mercury in fish and water flow to the
border from both sides). Each area involved participants from the two
principal research sites, Madison (WI), and Colstrip (MT), and other tech-
nical consultants, and required the assessment data from sources throughout
the region.
The task of the nir quality modeling group was (1) to determine what can
be predicted regarding the route and deposition of the proposed emissions in
the region, using a regional grid model with provisions for chemical trans-
formations and deposition; (2) to draw together information on current
background levels of air pollutants and all of the emission sources in the
northwestern Minnesota region and adjacent Canada; (3) to model all current
and proposed emissions so that the contribution of all regional inputs could
be analyzed against a context of total loadings in the region.
The goals of the terrestrial and aquatic effects groups were (1) to
characterize the sensitivity of the components of the terrestrial and aquatic
ecosystems to the gaseous and particulate pollutants; (2) to summarize
research results available on the responses of sensitive species as well as
to summarize the overall sensitivity of these associated ecosystems to the
current and expected levels of pollutants reaching the BWCA.
The assessment by these groups has proceeded around two principal
workshops and the preparations and follow-up for each workshop. Materials
were prepared for study prior to a problem definition workshop on each of the
three tasks (held in April, 1978). Detailed data summaries and first drafts
of the final report then were prepared during the spring and early summer,
leading to an assessment workshop (August, 1978) where the findings of the
model output, assessment of existing, conditions, and a review of existing
literature were evauated by participants from all groups.
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SECTION II
SUMMARY OF RESULTS AND CONCLUSIONS
The goal of this study was to use the most relevant data and analytical
methods to examine previously unanswered questions of potential effects from
the Atikokan power plant on ecosystems in the Boundary Waters Canoe Area
(BWCA) and Voyageurs National Park (VNP) of Minnesota. The principal steps
have been to focus on the ultimate deposition of emissions from the plant
(rather than only on pollutant concentrations), to use a time-varying grid
model with provision for atmospheric transformations, and to review In detail
all available data from the region on atmospheric deposition of pollutants,
and on water quality. The results are considered in relation to a review of
responses by terrestrial and aquatic organisms to changes in the chemistry of
this environment.
The study supports, In part, the conclusions reached previously
concerning the predicted air concentrations of sulfur dioxide but differs
significantly with the conclusions concerning the significance of future
impacts. When the total emissions from the proposed power plant are
considered, the increased loadings of sulfuric and nitric acids, fly ash and
mercury as an addition over and above other regional sources will, with high
probabilty, have significant consequences for the sensitive receptors in the
BWCA-VNP region, especially for the future of sport fisheries and other
aquatic resources. Additional research will be required to specify these and
other possible impacts in detail.
AIR QUALITY IMPACTS
A time varying grid model has been developed and applied to the plume
from the proposed Atikokan generating station. Preliminary validation steps
on the model have been carried out and a number of outside reviewers have
examined the model assumptions and output. Within the limits of the
available data, the model performance provides a basis for reasonable
confidence in the projected concentrations and deposition fluxes.
Conclusions of Fact
1. Using the coal type (western Canadian), sulfur content (0.8%), ash
content (12%) and operating conditions agreed upon by previous assessment
studies, the emissions from the Atikokan generating station are computed
to be 70,307 m tons/yr (77,500 tons/yr) of sulfur dioxide, 2,358 m
tons/yr (2,600 tons/yr) of fly ash, 41,630 m tons/yr (45,900 tons/yr) of
nitrogen oxides and 0.9 m tons/yr (1 ton/yr) of mercury. Other volatile
components of coal such as fluoride, arsenic, selenium, etc., will be
emitted and the amounts will vary depending on the source of coal.
2. The plume from the proposed Atikokan generating station will be carried
over the BWCA by NU to NE winds persisting for 3 to 6 hours. For the
6
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base study-year, 1 964, such conditions occurred during 49 time periods
totaling 9 10 hours or 10.3% of the year.
Probable Consequences
1. Model computations indicate emissions from the proposed Atikokan stack
reaching the BWCA region will increase atmospheric deposition of sulfate
by about 0.9 to 1.4 kg/hectare-year, fly ash by 18 g/ha-yr, and mercury
by 0.0016 g/ha-yr. These values will be added to the present seven-year
average atmospheric loading of 11 kg/ha-yr for sulfates. Fly ash
deposition in the region has not been measured and mercury deposition
based on snow cores is at most 0.013 g/ha per snow season.
2. The grid model computations indicate that the 3-hour SO2 concentration
would exceed the U.S. air quality class I regulations for protection of a
wilderness area 2 times per year; the 24-hour standard would be exceeded
3 times per year. The annual average SO2 standard would not be
exceeded.
3. Two-thirds of the particulate matter reaching the BWCA from the Atikokan
..j ii u- co t-|ian fly ash, and most of the sulfate will
4. Approximately half of the S02-plus-S04 and fly ash, and two-thirds of
the mercury deposition will occur during the snow season.
5. The amount of sulfur leaving the 100 x 100 km region by atmospheric
transport would be as much as 70% of the total emitted from the proposed
Atikokan power plant.
TERRKSTRIAL IMPACTS
Cpreclusions of Fact
1. The terrestrial ecosystems of the BWCA and VNP are dominated by
short-season species, two of which, white pine (Pinus strobus) and
trembling aspen (Populus tremulpides) are known to be particularly
sensitive to the gaseous emissions of coal-fired generating stations.
The white pine is the largest and most long-lived of species in the BWCA
(a life-span often over 250 years), and is essential to the lake-edge and
skyline features.
2. Soils of the BWCA-VNP region are mostly shallow (0 to 46 cm), of glacial
origin, coarse textured, derived from granites and other acid bedrock
types, low in cations and available nitrogen, and low in percent base
saturation.
3. Geochemical weathering of rocks and soils has, throughout the earth's
history, been dominated by the weak carbonic acid formed from carbon
dioxide and water. The nitric and sulphuric, acid components of atmo-
spheric depositon now being measured In the BWCA-VNP are sufficient to
modify the normal carbonic acid weathering of these soils and create a
geochemical cycle in which weak nitric and sulphuric acid are important.
be deposited as\SO2
7
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4. A number of lichen species are nmonp, the plants that are most sensitive
to gaseous coal combos t i on emissions and acid particulates. Lichens art;
an important part of the BWCA-VNP biota and make up the principal plant-
cover on five percent of the land area. Lichen species also have been
shown to be an important source of nitrogen (through N fixation) in a
number of nitrogen limited coniferous forest areas.
b. A number of insect groups with strong sensory systems, particularly
saprophagous and predaceous beetles, social bees (pollinators) and
parasitic wasps, have been shown to be reduced in abundance at very low
concentrations of air pollutants, apparently because of pollutant
avoidance or disorientation. Several plant-feeding insect groups have
been shown to increase rapidly when the activity of parasites or
predatory control insects is reduced, or the vigor of host plant species
is reduced, both of which have been shown to occur from gaseous pollutant
emissions.
Probable Impacts
1. Given what is presently known regarding the mobilization of toxic
elements by acid fallout, the increase in sulfuric and nitric acids
fallout expected from operation of the proposed Atikokan generating
station must be viewed with considerable concern. Some of the mobilized
elements are toxic to terrestrial vegetation after relatively small
changes in concentration are induced by additional acid fallout. The
projected additions of H+ through nitrate and sulphate, represent a
257plus percent increase over the presently unbuffered atmospheric acid
deposition, and appear likely to exceed soil buffering capacities. These
mechanisms lead to effects, as well, on small lakes that could begin to
receive increasing amounts of nutrient and toxic elements within a few
years. Detailed watershed geochemistry and mass balance studies will be
required to document such a response.
2. Small additions of acidity to the thin, rocky soils common in the BWCA,
coupled with the geochemical weathering changes that are probable, can be
expected to have relatively rapid and irreversible effects on outputs
from the nutrient cycles of these ecosystems. This will affect ground-
water quality and produce soil-mediated changes in cycling rates within
the ecosystems. Although the net changes in cation leaching due to
lowered soil pH is difficult to predict, If1" additions to some soils
will facilitate leaching nf essential plant nutrients.
Posslble Impacts
1. The projected ambient concentrations of total suspended particulates,
SO2, ozone, and acid particulates from the proposed Atikokan plant may
directly affect the growth and reproductive rates of sensitive pine
species. The presence of phytotoxic elements by leaching of cations
could produce similar effects. The possibility of such effects increases
as other major point sources of gaseous emissions are developed In the
region. Over periods of 100 to 200 years (the life-span of much of the
vegetation), even small effects on growth rates affect survivorship of
8
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the dominant species and could have important consequences on the
composition of the region's vegetation. Such plant responses could be
assessed as part of long-term watershed monitoring.
2. While visible effects on lichens that would be measurable within five
years are not anticipated at the projected pollutant levels, a slowing of
growth rates for a number of species is possible over a period of a few
decades, leading to detrimental effects on nitrogen fixation.
3. The lower pH of the forest soils could amplify trace element effects by
making these elements more available in .the food chain, and hence in
small herbivores, fish and birds at the top of the food chain. Long-term
monitoring will be needed to assess these effects.
4. Effects on insects at the proposed concentrations have not yet been
documented because work on the insect groups is sparse and has not
focused on the threshold for response. Additional emissions and higher
concentrations can be expected in the area in the next few years and
effects are known for the concentrations expected in the future.
Mobilization of toxic elements through insect food chains to small
mammals and birds is possible. Since pollutant injury to sensitive pine
species also is possible, Increased insect damage may occur. Additional
studies of the effects of low concentrations of SO2 on the olefactory
systems of pollinating and parasitic Hymenoptera, predatory beetles and
decomposer insects are urgently needed.
AQUATIC IMPACTS
Conclusions of Fact
1. The BWCA-VNP are In a region comparable in vulnerability to others which
have already been severely impacted by acid precipitation in Europe and
North America. Most BWCA-VNP surface waters have a poor buffering
capacity and many have a low pH (below 6.5) as well.
2. Precipitation in the near vicinity of the TWCA-VNP is strongly acid on
occasion, and the mean annual pH of precipitation is near the level where
damage begins.
3. Atmospheric acid sulfate loadings in the near vicinity of the BWCA-VNP
are at levels associated with the onset of severe lake acidification in
Sweden.
4. Mercury levels in fish, which are Lnc.reaso.d as lakes acidify, are already
high in some lakes in and near the HWCA-VNP.
5. Most of the area within a 100 km (62 mile) radius of Atikokan is in the
Rainy Lake watershed and drains to and into the international waters of
Rainy River, BWCA, VNP and Quetico lakes.
6. The varied, valuable fishery resource of the (5WCA-VNP includes many
species which have been reduced or eliminated by acid precipitation
elsewhere in the U.S. and Canada.
9
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7. Increased metal concentrations, sufficient themselves to cause problems,
often accompany reduced pH. As the pH is lowered, the forms of metals
present also become more toxic in most cases.
Probable Impacts
1. It is likely that vulnerable lakes in the BWCA-VNP and Quetico areas
(poorly buffered headwater lakes having small watersheds with shallow
soils of low buffering capacity) are already being affected by acidity
from atmospheric sources.
2. Although present atmospheric loadings of acid-producing material are
probably acidifying some BWCA-VNP-Quetico lakes, additional loadings from
Atikokan will accelerate the rate of acidification of vulnerable lakes
and endanger other lakes not presently being acidified.
Long-term studies of lake-water and stream-water chemistry in the BWCA
are needed, with special attention to accurate hydrological and chemical
budgets of inputs, outputs and storage in ecosystems susceptible to
damage by acidification to define the time scale precisely.
3. Given the probable changes in the existing pH levels of lake water, we
can project likely responses in the aquatic biota: reduction in decom-
position of organic matter; undesirable accumulation of certain nuisance
algae; decreases in phytoplankton species numbers, diversity, biomass,
and production per unit volume; elimination of some species and
simplification of zooplankton communities; alterations in benthic plant
and animal communities; and the loss of fish species preceded by
reproductive failure. These changes will occur over different time
spans: for some lakes, several years, for others, several decades.
4. Likely increases in the acidity of the water will increase the severity
of seasonal events such as acid flushing in the spring due to snow melt.
Even moderately buffered lakes may form a shallow, but highly acid, layer
of water from acid meltwater. This will result in a reduction in the
variety of different insect species emerging in the spring, and cause
mortality in exposed fish embryos.
A reconnaissance survey of the biota and productivity at all trophic
levels should be carried out. It would be followed by detailed, longterm
monitoring of population dynamics and lake metabolism, with special
attention to organisms and processes sensitive to acidification, in a
series of lakes of differing sensitivity to acid precipitation. Studies
currently going on in Scandinavia and the Adirondacks can serve as
models.
5. Increased acidity is likely to result in detrimental levels of aluminum
and of other trace elements in the lake water by increasing leaching and
creating more toxic forms of these elements. Detailed studies of
precipitation chemistry in the BWCA-VNP are needed on a long-term basis
(10 to 20 years), with special attention to loadings of acid, sulfate,
nitrate and heavy metals to define these changes.
10
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6. The projected additions of mercury and of acid to the Rainy River water-
shed are very likely to aggravate an existing problem of mercury levels
in fish tissues. Additional data will be required to define the precise
changes and sources.
Possible Impacts
1. Fish populations in the roost susceptible lakes of the BWCA-VNP and
Quetico will be eliminated by acid precipitation, some possibly within a
few years, and in many other lakes within a few decades.
2. The rate of acidification may be taking place more rapidly than first
anticipated, making it likely that important adverse effects, such as the
loss of important fish species, will occur much sooner at present
loadings.
3. The productivity and diversity of entire aquatic communities in these
lakes will be severely reduced over the same periods. Some of the most
vulnerable lakes may already have experienced reductions in pH levels and
undergone corresponding biological changes. The paucity of historical
baseline data makes such an analysis very difficult to perform at this
time.
4. It is possible that these (and others - groundwater quality) changes will
not be reversible within the forseeable future, even should the acidity
of precipitation be substantially reduced.
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SECTION III
AIR QUALITY IN THE BOUNDARY WATERS CANOE AREA (BWCA)
INTRODUCTION
Air quality in the BWCA of Minnesota can be degraded by a combination of
large emission sources within 80-160 km (50-100 miles) of the BWCA and
long-distance transport of pollutants which are accumulated during certain
periods in the Midwestern U.S. and Canada. Degradation may occur by
increasing ambient air concentrations of air pollutants and by the resulting
flux of these pollutants to the ground either by dry deposition or by removal
via rain or snow.
The air pollutant concentrations and/or deposition may cause damage to
vegetation and animal groups such as insects, and degrade visibility. The
deposition fluxes potentially may cause damage to fish and animals via the
water and soil. If the concentrations and deposition rates are low enough
(i.e., within some theoretical assimilative capacity for the region), no
significant damage will occur. Since the BWCA is a U.S. wilderness area, the
most sensitive effects must be considered. In order to assess the effects of
future increased pollutant loadings and concentrations, careful estimates of
the emissions near the BWCA, the transport, and the deposition are needed.
The objective of this section on Air Quality, therefore, is to develop
and utilize a grid type model of air pollution dispersion to assess the
ambient air concentrations and deposition fluxes in the BWCA due to emissions
from the proposed Atikokan generating station. Attention will be focused on
sulfur dioxide, sulfate aerosol, total fly ash particulates and mercury.
A map of the study region is shown in Figure 1. The region contains the
BWCA and the Quetico Provincial Park. The Atikokan generation station will
lie 80-120 km north of the BWCA. Sources of pollutant emissions due to
present electric power generation, mining activity, industrial and municipal
sources, which may have an impact on the BWCA, are considered as regional
contributors to the current air quality and atmospheric loadings. Most of
these sources are outside the grid considered in this report.
The BWCA-Quetico area has a cool continental climate characterized by
short, warm summers and long, cold winters: mean annual temperature 2°C
(36*F); mean July 17*C (63*F); mean January -15°C (6°F). The average annual
precipitation Is 71 cm (28 in), 64Z of which occurs as rain from May through
September, the growing season. Annual mean snowfall is about 152 cm (60 in),
and the ground is usually snow-covered from mid-November to mid-April.
12
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I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17
m i i rv.j r\w.i\
CANADA
INTERNATIONAL FALLS
QUETICO
MILES
) 20
BOUNDARY WATERS
1 CANOE AREA§T^
40
60
0 5 10 20
KILOMETERS
40
Figure 1.
Map of the study area showing inner and outer regions.
-------
The BWCA's landscape has a generally slight but locally rugged relief
left by preglacial erosion of the Canadian Shield. Elevations above sea
level range from 341 m (1,119 feet) at Crane Lake to 680 m (2,232 feet) in
the Misquah Hills; local differences in elevation range from 30 to 150 m.
The land is heavily wooded and 16.73! of the BWCA consists of lakes and
streams.
BACKGROUND AIR QUALITY DATA NEAR THE BWCA
The BWCA currently has especially clean air. The available monitoring
data near the BWCA are summarized in Table 1. The Fernberg Road site is a
remote site at the edge of the BWCA that has been run by the Minnesota
Copper-Nickel study. Monitoring data for sulfur dioxide, suspended
particulates, and bulk deposition is available from Feb.-Dec. 1977 and ozone
from May-Dec., (Valentine, 1978).
The sulfur dioxide levels at Fernberg during 1977 never exceeded the
threshold level of the instrument, which was 10 ug/m^ (4 ppb), and only
once during 1978.
The suspended particulate matter, as measured by a high volume sampler,
yielded an annual arithmetic average of 15 pg/m^ and an annual geometric
average of 11 pg/m^. There were 53 days of data, approximately once per
week. The maximum 24-hr reading was 66 ug/m^, which occurred on May 1,
1977.
The ozone data was recorded at Fernberg for 5,384 hours during May to
December of 1977. The arithmetic average of all hourly values was 0.030 ppra
and the geometric average was 0.027 ppm. The maximum hourly readings were
0.100 ppm and 0.101 ppm which occurred during the afternoons of May 28 and
July 19, 1977.
Since the ozone concentrations are due to long distance transport, it is
instructive to compare the Fernberg site with another site at Cloquet, MN,
west of Duluth. At Cloquet the ozone readings followed a similar pattern to
the Fernberg site but were slightly lower. The peak reading on July 19 was
0.070 ppra rather than 0.10 ppm, for example. The highest reading was 0.097
on August 20. The Cloquet site probably records lower ozone readings than
Fernberg because of scavenging of the ozone by local sources of nitric oxide
from automobiles.
The ozone measurements indicate that the Fernberg site is probably
representative of the region. It is assured that the SO2 and particulate
readings are representative. These data indicate that the ambient SO2 from
regional sources is converted to sulfates or the SO2 Is deposited out
before it reaches the Fernberg site instrument. The total deposition of
sulfate (wet plus dry) measured by the Minnesota Copper-Nickel study south of
the BWCA was 10-15 Kg/ha-yr during the 2 year period of 1976-78.
In addition, Ontario Hydro has monitored air and precipitation quality
at five sites near Atikokan. Continuous monitoring of SO2» O3 and NOX
14
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Table 1
Summary of Available Data on Air Pollutants In the Boundary Waters
Canoe Areas and Adjacent Ontario. See text for discussion.
Pollutant
Level
Location Recorded
Averaging
Pe rlod
MINNESOTA (near BWCA)
S02
Fernberg Road* < 10 g/lm'
Superior Nat'l Forest (A ppb)
Individual hourly
readings Feb-Dec 1977
°3
Fernberg Road* 0.10 ppa
Superior Nat'l Forest
Hourly maximum
May-Dec 1977
0.03 ppo
Average May-Dee 1977
°3
Cloquet, Minn.® 0.097 ppo
Hourly maximum
May-Dec 1977
Suspended
Particulates
Fernberg Road* 66 vg/n3
Superior Nat'l Forest
24-hr maximum
Feb-Dec 1977
15 ug/a3
Annual arithmetic
average Feb-Dec 1977
11 ug/n3
Annual geonctrlc
average Feb-Dec 1977
Bulk S04
Deposition
BWCAb 1.5 kg/ha
Average SO4 snow
loading, 65 sites,
March, 1978
Bulk SO4
Deposition
Minnesota Copper-Nickel* 10-15 kg/ha-yr
Project Area
Range 1976-78
ONTARIO (near Atlkokan)
SOj
Nym Lakec .02 ppo
(50 ug/«3)
Hourly maximum
1975-76
o3
Nym Lakec 0.10 ppn
Hourly maximum
1975-76
NOX
Nyn Lakec 0.01 pp«
Sunnier average
1975
NOX
Nyn Lake0 0.03 ppm
24-hour maximum
1975
NOX
Nyn Lakec 0.10 ppn
Hourly maximum
Bulk S04
Deposition
Atlkokan Region0 A and 7
Kg/ha-yr
6/75-4/76
Bulk S04
Deposition
Experimental lakesd 7-U Kg/ha-yr
Region (Kenora) (10.9 Kg/ha-yr)
1971-1977
Average
* Hlnnesota Pollution Control Agency, 1978
b Class, G. E.,
et al., 1979, see Appendix Table D-7
c Ontario Hydro,
, 1976
j
d Schlndler, D. W., 1978
15
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started in July 1975 (Acres, 1976). The Nym Lake site, which is located 17
km SSW of the generating station site near the Quetico boundary, is the most
remote site from the Steep Rock mines and will be briefly reviewed (see Table
1). The total deposition of sulfate measured at two sites was 4 and 7
Kg/ha-yr.
The minimum detectable SO2 level of 10 ppb was observed for short
times on 25 different days, and the levels near exceeded 25 ppb (50 ug/m^)
during the 10 month period reported. Ozone levels reached maximum levels of
0.100 ppm on two consecutive days during July 1975 and were generally similar
to the Fernberg site. When the ozone was high the sulfur dioxide was usually
not above threshold level of the instrument. The NOX levels typically
averaged 5 ppb during June and 10 ppb during July, Aug. and Sept. On
occasion the concentration reached an hourly value of 0.100 ppm, however,
these high values did not correspond to either high O3 or high SO2
levels. It appears that the SO2 is due primarily to local mining
activities, and that the O3 levels are due to long distance transport. The
elevated NOX levels may be due to local sources.
Measurements of bulk deposition of sulphate, wet-plus-dry fall, have
been carried out at three locations in the vicinity of the BWCA, Table 1.
The longest record, at the ELA lakes 180 km northwest of Atikokan, shows an
average recent sulphate deposition of 10.9 Kg/ha-yr. The average pH of the
rainfall here during 1974-77 is 4.86. The pre-settlement pH for rainfall in
this area appears to have been 5.7 (cf. carbonic acid equilibrium and data
for 1955-56 shown by Galloway and Cowling, 1978). ELA data show that 70% of
the nitrate and sulphate in the current rainfall is in a neutralized form.
Thirty percent is in the acid form and the H+ ions were assumed to divide
between SO4 and NO3 on a 2:1 ratio. This information yields an estimate
of 7.6 Kg/ha-yr of neutralized sulphate and 3.1 Kg/hg-yr of acid sulphate
producing the net depression in pH. Thus, depending on the historic
potential of atmospheric constituents to neutralize anthropogenic acid,
pre-settlement loadings of sulphate must lie between 0 and 7.6 Kg/ha-yr. For
purposes of further comparison a value of half this, 4 Kg, will be used.
ATIKOKAN EMISSIONS
The proposed Atikokan generating station consists of four 200 MW units
burning sub-bituminous or lignite coal from Saskatchewan with a sulfur
content not to exceed 0.8% and a maximum ash content of 1231 (Fry, 1977).
Electrostatic precipitators for fly-ash removal are to be employed. The
emissions have been calculated In Table 2 assuming an overall thermal
efficiency of 36X and a full load. The emission factors were obtained as
follows. For sulfur dioxide 38S is the current EPA handbook (EPA-AP-42)
value for pulverized coal boilers. The sulfate emission factor of 1,2
corresponds to the assumption that 2% of the sulfur is emitted directly as
sulfate. Mercury is assumed to go entirely up the stack (Billings, 1973).
The nitrogen oxide emission factor is based on the current U.S. emission
standard which reflects current boiler technology. There are to be 4 stacks
each 198 meters high with a 3.8 m exit diameter. The stack gas flow rate is
288 m^/sec and the exhaust temperature is 408*K. Representative coal
analysis are given in Appendix C,
16
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Table 2
Atikokan Power Plant Emissions (at a full load of 800 MW and assuming 36%
thermal efficiency the heat input rate is 7,59 x 10^ Btu/hr)
High
Low
Heating value (Btu/lb)
7,500
6,500
Sulfur content (X weight)
0.8
0.4
Ash content (% weight)
12.0
6.5
Mercury content (% weight)
2 x 10"5
2 x 10~5
Sulfur dioxide emission factor (lb/ton)
38S**
38S
Sulfate emission factor (lb/ton)
1.2S
1.2S
Total particulate emission factor* (lb/ton)
0.085A
0.085 A
Mercury emission factor (lb/ton)
20Hg
20Hg
Coal rate (full load), (tons/hour)
583
506
Sulfur dioxide emissions (g/s)
2,230
969
Sulfur dioxide emissions (tons/year)
77,500
33,700
Sulfate emissions (g/s)
67
29
Sulfate emissions (tons/year)
2,325
1,010
Total particulate emissions (g/s)
75
35
Total particulate emissions (tons/year)
2,600
1,226
Mercury emissions (g/s)
0.029
0.025
Mercury emissions (tons/year)
1.01
0.89
NOX emission factor (lb/lb*> Btu)
1.2
1.2
NOX emissions (g/s)
1,323
955
NOX emissions (tons/year)
45,900
34,500
* Assuming 99.5% removal in precipitator.
** S, A and Hg are weight X, e.g., S - 0.8.
17
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In addition, the Steep Rock Iron Mines at Atikokan currently emit an
estimated 14-27,000 m tons/yr (15-30,000 tons/yr) sulfur dioxide and
10-18,000 tn tons/yr (10-20,000 tons/yr) particulates. The Caland Ore Company
at Atikokan emits an estimated 254 ra tons/yr (280 tons/yr) sulfur dioxide and
1,490 tons/year particulates. Only the main stack of the Steep Rock Iron
Mine facility, which is 91 meters high will possibly influence the BWCA
directly, since the other stacks are short. These emission sources are
reportedly being closed in the near future and hence are not being considered
in this modeling effort.
ATMOSPHERIC DISPERSION, TRANSFORMATION AND DEPOSITION
A realistic air quality model to meet the objective of this study must
consider a number of physical and chemical processes. Consider a parcel of
air emitted from a tall stack. The advection caused by the wind diffuses
laterally and vertically at a rate which depends on the amount of turbulence
in the air. The turbulence depends on the wind speed and net heat flux. The
vertical spread is constrained by an inversion layer which moves up or down
depending on the net heat flux and overall pressure patterns in the
atmosphere. If the inversion is low the plume will rise above the inversion
and no pollutants will reach the ground unless there is precipitation. The
wind speed, wind direction and heat flux are continually changing as the
parcel of air is dispersing within the region, and hence a time-dependent
model is more appropriate than a steady-state model.
Certain pollutants within the plume can undergo chemical reaction as
they are being transported, such as the conversion of sulfur dioxide into
sulfate aerosol. The reaction rate depends on the concentration of the
reacting species as well as other species in the air and on the intensity of
the sunlight. As part of the parcel diffuses to the ground, it is partially
removed by dry deposition at the surface depending on the type of surface and
type of pollutant. When precipitation occurs, pollutants are scavenged at a
rate related to the amount and type of precipitation. The precipitation,
which is usually more acidic because of the pollutants, is deposited on the
ground.
Plume modeling is often done using a so-called Gaussian plume model,
such as the EPA CRSTER (Guldberg, 1977) model. Since this type of model is
not time-dependent and does not include pollutant transformation, or wet and
dry deposition processes, the Gaussian plume models are more appropriate to
smaller regions. For a study such as this a grid type model based on
numerical solution of the general, time-dependent diffusion equation is more
appropriate because the meteorological, chemical and deposition processes can
be more realistically simulated.
Before describing the modeling work, a general discussion of chemical
reactions in the plume, dry deposition processes is presented.
Plume Chemistry
The primary gases emitted from the stack of a power plant plume are
nitrogen, carbon dioxide and water vapor. The release of these gases from
18
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the regional sources will not have a direct known impact on the BWCA. Carbon
monoxide and low molecular weight hydrocarbon emissions are considered to be
small and thus will not be considered. Sulfur oxides, nitrogen oxides, total
particulate matter, halogens and mercury will be discussed in the remainder of
this sub-section.
Most of the sulfur in the combustion chamber is oxidized to SO2 although
a small percentage is oxidized to SO3 in the combustion chamber and reacts
with water vapor in the stack to form sulfuric acid. Approximately 27. of the
sulfur is in sulfate form in the plume close to the stack (Forrest, 1977,
1978). There is general agreement that SO2 continues to react in the plume
and form sulfate aerosol as the plume diffuses (Schwartz, 1978; Gillani, 1978).
Recent studies by Husar (1978) found that during noon hours the SO2
conversion rate was 1-4X per hour, while at night the conversion rate was below
0.5% per hour in the Labadie plume, which is from a 2,400 MW coal fired power
plant near St. Louis. The sulfate aerosol which is formed is primarily in the
light scattering size range (0.1-1 pm) so that visibility is reduced by sulfate
formation. The mechanism for sulfate conversion can be photochemical or
heterogeneous reactions in combination with particulate matter in the plume.
While theories exist for rapid conversion of SO2 to sulfates in the plume,
the exact mechanisms have not been established.
Nitrogen oxide (NO) is formed in the combustion chamber from nitrogen in
the supply air and nitrogen bound in the coal. Nitrogen oxide is generally
converted to nitrogen dioxide (NO2) in the plume as ambient ozone diffuses
into the plume.
The NO/NO2 ratio in a plume is difficult to model, and hence it is
customary to model NOX, which is NO plus NO2 weighted as NO2 •
Particulate matter in the form of fly ash is emitted from the stack in
mostly submicron size. The fly ash serves as condensation nuclei for aerosol
formation. The particulate matter can also serve as a catalyst for sulfur
dioxide reactions. In our modeling work we assume that the particulate
matter represents the fly ash only; the sulfate aerosol is modeled separately.
Mercury in coal is believed to be vaporized in the combustion chamber,
and emitted as a vapor. It is possible that part of the mercury may condense
on the fly ash as the plume cools. However, for modeling purposes mercury
should be considered in the vapor phase. Coal also contains trace amounts of
chlorine fluorine and bromine which can form the acids HC1, HF, HBr and
particulates containing these elements. These were not considered in detail
because of lack of information concerning their environmental behavior.
Dry Deposition
Dry deposition of gases occurs by absorption and adsorption on
vegetation, soil and surface water. Dry deposition of particulates occurs by
impaction onto the surface material. The dry deposition flux of any species
can be determined by multiplying the concentration of that species near the
ground by the effective deposition velocities. The deposition velocities
have been determined experimentally and have been shown to depend on the rate
19
-------
of diffusion and the characteristics of the underlying surface. Frequently a
deposition resistance is used, which is the inverse of the deposition velocity.
The total resistance is the sum of the aerodynamic resistance and the surface
resistance.
Calculation of the aerodynamic resistance will be discussed later. For
SO2 the surface resistance of tall forest lands, which is the majority of
the surface in the BWCA during summer, is generally agreed to be about
0.5 sec/cm (Shepherd, 1974; Chamberlain, 1966). The surface resistance of
snow to SC>2 is about 3 sec/cm (Dovland, 1976; Whelpdale, 1974). Also the
atmosphere tends to be more stable over snow and hence the deposition
velocity of SC>2 to enow is considerably lower than to summer vegetation.
The dry deposition velocity of particles is strongly dependent on
particle size. Most of the sulfate mass lies in the 0.1 to 1 pm diameter
range for which the deposition velocity is not expected to exceed 0.1 cm/sec
(Workshop, 1978). Hence we have used a surface resistance of 5 sec/cm for
both winter and summer for sulfate aerosol. Fly ash emitted from the stack
is also predominantly in this size range also and hence a deposition velocity,
of 0.1 cm/sec has been used.
Wet Deposition
The concentration of sulfate in precipitation is a consequence of
several cumulative processes occurring within and beneath the clouds.
Brownian motion, phoretic attachment, inertial impaction, and nucleation all
serve to remove the sulfate aerosol from the air and attach it to the cloud
and precipitation elements. However, Brownian and phoretic attachment
mechanisms cannot place sufficient SO4 mass into the cloud water to account
for observed concentrations, and inertial impaction of sub-cloud sulfate is
of second order importance when compared to other removal mechanisms (Scott,
1978).
Since sulfate particles are generally soluble, and are quite 6mall, with
the majority of mass distributed over particles with diameters less than 1.0
nm (Harrison et al., 1976), they should be effective as cloud condensation
nuclei. Indeed, if as Weiss et al. (1977) claim, the major portion of the
aerosol with diameters between 0.1 and 1,0 ym is sulfate, then the airborne
sulfate aerosol could be responsible for nearly all of the cloud droplets
appearing in continental clouds.
Sulfate may be generated within the cloud and precipitation water
through the oxidation of absorbed SO2. The oxidation processes appear to
be temperature dependent and often appear to rely on the presence of metal
catalysts. Laboratory and theoretical work also suggests that oxidants such
as O2» O3, and H2O2 are capable of producing substantial quantities
of sulfate in cloud water (see e.g., Levey et al., 1976 for an extensive
literature survey).
20
-------
Both the oxygen and ozone transformation mechanisms are pH dependent and
begin to decrease substantially in importance as the pH decreases to less
than 6 for O2 reactions and 4.5 for O3 reactions. The hydrogen peroxide
mechanism is relatively insensitive to acidity, but few measurements of
tropospheric H2O2 exist to determine the contribution to SO^ by this
oxidant. Ammonia can also play an important role in aqueous phase SO2
oxidation by neutralizing some of the H2SO4 that is formed and reducing
the acidity. However, recent solubility measurements by Drewes and Hales
(1979) imply that oxidation mechanisms based upon the presence of ammonia
proceed more slowly than previously thought.
Fortunately some evidence is beginning to accumulate suggesting that it
is not necessary to consider in-cloud conversion of SO2 to SO4 in order
to predict the sulfate concentration in precipitation. Recent observations
by Scott and Laulainen (1978), and modeling efforts by Scott (1978) have
suggested that for certain precipitation events, the sulfate concentration in
precipitation is determined largely by the sulfate concentration in the air
flowing into the storm system. Scott suggests that the sulfate concentration
in precipitation is inversely proportional to the precipitation rate and
strongly dependent upon the type of storm system producing the precipitation.
The removal of soluble, submicron, pollutant aerosol from clouds appears
to be accomplished primarily by large collector particles, such as snowflakes
or raindrops, sweeping downward through the cloud nnd capturing the small
cloud droplets containing high concentrations of the aerosol. The final
concentration in the precipitation reaching the ground is dependent upon two
features; first, the initial concentration in the collector particles as they
start their descent through the region of the cloud where accretion of cloud
droplets is the primary growth mechanism, and secondly, the concentration of
pollutant in the cloud water accreted by the collector particles.
The solubility of sulfate particles makes them extremely effective as
cloud condensation nuclei. The sulfate concentration in the collected cloud
droplets depends upon the amount of cloud water condensed about each
activated sulfate particle which, in turn, depends upon the number of
available aerosol, their size, and the intensity of the updraft velocity
within the cloud.
The model of sulfate removal by Scott (1978), considers the three basic
precipitation systems illustrated in Figure 2. In the first case (Figure
2a), the Bergeron or ice growth process is primarily responsible for
precipitation development. Ice crystals nucleate in the upper portions of
the cloud, grow rapidly to precipitation sized particles, aggregate with each
other, and accrete tiny cloud droplets. Even if melting should occur before
the ice particles reach cloud base, the hydrometeors are large enough so that
accretion of small cloud droplets continues to be the primary growth
mechanism*. The sulfate incorporated into the precipitation is assumed to be
predominantly that advected through the cloud base. This first case
* Hydrometeors refer to ice or water particles large enough to fall from the
cloud to the land surface
21
-------
e
X
o
(a) BERGERON CLOUD
4 -
2 --
0 J-
*
i
v
*
i
V
^ vO
?8 0_
o •
>* o
c
°3>
o°c
(b) WARM OR MARITIME CLOUD
E
i—
X
o
0 ' O
° ov V
0°C
(c) CONVECTIVE CLOUD
Figure 2. Qualitative description of synoptic situations en-
visioned for the model. The symbols represent: *,
ice particles; *, melting ice particles; 0, liquid
drops; o, cloud droplets; trajectory of air flow-
ing into the storm (solid lines) -- •+, motion of'
hydrometeors relative to the storm (dashed lines).
The vertical scale represents typical cloud'depths.
22
-------
represents a situation where the collector particle (snow) is relatively
pollutant free when it begins to accumulate liquid water. The ice nucleation
is in an environment subsaturated with respect to water and upon nuclei with
lattice structures similar to ice, such as silicas and clays (McDonald,
1964). Sulfate aerosol are not activated as cloud condensation nuclei in the
upper portions of the cloud, and are not initially incorporated into the
hydrometeor water. Sulfate pickup comes primarily through incorporation of
the dirty cloud water in the lower portions of the cloud. Surface precipi-
tation from this type of cloud may be snow or rain.
The Bergeron or cold cloud is felt to be responsible for the majority of
precipitation falling from layer type clouds over the continents (Mason,
1971). The precipitation from continuous rain or snow storms over northern
Minnesota almost certainly relies upon a Bergeron process for its
development.
In the second situation (Figure 2b), the ice growth process is assumed
to be ineffective in initiating precipitation. Rain develops entirely
through warm phase mechanisms. Gentle uplift (0.1 - 0.5 w s-^) is
implied and long times are available for precipitation sized drops to develop
by condensation and coalescence. A major fraction of the moisture and
pollutants are assumed to be transported through the sides of the storm. For
this second case, sulfate aerosol flowing into the storm at the higher levels
are activated in environs saturated with respect to water. The collector
particles therefore have an initial sulfate concentration when they begin
their descent through the lower portions of the cloud. Net sulfate pick up
is equal to the sum of the sulfate material activated in the collector
particles at their formation altitude, plus the sulfate accumulated by
accretion of the dirty cloud droplets near cloud base. Thus, this warm cloud
is capable of removing more sulfate than the cold cloud.
The third case (Figure 2c) considers precipitation development in
convective storms. Here strong updrafts produce large supersaturations and
large liquid water contents which enable combined condensation and
coalescence to produce precipitation size drops faster than they can be
removed by hydrometeors falling from above. The mass flux of moisture and
pollutants is assumed to be largely through the cloud base. In the
convective cloud, both the ice capture mechanism of the cold cloud and the
condensation, coalescence growth of the warm cloud are effective in removing
sulfate from the atmosphere. The removal potential exceeds that of either
the individual warm or cold clouds primarily because those droplets which
grow into collector particles have grown by coalescence in the lower portions
of the cloud where the cloud water contains high concentrations of sulfate.
Showery, summertime precipitation in Minnesota should exhibit removal
characteristics of the convective cloud; that is, extremely high
concentrations of sulfate should be associated with convective showers
affecting a small (approximately 1-102 of the total area) area at any one
time.
These qualitative results can be expressed explicitly in terms of a
washout ratio, E, defined as the ratio of sullate concentration in the
precipitation water (gguifate^water* t0 the sulfate concentration
23
-------
in air below the cloud base (gsuifate^air^ * figure 3, from Scott
(1978), illustrates the predicted variation in washout ratio as a function of
precipitation rate, J, for the cold cloud (curve 3), the warm cloud (curve
2), and the convective cloud (curve 1). For a fixed concentration of
airborne sulfate and for a given precipitation rate, Figure 3 predicts the
lowest sulfate concentrations in precipitation originating as snow. Factor 2
and 3 increases are predicted when precipitation develops by warm phase
mechanisms in stratiform clouds. The greatest sulfate concentrations are
predicted to occur in precipitation from convective clouds. The convective
and warm cloud mechanisms would be most prevalent during the summer months
while the ice growth mechanism would naturally occur during the winter.
If the precipitation is in the form of snow or originated as snow in the
upper portions of the clouds (curve 3), then the surface sulfate concen-
tration in precipitation is roughly proportional to over the
interval from J ¦ 0.2 to 2.0 mm h--*-. If the precipitation sized drops
develop independently of an ice stage, then the surface sulfate concentration
becomes more strongly dependent upon rainfall rate and upon the airborne
sulfate concentration at the inflow levels of the storm. If the precip-
itation forms without the benefit of an initial ice growth stage, then for
light precipitation rates (J-0.2 mm h-*), the sulfate concentrations in
precipitation water can increase by a factor of 70 or more over the ice-
dependent predictions. At more moderate precipitation rates (J<1 mm h-*)
the precipitation originating as snow is predicted to have about 1/3 to 1/2
the sulfate concentration of that originating on water droplets. At heavy
precipitation rates (J<7 mm h~*), the sulfate concentration is nearly
independent of the precipitation formation mechanisms.
The curve of Figure 4 provides a clue which might help to explain
natural seasonal variations in sulfate concentration detected in the
northeast U.S. Figure 4 illustrates the variability observed in the MAP3S
precipitation chemistry network (MAP3S, 1977). Although there is
considerable scatter to this precipitation chemistry data, there seems to be
a definite decline in winter concentrations of sulfate followed by an
increase during the warmer seasons. High concentrations in the summer may be
related to removal by convective storms, while winter time removal of sulfate
is likely associated with cold rain and snow storms. Similar seasonal
variations in sulfate removal are also expected in northern Minnesota.
In summary, both experimental and theoretical data are beginning to
accumulate, suggesting that sulfate deposition is seasonally dependent and
related to such features as storm type, precipitation rate, and concentration
of pollutant being drawn into the storms. Of the three storm situations
discussed above, the sulfate concentration in the precipitation falling on
the Boundary Waters Canoe Area (BWCA) should be best predicted by using the
cold cloud model, except for situations when the precipitation is clearly
from convective clouds.
The BWCA faces an additional Impact due to the washout of SO2» which
once in the surface waters is likely to convert to SO4. This conversion of
SO2 in surface waters may or may not present problems for the environment,
depending upon its concentration and acidity.
24
-------
Iff
o
LT)
c
3
10
2
10
10
100
1.0
0.01
PRECIPITATION RATE (mm h"1)
Figure 3. Washout ratio as a function of precipitation rate. Curve 1
represents predictions for intense convective storms or from
clouds where tops are warmer than 0°C; Curve 2 represents
predictions for storms where rain develops without the
assistance of an ice growth stage; Curve 3 is for storms where-
-------
PiNN STATE
12 -
r
o
<
or
O
u
o o
<
Lb
SEP OCT NOV DEC I JAN FEB MAR APR V.AY JUN JUL AUG SEP OCT NOV DEC
1976
JAN
1973
1977
Figure 4.
Sulfate concentrations in surface precipitation at Penn
State University, September 1976 through January, 1973.
The curve is an eyeball fit to individual data points.
-------
DESCRIPTION OF THE THREE-DIMENSIONAL DISPERSION MODEL
The model may be characterized as a grid type of atmospheric dispersion
model which numerically integrates the species continuity equation. Chemical
reaction between two species, horizontal advection, vertical diffusion, and
wet and dry deposition processes are simulated. The model computes temporal
and three-dimensional spatial concentration distributions due to single or
multiple point and area sources. A fully implicit finite difference scheme
is utilized so that numerical errors are minimal. A single station is used
to characterize the meteorological conditions throughout the grid. Three-
hour, 24-hour and annual average concentrations and deposition fluxes are
computed.
The model formulation, the numerical solution procedure and the
meteorological data used are described in the remainder of this section.
Model Formulation
Consider first a two component mixture undergoing a first order chemical
reaction. The pollutant species are adveeted by the wind, diffused in the
lateral and vertical direction, and are removed by dry and wet deposition.
The wind speed and diffuslvity vary with height, surface roughness and net
heat flux, as indicated In Figure 5. The plume is trapped by an elevated
inversion layer.
If we align the x-axes with the wind vector and use the fact that the
diffusion term in the x-direction is small compared to transport by the wind,
then the set of equations to be solved for two species C and S is:
3C ^ 9C .. 32C 3 3C , - „ ,
tt + u -vr - K -r—- - -r— (K— )=kC — W+Q (1)
3T °X y 3y2 3z z 3z c c
3S 3S 32s 3 3S . , u , ,0x
t— + vrr— - K -r—r - — (K — ) » k - W + Q (2)
at 9x y 3y2 3z z 3z C s s
at z ¦ 0
for
£ ¦ -vc <3)
i" -V (4>
k
C -» S. (5)
For example, C represents the concentration of sulfur dioxide and S
represents the concentration of sulfate aerosol. If for example mercury is
to be simulated, C represents mercury and S is zero. Equation 5 defines the
rate constant, k. W is the wet deposition flux, Q is the emission source and
Vq is the dry deposition velocity.
The wind speed (u) and vertical eddy diffuslvity (Kz) are calculated
as a function of height (z) according to the scheme outlined in Table 3 In
which the parameter L is defined as
u* P c
O.AgH
£ , (6)
27
-------
Heat Flux
v
Inversion Layer
Chemical Rxn.
Diffusity
J Wet T
Deposition
iifrb i-i^n^
Surface Roughness
5- X
Dry Deposition
Figure 5. Schematic diagram of the parameters
used in the grid model.
28
-------
Tab.i.e 3
Wind and Diffusivity Profiles
Stability
Vertical
Distance
Wind Speed Eddy
u
Diffusivity
K„
Z
0<«zsl
u* z+zn
T ln C-T"a'
.4 ZQ
4u* z
0<2"sl
U*r, ,Z + Z0, . 5.2 z!
T*[lnC Zq ) + T-l
4uaz/C1+ l -)
AND
Stable
0 . 25
4u*z(l- -g~)
0
-------
and n ,,
0.16 u
u*
1O810 fl ~ 1'8
o
Ji (7)
It should be noted the geostrophie wind (ug), the net heat flux (H)
and the surface roughness (z0) are required Inputs. Since only the surface
wind at 10 meters is available hourly, the program internally computes the
geostrophie wind.
The net heat flux is obtained from cloud cover and cloud ceiling height
data by first computing a radiation index according to the scheme used for
STAR data (Turner, 1964) and then the radiation index is converted by the
following procedure:
Radiation Index
4
3
2
1
0
-1
-2
H(cal/cm^ - min)
0.24
0.18
0.12
0.06
0
-0.03
-0.06
The lateral diffusivity is an important parameter which is not well-
known for the time and distance scales of this study. The available data has
led us to the assumption that K„ ¦ 100 Kz. This accounts for gusts which
veer and knock (in sailing terminology) and also accounts for a certain
amount of wind vector shift with height due to the Coriolis force.
Changes in the wind direction from hour to hour are handled by a
coordinate rotation transformation. In this way any arbitrary wind direction
can be simulated.
The deposition velocities (Vq) which appear in Equations 3 and 4
depend on an aerodynamic resistance (ra) and a surface resistance (rs),
VD - i . (8)
ra + rs
The aerodynamic resistance is represented by
r. - (9)
-------
The wet deposition removal rate is calculated according to the
procedures outlined in Appendix A. Using Equations A-22 we have,
Wc(rain) - 0.96 3 C J0*9, (10)
Wc(snow) » 0.48 B C J®*9 (l-exp(-2fn) ) , (11)
Wg(rain or snow) » 0.44 S (12)
C and S are the average sulfur dioxide and sulfate concentrations
(yg/m^) and J is the rate of precipitation (water equivalent) in mm/h.
From Eq. A-15, m is given by
3 - 1.56 + 0.44 In J. (13)
The parameter 0 depends on the pH of the rain according to Figure A-5, which
for this study has been simplified to the following equation,
logiQ 6 - -2 + 0.75 (pH-3.9) (14)
for pH less than 5.1; otherwise 3 - 0.067.
As explained in Appendix A,
pH - -log 10(2,000 Sw/96), (15)
where Sw is the sulfate concentration in the cloud drops from Eq. A-10,
Sw - 0.45 S J-0-27 (16)
The wet deposition fluxes are determined by multiplying Eqs. 10, 11, and 12 by
the height of the layer being scavenged, which is given by Eq. A-9. For this
study we have used a height of 2,000 meters as an approximation to Eq. A-9.
Numerical Solution of the Plume Model
The solution of the diffusion equation with the various terras as
described above can only be accomplished by numerical techniques. Equation
(1) with boundary and initial conditions is solved numerically by means of a
first order fully implicit finite difference technique. This method is
numerically stable for any step size. Consider a volume of fluid with sides
Ax, Ay, Az located at a point i+1, j, k. Properties at the point i, j, k, at
the time t are known but in the i+1 plane at time t + At are unknown.
Conservation of mass for a particular species in an element of fluid not
adjacent to a boundary may be written as:
ci+i,j,k(dxdydz/dt)
+ «kCi+i,j,k(dydz)
+ vk^ci+l,j,k~C^+l,j-l,k)^dxdz^
LIBRARY
U.S. Environmental Protection Agency
Corvallis Environmental Research Lab.
200 S.W 35th Street
CorvslUs, Oregon 97330
31
-------
+ C Ky )k < Ci+1, J, k-Ci+1 > J+J., k) < dxd r/dy)
+ k-1/2'C1"H, j,k~C'+l, j,k+l^d,"iy''iz'
+ k Ci+i.j.^dxdydz) + dxdy)
" Ci j k(dxdydz/dt) + ukci j k(dydz) + Qc (17>
Here C' denotes the unknown concentration at time t + At, and C denotes
the known concentration at time t. At a boundary one or more terms on the left
hand side is zero. A similar equation is written for each cell of fluid in the
i+1 plane, and the set of equations is solved simultaneously stepping along x
and then stepping through t. A similar equation is written for species S from
Eq. (2) and solved along with Eq. (1).
For an individual step it is seen that Eq. (11) can be written as
l*] 10 X W, C+At " U1 +
(18)
where
[A] is determined as a dispersion matrix (NUMY'NUMZ)^
large containing only known meteorological parameters and
step size,
[C] is the concentration vector NUMY times NUM2 long, the right
hand side contains only known terms, and NUMY and NUMZ are
the number of cells in the cross-wind and vertical directions,
respectively.
The set of equations (11) is solved by factoring A such that A « Ll/*\
where L is a lower triangular matrix and L™ is the transpose of L. This
may be readily done since A is a positive-definite, symmetric band matrix.
The solution of the system of linear equations is determined by lettering Y -
L^C and computing Y by back substitution in the equations LY » D. When Y
is known, C may be determined by back substitution in LTC ¦ Y.
Changes in wind direction were handled by means of a rotation of the
coordinate axes. Hence two grid systems are used - a rotating grid in which
the computations are done and a fixed system in which the results are stored.
The x and y coordinate of a grid point are transformed as follows:
XF - Xr cos (0) - Yr sin (0)
Yp - Xy sin (0) + Yr cos (0)
where 0 is the wind direction.
32
-------
A major difficulty in the procedure is that the grid rectangles don't
overlap in a uniform way, so the question arises of how to apportion the
concentrations for one grid to the grids for the other system. This was
overcome by subdividing a grid into a number of smaller grids and assigning
to each small grid the concentration of the larger divided by the number of
subgrids. The subdivision can be as fine as desired, but more subgrids means
greater computing time and cost. In this model there are 9 subgrids. The
final concentration is the sum of all the smaller grids of the rotation
system which overlap it. The concentrations originally calculated in the
rotating system have now been stored in the fixed system, so we can rotate
the grid to the new wind direction. Then we simply reverse the process and
subdivided the grids in the fixed system, use the above Fixed-to-Rotating
equations to transform the coordinates, arrive at the "already present"
concentrations in each larger grid in the rotating system, and begin the
model's numerical calculations for the next hour. This procedure of going
back and forth between the rotating and fixed grid systems for wind direction
changes continues for as long as there is a continuous set of meteorological
data. The errors created by the coordinate transformation are generally less
than 5%.
For the model runs reported here a box system of 13 x 17 x 6 high was
used with AX, AY « 9,655 m (6 mi) and AZ - 50 m for the lower three boxes and
AZ •* (ZM-150)/3 for the upper three boxes, where ZM is the height of the
inversion layer. The time step used in the model's numerical scheme was 10
minutes. The meteorological input, as previously noted, varies every hour.
The model can therefore simulate on a continuous basis and is limited only by
computer core space and time.
The required computer core space for a single non-reacting species was
28 K and for the SO2/SO4 reacting species was 40 K. The computing time
per hour of simulated time was approximately 9.7 sec for a single species and
20.1 sec for SO2/SO4. The computer used was a UNIVAC 1110 and the code
for the model is on file at the Madison Academic Computing Center.
The parameters in the model which are dependent on the type of pollutant
to be simulated are summarized in Table 4, and shows the values that we have
used.
Meteorological Data Used in the Model
International Falls, UN, was selected as the site for the meteorological
data. It is reasonably close to the BWCA and is the nearest site with a
consistent set of surface and upper air data. International Falls is
considered to be representative of the BWCA.
The year 1964 was chosen for the model runs because this was the last
year when hourly surface data was recorded. After 1964 the surface data is
available only every 3 hrs. The total precipitation was about 10% greater
than average during 1964. Upper air data, which is taken twice daily, are
used to obtain the height of the inversion layer. Hourly values of the
inversion height were obtained from a National Climatic Center data tape.
All other necessary data ts generated from the surface observation data tape.
33
-------
Table A
Model Parameters
Which Are Species
Dependent
Parameters
SO2 SO4
Fly-ash
Hg
Chemical reaction
0.5 (night time)
rate (%/hr)
2.0 (day time)
0
0
Dry deposition
surface resistance
(summer sec/cm)
0.5 5.0
5.0
*
(winter sec/cm)
3.0 5.0
5.0
*
Wet deposition
coefficient
** **
36
0.5
(Z/hr)
* For Hg a dry deposition velocity of 0.001 m/s was used rather than
specifying the surface resistance, which is not known.
** The washout of SO2 and SO^ was handled in a more complex manner than
the fly-ash and mercury. See text for a detailed description of the
precipitation washout formulation.
34
-------
The cloud cover, cloud ceiling height, day of Che year and time of day
are used to calculate a radiation index, which is used to define the net heat
flux, H, as indicated in the previous sub-section. The wind speed at the
inversion height, Ug, is calculated from the wind speed at 10 meters. In
summary the following meteorological data are needed as input to the model:
1) Surface wind speed
2) Surface wind direction
3) Net heat flux
4) Surface air temperature
5) Height of the inversion
6) Precipitation type and amount
The Atikokan generating station subtends an arc of about 90 degrees
across the BWCA. The model was run for those periods when the wind persisted
from the NW to NE direction for at least 6 hours. A duration of 6 hours or
more implies that the plume will be over the BWCA for 3 hours or more. There
were 49 different periods covering 901 hours or 10.3% of the year 1964 which
met this criteria and hence were used. Only winds from the NV) to NE were
considered in order to reduce the amount of computing time without seriously
influencing the results in the RWCA.
The total precipitation during the year was 68 cm (26.63 inches) of
water, and with winds from NE-NW sector the total precipitation was 4.9 cm
(1.92 inches) or 7.2%. The total rain for the region was 55.8 cm (21.96)
inches of water and the total snow was 11.9 cm (4.67 inches) of water. With
the winds out of the NE-NW sector, total rain was 3.1 cm (1.22 inches) of
water or 5.5% and the total snow was 2.0 cm (0.77 inches) of water or 16.4%.
Although the model is run from hourly data, it is instructive to consider
some seasonal and annual average data from International Falls. As shown in
Table 5 the wind is northerly 20% of the time, the annual mean wind through
the mixed layer is 7.2 m/sec, the annual night-time inversion height is 400 m
and the annual day-time inversion height is 1,300 tn. Frequently at night and
also sometimes during the day in winter the plume rise from a tall stack such
as Atikokan is in or above the inversion layer and hence isolated from the
ground.
PLUME MODF.L RESULTS FOR ATIKOKAN
The model was run for every hour in the year when the wind was from the
NW to NE sector causing the Atikokan plume to flow over the BWCA. Three
separate runs were made - one for sulfur dioxide and sulfates, one for
particulate matter and one for mercury. Ambient air concentrations, dry
deposition fluxes, and wet deposition fluxes for each cell in the region, and
for each hour were computed and stored on tape. Annual, seasonal, 24-hr, and
3-hr average ground-level concentrations were obtained, and frequency
distributions of 1-hr, 3-hr and 24-hr averages were tabulated by means of a
separate tape-processor program. The seasonal and annual wet and dry
deposition fluxes were obtained. The total mass of the particular pollutant
which is transported oat of the region by the wind during the year was also
computed.
-------
Table 5
Average Meteorological Data, International Falls, Minn., 1970-74
Wind Direction
MEAN
WIND
Inversion
Ht Cm)
Precip.
Snow*
Season
N
E
S
W
SPEED
(m/sec)
Night
Day
(in)
(in)
DJF
.18
.17
.25
.40
7.0
347
656
2. 08
30. 26
MAM
.21
.29
.21
.29
7.5
411
1646
4 .86
14. 34
JJA
.18
.18
.31
.33
6.9
337
1747
9.53
0
SON
.17
.18
.31
.34
7.4
511
1146
7.41
10. 20
Annual
.20
.20
.27
.33
7.2
400
1300
23.88
54 . 80
* The water equivalent of snow ic approximately 1/10 the snow depth.
-------
The ambient air concentrations and deposition fluxes were computed for
each grid point indicated in Figure 1. Since only winds from the NW to NT,
were used, it is appropriate to consider a traverse across the region in the
N-S direction starting with the grid containing the source at Atikokan.
Figures 6-10 present the model output as a function of distance due south of
Atikokan for sulfur dioxide and sulfates, fly-ash and mercury.
The annual arithmetic average ambient ground-level concentrations due to
the Atikokan generating station are presented in Fipure 6. In the BWCA the
levels were computed to be 0.25 yg/m^ for SO2 , 0.025 pg/m^ for SO4 ,
0.01 pg/m^ for fly-ash, and 4xl0~" Pg/tn^ for mercury. The 24-hour
average worst-case concentrations, which is a composite of the worst-case days
for each grid point, is shown in Figure 7. The worst-case day occurred on
February 23 along the N-S line. In the BWCA the highest 24-hr concentrations
were computed to be 10 wg/m^ SO2 , 0.75 Ug/m^ SO4 , 0.4 pg/ra^ fly-ash,
and 0.0015 pg/tn^ Hg. The 3-hr worst-case concentrations, which also
occurred in the BWCA on Feb. 23, are shown in Figure 8. In the BWCA the
levels were 30-35 Pg/m^ SO2 » 1.8 Vg/SO4 , 1 wg/ra^ fly-ash, and
0.0004 pg/m^ Hg.
The frequency of occurrence of 1-hr, 3-hr and 24-hr average SO2
concentrations at a grid point due south of Atikokan just across the U.S.
border in the BWCA is presented in Table 6. The results for the non-snow
season from April 15 - November 15, defined here as "summer", are also shown.
The summer season experiences significantly lower concentrations than the
winter (snow) season. This is because the inversion height is generally
higher in the summer and the thermal turbulence which disperses the plume is
greater.
The computed levels for sulfur dioxide and particulate matter may be
compared to the United States standards for wilderness areas. According to
the Clean Air Act Amraendments of 1977, for any class I area, the maximum
allowable increase in concentrations of sulfur dioxide and particulate matter
over the baseline concentration of such pollutants shall not exceed the
following amounts:
Particulate Matter
Annual geometric mean 5 tig/m-*
24-hr maximum 10
Sulfur dioxide
Annual arithmetic mean 2 pg/m^
24-hr maximum 5
3-hr maximum 25
The modeling results show that the 24-hr and the 3-hr SO2 standards
would be exceeded a few times during the year, during the snow season. The
annual average SO2 standard would not be exceeded. The particulate matter
standards may be addressed by adding the fly-ash and the sulfate concentration
levels. The results indicate that the particulate matter standards would not
be exceeded.
37
-------
1.4
1.0
0.6
0.2
0
10
Annual S02 (/zg/m3)
j i i ' i ' i i i i i i
Annual S04 (/xg/m3)
(- 0.03
Annual Fly-Ash (ug/rrp)
o 0.025
i i i i t
Annuol Hg g/m3)
h—BWCAH
I I t I i
J I I I I
20 40 60 80 100 120
DISTANCE SOUTH FROM SOURCE , km
Figure 6. Computed annual average concentrations
due south of Atikokan for S02, SO^,
fly-ash and mercury.
38
-------
20
16
12
8
4
0
1.25
1.0
z
o
H 0.5
<
en
t 0
UJ
o
z:
o
o
0.8 -
0.4
24-hr S02 (/j-g/m^) _
U.S. Class I Std.
i 1 L
I I I I
24-hr S04(/xg/m3)
i L
j L
24-hr Fly-Ash (/xg/m3) _
0
J I I 1 I I L
J L
24-hr Hg ( ng/m3)
0.3
0.2
0.1
° 20 40 GO 80 100 120
DISTANCE SOUTH FROM SOURCE, Km
1 I I
f*—BWC A"-j
¦ i ¦ i i i
Figure 7.
Computed 24-hour worst-case concentra-
tions due south of Atikokan for SO,, SO4,
fly-ash, and mercury.
39
-------
60
40
20
2
2 2.5
£
£T
H
0
LU
o
Z
o
o
3-hr S02 (/xg/m3)
U.S. Class I Std.
Q I'll 1 I I 1 I .J L
0 1 L
0.8-
0.4
0
3-hr S04 (/xg/m3)
I I L
3-hr Fly-Ash (/xg/m3)
1 ¦ i L
i i i
3-hr Hg (ng/m3)
¦ i i » i i i i
BWCAH
j i., ' _
20 40 60 80 100 120
DISTANCE SOUTH FROM SOURCE , km
Figure 8.
Computed 3-hour worst-case concentrations
due south of Atikokan for SC^, S0^, fly-
ash and mercury.
AO
-------
S02 Wet Deposition
(kg/hectare)
Deposit
hecta
z: 50
Deposition
hecta
y 100
hectare
BWCAH _
20 40 60 80 100 120
DISTANCE SOUTH FROM SOURCE,km
Figure 9. Computed annual and seasonal dry deposi-
tion flux due south of Atikokan for SO2,
S04, fly-ash and mercury. There are only
two seasons - summer and winter. Summer
is defined as when the snow is not on the
ground.
41
-------
I
0.5
0
40-
Z 20
S02 Dry Deposition
(kg / hectare)
S04 Dry Deposition
(g/hectare)
Summer
¦ i ¦
I I L
J 1 I L
Hg Dry Deposition
(mg/ hectare)
4/7
QUq/
Summer
Fiy-Ash Dry Deposition
(g/hectare)
nuQi h—BWCAH -
§un~)mGr
i i t i ¦ i i i '
20 40 60 80 100 120
DISTANCE SOUTH FROM SOURCE ,km
Figure 10. Computed annual and seasonal wet
deposition flux due south of Atikokan
for SO2, SO4, fly-ash and mercury.
There are two seasons - summer is rain
and winter is snow.
42
-------
Table 6.
Number of Periods per year When the SC>2 Concentration in the BWCA
is Calculated to be in a Given Range due to Atikokan Plume
SC>2 Concentration Range (ug/m3)
>0,<1 1-5 5-10 10-15 15-20 20-25 25-30 30-35 35-40 40-45 >45
1-hr ave.
397 343
90
36
17
8
6 1
1
1
0
(Summer only)
(243) (201)
(18)
(5)
(1)
(0)
(0) (0)
(0)
(0)
(0)
3-hr ave.
132 131
34
16
2
2
1 1
0
0
0
(Summer only)
(80) (6)
(1)
(0)
(0)
(0)
(0) (0)
(0)
(0
(0)
so2
Concentration
Range
(pg/m3)
>0, <1
1-2
2-3
3-4
4-5
S - 6
6-9
9-10 >10
24 hr ave. 50 4 3 1 1 2010
(Summer only) (27) (2) (2) (0) (0) (0) (0) (0) (0)
-------
Sri^Ulon'fluxes due to the Ulkokan generating station «, be ,„™.rl«<.
as follows for a location due south of the source in the B C .
S02
Dry
Deposition
Wet
Deposition
Winter
Summer
Annual
0.3
0.25
0.55
0.01 kg/hectare
0.02
0.03
so4
Dry
Deposition
Wet
Deposition
Winter
Summer
Annual
0.010
0.005
0.015
0.01 kg/hectare
0 .01
0.02
Fly-ash
Dry
Deposition
Wet
Depos ition
Winter
4
6 g/hectare
L'
Summer
2
0
12
Annual
6
Mercury
Dry
Deposition
Wet
Deposition
Winter
Summer
Annual
1
0.5
1.5
0.05 mg/hectare
0.05
0.10
The dry and wet deposition nay be added to obtain the total deposition.
If we assume that the SO? deposition is converted to sulfate at the surface
(oultiply by 1.5 for additional 02)» then the total sulfate deposition at
this location in the BWCA is 0.9 Kg/ha-yr. The fly-ash total deposition is 18
g/ha-yr and the mercury deposition is 0.0016 g/ha-yr. These deposition values
would, of course be an addition to the regional background deposition fluxes,
e«8. 11 Kg/ha-yr for sulfates (see Table 1).
Atmospheric Loadings in the Quetico Area
As indicated in Figures 9 and 10 the deposition loadings are much higher
in the northern Quetico than in the BWCA for the 10.32 of the time the winds
®re from the NE to NW for a duration of more than 6 hours. The watershed of
the Maligne River and others in the Quetico south of Atikokan drain to
international waters along the BWCA boundary. Hence deposition from the
44
-------
Atikokan plume within these watersheds must be considered in the total BWCA-VNF
impacts evaluation. Model estimates of deposition 35 km south of Atikokan in
the area of Sturgeon Lake are as follows:
It should be noted that these results for the proposed Atikokan source
are only the long duration windfield and 3-5 times these values will probably
be the minimum total and represent a 100 percent plus increase over the
current sulphate deposition in this area.
VALIDATION OF THE MODEL
In a brief study such as this it is not possible to complete direct
validation the model in the field. However, a number of approaches can be
used to determine the present level of confidence appropriate for the model.
First of all, a version of this model which does not include deposition
or chemical transformation has been used successfully in a seven county region
in Southeastern Wisconsin. A detailed emission inventory was provided by
state and local agencies. Computed annual average particulate concentrations
were compared with 25 high-volume particulate monitors and a correlation
coefficient of 0.87 was obtained. Computed annual average sulfur dioxide
concentrations, were validated with 6 monitoring stations and a correlation
coefficient of 0.78 was obtained (SEWTCPC, 1978), The modeling work is being
used to develop the Wisconsin Implementation Plan as required by the U.S.
Clean Air Act.
The validity of the model depends in part on the value of the parameters
selected for the execution of the model. The key parameters which are
dependent on the particular pollutant species to be modeled were summarized in
Table 4. These values were selected from experimental values in the
literature and are felt to be known within a factor of 2 except for the values
for mercury which are probably known only to a factor of 10. In addition the
surface roughness and the horizontal eddy diffusivity are important
parameters. One surface roughness must be selected for the entire region,
and the selected value of 1 meter represents typically wooded terrain. The
horizontal eddy diffusivity is not well known for this scale model, and more
research is needed on this parameter (see Liu, 1977). The model used a value
of 100 times the vertical diffusivity.
A sensitivity analysis was performed on the key parameters in the model.
A worst-case day was selected, and the model was run for 24 hours. The
sensitivity of the ground level concentration of SO2 to a factor of 2 change
in each of the key parameters was determined as shown in Figure 11. The most
sensitive parameter was the height of the inversion. This parameter was
measured at International Falls and hence well-known. The horizontal eddy
Annual sulfate deposition
Annual fly-ash deposition
Annual mercury deposition
3.4 Kg/ha-yr
88 g/ha-yr
4 mg/ha-yr
45
-------
ro
E
s
o*
«•
o
fee
cc
h-
z
Ll!
O
z
o
o
LU
>
UJ
_l
3
O
cr
o
e>
>
<
CJ
OJ
o
25r
23
21
19
17
15
13
II
9
7
5
3
I
'EDDY = Horizontal Eddy Diffusivity
. RR = Chemical Reaction Rate
• RS = Surface Resistance
ZM = Height of Inversion Layer
¦ ZR = Surface Roughness
2RS
2ZR
Base Cose
2RR
2EDDY
2ZM
10 30 50 70 90 110 130
DISTANCE DUE SOUTH OF ATIKOKAN ,km
Figure 11.
Results of the sensitivity tests of the
grid model showing the influence on SO2
concentration for a worst-case day.
46
-------
diffusivity was the next most sensitive parameter - a doubling decreased the
SC>2 concentration by 10-15%. The other three parameters - the chemical
reaction rate, the surface resistance and the surface roughness - when
doubled, changed the concentration by less than 10%.
The accuracy of the input data is another factor which influences the
validity of the results. Assumptions have been made on the type of coal used
and the reliability of the electrostatic precipitation. The meteorological
data - the wind speed, wind direction, solar intensity and inversion height,
and precipitation amount and type - will all influence the resultant output.
Nevertheless it is felt that the input data is rather well-known.
When using any complex model it is desirable to compare the results to
other models, and especially models of a less complex nature. Examination of
the similarities and differences between different modeling results can yield
confidence in the final results. Modeling results from a simple box model
approach, from Gaussian plume concepts and from the EPA CRSTER model are
summarized in Appendix B. These results lend support to the findings of the
numerical grid model.
SUMMARY DISCUSSION OF THE ATIKOKAN MODELING RESULTS
A time-dependent plume model which includes transport, diffusion, coupled
chemical transformation, and wet and dry deposition has been developed and
applied to Atikokan. A grid was set up which included Atikokan, Quetico
Provincial Park and the Boundary Waters Canoe Area. The model was run hour by
hour for an entire year for those hours when the wind was from the NW to NE.
Separate model runs were made for sulfur dioxide and sulfates, fly-ash, and
mercury. A sensitivity analysis of key model parameters was made and the
validity of the results was discussed.
The following conclusions are drawn from the modeling effort with respect
to the Atikokan plume on the BWCA:
1. The 3-hr and 24-hr worst-case sulfur dioxide concentrations exceed
the U.S. allowable incremental standards of 25 and 5 tig/m^,
respectively, for protection of a Class I wilderness area. The
frequency of occurrence of this exceedance is low, however. The
annual average SO2 concentration was 0.25 Ug/m^ which is 8 times
less than the U.S. standard.
2. The increase in particulate matter is not expected to approach the
U.S. allowable incremental standards for a Class I wilderness area.
The annual particulate (fly-ash plus sulfate) concentration was 0.03
yg/m^ and the worst-case 24-hr concentration was 1.1 yg/m^.
The particulate matter contains twice as much sulfate as fly-ash.
3. The total potential sulfate deposition was 0.9-1.4 Kg/hectare-year in
the BWCA which is significant compared to the existing regional
background deposition of 10 Kg/hectare-year.
47
-------
4. The total deposition of fly-ash was 0.018 Kg/hectare-year for the
BWCA.
5. Annual mercury ambient air concentrations were found to be 4 x
10~12 g/m3 an(j the total deposition flux was 1.6 x 10"^
g/hectare-year for the BWCA.
48
-------
SECTION IV
POTENTIAL EFFECTS OF COAL COMBUSTION EMISSIONS
ON THE TERRESTRIAL BIOTA OF THE BWCA
INTRODUCTION AND GOALS
The expanse of relatively pristine terrestrial ecosystems in Minnesota's
Boundary Waters Canoe Area is a major reason for its recognition as a unique
recreational resource in the United States. The flora and fauna growing in
the BWCA have not previously been subjected to elevated concentrations of
toxic air emissions or the deposition of chemically transformed products of
these emissions (see Section III). However, the emissions inventory of the
Air Quality Modeling section Indicates a gradual increase in toxicant
concentrations and deposition over previous very low levels (see Section
III), A careful assessment of the consequences of continued increases for
terrestrial species in these ecosystems now seems warranted.
The Terrestrial Effects section will:
1) Characterize the components of terrestrial ecosystems in the BWCA
that could be affected by elevated concentrations or increased
deposition, as a consequence of coal-burning emissions;
2) summarize the research results available for evaluating the
responses of sensitive species to changes in air, water and soil
characteristics, and the overall sensitivity of the ecosystems to
these changes;
3) define potential effects on plants, animals and ecosystems where
sufficient information is available to cause concern, but
is insufficient to quantify the magnitude or timing of responses.
Sensitivities of the regional biota to the emissions and deposition
products from coal-fired generating facilities have been reviewed In several
previous forms (Glass, 1978). Due to measureable differences in terrain,
meteorology, vegetation density, rainfall, and soil moisture from one
location to the next within the BWCA, absolute comparisons are not possible
for short- or long-term biological responses at specific sites. Thus,
responses to air pollutants and dry fall which hold for several locations
already studied must be used to evaluate potential impacts on other
locations, such as the BWCA.
Under relatively extreme emission loads, many impacts on ecosystems such
as the BWCA are well documented, some responses are evident in the short-
term (less than a decade) and others on a long-term (decades) time scale.
49
-------
Studies of other Influences on the vegetation of the BWCA, particularly the
effects of intermittent fire in the past, require the use of time scales of
hundreds of years. Although the studies presented here focus on relatively
immediate, often subtle impacts on species, it is apparent that these impacts
also should be viewed in a time frame of 100 or 200 years if their ultimate
effect upon the entire ecosystem is to be assessed fully.
BIOLOGICAL AND TEMPORAL CHARACTERISTICS OF THE BOUNDARY WATERS CANOE AREA
A wilderness unit within the Superior National Forest (Minnesota), the
BWCA runs for 177 Van (110 miles) along the US-Canadian boundary, varying from
16-48 km (10 to 30 miles) in width. It has a gross area of 439,000 ha.
(1,085,000 acres) with approximately 69,000 ha. (172,000 acres) in lakes and
streams over 4 ha. (10 acres) in size. Some 215,000 ha. (532,000 acres)
support remnants of the natural ecosystems of Minnesota's Laurentian shield
country, virgin areas with the nearly intact flora and fauna.
These virgin areas are those which have never been directly altered by
human activities such as logging, clearing, tree planting, farming, mining,
road building, etc. Almost all these areas, however, have been burned in the
past 400 years, and many virgin forests are postfire successional communities
less than 110 years old (Heinselman, 1973). It is these virgin areas of
natural vegetation patterns upon which this discussion will focus.
Part of the Superior Upland Physiographic Region, the BWCA's landscape
has a generally slight but locally rugged relief left by preglacial erosion.
Elevations above sea level range from 341 m (1,119 feet) at Crane Lake to 680
m (2,232 feet) in the Misquah Hills (Ohmann and Ream, 1971); local
differences in elevation range from 30 to 150 m (Heinselman, 1973). Most of
the relief of this area, glaciated repeatedly during the Pleistocene and
deglaciated some 16,000 years ago, is related to the contours of its
exclusively pre-Cambrian bedrock: metamorphosed sedimentary rock leading to
quartzite, metagraywacke and slate. In contiguous Quetico Provincial Park
(Ontario) the bedrock types are principally associated with a granite
batholith exposed as part of the Laurentian Shield.
A network of more than 1,000 interconnected lakes and streams occupy the
bedrock troughs and basins of the BWCA, some lying in granite (Saganaga Lake
and Lac La Croix) and some in ancient greenstones and slates (Knife Lake).
The landforms are determined by the configurations of the bedrock: slates
typically form long, narrow, steep ridges, and granites the low, irregular
round-topped hills (Ohmann and Ream, 1971).
Deposition was offset by glacial scouring which left bedrock expose on
many ridgetops, cliffs, and lakeshores, and a thin covering of till, outwash,
and lacustrine deposits varying considerably within short distances. Glacial
boulders are common within the soils derived from this sandy and gravelly
loam glacial deposition.
50
-------
Plant Community Types
The plant communities of the virgin upland forests have been quantita-
tively described by Ohmann and Ream (1971). As shown in Table 7, even after
60 years of fire control the jack pine (Plnus banksiana) communities remain
the most common of the virgin upland forest, followed closely by the
broadleaf group, which is largely dominated by aspen (Populus tremuloldes)
and birch (Betula papyrlfera). White pine (Pinus strobus) and red pine (£.
resinosa) communities made up 10% of the 106 virgin standards randomly
sampled by Ohmann and Ream (1971). The distribution of the vegetation types
in relation to the BWCA area is shown by the map in Figure 12.
Transitional between the Great Lakes-St. Lawrence and boreal forest
regions, biotic communities in the area have an abundance of boreal trees:
jack pine, black and white spruce (Plcea mariana, £. glauca), balsam fir
(Abies balsamea), tamarack (Larix lariclna), northern white cedar (Thuja
occidentalis), and paper birch. The two pines characteristic of the Great
Lakes Forest, eastern white pine and red pine are also plentiful (Heinselman,
1973). Citing Dean's preliminary 1971 study of the area wetland communities,
Heinselman (1973) indicates they are closely related to the glacial Lake
Agassiz peatland communities, a region some 160 km (100 miles) to the west.
Of the 12 community types described by Ohmann and Ream (1971), only the
lichen community type is nonforest. Characterized by the lack of many woody
plants and by the importance of lichens and mosses, this type comprises
slightly less than 5.17. of the stands in their random sample of 106 sites.
Ohmann and Ream grouped lichens other than the reindeer mosses, and mosses
other than the feather mosses, Dicranum, and the hairycap moss. Together
they make up 40% of the ground cover within the community. Another 30% of
the ground surface is bare rock. The reindeer mosses (actually lichens) are
also important in this essentially two-layered community.
Lichens and mosses are also an importnt component of the ground cover in
four other communities designated by Ohmann and Ream: jack pine (fir)—19%
of the ground cover; red pine—26%; black spruce—jack pine—59%; and the
budworm-disturbed balsam fir—46%, including herbs. As computed by Ohmann
and Ream, these communities make up 32% of the upland virgin vegetation area
in the BWCA. According to Ohmann and Ream the lichen community may be viewed
as an early stage of succession after some major disturbance, such as fire,
or as they indicate it has been described by Oosting (1956), as primary
succession on rock outcrop.
In the BWCA today tree lichens are found largely on the lower limbs of
old fir and spruce, and on dead balsam fir killed by the spruce budworm.
Ground lichens are most abundant on open bedrock ridges, and/upper slopes,
which become well covered by lichens 60-100 years after fire (Heinselman,
1973).
Stands comprising the white and red pine community types are slightly
older than those in most of the other communities and make up 9.5% of total
51
-------
Table 7. The virgin upland communities in the BWCA showing relative
importance of stands, types, and species; richness and
number of plant families represented in the stands.
Stands
Species
Community
Type
No.
Percent
Total
No.
Families
Lichen
6
5.7
32
19
Jack pine (oak)
11
10.A
81
25
Jack pina (fir)
,7i
6.6
95
30
Jack pine-Wackj spruce
6.6
83
26
Blacic spruce-jack pine
id
9.A
75
23
Aspen-birch
13
12.3
112
30
Maple-aspen-birch
15
1A.2
10 A
3A
White pine
6
5.7
80
23
Red pine
A
3.8
67
25
Budworm-disturbed balsam fir
10
9.A
102
31
Fir-birch
8
7.5
86
30
White-cedar
9
8.5
85
28
*Adapted from Ohmann, L.F. and R.R. Ream, \971. Wilderness ecology:
virgin plant communities of the Boundary Waters Canoe Area. USDA
Forest Serv. Res. Pap. NC-63.
52
-------
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-------
stands .sampled by Ohmann and Ream in 1971 (5.7% white pine; 3.8% red pine).
As described by these researchers the white pine community is really a two-
layer forest: an upper canopy of large, old white pines with scattered red
pines, and a lower layer of balsam fir trees and saplings. The
attractiveness of. the red pine community stems from the presence of open
stands of old, majestic red and white pines which survive fires along the
lakeshore, and are prominent along the rldgetops forming the skyline. The
understory is short on saplings and seedlings while shrubs and lichens
characteristic of dry conditions are dominant.
The mammals and birds of the area are also representative of a transi-
tion between the Great Lakes and boreal forest ecotones; The moose (Alces
alces), Canada lynx (Lynx canadensis), fisher (Martes pennatl), pine marten
(Martes americana), snowshoe hare (Lypus americana), spruce grouse
(Canachltes canadensis), Canada jay (Perisoneus canadensis), and (formerly)
the woodland caribou (Ranglfer caribou) are all species with boreal
affinities. The northern white-tailed deer (Odocoileus vlrglnlanus) and
bobcat (Lynx rufus) are species more typical of the Great Lakes forests. The
eastern timber wolf (Canis lupus), red squirrel (Tamiasciurus hudsonicus),
red fox (Vulpes fulva), beaver (Castor canadensis), otter (Lutra canadensis),
raink (Hustella vison), black bear (Ursus americanus), ruffed grouse (Bonasa
umbellus), bald eagle (Haliaeetus leucocephalus) , etc., are all species more
typical of the Great Lakes forests. Most of the native animals and birds
also have habitat requirements that correspond with niches in various post-
fire successional stages (Heinselman, 1973).
Long-Term Stability of the BWCA Landscape
Ohmann and Ream (1971) conclude from their studies that the structure
and composition of each stand in today's virgin forests are more closely
related to the length of time since the last fire, and probably to the
character of the fire and the age of composition of the former stand, than
all of the other environmental factors studied such as soils, aspect, slope,
or elevation.
The stand origin and fire year maps developed by Heinselman (1973)
indicate that from 1595 to 1973 nearly all of the one million-acre virgin
forest study area burned at least once, 1910 being the last year of major
burns. At least kkt. of the million-acre virgin study area was involved in
the drought year burns of 1893 and 1894. Many even-aged stands also date
from a similar drought-fire sequence 220 years ago in 1755-59. Those large
upland ridges and ridge complexes distant from or west of natural firebreaks
were the area most frequently or intensely burned. Such areas are today
often dominated by jack pine, black spruce, birch, and other sprout
hardwoods. White pine, red pine, white spruce, northern white cedar, black
ash, elm, and fir are relatively more abundant on those sites burned least
frequently or intensely: swamps, valleys, ravines, the lower slopes of high
ridges, islands, and the east, north, northwest, or southeast sides of large
lakes or streams. Very fire-sensitive northern white cedar has retreated to
the lakeshores where it forms a typical narrow fringe (Heinselman, 1973).
54
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Helnselman (1973) cites Ayres' 1899 observation that by 1855, due to its
long history of fire, only 20% of the region supported the mature pines
desired for lumber. Thus, Heinselman indicates, just a small fraction of the
BWCA was affected by the early logging, and the young stands, recent burns,
and scattered areas of older forest that covered three-fourths of the region
were little touched. As of 1973, he notes, the net land area undisturbed by
cutting exceeded 167,950 ha. (415,000 acres), most within the lands set aside
for national forest between 1902 and 1913. The Anderson bill (recently
passed by the U.S. Congress) eliminates logging as a management alternative
from the entire BWCA.
As indicated by Wright (1974), the same 370 years covered by
Heinselman's tree-ring/fire studies in the BWCA represent only a portion of
the total life-span of the forest. Although humans may have modified the
natural frequency of fire during those years, pollen curves and charcoal
profiles from the sediment of Lake of the Clouds (in the heart of the BWCA)
show major fires occurred about every 80 years for the last 1,000 years.
What Wright (1974) has called the "time factor in landscape evolution"
must be applied to environmental influences other than fire control. If we
look ahead 50, 100, or 200 years to how succession in the absence of a
natural constituent, fire, may significantly change the BWCA forest
communities, then it is equally appropriate to consider a similar time frame
for assessing what effects rising levels of pollutant deposition may
eventually have on these same communities. Such a long-range view provides
an important perspective on the possible significance of relatively
immediate, if subtle, effects now manifested in individual indicator species
in other ecosystems, where effects of exposure to increased doses of SO2»
N0X, TSP, HF, Hg are already known.
The almost unique vegetation resource which presently covers the BWCA
was initiated 300 to 100 years ago. Today's land managers and policy
decision-makers are stewards of whatever the landscape of this area is to be
200 years from now.
BI0TIC RESPONSES TO COAL-FIRED POWER PLANT EMISSIONS
The contributions to this section of the report have been summarized
from the various current research projects on the impact of coal-fired
generating stations and from the literature on what is known about the
BWCA ecosystem components and their response to known levels and durations of
exposure to point source pollutants from coal-fired power plants.
Figure 13 summarizes the types of terrestrial ecological effects that
might be anticipated from exposure to generating station emissions and
associated deposition. Direct effects may be anticipated from both dry and
wet deposition of air pollutants on ecosystem components (see Section III).
In addition to direct effects, a number of indirect effects may be manifested
through changes in ecosystem processes such as bioaccumulation of toxic
compounds, alterations in mineralization or rates of nutrient flow, and
changes in host parasite relationships.
55
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ANIMALS
VEGETATION
" \
COAL-FIRED POWER PLANT
EMISSIONS
SOILS
s
/
dry
< "*
WATER
KEY
— Material Mows Seeding to direct effects
— Material flows and/or Interactions that
could lead to Indirect effects (bloaccumulatlon,
nutrient cycling, host /parasite relationships,
etc.)
Figure 13.. Summary schematic of regional material exchange system ar.d
biological response processes.
-------
The discussion which follows considers such major emission products
(residuals) from the viewpoint of the plant, animal, and/or soil components
of the terrestrial ecosystem on which they could have important potential
effects. The material presented reflects data or information already
available. New data needs are identified by the inadequacy or lack of
results from long-term, lov-level exposures. The emission residuals
considered are those for which sufficient information is available to
anticipate some effect on an ecosystem component at some concentration, and
for which the air quality modeling work has provided estimated concentrations
and loadings in the BWCA.
Residuals of Concern
SO2 —
Sulfur dioxide and the effects of exposure to it have been studied more
than any other pollutant (Rennie and Holstead, 1977; Guderian, 1977; Benedict
et al., 1971; etc.). A wide variety of organisms are sensitive to damage
from exposure to elevated SO2 concentrations (Tibbitts et al. , 1978; EPRI,
1976; Van Haut and Stratman, 1970; etc.). Many organisms also exhibit
synergistic reactions to combinations of SO2) with other coal-fired power
plant emissions such as O3 or N0X (Dochinger et al., 1970; Kress and
Skelly, 1977; Houston, 1974a; etc.).
Given the number of extensive reviews of SO2 and its effects
(Braunstein et al., 1977; Glass, 1978; etc.), this section will not attempt
to recapitulate that material in its discussion. A reading of these and
other references in relation to the principal vegetation types reviewed
supports focusing on responses of pines, lichens, and soils in the BWCA.
N0X N02
Forest soil and insects are generally less sensitive to N02 than to
other major pollutants (NAS, 1977). Although organisms are more sensitve to
NO2 rather than to the other nitrous oxides, the usual measurement combines
the forms as NOx, and levels necessary to affect susceptible members of the
terrestrial ecosystem (vegetation) are much greater than for sulfur dioxide
and photochemical oxidants (MacLean, 1975). Estimates of the economic impact
of air pollutants on vegetation have not included N0X by itself, rather, it
has been combined with ozone and peroxyacethyl nitrate (PAN). However,
emission of N0X have been increasing substantially throughout the U.S. and
Canada, and the synergistic effects on plants from low concentrations of
NO2 and sulfur dioxide (found in experimental exposures), and of N0X in
the production of photochemical smog and acid precipitation pose the greatest
threat (Glass, 1978).
Ozone—
Photochemical oxidants, ozone (O3), and to a lesser extent, peroxy-
acetyl nitrates (PANs), are the most damaging air pollutants affecting
agriculture and forestry in the U.S. (Jacobson, 1977). Peroxyacetyl nitrate
(PAN) is more phytotoxic than O3, but the ambient concentration of PAN is
57
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much lower than O3 in most areas of the U.S. (Taylor, 1969). In the
northern Minnesota area it may be almost negligible. Formation of ozone in
the atmosphere has a complex dependence on the amounts of precursors
(nitrogen dioxide and hydrocarbons), meteorological conditions, and time of
day (NAS, 1977), but moderately high levels are being" observed in northern
Minnesota given the area's relative isolation from the usual ozone sources
(see Section III, Table 1). (Photochemical oxidants, including ozone, have
been problems in southern California for more than 30 years. The severity of
losses to agricultural crops, exclusive of forests and ornamental plantings,
had reached more than $55 million by the 1970's (Millecan, 1976).)
Trace elements—
Trace elements have been defined as those elements present in the crust
of the earth at less than 0.1% or 100,000 ppm. More than 63 of them are
found in coal. Some are more concentrated than others in coal, and there is
considerable variation in trace element concentration from different coal
sources. Most trace elements (including arsenic, beryllium, chromium,
copper, lead, selenium) appear to be at mean concentrations less than 7,000
pptn, notable exceptions being boron, zinc, and titanium (Ruch et al., 1974;
Zubovic, 1975). These trace components, however, are concentrated on the
surface of the flyash particles and are highly reactive (Glass, 1978). Of
the macro elements in coal (e.g., aluminum, calcium, iron, silicon, sulfur,
and sometimes titanium), only sulfur is the element of concern here. Sulfur
oxides represent the major pollutants of gaseous emissions and are mentioned
here because of the known ability of some metallic trace elements to catalyze
the further oxidation of sulfur oxides into more toxic substances capable of
greater respiratory damage than sulfur dioxide alone (Amdur and Underhill,
1970) or to interact and form metallic sulfates. Excessive deposition of
trace elements upon a balanced ecosystem has the potential to cause problems
because of the high toxicity of many trace elements and the potential for
bioaccumulation.
Acidic fallout (acid rain)—
While acidic fallout has been long studied by European researchers
(Oden, 1968), the phenomenon received only cursory attention by Canadian and
United States scientists until the early 1970's. However, since the
beginning of the decade scientists of both these North American countries
have expanded their interest in the long-term effects of acidic precipitation
and the precursors of this phenomenon. Canadian scientists*have shown that
acidic precipitation is a serious problem in both terrestrial and aquatic
ecosystems of Eastern Canada (Summers and Whelpdale, 1976; Beamish, 1976;
Stokes and Hutchinson, 1976).
In the United States a report to the Secretary of the Department of
Health, Education and Welfare by a special scientific advisory committee
considered the long-term consequences of the United States National Energy
Plan (NEP). This committee concluded that one of the most serious
environmental consequences of the expanded use of coal-fired power plants
will be increased acidic precipitation throughout the areas where the power
plants are located (U.S. Federal Register, 1978). While this advisory
committee supported the conversion from oil to a coal-based energy economy
58
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(NFJP) , they concluded that all converted and new facilities should install
the best available abatement technology to reduce to a minimum the precursors
of acidic precipitation.
Contributors reviewing the literature and current research for this
report on Minnesota reached the consensus that, for the BWCA, the principal
ecosystem components or organisms to be emphasized regarding the effects of
acid rain were pines, lichens, insects, and amphibians (direct impacts) and
soils (indirect impacts).
Impacted Components: Conifers (Pines) and Aspen
Effects of SO2 on pines—
The impact of the gaseous emissions of large coal-fired power plants
initially become evident in the responses of the most sensitive of the
species in any ecosystem. In the BWCA these sensitive species are lichens,
conifers of the genus Pinus and trembling aspen (Populus tremuloides). The
three dominant species of Pinus in the BWCA are Pinus strobus, P. resinosus,
and J?, banksiana. Of these three species, eastern white pine is the most
sensitive to SO2• Red pine (Pinus resinosus) and jack, pine (Pinus
banksiana) are considered about equally sensitive to SO2> but not as
sensitive as eastern white pine. Trembling aspen is a dominant species over
20 percent of the BWCA (See Table 7 and Figure 12) and Is recognized by
Dresinger and McGovern (1970) as a very sensitive species.
The major manifestations of pollution damage in these three species are
foliar tip necrosis, mottling chlorosis, basal necrosis of the needle tissues
beneath the fascicular sheaths, and premature needle casting. The premature
loss of needles from the second, third, and fourth-year internodes causes a
reduction in annual growth as well as the loss of normal health and vigor
which in turn predisposes those species to more severe impacts of other
abiotic (drought, frost, nutrient deficiencies) and biotic (insect infesta-
tions, root attaching fungi) causal agents (Carlson, 1978).
Several studies document the development of visible Injury symptoms on
eastern white pine by low level chamber fumigations. Costonis (1970)
reported tissue damage on new needles of eastern white pine after a single
one-hour treatment with 5 pphm SO2• Houston (1974a) observed necrosis in
elongating needles of eastern white pine after six hours of fumigation with
2.5 pphm S02> In a field study in the Sudbury, Ontario region, Linzon
(1971a) observed damage to eastern white pine at a seven-year fumigation
average of 0.4 pphm, a level of SO2 commensurate with the background levels
already being recorded in portions of adjacent Ontario (see Section III,
Table 1).
After field observations, Costonis (1972) reported that 6 pphm of SO2
caused acute injury to the new needles of eastern white pine after four hours
of exposure. Ozone measurements in the field did not exceed 4 pphm. Prelim-
inary laboratory tests conducted before these field studies indicated that
59
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sensitive white pines developed necrotic lesions after SOp exposure of 3
pphm for one hoar; if fumigation was continued for three hours, severe
necrosis on current needles occurred. Laboratory tests also revealed that
O3 fumigations of 15 pphm for four hours produced equivalent injuries.
Houston and Dochinger (1977) reported a decrease both in the number of
seeds produced/cone and in the percent of pollen germination in white pines
in a low level SO2 polluted area. Effects on red pines included decreases
in cone length, seed weight, percent seed germination, percent pollen
germination, and pollen tube length. None of the trees displayed foliar
injury patterns, indicating that low levels of air pollutants may be
affecting the reproductive tissues of pines at concentrations lower than
those required to produce visible injury. In the vicinity of a copper
smelter at White Pine, Michigan, low level SO2 exposure has caused no
plainly visible vegetation damage, but ring-widths of balsam fir and white
spruce suggest that growth has been substantially reduced in trees downwind
from the smelter (Kotar, 1978).
Dresinger and McGovern (1970) found trembling aspen to be the most
sensitive forest species to air pollution in the Sudbury area. Visual injury
to foliage was caused by SO2 concentrations of 42 pphm for one hour or 13
pphm for eight hours. Pollen tube elongation is inhibited at SO2
concentrations greater than 30 pphm for four hours (Karnosky and Stairs,
1974).
The Environmental Protection Agency (1976) attempted to classify the
susceptibility of various woody plants to SO2 and photochemical oxidants
based on foliar injury, growth loss, etc. They observed that eastern white
pine near the Sudbury, Ontario region (SO2 source) has a poorer
regenerative capacity to repeated SO2 exposures than various hardwoods
(aspen, birch). They also documented that red pine was very sensitive to
SO2 emissions.
Effects of N0X on pines—
Skelly et al. (1972) carried out field observations of eastern white
pines exposed to SO2 and NOx. The most severely affected trees were in
areas where the highest readings were 8.5 pphm NOx (one hour average), and
69 pphm SO2 (two hour average). They also found that oxides of nitrogen at
moderate concentrations acting alone or in combination with low SO2 concen-
trations caused acute to chronic damage in eastern white pine. Young seed-
lings were extremely susceptible to N0X fumigations. VanHaut and Strattman
(1967) observed damage to plants exposed to 250 pphm N0X for 4-8 hours.
Effects of ozone on pines and aspen—
In chamber studies conducted by the EPA, eastern white pine was
classified in the intermediate sensitivity range to O3 and red pine in the
tolerant range. Davis and Wood (1972) used chamber experiments to determine
the relative susceptibility of 18 conifers to ozone. They found jack pine to
be the most susceptible, damaged by four hours of 25 pphm O3. Eastern
white pine was also very sensitive, damaged by eight hours of 25 pphm O3,
while red pine was resistant (no injury manifestation) at these fumigation
levels.
60
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In a field study in West Virginia, Berry and Ripperton (1963) observed
damage to eastern white pines 48 hours after a one-hour fumigation of 5 pphm
0^- The damage observed was considered a "light attack" of emergence
tipburn, but severe symptoms were noticed following ambient O3 exposures of
6.5 pphm for a total of four hours during a 48-hour period. Using chamber
experiments, they determined O3 was the casual agent of the injury observed
in the field. (The damaged area was remote from any major sources of air
pollutants.) Ozone levels higher than these have already been observed in
the BWCA (see Section III, Table 1).
Botkin et al. (1971) observed that fumigations of O3 (50 pphm for four
hours and 80 pphm for three hours) suppressed photosynthesis of eastern white
pines. Further studies carried out by Botkin in 1972 determined that
photosynthetic depression occurs before visible O3 damage becomes apparent.
In a chamber experiment on five-year old eastern white pine they determined
that 50 pphm fumigations of O3 for four hours was threshold level for
photosynthetic suppression (Botkin et al., 1972).
Treshoro and Steward (1973) found visible injury to trembling aspen at
15 pphm O3 for two hours. Since this was the lowest concentration tested,
it does not establish the injury threshold, but does indicate that trembling
aspen is among the most sensitive species tested.
Effects of SO2 and O3 in combination on pines—
Eastern white pine is generally considered to be more susceptible than
other pines to a pollutant mix. Several studies support the finding that
greater than additive responses occur when eastern white pine is exposed to
both SO2 and O3: Costonsis, 1973; Banfield, 1972; Berry, 1971; Houston,
1974b; Houston and Stairs, 1973; and Jaeger and Banfield, 1970 (see also
Table 8). Menser and Heggestad (1966) support the findings that "tolerable
levels of a single pollutant can damage plants (in general) when in
association with another at an equally low level." These studies, however,
are mainly chamber studies and deal only with SO2 and O3. They do not
account for other pollutants and environmental stresses that occur In the
field.
Berry (1971) conducted chamber studies to determine the relative sensi-
tivities of red pine, jack pine, and eastern white pine seedlings to O3 and
SO2 fumigations. The three-, five-, and seven-week old seedlings were
exposed to two-hour fumigations of 25 pphm O3, 50 pphm O3, 25 pphm SO2 >
or 50 pphm SO2 • Jack pine was the most sensitive to both SO2 and O3,
but there was no significant difference in the sensitivities of the age
groups of any of the trees. At 50 pphm O3, red pine was less tolerant than
eastern white pine. SO2 fumigations at 25 pphm, however, were more
injurious to eastern white pine than to red pine. Red pine injury was
detected at 25 pphm O3 for two hours, but at 50 pphm O3, 87% of the 468
seedlings observed were injured (banding, flecking, tip necrosis). Injury
symptoms were detected from 24 to 48 hours after fumigation.
Jaeger and Banfield (1970) studied responses of eastern white pine to
prolonged exposures to O3, SO2» and a mixture of both pollutants. When
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Table 8. Summary of results available on native vegetation responses to SO2 in
combination with other pollutants.
Time Concentration Response of Vegetation Plant Species Author
6 hours/day
for 28 days
6 hours
4-8 hr/day
5 days/wk,
4-8 weeks
14 pphm SO2
+ 5 pphm O3
+ 10 pphm NO2
2.5 pphn SO2
+ 5 pphm O3
10 pphm SOj +
10 pphm O3
Significant growth reduction (measured
as height) compared to either ozone and
sulfur dioxide combined, or ozone alone.
Needles were significantly narrower
than for any other exposure. This
study is an example of growth reduction
with slight foliar symptoms. Foliar
symptoms response most sensitive in
early July.
20-28 day-old white pine needles on
ramets, exposed 9 am - 3 pm. All sensi-
tive clones adversely affected.
Response judged in terms of needle
elongation (growth) and foliar lesion
or tip necrosis. Author calls response
synergistic. 0.025 ppm SO2 or 0.05 ppra
» threshold; 0.10 ppm 0-j = 207. necrosis.
16% needle necrosis (chlorotic, yellow
spots, current year needles thin and
twisted), shedding of older needles far
exceeded damage responses from single
exposures. 0.1 ppm SO2 injured 47.
of needle area; 0.1 ppm O3 injured
3% of area.
Loblolly pine
Pinus taeda
(2 wks old)
Sycamore
(1 wk old)
Seedlings
Eastern white
pine
Pinus strobus
Eastern white
pine
Pinus strobus
Kress and
Skelly
1977
Houston
1974a,b
Dochir.ger
et al.
1970
-------
eastern white pine was exposed to 50 pphm of O3 and 50 pphm SC>2 for 10
days, profuse necrotic spotting occurred on new and one-year old needles.
The most significant finding was that at the above fumigation levels with
increasingly humid environments, severe necrotic spotting occurred after
three days. That is, the synergistic effect was much more severe with high
humidity. Banfield (1972) observed necrotic spotting and tipburn of eastern
white pine when exposed to 10 pphm O3 and 0.5 pphm SO2 for one to twelve
days in a chamber fumigation study.
Dochinger et al, (1970) observed injury to eastern white pines when they
were exposed to 10 pphm O3 for 10-20 days and 10 pphm SO2 for 10-20 days.
When exposed to 10 pphm of both O3 and SO2 for the same time intervals,
injury to the pines quadrupled.
Effects of trace elements on pines—
Accurate assessment of trace element Impact cannot be known without a
thorough characterization of endogenous levels of soil trace elements and the
processes ongoing within soil. Trace element cases, may exceed that from
fossil fuels. Trace element input is attentuated by distance from the
pollutant point source and by filtering action of the surrounding canopy,
Since more than 80% of the BWCA is forested (about 75% of this in coniferous
stands), most trace element emissions may impact the tree canopy directly.
Very little is known concerning the effects of most trace elements applied
directly to foliage.
Fluoride is known to be directly phytotoxic, but very little work has
been done on the susceptibility of either eastern white pine or red pine to
ambient concentrations of fluoride pollutants. In 1970 the Environmental
Protection Agency carried out field studies on fluoride-affected vegetation
in Glacier National Park, Montana, the closest boundary of which is 15 miles
northeast of a large aluminum reduction facility. They observed that tip
necrosis due to fluorides was clearly visible on older needles of sensitive
western white pine growing in areas deep within the interior of Clacier
National Park. Western white pine (Pinus monticola) was classified by EPA in
1976 as being "less sensitive" to airborne pollutants than eastern white pine
(Pinus strobus). In another report (1974), EPA observed tissue necrosis on
western white pine occurring at levels only two or three times higher than
background fluoride levels in healthy trees.
Linzon (1971) carried out studies during the 1969 growing season in the
Cornwall area of Ontario near three fluoride emitting industries. Early in
the growing season the current 1969 needles on eastern white pine had not
emerged, but the 1968 foliage displayed severe brown terminal necrosis with
many needles being prematurely lacking. In subsequent visits the 1969
needles displayed severe orange-red terminal necrosis. Studies carried out
in the summer of 1977 in the same area of Ontario by the University of
Montana documented severe visible injury to both eastern white pine and red
pine despite considerably lower fluoride concentrations in the needles than
determined by Linzon in 1971 (Miles, 1978).
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Solberg and Adams (1956) state that, in general, fumigation of
vegetation with HF or SC>2 raay produce temporary decreases in photosynthesis
in the absence of visible injury. They found that histological responses of
SO2 and HF were indistinguishable in ponderosa pine and apricot leaves.
Impacts of acidic precipitation on coniferous forests—
Effects on growth of adults of fully coniferous species have been
difficult to document with methods currently available. Several studies have
failed to identify significant effects (Abrahamsen et al., 1977; Tamm et al.,
1977) while others provide suggestive circumstantial evidence that acidic
precipitation has adversely affected growth of trees in coniferous forests
(Jonsson, 1977, Jonsson and Sundberg, 1972). Long-term growth effects are
exceedingly difficult to demonstrate because their cause may be confounded
through interaction with numerous variables. In addition, even if the long-
term effects on growth are very significant, significant changes in growth do
not usually occur within the time span of typical researach projects.
The quickest and most severe impact of acidic precipitation on soils is
likely to occur in the 1-2 cm horizon. Deeply rooted plants (e.g., trees)
are not likely to be directly affected very much by changes in this horizon,
but plants rooting in this zone (understory vegetation and germinating plants
of all types) may be affected considerably (Mayer and Ulrich, 1977). Effects
on understory vegetation may be very important because, at certain stages of
succession, a greater weight of chemical elements circulates through the
understory than through the trees. This has been demonstrated in old spruce
and pine forests in the U.S.S.R. (Ovington, 1962).
Perpetuation of a coniferous forest depends upon the continued
reproductive success of the conifers. Spruce (Picea abies) germination has a
broad optimum around pH 4.8 and is adversely affected at soil pH of 4.0 or
lower. Spruce seedling establishment has a narrow optimum at pH 4.9 and is
quite sensitive to pH's lower than this (Abramsen et al., 197). In a 20-week
study of the effects of acid rain on growth of white pine (Pinus strobus)
seedlings, best growth was found in seedlings exposed to rain of the lowest
pH (pH 2.3) (Wood and Bormann, 1977). This was presumed to be caused by the
increased nitrogen impact from the acid rain stimulating growth. Apparently,
once seedling establishment has occurred, the seedlings are relatively
tolerant of acidic soil. Considerable mineral leaching occurred throughout
the 20-week experiment. Availability of basic cations would probably have
become limiting to growth had the experiment been carried out over an
extended period.
Impacts of acidic precipitation are also reported in part in a U.S.
Forest Service Technical Report (Proceedings of the First International
Symposium on Acid Precipitation and the Forest Ecosystem, 1976) in which
European, Canadian, and United States scientists presented the data obtained
on both continents during the last 20 years.
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Summary of effects on pines—
Based on the above literature evidence, and the projected ambient air
levels o£ TSP, SO2 > N0X' an<* trace elements, it is possible, bat unlikely
that short-terra, visible damage will be incurred by the pines in the BWCA.
Acid rain damage to plant tissues seems possible in view of results
suggesting that the pH of rain under worst conditions may become as low as
3.5-4.3, although the projected frequency of these rains is not immediately
available (see Section III). Literature reports indicate that this range of
pH could alter growth parameters and reproductive success of conifers.
The long-term implications of small, sub-injurious effects on parameters
such as photosynthesis rates, radial growth, nutrient uptake, germination
success and life span could be substantial. Whether the effect would be
strong enough to affect community structure or the rate of secondary
succession is open to debate. In view of recent data which indicate impacts
may occur at levels of residuals lower than previously reported (Gordon et
al. , 1978; Kotar, 1978) the possibility of long-term effects must be
considered seriously. It is also obvious that signficant new research
programs focused on the most sensitive species, and or sub-injurious effects
mast be carried out if these probleroic issues are to be resolved.
Impacted Components: Lichens and Bryophytes (Sphagnum)
Effects of SO2 on lichens—
The adverse effects of gaseous SO2 on lichens are well-documented in
field and laboratory observations. The laboratory observations have
generally been made at SO2 levels of above 50 pphm and will not be expanded
upon here. The field observations have tended to concentrate on mapping
lichen communities around pollution sources, documenting the disappearance of
lichen species as one approaches the pollution source (LeBlanc and Rao,
1975). This approach seems to be accurate in determining zones of air
quality in urban and Industrial areas where there has been a pollution source
for a long period of time (e.g., Sudbury, Ontario; LeBlanc et al., 1972), and
where environmental conditions are such that no interruptions in adequate
indicator lichen cover would be expected. Also, where one is close enough to
the source that short-term acute effects can be easily observed (Clay Boswell
plant, Cohasset, Minn.; Coffin, L978).
LeBlanc and Rao (1973) indicate that lichens in the Sudbury, Ontario
area were not injured if the six-month growing season ambient SO2
concentration was less than 0.2 pphm; growing season average concentrations
of 0.6 to 3 pphm were adequate to produce chronic injury. Average growing
season concentrations above 3 pphm produced acute injury. Background levels
in the BWCA have reached 10 g/m^, or 0.37 pphm (see Section III, Table
1).
Significant decreases in respiration rates of lichen samples occurred in
100-200 days at median SO2 concentrations of 1.8 pphm in southeastern
Montana (Eversman, 1978), a level which could be approached in the BWCA given
projected effects from Atikokan (see Section III). Thalli of yellow-green
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lichens (Parmelia ehloroehroa, Usnea hirta) bleached to a yellower color
within 100 days arid the percentage of normally plasmolyzed* cells increased
from a baseline of 5—8% to 25-30% in 30 days (Eversman, 1978). Note: Usnea
hirta is an epiphyte on trunks and branches of ponderosa pine in southeastern
Montana. It also grows in the BWCA (Hale, 1969). This type of lichen
(fruticose) is particularly sensitive to air pollutants. Parmelai
chlorochroa lives on bare soil between grass clomps and shrubs on the
grasslands. A foliose lichen, it intergrades with western forms of _P.
taractica, found on exposed rocks in the BWCA (Hale, 1969).
At median SO2 values above 2 pphm in southeastern Montana, bleaching
and plasmolysis occurred faster, and _P. chlorochroa and U. hirta exhibited
symptoms of acute damage. Within 33 days of SO2 exposure at median concen-
trations greater than 3.3 pphm, plasmolysis of algal cells approached 100%
and the respiration rate of these lichens dropped significantly below that of
controls (Eversman, 1978). Selected indicator species in Minnesota, such as
P. caperata and IJ. subfloridana, could be expected to show accumulating
lethal effects of SO2 at median concentratins of approximately 2 pphm.
Effects of O3 on lichens—
The very few studies that have been made on the effects of O3 on
lichens indicate that at concentrations of about 25 pphm and below, O3 has
stimulatory effects. A study cited in Rosentreter and Ahmadjian (1977),
concluded that O3 may have induced production of young reproductive
structures in Cladonla coniocraea, a common ground species. They also cited
a study by Sernander-du-Rietz (1957) suggesting that lightning storms
stimulate fruiting of lichens.
Rosentreter and Ahmadjian (1977) found that O3 concentrations of 10,
30, 50, and 80 pphm for one week did not appreciably change the chlorophyll ji
content of the algae, the thallus color, or morphology of the reproductive
structures of C. arbuscula. Chlorophylls £ and b^ increased slightly at 10
pphm. Rosentreter and Ahmadjian (1977) agreed with Anderson and Sernander
that O3 may induce lichen fruiting. Lichens may thus respond
physiologically to levels of O3 already reached on occasion in the BWCA
(see Section III, Table 1). However, Nash and Sigal (1979) documented
significant reduction in gross photosynthesis in Parmella sulcata and
Hypogymnia enteromorpha when these lichens were fumigated with 0.5 and 0.8
ppm ozone.
Unpublished field data (Sigal, 1978) from the San Bernadino Mountains in
California show a marked reduction in percent cover of Letharia vulpina and
Nypogymnla enteromorpha on conifers in areas subjected to oxidnts (O3 and
PAN), compared with control sites.
Effects of trace elements on lichens—
Work involving lichens has not usually dealt with any potential/possible
effects of trace elements. One Michigan study conducted near Lake Superior
established an inverse relationship between lichen cover on tree bark and the
*Plasmolysis is the shrinking of the cytoplasm away from the wall of a living
cell due to water loss by exosmosis.
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presence of chloride precipitate found in snow (Brown, 1977). Lichen cover
varied from 85% at 0.001 gm/cm of chloride precipitate Co 0% at 0.012
gm/cm H2O chloride. Among the lichens eliminated at the higher concentra-
tions of chloride precipitate were J?, caperata, P^. exasperatula, and Physcla
millegrana, all present in the BWCA flora (Wetmore, 1978; Hale, 1969).
Effects of total suspended particulates on lichens—
Relatively little information is currently available regarding
potential/possible effects of TSP on lichens. In his previously cited study
of snow as an accumulator of air pollutants, Brown (1977) did record an
inverse relationship between lichen cover on tree bark and the amount of
total particulate matter present in the snow. At 0.045 gm/cm H2O of total
solid particulate, lichen cover was 85%, at 0.23 gm/cm it was 0%. But
Brown did not determine if this decrease was due to the levels of TSP or to
those of SO2 and chloride also measured.
Impacts of acidic precipitation on lichens—
Lichens are sensitive first to the ambient SO2 concentration, then to
the pH of stemflow water (Robitaille et al. , 1977). The gaseous SO2 and
particulate SO4 are adsorbed onto moist bark surfaces, as well as onto
lichen surfaces, a process which decreases pH.
Lotschert and Kohm (1977) compared ambient SO2 concentrations with
bark sulfur content and pH of deciduous trees (which have a higher natural pH
than conifers) in Frankfurt. Where the SO2 concentration was less than 2.8
pphm (0.09 tng/m ) , the bark pH was greater than 3.5 and there were the
"greatest number" of lichens. As SO2 concentration Increased to 3.9 pphm
(0.10-0.11 mg/m^), bark pH dropped to 3.1-3.2, and the lichens disappeared.
The buffering capacities of both bark and lichens decrease with acidic
precipitation (Robitaille et al., 1977). From this 1977 study these
researchers concluded that stemflow pH determined bark pH, thus the propor-
tions of sulfurous acid (H2SO3) and the very toxic HSO3, which in turn
determine the presence or absence of sensitive lichen species. Of the
derivatives SO2 forms with water, HSO3 is the most toxic to lichens
(Puckett et al., 1973: Robitaille et al., 1977). In addition, when the
HSO3 dissociates to H* and S03~, the ratio of S03~ to HSO3 (which
is 1:1 at pH 7) increases by a factor of 10 for each decrease of one unit in
pH (i.e., 10:1 at pH 6, 100:1 at pH A) (Turk and Wirth, 1975).
The mapping studies of Gilbert (1970) show decreasing bark pH and
decreasing lichen cover as SO2 increases, with lichens only surviving on
highly buffered substrates (e.g., limestone and calcareous soil). Conifer
trees, the habitat of many epiphytic lichens in northern Minnesota, probably
have bark pH of less than 5.00 (Gough, 1975). Thus, lichens on conifer trees
have very little pH "maneuvering space" and could be expected to be adversely
affected by increasing ambient SO2 and resulting acid precipitation
conditions before lichens on deciduous trees and calcareous substrates.
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Denison et al. (1977) reported less nitrogen fixation by Lobaria
pulmonaria at pH 2 than at pH 4, 6, or 8. As acid rain increases in Pacific
northwest forests, they expect the nitrogen-fixing activities on I..
pulmonaria and similar L,. oregana to decrease.
Impacts of acidic precipitation on Sphagnum—
Although much is known of the distribution of swamp and bog organisms in
relation to natural pH gradients, there is currently no complete study of the
effects of acid deposition upon wetland ecosystems (Gorham, 1978).
Gorham (1978) has observed completely "dead" peat bogs in the vicinity
of Sudbury, Ontario, where both acid and heavy metal pollution is extreme.
Apparently, a progressive decline in both biotlc diversity and productivity
occurs with increasing saturation of the peat exchange complexes by hydrogen
ions. Direct and secondary effects upon invertebrate and vertebrate animals
may be anticipated, but are essentially unknown as are effects upon bacteria
and fungi—which must be presumed vital to the breakdown of organic detritus
and the recycling of limiting nutrient elements such as nitrogen, phosphorus,
etc. (Gorham, 1978).
In Great Britain, Ferguson and Lee (1978) state that the disappearance
of Sphagnum species from the bog vegetation of the southern Pennines in Great
Britain is correlated with the Industrial Revolution of the past 200 years.
Peat profiles of the southern Pennines show that Sphagnum species were once a
much larger component of the blanket bog vegetation than they are now.
Results of the laboratory studies (artificial acid rain, immersion,
fumigation) reported by Ferguson and Lee (1978) suggest that the growth of a
number of Sphagnum species is sensitive to sulfur pollutants ("HSOj.SO^, SO2)
within the range of concentrations found in Great Britain today. The species
differ in their response to the pollutants; 0.5 oM -HSO3 eventually prove
lethal to the most sensitive species but reduced the growth rate of the most
resistant, JS. recurvum, by only 35Z.
Ferguson and Lee (1978) also note that In 1973 Tallis determined S_.
recurvum to be a recent dominant in the mire communities of north Cheshire.
The only Spagnum to exist in considerable quantities In the southern Pennines
today, it is confined to flush areas. The ability of j3. recurvum to with-
stand relatively high concentrations of the sulfur pollutants may contribute
to its ability to survive and achieve dominance.
Summary of effects on lichens and Sphagnum—
Lichens are among the most sensitive organisms to air pollution. Though
response thresholds for SO2 exposure have not been established for most
species, available information suggests that effects are not to be expected
at median SO2 concentrations below 0.2 pphm. Lichens appear to be tolerant
of short-term exposure to relatively high ozone concentrations (up to 80
pphm). Lichens on the trunks of conifers are probably those most susceptible
to direct effects of acid rain and SO2 because their substatum may have an
inherently low pH and be poorly buffered.
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Sphagnum has been shown to be sensitive to lowered pH due to acidic
rainfall near industrial areas. Thresholds for effects have not been
established.
Concentrations of those toxic emissions from Atikokan known to affect
lichens and Sphagnum are not expected to affect lichen populations in any
substantial manner quantitatively or qualitatively. Some worst case rainfall
events in the BWCA may have low enough pH to have some effect on some
species. Effects (if they occur) will be subtle and insidious.
Impacted Components; Arthropods (Insects
Effects of SO2 on insects—
The effects of air pollutants on insects and plants are complex. The
effects of environmental contaminants on insect/plant interfaces may be
reciprocal, acting on the insect through the plant or on the plant through
the insect. Air pollutants reported to have significant effects on
entomological systems include sulfur and nitrous oxides, ozone, hydrocarbons,
fluorocarbons, smog, dusts, acid mists, major and trace elements, and
radionuclides.
Air contaminants accumulate in the tissues of insects by ingestion,
respiration, or penetration through the cuticle. These substances may act
directly on an insect, be passed through food webs to the insect, or
indirectly affect the insect through alterations in food and habitat
resources. Toxic substances may be transferred through food chains to higher
trophic levels and accumulate in the insect predators and parasites. Pollin-
ators, particularly social insects such as bees, appear to be especially
susceptible to poisoning from the zootoxins they accumulate during their
foraging activities.
Known effects of air pollutants on insects include mortalities of sensi-
tive species, proliferation of pest insects in forests and croplands, loss of
parasitic and predacious insects, loss of saprophagous insects, and loss of
pollinators. Other effects include temporary or permanent changes in
behavior, reduced hatchability and fecundity, teratologies, and genetic
alterations such as chromosome disjunction. No one has attempted to estab-
lish the thresholds of dose responses. Reported relationships between
pollutant concentrations and changes in insect systems represent, for the
most part, historical incidents and not a reliable threshold of response.
The response threshold probably occurs at lower concentrations than reported.
Investigations of SC>2 effects by Bromenshenk (1979, 1978c) and
Bromenshenk and Gordon (1978) at the EPA Zonal Air Pollution Delivery System
(ZAPS) in southeastern Montana have demonstrated significant reductions in
decomposer beetles, particularly Canthon laevis on the fumigated plots of
ZAPS sites I and II.
Data from 15 cm, the lowest fumigation level measured, indicated that
the levels at which these beetles first responded did not exceed 2,1 to 2.6
pphm average for 30 days. Because S(>2 concentrations decreased closer to
the ground, this level probably was higher than that to which the beetles
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were responding. It should be noted that the decreased abundance (sometimes
termed activity abundance) occurred on the lowest SC>2 treatment plots at
both ZAPS I and II during 1976 and 1977. Beetle captures demonstrated a
significant inverse linear regression with increasing SC>2 expressed as the
reciprocal of the sulfation concentrations.
Similarly, Leetham et al. (1979) noted population reductions with
increasing SC>2 concentrations for the Coleopteran families, Curculionidae
and Carabidae (predators), the Lipidopteran family, Pyralidae (larvae) and
adult grasshoppers (Acrididae). Also population reductions were observed in
the high treatment plots at both the ZAPS areas for tardigrades and rotifers
in the soil.
Hillmann (1972) performed insect population studies near a 615 MW coal-
burning power generating station in Clearfield County, Pennsylvania, emitting
172 m tons (190 tons) of SC^/day. (Atikokan emissions are projected to
range from 83-192 m tons (92 to 212 tons) of SC^/day. See Section III,
Table 1A.) One site was located 1,219 m (4,000 feet) from the power plant,
the other 23.5 km (14.7 miles) from the power plant. Significantly greater
numbers of Aphididae and significantly lower numbers of parasitic Hymenoptera
(wasps) and social Apidae (bees) were captured at the site nearest to the
power plant. Since aphid numbers in the area exposed to greater amounts of
SC>2 increased concurrently with parasitic wasp decline, Hillmann concluded
that SO2 ®ay have induced host-parasite imbalance.
Frietag et al. (1973) conducted a field investigation on ground beetle
populations near a Kraft paper mill in Ontario, Canada, and found a drastic
reduction in the number of carabid fauna paralleled increasing fallout of
sodium sulfate (Na2S04).
Effects of O3 on insects—
Some work on the effects of O3 on insect systems has been done to
date. That which has been completed to date has been carried out under O3
levels higher than would be encountered in the BWCA-Quetico area.
Effects of N0X on insect9—
As with 03, very little seems to be known about the effects of oxides
of nitrogen on insect systems. That work which has been accomplished has
involved higher levels than would be experienced in the BWCA-Quetico area.
Effects of trace elements on insects—
Studies have shown that a large number of trace elements can move
through insect systems, often accumulating in Insects at the higher trophic
levels. Many of these elements are toxic to insects at relatively low
concentrations and many are toxic to Insects at levels lower than those which
affect mammals.
The most extensive trace element work has been carried out on substances
harmful to honeybees (Debackere, 1972; Toshkov et al., 1974; Steche, 1975;
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Lillie, 1972—all are review articles). Because of their extensive foraging
activities, bee3 contact, gather, and consume these materials. Bees also are
magnifiers of noxious substances in their environs. Pesticide studies
indicate that pollinators smaller than honeybees may be more susceptible to
toxicosis because they receive a proportionally larger dose relative to body
size (Johansen, 1972).
There are a few studies of particular relevance to problems associated
with emissions from coal-fired power plants. Svoboda (1962) found that about
500 bee colonies were destroyed within a 6 km radius of a power plant near
Trantenak which released arsenic into the air.
Hillmann (1972) has found social pollinators and parasites (which are
similar in terms of trophic relations to predators) to be most severely
impacted by power plant emissions. He recorded a significant decrease In
social insects such as bumblebees and predatory wasps near a 615 HW power
plant in Pennsylvania as compared to populations at a site 23.5 km (14.7
miles) away. Hillman correlated declines in insect abundance with SO}"
levels but did not analyze for trace elements. Many trace elements are more
toxic to bees than sulfur dioxide (see review by Debackere, 1972).
Dewey (1972) found relatively high fluoride levels in the 1,005 preda-
tory insects collected near an aluminum smelter which reportedly emitted
between 1,134-2,837 kg/day (2,500 and 7,600 pounds/day) of fluoride. Four
major groups of insects were collected within a half mile of the plant:
tissues of pollinators contained 5,800 to 58,500 pphm fluoride; predators 610
to 17,000 pphm; foliage feeders 2,130 to 25,500 pphm; cambial feeders 850 to
5,250 pphm. Levels in the control groups, taken at least 80 km (50 miles)
away, ranged from 350 to 1,650 pphm.
Bromenshenk (1977, 1978a, b, 1979) reported that preoperational and
postoperational studies of honeybees taken from commercial apiaries near two
350 MW power plants in southeastern Montana showed significant increases in
the levels of fluorides in or on the tissues of adult worker honeybees.
After one year of operation, during which neither plant had been in
continuous operation and both had operated at one-third to one-half capacity,
fluorides increased by as much as twofold in bees taken from apiaries
downwind and as far as 15 km away from the plants. There were no increases
upwind from the power plant.
Other elements from coal combustion also affect insect populations.
Prior to the development of synthetic organic insecticides, several inorganic
chemicals were widely utilized for insect control. These Included compounds
of arsenic, fluoride, mercury selenium, antimony, boron, and thallium
(O'Brien, 1967). The first six, and possibly all seven, are released by
combustion of coal in electric power generating stations. The mercury
content of the coal, emission rates of Hg, deposition fluxes, and background
levels in fish from lakes of the BWCA have been characterized elsewhere in
this report (See Table 2 and Figures 7, 8, 9, 10). Based on concentrations
in Saskatchewan lignite coal (Appendix C), the ratios of some other toxic
elements to mercury in coal are 268-430 for fluoride, 21-34 for arsenic,
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0.59-3.0 for cadmium, 2.5-4.0 for selenium. Taking into account the
concentration in precipitator flyash, and assuming that these materials are
emitted in ways similar to mercury, estimated emissions as a ratio to mercury
are 233-399 for fluoride, 14-28 for arsenic, 0.42-2.4 for cadmium and 1.3-3.2
for selenium.
Fluoride and arsenic are likely to be released in quantities much
greater than mercury, and they are of particular concern as regards
long-term, low-level exposures, since many compounds of fluoride and arsenic
act most effecively through slow release by weathering and rapid release in
the gut (O'Brien, 1967). In addition, honeybees and presumably other
pollinators are magnifiers of arsenic and fluoride in"their environs
(Bromenshenk, 1979). According th Debackere (1972) danger to bees from
arsenic poisoning is greatest when: (1) the wind has blown in the same
direction for extended periods, (2) precipitation has been low or infrequent,
(3) in spring when blossoms are few and foraging is intense, and (4) after a
heavy dew, fog or mist. Whereas arsenic poisoning often causes sudden
die-off for a few days, fluoride poisoning usually occurs as death over a
long period (Lillie, 1972; Debackere, 1972). Both fluoride and arsenic
compounds may be stored in food supplies resulting in even longer exposure
periods (Bromenshenk, 1978a) and severe bee kills near industrial sources of
arsenic and fluoride are well documented (Lillie, 1972; Debackere, 1972).
In the later section on aquatics (Section V) concern is expressed that:
(1) mercury has been found to occur in fish at levels in excess of FDA
standards, (2) the sources of mercury are unknown, and (3) emissions from the
Atikokan power plant may aggrevate the levels. Whatever the source, where
there is mercury, there is also likely to be elevated levels of other
injurious trace elements. In view of the high toxicity of arsenic and
fluoride to insects, and because of large quantities of these materials (in
comparison to mercury) are to be emitted by the Atikokan power plant, more
information is needed about the background levels of these substances in the
BWCA and in the insects, vegetation, and soil of the region. With this
background data, an evaluation could be made of the significance of the worst
case concentrations and depositions for enthomological systems.
Summary of effects on Insects—
Although response to thresholds exposures to pollutants have not been
established, a number of insect groups, with strong sensory systems,
particularly saphrophagous and predaceous beetles, social bees (pollinators)
and parasitic wasps, have been shown to be reduced in abundance at very low
concentrations of air pollutants, apparently because of pollutant avoidance
and/or disorientation. Several plant-feeding insect groups increase rapidly
when the activity of parasite or predator control insects is reduced, or the
vigor of host plant species is reduced, both of which have been shown to
occur from gaseous air emissions. If physiological stress is demonstrated by
the host coniferous trees in the BWCA, concurrent alterations in
entomological systems will occur. The available literature suggests that
disturbances in the population dynamics of phytophagous forest insects may
occur at levels below those manifesting visible injury to pines. Direct
injury to the vegetation of the BWCA by exposures to pollutants from the
Atikokan power plant, and from other regional sources if incurred, could be
intensified by insect interactions.
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Impacted Components: Amphibians
In the United States, 50% of the frog and toad species breed in tempor-
ary pools formed annually by accumulated rain and melted snow. One-third of
the species of salamanders in the U.S. that are aquatic before metamorphosing
into terrestrial adults also breed In temporary ponds. Such ponds are more
fragile than lakes or streams because their acidic precipitation input has
little contact with soil buffer systems and is not diluted by mixing with
standing water (Pough, 1976).
A study of embryonic mortality of spotted salamanders (Ambystoma
maculatum) (Pough, 1976) showed less than 1% egg mortality in pools near
neutrality, but more than 60% in low pH (less than 6) ponds, with an abrupt
transition in mortality below pH 6. Furthermore, field results were
reproducible in the laboratory, eliminating effects of both predation and
temperature.
Other studies of anurans include one in which the breeding sites of most
anurans in or near the New Jersey Pine Barrens were limited to grassy ponds
and gravel pits resulting from the normally lower pH (3.6-5.2) of sphagnous
pools (Gosner and Black, 1957). Prescott et al. (1974) postulate that acidi-
fication of anuran breeding sites may be contributing to the recent decline
in British frog populations. Pough (1976) reiterates the earlier observa-
tions of several authors that the significance of any widespread failure of
salamander reproduction will have far-reaching consequences. Salamanders in
temporary ponds are an important predator in dipteran larvae (flies), and an
important energy source for higher trophic levels In an ecosystem (as are
other anurans such as frogs). Pough also notes that these ponds are major
breeding sites for many invertebrates as well. Changes in these ponds could
therefore limit the breeding of numerous species, while allowing pest species
to flourish.
Some changes in the acidity of standing pools in the BWCA may occur due
to acidic snow melt and acidic precipitation. If this change occurs in the
spring, salamander reproduction may be affected.
Impacted Components; Soils
The configuration of granites, slates and argilites, and ultrabasic
bedrocks In the BWCA have determined the local patterns of soils and
landforms. Glacial scouring also has exposed the bedrock on many ridges and
left only a shallow varying cover of fill on the slopes and ravines.
Although locally some soils are deep, there are also large areas of thin
rocky soils derived from sandy glacial deposits. These are among the most
sensitive soils in the Superior National Forest area (Helnselman, 1977).
Distribution of poorly buffered soils—
A number of soil surveys have been carried out on parts of the BWCA, but
one report, "Soil Survey of Kawishlwl Area, Minnesota" (Prettyman, 1978)
covered an area central to the BWCA and included the soil type boundaries on
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printed aerial photographs. Lakes and streams associated with those deep
soil types which do ocur in the BWCA seem less likely to show effects from
acid rainfall within the immediate future.
The report by Prettyman describes 22 soil mapping units in the Kawishiwi
area. These are grouped into roughly 12 soil types, half loosely defined
(e.g., "peat and muck" and "poorly drained loamy soils"). The principal soil
types covering a large acreage are the following:
Barto
Conic
Insula
Mesaba
Quetico Rock Complex
Gravelly coarse sandy loam
Gravelly sandy loam
Gravelly sandy loam
Gravelly sandy loam
Loam
Of these five types, the Mesaba and Conic soils are described as usually
deep soils, 50-130 cm (20-40 inches) to bedrock, while the Barto and Insula
soils are 13-50 cm (5-20 inches) in depth. The Quetico Rock Complex has
soils which range from 10-20 cm (4-8 inches) in depth, and although its
texture is given as "loam," this texture refers to the portion of the soil
that is not coarse fragments and small rocks. Thus, if the capacity of the
soil to withstand additions of hydrogen ions can be measured by a combination
of soil texture and total soil depth (within the specified mineralogy of the
Canadian Shield bedrock types), then we can define a soil grouping within the
Kawishiwi area by combining the three shallow soils, Barto, Insula, and
Quetico, despite the fact that some differences in textute and geological
origin can be recognized.
Chemical data on these shallow soils are quite limited. However,
results of a number of analyses for the Barto soils have been provided by
personal communication from Dr. Perryman. These results indicate the
following cation exchange capacity and X base saturation:
Soil
Series
Horizon
_EiL
C • E. C«
meg/lOOg
av.
Base %
Saturation
Barto B 21 4.8 24.21 18.63
B 22 5.2 21.95 16.58
B 3 5.7 13.78 10.39
The data here contrasts with similar analyses for Mesaba soils. The latter
have 37% base saturation in the parent material horizon (compared with 10X
for Barto soils). The higher base saturation in the upper horizons of Barto
soils (18%) probably reflects the increased organic matter and clay content
and the different type of exchange sites present there.
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Bedrock geology—
Bedrock in the Voyageur's National Park (VNP) and the Boundary Waters
Canoe Area (BWCA) shows a wide variation in rock types. All bedrock found in
the two parks is part of the Precarabrian (>600 m.y.) Canadian Shield, and Is
covered by varying depths of glacial till, outwash, and lacustrine material
deposited during the Wisconsin stage of glaciation. Bedrock in the VNP is
part of a high grade raetamorphic-granite terrain, with gneisses, migmatites,
and granites as major rock types; minor feldspathic quartzite and
metaconglomerate is also present. Preliminary visual estimates of rock types
present in the VNP include 50% (of park area) metagraywacke and biotite
schist, 20% schist-rich migmatite with 25 to 75% paleosome (a migmatite is a
rock which has been raised to temperatures and pressures high enough to cause
partial melting; paleosorae is that portion of rock which does not melt), 15%
granite-rich migmatite with 5 to 25% paleosome, 5% granite, 5% feldspathic
quartzite and metaconglomerate, 3% quartz-feldspar gneiss, and 2%
leucogranite.
The BWCA contains rocks generally representative of a much lower
metamorphic grade terrain than that seen in the VNP. A much wider variety of
rock types is also present in the BWCA than in the VNP. The western portion
of the BWCA, that west of R8W, consists dominantly of rocks of the Vermilion
Massif, a series of granitic intrusives, ranging from diorite to granite in
composition. The migmatites found in the VNP represent the northern contact
zone of the Vermilion Massif with surrounding country rock (Southwick, 1972).
Rocks of the Vermilion Massif, together with granitic intrusives found in the
central portion of the BWCA comprise approximately (visual estimate) 40% of
the total BWCA.
The central portion of the BWCA, designated as occurring between R8W
(and to R11W below Highway 18) and R1W (below the Gunflint Trail), is
dominated by rocks of the Duluth Complex, a series of mafic intrusions
ranging from gabbroic to troctolitic to anorthositic. Rocks of the Duluth
Complex comprise approximately 40% of the BWCA. Also present are several
small granitic intrusives and the Saganaga batholith. These intrusives were
included with the Vermilion Massif for percentage area covered. The
remainder of the central area appears to be underlain by rocks of the Knife
Lake group. These include slate-graywacke, conglomerate, arkose-graywacke,
agglomerate, and andesltic porphyry (McLimans, 1972). Rocks of this type
comprise approximately 12% of the total BWCA.
The eastern portion of the BWCA, that between R2W (above the Gunflint
Trail) and R2E, consists of rocks (grayvacke and argillite) of the Rove
formation which were intruded by a series of diabasic dikes and sills. Rocks
of the two types comprise approximately 8% of the BWCA.
Effects of acidic precipitation on soils—
The absence of a large soil volume for geological weathering greatly
influences the potential for small watersheds to withstand changes in the
rate of addition of hydrogen and sulfate ions from the atmosphere. These
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pollutants are likely to enter the soil environment primarily through
precipitation, stem flow (precipitation draining along the trunks and stems
of vegetation), and throughfall (precipitation filtering through the forest
canopy). Pollutants transported long range will probably enter forest
systems primarily through precipitation. Effluents from local sources may
also contribute to this regional precipitation loading. In addition,
quantities of local pollution will be dry deposited on vegetation. The
fraction of this material which is not biologically assimilated will be
subject to leaching by precipitation and will enter the soil as stem flow or
throughfall. Stem flow and throughfall may be considerably enriched in
pollutants compared to precipitation carrying only the regional atmospheric
load (Abrahatnsen et al., 1977).
The most significant soil mediated effects may result from the fact that
rainfall bearing pollutant loads Initiated as SO2 or N0X has depressed
pH.
Effects of Acid Precipitation on Geochemical Weathering—
Since the pH of water In contact with minerals has a marked effect on
weathering products which result during the breakdown of mineral, changes in
the pH of precipitation also have effects on weathering. Through hydrolysis,
specific cations can be removed from the mineral, allowing a more rapid
change of crystal structure. Jenny (1950) showed H+ replacing Na, K, or Ca
in the crystal structure or bonding with an 0 to form an OH" group. The
H* is very important because its size allows easy penetration into the
mineral, and its high charge to radius ratio has a marked disrupting
influence on the crystal's charge balance (Loughnan, 1969).
Birkeland (1974) determined a series of mobilities for various ions and
found:
Ca+2 > Na+1 > Mg+2 > K+1 > Si+4 > Fe+3 > A
Under normal pR, values for Fe+^ and Al+^ are generally so low as to
be negligible. Situations do occur, however, where the pH is such as to
allow Al to become soluble. In well drained northern soils containing
abundant organic matter a pH of < 4 is possible. AI2O3 ®ay become mobilel+^
and migrate to a less acidic area and be precipitated (Loughnan, 1969).
Where precipitation » evaporation and the soils are very permeable
several pH dependent responses are observed:
1) most of the Na, K, Ca, and Mg is leached.
2) AI2O3 and SiP2 are released.
a. if soils are neutral to alkaline with low Ca and Mg, SiC>2 ®ay
leave in solution as does Na* and K*
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b. If moderately acidic (4.5-6.5) Si02 and Al^O-j are immobile
with the development of clay or a fine-grained mixture of
gibbsite (A1(0H)3) and quartz (SiC^).
c. if highly acidic and rich in humic or other organic material,
AI2O3 and Fe2C>3 may be removed in solution (Moore and
Maynard, 1929). See Figure 14.
The separation of Al and Fe may also be seen in soils which show some
evidence of podzolization, a process where Fe, Al, and organic material is
leached from an eluvial (exit) horizon to an elovial (into) horizon below.
Recent work suggests Fe and Al are carried as part of a metallo-organic
chelating complex, of which fulvic acids are thought to be the common
chelating compounds for a number of soils. Fulvic acids are produced in the.
A or 0 horizons and chelate with Al+^ and Fe+^ ions or with Al and Fe
hydroxy ions. Because these compounds are water soluble they are carried
downward with percolating water. At some depth in soils, the complexes are
destroyed and the metals deposited, but if the percolating water reaches a
soil or bedrock channel, the metals can be carried with the organics to a
stream or lake. Schuylenborgh (1965) suggested the organic portion of the
molecule may be destroyed by microbial action, with release of the cation.
Work by Schnitzer (1971) clarified the fulvic acid-metal complex
transfer. Under constant pH the complexes become more insoluble as metal
ions are added to the fulvic acid solution, 1:1 molar Fe+^-Sl+^~
fulvic acid complexes were completely soluble while 6:1 complexes are water
insoluble. Even 2:1 complexes showed decreasing solubiLity.
Thus transfer of Al and Fe J could be envisioned as follows.
Fulvic acid is formed in the A or 0 horizon and, being completely water
soluble, is transported downward by percolating waters, constantly picking up
Fe+^ and Al+^. As more metallic ions are picked up, the complex
becomes insoluble and can be precipitated in the B horizon if it has not
reached a bedrock surface or stream channel. Schnitzer (1971) showed that up
to 56 g of iron or 27 g of aluminum can be dissolved and kept in a solution
by 670 g of fulvic acid. This is equivalent to 84 mg of iron or 40 mg of
aluminum per g of fulvic acid.
Recent experiments indicate that acid precipitation also can affect the
availability of nitrogen in the soil, decrease soil respiration, and increase
leaching of nutrient ions from the soil (Glass, 1978). Since acid rainfall
adversely affects many other components of the soil-plant-water relationship,
it has not yet been possible to demonstrate unambiguously the nature of
causal relationships in the field. It is possible that acid damage to
shallow, poorly buffered soils might initially be partly offset by the
nutritional benefits gained from nitrogen compounds commonly occurring in the
acid rain. Changes detected to date in soil processes are too small to
affect plant growth, but the studies have been in areas of deeper soils than
in the BWCA. In addition, the acidification of soils is a continuous loss of
essential cations, and eventually the addition of nitrogen is of no advantage
if other nutrients are not available.
77
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O w 4 5 6 7 8
Soi! pH
Figure 14. General exchange relationships between pH and
cations. (From Buckman and Brady, 1969, j_n
Birkeland, 1974).
-------
The H+ additions associated with the projected increase in SO/,
deposition of 0.9-1.4 kg/ha/yr over the apparent presettlement depositon of
4-5 kg/ha/yr (see Section III) appears to be an increase of consequence for
the more poorly buffered soils in this region.
Impacted Components: Nutrient Cycling
Soil mediated effects of acidity on vegetation—
Although the relationships between soil acidity and vegetation growth,
metabolism, and reproduction are receiving increasing attention, many areas
of uncertainty remain. The following discussion will focus on available
information concerning soil mediated effects on: 1) decomposition of organic
matter; 2) effects of cation losses and mobilized toxic elements on growth of
coniferous species; and 3) reproduction of coniferous species.
Any potential reduction in a soil's cation exchange capacity and
essential nutrients, such as discussed in the previous section, will affect
the growth of the trees it supports. In general, forest plants obtain the
nutrients necessary for metabolism and growth primarily from soil.
Atmospheric sources are either indirect (mediated by soil), or secondary in
importance. Therefore, the potential for reduced availability of these
nutrients in forest soils is of concern.
In an unmanaged forest near its climax successional state important
macro- and micronutrients tend to be conserved in the soil-plant system.
Most remain within the cycle of organic production, decomposition, mineral-
ization followed by reincorporation into living material. Leaching losses in
groundwater are minimal (Frink and Voigt, 1977). Nutrient cycles are not
closed, however. Precipitation and nitrogen fixation are important sources
of nutrients to the forest (Orvington, 1962) and additional supplies of
nutrients are made available by weathering of soil particles. These inputs
are countered by some groundwater leaching. Potential effects on plant-soil
interactions may result from impacts on inputs and outputs to nutrient cycles
as well as soil mediated changes in rate within the cycles.
Since Al+ is highly toxic to plants, the mobilization of this element
by additions of H+ to the soil medium can have important detrimental
effects on nutrient utilization and growth. Although A1 toxicity is well
known for crop plants, it is only now being investigated for the common tree
species (McCormick and Steiner, 1979).
Sulfur and nitrogen cycles—
The capacity of a forest to utilize additional sulfur Is often closely
related to the nitrogen cycle. The two nutrients are usually utilized in a
fixed ratio. If nitrogen is abundant the system may be sulfur limited and
have a, considerable capacity to absorb anthropogenic sulfate. Such inputs of
sulfates might well stimulate increased growth. In such cases H2SO4 in
rainfall might not Increase soil acidity or degrade the nutrient pool.
However, mature timber stands are more likely to be nitrogen limited than
79
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sulfur limited. If the capacity of these systems to utilize anthropogenic
sulfur inputs is exceeded, deleterious effects of H2SO4 on the
ecosystem's nutrient pool are possible.
As in the sulfur cycle, overall production and consumption of H* ions
in the nitrogen cycle is balanced. However, loss of soil bases and acidifi-
cation are still possible. When mineralization occurs followed by oxidation
of ammonium ion to nitrate, H* ions formed will replace basic cations.
These basic cations are then subject to leaching in association with nitrate
ions as water passes through the soil profile if conditions allow any buildup
of nitrate ion (e.g., if the system is other than nitrate limited) (Reuss,
1977).
Most natural ecosystems tend to maintain low nitrate levels because
nitrates formed are rapidly taken up by the vegetation. In nitrogen-limited
forests anthropogenic nitrates may stimulate plant growth. This would
prevent increased soil acidity due to processes within the nitrogen cycle and
also accelerate sulfate uptake reducing the potential for acidification due
to processes in the sulfur cycle.
Acid rain is postulated to decrease decomposition rates through adverse
effects on microbial activity (Oden, 1976; Glass, 1978). It appears that
soil pH's below 3.5 are required before effects on decomposition of pine
needles can be seen (Abraharasen et al., 1977). Negative effects of soil
acidification in pine forests on microbial activity have been shown but the
effect on decomposition was unclear (Tamm et al., 1977).
The direct effects of pollutants on ground beetles cited earlier can
have a marked effect on rates within the nutrient cycle. Benefits of
decomposer beetles include the return of nitrogen and inorganic phosphate,
the reduction of surface runoff, burial and mechanical breakdown of organic
materials, decreasing wastage of organic materials, Increased surface storage
of nutrients, reduced loss of nutrients In runoff, and increased infiltration
and storage of moisture in the soil. In addition, these arthropods serve as
food for other Insects and higher animals, aid in the dispersal of soil
microflora and microfauna, and may compete with less desirable (from a human
viewpoint) insects such as hornflies for organic material resources (McQueen,
1975; McKinney and Morley, 1975; Ritcher, 1958), In forest systems as much
as 90Z of the net primary production does not pass through herbivore food
chains but is deposited on the soil as litter and Is acted on by complexes of
animals, fungi, and bacteria (Whittaker, 1970; Crossley, 1970; Kurcheva,
1960; Edwards and Heath, 1963; and others). Examples of resource
partitioning by saprophagous arthropods are numerous, and the role of
saprophagous arthropods in resource partitioning and their use as indicators
of environmental quality has been reviewed by Cornaby (1975, 1978). He
comments that they may have an exploitable role in the deactivation of
noxious materials and decomposition of slowly degrading materials. Also, he
points out that they may be very important as regulators of the rate of
release of nutrients and as detectors of subcritical levels of pollutants In
soils.
80
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Specialists in the field of soil/litter arthropods seem to agree that
these insects are susceptible to harm from pollutants and that they may
affect important functional components of ecosystems. Bases on a theoretical
study, Harte and Levy (1975) and Dudzek et al. (1976) concluded that damage
to decomposers or nutrient pools is a potential source of instability to the
entire ecosystem.
Influence of affected lichen on nitrogen Inputs in forests—The poten-
tial reduction in nitrogen-fixing lichens or in their rate of nitrogen
fixation would have most affect in highly nitrogen-deficient soils, such as
those in the BWCA.
While most lichens contain only green algae, several genera contain only
nitrogen-fixing bluegreen algae or bluegreen algae in addition to their green
algae. Lobaria pulmonaria (on Thuja occidentalis and sandy rocks in northern
Minnesota), many Peltlgera and Nephroma species (on soils, duff and moss),
and Sterocaulon paschale (soil), contain bluegreen and green algae.
Leptogium and Collema species (on soil and rock) contain only bluegreen
algae. The percent coverage of these lichens and their contributions to the
nitrogen regime of the Minnesota forests is not presently known.
Forman and Downden (1977) manipulated laboratory figures (Scott, 1956;
Henriksson and Simu, 1971; Millbank and Kershaw, 1969) for amounts of fixed
nitrogen, and determined that three Peltigera species (_P. canina, P.
rufescens, and J?, praetextata) would fix a total of 0.05-0.6 g N (n? lichen
cover)-* day-* in a spruce-fir forest in Colorado.
Denison et al. (1977) investigated the current status of N2 fixation
in western Washington forests and the potential effects of acid rain on this
process. It is thought that even the low concentrations of SO2 now found
in this area have a deleterious effect on N2 fixation by restricting the
distribution of the ephiphytic N2 fixing lichens, Lobaria pulmonaria. This
species, also present In the BWCA, is found in the Pacific northwest forests
only where the mean annual SO2 concentration is less than 5 g/m^ (0.175
pphm), a figure lower than some background levels already recorded in the
BWCA (see Section III, Table 1). Lobaria pulmonaria fixes 100 times more
nitrogen than does litter and 10,000 times more nitrogen than soil organisms
in these acid forests. The sensitivities of Peltlgera species are not
known.
The rate of fixation of L. pulmonaria is about three times that of JL.
oregana (Denison et al., 1977) which was found to be the major N2 fixer of
old growth and coniferous forests in the Pacific northwest. After exposure
to H2SO4 of pH A or less, JL. oregana fixes less N2.
Kalllo and Varheenmaa (1974) exposed Stereocaulon paschale and Nephroma
articum to the air of Turku. Finland where maximum SO2 values in 1969 were
5.36 pphm SO2 (153 g SOj/m^) with NO3 and sulfates. Nitrogen fixato
decreased to 10-20% of controls. They suggest that the SO2 combined with on to
81
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water on the lichen structures containing the bluegreen algae decreases the
pH of the medium sufficiently to interfere with the metabolism of the
bluegreen algae.
Influence of Affected Trees on Insect Populations
Three authors have reviewed interactions among air pollutants, plants,
and insects (Heagle, 1973; Hay, 1975; Ciesla, 1975). Heagle notes "a common
finding is that trees injured and weakened by pollutants are more likely to
be atacked by insects that normally require weakened trees for successful
reproduction." Ciesla (1975) concludes that photochemical oxidant injury to
ponderosa pines in the San Bernardino Mountains predisposed the trees to bark
beetle attack. The understanding of the physiological mechanisms involved
needs to be determined for other combinations of pollutants, trees, and
insects.
Peat insects do not always proliferate in areas subjected to air pollu-
tion stress. In some instances, declines in pest insect populations have
been observed. The difference in response appears to be a result of
interactions of many variables. One variable seems to be feeding habit.
There are several lines of evidence that stress from pollutants such as SO2
and natural occurrences such as drought may reduce the tannin content of
leaves (Feeney, 1968, oak leaves) and needles which results in more free or
unbound protein foliage. Because of this, the foliage becomes more
nutritious and a "better" diet for foliage-feeding insects (G. Orians,
University of Washington, personal communication).
Our understanding of the effects of air pollutants on tree-insect
relations depends almost entirely on geographical historical surveys of trees
severely damaged by pollutants, insects, or combinations of the two. No
attempts have been made to determine dose-response thresholds. In most
cases, patterns of insect outbreak relative to a pollution source, deviations
from normal outbreak patterns, or the appearance of insects in outbreak
levels which rarely reach epidemic levels have been described (Ciesla, 1975).
Carlson et al. (1974) used stepwise multiple regression analyses and demon-
strated that foliar fluoride content was significantly related to damage
caused by complexes of foliage-feeding Insects. Table 9 attempts to identify
some of the observed insect-tree-pollution interactions.
In an attempt to identify research problems considered critical for an
acceptable understanding of the interactions of air pollution and wood
vegetation, Bromenshenk and Carlson (1975) concluded, "There can be no doubt
that air contaminants are harmful to insect pollinators, although the exact
processes are not understood. Many forest trees and shrubs would not produce
seeds or reproduce themselves without insect pollinators...". Changes in the
population dynamics of forest pest insects may result from a predispositon of
the host to insect attack, as described in the section on pollution-insect-
plant interfaces.
82
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Table 9. Summary of results available on
Host
Insect
Ponderosa pine
Dendroctonus brevicomis
(western pine bark beetle)
Douglas fir
Orgyla pseudotsugata
(Douglas fir tussock moth)
Sitka spruce
(Picea sitchensis)
Western hemlock
(Tsuga
heteorophylla)
Ponderosa pine
(Plnus ponderosa)
Aclerls gloverana (wes tern
blackheaded budworm)
Neodiprion tsugae (hemlock
sawfly)
Ectropis crepuscularia
(saddle-backed looper)
Dendroctonus brevicomis
Scotch pine
Norway spruce
Pines
Bark beetles (several
species)
Bark beetles and other
insects Pissodes spp.
(weevil), Ipstypographus
(engraver beetles)
insect responses to SO2 and other pollutants.*
Pollu- Population
tant Source Response Author
SO.
Smelter
Kellogg,
Idaho
High incidence
Evenden (1923)
SO-
Pulp mill
Missoula,
Montana
Outbreaks not
related to source
Carlson et al.
(1974)
Tunnock et al.
(1974)
SO2 Pulp mill
Ketchikan,
Alaska
High incidence
(correlated with
high foliar SO2)
Laurent and Baker
(1975)
SO2 Smelter
Trail, British
Columbia
Pollutant primary
agent of injury
Keen and Evenden
(1929)
SO-
Industrial
High incidence
Bosener (1969)
SO2 Industrial
(multiple source)
High incidence
Donanbauer (1968)
-------
Table 9. (continued)
Pollu-
Host Insect tant
Oak
Bark beetles
SO-
Ponderosa pine
Lodgepole pine
Pendroctonus spp.
Ips spp.
SO,
00
Scotch pine
Red, Scotch,
Austrian
Tomlcus pinlperda
Melanophila cyanea
(bark beetles)
Rhyaclona bull!ana
SO,
White pine
Plssodes strobl
(white pine weevil)
S02
Pine and spruce
Plssodes spp.
SO*
Pines
Scotch
Acantholyda nemoralls
(web wo rm)
SO,
Pines
Scotch
Exotelia dodecella
SO,
Scotch pine
and others
Paratetranychus unungis
Exotelia dodecella
Acantholyda nemoralls
SO,
Source
Population
Response
Author
Paper mill
Smelter
Trail, British
Columbia
Industrial
High incidence
High incidence
Decreased
incidence
Koch (1935)
Scheffer and
Hedgcock (1955)
Templin (19.62)
High incidence
of Rhyaclonia,
few parasites
Smelter
Sudbury,
Ontario
Less damage
(galls) near
smelter
Linzon
(1958, 1966)
Industrial
Industrial
Industrial
Industrial
High incidence
Decreased
incidence
Unaffected
High incidence
Kudela and
Novakova (1962)
Sierpinski
(1967)
Sierpinski
(1966, 1967)
Sierpinski
(1966, 1971)
-------
Table 9, (continued)
Host
Insect
Ponderosa pine
Dendroctonus brevicomis
(western pine beetle)
Oaks
Biston betularia
(cryptic moth)
Spruce
Adelges abletus
(gall louse)
Norway and
white spruce
Adelgesab1e t us
Oaks and other
deciduous trees
Porthetria dlspar
(gypsy moth) (larvae)
Fir
Bark beetles and weevil
Pollutant Source
Population
Response
Author
Urban
High incidence
photochemical
oxidants
Stark et al.
(1963)
Cobb et al.
(1968a,b)
Miller et al.
(1968)
significant positive association with SO2, non-
significant barely positive association with
saoke
Bishop et al.
(1975)
smoke
Indus trial
High incidence
correlated with
pollution damage
Ranft (1968)
Industrial
High incidence
correlated with
pollution damage
Wentzel (1965)
NaF
Laboratory
oral dose,
0.05 mg
Industrial
Toxic dose
Decreased
incidence; F
thought to be
toxic
Weismann and
Svatarakova
(1973)
Pfeffer (1963)
-------
Table 9. (continued)
Population
Host
Insect
Pollut&nt
Source
Response
Author
Western hemlock
Ectropis crepuscularla
F
Aluminum smelter
High incidence
Silver
(1961)
Lodgepole
(saddle-backed looper)
Choristoneura fumiferana
(spruce budworm)
Kitimat, British
Columbia
Ponderoaa pine
Nuculaspis californica
F
Aluminum smelter
Infestation
Compton
et al.
(black pine leaf scale)
The Dalles,
existed before
(1961)
Oregon
smelter. Dust
and chemical
sprays may have
caused outbreaks.
Edmunds
(1973)
Lodgepole pine
Four species of insects
F
Aluminum smelter
Outbreak confined
Carlson
and
Phenacaspis pinifoliae
Columbia Falls,
to areas where
Dewey
(pine needle scale)
Montana
foliar fluorides
were at least
30 ppm
Carlson
(1974)
et al.
Conifers
33 species
liquid
Accidental spill
High incidence
Wong and Melvi:
(4 orders, 19 families)
hydrocarbon
concentrate
Strachan, Alberta
in dead crowns
(1973)
Ponderosa pine
Nuculaspis californica
F
Smelter, roads,
High incidence
Ciesla
(1975)
dus t
chicken hatchery
area of nonvisi-
in terpretatic"
Spokane, Washing-
ble damage; low
Johnson
(1950)
ton
incidence area
visible F damage
*In most cases, pollutant doses have not been included because they were not measured. In the remaining cases
levels measured were observed after damage by both pollutants and insects, and thus have little relevance to
dose-response thresholds.
-------
Bioaccumulation
Many trace elements ar«? accumulated ;hh1 i:oncent r» ted through food cb-iin
processes. Organisms at higher trophic levels often have higher tissue
concentrations than do their prey, Potentially toxic cniipoonds from the
Atikokan generating facility may become accessible and toxic to various
organisms through this process of biological magnification. The processes by
which this could occur are discussed below.
Trace element availability from soils and plant uptake—
Factors affecting trace element availability include pH, organic natter
content, soil drainage, soil microorganism content, cation exchange capacity
(CEC), and ani on content. Plant root components may also affect nutrient
uptake by releasing organic compounds into the surrounding soil, modifying
the soil environment, and thereby modifying trace element uptake (Tiffin,
1977).
Soils already high in various trace elements may bo more vulnerable to
additional trace element load, although in depleted or nutrient poor soils
various trace elements (e.g., Mo, B, J5n) may improve the nutrient composi-
tion, In recent studies of the environmental impact of trace elements added
to soils as a result of coal combustion (Dvorak et al., 1977; Dvorak ct al.,
1977; Vaughan et at., 1975), predictions of particulate deposition for areas
proximate to the power plant model amounted to less than 10% of the total
endogenous content of trace elements. However, each impacted sitt; must be
examined individually since these models assumed worldwide soil concentra-
tions of trace elements and the variability factor among various soils may be
fls much as several hundred.
The rates and processes involving trace elements are complex and Factors
controlling trace element uptake in plants are not yet very well understood.
Once absorbed into the root system, however, they may be translocated to
shoots which herbivorous animals may consume. Plants as well. as animals vary
In their sensitivity to trace element accumulation, and different plant and
animal organs respond differently with respect to trace clement vtptake.
Obviously, the elements that are taken up In large quantities and stored In
organs preferred by certain wildlife forms constitute a hazard to each
trophic level in which this occurs. Furthermore, the rate of vegetation
turnover from grazing wildlife will modify the rate at which material stored
In shoots Is recycled to the soil.
The bioaccumulatlon potential in various food chains requires much more
study in terrestrial animals. Food habits change seasonally, and seasonal
Movements may take animals out of the path of the area of particulate
fallout, unless winds mix the pollutant path over a large area. This fallout
»ay be exacerbated by secondary pollutant sources from outlying areas, such
as Is expected for the BWCA from the industrial notth as well as areas on
®lther side of the Mississippi River, extending down to the Gulf of Muxlco,
Incremental deposition of trace elements from the Atikokan facility onto
the BWCA is estimated to be comparatively swall. The increase in deposition
Hg predicted in Section lit Is being further InveKtlgated.
H7
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lopact of trace elements on terrestrial vertebrates—
The penetration of trace elements into animal systems largely occurs by
inhalation and ingestion (in food or water). Cutaneous absorption becomes
®ore critical in aquatic vertebrates, especially amphibians (such as
8alamanders and frogs) and fish (which can absorb certain elements through
their gills). Virtually no information is available on the long-term effect
°f low-dosage intake of various trace elements upon wildlife species,
information essential to an understading of the long-term and/or cumulative
®ffects of trace element accumulation.
Dewey's (1972) investigations show that fluorides may build up in
insects of the higher trophic levels, and he expressed concern that fluoride
Accumulated by insects could affect insectivores up the food chain. Gordon
®t al. (1978) are attempting to determine that portion of the diet of deer
®ice which constitutes a fluoride source for mice with excessive fluoride in
their femurs. Their data indicate that insects represent a considerable
Percentage of the diet.
Kovacevic and Danon (1952, 1959) analyzed stomachs of 136 species (34
families) of birds in Yugoslavia and found beetles representing 31 species
(17 families). Numerous other studies both in Europe and the United States
attest to the importance of insects as a food resource to birds. Thiele
(1^77) provides a review of the predators of a specific family of insects-
the Carabids. He lists hedgehogs, shrews, moles, bats, rodents, mice, and
Hrds (including owls and other birds of prey).
The population of timber wolves (Canis lupus) in northern Minnesota is
the largest of the continental 48 states. Because of their size wolves do
appear to be immediately vulnerable to trace element discharge, unless it
Exceeds processing limits of soils and plant systems. Wolves follow their
P^ey, which are declining. In time wolves will perhaps take more moose or
leaver or other mammals as food items. As herbivores, these animals will
constitute the interface between trace elements in plants and in wolves.
The eastern pine marten (Martes americana amerlcana) is a fur-bearing
Carnivore of considerable economic value in past years. Since the principal
^®SulaT food item for the marten is the small mammal (such as the red backed
v°le ClethrionomyB gapperi in the BWCA), the greatest impact of trace
elements upon marten populations is likely to be exerted through small mammal
Populations. Voles nay be impacted by selected roots with high storage
|*vels of trace elements or through water supply (this may be obtained in
*©od).
The bald eagle (Haliaeetua leucocephalua) and osprey (Patvdion hallaetus
Sfrdinensis) rely upon fish for food items although other vertebrates appear
be eaten as well. Ospreys have been known to take several species of
••all mammals, other birds, reptiles, and frogs, as well as occasional
Crustaceans, sea snails, and beetles. The bald eagle diet in northcentral
Minnesota consists of 90% fish, 8* birds, and 2X mammals and invertebrates
(tunstan and Harper, 1975). Obviously, trace element effects on raptors are
®*«t considered in view of their fish diet. Scientists have determined that
ll levels in fish are already high in some lakes in northeastern Minnesota
Sections V and VI).
83
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Many other changes in major or key ecosystem processes, other than those
discussed, probably occur. However, due to lack of information on the effect
of pollutants on insect populations, food chains, and on the composition of
the ecosystems of the BWCA, it is premature to predict the potential economic
and/or ecological damage.
There are also too many unknowns to make any reliable statements con-
cerning the effects of the At.ikokan facility on trace element, fluxes through
food chains. Lakes already high in Hg may experience additional loads if
acid rain causes the release of existing sediment bound Hg. Top carnivores
and fish consumers, such as raptors and aquatic mammals, are likely to
accumulate additional Hg, but the pace of bioaccumulation may vary consider-
ably within the BWCA. The low rates of trace element deposition within the
BWCA from Atikokan imply negligible short-term effects, hut possible
long-term consequences.
APPLICATION OF RESPONSE INFORMATION TO THE BOUNDARY WATERS CANOE AREA
The Impacts of air pollutants on terrestrial ecosystems and their compo-
nents can be grouped into four major categories: 1) acute-direct effects on
ecosystem components; 2) acute-indirect effects on components and complete
ecosystems; 3) chronic-direct effects on ecosystem components; and 4)
chronic-indirect effects on components and ecosystems. Each of these types
of Impacts may have significance to the continued functioning of a given
ecosystem. To date the majority of data collected relate only to the first
category of impacts, acute-direct. However, in some cases acute-indirect and
chronic effects may be more important to the overall ecosystem than the
acute-direct effects because the latter relate to factors such as forest
productivity, community diversity, and ecosystem stability.
The severe limitations on data applicable to acute-indirect and chronic
effects indicate a limit in the "state of the art" rather than an absence of
impacts. These limitations have several causes: lack of long-term baseline
studies; lack of instruments which can measure very low levels of air pollu-
tants; and, perhaps most important, limitations In techniques which can first
measure the subtle changes occurring in ecosystems due to low levels of
pollution and then relate these changes to those levels of pollution.
Although data on direct and indirect effects from chronic-low level air
pollution are limited, basic ecological principles indicate the potential for
significant effects on the terrestrial ecosystems. These effects must be
extrapolated from studies of short-term effects and the limits and the
sensitivity of such extrapolations must be taken into account. Through their
influence on the generation of oxidants, acid particulates, and acid precipi-
tation, the indirect effects of emissions contribute to regional loading and
are likely to be the most serious effects for the Quetico-BWCA area.
In air pollution impact studies a few characteristics hold fairly
consistent regardless of the differences between two or more physical and
biological areas:
1) Coniferous and lichen species within a polluted area are almost
invariable the first plants to manifest symptoms of injury, usually
because of toxic gases; and
89
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2) Plant species growing along ridge tops or on any moderately elevated
area will accumulate greater effects from the. phytotoxic gases than
the same species growing in the valleys, or riparian areas.
The following statements of projected significance for the BWCA are a
synthesis of the research and literature previously cited in the terrestrial
section and, when possible, anticipate explicit responses from applicable
findings,
Significance for Pines in the BWCA
The most sensitive native higher plant species for which there is infor-
mation is the eastern white pine, a prominent canopy tree. This species is
known to have been lost entirely from large areas subjected to frequent
exposures of high SO2 levels. However, it can persist for many years with
moderate levels of damage each year. In this situation growth is slowed, the
trees are leas resistant to insect outbreak, and longevity is reduced.
Red pine and jack pine, the other two most dominant pine species in the
BWCA may be less sensitive to SO2 than eastern white pine. As such, at
increased SO2 levels, they would be expected to exhibit a lesser degree of
both visible and nonvisible effects than eastern white pine.
In general, most acid rain damage to plant tissues will occur over a
long period of time (many growing seasons or more) and, therefore, will be
difficult to evaluate. The earliest manifestation of acid damage in conifer
needle tissues will probably be the cessation of meristem activity in the
basal areas, causing the needles to be dwarfed and, in later stages, to abort
and be cast prematurely from the branch (Northern Cheyenne Tribe, 1976).
Although slightly acidic rain in an area may not cause dwarfing during early
•needle development, damage of the basal tissues may occur one to three years
later.
If the ambient concentrations of total solid particulates, SO2 , O3,
and trace elements attributable to Atikokan are no higher than projected, it
is unlikely that short term, visible damage will occur. However, several
recent studies suggest that growth and reproductive rates may be affected at
lower ambient pollution levels than those necessary to cause visible injury,
levels commensurate with SO2 background levels already being recorded in
the BWCA and adjacent Ontario (see Section III, Table 1). The usual time for
planning and developing the forest cover of a state forest, private property,
or recreational area is seldom less than 50 to 100 years. More often it Is
as much as 200 years. White pine ordinarily live 350 to 400 years. Plant
scientists and recreational area managers have, therefore, had to take a
long-term view of their resource and look at its development over tens of
decades. Over these periods, even small effects on the growth rates or life
span of the dominant species can have major consequences fof the regional
vegetation.
Significance for Lichens In the BWCA
Direct, visible effects on lichens are not anticipated at the projected
ambient pollution levels attributable to the Atikokan facility. The
90
-------
thresholds for more subtle effects are unknown. As more pollution sources
begin operation near the BWCA a complex interaction of potential lichen
species substitutions, changes in nitrogen balances, and other effects may
begin. Since the nitrogen-fixing species (Lobaria [hilmonar ia, many Peltlgera
spp., '
Nephroma, Collema, Leptogium, and Stereocaalon paschalc) are present in the
Minnesota coniferous forests, detrimental effects on these components of the
forest ecosystem could lead to a significant loss to the nitrogen regime.
Although the ultimate consequences are not expected to be great, their degree
cannot be reliably predicted at this time.
Slgnifleanee for Insects in the flWCA
The threshold for air pollution impacts on plant/insect relationships
are unknown. Effects at the concentrations for the BWCA have not heen
documented. If effects occur they will probably he manifested as:
1) Injury to pollination systems dependent upon or benefited by insect
pollination (primarily by native pollinators). Compiled lists of
plants benefited by or dependent upon insect pollination for seed
production, or utilized by insects as food resources are lengthy;
2) Changes in the pest insect populations of conifer and hardwood
forests;
3) Alteration in litter/soil subsystems resulting from harm to
saprophagous and predacious insects;
A) Mobilization of zootoxins through insect food chains to small
mammals and birds; and
5) Changes in key ecosystem processes or components which cannot be
identified in advance due to lack of information on the functioning
of insect populations in the BWCA.
The Potential for the Bioaccumulation of Toxic Materials in the BWCA
The high density of forest vegetation in the BWCA potentially could
absorb and render unavailable much of the toxic material deposited from
aerial fallout. Trace elements could be expected to increase slightly in the
trees themselves (needles, seeds, bark, etc.) from direct dry deposition or
from secondary storage. Under the impact of acid rain the forest soils would
have lower cation exchange and organic matter content. Hence, trace elements
impact would be amplified by making the elements more available (due to low
pil), and accumulating in small herbivores and fish.
Several fish species (e.g., bullhead, suckers, pike) form much of the
diet of osprey and eagle. Experimental work is needed to determine element
sensitivity and rates of bioaccumulation in these top carnivores of the
terrestrial system. Scientists have determined that mercury levels in fish
are already high in some lakes of northeastern Minnesota. Input from the
Atikokan plant itself may held shift the balance further toward decreased
fish reproduction and/or harmful levels of ingestion by raptors (see Section
91
-------
The BWCA also lies within the upper Mississippi flyway for migrating
birds. Incremental pollution damage to the BWCA ecosystem may harm not only
indigenous biota but also affect migrants which pass through the area to
feed. Many waterfowl are sediment filter-feeders, taking both invertebrates
and algae. These detrital materials may contain moderate levels of trace
elements in low pH systems, injurious to various birds.
Significance for Nutrient Cycles in the BWCA
Generalizations about the potential effects of acid rain on soils and
soil-plant interactions must be interpreted carefully because the BWCA is a
mosaic of diverse environments. Soils in the BWCA are already acid (pH 4 to
pH 5.7 at various depths). In many areas there is a 5-10 cm (2-4 inch) humus
layer with pH about 4, low cation exchange capacity (10-30 meq/100 g), and
high buffering capacity. However, for even sensitive soils, further
acidification by air pollutants whenever they are 15 cm (6 inches) or more in
depth will be a slow process. Probably considerable time will elapse before
growth effects can be recognized. Sulfur and nitrogen entering the system in
precipitation could be a small nutrient source for the system.
Effects will be first noticeable on shallow soils or bare bedrock
systems. U.S. Forest Service studies have indicated that because thin, rocky
soils are widespread,the BWCA lands are the least productive and most
sensitive in the Superior National Forest (Heinselman, 1977). Even small
additions of acidity to these systems could have relatively short-term,
irreversible effects.
Lake and Watershed Chemistry in Relation to BWCA Soils
Using the over-printed, six photo maps provided in the Kawishiwi Area
Soil Report described earlier (Prettyman, 1978), mapping of an area central
to the BWCA was carried out on all portions in which the potentially
sensitive soil types (shallow coarse soils overylying igneous bedrock)
predominate. This mapping is summarized on an index sheet, Figure 15. An
example of the pattern among the soils and the distribution of lakes is shown
in a copy of mapsheet number one, Figure 16.
Potentially sensitive headwater lakes—
Within the areas of shallow soils it is possible to recognize additional
criteria to define individual lakes most likely to show responses in lake
chemistry due to changes in rainfall chemistry. These criteria would include
the following:
1. No stream or spring inlets (i.e., headwater lakes);
2. Hard rock basins permitting no leakage except to the lake;
3. Shallow, coarse, or negligible soils throughout the watershed;
4. The absence of any significant adjacent wetland or peat; and
5. The watershed in which the adjacent land area is of about the same
or less than twice the area of the lake.
92
-------
'r^Sy^sS *«»•'# 10
tlMo:
iN**t I 0
CANADA
aii««k
t/on
F)0 R S ST
AVr.lt
INDEX TO MAP SH££TS
KAWISHIWI AHKA. MlNNKSOTA
PAHTS OKUKK ANI» i "i x >K 4 n[ s J H >
Figure 15. Outline map of the areas of sensitive soils (shaded) within the
Kawishiwi Area Soils Map.
-------
*" r.->v- fp
' ¦ \ M-' y / j ¦. ?/(/
esti:k
LA hi
<5&V*iU
^Lii'^*f5sV*¦> f- j1;
¦£•¦. ;4/er tr-yi''
g
yfcffs^igg
~VC1/
KM fSLA h
'-€-±
i
XitT**- ¦¦*'' ¦ 4P' WW-YSLr
SPitfrM rh. Awm wife
Figure 16. Sample sheet of the soil map of the Kawishiwi Area showing sensitive
soil areas (shaded), and the location cf six potentially sensitive
lakes (see arrows).
-------
During the coarse of the mapping Kawishiwi area soils into a "sensitive"
group, a series of 16 small lakes were identified within the mapping area,
each apparently meeting roost of the above criteria. This assessment has been
based on the experience of the author in studies of the soils and vegetation
in the Kawishiwi and BVICA areas, combined with interpretation of the soil
mapping and evidence of drainage channels and wetlands from the aerial photo-
graphs. Field inspection of these and 200-300 other small lakes in this area
may reveal that some of the 16 lakes identified as "susceptible" may fail to
meet the above criteria fully, and that other small sensitive lakes have been
missed. However, these 16 lakes appear to be among the most likely
candidates for chemical and biological change if such changes are to be found
in the BWCA. It is urgent that observations of chemical characteristics be
made on these lakes at the earliest possible date. The lake locations and
characteristics are summarized in Table 10.
95
-------
Table 10. Potentially sensitive headwater lakes.*
Lake
No.
Sheet
No. t
Lake Name
Location
Approximate
Lake Size
(acres)
Approximate
Watershed
(acres)
Comnen cs
1
1
tLake of the Clouds
Center S.H.I
40
SO
studied since 1967
2
1
^Rivalry Lake
i
T
jL
mile N. irl
10
15
—
3
1
Eabla Lake
1
mile N.E. #2
20
40
some peat
4
1
Clam Lake
2
miles S.E. ill
35
15
—
5
1
Unnamed
2
miles N.E. #4
S
10
—
6
1
Unnamed
1
4
mile S. Araober Lake
15
15
easterly of 2 lake
7
3
Spigot Lake
1
4
irvile E. Sucker Lake
25
40
—
8
4
Bedford Lake
1
2
mile S. Skoda Lake
40
60
some peat
9
5
Unnamed
1
mile N.W. Sema L.?ke
15
15
—
10
7
Unnamed
1
2
mile E, Newfound Lake
35
60
—
li
8
Suing Lake
T
mile S. Ashigan Lake
20
30
—
12
10
Wisp Lake
1
mile E. Duck Lake
20
30
long, narrov
13
13
Hood Lake
Center, W. side of sheet
35
50
some peat
14
15
^Pat Lake
1
2
mile E. Bug Lake
15
15
outs tanding
15
15
Alcove Lake
t
2
mile W. Wine Lake
40
80
—
16
19
Ella Lake
1
2
mile E. Grace Lake
80
100
some peat
*As determined by the criteria listed on page IV-38.
tin Prettyman 1978.
tOutstanding candidate lakes for intensive study; appear to meet all criteria.
-------
SECTION V
IMPACTS OF ACIDIFICATION ON AQUATIC ECOSYSTEMS OF THE BOUNDARY WATERS
CANOE AREA (BWCA) AND VOYAGEURS NATIONAL PARK. (VNP)
INTRODUCTION
Deposition of acid from the atmosphere, with consequent severe effects
upon aquatic ecosystems, is by now a well known phenomenon (Dochlnger and
Seliga, 1976). Both sulfuric and nitric acids are involved, and hydroelorlc
acid may be a much more local source (Corham, 1976). Many other toxins are
deposited In addition to acids, including heavy metals, and a variety of
hydrocarbons, as well as nutrients such as nitrogen, potassium, calcium, and
probably phosphorus (Gorham, 1976; 1978; Lunde et al., 1976; Henriksen and
Wright, 1976).
These pollutants may exert a wide range of effects upon organisms and
ecosystems, particularly oligotrophia (or nutrient-poor) ecosystems. There
is a strong likelihood of both synergistic and antagonistic interactions.
These have been little investigated, although It is known that metal toxicity
may increase with increasing acidity. The acid may also have indirect effect
upon the toxicity of other ecosystem components (e.g., soil-derived metals,
such as aluminum and several trace metals) and upon the availability of
nutrients through weathering and biological activity (e.g., N, P, K, Ca,
etc.) (Glass, 1977).
The impact of increased acid loading and nutrients is determined by the
vulnerability of aquatic ecosystems. Geologic, physical and chemical charac-
teristics of the aquatic environment are important variables in determining
the level of vulnerability. Blotic effects range from acute toxicity and
impairment or failure of reproduction within species, to lowered production
and less biotic diversity in communities which in turn may lead to a decrease
in ecosystem stability.
This section is a discussion of the impact of acidification on aquatic
ecosystems of temperate North America and Europe and the application of these
findings to the BWCA-VNP receptors. Comprehensive data on all aquatic organ-
isms present In the BWCA-VNP are lacking. However, the information discussed
can be related to the BWCA-VNP by utilizing data collected in similar
adjacent areas. The Minnesota Copper-Nickel Study Area (MCNSA) (a 5,515 sq.
km. area of northeastern Minnesota south of the BWCA, including Ely, Minne-
sota) and the Experimental Lakes Area (ELA) of Ontario are located adjacent
to and 150 km from, respectively, the BWCA-VNP. Because of the similar
terrestrial and geological character of the areas, species present in both of
these study areas can be considered to be generally representative of the
species present in the BWCA-VNP. Therefore, lists of aquatic organisms found
in the MCNSA are included in Appendix D (Minn, Environ. Quality Board, 1978).
97
-------
Specific information about the aquatic organisms present in the ELA can be
found in Vol. 28(2) of the Journal of the Fisheries Research Board of Canada,
February 1971. Information on the chemistry and fishes of 109 ELA lakes can
be found in Beamish et al. (1976).
CHARACTERISTICS OF LAKES VULNERABLE TO ACIDIFICATION
Lakes in eastern Canada and the northeastern United States are generally
very sensitive to acidification. Calcareous bedrock, overburden, and soil
are scarce in these regions, so that surface waters are poorly buffered
(Figure 17). Lakes of this type in Scandinavia have been severely damaged by
anthropogenic SO2 sources several hundred kilometers away (Overrein, 1977).
Similar sources exist within a few hundred kilometers of lakes in the
southern Precambrian Shield areas of North America, and it is likely that the
most vulnerable waters are already af£e.eted. It therefore seems important to
identify physical and chemical characteristics of these most sensitive waters
so that they can be closely examined and monitored for symptoms of increasing
acidity or other changes.
Physical Factors in the Characterization of Vulnerable Lakes
For any given geological substrate, lakes with the smallest ratio of
drainage area to lake volume may have the poorest buffering due to the small
area of substrate available for neutralization by weathering. Lakes at
higher elevations are often affected first because more piecipitation usually
falls in such areas, resulting in greater deposition. Such lakes also are
likely to be headwaters, or at least high in the order of lakes in a chain,
and likely to have less calcareous material in their drainages. Greater
volume (depth) allows greater capacity for diluting acid inputs. Few exact
studies of the efficiency of acidification exist, due to the difficulty of
quantifying acid inputs and outputs in affected areas.
The location of Atikokan Is of special significance since a large
portion of the area, within a 100 km radius, ts in the Rainy Lake Watershed
(Figure 18). The rivers within the 38,100 sq. km watershed flow toward the
United States/Canadian border lakes. Streams and lakes east of the
Laurentian Divide flow toward Lake Superior. Lakes to the west of the Divide
drain into the western edge of Rainy Lake where the water flows at an annual
average rate of 280,000 1/s through the dain at International Falls, Minnesota
before it starts a northwest course through Lake of the Woods, Lake Winnipeg,
and into Hudson Bay.
The entire Quetico Provincial Park and Voyageurs National Park are
within the Rainy Lake Basin. Most of the EWCA is included, except for .the
eastern section, which is part of the Lake Superior watershed (Figure 19 and
20). Of a park total of 88,800 hectares, several thousand of the 34,700
hectares of recreational water in the VHP were created by dams, leaving
54,080 hectares of land. VNP has 31 named lakes and 422 unnamed swampy ponds
larger than two hectares. The BWCA has a surface area of 439,100 hectares
patterned by 1,493 lakes greater than 2 hectares, and over 480 km of major
fishing and boating rivers in addition to numerous streams and creeks.
98
-------
Figure 17. Regions of North America containing lakes that
are sensitive to acidification by acid
precipitation, based on bedrock geology.
Calcareous overburden will modify this picture
somewhat. (From Galloway and Cowling, 1977.)
99
-------
/
\%*4
Mr
0 * r j ft , c
f><
t
, (('rC, A?>s
UO^v^tV?^
-.- /y V^t^A xr
Vs yyv^Tt
¦ :\'l V "iA /\,» iv W_ . M i
LE5fNp
UftiJe-3 Stoles/Ccrodo
Bcrazr Lc«et
...
Ra»ny Lo*e watershed
Sosjn Bx/XJory
....
V/oierihei Boundary ..
....
Mopf Rtvtr Flow
.... -—"
Direction cf flow
....
Loi»e Svpencr Watershed..
>-V/5%on Bey Wotershed
Lou of The Woods
watershed
.... >—
h>Mm,
/
>i&Y&,-*t.
7r" y
\'^' !~\'- ~ ''-'ITS;
u«&$k^
W 5
•• •* . *»*¦""; Ay"
^ V'9^u v r®\ /
vfc^TOi^J# V"cK T*
v.X s^) ^)r^-
\/Y -/ ^
WATERSHED AREA
RAINY LAKE BASIN
\ Z- M IN N E S O T A |" h'-/.(
- \Jy
-------
PROFILE OF WATERS ALONG THE INTERNATIONAL BOUNDARY
lake Superior to rainy lake resevoir
1400_
>100
oj
112 00
liiOO
LAKE
OF THE
0 A S I N
SUPERIOR
BASIN
WOODS
1000
Pig f on
Foils
iSOO «
(-9C0
,800
700
ROO
! ¦ • i i , i _j i i i 1 1 i_
174 1 68 162 156 I SO 144 liB 132 126 120 |I4 iOB 102 95
I Approiimol* Vertically Projected 0.Honct from Lake SuPeriar
6 00
66 SO
I Mile i)
54
36
42
Figure 19. Profile of waters along the international boundary, Lake Superior to Rainy Lake Reservoir.
(From Minnesota Pollution Control Agency, 1969.)
-------
gzzmsK
imertoJ LOur*
t*TO
RAWY L*Xl
JULY 1978
-------
Cheroical Charact e r i g t i c s and Responses of Vulnerable Lake_s
Alkalinity, or the capacity of a solution to neutralize acid, is the
parameter which reflects the sensitivity of lake water to pH change resulting
from strong acid input.
Any ion that enters into chemical reaction with strong acid, signifi-
cantly above the endpoint pH, can contribute to titrated alkalinity.
1) Alkalinity = [Cations] - [Anions] .
Alkalinity » 2[Ca ] + 2(Mg ] + [Na 1 + [K ] - 2[SO^"] - [NO^ ] - [CI ].
For the most part, alkalinity is produced by anions or molecular species of
weak acids which are not fully dissociated above a ptl of 4 . 5. In most
natural water, the alkalinity is practically all produced by dissolved
carbonate and bicarbonate ions. A definition expressing alkalinity in terms
of the "changeable" ions present is given in equation (2) (Deffeyes, 1965):
2) Alkalinity - [HO)"1] + ZlCO^2] + (OH-1) + X - (H+) ,
with [x] giving the sum of the equivalents of noncarbonate weak acid species
(e.g., organic acids, silicate, ammonia) where applicable. In humic lakes of
low total alkalinity, organic acid anions (carboxylates) may comprise the
major fraction of the alkalinity (Beck et al., 1974). Equilibrium pH levels
in these brown water lakes will be lower than in purely bicarbonate buffered
waters because of the lower pKa's (4—5) of the carboxylic acids, compared to
carbonic acid (pKa 6.3). This also means that for comparable levels of total
alkalinity, a given level of strong acid input will produce a lower pH in
humic water than in pure bicarbonate water. The charge in hydrogen ion
concentration per unit change in alkalinity (A [K+]/AAlkal.tnity) is thus
determined by the total concentrations and species of weak acid present.
It is important to note that under any system of reporting titrated
alkalinity now in use the effects of all the anions which may react when a
strong acid is added are lumped together and reported as an equivalent amount
or a single substance or in terms of postulated ions (e.g., CaCO-} mg/l or
HCO3"1 eq/D.
Irrespective of differences in the content of weak acids and their
influence on relative pH change, the distinguishing feature of all lakes
potentially sensitive to acidification is low total alkalinity. For lakes
situtated in regions of hard bedrock resistant to weathering, low alkalinity
is imparted by low concentrations of base-forming cations. Throughout large
areas of the Precambrian Shield, carbonates are undetectably low in lake
watersheds. In other areas, calcareous drift deposited by receding glaciers,
lacustrine clays (for example, in the Lake Agassiz basin), or marine
sediments help to buffer lakes, rendering thera less vulnerable to acidifi-
cation. The most vulnerable lakes, in granite (noncaleareous) regions have
conductivities as low as 10 to 20pmhos cm-^, and alkalinities of 10 to 20
yeq/1. Some BWCA-VNP lakes are as low as this in neutralizing capacity and many
approch these levels. Figure 21 gives the percentage distribution of 85
BWCA-VNP lakes versus the water alkalinity observed in November 1978 (Glass et
al., 1979, see also Appendix D).
103
-------
Alkalinity Distribution of 85 BWCA-VNP Lakes (Fall, 1978)
25
CP
CL
t/J
0-5
0-
100
5-10 10-I5 15-20 20-25 25*20 30*35 35*40 40*45 4 5*50 50"55 55*60 60"65 65"70 70*75 75*80 GO*85
100- 200" 300- 400" 500' 600* 700" 6O0" 90 O* 1000- 1100" 1200* 1300" 1400" 1500" ISOO*
200 300 400 500 600 700 eOO 900 1000 1100 1200 BOO 1400 1500 !6C0 1730
65-90
1700-
1800
1200-
. |> .. ,, . _^-asCaC03, mg/l (upper scale)
Alkalinity (total)
-------
Atmospheric ActdIf1ction of BWCA-VNP Lakes
Several lines of evidence suggest that some lakes in the BWCA are at or
near the threshold of serious acidification, severe enough to initiate
species depletion and lowered productivity;
1) The mean annual pH of precipitation in several areas on the Laurentian
Shield of eastern North America — both adjacent to and far from the BWCA —
Is often at or below A.8 (Table 11). This is the minimum mean annual pH level(Cl-^
observed to be without major biotic consequences (so far) in southern
Scandinavia (Wright and Gjessing, 1976). The pH of precipitation in these
Laurentian Shield areas seems likely to have declined since the mid-1950's,
when it may well have been above 5.6 (cf. Likens, 1976), Nowadays it is
frequently observed to fall (in separate precipitation events) below pH 4.5.
A mean annual precipitation pH of less than 4.5 (only twice the hydrogen ion
concentratln at pH 4.8) is associated with severe damage to the biota both in
southern Scandinavia (Wright and Gjessing, 1976) and in the Adirondack
Mountains of New York (Schofield, 1976a) and has led lake pH in many
instances to fall well below 5 from initial levels well above 6.
2) Many lakes in the BWCA-VNP are somewhat acid (pH 6.1-6.3) and low in
alkalinity (<100 p equiv/1), as shown in Figure 22. They also exhibit Calcite
Saturation Indices (CSI) (Conroy, et al. 1974; Kramer, 1976) high enough to
suggest great susceptibility to damage by acid loading (Table 12). Moreover,
these are not the most acid lakes in the BWCA. Wright (1974) has reported one
lake with a mean pH of 5.7, and it is likely that there are others of the 2,000
plus lakes with even lower values.
3) Sulfate loadings to northern Minnesota from historic background and
distant urban/industrial sources now amount to an average of about 10
kg/ha-yr ranging from 4-14 kg/ha-yr, see Table 1. Such loadings appear to
have reached a level that is extremely critical for lake acidification.
Dickson (1978) has shown that, in southern Sweden, sulfate loadings of as
little as 5 kg/ha-yr appear to lower the pH of some lakes below their initial
levels of about 6.5 (sensitive lakes with low neutralization capacity in
their surroundings) or 7.0 (less sensitive lakes with greater neutralization
capacity). In the more sensitive lakes, as sulfate loading enters the range
10-20 kg/ha-yr, pH declines very sharply from above 6 down nearly to 5
(Figure 23). Further sulfate loading produces a much slower decline in lake
pH, about 60 kg/ha-yr being required to lower it to slightly above 4.
Any additional sulfate loading from the Atikokan power plant, e.g.,
0.9-1.4 kg/ha-yr to some BWCA lakes, and 3.4-5.1 kg/ha-yr to some Quetico
lakes, is likely to tip the balance further toward the point of severe
acidification effects upon aquatic ecosystems, of the kind observed in
southern Scandinavia, the La Cloche Mountains of N.W. Ontario, and the
Adirondack Mountains of New York. There, however, the most severe
acidification — to levels of pH near 4 — has required loadings of about 60
kg/ha-yr. It may be noted that the strong acid loadings observed in southern
Scandinavia, the La Cloche Mountains and the Adirondacks have resulted in
very rapid declines of lake pH, The rate of acidification has ranged between
-0.02 and -0.06 pH units/yr in southern Scandinavia, where original lake pH
values ranged from 6.2 to 7.3, and between -0.05 and -0.10 units/yr in
105
-------
Table 11. The pH of precipitation on the Laurentian Shield of eastern North America
Location
Precipitation
Period
pH
Mean Minimum
Reference
BWCA, Minn.
Rain and
snow,
39 samples
1972
5.6
5.0
Wright, 1974
BWCA, Minn.
Snow, 36
sites
1977-78
4.8
4.0
Glass et al., 1979
Hovland, Minn.
Rain, vol-weighted
Mar-Nov 78
4.8
4.0
Gorham, 1979
Ely, Minn.
Rain
1971-L975
5.7
3.7
EPA, 1975
Ely, Minn.
Snow
1971-1975
5.2
4.2
EPA, 1975
Rural N.E. Minn.
Snow
Mar 7 5
4.9
4.5
Gorham, 1978
Rural N.E. Minn.
Snow
Dec 75
5.2
4.8
Gorliam, 1978
ELA, W. Ontario
Rain and
snow,
vol-weighted
Jan-Dec 7 5
5.0
4.3
Schindler, 1978
ELA, W. Ontario
Rain and
snow,
vol-weighted
Jan-Dec 76
4.9
4.2
Schindler, 1978
ELA, W. Ontario
Rain and
snow,
vol-weighted
Jan-Dec 7 7
4.7
3.9
Schindler, 1978
ELA, W. Ontario
Rain and
snow,
vol-weighted
Jan-Dec 78
4.9
3.8
Schindler, 1978
LaCloche Mts, Ont.
Precip.
Early 70's
4.3-4.4
Beamish, 1976
Sudbury, Ont.
Precip.
Early 70's
4,5
Beamish, 1976
Nova Scotia
Rain and
snow,
vol-weighted
1977-78
4.8
3.9
Gorham, 1979
-------
o
-J
8.0
1500
1000
500
7.5
7.0
pH 6.5
6.0
5.5
J — 1
•
..... .,
. NOT SUSCEPTIBLE
• •
• •
• t « •
• •
-
m
•
SUSCEPTIBLE
(KRAMER
•
• • •
* 1976)
• lyit
POTENTIALLY •
-
•
• •O*
BWCA-VNP LAKES
SUSCEPTIBLE
t • c»
(*101-709, FALL '78)
•• mm
• 9-
-
m •
-
4>
• •
•
-
¦
-
FISHERY:
MEAN DANGER
1 1
pH THRESHOLD
i
8.0
1500
7.5
1000
7.0
6.5 pH
6.0
5.5
500
5.0
ALKALINITY (peq/\)
Figure 22. The relationship between pH and alkalinity in 85 BVCA-VNP
lakes.
-------
Table 12. Calcite saturation indices (CSI) for 85
BWCA.-VNP lakes, calculated according to Conroy et al.,
(1974) and Kramer (1976)
Percentage
of lakes
est
index
CSI
classification
10.6
<1
Terrain is most stable and
not susceptible to change
18.8
1-2
Possibly susceptible to change
34.1
2-3
Probably susceptible to change
29 .4
3-4
Susceptible to change
7.1
4-5
Highly susceptible to change
CSI " p(Ca^+) + p(Alk) - p(H+) + pk, where p(x) -
-logj^Q (x)t pk = +2, (Ca^+) is given as mol/1 and
(Alk) and (H+) are given as eq/l.
108
-------
1QD
Q.
oa
(2)
30 60 90
Sulfate Loading to Lake Water (Kg/ha/yr)
(1) Lakes with extremely sensitive surroundings.
(2) Lakes with slightly less sensitive surroundings.
Figure 23. Data from lakes in southern Sweden shewing the relationship
between acid loading and pH change for very sensitive and
somewhat less sensitive surroundings. (From Dickson, 1978.)
-------
eastern North America, where the original lake pH ranged fro,:; 3.0 to 6.7
(Wright and Gjessing, 1976). Such rapid declines are not expected in the
BWCA unless acid loadings increase considerably above present levels.
However, slower declines in lake pH may be occurring even with present
loadings, and cannot be viewed with equanimity.
An experimental example illustrates how sensitive lakes with low
alkalinity are. In 1976 and 1977 , a total of 1.14 eq/1 of H^~ were added to
an ELA lake (f?223) surface as H2SO4 (Schindler et al., 1979). This
reduced the bicarbonate content of the lake from an original value of 86
eql-* to 10 eql-^. Since the original pH of precipitation was
A.95, this acidification regime is equivalent to changing the pH of
precipitation to 4.2 for a period of 10 years (D. Schindler, personal
communication). Lake 223 is not one of the most vulnerable lakes in the
region. Its bicarbonate value is slightly above the mean. Other lakes in
the area have alkalinities as low as 8% of that of Lake 223. Such lakes may
be seriously affected by precipitation which has been acidified to even a few
tenths of a pH unit more acid than normal. Figure 24 demonstrates the effect
of acid addition on the pH of water from selected BWCA-VNP lakes influenced
by the alkalinity and CSI of the water. Note the large differences in acid
required to reach pH 5, a value critical for most fish reproduction.
In addition to the shifts in major ion composition that constitute
acidification, significant changes in certain trace metals and organic
fractions of acidified lakes have been observed. Increased concentrations of
aluminum, manganese, zinc, copper, and nickel have been reported in lake
water from acidified regions (Dickson, 1975; Schofield, 197 6b; Wright and
Gjessing, 1976; Dillion et al., 1977). These increased metal concentrations
may be due in part to increased atmospheric loading (Ni, Cu) associated with
specific pollutant sources, and to increased leaching from soils or lake
sediment (Al, Mn, Zn). Schofield (1977) determined 0.25 - 1.0 ppra aluminum
leached from soil by snowmelt water at pH 4.4 - 5.9 to be a major factor in
causing severe gill damage and mortality among larval brook trout, a fish
species found in the BWCA as well as the Adirondacks. Mobility of these
metals is also enhanced at low pH levels. Increased transparency reported in
some acidified lakes (Dickson, 1975; Schofield, 1976a) may be due to
precipitation of humic and fulvic acids at low pH and high aluminum
concentrations (Dickson, 1977).
Marked temporal and spatial variations in strong acid and metal
concentrations have been observed in lakes and streams as a result of snow
melt (Johannessen et al., 1975; Schofield, 1977; Siegel, 1979). During the
initial phase of melting, acids stored in the snow pack are leached out by
water percolating down through the snow pack. Strong acids are thus concen-
trated in the early fractions of meltwater leaving the snow pack. Passage of
this acid meltwater through ice covered lakes, at low levels of discharge,
results in the temporary formation of a shallow (usually <1 meter) , but
highly acid layer of surface water under the ice. This phenomenon has even
been observed in moderately well buffered lakes In the Adirondack region
(Schofield, 1976). Sensitivity of lakes to this short term, but intense,
form of acldifiction is thus governed more by the physical process of acid
concentration from the snow pack and transport of meltwater under ice cover,
110
-------
Acid titration of selected BWCA-Vf\P lakes
(4023
Alkalinity os ppm CoCOx
Loxe number
CoJclie Saturation Index
0.0
2500 3000 3500
Microequivolents [H+] added per liter of lake water
4000
5000
13.2
(600)
2 2
200
(504)
1.8
AfkolinHy 09 ppm C0CO3
Lake number
Colette Saturation indrt
500
1000 1500 2000 2500 3000 5500 4000
Microequivolents tH'] added per liter of lake water
4500
5000
Figure 24. Acid titration of selected BWCA-VNP lakes.
Ill
-------
than by alkalinity of the lake water alone. The degree and time of meltwater
In contact with soils in the drainage system will also significantly affect
acid and metal levels in the runoff. Table 13 shows snow-melt water quality
from BWCA-VNP from samples collected in March 1978. First melt water
contains concentrations of acids 2-3 times the mean values for the samples.
Measured snow loadings for 1977-1978 are given in Appendix D.
The concentrations of most trace elements in the surface waters of the
BWCA-VNP are generally low (Poldoski and Glass, 1975; Glass et al., 1979).
(See also Appendix D for recent measurements on 85 BWCA-VNP lakes.) Because
of the low concentrations of most components, increased concentrations will
result in greater percentages of toxic metals present in biologically active
forms (Glass, 1977; Poldoski and Glass, 1975).
Another concern related to acidification in northern Minnesota is the
recent (1976) discovery of elevated mercury, Hg, residues in fish in several
BWCA lakes (Minnesota DNR, 1978). Mean Hg levels in fish from two large
lakes, Basswood and Sand Point, exceeded the 1978 FDA action level of 0.5
pptn. Figure 25 and Tables 8-10 in Appendix D provide data on the mercury
levels in fish from lakes from the BWCA-VNP region. These fish are from
lakes that previously would not have been considered endangered by
acidification. No specific source for the mercury contamination has yet been
identified. Two hypothesized sources are fallout from regional atmospheric
concentrations of fossil fuel combustion products, and mobilization of
mercury from bedrock geological sources, or both.
Regardless of its source, the Hg problem in the BWCA is likely to be
aggravated in several ways by increased combustion product deposition. The
direct addition of more mercury is one such way (see Dispersion and Deposi-
tion Modeling report). Lower pH may increase the mobility of mercury from
sediments and rocks. Studying the relation of acidification to mercury
accumulation in fish in Sweden, Jernelov (1976) and others (Brouzes et al.,
1977) have found that the formation of methylmercury, the form of mercury
most rapidly accumulated in tissues, is enhanced at pH levels below 6. In
addition, fish are thought to take up methylmercury more rapidly at low pH.
The net effect of reduced pH on accumulation is well illustrated by Figure 26
in which Hg residues in brook trout from Adirondack lakes are compared (C.
Schofield, personal communication). Trout from acid drainage lakes had mean
tissue concentrations that were three times higher than those of trout from
limed, seepage and bog lakes.
IMPACTS UPON AQUATIC COMMUNITIES
The most obvious biological effects of acidification occur to fish
populations. Less conspicuous, but no less severe damage also occurs to
other organisms ranging from frogs to microbes. In fact, acidification
affects organisms at all trophic levels in freshwaters. The number of
species is reduced, biomass is altered, and major processes are interrupted.
Although the literature concerning effects of acid mine drainage (AMD)
on freshwater ecosystems is extensive, it is not directly applicable to the
acid precipitation problem. Often the uncontaminated waters of coal mining
areas have higher alkalinity and hardness than the very soft waters acidified
112
-------
Table 13. Snow-melt water enrichment of dissolved components; concentrations and
percent of total mass found in melted snow as a function of % melted (average of
three sites in BWCA-VNP).
Concentration and % total mass of components found in melted snow
% snow [H+] TnhTH [SO4] [NO3) [Cf] IF")
melt pH % mg/1 % rag/1 % mg/1 Z mg/1 X mg/1 %
10
4.26
(18)
0.15
(14)
1.8
(21)
2.3
(18)
0.15
(14)
0.02
(14)
20
4.25
(19)
0.19
(18)
1.9
(23)
2.4
(19)
0.16
(15)
0.02
(14)
30
4.30
(17)
0.16
(15)
1.7
(21)
2.3
(17)
0.15
(14)
0.02
(14)
40
4 .46
(ID
0.11
(11)
1.0
(12)
1.5
(11)
0.11
(10)
0.02
(14)
50
4.63
(7)
0.08
(8)
0.5
(6)
1.0
(8)
0.11
(10)
0.01
(7)
60
4.71
(6)
0.08
(8)
0.4
(4)
0.8
(7)
0.08
(7)
0.01
(7)
70
4.76
(5)
0.07
(7)
0.3
(4)
0.8
(6)
0.09
(8)
0.01
(7)
80
4.80
(6)
0.07
(7)
0.3
(4)
0.6
(5)
0.08
(7)
0.01
(7)
90
4.82
(5)
0.07
(7)
0.3
(3)
0.7
(5)
0.09
(8)
0.01
(7)
100
4.86
(5)
0.07
(7)
0.2
(2)
0.6
(5)
0.07
(6)
0.01
(7)
113
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Walleye, 1977, Northern Minnesota
-left column, less than 15 inches
-right column, 15 inches and over
A
A
A
O O Oc.owood L.
~ A Burntiide L.
H a • '"Oil L.
bo a a Kobetogama L.
O BO n ® Gun(lin) L,
n ua (¦ 8 Nainokon L.
D Dfl (1A O Sond Point L
0 OH n A a Psllcan L.
CO qq sjni Q Vermillion L.
QC3 oa |)S a Trout L.
ao ®a kh « p;kt R-
OQ oa KQ A While Iron L.
oq oa a a
DO A3 OO A a
~I* I»rt wo A ~
Oa «a «o 4i e A
08 OA • » At! OA A
a a *a ao aw ao n a
6A OA «A uw AO (I A
AA »A «o ©» so ® Q
M *a oo «u »o u a a
AA • • oo ao o o a
AA AA OO BO O u ° „ 0
AA AO OO OA OO A O O O O O 0
.M oo OO OO OO O o O A o a o 9 n o o o
^" I~r 1—r r~> t—?——r"i r~i r~' n n 1—I r t i 1—i 1—i i r r v— i r r ~r i r"~' ' , 1 _I , , 1 "T.
02- 0 5- 04- OS- 06- 07- 00- Oy- 10- II- 12- 1.3- H- 15- IG- 1.7- 18- 19" 2 0" 1 I- 2 2" 2
o 29 O S9 049 0 59 069 079 0 89 0 S9 V09 119 129 159 I AO 159 169 179 189 199 2 09 in 2 to 2.
Mercury Concentration
>»
o
c
0)
Z3
cr
03
0
a
Q
2
A
A
0
A
Q
A
Q
A
*
A
•
A
5
A
o
a
•
a
»
a
«o
u
OA
a
a
OA
a
AA
a
AA
0
AO
0
B
AU
a
oo
ACI
0
§
00
SB
1%
OO
m
a
oa
oo
a
OO
00
a
oa
OQ
u
OA
HQ
•a
• A
UiJ
MCJ
«A
an
•a
• A
ua
•a
• A
KQ
• 0
#A
oa
• A
AA
OQ
• X
OA
n
• A
OA
AA
OA
0
AA
OA
OA
B
OA
OA
OO
A
OA
OA
OO
1
1 1
^ i
1 »
00-
0.1-
02-
0 3-
0.0*
019
0.29
0 39
Northern Pike, 1977, Northern Minnesota
-left column, less than 21 inches
-right column, 21 inches and over
O Bosswood L.
ABurrvliide L.
• fall l_.
A Kabctogamo l_
O Gunfllnl L.
Q Nomakon L.
o Sond Point L.
Q Pelican L
O Vermillion L.
Q Trout L.
A While Iron L,
O Colby L.
• Greenwood L.
O Gobbro L.
O
« 1 9
O A 9
• OB
oo oo a
T— T—t t I " I I T 1 I 1 I I—I ' I" I " |—I 1—T —I——'—)—t—1 1
04- 0 5- OS" 0.7- 0.8" 09" 1.0- I.I" 12- 15- 14- | ]•
0.49 0 59 069 0.79 0 8# 0 99 109 1.19 t.7.9 1.19 1.49 |.J#
Mercury Concentration
Figure 25. The relationship between size and mercury concentrations
of Walleye and Northern Pike taken from selected BWCA-
VNP area lakes.
114
-------
1.00
Acid drainage lakes
• •
o
oo
o
o
o°"°'
eft °
Cl
Ql
>> 0.10
0.05
Limed, seepage & bog lakes
20
40
30
Length (cm)
Figure 26. Regressions of iog mercury concentration against total length
for brook trout sampled from acid drainage lakes and limed,
seepage, and bog lakes in the Adironacks. (^, adjusted
mean mercury concentrations from the two classes, for
convariance analysis.) (After Schofield, 1978.)
115
-------
by acid precipitation. Acid mine drainage water usually has n heavy load of
iron and other heavy metals, and frequently depresses the oxygen
concentration of receiving waters. High turbidity and the presence of
chemical floe are also common and greatly alter aquatic habitats. These
factors make it very difficult to extrapolate observations frora AMD
situations to those in the Lnurentian Shield, for example. The evidence used
In this report is taken primarily from literature pertaining to acid
precipitation, although some reference to AMD literature is made where
relevant.
The variety of species of both plants and invertebrate animals occurring
in fresh waters is enormous, and the kinds of organisms present differ
markedly from one locale to another even though water chemistry may be
similar. It Is at best difficult and probably futile to try to interpret
ecosystem damage at lower trophic levels by comparing lists of species. On
the other hand, changes In major processes such as primary and secondary
production, and decomposition can be broadly described and compared. Effects
of stress on the major functional guilds may be compared from place to place.
Finally, a few groups of organisms seem to be remarkably insensitive to
strong mineral acidity and are common to many acid environments, while some
other groups are clearly intolerant of pH levels below 6.0 to 5.5.
Effects on Microblota
The production of fish and other animal life in a lake is ultimately
dependent upon the availability of organic food resources, primarily plant
materials. The sources of organic materials may be divided into two major
categories: autochthonous, originating by primary production in the lake,
and allochthonous, transported into the lake by inflowing water, airborne
litter, or dissolved in rain. The relative importance of each of these
sources varies greatly from lake to lake. One principal route for both
autochthonous and allochthonous organic matter into the trophic system of a
lake is via the detritus (organic particulate matter).
Bacterial consumption and mineralization of organic matter, both parti-
culate (POM) and dissolved (DOM), allows a cycling of carbon which dominates
the structure and the functioning of the system and provides what Wetzel
(1975) has called a fundamental stability to the system. In the deep, open
water of the pelagic zone, where phytoplankton production normally provides a
substantial portion of the nonrefractory organic matter, bacteria rapidly
assimilate dissolved labile organic substances (DOM) derived from photo-
synthesis and convert them into bacterial blomass (Hellebust, 1974; Fogg,
1977), Only a small portion of the DOM refractory material is likely to
survive longer than 24 hours (Saunders and Storch, 1971). The bacterial
raineralization rate of POM appears to be rather slow, a few percent per day
(Wiebe and Smith, 1977; Cole and Likens, 1979), so that this new biomass is
actually available to other trophic levels. Not only do the bacteria
conserve the energy stored in labile DOM, which otherwise would be lost from
the system, but they also convert (at a slower rate) some of the refractory
^OM into a usable form. Fungal and bacterial communities render other POM
into forms which are useful for detritivores (Boling et al., 1975). The
significance of these activities to ecosystem energetics can be better
appreciated when one considers that on the order of 90% of the organic carbon
116
-------
in the water column is DOM and that detrital POM is many times larger than
the total living carbon biomass.
There are other sources of detritus in the pelagic zone. In some lakes,
particularly smaller and/or shallow lakes, macrophytes and benthic algae are
important sources of autochthonous organic carbon. Material from these
plants may contribute significantly to detritus in the pelagic zone. In
deciduous forest lakes, leaf litter falling or blown onto the surface has
been found to be 200-500 g dry leaves per meter of wooded shore line (Jordan
and Likens, 1975; Gasith and Hasler, 1976).. This forest litter plus that
which is added by stream inputs, contribute to both DOM (after leaching) and
POM.
Water column detritus generated from all of these sources has three
Possible fates. It can be transformed biologically, it can sink to the
sediments where it accumulates and/or is transformed biologically, or it is
lost from the system by outflow. In the first two cases, microbial activity
plays a key role in removing detritus.
The inhibition of microbial decomposition can have profound effects
throughout an aquatic ecosystem. Detritus removal, conservation of energy,
nutrient recycling, primary production, detritivore production and thus
production at higher trophic levels, can all be affected by changes in
Microbial activity.
Several investigations have indicated that microbial decomposition is
Sreatly inhibited in waters affected by acid precipitation. An abnormal
accumulation of coarse organic detritus has been observed on the bottoms of
six Swedish lakes where the pH decreased by 1.4 to 1.7 units in the past
three to four decades (Grahn et al., 1974). Bacterial activity apparently
decreased, while in some of the lakes the sediment surfaces over large areas
were made up of dense felts of fungus hyphae. In one of the lakes, CardsJon,
85% of the bottom in the 0-2 m depth zone was covered with a thick felt of
fungus. Lime treatment caused a rapid decomposition of the organic litter as
Veil as great reductions of the fungal felt (Andersson et al 1974),
indicating that an inhibition of bacterial activities had taken place at low
PH. Similar neutralizations of acidified lakes in Canada resulted in a
•ignifleant increase in aerobic heterotrophic bacteria in the water column
(Schneider et al., 1975). Results from field and laboratory experiments with
"Utterbags in Norway (Hendrey et al., 1976) also indicate reduced weight loss
leaves in acidic waters. Dissolved organic carbon (DOC) in the inflowing
*ater was found to contribute ca. 50% of allochthonous inputs and 8% of all
°*8anic carbon in Mirror Lake, while fine particulate organic carbon (FPOC)
negligible (Jordan and Likens, 1975). The extent to which this DOC input
converted to bacterial biomass or otherwise enters into the energetics of
* lake is not known. Observations of abnormal accumulations of organic
^bris have also been made in AMD waters in South Africa (Harrison, 1958) and
Vest Virginia (J. DeCosta, personal communication).
In laboratory experiments, Bick and Drews (1973) found that the decompo-
sition rate of peptone by microbiota decreased with pH and that the oxidation
** anmonia ceased below PH 5. Bacterial cell counts and the species number
of ciliates also decreased. Numerous other studies indicate that the
117
-------
microbial decomposition of organic materials is markedly reduced at pH levels
commonly encountered in lakes affected by acid precipitation (Hendrcy et al.,
1976).
Accumulations of organic debris and extensive mats of fungus hyphae, as
observed in the Swedish lakes (Grahn et al., 1974); both seal off the mineral
sediments from interactions with- the overlying water and hold organically
bound nutrients which would otherwise have become available if normal
decomposition had occurred. The reduction in nutrient availability can be
expected to have a negative feedback effect on the organisms, further
ihibiting their activities. The reduction of nutrient supplies to the water
column from the sediments, because of the physical covering and from reduced
®ineralization of organic materials in the water itself, will lead to reduced
Phytoplankton productivity. These ideas have been formulated into the
hypothesis of "self-accelerating oligotrophication" by Grahn et al. (1974).
Qualitative observations support this hypothesis, but quantitative evaluation
is lacking.
Reduction of microdecomposer activities may have a direct effect upon
the invertebrates. Although certain benthic invertebrates appear to feed
directly on the allochthonous detritus material, it seems that "conditioned"
(colonized by microorganisms) material is preferred, and that the nutritional
Value of the detritus is highly increased by conditioning (Boling et al.,
1975), Bacteria may also be a food source to be removed by the filtering
apparatus of organisms such as the Calanoida. An inhibition of the micro-
biota or a reduction in microbial decomposition processes would therefore
have a direct impact on the lakes' animal communities.
Because of the low temperature and lack of nutrients in the BWCA-VNP
haters for in-lake energy fixation, the terrestrial production of energy in
the form of plant detritus is very important for supplying energy to the food
chain as well as transferring nutrients to the aquatic production system.
the decomposition and transformation of the detritus is reduced or
eliminated by acidification, then less energy is available for ultimate fish
Production. Since the waters of the BWCA-VNP are generally infertile and
#uPport relatively low concentrations of fish, the resultant decrease in the
fish crops would be expected to decrease to levels even lower than those at
the present time.
Jffec ts on Benthic Plants
In waters affected by acid precipitation major changes occur within
Want communities. Most of the available data are qualitative and descrip-
tive although some experimentation has been done. Intact lake sediment cores
*hich include the rooted macrophyte Lobelia dortmanna were incubated at four
w* levels (4.0, 4.5, 5.5, 6.0) at Tovdal in southern Norway.^ The growth and
^oductivity of the plant (O2 production) were reduced by 75X at, pH 4
spared to the control (pH 4.3 - 5.5) and the period of flowering was
^•layed 10 days at the low pH (Laake, 1976).
In five lakes of the Swedish west coast, a region severely affected by
*tld precipitation, Grahn (1975) reports that in the past three to five
4«cades the macrophyte communities dominated by Sphagnum have expanded. In
118
-------
the sheltered and shaded locality Lake Orvattnet, in the 0-2 m depth zone,
the bottom area covered by Sphagnum increased from 8% to 63% between 1967 and
1974. In the 4-6 m depth zone, the increase was from 4% to 30%. At the same
time, pH in Orvattnet decreased 0.8 units to^4.8, Similar growths of
Sphagnum occur in other Swedish lakes, in Norwegian lakes and in AMD water as
well (Harrison, 1958; Harrison and Agnew, 1962; Hagstrom, 1977). At the pH
of these acid waters, essentially all of the available inorganic carbon is in
the form of CO2 or H2OO3. Conditions are more favorable for Sphagnum,
an acidophile which is not able to utilize HCO3 as do many other
aquatic plants. The moss appears to simply outgrow the flowering plants
under acid condition?!.
In developing their hypothesis on oligotrophies i.on, Grahn et nl. ( 1974)
have stressed two biologically important consequences of this Sphagnum
expansion. First, Sphagnum lias an ion-exchange capacity which results in tho
withdrawal of base ions such as Ca from solution, thus reducing their avail-
ability to other organisms. Secondly, dense growths of Sphagnum form a
distinct biotype which is unsuitable for many members of the bottom fauna.
Under some acid conditions, unusual accumulations of both epiphytic and
*pilithic algae may occur. In the Swedish lakes, C.rahn et al. (1974) report
that Mougeotia and Batrachospermurn become important components of the
benthos. In Lake Oggevatn (pll 4.6), a clear-water lake in southern Norway,
not only is Sphagnum beginning to replace Lobelia dortmanna and Isoetes
lacustris. but these macrophytcs have been observed to he festooned with
filamentous algae.
Heavy growths of filamentous algae and mosses occur not only in
atidified lakes, but have also been reported in streams in Norway affected by
acidification. In experiments in artificial stream channels using water and
the naturally seeded algae from an acidified brook (pH 4.3 - 5.5), increasing
the acidity to pH 4 by addition of sulfuric acid led to an increased accumu-
lation of algae compared to an unmodified control (Hendroy, 1976). The flora
was dominated by Binuclearia tatrana, Mougeotia sp., Eunotia lnnarls,
^abellaria flocculosa and Dinobryon sp., each accounting for at least 20% of
the flora at one time or another. The rate of radioactive carbon uptake per
Unit of chlorophyll in the channels, measured on two occasions, was found to
he lower in the acid channel by ^30%, suggesting greater algal blomass
^cumulation at low pH despite lower productivity.
Several factors may contribute to these unusual accumulations of certain
algae. The intolerance of various species to low pH or consequent chemical
Changes (Moss, 1973) will allow just a few algal species to utilize the
Nutrients available in these predominantly oligotrophic waters. Many species
°f invertebrates are absent at low pH and removal of algae by grazing is
Probably diminished. Microbial decomposition is inhibited, as was previously
noted, also reducing the removal of algal mass.
In the BWCA-VNP, reduction in growth and production of benthic plants
will probably not be important since the lakes most likely to be acidified
the same lakes which have few, if any, aquatic plants. If indeed cho two
^«re to co-exist, then decreases in benthic plants could reduce juvenile fish
*®cruitment for those species which utilize macrophyte beds for nursery
**«a$. The btomass of benthic plants usually enters the detrital food chain
reductions in this energy source could reduce fish standing crops. If
119
-------
filamentous algae were to be established during acidification, the visual
aesthetics of pristine lake shorelines could be reduced.
Effects on Phytoplankton
There is no consistency among various investigations as to which taxa
are likely to be dominant under conditions of acidification. The Pyrrophyta
raay be more common (e.g. , species of Perldinium and Gymnodiniuni) than others
in lakes near pH 4.0, With decreasing pH in the range 6.0 to 4.0, many
species of the Chlorophyta are eliminated, although a few tolerant forms are
found in the acid range. In their survey of 155 Swedish West Coast lakes,
Aimer et al. (1974) found that blucgreen algae became less important with
decreasing pH, but Kwiatkowski and Roff (1976) found the opposite to be true
in lakes of the Sudbury, Ontario, region.
There are, however, conspicuous decreases in phytoplankton species
number, species diversity, biomass and production per unit volume (mg/m^)
Mith decreasing pH. Lake clarity and the compensation depth increase with
lake acidification, so that primary production (mg/m^), although lower in
acid than non-acid lakes, is not as severely depressed as is production per
unit volume (Johnson et al., 1970; Aimer et al., 1974; Hendrey and Wright,
*976; Kwiatkowski and Roff, 1976). The low phytoplankton biomass (<1 mg/l)
has been correlated to the concentration of available phosphorus, which
Senerally decreases with lower lake pH (Aimer et al., 1974). Low avail-
®bility of inorganic carbon has also been suggested as a factor limiting
Primary production in acidic lakes (King, 1970; Johnson et al., 1970).
In the BWCA-VNP, if production is decreased, the energy available for
food chain transfer is reduced and an effect on total fish production would
k® expected. If the grazing zooplankton are reduced before the phytoplankton
at"e affected, the fish population will respond to the zooplankton while the
algal populations will not be utilized, possibly removing nutrients from the
Production system without being recycled.
jffects on Invertebrates
Zooplankton analyzed from net samples collected form 84 lakes in Sweden
®howed that acidification caused the elimination of many species and led to
®i®plification of zooplankton communities (Aimer et al., 1974). Crustacean
*°°plankton were sampled in 57 lakes during a Norwegian lake survey in 1974
^Hendrey and Wright, 1976), and the number of species observed was found to
^crease with pH. The distributions and associations of crustacean zooplank-
in 47 lakes of a region of Ontario affected by acid precipitation were
•trongly related to pH and to the number of fish species present in the
lakes. However, fish and zooplankton were each correlated with the same
li®nological variables, especially pH (Sprules, 1975a, 1975b), Zooplankton
^°®munities become less complex with fewer species present as acidity
^creases. Food supply, feeding habits and grazing of zooplankton will
Probably be altered following acidification, as a consequence of decreased
®iomass and species composition of planktonic algae and bacteria. Parsons
V1968) reports that in streams continuously polluted by AMD, the number of
120
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zooplankton species was small compared to the numbers of individuals, and to
less polluted conditions downstream.
Surveys at many sites receiving acid precipitation in Norway, Sweden and
North America (Andersson et al., 1974; Conroy et al., 1975; Hendrey and
Wright, 1976, Borgstr^m, et al., 1976) have shown that waters affected by
acid precipitation have fewer species of benthic invertebrates than
localities which are less acid. In 832 lakes, J. fikland (1969) found no
snails at pH values below 5.2; snails were rare in the pll range 5.2 - 5.8 and
occurred less frequently in the pH range 5.8 - 6.6 than in more neutral or
alkaline waters. The araphlpod Gammarus lacustris, an important element in
the diet of trout in Norwegian lakes where it occurs, is not found in lakes
with pH less than 6.0 (K. A. 011and, 1969). Experimental investigations
have shown that the adults of this species cannot tolerate 24-48 hours of
exposure to pH 5.0 (Borgstr<5m and Hendrey, 1976).
In the River Duddon in England, pH is the overriding factor which
Prevents permanent colonization by a number of species of benthic inverte-
brates, primarily herbivores, of the upper acidified reaches of the river
(Sutcliffe and Carrick, 1973). In the more acid tributaries (pH <5.7) the
fauna consisted of an impoverished Plecopteran community. Ephemeroptera,
Trlchoptera, Ancylus (Gastropoda) and Gammarus (Amphlpoda) were absent. The
Epiphytic algal flora w.as reduced (in contrast to increases noted In Norway),
ar>d litter decomposition was retarded. The food supply of the herbivores was
apparently decreased, and this may have played a role in the simplification
°f the benthic fauna. Quantitative data concerning the effects of low pH on
the benthic fauna are also available for some acid Norwegian lakes (Hendrey
al., 1976), where notably low standing crops have been observed.
Many studies of invertebrate communities in streams receiving AMD have
been conducted. Comparisons are usually made between affected and unaffected
Zones or tributaries, and experimental acidification has been performed
(Herricks and Cairns, 1974). The numbers of species, species diversity, and
Homass are usually greatly reduced. Generally, In AMD waters Chironomidae
(®idges) and Sialls (alderfly) are the most tolerant macro-invertebrates,
^•he order Trichoptera has more tolerant species than does Ephemeroptera (May
*lies) (Harrison, 1958; Harrison and Agnew, 1962; Dinsmore, 1968; Parsons,
1977; Dills and Rogers, 1974; Wojcik and Butler, 1977).
This order of tolerance is essentially the same as is seen in waters
®cldified by acid precipitation. However, the Hemiptera, Notonectldae (back-
dimmer), Corixidae (waterboatman), and Gerrldae (water strlder) are often
Abundant in acidified soft waters at pH as low as 4.0. This may, in part, be
to lack of fish predation, as well as their partial adaptation to
terrestrial living.
Benthic plant communities in lakes may be greatly altered as a conse-
quence of lake or stream acidification (as discussed above). Under these
Conditions, benthic invertebrate populations may be affected by starvation,
*v*tuation or extinction due to the loss of preferred habitat. Chironomids
Oliver, 1971) and other benthic invertebrates (Cummins, 1973), present in
*a-ny of the poorly buffered northeastern lakes, have diverse feeding habits
121
-------
and habitats. These invertebratevS, in many situations, will be affected by
altered decomposition cycles and variations in available foods caused by
increased acidification.
The tolerance of aquatic invertebrates to low pH varies over their life
cycles, and the emergence of adult insects seems to be a period particularly
sensitive to lower pH levels. Bell (1972) and Moss (1973), in similar
studies with Trichoptera and Ephemeroptera, found emergence patterns to be
affected at pH levels which were higher than the 30 day survival limits.
Many species of aquatic insects emerge early in the spring, even through
cracks in the ice and snow cover. Due to the contamination of spring
»eltwaters by atmospheric pollutants, including heavy metals (Hagen and
Langeland, 1973; Hultberg, 1975; Johannessen et al., 1975; Henriksen and
Wright, 1976) the early emergers must, in many cases, be exposed to the least
desirable water conditions.
Changes in invertebrate communities will influence other components of
the food chains. Benthic invertebrates assist with the essential function of
removing dead organic material. In litterbag experiments, the effects of
invertebrates on leaf decomposition were much more evident at higher pH than
at low pH (Hendry et al., 1976). A reduction of grazing by benthic
invertebrates may also contribute to the accumulation of attached algae in
acidified lakes and streams.
A short reach of Norris Brook, a tributary to Hubbard Brook in New
Hampshire, was acidified to pH 4 in the spring-summer of 1977 to evaluate the
Effects of acidification on a stream ecosystem. Excessive accumulations of
®lgae occurred, bacterial biomass and heterotrophic activity per unit of
Organic matter were reduced, and both invertebrate diversity and biomass
decreased (Hall et al., 1979).
In unstressed lake ecosystems there tends to be a continuous emergence
°* different insect species available to predators from spring to autumn. In
«cid-stressed ecosystems the variety of prey is reduced and periods may be
®xPected to occur in which the amount of prey available to fish, waterfowl,
80ngbirds and other predators is diminished.
In relation to the BWCA-VNP, these organisms, both zooplankton and
b*nthos, are the algal grazers and detritivores which transfer energy from
vegetable to animal biomass. Factors adversely affecting these organisms
"ill adversely affect the transfer of energy through the food chains and
Ultimately affect the fish product.
£l£gct on Vertebrates-Fish
„ The loss of fish species with increasing acidity has been well
-Jocwented in Scandinavia and in North Aaerica, In Sweden Hultberg and
Benson (1970) collected all of the Ubh in two lakes acidified by acid
Precipitation At a oH of 4.8 one lake contained a single yellow perch and
:>«!!X S..i *«•««rInei2S
^ lost It. former perch population. Jen.en and Snekvlk (1972) recorded the
nation of «!»!! and ?rout population, fro. «any river, and Lkea tn
-------
southern Norway. In Canada, Beamish and Harvey (1972) described Che loss of
8 species of fish from a lake as the pH fell from 6.8 to 4.4. Beamish et al.
(1975) recorded the loss of fish from another lake undergoing acidification,
and Harvey ( 197 5) reviewed the effects of acidification on the. fish popula-
tions in a group of 68 lakes.
The tolerance of fishes to low pH has been studied under laboratory
conditions for half a century. This effort has been directed at recording
the death of fishes in relation to hydrogen ion concent r.i t ion and duration of
exposure (Douderoff and Katz, 1950; Lloyd and .Jordan, 1964; EIFAC, 1968;
Anon., 1973). The results of these works are statements of criteria or pH
tolerance of various fish species.
In the natural environment, fishes may be exposed to adverse levels of
acidity throughout their life. Thus p!l will act to control their survival or
well-being at the most critical stage or time in their life-historv.
Accumulation of acidic snow gives rise to spring run-off of acid water which
coincides with the time of spawning of many fish species. Headwater lakes
undergo more rapid acidification than those lower in the watershed, as a
function of flushing rate and buffering capacity of the drainage basin.
Thus, fish tend to be lost first from headwater lakes. Ironically, these are
the lakes least visited by anglers, biologists, etc., and our experience
heretofore has been that these lakes have not received sufficient attention.
One of the effects commonly observed in populations of acid-stressed
fishes is a failure to reproduce successfully, often manifest by an absence
of young fish (Hultberg and Stenson, 1970; Beamish and Harvey, 1972; Ryan and
Harvey, 1977). The cause, of this reproductive failure varies from species to
species. In one population of white suckers, females failed to reach
spawning condition (Beamish and Harvey, 1972); physiologiclly these fish did
not show the normal pattern in protein bound serum calcium (Beamish et al.,
1975). Lockhart and Lutz (1977) have also proposed disruption of Ca
metabolism as an explanation for losses of fish from acid lakes. Another
mechanism of action is the disruption of spawning behavior (Conroy et al.,
1974).
In some species spawning has been successful, but there was no
recruitment into year class 0, indicating lesser tolerance of eggs and larvae
(Milbrink and Johansson, 1975) or greater susceptibility of young or small
fish such as Robinson et al. (1976) found for brook trout. Two recent
laboratory chronic exposures (Metiendez, L976; Smith, 1 977) have demonstrated
a reduction in the hatchabi .1 i ty of brook trout embryos at pH 6.0 and lower.
Both investigators commented that continual exposure to pH values below 6.5
would be highly detrimental. Trojnnr (1977a) observed reduced hatchability
of brook trout embryos at pH 5.6. In a study of lake trout in the acidified
lake number 223 of the ELA, L. Kennedy (personal communication) found that
lower egg weights and drastically reduced survival were produced at a pH of
5.75, The absence of a previous year class Indicated that similar effects
might have occurred when the pH was 6.0. These data indicate that the lake
trout, one of the most sought after and valuable fish species in the
®WCA-VNP, is highly vulnerable to the effects of acidification.
-------
Other species found in the BWCA area are also very sensitive to low pH.
Mount (1973) observed a reduction in embryo production and hatchability at pH
5.9 in fathead minnows. A pH of 5.6 was found to be marginal for vital life
functions. A reduction in the development of white suckers to the swim-up
(early larval) stage occurred at pH 5.3 and lower (Trojnar, 1977b), Embryo
Production, embryo fertility and fry growth were impaired at pH 6.0 and lower
among flagfish (Jordanella floridae), a species not found in the BWCA (Craig
and Baski, 1977). Generally speaking, several fish species have been found
to be sensitive to pH levels around 6.0 or a little above.
Laboratory-determined effects appear to agree closely with field obser-
vations made in the LaCloche Mountain lakes area near Sudbury, Ontario. The
PH at which various species disappeared from lakes are shown in Table 14
Prepared by Beamish (1976).
Acute physiological effects of acid have also been investigated. It is
known that brook trout suffer malfunction of sodium regulation and lose
®Xcessive amounts of this ion to the water (Packer and Dunson, 1970). These
aUthors suggest (1972) that anoxia may be the primary cause of death in
Wishes exposed to very low pH. Leivestad and Muniz (1976) also observed an
inability of acid-stressed fish to regulate plasma sodium and chloride
^fivels, Mudge et al. (1977) found evidence of an inhibition of RNA synthesis
and presumably of steroidogenesis in interrenal tissue.
Whatever the mechanism of action of the acid stress, serious changes in
the population structure can result. Beamish and Harvey (1972) noted the
Compiete absence of one age class (5-year-old fish) in a population of white
®Uckers, probably resulting from an acid pulse five years earlier. In
®nother population of white suckers, older animals were lost in response to
Sradual acidification, with maximum age declining from 16 years to 7 years
'Beamish et al,, 1975). Spinal deformity resulting from disintegration of
8everal vertebrae in adult fish was also observed.
The more common effect of acidification is to reduce the population to a
'"•all number of older individuals. This has been observed in Scandinavia
»Hultbert and Stenson, 1970) and in a group of acid-stressed lakes in Canada
pyan and Harvey, 1977). In some species the growth rate of survivors in
lnfcreaged, presumably in response to reduced competition for food.
These changes in the form of populations precedes their extinction,
"ere is a long and increasing list of water bodies from which some or all
M e*> populations have been lost due to low pH. Major rivers in southern
°rvay have reduced populations of trout and salmon and large kills have been
**torded In association with acid precipitation (Jensen and Snekvik, 1972).
thofield (1975, 1976a) described the acidification and loss of fishes from a
*r8e group of lakes in the Adirondack Mountains. Lakes at pH 4.5 - 5
gelded no fish in response to survey netting. In the LaCloche Mountains of
^tario, a study of 67 lakes yielded 28 that had lost the majority of their
many of these lakes had supported good sport fisheries until relatively
•tently (Beamish, 1976). Many of the remaining lakes showed reduced numbers
fishes, perhaps influenced by changes in other organism populations (see
®ctlon on Effects on Invertebrates),
124
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Table 14. Approximate pH at which fish in the LaCloche
Mountain lakes, Ontario, stopped reproduction (after
Beamish, 1976)
pH Species Family
6.0+
to 5.5
Stnallmouth bass
Micropterus dolomieui
Centrarchidae
Walleye
Stizostedion vitreutn
Percidae
Burbot
Lota lota
Gadidae
5.5
to
5.2
Lake trout
Salvelinus namaycush
Troutperch
Percopsis omiscomaycus
Salmonidae
Percopsldae
5.2
to
4.7
Brown bullhead
Ictalurus nebulosus
White sucker
Catostoraus commersoni
Rock bass
Arabloplites rupestris
Ictaluridae
Catostomidae
Centrarchidae
A.7
to
4.5
Lake herring
Coregonus artedii
Yellow perch
Perca flavescens
Lake chub
Coueslus plumbeiiR
Salmonidae
Percidae
Cyprinidae
125
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Host likely the early effects of acidification of BWCA-VNP lakes will be
a decrease in fish production, but very quickly direct effects on the fish
community will be apparent. Loss of production followed by loss of desirable
sPecies and complete elimination of fish would be expected in the sensitive
lakes in the BWCA-VNP. Little or no effect is expected for non-sensitive
lakes and watersheds.
¦Iljects on Other Vertebrates
Vertebrate animals other than fishes have received scant attention.
®irds and mammals which feed on fish are faced with a reduction or loss of
food supply. In the LaCloche Mountain lakes, for example, loons continued to
"e8t on and attempted to fish in lakes which had lost much or all of their
life.
Amphibians are especially prone to acidification of shallow surface
Waters. Pough (1976) has described effects of acid precipitation on Spotted
Salamanders (Ambystoma jeffersonlanum and A. maculatum), which breed in
^temporary rain pools. Below pH 5 and 7, respectively, these species suffered
mortality during hatching in laboratory tests. This mortality was
Associated with distinctive embryonic malformations. The development of
*®lamander eggs in five ponds near Ithaca, New York, ranging from pTl 4.5 -
•0 was observed. An abrupt transition from low to high mortality occurred
filow pH 6. Although a synergistic effect of several stresses may have been
P°8sible, the studies suggested that pH was the critical variable. Pough
cites studies which indicate a decline in British frog populations.
Hagstrom (1977) has investigated frog populations in Tranevatten, a lake
®cldifiecj by acid precipitation, near Gothenburg, Sweden. The lake pH has
Alined to 4.0 - 4.5 and all fish have been eliminated. The frog species
temporaria is being eliminated as well. Currently, only adults 8-10
old are found. While many eggs were observed in 1974, few were found
1977. The few larva observed in 1977 subsequently died. A toad species,
**^2. bufo, is also being eliminated from this lake.
Frogs and salamanders are important predators on invertebrates in lakes
« puddles or pools, including mosquitoes and other pests. In turn, they
themselves important prey for higher trophic levels in an ecosystem
<4P°ugh, 1976).
SuMMARY
¦¦¦ Acid precipitation, by causing increased acidity in lakes, streams,
#®°ls and puddles, can cause slight to severe alteration in communities of
^atic organisms. The effects are similar to those observed in waters
®Ceiving acid mine drainage (AMD), but the toxicology and chemistry is not
* greatly complicated by the presence of high concentrations of heavy
.6tals, chemical floes, turbidity, etc., such as are found in AMD. Bacterial
'Composition is reduced and fungi dominate saprotrophic communities.
Sanic debris accumulates rapidly. Nutrient salts are taken up by plants
J®** rant of low pH (mosses, filamentous algae) and by fungi. Thick mats of
®se organisms and organic debris may develop which inhibit sedtment-to-water
126
-------
t and mineral exchange, and choke out other aquatic plants. Phytop-
species diversity, biomass and production are reduced. Zooplankton
thic invertebrate species diversity and biomass are reduced. Ulti-
the rema ining benthic fauna consists of tubificids and Chironomus
larvae in the sediments. Some tolerant species of stoneflies~and
!3 persist as does the alderfly, Air breathing Insects (water boatman,
.mmer, water stridor) may become abundant. Fish populations are
[ or eliminated, with some of the most sought after species (brook
walleye, smallroouth bass) being the most sensitive and therefore among
•st to be affected. Toxicity or elevated tissue concentrations of
may result either from direct deposition or Increased mobilization or
Amphibian species may be eliminated. And finally, populations or
•ies of higher terrestrial vertebrates that utilize aquatic organisms
)d or recreation are likely to be altered.
Edification of the BWCA-VNP is going to affect the fish communities in
: the lakes, either by reducing populations, changing species
Ltion, or directly eliminating fish from the lakes. As the acid load
;es or continues, more lakes will fall in the affected category,
the small headwater lakes in poorly buffered watersheds are the most
candidates for impact, the importance of these lakes in the total
:ional picture Is unknown. However, as more lakes are eventually
id, the whole philosophy behind the wilderness experience that forms
lis of the establishment of the BWCA-VNP will be violated and the part
BWCA which provides recreation will be reduced. Few people who
i the BWCA-VNP could be expected to enjoy areas made fishless by
ints from human activity.
127
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APPENDIX A
WET REMOVAL RATES FOR SO2 GAS AND SO4 AEROSOL
In most models describing pollutant transport, transformation, and removal
one typically finds an equation of the form
^ - - An + S (A 1)
where n represents the mass concentration of pollutant, and X represents a
rainout or washout coefficient. The symbol S denotes all other pollutant
sources sinks such as photochemical production, chemical conversions, and
dry deposition. Neglecting these additional source-sink terms and considering
only the wet removal processes, the solution to (A-l) becomes
n = n0 exp (-At) (A~2)
where nQ represents the initial concentration of pollutant. When used as a
description for wet removal of pollutants, (A~2) is generally applied over some
vertical depth of the atmosphere such as the mixing layer, the cloud layer, or
the troposphere.
Although wet removal is generally considered to be described by first
order expressions such (A-l), it is not intuitively obvious that it should be,
or can be described in 6uch a manner. Indeed, we will show chat the first
order assumption is not strictly correct. However, a first order expression
can be approximated after considering basic principles. The following
derivation will clearly illustrate the conditions under which the application
of (A-l) is appropriate and will determine the form of \ for the wet removal of
SO2 8aE anc^ aerosol.
Wet Removal of Pollutants
An exact description of the local time variation of pollutant concen-
tration results from applying the. basic continuity equation; i.e.,
a
(A-3)
Here v represents the three dimensional wind vector with the vertical
component described by
V3 3 w-vf (A-4)
where w is the vertical wind speed and Vf (positive) is the fall speed of
precipitation particles. Application of (A— 3) for the description of wet
ISA
-------
removal, implies that pollutant is carried to and from the volume of interest
only by the wind and falling precipitation. Assuming that boundary layer flow
in the atmosphere is nondivergent and rearranging (A-3) in terms of a sub-
stantial derivative, results in a form analogous to (A-l),
dn . (A-5)
ar dz
Integration over height, z, provides the desired expression for describing the
wet removal of pollutants from the atmosphere;
(nvf)z ~ (nvf)z
o (A-6)
dn »
dt z - zQ
where n represents the vertical average over a column extending from zQ
to z. Therefore instead of finding that pollutant removal is directly
proportional to the pollutant concentration as in (A-l), we find that removal
is actually determined by the vertical flux divergence of pollutant in the
column under consideration. The rate of mass (concentration) removal is a
consequence of the mass flux of pollutant into the top of a volume minus the
mass flux of pollutant out the bottom.
For wet removal, the mass flux of pollutant past a particular level can be
represented by the precipitation rate, j, multiplied by the pollutant concen-
tration of the precipitation water, C, where j has the units of a water flux,
and C has units of mass of pollutant per mass of water. Thus, the flux
divergence can be represented by
(jC), - (jC>.
dti
dt
z - z.
C A— 7)
A major difficulty in describing the wet removal of pollutants is
determination of the vertical extent of the region being scavenged. Modelers
often wish to determine pollutant removal for a layer of fixed thickness and
generally apply (A-l) to a surface layer of air. However, unless the surface
layer encompasses the entire vertical extent of the region being cleansed by
precipitation, such an approach will produce only a crude approximation to the
true removal. As (A— 7) illustrates, both the flux into and out of the surface,
layer must be considered. Without the assistance of detailed vertical profiles
of precipitation rates and pollutant concentration, the flux into the top of a
surface layer will be indeterminate. Currently detailed vertical profiles of
precipitation and pollutant concentration are unavailable. Thus we find our
first restriction to apply (A— 7) or (A-l); the layer under consideration must
extend to heights where the wet, downward flux of pollutant is near zero.
155
-------
Wet Removal of Sulfate Aerosol
Figure A-l represents the simplest case for wet removal. Sulfate aerosol
removal is considered, and the removal model described by Scott (1978) is
employed. Briefly, the model assumes that in the portion of the figure above
cloud base, cloud droplets are nucleated on sulfate condensation nuclei. Large
collector particles (snowflak.es) then enter the box from above and, as they
descend, grow to larger sizes primarily by accretion of the cloud droplets.
The process envisioned here is one of precipitation development in a cold cloud
by the Bergeron process. The sweeping out of a dirty layer of cloud water
above the cloud base by relatively pure collector particles is the major removal
mechanism. The region of the cloud where precipitation growth is primarily by
accretion of cloud droplets is designated as the riming zone. Since the snow-
flakes are assumed to be relatively sulfate free when they enter the riming
zone, the wet, downward pollutant flux at the top of riming zone is zero.
The thickness of the riming zone can be estimated from the fall speed of a
typical collector particle and from the time required for the particles to grow
to raindrop sizes. By utilizing the work of Kessler (1969), the fall speed of
che median volume drop can be exressed in terms of the precipitation rate as
vf = 3.89 J°•105 (m/s), (A-8)
where here, J represents the precipitation rate in mm h"*. In continuous
rainfalls, precipitation rates generally average between 0.5 and 1.0 mm
h""!, for such rainfall rates, the median volume drop diameter is roughly
between 0.7 and 1.0 mm. Millimeter sized ice particles can be produced by
riming, 5 to 13 minutes in mixed phase clouds with water concentrations near
1 g (Hindman and Johnson, 1972; Scott, 1976). Therefore, a time of 9
minutes is felt to be an appropriate estimate for the time collector particles
remain in the riming zone while growing to precipitation sizes.
Taking the height of the riming zone to be defined by collector particle
velocity (A~8), a multiplying by the time of collector particle growth in the
riming zone gives the riming zone thickness, i?., as
Az - 2100 j0.105 (m)| (A_9)
Thus, the thickness of the riming zone is generally near 2000 m and weakly
depends upon precipitation rate.
The distance from the ground to cloud base in a precipitating cloud is
typically small compared to 2000 m. Therefore, Az can be considered to
represent the distance from the ground to the top of the riming zone. Since
z— Zq %Az, the flux divergence over the entire column extending from the
ground to the top of the riming zone can then be evaluated by computing only
the pollutant flux at the surface.
The concentration of sulfate in the precipitation water reaching the
surface can be parameterized in terms of the sulfate concentration of the air
being drawn into the cloud base. Fitting curve 3 of Figure 2 in Scott (1978)
with a least square curve for 0.13
-------
of sulfate (grams of sulfate per gram of water) as
C - 0.46 xg(S04)j~0'27 (A-10)
here XgCsO^) is the clear air concentration of sulfate (grams of sulfate
er of air) being drawn into the cloud at cloud base. Generally, the
wht
per m-5 of air) being
subcloud air is well mixed and the sulfate concentration should be fairly
uniform between the ground and cloud base. Therefore we approximate Xg with
the surface air concentration of sulfate.
Combining (A-7), (A-9), and (A-10), the wet removal rate for sulfate can
be expressed as
dx(S°4) - - 0.22 xg(SOA)j°*625 (A-ll)
d t
where X(SO^) represents the average SO^ aerosol concentration (grams of
sulfate per m of air) in the layer extending from the ground to the top of
the riming zone.
Removal of SO? by Snow
Much of the preceding material can be used to describe the wet removal of
SO2 • ^or t^ie simplest case, that of SO2 scavenging by snow, a direct
analogy follows. Here we assume that the bulk, of SO2 picked up by frozen
collator particles occiirs as these particles capture cloud droplets in the
riming zone. The dissolved SOp in these cloud droplets is assumed to be in
equilibrium with the environment, which, if the SO2 air concentration
decreases monotonically with height, implies that the droplets at the upper
portions of the riming zone will contain less SO2 than those droplets near
cloud base. As the snowflakes collect cloud droplets, the droplets will freez<
rapidly* and will have no opportunity to adjust to new equilibrium values as
they are carried to lower levels in the cloud.
Since the wet, downward, flux of SO2 through the upper boundary of the
riming zone if negligible, the S02 removal rate by snow is determined by
evaluating the pollutant flux at the ground. Written in terms of flux
divergence over the riming zone, the wet SO2 removal rate is given by
dX(S02)
dt
snow
- JC
Az
= 0,48 J°.9c (A-12)
where C represents the dissolved SO2 concentration in the snowflakes arriving
at the ground.
From Scott (1978), the final concentration of pollutant in a collector
particle passing through the riming zone is given by
C » C[l - exp(-2m)] (A-13)
157
-------
where C is the vertical average of Che SO2 water concentration in the
riming zone, and m is the vertical average of the cloud water concen-
tration. Then, taking C to equal the arithmetic average of the equilibrium
concentration at the ground, C , and at the. top of the riming zone, and
setting the upper level concentration equal to zero results in
dX(S02)
- - 0.24 C„J°-9(l-exp(~2i) (A-14)
dt snow fo
Furthermore, Scott (1978) has presented an expression relating precipitation
rate to cloud water concentration;
nv «• 1.56 + 0.44 n J (A-15)
Equation (A-15) was intended to generalize all precipitation events. However,
no liquid water needs to be present in snow clouds. Caution should be
exercised when applying it to snowfalls, particularly when precipitation rates
uj-g very light.
Values of C~ can be obtained from Figure A-2 which presents equlibriura
concentrations of SO2 as a function of pH and SO2 air concentration, The
cUrves of Figure A-2 result from the simultaneous solution of three equilibrium
equations describing the dissociation of SO2 in water (e.g., see Appendix A,
Easter and Hobbr,, 1974).
Removal of SO? by Rain
To extend these concepts to SO? removal by rain scavenging, consider the
features illustrated in Figure A-3. Again the riming zone is represented by
the distance (z-zQ), while the freezing level height is designated by (zf-
z ). For this mo^el, snowflakes, as before, are assumed to accrete cloud
droplets containing dissolved S0£ and then to melt to raindrops after falling
through the freezing level. In applying the flux divergence concept, the
vertical fluxes in and out of each of the two boxes in Figure A-3 must be
considered. In the upper box, the only change in SO2 concentration results
from a downward flux through the freezing level. As in the purely snow case,
the amount removed is
dX(S02)
d t
(z-zf)
ice
j(zf) C(zf)
(A-16)
where both the precipitation rate, and the SO2 concentration in the snow are
evaluated at the freezing level. Below the freezing level, the removal due to
rain is
dX(S02)
___
j(zf) C(zf) - j(z0) C(z0)
(A-17 )
(Z f~2q)
liquid
158
-------
where j(zQ) and C(zQ) are ground values. Below the freezing level, the S02
concentration in the drops is assumed to be determined solely by establishing an
equilibrium concentration between the dissolved and airborne S02.
In order to derive a removal rate that is analogous to the previous removal
rates and applied over the entire region being scavenged (the top of the riming zone
to the ground) a weighted average over both boxes is performed;
dX(S02)
dt
(z-zf)
r IX ( S C) 2)
dt"
ice
+ 2). That is,
ex(so2).
(A-20)
Thus, the expressions describing wet removal of S02 and SO4 (Equations 11,
14, 19) can be generalized to
dX
It
- K XgJa
(A-21)
Notice that (21) is not an exact first order expression, as was assumed
a-priori in (1). The average wet removal of S02 and SO^ for a layer
depends not on the average pollutant concentration in the layer, but upon the
surface level concentration in the layer. If the surface level concentration,
Xg, can be expressed in terms of a layer average, then the first order
relationship of (1) will result. For example, suppose the surface level
concentrations of S02 and SO4 decrease linearly to zero at the top of the
riming zone. Then Xg ¦ 2X and
dX(SO4)
dt
0.44 X(S
-------
Another common situation is to assume a Gaussain profile Cor a plume. Then
Xg - X Az/ [1.25 az erf(^z/(l.blcrz))]
- r x
Substitution of (A-23) into A-ll, A-14 and A-19 gives
d*(s2 and SO4
by precipitation, calculations to determine sulfur depostion and rainwater
acidity follow directly, in fact, the flux of SO2 or SO4 is obtained by
multiplying (A-21) by the region being scavenged, Az, which is defined by
(A-9)• A3 ^or raaJor portion of acidity found in rainwater can be
attributed to the incorporation of sulfate (Granat, 1977). Indeed, as Figure
A-4 illustrates, a good approximation to rainwater pH results from assuming two
hydrogen ion9 for every sulfate ion (Dana, 1978). The figure presents
precipitation chemistry data collected from the MAP3S precipitation chemistry
network and suggests that during the summer months when nitrate concentrations
in precipitation water are the lowest, the two hydrogen to one sulfate ion is
regularly observed. During the winter months when nitrates play a greater role
in determining rainfall acidity, there is an excess of hydrogen ions;
resulting in the molar ratio of hydrogen to sulfate being greater than 2.
Still, at pH values less than 4.3, the assumption of [H]/[S0^J ¦ 2 is quite
good. Thus, determination of the sulfate concentration in precipitation water
should provide accurate estimates of rainfall pH.
160
-------
REFERENCES - APPENDIX A
Dana, M. T. 1978, Seasonal Trends of SO21 SO4, NH4 and NO3 In
Precipitation, MAP3S Precipitation Chemistry Network. Presented at the
MAP3S Precipitation Chemistry Network Meeting, May 11-12, 1978, Ithaca,
N.Y.
Granat, L. 1977. Sulfate in Precipitation as Observed by Che European
Atmospheric Chemistry Network", Presented at the International Symposium
on Sulfur in the Atmosphere, September 7-14, Dubrovnik, Yugoslavia, 1977.
Hindman, E. E., II, and D. B. Johnson. 1972. Numerical Simulation of Ice
Particle Growth in a Cloud of Supercooled Water Droplets. J. Atmos. Sci.,
29:1313-1321.
Kessler, E. 1969. On the Distribution and Continuity of Water, Substance In
Atmospheric Circulation. Meteor. Monogr., 10(32):1—B4.
MAP3S Precipitation Chemistry Network, First periodic summary report.
Battelle, Pacific Northwest Laboratories, Richland, U'a., 99352. In
press. 1977.
Scott, B. C. 1976. A Theoretical Study of the Evolution of Mixed Phase
Cumulus Clouds. PhD Dissertation, University of Washington, 209.
Scott, B. C. 1978. Parameterization of Sulfate Removal by Precipitation. J.
of Appl. Meteor. In press.
161
-------
FIGURE CAPTIONS FOR APPENDIX A
Figure A-l
Figure A-2
Figure A-3
Figure A-4
The volume considered for sulfate removal. The
symbols represent: *, ice particles; 0, liquid
drops; o, cloud droplets; the direction of
the sulfate flux at the upper and lower bound-
aries of the volume.
Curves of Cg/xg as a function of pH. The labels
for the curves represent SO2 air concentrations
(yg/m3). The units of Cg and Xg are grams of
dissolved SO2 per gram of water and grams of air-
borne SO2 per cubic meter of air, respectively.
The volume considered for wet SO2 removal by
snow and rain. The ground is at z0 and the top
of the riming zone is at z. The freezing level
is at Zf. The air concentration of SC^ is assumed
to decrease with height.
Observed relationships between the ion concentra-
tions of H and SO4 for (a); summer, 1977, and (b),
winter, 1977-78. The solid line represents two
hydrogen moles for every sulfate mole, while the
circles represent data points.
162
-------
*
CLOUD BASE
GROUND
RIMING ZON
Figure A-l
163
-------
tr> o
L 10
ID"3
2780 K
3.0 3,5 4i,0 4.5 5.0 5.5 6,0
Figure A-2 ^
164
-------
FREEZING
LEVEL
GROUND
A
2 km
Z
1 km
^'.*ure A_ j
-------
lonn
10
1
1
100
1000
Figure A-H(a)
166
-------
1000
100
oo
oo
+
n:
100
Figure A-U(b)
167
-------
APPENDIX B
SIMPLE MODEL CALCULATIONS APPLIED TO ATIKOKAN
Annual averages, and 3-hour and 24-hour worst case concentrations and
deposition fluxes may be estimated using simplified models. These calculations
provide a comparison to the more complicated grid model.
Annual Average Concentrations
The single box model approach is used. Since all possible meteorological
conditions occur in a year we may consider that the plume is uniformly mixed in
a cylindrical box. Assume that the wind blows with equal frequency in all
directions. From conservation of mass,
Q - 2n x L U C,
or,
r = 2
2ir x LU.
C is the annual ambient air concentration (pg/m^) at distance x (m) from the
source Q (ug/sec). U is the average annual wind speed (m/sec) through the
average mixed layer of height L(m). Let us now divide this result by 2 to
account for the time when the plume is in stable air and hence not dispersing
to the ground. The equation to be evaluated is then
u 4ir x LU.
Holtzworth gives the mean annual day time value of L at International Falls as
1300 m and the mean annual wind U as 7.2 m/sec. We choose x ¦ 80 km as the
distance from Atikokan to the center of the BWCA. For the Indicated emission
rates, Q, the annual average concentrations, C, are as follows:
Species
_8_
Q(sec)
C(S5)
C(ppb)
so2
2230
.24
.09
S04
335*
.04
.01
PM
328
.04
Hg
0.0290
3 x 10"6
.001
NOX as N02
1320
.14
.005
* Assumed 2X/Hr conversion of SO2 to SO4 plus
2% conversion in the stack.
168
-------
The EPA CRSTER model which runs a Gaussian plume calculation for every
hour of the year gave an annual average SO2 concentration at 80 km due south
as 0.25 pg/m (Goklany, 1978).
Three-Hour Worst-Case Concentrations
Assume that the plume is fully trapped and calculate the plume centerlLne
concentration for neutral stability at 80 km downwind. The Gaussian plume
result is,
r . 9
' 2iroy
Because of plume meancioring an average concentration across the plume is more
appropriate than the centerline value. The width of the plume is taken as
4.3 Oy and the result is,
r „ o-_4 q
,/^TT Oy TLU .
For neutral stability ay 0 0.13 x 0.903 and assuming x = 80 km, u «• 5 m/sec
and L 3 500 m we have,
Q(g/sec)
C = 106.5 .
In order for this to represent a 3-hour average concentration the wind
would have to blow steadily in one direction for 7 hours since the travel to
the receptor is about 4 hours. Hence, this is an upper limit to the real
situation. The results of this 3-hour calculation are as follows:
_S_
Species
Q(sec)
C(nr*)
C(ppb)
so2
2230
21
8
S0A
335
3
1
PM
328
3
Hg
0.0290
0.0003
4 x 10'
NOX as N02
1320
12
6
The EPA CRSTER model calculated the highest 3-hour concentration of SO2
at 80 km south-southeast as 20 ug/m^.
24-Hour Worst-Case Concentrations
The 24-hour case cannot be calculated without having actual meteorological
data because conditions do not persist in the atmosphere for 24-hours. The EPA
CRSTER model calculated the highest 24-hour SO2 concentration 80 km south of
Atikokan as 5 yg/m^. Taking this in relation to the emissions we have the
following 24-hour wor6t-c.ase concentrations,
169
-------
Species
jlK
Q( sec)
C(n?)
C(ppb)
so2
soA
PM
Hg
NOX as N02
2230
335
328
0.0290
1320
5
1
1
0.00006
3
2
0.2
7 x 10"'
1.6
Annual Average Dry Deposition
The annual average dry deposition flux may be estimated by multiplying an
effective depositive velocity, VD, by the annual average concentration,
fDRY C VD ^g/ra2 - sec)
or
I?DRY ™ 315 C VD (kg/hectare-year)
This assumes that the ambient air concentration is not significantly decreased
due to dry deposition upwind of the receptor point in question. Hence the
calculation is an upper limit. The annual average dry deposition fluxes are as
follows:
Species Vp(cm/eec) F^yCkg/hect are-year)
S02 1 °-75
SO4 0.1 0.014
PM 0.1 0.014
Hg 0.1 1 x 10~6
N0X as N02 0.5 0.22
Wet Deposition Fluxes
For typical rainfall rates of 1 mm/h continuous rainfalls, the procedure
outlined in Appendix A yields a concentration of 1.8 mg/l for the sulfate in
precipitation assuming an average sulfate concentration of 3 yg/m^ in the
air. By assuming 2 hydrogen moles for every sulfate mole, the sulfate
concentration converts to a rainfall pH of 4.4, and 3 - .0237. The removal
rate for 21 pg/m3 of SO2 is,
wso2 " 0,24 g/®3 ~h) >
and for 3 yg/m^ of SO4 is
wSq4 " 1«° ^8/m3 -h).
170
-------
Using a height of 1,300 m for Che mixed layer the deposition rate due to rain
is,
Fwft^S02^ " 3 (g/hectare-h),
Fygx^SO^) ¦ 13 (g/hectare-h).
For snow let us assume a typical precipitation rate of 0.5 mm/h. Then
m ¦ 1.25 and,
WSq2 = *23 (pg/m3~h)
Ws0^ " -63 (m g/fn3~h)
And using 1,300 m for the mixed layer, the deposition rate due to snow is
FWET(S02) ° 3 (g/hectare-h)
^WET^Oa) " 8 (g/hectare-h)
Wet deposition of particulate matter may be estimated by using an
appropriate wash-out coefficient, The wash-out coefficient is a function to
particle size and the droplet size. The fly ash particles that escape the
electrostatic precipitation will be predominantly in the 0.1 to 1 m range and
we have selected a wash-out coefficient of 0.036 per hour. For mercury we
assume a wash-out coefficient of 0.005 per hour. The scavenging mechanism for
NOX is not known. The equation to be used is,
FWET = ACZm W»2-hour).
Using a height of 1300 m for the mixed layer, the deposition rates in the plume
due to rain is,
F^^PM) ° 1.4 (g/hectare-hour)
FypiT^S) = 4 x 10-6 (g/hectare-hour)
Annual Average Deposition
During the model year of 1964 there were 43 hours of rain and 46 hours of
snow when the winds were from the north-east to northwest. This information
may be used to calculate an annual average wet deposition flux, however, since
the plume would cover roughly a 15° sector and any given time, we should use
only 1/6 of this time. The estimated annual average deposition fluxes due to
Atikokan are summarized below:
Deposition
(kg/hectare-year)
S02
S0A
PM
Hg
Rain
Snow
Dry
0.02
0.02
0.75
0.10
0.06
0.01
0.01
0.01
0.01
3
3
1
x 10"8
x 10-8
x 10"6
Total
0.79
0.17
0.03
1
x 10~6
171
-------
The deposition rates for SO^ are probably an upper limit because up-wind
removal between Atikokan and the BWCA due to wet and dry deposition would
decrease the concentrations used in the calculation. The wet deposition of
SC>2 might be increased since the pH of the rain would be less and therefore
the scavenging coefficient would be greater.
REFERENCES - APPENDIX B
Goklany, I. M. 1978. U.S. Environmental Protection Agency, Region V,
Chicago, 111. Personal communication.
172
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APPENDIX C
Representative Analysis of Coal and Fly Ash for Major and Trace
Components: Southern Saskatchewan Lignite. G. E. Glass, unpublished.
Component
Aluminum (%)
Antimony (ppra)
Arsenic (ppm)
Ash (%)
Barium (%)
Beryllium (ppm)
Bismuth (ppm)
Boron (ppm)
Bromine (ppm)
Cadmium
Calcium
Cerium
Cesium
Chlorine
(ppm)
(%)
(ppm)
(ppm)
(ppm)
Coal
1.7
1.1
6.8
22
0.05
<0.14
9
37
2.7
<0.6
1.8
Chromium (pptn) 25
Cobalt (ppm) 9
Copper (pptn) 46
Fluorine (pptn) 86
Gallium (ppm) ~
Gold (ppm) —
Hafnium (ppm) ~
Heat content (BTU) 8,600
Holmium (ppm) -
Iron (36) 0.6
Lead (ppm) <29
Ash
1,
Component
Coal
9.4 Lithium (ppm)
2.1 Magnesium (%)
19 Manganese (ppm)
Mercury (ppra)
0.50 Molybdenum (ppm)
3 Nickel (ppm)
Phosphorus (%)
400 Potassium (%)
2.0 Rubidium (ppm)
1.8 Silicon (%)
8.1 Selenium (ppm)
112 Silver (ppm)
3 Sodium (%)
460 Strontium (%)
60 Sulfur (%)
9 Tantalum (ppm)
43 Titanium (%)
94 Tellurium (ppm)
090 Thallium (ppm)
0.005 Thorium (ppm)
12 Tungsten (ppm)
Uranium (ppm)
6 Vanadium (ppm)
2.2 Zinc (ppm)
30 Zirconium (ppm)
Ash
9
-
0.45
2.5
180
400
0.3
-
9
20
37
39
0.15
-
0.4
-
-
40
4
-
0.8
<3
-
0.4
0.2
2
0.02
0.2
0.8
0.48
-
1.7
0.05
-
-
90
<0.5
-
-
14
-
2.5
8
11
20
70
40
20
80
240
173
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APPENDIX D
Table D-l Fishes known to be present in the BWCA and border lakes from records
of the Minnesota DNR Area Fisheries Headquarters in Ely, Finland,
and Grand Marais, Minn., personnal communication, and from Eddy and
Underhill (1974).
Table D-2 Lake benthic invertebrates collected from five large lakes in
Superior National Forest by the Minnesota Copper-Nickel Study Group
(MCNSG) in 1976.
Table D-3 Zooplankton collected by the MCNSG in 1976 and 1977.
Table D-4 Phytoplankton collected by the MCNSG during the fall and summer of
1976 and 1977.
Table D~5 BWCA-VNP water quality - November 1978: laboratory analysis USFS
Winton, MN., unless noted.
Table D-6 BWCA-VNP water quality - November 1978: field + descriptive data
(lakes within and near the BWCA and VNP sampled 11/6, 7, 8, 9,/7 8
and 11/15, 16/78).
Table D-7 Summary of snow data from the BWCA region for the period November
1977 - March 1978: bulk concentrations in melted snow and
calculated loadings.
Table D-8 Mercury concentrations in fish from selected Northern Minnesota
lakes (data from Minnesota DNR, 1978).
Table D-9 Relative sizes (inches) and mercury content (pptn) of walleye from
12 Northern Minnesota waters, 1977.
Table D-10 Relative sizes (inches) and mercury content (ppm) of pike from 14
Northern Minnesota waters, 1977.
Figure D-ll Distribution of lake surface areas for BWCA and fall 1978 sampling.
174
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Table D~1
Fishes known to be present in the 8WCA and border lakes from records of the
Minnesota DNR Area Fisheries Headquarters in Ely, Finland, and Grand Marais,
Minn., persormal communication, and from Eddy and Underbill (1974).
Silver lamprey, Ichthyomyzon nnicuspls
Lake sturgeon, Acipenser fulvescens
Goldeye, Hiodon alosoides
Mooneye, Hiodon terglsus
Brook trout, Salvelinus fontinalis
Lake trout, Salvelinus namaycush
Rainbow trout, Salmo gairdnerl
Lake whitefish, Coregonus clupeaformls
Cisco, Coregonus artedl
Central mudminnow, Umbra limi
Northern pike, Esox luclus
Muskellunge, Esox masquinongy
Longnose dace, Rhinichthys cataractae
Lake chub, Couesius plumbeus
Creek chub, Semotilus atromaculatus
Pearl dace, Semotilus margari ta
Northern redbelly dace, Chrosomus eos
Finescale dace, Chrosomus neogaeus
Golden shiner, Notercigonus crysoleucas
Bluntnose minnow, Pimephales notatus
Fathead minnow, Pimephales promelas
Mimic shiner, Notropls volucellus
Common shiner, Notropis cornutus
Spottail shiner, Notropis hudsonlus
Blacknose shiner, Notropis heterolepis
Brassy minnow, Hybognathus hankinsoni
Northern redhorse, Moxostoma macrolepidotum
White sucker, Catostomus commersonl
Longnose sucker, Catostomus catostomus
Brown bullhead, Ictalurus nebulosus
Black bullhead, Ictalurus melas
Tadpole madtom, Noturus gyrinus
Trout-perch, Percopsis omiscomaycus
Burbot, Lota lota
Brook stickleback, Culaea inconstans
Largemouth bass, Micropterus salmoides
Smallmouth bass, Micropterus dolomleui
Rock bass, Ambloplites rupestris
Green sunfish, Lepomis cyanellus
Bluegill, Lepomis macrochirus
Pumpkinseed, Lepomis gibbosus
Black crappie, Pomoxls nigromaculatus
Eddy and Underhill. 1974. Northern Fishes. University of Minnesota Press,
Minneapolis, Minn, 414 pp.
Yellow perch, Perca flavescens
Sauger, Stizostedion canadense
Walleye, Stizostedion vitreum vitreum
Log perch, Percina caprodes
River darter, Percina shumardi
Johnny darter, F.theostoma nigrum
Iowa darter, Etheostoma exile
Mottled sculpin, Cottus bairdi
Slimy sculpin, Cottus cognatus
175
-------
Table D-2
Lake benthic invertebrates collected from five large lakes in Superior
National Forest by the Minnesota Copper-Nickel Study Group (MCNSG) in 1976.
PLECOPTERA
Capniidae
Acroneurla lycorias
Perline11a drymo
EPHEMEROPTERA
Isonychla sp.
Siphlonuridae
Slphlonurus sp.
S!phlonurus marshall!
Heptagenlidae
Arthroplea blpunctata
Stenacron sp.
Stenacron candidum
Stenacron interpunctatum
Stenacron minnetonka
Stenonema sp.
Stenonemn trlpunctatum
Siphloplecton lnterlineatum
Bactidae
Calllbactis sp.
Clocon sp.
Leptophlebiidae
Leptophleb!a sp.
Ephemerella sp.
Ephemerella verslmilis
Ephemerella temporalis
Caenls sp.
Ephemera stmulans
Hexagenia sp.
Hexagenia llmbata
ODONATA
Coenagrionidae
Enallagma sp.
Comphidae
Dromogomphus spinosus
Hagenlus brevlstylus
Acshnidae
Acshna sp.
Basiaeschna janata
Boycria sp.
Boycrla vlnosa
Dldymops transversa
Macromia sp.
(continued)
ODONTA (continued)
Macromia illlnolensis
Somatochlora Williamson!
Notonecta sp.
'Ranatra sp.
Belostroma sp.
Lethocerus sp.
Corixidae
TRICHOPTERA
Nyctlophylax moestus
Polycentropus cinereus
Polycentropus interrupta
Hydroptillidae
Agraylea sp.
Hydroptila sp.
Ochrotrichia sp.
Agrypnla improba
Banksiola crotchl
Phrygabea c inerea
Ptllostomis sp.
Limnephilidae
Gramotaulls sp.
Nemotaullus host 11 is
Pycnopsyche guttifer
Agarodes distinctum
Molanna sp.
Molanna blenda
Molanne tryphena
Helicopysche borealis
Ceraclea sp.
Ceraclea neffl
Ceraclea resurgens
Triaenodes injusta
Triaenodes tarda
MEGALOPTERA
Chauloideg rastrlcornis
Stalls sp.
COLEOPTERA
Haliplus sp.
Dytisc idae
Cyrinidae
Dlneutus sp.
176
-------
Table D-2 (continued)
COLEOPTERA (continued)
Cyrinus sp.
Hydrophilidae
Ectopria nervosa
Dubiraphia sp.
Macronychus glabratus
Donacla sp.
GASTROPODA (continued)
_H. carpanulata
11* corpulentum
ii* trivolvis
Hellsomi sp.
Physa gvrlna
Sphaerium strintinum
Stagnicola sp.
DIPTERA
Tabenidae
Aedes sp.
Chironomidae
Clinotanypus sp.
Conchapelopla sp
OTHER
PELECYPODS
Sphaeriidae
Lepidoptera
Dicrotendlpes sp.
Endochironomus sp.
Euklefferriella sp.
Glyptotendipes sp.
Larsia sp.
Palpomyia group
Polypedilum sp.
Procladius sp.
Stenochironomus sp.
Xenochironomus sp.
Chironomidae pupae
DECAPODA
CRUSTACEA
Crangonyx sp.
Hyalella azteca
NEMATODA
TURBELLARIA
HIRUDINEA
OLIGOCHAETA
GASTROPODA
of. Amnlcola limosa
Carpeloma decisum
Perrissia sp.
Cyraulus sp.
Hellsoma anceps
177
-------
Table D-3
Zuoplnnkton collected by the MCNSG in 1976 and 1977.
ROTIFERA CLADOCERA
Keratella cochlearis
Bosimina longirostris
Polyarthra vulgaris
Daphnia galeata mendotae
Synchaeta sp.
Holopedium gibberutn
Conehilus sp.
Daphnia retrocurva
Kellicottia congisplna
Diaphanosoma sp.
Trichocera cylindrica
Chydorus sphaericus
Kellicottia bostoniensis
Ceriodaphnia lacustris
Collotheca sp.
Daphnia pulex
Trichocera similis
Leptodora kindtii
Filinia longiseta
Daphnia shodleri
Keratella quadrata
Alona circumfimbriata
Ploesoma truncatum
Ceriodaphnia quadrangula
Pompholyx sulcata
Alona guttata
Trichocera porcellus
Ceriodaphnia sp.
Hexathra sp.
Chydorus bicornutus
Ploesoma lenticulare
Daphnia catawba
Lecane sp.
Daphnia longirerais
Trichocera multicrinis
D. parvula
Asplanchna sp.
J). sp.
Lophochavis salpine
Trichocera weberi
COPEPODA
Brachionus sp.
Tropocyclops prasinus
Lophocharis sp.
(Cvclopoida)
Trichocera elongate
Cyclops bicuspidatus thomasi
Trichocera longiseta
(Cyclopoida)
Ascomorpha sp.
Diaptomus oregonensis
Rnthlanis dilatata
(Calanoida)
Hexarthra mira
F.pischura lacustris
Ploesoma hudsoni
(Calanoida)
Testudinella patina
Cyclops vernalis
Trichocera sp.
(Cyclopoida)
Trichotria tetractis
Mesocyclops edax
Ascomorpha ovalis
(Cyclopoida)
A. saltans
Diaptomus minutus
Bdelloid sp.
(Calanoida)
Brachionus quadridentatus
Ergasilis chautaquaensis
Cephalodella intuda
(Cyclopoida)
F.uchlanls sp.
Macrocyclops albidus
Kcritella hi emails
(Cyclopoida)
K. paludosa
Eucyclops agilis
K. serrulata
(Cyclopoida)
K. taurocephala
Orthocyclops modestus
Notholca acuminata
(Cyclopoida)
Notholca sp.
Diaptomus sicilis
Rotaria peturia
(Calanoida)
Synchaeta stylata
178
-------
Table D-4
Phytoplankton collected by the MCNSG during the fall and summer of
1976 and 1977.
BACILLARIOPHYTA
Asterlonella formosa
Cyclotella bodanlca
Fragllarla crotonensls
Meloslra ambigua
Meloslra dlstaris
Nltz8chla sp.
Tabellarla fenestrata
CHLOROPHYTA
Anki strodesmus falcatns
including varieties
arlcularls & mirabllls
F,n r-r Braunl i
Oocystis r,p.
CYANOPHYTA
Agmenellum quadruplicating
(Merismorcdia glauca)
Aphanocapsa delicatisslma
Coelo.sphaerium Kuetzinglanum
CHRYSOPHYTA
Dinobryon bavaricum
Dinobryon dlvergens
Dinobryon sertularia var.
protuberans
CRYPTOPRYTA
Cryptononas erosa
PYRRHOPHYTA
Ceratim hirundinella
179
-------
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7 «w*0>t»4lrf*r J' #11**9*.
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3.
-------
T*bU T\-6. K*T.*-V>r wa^or OmUI> H«w**>or Wl». FUW ~ DttcrltltOft T>%ta U^tPK — toi
tramalttanea
(ft)
Voluoa hoctara
hactara
CSi>
101
No n»*a
63,1 IK,24
1170
0.43
4.26
<5.9
70.2
7
1.67
102
Pm Soup
63,10*,18
-
-
1170
0.48
3.82
109.5
86.3
4
*0.14
103
Daft I •
63,10W, 17
-
-
12)0
0.83
9.61
94, 1
7 5.6
4
0.12
104
ka*1n«la
63,10*, 14
-
-
1240
0.70
4.93
60.4
65.6
10
0.74
109
Ho nana
63,9V, 10
-
-
1210
1.16
4.95
23,7
58.8
4
98
3.73
201
Chara
67,14V, 16
X
-
1180
0.92
4.52
17.8
70.9
16
179
4.21
207
Thm*
67,14V,)8
X
-
—
0,91
5.62
19.1
• 3.9
50
71
692
4 J) 3
203
fat
67,15*,14
X
-
1220
1.09
6.79
J 8 .4
87.6
99
32
291
3.68
204
Mor«»«y
6"7,15*,4
K
-
1120
0.96
5,76
22.3
82.5
30
199
2.53
205
Worth
67,19*,3
x
-
1100
0.72
3.06
23.1
74.3
24
1812
3.4 1
?06
Dovra
67,16«,20
*
-
1160
1.16
4.52
19.6
69.2
97
1472
3.4 7
?07
Mo
67,16*,29
x
-
1260
1.00
4.42
16.5
78.0
11
69
4.17
206
Ruby*
66 , t4tf,6
X
-
1250
1.06
3.97
22.4
86.2
26
186
3.4»
209
Warpaint*
66,14*,7
X
-
1260
1.20
3.25
16.7
84.5
23
77
4.43
210
Aqwwa^a*
66,14*,8
X
-
1220
1.24
3.53
18.2
80.7
14
126
4.28
2 11
Cw»rald*
66, t4«,6
X
-
1260
1,35
3.74
18.9
84.6
32
374
3.51
212
Cridtfla
64 ,9W,2F
X
-
ueo
0.70
3.00
31.2
67.7
14
2.20
213
Flat*
64,QW.?S
-
-
1480
0.89
4.94
45.8
87.0
24
1.20
714
Cnn f»
63,9W,33
-
-
1460
*at«r
samp t« on (y
8
>.07
215
Mo na*a
64,10*,36
-
-
1380
*at*r
se«apl« only
4
0.10
301
No na**a
69,17* ,32
-
V
1320
1.07
3.52
32.5
76.1
4
1 .88
X>2
Tooth
68,t8*,3
-
¦
1380
0.96
5.56
26.1
81 .4
29
192
2.79
303
SprIng
66 ,19*,19
-
1300
1 ,07
6.87
79.2
86.2
103
2.52
XX
Wlyapka
«,!«*, J 7
-
X
14Q0
1,19
4.38
25.8
65.9
25
372
3.02
305
*»lr
70,1**,>4
-
¦
13*>
1,51
4.27
18.4
68,4
26
3.70
306.
Mo
T0,20«,30
-
X
—
1.02
4.78
2 • .2
77.1
11
83
3 .70
307
Mo w.t*a
70,20*.30
"
X
1360
1.04
4.59
10.7
71.1
9
123
3.57
V»
S*oap«ck
70,20*1,34
"
X
1360
1.02
4.71
19.6
74.6 "
127
1126
4.27
509
L i tt1 a SNo*p»ck
69,20*,3
-
X
1380
1.09
4.13
19.9
79.0
69
146
3.56
3 10
Qu»rt«r||n«
69,20*,12
-
X
1320
1.13
4.61
20.4
71.7
12
66
3.71
311
f tsfMMOWttk
70,19*,21
-
X
1320
1.13
4.97
22.7
82.6
28
56
3.01
3»7
lolt*«
70,20*.»»
-
X
1320
1.12
6.07
25.5
84.5
38
294
3.31
313
Locator
70,21*,22
-
X
1300
1.37
6.14
24.5
81.8
57
1366
3.39
314
Tin Can MIka
64,!1*,5
X
-
t?90
0.90
5.50
22.0
03.0
57
311
3.04
315
San4p1*
64,n*,7
-
-
—
1.06
6.n
23.7
83.0
28
2.85
316
Lou 1 %
64,1?*,12
-
-
1405
1.27
5.66
19.4
87.4
8
34
3.40
401
T ot«n
66,6*. 35
X
-
1540
1.07
4.50
53.C
76.7
7
0.99
402
Zmttla
66,6*.33
X
-
1570
1.15
4.00
35.?
83,5
4
1 .8 7
*03
L. ot tf.a Cloud*
65.6* ,4
X
-
1590
1.14
5.40
31.1
89.3
100
12
67
2.39
404
Cta«
65.0W.I0
X
-
1.01
3.73
47.f
90.0
1 1
1.0 7
405
No nama
65,6*.18
K
-
1530
1.31
5.99
41.5
88.9
3
1 i
1.42
406
Roq
65,5*.16
X
-
1465
1.58
6.52
66.7
85.4
24
0.55
407
Cup
65,6*.It
X
-
t490
1.00
4.81
29.5
78.5
8
2.45
409
Out ton
65,6* ,6
X
-
1500
1.19
5.48
33.7
06.9
12
1 .94
409
Sa«na
65,7* ,25
X
-
1420
1 .20
6.08
54.5
84.2
35
0.98
4 10
Mis«u«
63,8*.t9
¦
-
1520
1.04
4.50
73,2
79.3
25
3.07
411
Mood
63,8*,17
X
-
1460
1.18
3.93
25.3
83.2
to
2.63
412
HaraoAy
64,7*,28
X
-
1490
1.07
5.62
31.3
84.7
12
2.47
413
B*l«y
64,7*,13
X
-
1550
1.03
4.63
42.7
64.3
5
2.21
4 14
fe»4fa
-------
T«bi* D—6 (Co*iT I)
Oapti ot Ctwactf Ittlci
Location
pro&a
Prob®
Prob*
Maxlnjs
i«r aca
Ha*ar&h«4
"N, «
£Iftvatlo*
ta»c.
Co«4wct t»l *Y
Protoa f
tfapth
are*
ar»«
SimNw
L»** *a»»
*«t 1 l«w
ftwTA"
«r»r*
Ut.l
<«l
<*C1
U*»*o/c«*7l
franwi 1 tt*«ca
(Itl
fc*d»r#
cs>
5C2
H®rrl^an
66, '6w,5
X
1270
1.54
2.71
20,6
7S.4
19
1)9
3.35
SO J
Lo«6f Pa*n«%s
66,1 5«,15
¦
-
1215
1.02
3,01
10.6
63.5
35
~ It
2 M91
3.52
504
} * onh 1 »f*
67,1&*,||
-
-
1180
1.12
2.90
35.2
80.4
62
1.83
505
Loog
67,!5*,?
-
-
1220
1*12
1.65
5S.5
76.6
180
0.68
506
King wl I 11 a*
Harrow*
67,t?w,»
1
1060
1.11
5.91
4 .6
77.0
6lt
1.78
507
f*BU t > n*
65,16*,t2
-
-
1500
1.05
2.12
19.8
70.7
25
25
97
3.4J
506
POCk 1«la0
2.32
605
Gog#blc
65,?E,30
K
-
1600
1.09
3. 1®
31.?
64.9
60
23
126
2.07
606
flocfcy
64,1 ,2
-
1550
0,97
2.7*
37.6
83.5
26
2.22
607
ft aw
63.1W.9
X
-
1655
0.92
2.64
27.1
80 J
27
2.27
60S „
1111!• Trout
63,I*, 5
M
-
1660
0.96
2.71
30.8
87.2
51
2.24
609
G«skIn
64,?«,22
It
-
1640
1.17
3.03
25.5
66.4
60
»40T
3691
2.94
6 »0
P«r t r t tf-j#
65,1w.X)
H
-
1750
1.51
3.94
4C.5
S3 .8
«0
1.92
611
Top par
65,2«.27
~
-
1P00
0.95
?.*>
44,t
87.5
16
87
'.51
612
T*p*4
66, 4 m, 54
-
-
1470
1.06
J.>9
25.9
73.5
32
2.59
701
C tv b U f
67 »4«r, 7
X
-
1740
1 .02
2.'4
23.7
60.5
316
2.93
3.02
702
A 1 tor
ft?,5«.1
X
-
1770
1.09
2.90
24.2
83.5
4 14
705
A1 ! C"Ov»<>
65.7W.1
X
-
1490
1.12
3.4-J
22.4
80.7
6Ut
37637
2.99
704
lnsuia
65.0*,15
*
-
<500
t .26
2.61
21.0
83.2
uoo
2.78
705
Sno«toAli
64(a«,i9
X
-
1470
1.03
5.06
?S.9
83 .6
721
64 17
2.45
705
1 ah* T«o
63,9«,27
V
-
1550
1 .01
2.48
?2.e
•0.2
189t
2.87
7C?
67,9,5
X
-
1560
i.oa
7.62
26.3
64.9
263
2.65
70«
Pa 11ro
62,9,8
X
-
1590
1 .09
2.69
25.0
86.4
173
2.52
1
-------
Table 0-7. Summary of Snow Data from the B*F , March 1978. Component Concentrations In Melted Snow and
Ca\cu\o^o4
H+
nh4+
S04"2
NCXj-
CI"
r
B
Cr
Mn
Hg
Components:
as H
as N
as SO^
as NOj
as CI
as F
as B
as Cr
as Mn
as Hg
d1ssolved
dlssolved
d 1 ssolved
acid
acid
acid
exchangeable
exchangeable
axchangeab le
total
Canopy Type:
Con 1ferous
(19 sites, mean moisture
content of snow
9 cm)
Mean
0.0139
0.089
1.80
1.33
0.27
0.025
<0.C05
<0.005
0.0I2<
0.000 014*
concentratIon
(pH 4.85)
0.0021*
0.0014*
0.0052
(mg/1)
Mean
0.0121
0.075
1.62
1.15
0.24
0.020
<0.005
<0.005
0.01 1*
0.000 013*
1oadIng
0.0016<
0.0013*
0.0046
Kg/ha
DecIduous
(17 sites, mean moisture
content of snow
13 cm)
Mean
0.0170
0.1 1 1
1.08
1 .20
0.15
0.020
<0.005
<0.005
0.008*
0.000 01 I*
contentratlon
(pH 4.77)
0.0018?
0.0014?
0.004?
(mg/l)
Mean
0.0225
0.10 1
.4 1
1.46
0.27
0.019
<0.005
<0.005
0.009?
0.000 015*
load 1ng
0.0017*
o.ooie?
0.004*
Kg/ha
Mean Watershed
Va1ues
(assuming con
1 ferous 60j,
deciduous 40J)
Mean
0.0151
0.099 1
.53
1.29
0.22
0.023
<0.005
<0.005
0.01 !<
0.000 013*
concentration
(pH 4.82)
0.0020<
0.0014<
0.005
(mg/1)
Mean
0.0163
0.086 1
.53
1.29
0.22
0.020
<0.005
<0.005
0.010?
0.000 013?
loading
0.0010?
0.0015?
0.005
Kg/ha
2 Computed values of the mean o/er-estImate of the acutal value because the non-measureable values were entered as the numerical
less-than value, rather than zero.
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Table D-8
Mercury concentrations in fish from selected Northern Minnesota lakes
(data from Minnesota DNR, 1978).
Lake Species No. fish
Expected size
Range, (inches) at the
length Range, 0.5 ppra
(inches) ppra Hg threshold
Vermilion L.
Walleye
30
12.4
-
23.0
0.09
-
0.73
25
Northern Pike
22
17.6
-
33.0
0.10
-
0.47
N/A
Trout L.
Walleye
25
14.0
-
21.4
0.20
—
0.95
18
Northern Pike
5
20.0
-
30.0
0.25
0.98
24
Lake Trout
15
15.0
-
24.8
0.11
—
0.50
Smallmouth Bass
5
11 .3
-
14.8
0.28
-
0.42
Pelican L.
Walleye
6
9.5
-
25.9
0.10
_
0.87
20
Northern Pike
25
10.8
-
28.2
0 .13
.
0 .69
30
Smallmouth Bass
5
13.1
-
15.4
0.13
-
0.36
Basswood L.
Walleye
28
12.5
-
29.0
0.24
,
1.95
15
Northern Pike
25
15.5
-
25.5
0.23
-
0.86
21
garid Point L.
Walleye
8
11.8
-
21.0
0.25
—
2.67
13
Northern Pike
7
19.2
-
24.5
0.21
-
0.83
22
j^^niakan L.
Walleye
10
11.5
-
17.5
0.13
—
0.58
>30
Northern Pike
4
15.5
-
23.3
0.09
-
0.28
N/A
K.abetogama L.
Walleye
26
9.4
-
21.3
0.03
—
0.40
>30
Northern Pike
10
15.8
-
30.5
0.09
-
0.24
gurntside L.
Walleye
6
11.2
-
24.0
0.18
—
0.95
17
Northern Pike
34
19.5
-
32.0
0.19
-
1.01
28
Lake Trout
4
21.0
-
28.0
0.37
—
0.76
Smallmouth Bass
9
9.0
-
18.0
0.27
-
0.65
White Iron L.
Walleye
26
11.0
-
21.5
0.26
_
0.78
15
Northern Pike
25
15.2
-
23.7
0.21
-
0.58
24
White Suckers
20
12.8
-
20.0
0.03
-
0.27
Yellow Perch
25
5.2
-
10.6
0.10
-
0.68
Fall L.
Walleye
24
9.3
-
18.8
0.21
—
0.53
25
Northern Pike
25
14.0
-
40.7
0.15
-
1 .29
23
White Suckers
24
8.8
-
22.1
0.04
-
0.35
Yellow Perch
24
5.2
-
11.3
0.09
-
0.50
Gunflint L.
Walleye
24
10.0
-
26.0
0.21
_
1.23
16
Northern Pike
18
14.0
-
28.0
0.12
-
0.56
29
Colby i.
Northern Pike
20
6.7
-
21.0
0.09
—
0.80
18
White Suckers
21
13.1
-
19.6
0.09
-
0.62
Yellow Perch
25
5.3
-
8.6
0.15
-
0.53
Greenwood L.
Northern Pike
25
14.9
-
27.7
0.31
_
0.75
19
White Suckers
25
8.5
-
18.8
0.07
-
0.56
Yellow Perch
25
5.4
-
10.9
0.08
-
0.68
Gabbro L.
Northern Pike
21
17.6
-
34.5
0.22
0.95
22
White Suckers
25
8.8
-
22.0
0.03
—
0.20
Yellow Perch
25
5.7
-
9.6
0.08
-
0.88
Pike River
Walleye
8
14.2
-
29.0
0.46
-
1.50
18 (est.)
19 (est.)
22 (est.)
185
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Table D- £
Relative sizes (inches) and mercury content (ppm) of walleye from 12 Northern Minnesota waters, 1977.
Total
0.5 ppm
Hg and
over
Under
0.5 ppm
Hg
Under
15"
15" and
over
Under 15",
under 0.5 ppm
Under 15",
0.5 ppm and
over Hg
15" and over,
under 0.5 ppm
15" and over,
0.5 ppm
and over
Basswood L.
28
16
12
9
19
7
2
5
14
Burntside L.
6
2
4
3
3
3
0
1
2
Fall L.
24
2
22
17
7
17
0
5
2
Kabetogama L.
26
0
26
8
18
8
0
18
0
Gunflint L.
24
10
14
8
16
8
0
6
10
Namakan L.
10
2
8
5
5
3
2
5
0
Sand Point L.
8
6
2
2
6
1
1
1
5
Pelican L.
6
2
4
2
4
2
0
2
2
Vermilion L.
30
2
28
12
18
12
0
16
2
Trout L.
25
6
19
9
16
8
1
11
5
Pike River
8
5
3
1
7
1
0
2
5
White Iron L.
26
9
17
17
9
14
3
3
6
Total
221
62
159
93
128
84
9
75
53
Z, based on
221 fish
100
28
72
42
58
38
4
34
24
128 fish 15" and over; 59Z under 0.5 ppm, 41Z 0.5 ppm and over.
93 fish under 15"; 902 under 0.5 ppm, 10Z 0.5 ppm and over.
-------
Table D- 10
Relative sizes (inches) and mercury content (ppm) of pike from 14 Northern Minnesota waters, 1977,
Under 21",
21" and over,
0.5 ppm
Under
Under
21" and
Under 21",
0.5 ppm
21" and over,
0.5 ppm
Total
and over
0.5 ppm
21"
over
under 0.5 ppa
and over
under 0.5 ppa
and over
Basswood L.
25
10
15
13
12
10
3
5
7
Burntside L.
34
8
26
2
32
2
0
24
8
Fall L.
25
8
17
17
8
16
1
I
7
Kabetogama L.
10
0
10
4
6
4
0
6
0
Gunflint L.
18
1
17
12
6
12
0
5
1
Namakan L.
4
0
4
3
1
3
0
1
0
Sand Point L.
7
5
2
4
3
4
0
1
2
Pelican L.
25
2
23
14
11
14
0
9
2
Vermilion L.
22
0
22
5
17
5
0
17
0
Trout L.
5
2
3
1
4
1
0
2
2
White Iron L.
25
1
24
18
7
18
0
6
i
Colby L.
20
9
11
19
1
11
8
0
1
Greenwood L.
25
7
18
22
3
18
4
0
3
Gabbro L.
21
12
9
10
11
8
2
4
7
Total
266
65
201
144
122
126
18
81
41
X, based on
266 fish
100
24
76
54
46
47
7
30
15
122 fish 21"
and over;
34Z 0.5 ppm
and over
, 66Z under 0.5 ppm.
144 fish under 21"; 12
.SX 0.5 ppm
and over,
87.52
under 0.5 ppm
•
-------
oc
30
8.
c
Lake Surface Area (hectare)
Figure D-ll DISTRIBUTION OF LAKE SURFACE AREAS FOR BWCA AND FALL 1973 SAMPLING.
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