United States
Environmental Protection
Agency
Environmental Research
Laboratory
Duluth MN 55804
Research and Development
EPA-600/S3-84-070 July 1984
Project Summary
Impacts of Coal Combustion on
Trace Elements in the
Environment: Wisconsin Power
Plant Impact Study
Philip A. Helmke, Wayne P. Robarge, Myles B. Schoenfield, Paula Burger,
Robert D. Koons, and John E. Thresher
This report describes the influence of
the Columbia Generating Station on
trace elements in the environment
surrounding the plant. It is part of a
larger study which documents a broad
spectrum of environmental impacts
stemming from construction and oper-
ation of a 1050 MW coal-fired power
plant in south central Wisconsin.
Samples of coal, fly ash. aerosolic
dust, material from the ash pit, and
organisms living in the vicinity of the
power plant were analyzed to deter-
mine the partitioning of elements
during combustion; the distribution of
fly ash particles according to size; the
composition of aerosolic dust; the
distribution of fly ash from the Columbia
power plant in the environment sur-
rounding the generating station; the
processes of devitrification and recrys-
tallization taking place in the ash pit; the
effects of fly ash effluent on concentra-
tions of elements in aquatic organisms
living in the drainage system of the ash
pit; the effects of aerosolic dust on oak
leaves, including possible injury and the
trace element composition of the
leaves.
Analytical methods included electron
microscopy, x-ray fluorescence, x-ray
diffraction, and neutron activation.
During combustion, a marked frac-
tionation of elements takes place, which
results in the enrichment of volatile
elements on the surface of fly ash
particles. This fractionation is related to
factors such as the size and resistivity
of fly ash particles. Concentrations of
Fe decrease in the last stages of the
electrostatic precipitators, but those of
Hf, K, and Se remain about the same,
and all others increase. The potential
effects of reactive trace elements
concentrated on particle surfaces may
be overlooked if only the bulk elemental
composition of the particles is considered.
In terms of bulk composition, only
boron potentially poses an obvious
problem in agricultural uses of fly ash.
There was no significant evidence of
damage to oak leaves from aerosolic
dust in general or from Columbia fly ash
in particular or of any effect of fly ash or
dust on the elemental composition of
oak leaves. In the studies of aquatic
invertebrates, concentrations of Ba, Cr,
Se, and possibly Sb were significantly
higher in animals taken from the
drainage system of the ash pit than in
controls. Guidelines were established
for selecting test species and proce-
dures developed for estimating the
contribution of contamination from
sediments and gut contents to the
analytical results.
This Project Summary was developed
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).
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Introduction
The full report is one of a series on the
environmental effects of the Columbia
Generating Station, a 1050 MW coal-
fired power plant in south central
Wisconsin The first unit of the plant
began operation in April, 1975, and the
second, in June, 1978. Each unit burns
about 4535 metric tons/day of pulverized,
low sulfur, subbitummous western coal,
which has an ash content of 7 to 8%.
The broad goal of the project was to
document environmental change resul-
ting from construction and operation of
the power plant Within that framework,
the goal of this study was to determine
the influence of the power plant on trace
elements in the environment surround-
ing the plant. The goal suggested three
specific objectives.
• To measure the distribution and ele-
mental composition of fly ash and
possible volatile materials in the vi-
cinity of the generating station
• To elucidate the reactions and fate of
fly ash m the environment.
• To assess the availability of trace ele-
ments in fly ash to the biota
Methods
Coal, Fly Ash, and Aerosolic
Dust
The purpose of these analyses was to
determine the partitioning of elements
during combustion, the distribution of
fly ash particles according to size, the
composition of aerosolic dust, the distri-
bution of fly ash from the Columbia
Generating Station in the environment
surrounding the station, andtheprocess-
es of devitrification and recrystallization
taking place in the ash pit. For these
studies, samples were obtained as
follows
1. The Wisconsin Power and Light
Company (WPL) provided samples of
coal burned at Columbia on various
dates in 1975 and 1978. For com-
parison, samples of an eastern coal
from Illinois were also analyzed.
2 WPL collected fly ash from each of
the stages of the electrostatic precip-
itators and from the base of the
stack. They also provided one sample
of bottom slag.
3 Samples were dug from the upper 60
cm of material in the ash pit
4 Water was collected from the ash
pit and its drainage system. The
water was filtered through 0.45 /urn
Millipore filters to separate particu-
late material, and both filtrate and
residue were analyzed
5. Aerosolic dust was collected in
fallout buckets at eight sites around
the power plant, up to a distance of
1 9 km. In the laboratory, contents of
the buckets were washed onto 0 45
or 0.1 fjm Millipore or Nucleopore
filters. After filtration, the filters
were dried at 60 °C and the weight of
the collected particles was deter-
mined
All samples were analyzed by neutron
activation procedures to determine their
content of trace elements. For some
samples, major elements were deter-
mined by x-ray fluorescence. In selected
cases, determinations were made of both
total composition and surface composi-
tion of fly ash particles. Mineral species in
samples from the ash pit were identified
by x-ray diffraction and electron micro-
scopy.
Aquatic Invertebrates
The primary objective of this part of the
study was to determine the effects of ash
effluent on the concentration of elements
in aquatic organisms living in the
drainage system of the ash pit. Experi-
mental animals represented three genera
of crustaceans and seven genera of
insects (Table 1) These organisms were
usually abundant in the study area, they
are near the base of ecologically impor-
tant food chains, and they represent a
variety of types of feeders.
The general approach for determining
the impact of the generating station was
to compare elemental concentrations in
animals collected before and after the
station went into operation After the
station began operating, additional
control specimens were taken from
nearby sites not affected by the ash
effluent.
Specimens were collected with a nylon
dip net or in artificial substrate samplers.
They were washed in distilled-deionized
water, blotted dry, counted, weighed, and
frozen. For analysis by nondestructive
neutron activation, samples were freeze-
dned, weighed, and irradiated m the
University of Wisconsin nuclear reactor
Samples and standards were radioassayed
at various times after irradiaton, by
methods described m the literature.
Oak Leaves
The small percentage of fly ash that
escapes the electrostatic precipitators
and leaves the stack of modern coal-fired
power plants is dispersed widely in the
environment. This fly ash, together with
other anthropogenic and natural dusts,
forms the aerosolic dust that is continu-
ously removed from the atmosphere by
various processes. Part of it is deposited
on vegetation, where certain elements
theoretically could dissolve and cause
injury or be taken up by the plant. Oak
leaves were chosen for determining
whether such injury or uptake does
occur, because oaks are common in the
study area and their deep and extensive
root systems should minimize variations
in the uptake of elements from the soil.
The objectives of this part of the study
were to establish baseline data for oak
leaves as a foundation for future studies
and to determine the effect, if any, of fly
ash from the Columbia Generating
Station on oak leaves.
Leaves from white oak (Quercus alba),
black oak (Q. velutina), and red oak (Q.
rubra) were collected at four sites up to 12
km from the power plant. Leaves were
sampled four times during each growing
season.
Electron microscopy with x-ray fluo-
rescence revealed the types of inorganic
particles on the leaf surface. These
particles could not be removed effectively
by washing. Elements such as Sc, Ga,
and Hf, which do not accumulate signifi-
cantly in leaves but occur at relatively
high concentrations m inorganic dusts,
were used to indicate the extent of
inorganic contamination. Leaf samples
were analyzed by nondestructive and
radiochemical neutron activation.
Table 1 . Taxonomic Information for Invertebrates Analyzes
Class Order Family
Crustacea
Insecta
Amphipoda
Isopoda
Coleoptera
Hemiptera
Odonata
Gamandae
Tahtridae
Asellidae
Gyrmidae
Corixidae
Aeshnidae
Corulndae
Libelluhdae
Genus and species
Gammarus
Hyallela azteca
Asellus racovitzai
Dineutus
Hesperocorixa
Sigara
Anax
Tetragoneuria
Libellula ,
Sympetrium '
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Findings and
Recommendations
Coal, Fly Ash, and Aerosolic
Dust
Table 2 presents results of some
analyses of coal andflyash, includingone
sample of bottom slag. Although the bulk
composition of coal burned at the power
plant varies slightly from batch to batch
and the bulk composition of fly ash also
varies, these results are typical.
The major portion of each element in the
coal is associated with silicates or other
inorganic constituents rather than with
the carbon The high concentrations of Ca
in coals from Wyoming and Montana
result from their high content of CaCOs,
which is usually accompanied by low
concentrations of other elements except
for Mg, Sr, and Ba. By comparison,
samples of eastern coal from Illinois had
relatively high levels of such elements as
As, Cr, Fe, Rb, Se, and Zn.
During the gaseous phase of combus-
tion, particles of fly ash form a highly
reactive surface on which elements that
are volatile at the temperature of the
flame condense as heat is extracted from
the flue gas The fractionation of the
elements is related to various factors,
including size and resistivity of particles
as well as condensation of volatile
elements. Thus, concentrations of Fe
decrease in the last stages of the
precipitator, those of Hf, K, and Se remain
about the same, and all others increase
The surface enrichment of certain
elements, many of which are toxic,
represents one of the potentially harmful
environmental impacts of fly ash Previous
assessments of the possible impactsof fly
ash have underestimated the potential
availability of those elements concen-
trated on the surface. A comparison of
surface analysis and bulk analysis shows
surface-bulk ratios of 33:1 for Th, 3 5 1
for Cr, 11.7.1 for Zn, and 2 5'1 for As.
Disposal or use of fly ash must be
carefully evaluated with this surface
enrichment in mind To add to the
complexity of the problem, some particles
Table 2. Elemental Composition (ng/g) of Coal and Ash Samples, as Determined by Neutron
Activation Analysis
Element
As
Ba
Ca
Cd
Ce
Co
Cr
Cs
Cu
Eu
Fe
Ga
Hf
Hg
K
La
Lu
Mn
Na
Nd
Rb
Sb
Sc
Se
Sm
Tb
Th
U
Yb
Zn
Coal"
10
640
1 1,500
62
0.46
3.8
0 12
7.0
0.09
2,600
0 76
0.03
228
3.7
004
T16
170
29
1.4
0.76
1.0
0.08
0.52
001
2.2
056
024
49
Bottom
slag2
1 7
4,500
94,000
-
59
66
36
087
-
1 7
9,400
10
-
3,100
35
046
-
2,200
30
-
1 5
89
22
52
0 77
21
35
3 1
Stage 13
8.0
7,200
9.1
0.9
70
7.8
38
1'2
60
0.97
7,900
24
88
<0002
0.35
37
048
860
1,900
29
16
42
98
28
57
1.2
22
7
29
50
Stage 23
21
8,200
12
1 6
96
11
64
1.5
90
1 3
69
52
86
<0002
044
52
062
1,100
2,400
40
24
9 1
14
26
8.1
1 6
29
10
35
79
Stage 33
24
10.000
13
1 5
99
11
68
1 4
100
1 4
34
61
88
<0003
036
54
0.64
1,100
2,400
42
18
11
14
3 1
85
1.6
30
12
34
83
Ash pit
particles'
13
17,000
11,000
14
2.5
130
1 4
020
2.8
0 77
-
1,700
7 7
0 17
820
13
5
50
1 7
1 4
0 15
3 1
24
036
38
^Average values for four samples burned in May 1975
2S'ample taken September 5, 1975.
3Samples taken September 5, 1975, from electrostatic precipitators. Stage 1 represents material
closest to combustion chamber. Stage 3, material closest to stack.
^Suspended material from ash pit water as it enters the drainage ditch and is diluted with water from
outside the system
of ash are hollow and contain smaller
particles, presenting the theoretical
potential for timed-release effects which
may not be observable until some future
date.
Fly ash from the Columbia power plant
has some of the highest concentrations of
Ca and Ba reported, and its reaction when
mixed with water is strongly basic
Because of the high content of Ca, the fly
ash has potential as a liming agent on
agricultural soils Ability to control
fugitive dust during application and to
retard the availability of free lime so that
larger, less frequent applications could be
made would enhance the usefulness of
fly ash in agriculture. Again, the possible
toxicity of readily available surface
constituents should be considered. In
bulk analyses, Hg is found in uniformly
low concentrations in all samples Levels
of B, which ranged from 500 to 800/ug/g,
are high enough to cause symptoms of
severe boron toxicity in plants if large
amounts of fly ash were applied to the
soil. Bulk concentrations of B, Ba, Ca, Na,
Sb, and Se are greater in Columbia fly ash
than in most soils, but only B potentially
poses an obvious problem in the useof fly
ash as a soil amendment
The mean size of fly ash particles
decreases from stage to stage of the
electrostatic precipitators It is primarily
the smallest particles, along with gases,
that escape from the stack Particles of fly
ash can be distinguised from other dust
by their shape, as revealed through
electron microscopy Dust particles are
angular, while fly ash particles are
spherical
Fly ash from the Columbia plant can be
further differentiated by its chemical
composition and by the smooth, glassy
surface of its particles Particles of fly ash
that have come from sources at greater
distances have a pitted surface. X-ray
fluorescence analysis showed that back-
ground fly ash had concentrations of
Si>AI, K>Ca, and detectable concentra-
tions of S, Cr, Mn, Co, and Na Columbia
fly ash had concentrations of Si=AI and
Ca>K, and the other elements were
present at very low or undetectable
levels
The flux of fly ash deposited in fallout
buckets was a few tenths of a mg/m2/day
over a period of one month Ash from
Columbia generally made up less than
10% of the total, except when a fumiga-
tion occurred Samples collected in
fallout buckets had bulk concentrations
of most trace elements similar to those in
local soil, although Br, Hg, Sb, Se, and to a
lesser extent U, Th, and Zn were at
significantly higher levels in the dust. Fly
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ash may be the source of the excess Sb,
Se, Th, and U, but it is definitely not the
source of excess Hg. It is also possible
that the same processes that result in
enrichment of fly ash in certain elements
are responsible for the high concentra-
tions of these elements in other aerosolic
dusts as well.
Fresh fly ash consists mostly of glassy,
amorphous material. Small amounts of
quartz, anhydrite, magnetite, hematite,
periclase, and CaO are in the fly ash from
Columbia. Several new minerals form
after the ash is mixed with water and
slurned to the ash pond, the most
important being the calcium aluminate
sulfates and calcium aluminate silicates
These minerals contribute to the strength
and properties of Portland cement and,
undoubtedly, to the hardness of the fly
ash in the ash pond. Further research
should explore the pozzolanic reactions of
fly ash so that new uses for the ash can be
developed. Similar reactions may reduce
SCU pollution in other wastes, because
calcium aluminate sulfates are much less
soluble than gypsum.
Concentrations of dissolved Al, Ba, Ca,
and Cr as CrO42~ are much higher in
water from the ash pit and its drainage
system than in unaffected waters. Some
of theCrC>42~ is reduced to Cr3+ in the lower
portions of the drainage system, where it
precipitates as Cr(OH)3. AI(OH)3 also
precipitates as the pH decreases. The
system is saturated with BaSO/i, which
precipitates as water from the ash pit is
diluted with less basic water. All these
materials coat the substrate of the
drainage system and may disrupt the
habitat and life cycles of organisms living
in the water
Aquatic Invertebrates
To be useful in the monitoring of trace
elements in ecosystems, an organism
should be relatively common and be dis-
tributed throughout the study area, be
amendable to collection and analysis, and
have been present long enough to reflect
conditions at the site of collection. It
should also be able to survive in a wide
range of conditions, have concentrations
of trace elements that are high enough to
be correlated with environmental condi-
tions and high enough for accurate and
precise analysis Of the organisms listed
in Table 1,/4se//t/sracowfza/andOdonata
meet these criteria best.
One of the difficulties in measuring the
uptake of trace elements by aquatic
organisms is eliminating contamination
by sediments and ingested food. After
mixed success in attempts to wash the
animals and keep them alive in clean
water until their guts were empty, Scwas
chosen as the best indicator of inorganic
contamination, and the effects of extra-
neous material on the elemental composi-
tion samples of organisms was estimated
from mterelement ratios and a mass
balance for each element. The degree of
contamination was related to the habitat
and feeding patterns of the organism
Benthic detritus-feeders such as A.
racovitzae were the most contaminated,
the herbivorous Corixidae and Gammarus
species had an intermediate level of
contamination; and the surface feeding
Dineutus species were least contami-
nated. Carnivores may be contaminated
by the gut contents of their prey.
Of the elements studied, the concen-
trations of Ba, Cr, Se, and possibly Sb
were significantly higher in aquatic
invertebrates taken from the drainage
system of the ash pit than in controls. The
differences were most easily measured in
A. racovitzai, but they were also evident
in Hyallela azteca and Odonata. Data for
A. racovitzai, corrected for contamination,
show Se 10 to 20 times higher than in
controls, Cr<1//g/g in controls but up to 7
/ug/g in affected samples, and Ba from 2
to 10 times higher than in controls. In
addition to providing information on the
bioavailability of elements in the ash
effluent, these results can form a base for
future studies of the effects of trace
elements on organisms.
Oak Leaves
Aerosolic dust is deposited on leaf
surfaces and a significant portion of this is
fly ash. The amount of fly ash increases
throughout the growing season, indicat-
ing that wind and rain do not remove fly
ash from leaves very efficiently
Tracer studies showed that oak leaves
do not bioaccumulate Sc. Assuming that
all the Sc found in the analysis of oak
leaves represented contamination by
aerosolic dust, the proportion of other
elements contributed by dust can be
calculated by a method similar to that
used for aquatic invertebrates Results
indicate that most of the Ba, Br, Ca, Cs,
Cu, Hg, K, Rb, and Zn found in the leaves
was indigenous; most of the La, Sb, Sc,
and Sm was from aerosolic contamina-
tion; and the content of As, Co, and Fe was
derived from both sources. Levels of As,
Sb, Se, Hg, Th, and U (toxic elements of
concern in this study) were consistently
low or below detection limits.
Concentrations of various elements in
oak leaves change rapidly during devel-
opment of leaves in May and June but
remain relatively constant thereafter. The
elemental composition of oak leaves is
similar from year to year and from site to
site for any given stage of the growing
season.
Although no effects of fly ash from the
Columbia power plant were detected in
this study, future studies should search
for possible physical effects of alkaline or
acid particles of fly ash on leaves. Data
presented in the full report serve as a
baseline for future studies evaluating the
additional loading of the atmosphere with
aerosolic dust as new facilities come into
operation
&U. S. GOVERNMENT PRINTING OFFICE: 1984/759-102/10628
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Philip A. Helmke, Wayne P. Robarge. Myles B. Schoenfield, Paula Burger, Robert
D. Koons. and John E. Thresher are with Water Resources Center and Institute
for Environmental Studies, University of Wisconsin-Madison, Madison, I/I//
53706.
Gary E. Glass is the EPA Project Officer (see be low).
The complete report, entitled "Impacts of Coal Combustion on Trace Elements in
the Environment: Wisconsin Power Plant Impact Study," (Order No. PB 84-207
638; Cost: $13.00, subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA22J61
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Environmental Research Laboratory
U.S. Environmental Protection Agency
Duluth, MN 55804
United States-
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
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