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2 Emissions of Sulfur Dioxide and Nitrogen Oxides and Trends for Eastern North America Rudolf B. Husar INTRODUCTION Air pollution is caused when an element or a compound is removed from its long-term geochemical reservoir and, with the help of the atmosphere, dispersed and transferred to another long-term geochemical reservoir. The elements redistributed in this manner are carbon, sulfur, nitrogen, and the crustal elements, including metals. Another type of air pollution occurs when human activities produce and disperse compounds that are completely foreign to nature, such as DOT, polychlorinated biphenyls, dioxin, and some nuclear fission products. The production and fate of these compounds will not be discussed further in this chapter. We continue removing or mining carbon, sulfur, nitro- gen, and crustal material from the Earth's long-term reservoir for two purposes: to "produce" energy from the fossil fuels and to manufacture from extracted minerals disposable or permanent objects for societal use. Most pollutants are emitted from the land into the air, with the atmosphere serving as a medium for dispersion and chemical reactions during the transport. The atmosphere redistributes the emitted materials onto the biota, land, lakes, and oceans. The role of the rivers is primarily in gathering these materials from the land and trans- ferring them to their long-term storage in the oceans. Certain volatile pollutants may also be re-emitted from land or from lakes. 48

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49 Examples of the Flow Rates of Sulfur and Nitrogen from Natural Processes and from Human Activities It is worth considering a few estimates of flow rates of sulfur and nitrogen from simple back-of-the-envelope calculations. If all the coal consumed in the United States over the past century (500 million tons/yr) were piled into a single mountain, it would occupy 25 cubic kilometers, i.e., a pyramid with a base area of 6 km x 6 km, 2 km high. Spread over the entire eastern half of the United States, it would be a layer of about 1-cm thickness. This means that from a geophysical weathering perspective, about 150 g m~2 yr~1 of crustal mineral material currently goes up in smoke, considering only coal consumption in the eastern United States. By com- parison, the natural weathering of the Earth's surface minerals as they are carried by rivers to the oceans is about 20 g m 2 yr~l. Thus human activities sig- nificantly enhance the natural redistribution of the Earth's crustal material over eastern North America. Over the past 100 years the average emission density over eastern North America was about 1-2 g sulfur m~2 yr~ . Most of that sulfur returns to the ground some- where over eastern North America, resulting in an average sulfur flow of 100 g sulfur m 2 100 yr 1. By comparison, the total sulfur content of soils is 3-30 g sulfur/m2. Hence, the yearly sulfur flow through soils from human activities is comparable to the natural sulfur content of the soil itself. It is also instructive to consider the sulfur and nitrogen flow from a biological perspective: in the United States, the average daily per capita emission rate to the atmosphere is roughly 200 g sulfur (400 g sulfur dioxide) and 100 g nitrogen (300 g nitrogen dioxide). This is comparable in weight to the daily per capita food consumption. The sulfur emission rate from anthropogenic sources in the United States is about 15 x 1012 g sulfur yr . Distributing these emissions uniformly over the contiguous United States with an area of 8 x 1012 m2, we arrive at an average emission density of 2 g sulfur m~2 yr~l. This is comparable to the density of sulfur contained and removed yearly from the soil by harvesting agricultural products, such as corn and wheat (Beaton et al. 1974). The biosphere is a thin shell of living matter on the Earth's surface. It is responsible for a grand-scale cycling of energy and chemical elements. Functionally,

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50 this biological cycling is maintained by three groups: producers, consumers, and decomposers. The producers are plants and some bacteria capable of producing their own food photosynthetically or by chemical synthesis. The consumers are animals that obtain their energy and protein directly by grazing, feeding on other animals, or both. The decomposers are fungi and bacteria that decompose the organic matter of producers and consumers into inorganic substances that can be reused as food by the producers they are the recyclers of the biosphere. Nature is capable of sustaining the producer-consumer-decomposer cycle indefinitely with the Sun as the energy source. The smallest such entity that is self-sufficient is an ecosystem. Functionally, human activities that perturb the natural environment can be divided into similar components (Figure 2.1). Producing activities include energy production (fossil fuels), manufacturing (nonfuel minerals), and growing food. The consumers are humans and their domestic animals. Decomposing or recycling activities include treatment of waste water, recycling of metals, and the burning of refuse. However, whereas an ecosystem relies on its decomposers for a complete recycling of its elements, the system created by human activity lacks such efficient decomposers. As such, manufactured materials that are no longer needed and waste by-products of indus- trial activity are disposed into the physical environment. The process of adding unwanted material to the environment is called pollution. The material that is not recycled is distributed by the atmosphere and the hydrosphere and delivered to the biological and geochemical receptors. The above scheme permits a convenient accounting for the flow of materials in society from the producers to consumers to the receptors. ; Pollutant Flow Diagram The flow of matter from the producers to consumers and subsequently to the receptors is depicted schematically in Figure 2.2. Most of the production of potential pollutants begins with mining, that is, removing a substance from its long-term geochemical reservoir. The amount of pollutant mass, Mi, mobilized by mining (tons/yr) is the production rate Pi (tons/yr) of the raw material (coal, oil, smelting ore, etc.) multiplied by the concentration Ci (grams/ton) of the impurity (sulfur, mercury, lead, etc.): Mi = ciPi.

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51 NATU RAL CH EM ICAL CYCLI NG Pla nts External world ~V' Animals Microorga nisms Producers ~ - - [ Recyclers FLOW OF CHEMICALS FROM HUMAN ACTIVITY _ Mobi I izers Prod ucers J L External world _~. '_~;;~_ ski. Emitters Receptors Recyclers FIGURE 2.1 Diagrams of the movement of chemicals and materials through (top) the natural ecosystem and (bottom) a system resulting from human activity.

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52 PRODUCERS CONSUMERS RECEPTORS Mining Combustion Deposition surface transfer, s atmospheric transfer, ajk ,~ a11~ s33 M U R. K mass moved used at received by producer consumer at receptor c; - contaminant concentration Pj - production Mj = cjPj U jj = sjjMj R jjk = ajkSiiCiPi Uj = ~ s jjMj Rjk = ajkU Uj = ~ SjjCiPi Rk = ~ ajkUj Rk = ~ ajk ~ s jjCiP FIGURE 2.2 Schematic illustration of key matrices in the flow of material from the producer to the consumer to the receptor. Matter is transferred from the producer to the consumer by ground transportation, including railroads, trucks, and barges. Functionally, surface transport redistributes the mined substances over a large geographical area. In principle, every producer, i, may deliver its product to any consumer, j. Mathematically, this producer-consumer transfer is characterized by a surface transfer matrix, Al].

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53 The amount of matter, Uij, originating from producer i and used at consumer j is sijMi. The total amount of matter reaching the consumer j is the sum of the matter produced by all producers multiplied by their respective surface transfer matrix elements. The next transfer occurs between the consumer, or emitter, and the environmental receptors. The consumer is located where the combustion or smelting occurs, and the receptor is located where the pollutant falls fol- lowing its atmospheric transit. Again, in principle all emitters j can transfer matter through the atmosphere to all receptors k. Hence, the matter received at receptor k that originated at consumer (emitter) j, Rjk, is the product of the use rate Uj times the atmospheric transfer matrix, a k, from emitter j to receptor k. The total amount o] matter deposited at receptor k is the sum of the use rates Uj at each emitter weighted by its atmospheric transfer matrix element. the numeric values of the Mi, ci, and si are discussed in detail; discussion of the atmospheric transfer matrix ask is beyond the scope of this report. The emission estimate at any given emission site U (tons/yr) is calculated as follows: Uj = sijoiPi, where Pi In this chapter, (tons/yr) is the fuel and metals production rate at a given mining region, ci (weight fraction) is the concentration of sulfur in fuel and ore, and sij is a dimensionless transfer matrix element between producer S and consumers of fuel and ores. PRODUCTION AND CONSUMPTION OF FUELS AND METALS Combustion of coal and oil products, along with the smelting of metals, produces the bulk of the anthropogenic sulfur and nitrogen emissions to the atmosphere over North America. The driving force for fuel combustion is the demand for energy by the different economic sectors. Energy Demand of the United States From the turn of the century to the 1970s, U.S. energy consumption has been characterized by a steady increase in total consumption and shifts from one fuel to another (Figure 2.3). From 1850 to about 1880 wood was the primary energy source. By 1900, and during the first quarter of this century, rising energy demand was matched

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oc9 0.8 O . 7 54 5G 45 40 35 30 25 20 15 10 c llilllllll~ llllllllllllllllllllll~ rrrlllllllllllIlllllllIlllllllllllllllllllllllllllTrTnlFrT~rTmTn1TTTnllllllllllllllllllllllllllllllllll _ a . 50 _ 45 40 , 'OIL 35 . ~ l ,' 'GRS 25 i! ''' _ 30 20 15 _ 10 _ 5 O ~ ,.~ l., ,lt~l.~ -I ~''-' - 1 ~ ,,,I.~ il,l.ll , l O 850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 t97Q 1980 1990 2000 TERR Illllll l Illllllll Illllllll Illllllll Illllllll lIIIIIIII Illllllll Illllllll Illlllill ~rlllllll Ir~l I I I I ! ,~SL]l~-'ll""""l""l""l"""' W0CO ~ NRTURPL GRS O . O I I I 1 111111 , 1 1.~ ~ 1 111111111111 111111111 11 11, 1 111111 11.111 111 11 _ 850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 20co TERR _ 0~9 _ 0.8 n ~ . 4 0.1 . FIGURE 2.3 Trend for U.S. fossil fuel consumption since 1850. (a) Consumption by fuel type; (b) fraction of total energy by fuel type. Data for 1850 to 1880 from U.S. Bureau of the Census (1975); data from 1880 to 1932 from U.S. Geological Survey, Yearbooks (1880-1932); data from 1933 to 1980 from U.S. Bureau of Mines, Mineral Yearbooks (1933-1980).

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55 by the increasing use of coal. The depression years of the early 1930s are reflected in the sharp drop of coal consumption, which increased again during the war years in the early to mid-1940s. Coal consumption declined to another minimum in 1960, because the increasing energy demands were supplied by cleaner fuels, natural gas and petroleum. Accelerated oil and gas consumption began in the late 1930s and 1940s, such that by 1950 the energy supplied by oil exceeded that of coal and maintained its rise up to the early 1970s. The 1973 oil embargo is reflected as a small rinole. The second dip, in the late ,, _ 1970s and early 1980s, reflects another oil embargo and reduced industrial activity. The 1950s and 1960s were the years of strong increase in natural gas consumption, which by 1960 also surpassed coal as an energy source. Nuclear energy began to supply a detectable fraction of the total energy consumption in the United States only after 1970. Coal Reserves and Production In the United States, coal is mined in three regions: Appalachia, the Midwest (Interior), and the West. The coals in the regions differ in quality and concentration of impurities such as sulfur. The coal production data used in this chapter were obtained from Mineral Yearbooks (U.S. Bureau of Mines 1933-1980) and from Mineral Resources of the United States Yearbooks (U.S. Geological Survey 1880-1932). Figure 2.4(a) shows the time-dependent contributions of the three regions to the national production of coal. The output of the Appalachian districts spanning Pennsylvania to Alabama is shown on the lowest curve. The curve shows that Appalachian production has remained at about 300 million tons/yr since about 1920. The second shaded area in Figure 2.4(a) is the contribution of the Interior region, which includes western Kentucky, Indiana, Illinois, Missouri, and Texas. The third area, negligible until around 1970, represents the contribution from the West. These curves reveal that a major shift in the coal production occurred at around 1970, when the production of Western coal became significant. Remark- ably, within the span of a decade, low-sulfur Western coal captured a quarter of the United States coal market.

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56 The coal production within the Appalachian region has also shifted substantially since 1900, as depicted in Figure 2.4(b). From about 1910 to the early 1920s the Pennsylvania coal production was about 160 million tons/yr, which has dropped to about 80 million tons in the post-World War II period. West Virginia production peaked during World War II and declined in the late 1960s. East Kentucky, on the other hand, had low production rates up to about 1960, and now it exceeds that of Pennsylvania. Similar trends are shown in the production data for three districts in the Interior region: Illinois, Indiana, and western Kentucky (Figure 2.4(c)). The significance of these shifts to sulfur emissions is that each coal-producing district has its own range of sulfur content: a shift in the relative production rate results in a change of the average sulfur content and sulfur production. The coal-production data described above define the raw material production rate Pi shown in Figure 2.2. 900- soo - 700 ~ 600- 200- 100- a U.S. Total ~ ,`' West Get r ~ .... I nterio r ....... ,., ~ , ~ , ~ I ~ I ~ I I Tall I ~ I I ~ ~ I I ~ 1870 1890 1910 1930 1950 1970 1990 FIGURE 2.4 (a) Coal production in the three U.S. coal- producing regions: Appalachia, Interior, and West; (b) trends in Appalachian coal production; (c) trends in Interior coal production. Data from U.S. Geological Survey Yearbooks (1880-1932); U.S. Bureau of Mines, Mineral Yearbooks (1933-1980); Energy Information Administration, 1983.

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57 Sulfur Content The next parameter that will be examined is ci, the concentration of the contaminant sulfur, for each coal-producing regione Knowing the production rate P and concentration ci permits the calculation of the mass of contaminant, Mi = ciPi, that is mobilized by each producer. 180 - 170 - - 180- 150 - 140 - 130 - 120 - 110 - ~oo 90 ~o 70 ~0 50 40 30 20 10 b Pennsylvania ~ / . ~ ~ 1 1 ~ V f W. Virginia 0~ E. Kentucky o 1870 1890 1910 1930 1950 1970 ~ .... , ' ., .,, .,, , ., , , ,,, .,,, , .,, .,, .,, , , ' . 90 - 80 - 70 - Cr: 60 - z o z o J 50 - 40 - 30 - 20 - 10 - c ~ ~ I llinois ~h~^Q' .' I /-k ,~W !~ . =~ tucky __. .. ............ . . . . MA O ~ 1870 1890 1910 1930 1950 1970 FIGURE 2.4 (continued).

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58 o I J o~ ~\\\\\~ o ~o o ~ ~ ~ N ' A Z o tr C~ _ ~ ~n ~_ 0 10 0 a 0 0 ~ _ _ 0 (SUol Uo!ll!q) 3AU3S3H 1~00 ~n z ~\\\\\\~- O O O O O O O O D O O O O O O O O O O O 0 0 ~ 0 en ~ ~ c~ _ 0 0 ~ r~ ~ c7 ~ e7 c~ _ _ _ _ _ _ _ _ _ _ (suOl U!ll!q) 3AB3S3H 1~00 V Q . A~ o cn =, V ~- ~\\\~ , . . . . o o o o o o o o (SUO1 U!ll!q) 3AB3S3H 1~00 .L U) ~' ,,~,\\,\,\\\\~' o o o o o o o o o o o o o o o o o ~ ~ a ~ ~ N O ~ O t~ ~ ~ ~ ~ C. _ _ _ _ _ _ _ _ (suOl Uo!ll!q) 3AU3S38 1~00 o ~ O Y ~ a a~ A U. z 8 G a~ , (V) _ - o o V I ~ o == U) V 3 C' C, ~ o V s~ U1 U~ ~ t Q U] a s~ ~ O O ~ ,1 CQ ~ =: 3 a o ~ - O ln - t - Q _ ,' U] a o o U] o s E~

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82 with those in the 1930s and early 1900s but are substan- tially below those of the 1920s, 1940s, and 1960s. The emission trend for the eastern states south of the Ohio River (Region C) is given in Figure 2.24(d). The emissions were relatively low in the southeastern United States until about 1960, when a strong Increase occurred. This upward trend has persisted into 1980s. The sulfur emission trend for the industrialized Midwest (Region D), including Illinois, Indiana, Michigan, Missouri, and Ohio, is given in Figure 2.24(e). The emission trend in this region shows a doubling since the turn of the century with peaks in the 1920s, 1940s, and 1970s and depressions in the 1930s and 1950s. The sulfur emission trend for the upper Midwest (Region E)--Iowa, Minnesota, and Wisconsin--is given in Figure 2.24(f). The emissions in this region, currently less than 1 million tons/yr, have been consistently low over the last 100 years. A comparison of sulfur emission densities north and south of the Ohio River is given in Figure 2.25, expressed as emission per unit area (g sulfur m~ yr~l). Emissions north of the Ohio River (Regions A, B. D, and E) have increased about 33 percent since the 1920s. In contrast, emissions south of the Ohio River (Region C) show a threefold increase since the 1930s. Currently, the sulfur emission densities are comparable for the regions north and south of the Ohio River. REGIONAL TRENDS IN EMISSIONS OF NITROGEN OXIDES Nitrogen oxides constitute the second major source of acidifying compounds. The overwhelming fraction of nitrogen oxide emissions arises from the combustion of fossil fuels; emissions from metal-orocessinq plants are insignificant. two important _ Fuel consumption data constitute one of inputs needed for estimating nitrogen oxide emissions. The other is data for nitrogen oxide emission factors. For a given source of combustion, this factor is the quantity of nitrogen oxide emitted per unit of fuel consumed. Estimating historical emission trends of nitrogen oxides is difficult because most of the nitrogen oxide is formed by the fixation of atmospheric nitrogen at high temperatures of combustion rather than by oxidation of the nitrogen contained in the fuel. The nitrogen oxide emissions depend primarily on the combustion temperature

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83 5 ! - ~5 Cow ~ 3~ 1 Ij\~ North Elf South ~ \r~ car or l r1~ ~''""''""''''1"'''''''''''''''''1'''''''''''''''''''i'''""''''"''''''1'''''''''''''''''' 1880 1900 1920 1940 YEAR 1 96t3 ~ 980 2000 FIGURE 2.25 Sulfur emission densities for regions north (Regions A, B. D, E) and south (Region C) of the Ohio River. and to a lesser degree on fuel properties. Since com- bustion processes in internal-combustion engines and boilers have undoubtedly changed since the turn of the century, it is likely that nitrogen oxide emission factors also have changed historically. Because combustion parameters can vary randomly over a wide range, and because information on historical combustion processes is generally lacking, assumptions concerning changes in emission factors over time constitute the major source of uncertainty in developing trends in nitrogen oxide emissions. The emission factors for 1970 to 1980 used in this chapter were derived from extensive inventories that list nitrogen oxide emission factors according to source type of combustion (U.S. Environmental Protection Agency 1977, 1978). The numerous emission factors listed in these compilations were aggregated into four weighted-average emission factors by fuel type: coal, gasoline, natural gas, and other petroleum products. The emission factors

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84 10 9 0 0 co of o Cat 7 LL rL 5 LL o l 4 Or ' o / / / / / Coal (tons NOX/l 000 ton) Gasoline (tons NOX/1 000 barrels) .... . _~ 3 Natural Gas (tons NO/100 rnill~on ft ) Other Petroleum (tons NOX/1000 barrels) 1880 1900 1920 1940 YEAR 1 960 1 980 2000 FIGURE 2.26 Trends in emission factors of nitrogen oxide by fuel type. Emission factors from the period of 1970 to 1980 were derived from data given from the U.S. Environmental Protection Agency (1977, 1978). For the period from 1880 to 1970, trends of historical emission factors were assumed to be linear, with slopes varying by fuel type. before 1970 were estimated to reflect the fact that the average combustion temperature, and hence the production of nitrogen oxide per unit of fuel consumed, was lower, especially for coal combustion, over the past 100 years (Figure 2.26). A simple linear trend was assumed for all emission factors. For coal combustion the emission factor was assumed to increase fivefold from 1880 to 1970. For combustion of gasoline and natural gas the emission factors were assumed to increase by 50 and 100 percent, respectively, during the same period. The emission factor for other petroleum products was assumed to be constant over time. Based on these estimates of emission factors and data on fuel consumption, regional emission trends were calculated (Figure 2.27). The shaded areas represent a range of uncertainty of +30 percent, reflecting the large uncertainties inherently associated with the

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85 20 r a > 18 ~x 1 6 z 14 z 12 O 10 O 8 6 4 o 1 9 8 x 0 7 ~ 6 0 5 z 4 o 3 J 2 1 o Eastern United States If - _~ C REGION C r\,( ,_ ~ : ,~ :::1 f ~ ~ :~ :~W 9 8 v 1 880 1 900 1 920 1 940 1 960 1 980 2000 YEAR OR 8 7 6 5 4 _ b REGION B 3 ,_ 2 _ ~~- ~~: NI~ ~ 1 _ ~ O ~1 1 REGION D o f NOx emission density North-South / r 1~ North of , <~ A/ Ohio River i / South of ~V" ~ Ohio River O = 1 1 1 880 1 900 1 920 1 940 1 960 1 980 2000 YEAR FIGURE 2.27 (a) Trends in emissions of nitrogen oxides in the eastern United States (the aggregate of Regions B. C, D, and E); (b) Region B; (c) Region C; (d) Region D; (e) Region E; (f) trends in emission densities of regions north (Regions B. D, and E) and south (Region C) of the Ohio River. assumptions made in these calculations. For the eastern United States (the aggregate of Regions B. C, D, and E; Figure 2.27(a)), the estimates indicate a strong monotonic increase since the late 1800s. Evidently, there has been no significant change since the mid-1970s. The nitrogen oxide emission estimates for Region B are given in Figure 2.27(b). A steady increase is evident since the turn of the century, leading to a peak in the late 1970s. The emission trend for states south of the Ohio River (Region C; Figure 2.27(c)) shows a roughly

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86 exponential increase since the turn of the century. The nitrogen oxide emission trend for the industrialized Midwestern states (Illinois, Indiana, Michigan, Missouri, and Ohio (Region D)) is shown in Figure 2.27(d). This trend resembles that of the northeastern states, showing a roughly linear increase since the 1920s. The upper Midwestern states (Iowa, Minnesota, and Wisconsin (Region E)) show a steady upward trend (Figure 2.27(e)). However, the tonnage of nitrogen oxide emissions is substantially less than those for the northeastern, southeastern, and other Midwestern states. A comparison of trends in nitrogen oxide emission densities north (Regions B. D, and E) and south (Region C) of the Ohio River is given Figure 2.27(f). The northern states show a roughly linear increase since the 1920s, while the growth was roughly exponential in the Southeast. Currently, the emission densities in the two regions are almost equivalent. COMPARISONS WITH OTHER TREND ESTIMATES Sulfur Dioxide The methodology presented in this chapter for estimating sulfur emission trends is for the most part similar to other approaches found in the literature. Emissions estimates are derived from information on the consumption of fossil fuels and the smelting of metals. The methodology differs from other reports by the way in which sulfur content of coal is estimated. The method described here uses mining data to determine the tonnage and distribution of the sulfur content in the coal at the mining site and information on the transport of the coal to the consumer to determine the emission source. From such an analysis it is possible to specify the uncertainty in sulfur emissions based on the sulfur distribution function of the mined coal. Recently, an extensive compilation of emissions of sulfur dioxide and nitrogen oxides was developed by Gschwandtner et al. (1985). They report yearly state-by-state emissions estimates in the United States from 1900 to 1980. The difference between their analysis and the one presented here is in the method for calculating the sulfur content of coal in each state and estimating its uncertainty as a function of time.

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87 A direct comparison of the results of the two estimates is shown in Figure 2.28. The shaded areas represent the estimated range of uncertainty in our analysis, and the diamonds represent the results of Gschwandtner et al. As shown in Figure 2.28(a) for the eastern United States (Regions B. C, D, and E), the estimates agree qualita- tively over much of the time period since 1900. Both estimates show peaks in the 1920s and in the early to mid-1940s. Both show steeply rising emissions in the 1960s and dips in the 1930s and 1950s. However, the estimates differ in some respects. Until about 1970 the estimate of Gschwandtner et al. for the eastern United States is consistently higher than our estimate. Furthermore, beginning around 1970 the trends appear to diverge. The estimate of Gschwandtner et al. shows a decrease in emissions in the eastern United States that continues through the 1970s. Our estimate suggests either no change or a possible increase, although the difference between the two estimates lies within the range of estimated uncertainty (see the shaded area, Figure 2.28(a)). A comparison of the emission trends is shown for three states in Figures 2.28(b)-2.28(d) to illustrate in more detail the extent of the differences in the two data sets. For Illinois, our estimate is substantially below that of Gschwandtner et al., except for the 1970s; the trend estimates for the state of Georgia are almost identical; for New York, the two estimates overlap since the 1930s but deviate before that time. These differences undoubtedly arise from the different assumptions employed in deriving the estimates. Nitrogen Oxides Gschwandtner et al. (1985) have also developed compr hensive estimates of emissions of nitrogen oxides. A comparison of our estimates with theirs is shown in Figure 2.29. Our analysis attempts to account for changes in emission factors that may have occurred over the past 100 years because of changes in average temperatures of combustion; the estimates of Gschwandtner et al. did not attempt such a correction. Nevertheless, as shown in the figure, after about 1930 the two estimates fall well within the range of estimated uncertainty, except for the lower estimates of Gschwandtner et al. for Region B in the 1970s.

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88 a) Q ~ 3 ~ s s a) 'a> _ . c~ ~ o8~ o on a ~= <~= 3~- ~ ~ ~~= ~ X ~ ~ ~ U] _ _ _ _ o o o o o o o o o o o o ~~ . __ . U] a)-- ~ ~ a) ~ ~ ~ ~ A. - _ _ ~ O~ ~~N ~ $~w x o :, s ~ 3 JJ A, o ~ 0 to ~ ~ o O O 0 0 3 so HA/S SNOT NOlilIW BA/S SNOT ONUSnOH1 ~ ~ ~ ~ ~ a; ~ a' (U ~ Q. V ITS ~ {d H = At) =.~1 ~ ~ U. en ~

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89 20 18 16 14 12 10 6 4 o x o he o of o J CC 9 ~ 8 O 7 to 6 O 5 an 4 oJ 3 A 2 1 O 1880 1900 1920 1940 1960 1980 2000 Eastern United States l ~ r! ~ I/' 1 ,' 1 1 1 1 REGION C Vent ~~ Jf -1~ 1 YEAR 9 8 7 6 5 4 1 o O: 9 8 O 7 can 6 O 5 o 3 A 2 1 b REGION B _ ~ d REGION D LO o 1880 1900 1 920 1940 1960 1980 2000 YEAR FIGURE 2.29 Comparison of estimates in nitrogen oxide emission trends reported in this chapter with the estimates of Gschwandtner et al. (1985) (dark lines) for (a) the eastern United States (Regions B. C, D, and E); (b) Region B; (c) Region C; (d) Region D. SUMMARY Sulfur emission trends for the eastern half of the United States and southeastern Canada are reconstructed for the past 100 years (1880-1980). The approach adopted uses a sulfur-flow accounting scheme from production in mines through distribution over land to emission sources. The average sulfur content of coal consumed in each state is estimated in this manner. The state-by-state sulfur emissions are calculated as the product of coal consumed and the average sulfur content. Coal combustion accounts for most of the current sulfur emissions, which are estimated to be between 11 and 15 million tons of sulfur/yr. Sulfur mobilization by oil products increased from the 1940s until about the 1960s, when it leveled off at 3 to 4 million tons of sulfur/yr. Since 1978 there has been a significant reduction of oil sulfur emissions that is attributed to reduced oil imports and increased sulfur recycling at refineries.

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go The sulfur mobilization from copper and zinc smelting fluctuated from 0.5 to 1.5 million tons of sulfur/yr since the turn of the century. These emissions have dropped significantly since 1970 as a consequence of reduced sulfur production and increased sulfur recovery. In eastern North America, sulfur dioxide emissions showed the most rapid rate of increase in the period from approximately 1880 to 1910. Since then sulfur emissions have increased overall by about SO percent, but the increase has not been monotonic. Rather, the emissions have fluctuated between peaks and dips as a result of social, political, and economic factors. The 1920s, early 1940s, and late 1960s were "peak n periods, whereas the 1930s and the 1950s were periods of declining . emlss cons . Eastern North America was divided into five regions (see Figure 2.23). Until about 1970, emissions in each of these regions, although differing in magnitude, exhibited for the most Part similar patterns of peaks and dips described above for the entire area. After about 1970 strong regional differences in trends of sulfur dioxide emissions emerged. The most distinctive differ- ences were between the regions north and south of the Ohio River. Southeastern Canada (Region A) and the northeastern United States (Region B) show distinct downward trends. The southeastern United States (Region C) exhibits a steeply increasing trend. The midwestern United States (Region D) shows little change or perhaps a slightly increasing trend in sulfur dioxide emissions, and emissions in the north central United States (Region E) have remained low. Nitrogen oxides are produced during combustion of fossil fuels and arise mainly through the fixation of atmospheric nitrogen at high temperatures. Thus, nitrogen oxide emissions depend primarily on the combustion process rather than on fuel properties. Hence, the nitrogen oxide emission trends have substantially higher uncertainties than those for sulfur dioxide. The regional nitrogen oxide emission trends indicate that in the states both north and south of the Ohio River, emissions have increased monotonically since the turn of the century. The northern states (Regions B. D, and E) show a roughly linear increase since that time, while the southern states (Region C) exhibit an exponential increase. A comparison is made of trends in emissions of sulfur dioxide obtained in our analysis with those from a recent comprehensive report. Similarities and differences are ~ . .. . . . . .

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91 examined. A similar comparison is presented for nitrogen . . Oxide emissions. ACKNOWLEDGMENTS The development of the SOX and NOX emission inventories was supported by the Washington University School of Engineering and Applied Sciences and by the National Academy of Sciences. Janja Djukic Husar was instrumental in the acquisition of the data sets. Her help is greatly appreciated. REFERENCES Beaton, J. D., D. W. Bixby, S. L. Tisdale, and J. S. Platou. 1974. Fertilizer sulfur, status and potential U.S. Technical Bulletin No. 21, The Sulfur Institute, Washington, D.C., and London. Carrales M., Jr., and R. W. Martin. 1975. Sulfur content of crude oils. Information Circular 8676. U.S. Bureau of Mines, Department of Interior, Washington, D.C. Energy Information Administration. 1977-1982. U.S. Department of Energy, Washington, D.C. Quarterly Reports, June 1977 to December 1982. Energy Information Administration. 1981. Content in coal shipments, 1978. U.S. Department of Energy, Washington, D.C. DOE/EIA-0263(78). Energy Information Administration. 1983. Coal distribution, January-December, 1982. U.S. Department of Energy, Washington, D.C. DOE/EIA-0125(82/4Q). Gschwandtner, Ge ~ K. C. Gschwandtner, and K. Eldridge. . 1985. Historic emissions of sulfur and nitrogen oxides in the United States from 1900 to 1980. Volume I. Results. U. S. Environmental Protection Agency. EPA-600/7-85-009a. Hamilton, P. A., D. H. White, Jr., and T. K. Matson. 1975. The reserve base of U.S. coals by sulfur content. 2. The western states. Information Circular 8693, U.S. Bureau of Mines, Department of the Interior, Washington, D.C. Husar, R. B., J. M. Holloway, D. E. Patterson, and W. E. Wilson. 1981. Spatial and temporal pattern of eastern U.S. haziness: a summary. Atmos. Environ. 15:1919-1928. Lesher, C. E. 1917. Coal in 1917. U. S. Geological Survey. Part B. Mineral Resources of the United States. Part II, pp. 1908-1956.

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92 Thompson, D. R., and H. F. York. 1975. The reserve base of U.S. coals by sulfur content. 1. The eastern states. Information Circular 8680, U.S. Bureau of Mines, Department of the Interior, Washington, D.C. Tryon, F. G. and H. O. Rogers. 1927. Consumption of bituminous coal. U.S. Geological Survey, Mineral Resources of the United States. Part II, pp. 1908-1956. United States-Canada Memorandum of Intent on Transboundary Air Pollution. Atmospheric Sciences and Analysis Work Group 2. 1982. Report No. 2F-M. U.S. Bureau of the Census. 1889. Census of Manufacturing, Washington, D.C. U.S. Bureau of the Census. 1919. Census of Manufacturing, Washington, D.C. U.S. Bureau of the Census. 1975. Historical statistics of the United States, colonial times to 1970. U.S. Department of the Interior, Washington, D.C., pp. 587-588. U.S. Bureau of Mines. Minerals Yearbook. U.S. Department of the Interior, Washington, D.C. Annual Publications, 1933-1980. U.S. Bureau of Mines. Minerals Yearbook. U.S. Department of the Interior, Washington, D.C. Annual Publications, 1944-1980. U.S. Bureau of Mines. Distribution of bituminous coal and lignite shipments. U.S. Department of the Interior, Washington, D.C. Quarterly Publications, 1957-1977. U.S. Bureau of Mines. 1971. Control of sulfur oxides, emissions, in copper, lead, and zinc smelting (with list of references). Information Circular 8527, U.S. Department of the Interior, Washington, D.C. U.S. Bureau of Statistics. 1917. Statistics of railways in the United States. Interstate CoIIunerce Commission, Washington, D.C. U.S. Environmental Protection Agency. 1977. Compilation of Air Pollutant Emission Factors. AP-42, 3rd ed . (NTIS PB-275525), Supplements 1-7 and 8-14. Springfield, Va.: National Technical Information Service. U e Se Environmental Protection Agency. 1978. Mobile source emission factors. EPA-400/9-78-005 (NTIS PB295672/A17), Washington, D.C. U.S. Geological Survey. 1880-1932. Mineral Resources of the United States. Yearbooks, U.S. Department of the Interior, Washington, D.C.