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4 Global Tropospheric Chemistry- A Cad to Action In the past 12 years, the National Research Council has issued at least 10 reports concerned wholly or partly with atmospheric chemistry. Most of these reports have focused on identified atmospheric environmental prob- lems and ways to alleviate damage to the environment. For example, the issues arising from fossil fuel combus- tion, stratospheric ozone perturbations due to super- sonic aircraft, and man-made chlorofluorocarbons and airborne particles and their effects have been studied and exposed in these reports. A recent reports on acid deposition in North America adds to this impressive body of literature. The latter report was commissioned and prepared in an attempt to discern, from available information, scientific conclusions that could lead to for- mulation of public policy. By contrast and in response to the charge provided to our panel (see Preface to this report), the present report looks ahead to future research. We conclude that a global study of tropospheric chemistry is needed to provide answers to major questions about the chemistry of the world's atmosphere and the effects of this chemistry on 'Acid Deposition: Atmospheric Processes in Eastern North Amer- ica, A Review of Current Scientific Understanding, Committee on Atmospheric Transport and Chemical Transformation in Acid Pre- cipitation, National Academy Press, Washington, D.C., lg83, 375 PP the physical state of the atmosphere. This conclusion arose from an assessment of the current state of atmo- spheric chemistry knowledge (see Part II of this report). Further, we attempt to outline an overall scientific strat- egy to allow the identified objectives to be attained eco- nomically. Although the scientific strategy adopts the intellectual framework of geochemical and biogeochem- ical cycling of chemical elements, the proposed research program has a strong heuristic character. In many re- spects, the proposed research program is similar to pro- grams envisioned earlier in National Aeronautics and Space Administration reports and in less formal discus- sions involving U.S. and European scientists and Na- tional Science Foundation staff. The focus on the global troposphere is required scien- tifically. It does not preclude attention to existing ques- tions of smaller-scale air pollution. Indeed, we believe that the knowledge to be gained from the research we propose will permit much sounder assessments of many pollution issues and eventually more effective protection and management of the world's natural resources. The major observational elements of the proposed Global Tropospheric Chemistry Program are outlined in Figure 4.1. The four major field studies biological sources, global distribution and long-range transport, photochemical transformation, and conversion and re- moval are illustrated along with their component ex- periments. These field studies, combined with data on 50

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A CALL TO ACTION Biological Sources of Atmospheric U Individual Biome Experiments 1 1 1 1 1 1 1 1 7ZY 51 Global Distributions l and Long-Range Transpor1 Study _ Distri buttons Netwo rk 1 . Long-Term Trends = Photochemical Transformation Study Theory Validation Experiments Surface So urce/ R eceptor Network ~ Conversion and | | Removal Study | Concentration Distri button Experiment . 1 __ Wet Removal I Dry Removal | Experiment Program | AL GLOBAL TROPOSPHERIC CHEMISTRY SYSTEMS MODELS AND SUBMOC)ELS FIGURE 4.1 Major observational elements in the proposed Global Tropospheric Chemistry Program. the rates and mechanisms of atmospheric chemical reac- tions determined in the laboratory, will provide data for the development of Global Tropospheric Chemistry Systems Models. These global TCSMs are necessary if we are to obtain both a comprehensive understanding of global tropospheric cycles and a predictive capability in the future. Because the proposed program is one of basic re- search, the focus is on questions and concepts rather than on a detailed plan of execution. Accordingly, a detailed estimate of pro gram cost is not attempted. It is clear, however, that incremental funding of several tens of millions of dollars per year for a decade or more would be required to support the proposed investigations. Fi- nally, it should be emphasized that we have outlined only the U. S. national component of a necessarily inter- national research program for which there appears to be significant and growing support.

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