vvEPA
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United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
Research and Development
EPA-600/S3-82-068 Oct. 1982!
Project Summary
Impact of Air Pollution on
Vegetation Near the
Columbia Generating Station
Wisconsin Power Plant
Impact Study
T. W. Tibbitts, S. Will-Wolf, D. F. Karnowsky, and D. M. Olszyk
This report documents the extent of
air pollution from the 1050 MW coal-
fired Columbia Generating Station
and its impact on vegetation. The
station, located in south central
Wisconsin, began operation in 1975.
Monitoring activities began in 1971
and continued through 1978.
Background concentrations of SO2
and NO2 were generally higher than
amounts emitted from the power
plant. SO2 emissions produced an
average of two fumigations per month
at ground level, at concentrations
between 100 and 250 /ug/m3 for two-
to three-hour periods. At one station,
a maximum of 389 /ug/m3 was re-
corded. NO2 emissions produced
fumigations at concentrations between
60 and 80 /ug/m3 for two- to three-
hour periods, with a maximum of 101
/ug/m3 for one hour. Ambient ozone
levels occasionally reached 140 to
180 /ug/m3. A maximum of 311
/ug/m3 was recorded with clear skies
and southerly winds.
Alfalfa, lichens, and white pine were
sampled in the field before and after
the power plant began operating.
Alfalfa showed no visible evidence of
injury from air pollutants, and there
was no change in yield of harvestable
forage at 16 sites. Samples of alfalfa
collected in 1978 contained signifi-
cantly more S than samples collected
in 1974, but both values were within
the optimum range of S content for
alfalfa and within the range of the
normal annual variation of S uptake
from soil.
Each year, before the power plant
began to operate, from 1 to 4% of
white pine trees at 15 sites showed
injury to needles from air pollution.
This proportion did not increase after
the station began operating; nor did
operation of the power plant cause a
decrease in the number of species of
lichens on oak trees at 29 sites. A few
species showed statistically signifi-
cant changes in distribution between
the 1974 sampling and the 1978
sampling, but these changes were of
questionable importance because the
species involved were relatively un-
common, occurring on less than 10%
of the trees.
Studies in open-top field chambers
revealed no measurable effect of air
pollution on growth or yield of alfalfa.
However, the large variations of yield
in the field plot limited the significance
of comparisons. Furthermore, levels
of radiation and evaporation differed
between open areas and the experi-
mental chambers.
In controlled environment studies of
crop species grown in the area.
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varieties of alfalfa, carrots, mint, peas,
beans, and trembling aspen were
exposed to SO2 and O3 to establish
threshold levels for injury- All species
tested had thresholds for SO2 higher
than concentrations recorded around
the generating station, and only
trembling aspen had a threshold for O3
lower than concentrations found
around the station. When plants were
exposed to SO2 and O3 in combina-
tion, thresholds for injury were lowered.
Again, only trembling aspen was
injured by a combination of SO2 plus
Oa that was less than the levels of
these pollutants around the generating
station.
This Project Summary was devel-
oped by EPA 's Environmental Research
Laboratory, Duluth, MN, to announce
key findings of the research project
that is fully documented in a separate
report of the same title (see Project
Report ordering information at back).
Background
The research described in this report
was undertaken to document the
incidence of injury by air pollution to
terrestrial vegetation, before and after
a new power plant began operating. The
study area was within a circle of radius
15 km from the Columbia Generating
Station near Portage, in south central
Wisconsin. This is an area of rolling
farmland, the only major elevation
being a ridge rising 200 to 250 m above
the station, to the west. Prevailing
winds are southwesterly during sum-
mer and northwesterly during winter.
The only other important source of air
pollution within 120km of the site is the
Madison metropolitan area, with its
population of 225,000.
The Columbia Generating Station
burns subbituminous western coal with
an average sulfur content of 0.8%. It has
two generating units, each with a
capacity of 527 MW. The first unit went
on line in March 1975, and the second,
in June 1978. This study covers the
period from 1971 through 1978.
Approach
This study consisted of three major
areas of research:
1. Monitoring of ambient air nearthe
generating station. This was to
establish background concentra-
tions of major air pollutants before
the power plant began operating
and, later, to measure emissions
from the station itself. The pollu-
tants monitored were nitrogen
oxides (NOX), sulfur dioxide (SO2),
and ozone (O3).
2. Field sampling of several plant
species known to be bioindicators
of SC»2. Species sampled regularly
were alfalfa (Medicago saliva L.),
eastern white pine (Pinus strobus
L.), and lichen species growing on
black oaks. Two other sensitive
native species, blackberry (Rubus
sp.) and giant ragweed (Ambrosia
trifida L.), were observed in con-
junction with the alfalfa sampling.
3. Controlled environment experi-
ments to measure threshold levels
of sensitivity to SO2 and Oa and to
determine dose-response rela-
tionships. Test species included
varieties of five crops commonly
grown in the vicinity of the power
plant and one tree species, trem-
bling aspen (Populus tremuloides
Mich.). The crop plants were
varieties of pea (Pisum sativum L.},
carrot (Daucus carota L.), mint
(Mentha piperita L), bean (Phase-
olus vulgaris L.), and alfalfa.
Specific measurements were made as
described below:
1. Four SO2 monitors were placed
within 10 km of the station and
two more at 15 km. NOX and Os
were monitored at two sites within
10km.
2. Fifteen white pine plantations of
from 20 to 350 trees were moni-
tored. These plantations were
within 12 km of the power plant, in
all directions from it. Each tree
was checked for foliar injury
during the fall, and at the end of
the study needles were sampled
from six sites for determination of
their S content.
3. Samples of lichens were taken
from 10 black oak trees at each of
29 sites in the winter before the
plant went into operation and from
10 adjacent trees at each site at
the end of the study. Trees were
chosen at 5, 10, 16, 32 and 48 km
from the station. On each tree
sampled, two quadrats of bark 25
cm on a side and 1.4 m above the
ground were sampled. One was on
the side facing the generating
station and the other was on the
opposite side Bark was removed
and taken to the laboratory for
species identification.
4. A permanent network of monitor-
ing sites for alfalfa was established
in 1971. In subsequent years, if
the field was planted in another
crop or if the alfalfa stand became
very poor, a new field was chosen
within 0.5 km of the original one
No site was within 18 m of a road
or field boundary. Sites were
sampled three times during each
summer, just before the normal
harvesting times. After plants
were scored for the degree of
chlorosis and necrosis of the
leaves, yield was determined by
fresh and dry weights of all the
plants in four 0.2 m2 plots at each
site. S content of the leaves was
determined from the first harvest
in 1973 and 1978.
5. Nine plots of alfalfa were estab-
lished for tests in open-top field
chambers. Three plots had cham-
bers with charcoal filters, three
had chambers without filters, and
three were open field plots with no
chambers. The alfalfa in each plot
was harvested three times during
one growing season, to determine
leaf injury, plant height, and yield.
Levels of radiation and rates of
evaporation were measured in all
plots.
6. Varieties of peas, beans, carrots,
alfalfa, and mint were grown in
controlled-environment rooms
under conditions which produced
succulent plants sensitive to
pollution. Two plexiglass chambers
were used for experiments. In the
control chamber, plants were
maintained in filtered "clean" air
In the fumigation chamber, plants
were exposed to different concen-
trations of S02 and O3 for varying
lengths of time. The extent of
visible injury to the leaves was
established or measured for each
species, and the chlorophyll con-
tent of pea, bean, and alfalfa
leaves was determined. Similar
studies were done on green-
house-grown plants from trembling
aspen root cuttings.
Findings and Conclusions
Air Pollution Monitoring
Emissions from the generating station
caused ground-level fumigations of
SOa at concentrations of from 50 to 350
//g/m3. These episodes usually lasted
two or three hours. Levels exceeding
240/ug/m3 (0.10 ppm) occurred during
no more than five hourly intervals per
year at any site, and did not occur at all
at distances greater than 10 km from the
station. The average number of fumiga-
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tions per month per site was 1.8 (Table 1
and Figure 1).
NOa emissions produced fumigations
at concentrations between 60 and 80
fjg/m3 for two- to three-hour periods,
with a maximum of 101 /ug/m3 for one
hour.
There is evidence that the major part
of the SOa and NOX recorded by
monitors originated in urban areas to
the south, from Madison and Chicago
and perhaps as far as St. Louis.
Ambient ozone levels occasionally
reached 150 to 180 /yg/m3. With clear
skies and southerly winds, a maximum
of 311 fjg/m3 was recorded.
• Continuous monitoring for S02,
NOX, and Oa indicated that levels of
these emissions from the gener-
ating station were low in compari-
son to background levels and were
not high enough to cause serious
damage to plants.
Effects on White Pines
Tipburn injury occurred on an average
of from 2.3% to 2.5% of white pines both
before and during operation of the
generating station. The number of
injured trees varied considerably from
year-to-year. This variation probably
resulted not only from variations in
levels of pollutants but also from
variations in growing conditions which
caused greater or lesser sensitivity to
pollutants.
Although both SOaandOaoccurredat
levels capable of causing injury to white
pine, the frequency of potentially
harmful Oa levels was much higher than
that for S02. It is likely, therefore, that
the injury observed was due primarily to
03.
The S content of pine needles did not
differ significantly in different directions
from the generating station, nor was S
content correlated with the amount of
tipburn observed. The results of this
sampling were not conclusive, how-
ever, because of the large variation m S
levels between trees at the same site.
• Needles of white pine showed
evidence of tipburn injury from
ambient levels of SO2 and O3. This
injury resulted from background
levels of pollutants, primarily Os. It
did not increase after the power
plant began operating.
Effect on Lichens
There were no decreases in either the
number of lichen species or in the
frequency of their occurrence. Statisti-
cally significant changes did occur in
Table 1. Number of Days with Fumigations of SOz at Monitoring Sites Near the
Columbia Generating Stations from May 1976 through June 1978*
Period with
Site
Lake George (6 km E)
Dekorra (4 km SSW)
Messer (8 km W)
Genrich (8 km N)
Bernander (14 km E)
Russell (16 km NE)
Total
(days)
49
55
35
60
55
34
Monthly A verage
(days)
1.9
2.1
1.3
2.3
2.1
1.3
Valid Data
91
95
96
94
96
93
*A fumigation was defined as the occurrence for at least a one-hour period of
concentration at one site that exceeded by 50 ug/m3 the average concentration at the
other sites during a time when the wind direction was ± 45° from the Columbia
Generating Station toward the site.
O Approximate location of stack
• Air pollution monitoring sites
Figure 1. Location of air pollution monitoring sites around the Columbia Gen-
erating Station.
the distribution of 3 of the 48 species
identified, but these species were found
on less than 10% of the trees sampled
and at less than half of the sites. The
rarity of these species makes it difficult
to evaluate the importance of the
changes observed.
• Air pollution from the power plant
had no effect on populations of
lichens growing on black oaks.
> US GOVERNMENT PRINTING OFFICE 1882-559-017/0849
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Effects on Alfalfa and
Native Plants
Alfalfa, blackberry, and giant ragweed
showed no symptoms of injury from
S02. The amount of chlorosis and
necrosis on the plants did not increase
when the power plant began operating.
Yields of alfalfa varied greatly from
field to field and from year to year.
However, no consistent decreases oc-
curred after the station began operating,
even in those fields experiencing the
greatest increases in SO2 from the
station.
Sulfur levels in alfalfa leaves were
higher in 1978 than in 1974. This
increase, however, was within the
range of normal annual variation and
was well below levels that would cause
injury to the tissue. In fact, many of the
alfalfa fields in Wisconsin are deficient
in S, and additional S from the power
plant might benefit the crop.
Data from the experiments with field
chambers documented differences in
the microenvironments of the chambers
versus the open field. Radiation levels in
all plots were approximately the same
when the sun was either low in the sky
or near the zenith, but during morning
and afternoon levels were about 15%
lower in the chambers. Rates of evapo-
ration were higher in the open plots;
which subjected plants in the open plots
to greater water stress, probably ren-
dering them less sensitive to pollution.
Growth of plants in the chambers was
faster than that of field-grown plants
early in the season, and at the end of the
season the chambers protected the
plants from early frosts.
• Alfalfa fields surrounding the
power plant exhibited no evidence
of air pollution injury. The sulfur
concentration of alfalfa forage did
not exceed normal levels.
Experiments in open-top field
chambers failed to demonstrate
any effect of ambient pollution on
growth and yield of alfalfa.
Controlled Environment
Studies
The experimental species exhibited
large differences in sensitivity to S02
and Oa. The most sensitive species was
trembling aspen. Although the thresh-
old level for injury from S02 was higher
than any levels monitored around the
power plant, the threshold for injury
from Os was belowthe high background
concentrations found in the area a round
the power plant.
Among crop plants, the most sensitive
were alfalfa and peas. Even these
species, however, had sensitivity thresh-
olds above the maximum levels of
pollutants recorded in the field. For
peas, the threshold level of sensitivity
to combinations of SO2and 03 was only
slightly higher than maximum levels of
these substances in the field. Neverthe-
less, the chance of injury from the
combination of pollutants is small
because elevated concentrations of the
two pollutants rarely occur simulta-
neously.
• Crop plants are not threatened by
the concentrations of air pollutants
commonly found around the Co-
lumbia Generating Station. Occa-
sional high levels of Os may cause
minor injury to trembling aspen.
T. W. Tibbitts, S. Will-Wolf, D. F. Karnowsky. and D. M. Olszyk are with the
Institute for Environmental Studies, University of Wisconsin, Madison, Wl
53706.
Gary E. Glass is the EPA Project Officer (see below).
The complete report, entitled "Impact of Air Pollution on Vegetation Near the
Columbia Generating Station: Wisconsin Power Plant Impact Study," (Order
No. PB 82-258 591; Cost: $19.50, subject to change) will be available only
from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
6201 Congdon Blvd.
Duluth, MN 55804
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
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Fees Paid
Environmental
Protection
Agency
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Penalty for Private Use $300
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