United States
Environmental Protection
Agency
Research and Development
Office of Energy. Minerals, and
Industry
Washington DC 20460
EPA-600/7-78-146
July 1978
An Assessment
of Mercury Emissions
From Fossil Fueled
Power Plants
Interagency
Energy/Environment
R&D Program
Report
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4 Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Inleragency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the INTERAGENCY ENERGY-ENVIRONMENT
RESEARCH AND DEVELOPMENT series. Reports in this series result from the
effort funded under the 17-agency Federal Energy/Environment Research and
Development Program. These studies relate to EPA's mission to protect the public
health and welfare from adverse effects of pollutants associated with energy sys-
tems. The goal of the Program is to assure the rapid development of domestic
energy supplies in an environmentally-compatible manner by providing the nec-
essary environmental data and control technology. Investigations include analy-
ses of the transport of energy-related pollutants and their health and ecological
effects; assessments of. and development of, control technologies for energy
systems; and integrated assessments of a wide range of energy-related environ-
mental issues.
This document is available to the public through the National Technical Informa-
tion Service, Springfield. Virginia 22161.
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AN ASSESSMENT OF MERCURY EMISSIONS
FROM
FOSSIL FUELED POWER PLANTS
BY
GERALD R. GOLDGRABEN
PAUL CLIFFORD
KITKRICKENBERGER
NORMAN ZIMMERMAN
DENNIS MARTIN
EPA Contract No. 68-01-3539
Project Officer
David Graham
Energy Processes Division
Office of Energy, Minerals and Industry
Office of Research and Development
Washington. D.C. 20460
Office of Energy, Minerals and Industry
Office of Research & Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
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DISCLAIMER
This report has been reviewed by Che Office of Energy, Minerals and
Industry, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
ii
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CONTENTS
Page
FIGURES iv
TABLES v
ACKNOWLEDGMENT vi
1 . Summary 1
2. Conclusions 5
3. Recommendations b
A. Introduction H
Objective K
Organization of the Report H
5. Biological Effects and the Regulation of Mercurv 10
Health and Ecological Effects 10
Standards and Regulations 14
6. Importance of Power Plant Emissions 24
Estimate of Mercurv Emissions from Power Plants 24
Relative Importance of Power Plant Emissions 29
Identification of Other Sources of Mercury Emissions 29
Quantitative Estimate of Emissions From Other Sources .... 35
Comparision of Power Plant Emissions with Emissions from
Other Sources 41
Mercury Emission Control and Projections 45
Technology of Power Plant Control Systems 45
Electrostatic Precipitators 45
Scrubbers 4^
Baghouses 47
Technology of Control Systems for Other Industries 47
Mining and Smelting 48
Chlor-Alkali Manufacturing 48
Mercurials 48
Electrical Apparatus 48
Industrial Instruments and Controls 48
Paint Manufacturing 48
Projected Mercury Emissions and Controls 49
7. Transport and Fate of Mercury Emissions from Power Plants 55
Conceptual Model and Intermedia Transfers 55
Significance of Power Plant Emissions on Ambient Concentrations . . 57
Air 58
Water 61
Soil 73
•Chemical, Physical and Biological Transformations 78
Air 78
Water 79
Soil 86
8. Literature Cited 88
iii
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FIGURES
Figure Number Page
1 Comparison of Mercury Losses Between Utilities
and Man-Made Sources by Region ( 1974) 44
2 Conceptual Cyclic Model of Mercury Transport in
the Environment 56
3 Common Pathways or Mercury Transformation in Water 80
4 Distribution of Mercury Compounds in the Environment 81
5 Phase Diagram for Solid and Liquid Mercury Species 84
6 Phase Diagram for Aqueous Mercury Species 85
iv
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TABLES
Number
Page
1 Mercury Content of Plants and Animals ............ 13
2 Mercury in Preserved Fish .................. 15
3 Mercury Content of Lake Ceoree Fish - 1970 ......... 16
4 Summary of Federal Regulations Limiting Mercury ....... 17
5 Summary of Coal and Oil I'sage for Electric
Power Generation for 1974 .................. 25
6 Mercury Content of Coals
1 Mercury Contribution from Electric Power
Generation by Region, 1974
8 Estimated Mercury Losses to Environment, 1974
9 Regional Distribution of Mercury Losses in the
United States in 1973
10 Proiected Mercury Losses to the Environment, 1983 50
11 Mercury Losses to the Environment - Ranked by Source .... 51
12 Summary of Atmospheric Mercurv Concentrations in
California 59
13 Compilation of Mercury Values for Dissolved,
Suspended, and Bottom Sediments 63
14 Summary of Mercury Content in Fresh Water Bodies
on a Regional Basis 71
15 Concentrations of Mercury in Soils of the Contiguous
United States 74
16 Metal Concentration Related to Land Use Patterns 75
17 Relative Solubilities of Mercury and Some Mercury
Compounds 82
18 Mercury Content of Ores, Rocks, and Minerals 87
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ACKNOWLEDGMENT
The authors of this report are grateful to
their expert review of this report:
Dr. Stephen J. Gage
Mr. Frank T. Princiotta
Mr. David Graham
Mr. John P. Lehman
Mr. George W. Walsh
Mr. John Lum
Mr. Ronald A. Venezia
Dr. Harvey W. Holm
Dr. William Fulkerson
Dr. Robert I. Van Hook
Dr. James Riese
the following persons for
United
United
Un i t ed
United
United
United
United
United
States
States
States
States
States
States
States
States
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ronment a 1
ronmental
ronmenta I
ronmental
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ronmental
ronmental
ronmental
Protect
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Protect
Protect
ion
ion
ion
ion
ion
ion
ion
ion
Agency
Agency
Agency
Agency
Agency
Agency
Agency
Agency
Oak Ridge National Laboratory
Oak Ridge National Laboratory
Council of Environmental Quality
The opinions expressed in this report are those of the authors and do
not necessarily reflect those of the reviewers.
vi
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SECTION !
SUMMARY
The uses as well as the harmful effects of mercurv have beep known to
man for centuries. The hazards of mercury have been brought to the forefront,
in recent years, by the disaster which occurred in Minamata, .Japan, beginning
in 1956. MethyImercury, produced in the environment from an inorganic
catalyst discharged in the effluent of an .icetaldehyde plant, was found to be
responsible for the series of poisonings among the villagers. This type of
episode was later repeated in Niigata, Japan, in 1964.
The toxicity of mercurv depends upon its chemical form, the most toxic
being me thyImercury. Within the environment and within ecosystems, various
forms of mercury can be transformed into methvlmercury compounds. This form
may concentrate along the food chain, passing on to man through consumption
of fish and shellfish. MethyImercury. when ingested by man, is almost
entirely absorbed, with its loss from the body occurring at a slow rate.
Mercury poisoning affects mainly the brain and other components of the
nervous system, although other organs may also be affected. An acceptable
intake (mercury vapor and methyImercury) is considered to be 30 microerams
per day, for a 70 kg person, from air, water, and food. An average diet
(water and food) over a long period of time is estimated to contain 10
micrograms per day of mercury. This leaves 20 micrograms per day to be
contributed by air. However, an intake of 4 micrograms of methyImercury
per kilogram of bodyweight per day would result in mercury intoxication of
an adult.^
Mercury levels in various animals, fish, and plants in man's food chain
are shown in Table I.6 In response to the hazard of mercury, the Environ-
mental Protection Agency, Food and Drug Administration, the Department of
Health, Education and Welfare (via NIOSH) and the Department of Labor (via
OSHA) have promulgated regulations and/or recommendations for ambieit work-
place concentrations and industrial emissions. These are summarized in Table
4.8-15
Mercury is classified as a hazardous air pollutant under Section 112 of
the Clean Air Act. In determining the industrial emission standard, shown in
Table 4, the health effects were considered together with an adequate safety
factor. An ambient air concentration of 1 g/m^ was found to be compatible
with the emission standard in safeguarding health.5
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Fossil fuel-fired power plants contribute mercury to the environment as
a result of the combustion of coal and oil. A total of 968 such power plants
generated 1.4 x 10^ KWh net in 1974 from the combustion of approximately
4 x 10^ tons of coal and 5 x 10^ barrels of oil. 19 Based upon a number
of studies, the mercury content of an average coal was found to be 2.1 x 10~'
tons Hg/ton coal (0.21 ppm), while an average'oil had 31.9 x 10"^ Ibs/gallon
(0.1 ppm).21-25,30 Assuming these average values for these fossil fuels,
82 tons of mercury were available to be emitted to the environment from coal
and 76 tons from oil in 1974, based upon industry consumption figures. If
all of the available mercury from power plants (158 tons) were uniformly
deposited over the land area of the 48 contiguous states, to a depth of 2
cm, the mercury concentration in the soil would be 0.34 ppb compared with
the average soil concentration of the United States of 71 ppb.86
Fossil fuel use by utilities was divided into regions as defined in
Table 7. One-third of the total mercury available in coal was in the East
North Central states, while 29 percent and 26 percent of that available in
oil was in the South Atlantic and Middle Atlantic states respectively.
Coal-fired plants emit about 90 percent of this mercury content in the stack
gas, with the other 10 percent remaining in the ash to be deposited on land.
Oil combustion yields all its mercury to the stack gas.™~33
Total mercury losses from utilities, however, appear to represent
less than 8 percent of the more than 2000 tons lost to the environment
by all man-made sources in 1974. The mercury losses were from mining
and smelting, unregulated sources, manufacturing and processing, and from the
consumption of the products of those industries. These are detailed in Table
8. The mercury consumed by the manufacturing and processing industries in
1974 totaled 2,220 tons. Since U.S. mercury mines produced 83 tons, the
difference consisted of reclaimed and imported mercury.
On a regional basis, the largest mercury losses from man-made sources to
the environment, 51 percent according to 1973 figures, occurred in the Middle
Atlantic, East North Central, and South Atlantic regions. These same areas
accounted for 63 percent of the total mercury losses from electric power
generation in 1974. The largest losses from natural sources, 53 percent,
were in the Mountain states and Pacific states regions. These are also the
areas of most mercury deposits and mineralization.
When compared to all man-made sources on a national basis for 1974,
utility losses ranked fourth overall, contributing less than 8 percent.
Utility losses ranked second for air emissions (24 percent of all losses to
air) and ninth in losses to land (0.6 percent of all losses to land). Direct
loss of mercury from power plants to water does not occur. Rather, their
contribution to water results from the transport of mercury from the other
media to water.
Mercury losses to the environment by utilities, and used in ranking, are
based on uncontrolled emissions. A review of control technology reveals that
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mercury emissions are not directly controlled. However, it is estimated thit
as much as one-third of these emissions mav be controlled if SOo scrubhine
*i *? / Q ~~
devices are in use.JZ>^° Considering an increase in power generation and
the use of S02 scrubbers by utilities, it is projected that by 1^M3( utili-
ties will rank second with 12 percent of the total mercury losses. It is
estimated that in 1983 utilities will rank first in air emissions with
230 tons (30 percent of the losses) and seventh in losses to the land with
25 tons (2 percent of the total) for that media. The total Losses of
mercury by utilities is estimated to be 255 tons in 1983 as compared with
158 tons in 1974. These losses still represent a small part of all mercurv
losses to the environment.
The mercury hazard depends on both the concentration of mercury and its
chemical form in the environment. MethyImercury compounds, as stated pre-
viously, are the most toxic. Chemical and biological activity can methylate
other forms of mercury thus producing the toxic form. With the addition of
physical transformations, the various forms of mercury are transported within
the cycle as shown in Figure 2. It is not possible to estimate the amount of
mercury and its residence time in the various environmental media within the
cycle or along the pathways of transport from current data. A number of
studies have indicated the range of ambient concentrations. Normal ambient
concentrations in city air have been estimated at 0.0008-0.OH ppb, with
concentrations as high as 30 ppb occasionally observed.™ Rural areas ar.
estimated to have a concentration range of 0.0006-0.008 ppb.^1 The concen-
tration of mercury in industrial workplace air has been reported to be as
high as 42 ppb, while air near a geothermal steam veYit has been measure
at 23.5 ppb.56
A worst case condition in the New York City area was considered in
determining the effect of mercury emissions from power plants on ambient air
concentrations. The scenario considered mercury emissions from the 21 plants
in New York City and the immediately adjacent area in New Jersev. The
mercury was emitted in stack gas during 1974 and remained, in total, within
the 400 square mile area in which it was emitted. These assumptions were
made to determine if mercury concentrations could reach hazardous levels
under any circumstances. The assumptions were that an entire year's mercurv
emission from all these power plants was retained in the area at one time,
and that no ventilation occurred. The scenario would never occur as emis-
sions would be distributed over the year and meteorological conditions would
preclude such stagnation, providing for dispersal and dilution. For an
assumed air column of 12 km altitude, the ambient air concentration of
mercury from this source alone was found to be 0.65 g/mj (0.52 ppb.)
This is based upon actual fuel use. The EPA recommended ambient air con-
centration for 24 hours is <_\ .0 g/m^.^ The same calculation, assuming
all the electricity generated from these plants was only from the combustion
of coal rather than the 1974 quantities of both coal and oil, showed a 42
percent lower mercury concentration in air. Therefore, mercurv emissions
from power plants are not expected to cause an ambient air quality problem.
Observed and calculated ambient concentrations, around actual power plants .is
well as other areas, were orders of magnitude below the standard.
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Ambient water concentrations are defined in terms of dissolved mercury,
suspended mercury, and mercury in bottom sediments. On both a regional and
a national basis the ambient concentrations of all the waterways, whose data
were reviewed, averaged well below 2 ppb.84 This is well within the
drinking water standard of 2 ppb, established by EPA as the highest accep-
table concentration of mercury allowable for drinking water. '•^ These same
fresh water bodies may, however, exceed the EPA standard for freshwater
aquatic life and wildlife of 0.05 ppb.^ The detectability limits of the
analytical methods used in gathering the data preclude comparison to the
standard.
To determine if mercury concentrations in water could reach hazardous
levels due to power plant emissions, a scenario similar to that used for the
ambient air case was developed for water. In this case, all the emissions to
the air were washed out into a river. The ambient water concentraton was
calculated to be 0.47 ppb, within the drinking water standard but exceeding
the more stringent freshwater aquatic standard. This improbable and excessive
case could not occur since complete deposition, whether in water or locally,
has never been shown to occur. Distribution of deposited mercury and its
dilution would further reduce this concentration by orders of magnitude.
These results would be in line with available ambient water quality data.
Existing studies do not indicate a direct relationship between the
dissolved mercury concentration in water and mercury emissions from a power
plant.°5 Elevated levels' have occurred in bottom sediments. While the
power plant emissions may have contributed to the condition, it could not
be shown to have a direct, quantitative causal effect.
The average concentration of mercury in soils in the United States was
found to be 71 ppb, although there are some estimates of 100 ppb or slightly
higher."" A number of studies have been carried out which have attempted
to correlate higher than average soil concentrations with discharges from a
particular areas source, generally with inconclusive results.35,70,85,87-91
In order to determine the effect of mercury emissions from a power plant on
land the previous scenario was again considered. When the entire year's
mercury emission to the air was deposited on the 400 square mile area con-
sidered, the ambient soil concentration, assuming a depth of 2 cm, was cal-
culated to be 145 ppb. This is above the geometric-mean concentration for
L'.S. soils. The factors of partial deposition, plume dispersion, transport
mechanisms, and transformations of mercury would greatly reduce this concen-
tration. A 20 percent assumed deposition alone reduced it to 29 ppb. Actual
studies around plants confirm the conclusion that some elevated mercury
levels may be found locally, with only partial deposition occurring.85,91
However, direct relationship to a power plant as a source could not be
shown.
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SECTION 2
CONCLUSIONS
Several conclusions were drawn, as a result of the available information
and scenarios, concerning power plants and mercury emissions to the environment
• EPA should not develop specific control technology for mercury
emissions from power plants at the present time. The bases for
this conclusion are: (1) the relatively small contribution of
mercury from power plants (158 tons in 1974) when considering all
man-made sources (2169 tons in 1974) and all natural sources
(1329 tons in 1974); (2) the apparent capability of sulfur
dioxide scrubbers to control possibly one-third of the mercury
emissions to air; (3) no conclusive evidence of contamination
quantitatively attributable to power plants; and (4) the rela-
tively small contribution of mercury projected to be emitted to
the environment from power plants in 1983 (255 tons) relative to
projected losses from all man-made sources (2131 tons in 1983).
• There is no convincing evidence, from existing data or from our
scenarios, that mercury emissions from power plants significantly
affect the ambient mercury concentrations in air, water, or land.
However, the data are few in number and most cases, of dubious
quali ty.
• Neither the empirical data nor the scenarios indicate a hazard as
a result of mercury emissions from power plants. There are no
reported incidents known of acute toxicity of mercury from power
plant emissions. Incidents of chronic toxicity, associated with
power plant emissions, have not been found.
• There is a need to develop better data concerning mercury
concentrations, transformations, and transport in the environ-
ment, as well as the relationship between ambient concentra-
tions and emissions from various sources.
• The most significant loss of mercury to the environment is from
the consumption of manufactured or processed products containing
mercury. This loss accounted for 52 percent (1120 tons) of all
man-made mercury losses in 1974. It also represented 60 percent
(830 tons) of all man-made mercury losses to the land. Recycling
could have had an impact on 34 percent (738 tons) of the total
man-made mercury emissions, based upon 1974 figures.
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SECTION 3
RECOMMENDATIONS
This study has found no evidence of a problem as a result of power
plant emissions to the environment. If there had been widespread and
excessive concentrations of mercury in the environment and data analysis
would have indicated a pattern implicating a specific source, such as power
plants, then a control program would have been recommended. Inasmuch as
there is presently no obvious problem, no such program is recommended.
However, there is doubt as to whether or not available data, upon which this
report is based, are correct.
It is recommended that, in view of EPA's limited resources and the
findings of this report, a limited program be funded. This program would
serve to provide reliable data to substantiate or negate the information used
in arriving at conclusions. The following areas of study are recommended:
• Sampling and analysis of soil samples surrounding a power
plant, including a characterization of soil type and forms
of mercury present.
• Sampling and analysis of plants, especially food crops, and
animals in the same area. The key points on which to concen-
trate are biomagnification, and the forms of mercury present.
Should these data then indicate a problem, then a phased program
may be undertaken to further define the problem and develop abatement
techniques. Elements of an expanded program, should the need arise,
may include the following:
• A complete mercury balance of coal-, oil-, and gas-fired power
plants, including the analysis for the different forms of mercury.
• Efficiency of currently used scrubber systems on the control
of mercury emissions under varying conditions.
• A sampling and analysis program for determining mercury con-
centrations in ambient air, water, sediments, soils, and plants.
The program should be of a magnitude that will provide the nec-
essary reliable data which may be used to indicate source re-
lationship, define the fate, and characterize the transport mech-
anisms of mercury in the environment.
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• Developing and calibrating a diffusion model for mercury
emissions, testing the model on power plant sources.
• Develop criteria for mercurv control technology.
• Development and demonstration of control techniques.
• Implementation planning for the selected control technique(s),
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SECTION 4
INTRODUCTION
OBJECTIVE
The objective of this study was to determine the need for develop-
ing methods for the control of mercury emissions from power plants and
other sources and assessing the relationship and significance of the
emissions to ambient concentrations.
ORGANIZATION OF THE REPORT
The report includes estimates of mercury emissions, as well as data
from scenarios and empirical studies in assessing the significance of
mercury emissions from power plants. Conclusions are developed based upon
the assessment. The health and ecological effects of mercury are reviewed
in Section 5. Several well documented cases of mercury poisoning are
described, such as those in Japan and Sweden. In order to understand these
types of occurrences, the toxicity of mercury and the symptoms which it
produces are described. The amount of mercury which may be tolerated by the
body is reviewed in relation to the concentrations of mercury found in
the food chain.
The known toxicity of mercury and its occurrence in the environment had
led to promulgation of regulations. The standards, regulations, and recom-
mendations are tabulated and discussed. This provides a basis of comparison
when assessing the importance of sources emitting mercury.
Fossil fuels are the source of mercury emissions from power plants.
The average mercury content of the fuels is presented, as determined from
the literature. The consumption of these fuels is tabulated for 1974, on
both a national and a regional basis. These data on fossil fuels are the
basis for calculating the mercury released by power plants.
In addition to power plants, other sources of mercury are examined.
The amount of mercury used by these industries and lost to air, water, and
land is estimated. These emissions are then placed in perspective to power
plant emissions in terms of relative mercury contributions. The amount of
mercury ultimately reaching the environment, when compared with the amount
available for release, is dependent upon emission control systems. The
present technology of power plant control systems is briefly reviewed as are
control technologies of other industries which are sources of mercury.
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The significance of power plant emissions can on 1 v be assessed when
one considers the fate and transport of the mercury and mt-rcury compounds
emitted. A model is proposed for the cycle of mercury through tin- environ-
ment, showing the pathways and mechanisms of transport between the media.
To assess the effects of emissions on air, in water, and on land
ambient concentrations in each of these media are eva luat'-d. The relative
effects of mercury emissions from power plants on the ambient concentrations,
on a worst case basis, are calculated using scenarios. Documented, empirical
studies, relating power plant emissions to ambient concentrations, are
reviewed and evaluated in relation to the results of the scenarios.
The report examines the chemical, physical, and biological transfor-
mations which occur in each medium. These transformations provide a b.isis
for assessing the problem of mercury in the environment.
Most data used in this report are for the year 1974 because that year's
data was the most complete available. In several c.ises only 1973 data or
1975 data were available. Where possible these data were extrapolated to
reflect probable 1974 values.
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SECTION 5
BIOLOGICAL EFFECTS AND THE REGULATION OF MERCURY
HEALTH AND ECOLOGICAL EFFECTS
Background
Mercury has been produced and used by man for centuries. Cinnabar (HgS)
was used in ancient Egypt and Babylon. The dangers of mercury to humans has
also been known for a long time. The early Greeks realized mercury was
dangerous when swallowed. The earliest known case of mercury poisoning was
in 1579 of a European mine worker. Typical symptoms were identified in the
late 18th century. During the past few hundred years one of the industries
most responsible for occupational mercury poisoning was the hatter's trade.
Mercuric nitrate was used for carroting, or dyeing, of the fur. Frequently
whole families that worked in this trade suffered from the disease. >
Recently, there have been several localized cases of poisoning around
the world which have renewed concern about the hazards of mercury to man.
One of the most renowned was the Minamata disaster in Japan. The first case
of mercury poisoning in this fishing community was discovered in May, 1956
when a six-year old girl was found to be suffering from an unknown cerebral
disease. Eight more cases were reported later that month. By November,
1956, the cause of the disease had been identified as a heavy metal contained
in fish and shellfish. It was not until 1960 that an organic mercury com-
pound was identified as the cause. In 1962, after an exhaustive study by
the Kumamota University, it was concluded that methyl mercury generated from
the inorganic mercury catalyst used in acetaldehyde manufacture and discharged
in the effluent of a nearby plant, was responsible for the poisoning. The
mercury had concentrated in the fish, a main item in the villagers' diet.
Since the plant installed mercury control devices, no further outbreaks of
mercury poisoning have occurred. The total number of recorded cases of
Minamata Disease was 121, of which 22 were congenital. Of the 121
recorded cases, 54 resulted in death.
A second outbreak similar to that in Minamata occurred in Niigata,
Japan, during 1964. In this case, 49 persons were afflicted, six of whom
died. Once again, an acetaldehyde manufacturing plant using a mercury
catalyst was identified as the source of the mercury. In 1969, all indus-
trial facilities manufacturing acetaldehyde and using mercury catalysts were
closed.
Sweden first became interested in the mercury problem during the 1950"s
when a decline in the bird population occurred. This decline was attributed
10
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to methylmercury poisoning from seed grain. Having been alerted by the
Minamata disaster, a national conference was called in 1965. It was decided
that the major sources of mercury were seed dressings, pulp and paper
processing, and chloralkali plants. In 1966, the use of methylmercury
compounds as seed dressings was stopped. In 1967, the use of phenylmercury
compounds in the pulp and paper industry was banned and measures were
enacted to restrain discharge of mercury from chlor-alkali plants.
In 1969, a family in New Mexico was poisoned by eating meat from a hog
which had been fed mercury treated seed. In 1970, Idaho found that 25 per-
cent of 300 wild pheasants contained over 1 mg of mercury per kg of body
weight and therefore recommended reduced consumption of this fowl.
In 1970 it was discovered that fish from lakes along the United States-
Canada border contained large amounts of mercury. Fishing was therefore
banned on Lake St. Clair, Lakes Huron, Erie, and Ontario, most of the St.
Lawrence River, Hudson Bay, Howe Sound, and Dalhousie Harbor.
Toxicity of Mercury and Symptoms of Mercury Poisoning
Hazards of mercury are related principally to the toxicity of mercury
and the localized occurrence of high concentrations in the environment.
Unlike other trace metals, mercury is not essential to the life process of
any known organism. Toxicity of mercury depends upon the chemical form, the
most toxic being methylmercury compounds. In an aquatic ecosystem other
forms of mercury can be converted into methylmercury. Methylmercury is
concentrated along the food chain and is eventually passed to man through
the consumption of fish and shellfish.
In humans, ingested methyl mercury is almost entirely absorbed from the
gastrointestinal tract. In addition, it is neurotoxic and its loss from the
body is slow. The critical parts of the body affected are the brain and
nervous system. Unborn children are especially endangered because mercury
is concentrated in the fetus.
Symptoms of inorganic and organic mercury poisoning are similar.
They include sensory disturbances including, uncoordinated movement and
impairment of hearing and eyesight, appearance of gingivitis, stomatitis,
erethism, and tremor. Effects to the respiratory system include pneumonitis,
bronchitis, chest pains, dyspepsia, and coughing. Ingestion of some inorganic
mercurial compounds such as mercuric chloride causes irritation and corrosion
of the body tissue contacted. In the congenital form cerebral infantile
paralysis, mental retardation, speech retardation, salivation and malfunctions
in bofly mobility also appear. Pathological studies showed that four to six
years after poisoning there were changes in the white matter of the brain.
Other changes were tissue coarseness, sclerrosis, thinning of myelin and
degeneration and withering of the cerebral cortex.1|2,3
11
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Unfortunately, the early symptoms of mercury poisoning resulting from
chronic exposure may be ignored or attributed to other causes by the af-
flicted individual. Often, symptoms are thought to be linked to mental
strain, and the wrong type of medical help is sought.
The organ which, in almost all instances, exhibits the highest
concentration of mercury is the liver. Kidney damage may also result, which
may or may not be reflected in mercury being detected in the urine.
Mercury poisoning occurs when mercury combines with certain enzymes,
thus inhibiting their action. This reaction takes place because many
enzymes contain sulfhydryl groups (SH). Mercury readily combines with the
sulfur replacing the hydrogen and forming a covalent bond.
The antidote for mercury poisoning is BAL (dimercaprol 2,3-Dimercapto-
1-propanol). It contains sulfhydryl groups which form a stable mercaptide
ring which is water soluble and readily eliminated from the body.2
Acceptable Daily Average Intake of Mercury
In Sweden, a provisional, tolerable weekly intake of 0.3 mg of total
mercury per person, of which no more than 0.2 mg should be methyl mercury,
has been established. This is 0.005 mg and 0.0033 mg respectively, per kg
of body weight for a 60 kg (134 Ib.) person.-* If fish were contaminated
with 1.0 mgHg/kg, the average person's diet should not exceed 210 grams of
this fish per week.
Concentrations of total mercury in the blood of 0.2 mg/g and in the
hair of 60 mg/g may be indicative of mercury poisoning in humans. These
levels correspond to an average daily intake of mercury of 0.3 mg. An
average daily intake of 0.03 mg is probably safe.3
The EPA, in promulgating the National Emission Standard for mercury as
a hazardous air pollutant, considered the total mercury exposures of the
individual, the air-, water-, and food-borne burdens. Based upon a number of
studies, both animal experiments and human episodes of mercury poisoning, it
was concluded that 4 micrograms of methylmercury per kilogram of bodyweight
per day would result in the intoxication of a sensitive adult.5 in
addition, 100 micrograms of mercury per cubic meter of air also involves a
definite risk of mercury intoxication. When an "ample margin of safety" was
considered, for exposures to methymercury in the diet and mercury vapor
in air, it was concluded that an acceptable exposure would be 30 micro-
grams per day for a 70 kg man.
Levels of Mercury Found in Plants and Animals
Natural and contaminated concentrations of mercury found in plants and
animals are listed in Table 1. Natural levels in fish range from 0.005 to
12
-------
Species
Fresh Water Fish
Marine Fish
Tuna
Swordfish
Drifter Fish
Shellfish
Crayfish
Crabs
Farm Products
Eggs
Plants
Fruits
Wheat, Barley
Rice
Vegetables
Roots
Potato
TABLE 1
MERCURY CONTENT OF PLANTS AND ANIMALSa>b
Natural Level(ppm)
0.005 - 0.2
0.050
0. 18
0.010
0.010
0.020
0.30
0.30
0.50
0.20
0.005 - 0.009
0.04
0.008
0.005
0.001
0.013
0.003
0.32
0.09
0,08
Observed
Contaminated Level(ppin)
9.08 - 10.6
2.5
2.4
1.7
0.30 - 0.80
1.55 - 13.4
0.26
0.40
0.24
0.57
0.18
0.23
- 2.40
aReference 6
"On a dry weight basis
13
-------
0.05 ppm on a dry basis. Contaminated levels range from 0.30 to 13.4 ppm.
Natural levels in plants range from 0.001 to 0.32 ppm. Contaminated levels
range from 0.18 to 2.40
A listing of mercury content of museum fish is shown in Table 2.
A listing of mercury in Lake George fish caught in 1970 is shown in Table 3.
Lake George fish data were available and served as a comparison to the
museum fish data. Bioaccumulation has been occurring for decades even
before major man-made discharges of mercury began entering the waterways.
Lake trout caught in 1939 showed higher values for mercury than those caught
in 1970. However, both specimens are well above the recommended limit of 0.5
ppm for fish.
STANDARDS AND REGULATIONS
The toxic nature of mercury and its increased levels of emission
to the environment has necessitated the formulation of regulations to
control discharges. To date the Environmental Protection Agency, Food and
Drug Administration, and Department of Health, Education and Welfare have
published standards, the latter recommending standards to the Labor Depart-
ment for promulgation. Mercury is regulated by EPA for ocean dumping, its
presence in pesticides and drinking water, as an emission to air, and as an
emission to navigable waters. FDA regulates the amount of mercury which may
be contained in shellfish. The amount of mercury in the air of any work
place is regulated by the Department of Labor through OSHA through enforce-
ment of HEW (NIOSH) recommended standards. The current standard is 0.05
g/nH for 8 hours. These are summarized in Table 4.°~*^
Discharge Regulations
On March 31, 1971 the EPA listed three hazardous air pollutants,
among them mercury, under Section 112 of the Clean Air Act as amended.
The Administrator's judgment that they "may cause, or contribute to, an
increase in mortality or an increase in serious irreversible, or incapaci-
tating reversible illness" was the basis for the determination that they
were hazardous. '* Mercury levels in air, water and food were considered
in determining safe levels and discharge rates.
The National Emission Standards for Hazardous Air Pollutants were
promulgated on April 6, 1973 and amended Oct. 3, 1975. Emissions to the
atmosphere of mercury from ore processing facilities and mercury cell
chlor-alkali plants are not to exceed 2300 grams of mercury per 24-hour
period. Emissions to the atmosphere from sludge incineration plants, sludge
drying plants, or a combination of those which process wastewater treatment
plant sludges are not to exceed 3200 grams of mercury per 24-hour period.
The basis for these emission levels was the result of an analysis of
mercury poisoning episodes in Japan, Sweden and Iraq, indicating that 4
14
-------
TABLE 2
MERCURY IN PRESERVED FISH3
SPECIES
Walleyed Pike
Walleyed Pike
Small Mouth Bass
Landlocked Salmon
Landlocked Salmon
Landlocked Salmon
Lake Trout
Small Mouth Bass
Walleyed Pike
Great Northern Pike
Great Northern Pike
Small Mouth Bass
Small Mouth Bass
Whitefish
Whitef ish
Small Mouth Bass
Rainbow Trout
*
a Reference 7
LOCATION
Lake Ontario
Ticonderoga Creek
Lang Pond
Forked Lake
Lake George
Lake George
Schroon Lake
Beaver River
Beaver River
Lake Erie
Lake George
Lake George
Lake Erie
Lake Huron
Saranac Lake
Sunapee Lake
Callicoon Creek
YEAR
1939
1929
1930
1933
1923
1934
1932
1880
1880
pre-1889
pre-1889
1900
1900
1919
1897
1896
1912
Hg (ppm)
0.69
0.76
0.31
0.63
0.36
0.20
1.53
0.44
0.47
0.68
0.62
0.41
1.87
0.39
0.49
0.41
0.69
15
-------
TABLE 3
MERCURY CONTENT OF LAKE GEORGE FISH - 1970a
Species Hg (ppm)
Lake Trout 1.20
Lake Trout 1.03
Rainbow Trout 0.92
Small Mouth Bass 0.55
Small Mouth Bass 0.53
a Reference 7
16
-------
AGENCY
STANDARD
TABLE 4.
RECEIVING BODY
SUMMARY OF FEDERAL REGULATIONS LIMITING MERCURY
LEGISLATIVE MANDATE
REMARKS
EPA
Air
EPA
Air
EPA
Effluent
Guidelines
EPA
Toxic
Substances
EPA
Toxic
Substances
EPA
Toxic
Substances
2300 gas/24 hrs
3200 gas/24 hrs
Air
Air
0.002 mg/1 (dally) Navigable waters
0.001 mg/t (30-day)
avg.) ,
EPA 0.00028 k/g/kkg
Effluent (dally)
Guidelines 0.00014 kg/kkg
(30-day avg.)
No discharge
20 ug/t
2.0 Mg/t
Navigable waters
streams, lakes,
estuaries with
flow <10cfs or
lakes with area
< 500 ac
fresh water bodies
larger than In a)
and have flow lOx
>_ waste stream
fresh water bodies
larger than a) and
have a flow <10x
waste strean
Discharges
Section 112 of Clean Air Act Amend-
ment « (P.L. 91-604) enacted In 1970
4/6/73 PB. 10/14/75 (revised)
Section 112 of Clean Air Act Amend-
ment. (P.L. 91-604) enacted In 1970
10/14/75 Pn
Sections 301. 304, 306 and 307 of
Federal Water Pollution Control Act
Amendment* (P.L. 92-500} enacted
October 18, 1972. 10/6/75 Pm
Sections 301, 304, 306 and 307 of
Federal Water Pollution Control Act
Amendments (P.L. 92-500) enacted
October 18, 1972. 3/12/74 Pn
Section 307 of Federal Water Pollu-
tion Control Act Amendments (P.L.
92-500) enacted October 18, 1972
12/27/73 P
Same
Same
Covers stationary sources which process mercury ore, or
use mercury cells to produce chlorine gas and alkali
metal hydroxide.
Covers stationary sources which Incinerate or dry waste
water treatment sludge.
Covers mining and dressing of mercury ores and
precious metals.
Covers Inorganic chemicals - KOH production.
Under the mandate of the FWPCA amendments of 1972, EPA
proposed these regulations for toxic subatsnces. As a
result of controversy which arose during the course of
public hearings, the regulations were never promulgated
The Toxic Substances Control Act of October 1976 super-
ceded the above mandate. EPA Is presently Implementing
this Act.
Same
"References B-14
-------
AGENCY
STANDARD
RECEIVING BODY
TABLE 4. (Continued)
LEGISLATIVE MANDATE
REMARKS
EPA 100 Ug/t
Toxic
Substances
EPA 10.0 ug/t
Toxic
Substances
EPA 1.62 Ib/day
Toxic
Substances
EPA 27.0 Ib/day
00 Toxic
Substances
EPA 32.4 Ib/day
Toxic
Substances
EPA 0.7S ng/kg
Ocean
Dunping
EPA 1.5 Big/kg
Ocean
Dunplng
salt water bodies
larger than a) w/
flow >. lOx waste
stream
•alt water bodies
larger than a)
with flow <10x
waste streaa
lake regardless
of receiving wster
flow
estusry regardless
of flow
coastal waters
regardless of flow
oceans
oceans
Discharges
Same Sane
Same Sane
Sane Same
Sane Sane
Same Same
Sections 403 and 404 of Federal Mercury and Its compounds may not be present in any
Water Pollution Control Act Amend- solid phase of a waste greater than 0.75 mg/kg.
nents (P.L. 92-500) enacted October
18, 1972 and Title I of the Marine
Protection! Research and Sanctuaries
Act enacted October 23, 1972 (P.L.
92-532). 10/15/73 Pm
Sane Total concentration of mercury In liquid phase of a
waste does not exceed 1.5 ag/kg.
-------
TABLE 4. (Continued)
ACENCV STANDABD RECEIVING BODY LEGISLATIVE MANDATE REMARKS
Discharges
EPA Harmful any media Section 311 of the Federal Hater This regulation class!ties Hg on the basis of toxic to
Hazardous quantity - 1 Ib Pollution Control Act Amendments aquatic animal life. It falls Into the most toxic sub-
Substances (F.L. 92-500) enacted October 18, part because It has an LC53 of ^ „„,„ palnts B|tMn cm preservatlves
2. Snow mold on golf course greens
3. Dutch elm disease
6. Outdoor fabrics (not indoor or clothing) for
mildew protection
5. Brown mold on lumber
6. Seed treatment cancelled effective 8/31/78
7. Against summer diseases cancelled effective 8/31/78
Ambient
HEW 0.05 mg/m-* air N/A. 1973 Suggested standard published In criterion document
NIOSH for an 8-hr. transmitted to Department of Labor.
work day
-------
AGENCY
STAMP ARD
RECEIVING BODY
TABLE ft. (Concluded)
LEGISLATIVE MANDATE
REMARKS
IS)
O
EPA
Quality
Criteria
for Water
EPA
Drinking
Water
FDA
Shellfish
2.0 ug/l for water supply
domestic water
supply (health)
0.05 ug/l for fresh fresh water
water aquatic life
and wildlife
0.10 ug/e for salt water
marine aquatic life
0.002 mg/t drinking water
0.50 ppm shellfish
Ambient
N/A
Sections 1412, 1414. 1415, and 1450 of
the Public Health Service' Act aa aaended
by the Safe Drinking Water Act (P.L.
93-523). 12/24/75 Pm
Sections 306. 402, 406 and 701 of the
Federal Food, Drug, and Cosmetic Act
Standards exist as criteria, formulated on basis of
toxlcity studies on aquatic organism*.
These regulations exist as Interim primary regula-
tions.
NOTE:
P - Proposed
Pm - Promulgated
-------
micrograms of methylmercury per kilogram of body weight per day would cause
mercury intoxication of a sensitive adult. The EPA, in arriving at an ample
safety margin, assumed exposure to both methylmercury in the diet and mer-
cury vapor in air were equivalent and additive. Based on further assump-
tions of average mercury levels found in the diet together with the average
inhilation rate of 20 cubic meters of air per day. the air could not have an
average daily concentration greater than 1 g/m.^ The regulations were
aimed at those industries which were found by EPA to emit mercury that could
cause the ambient concentration of 1 g/m-^ to be exceeded. The emission
limits were therefore established for those industries at levels which would
not cause that ambient concentration to be exceeded.
The limit for sludge incineration and drying plants is based on main-
taining an average ambient mercury concentration of 1 g/m-' over a 30 day
period. With an assumed average emission rate of 1.5 grams of mercury per
ton, and with wet scrubbers being used, a 2132 tons-per-day (dry solids)
plant would approach the limit. However, there are no known existing or
anticipated wastewater plants which approach this size. The average emis-
sion rates were based on EPA tests of 42 treatment plant sludges.1^,16
On March 12, 1974, guidelines were promulgated by EPA covering discharge
to navigable waters of wastes from the manufacture of inorganic chemicals.
That subcategory which specifically limits mercury is the production of
potassium hydroxide (KOH). The daily allowable discharge is 0.00028 kg
Hg/kkg of product. The 30-day average is 0.00014 kg/kkg of product.
On October 6, 1975, guidelines were promulgated by EPA covering dis-
charges to navigable waters of wastes from the areas in which mining and
dressing of mercury occurs. These guidelines were issued under the auth-
ority of the Federal Water Pollution Control Act as amended by the Federal
Water Control Act Amendments of 1972. The daily limit is a concentration of
0.002 mg/1 in the discharge stream with the 30-day average being 0.001 mg/1.
Toxic substances standards were proposed December 27, 1973 by the EPA
in accordance with section 307(a) of the Federal Water Pollution Control Act
Amendments of 1972. These standards have not yet been promulgated. They
cover mercury and all mercury compounds. Toxicological data, hydrodynamic
data, margins of safety, and calculations of acute and chronic limitations
were considered in setting the proposed standards. Standards are expressed
in terms of total weight discharged and weight discharged per unit of flow.
The proposed standards limit the discharges to streams, lakes, estuaries,
and coastal waters and are based on flow and area of the receiving body.
The Toxic Substances Control Act of October 1976 supercedes these proposed
standards. No standards have been promulgated under the Act thus far.
Standards regulating the discharge of materials into the oceans were
promulgated in the Federal Register on October 15, 1973. These standards
are to prevent or strictly regulate the dumping or other discharge into the
ocean waters of any material in quantities which would adversely affect
21
-------
human health, welfare or amenities, the marine environment, ecological
systems, economic potentialities, as well as plankton, fish, shellfish,
wildlife, shorelines, or beaches. Mercury and its compounds are not to be
present in any solid phase of a waste in concentrations greater than 0.57
mgHg/kg and the total concentration of mercury in the liquid phase of a
waste are not to exceed 1.5 mgHg/kg.
Standards for hazardous materials were proposed in the Federal Register
on December 30, 1975, under Section 311(b) (2) (A) of the Federal Water
Pollution Control Act Amendments of 1972. This regulation classifies
mercury on the basis of toxicity to aquatic animal life. It falls into the
most toxic designation because it has an LCjQ of <1 ppm. An LC50is the
mean lethal concentration, or the concentration at which 50 percent of the
test species die. The maximum amount which may be released to the aquatic
environment as a result of an accident is defined as the contents of the
smallest commercial container size. For this class of substances, this
container was determined to be 1 Ib. (0.454 kg). This regulation treats all
releases as accidental and on an intermittent basis. Penalty payments are
calculated on the basis of toxicity and amount released. The substances
covered are mercuric nitrate,, mercuric acetate, mercuric cyanide, mercuric
sulfate, mercuric thiocyanate, and mercurous nitrate.
As a result of hearings held by EPA in September, 1975, all pesticides
containing mercury except those for the purposes listed below were cancelled,
(1) Preservatives for water based paints
(2) Prevention of snow mold on golf course greens
(3) Prevention of Dutch elm disease
(4) Protection against mildew on outdoor (not indoor) fabrics
(5) Prevention of brown mold on lumber
(6) Seed treatment (cancellation effective August 31, 1978)
(7) Prevention of summer disease (cancellation effective
August 31, 1978).
Ambient Regulations
NIOSH has suggested standards for the control of mercury in the work
place. These standards were published in the form of a criterion document
transmitted to the Department of Labor in 1973. The suggested minimum
acceptable level is 0.05 g/m^ of air during an eight-hour work day.
EPA issued quality criteria for mercury concentrations in water.H
Three different types of water were covered—domestic water supply, fresh
22
-------
water, and marine water. The limits ware based upon known toxic levels in
humans and toxicity studies on several species of fish and invertebrates.
Of special concern was the ability of some organisms to methylate mercury.
The domestic water supply criterion is 2.0 g/1.
The standard for levels in water was based on the premise that the FDA
established guideline for edible fish at 0.5 mg/kg of body weight should not
be exceeded. A mercury concentration factor of 10,000 for certain fresh
water species has been found. The level for fresh water was reached by
dividing the FDA standard of 0.5 mg/1 by 10,000 to yield 0.05 g/1.
The natural level for sea water was found to be about 0.1 g/1 of
mercury. This was an order or magnitude below that which represents a
threat to selected species of marine organisms. Thus, 0.1 g/1 became the
recommended criterion.
Drinking water standards were promulgated December 24, 1975, in ac-
cordance with sections 1412, 1414, 1415, and 1450 of the Public Health
Service Act as amended by the Safe Drinking Water Act (P.L. 93-523). This
standard, 0.002 ppm, was based on a consumption level of two liters of water
per day. This amounted to a daily intake of 0.004 mg. Those public water
systems covered must serve at least fifteen service connections used by
year-round residents or serve at least twenty-five year-round residents.
On December 6, 1974, the Food and Drug Administration published in
the Federal Register the action level for mercury in fish and shellfish.
Mercury in edible fish tissue is almost completely methylmercury. In shrimp
and lobster, limited testing indicated that mercury was also in the methylated
form. However, there were no analytical procedures that are capable of
measuring levels of methylmercury necessary for regulatory purposes.
Consequently, the standard was expressed in terms of total mercury. An
action level of 0.50 ppm was established for mercury in fish and shellfish
(mollusks and crustaceans), both raw and processed.
23
-------
SECTION 6
IMPORTANCE OF POWER PLANT EMISSIONS
ESTIMATE OF MERCURY EMISSIONS FROM POWER PLANTS
Fossil fuel-fired power plants contribute mercury to the environment
through the combustion process. Since the composition of oil and coal
j eludes a number of elements and compounds, including mercury and volatile
mercury compounds, the combustion process releases mercury in addition to
other elements.^ Coal and oil fired power plants accounted for 11.4 x
10^1 Kwh or almost 60 percent of the total power generated in 1975, of
which coal fired plants provided 75 percent of that, or 8.5 x 10^ Kwh.
The fossil fuel requirements to produce that power were 4 x 10° tons of
coal and 5 x 10° barrels of oil.^° The coal and oil consumed and the
electric power which was generated were approximately the same in 1974 as in
1975.1" The consumption of these fuels by state, geographic region, and
nationally are shown in Table 5. We selected 1974 data for this report
because that year's data was the most complete set available.
The East North Central and East South Central states generated about 32
percent of the net power in 1974 from 35 percent of the approximately 968
fossil fuel-fired steam electric plants, with 92 percent and 93 percent of
the Btu respectively, derived from coal combustion. This accounted for
about 50 percent of the 393.6 x 10" tons of coal used in power plants that
year. Similarly, the New England, Middle Atlantic, and Pacific states
generated about 21 percent of the net power from 20 percent of the power
plants with 87 percent, 42 percent and 56 percent of the Btu, respectively,
derived from the combustion of oil.
The mercury found in these fuels can vary substantially depending on
the source of the fuel. Mercury content of coals from different sources has
been measured by several investigators.21~25
Table 6 shows the variation in the mercury content of 800 coal samples,
summarized according to geographic distribution. The data presented are
averages of all the coal samples tested by the Geological Survey from each
of the states within a region.^ Based upon the coal production in each
of those regions, Appalachian coal, amounting to 66 percent of the total
coal produced in 1974, could account for about 74 percent of mercury from
this source. This compares with Midwest coal, amounting to 16 percent of the
production while accounting for about II percent of the mercury estimated to
be present in coal.
24
-------
TULI 3. nnun or 00*1 *•> on. tn*oi rot ILKTUC rom amtavm rot i*»*
-.1-
MO M(U04
Cuonortlror
MlM
KoMOehMotu
•OH (OOOOkln
Ihnilo loiooo1
toroBK
•UUo AtlMtlc
MV Joiooy
M* Toik Itou
(loci net
I.T.C.
OoOMTllOBlo
loot Port* CootrU
IlllMU
ln«ooi
Mcfcluo
Ok lo
VlOCOMlO
HMI forth CMtrol
lovo
•MOM
WOMOOU
lUooouri
MOtMM
1. Dokoto
1. Dokou
»o»U> UlooUc
Dounra
»• e. .-•
riorUo . .- *
Boiiulo • .' "
Tirrlon< *
1. Coraliio
1. CorallM
Tlrtiilo
». Tlrtlolo
toot South Cootrol
OlMOM
• onliuoy
•uouolool
Tooooooo*.
WMt Sootli Cootrol
•rtoMM
OUohOBO
TOXM
MOUBUlOO
tniooo
Nootono
•ovodo
•o» Ikulco
Otok
WydOdni
rocific'
Colllonlo
Uoobloitoo
O.I. TOTAL
*urorooco 11
eTho ooouot of oowor
tbo Iul«llo4 eopoc
•o. of riomu1
34
13
6 •
U
3
4
3
H
11
36
(U)
61
164
M
47
It
111
37
33
4*
11
It
12
7
110
3
1
41
13
11
14 .
17
1)
1)
37
14
11
1*
1
1*0
10
13
It
M
10
11
10
4
6
11
11
1
43
)|
7
161 161
|oaoroto4. !•
Ity, which lo
Fool DM'
( **'} bonolo)
«*, 777.1 1,137 70,101
14,150.6
1,1*7.3
13,111.3
3.1*6.1
1,1*3.6
13*.*
174.H3.0 **.**! 116.7(0
13.U1.6
61,3*0.1
(33,376.4)
17,1*1.3
301.0(1.1 131.73* 24.717
6t,3OO.t
36,0*1,7
97,131.1
H.ttO.t
11,345.3
**.**!. 4 36,*M 1.141
11, 161. 6
ujoo.t
16,13*.*
33,763.1
4.476.1 •
3.7*1.*
676.1
213.421.1 71.311 1*0.771
6,330.0
1,301.*
63,347.}
31, 33*. 6
24,141.4
30,6*4.6
16,361.0
26,111.1
60,133.1
130,173.1 63,171 1.763
41,112.0
51.110.6
11,0(0.7
45.411.4
212.4*1.2 5,117 10,771
7,911.*
11 'too.*
13*,?M.3
70,473.1 16 377 t 106
u!l31.6
1,171.6
12 .0*1.0
11,111.6
1.176.7
1.614.1
671.1 1,113 70,61)
70,431.1
4,214.4
1,411,111.1 313,56) 476, )IO
too th* oomntl eonoioMd by th« povor plant lor th*1r ovn u
ihm oulouo tonoritor nooiplit* r«tlo|.
I Of TOUl (to Mt OOMCOUM* * ^ J"^' °**4
Cool Oil Cool Oil Cool Oil
11 17 3,1*3.6 40, 6*1. ( 0.3* 14.16
3* 42 17,141.1 73,433.* 11.33 16.61
•1 3 276,1*3.3 13,034.1 33.7) 3.11
67 1 63.211.3 1.U1.1 !.)! 0.62
63 » 171,613.6 (3,616.6 !*.•! 21.33
13 3 1*0,113.1 4,516.3 16.13 l.(4
•
) 6 6,374.1 12,746.2 1.31 4.U
1 56 6,720.6 41,617.0 0.74 14. M
51 20 12). 81). J 211,452 91.11 100.00
«•. Th« ooc fooorotlon ooouato to opproxlBotoly 471 of
t« M auch u 51 hl*h In c
Mtl uy0a ttM TBltitlvf) p*rc«n
foa .• OOE Included •• th«
irl.ioa with r*dcr*l to**i CoMUatloa ••cl-«t». .Uf. 20
of th»j »mtB|« Btu cootcot for «ch fu«l M.iumJn( th» covbiutlon •fflclvocy of bothull
2 pl«nt« lifted loi th«t •tit* w«r« both |t* fired.
•nd coal •[• thm •*_*•,
-------
TABLE 6. MERCURY CONTENT OF COALS
Region
Appalachia
Midwest
Gulf
N. Great
Plains
Rockies
Other
Total
Average ,
Mercury Content
ppm
0.23
0.14
0.18
0.09
0.06
0.42
0.213
ID'9
tons/ton
230
140
180
90
60
420
208
2
Coal Production
10 tons
408
97
20
43
17
25
610
% of
Total
67
16
3
7
3
4
Total Mercury
(tons)
93.8
13.6
3.6
3.9
1.0
10.5
126
Reference 25
Reference 26, 27; 1974 data. Anthracite, Bituminous, and Lignite
for all uses.
Weighted averaged based on % of coal produced.
26
-------
The amounts of mercury in tho co.il from the different regions are based
upon averages of channel and core samples. Variations can occur within a
coal seam which may assay either significantly higher or lower than the
average. Based upon the averages, however, the total amount of mercury
available to be released to the environment was approximately 126 tons
from the 610 x 10" tons mined. This amount of coal mined was about 2 p>-r-
cent greater than in 1973, according to available data.
The total tonnage of coal produced was used not only for electric
power generation, but for coke and gas plants and other uses. Distribution
figures for 1974 showed that of a total coal production (bituminous coal and
lignite) in 1974 of 610 x 10" tons, about 65 percent was used by electric
utilities, 16 percent in coke and gas plants, while 19 percent went to all
other uses.^H The oil embargo imposed by the Organization of Petroleum
Exporting Countries in the last quarter of 1973 sparked interest in the use
of coal. It is assumed that the conversion of oil-fired plants to dual
or coal-fired use did not appreciably increase the electric utilities
share of coal consumption until late 1975. This would be due to the time
lag in both the regulatory agency approval process and the physical conver-
sion time. Assuming a 10 percent overall increase in the share of coal used
by electric utilities from 1973 to 1975, the mercury contained in the utili-
ties' coal for 1975 is approximately 90 tons.
The mercury content of fuel oil has been shown to vary from 0.002
1 7 *? 1 •
ppm to as much as 10 ppm.i'>-'1 An average mercury concentration which
may be applied to fuel oil is 0.1 ppm, which may also be expressed as
32 x 10~^ pounds per barrel (1 barrel equals 42 U.S. gallons). This
is an average of values for domestic and foreign oil.2' Table 7 shows the
distribution of oil by region for use in electric power generation in 1974.
The Middle Atlantic and South Atlantic regions, which together generated
one-third of net generated electric power in the United States, accounted
for 65 percent of all the fuel oil used for electric power generation.
Assuming the average concentration of fuel oil to be O.I ppm this amounted
to 42.7 tons of mercury for the year 1974. The amount of mercury present in
the oil used for all electric power generation in 1974 in the United States
was approximately 76 tons.
The combustion of oil produces about 2.9 times as much mercury, for
release to the atmosphere, as does coal in generating the same net kilowatt-
hours of electricity based on calculated average mercury content of each
fuel and accepted fuel conversion rates.^ If power plants would be
covered by the EPA maximum mercury emission standard of 3200 grams per day,
established for selected sources, an uncontrolled 1,000 MWe oil-fired power
plant would emit about 141 percent of the maximum allowable emissions, while
a coal fired plant of that size would emit about 50 percent of the limit.
Power plants are not covered by the regulation.
The Four Corners power plant in New Mexico was estimated to require a
maximum mercury emission rate of 9.57 x 10^ g/day before the monthly
27
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TABLE 7. MERCURY CONTRIBUTION FROM ELECTRIC POWER GENERATION BY REGION, 1974
Region
New England
Middle Atlantic
East North Central
West North Central
South Atlantic
East South Central
West South Central
Mountain
Pacific
Total U.S.
COAL
Usage"
(103 tons)
2,137
44,681
132,754
36,939
78,381
63,972
5,197
26,577
2,925
393,563
Total Hg Content
(tons)
0.44
9.3
27.6
7.7
16.3
13.3
1.1
5.5
0.6
81.8
Hg Emitted toC>f|g
Stack Gas (tons)
0.40
8.4
24.8
6.9
14.7
12.1
1.0
5.0
0.5
73.8
Hg In AshC
(tons)
<0.1
0.9
2.8
0.8
1.6
1.2
0.1
0.5
0.1
9
OIL
Usage"
(103 barrels)
70,808
126,790
24,727
2,942
140,779
8.763
20.772
9.906
70,893
476,380
Hg Emlttedd'e>f'8
to Stack Gas
(tons)
11.3
20.2
3.9
0.5
22.5
1.4
3.3
1.6
11.3
76.0
Total Emissions
to
Stack Gas (tons)
11.7
28.6
28.7
7.4
37.2
13.5
4.3
6.6
*
11.8
149.8
ro
oo
"From Table 5
h —Q
From calculation of a weighted average mercury content of U.S. coal, from Table 6, of 208 x 10 tons Hg/ton coal.
cBased upon 90Z emitted in the stack gas, and 10Z remaining found in the ash. Ref. 30-33
Based on an average mercury content of 31.9 x 10 Ibs. Hg/bbl., 0.1 ppm. Ref. 17, 21
eAssuming all mercury in the oil is emitted in the stack gas.
This is the amount of mercury which is estimated to enter the stack gas. Scrubbing equipment in the line, with
the exception of an electrostatic preclpltator, may reduce the amount of mercury ultimately released to the atmosphere.
BBased upon uncontrolled emissions.
-------
average ambient concentration of 1.0 R/m^ would have been exceeded.29
This ambient concentration was the guideline for the emission standard. If
an ambient concentration were to be the measure of emission level, then
the above 1000 MWe plants for the same location and conditions, are
emitting 1.4 percent and 0.5 percent of the guideline ambient concentration.
Utilities burned 3 x 10^ scf of gas to generate electricity in
1974.1^ While gas, a fossil fuel, has been estimated to have an average
mercury concentration of 40 ppb, we have not included the approximately 5
tons of mercury which may be attributable to this fuel. The processing of
the gas to eliminate hydrogen sulfide, prior to insertion into the pipeline
system, as well as the reported formation of insoluble mercury compounds
(e.g. sulfides) on pipeline walls may reduce the mercury concentration in
delivered gas to 1 to 2 ppb.30
The type of fuel as well as the configuration of the stack gas control
system will ultimately determine the amount of mercury which actually enters
the air. The combustion of coal emits 90 percent of the mercury content
into the stack gas and leaves 10 percent remaining in the ash. All of the
mercury, however, is considered to enter the stack gas in the combustion of
oil. ^"-^ The widespread use of scrubbers for gaseous and particulate
emissions may remove mercury from the stack gas. Few studies have been
done, and those quite limited, to determine the removal of mercury by
scrubbers and precipitators. The use of electrostatic precipitators was
shown to have no effect on mercury emissions. -^ >33 Sulfur dioxide
scrubbing systems, however, have been shown to remove about 1/3 of the
mercury from the stack gas. ^ However, the worst case would be to assume
that all the mercury in the stack gas (90 percent of that in coal and 100
percent of that in oil) is emitted to the atmosphere.
RELATIVE IMPORTANCE OF POWER PLANT EMISSIONS
Mercury emissions from power plants is but one source of mercury
to the environment. This section will identify and define the extent
of the other sources, natural as well as anthropogenic, and place electric
power generation in perspective as a source of mercury.
Identification of Other Sources of Mercury Emissions
Mercury enters the environment (air, land, and water) from mining
operations, utilities and other unregulated sources, manufacturing, consump=
tion of mercury and its derivatives, and through natural release of mercury
from the earth. The varied applications of mercury are as a result of its
unusual combination of useful properties, such as liquidity at ambient
temperatures, high surface tension, uniform volume expansion, good electrical
conductivity, high density, chemical stability, alloy capability, and
toxicity of its compounds.
2*
-------
Mercury Mining and Smelting—
Mercury mines are an obvious source of mercury pollution. In 1973
there were 24 producing mines, 35 percent fewer than in 1972. By the
end of 1973 six remained active while seven mines reported production
only from dumps, cleanup operations, or as a by product. Seven other
had production levels not exceeding 10 flasks (1 flask = 76 pounds).
Of the total 1973 production of 2,171 flasks, 83 percent came from the 5
mines with production levels greater than 100 flasks.-*5 The first
quarter of 1974 found only five operating mines, compared to 149 producing
mines in the boom of the 1960's.
The refining of low-grade ores provides an additional source of mercury.
Beneficiation (concentration) of mercury ores takes on increased importance
with a depletion of high-grade ores. Beneficiation methods include hand
sorting, crushing, screening, jiggling, tabling, and flotation. Flotation
is the most efficient, producing a 25-50 percent concentrate, with mercury
recovery of 90 percent. The conventional process for extracting mercury
from ores, called roasting, is a distillation process in which the ore is
heated in a furnace or retort to vaporize the mercury, after which it is
condensed to the liquid metal. Recovery averages about 95 percent for
furnace plants and 98 percent for retort operations. The resulting product
is 99.9 percent pure.^'
Copper Smelting—
Mercury is commonly found with other mineral deposits such as lead,
copper, and zinc. The mining and smelting processes for these metals are
also a source of mercury emissions to the environment. Among these, copper
smelting may produce considerable quantities of mercury.
About 1/4 of the world's copper is produced in the United States.
Copper is mined in eight states with Arizona accounting for about half of
the U.S. production. Approximately 225,000 tons of ore was processed in
1973.30
Copper is generally produced from open pit mined ores. The principal
steps involved are mechanical concentration, smelting, conversion to blister
copper, and electrolytic refining. Some mercury would be emitted during
mining as a result of degassing when the mineral deposit is exposed.
Mercury has the highest probability of being emitted from pyrometallurgical
processes, that is, where high temperatures would drive off mercury as
vapor. Smelting is carried out in a reverberatory furnace or the newer
electric furnace. The reverberatory furnace operates at a temperature of
about 1480°C, at which point almost all the mercury in the ores would be
released. The gases from the furnace are generally passed through scrubbers,
which would ultimately affect the amount of mercury actually released to
the environment.
30
-------
Chlor-Alka1i Manufacturing—
Chlor-Alkali manufacturing is another source of mercury in the environ-
ment as a result of the consumption of large quantities of mercury. Approxi-
mately 16 million tons per year of chlorine (gas and liquid) were produced
in the United States in 1973 and 1974.38 In 1973 the chlor-alkali indus-
try consumed 24 percent of the mercury used in the United States (almost
1 million Ibs).-*" A principle method of producing chlorine and caustic soda
(NaOH) is by the electrolysis of brine, where the cathode is flowing mercury.
Known as the mercury cell, it is the most widely used process in the indus-
try, the other being the diaphragm cell.38>39 Five plants in the United
States use the Downs process (fused salt).28 Of the 69 plants in the
U.S., 27 use the mercury cell exclusively or in conjunction with the dia-
phragm cell. The mercury cells accounted for approximately 22 percent of
the total installed chlorine production capacity in the U.S. in 1975, a
decrease of 3 percent from 1973 and 1974 figures.38
The mercury cell technique, for the production of chlorine and NaOH
from brine (a 25 percent NaCl solution), used an electrolyzer and a decom-
poser. In the electrolyzer an electric current is conducted through the
brine by closing the loop between an anode and a flowing mercury cathode.
Chlorine is liberated at the anode and a liquid alkali metal amalgam (NaHg)
is formed with the flowing cathode. This amalgam is cycled through the
decomposer where it is reacted with water to form caustic soda (NaOH) and
hydrogen gas. Excess mercury is removed and the remaining mercury is
recycled.30,40 Mercury losses to the environment occur throughout the
process.
Manufacture of Mercurials—
The manufacture of mercury compounds includes organic and inorganic
mercurials which are used for agriculture, medicinals, catalysts, paint and
Pharmaceuticals. About 20 percent of the United States consumption of mercury
in 1973 was in this manufacturing category. The consumption of the mercurials
accounted for about 400 tons in 1973, with 70 percent of that being used for
paint. Agricutural consumption includes fungicides and bactericides for
industrial purposes. Mercury is used in paints for mildew-proofing and
antifouling. Mercury compounds used as catalysts are used in the synthesis
of both vinyl chloride monomer (VCM) and anthraquinone dyes. They also find
use in foaming urethane in place.
Mercurial production is generally a batch operation. Most manufacturing
facilities are located in New Jersey. Losses of mercury from the production
of mercurials is primarily to water with minor quantities emitted to air and
land. The losses from the use of manufactured catalysts are primarily to
land.
Battery Manufacturing—
Battery manufacturing consumed about 30 percent of the mercury used
in the United States in 1973. Most losses occured as a result of batteries
31
-------
being discarded by the consumer. Approximately 92 percent of this went to
landfills with 8 percent going to public incineration. Of the seven types
of batteries in which mercury was used, three comprised 99.5 percent of the.
mercury losses in 1973. These were the zinc-carbon dry cell, the alkaline-
manganese dioxide dry cell, and the Ruben cell. As of 1973 there were 35
plants which manufactured these three types of batteries. ^
The Zinc-Carbon Dry cells use mercury primarily as a paste applied to
paperboard separators. The major losses of mercury during the manufacture
of this type of battery occur with the disposal of rejected batteries in
landfills. In addition, since their recycling is uneconomical, the ultimate
disposal by the consumer, mostly to landfills, represents a significant loss
of mercury.
Mercury is used as the anode, in amalgamation with powdered zinc, in
the Alkaline-Manganese Dioxide Dry Cell. The major losses with this type
are the same as with the previous type of battery.
The Ruben Mercury batteries use an amalgam of zinc and metallic
mercury as the anode, while red mercury oxide pressed with graphite is the
cathode. Losses are minimal during manufacturing. However, the rejected
cells are processed to reclaim mercury. The recovery process involves
incineration in a furnace, with the residue going to a landfill. Most
losses from this source, as previously, are associated with consumers
discarding batteries.
Electric Lamp Manufacturing —
Mercury has been used in electric lamp manufacturing, namely the
fluorescent, mercury vapor, metal halide, and high-pressure sodium types.
About 95 percent of the mercury used in such manufacturing is for fluores-
cent lights. Most losses went to landfills with the remainder into the air.
The greatest losses occured from bulbs discarded by consumers. Out of
approximately 69 United States plants manufacturing electric lamps in 1973,
47 manufactured mercury lamps. In 1973 the industry consumed approximately
2.3 percent of the mercury used in the United States (almost 48
A typical fluorescent lamp manufacturing process involves the injection
of metallic mercury, starting gas (usually argon), and other materials into
a quartz tube, which is then sealed. About 5 percent of the losses during
manufacturing are due to spilling and breakage.
Industrial Instruments Manufacturing —
Industrial instruments manufacturing, primarily switchgear and switch-
board apparatus and mechanical measuring and control instruments consumed
approximately 13 percent of the mercury used in the United States in
1973.^2 This represented an estimated 81 percent of mercury used in all
32
-------
instrument manufacturing.^ Metallic mercury is the primary form of
mercury used in this industry. The reason for its use are primarily
its properties of remaining liquid at ordinary temperatures, high electrical
conductivity, excellent high thermal conductivity, and regular thermal
expansion. Typical of the measuring and control instruments are the mercury-
in-glass thermometer, thermostats, thermoregulators, manometers, barometers,
navigational devices and medical instruments (blood CO^ analyzers, etc.).
More than half of the mercury used in the instrument industry was recycled
or reclaimed as a result of manufacturing practices and industrial consumers
whose equipment is traded in and/or serviced.
The primary manufacturing operations, for this entire classification in
which mercury is lost to the environment are the filling process and testing
and storage. During the filling process, when the instruments are loaded
with premeasured amounts of mercury, the losses occur as a result of spillage
and volatilization. Testing and storage losses occur for similar reasons as
well as during cleaning instruments. However, considerable losses occur as
a result of consumer discarding of devices containing mercury.
Paint Manufacturing—
The paint manufacturing industry accounted for 14% of the mercury used
in 1973.^2 Only a small quantity was used for mildew-proofing substances,
with the remainder being used for paint additives. Phenylmercuric compounds,
especially phenylmercuric acetate and phenylmercuric oleate, are used in
latex and solvent paints as a bactericide and a fungicide. These compounds
had found wide use in antifouling paints. However, toxic effects on living
organisms have reduced or eliminated their use in marine antifouling paints.
As of 1973 there were almost 2,300 paint manufacturers of which 30 accounted
for approximately 90% of the manufactured product value. -*0
Paint is manufactured by a batch process, with the ingredients mixed in
vessels whose capacity ranges from a few hundred to several thousand gallons.
Mercury is lost both as a result of bad batches and from cleaning of the
vessels. These losses are to land, water, and air. Smaller manufacturing
plants tend to dump wastes down the sewer. Other mercury losses during
manufacturing occur from spills and volatilization. Final consumption
accounts for the major loss of mercury as a result of volatilization following
application.
Agricultural Consumption—
-The agricultural use of organomercurial pesticides has been drastically
curtailed as a result of EPA pesticide actions and anticipated actions. The
major organomercurial has been phenylmercuric acetate (PMA), replacing the
more effective alkylmercurials. This source of mercury to the environment
occurs mostly from the land after the planting of mercury-treated seeds.
Compared with the alkylmercurials, the lack of affinity for soil components
of PMA allows for deeper penetration into the soil, where its solubility
33
-------
permits leaching. Additional losses occur through ingestion by wildlife and
man, as well as volatilization from the soil. Mercury emissions to water
occur from washing of equipment and trucks transporting treated materials.
Non-agricultural pesticide use, for the turf industry, also contributes
mercury to the air as a result of spraying and vaporization following
application. Surface runoff creates an additional source of mercury to
water in nonagricultural uses because of the increased frequency of watering.
Pharmaceuticals—
The pharmaceutical industry has used mercury compounds in antiseptics,
diuretics, and skin preparations; for sterilization of instruments; and as
preservatives in cosmetics and soaps. The use of mercury in this industry
has declined over the years due to availability of effective non-mercurial
substitutes and the toxicity of mercury. Production losses to the environment
come from disposal of residues in landfills. There are also contributions
to the air and water, the latter as a result of washing off the body or
in human wastes.
Laboratory Consumption—
Another source of mercury is the laboratory, which uses metallic mercury
and mercurial compounds for reagents, indicators, use as a sealer and in
vacuum pumps, for radioactive diagnosis, and as a tissue fixative. Mercury
from laboratory use is emitted to the air as a result of incineration of
bandages and supplies, and to the water as a result of flushing away fixative
solutions, spills and cleansing laboratory apparatus. The remainder is lost
to the land by disposal. More than half of the mercury used in this general
application is recycled.
Dental Applications—
The use of mercury in dental applications provides an additional
source to the environment. The manufacturing of mercury amalgam for
fillings uses approximately 4 percent of the total mercury consumed in the
United States.-^ The process involves combining a silver-tin alloy
(powdered) with metallic mercury. The ingredients are placed in a mortar
within a capsule, which is then vigorously shaken. The resulting metallic
putty, used to fill the cavity, is condensed and polished, with the excess
amalgam removed during the condensing process. Losses can occur through
vaporization from open or poorly closed storage containers or from spillage.
Rinsing of the patient's mouth causes mercury to enter the wastewater
system.
Municipal Wastewater Treatment—
Municipal waste treatment plants collect effluents from both residential
and industrial users. The mercury found in the waste stream emanates from
those manufacturing and end use areas previously discussed. As a result of
34
-------
the treatment processes in use, mercury can enter the receiving waters or
can be emitted to land through disposal of sludge. If sludge incineration
is used as an ultimate disposal method then mercury is emitted to the air.
Municipal Solid Waste Disposal—
Municipal solid waste disposal systems provide for the collection,
processing, and ultimate disposal of solid wastes. The ultimate disposal
methods are landfill or incineration. As a result of widespread use of
mercury, mercury is found in the leachate from landfills as well as incin-
erator particulate emissions.^2,43 There are over 18,500 landfill sites
and almost 200 municipal incinerators operating.^0
Natural Sources—
In addition to the anthropogenic sources, nature remains a major source
of mercury to the environment. The natural occurrence of mercury in the
earth's crust is the source from which mercury vaporizes from the land
surface and leaches out into ground water and ultimately to surface water
and its sediments.
Quantitative Estimate of Emissions from Other Sources
In order to make an assessment of the mercury emissions from power plants
it is necessary to know what the various sources of mercury are and the
extent of their contribution to the environment. Table 8 shows the estimated
losses on a national basis, to all media from these sources for 1974.
The amount of mercury mined and the amounts of mercury consumed
by the various "Manufacturing and Processing" categories were obtained
from Bureau of Mines data.^-> The distribution of mercury losses to
air, land, and water was based upon the URS study of these sources in which
they characterized the losses by process.™ Since their study was for
1973, we substituted 1974 mercury inputs to these industries and used their
percentage losses to arrive at the data in Table 8. Similarly, we used the
ratios of mercury which they found, after the manufacturing process, to
remain in the products for consumption, and applied them to 1974 data. The
data for mercury losses by utilities were derived in this report.
The URS report was used as a base because it was believed that the data
base and depth of study was the most complete information available. Their
assumptions appeared to be valid, except where we made note in this report.
Mining and Smelting—
Mercury production from mining has declined over the years from a high
of 1125 tons in 1969 to 83 tons in 1974. The 1974 figure was approximately
2 tons more than in 1973. The 83 tons produced were from 18 mines located
in western states. It was estimated that 2 percent to 3 percent of the
mercury was lost through stack emissions, on an industry-wide basis.46
35
-------
TABLE B. ESTIMATED MERCURY LOSSES TO THE ENVIRONMENT, 1974*
Mercury^
Consumed
(Tons)
Mining & Sheltlng
Mercury
Copper
Other
Subtotal (X of total
for media)
tare la ted Source!
Utilities (Oil & goal)
Other unregulated
Waite Treataent
Incineration
Subtotal (X of total
for media)
Manufacturing & Processing
Agriculture
Catalysts
Dental Preparations
Electrical Apparatus Batteries
Leaps
Chlor-Alkall Prep.- Electrolytic
Industrial Controls & Instrunents
Control Inst.
Switches and Relays
Paint:
Antlfoullng
Mildew-Proofing & additives
Paper & Pulp Manufacture
?harmaceutlcals
Amalgamation
Other
Subtotal (X of total
for media)
tonsumption
Agricultural Pesticides
Non-Agricultural Pesticides
Electrical Apparatua Batteries
Loops
Paint
General Laboratory Use
Dental Applications
Catalysts
Pharmaceut Icals
Industrial Controls & Instruments
Subtotal (X of totel
for media)
TOTAL
Natural (degassing & runoff)
"e
105*
-
168
-
-
-
-
_
37
49
115
748
642
J
1911
45'
0.2
2S9
-
23
-
93
2.202
25
11
659
51
2S6
18
82
49
23
233
1.407(63*)
Air
2
58e
lle
7K11X)
ISO8
6°.k
26 '
41*
277(45X)
-
-
2
-
0.1
22
0.1*
0.1
0.0002
0.28
-
-
-
21
45.5(71)
2
1
52
6
156
2
-
0.2
1.8
5
226(37X)
619.5
1,121
1,740.5
Mercury
Land
7
44
3e
54 (4Z)
B8
42 a k
39 •'*
4.6*
Losses (Tom)
Vater
-
3.
1*
4(2X)
.
'ak
65 •'"
_
93.6(7X) 6709X)
0.7
-
3.5
2.0
349
1.8"
1.1*
0.0017
2.2
-
0.02
-
39
399 (29Z)
13
607
AS
8
1
-
48.8
1.2
100
830(601)
1,376.6
_
1,376.6
0.8
0.2
-
-
-
3
a
a
0.0005
0.62
-
-
33
37.6(221)
10
4
-
-
1
5
24
-
20
-
64(67X) 1
172.6 2
208 1
380.6 3
Total
9
105
15
129(6X)
158
104
130 "
45.6
437.6(20%)
1.5
0.2
2
3.5
2.1
374
1.9
1.1
0.1
3.1
-
0.1
93
482.6(22X)
25
11
659
51
165
8
24
49
23
105
.120(521)
.169(621)
.229(381)
,498
Losses
Air
0.01
0.4
0,07
1
0.4
0.2
0,3
-
-
0.1
"
0.007
0.15
0.0007
0.0007
0
0.002
-
-
0.14
0.01
0.007
0.35
0.04
1.04
0.01
-
0.001
0.01
0.03
Relative to
Land
0.97
5.5
0,4
1
5.3
S
0,6
0.1
-
-
0.4
0,25
43.5
0.2
0.1
0.0002
0.3
-
0/0025
5.0
1.5
0.75.
76
5.5
1.0
0.0125
-
6.1
0.15
12.5
Power Plant Losses
Water Total
0,06
0.7
0.09
1 1
0.7
O.B
0.3
0.009
0.001
0.01
0.02
0.01
2.4
-
0.02
-
_
0.6
0.2
0.07
4.2
0.3
1.04
0.05
-.15
0.}
0.15
0.07
u>
-------
Table 8
Footnotes
aBased upon the same percent lost in 1973 as given in Reference 30.
"These data are from the Dept. of the Interior, Bureau of Mines, Reference
cThe amount produced in 1974. Reference 45.
^Normalized losses with utilities as 1.
eBased upon the projected annual growth rate of the industry as stated in
Reference 30.
*These quantities represent the approximate amounts of mercury that remain
in the consumer use area after manufacturing losses.
gFrom Table 7.
^These sources include livestock, residential fuel oil, refinery, coke
ovens, etc., but excludes utilities. The mercury losses are assumed
to be those as in reference 30 but with a 5 percent growth rate assumed
for 1974.
1The total mercury consumed by the industrial instrument industry for 1974
was 236 tons. The division of 81 percent to control instruments and 19
percent to relays & switches are assumed to be the same as in 1973 as in
reference 30.
^Waste treatment streams and incineration are final disposal methods.
The mercury found in waste treatment streams most probably includes
the amount dumped by industrial operations as well as consumers. The
amount estimated to be emitted from incineration may also include those
items containing mercury, discarded by industry and consumer alike, which
appear under other categories as losses to land. It is assumed that 8
percent of all solid waste is incinerated.
percentage of mercury remaining in the consumption sector after
manufacturing and processing.
37
-------
According to present technology it was estimated that about 8 percent of the
mercury is lost to the land as a result of dust and tailings from the kiln
during processing.30 Losses from mining of the ores are insignificant.
Copper smelting is a larger source of mercury than mercury smelting.
An estimated 105 tons of mercury was released from the processing of over
223,000 tons of ore in 1973. Even though copper production is highly variable
we have assumed that the 1974 mercury losses from this source remained the
same as was reported for 1973. While the average mercury content in copper
ore is 0.5 ppm, the concentration range in ore has been found to be 0.1 to
40 ppm.^ Mercury losses from the copper smelting source were primarily
to the air (55 percent) and land (42 percent). The losses to air were a
result of emissions from the furnace stack gas and the off gas from the
reactor, which converts S02 to sulfuric acid. The emissions to land were
from the tailings following ore concentration.
From 1973 figures, more than 83 percent of the smelter production
originated in the Mountain States region, with the Pacific region (Washington)
and West South Central regions each contributing about 6 percent and the
East North Central region (Michigan) contributing 4 percent.
Other mining operations such as zinc and lead mining and smelting as
well as cement and lime processing, accounted for 12 percent of the losses
from the mining and smelting industry. The industry as a whole accounted
for approximately 6 percent of all man-made mercury loses, but 11 percent of
all man-made losses to the air.
Unregulated Sources—
The sources grouped here include: utilities; residential, commercial,
and industrial use of fossil fuels; refineries; tar and asphalt; coke ovens;
livestock; waste treatment, and incineration. The utilities' use of fossil
fuel with subsequent mercury losses to the environment have been discussed
previously in this report.
Wastewater treatment and incineration are final disposal methods. The
estimated mercury losses from these sources are shown to place these final
disposal sources in perspective with the producing sources. The mercury
found in wastewater treatment facilities comes from the mercury-containing
wastes disposed of by other industries. The mercury emissions from the
wastewater treatment process amounted to an estimated 130 tons in 1974
based upon an estimated 10% growth in sewer discharges since 1968. It
was also assumed that the national average mercury concentration was 2.0
ppb.30 The mercury from the wastewater treatment process was emitted to
the air (26 tons, or 20 percent), land (39 tons or 30 percent), and water
(65 tons or 50 percent) as a result of vaporization, incineration, land
disposal and water discharge.30
The mercury emissions from wastewater treatment would be primarily in
urban, industrial high density areas where the large treatment facilities
are needed and built. It was estimated that approximately two-thirds of the
38
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wastewater treatment capacity was east of the Mississippi River, with more
than half of that concentrated in the northeast quandrant of the United
States.
All the remaining "Unregulated Sources" accounted for about one fourth
(104 tons) of this source category (Table 8). These mercury emissions are
to air (60 percent) and land (42 percent) with the water receiving virtually
no direct emission. There is no apparent geographic concentration of these
sources, but rather are scattered throughout the country.
All "Unregulated Sources," including the wastewater treatment contri-
bution, accounted for 20 percent of the total man-made mercury losses. Their
predominant contribution was to air, accounting for 45 percent of all
man-made mercury emissions to that media.
Manufacturing and Processing—
This source category used 2,202 tons of mercury according to 1974
figures,3^ while losing approximately 22 percent of it to the environment.
The mercury consumed included that which was U.S. mined and produced,
reclaimed (secondary) and imported. As a group this category accounted for
22 percent (483 tons) of all man-made losses to the environment but 22
percent of all the man-made mercury lost to water, 29 percent to the land,
and 7 percent to the air. More than 77 percent (374 tons) of this category's
total losses originated with one industry, chlor-alkali manufacturing.
Another 18 percent was lost from other sources.
The chlor-alkali industry used the second largest amount of mercury of
any manufacturing/processing industry, 642 tons in 1974. Of this amount,
58 percent (374 tons) was lost in the various operations of the electrolytic
mercury cell process. Most of this loss, an estimated 349 tons, was disposed
of to the land. There were 29 chlorine plants, using the mercury cell,
located in various parts of the country with almost 75 percent of all
mercury emissions occuring from plants in the Southern states, which consist
of the South Atlantic, E. South Central, and W. South Central regions.^
The total emissions to all media in this geographical area, approximately
evenly divided among the three regions, was estimated at 212 tons which is
about one third of all the mercury consumed by the industry in 1974. The
plants located in the states of New York and New Jersey alone accounted for
14 percent, or 41 tons, of the total estimated mercury loss to the environment.
Most of the emissions in this industry, about 90 percent, were to land.
These estimates were based upon an estimated 3 percent growth in production
between 1973 and 1974 which was applied to the losses to the environment as
tabulated for 1973.30>38
*
The 93 tons of mercury emitted by the sources classified as "other" was
distributed to all media with approximately 40 percent going to land, 35
percent to water, and 23 percent to the air. Geographic distribution
was not identifiable from present data. The "Other" category, as described
by URS, consisted of many small, diverse uses, often by small manufacturers
or processors. Since these would have been difficult to trace, and since
39
-------
the use appeared to be diverse and widespread, no attempt was made to refine
this category.
•
Consumption—
It was estimated that approximately 63 percent (1400 tons) of the
mercury consumed in 1974 by manufacturing and processing was passed on in
products for consumption. About 1120 tons of this mercury was lost to the
environment, which represented more than half of all man-made losses of
mer :ury to the environment. The remaining 20 percent either remained with
the product or was recycled. The largest proportion of this, an estimated
83r tons, was lost to land. This represented 60 percent of all mercury
losses to land for all categories. The largest single contributor to this
loss was the electrical apparatus industry, which accounted for 652 tons or
79 percent of the land losses from consumption. This large loss, which
represented 87 percent of the mercury used by that industry, was due to the
discarding of batteries and lamps after use in landfills. The second
largest source of mercury to land was from industrial controls and instrument
manufacturing, which, as a result of discarded products lost 100 tons in
1974. This represented 43 percent of the mercury used in that industry's
end products, and 95 percent of the total lost for that industry. The only
other major source of mercury to the land was from the use of catalysts where
99 percent of the mercury used in its manufacture was lost to land after
use.
The next largest loss, resulting from consumption of mercury containing
products, was to air. This accounted for 226 tons or 37 percent of all
man-made mercury losses to the air in 1974. The largest source, accounting
for 69 percent of these losses (156 tons) was from paint. Its use in such
products as latex paint has wide application. There were 256 tons of
mercury available in paints in 1974 of which 61 percent (156 tons) was lost
to the air through vaporization. Another 36 percent remained bonded to the
painted surface. The second largest, and only other, major source of
mercury to air in this category was from electrical apparatus consumption.
The 58 tons lost to the air were the result of discarded batteries and lamps
entering incinerators, and during which process mercury was vaporized.
The smallest loss of mercury, which resulted from product consumption,
was the loss to water, which accounted for 6 percent (64 tons) of this
category's losses but 37 percent of all man-made mercury losses to water.
Dental applications and Pharmaceuticals accounted for 70 percent of the 64
tons of mercury involved (24 and 20 tons respectively), followed by agricul-
tural pesticides (10 tons). These mercury losses resulted from products
being flushed into sewers or contained in runoff.
General—
Of the approximately 2169 tons of mercury lost from man-made sources in
1974, the consumption category accounted for more than half, followed by
manufacturing and processing (22 percent), unregulated sources (20 percent)
and mining and smelting (6 percent). There were, however, natural sources
of mercury which were estimated at 1329 tons, or 61 percent of the amount
40
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released to the environment in 1974 from all man-made sources.^0 This
natural mercury was emitted to the air through the mechanisms of degassing
and runoff. These tnachanisms will be discussed later in the report. The
source is a combination of the natural mercury found in the earth's crust
and mercury which was lost to land or water becoming volatilized. This
source, while uncontrollable, was the largest single source of mercury
to the environment, representing 38 percent of all mercury lost to the
environment.
When comparing the mercury lost from natural and man-made sources, it
was estimated that natural sources lost about 1.8 times the amount of
mercury to land and 1.2 times the amount to water that all man-made sources
lost to each of these media. The distribution of mercury lost from man-made
and natural sources to the environment, on a regional basis, is shown in
Table 9.
Comparison of Power Plant Emissions with Emissions From Other Sources
The previous section dealt with the magnitude of the various sources of
mercury in absolute terms. In order to assess the emissions from power
plants it is necessary to examine the relative magnitude of this source with
respect to the other sources on both a national and regional basis. Table 8
presents the mercury losses to the environment from power plants relative to
the other sources. In this comparison, the mercury losses from utilities
were considered one with the others normalized to that base.
Examining total losses from all man-made mercury sources in 1974,
(Table 8) utilities ranked fourth «8 percent of total man-made mercury
emissions), on a nationwide basis, after Electrical Apparatus-Battery
Consumption (33 percent of total), Chlor-Alkali Manufacturing (17 percent),
and Paint-Consumption (8 percent). Wastewater treatment as a source ranks
behind utilities with about 6 percent of the total mercury lost. Following
close behind utilities, each representing 5 percent of the mercury losses,
were Copper Smelting, Other Unregulated Sources, and the Consumption of
Industrial Controls and Instruments. If natural sources are considered, then
they would rank out in front having mercury losses to the environment of
the order of magnitude of almost 8 times those of utilities. Utilities, as
a source, would then be moved down to fifth place in relative losses of
mercury. In comparison, utilities ranked fifth in 1973 with about 4 percent
of total mercury lost.™
The relative amount of mercury lost by utilities to the atmosphere
compared to the other sources, again on a nationwide basis, was different
than when compared on a total basis. Only one other source exceeded it, and
that was the loss from paint consumption due to vaporization. The relative
loss between the two sources is 1.04:1, with 156 and 150 tons respectively.
The next closest sources are Copper Smelting and Other Unregulated Sources
with 58 and 60 tons respectively, followed by Electrical Apparatus Consumption
(Batteries) at approximately one-third the utility emissions, and incineration
at <0.3 that of utilities.
41
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TABLE 9- REGIONAL DISTRIBUTION OF MERCURY
LOSSES IN THE UNITED STATES IN 1973
(cons)
Region1*
New England
Middle
Atlantic
East North
Central
West North
Central
South Atlantic
East South
Central
West South
Central
Mountain
Pacific
TOTALS
From Man-Made
Sources to
Air Land Water
26.3 54.3 5.4
93.4 183.2 17.2
96.0 182.5 19.1
38.0 76.0 9.0
68.5 173.1 13.3
39.1 120.7 6.6
V
46.1 135.5 9.0
56.8 34.3 6.0
50.3 96.4 10.0
514.5 1056 95.6
From Natural
Sources to
Air Water
18.1 1.0
40.2 1.8
49.6 8.8
95.1 22.8
93.1 8.5
37.2 19.3
89.0 52.0
448.9 63.9
157.8 30.0
1029 208.1
From Wastewater
Treatment
2.8
9.8
10.4
4.0
7.0
3.0
5.6
2.2
6.5
51.3
Total
(tons)
107.9
345.6
366.4
244.9
363.5
225.9
337.2
612.1
351.0
2954.5
*Reference 30
The regions are the same as In Table 5
42
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Mercury losses directly to the water are considered to be zero for
utilities. Mercury from power plant emissions contribute to the ambient
mercury concentration of water, but primarily as a result of transfer
mechanisms from other media as will be discussed in Section 7. Fifteen of
the other sources contributed mercury to water, ranging from 0.2 tons from
catalyst production to 65 tons from waste treatment.
The loss of mercury to land by utilities occurs when ashes containing
mercury are disposed of in a landfill. To be conservative it is assumed that
10 percent of the mercury in coal is ultimately found in the ash, while all
the mercury in oil enters the stack gas.^2-25 Based upon utility consumption
of fossil fuels, utilities ranked ninth among the sources, along with paint
consumption. The most pronounced differences were with the chlor-alkali
industry, with 43.5 times the mercury losses to land and with the consumption
of electrical apparatus - batteries and lamps - with combined losses of
mercury to land of 81.5 times those of utilities (76 and 5.5 times respec-
tively), or 652 tons. These were followed by the consumption of industrial
controls and instruments at 12.5 times the amount of mercury. In addition,
if wastewater treatment is considered an independent source, it would rank
ahead of utilities with 4.9 times the amount of mercury lost to land.
A relative ranking, considering the losses from natural sources, such
as degassing, would place utilities third. Degassing contributed 7.5 times
more mercury to the air than utilities. However, more than half the mercury
lost to the air from degassing occurred in the Mountain and Pacific regions.
One method of assessing the contribution of utility losses to total
man-made mercury losses is to examine the ratio of the two on a regional
basis as well as the trend from region to region. Figure 1 is a graphical
representation of the relationship between utility and total man-made losses
of mercury to the air, on a regional basis.
The largest contribution by power plants to all mercury emissions to the
environment was 12.3 percent in the South Atlantic region. The power plants
in this region accounted for 20 percent of the net electrical generation in
the United States in 1974, with 93 percent of the Btu as a result of the
combustion of coal and oil. The lowest proportional contribution occurred
in the West South Central region where power plants contributed 1.9 percent
of all mercury emissions. Power plants in this region produced 15 percent
of the total net electricity generated in the United States. However, only
9 percent of the Btu's produced in generating the power were from the
combustion of coal and oil.
The contribution of power plants on a percentage basis to mercury
emissions to the air, as compared with total mercury emissions, was consider-
ably greater. The power plants contributed an estimated 47 percent of all
air emissions in the South Atlantic region. While this represented the
highest estimated amount of mercury emitted to the air from power plants in
a region, the highest regional emissions to air from all sources occurred in
the Middle Atlantic and East North Central regions (107 and 110 tons respec-
tively). In these regions, the contributions to the air from power plants
43
-------
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Q All Man-Made Sources
f^ Utilities (Power Plants)
A Mercury Emissions to All Media
B Mercury Emissions to Air
(%) Percent of All Man-Made Losses
Attributable to Utilities
a Utility Data from Table 7. Based
on Uncontrolled Emissions
b Total Man-Made Source Data from
Table 9 (Reference 30) and Adjusted
to 1974 Assuming a Factor of 1 .237
Applied to Total Mercury Emissions
_ and a Factor of 1.146 Applied to
#
(O
m
Mercury Emissions to the Air
.y
1
__
«
§
U
AB AB AB AB AB AB AB AB AB
Figure 1. Comparison of mercury losses between utilities and all man-made sources, by region (1974)?'°
-------
were each about 26 percent while together providing about one-third of the
net power generated in the United States (12.4 and 21.3 percent respectively).
The lowest contributions were in the West South Central and Mountain regions
(8.1 and 10.1 percent). The West South Central region accounted for about
25 percent of the mercury lost from the chlor-alkali industry, while the
Mountain region accounted for much of the smelting.
The regional data for all man-made sources was available for 1973.30
Total man-made mercury emissions to the environment for 1974 indicated an
increase of 23.7 percent over the 1973 data. As a basis for comparing 1974
power plant emission data from this report to regional data from all man-made
sources, a factor of 1.237 was applied to the 1973 regional data found in
the literature. Similarly for emissions to air, a factor of 1.146 was applied
regionally. The accuracy of some of the 1973 data used may be questionable,
especially in regard to power plant emissions which were included in the
all-sources data. The power plant emission data used in this report are 2.5
greater than those in the URS Research Company report. The larger values
were used as they were based upon power plant operating data for 1974, which
included fuel mix, as well as the average mercury content of the fuels.19,30
However, these data are still useful in assessing the relative importance of
power plant emissions. While they may have accounted for almost half of the
mercury emissions to the air in a particular region, they were a relatively
small contributor to the mercury emitted to the environment. They may, in
fact, have been smaller yet as a result of some mercury removal which may
have occurred in the use of required emission control equipment by power
plants. The data for other sources appear to have included any emission
controls normally associated with a particular industry's operations.
MERCURY EMISSION CONTROL AND PROJECTIONS
There is presently no mercury emission control technology used by utili-
ties. There are industries which, through recycling and good "housekeeping"
practices, are able to limit mercury losses. This section will briefly
review current power plant control systems as well as those used by industries
considered to be sources of mercury to the environment. Mercury emissions
are projected to 1983 based upon future consumption and controls. The
relative importance of power plant mercury emissions is examined with
respect to the projections.
Technology of Power Plant Control Systems
At present the three devices most often used for control of pollutants
from power plants are electrostatic precipitators, baghouses, and scrubbers.
Brief descriptions of each device follow with an estimate of their effec-
tiveness in reducing mercury emissions.
Electrostatic Precipitators—
Electrostatic precipitators (ESP) are efficient devices for the removal
of particulates from gas streams. Particulate removal efficiencies of over
99 percent are common in properly maintained utility applications. The
process involves three basic steps: charge, transport, and particulate
45
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collection. An ionizing effect is created by means of a very high voltage
discharge through a wire parallel to and between two collection plates.
This applied discharge impresses on the particulate matter a charge opposite
to that of the collection plates. The opposite charge on the particulates
will cause the transport of these particulates, in the stack gas, to the
oppositely charged plates. The third step removes the particulate from the
collection plate, by rapping the plates, using mechanical hammers, causing
the collected particulate to fall to the hopper below.
A number of factors influence the collection efficiency of the ESP,
including particle size, gas stream velocity, particulate resistivity, and
corona strength. Since mercury is usually in the vapor form at normal stack
temperatures (300°F) it would be expected that little if any mercury will be
collected by an ESP. Limited testing on power plants equipped with ESP has
substantiated this assumption.32,35,48 Samples generally were collected
in the breaching on the outlet side of the electrostatic precipitator,
in addition to various other locations from the fly ash hoppers to the
stack. The limited sampling indicated the loss of mercury primarily as a
vapor, thus escaping capture by the ESP. There were few data points collected,
and in some cases the testing program was incomplete. Analytical methods
also varied. When material balances were done around a power plant imbalances
were found, which ranged as high as 85 percent. One way to promote mercury
collection by an ESP would be to lower the flue gas temperature causing
condensation of the vapor and subsequent adsorption onto the particulate,
which in turn would be collected. Current heat recovery equipment is not
suitable for lowering the flue gas temperature much beyond what it now does,
and diluting the flue gas with ambient air is probably uneconomical since
the cost of an ESP depends upon the volume of flue gas treated. In addition,
reduction of stack gas temperature can create problems in releasing the
stack gas to the atmosphere. A reduced temperature differential slows both
the effective rate and the height of the discharge causing dispersal
at a significantly lower altitude. To obviate the problem the gas would
have to be reheated prior to exiting the stack, an expensive operation. In
summary, therefore, it is not anticipated that electrostatic precipitation
can play a role in controlling mercury emissions from power plants.
Scrubbers—
Scrubbers, are used in power plants for the control of particulates
and/or gaseous pollutants. Particulate scrubbers are generally a cyclone
design of a wet or dry type. The basic operating principle is the inertial
separation of particulates from a gas stream. The stack gas enters the
cyclone tangentially causing the particulate matter to be pulled to the
walls of the cone while spiralling downward. A hopper beneath the cyclone
collects the falling particulates allowing the cleaned (scrubbed ) gas to
exit upward through the exhaust port in the center of the scrubber body.
Efficiency may be increased by means of a water spray which causes particle
agglomeration and promotes the scrubbing action.
Gaseous pollutants are scrubbed using a material, usually a liquid,
which either through adsorption or reaction selectively removes the undesirable
component(s). The operating mechanism is diffusion of the pollutant to the
46
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scrubbing medium upon contact. The principle gaseous component for which
scrubbers are used is sulfur dioxide. There are a number of S02 scrubber
systems in use and under study. A description of these systems is beyond
the scope of this document.
Mercury emissions may be expected to be reduced by the action of
scrubbers. Investigations into the effect of scrubbers on mercury emissions
are not known to have been conducted. Some limited data were available from
a scrubber study which included spot analyses of a number of substances
including mercury.32,48 -phe data indicated that mercury emissions may be
reduced by up to a third when the flue gas was scrubbed for S02.
Baghouses—
Fabric filtration is an efficient means for removing particulate from
gas streams. High efficiencies, even for sub-micron particulates, have been
obtained. The principal mechanism of collection is impaction. The fabric
traps the larger particulates, closing the open mesh area substantially.
The cake which builds up is able to stop smaller and smaller particles from
getting through with the passing stack gas. The pressure drop increases
with the buildup until bag cleaning is required. Baghouses must withstand a
variety of operating temperatures depending upon application. A variety of
fabrics are available to cope with these temperature ranges.
The temperatures at which most baghouses are maintained are sufficient
to prevent condensation. Some mercury may, however, be adsorbed or chemically
react with the filter cake effectively reducing emissions. The only data
available are from a study which investigated the fate of mercury in the
combustion of coal in a bench type unit.34 in this study 55 to 60 percent
of the mercury in the coal was found on particulate collected by the baghouse
(operated above 300°F) while only 31 to 36 percent was found in particulate
from a larger unit which used mechanical collectors. It is reasonable
to assume that adsorption may have been a primary mechanism in mercury
collection. Without further study, however, it is impossible to extend
these results to field units because of the differences in temperature,
mercury concentration, and physical/chemical fly ash characteristics.
Technology of Control Systems for Other Industries
The control techniques used in sources other than power plants are
often similar. Under normal circumstances particulate control systems are
either ESP, cyclone, or baghouse. Depending upon a number of parameters,
their ability to remove mercury from the gas stream will probably vary
considerably. A lack of comprehensive data precludes rendering any judgments
in this regard.
Where substantial quantities of sulfur dioxide are present and must be
scrubbed from the gas stream as mandated by law, special control systems are
used. These are basically process units whose output or end product is
commercially usable sulfuric acid or elemental sulfur. As with other
systems, there is little known about their effect on controlling mercury
emissions.
47
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Current systems for the control of mercury emissions for various sources
other than power plants will be reviewed in this section.
Liquid effluents and sludges are handled either through waste treatment
techniques or landfilling. The former may cause mercury to be captured in a
sludge. These sludges are either burned-or placed in a landfill. Neither
controls the mercury, but merely transfers it to a different medium for
release to the environment. These methods will not be discussed here.
Mining and Smelting—
Current mercury recovery plants extract ore, crush it, and feed it to a
rotary kiln. The dust from crushing is uncontrolled. There is little
mercury at this point, because there are only 5 Ibs. of mercury for each ton
of ore. The effluent gases from the kiln are passed through a scrubber
(cyclone) to collect dust. The mercury passes, as a vapor, to a condenser
where the mercury is removed. Industrial losses occur at this point with
the effluent gases passing directly through the stack.
The copper smelting process uses both cyclones and electrostatic
precipitators on the exhaust of the reverberatory furnace. These have
little effect on capturing mercury according to one industry flow diagram."
The converter exhaust, however, passes through a reactor for producing
sulfuric acid. Indications are that two-thirds of the mercury in the
exhaust will remain in the sulfuric acid.
Chlor-Alkali Manufacturing—
The mercury cell process emits mercury with hydrogen during the decom-
posing of sodium amalgam formed in the cell. Cooling to 55°C from 80°C is
effective in retaining 98 percent of the mercury, the remainder being
emitted during the flowing of the hydrogen.
Mercurials—
Most losses involve liquid wastes or applications to land, neither of
which control the emission.
Electrical Apparatus—
The production of batteries accounts for small losses. Recycling is
used in the manufacture of Ruben mercury batteries, thus controlling mercury
losses. Losses which do occur are uncontrolled and involve discarding the
product. The manufacturing of fluorescent lamps has no controls. Losses are
from broken and discarded products.
Industrial Instruments and Controls—
Manufacturing losses are small, with no special control systems. Major
losses occur as a result of discarding products.
Paint Manufacturing—
There are no special control systems used. One major problem arises as
a result of small manufacturers who flush wastes down the sewer, rather than
treating it or disposing of it properly.
48
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Projected Mercury Emissions and Controls
A projection of mercury losses to the environment in 1983 was made to
coincide with EPA emission standards which have been established for that
year. The data are based upon a technological assessment of mercury and its
compounds conducted by URS Research Company.^0 The data are shown in Table
10. The URS report as mentioned, was used because of its comprehensive
data. The data in the 1983 projection had been arrived at through a number
of assumptions for each industry in terms of product demand, population
growth, process efficiencies, control technologies, and regulatory requirements.
The bases for these projections will be briefly discussed as will the
relative importance of projected power plant emissions to the other sources.
A number of conclusions can be drawn from the projections as shown in
Table 10 when compared with the 1974 figures in Table 8. On an overall
basis, the total mercury loss for all sources projected for 1983 are about
2 percent lower than for 1974. The mercury loss to air is projected to
increase 26 percent as a result of an anticipated increase in power plant
emissions. Emissions to both land and water are expected to decrease in
1983 by 13 percent and 12 percent respectively. Both the "Unregulated
Sources", and "Consumption" are estimated to show an overall increase by
1983 of 32 percent and 18 percent respectively, while "Mining and Smelting"
and "Manufacturing and Processing" will decrease by 53 percent and 64
percent respectively.
The ranking of mercury losses to the environment by sources and by
media for 1974 and 1983, is shown in Table 11. A relative ranking of
sources, based upon the 1983 projections, would place utilities first in
mercury losses to the air with an estimated 230 tons (30 percent of all
losses to air). Other major ranked sources of mercury to the air include
Paint Consumption with 191 tons (25 percent), Battery Consumption with 119
tons (15 percent), and Other Unregulated Sources with 92 tons (12 percent).
This compares with a ranking of second for Utilities in 1974 with 24 percent
of all losses to air, behind Paint Consumption which ranked first with 2r>
percent. Utilities are estimated to rank seventh in mercury losses to land
with 25 tons (2 percent of losses to land). This compares to the 8 tons
lost to land in 1974 (0.6 percent of land losses). Consumption of Electrical
Apparatus-Batteries are projected to rank first with an estimated 691 tons
(58 percent). Utilities are not considere'd to lose mercury directly to
water. Many of the bases of the projected losses are 1973 consumption and
emissions figures.
• Mercury production may increase in this country 10-50 fold over
1973 production. Emissions from new plants, however should be reduced as a
result of an increase in process efficiency and control technology.
• Projections for copper mining and smelting emissions are based
upon the increased concern by and regulation of the industry to clean up
major pollutants. The economic feasibility of mercury recovery may result
in approximately 85 percent of the mercury now lost by copper mining and
smelting operations being recovered.
49
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TABLE 10. PROJECTED MERCURY LOSSES TO THE ENVIRONMENT, 1983
SOURCE
Mining and Smelting
Mercury
Capper
Other
Subtotal (X of Total for Media)
Unregulated Sources
Utilities
Other ,
Waste Treatmgnt
Incineration
Subtotal (X of Total for Media)
Manufacturing and Processing
Catalysts
I Electrical Apparatus - Batteries
, Lamps
Chlor-Alkall
Industrial Controls and Instruments
Mercurial Mfg.
Paint Mfg.
i Other Mfg.
Subtotal (X of Total for Media)
I
Consumption
Agricultural Pesticides
Non-Agricultural Pesticides
Electrical Apparatus - Batteries
Lamps
Industrial Controls and Instruments
Paint
General Laboratory Use
Dental Applications
Pharmaceut Icals
i Catalysts
Other
Subtotal (X of Total for Media)
AIR
w
23b
3
18C
44 (6X)
h
230°
92C
20
23
365(47X)
0.02
0.2
0.2
14
0.2
0.01
0.3
18
32.93(4X)
-
5.
119
9
11
191
1
-
1
0.2C
337(4351)
Total ' 779
i
MERCURY LOSSES
LAND
-
9
5°
14(1X)
b
25
67C
36
23
151U3X)
8
4
3
53
4
0.02
3
35
110(9X)
9
"b
691°
56
127
9
1
-
2
4C
923 (77Z)
1198
(TONS)
WATER
-
0.2
1.4C
1.6UZ)
-
4C
59
63(41X)
0.03
0.1
-
0.1
-
0.5
0.1
30
30TB120X)
2
19
-
-
_
1
2
13
20
-
57(33;)
152
TOTAL
h
23
12.2
24.4
59.6 (3X>
b
255c
163°
115
580 (27Z>
8.1
4.3
3.2
67.1
4.2
0.5
3.4
83
173.8 (8X)
11
48.
810
65
136
201
4
13
23
4.2C
1317.2 (62Z)
2131
LOSSES
AIR
0.1
^0.1
0.1
1
0.4
3.1
0.1
"0.1
^<0. 1
«0. 1
1 <0. 1
«0.1
<<0. 1
< '0.1
0.1
0
<0. 1
0.5
< 0.1
< 0.1
0.8
"0.1
0
«0 . 1
«0 . 1
RELATIVE TO POWER PLANT LOSSES
LAND WATER
0
0.4
0.2
1 (5)
2.7 (3)
1.4 (6)
0.9 (8)
0.3
0.2
0.1
2.1
0.2
<'0.1
0.1
1.4
0.4
1.0
27.6
2.2
5.0
0.4
< 0.1
0
< 0.1
0.2
(RANK)
TOTAL
0.1
<0.1
0.1
1
0.6 :
3.5 !
0.2
•-0.1
• 0.1
'0.1
0.3
< 0.1
< • 0.1
'0.1
0.3
< 0. 1
0.2
3.2
0.3
0.5
0.8
<0.1 i
'0.1
0.1
<0. 1
a Reference 30
b The highest estimate when a high-low estimate was made.
c Estimated at 5X Increase per year, with emission controls limited to present technology.
d These figures do not represent a material balance.
-------
TABU 11. HUCUIIT LOSSES TO THE CKVItOmOIT - (AMtED BY SOllCt
Ui
M
IUCK HERCUtY LOSSLS (TOSS), 147.
AIR LAND UATLK TOTAL
1 r-tnl Con.uHp. (116) B«ll*rv Con.u«p (ton Ui.t* fr.xt.wnt (45) R4tt«ry Con«u«p. <*">
A .imi" """• — ^.Jjjm.* "—......-" 1>CI"" -^^n — r*ut Con>u^' — ^!?1
6 liu lot- rail on (til) ' opcrr sarlfLng i*.i.i r^n'l L*h lie* O) ri>rprr >OM-Uinn
Co,>pvr SaffUlnj 1" Oth»r Htf. (41)
V , ''(her Hf,i ij|) faint ( nn*ij«r
I'tltiitft <8) Otti*r Unt»|. Cl Leap Consuap. (11)
;
10 ! t'lhrr Hlnlnj * Htrmtt S**ltln» ( ?>
ntlirt Hi UMK
<2) (8) i bMlIll.K (1) C4(4lv.t> L,r,.v,.r. 1 '.-»
1
HCRCURY LOSSES 1TOHS). 118)
AIR tAso MAIU TI|"AI
ir^;;;*^;,. \l}\ o,ur-*u.u «.. Other Nlntm il.-)
Ind. Lont.(. In*t. U«p Loni^ap (bit
1 »«• ill. i\.pprr '.•ciiln* Ol r«lnt Con»jrip. (l>
Am i. r*.i.
.,.,,,.,„ ,., «.„„,.,-,.. ,..„ ,.,.„„-,
!«»••• arr b«>*d upun um. onttolled r»i
r* rt and IU
-------
• Power plants are expected to increase net power generation by an
estimated 63 percent to 2.3 x 1012kwh in 1983.18 Utility use of
fossil fuel is projected to increase in 1983 by 73 percent for coal and
49 percent for oil.^9 The increased use, of coal in place of oil will
reduce the mercury emissions to air per kilowatt hour of electricity gener-
ated. Based upon fuel rates and average mercury concentrations in both
coal and oil, the use of coal produces about one-third of the mercury than
does oil per kilowatt hour of electricity generated. A shift in geographic
coal mining patterns to the Northern Great Plains is expected by the mid-
1980' s.l° The concentration of mercury in this coal is about one-third
that of Appalachian coal. It is expected to go from its present 8 percent
(52 million tons) of the coal produced to almost 30 percent (305 million
tons) in 1985.18
As was discussed, the mercury contribution from gas was not considered.
It is considered that the consumption of gas by utilities as a fuel to
generate electricity will decrease about 42 percent. If one would assume no
mercury removal prior to the transmission of the gas, it would yield an
estimated 2.9 tons to the air (1 percent of the utility losses). It is
assumed from current utility schedules that approximately 14 percent of the
net power generated will be under S02 scrubbers by 1983." The estimated
mercury loss to the air is based upon this assumption together with an
assumed 33 percent mercury scrubbing efficiency. The projected power plant
emissions used in Table 10 are almost three times larger than the URS study
report data. These larger values were used because they were based upon the
above factors which appeared to be the best available projections of electric
industry growth, and fuel production, as well as known scrubber committments
for utilities.
• It is assumed that the chlor-alkali industry will not expand mercury
cell chlorine production, thus decreasing mercury loss to the environment by
82 percent by 1983. This reduction will be due to the new source performance
standard (NSPS), currently in progress (1977) at EPA, for chlor-alkali
plants which would establish a zero emission limit for new plants. This
would essentially force all new plants to use asbestos diaphragm or membrane
cells. Reductions will also result from plant compliance with existing
regulations and improved housekeeping procedures relating to mercury account-
ability. Emissions to the air should be reduced by 36 percent through
increased control of the hydrogen stack emission and tighter internal
controls. Water losses will be substantially reduced by compliance with
regulations and through best available treatement standards limiting discharges
to 0.05kg/day. Land losses will be greatly reduced by techniques which are
currently in development to recover mercury in sludges.
• Production of mercurials is expected to remain steady or slightly
decrease in the future due primarily to the hazardous nature of the compounds
and declining demand among end users. Discharge from production will decrease
by the development of methods to remove trace quantities from water effluents.
Most of these methods are based upon the precipitation of mercuric sulfide
from the effluent stream by injection of sodium sulfide. Molecular sieves,
52
-------
which will probably be in use by the chlor-alkali industry as a secondary
tail-end device, may be used as a primary device in the manufacturing of
mercurials.
• Consumption of mercurials in pharmaceuticals by consumers will
probably drop from 23 tons in 1973 to 19 tons in 1983, due to the decline in
the use of mercury in diuretics and skin preparations. Pharmaceutical
industry consumption of mercury in 1974 remained at the same level as in
1973. Relative losses to different media will probably remain at the same
level.
• Primary battery production is expected to increase by 45 percent
from 1973 to 1983 with no change in the manufacturing process. Due to tight
internal controls, manufacturing losses should be reduced to 0.5 percent of
the mercury used in production. Losses to landfills should increase by 31
percent if recycling approaches 10 percent (currently 5 percent) and decrease
by 27 percent if a 50 percent recycling program is implemented.
• The proportion of electric lamps using mercury is expected to
increase approximately 50 percent between 1973 and 1983, but tight controls
should limit manufacturing loss to 4 percent of total input. If a 5 percent
recycling program is initiated, mercury losses to landfills will increase by
only 43 percent.
• The industrial controls and instrument industry is projected
to exhibit a 14 percent growth rate for this period. Since recycling
is not expected to increase (presently 55 percent) the increase in emissions
should also be 14 percent. The URS 1983 projection for this industry
may not hold insofar as the average 1974 loss of mercury during manufacturing
and consumption (Table 8) was apparently 15 percent lower than their loss
data for 1973.30
• A 5 percent growth rate in paint manufacturing coupled with a 50
percent reduction in mercury usage would result in the same amount of
mercury being emitted to the environment in 1983 as was emitted in 1973.
• An assumption with regard to agricultural pesticide use, is that
without further regulation the decrease in use of mercuric pesticides would
be about 50 percent by 1983.
• Use and dispersion to the environment of non-agricultural pesticides
containing mercury is assumed to be constant, according to URS. When
compared with 1974 figures, there may be an increase of 436 percent.
• Mercury losses to the environment from laboratory use should drop by
a factor of 50 percent or more as recycling of laboratory mercury increases
to 80 percent.
• Municipal waste treatment technology will probably remain unchanged
based upon current funding and construction trends. Most plants will pro-
vide secondary treatment, with a few providing tertiary treatment. Reductions
53
-------
in industrial emissions of mercury could have a significant effect on the
amount of mercury to be found in waste treatment plants in 1983. Presently,
industrial emissions account for about 35 percent of the input.™ Recycling
by institutional mercury users would also reduce mercury emissions. It is
also assumed that sludge incinceration will decrease by 50 percent due
to air pollution regulations and energy conservation problems.
• While the total amount of solid waste generated is expected to
increase substantially by 1983, the amount of mercury-containing wastes is
expected to decrease due to greater industrial control and a decline in the
use of mercury in some manufacturing sectors. An increase in resource
recovery operations and solid waste regulation of hazardous substances is
also assumed. A decrease in air emissions is anticipated as a result of the
use of tail-end mercury recovery units for thermal conversion processes,
whose efficiency is assumed to be 50 percent. These factors will tend
to decrease the mercury containing wastes presently incinerated. Decreases
in water emissions should result from improved landfill practices.
54
-------
SECTION 7
TRANSPORT AND FATE OF MERCURY EMISSIONS FROM POWER PLANTS
The mercury which enters the environment, as a result of the various
source emissions previously discussed, can be in various chemical forms.
These different chemical forms interact within the environmental media (air,
water and land) in a complex manner. The fate and transport of mercury in
the environment is characterized, as are ambient concentrations. A number
of studies are cited which provided ambient concentration data. It is the
purpose of this section to examine the mercury emissions from power plants
as to their contribution to and effect on ambient mercury concentrations.
The significance of these power plant effects was shown through specific
studies which have been conducted and through scenarios which were created
to illustrate effects under implausible conditions. The purpose of using
implausible conditions was to determine if the ambient concentrations would
be found to be within standards, under these conditions. If so, then
emissions would be considered not to be a problem.
CONCEPTUAL MODEL AND INTERMEDIA TRANSFERS
The presence and the behavior of mercury in the environment may be
described by a cycle, as shown in Figure 2, and as proposed by others.22,39,40
It has been shown that the various sources, anthropogenic and natural, lose
mercury to the air, land, and water. These losses to the media may be direct
or indirect, and all occur by means of transfer mechanisms or pathways.
Mercury is emitted to the air, as a result of volatilization during combustion
or other process. Depending upon meteorological parameters and the consti-
tutents present in the air, the mercury may undergo transformations which
will be discussed and intermedia transfers. The result may be a rapid
mercury transfer to land or to water, or it may be a retention in the
atmosphere for an indefinite period of time before transfer, or it may
be dispersed and remain in the atmosphere. The direct transfer to land may
occur through one of three possible paths.
Particulate matter, onto which mercury was adsorbed, when settling out
of the atmosphere to impact and interact with the land, is considered dry
fallout. Wet fallout refers to washing of mercury out of the air, either
through solubilizing the vapor or adsorption onto particulates during
precipitation (rain, snow, etc.). The third is solid adsorption at the
vapor/land interface. This may result from normal surface contact or
plume touchdown. Direct transfer to water may occur via similar mechanisms,
55
-------
312'
Based upon 100 <
in
0V
Upper Atmosphere
Sink
Power Other
Plant Point
Emissions Sources Natural
Natural
747 "" »
Other Sources
n.a.
912
5
Power Plant
Emissions
Natural
Anthropogenic
(other)
Power Plant
Emissions
I
Chemical Transformations
Physical Transformations
Biological Transformations
II
|1
Dry fallout
Wet fallout
(Liquid Adsorption)
Vapor/Water Interface
Land
Water & Sediments
Chemical Transformations
Physical Transformations
Biological Transformations
Chemical Transformations
Physical Transformations
Biological Transformations
T
Urban run-off
Agricultural run-off
Leaching
Immobilization Mechanism
Land Sink
Marshes
-»>- and
Oceans
(mercury sink ?)
NOTE: All numbers are in
tons. They are
based on data in
Table 8.
Figure 2. Conceptual cyclic model of mercury transport in the environment.
-------
dry and wet fallout onto surface waters and liquid absorption at the vapor/
water interface. An additional transfer may be from air to certain biota
through natural uptake such as respiration or ingestion.
Mercury in the soil is the result of disposal of solid waste of various
substances containing mercury, contributions from natural deposits, and
transfers from the atmosphere and biota. There are several pathways which
permit transport of mercury to the air, water, and biota. Volatilization of
mercury in soils is the mechanism which transfers mercury from land to air.
Runoff in urban areas carries matter on which mercury is adsorbed, or with
which it is combined, into surface waters (streams, rivers, lakes), thus
transferring mercury from land to water and sediments. Agricultural runoff
containing mercury in the form of pesticides, applied either as a spray or
on treated seeds, eventually is transferred to water and sediments. Some
mercury may be carried downward by percolation, possibly becoming immobilized
through chemical combination. Leaching can transport mercury to surface
water or ground water. Biota can receive mercury in the uptake of land
based nutrition. Similarly, mercury can be returned to land from biota as
wastes.
While such a cycle may be conceptualized along with its intermedia
mechanisms for transfer, it is not possible, with the data at hand, to
measure rates and quantities transferred. It is possible, however, to
define ranges for the relative ambient concentrations of mercury in the
various media as a result of source emission and subsequent transport
phenomena. The significance of mercury emissions from power plants on
ambient concentrations may then be evaluated.
SIGNIFICANCE OF POWER PLANT EMISSIONS ON AMBIENT CONCENTRATIONS
The following conclusions, regarding the significance of mercury
emissions from power plants and the fate and transport of mercury in
the environment, arise from the discussions found in the remainder of
Chapter 7:
• Mercury emissions from power plants generally have an
insignificant effect on ambient concentrations (air, water,
and land). A detectable increase in soil concentrations
on a local basis may, however, occur. While mercury
concentrations in soil may be significant on an absolute basis,
its significance on a relative basis is not known.
• Mercury levels may increase in a closed water system, with
no apparent direct man-made inputs, as a result of both
accumulation in the sediments and bioamplification.
• As much as 86 percent of the mercury transported by water is
in solution, the remainder being on suspended particulate or
re-entrained bottom sediments.
57
-------
Mercury in solution will ultimately be carried to the oceans as
will up to 20 percent carried on particulate. The remainder,
carried on particulate, will be deposited in coastal areas.
Atmospheric input may effect near-shore ocean concentrations.
However, what available data there is, is not significant.
Air
Studies of the ambient concentration of mercury in air have been
conducted but are not definitive.30,51-56 jn a report assessing mercury
in the environment, the range of ambient concentrations of mercury in city
air was given as 0.001 ppb-20.0 ppb and in urban air as high as about 30
ppb.30 City figures represented the downtown area, while urban figures
represented the populated area around the city. These values are on a
weight to weight basis.
Kothny examined the ambient atmospheric concentration associated
with mercury sources and determined that rural areas had a concentration
range of 0.0006 - 0.008 ppb.51 The recommended ambient air concentration,
which was the basis for the National Emission Standard for mercury, is
1.0 g/m3(0.8 ppb). In addition, he determined that the ambient concentration
range of indoor air was 0.02 - 0.25 ppb, while industrial and commercial
atmosphere was as high as 42 ppb. This is generally lower than the NIOSH
recommended workplace exposure of 0.05 mg/m^(40 ppb). The high values for
indoor air were ascribed to the mercury volatilized from latex paint and PVC
materials commonly used. Indoor industrial concentrations were associated
with chlor-alkali plants, dental offices and various manufacturing sources.
Ambient mercury concentration ranges, during the winter, in the San
Francisco area were found to be 0.0004 ppb - 0.02 ppb while those during the
summer months were from 0.0008 ppb - 0.04 ppb.53 A study performed in
California measured elemental mercury in the vicinity of natural sources
(mines, geothermal vents, etc.), industrial sites, waste treatment and
disposal areas, and in the urban environment (downtown San Francisco).56
Ground level concentrations at the Geysers, an area of geothermal vents
and natural sources of mercury, varied from 0.16 ppb to a peak of 22.5
ppb. A summary of the data for various areas is shown in Table 12.
The previous study indicated elevated mercury levels downwind of such
sources as incinerators, industrial plants and natural deposits. For
example, it had been suggested that mercury from the Geysers steam vent was
being blown 20 miles north to Clear Lake and deposited in the water, where
elevated mercury levels in fish have been detected. This data is inconclusive,
since it has not been possible to trace an industrial plume for mercury for
more than 1.5 miles.
The sources which emit mercury to the air are dispersed over a wide
geographic area. A high density of certain sources such as power plants,
can be found in urban areas. Although generalized models have been developed,
58
-------
TABLE 12. SUMMARY OF ATMOSPHERIC MERCURY CONCENTRATIONS IN CALIFORNIA
Site
Date
Mercury
Wind Measurements
Background Peak Value
Remarks
\o
Natural Sources
Abbott Mine
Clear Lake
The Geysers
New Almadon
Other Sources0
Berkeley
Oakland/Emeryville
Pittsburg
San Francisco
Richmond
San Carlos
2/12
2/12
4/2
2/13
1/4
3/2A
3/22
3/24
3/26
3/30
3/30
A/5
A/6
2/11
2/12
2/25
3/22
A/1
3/18
3/19
1/19-1/26
A/7-8
3/29
3/29
A/6
(PM)
(PM)
(PM)
(PM
(PM)
(PM)
(AM)
(AM)
(PM)
(PM)
(PM)
(PM)
(PM)
(PM)
(AM)
(AM)
(PM)
(AM-PM)
(PM)
(PM)
(AM-PM)
(AM-PM)
(AM)
(PM)
(AM)
E
E
W
W
(Negl.)
NW
W
W
W
W
NW
W
W
N
NW
N
WNW
N
-
-
-
-
NW
W
-
0
0
0
0.200-0.800
0
0.005-0.015
0.010
_
0.010
0
0
0
0
0.050
0
0.006
0.005
0
0
0
0
0
0
0.005
0
0.470
0.150
0.200
28.100
1.500
O.AA9
0.800
O.AA9
0.15A
1.050
0.196
0.688
0.110
0.770
1.000
0.006
0.010
4.141
0.278
0.152
0.100
0.035
1.400
2.000
0.021
Low population density
Resort area, "
it M
Rural resort area
Rural
Rural
Light Indust. - resid.
ii M
i i
i ii
Light industrial
n ii
i n
Industrial area
ii M
On boat
Residential
Indust. - Residential
Commercial area
n n
Financial District
II M
Residential (near school)
n ii
Light Industrial
Recommended EPA Ambient Air Concentration
1.0
a Reference 56
b All locations were sampled in 1971.
c Sources Include sewage treatment plant outfalls, waste disposal
areas, industrial sites, incinerators, and urban areas.
d Reference 5
-------
the specific dispersion characteristics of mercury in a plume is unknown.
This report indicates that at least part of the mercury in the air is
transported to the land and water.
The relative effect of mercury emissions from power plants can be
assessed through a scenario or an actual study of an isolated power plant.
A scenario was constructed to determine the atmospheric burden of
mercury emissions, and assess the effects, under improbable and excessive
conditions. The New York City area of about 400 square miles was selected,
with a population density of approximately 25,000 persons per square mile.
This area accounted for about 34 x 10^ Kwh, or 2.4 percent of the total
net kilowatt hours generated in the United States in 1974. The electricity
was generated at 9 power plants in New York City and 6 in the adjacent area
of New Jersey. The following assumptions were made:
• All the mercury from the combustion of the actual oil used
and 90 percent of the mercury in the coal actually used in
these plants was emitted to the air.
• All the mercury emitted remains in the air, with no
intermedia transport.
• A 12 km altitude is considered above the 400 sq. mi. area
thus defining an atmospheric volume.
• All the mercury emissions from these plants for the entire
year remain in this volume of air.
• All the mercury is evenly distributed within this volume
of air.
• There is absolute stagnation, that is, no air enters or
leaves this volume.
These assumptions were made improbable and excessive to illustrate
an extreme as well as an impossible case. The scenario would, of course,
not occur because the emissions would be distributed throughout the year,
meteorological conditions would disperse the mercury, and intermedia transfers
would remove mercury from the air.
The mercury burden to this atmospheric volume as a result of these
power plant emissions under the assumed conditions, is 0.65 g/nr* or a
concentration of 0.52 ppb (wt/wt). When compared with the EPA ambient
guideline concentration of 1.0 g/m^, there remained a safety factor of
1.5, if the minimum ambient background concentration (0.001 g/nH) was
present. With an assumed high background concentration of 20.0 ppb (25
g/m^) the guideline value is exceeded with a calculated value of 25.65
g/m^. When compared to the NIOSH recommended workplace exposure of
O.OSmg/m^ for 3 hours, there was a safety factor of 77, when the minimum
ambient concentration of 0.001 g/m' is considered. Assuming the high back-
ground concentration (25 g/nr*) there still remained a safety factor of 1.9.
60
-------
A calculation was also made to determine the effects of the type of
fossil fuel used in generating this same power. Oil yields about three
times the mercury that would be emitted by the combustion of coal in generating
1 net KWh. This calculation was based on average mercury content of the
fuels and accepted fuel conversion rates.^ The results show that there
would have been a 65 percent reduction in the ambient air concentration, to
0.22 g/m->, if coal was used in place of oil.
There have been studies to determine the elemental analysis of fuels, fly
ash, slag, and flue gas, the emission factors for some pollutants, as well
as the mass balance for an operating power plant.^>2^>22,25,29,32,46,57-63
The mercury emissions from power plants, in terms of emission rates and
resulting ambient air concentration, has been calculated for the Four
Corners and San Juan power plants.29
The Four Corners power plant in New Mexico was estimated to require an
emission rate 43 times the average daily emission of the power plants in the
previous scenario in order to exceed the EPA guideline ambient air concen-
tration of 1.0 g/m-* (cf Section 6).™ Based upon the emission at Four
Corners, the ambient mercury concentration (24 hour average) was calculated
by the EPA to be 0.0365 g/nP or less than 4 percent of the EPA ambient
guidelines. This was based on a proportionality technique using a diffusion
model and a rollback calculation.29,64
Projecting this same calculation to the New York City scenario, and
assuming all the New York City area plants to be a single point source, the
maximum emission to preclude violation of the 1.0 g/oH ambient concentration
would be 330 kg Hg/day. This is almost 15 times more than these plants emitted
in total in 1974. Alternatively, the estimated monthly average ambient air
concentration of mercury resulting from the actual estimated mercury emission,
is 6.7 x 10"^ gHg/m^. This provides a safety factor of about 1500.
Water
Many of the waterways in the United States have been the subject
of studies and surveys concerning the mercury content of water and sediments.
For the purpose of this report we considered four types: lakes, rivers,
estuaries, and oceans.
Based on an examination and compilation of data from a number of
studies and surveys, the following ranges represent uncontaminated ambient
mercury levels in the water and sediments:
Average dissolved Hg content of fresh water bodies 0.01-O.lppb
(lakes, rivers, streams)
Average dissolved Hg content of oceans 0.03-0.3ppb
Average Hg content of suspended sediments 0.1-l.Oppb
Average Hg content of bottom sediments 10-100ppb
61
-------
The studies used in compiling the ambient concentration ranges were
selected as representing a wide geographical area, a wide range of salinities
and water body types, and data on mercury in the dissolved, suspended, and
settled state. These data are presented in Table 13 grouped according to
the water body type. Table 14 presents ambient concentrations of dissolved
and suspended mercury in water from USGS of sampling station data within
regions.°^ These regions were those used in Section 6 (Tables 5,7,etc.) to
define the distribution of power plants. Few studies were comprehensive
in measuring both mercury dissolved in the water and present in suspended,
and bottom sediments. Similarly, the studies as a whole, while covering a
wide geographical area, were not sufficiently comprehensive in the types or
locations of waterways to provide a more representative basis for determining
background and contamination levels of mercury.
The data showed the concentration of mercury in the fresh water bodies
tabulated to be well within the EPA drinking water standard of 2 g/1.
However, the various fresh water bodies may have all exceeded the EPA
standard for freshwater aquatic life and wildlife of 0.05 g/1. This is
difficult to state with certainty as the methods of analysis used varied and
in many instances were unable to detect such low concentrations. Variations
in observed mercury concentrations in water and sediments may have been a
result of either long-term accumulations or source inputs.
An example of increased mercury levels in a body of water, with
no apparent source inputs, may be demonstrated by a study of Lake Powell."
Lake Powell is a reservoir in New Mexico, fed by the Colorado River, located
approximately 4 miles from the Navajo power plant at Page, Arizona. Although
the Lake was far removed from man-made sources of mercury prior to the
Navajo plant going on-line, accumulation of mercury in sediments, and
bioamplification in marine life was observed. Mercury concentrations in
game fish had been found to exceed the current HEW-FDA "action level"
of 0.500 ppm.14
With the scheduled start-up of the Navajo plant, the effects of this
potential mercury source on Lake Powell were estimated."•* It was concluded
that the mercury emissions, resulting from the consumption of an estimated
5.9 million tons of coal per year, would enter the lake drainage in the
amount of 8 percent of the present total accumulation in the lake. This was
based, however, on an unsubstantiated assumption that 40% of the mercury
emissions from the power plant would enter the lake drainage.
Variation in the mercury concentrations of water, suspended particulate,
and bottom sediments occur as a result of the transport of mercury within
the aquatic environment. The concentration of mercury associated with
sediments (0.1-1.0 ppb) was found to be higher than that in the water
(dissolved mercury) (0.01 -O.lppb). However, between 55 percent and 86
percent of the total amount of mercury transported was believed to be in
solution.68,83 This would be due to the large volume of flowing water as
opposed to the much smaller amount of sediments which is suspended and
carried with the water.
62
-------
TABLE 13. COMPILATION OF Hg VALUES FOR DISSOLVED, SUSPENDED, i BOTTOM SEDIMENTS
PAGE: 1 of 8
SOURCE
LAKE POWELL65
COLORADO R.65
FORBIDDEN CANYON 65
RIVERS IN ITALY*
AND GERMANY51
RHINE R1VE866
EMS66
NORMAL STREAMS,
RIVERS AND LAKES 67
..ORMAL G8D WATER *'
WALKER BRANCH58
EAST FORK
WEST FORK68
RIVERS OF EUROPEAN
USSR6'
SAALE RIVER
GERMANY6'
RIVER SEINE69
UNCONTAMINATED RIVERS
(ITALY)6'
RIVERS NEAR Hg DE-
POSITS (ITALY)69
Hg,H.O
(ppB)
dil«olv*d
0,01
<0.1
26
.01-
.05
0.6
0.01-
0.1
.01-0.1
30
30
0.4-2.8
0.035-
O.H5
0.05-1
0.01-
0.05
136
SUSP.
8100-16500
11700-17700
Bg,S*d
(ppb)
49
ORIGINAL MUD 23,000
EROSION MUD 9,000
FLOOD PLAINS 3000-1 300(
3000
COMMENTS
UATEB SAMPLE, PBPSIIMAM V nTSSnl.W.n
WATER SAMPLE, PRESUMABLY DISSOLVED
PROCESSED SEWAGE RELEASED, PRESUMABLY DISSOLVED
16 t»M FRACTION
U)
-------
TABLE 13. COMPILATION OF Hg VALUES TOR DISSOLVED. SUSPENDED, & BOTTOM SEDIMENTS
PACE: 2 of 8
SOURCE
FLAMBEAU FLOW ACE. WIS.
OUTLET OT LAKE MICHIGAN*0
PINE CREEK70
BLACK RIVER70
WEST BASIN70
MARINAS 70
EAST BASIN70
SHIPPING CHANNEL70
GRAND RIVER
1 mi. UPSTREAM MOUTH70
MOUTH69
LAKE. 1 Bl. W. OP MOUTH
70
LAKE, 2 mi. V. OP MOUTH
70
LAKE, 7 ml. W. OP MOUTH
70
LAKE. 5 mi. NW OF MOUTH
KLEIN LAKE 70
BS.H.O
-------
PAGE: 3 of 8
TABLE 13. COMPILATION OF Hg VALUES FOR DISSOLVED, SUSPENDED, & BOTTOM SEDIMENTS
SOURCE
ST. CLAIR RIVES71
DETROIT RIVER71
197172
OTTAWA RIVER I
2
3
1973
1
2
3
STREAMS NEAR
HUNTSVILLE. ALA.73
LAKE MICHIGAN71
RIVER & gnd WATER75
RAIN MATER75
LaHAVE R
NOVA SCOTIA
SOUTHERN LAKE
MICHIGAN76
ASHTASULA R.77
ASHTABULA HARBOR77
LAKE ERIE77
FIELDS BROOK77
Hg.H-0
-------
PAGE: 4 of 8
TABLE 13. COMPILATION OF Hg VALUES FOR DISSOLVED. SUSPENDED, & BOTTOM SEDIMENTS
SOURCE
CUYAHOCA RIVER77
CLEVELAND HARBOR77
GRAND RIVER77
FAIRPORT HARBOR77
MAUMEE RIVER77
MAUHEE BAY77
SANDUSKY BAY77
UHAVE R. AND
ESTUARY"
RED CEDAR R. MICH.79
LAKE ERIE80
RIVER AND GROUND
WATER81
RAIN HATER81
DELAWARE STREAMS81
DELAWARE RAINWATER81
DELAWARE RIVER81
Hg.H-0
(ppE)
dissolved
.036 -
0.380
O.OS
0.1S
0.5
0.4
<0. 1
SUSP.
3590 -
34400
Hg.Sed
(ppb)
1-290
10-63
69-730
4-123
1-87
3-86
3-180
90-
1060
40-400
SURFACE - 500-4000
DEEPER - 40-90
COMMENTS
-------
PACE: 5 of 8
TABLE 13. COMPILATION OF Hg VALUES FOR DISSOLVED, SUSPENDED, & BOTTOM SEDIMENTS
SOURCE
JANES RIVER82
YORK82
RAPPAHANNOCK82
PEE DEE83
BLACK83
SAHTO83
COOPER
SAVANNAH83
OCEECHEE83
ALTAMAHA83
SATILIA83
ST. JOHNS83
RIVER THAMES69
MINAKATA BAY69
SAN FRANCISCO BAY71
MINAMATA BAY75
Hg.H-0-
(ppl)
dissolved
0.06,
0.06
O.OS
0.04
0.07
0.07
O.OS
0.07
O.OS
0.045 - 2.85
1.6 - 3.6
1-10
SUSP.
500
600
200
1000
700
600
700
400
600
Hg.S.d
(ppb)
910
1320
950
70
6900
COMMENTS
REPRESENTS THE AVERAGE OF 23 SAMPLING POINTS BETWEEN 5-83 MILES
REPRESENTS THE AVERAGE OF 7 SAMPLING POINTS BETWEEN 5-35 MILES
REPRESENTS THE AVERAGE OF 9 SAMPLING POINTS BETWEEN 5-45 MILES
•
. MARSH CORES - DRY WEIGHT BASIS
-------
PACE: 6 of 8
TABLE 13. COMPILATION OF Hg VALUES FOR DISSOLVED, SUSPENDED, & BOTTOM SEDIMENTS
SOURCE
TIDAL THAMES R. 75
SAN FRANCISCO BAY75
DELAWARE BAY81
SAN FRANCISCO BAY81
NEW HAVEN HARBOR
CONN.81
UHAVE Rft 4
ESTURARY81
DELAWARE BAY SHELL-
FISH BANKS81
MURDERKILL R. DELA.81
ST. JOHE R., DELA.81
MINAMATA BAY81
UHAVE R. & ESTUARY81
DELAWARE BAY81
DELAWARE BASIN R.81
OCEAN51
Hg.H.O
(ppB)
dissolved
1-5 (T)
1.6 - 3.6
0.036 -
0.380(1)
0.28(T)
0.33(T)
0.03 - 0.27
SUSP.
0.045-
2.85(1)
20-2000
Avg. 300
Hg.Sed
(ppb)
1-4
300
780
340
730
240
630
COMMENTS
00
-------
FACE: 7 of 8
TABLE 13. COMPILATION OF Hg VALUES FOR DISSOLVED. SUSPENDED. & BOTTOM SBDIHFNTS
SOURCE
NORTH SEA66
SEA WATER
OCEANS AND SEAS67
NORTH SEA69
LAHAPO DEEP
PACIFIC OCEAN
3000m DEPTH69
(PACIFIC OCEAN)
SEA WATER75
OCEANS75
DEEP SEA cone.75
NE ATLANTIC75
EASTERN PACIFIC75
ENGLISH CHANNEL
NEARBY RIVERS75
SEA WATER81
SOUTHERN CALIF.
COAST81
Hg.H-0
(ppl)
dissolved
0.1
<0.1
0.005 - 5.0
0.03
0.08 - 0.15
0.15 - 0.27
0.1
0.03
0.27
0.013 - 0.018
0.022 - 0.173
0.02
0.01
0.1
SUSP.
Hg.Sad
(ppb)
340
COMMENTS
-------
PACE: 8 of 8
TABLE 13. COMPILATION OF Hg VALUES FOR DISSOLVED, SUSPENDED, & BOTTOM SEDIMENTS
SOURCE
NW PACIFIC81
ENGLISH CHANNEL81
HE ATLANTIC81
ATLANTIC OCEAN81
Hg,H,0
(ppfi)
dissolved
0.06 - 0.27
0.014 - 0.2KT)
<0.03 - 0.020(T)
0.10(T)
SUSP.
•
Hg,S«d
(ppb)
COMMENTS
-------
TABLE 14. SUMMARY OF MERCURY CONTENT IN FRESH HATER BODIES ON A REGIONAL BASIS*'1
Kg, dissolved
ppb
Hg, suspended
ppb
Hg, dissolved
ppb
Hg, suspended
New England
Connecticut (26)
Maine (7)
Massachusetts (14)
Nev Hampshire (4)
Rhode Island (4)
Vermont (3)
Middle Atlantic
New Jersey (18)
New York (34)
Pennsylvania (43)
East North Central
Illinois (19)
Indiana (21)
Michigan (19)
Ohio (24)
Wisconsin (16)
West North Central
Iowa (11)
Kansas (12)
Minnesota (10)
Missouri (13)
Nebraska (10)
North Dakota (7)
South Dakota (7)
0.5
0.5
0.5
O.S
0.5
0.5
0.5
0.5
0.5
0.18
0.66
0.53
1.35
0.5
South Atlantic
Delaware (4)
Washington, B.C.
Florida (17)
(1)
0.5
0.51
0.5
0.55
0.5
0.5
0.5
0.52
0.5
0.66
0.54
0.54
0.86
0.54
0.73
1.73
0.51
1.16
0.59
0.79
0.53
0.5
0.5
0.83
South Atlantic
Georgia (17)
Maryland (13)
North Carolina (21)
South Carolina (16)
Virginia (11)
West Virginia (12)
East South Central
Alabama (18)
Kentucky (8)
Mississippi (10)
Tennessee (12)
West South Central
Arkansas (13)
Louisiana (13)
Oklahoma (12)
Texas (30)
Mountain
Arizona (11)
Colorado (19)
Montana (8)
Nevada (8)
New Mexico (15)
Utah (11)
Wyoming (9)
Idaho (8)
Pacific
California (32)
Washington (14)
Alaska (9)
Hawaii (8)
0.1
0.4
0.49
0.5
0.17
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.5
0.66
0.99
0.5
0.53
0.55
0.63
0.55
0.66
0.51
0.5
0.73
0.5
0.56
0.5
1.68
1.31
0.5
0.57
0.81
'Reference 84
bThese data represent the average of several sampling sites within each state. The numbers In parenthesis after the states indicate the
total number of samples.
-------
The surface area of the suspended material is an important factor in
transporting mercury adsorbed on sediments. Even though higher salinities
cause floculation and ultimately the deposition of sediment, it was found
that there may be an increase in the mercury concentration towards the mouth
of an estuary because the fine grained particulate which adsorb greater
amounts of mercury were still in suspension.79
Mercury in solution will ultimately be carried to the oceans as would
up to an estimated 20 percent of the mercury carried on particulates. The
r nainder, carried on particulate, would be deposited in coastal areas.^3
The residence time of mercury in a Georgian estuarine environment, as
estimated by Windom, was given as 17 months. It was also estimated that the
average half-life of mercury in sediments was 0.78 years. '*• The half-life
denotes the period of time until the concentration is half that of the
original.
It was found that mercury concentration in the coastal environment
exhibited seasonal variation.^3 These variations ranged from 0.005;ppb to
0.3 ppb. The EPA standard for marine waters is 0.1 ppb. These variations
could not be explained by variations in estuarine concentration. However,
they appeared to be related to offshore winds, whose concentration was found
to correlate with the concentration in the water column. This would imply
the effect of atmospheric input. While this would be related to mercury
emissions to the air an estimate of the effect of mercury emitted from
power plants cannot be shown.
The relative effect of mercury emissions from power plants on the
aquatic environment can be assessed through a scenario or by an actual study
of an isolated power plant.
The scenario constructed was the same as previously described in the
discussion on the ambient air concentrations, as an improbable and excessive
situation. The following assumptions were made in assessing the effects of
power plant emissions on ambient water concentrations:
• All the mercury from the combustion of the actual oil used
and 90 percent of the mercury in the actual coal used in the 15
power plants was emitted to the air.
• All of the mercury in the air is deposited in a river as
a result of rain, falling at a rate of 45 inches per year.
All the rain enters the river.
• A river, with an average flow of 18,000 cubic feet per
second, is the receptor. This would be a reasonable
composite of 3 rivers in the New York City area.
• All the mercury emissions for the entire year are deposited
in the river within a 20 mile length, with no further
transport.
72
-------
• The volume of river water passing the 20 mile length and
the volume of rain water for one year's time are the
dilution factors.
These improbable assumptions were chosen to illustrate an extreme case.
A mercury plume is not expected to always touch down adjacent to the source,
nor to completely transport from the air to one or more media.
Under the conditions specified, the total power plant emissions dis-
solved in the specified river volume results in an ambient water concentration
of 0.47 ppb. When compared with the drinking water standard there is a
safety factor of 4.25. However, the resulting concentration exceeds the
freshwater standard by a factor of 9.4. These conditions could, of course,
never occur since the entire plume would not be dissolved in the adjacent
water as a result of dispersion of the plume in the atmosphere. The effects
would therefore, be reduced.
Deposition rates of mercury from the atmosphere are not known. A
scenario study of the effects of mercury emissions from a 1000 MWe power
plant estimated, depositional rates at various distances from the source.^
Assuming a depositional rate of 2.7 percent of the plume for our previous
scenario, the river water concentration would be 0.013 ppb. Compared with
EPA drinking water and freshwater standards this condition maintains safety
factors of 154 and 3.8 respectively.
The effects of mercury emissions from a single power plant on ambient
concentrations were investigated." The study involved a 1200 MWe power
plant situated on a lake, whose water was used for cooling purposes, and
surrounded by a watershed. Lake sediment samples showed mean concen-
trations of 0.049 ppm in the 6 years since the plant went into operation as
compared to 0.037 ppm prior to operation. A reduction in concentrations
for several years corresponded with the discontinuation of the practice of
reinjecting fly ash into the furnace. It was believed that this practice
overloaded the electrostatic precipitators which resulted in the emission of
large quantities of particulate matter into the air. Mercury concentrations
in fish in the lake never reached the U.S. Food and Drug tolerance limit of
0.5 ppm for fish. A conclusion drawn by the authors of this study was that
mercury did not appear to be a serious pollutant in the lake.
Soil
To date there has been only one comprehensive study to determine
mercury concentrations in soils of the United States.86 The results
of this study are presented in Table 15.
73
-------
TABLE 15 - CONCENTRATIONS OF MERCURY IN SOILS OF THE
CONTIGUOUS UNITED STATES (ppb)a
GEOMETRIC GEOMETRIC ARITHMETIC
AREA NO. OF SAMPLES RANGE MEAN DEVIATION MEAN
Entire U.S. 912 10-4,600 71 2.6 112
Western U.S.
(West of 97th 492 10-4,600 55 2.46 83
Meridian)
Eastern U.S. 420 10-3,400 96 2.53 147
(East of 97th
Meridian)
aReference 86
The soils evaluated in this study were sampled at a depth of eight inches in
an effort to eliminate any effect of surficial contamination. Soils from the
Eastern U.S. showed a higher concentration of mercury than did those west of
the 97th Meridian. While this result may not have been expected, since all
mercury deposits in the U.S. are located in the west, the higher concentration
in the eastern U.S. may have reflected a higher mercury content in the
underlying rock with subsequent migration towards the surface. Many of the
highest single concentrations detected were, however, from samples in the
western U.S.
There have been several attempts at correlating mercury concentrations
in soils with point sources.35,70,85,87-91 Resuits of the analyses of
soils from various land use areas for metals showed a tendency toward higher
concentrations in other than residential use areas, which may have indicated
a contribution from industrial operations.™ A data summary is shown in
Table 16.
The contribution of emissions from two of the largest sources of mercury
to land, copper smelting and chlor-alkali manufacturing, have been studied.**'»
The soils around a copper smelter, in operation for 84 years, were found to
have mercury concentrations ten (10) times the background levels within
1.6km (1 mile) of the plant.**? No differences were detected beyond 6.4km
(4 miles). Similar results were found in the snow around a chlor-alkali
plant.'" The highest concentrations of mercury were found within 500
meters of the plant. Approximately 3.6 percent of the mercury emissions
were found in the area from 0.5 to 5 kilometers. Mercury emissions from
this plant were from a 10-15 meter high stack at a temperature of between 0°
and 10°C. The results of these two studies indicated the local increase in
ambient soil concentrations can occur. These source induced increases may
have been a result of short term favorable deposition conditions and long
term accumulation. These studies would not apply to power plants because
of the much greater stack heights as well as elevated temperatures of the
stack gas representative of power plants.
74
-------
l/l
TABLE 16. METAL CONCENTRATION RELATED TO LAND USE PATTERNS3
Ag Ca Cd Co Cr Cu Fe Hg N1 Pb Zn
RESIDENTIAL
N = 70
AGRICULTURAL
N = 91
INDUSTRIAL
N = 86
AIRPORT
N = 7
median
mean
std dev
median
mean
std dev
median
mean
std dev
median
mean
std dev
0.
0.13
0.19
0.
0.19
0.25
0.4
0.37
0.33
0.4
0.29
0.30
1,000
2,300
2,600
800
1,400
1,900
1,900
3,200
3,000
3,700
4,100
3,800
0.4
0.41
0.44
0.4
0.57
0.52
0.7
0.66
0.54
0.7
0.77
0.56
2.
2.3
1.5
2.5
2.7
1.5
2.
2.8
1.8
8.
7.9
2.7
1.6
3.2
3.3
3.9
4,6
3.6
6.0
8.5
9.0
22.
17.6
8.9
7.5
8.0
4.5
5.6
8.8
6.0
11.2
16.3
14.3
9.4
10.4
2.1
2,000
2,200
1,100
2,200
2,600
1,600
3,200
3,100
1,400
7,000
6,200
1,600
0.07
0.10
0.10
0.09
0.11
0.09
0.11
0.14
0.10
0.17
0.33
0.18
4.
5.4
4.1
6.
5.6
4.4
7.
8.3
5.2
11.
12.3
5.9
15.
17.9
12.6
11.
15.4
14.9
22.
47.7
59.6
14.
17.9
8.4
17.
21.1
12.5
17.
22.1
12.9
32.
56.6
63.1
36.
36.6
15.0
INDUSTRIAL/RESIDENTIAL 2.85 1.39 1.61 1.22 2.66 2.04 1.41 1.40 1.54 2.62 2.68
AIRPORT/RESIDENTIAL 2.24 1.78 1.88 3.43 5.50 1.30 2.82 3.30 2.28 1.00 1.74
Reference 70
-------
The effects of power plant emissions on ambient soil concentration are
of concern because of possible effects on plants, animals, food, and humans.
Attempts have been made to correlate their emissions with ambient soil
concentrations.35,46,85,88,89,91
Two of the studies resulted in no detection of increased soil or plant
concentrations from mercury emissions within 32 and 50 km respectively.",88
Another study indicated less than 2 percent of the mercury emitted was
deposited within 8 km, the remainder probably being widely dispersed.°"
Mercury contamination of the ground around a chemical plant in Northern
Virginia was studied in an effort to determine the source."^ The local
health agency collected samples within Alexandria, Virginia and along the
shore of the Potomac around Oronoco Bay. The concentration in the soil
samples ranged from <0.18 ppm to 17.6 ppm. They considered the normal soil
background to be 0.5ppm. The conclusion of the local health agency was that
a local coal-burning power plant was the source. Their calculations,
based upon 22 samples, indicated that the total amount of the mercury
emitted by the plant was deposited within a 1.6 km (one mile) radius and
remained within a 7 cm depth. Although the power plant had no emission
controls for most of its 25 year operating history, the small number of
samples analyzed and the calculation of deposition would leave their conclu-
sion open to question. The power plant was most probably only one of
several sources contributing to elevated soil concentrations over the
years.
A study of an isolated 1200MWe power plant, located in the center of a
watershed in Illinois, concluded that there was a statistically significant
increase of mercury concentration in the soil northeast of the plant, the
direction of the prevailing wind.^5 The background level was assumed to be
0.015 ppm, found southwest of the plant, as compared to the higher levels of
0.022 ppm downwind. These elevated values are less than 1/3 of the geometric
mean mercury concentration for the United States. It was also concluded
that between 26 percent and 70 percent of the total mercury emissions of the
plant, since being put into operation, was incorporated into the soil within
a 19.3 km radius of the plant. This conclusion, however, was based upon
assumptions and extrapolation of measured surface soil concentrations to
plow depth (17 cm.). The soil data was presented without any distinction
being made as to the type of soil surrounding the plant from which the
samples were taken. There was a difference in the soil between the northern
and southern sides of the plant. These soils may interact with mercury
differently thus affecting the mercury levels found, its form(s), and
residence time. The implication was that much of the mercury emitted was
deposited within 20 km and remained immobile, neither occurance of which
has ever been proven.
A model was constructed to describe the transport and deposition of
mercury from the atmosphere, and to determine the increase in the mercury
concentration of soil within a 25 km radius due to a 1000 MWe power plant
and an incinerator as point sources.^° The conclusions were, that even
76
-------
though incinerator deposition is more local than power plants, only a small
amount of the mercury emitted is deposited locally, with at least four-fifths
of the mercury remaining airborne to be further dispersed.
*
Using the scenario previously constructed, of the 15 power plants, in
the New York City area, the following assumptions were made to create an
improbable and excessive case:
• All the mercury from the combustion of the actual oil
used and 90 percent of the mercury in the actual coal used
in the 15 power plants was emitted to the air.
• All of the mercury emitted to the air in one year is
deposited uniformly over the 400 square miles.
• The mercury is deposited within the first 2 cm of soil.
• The entire mercury deposition remains in this volume of
soil.
This improbable scenario resulted in a soil concentration of 145 ppb
due to the emissions, which is two times the geometric mean concentrations
for United States soils. If 20 percent of the mercury emitted is assumed to
be deposited within this same area, the resulting concentration is 29 ppb,
or 40 percent of the United States geometric mean concentration. Neither
case could occur since the emissions would be distributed throughout the
year, and transport and transformation mechanisms would be present to
further lessen the impact.
However, buildup of mercury in the soil could occur over the long term.
Additional factors affecting deposition of mercury would be the emissions
conditions from the power plant, such as stack height, buoyancy, dispersion,
and dilution. From these examples it can be concluded that:
• No definitive studies have been performed which would allow
the quantifying of the effects of mercury emissions from
power plants on soil.
• Elevated concentrations in the soil have been observed in
the vicinity of power plants.85,91
• A distance from a plant can be reached beyond which there
will be no detectable increase in soil concentration.
This is due in part to the limited amount of the mercury
emissions being dispersed and distributed over increasingly
larger areas. Another factor would be the revolatilization
of mercury with subsequent reentry into the atmosphere
to be further dispersed.^6»51
77
-------
CHEMICAL, PHYSICAL, AND BIOLOGICAL TRANSFORMATIONS
The transport of mercury between environmental media as well as the
subsequent concentration, depend in part, on the form in which mercury
exists and the transformations which it may undergo. This section examines
these transformations with respect to the presence of mercury in the
environment.
Air
Mercury enters the air as metallic vapor (Hg°), organic mercury
compounds or other compounds.92,93 Metallic mercury is transported into
the air by vaporization, because of its high vapor pressure at normal tempera-
tures. The vapor pressure at normal temperatures is 1.2 x 10~^ mm Hg at
20°C, and increases with the temperature. The saturation concentration
of mercury in the air at room temperature is 10-15 rag Hg/m-*. Vaporization
is evidenced by higher ambient air concentrations over areas with mercury
deposits than over non-mineralized areas.
Ionized forms of mercury can be transformed into volatile forms
by three processes. These are chemical reduction to the elemental form,
reduction through the action of organisms, and biotransfonnation into
volatile organomercury compounds such as short chain alkyl mercurials.
Chemical reduction, while carried out in laboratory experiments, has not
been studied in nature. One laboratory observation was made by Kimura and
Miller, in which about 15 percent of added phenyl mercury acetate was
converted to metallic mercury vapor in 28 days, while ethyl mercury was only
partly converted and methyl mercury not at all.92 xhe latter two, however,
volatilized in their original forms.
The volatilization of mercury induced by bacterial activity, while not
studied extensively, has been observed by Barker.92 His data showed that
live Pseudomonas released 4-30 times as much mercury as dead control cells.
Biotransfonnation by animals has been shown by experiments with rats in
which labelled mercury ion was found in the exhaled breath of rats which had
been injected with radioactive mercury. Natural evapo-transpiration from
vegetation has also been observed.•",51
The rate of vaporization of mercury and some inorganic mercury compounds
has been shown to decrease in the following sequence:'^
Hg° > Hg2Cl2 > HgCl2 > HgS > HgO
Vapor pressure of mercurial fungicide is greater for methyl and ethyl forms
than phenyl forms, 0.8-23 x 10~* mm Hg @ 35°C versus 0.8-17 x 10~6 mm Hg
@ 35°C. Methyl mercuric chloride was found to be the most volatile of
the methyl, ethyl, and phenyl compounds tested, with a value of 23 x
10~3 mm Hg @ 35°C. The methyl and ethyl forms tested, other than methyl
mercuric chloride, have a similar volatility to that of metallic mercury,
1.2 - 3.4 x 10~3 mm Hg.95
78
-------
Mercury emissions from power plants may form HgS on cooling. However,
the mercury emissions are most probably in the metallic or non-charged
state, namely Hg°. The Hg° in the atmosphere may condense or be adsorbed
onto particulates. However, nothing is known about the fate and transport
of mercury in the atmosphere.
The mercury released by the power plant in the plume may be carried
over a wide geographic area to be dispersed to the environment. There are
differences of opinion concerning the distance and rate at which Hg° is
deposited from the original power plant source.^5,46,85,88,89,91
These opinions include: all emissions deposited in the immediate
vicinity of the plant (within 1 mile); 2-20% deposited within 20 km.;
26-70 percent within 19.3 km; 2 percent within 8 km.; and none detected
within the first 32 and 50 km. Present information does not provide answers
to the questions of either the deposition rate of mercury nor the dis-
tance over which mercury may be transported.
The dispersal and distance traversed by the plume is dependent upon
such factors as stack height, plume buoyancy, and meteorological conditions.
Water
The effect of power plant emissions of mercury on man and the environment,
depends upon the concentrations of the various resulting forms of mercury
and their toxicity. Some forms of mercury have a greater toxicity, such as
the organomercurials, (monomethyl and dimethyl mercury), while other forms
have a lower relative toxicity. Therefore, total mercury concentrations are
not sufficient to assess the mercury hazard.
The objective of this section is to define the transformations of
mercury in water and the conditions which lead to these transformations.
Figure 3 represents the common pathways in water for the transformation of
Hg°. Figure 4 shows the distribution of mercury compounds in the environment.
Physical Transformation—
It is uncertain whether or not there is significant transfer of mercury
directly from air to water. The direct intersection of a plume with a
body of water may provide for the direct transfer of mercury. The other
path, indirect transfer, involves the deposition on the ground followed by
runoff. The exact nature of the transport and transformation of mercury is
not known.
Chemical Transformation—
The highest concentrations of mercury is found in the sediments as
compared with mercury dissolved in water. The relative solubility of the
various mercurous and mercuric compounds will determine the partitioning
between mercury on particulate and dissolved mercury. The relative solu-
bilities of mercury and some mercury compounds are listed in Table 17.
79
-------
Hg'
» Hg2 x f-Hg1^ +- CH3Hg +
(mercurous ion)
Compounds
Compounds
— ICH3)2 Hg
B Organir Hg-N
Compounds
, Organic Mercury
Ligands
(mercuric ion)
Figure 3. Common pathways of mercury transformation in water.
80
-------
Sources
Air
Nitrogen &
organic
compounds
HgX2 HgS
Bottom Sediment
Figure 4. Distribution of mercury compounds in the environment.
81
-------
TABLE 17
RELATIVE SOLUBILITIES OF MERCURY AND SOME MERCURY COMPOUNDS3
Substance
Mercury, Hg"
Mercurous Chloride,
Mercuric Chloride, HgCl2
Mercurous Oxide,
Mercuric Oxide, HgO
Cinnabar, HgS
Metacinnabar, HgS
Dimethylmercury, Hg
Me thy Imer curie Chloride, C^HgCl
Methylmercuric Iodide,
a Reference 96
b Reference 97
Solubulity (cold water)
insoluble
2 mg/1 9 25°C
69 gr/1 @ 20°C
insoluble
53 mg/1 9 25°C
0.01 mg/1 (8 18°C
insoluble
very slightly soluble^
no available data
insoluble
82
-------
Solid and liquid forms of mercury are stable and soluble under certain
conditions of pH and redox potential in most natural waters. Calculations
were made and plotted for species at 25°C and 1 atmosphere of pressure.98
These are shown in Figures 5 and 6.
Figure 5 shows the fields of stability for various inorganic compounds
of mercury where the system is aqueous containing 36 ppm Cl~, 96 ppm
SO^ = at 25°C and 1 atmosphere pressure as a function of Eh and pH. Both
solid and liquid forms of mercury may exist depending upon the conditions.
If liquid metallic mercury is formed it may volatilize and escape to the
open atmosphere. In well-oxygenated waters where there is a positive Eh and
the pH is between 5.5 and 9 (8.3 = average pH of natural waters), liquid
metallic mercury and solid HgO would be predominant. Under more acidic
conditions solid mercury chlorides would exist. In poorly oxygenated
waters where reducing conditions exist solid HgS will be the predominant
species.
Figure 6 shows the fields of stability for aqueous mercury species
under the conditions stated above as a function of Eh and pH. In well
oxygenated waters of a positive Eh above 0.3 volts and pH between 5.5 and 9,
Hg° (aq), and Hg(OH)2° (aq), HgCl2° (aq), and Hg2*2 will be the major
species found. At lower Eh values and decreasing pH soluble mercury sulfide
species [Hg(HS)2° (aq) and (HgS2~2) (aq)] will begin to predominate.98,99,
Biological Transformation—
Transformation of the various forms of mercury may occur through
biological mechanisms. Micro-organisms are the primary source of transfor-
mation, although many organisms, including mammals, have biochemical systems
capable of methylating a variety of compounds.100~10° Consideration must
therefore be given to the assessment of micro-organisms present in any given
body of water.
The micro-organisms considered to be methylators are primarily aerobic
and anaerobic bacteria. The mechanism and conditions under which they
methylate are discussed in the literature.107"115 An estimate of the
annual production rate of methylmercury was 50 g/g of total mercury. Most
mercury in the water adsorbs onto living cells or suspended particles, with
significant concentrations having been found in the intestines of feeding
fish and other organisms.112,116-118.
, Most mercury which enters the aqueous environment becomes methylated,
forming the methyl or dimethyl species depending upon conditions. The more
volatile dimethyl form is more toxic than the methyl form. The potential
hazard depends on toxicity, rate of breakdown, and duration and type of
exposure. Concentrations are usually not high enough to cause acute
posioning. However, many organisms concentrate mercury in their tissues
which can lead to their death or ultimately cause chronic mercury poisoning
humans if the organisms are ingested. Chronic poisoning is dependent
upon concentration, rate of ingestion, and time.
83
-------
1.20
1.00 -
0 2
8 Reference 98
Figure 5. Phase diagram for solid and liquid mercury species.3
-------
1.20
1.00 -
-.60
-.80
0 2
a Reference 98
Figure 6. Phase diagram for aqueous mercury species:
85
-------
Soil
Mercury deposits occur in nature in a number of forms, primarily
cinnabar, HgS. The presence of mercury in the various ores and rock
formations are shown in Table 18. Mercury, in trace quantities, migrates to
the general environment from these natural sources. Some of this is probably
as HgS. Mercuric sulfide, HgS, is virtually insoluble in water, and also
has a very low vapor pressure. Where alkaline reducing conditions exist,
along with the sulfide concentrations, the formation of the rather soluble
^ ion may facilitate mercury transport.
The increased presence of Hg2Cl2, with increasing distance from
natural deposits, may lead to the conversion to Hg° and HgCl2 near
the surface. This is expected to occur near the surface in the presence
of water and ultraviolet radiation. Since HgCl2 is soluble it may be
expected to pass into solution and be transported as leachate until a change
in pH occurs. The stability diagrams for various pH - Eh conditions have
been discussed previously in Section 7 and shown in Figures 5 and 6.
Methylation of the divalent mercury ion has also been found to occur in
soil systems. The production of methylmercury was found to be affected by
soil concentrations of mercury, soil texture, soil water content, soil
temperature, and time and to be directly proportional to percent clay content.
A decrease of methylmercury concentrations in soil with time has been
observed. The methylmercury production rate in natural soil systems has not
yet been quantified, but laboratory studies have indicated that under certain
conditions methylmercury production could be a significant part of the
cycling process. 1^
A quantification of the effect of each mechanism is not feasible
due to the interaction of the various elements, the complexity of the
mercury cycle, and the dependence on local conditions. However, some
general statement concerning transformations can be made. The degassing
rate of a number of non-mineralized and mineralized areas was measured. *20
It was estimated that a natural background degassing level for non-mineralized
areas was 0.2 g/m^/day with higher rates for mineralized areas. ^0 jt
was also concluded in this study that concentrations at the soil/air interface
correlated best with mercury concentrations in underlying deposits and not
with surface concentrations. A rough correlation between soil concentrations
and degassing rate probability exists but due to the number of factors such
as temperature, barometric pressure, soil type, etc. a relationship has not
as yet been developed. Mercury which is not degassed may become organically
bound to the soil and immobilized.
The quantitative relationship of these transformations to mercury
emissions from power plants cannot be determined. With definitive information
regarding the deposition of mercury from a power plant plume, the transforma-
tions and ultimate fate of the mercury could be determined. However, as
previously discussed, the initial information is as yet still unknown.
86
-------
TABLE is. MERCURY CONTENT op ORES, ROCKS, AND MINERALS*
MINERAL
tetrahedrlte
grey copper ores
sphalerite
wurtzlte
stibnite
realgar
pyrite
galena
chalcopyrlte
bornlte
bournonlte
chalcocite
marcasite
pyrrhotlte
molybdenite
arsenopyrite
orplment
native gold
native silver
barite
cerussite
dolomite
fluorite
calcite
aragonite
siderite
chalcedony and
opaline silicas
H**a * ***
pyrolusite
hydrated iron oxides
graphite
coal
gypsum
NORMAL
RANGE
(ppn)
LIMITS
10. -1
5.0 -
0.1 -
0.1 -
0.1 -
0.2 -
0.1 -
0.04 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
0.1 -
1.0 -
1.0 -
0.2 -
0.1 -
0.1 -
0.01 -
0.01 -
0.01 -
0.01 -
0.01 -
Om
. \j i
1.0 -1
0.10 -
0.5 -
0.05 -
0.01 -
,000
500
200
200
150
150
100
70
40
30
25
25
20
5
5
3
3
100
100
200
200
50
50
20
20
10
10
9
C
,000
500
10
10
4
HIGHEST
REPORTED
CONTENT
(X)
17.6 ;21
14.
1.
0.03
1.3
2.2
2.
0.02
-
-
.
-
0.07
_
-
60.
30.
0.5
0.1
.
0.01
0.03
3.7
0.01
-
-
2.
0.2
0.01
2.
~
ROCK TYPE
(a) IGNEOUS
Ultrabasic (dunite, kimberlite, etc.)
Basic intrusives (gabbro, diabase, etc.)
Basic extrusives (basalt, etc.)
Intermediate Intrusives (diorlte, etc.)
Intermediate extrusives (andesite, etc.)
Acidic Intrusives (granite, granodioHte,
syenite)
Acidic extrusfves (rhyolite, trachyte, etc.)
Alkali-rich rocks (nepheline, syenite,
phono lite, etc. )
(b) METAMORPHIC
Quartzites
Amphlbolltes
Hornfeis
Schists
Gneisses
Marbles, crystalline dolomites
(c) SEDIMENTARY
Recent sediments: stream and river
lake
ocean and sea
Sandstones, arkoses, conglomerates
Shales, argil 11 tes, muds tones
Carbonaceous shales, bituminous shales
Limestones, dolomites
EvapoHtes: gypsum, anhydrite
halite, sylvlte, etc.
Rock phosphates (composite samples)
RANGE
7 - 250
5 - 84
5 - 40
13 - 64
20 - 200
7 - 200
2 - 200
40 -1400
10 - 100
30 - 90
35 - 400
10 -1000
25 - 100
10 - 100
10 - 700
10 - 700
< 10 -2000
< 1 0 - 300
5 - 300
100 -3250
< 10 - 220
< 10 - 60
20 - 200
MEAN
168
28
20
38
66
62
62
450
53
50
225
100
50
50
73
73
100
55
67
437
40
25
30
f. V
'Reference 47
-------
SECTION 8
LITERATURE CITED
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88
-------
13. Public Health Sevice Act as amended by the Safe Drinking Water Act
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90
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•
92
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