Chemistry of the Upper and Lower Atmosphere (eBook)

Theory, Experiments, and Applications

Barbara J. Finlayson-Pitts, James N. Pitts Jr. (Autoren)

eBook Download: PDF | EPUB

1999 | 1. Auflage
969 Seiten
Elsevier Science (Verlag)
978-0-08-052907-3 (ISBN)

Infos

Here is the most comprehensive and up-to-date treatment of one of the hottest areas of chemical research. The treatment of fundamental kinetics and photochemistry will be highly useful to chemistry students and their instructors at the graduate level, as well as postdoctoral fellows entering this new, exciting, and well-funded field with a Ph.D. in a related discipline (e.g., analytical, organic, or physical chemistry, chemical physics, etc.). Chemistry of the Upper and Lower Atmosphere provides postgraduate researchers and teachers with a uniquely detailed, comprehensive, and authoritative resource. The text bridges the 'gap' between the fundamental chemistry of the earth's atmosphere and 'real world' examples of its application to the development of sound scientific risk assessments and associated risk management control strategies for both tropospheric and stratospheric pollutants.

• Serves as a graduate textbook and 'must have' reference for all atmospheric scientists
• Provides more than 5000 references to the literature through the end of 1998
• Presents tables of new actinic flux data for the troposphere and stratospher (0-40km)
• Summarizes kinetic and photochemical date for the troposphere and stratosphere
• Features problems at the end of most chapters to enhance the book's use in teaching
• Includes applications of the OZIPR box model with comprehensive chemistry for student use

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Here is the most comprehensive and up-to-date treatment of one of the hottest areas of chemical research. The treatment of fundamental kinetics and photochemistry will be highly useful to chemistry students and their instructors at the graduate level, as well as postdoctoral fellows entering this new, exciting, and well-funded field with a Ph.D. in a related discipline (e.g., analytical, organic, or physical chemistry, chemical physics, etc.). Chemistry of the Upper and Lower Atmosphere provides postgraduate researchers and teachers with a uniquely detailed, comprehensive, and authoritative resource. The text bridges the "e;gap"e; between the fundamental chemistry of the earth's atmosphere and "e;real world"e; examples of its application to the development of sound scientific risk assessments and associated risk management control strategies for both tropospheric and stratospheric pollutants. Serves as a graduate textbook and "e;must have"e; reference for all atmospheric scientists Provides more than 5000 references to the literature through the end of 1998 Presents tables of new actinic flux data for the troposphere and stratospher (0-40km) Summarizes kinetic and photochemical date for the troposphere and stratosphere Features problems at the end of most chapters to enhance the book's use in teaching Includes applications of the OZIPR box model with comprehensive chemistry for student use

Inhalt

Cover 1
Contents 8
Preface 18
About the Authors 20
Acknowledgments 22
Chapter 1. Overview of the Chemistry of Polluted and Remote Atmospheres 24
A. REGIONS AND CHARACTERISTICS OF THE ATMOSPHERE 25
B. AIR POLLUTION AND THE CHEMISTRY OF OUR TROPOSPHERE 26
1. Historical Perspectives: Ancient and Medieval Times 26
2. "London" Smog: Sulfur Dioxide, Acidic Aerosols, and Soot 26
3. "Los Angeles" Smog: Ozone and Photochemical Oxidants 27
4. Acid Deposition 31
C. CHEMISTRY OF THE NATURAL TROPOSPHERE: REMOTE ATMOSPHERES 32
D. CHEMISTRY OF THE STRATOSPHERE 33
E. GLOBAL CLIMATE CHANGE 34
F. INDOOR AIR POLLUTION 36
G. DISCUSSION TOPIC AND OZIPR MODEL 36
1. Discussion Topic: "Background Ozone" 36
2. OZIPR Model 36
REFERENCES 36
Chapter 2. The Atmospheric System 38
A. EMISSIONS 38
1. Oxides of Nitrogen 40
2. Volatile Organic Compounds (VOC) 41
3. Carbon Monoxide 43
4. Sulfur Compounds 43
5. Total Suspended Particles (TSP), PM10, and PM2.5 44
6. Lead 48
B. METEOROLOGY 49
1. Lapse Rate: Temperature and Altitude 49
2. Potential Temperature 51
3. Temperature Inversions 51
C. REMOVAL FROM THE ATMOSPHERE: WET AND DRY DEPOSITION 53
D. TYPICAL AMBIENT CONCENTRATIONS AND AIR QUALITY STANDARDS 56
1. Units of Concentrations and Conversions 56
2. Criteria and Noncriteria Pollutants and Air Quality Standards 58
E. EFFECTS ON VISIBILITY AND MATERIALS 60
F. ECONOMICS 61
G. ATMOSPHERIC CHEMISTRY: RISK ASSESSMENTS AND PUBLIC POLICIES FOR AIR POLLUTION CONTROL 61
H. PROBLEMS 62
REFERENCES 62
Chapter 3. Spectroscopy and Photochemistry: Fundamentals 66
A. BASIC PRINCIPLES 66
1. Molecular Energy Levels and Absorption and Emission Spectroscopy 66
2. Fates of Electronically Excited Molecules 73
B. ABSORPTION OF LIGHT 75
1. Basic Relationships 75
2. The Beer – Lambert Law 76
C. ATMOSPHERIC PHOTOCHEMISTRY 78
1. Solar Radiation and Its Transmission through the Atmosphere 78
2. Calculating Photolysis Rates in the Atmosphere 84
3. Procedure for Calculating Photolysis Rates 99
4. Example: Photolysis of Acetaldehyde at the Earth's Surface 104
D. PROBLEMS 106
REFERENCES 107
Chapter 4. Photochemistry of Important Atmospheric Species 109
A. MOLECULAR OXYGEN 109
1. Absorption Spectra 109
2. Photochemistry 112
B. OZONE 113
1. Absorption Spectra 113
2. Photochemistry 114
C. NITROGEN DIOXIDE 118
1. Absorption Spectra 118
2. Photochemistry 119
D. NITRIC ACID 121
E. NITROUS ACID 122
F. PEROXYNITRIC ACID 123
G. NITRATE RADICAL 123
H. DINITROGEN PENTOXIDE 124
I. NITROUS OXIDE 124
J. ORGANIC NITRATES AND PEROXYACETYL NITRATE 125
1. Organic Nitrates 125
2. Peroxyacetyl Nitrate 126
K. SULFUR DIOXIDE AND SULFUR TRIOXIDE 126
1. SO2 126
2. SO3 128
L. HYDROGEN PEROXIDE AND ORGANIC HYDROPEROXIDES 130
M. ALDEHYDES AND KETONES 130
N. CHLORINE NITRATE (ClONO2) AND BROMINE NITRATE (BrONO2) 134
O. HCl AND HBr 136
P. THE HALOGENS 137
Q. ClO, BrO, AND IO 137
R. ClOOCl 137
S. OClO 138
T. HOCl, HOBr, AND HOI 138
U. NITROSYL CHLORIDE (ClNO) AND NITRYL CHLORIDE (ClNO2) 140
V. HALOGENATED METHANES AND ETHANES 140
W. PROBLEMS 140
REFERENCES 149
Chapter 5. Kinetics and Atmospheric Chemistry 153
A. FUNDAMENTAL PRINCIPLES OF GAS-PHASE KINETICS 153
1. Definitions 153
2. Termolecular Reactions and Pressure Dependence of Rate Constants 156
3. Temperature Dependence of Rate Constants 161
B. LABORATORY TECHNIQUES FOR DETERMINING ABSOLUTE RATE CONSTANTS FOR GAS-PHASE REACTIONS 164
1. Kinetic Analysis 165
2. Fast-Flow Systems 165
3. Flash Photolysis Systems 168
4. Pulse Radiolysis 169
5. Cavity Ring Down Method 170
6. Static Techniques 171
C. LABORATORY TECHNIQUES FOR DETERMINING RELATIVE RATE CONSTANTS FOR GAS-PHASE REACTIONS 172
D. REACTIONS IN SOLUTION 174
1. Interactions of Gaseous Air Pollutants with Atmospheric Aqueous Solutions 174
2. Diffusion-Controlled Reactions of Uncharged Nonpolar Species in Solution 175
3. Reactions of Charged Species in Solution 176
4. Experimental Techniques Used for Studying Solution Reactions 178
E. LABORATORY TECHNIQUES FOR STUDYING HETEROGENEOUS REACTIONS 179
1. Analysis of Systems with Gas- and Liquid-Phase Diffusion, Mass Accommodation, and Reactions in the Liquid Phase or at the Interface 181
2. Knudsen Cells 188
3. Flow Tube Studies 190
4. Falling-Droplet Apparatus 190
5. Bubble Apparatus 191
6. Aerosol Chambers 191
7. Liquid Jet Apparatus 192
8. DRIFTS 194
9. Surface Science Techniques 194
10. Other Methods 195
F. COMPILATIONS OF KINETIC DATA FOR ATMOSPHERIC REACTIONS 195
G. PROBLEMS 197
REFERENCES 198
Chapter 6. Rates and Mechanisms of Gas-Phase Reactions in Irradiated Organic – NOx – Air Mixtures 202
A. SOURCES OF OXIDANTS IN THE TROPOSPHERE: OH, O3, NO3, HO2, AND Cl 202
1. OH 202
2. O3 203
3. NO3 203
4. HO2 203
5. Cl 203
B. LIFETIMES OF TYPICAL ORGANICS IN THE TROPOSPHERE 204
C. REACTIONS OF ALKANES 205
1. Hydroxyl Radical (OH) 205
2. Nitrate Radical (NO3) 207
3. Chlorine Atoms (Cl) 207
D. REACTIONS OF ALKYL (R), ALKYLPEROXY (RO2), AND ALKOXY (RO) RADICALS IN AIR 208
1. Alkyl Radicals (R) 208
2. Alkylperoxy Radicals (RO2) 208
3. Alkoxy Radicals (RO) 211
4. Summary of R, RO2, and RO Radical Reactions in the Troposphere 214
E. REACTIONS OF ALKENES (INCLUDING BIOGENICS) 214
1. Hydroxyl Radical (OH) 214
2. Ozone (O3) 219
3. Nitrate Radical (NO3) 224
4. Chlorine Atoms (Cl) 228
5. Nitrogen Dioxide (NO2) 229
F. REACTIONS OF ALKYNES 229
1. Hydroxyl Radical (OH) 229
G. REACTIONS OF SIMPLE AROMATIC HYDROCARBONS 230
1. Hydroxyl Radical (OH) 230
2. Nitrate Radical (NO3) 235
3. Chlorine Atoms (Cl) 235
H. REACTIONS OF OXYGEN-CONTAINING ORGANICS 236
1. Reactions of OH, NO3, and Cl 236
2. Hydroperoxyl Radical (HO2) 239
I. REACTIONS OF NITROGENOUS ORGANICS 240
1. Peroxyacetyl Nitrate and Its Homologs 240
2. Alkyl Nitrates and Nitrites 243
3. Amines, Nitrosamines, and Hydrazines 244
J. CHEMISTRY OF REMOTE REGIONS 248
1. Emissions of Biogenic Organics 248
2. Chemistry 254
3. Upper Troposphere 262
4. Arctic 264
K. ATMOSPHERIC CHEMISTRY AND BIOMASS BURNING 267
L. PROBLEMS 270
REFERENCES 271
Chapter 7. Chemistry of Inorganic Nitrogen Compounds 287
A. OXIDATION OF NO TO NO2 AND THE LEIGHTON RELATIONSHIP 288
B. OXIDATION OF NO2 289
1. Daytime Gas-Phase Reaction with OH 289
2. Nighttime Reactions to Form NO3 and N2O5 290
3. Reactions of NO and NO2 with Water and Alcohols 291
4. Other Reactions of NO2 295
C. ATMOSPHERIC CHEMISTRY OF HONO 296
1. Formation of HONO 296
2. Atmospheric Fates of HONO 297
D. REACTIONS OF NO3 AND N2O5 299
1. Reactions of NO3 299
2. Reactions of N2O5 302
E. ATMOSPHERIC CHEMISTRY OF HNO3 304
1. Formation 304
2. Tropospheric Fates 304
F. "MISSING" NOy 309
G. AMMONIA (NH3) 309
H. PROBLEMS 310
REFERENCES 311
Chapter 8. Acid Deposition: Formation and Fates of Inorganic and Organic Acids in the Troposphere 317
A. CONTRIBUTION OF H2SO4, HNO3, HONO, AND ORGANIC ACIDS 317
B. SOLUBILITY OF GASES IN RAIN, FOGS, AND CLOUDS: HENRY'S LAW AND AQUEOUS-PHASE EQUILIBRIA 318
C. OXIDATION OF SO2 319
1. Field Studies 319
2. Oxidation in the Gas Phase 321
3. Oxidation in the Aqueous Phase 324
4. Oxidation on Surfaces 347
5. Relative Importance of Various Oxidation Pathways for SO2 348
D. ORGANIC ACIDS 349
E. OXIDATION OF SULFUR COMPOUNDS OTHER THAN SO2 351
1. Reactions of Dimethyl Sulfide (CH3SCH3) 352
2. Dimethyl Disulfide (CH3SSCH3) 357
3. Methyl Mercaptan (CH3SH) 357
4. Hydrogen Sulfide (H2S) 358
5. Carbon Disulfide (CS2) 358
6. Carbonyl Sulfide (COS) 359
F. PROBLEMS 359
REFERENCES 360
Chapter 9. Particles in the Troposphere 372
A. PHYSICAL PROPERTIES 372
1. Some Definitions 372
2. Size Distributions 374
3. Particle Motion 385
4. Light Scattering and Absorption and Their Relationship to Visibility Reduction 388
B. REACTIONS INVOLVED IN PARTICLE FORMATION AND GROWTH 398
1. Nucleation, Condensation, and Coagulation 398
2. Reactions of Gases at Particle Surfaces 402
3. Reactions in the Aqueous Phase 403
4. Relative Importance of Various Aerosol Growth Mechanisms 403
C. CHEMICAL COMPOSITION OF TROPOSPHERIC AEROSOLS 403
1. Inorganic Species 404
2. Organics 416
D. GAS – PARTICLE DISTRIBUTION OF SEMIVOLATILE ORGANICS 435
1. Adsorption on Solid Particles 436
2. Absorption into Liquids 440
3. Octanol – Air Partitioning Coefficients 443
E. PROBLEMS 446
REFERENCES 446
Chapter 10. Airborne Polycyclic Aromatic Hydrocarbons and Their Derivatives: Atmospheric Chemistry and Toxicological Implications 459
A. NOMENCLATURE AND SELECTED PHYSICAL AND SPECTROSCOPIC PROPERTIES OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) AND POLYCYCLIC AROMATIC COMPOUNDS (PACs) 463
1. Combustion-Generated PAHs and PACs 463
2. Structures and IUPAC Rules for Nomenclature 463
3. Solubilities and Vapor Pressures 474
4. Gas – Particle Partitioning, Sampling Techniques, and Ambient Levels of Selected PAHs and PACs 476
5. Absorption and Emission Spectra of Selected PAHs and PACs 484
B. BIOLOGICAL PROPERTIES OF PAHs AND PACs. I: CARCINOGENICITY 489
1. Historical Perspective: Benzo[a]pyrene, the "Classic Chemical Carcinogen" 489
2. Carcinogenicity of PAHs, Cancer Potencies, and Potency Equivalence Factors 490
3. Carcinogenicity of Nitroarenes and Other Nitro-PACs 496
C. BIOLOGICAL PROPERTIES OF PAHs AND PACs. II: MUTAGENICITY 498
1. Short-Term Tests for Genetic and Related Effects 498
2. The Ames Salmonella typhimurium Reversion Assay 498
3. The Salmonella TM677 "Forward Mutation" Assay 506
4. Human Cell Mutagenicities of PAHs and PACs 507
D. BACTERIAL AND HUMAN CELL MUTAGENICITIES OF POLLUTED AMBIENT AIR 509
1. Bacterial Mutagenicity of Urban Air: A Worldwide Phenomenon 509
2. Sources, Ambient Levels, Transport, and Transformation: Some Case Studies 514
3. Bioassay-Directed Chemical Analysis for PAHs and PACs in Fine Ambient Aerosols Using a Human Cell Assay 520
4. Bioassay-Directed Chemical Analysis for Vapor-Phase and Particle-Phase PAHs and PACs in Ambient Air Using Bacterial Assays 525
E. ATMOSPHERIC FATES OF PARTICLE-ASSOCIATED PAHs: HETEROGENEOUS REACTIONS 527
1. Background 527
2. Theoretical and Experimental Structure – Reactivity Relationships 528
3. Field Studies of Atmospheric Reactions: Transport and Transformation 530
4. Photochemical Reactions of Particle-Associated PAHs 533
5. Gas – Particle Reactions 536
6. Atmospheric Fates of Particle-Associated Nitroarenes 541
F. REACTIONS OF GAS-PHASE PAHs: ATMOSPHERIC FORMATION OF MUTAGENIC NITROARENES 542
1. Combustion-Generated Primary Emissions of Nitroarenes 542
2. Atmospheric Formation of Nitro-PAHs and Nitro-PACs 543
REFERENCES 550
Chapter 11. Analytical Methods and Typical Atmospheric Concentrations for Gases and Particles 570
A. GASES 571
1. Optical Spectroscopic Techniques 571
2. Mass Spectrometry 584
3. Filters, Denuders, Transition Flow Reactors, Mist Chambers, and Scrubbers 590
4. Methods for, and Tropospheric Levels of, Specific Gases 592
5. Generation of Standard Gas Mixtures 630
B. PARTICLES 631
1. Sampling and Collection of Particles 631
2. Measurement of Physical Characteristics: Mass and Size 635
3. Measurement of Chemical Composition 642
4. Real-Time Monitoring Techniques for Particles 649
5. Generation of Calibration Aerosols 655
C. PROBLEMS 658
REFERENCES 659
Chapter 12. Homogeneous and Heterogeneous Chemistry in the Stratosphere 680
A. CHEMISTRY OF THE UNPERTURBED STRATOSPHERE 680
1. Stratosphere – Troposphere Exchange (STE) 681
2. Chapman Cycle and NOx Chemistry 683
B. HIGH-SPEED CIVIL TRANSPORT (HSCT), ROCKETS, AND THE SPACE SHUTTLE 685
1. HSCT 685
2. Space Shuttle and Solid Rocket Motors 690
C. CHLOROFLUOROCARBONS 692
1. Types, Nomenclature, and Uses 692
2. Lifetimes and Atmospheric Fates of CFCs and Halons 693
3. Gas-Phase Chemistry in the Stratosphere 696
4. Antarctic "Ozone Hole" 698
5. Polar Stratospheric Clouds (PSCs) and Aerosols 703
6. Effects of Volcanic Eruptions 713
7. Ozone Depletion in the Arctic 719
8. Ozone Destruction in the Midlatitudes 723
D. CONTRIBUTION OF BROMINATED ORGANICS 724
1. Sources and Sinks of Brominated Organics 724
2. Bromine Chemistry in the Stratosphere 725
E. CONTRIBUTION OF IODINE-CONTAINING ORGANICS 729
F. SUMMARY 730
G. PROBLEMS 730
REFERENCES 731
Chapter 13. Scientific Basis for Control of Halogenated Organics 750
A. INTERNATIONAL AGREEMENTS ON PHASEOUT OF HALOGENATED ORGANICS 750
B. OZONE DEPLETION POTENTIALS (ODP) 753
C. TRENDS IN CFCs, THEIR REPLACEMENTS, STRATOSPHERIC O3, AND SURFACE UV 756
1. Trends in CFCs and Their Replacements 756
2. Trends in Stratospheric O3 759
3. Trends in Surface Ultraviolet Radiation 764
D. TROPOSPHERIC CHEMISTRY OF ALTERNATE CFCs 767
1. Kinetics of OH Reactions 767
2. Tropospheric Chemistry 769
E. SUMMARY 776
F. PROBLEMS 776
REFERENCES 776
Chapter 14. Global Tropospheric Chemistry and Climate Change 785
A. RADIATION BALANCE OF THE ATMOSPHERE: THE GREENHOUSE EFFECT 786
1. Global Absorption and Emission of Radiation 786
2. Radiative Transfer Processes in the Atmosphere 789
3. Dependence of Net Infrared Absorption on Atmospheric Concentrations 792
B. CONTRIBUTION OF TRACE GASES TO THE GREENHOUSE EFFECT 793
1. Infrared Absorption by Trace Gases 793
2. Trends in Trace Gas Concentrations 796
3. Radiative Forcing by Greenhouse Gases and Global Warming Potentials 806
C. AEROSOL PARTICLES, ATMOSPHERIC RADIATION, AND CLIMATE CHANGE 811
1. Direct Effects 812
2. Indirect Effects of Aerosol Particles 822
D. SOME OTHER FACTORS AFFECTING GLOBAL CLIMATE 837
1. Absorption of Solar Radiation by Clouds 837
2. Feedbacks: Water Vapor, Clouds, and the "Supergreenhouse Effect" 842
3. Solar Variability 844
4. Volcanic Eruptions 845
5. Oceans 845
E. OBSERVATIONS OF CLIMATE CHANGES 846
1. Observed Temperature Trends 846
2. Other Climate Changes 851
F. THE FUTURE 851
G. PROBLEMS 852
REFERENCES 852
Chapter 15. Indoor Air Pollution: Sources, Levels, Chemistry, and Fates 867
A. RADON 867
B. OXIDES OF NITROGEN 869
1. Levels of NOx 869
2. HONO and HNO3 870
C. CO AND SO2 872
D. VOLATILE ORGANIC COMPOUNDS 873
E. OZONE 882
F. INDOOR VOC – NOx – O3 CHEMISTRY 882
G. PARTICLES 884
H. PROBLEMS 888
REFERENCES 888
Chapter 16. Applications of Atmospheric Chemistry: Air Pollution Control Strategies and Risk Assessments for Tropospheric Ozone and Associated Photochemical Oxidants, Acids, Particles, and Hazardous Air Pollutants 894
A. TROPOSPHERIC OZONE AND ASSOCIATED PHOTOCHEMICAL OXIDANTS 894
1. Environmental Chambers 895
2. Isopleths for Ozone and Other Photochemically Derived Species 905
3. Models 909
B. REACTIVITY OF VOC 930
1. Typical Reactivity Scales 930
2. Application to Control of Mobile Source Emissions 932
C. FIELD OBSERVATIONS OF VOC, NOx , AND O3 936
D. ALTERNATE FUELS 941
1. Reformulated Gasolines 941
2. Compressed Natural Gas (CNG) 942
3. Liquefied Petroleum Gas (LPG) 943
4. Alcohol Fuels and Blends with Gasoline 943
5. Hydrogen 944
6. Electric Vehicles 944
E. CONTROL OF ACIDS 944
F. CONTROL OF PARTICLES 946
G. ATMOSPHERIC CHEMISTRY AND RISK ASSESSMENTS OF HAZARDOUS AIR POLLUTANTS 948
H. PROBLEMS 953
REFERENCES 955
Appendix I: Enthalpies of Formation of Some Gaseous Molecules, Atoms, and Free Radicals at 298 K 966
Appendix II: Bond Dissociation Energies 968
Appendix III: Running the OZIPR Model 970
Appendix IV: Some Relevant Web Sites 972
Appendix V: Pressures and Temperatures for Standard Atmosphere 974
Appendix VI: Answers to Selected Problems 975
Subject Index 980

Textauszug

CHAPTER 2 The Atmospheric System

As discussed in Chapter 1, much of our understanding of the chemistry of our atmosphere is based on early studies of air pollution; these are often treated in the context of an overall “system.” This approach starts with the various sources of anthropogenic and natural emissions and tracks the resulting pollutants through their atmospheric transport, transformations, and ambient concentrations—on local, regional, and global scales—to their ultimate chemical and physical fates, including their impacts on our health and environment.

Figure 2.1 is a simplified diagram illustrating the major elements. Primary pollutants are defined as those emitted directly into the air, e.g., SO2, NO, CO, Pb, organics [including HAPS (hazardous air pollutants)], and combustion-generated particulate matter (PM). Sources may be anthropogenic, biogenic, geogenic, or some combination thereof. Once in the atmosphere, they are subjected to dispersion and transport, i.e., meteorology, and simultaneously to chemical and physical transformations into gaseous and particulate secondary pollutants; the latter are defined as those formed from reactions of the primary pollutants in air. Both primary and secondary pollutants are removed at the earth’s surface via wet or dry deposition and, in the processes of transport, transformation, and deposition, can impact a variety of receptors, for example, humans, animals, aquatic ecosystems, forests and agricultural crops, and materials.

FIGURE 2.1 The atmospheric air pollution system.

From a detailed knowledge of the emissions, topography, meteorology, chemistry, and deposition processes, one can develop mathematical models that predict the concentrations of primary and secondary pollutants as a function of time at various locations. Depending on the particular model, these may describe pollutant concentrations over a variety of scales:

• In a plume from a specific point source (plume models)

• In an air basin from a combination of diverse mobile and stationary sources (airshed models)

• Over a large geographical area downwind from a group of sources (long-range transport and regional models)

• Over the entire earth (global models)

To test these models, their predictions must be compared to the observed concentrations of various species; model inputs are adjusted to obtain acceptable agreement between the observed and predicted values. These models can then be used, in combination with the documented impacts on receptors, to develop health and/or environmental risk assessments and various control strategy options.

Finally, through legislative and administrative action, health-protective and cost-effective risk-management decisions can be made, and regulatory actions implemented, that directly affect the starting point of our atmospheric system, that is, the primary emissions and their sources.

To place the remainder of this book on atmospheric chemistry in perspective, the various components of our “atmospheric system” are treated briefly next.

A. EMISSIONS

In describing a given air mass and the chemical reactions occurring therein, one must consider both natural and anthropogenic sources of primary emissions and evaluate their relative importance. Thus the impact on air quality of natural emissions can be an important issue because cost-effective control strategies must take into account the relative strengths of emissions from all sources, not just those of anthropogenic origin. However, it is not only the relative amounts of total emissions that must be considered but also the chemical nature of the emissions, e.g., their reactivities and their temporal and spatial distributions.

Emissions inventories are typically obtained by combining the rate of emissions from various sources (the “emission factors”) with the number of each type of source and the time over which the emissions occur. Inventories are compiled in various formats. For example, they can be assembled for various individual anthropogenic processes such as refining, or natural processes such as volcanic eruptions, in which emissions of all of the relevant species associated with that event are estimated. Alternatively, and more commonly, emissions inventories are compiled by species, showing the various sources that contribute to the total emissions of each.

Emission factors for various sources in the United States have been published by the Environmental Protection Agency in the form of the documentAIRCHIEF, short for the Air Clearing House for Inventories and Emission Factors. Such data are available on CD-ROM as well as on-line through the EPA Web site (see Appendix IV). In Europe, the Commission of the European Communities has published a handbook of emission factors as well (e.g., see CEC (1988, 1989, 1991), McInnes (1996), and Web site in Appendix IV). Emissions inventories and emission factors for Europe are also found in the volume edited by Fenger et al. (1998).

On a global scale, emissions inventories for a variety of species are currently under development under the auspices of the International Global Atmospheric Chemistry Project (IGAC), and various available inventories are described by Graedel et al. (1993). Data for some of the major pollutants follow.

1. Oxides of Nitrogen

We shall follow here the convention in current use that defines NOx as the sum of (NO + NO2) and NOy as the sum of all reactive nitrogen-containing species, e.g., NOy = (NO + NO2 + HNO3 + PAN + HONO + NO3 + N2O5 + organic nitrates etc.). By far the most significant species emitted by anthropogenic processes is nitric oxide, produced when N2 and O2 in air react during high-temperature combustion processes. In addition, some NOx is formed from nitrogen in the fuel. Smaller amounts of NO2 are produced by the further oxidation of NO; trace amounts of other nitrogenous species such as HNO3 are also formed.

The fraction of the total that is emitted as NO clearly depends on the conditions associated with the specific combustion process. While most (typically > 90%) of the NOx emitted is believed to be in the form of NO, the fraction of NO2 can vary from less than 1% to more than 30% (e.g., Lenner, 1987).

Figure 2.2 shows the contribution of various sources to the total anthropogenic NOx emissions, 23 × 106 short tons, or 21 Tg (expressed as NO2), in the United States in 1996 (1 Tg = 1 teragram = 1012 g and one short ton = 0.907 × 106 g). This can be compared to total global anthropogenic emissions of approximately 72 Tg of NOx (expressed as NO2) (Müller, 1992).

FIGURE 2.2 Contribution of various sources to total anthropogenic NOx emissions in the United States in 1996.

(from EPA, 1999)

Figure 2.3 shows the trend in NOx emissions for North America, Europe, the USSR, and Asia from 1970 to 1986 (Hameed and Dignon, 1992). While those of North America and Europe have decreased or leveled off, those from Asia and the USSR increased significantly, a trend that has continued. Figure 2.4a shows the geographical pattern of the emission flux of NOx in Asia in 1987 (Akimoto and Narita, 1994). Clearly, Japan and China are major contributors to the flux of NOx in this region, with the City of Tokyo having the highest emission flux rate.

FIGURE 2.3 NOx emissions in million tons of equivalent NO2 for the period 1970 to 1986 for Asia, Europe, North America, and the USSR.

(from Hameed and Dignon, 1992)

FIGURE 2.4 (a) Pattern of 1987 annual emission flux of NOx. in Asia (in units of millimoles as N per m2 per year) (from Akimoto and Narita, 1994). (b) Estimated relative rates of biogenic emissions of NO in the United States in 1990.

(from EPA, 1995)

There are also significant natural sources of oxides of nitrogen, in particular nitric oxide, which is produced by biomass burning as well as by soils where nitrification, denitrification, and the decomposition of nitrite (NO2−) contribute to NO production. Figure 2.4b, for example, shows the relative emission rates for biogenically produced NO in the United States in 1990 (EPA, 1995).

Another important natural source is NOx produced by lightning, with recent estimates in the range of 10–33 Tg yr−1 as NO2 (Flatøy and Hov, 1997; Price et al., 1997a, 1997b; Wang et al., 1998). By comparison to the estimated emissions from biomass burning and continental biogenic sources (Table 2.1), it is seen that lightning is quite important.

TABLE 2.1 Global Emission Estimates for CO, NOx, CH4, and VOC from Both Anthropogenic and Natural Sources (in Tg/yr)a

There is also some NO produced from the oxidation of NH3 by photochemical processes in oceans and by some terrestrial...

Produkt-Details

• Erscheint lt. Verlag: 17.11.1999
• Sprache: englisch
• Themenwelt: Sachbuch/Ratgeber
• Themenwelt: Naturwissenschaften ► Biologie ► Ökologie / Naturschutz
• Themenwelt: Naturwissenschaften ► Chemie ► Analytische Chemie
• Themenwelt: Naturwissenschaften ► Chemie ► Physikalische Chemie
• Themenwelt: Naturwissenschaften ► Chemie ► Technische Chemie
• Themenwelt: Naturwissenschaften ► Geowissenschaften ► Meteorologie / Klimatologie
• Themenwelt: Naturwissenschaften ► Physik / Astronomie ► Angewandte Physik
• Themenwelt: Sozialwissenschaften ► Soziologie
• Themenwelt: Technik ► Bauwesen
• Themenwelt: Technik ► Umwelttechnik / Biotechnologie
• ISBN-10: 0-08-052907-0 / 0080529070
• ISBN-13: 978-0-08-052907-3 / 9780080529073