### Spatial and Seasonal Patterns a nd Temporal Variability of Haze and its Constituents in the United States Report IV

Principal Author: Linsey J. DeBell 1

1 Cooperative Institute for Research in the Atmosphere Colorado State University Fort Collins, CO 80523-1375

Contributors: Kristi A. Gebhart 2

Jenny L. Hand 1

William C. Malm 2

Marc L. Pitchford 3

Bret A. Schichtel 2

Warren H. White 4

2 National Park Service CSU/CIRA Fort Collins, CO 80523-1375

3 National Oceanic and Atmospheric Administration Desert Research Institute Las Vegas, NV 89119-7363

4 Crocker Nuclear Laboratory University of California

Davis, CA 95616-8569

Disclaimer The assumptions, findings, conclusions, judgments , and views presented he rein are those of the authors and should not be interpreted as necessa rily representing the National Park Service or National Oceanic and Atmosphe ric Administration policies.i TABLE OF CONTENTS

Overview and Summary ........................................................................................................... ...S-1

S.1 Optical and Aerosol Data ................................................................................................S-2 S.2 Spatial Trends in Aerosol C oncentration and Extinction................................................S-6 S.3 Spatial Variability Of Average Monthly Patt erns In Fine Aerosol Species Concentrations And Aerosol Extinction Coefficients......................................................................................S-14 S.4 Temporal Trends in Fine Aerosol Species Concentrations and Aerosol Extinction.....S-18 S.5 IMPROVE Data Quality Assurance..............................................................................S-19 S.6 Special Studies Associated with the IMPROVE program ............................................S-19 References..................................................................................................................... .............S-21 Chapter 1: IMPROVE Network – Purpose, Design, and History................................................... 1 1.1 Objectives of Visibility Mon itoring under the IMPROVE Program.................................. 2 1.2 Overview of the IMPROVE Monitoring Network............................................................. 4 1.2.1 Current and Histori cal Sampler Siting ......................................................................... 4 1.2.2 Aerosol Sampling and Analysis ................................................................................. 14 1.2.3 Optical Sampling and Analysis.................................................................................. 20 1.3 Protocol and Equipment Changes .................................................................................... 24 1.3.1 Analytical Changes .................................................................................................... 25 1.3.1.1. Transition from PIXE to XRF .......................................................................... 25 1.3.1.2. Alternate Nylon Filter Extraction Procedure .................................................... 25 1.3.2 Sampling Equipment Changes ................................................................................... 26 1.3.2.1. Transition from Version I to Version II IMPROVE Sampler .......................... 26 1.3.2.2. Denuder Coating Modified ............................................................................... 26 1.3.2.3. Changes in Nylon Filter Size ............................................................................ 26 1.3.2.4. Changes in Nylon Filter Manufacturer ............................................................. 26 1.3.3 Data Processing Changes ........................................................................................... 27 1.3.3.1. Change in the Reporting of Gravimetric Measurements .................................. 27 1.3.3.2. Change in Batch Size Used in Da ta Processing Routines at CNL.................... 27 1.3.3.3. Change in Flow Rate Validation Flag Definitions............................................ 27 1.3.3.4. Change in Flow Rate Calculations.................................................................... 27 1.3.3.5. Spectral Corrections to S and Al Data from the XRF Cu Anode System ........ 28 1.3.3.6. Change in the Reporting of Organic Pyrolyzed Carbon (OP) Concentrations ...... 28 1.4 The Comparison of Concentrations fro m Collocated IMPROVE and STN Monitoring Sites ......................................................................................................................... ................. 29 References..................................................................................................................... ................ 31 Chapter 2: Spatial Distributions of Reconstr ucted Mass and Mass Budge ts and Reconstructed Light Extinction and Light-Extinction Budgets .................................................................... 33 2.1 Estimation of Aerosol Species Mass ................................................................................ 33 2.2 Reconstructing Light Extinction from Aerosol Measurements........................................ 36 2.2.1 Extinction Model........................................................................................................ 3 7ii 2.3 Completeness Criteria ...................................................................................................... 41 2.4 Spatial Trends in Aerosol Concen trations in the United States ....................................... 42 2.4.1 Fine Particle Ammonium Sulfate Mass ..................................................................... 42 2.4.2 Fine Particle Carbon Mass ......................................................................................... 44 2.4.3 Fine Particle Ammonium Nitrate Mass...................................................................... 46 2.4.4 Fine Particle Soil Mass............................................................................................... 47 2.4.5 Reconstructed Fine Mass ........................................................................................... 48 2.4.6 Coarse Mass .............................................................................................................. . 49 2.5 Spatial Trends in Particulate Extinction in the United States........................................... 63 2.5.1 Fine Particle Ammonium Sulfate Extinction ............................................................. 63 2.5.2 Fine Particle Carbon Extinction ................................................................................. 64 2.5.3 Fine Particle Ammonium Nitrate Extinction ............................................................. 65 2.5.4 Fine Particle Soil Extinction ...................................................................................... 65 2.5.5 Coarse Mass Particle Extinction ................................................................................ 66 2.5.6 Total Reconstructed Particulate Extinction (b ext )....................................................... 67 2.5.7 Visibility Expressed in Deciviews ............................................................................. 67 References..................................................................................................................... ................ 80 Chapter 3: Spatial Variability of Average Monthly Patterns in Fine Aerosol Species Concentrations and Particulat e Extinction Coefficients ............................................................... 86

3.1 Spatial Variability of Average Monthly Patterns in Fine Aerosol Species Concentrations ... 87 3.1.1 Fine Particle Ammonium Sulfate Mass ..................................................................... 87 3.1.2 Fine Particle Organic Carbon Mass ........................................................................... 88 3.1.3 Fine Particle Light-Absorbing Carbon Mass ............................................................. 89 3.1.4 Fine Particle Ammonium Nitrate Mass...................................................................... 90 3.1.5 Fine Particle Soil Concentrations............................................................................... 91 3.2 Spatial Variability of Average Monthly Patt erns in Particulate Ex tinction Coefficients105 3.2.1 Fine Particle Ammonium Sulfate Extinction ........................................................... 105 3.2.2 Fine Particle Organic Carbon Extinction ................................................................. 106 3.3 Fine Particle Light-Absorbing Carbon Extinction ......................................................... 107 3.3.1 Fine Particle Ammonium Nitrate Extinction ........................................................... 107 3.3.2 Fine Particle Soil Extinction .................................................................................... 108 3.3.3 Coarse Particle Mass Extinction .............................................................................. 108 References..................................................................................................................... .............. 119 Chapter 4: Temporal Trends in Fine Aerosol Species Concentrations and Aerosol Extinction. 120

4.1 Estimating Measurement Uncertainty in an Ambient Sulfate Trend ............................. 120 4.2 A 10-Year Spatial and Temporal Trend of Sulfate across the United States ................. 122 4.2.1 Introduction............................................................................................................. . 122 4.2.2 Yearly Temporal Trends of the 20 thand 80 thPercentile SO 4 = Concentrations........ 123 4.2.3 Yearly Temporal Trends of NET SO 2 Emissions .................................................... 125 4.2.4 Regional Comparisons of SO 2 Emissions and SO 4 = Concentrations ....................... 126 4.3 Trends in the Haze Index................................................................................................ 127iii 4.4 Organic and Elemental Carbon Long-Term Trends and Spatial Patterns in the Rural United States.................................................................................................................. .......... 129 4.4.1 Introduction............................................................................................................. . 129 4.4.2 EC and OC Long-Term Trends................................................................................ 130 4.5 VIEWS Annual Summary Trends Tools........................................................................ 133 References..................................................................................................................... .............. 135 Chapter 5: IMPROVE Data Quality Assurance.......................................................................... 137

5.1 Overview of the IMPROVE Network’s Qual ity Assurance System and Data Validation Procedures Conducted by CIRA.............................................................................................. 137 5.1.1 Sampling and Analysis............................................................................................. 138 5.1.2 Overview of the IMPROVE QA System ................................................................. 138 5.1.2.1. Roles and Responsibilities .............................................................................. 138 5.1.2.2. Data Quality Objectives.................................................................................. 139 5.1.2.2.1. Precision, Accuracy, and MQL/MDL ...................................................... 139 5.1.2.2.2. Completeness............................................................................................ 139 5.1.2.2.3. Representativeness.................................................................................... 139 5.1.2.2.4. Comparability ........................................................................................... 140 5.1.2.3. Documentation................................................................................................ 140 5.1.3 Data Validation ........................................................................................................ 14 0 5.1.3.1. Data Integrity Tests Performed at CIRA ........................................................ 141 5.1.3.2. Spatial and Temporal Comparabil ity Checks Performed at CIRA................. 142 5.1.3.2.1. Mass.......................................................................................................... 142 5.1.3.2.2. Sulfate....................................................................................................... 144 5.1.3.2.3. Soil Elements............................................................................................ 149 5.1.3.2.4. Carbon ...................................................................................................... 154 5.1.3.2.5. Nitrate ....................................................................................................... 156 5.1.3.2.6. Cut Point................................................................................................... 157 5.1.4 Examples of Data Quality Issues Discovered by CIRA in the 2004 Data ............... 158 5.1.5 Glossary of Terms .................................................................................................... 164 5.1.6 Data Acquisition, Quality Control, and Data Management ..................................... 165 5.1.6.1. A.1 Sample Handling...................................................................................... 165 5.1.6.2. A.2 Sample Analysis....................................................................................... 166 5.1.7 Data Validation Activities at CNL........................................................................... 168 5.1.7.1. Flow Rate Audits and An alysis Performed by CNL....................................... 168 5.1.7.2. Accuracy, Uncertainty, and MQL Checks on QC Samples Performed at CNL .. 169 5.1.7.3. Internal Consistency Checks Performed at CNL............................................ 170 5.1.7.3.1. Iron............................................................................................................ 170 5.1.7.3.2. Mass.......................................................................................................... 170 5.1.7.3.3. Sulfate....................................................................................................... 170 5.1.7.3.4. Carbon ...................................................................................................... 170 5.2 Outcomes from a Historical Review of IMPROVE Data .............................................. 171iv 5.2.1 Introduction............................................................................................................. . 171 5.2.2 Measured Fine Mass versus R econstructed Fine Mass Review............................... 171 5.2.3 Sulfate Review ......................................................................................................... 17 1 5.2.4 Soil ..................................................................................................................... ...... 172 5.2.5 Carbon ................................................................................................................... ... 173 5.2.6 Nitrate.................................................................................................................. ..... 173 5.2.7 Cut Point................................................................................................................ ... 174 5.3 Nitrate Sampling Methods Investigation........................................................................ 175 5.3.1 Introduction............................................................................................................. . 175 5.3.2 Methods.................................................................................................................. .. 175 5.3.2.1. Field Sites ....................................................................................................... 175 5.3.2.2. Sampling and Analysis Protocol for Filter Comparisons ............................... 175 5.3.2.3. Sampling and Analysis Protocol for Denuder Comparisons .......................... 176 5.3.3 Conclusions .............................................................................................................. 176 5.3.3.1. Particulate Nitrate Measur ement Using Nylon Filters.................................... 176 5.3.3.2. Loss of Fine Particle Ammoni um from Denuded Nylon Filters .................... 177 5.3.3.3. Efficiency of IMPROVE Network De nuders for Removing Nitric Acid....... 177 References..................................................................................................................... .............. 178 Chapter 6: Special Monitoring Studies & Data Analyses Associated with the IMPROVE Program........................................................................................................................ ............... 179

6.1 Executive Summary: Big Bend Regional Aeroso l and Visibility Ob servational (BRAVO) Study Results: Air Quality Data and Source A ttribution Analyses Results from the National Park Service / Cooperative Institute for Research in the Atmosphere .................................... 180 6.1.1 Characterization of Big Bend’s Haze....................................................................... 181 6.1.2 Apportionment of Big Bend’s Sulfate Haze ............................................................ 183 6.1.2.1. Spatial Patterns of Aerosol Components ........................................................ 185 6.1.2.2. Airmass Transport to Big Bend dur ing BRAVO Days with High and Low Particulate Sulfate Concentrations.................................................................................. 185 6.1.2.3. Quantitative Source Apportionment of Big Bend’s Sulfate Haze .................. 187 6.1.2.4. The Contribution of Sulfur Source Regi ons to Particulate Haze Levels at Big Bend National Park during the BRAVO Study Period................................................... 190 6.1.3 Application of the Source Attribution Results to Ot her Months and Years ............ 193 6.1.4 Implications............................................................................................................. . 194 6.2 Executive Summary: The Yosemite Aerosol Characterization Study ........................... 196 6.2.1 Study Objectives ...................................................................................................... 197 6.2.2 Study Findings ......................................................................................................... 19 7 6.3 Executive Summary: Review of the IMPR OVE Equation for Estimating Ambient Light Extinction Coefficients ........................................................................................................ .... 203 6.3.1 Introduction............................................................................................................. . 203 6.3.2 Particulate Organi c Matter and the R oc Multiplier ................................................... 204 6.3.3 Scattering Enhancement Curve ( f(RH) ) ................................................................... 206v 6.3.4 Sea Salt................................................................................................................. .... 207 6.3.5 Mass Scattering Efficiencies .................................................................................... 208 6.3.6 Site-Specific Rayleigh Scattering ............................................................................ 210 6.3.7 Light Absorption by NO 2 ......................................................................................... 210 6.3.8 New IMPROVE Equation........................................................................................ 210 References..................................................................................................................... .............. 212

6.4 Coarse Particle Speciation at Selected Locations in the Rural Continental United States .. 215 Abstract....................................................................................................................... ................ 215 6.4.1 Introduction............................................................................................................. . 215 6.4.2 Particulate Samplers................................................................................................. 216 6.4.3 Estimation of Aerosol Mass ..................................................................................... 217 6.4.4 The Data Set............................................................................................................. 219 6.4.5 Spatial Variability of Coarse and Fine Monthly Patterns in Species Mass Concentrations ................................................................................................................. ... 220 6.4.6 Summary .................................................................................................................. 227 References..................................................................................................................... .............. 229

6.5 The Comparability of IMPROVE and STN Measurements—A Summary of the Results and Conclusions from an Analysis of Collocat ed Measurements Detailed in Appendix E .... 238 Chapter 7: Bibliography of Journa l Articles using IMPROVE Data.......................................... 241

Appendices A–E available on cd or at http://vista.cira.colostate.edu/improve/Publications/improve_reports.htm

Appendix A: Annual Average Reconstructed Fi ne Mass and Aerosol Extinction Budgets for Each Site

Appendix B: Seasonal and Annual Regional Re constructed Fine Mass and Reconstructed Extinction Budgets

Appendix C: Monthly and Annual Reconstructe d Fine Mass and Reconstructed Extinction and their Associated Budgets from th e IMPROVE Network for 2000 through 2004

Appendix D: Articles Reporting the Results from IMPROVE Special Monitoring Studies Conducted since 2000

Appendix E: An Assessment of Measurement Erro rs in the IMPROVE and STN Networks from In-Network and Cross-Network Collocated Data and the Estimated Co mparability of Data Collected from the Two Networksvi LIST OF FIGURES

Figure S.1. The locations current and disc ontinued IMPROVE and IMPROVE protocol monitoring sites as of December 2004. The IMPR OVE regions used for grouping the sites in some analyses in this report are indicated by gr een shading and bold text. Urban sites included in the IMPROVE network for quality assurance purposes are identified by stars. .........................S-5 Figure S.2. Five-year average (2000–2004) deciview (DV) using only IMPROVE data. ..........S-8 Figure S.3. Five-year average ( 2000–2004) reconstructed particulat e light extinction using only IMPROVE data................................................................................................................... .........S-9 Figure S.4. Five-year average (2000–2004) sulfate light scattering using only IMPROVE data .....S-9 Figure S.5. Five-year average (2000–2004) sulfate light scatte ring using IMPROVE and STN data........................................................................................................................... ..................S-10 Figure S.6. Five-year average ( 2000–2004) organic carbon light sc attering using only IMPROVE data........................................................................................................................... ..................S-10 Figure S.7. Five-year average ( 2000–2004) organic carbon light sc attering using IMPROVE and STN data. ...................................................................................................................... .............S-11 Figure S.8. Five-year average (2000–2004) ammonium nitrate light scattering using only IMPROVE data................................................................................................................... .......S-11 Figure S.9. Five-year average (2000–2004) ammonium nitrate lig ht scattering using IMPROVE and STN data................................................................................................................... ...........S-12 Figure S.10. Five-year average (2000–2004) fine soil light scatte ring using only IMPROVE data.

............................................................................................................................... .....................S-12 Figure S.11. Five-year average (2000–2004) fine soil light scat tering using IMPROVE and STN data. Note comparisons of collocated data indica te the STN fine soil c oncentrations and light scattering were typically 30% smaller th an from the IMPROVE monitors. .............................S-13 Figure S.12. Five-year average (2000–2004) coarse mass light sc attering using only IMPROVE data........................................................................................................................... ..................S-13 Figure S.13. Monthly particulate co ntributions to reconstructed b ext (Mm -1 ) for regions in the eastern United States using IMPROVE data (t op) and STN data (bottom). Note, STN does not

measure coarse mass............................................................................................................ ......S-15 Figure S.14. Monthly particulate co ntributions to reconstructed b ext (Mm -1 ) for regions in the southwestern United States usi ng IMPROVE data (top) and STN data (bottom). Note, STN does not measure co arse mass........................................................................................................ ....S-16 Figure S.15. Monthly particulate co ntributions to reconstructed b ext (Mm -1 ) for regions in the northwestern United States usi ng IMPROVE data (top) and STN data (bottom). Note, STN does not measure co arse mass........................................................................................................ ....S-17 Figure 1.1. All Class I areas of the contiguous Unite d States are identified on the map. The color coding identifies the managing agency of each Class I area. ......................................................... 3 Figure 1.2. The locations of IMPROVE and IM PROVE protocol sites are shown for all discontinued and current sites as of December 2004. The IMPROVE regions used for groupingvii the sites in some analyses in this report are indicated by green shading and italicized text. Urban sites included in the IMPROVE network for qualityassurance purposes are identified by stars. . 5 Figure 1.3. Schematic view of the IMPROVE sample r showing the four modules with separate inlets and pumps. The substrates with analys es performed for each module are also shown. .... 15 Figure 1.4. Schematic of a new version of the IMPROVE sampler PM 2.5 module...................... 17 Figure 2.1. RH factors (f T (RH)) derived from Tang’s ammo nium sulfate growth curves smoothed between the crystallization and deliquescence points. ................................................. 39 Figure 2.2. Isopleth maps of annual ammonium sulf ate concentrations inpanels a and b and percent contributions to reconstructed fine mass in panels c and d. Panels a–d include all sites from the IMPROVE network that met the prescrib ed completeness criteria including the urban sites from 2000–2004. Panels b and d also include all sites from the STN network that met the prescribed completeness criteria............................................................................................... .... 52 Figure 2.3. Isopleth maps of annual total carbon con centrations. Panels a and b include all sites from the IMPROVE network that met the prescrib ed completeness criteria including the urban sites for 2000–2004. Panel b also includes all sites from the STN network that met the prescribed completeness criteria............................................................................................... .... 53 Figure 2.4. Isopleth maps of annual organic carbon c oncentrations in panels a and b and percent contributions to reconstructed fine mass in panels c and d. Panels a–d include all sites from the IMPROVE network that met the prescribed comp leteness criteria including the urban sites for 2000–2004. Panels b and d also include all sites from the STN network that met the prescribed completeness criteria.......................................................................................................... ........... 55 Figure 2.5. Isopleth maps of annual light-absorbing carbon concentrations in panels a and b and percent contributions to reconstructed fine mass in panels c and d. Panels a–d include all sites from the IMPROVE network that met the prescrib ed completeness criteria including the urban sites for 2000–2004. Panels b and d also include all sites from the STN network that met the prescribed completeness criteria............................................................................................... .... 57 Figure 2.6. Isopleth maps of annual ammonium nitr ate concentrations inpanels a and b and percent contributions to reconstructed fine mass in panels c and d. Panels a–d include all sites from the IMPROVE network that met the prescrib ed completeness criteria including the urban sites for 2000–2004. Panels b and d also include all sites from the STN network that met the prescribed completeness criteria............................................................................................... .... 59 Figure 2.7. Isopleth maps of annual soil concen trations in panels a and b and percent contributions to reconstructed fine mass in panels c and d. Panels a–d include all sites from the IMPROVE network that met the prescribed comp leteness criteria including the urban sites for 2000–2004. Panels b and d also include all sites from the STN network that met the prescribed completeness criteria.......................................................................................................... ........... 61 Figure 2.8. Isopleth maps of annual reconstructed fine mass concentrations. Panels a and b include all sites from the IMPR OVE network that met the prescribed completeness criteria including the urban sites for 2000–2004. Panel b al so includes all site s from the STN network that met the prescribed co mpleteness criteria. .............................................................................. 62viii Figure 2.9. Isopleth map of annual coarse mass concentrations; includes all sites from the IMPROVE network that met the prescribed comp leteness criteria including the urban sites for 2000–2004...................................................................................................................... ............... 63 Figure 2.10. Isopleth maps of annual ammonium sulfat e extinction coefficients in panels a and b and percent contribution to recons tructed particulate extinction in panel c. Panels a, b, and c include all sites from the IMPR OVE network that met the prescribed completeness criteria including the urban sites for 2000–2004. Panel b al so includes all site s from the STN network that met prescribed completeness criteria..................................................................................... 6 9 Figure 2.11. Isopleth maps of annual organic mass by carbon extinction coefficients in panels a and b and percent contribution to r econstructed particulate extinction in panel c. Panels a, b, and c include all sites from the IMPROVE network th at met the prescribed completeness criteria including the urban sites for 2000–2004. Panel b al so includes all site s from the STN network that met prescribed completeness criteria..................................................................................... 7 1 Figure 2.12. Isopleth maps of annua l light-absorbing carbon extinction coefficients in panels a and b and percent contribution to r econstructed particulate extinction in panel c. Panels a, b, and c include all sites from the IMPROVE network th at met the prescribed completeness criteria including the urban sites for 2000–2004. Panel b al so includes all site s from the STN network that met prescribed completeness criteria..................................................................................... 7 3 Figure 2.13. Isopleth maps of annual ammonium nitrat e extinction coefficients in panels a and b and percent contribution to recons tructed particulate extinction in panel c. Panels a, b, and c include all sites from the IMPR OVE network that met the prescribed completeness criteria including the urban sites for 2000–2004. Panel b al so includes all site s from the STN network that met prescribed completeness criteria..................................................................................... 7 5 Figure 2.14. Isopleth maps of annual fine soil exti nction coefficients in panels a and b and percent contribution to reconstructe d particulate extinction in panel c. Panels a, b, and c include all sites from the IMPROVE network that met th e prescribed completeness criteria including the urban sites for 2000–2004. Panel b also includes all sites from the ST N network that met prescribed completeness criteria............................................................................................... .... 77 Figure 2.15. Isopleth maps of annual coarse mass ex tinction coefficients in panel a and percent contribution to reconstructed part iculate extinction in panel b. Panels a an d b include all sites from the IMPROVE network that met the prescrib ed completeness criteria including the urban sites for 2000–2004............................................................................................................ ........... 78 Figure 2.16. Isopleth map of annual tota l reconstructed partic ulate extinction in pa nel a. Includes all sites from the IMPROVE network that met th e prescribed completeness criteria including the urban sites for 2000–2004. Rayleigh s cattering was not included............................................... 79 Figure 2.17. Isopleth map of annual visi bility in deciviews in panel a. Includes all sites from the IMPROVE network that met the prescribed comp leteness criteria including the urban sites for 2000–2004...................................................................................................................... ............... 79 Figure 3.1. Map of stacked bar charts of monthly mean concentrations ( μ g/m 3 ) of fine aerosol species in the northwestern U.S. re gions of the IMPROVE network........................................... 93 Figure 3.2. Map of stacked bar charts of monthly mean concentrations ( μ g/m 3 ) of fine aerosol species in the northwestern U.S. regions of the STN network. .................................................... 94ix Figure 3.3. Map of stacked bar charts of monthly mean concentrations ( μ g/m 3 ) of fine aerosol species in the southwestern U.S. regions of the IMPROVE network........................................... 95 Figure 3.4. Map of stacked bar charts of monthly mean concentrations ( μ g/m 3 ) of fine aerosol species in the southwestern U.S. regions of the STN network. .................................................... 96 Figure 3.5. Map of stacked bar charts of monthly mean concentrations ( μ g/m 3 ) of fine aerosol species in the eastern U.S. regi ons of the IMPROVE network. ................................................... 97 Figure 3.6. Map of stacked bar charts of monthly mean concentrations ( μ g/m 3 ) of fine aerosol species in the eastern U.S. re gions of the STN network............................................................... 98 Figure 3.7. Map of stacked bar charts of monthly pe rcent contributi on to reconstructed fine mass (%) of fine aerosol species in the northwester n U.S. regions of the IMPROVE network............ 99 Figure 3.8. Map of stacked bar charts of monthly pe rcent contributi on to reconstructed fine mass (%) of fine aerosol species in the northwestern U.S. regions of the STN network. ................... 100 Figure 3.9. Map of stacked bar charts of monthly pe rcent contributi on to reconstructed fine mass (%) of fine aerosol species in the southweste rn U.S. regions of the IMPROVE network.......... 101 Figure 3.10. Map of stacked bar charts of monthl y percent contribution to reconstructed fine mass (%) of fine aerosol species in the southw estern U.S. regions of the STN network........... 102 Figure 3.11. Map of stacked bar charts of monthl y percent contribution to reconstructed fine mass (%) of fine aerosol species in the eastern U.S. regions of the IMPROVE network. ......... 103 Figure 3.12. Map of stacked bar charts of monthl y percent contribution to reconstructed fine mass (%) of fine aerosol species in the easte rn U.S. regions of the STN network..................... 104 Figure 3.13. Map showing stacked bar charts of monthly distributi ons of particulate extinction coefficients for the northwestern U.S. regions of the IMPROVE network. Starting from the base of the chart, ammonium sulfat e, organics, light-absorbing car bon, ammonium nitrate, soil, and coarse mass are the order of presentation. .................................................................................. 110 Figure 3.14. Map showing stacked bar charts of monthly distributions of fine particulate extinction coefficients (Mm -1 ) for the northwestern U.S. regions of the STN network. Starting from the base of the chart, ammonium sulf ate, organics, light-abs orbing carbon, ammonium nitrate, and soil are the order of presentation. Coarse mass measur ements were not available for STN and so are not included.................................................................................................... ... 111 Figure 3.15. Map showing stacked bar charts of monthly distributi ons of particulate extinction coefficients (Mm -1 ) for the southwestern U.S. regions of the IMPROVE network. Starting from the base of the chart, ammonium sulfate, or ganics, light-absorbing car bon, ammonium nitrate, soil, and coarse mass are the order of presentation..................................................................... 112 Figure 3.16. Map showing stacked bar charts of monthly distributions of fine particulate extinction coefficients (Mm -1 ) for the southwestern U.S. regions of the STN network. Starting from the base of the chart, ammonium sulf ate, organics, light-abs orbing carbon, ammonium nitrate, and soil are the order of presentation. Coarse mass measur ements were not available for STN and so are not included.................................................................................................... ... 113 Figure 3.17. Map showing stacked bar charts of monthly distributi ons of particulate extinction coefficients (Mm -1 ) for the eastern U.S. regions of the IMPROVE network. Starting from thex base of the chart, ammonium sulfate, organics , light-absorbing carbon, ammonium nitrate, soil, and coarse mass are the order of presentation. ........................................................................... 114 Figure 3.18. Map showing stacked bar charts of monthly distributions of fine particulate extinction coefficients (Mm -1 ) for the eastern U.S. regions of the STN network. Starting from the base of the chart, ammonium sulfate, organi cs, light-absorbing carbon, ammonium nitrate, and soil are the order of presentation. Coarse mass m easurements were not av ailable for STN and so are not included............................................................................................................... ............ 115 Figure 3.19. Map showing stacked bar charts of monthly percent contribution to reconstructed particulate extinction (%) for particulate extinction coefficients for the northwest U.S. regions of the IMPROVE network. Starting from the base of the chart, ammonium sulfate, organics, lightabsorbing carbon, ammonium nitrate, soil, and co arse mass are the order of presentation........ 116 Figure 3.20. Map showing stacked bar charts of monthly percent contribution to reconstructed particulate extinction (%) for particulate extinction coefficients for the southwest U.S. regions of the IMPROVE network. Starting from the base of the chart, ammonium sulfate, organics, lightabsorbing carbon, ammonium nitrate, soil, and co arse mass are the order of presentation........ 117 Figure 3.21. Map showing stacked bar charts of monthly percent contribution to reconstructed particulate extinction (%) for particulate extinctio n coefficients for the eastern U.S. regions of the IMPROVE network. Starting from the base of the chart, ammonium sulfate, organics, lightabsorbing carbon, ammonium nitrate, soil, and co arse mass are the order of presentation........ 118 Figure 4.1. Ratio of 24-hour sulfate concentrat ions measured by collocated and routine IMPROVE B modules at Big Bend NP. ..................................................................................... 121 Figure 4.2. Summary of the results of Theil regressions for the 80 thpercentile

− 2 4 SO (3*S for IMPROVE program) concentrations from 1989 to 1999. Solid up or down arrows show which sites have trends with a signifi cance level of at leas t 10%. Arrows with enclosed hatch lines show whether the trend was up or down but not st atistically significant. Arrows with a bar across the tail represent CASTNet sites, wh ile arrows without the bar show IMPROVE monitoring sites. The numbers are the percent changes from the overall median of the 80th percentile..................................................................................................................... ................ 124 Figure 4.3. Summary of the results of Theil regressions for the 20 thpercentile

− 2 4 SO (3*S for IMPROVE program) concentrations from 1989 to 1999. Solid up or down arrows show which sites have a trend with a signifi cance level of at leas t 10%. Arrows with enclosed hatch lines show whether the trend was up or down but not st atistically significant. Arrows with a bar across the tail represent CASTNet sites, wh ile arrows without the bar show IMPROVE monitoring sites. The numbers are the percent changes from the overall median of the 20th percentile..................................................................................................................... ................ 125 Figure 4.4. The percent ch ange in the NET SO 2 emissions for each state in the conterminous United States from 1990 through 1999. The light gr ay states have decreasing trends, while the dark gray states have increasing trends. Stat es without hatch marks have trends that are significant with two-sided P valu es below 0.1. The percent change s were calculated by dividing the change in emissions over the 10-year peri od by the 1990 emissions estimated from the trend line. The 1999 SO 2 emission rates for each state are in parentheses. ........................................ 126xi Figure 4.5. Comparison of the 80 thpercentile

− 2 4 SO concentrations (3*S for IMPROVE program) and NET SO 2 emissions aggregated over northeastern, southeastern, south-middle, and western United States regions. In each plot the

− 2 4 SO and SO 2 emission scales have a factor of 3 change between the low and high values. ............................................................................................... 127 Figure 4.6. Theil trends in the haze index of the annual average 20% best visibility days........ 128 Figure 4.7. Theil trends in the haze index of th e annual average 20% worst visibility days...... 129 Figure 4.8. The wintertime elemen tal carbon trend using IMPROVE data from monitoring sites with a minimum of 7 years of data. The triangles indicate a increasing (u p) or decreasing (down) trend, and black arrows have a significant trend at the 0.05 level. The isop leths are the slope of the trend line as the % change from the median EC concentration per 10 years........................ 130 Figure 4.9. The wintertime organic carbon trend using IMPROVE data from monitoring sites with a minimum of 7 years of data. ............................................................................................ 1 31 Figure 4.10. The summertime elemental carbon tr end using IMPROVE data from monitoring sites with a minimum of 7 years of data. .................................................................................... 132 Figure 4.11. The summertime organic carbon trend us ing IMPROVE data from monitoring sites with a minimum of 7 years of data. ............................................................................................ 1 33 Figure 5.1. An example of the data validation ch arts from the fall 2004 report. Reconstructed fine mass concentrations, measured fine mass, a nd the reconstructed fine mass to measured fine mass concentration ratios are shown for the 2001–2004 time period at BIBE1. Definitions of all terms used in the axis titles can be found in the glossary in section 5.1.5 of this document...... 144 Figure 5.2. An example of the data validation charts from the fall 2004 report. Sulfate concentrations, sulfur concentratio ns, and the sulfate to sulfur c oncentration ratios are shown for the 2001–2004 time period at OLYM1. Definitions of all terms used in the axis titles can be found in the glossary in sec tion 5.1.5 of this document.............................................................. 147 Figure 5.3. An example of the data validation charts from the fall 2004 report. Z scores calculated from the sulfate and sulfur concentrati ons and reported uncertainties are shown for the 2001–2004 time period at OLYM1. Definitions of all term s used in the axis titles can be found in the glossary in section 5.1.5 of this document............................................................................ 148 Figure 5.4. The percentage of valid sample pair s with significant disagreement between SO 4 = and 3*S are calculated for each month. This provides a way of tracking 1) the overall magnitude of the number of sample pairs with poor agreement re lative to the number of samples collected, as well as 2) the direction of bi as at the network level. .................................................................. 149 Figure 5.5. An example of the data validation charts from the fall 2004 report. Aluminum concentrations, iron concentrations, and the alum inum to iron enrichmentfactors are shown for the 2001–2004 time period at DENA1. Definitions of all terms used in the axis titles can be found in the glossary in sec tion 5.1.5 of this document.............................................................. 150 Figure 5.6. An example of the data validation charts from the fall 2004 report. Calcium concentrations, iron concentrations, and the calciu m to iron enrichment factors are shown for the 2001–2004 time period at DENA1. Definitions of all term s used in the axis titles can be found in the glossary in section 5.1.5 of this document............................................................................ 151xii Figure 5.7. An example of the data validation charts from the fall 2004 report. Silicon concentrations, iron concentrations, and the silic on to iron enrichment factors are shown for the 2001–2004 time period at DENA1. Definitions of all term s used in the axis titles can be found in the glossary in section 5.1.5 of this document............................................................................ 152 Figure 5.8. An example of the data validation charts from the fall 2004 report. Titanium concentrations, iron concentrations, and the titani um to iron enrichment f actors are shown for the 2001–2004 time period at DENA1. Definitions of all term s used in the axis titles can be found in the glossary in section 5.1.5 of this document............................................................................ 153 Figure 5.9. An example of the data validati on charts from the fall 2004 report. Soil concentrations, the A module cut point and the soil to reconstructed mass concentration ratios are shown for the 2001–2004 time period at DENA1. Definiti ons of all terms used in the axis titles can be found in the glossary in section 5.1.5 of this document. ................................................. 154 Figure 5.10. An example of the data validation ch arts from the fall 2004 report. Organic carbon concentrations, elemental carbon concentrations, and the organic carbon to elemental carbon concentration ratios are shown for the 2001–2004 tim e period at YOSE1. Definitions of all terms used in the axis titles can be found in the glossary in section 5.1.5 of this document................ 155 Figure 5.11. An example of the data validati on charts from the fall 2004 report. OMC concentrations, OMH concentrations, and the OM H to OMC concentration ratios are shown for the 2001–2004 time period at ACAD1. Definitions of all terms used in the axis titles can be found in the glossary in sec tion 5.1.5 of this document.............................................................. 156 Figure 5.12. An example of the data validation charts from the fall 2004 report. Nitrate concentrations, reconstructed fine mass con centrations, and the a mmonium nitrate to reconstructed fine mass concentration ra tios are shown for the 2001–2004 time period at ACAD1. Definitions of all terms used in the axis titles can be found in th e glossary in section 5.1.5 of this document......................................................................................................... ........ 157 Figure 5.13. An example of the data validation ch arts from the fall 2004 report. Equation 3 in section 5.1.7 is used to calculate the A, B, and C module cut points fr om the reported flow rates. The cut points for the A, B, and C modules ar e shown for the fall–December 2004 data delivery batch at VOYA2. Definitions of all terms used in the axis titles can be found in the glossary in section 5.1.5 of this document. ................................................................................................ ... 158 Figure 5.14. An example of the flow rate problem discovered in the data validation charts from the fall 2004 report. Equation 3 in section 5.1.7 is used to calculate the A, B, and C module cut points from the reported flow rates. The cut points for the A, B, and C modules are shown for the fall–December 2004 data delivery batch at HOOV1. Definitions of all te rms used in the axis titles can be found in the glossary in section 5.1.5 of this document. ........................................ 160 Figure 5.15. An example of the data validation ch arts from CNL (a) and from CIRA’s summer 2004 report (b). Panel a shows su lfate and three times sulfur c oncentrations for summer 2004 at CHAS1. Panel b shows sulfate conc entrations, sulfur concentrati ons, and the sulfate to sulfur concentration ratios for 2001–2004 at CHAS1. Wh ile the incomplete sampling on the A module is obvious in panel b, the sulfate to sulfur discrepancies in pane l a do not look similarly alarming. The sampling problem, which is obvious starti ng in early 2003, was not caught until the 2004 data were examined at CIRA and was not fu lly acted upon until the summer of 2004. Definitionsxiii of all terms used in the axis ti tles can be found in the glossary in section 5.1.5 of this document.

............................................................................................................................... ...................... 163 Figure 5.16. The plot shows the 50% cut point as a function of flow rate as determined by two separate collection efficiency tests. The co llection efficiency of the IMPROVE cyclone was characterized at the Health Sciences Instrumentat ion Facility at the University of California at Davis. The efficiency was measured as a func tion of particle size and flow rate using two separate methods: PSL and SPART. The PSL method uses microspheres of fluorescent polystyrene latex particles (PSL) produced by a Lovelace nebulizer and a vibrating stream generator and analyzed by electron microgra phs. The SPART method uses a mixture of PSL particles produced by a Lovelace nebulizer and analyzed by a single particle aerodynamic relaxation time (SPART) analyzer. The aerodynamic diameter for 50% collection, d50, was determined for each flow rate. ................................................................................................. ... 168 Figure 6.1. A terrain map of Texas and Mexico as well as some major cities and points of interest from the BRAVO study. .......................................................................................................... ... 181 Figure 6.2. Big Bend’s particulate light extinction budget during BRAVO. ............................. 182 Figure 6.3. Big Bend National Park fi ve-year light extinction budget. All days with that fall on the same day of the year were averaged togeth er, then the data were smoothed using a 15-day moving average................................................................................................................. .......... 183 Figure 6.4. (Left) SO 2 emissions based on the 1999 BRAVO em issions inventory used in the REMSAD and CMAQ-MADRID modeling. No em issions were included beyond the black outline shown in the figure. Mexico City and Po pocatepetl volcano emissions are located in the three most southern emission grid cells...................................................................................... 18 4 Figure 6.5. Fraction of time that air parcels spent during ten-day traj ectories for periods with the a) 20% highest concentrations of particulate sulfate compounds and b) for the periods with the 20% lowest concentrations of particulate sulfate during the BRAVO study period July through October 1999................................................................................................................... ............ 186 Figure 6.6. Airmass transport patterns to Big Be nd, TX, during three sulf ate episodes. Each isopleth shows the most likely pathway the airm ass traversed prior to impacting Big Bend..... 187 Figure 6.7. Estimates by several data analysis and modeling methods of the study-period averaged percent contributions to particulate su lfate at Big Bend by U.S. and Mexico sources. TAGIT only attributed the Carbón power pl ants, while CMAQ and Synthesized CMAQ attribution did not distinguishCarbón from Mexico. ................................................................. 189 Figure 6.8. Smoothed daily estimates by source regions to particulate sulfate concentration (top plot) and fraction of total predic ted particulate sulfate (bottom pl ot) at Big Bend during the study period. ........................................................................................................................ ................. 190 Figure 6.9. Estimated contributions to particul ate haze by various part iculate sulfate source regions. The top plot shows the absolute haze contributions by the vari ous particulate sulfate sources as well as the total particulate haze le vel (black line). The bottom plot shows the fractional contribution to h aze by the various sources................................................................ 191 Figure 6.10. Estimated contributions by particulate sulfate source re gions to Big Bend particulate haze levels for the 20% haziest days and the 20% least hazy days of the BRAVO study period.

............................................................................................................................... ...................... 192xiv Figure 6.11. Examples of geographic distribution of the fraction of time that air parcels spend during the five days prior to ar riving at Big Bend National Park for the months of January, May, July, and September based upon a five-year analysis period (1998 to 2002)............................. 194 Figure 6.12. Annual variation of or ganic carbon mass concentrations in the fine mode of the aerosol (PM 2.5 ), from data obtained from the IMPROVE database (http://vista.cira.colostate.edu/vi ews/). A measure of interannual variability is indicated by the yellow shaded area, which envelops one standard deviation in the data. Blue lines indicate the fraction of fine particulate mass concentration apportioned to organic car bon over the long-term average and for 2002........................................................................................................... ........ 196 Figure 6.13. Fine mass concentrations reconstruc ted from individual species concentration measurements, plotted against fine mass concentr ations determined by gravimetry (weighing of filters). Reconstructions are shown for two assumptions regarding the elemental-to-molecular mass conversion for organic carbon. .......................................................................................... 19 8 Figure 6.14. PM 10 aerosol mass concentrations rec onstructed from individual species concentration measurements, for the Tur tleback Dome and Valley Floor sites......................... 199 Figure 6.15. Reconstructed, study-av eraged extinction budget at Turtleback Dome. All species except coarse mass are in the fine aerosol mode. ....................................................................... 200 Figure 6.16. MODIS image (August 18) of smoke from fires (red areas) in Oregon and in Sequoia National Park transported into California’s Central Valley.......................................... 201 Figure 6.17. Study-averaged source c ontributions of fine aerosol organic carbon (expressed as % of OC) at Turtleback Dome. ..................................................................................................... .. 202 Figure 6.18. Annual mean value of R oc multiplier derived from an ordinary least square multilinear regression analysis. .................................................................................................... ....... 206 Figure 6.19. Map of the mean ammonium sulfate mass scattering efficiency (m 2 g -1 ). The size of the circle reflects the magnitude of the effici ency, which is printed near the circle................... 209 Figure 6.20. Map of the mean POM mass scattering efficiency (m 2 g -1 ). The size of the circle reflects the magnitude of the efficiency, which is printed near the circle. ................................. 209 Figure 6.21. Scatter plot of gravimetric and reconstructed fine mass. An ordinary least square slope with the intercept set equa l to 0 is 1.03 ± 0.004 with an R2 = 96. ..................................... 232 Figure 6.22. Scatter plot of gravimetric and reconstructed coarse mass. An ordinary least square slope with the intercept set equa l to 0 is 0.95 ± 0.01 with an R 2 = 81. ....................................... 233 Figure 6.23. A map of stacked bar charts showing th e fine mass concentration of each species at each of the nine locations at which measurements were made. The continuous lines are running averages of the data collected hist orically at each monitoring site............................................. 234 Figure 6.24. A map of stacked bar charts showing th e coarse mass concentration of each species at each of the nine locations at which measur ements were made. The continuous lines are running averages of the data collected hi storically at each monitoring site. .............................. 235 Figure 6.25. A map of stacked bar charts showing the fractional contribution of each fine mass species to gravimetric mass at each of the nine locations at which measurements were made.. 236xv Figure 6.26. A map of stacked bar charts showing th e fractional contribution of each coarse mass species to gravimetric mass at each of the nine locations at which measurements were made. The stacked bar chart for the month of January is not shown for Sequoia National Park because of a large uncertainty in PM 10 gravimetric mass. ....................................................................... 237xvi LIST OF TABLES

Table S.1. IMPROVE monitoring site s listed according to region. The monitoring site codes are in parentheses................................................................................................................. ..............S-2 Table 1.1. Discontinued and current IMPROVE partic ulate monitoring sites. The site groupings are displayed in Figure 1.2.................................................................................................... .......... 6 Table 1.2. Class I areas and the representative monitoring site.................................................... 11

Table 1.3. Sites with a fifth collocated module. ........................................................................... 17

Table 1.4. Transmissometer receiver and transmitter locations. .................................................. 21 Table 1.5. IMPROVE nephelometer network site locations......................................................... 23 Table 1.6. Major network-wide changes in sampling, analysis and data reporting...................... 28 Table 1.7. Comparison of annual average concentrations between collocated IMPROVE and STN monitoring sites. .......................................................................................................... ......... 30 Table 2.1. IMPROVE equations. .................................................................................................. 35 Table 4.1. Five-year trends in measurement differences at Shenandoah NP.............................. 121 Table 4.2. Important differences between sample rs deployed in the CASTNet and IMPROVE networks....................................................................................................................... ............... 123 Table 5.1. Data validation levels as defined by IMPROVE. ...................................................... 140

Table 5.2. Flow rate-related validation flag definitions and application criteria........................ 169 Table 6.1. Site description. ................................................................................................... ...... 216 Table 6.2. Assumed molecular forms of each partic ulate species and method of estimation used.

............................................................................................................................... ...................... 217 Table 6.3. Statistical summary of all fine ma ss and fine mass species concentrations. ............. 219 Table 6.4. Statistical summary of all coarse ma ss and coarse mass species concentrations. ..... 219 Table 6.5. Statistical summary of annual fine mass and fine mass species concentrations by site.

............................................................................................................................... ...................... 220 Table 6.6. Statistical summary of annual coarse mass and coarse mass species concentrations by site........................................................................................................................... .................... 222