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OCR for page 35
4. ANTHROPOGENIC SOURCES OF ATMOSPHERIC SUBSTANCES
An enormous number and variety of anthropogenic sources emit
substances into the atmosphere. Manufactured products are atomized
and vaporized; particulate matter and dust are released from
construction, mining, and industrial activities; gases and vapors form
at high temperatures during the combustion of fossil fuels, ore
smelting, and cement manufacturing.
In this report we concentrate on the combustion of fossil fuels
because this is the source of a major part of the anthropogenic
substances in the atmosphere (see, e.g., Bertine and Goldberg 1971,
Keeling and Bacastow 1977, Robinson 1977, Galloway and Whelpdale 1980,
Shinn and Lynn 1979~. Fossil fuels represent the largest mass of raw
materials subject to high-temperature combustion processes. Certain
types of coal and petroleum are enriched with potentially toxic metals
{e.g., Hg, Se, As, Cd, and Zn) as well as radioactive elements and
organic compounds, many of which are released to the atmosphere during
combustion. Significant changes in the qualitative and quantitative
patterns of fossil fuel consumption are expected during the next few
decades with consequent changes in emissions to the atmosphere.
Some emissions from the combustion of fossil fuels enter the
atmosphere as gases, such as sulfur dioxide, nitrogen oxides,
elemental mercury, and volatile organic compounds (U.S. EPA 1978a,
Morris et al. 1979, Lindberg 1980~. Others enter as solid or liquid
particles, the so-called primary aerosols (Robinson 1977, Block and
Dams 1976~. In addition, so-called secondary aerosols form from the
gases--e.g., sulfur dioxide is transformed into ammonium sulfate
(Husar et al. 1978, NRC 1978a). Volatile inorganic trace elements can
also undergo transformations to particulate form during dispersion and
cooling of combustion gases (Kaakinen et al. 1975~. Atmospheric
transformations, transport, and deposition of fossil fuel pollutants
will be discussed in the next chapter.
35
,
OCR for page 36
36
PATTERNS OF FOS S I L FUEL USE
Global patterns of fossil fuel consumption and associated
emissions have evolved over the past century in response to
demographic, economic, and technological factors. Recent papers by
Brown (1976), Hafele and Sassin (1977), and others have documented
historical patterns of fossil fuel use. We review selected data on
spatial and temporal patterns of fossil fuel use here to illustrate
the potential for changing patterns of anthropogenic emissions to the
atmosphere.
A central task for an assessment of atmosphere-biosphere
interactions is the development of emissions inventories and
projections. But because quantitative data on fuel consumption are
generally available for most countries, while emissions data are often
of poor quality or are not available at all, we must focus on
consumption. With fuel consumption data, projections of emissions can
be made using knowledge or assumptions concerning variables such as
combustion technology, emissions-control technology, and patterns of
operation (e.g., seasonal variations in electrical energy demand).
Total consumption of fossil fuel energy has grown at an average
rate of 5 percent per year since 1900. Primary fossil fuel
consumption over the past few decades is summarized in Figure 4.1. In
the early stages of growth in fossil fuel use, coal was the most
widely used fuel, whereas since 1950 oil and gas have become
predominant, accounting for approximately 73 percent of present
primary energy consumption (Hafele and Sassin 1977). The pattern of
increasing global energy demand and fossil fuel use reflects the
transition from a totally agricultural society to a partially
industrialized one. Industrial development has been accelerated by
the transition from a wood-fueled economy to a coal-fueled and then to
an oil- and gas-fueled one; each successive energy source has provided
increased energy efficiency with consequent positive feedback
increasing total consumption. There has also been a tendency to
centralize the location of fossil fuel burning usually near large
urban areas.
Figure 4.2 shows proportional shares of the global energy market
that each of these 4 fuel sources has supplied over time. Marchetti
(1975) has demonstrated that primary fuel transitions to date have all
exhibited similar dynamics. Each new energy source has taken roughly
100 years to grow from 1 percent to 50 percent of the global energy
market. These data have important implications for the development of
inventories and projections of global pollutant emission. An
emissions forecast must include proper time dependence on the
introduction of new pollution sources and the phasing out of replaced
sources.
Most pollutants do not have sufficiently long residence times in
the atmosphere to become globally distributed (see Chapter 5). With
the exception of CO2, lead, mercury, and perhaps a few other
compounds, energy-related emissions are primarily of concern at
present because of potential effects on atmospheric and ecological
processes within a local, interregional, or continental area. Thus,
OCR for page 37
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an assessment of potential effects of fossil fuel use on environmental
quality must consider the geographical distribution of fossil fuel
emissions.
Regional energy flux density is shown in Figure 4.3. About 90
percent of fossil fuels are consumed in the Northern Hemisphere.
Three centers of industrial activity are especially important:
eastern North America, Europe, and China-Japan region. As we shall
discuss in Chapter 5, this has important implications for pollutants
that are transported interregionally in the hemisphere but not
globally. A detailed tabulation of annual energy consumption for each
nation can be obtained in reports published by the United Nations
(1976, 1978). The past increase in total energy consumption and
shifts from one fuel to another in the United States have largely
paralleled the patterns of global use.
Coal represents over 90 percent of U.S. fossil fuel reserves but
currently supplies only 20 percent of U.S. energy needs. Its use will
probably grow as a result of the recent oil crisis and public
opposition to nuclear power. While total coal consumption has
remained more or less constant through most of this century (Figure
4.4), there has been a dramatic shift in the economic sectors that
consume coal. Before 1940, coal consumption was divided among
railroad power, residential and commercial heating, oven coke
production, and other industrial processes. The railroad demand was
particularly high during the war years of the mid-1940s. Then, within
one decade, the l950s, coal consumption by railroads and by the
residential-commercial sector all but vanished. Currently, electric
utilities are the main coal consumers, and the trend of total coal use
in the United States since 1960 has been determined by the demands of
the electric utilities.
The result has been that, in recent years, a higher proportion of
coal emissions has come from large point sources with very tall smoke
stacks. This means that the emissions can spread over a larger area
before they fall or are washed to the ground. At the same time,
increased use of air-conditioning has meant increased demand for
electricity during the summer, a season that may favor more rapid
chemical transformation in the atmosphere of the power plant emissions
because of the higher ambient temperatures.
ATMOSPHERIC EMISSIONS FROM FOSSIL FUEL BURNING
In the absence of direct measurements of emissions, an assessment
of atmospheric emissions of specific substances is dependent on
quantitative inventories of the total mass (e.g., of coal used) or
surface exposure (e.g., for volatile emissions from natural soils or
vegetation) of the various sources and their chemical composition. An
emission flux is obtained by multiplying the mass of the source by the
appropriate emission rate. Some data on rates of fossil fuel use and
raw-material refining for production of industrial materials are
available in publications by the United Nations, World Bank, U.S.
Department of Energy, and U. S. Bureau of Mines. Omission rates,
OCR for page 39
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FIGURE 4.4 Coal consumption in the United States. Initially, coal was
used primarily for railroads and for residential and commercial heating.
Since 1960, however, the trend in total coal use has been determined by
electric utility use. SOURCE: NRC (1978a).
OCR for page 41
41
particularly for high priority, health-related pollutants, are
compiled by the U.S. Environmental Protection Agency (U.S. EPA 1977~.
A comparison of natural and anthropogenic emissions at the global,
national, and regional levels is a first key step in a careful
assessment of potential ecological consequences. An example of this
approach for sulfur sources in eastern North America is summarized in
Table 4.1.
Oxides~of Sulfur and Nitrogen
Sulfur dioxide was emitted from man-made sources in the United
States at an estimated rate of 30 x 1012 g per year in 1973 (Figure
4.5~. Fuel combustion exclusive of transportation accounted for 78
percent, industrial processes (metal smelting, chemical industries and
manufacturing, etc.) for 20 percent, and transportation for 2
percent. With the exception of fuels used in transportation, about 65
percent of the national anthropogenic sulfur oxide emissions came from
coal combustion and about 13 percent from oil combustion.
Some 85 percent of the sulfur dioxide emitted in the United States
is released east of the Rocky Mountains, with the highest emission
density in the vicinity of the Ohio River Valley (Ohio, Pennsylvania,
and Indiana). The emission density for the states in the Ohio River
Valley region ranges between 10 and 30 g/m2 per year of sulfur
dioxide. East of the Rocky Mountains coal contributes 71 percent and
oil, 20 percent of the total sulfur dioxide emissions. Hence, coal
combustion and, to a lesser degrees oil consumption are a proper index
of the emissions of sulfur oxides (SOx) over the eastern United
States, and state-by-state trends of coal consumption are useful
indicators of regional SOX emission trends.
Emissions from electric utilities constitute a growing share of
the total SOx emissions (Figure 4.5). In 1973, utilities
contributed about 60 percent of the SOX emissions east of the
Mississippi. According to EPA estimates, SOX emissions will
increase by about 30 percent in Texas by 1985. Even with more
stringent standards applied to new power plants SOX emissions are
predicted to continue at about their present level while the nitrogen
oxide (NOx) emissions are projected to increase (Figure 4.67.
The national NOX emissions of about 22 x 1012 g per year arise
in roughly equal proportions from automobiles, industry, and electric
utilities. The emission density of NOX, as seen in Figure 4.7, is
highest in the Boston-Washington corridor, and second highest in the
Ohio River Valley states of Indiana, Ohio, and Pennsylvania. The
oxides of nitrogen play important roles in a wide range of atmospheric
processes which include the formation of aerosols, photochemical
reactions in both the troposphere and stratosphere, the formation of
acid precipitation, and the degradation of air quality in urban areas
(NRC 1977c and 1978d, Crutzen 1979, Kelly et al. 1980~. Figure 4.8
illustrates the major sources, pathways, and removal mechanisms for
atmospheric nitrogen species--exclusive of molecular nitrogen--that
are of particular significance to atmosphere-biosphere interactions.
OCR for page 42
42
TABLE 4.1 Atmospheric Sulfur Budget for Eastern North America
(X 10} 2 g/year)
Magnitude for Eastern
Canada U.S.A.
North America
Inputs
Man-made emissions 2.1 14 16
Natural emissions,
sea spray, internal 0.06 0.06
terrestrial biogenic 0.06 0.04 0.1
marine biogenic 0.2 0.4 0.6
Inflowfrom oceans 0.04 0.02 0.06
Inflow from west 0.1 0.4 0.5
Inflow to U.S. from Canada 0.7
Inflow to Canada from U.S. 2.0
Total 4.6 15.6 17.4
Outputs
Wet deposition 3.0
Dry deposition 1.2
Outflow to oceans 0.4
Outflow from Canada to U.S. 0.7
Outflow from U.S. to Canada 2.0
2.5
3.3
3.9
5.5
4.5
4.3
Total 5.3 11.7 14.3
SOURCE: Galloway and Whelpdale. Reprinted with permission
from Atmospheric Environment, vol. 14, J.N. Galloway and D.M.
Whelpdale, "An Atmospheric Sulfur Budget for Eastern North
America". Copyright (~)1980 by Pergamon Press, Ltd.
OCR for page 43
43
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YEAR
FIGURE 4.5 Sulfur oxide emissions in the United
States by source, 194~1975. From 1940 to 1960 the
reduction of SOX emissions from industrial fuel con-
sumption was balanced by increase of SOX emissions
from electric utilities. Since 1960 the sharp increase
in SOX emissions was essentially due to electric
utilities. SOURCE: NRC (1978a).
OCR for page 44
44
Nitrogen Oxides
20
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STATIONARY SOURCES
Other
Industrial Combustion
Electric Utilities
TRANSPORTATION SOURCES
EM Trucks
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1975 1990
Sulfur Oxides
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FIGURE 4.6 Net emissions of nitrogen oxides and sulfur oxides for the United States by
source for 1975 and projections for 1990. Projections are based on 1979 emissions regulations
and national energy use projections. SOURCE: Mitre Corporation (1979).
OCR for page 45
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But many of the details of the sources, transport, sinks, and reaction
kinetics of most tropospheric trace nitrogen species are incompletely
understood.
The major anthropogenic source of NOX (NO and NO2) in the
United States is fossil fuel combustion, and a decline in NOX
emissions projected for automobiles will more than be offset by
increased emissions from stationary sources (Figure 4.6~. By 1985
stationary sources are expected to account for 70 percent of
anthropogenic NOX emissions (US EPA 1980~. Trends in total NOX
emissions have been strongly upward, with almost a three-fold increase
over the past 25 years (Table 4.2~. Significant increases in NOX
emissions are forecast for the remainder of the century, primarily due
to emissions associated with increased coal use in the electric
utility and industrial sectors of the U.S. economy.
Nitrogen oxides produced by fossil fuel combustion can create
local pollutant levels that are 10 to 100 times greater than natural.
However, the regional and global significance of anthropogenic NOX
emissions remains a major problem area for research. Recent estimates
of global NOX production by lightning range from 1.8 x 1012 g to
18 x 1012 g of nitrogen per year (Chameides et al. 1977, Levine et
al. 1981~. If the lower value is correct, NOX emissions from
anthropogenic sources, estimated to be at least 20 x 1012 g of
nitrogen per year, may be a major source of NOX to the global
troposphere (Levine et al. 1981~. Biomass burning is also postulated
to be an important source of NOX, with a calculated potential source
strength of 20 to 100 x 1012 g of nitrogen per year (Crutzen et al.
1979~. Clearly, reducing the uncertainty in estimates of natural
sources of NOX is fundamental to an assessment of the significance
of anthropogenic NOX emissions on regional and global air quality.
NOx emissions are hypothesized to affect the biosphere through
human health effects (NRC 1977c) and through conversion to nitric
acid, which may contribute substantially to the acid rain problem (NRC
1978d). These, and other problems related to the nitrogen cycle, can
only be resolved by increased research on the biogeochemical cycling
of nitrogen oxides.
Trace Metals
Data on emissions of trace metals are very limited, and there is
an urgent need for quantitative data on specific rates of emission for
both industrial processes and natural volatilization from soils and
vegetation. Goldberg (1976) and Harriss and Hohenemser (1978) have
discussed emission factors for mercury, for example, but critical
difficulties are encountered in obtaining data on the mercury content
of certain fossil fuels and raw materials used for metals production
and, more importantly, in rates of volatilization from natural
surfaces. A summary of various attempts at quantification of
anthropogenic mercury emissions is illustrated in Table 4.3. The
range in these estimates demonstrates that uncertainties over
anthropogenic mercury emissions are at least one order of magnitude.
OCR for page 48
48
TABLE 4.2 Total U.S. NOX Emissions for the Years 1950
and 1975 (X 10~2 g/year)
1950 1975
Utility combustion
Other combustion
Non-ferrous smelters
Other industrial processes
Transportation
Total
1.1 6.1
3.7
neg.
0.3
3.0
8.1
5.5
neg.
0.7
9.9
22.2
NOTE: Values are prorated on the basis of five categories of
emission sources. For 1975 the U.S. point sources are at their
1977-1978 emission rate, whereas area sources are at their
1973-1977 emission rate.
SOURCE: U.S.-Canada Research Consultation Group on
LRTAP (1979).
OCR for page 49
49
TABLE 4.3 Range in Emanates of Anthropogenic Mercury
Emissions to the Global Atmosphere (X 10 g/year)
Emission Source
Mercury Flux Estimatesa
Coal combustion
Oil and gas combustion
Metals refining
Chlor-aLkali production
Cement manufacturing
Total emissions 11.5-137.4
0.017-63.8
0.6-22.9
7.3-20.0
2.6-30.0
1.0-1.3
aThe range in global mercury emission fluxes were obtained
from a review of Bertine and Goldberg (1971), Garrets et al.
(1975), Joensau (1971), Harriss and Hohenemser (1978),
NRC (1978c), and Lantzy and Mackenzie (1979).
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50
Uncertainties regarding natural sources of mercury are much worse,
thus we cannot begin to make reasonable comparisons of anthropogenic
and natural mercury sources at present. And the data base on
atmospheric emissions for other trace metals and even for most
compounds is poorer than that for mercury, indicating the serious
problems with uncertainty in making emissions inventories with such
limited data.
Estimates of the fluxes of metals to the atmosphere from fossil
fuel burning have been made by Bertine and Goldberg (1971), using
figures for the consumption of fossil fuels from 1967: 1.75 x 1015
g of coal; 1.04 x 1015 g of lignite; 1.63 x 1015 g of oil, and
0.66 x 1015 g of natural gas. The literature was surveyed for
reasonable values of the elemental contents of these fuels, and the
authors assumed that the fly ash released to the atmosphere from the
burning of coals and oils is about 10 percent of the total ash and
that 50 percent of the coal is used in the manufacture of coke. The
results are given in Table 4.4. For such elements as barium and
mercury, mobilization from fossil fuels to the atmosphere appears to
be within an order of magnitude of the river fluxes of these metals to
the oceans--which is to say that society has become an important
geological agent.
For certain elements these estimates may be low, because
volatilization may be selective. Emission spectrographers have noted
that there is a preferential volatility of some elements such as
arsenic, mercury, cadmium, tin, antimony, lead, zinc, thallium,
silver, and bismuth under the high temperature conditions they employ
in the direct current electric arc. The fluxes of these metals given
in Table 4.4 may be underestimated because they do not take this
preferential volatility into account.
There are few data on emissions to the atmosphere from human
activities other than fossil fuel use. Nriagu (1979) has estimated
the emissions of 5 metals--cadmium, copper, lead, nickel, and
zinc--from a variety of anthropogenic activities and sources. These
estimates are given in Table 4.5 along with the natural worldwide flux
for these 5 trace metals. The data presented for trace metal fluxes
from coal and oil combustion differ somewhat from those of Bertine and
Goldberg given in Table 4.4, but in any case, anthropogenic emissions
to the atmosphere exceed natural emissions for these 5 metals.
Similar fluxes of some trace metals to the atmosphere appear to
result from cement production, which equaled 5.7 x 1014 grams/year
in 1972 (Goldberg 1976). About 95 percent of this output is Portland
cement, whose chemical formulation can be considered as one-third
shale and two-thirds limestone. Cement is produced by roasting such a
mixture at temperatures between 1,450° and 1,600°C, for 2 to 4 hours.
Metals whose oxides have boiling points below 2,000°C can be expected
to be volatilized.
Hypothesized mobilization of some trace metals to the atmosphere
as a result of cement production is given in Table 4.6. Vaporization
by this process appears greater than that by fossil fuel burning for
such elements as arsenic, boron, lead, selenium, and zinc. This may
be true for other metals for which data on boiling points are not at
OCR for page 51
51
TABLE 4.4 Amounts of Elements Mobilized into the Atmosphere as a Result of Weathering Processes and the Combustion of Fossil Fuels
Weathering Mobilization
Fossil Fuel Concentration (ppm) Fossil Fuel Mobilization (X 109 g/year) (x 109 g/year)
.
Element Coal Oil Coal Oil Total River Flow Sediments
Li 65 9 110 12
Be 3 0.0004 0.41 0.00006 0 41 5.6
B 75 0.002 10.5 0.0003 10.5 360
Na 2,000 2 280 0.33~ 280 230,000 57,000
Mg 2,000 0.1 280 0.02 280 148,000 42,000
Al 10,000 0.5 1,400 0.08 1,400 14,000 140,000
p 500 70 720
S 20,000 3,400 2,800 550 3,400 140,000
Cl 1,000 140 280,000
K 1,000 140 83,000 48,000
Ca 10,000 5 1,400 0.82 1,400 540,000 70,000
Sc 5 0.001 0.7 0.0002 0.7 0.14 10
Ti 500 0.1 70 0.02 70 108 9,000
V 25 50 3.5 8.2 12 32 280
Cr 10 0.3 1.4 0.05 1.5 36 200
Mn 50 0.1 7 0.02 7 250 2,000
Fe 10,000 2.5 1,400 0.41 1,400 24,000 100,000
Co 5 0.2 0.7 0.03 0.7 7.2 8
Ni 15 10 2.1 1.6 3.7 11 160
Cu 15 0.14 2.1 0.023 2.1 250 80
Zn 50 0.25 7 0.04 7 720 80
Ga 7 0.01 1 0.002 1 3 30
Ge 5 0.001 0.7 0.0002 0.7 12
As 5 0.01 0.7 0.002 0.7 72
Se 3 0.17 0.42 0.03 0.45 7.2
Rb 100 14 36 60(,
Sr 500 0.1 70 0.02 70 1,800 600
Y 10 0.001 1.4 0.0002 1.4 25 60
Mo 5 10 0.7 1.6 2.3 36 28
Ag 0.5 0.0001 0.07 0.00002 0.07 11 0.03
Cd 0.01 0.002 0.5
Sn 2 0.01 0.28 0.002 0.28 11
Ba 500 0.1 70 0.02 70 360 500
La 10 0.005 1.4 0.0008 1.4 7.2 40
Ce 11.5 0.01 1.6 0.002 1.6 2.2 90
Pr 2.2 0.31 1.1 11
Nd 4.7 0.65 7.2 50
Sm 1.6 0.22 1.1 13
Eu 0.7 0.1 0.25 2.1
Gd 1.6 0.22 1.4 13
Tb 0.3 0.042 0.29
Ho 0.3 0.042 0.36 2.3
Er 0.6 0.001 0.085 0.0002 0.085 1.8 5.0
Tm 0.1 0.014 0.32 0.4
Yb 0.5 0.07 1.8 5.3
Lu 0.07 0.01 0.29 1.5
Re 0.05 0.007 0.001
Hg 0.012 10 0.0017 1.6 1.6 2.5 1.0
Pb 25 0.3 3.5 0.05 3.6 110 21
Bi 5.5 0.75 0.6
U 1.0 0.001 0.14 0.001 0.14 11 8
SOURCE: Bertine and Goldberg (1971). Bertine and Goldberg used values from a variety of sources discussed in their paper. Reprinted with
permission from Science 172:233-235. Copyright C)1971 by the American Association for the Advancement of Science.
OCR for page 52
52
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nox emissions
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present available. In some cases where the oxides decomposed upon
heating below 2,000°C, the volatility of the metal was used. The
calculated emissions for Pb, Cd, and Zn from cement production given
in Table 4.6 compare satisfactorily with the emissions for these
metals given in Table 4.5 for industrial applications. Such a
comparison assumes that the fluxes listed for industrial applications
result primarily from cement production, and also takes into account
the fact that there may be a systematic bias for high fluxes in the
cement production model used to calculate the values given in Table
4.6.
Organic Compounds
Anthropogenic emissions of organic compounds have received
substantial attention because of their effect on air quality in urban
areas. The emphasis has been on gaseous reactive hydrocarbons, which
lead to photochemical smog including high ozone concentrations, and on
particulate polycyclic compounds that have mutagenic and carcinogenic
properties. This section summarizes current data on anthropogenic
organic emissions and briefly discusses the possible effect of new
energy technologies on the nature of these emissions.
Global anthropogenic emissions of non-methane hydrocarbons are
estimated to be approximately 80 x 1012 g per year (Duce 1978~.
Duce derived this emission rate from the earlier estimates of Robinson
and Robbins (1968) and more recent data from the U.S. Environmental
Protection Agency (1976) for the United States. These emissions
originate primarily from fossil fuel burning. Although global
anthropogenic emissions of gaseous organics are approximately one
order of magnitude lower than natural emissions, emissions are mostly
confined to the industrialized regions of the Northern Hemisphere and
have significant effect on air quality in these regions.
Anthropogenic emissions of particulate organic carbon were
estimated by Duce (1978) to be approximately 30 x 1012 g per year in
1973-74 period. Duce broke down emissions data by type of industrial
source and separated particulates into two size fractions, greater
than and less than 1 micron diameter (Table 4.7~. Four major
sources--coal, petroleum, noncommercial fuel, and agricultural
burning--account for approximately 80 percent of the total
anthropogenic emissions of organic carbon particles. The molecular
composition of these anthropogenic emissions has been reviewed (e.g.
Grosjean 1977, Graedel 1978~. Because of their adverse health
effects, the polycyclic aromatic hydrocarbons (PAM) have received
considerable attention (NRC 1972), and specific emission factors for
anthropogenic sources of benzofa~pyrene and other PAH are now
available (U.S. EPA 1978b).
Both increased emissions of existing organic pollutants and
emissions of new pollutants may result from emerging fossil fuel
technologies (coal gasification and liquefaction, shale oil and tar
sand exploitation) and from increasing use of diesel and
gasoline-alcohol ("gasohol") fuels. Moderate to large increases in
55
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particulate PAH emissions are expected to result from increased use of
coal, fuels from coal gasification and liquefaction, and shale-derived
fuels; use of diesel-powered vehicles (NRC 1981b); and burning of wood
for domestic heating (e.g., Butcher and Sorenson 1979~.
Organic pollutants other than PAN that may require attention
include phenols from coal process waters (Guerin 1977), aldehydes in
diesel-powered vehicle exhaust (NRC 1981b), and unburned alcohol as
well as aldehydes in exhaust from gasohol-powered vehicles (Allsup and
Eccleston 1980~. In addition, new heteroatomic organic pollutants
including sulfur-containing and nitrogen-containing compounds may be
emitted to the atmosphere as a result of fuel conversion processes.
These organic gases include mercaptans, sulfides, thiophenes, furans,
pyrroles, and pyridines (Sickles et al. 1977~. The environmental
persistence and fate of these compounds have received little or no
attention to date.
SUMMARY
Fossil fuel burning, primarily of coal and oil, contribute most of
the anthropogenic constituents of the atmosphere, and the bulk of the
burning is done in the Northern Hemisphere, primarily in North
America, Europe, and Japan. The emerging fuel technologies (coal
gasification, shale oil, tar sands, etc.) as well as the increased use
of diesel and alcohol fuels may alter the magnitude and character of
pollutant fluxes to the atmosphere in the future.
Gaseous pollutants include sulfur dioxide, nitrogen oxides,
organic compounds, and trace metals. After entering the atmosphere
they may be oxidized (sulfur dioxide going to sulfate, the nitrogen
oxides going to nitrate), associate with aerosols, or be degraded.
Almost without exception they return quantitatively to the earth's
surface.
Trace metals from fossil fuel combustion or cement production may
initially enter the atmosphere as gases but, in general t quickly
become associated with the aerosols or form aerosols. Both fossil
fuel combustion and cement production are introducing some metals to
the atmosphere at rates comparable to river fluxes to the oceans,
showing that such activities have made society an important geological
agent.
The particulate organic carbon releases that come from coal,
petroleum, noncommercial fuel, and agricultural burning account for 80
percent of the fluxes. Of particular concern are the polycyclic
aromatic hydrocarbons, which pose a direct health hazard.
