Protecting Visibility in National Parks and Wilderness Areas -- Copyright -- Preface -- Other Recent Reports of the Board on Environmental Studies and Toxicology -- Contents -- Protecting Visibility in National Parks and Wilderness Areas Executive Summary -- THE CHARGE TO THE COMMITTEE -- THE COMMITTEE'S APPROACH TO ITS CHARGE -- GENERAL CONCLUSIONS AND RECOMMENDATIONS -- RECOMMENDED RESEARCH -- Monitoring Strategies -- Measurement Methods -- Source-Apportionment Modeling -- Emission Controls -- FUTURE DIRECTIONS FOR PROTECTING AND IMPROVING VISIBILITY -- Protecting Visibility in National Parks and Wilderness Areas -- 1 Introduction -- HAZE FORMATION AND VISIBILITY IMPAIRMENT -- DIFFICULTIES IN DEVELOPING EFFECTIVE PROGRAMS -- Scientific Difficulties -- Regulatory Difficulties -- SCOPE OF THE REPORT -- 2 Visibility Conditions in the United States -- CURRENT VISIBILITY CONDITIONS -- Geographical Patterns -- Seasonal Patterns -- Statistical Patterns -- Historical Trends -- SOURCES OF VISIBILITY-IMPAIRING MATERIALS -- Natural Sources -- Anthropogenic Sources -- SUMMARY -- 3 Legal and Institutional Context -- PRESENT VISIBILITY PROTECTION PROGRAMS -- The Clean Air Act -- Relevant Provisions -- Basic Principles -- Implementation of the Visibility Protection Programs -- Funding Issues -- State Visibility Protection Programs -- Oregon -- Washington -- Vermont -- ALTERNATIVE REGULATORY APPROACHES -- Air Quality Management Approach -- Technology-Based Approach -- Nondegradation Approach -- Market-Based Approaches -- The Present Visibility Program Compared with Possible Future Approaches -- SUMMARY -- 4 Haze Formation and Visibility Impairment -- FUNDAMENTALS OF VISIBILITY AND RELATED MEASUREMENTS -- Fundamental Processes in Visibility -- Visibility Measurements -- Relationship between Particle Concentrations and Visibility.

Empirical Relationships between Airborne Particles and Visibility -- Aerosol Chemistry and Particle Size Distributions -- Particle Optics and Visibility -- Some Experimental Difficulties in Aerosol Chemistry Studies -- THE ROLE OF METEOROLOGY -- Transport -- Dispersion -- Deposition and Resuspension -- Wet Deposition -- Dry Deposition -- Resuspension of Soil Dust -- STRATEGIES FOR VISIBILITY MEASUREMENT PROGRAMS -- Criteria for Monitoring Programs -- Examples of Visibility Measurement Programs -- The Interagency Monitoring of Protected Visual Environments Program -- State Programs -- Intensive Programs -- MODELING OF AEROSOL EFFECTS ON VISIBILITY -- Optical Modeling (Mie Theory) -- Empirical Optical Models -- Perceptual Air-Quality Modeling -- EXPERIMENTAL DESIGN, QUALITY ASSURANCE, AND QUALITY CONTROL -- SUMMARY AND CONCLUSION -- 5 Source Identification and Apportionment Methods -- CRITERIA FOR EVALUATING SOURCE IDENTIFICATION AND APPORTIONMENT METHODS -- Technical Adequacy -- Validity -- Compatibility of Source and Optics Models -- Input Data Requirements -- Evaluation of Model Performance -- Source Separation -- Temporal Variability -- Geographic Context -- Source Configurations -- Error Analysis and Biases -- Availability -- Administrative Feasibility -- Resources -- Regulatory Compatibility -- Multijurisdictional Implementation -- Communication -- Economic Efficiency -- Flexibility -- Balance -- CRITIQUE OF SOURCE IDENTIFICATION AND APPORTIONMENT METHODS -- Source Identification Methods -- Visual and Photographic Systems -- Emission Inventories and Source Activity -- Simple Tracer Applications -- Evaluation of Source Identification Methods -- Speciated Rollback Models -- Technical Adequacy -- Administrative Feasibility -- Economic Efficiency -- Flexibility -- Balance -- Summary -- Chemical Mass Balance Receptor Models -- Technical Adequacy.

Administrative Feasibility -- Economic Efficiency -- Flexibility -- Balance -- Summary -- Models Based on Regression Analysis -- Technical Adequacy -- Administrative Feasibility -- Economic Efficiency -- Flexibility -- Balance -- Models for Transport Only and Transport with Linear Chemistry -- Technical Adequacy -- Administrative Feasibility -- Economic Efficiency -- Flexibility -- Balance -- Mechanistic Models for Transport and Explicit Chemistry -- Technical Adequacy -- Administrative Feasibility -- Economic Efficiency -- Flexibility -- Balance -- Summary -- Hybrid Models -- SINGLE-SOURCE MODELING PROBLEMS -- Widespread Haze and Plume Blight -- Critique of Single-Source Plume Blight Models -- Technical Adequacy -- Administrative Feasibility -- Flexibility -- Balance -- Bridging the Gap between Near-Source Models and the Regional Scale -- SELECTION OF MODELS TO ADDRESS OTHER AIR-QUALITY PROBLEMS -- SUMMARY -- 6 Emission Controls and Visibility -- APPORTIONMENT OF REGIONAL HAZE USING A SPECIATED ROLLBACK MODEL -- POTENTIAL VISIBILITY IMPROVEMENTS FROM EMISSION CONTROLS -- RELATIONSHIP BETWEEN VISIBILITY AND OTHER AIR-QUALITY PROBLEMS -- CONCLUSIONS -- 7 Conclusions and Recommendations -- GENERAL CONCLUSIONS -- RECOMMENDED RESEARCH STRATEGIES -- RECOMMENDED MONITORING STRATEGIES -- RECOMMENDED MEASUREMENT METHODS -- Aerosol Measurements -- Optical Measurements -- RECOMMENDED SOURCE APPORTIONMENT MODELING RESEARCH -- Emission Inventories -- Source emissions data must be integrated accurately into overall emission inventories -- Model Validation and Field Studies -- Receptor Models -- Mechanistic Models -- RECOMMENDED CONTROL TECHNOLOGY RESEARCH -- SUMMARY -- References -- Appendix A Scientific Background Information -- ATMOSPHERIC CHEMISTRY AND SECONDARY PARTICLE PRODUCTION -- Sulfate Aerosol Chemistry -- Nitrate Aerosol Chemistry.

Ammonium Aerosol Chemistry -- Organic Aerosol Chemistry -- METEOROLOGY -- Surface-Wind Measurements -- Non-Surface-Wind Measurements -- Balloon Studies -- Tower Studies -- Remote Sensing -- Moisture Measurements -- Appendix B Measurement Methods -- GAS-PHASE CHEMICAL MEASUREMENTS -- Gaseous Sulfur Dioxide -- Oxides of Nitrogen -- Ozone -- Ammonia -- Hydrogen Peroxide -- Gas-Phase Organic Carbon Compounds -- Conclusions -- MEASUREMENTS OF ATMOSPHERIC PARTICLES -- Particle Size Distribution -- Single-Particle Optical Counters -- Electrical Mobility Analyzers -- Particle Mass and Chemical Size Distributions -- Particle Bounce -- Particle Shape and Density -- Chemical Changes in the Sample -- Sampling Inlets -- Electron Microscopic Analyses of Single Particles -- Organic and Elemental Carbon Analysis -- Water Content of Airborne Particles -- Continuous Measurements -- OPTICAL MEASUREMENTS -- Point-Measurement Methods -- Scattering-Coefficient Measurements: Integrating Nephelometry -- Absorption Coefficient Measurements -- Photoacoustic Spectroscopy -- Filter Techniques -- Sight-Path Techniques -- Remote Sensing Techniques -- Summary -- TRACERS IN THE ENVIRONMENT -- PERCEPTION MEASUREMENT -- Human Response to Visual Air Quality -- Field Judgments by Experienced Observers -- Judgments of Photographs -- Field Judgments by Passersby -- Airport Visibility -- Perceptual Cues -- Summary -- Appendix C Source Identification and Apportionment Models -- SPECIATED ROLLBACK MODELS -- RECEPTOR-ORIENTED MODELS BASED ON CHEMICAL SIGNATURES -- CMB Models -- Theory of the CMB Model -- Derivation and Solutions -- CMB Model Assumptions -- CMB Model Validation Studies -- Apportionment of Light Extinction -- Regression Analysis -- Background -- Statistical Assumptions and Consequences of Violation -- Practical Guidelines -- PLUME BLIGHT MODELS.

MODELS FOR TRANSPORT ONLY AND FOR TRANSPORT WITH LINEAR CHEMISTRY -- Back Trajectory Analysis -- Transport-Only Analyses -- Transport with Linear Chemistry -- MECHANISTIC MODELS FOR TRANSPORT AND CHEMICAL REACTION -- Hybrid Models -- Linear-Chemistry-CMB Hybrid Models -- Appendix D Control Techniques -- POWER PLANTS -- Sulfur Dioxide Control Technologies -- Wet Flue Gas Desulfurization -- Spray Dry Flue Gas Desulfurization -- Control of Plume Opacity -- NOx Emissions Control -- NOx Reduction by Combustion Modification -- Postcombustion NOx Reduction -- Clean Coal Technologies -- Sorbent Injection -- Fluidized Bed Combustion -- Combined NOx and SOx Reduction -- Integrated Gasification Combined Cycle -- Integrated Gasification Fuel Cell -- Alternative Emission Reduction Methods -- Switching to Low-Sulfur Coal -- Switching to Natural Gas -- Environmental Dispatching -- Energy Efficiency and Demand Management -- INDUSTRIAL BOILERS -- NONFERROUS SMELTERS -- PETROLEUM AND CHEMICAL INDUSTRIES -- Sulfur Oxide Control at Refineries and Chemical Plants -- Control of VOC Emissions from Petroleum Refining and Marketing -- DIESEL-FUELED MOTOR VEHICLES -- Trap Oxidizers -- Catalytic Converters -- GASOLINE-FUELED MOTOR VEHICLES -- Fuel Modification -- Natural Gas -- Liquified Petroleum Gas -- Methanol -- PRESCRIBED FORESTRY AND AGRICULTURAL BURNING -- Prescribed Forestry Burning -- Emission Control Measures -- Control Costs -- Alternative Treatment Methods -- Agricultural Burning -- Other Biomass Burning -- Future Directions -- RESIDENTIAL WOOD COMBUSTION -- Wood-Stove Emissions -- Wood-Burning Control Technologies -- Public Education Programs -- Wood-Stove Certification Programs -- Reduced Dependence on Wood -- Wood-Burning Curtailment -- Future Conditions -- FUGITIVE DUST -- Agricultural Operations -- Paved and Unpaved Road Dust -- Process Fugitives.

FEEDLOTS AND OTHER SOURCES OF AMMONIA.