Regional Air Pollution and Vegetation - C&EN Global Enterprise (ACS

Aug 6, 1990 - The harmful effects of air pollution on vegetation have long been known. In the 1920s and 1930s, smelters such as those in Trail, Britis...
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Regional Air Pollution and Vegetation Reviewed by Jean Fincher

The harmful effects of air pollution on v e g e t a t i o n h a v e l o n g b e e n known. In the 1920s and 1930s, smelters such as those in Trail, British Columbia, and Anaconda, Mont., released large amounts of sulfur dioxide that severely injured local vegetation. Hydrogen fluoride emissions from an aluminum reduction facility in Spokane, Wash., also resulted in injury to trees and other vegetation. These old plants and smelters could be identified as point sources of pollution. Their emissions caused injury to plant foliage that could be reproduced under controlled experimental conditions. Demands for pollution control forced many industries to restrict local emissions. However, the primary technical approach they used was to increase the height of stacks, thus reducing local impacts and distributing some of their pollutants into the air over much greater distances. As a result, local effects were mitigated, and now the air pollutants of most concern cannot be traced back to a single point. Much of today's pollution is the product of complex chemical reactions in the atmosphere, combined with long-distance transport. Thus, sulfur dioxide, rather than having local effects, is mostly oxidized to sulfate and deposited at a distance as a component of acid rain. Ozone and acid rain are regional problems that result from combined pollutants from many sources. At the same time that local effects were being diminished, the number of air pollution sources and total emissions to the atmosphere have increased greatly. For example, annual sulfur dioxide emissions in the U.S. rose from less than 10 million tons in 1940 to 29 million tons a year in the late 1970s, to the current approximately 22 million tons. In the early 1980s, reports of injury to plants that could not easily be 30

August 6, 1990 C&EN

Effects of widespread air pollution on trees are difficult to establish with any certainty "Air Pollution's Toll on Forests & Crops" edited by James J. MacKenzie and Mohamed T. El-Ashry, Yale University Press, 92A Yale Station, New Haven, Conn. 06520, 1990, 363 pages, $38.50

attributed to natural stresses or point sources of emissions raised the possibility that the injury was due to this new low-level, widespread pollution. The specter of a more diffuse pollution load causing long-term injury, that only then was being recognized, was of great concern. What other changes had been induced in the environment that might not surface for 20 or more years? "Air Pollution's Toll on Forests & Crops" summarizes much of the current knowledge on the effects of acidic deposition and ozone on vegetation. The editors, James J. MacKenzie and Mohamed T. El-Ashry,

both on the staff of the World Resources Institute, provide an introductory summary and a chapter on policy issues. Economic issues are discussed in many of the chapters. In the early 1980s, perception of a simultaneous widespread decline in the forests of Europe, the U.S., and Canada aroused speculation that acid rain was a primary cause. A large U.S. government-funded research program, the National Acid Precipitation Assessment Program, was established about 10 years ago to determine the effects of acid rain on natural systems. The majority of the authors of "Air Pollution's Toll on Forests & Crops" are scientists who have been actively involved in research and evaluation of findings done in conjunction with that program. Readers of science accounts in the popular press might be surprised at the tone of the articles in this volume. Many newspaper, magazine, and television reports vividly portray acid rain as the culprit in forest decline. Although its dangers have been widely reported in the media and debated by politicians, scientists have difficulty documenting these effects because of a lack of baseline information and the intricate web of natural biotic and abiotic stresses. In fact, there is little or no evidence that acid rain has an effect on crop systems. Acid rain, at pH values that currently exist in the U.S., does not directly damage foliage. And in managed agricultural systems, where liming and use of fertilizer are the norm, changes in soils associated with acidic deposition or leaching are difficult, if not impossible, to measure. Nevertheless, Walter W. Heck of North Carolina State University, the author of a chapter on crops, claims that the lack of detectable effects on productivity of most crops may be due to imperfect experimental designs; he calls for more research on this topic. It is in unmanaged systems, how-

ever, where the greatest effects of acid deposition on soil nutrients might be expected. Forests subjected to years of acid rain could suffer from aluminum toxicity and nutrient deficiencies because ions have been leached from the soil. In contrast to acid rain, the effects of ozone, another pollutant that occurs on a regional scale, have been relatively easy to establish. For example, the Environmental Protection Agency-funded National Crop Loss Assessment Network project, established in the early 1980s, found that ozone at current levels reduces the yield of several important crops and has significant economic impact. Ozone also clearly is a factor in the injury of trees, especially ponderosa and Jeffrey pine in California, as explained in a chapter by Paul R. Miller of the U.S. Department of Agriculture Forest Service in Riverside, Calif. However, in the eastern U.S., even the existence of forest decline has aroused heated debates in scientific circles, as Robert I. Bruck of North Carolina State University explains. What has resulted is an appreciation of how little is known about forests. Information on the normal structure and function of forests is so scant that trying to discern an impact from air pollution has been surrounded by controversy. The controversy has been exacerbated by the use in the media of illustrations in which pollution is not the primary cause of tree death. The premier example of this is the repeated appearance in magazines and newspapers of pictures of the summit of Mount Mitchell, N.C., covered by dead fir trees. Most scientists attribute this to an imported insect, the balsam wooly adelgid, and find little or no evidence that air p o l l u t i o n has i n f l u e n c e d the progress of this pest. At high elevations, however, acidic cloud water may be having an impact on trees. Arthur H. Johnson of the University of Pennsylvania and Thomas G. Siccama of Yale University summarize evidence for interactions between climatic factors and air pollution in forest decline on Whiteface Mountain, N.Y. Here, the complexities become very clear. Scientists are trying to determine if

chronic doses of air pollutants are having an adverse effect over and above the many other factors known to affect tree growth. Drought, freezing and high temperatures, low levels of soil nutrients, competition, insect outbreaks, fire, past logging, and forest management, all have profound effects on tree growth. This raises the question of whether we can ever say that air pollution is the most important stress, rather than just part of a mixture of stresses, or at what point this one additional stress becomes too much for a tree. The complexities of forest decline have prompted a reconsideration of underlying assumptions in science concerning the nature of evidence, what constitutes scientific proof, how to apply epidemiological techniques to populations of trees, and whether Koch's postulates on the causes of infection can be applied to organisms that live 100 to 200 years and may take decades to die. With the advent of renewed concern about global climate change, a scenario similar to the acid rain story is being played out. Questions on the role of science and scientists in setting environmental policy are beginning to reoccur. Many respected scientists cringe at the widespread use of predictions about the greenhouse effect derived from simplistic models. Once again, the press and environmental groups have far

more confidence in the reliability of the data than most scientists have. Some groups even argue that automobile emissions should be controlled lest they cause changes in global climate. The risk of global climate change is not a new problem but merely a continuation of the effects of air pollution. Release of chemicals into the atmosphere is not a benign process. Many local effects stem from individual factories. Now regional and international effects are caused by long-distance transport. In the future, we will see global effects. Local damage was easy to detect and could be controlled with economic and political pressure from outside the community that relied on the offending plant for employment. Regional effects and responses resulting from chronically low doses have been more difficult to document. But we are gradually learning what to look for in the field and how to design appropriate experiments. The effects of global pollution may prove to be even more difficult to establish using rigorous scientific proof. But to assume that there will be no change if we continue to release chemicals into the atmosphere is foolhardy. Jean Fincher, senior research associate at Boyce Thompson Institute for Plant Research at Cornell University, currently is doing research on the effects of air pollution on native plants. •

Auger Spectroscopy and Electronic Structure. G. Cubiotti, G. Mondio, K. Wandelt, editors, x + 277 pages. Springer-Verlag New York, 175 Fifth Ave., New York, N.Y. 10010. 1989. $58.90.

Chemical Engineering Design Project: A Case Study Approach. Martyn S. Ray, David W. Johnston, xxv + 357 pages. Harwood Academic Publishers, P.O. Box 786, Cooper Station, New York, N.Y. 10276. 1989. $90 hardback, $49 paperback.

Biotechnology: A Textbook of Industrial Microbiology. 2nd Ed. Wulf Crueger, Anneliese Crueger. x + 357 pages. Sinauer Associates Inc., Publishers, Sunderland, Mass. 01375-0407. 1990. $44.95.

Chemical Grouting. 2nd Ed. Reuben H. Karol. xii + 465 pages. Marcel Dekker, 270 Madison Ave., New York, N.Y. 10016. 1990. $99.75 U.S. & Canada, $119.50 elsewhere.

Carbohydrate Chemistry. Vol. 21. Part 1. N. R. Williams et al. xiv + 297 pages. Royal Society of Chemistry, Distribution Centre, Letchworth, Herts SG6 1HN, England. 1989. $146, £75.

Chemical Reactor Analysis and Design. 2nd Ed. Gilbert F. Froment, Kenneth B. Bischoff. xxxiv + 664 pages. John Wiley & Sons, 605 Third Ave., New York, N.Y. 10016. 1990. $59.95.

Catalysis. Vol. 8. G. C Bond et al. x + 203 pages. Royal Society of Chemistry, Distribution Centre, Letchworth, Herts SG6 1HN, England. 1989. $134, £70.

Chemical Synthesis of Advanced Ceramic Materials. David Segal, xv + 182 pages. Cambridge University Press, 32 East 57th St., New York, N.Y. 10022. 1989. $59.50. August 6, 1990 C&EN

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Books Chemistry at Interfaces. Finlay MacRitchie, x + 283 pages. Academic Press, 1250 Sixth Ave., San Diego, Calif. 92101. 1990. $49.95. Chemistry of Coal Weathering. Charles R. Nelson, editor, x + 230 pages. Elsevier Science Publishing Co., P.O. Box 882, Madison Square Station, New York, N.Y. 10159. 1989. $134.25. C o l l e g e P h y s i c s . 3rd Ed. J o h n J. O'Dwyer. xiv + 881 pages. Brooks/ Cole Publishing Co., 511 Forest Lodge Rd., Pacific Grove, Calif. 93950-5098. 1990. $59.50. Cosmetic and Toiletry Formulations. 2nd Ed. Ernest W. Flick, xxxi + 971 pages. Noyes Publications, Mill Rd. at Grand Ave., Park Ridge, N.J. 07656. 1990. $125. Cryopumping: Theory and Practice. Rene A. Haefer. xx + 435 pages. Oxford University Press, 200 Madison Ave., New York, N.Y. 10016. 1989. $125. Detection-Oriented Derivatization Techniques in Liquid Chromatography. Henk Lingeman, Willy J. M. Un-

derberg, editors, xvi + 389 pages. Marcel Dekker, 270 Madison Ave., New York, N.Y. 10016. 1990. $99.75 U.S. & Canada, $119.50 elsewhere.

Gmelin Handbook of Inorganic & Organometallic Chemistry: Formula Index, 2nd Supp., Vol. 8: C33-Cf. MaxPlanck Society for the Advancement of Science, xxi + 330 pages. SpringerDevelopments in Meat Science — 4. RalVerlag New York, 175 Fifth Ave., ston Lawrie, editor, x + 361 pages. New York, N.Y. 10010. 1990. $740.10. Elsevier Science Publishing Co., P.O. Box 882, Madison Square Station, New Gmelin Handbook of Inorganic & Organometallic Chemistry: Formula InYork, N.Y. 10159. 1989. $93.75. dex, 2nd Supp., Vol. 9: Cl-Ho. MaxPlanck Society for the Advancement Dynamic Properties of Biomolecular of Science, x + 273 pages. SpringerAssemblies. S. E. Harding, A. J. Rowe, Verlag New York, 175 Fifth Ave., editors, viii + 373 pages. Royal Society New York, N.Y. 10010. 1990. $803.70. of Chemistry, Distribution Centre, Letchworth, Herts SG6 1HN, England. Gmelin Handbook of Inorganic & Or1989. $86, £45. ganometallic Chemistry: Formula Index, 2nd Supp., Vol. 10: I-Zr. MaxThe Foundations of Laboratory Safety: Planck Society for the Advancement A Guide for the Biomedical Laboraof Science, x + 307 pages. Springertory. Stephen R. Rayburn. xiii + 418 Verlag New York, 175 Fifth Ave., pages. Springer-Verlag New York, 175 New York, N.Y. 10010. 1990. $928.80. Fifth Ave., New York, N.Y. 10010. 1990. $59. Gmelin Handbook of Inorganic & Organometallic Chemistry: Manganese General Chemistry: Principles and D7: Coordination Compounds 7. Structure. 5th Ed. James E. Brady, Max-Planck Society for the Advancexviii + 852 pages. John Wiley & Sons, ment of Science, xvi -I- 289 pages. 605 Third Ave., N e w York, N.Y. Springer-Verlag New York, 175 Fifth 10016. 1990. $49.95. Ave., New York, N.Y. 10010. 1990. $809.20.

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Gmelin Handbook of Inorganic & Organometallic Chemistry: SulfurNitrogen Compounds. Part 6: Compounds of Sulfur with Oxidation Number IV. Max-Planck Society for the Advancement of Science, xxi + 330 pages. Springer-Verlag New York, 175 Fifth Ave., New York, N.Y. 10010. 1990. $1028.20. Handbook of Plasma Processing Technology: Fundamentals, Etching, Deposition, and Surface Interactions. Stephen M. Rossnagel, Jerome J. Cuomo, William D. Westwood, editors, xxiii + 523 pages. Noyes Publications, Mill Rd. at Grand Ave., Park Ridge, N.J. 07656. 1990. $86. Handbook on the Physics and Chemistry of Rare Earths. Vol. 12. Karl A. Gschneidner Jr., LeRoy Eyring, editors, xi + 486 pages. Elsevier Science Publishing Co., P.O. Box 882, Madison Square Station, New York, N.Y. 10159. 1989. $131.75. Handbook of Statistical Methods for Engineers and Scientists. Harrison M. Wadsworth Jr., editor, x + 720 pages. McGraw-Hill, 1221 Ave. of the Americas, N e w York, N.Y. 10020. 1990. $76.50. The Hazardous Waste Q & A. Travis P. Wagner, xx + 404 pages. Van Nostrand Reinhold, 115 Fifth Ave., New York, N.Y. 10003. 1989. $42.95. •