Library Index » Science Encyclopedia » Acid Rain - What Is Acid Rain?, Factors Affecting Acid Deposition, Sources Of Sulfate And Nitrate Inthe Atmosphere

Acid Rain - Effects Of Acid Deposition Onliving Organisms

tier gas manufacturing categories

An ecosystem is a particular environment and the biological organisms that live there. Ecosystems can be global or tiny. The plants and animals living within an ecosystem are interdependent. For example, frogs eat water insects. If the insects disappear because of acid deposition effects, the frogs may not thrive because part of their food supply has disappeared. Because of the many and varied interconnections among the plants, animals, and microorganisms living in an ecosystem, changes in pH may change the ecosystem's biodiversity or overall health.

The duration of the effects of acid rain on living organisms can vary from a few hours to many years. For example, soils that are depleted of essential nutrients may take decades or even centuries to recover. Once acid rain is reduced to normal levels, the slow process of nutrient buildup in the soil is dependent on the gradual succession over time of plant life. Plants that are tolerant of depleted soils will restore nutrients over time as they grow, die, and decompose, putting essential nutrients back in the soils. In the natural order, these plants will be followed by other plants that require more nutrient-rich soil, and as they grow, die, and decompose they will return more nutrients to the soil. Animals attracted to each stage of plant succession will also add their wastes to the process, bringing in additional nutrients. This process will continue through time until a healthy, balanced population appropriate to the ecosystem is restored.

Aquatic Systems

The effects of acid rain on aquatic systems are varied and many. They include great harm or death to fish, diminished fish populations, loss of a species in a particular water body, and reduction in biodiversity. As acid rain moves through soils in a watershed, aluminum is released from soils into the lakes and streams. As the pH lowers in a water body, the aluminum level climbs. Both low pH and elevated aluminum levels are toxic to fish (aluminum burns the gills of fish and accumulates in organs, causing organ damage). They can also cause chronic stress, which does not immediately kill an individual fish, but impairs its ability to take in the oxygen, salts, and nutrients needed to stay alive.

Freshwater fish need to maintain their osmoregulation to stay alive. Osmoregulation is the process of maintaining the delicate balance of salts and minerals in their tissues. Acid molecules stimulate the formation of mucus in the gills, which interferes with their ability to absorb oxygen. If mucus buildup continues, the fish suffocate. In addition, a low pH disrupts the balance of salts in fish and other aquatic life, interfering with reproduction and maintenance of bones or exoskeleton.

TABLE 9.1
Sulfur dioxide emission trends by source category, selected years 1970–2002

Source category 1970 1975 1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002
  Total all sources 31,218 28,043 25,925 23,307 23,076 18,619 18,385 18,840 18,944 17,545 16,347 15,932 15,353
Fuel combustion total (tier 0–01) 23,456 22,661 21,391 20,021 20,290 16,230 16,252 16,649 16,743 15,338 14,163 13,735 13,168
Fuel combustion electric utility (tier 1–01) 17,398 18,268 17,469 16,272 15,909 12,080 12,767 13,195 13,416 12,583 11,396 10,850 10,293
Coal 15,799 16,756 16,073 15,630 15,220 11,603 12,241 12,614 12,469 11,746 10,623 10,004 9,732
  Bituminous 9,574 10,161 NA 14,029 13,371 8,609 9,033 9,516 9,356 9,313 8,434 7,866 7,317
  Subbituminous 4,716 5,005 NA 1,292 1,415 2,345 2,632 2,490 2,486 1,669 1,551 1,531 1,949
  Anthracite & lignite 1,509 1,590 NA 309 434 649 576 608 627 763 638 607 465
Oil 1,598 1,511 1,395 612 639 413 461 514 762 594 482 529 343
  Residual 1,578 1,462 NA 604 629 408 454 509 756 559 446 492 330
  Distillate 20 49 NA 8 10 5 6 5 6 35 37 37 13
Gas 1 1 1 1 1 9 7 6 6 177 232 262 8
Other NA NA NA NA NA NA 5 5 122 54 45 42 197
Internal combustion NA NA NA 30 49 55 53 56 57 12 14 13 13
Fuel combustion industrial (tier 1–02) 4,568 3,310 2,951 3,169 3,550 3,357 2,849 2,805 2,740 2,135 2,139 2,243 2,299
Coal 3,129 1,870 1,527 1,818 1,914 1,728 1,311 1,306 1,273 1,054 1,024 1,096 1,143
  Bituminous 2,171 1,297 1,058 1,347 1,050 1,003 875 876 857 646 628 661 634
  Subbituminous 669 399 326 28 50 81 63 63 61 46 47 60 90
  Anthracite & lignite 289 174 144 90 67 68 61 60 57 60 58 64 117
  Other NA NA NA 353 746 576 312 306 298 301 291 311 302
Oil 1,229 1,139 1,065 862 927 912 805 764 738 526 554 579 534
  Residual 956 825 851 671 687 701 623 578 559 366 395 403 368
  Distillate 98 144 85 111 198 191 158 161 156 142 141 157 148
  Other 175 171 129 80 42 20 23 25 23 18 19 18 18
Gas 140 263 299 397 543 548 574 582 578 407 415 414 472
Other 70 38 60 86 158 147 139 133 132 132 129 137 139
Internal combustion NA NA NA 7 9 23 20 19 19 16 17 18 10
Fuel combustion other (tier 1–03) 1,490 1,082 971 579 831 793 636 648 586 620 628 642 575
Commercial/institutional coal 109 147 110 158 212 200 178 184 196 146 148 152 148
Commercial/institutional oil 883 638 637 239 425 397 307 314 250 256 261 267 258
Commercial/institutional gas 1 1 1 2 7 8 10 10 10 12 12 15 14
Miscellaneous fuel combustion (except residential) NA NA NA 1 6 5 5 5 5 7 7 7 5
Residential wood 6 7 13 13 7 7 7 5 5 6 5 5 4
Residential other 492 290 211 167 175 176 131 130 121 195 196 197 146
  Distillate oil 212 196 157 128 137 144 108 106 97 125 125 126 132
  Bituminous/subbituminous coal 260 76 43 29 30 24 17 18 18 46 46 46 11
  Other 20 18 11 10 9 8 6 6 6 25 25 25 3
Industrial processes total (tier 0–02) 7,101 4,728 3,807 2,467 1,900 1,638 1,403 1,459 1,464 1,364 1,418 1,464 1,399
Chemical & allied product manufacturing (tier 1–04) 591 367 280 456 297 286 255 259 261 325 338 342 328
Organic chemical manufacturing NA NA NA 16 10 8 4 4 4 5 6 6 7
Inorganic chemical manufacturing 591 358 271 354 214 199 173 176 178 161 165 169 167
  Sulfur compounds 591 358 271 346 211 195 171 174 176 141 144 148 151
  Other NA NA NA 8 2 4 2 2 2 20 21 21 16
Polymer & resin manufacturing NA NA NA 7 1 0 1 1 1 1 1 1 1
Agricultural chemical manufacturing NA NA NA 4 5 5 1 1 1 45 51 46 46
Paint, varnish, lacquer, enamel manufacturing NA NA NA NA NA 0 0 0 0 0 0 0 0
Pharmaceutical manufacturing NA NA NA 0 0 0 0 0 0 0 0 0 0
Other chemical manufacturing NA 8 10 76 67 74 76 76 77 112 115 119 106

TABLE 9.1
Sulfur dioxide emission trends by source category, selected years 1970–2002 [CONTINUED]

Source category 1970 1975 1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002
Metals processing (tier 1–05) 4,775 2,849 1,842 1,042 726 530 389 407 405 304 313 332 271
Non-ferrous metals processing 4,060 2,165 1,279 853 517 361 266 276 274 193 199 211 155
  Copper 3,507 1,946 1,080 655 323 177 93 99 98 48 50 53 33
  Lead 77 34 34 121 129 126 111 113 114 79 81 87 63
  Zinc 80 72 95 62 60 53 57 59 57 57 58 61 51
  Other 396 113 71 14 4 6 5 5 5 9 9 10 8
Ferrous metals processing 715 684 562 172 186 151 106 114 114 93 96 102 99
Metals processing NEC NA NA NA 18 22 18 17 17 17 18 18 18 17
Petroleum & related industries (tier 1–06) 881 727 734 505 430 369 335 344 342 312 316 319 348
Oil & gas production 111 173 157 204 122 89 90 90 90 98 100 102 102
  Natural gas 111 173 157 202 120 88 89 90 89 95 97 99 96
  Other NA NA NA 2 2 1 1 1 1 3 3 3 6
Petroleum refineries & related industries 770 554 577 300 304 271 238 246 245 205 207 208 237
  Fluid catalytic cracking units 480 318 330 212 183 188 157 163 162 137 137 138 148
  Other 290 236 247 88 121 83 81 83 83 68 70 70 89
Asphalt manufacturing NA NA NA 1 4 9 8 8 8 9 9 9 9
Other industrial processes (tier 1–07) 846 740 918 425 399 403 386 409 415 382 410 429 416
Agriculture, food, & kindred products NA NA NA 3 3 3 4 4 4 8 8 8 9
Textiles, leather, & apparel products NA NA NA 0 0 0 0 0 0 0 0 0 0
Wood, pulp & paper, & publishing products 169 168 223 131 116 114 101 105 107 99 103 105 94
Rubber & miscellaneous plastic products NA NA NA 1 0 0 1 1 1 1 1 2 0
Mineral products 677 571 694 286 275 282 266 285 288 250 273 289 300
  Cement manufacturing 618 511 630 192 181 171 167 181 183 153 162 173 177
  Other 59 60 64 95 94 111 99 103 105 97 111 116 123
Machinery products NA NA NA 0 0 1 0 0 0 0 0 0 0
Electronic equipment NA NA NA 0 0 0 0 0 0 0 0 0 0
Transportation equipment NA NA NA NA NA 0 0 0 0 0 0 0 0
Miscellaneous industrial processes NA NA NA 3 5 4 13 13 14 23 23 24 14
Solvent utilization (tier 1–08) NA NA NA 1 0 1 1 1 1 1 1 1 2
Degreasing NA NA NA 0 0 0 0 0 0 0 0 0 1
Graphic arts NA NA NA 0 0 0 0 0 0 0 0 0 0
Dry cleaning NA NA NA NA NA 0 0 0 0 0 0 0 0
Surface coating NA NA NA 1 0 0 0 0 0 0 1 1 0
Other industrial NA NA NA 0 0 0 1 1 1 1 1 1 0
Storage & transport (tier 1–09) NA NA NA 4 7 2 5 5 5 6 6 7 5
Bulk terminals & plants NA NA NA NA 0 0 1 1 1 1 1 1 0
Petroleum & petroleum product storage NA NA NA 0 5 0 0 0 0 1 1 1 1
Petroleum & petroleum product transport NA NA NA 1 0 0 1 1 2 2 2 2 0
Service stations: stage II NA NA NA NA NA 0 0 0 0 0 0 0 0
Organic chemical storage NA NA NA 1 0 0 0 0 0 0 0 0 2
Organic chemical transport NA NA NA NA 0 0 0 0 0 0 0 0 0
Inorganic chemical storage NA NA NA 0 0 0 0 0 0 0 0 0 0
Inorganic chemical transport NA NA NA 0 0 0 0 0 0 0 0 0 0
Bulk materials storage storage NA NA NA 1 1 1 2 2 2 2 2 2 2

TABLE 9.1
Sulfur dioxide emission trends by source category, selected years 1970–2002 [CONTINUED]
SOURCE: Adapted from "National Emission Trends: Sulfur Dioxide Emissions (Thousand Short Tons)," in 1970–2002 Average Annual Emissions, All Criteria Pollutants, U.S. Environmental Protection Agency, January 2005, http://www.epa.gov/ttn/chief/trends/ (accessed April 14, 2005)

Source category 1970 1975 1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002
Waste disposal & recycling (tier 1–10) 8 46 33 34 42 47 32 33 34 34 34 35 28
Incineration 4 29 21 25 32 35 27 27 28 27 26 27 20
  Industrial NA NA NA 10 5 8 6 6 7 7 7 7 3
  Other 4 29 21 15 26 27 20 21 21 20 20 20 18
Open burning 4 17 12 9 11 11 5 5 5 5 5 5 4
  Industrial NA NA NA 0 0 0 0 0 0 0 0 0 0
  Land clearing debris NA NA NA NA NA NA NA NA NA NA NA NA NA
  Other 4 17 12 8 10 11 5 5 5 5 5 5 4
POTW NA NA NA NA 0 0 0 0 0 0 0 0 0
Industrial waste water NA NA NA NA 0 0 0 0 0 0 0 0 1
TSDF NA NA NA NA 0 0 0 0 0 0 0 0 0
Landfills NA NA NA 0 0 0 1 1 1 1 1 2 2
  Industrial NA NA NA 0 0 0 0 0 0 0 0 0 0
  Other NA NA NA 0 0 0 0 0 0 1 1 1 1
Other NA NA NA 0 0 0 0 0 0 0 0 1 1
Transportation total (tier 0–03) 551 635 717 808 874 742 715 725 732 776 697 688 696
Highway vehicles (tier 1–11) 273 334 394 455 503 335 302 304 300 300 260 248 275
Light-duty gas vehicles & motorcycles 129 125 120 116 111 112 112 105 106 110 103 96 93
  Light-duty gas vehicles 128 124 120 116 111 111 112 105 106 109 102 96 93
  Motorcycles 1 1 1 1 1 0 0 0 0 0 0 0 0
Light-duty gas trucks 24 30 36 42 52 69 72 70 70 72 70 70 65
  Light-duty gas trucks 1 13 17 21 25 31 45 48 47 47 48 47 48 45
  Light-duty gas trucks 2 11 13 15 17 21 23 24 24 24 24 23 22 20
Heavy-duty gas vehicles 17 17 16 16 16 17 17 15 15 15 14 12 12
Diesel 103 162 221 280 324 138 101 113 109 104 73 70 105
Off-highway (tier 1–12) 278 301 323 354 371 406 413 422 432 475 437 440 420
Non-road gasoline 6 7 8 9 9 11 11 10 10 11 11 11 8
Non-road diesel 31 55 79 105 131 168 176 181 187 222 198 204 198
Aircraft 6 6 7 7 7 7 7 8 8 8 9 8 8
Marine vessels 160 162 156 173 167 160 159 165 170 176 163 161 160
Railroads 75 71 73 59 56 59 60 58 56 58 56 57 47
Other 0 0 0 0 0 0 0 0 0 0 0 0 0
Miscellaneous (tier 0–04) 110 20 11 11 12 10 15 7 6 67 70 44 91
Miscellaneous (tier 1–13) 110 20 11 11 12 10 15 7 6 67 70 44 91
Agriculture & forestry NA NA NA NA NA NA NA NA NA 0 NA NA NA
Other combustion 10 20 11 11 12 10 15 6 6 67 70 44 91
Fugitive dust NA NA NA NA 0 0 0 0 0 0 0 0 0
Other NA NA NA NA NA NA 0 0 0 0 0 0 0
Note:
Subtotals are provided at selected tier levels.
Total all sources = sum of the 4 tier 0 categories which are bolded and separated by blank lines.
The tier 0 categories are further divided into the 13 tier 1 categories which are bolded with no line separation and are under their respective tier 0 categories.
The tier 1 categories are further divided into tier 2 categories which are not bolded and are under their respective tier 1 categories.
The tier 2 categories are further divided into tier 3 categories which are italicized and under their respective tier 2 categories.

TABLE 9.2
Nitrogen oxide emission trends, by source category, selected years 1970–2002

Source category 1970 1975 1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002
  Total all sources 26,883 26,377 27,079 25,757 25,529 24,956 24,787 24,705 24,348 22,845 22,598 21,547 21,102
Fuel combustion total (tier 0–01) 10,061 10,486 11,320 10,048 10,894 10,827 10,513 10,554 10,383 9,198 8,819 8,454 8,294
Fuel combustion electric utility (tier 1–01) 4,900 5,694 7,024 6,127 6,663 6,384 6,164 6,276 6,232 5,721 5,330 4,917 4,699
Coal 3,888 4,828 6,123 5,240 5,642 5,579 5,601 5,644 5,436 4,909 4,563 4,208 4,094
  Bituminous 2,112 2,590 3,439 4,378 4,532 3,830 3,802 3,828 3,635 3,512 3,218 2,937 2,632
  Subbituminous 1,041 1,276 1,694 668 857 1,475 1,570 1,591 1,575 1,137 1,087 1,035 1,296
  Anthracite & lignite 344 414 542 194 254 273 229 225 226 256 255 233 163
  Other 391 548 447 NA NA NA NA NA NA 3 3 3 3
Oil 1,012 866 901 193 221 96 118 145 223 201 166 170 130
  Residual 40 101 39 178 207 94 116 142 220 185 152 156 121
  Distillate 972 765 862 15 14 2 2 2 3 16 14 13 8
  Other NA NA NA NA 0 NA NA NA NA NA NA NA NA
Gas NA NA NA 646 565 562 285 319 381 434 422 359 270
  Natural NA NA NA 646 565 562 273 306 363 426 414 352 264
  Process NA NA NA NA NA NA 12 13 19 7 8 7 6
Other NA NA NA NA NA NA 7 8 28 41 40 41 54
Internal combustion NA NA NA 48 235 148 153 161 164 137 140 139 152
Fuel combustion industrial (tier 1–02) 4,325 4,007 3,555 3,209 3,035 3,144 3,151 3,101 3,050 2,709 2,723 2,757 2,870
Coal 771 520 444 608 584 597 540 537 524 419 408 432 447
  Bituminous 532 359 306 430 399 412 366 364 357 244 237 250 232
  Subbituminous 164 111 94 14 18 46 46 46 44 35 34 36 62
  Anthracite & lignite 75 51 44 33 26 26 19 19 18 22 21 23 35
  Other NA NA NA 131 141 112 109 108 105 118 114 122 119
Oil 332 354 286 309 265 247 224 216 209 192 201 214 175
  Residual 228 186 179 191 180 156 140 130 126 104 112 115 86
  Distillate 104 112 63 89 71 73 73 74 72 81 81 91 80
  Other NA 56 44 29 14 17 11 12 11 8 8 8 8
Gas 3,060 2,983 2,619 1,520 1,181 1,324 1,204 1,189 1,175 1,033 1,048 1,044 1,058
  Natural 3,053 2,837 2,469 1,282 967 1,102 992 970 958 835 845 848 837
  Process 8 5 5 227 211 220 210 216 215 197 202 195 219
  Other NA 140 145 11 3 2 3 3 3 1 1 1 3
Other 162 149 205 118 131 123 119 113 114 142 140 148 145
  Wood/bark waste 102 108 138 89 89 84 83 79 80 100 99 106 100
  Liquid waste NA NA NA 12 8 11 9 8 8 7 7 7 9
  Other 60 41 67 17 34 28 27 26 25 36 35 36 36
Internal combustion NA NA NA 655 873 854 1,064 1,045 1,028 923 926 918 1,045
Fuel combustion other (tier 1–03) 836 785 741 712 1,196 1,298 1,197 1,177 1,101 768 766 779 725
Commercial/institutional coal 23 33 25 37 40 38 33 35 37 36 37 38 38
Commercial/institutional oil 210 176 155 106 97 103 95 97 80 81 83 85 75
Commercial/institutional gas 120 125 131 145 200 231 247 252 243 244 249 257 229
Miscellaneous fuel combustion (except residential) NA NA NA 11 34 30 22 23 23 35 36 37 24
Residential wood 44 39 74 88 46 49 30 30 30 45 33 33 28
Residential other 439 412 356 326 780 847 770 740 688 326 328 330 332
  Distillate oil 118 113 85 75 209 210 193 188 172 53 53 53 56
  Natural gas 242 246 238 248 449 519 470 437 400 208 209 211 235
  Other 79 54 33 3 121 118 108 114 117 65 66 66 42

TABLE 9.2
Nitrogen oxide emission trends, by source category, selected years 1970–2002 [CONTINUED]

Source category 1970 1975 1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002
Industrial processes total (tier 0–02) 1,215 697 666 891 892 873 950 994 1,010 940 943 977 1,000
Chemical & allied product manufacturing (tier 1–04) 271 221 213 262 168 158 125 127 129 102 105 107 105
Organic chemical manufacturing 70 53 54 37 18 20 21 21 21 14 15 15 18
Inorganic chemical manufacturing 201 168 159 22 12 7 6 6 6 7 7 8 8
Polymer & resin manufacturing NA NA NA 22 6 4 3 3 3 2 2 3 3
Agricultural chemical manufacturing NA NA NA 143 80 74 50 51 52 48 49 49 48
Paint, varnish, lacquer, enamel manufacturing NA NA NA 0 0 0 0 0 0 0 0 0 0
Pharmaceutical manufacturing NA NA NA 0 0 0 0 0 0 0 0 0 0
Other chemical manufacturing NA NA NA 38 52 54 45 46 47 31 31 32 29
Metals processing (tier 1–05) 77 73 65 87 97 98 83 89 89 86 89 94 84
Non-ferrous metals processing NA NA NA 16 14 12 11 12 12 9 9 9 9
Ferrous metals processing 77 73 65 58 78 83 66 71 71 71 73 78 68
Metals processing NEC NA NA NA 13 6 4 7 7 6 7 7 7 7
Petroleum & related industries (tier 1–06) 240 63 72 124 153 110 139 143 143 120 122 124 149
Oil & gas production NA NA NA 69 104 58 86 88 88 66 67 69 68
Petroleum refineries & related industries 240 63 72 55 47 48 47 48 48 46 46 47 46
Asphalt manufacturing NA NA NA 1 3 5 7 7 7 8 9 9 35
Other industrial processes (tier 1–07) 187 182 205 327 378 399 433 460 467 451 479 501 487
Agriculture, food, & kindred products NA NA NA 5 3 6 5 5 5 8 8 4 8
Textiles, leather, & apparel products NA NA NA 0 0 0 1 1 1 0 0 0 0
Wood, pulp & paper, & publishing products 18 18 24 73 91 89 86 89 91 93 96 99 83
Rubber & miscellaneous plastic products NA NA NA 0 0 0 0 0 0 0 1 1 0
Mineral products 169 164 181 239 270 287 327 350 355 338 361 383 385
  Cement manufacturing 97 89 98 137 151 153 196 212 214 181 190 203 214
  Glass manufacturing 48 53 60 48 59 67 69 74 76 67 71 75 73
  Other 24 23 23 54 61 66 62 64 65 90 100 105 98
Machinery products NA NA NA 2 3 7 2 3 3 1 1 1 1
Electronic equipment NA NA NA NA 0 0 0 0 0 0 0 0 0
Transportation equipment NA NA NA 0 0 0 0 0 0 0 0 0 0
Miscellaneous industrial processes NA NA NA 8 10 10 12 12 12 11 11 12 9
Solvent utilization (tier 1–08) NA NA NA 2 1 3 2 3 3 4 4 4 8
Degreasing NA NA NA 0 0 0 0 0 0 0 0 0 3
Graphic arts NA NA NA 0 0 1 1 1 1 1 1 1 1
Dry cleaning NA NA NA NA 0 0 0 0 0 0 0 0 0
Surface coating NA NA NA 2 1 2 2 2 2 3 3 3 3
Other industrial NA NA NA 0 0 0 0 0 0 0 0 0 0
Nonindustrial NA NA NA NA 0 0 0 0 0 0 0 0 0
Solvent utilization NEC NA NA NA NA NA 0 0 0 0 0 0 0 0
Storage & transport (tier 1–09) NA NA NA 2 3 6 15 16 16 14 15 16 16
Bulk terminals & plants NA NA NA NA 0 1 2 2 2 2 2 2 0
Petroleum & petroleum product storage NA NA NA 1 2 0 7 8 8 1 1 1 1
Petroleum & petroleum product transport NA NA NA 0 0 0 0 0 0 0 0 0 0
Service stations: stage I NA NA NA NA NA NA 0 0 0 0 0 0 0
Service stations: stage II NA NA NA NA NA 0 0 0 0 0 0 0 0
Organic chemical storage NA NA NA 1 0 4 4 4 4 3 3 3 5
Organic chemical transport NA NA NA NA 0 0 0 0 0 0 0 0 0
Inorganic chemical storage NA NA NA 0 0 0 0 0 0 0 0 0 0
Bulk materials storage NA NA NA 0 0 1 2 2 2 8 9 9 9

TABLE 9.2
Nitrogen oxide emission trends, by source category, selected years 1970–2002 [CONTINUED]

Source category 1970 1975 1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002
Waste disposal & recycling (tier 1–10) 440 159 111 87 91 99 153 157 163 162 129 130 152
Incineration 110 56 37 27 49 53 51 53 54 54 56 57 51
Open burning 330 103 74 59 42 44 98 101 106 103 68 68 95
POTW NA NA NA NA 0 0 0 0 0 0 0 0 0
Industrial waste water NA NA NA NA 0 0 0 0 0 0 0 0 0
TSDF NA NA NA NA 0 0 0 0 0 0 0 0 0
Landfills NA NA NA 0 0 1 2 2 2 4 4 4 4
Other NA NA NA 0 0 1 1 1 1 0 0 0 1
Transportation total (tier 0–03) 15,277 15,029 14,845 14,508 13,373 12,989 12,912 12,970 12,776 12,456 12,560 11,932 11,452
Highway vehicles (tier 1–11) 12,624 12,061 11,493 10,932 9,592 8,876 8,733 8,792 8,619 8,371 8,394 7,774 7,365
Light-duty gas vehicles & motorcycles 8,542 7,587 6,632 5,681 4,262 3,049 2,806 2,522 2,387 2,430 2,312 2,181 2,166
  Light-duty gas vehicles 8,542 7,583 6,621 5,663 4,240 3,033 2,792 2,507 2,372 2,415 2,297 2,168 2,152
  Motorcycles 0 4 11 18 22 15 14 15 15 15 15 14 14
Light-duty gas trucks 1,540 1,559 1,578 1,598 1,504 1,461 1,452 1,459 1,453 1,450 1,436 1,469 1,401
  Light-duty gas trucks 1 868 915 962 1,009 962 997 1,004 973 960 1,014 999 1,036 974
  Light-duty gas trucks 2 672 644 616 589 542 464 448 486 493 436 437 434 427
Heavy-duty gas vehicles 723 674 624 575 567 516 506 447 417 481 453 421 404
Diesels ,833 2,241 2,659 3,078 3,259 3,850 3,968 4,365 4,362 4,010 4,192 3,702 3,395
  Heavy-duty diesel vehicles 1,764 2,175 2,585 2,997 3,194 3,816 3,940 4,021 4,077 3,986 4,178 3,687 3,378
  Light-duty diesel trucks 70 58 47 36 23 14 12 331 274 13 6 9 9
  Light-duty diesel vehicles 0 8 26 44 43 21 16 13 11 12 7 7 7
Off-highway (tier 1–12) 2,652 2,968 3,353 3,576 3,781 4,113 4,179 4,178 4,156 4,084 4,167 4,158 4,086
Non-road gasoline 90 102 108 114 120 141 145 163 176 204 192 190 211
  Recreational 4 8 8 7 7 8 9 10 10 11 10 10 11
  Construction 4 4 4 4 4 5 5 6 6 6 6 60 6
  Industrial 30 27 24 21 18 16 15 16 16 29 14 13 13
  Lawn & garden 19 25 31 36 42 55 57 68 76 73 86 86 93
  Farm 2 2 3 3 3 4 4 4 4 5 4 4 5
  Light commercial 2 5 8 11 14 20 21 26 30 32 35 35 39
  Logging 0 0 0 0 0 0 0 0 0 0 0 0 1
  Airport service 0 0 0 0 0 0 0 0 0 2 0 0 0
  Railway maintenance 0 0 0 0 0 0 0 0 0 0 0 0 0
  Recreational marine vessels 30 30 31 31 32 33 34 34 34 45 35 36 42
Non-road diesel 374 653 943 1,246 1,454 1,585 1,611 1,613 1,613 1,734 1,600 1,588 1,600
  Recreational 0 1 1 1 1 2 2 2 2 2 2 2 2
  Construction 167 312 456 600 702 764 776 774 772 858 762 754 764
  Industrial 35 67 99 131 136 139 140 139 138 126 133 132 132
  Lawn & garden 0 0 0 11 24 35 38 40 42 38 45 46 49
  Farm 112 209 307 404 478 523 532 533 533 576 530 525 521
  Light commercial 0 5 20 34 48 62 65 67 69 73 72 74 76
  Logging 57 54 50 47 39 31 29 26 25 27 22 21 20
  Airport service 0 0 0 3 7 8 9 9 9 11 9 9 9
  Railway maintenance 0 0 1 2 2 3 3 3 3 3 3 3 3
  Recreational marine vessels 3 6 10 13 16 19 20 20 21 21 22 23 24
Aircraft 50 56 63 69 70 73 74 83 91 96 88 81 81
Marine vessels 978 986 951 1,043 1,003 1,049 1,058 1,008 958 857 1,008 1,013 1,011
  Diesel NA NA 750 822 791 835 844 801 757 672 795 799 797
  Residual oil NA NA 201 221 212 213 213 207 200 182 214 215 214
  Other NA NA NA NA NA NA NA NA NA 2 NA NA NA

TABLE 9.2
Nitrogen oxide emission trends, by source category, selected years 1970–2002 [CONTINUED]
SOURCE: Adapted from "National Emission Trends: Nitrogen Oxide Emissions (Thousand Short Tons)," in 1970–2002 Average Annual Emissions, All Criteria Pollutants, U.S. Environmental Protection Agency, January 2005, http://www.epa.gov/ttn/chief/trends/ (accessed April 14, 2005)

Source category 1970 1975 1980 1985 1990 1995 1996 1997 1998 1999 2000 2001 2002
Railroads 1,136 1,108 1,185 958 945 1,031 1,048 1,061 1,073 939 1,001 999 889
Other 24 63 104 145 189 234 243 251 246 255 278 286 295
  Liquified petroleum gas 5 43 81 120 162 204 213 221 215 215 246 254 262
  Compressed natural gas 19 21 23 25 27 30 30 30 31 39 32 32 33
Miscellaneous (tier 0–04) 330 165 248 310 369 267 412 187 179 251 276 184 356
Miscellaneous (tier 1–13) 330 165 248 310 369 267 412 187 179 251 276 184 356
Agriculture & forestry NA NA NA NA NA NA NA NA NA 2 NA NA 2
  Agricultural livestock NA NA NA NA NA NA NA NA NA 2 NA NA 2
Other combustion 330 165 248 310 368 265 412 187 179 249 276 184 354
Health services NA NA NA NA NA 0 0 0 0 0 0 0 0
Cooling towers NA NA NA NA NA 0 NA NA NA NA NA NA NA
Fugitive dust NA NA NA NA 1 1 0 0 0 0 0 0 0
Other NA NA NA NA NA NA 0 0 0 NA NA NA NA
Subtotals are provided at selected tier levels.
Total all sources = sum of the 4 tier 0 categories which are bolded and separated by blank lines.
The tier 0 categories are further divided into the 13 tier 1 categories which are bolded with no line separation and are under their respective tier 0 categories.
The tier 1 categories are further divided into tier 2 categories which are not bolded and are under their respective tier 1 categories.
The tier 2 categories are further divided into tier 3 categories which are italicized and under their respective tier 2 categories.

Some aquatic plants and animals are able to tolerate more acidic waters. For example, frogs can tolerate lower pH than trout, crayfish, or clams. Acid-sensitive species, however, are lost as pH declines. It is usually the young of most species that are the most sensitive to environmental conditions. For example, at less than pH 5, trout and salmon eggs cannot hatch. At lower pH levels (pH 4 to 4.9), some adult fish die. Some extremely hardy fish such as the roach (a type of carp) can survive at a pH as low as 3.5 if the change is gradual and they have time to adjust.

Other effects include:

  • Sudden, short-term shifts in pH levels, resulting in acid shock to freshwater ecosystems
  • Gradual declines in fish populations and numbers of adult and juvenile fish over time as pH decreases
  • Unsuccessful reproduction by many aquatic species, including poor egg production, abnormal eggs, and poor juvenile survival
  • Physical impairment in juveniles of some species
  • Loss of the ability in salmon to find home streams because of impaired sense of smell
  • Loss of important components of the food web, leading to poor nutrition or starvation in species dependent on those components
  • Changes in the plant and animal species within an ecosystem

Nitrogen has been shown to play an important role in both episodic and long-term acidification. It is also an important nutrient, but excess nitrogen can cause water quality degradation. Of the nitrogen released into the atmosphere through human activities, 10% to 45% is transported to U.S. oceans and estuaries through air deposition. In Chesapeake Bay, for example, 30% of the nitrogen contributed from human-made sources is atmospheric deposition.

Another area in which excess nitrogen from acid deposition, among other sources, is being watched very carefully is along the coastline. Studies of a phenomenon nicknamed dead zones have been underway for many years. The term dead zone actually refers to a state of hypoxia. A water body that is suffering from hypoxia is one in which excess nitrogen has caused the dissolved oxygen in the water to deplete to the point where the water can no longer support life. The three sources of nitrogen known to cause large dead zones to appear every summer in the Gulf of Mexico are agricultural run-off, industrial waste, and acid deposition.

Forest Systems

Acid deposition can have serious impacts on trees and soils, causing slower growth, injury, or death of forests. Acid deposition has been implicated in forest and soil degradation in the eastern United States, particularly in the high elevations of the Appalachian Mountains from Georgia to Maine, an area including the Shenandoah and Great Smoky Mountain National Parks.

When rain falls to the forest floor, the buffering capacity of the soil may neutralize some or all of its acidity. Differences in soil-buffering capacity is the reason that some areas that receive a lot of acid rain show little damage while other areas that receive the same amount show a lot of damage. The ability of forest soil to resist becoming acidified depends on the thickness of the soil and the type of bedrock below the soil.

When the soils cannot buffer the acid rain, vital nutrients present in the soil, such as calcium and magnesium, are stripped away by the acid-driven reactions. Aluminum, a toxic element present in all soils, is made more available to the trees and taken up by their roots. The combination of toxic aluminum and poor nutrition retard growth, make the trees more vulnerable to infection, and can eventually kill the trees.

In March 1999 the U.S. Geological Survey (USGS), in Soil Calcium Depletion Linked to Acid Rain and Forest Growth in the Eastern United States, reported that calcium levels in forest soils had declined at locations in ten states in the eastern United States. Calcium is necessary to neutralize acid rain and is an essential nutrient for tree growth. Sugar maple and red spruce trees, in particular, showed reduced resistance to stresses such as insect defoliation and low winter temperatures. Although the specific relationships among calcium availability, acid rain, and forest growth are uncertain, Dr. Gregory Lawrence, scientist and coauthor of the report, speculated:

Acid rain releases aluminum from the underlying mineral soil layer, which is followed by the upward transport of the aluminum into the forest floor (the nutrient-rich organic soil layer where root activity is greatest) by root uptake and water movement. The result is that aluminum replaces calcium, and the trees have a harder time trying to get the needed calcium from the soil layer.

Acid deposition can affect trees in other ways. Sulfur dioxide that has not been converted to sulfuric acid has been shown to clog up the leaf stomata (tiny openings in leaves where gases diffuse in and out), impairing plant respiration and photosynthesis. Nitric acid and nitrogen oxide have been shown to stimulate tree growth outside the growing season, leaving trees vulnerable to winterkill. Forests in high mountain regions often are surrounded by acidic clouds and fog that are more acidic than rainfall. Scientists believe that when the tree leaves and needles are frequently wetted in this acid fog, essential nutrients are stripped away. Loss of nutrients in the foliage makes the trees more vulnerable to other environmental threats, particularly winterkill. Winterkill resulting in damage or death is the result of naturally occurring stress caused by cold, wind, ice, and dehydration on trees and other woody plants that have been weakened by insect damage, nutrient deficiency, or drought.

Plants that are found in locations that are susceptible to high acid deposition experience the same fate as trees. The processes causing growth retardation and ultimately death are believed to be the same.

Human Health

Acid rain feels, tastes, and looks just like clean rain. Sulfur dioxide and nitric oxides, the pollutants that cause acid rain, however, can damage human health. These gases interact with particulate in the atmosphere to form aerosols (a mixture of very tiny liquid and solid particles) that can travel long distances transported by winds. When inhaled, aerosols penetrate deep into the lungs and are readily retained. Because of their very fine size, they can also penetrate indoors through ventilation systems.

Air pollution studies have indicated that elevated levels of acidic particles can cause asthma attacks, particularly in adolescents, and can also impair the ability of the upper respiratory tract to remove other potentially harmful particles. Some scientific studies have also established a relationship between elevated levels of fine particles and increased deaths from heart and lung disorders, such as bronchitis and asthma. Other scientists believe that these pollutants may increase the health risks to those over age sixty-five; those with asthma, chronic bronchitis, and emphysema; pregnant women; and those with histories of heart disease.

In "Effects of Acid Rain: Human Health" (Environmental Protection Agency, http://www.epa.gov/airmarkets/acidrain/effects/health.html, November 12, 2003), the EPA reported that sulfate aerosols make up about 25% of fine particles in the air in the eastern United States. Lowering emissions from power plants that contain fine sulfate and nitrate particles should eventually reduce the incidence and severity of the health problems believed related to these pollutants. The EPA estimated that when fully implemented in 2010, the public health benefits of the Acid Rain Program (created by Congress under Title IV of the 1990 Clean Air Act Amendments) would be about $50 billion annually in reduced health care costs because of decreases in emergency room visits, hospital admissions, and number of deaths.

Decreased nitric acid emissions are expected to lower the amount of ozone formed. Ozone is believed to increase the risk of illness or death from lung inflammation, including asthma and emphysema.

An indirect effect of acid deposition on human health is the increased reactivity in acid water of toxic metals and other chemicals. Increased reactivity means that the chemicals and toxic metals in the water are more likely to be taken up in fruits, vegetables, and animal tissue. Air deposition is believed to be the leading source of mercury bioaccumulation in fish. This sort of bioaccumulation has led to advisories against eating certain kinds of fish.

The principal pollutants generated by coal combustion that can cause health problems are particulate, sulfur and nitrogen oxides, trace elements (such as arsenic, fluorine, selenium, and the radionuclides, uranium, and thorium), and organic compounds as a result of incomplete coal combustion. Some of these trace elements have been shown to cause severe health effects in other countries, such as China, Romania, and Bulgaria.

The EPA conducted a detailed study of possible health effects that can come from the exposure to emissions of about twenty potentially toxic substances from coal-burning electric utilities. In this study, the EPA used USGS information on U.S. coal quality to assess the potential health impact of fourteen potentially toxic trace elements that may be mobilized by coal burning. The USGS fact sheet Health Impacts of Coal Combustion (July 2000) reported that, with the possible exception of mercury, there is no compelling evidence to indicate that emissions from U.S. coal-burning electric utilities cause human health problems. The absence of detectable health problems was credited in part to the use in the United States of coals that contain low to moderate amounts of sulfur and other potentially toxic trace elements. Another reason for the absence of detectable health problems was the common use of sophisticated pollution control systems by coal-burning utilities. These systems are specifically designed to reduce the emission of hazardous elements.

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