Spatial and Seasonal Patterns and Temporal Variability of Haze 

and its Constituents in the United States 

Report IV 

Principal Author: 

Linsey J. DeBell1

1

Cooperative Institute for Research in the Atmosphere 

Colorado State University 

Fort Collins, CO 80523-1375 

Contributors: 

Kristi A. Gebhart2 

Jenny L. Hand1

William C. Malm2 

Marc L. Pitchford3 

Bret A. Schichtel2

Warren H. White4

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 herein are those of the 

authors and should not be interpreted as necessarily representing the National Park Service or 

National Oceanic and Atmospheric 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 Concentration and Extinction................................................S-6 

S.3 Spatial Variability Of Average Monthly Patterns 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 Monitoring under the IMPROVE Program.................................. 2 

1.2 Overview of the IMPROVE Monitoring Network............................................................. 4 

1.2.1 Current and Historical 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 Data 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 from Collocated IMPROVE and STN Monitoring 

Sites .......................................................................................................................................... 29 

References..................................................................................................................................... 31 

Chapter 2: Spatial Distributions of Reconstructed Mass and Mass Budgets 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........................................................................................................ 37 
ii 

2.3 Completeness Criteria ...................................................................................................... 41 

2.4 Spatial Trends in Aerosol Concentrations 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 (bext)....................................................... 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 Particulate 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 Patterns in Particulate Extinction 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 20th and 80th Percentile SO4

=

 Concentrations........ 123 

4.2.3 Yearly Temporal Trends of NET SO2 Emissions .................................................... 125 

4.2.4 Regional Comparisons of SO2 Emissions and SO4

=

 Concentrations ....................... 126 

4.3 Trends in the Haze Index................................................................................................ 127
iii 

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 Quality 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 ........................................................................................................ 140 

5.1.3.1. Data Integrity Tests Performed at CIRA ........................................................ 141 

5.1.3.2. Spatial and Temporal Comparability 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 Analysis 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 .............................................. 171 
iv 

5.2.1 Introduction.............................................................................................................. 171 

5.2.2 Measured Fine Mass versus Reconstructed Fine Mass Review............................... 171 

5.2.3 Sulfate Review ......................................................................................................... 171 

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 Measurement Using Nylon Filters.................................... 176 

5.3.3.2. Loss of Fine Particle Ammonium from Denuded Nylon Filters .................... 177 

5.3.3.3. Efficiency of IMPROVE Network Denuders 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 Aerosol and Visibility Observational (BRAVO) 

Study Results: Air Quality Data and Source Attribution 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 during 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 Regions 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 Other 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 ......................................................................................................... 197 

6.3 Executive Summary: Review of the IMPROVE Equation for Estimating Ambient Light 

Extinction Coefficients ............................................................................................................ 203 

6.3.1 Introduction.............................................................................................................. 203 

6.3.2 Particulate Organic Matter and the Roc Multiplier ................................................... 204 

6.3.3 Scattering Enhancement Curve (f(RH)) ................................................................... 206 
v 

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 NO2 ......................................................................................... 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 Collocated Measurements Detailed in Appendix E .... 238 

Chapter 7: Bibliography of Journal 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 Fine Mass and Aerosol Extinction Budgets for 

Each Site 

Appendix B: Seasonal and Annual Regional Reconstructed Fine Mass and Reconstructed 

Extinction Budgets 

Appendix C: Monthly and Annual Reconstructed Fine Mass and Reconstructed Extinction and 

their Associated Budgets from the 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 Errors in the IMPROVE and STN Networks from 

In-Network and Cross-Network Collocated Data and the Estimated Comparability of Data 

Collected from the Two Networks 
vi 

LIST OF FIGURES 

Figure S.1. The locations current and discontinued IMPROVE and IMPROVE protocol 

monitoring sites as of December 2004. The IMPROVE regions used for grouping the sites in 

some analyses in this report are indicated by green 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 particulate 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 scattering using IMPROVE and STN 

data.............................................................................................................................................S-10 

Figure S.6. Five-year average (2000–2004) organic carbon light scattering using only IMPROVE 

data.............................................................................................................................................S-10 

Figure S.7. Five-year average (2000–2004) organic carbon light scattering 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 light scattering using IMPROVE 

and STN data..............................................................................................................................S-12 

Figure S.10. Five-year average (2000–2004) fine soil light scattering using only IMPROVE data.

....................................................................................................................................................S-12 

Figure S.11. Five-year average (2000–2004) fine soil light scattering using IMPROVE and STN 

data. Note comparisons of collocated data indicate the STN fine soil concentrations and light 

scattering were typically 30% smaller than from the IMPROVE monitors. .............................S-13 

Figure S.12. Five-year average (2000–2004) coarse mass light scattering using only IMPROVE 

data.............................................................................................................................................S-13 

Figure S.13. Monthly particulate contributions to reconstructed bext (Mm-1) for regions in the 

eastern United States using IMPROVE data (top) and STN data (bottom). Note, STN does not 

measure coarse mass..................................................................................................................S-15 

Figure S.14. Monthly particulate contributions to reconstructed bext (Mm-1) for regions in the 

southwestern United States using IMPROVE data (top) and STN data (bottom). Note, STN does 

not measure coarse mass............................................................................................................S-16 

Figure S.15. Monthly particulate contributions to reconstructed bext (Mm-1) for regions in the 

northwestern United States using IMPROVE data (top) and STN data (bottom). Note, STN does 

not measure coarse mass............................................................................................................S-17 

Figure 1.1. All Class I areas of the contiguous United 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 IMPROVE protocol sites are shown for all 

discontinued and current sites as of December 2004. The IMPROVE regions used for grouping 
vii 

the sites in some analyses in this report are indicated by green shading and italicized text. Urban 

sites included in the IMPROVE network for quality assurance purposes are identified by stars. . 5 

Figure 1.3. Schematic view of the IMPROVE sampler showing the four modules with separate 

inlets and pumps. The substrates with analyses performed for each module are also shown. .... 15 

Figure 1.4. Schematic of a new version of the IMPROVE sampler PM2.5 module...................... 17 

Figure 2.1. RH factors (fT (RH)) derived from Tang’s ammonium sulfate growth curves 

smoothed between the crystallization and deliquescence points. ................................................. 39 

Figure 2.2. Isopleth maps of annual ammonium sulfate 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 prescribed 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 concentrations. Panels a and b include all sites 

from the IMPROVE network that met the prescribed 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 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 prescribed 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..................................................................................................................... 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 prescribed 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 nitrate 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 prescribed 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 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 prescribed 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..................................................................................................................... 61 

Figure 2.8. Isopleth maps of annual reconstructed fine mass concentrations. Panels a and b 

include all sites from the IMPROVE network that met the prescribed 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. .............................................................................. 62 
viii 

Figure 2.9. Isopleth map of annual coarse mass concentrations; includes all sites from the 

IMPROVE network that met the prescribed completeness criteria including the urban sites for 

2000–2004..................................................................................................................................... 63 

Figure 2.10. Isopleth maps of annual ammonium sulfate extinction coefficients in panels a and b 

and percent contribution to reconstructed particulate extinction in panel c. Panels a, b, and c 

include all sites from the IMPROVE network that met the prescribed completeness criteria 

including the urban sites for 2000–2004. Panel b also includes all sites from the STN network 

that met prescribed completeness criteria..................................................................................... 69 

Figure 2.11. Isopleth maps of annual organic mass by carbon extinction coefficients in panels a 

and b and percent contribution to reconstructed particulate extinction in panel c. Panels a, b, and 

c include all sites from the IMPROVE network that met the prescribed completeness criteria 

including the urban sites for 2000–2004. Panel b also includes all sites from the STN network 

that met prescribed completeness criteria..................................................................................... 71 

Figure 2.12. Isopleth maps of annual light-absorbing carbon extinction coefficients in panels a 

and b and percent contribution to reconstructed particulate extinction in panel c. Panels a, b, and 

c include all sites from the IMPROVE network that met the prescribed completeness criteria 

including the urban sites for 2000–2004. Panel b also includes all sites from the STN network 

that met prescribed completeness criteria..................................................................................... 73 

Figure 2.13. Isopleth maps of annual ammonium nitrate extinction coefficients in panels a and b 

and percent contribution to reconstructed particulate extinction in panel c. Panels a, b, and c 

include all sites from the IMPROVE network that met the prescribed completeness criteria 

including the urban sites for 2000–2004. Panel b also includes all sites from the STN network 

that met prescribed completeness criteria..................................................................................... 75 

Figure 2.14. Isopleth maps of annual fine soil extinction coefficients in panels a and b and 

percent contribution to reconstructed particulate extinction in panel c. Panels a, b, and c include 

all sites from the IMPROVE network that met the prescribed completeness criteria including the 

urban sites for 2000–2004. Panel b also includes all sites from the STN network that met 

prescribed completeness criteria................................................................................................... 77 

Figure 2.15. Isopleth maps of annual coarse mass extinction coefficients in panel a and percent 

contribution to reconstructed particulate extinction in panel b. Panels a and b include all sites 

from the IMPROVE network that met the prescribed completeness criteria including the urban 

sites for 2000–2004....................................................................................................................... 78 

Figure 2.16. Isopleth map of annual total reconstructed particulate extinction in panel a. Includes 

all sites from the IMPROVE network that met the prescribed completeness criteria including the 

urban sites for 2000–2004. Rayleigh scattering was not included............................................... 79 

Figure 2.17. Isopleth map of annual visibility in deciviews in panel a. Includes all sites from the 

IMPROVE network that met the prescribed completeness criteria including the urban sites for 

2000–2004..................................................................................................................................... 79 

Figure 3.1. Map of stacked bar charts of monthly mean concentrations (μg/m3

) of fine aerosol 

species in the northwestern U.S. regions of the IMPROVE network........................................... 93 

Figure 3.2. Map of stacked bar charts of monthly mean concentrations (μg/m3

) of fine aerosol 

species in the northwestern U.S. regions of the STN network. .................................................... 94 
ix 

Figure 3.3. Map of stacked bar charts of monthly mean concentrations (μg/m3

) 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 (μg/m3

) 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 (μg/m3) of fine aerosol 

species in the eastern U.S. regions of the IMPROVE network. ................................................... 97 

Figure 3.6. Map of stacked bar charts of monthly mean concentrations (μg/m3

) of fine aerosol 

species in the eastern U.S. regions of the STN network............................................................... 98 

Figure 3.7. Map of stacked bar charts of monthly percent contribution to reconstructed fine mass 

(%) of fine aerosol species in the northwestern U.S. regions of the IMPROVE network............ 99 

Figure 3.8. Map of stacked bar charts of monthly percent contribution 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 percent contribution to reconstructed fine mass 

(%) of fine aerosol species in the southwestern U.S. regions of the IMPROVE network.......... 101 

Figure 3.10. Map of stacked bar charts of monthly percent contribution to reconstructed fine 

mass (%) of fine aerosol species in the southwestern U.S. regions of the STN network........... 102 

Figure 3.11. Map of stacked bar charts of monthly 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 monthly percent contribution to reconstructed fine 

mass (%) of fine aerosol species in the eastern U.S. regions of the STN network..................... 104 

Figure 3.13. Map showing stacked bar charts of monthly distributions of particulate extinction 

coefficients for the northwestern U.S. regions of the IMPROVE network. Starting from the base 

of the chart, ammonium sulfate, organics, light-absorbing carbon, 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 sulfate, organics, light-absorbing carbon, ammonium 

nitrate, and soil are the order of presentation. Coarse mass measurements were not available for 

STN and so are not included....................................................................................................... 111 

Figure 3.15. Map showing stacked bar charts of monthly distributions 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, organics, light-absorbing carbon, 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 sulfate, organics, light-absorbing carbon, ammonium 

nitrate, and soil are the order of presentation. Coarse mass measurements were not available for 

STN and so are not included....................................................................................................... 113 

Figure 3.17. Map showing stacked bar charts of monthly distributions of particulate extinction 

coefficients (Mm-1) for the eastern U.S. regions of the IMPROVE network. Starting from the 
x 

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, organics, light-absorbing carbon, ammonium nitrate, and 

soil are the order of presentation. Coarse mass measurements were not available 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 coarse 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 coarse 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 extinction 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 coarse mass are the order of presentation........ 118 

Figure 4.1. Ratio of 24-hour sulfate concentrations 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 80th percentile 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 significance level of at least 10%. Arrows with enclosed hatch lines 

show whether the trend was up or down but not statistically significant. Arrows with a bar 

across the tail represent CASTNet sites, while 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 20th percentile 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 significance level of at least 10%. Arrows with enclosed hatch lines 

show whether the trend was up or down but not statistically significant. Arrows with a bar 

across the tail represent CASTNet sites, while 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 change in the NET SO2 emissions for each state in the conterminous 

United States from 1990 through 1999. The light gray states have decreasing trends, while the 

dark gray states have increasing trends. States without hatch marks have trends that are 

significant with two-sided P values below 0.1. The percent changes were calculated by dividing 

the change in emissions over the 10-year period by the 1990 emissions estimated from the trend 

line. The 1999 SO2 emission rates for each state are in parentheses. ........................................ 126 
xi 

Figure 4.5. Comparison of the 80th percentile 2−

4 SO concentrations (3*S for IMPROVE program) 

and NET SO2 emissions aggregated over northeastern, southeastern, south-middle, and western 

United States regions. In each plot the 2−

4 SO and SO2 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 the annual average 20% worst visibility days...... 129 

Figure 4.8. The wintertime elemental carbon trend using IMPROVE data from monitoring sites 

with a minimum of 7 years of data. The triangles indicate a increasing (up) or decreasing (down) 

trend, and black arrows have a significant trend at the 0.05 level. The isopleths 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. ............................................................................................ 131 

Figure 4.10. The summertime elemental carbon trend using IMPROVE data from monitoring 

sites with a minimum of 7 years of data. .................................................................................... 132

Figure 4.11. The summertime organic carbon trend using IMPROVE data from monitoring sites 

with a minimum of 7 years of data. ............................................................................................ 133 

Figure 5.1. An example of the data validation charts from the fall 2004 report. Reconstructed 

fine mass concentrations, measured fine mass, and 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 concentrations, and the sulfate to sulfur concentration 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 section 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 concentrations and reported uncertainties 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 section 5.1.5 of this document............................................................................ 148 

Figure 5.4. The percentage of valid sample pairs with significant disagreement between SO4

=

 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 relative to the number of samples collected, as 

well as 2) the direction of bias 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 aluminum to iron enrichment factors 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 section 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 calcium to iron enrichment factors 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 section 5.1.5 of this document............................................................................ 151 
xii 

Figure 5.7. An example of the data validation charts from the fall 2004 report. Silicon 

concentrations, iron concentrations, and the silicon to iron enrichment factors 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 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 titanium to iron enrichment factors 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 section 5.1.5 of this document............................................................................ 153 

Figure 5.9. An example of the data validation 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. Definitions 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 charts 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 time 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 validation charts from the fall 2004 report. OMC 

concentrations, OMH concentrations, and the OMH 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 section 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 concentrations, and the ammonium nitrate to 

reconstructed fine mass 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 section 

5.1.5 of this document................................................................................................................. 157 

Figure 5.13. An example of 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 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 terms 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 charts from CNL (a) and from CIRA’s summer 

2004 report (b). Panel a shows sulfate and three times sulfur concentrations for summer 2004 at 

CHAS1. Panel b shows sulfate concentrations, sulfur concentrations, and the sulfate to sulfur 

concentration ratios for 2001–2004 at CHAS1. While the incomplete sampling on the A module 

is obvious in panel b, the sulfate to sulfur discrepancies in panel a do not look similarly alarming. 

The sampling problem, which is obvious starting in early 2003, was not caught until the 2004 

data were examined at CIRA and was not fully acted upon until the summer of 2004. Definitions 
xiii 

of all terms used in the axis titles 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 collection efficiency of the IMPROVE cyclone was 

characterized at the Health Sciences Instrumentation Facility at the University of California at 

Davis. The efficiency was measured as a function 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 micrographs. 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 five-year light extinction budget. All days with that fall on 

the same day of the year were averaged together, then the data were smoothed using a 15-day 

moving average........................................................................................................................... 183 

Figure 6.4. (Left) SO2 emissions based on the 1999 BRAVO emissions inventory used in the 

REMSAD and CMAQ-MADRID modeling. No emissions were included beyond the black 

outline shown in the figure. Mexico City and Popocatepetl volcano emissions are located in the 

three most southern emission grid cells...................................................................................... 184 

Figure 6.5. Fraction of time that air parcels spent during ten-day trajectories 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 Bend, TX, during three sulfate episodes. Each 

isopleth shows the most likely pathway the airmass 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 sulfate at Big Bend by U.S. and Mexico sources. 

TAGIT only attributed the Carbón power plants, while CMAQ and Synthesized CMAQ 

attribution did not distinguish Carbón from Mexico. ................................................................. 189 

Figure 6.8. Smoothed daily estimates by source regions to particulate sulfate concentration (top 

plot) and fraction of total predicted particulate sulfate (bottom plot) at Big Bend during the study 

period. ......................................................................................................................................... 190 

Figure 6.9. Estimated contributions to particulate haze by various particulate sulfate source 

regions. The top plot shows the absolute haze contributions by the various particulate sulfate 

sources as well as the total particulate haze level (black line). The bottom plot shows the 

fractional contribution to haze by the various sources................................................................ 191 

Figure 6.10. Estimated contributions by particulate sulfate source regions to Big Bend particulate 

haze levels for the 20% haziest days and the 20% least hazy days of the BRAVO study period.

..................................................................................................................................................... 192 
xiv 

Figure 6.11. Examples of geographic distribution of the fraction of time that air parcels spend 

during the five days prior to arriving 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 organic carbon mass concentrations in the fine mode of the 

aerosol (PM2.5), from data obtained from the IMPROVE database 

(http://vista.cira.colostate.edu/views/). 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 carbon over the long-term 

average and for 2002................................................................................................................... 196 

Figure 6.13. Fine mass concentrations reconstructed from individual species concentration 

measurements, plotted against fine mass concentrations determined by gravimetry (weighing of 

filters). Reconstructions are shown for two assumptions regarding the elemental-to-molecular 

mass conversion for organic carbon. .......................................................................................... 198 

Figure 6.14. PM10 aerosol mass concentrations reconstructed from individual species 

concentration measurements, for the Turtleback Dome and Valley Floor sites......................... 199 

Figure 6.15. Reconstructed, study-averaged 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 contributions of fine aerosol organic carbon (expressed as % 

of OC) at Turtleback Dome. ....................................................................................................... 202 

Figure 6.18. Annual mean value of Roc multiplier derived from an ordinary least square multilinear regression analysis. ........................................................................................................... 206 

Figure 6.19. Map of the mean ammonium sulfate mass scattering efficiency (m2 g

-1). The size of 

the circle reflects the magnitude of the efficiency, which is printed near the circle................... 209 

Figure 6.20. Map of the mean POM mass scattering efficiency (m2 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 equal 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 equal to 0 is 0.95 ± 0.01 with an R2 = 81. ....................................... 233 

Figure 6.23. A map of stacked bar charts showing the 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 historically at each monitoring site............................................. 234 

Figure 6.24. A map of stacked bar charts showing the coarse 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 historically 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.. 236 
xv 

Figure 6.26. A map of stacked bar charts showing the 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 PM10 gravimetric mass. ....................................................................... 237 
xvi 

LIST OF TABLES

Table S.1. IMPROVE monitoring sites listed according to region. The monitoring site codes are 

in parentheses...............................................................................................................................S-2 

Table 1.1. Discontinued and current IMPROVE particulate 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 samplers 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 particulate species and method of estimation used.

..................................................................................................................................................... 217 

Table 6.3. Statistical summary of all fine mass and fine mass species concentrations. ............. 219 

Table 6.4. Statistical summary of all coarse mass 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