Spatial and Seasonal Patterns and Temporal Variability of Haze and its Constituents in the United States

Transcription

1 IIMP MPR RO V E Interagency Monitoring of Protected Visual Environments Spatial and Seasonal Patterns and Temporal Variability of Haze and its Constituents in the United States Acadia NP PM2.5 (µg/m3) 8 50th Percentile Year 2005 Report V June 2011 ISSN ISSN CIRA Cooperative Institute for Research in the Atmosphere 2010

2 In celebration of the IMPROVE network s 25 th anniversary, we dedicate this report to all of the hard working operators, technicians, and scientists who have contributed to the success of the IMPROVE network over the years. Description of the cover: The front cover displays a split screen of two images from Acadia National Park that represent visibility levels corresponding to the 50 th percentile, PM 2.5 fine mass aerosol concentrations in 1989 (left) compared to those in 2008 (right). A noticeable improvement in visibility levels occurred due to the decrease in aerosol concentrations over the 20-year span. We used the WinHaze computer software program (Air Resource Specialists, 2011), a powerful tool for visualizing the impact of aerosol trends on visibility conditions.

3 Spatial and Seasonal Patterns and Temporal Variability of Haze and its Constituents in the United States Report V ISSN Principal Author: Jenny L. Hand 1 1 Cooperative Institute for Research in the Atmosphere Colorado State University Fort Collins, CO Scott A. Copeland 1 Derek E. Day 1 Ann M. Dillner 2 Hege Indresand 2 William C. Malm 1 Contributors: Chuck E. McDade 2 Charles T. (Tom) Moore, Jr. 3 Marc L. Pitchford 4 Bret A. Schichtel 5 John G. Watson 6 2 Crocker Nuclear Laboratory University of California Davis, CA Western Governors Association Western Regional Air Partnership CSU/CIRA Fort Collins, CO National Oceanic and Atmospheric Administration Desert Research Institute Las Vegas, NV National Park Service CSU/CIRA Fort Collins, CO Desert Research Institute Reno, NV 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.

4 TABLE OF CONTENTS Overview and Summary... S-1 S.1 Introduction... S-1 S.2 Aerosol Data... S-2 S.3 Spatial Patterns in Rural and Urban Speciated Aerosol Concentrations: Implications for Urban Excess... S-7 S.3.1 Ammonium Sulfate... S-8 S.3.2 Ammonium Nitrate... S-9 S.3.3 Particulate Organic Matter... S-10 S.3.4 Light Absorbing Carbon... S-11 S.4 Seasonal Distributions in Aerosol Mass Concentrations... S-12 S.4.1 Ammonium Sulfate... S-13 S.4.2 Ammonium Nitrate... S-13 S.4.3 Particulate Organic Matter... S-14 S.4.4 Light Absorbing Carbon... S-15 S.4.5 PM 2.5 Soil Mass... S-15 S.4.6 PM 2.5 Gravimetric Fine Mass... S-16 S.4.7 Discussion... S-17 S.5 Spatial and Seasonal Patterns in Relative Reconstructed Aerosol Light Extinction Coefficients... S-18 S.5.1 Deciview... S-19 S.5.2 Ammonium Sulfate Light Extinction Coefficients... S-21 S.5.3 Ammonium Nitrate Light Extinction Coefficients... S-24 S.5.4 Particulate Organic Matter Light Extinction Coefficients... S-24 S.5.5 Light Absorbing Carbon Light Extinction Coefficients... S-24 S.5.6 PM 2.5 Soil Mass Light Extinction Coefficients... S-25 S.6 Trends in IMPROVE Speciated Aerosol Mass Concentrations... S-25 S.6.1 Sulfate Ion Trends... S-26 S.6.2 Nitrate Ion Trends... S-27 S.6.3 Total Carbon Trends... S-29 S.6.4 Gravimetric PM 2.5 Fine Mass Trends... S-30 S.7 Regional Haze Rule Metrics... S-32 References... S-33 i

5 Chapter 1. Interagency Monitoring of Protected Visual Environments (IMPROVE) Network: Configuration and Measurements Introduction Overview of the Improve Monitoring Network Site Location Aerosol Sampling and Analysis Optical Sampling and Analysis Protocol and Equipment Changes Analytical Changes Introduction of a New Model Carbon Analyzer Transition from He Flush to Vacuum Chamber Cu-Anode XRF Introduction of New Calibration Foils for Mo-Anode XRF Processing XRF Calibration Data New XRF Quality Assurance Reports & Clarification of Data Acceptance Criteria Sampling Equipment Changes Filter Masks Removed Quartz Backup Filters Added at Six Sites New Cassette Design for the IMPROVE Sampler Data Processing Changes Change in the Definition of Flow Rate Native Flags Changes or Interferences Noted Through Data Analysis Sulfur Interference in the Determination of Silicon Shifts in the S/SO 4 = Ratio Chemical Speciation Network References Chapter 2. Spatial Patterns of Speciated PM 2.5 Aerosol Mass Concentrations Aerosol Species Composition PM 2.5 Ammonium Sulfate Mass Concentrations PM 2.5 Ammonium Nitrate Mass Concentrations PM 2.5 Particulate Organic Matter and Light Absorbing Carbon Mass Concentrations PM 2.5 Soil Mass Concentration ii

6 2.1.5 PM 2.5 Sea Salt Mass Concentration PM 2.5 Gravimetric Fine Mass and Reconstructed Fine Mass PM 2.5 Mass Difference PM 10 and Coarse Mass Concentrations Spatial Patterns in Annual Mean Mass Concentrations PM 2.5 Ammonium Sulfate Mass PM 2.5 Ammonium Nitrate Mass PM 2.5 Particulate Organic Matter Mass PM 2.5 Light Absorbing Carbon Mass PM 2.5 Soil Mass PM 2.5 Sea Salt Mass PM 2.5 Gravimetric Fine Mass PM 2.5 Reconstructed Fine Mass Differences in PM 2.5 Gravimetric and Reconstructed Fine Mass Coarse Mass PM 10 Mass References Chapter 3. Reconstructed Aerosol Light Extinction Coefficients IMPROVE Aerosol Light Extinction Coefficient Algorithm PM 2.5 Ammonium Sulfate Light Extinction Coefficients PM 2.5 Ammonium Nitrate Light Extinction Coefficients PM 2.5 Particulate Organic Matter Light Extinction Coefficients PM 2.5 Light Absorbing Carbon Light Extinction Coefficients PM 2.5 Fine Soil Light Extinction Coefficients PM 2.5 Sea salt Extinction Coefficients PM 2.5 Reconstructed Aerosol Light Extinction Coefficients Coarse Mass Light Extinction Coefficients PM 2.5 Deciview References Chapter 4. Seasonal Distributions of PM 2.5 Aerosol Mass Concentrations PM 2.5 Ammonium Sulfate Mass Concentrations PM 2.5 Ammonium Nitrate Mass Concentrations PM 2.5 Particulate Organic Matter Mass Concentrations iii

7 4.4 PM 2.5 Light Absorbing Carbon Mass Concentrations PM 2.5 Soil Mass Concentrations PM 2.5 Sea Salt Mass Concentrations PM 2.5 Gravimetric Fine Mass Concentrations Coarse Mass Concentrations Discussion References Chapter 5. Seasonal Distribution of PM 2.5 Reconstructed Aerosol Light Extinction Coefficients PM 2.5 Ammonium Sulfate Light Extinction Coefficients PM 2.5 Ammonium Nitrate Light Extinction Coefficients PM 2.5 Particulate Organic Matter Light Extinction Coefficients PM 2.5 Light Absorbing Carbon Light Extinction Coefficient PM 2.5 Soil Light Extinction Coefficients PM 2.5 Sea Salt Light Extinction Coefficients PM 2.5 Reconstructed Aerosol Light Extinction Coefficients Coarse Mass Light Extinction Coefficients PM 2.5 Deciview Summary References Chapter 6. Trends in IMPROVE Speciated Aerosol Concentrations Sulfate Ion Trends Nitrate Ion Trends Total Carbon Trends PM 2.5 Soil Trends Gravimetric PM 2.5 Fine Mass Trends Coarse Mass Trends PM 10 Gravimetric Mass Trends References Chapter 7. Urban Excess in PM 2.5 Speciated Aerosol Concentrations Introduction and Method Ammonium Sulfate Ammonium Nitrate iv

8 7.4 Particulate Organic Matter Light Absorbing Carbon PM 2.5 Gravimetric Fine Mass Summary References Chapter 8. Uncertainties in PM 2.5 Gravimetric and Speciation Measurements Abstract Implications Introduction Sample Collection Systems Interagency Monitoring of Protected Visual Environments (IMPROVE) The Chemical Speciation Network (CSN) Exploration of the Differences in the IMPROVE and CSN Carbon Measurements Relating CSN to IMPROVE Carbon Concentrations Converting CSN to IMPROVE Carbon Concentrations Comparison of Reconstructed to Measured Mass Investigating Bias Associated with each Species Bias in Gravimetric Mass Bias in Reconstructed Mass Spatial and Seasonal Variability in PM 2.5 and RPM 2.5 Biases Summary References Chapter 9. Regional Haze Rule Progress Tracking Metrics Introduction Regional Haze Rule Assessment Uniform Rate of Progress Regional Haze Rule Metric Assessment of Change in Regional Haze from the Baseline ( ) to Period 1 ( ) Case Studies of Regional Haze Rule Progress Boundary Waters Canoe Area Wilderness, Minnesota Great Smoky Mountains National Park, Tennessee/North Carolina v

9 9.4.3 Mesa Verde National Park, Colorado Hell s Canyon Wilderness, Oregon/Idaho Agua Tibia Wilderness, California References Chapter 10. X-Ray Fluorescence Reference Materials from an Aerosol Generation System Introduction Aerosol Generation System Testing and Verification Chapter 11. Ammonia and Ammonium Measurements from Passive, Modified IMPROVE and CASTNET Samplers Introduction Instrumentation URG Sampler IMPROVE Sampler CASTNET Sampler Passive Samplers Comparisons of Data from CASTNET, URG, and IMPROVE Samplers IMPROVE versus URG CASTNET versus URG Ammonia Comparisons from CASTNET, Passive, and URG Samplers Summary References Chapter 12. IMPROVE Measurements Bibliography Appendices available at or on cd by request. Appendix A: Comparisons of IMPROVE and CSN Daily Speciated Aerosol Concentrations at Collocated Sites Appendix B: Annual Mean Mass Concentrations and PM 2.5 Mass Fractions for Each Site Appendix C: Annual Mean Reconstructed Light Extinction Coefficients (b ext ) and PM 2.5 b ext Fractions for Each Site Appendix D: Regional Monthly Mean Mass Concentrations and PM 2.5 Mass Fractions vi

10 Appendix E: Regional Monthly Mean Mass Concentrations and PM 2.5 Mass Fractions Appendix F1: IMPROVE 20-Yr Normalized Trends ( ) Appendix F2: IMPROVE 9-Yr Normalized Trends ( ) Appendix G: Supplemental Analysis for Chapter 9 G.1. Regional Haze Rule IMPROVE Progress Tracking Site Data Results by State G.2. Spatial Maps of Regional Haze Rule Metrics vii

11 LIST OF FIGURES Figure S.2.1. Locations of IMPROVE and IMPROVE protocol sites for all discontinued and current sites. The IMPROVE regions used for grouping the sites are indicated by shading and bold text. Urban sites included in the IMPROVE network for quality assurance purposes are identified by stars.... S-4 Figure S.2.2. Current and discontinued Chemical Speciation Network (CSN) sites (grey and orange) operated by the Environmental Protection Agency. Regions are shown as shaded areas and bold text. The sites included in the analyses in this report are shown as orange circles.... S-5 Figure S.3.1. (a) IMPROVE and CSN PM 2.5 ammonium sulfate (AS) annual mean mass concentrations (μg m -3 ). (b) Interpolated ratios of urban (CSN) to rural (IMPROVE) annual mean AS concentrations for IMPROVE sites are shown as circles; CSN sites used in the analysis are shown as squares. CSN sites with no IMPROVE site within 150 km are shown as triangles. These sites were not used in the analysis.... S-9 Figure S.3.2. (a) IMPROVE and CSN PM 2.5 ammonium nitrate (AN) annual mean mass concentrations (μg m -3 ). (b) Interpolated ratios of urban (CSN) to rural (IMPROVE) annual mean AN concentrations for IMPROVE sites are shown as circles; CSN sites used in the analysis are shown as squares. CSN sites with no IMPROVE site within 150 km are shown as triangles. These sites were not used in the analysis.... S-10 Figure S.3.3. (a) IMPROVE and CSN PM 2.5 particulate organic matter (POM) annual mean mass concentrations (μg m -3 ). (b) Interpolated ratios of urban (CSN) to rural (IMPROVE) annual mean POM concentrations for IMPROVE sites are shown as circles; CSN sites used in the analysis are shown as squares. CSN sites with no IMPROVE site within 150 km are shown as triangles. These sites were not used in the analysis.... S-10 Figure S.3.4. (a) IMPROVE and CSN PM 2.5 light absorbing carbon (LAC) annual mean mass concentrations (μg m -3 ). (b) Interpolated ratios of urban (CSN) to rural (IMPROVE) annual mean LAC concentrations for IMPROVE sites are shown as circles; CSN sites used in the analysis are shown as squares. CSN sites with no IMPROVE site within 150 km are shown as triangles. These sites were not used in the analysis.... S-11 Figure S.4.1. (a) Seasonal variability for monthly mean IMPROVE ammonium sulfate (AS) mass concentrations. (b) The same as (a), but for the CSN. The color of the upwardpointing triangle refers to the season with the maximum monthly mean concentration, and the downward-pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration.... S-13 Figure S.4.2. (a) Seasonal variability for monthly mean IMPROVE ammonium nitrate (AN) mass concentrations. (b) The same as (a), but for the CSN. The color of the upward-pointing triangle refers to the season with the maximum monthly mean concentration, and the downward-pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration.... S-14 Figure S.4.3. (a) Seasonal variability for monthly mean IMPROVE particulate organic matter (POM) mass concentrations. (b) The same as (a), but for the CSN. The color of the upward-pointing triangle refers to the season with the maximum monthly mean viii

12 concentration, and the downward-pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration.... S-14 Figure S.4.4. (a) Seasonal variability for monthly mean IMPROVE light absorbing carbon (LAC) mass concentrations. (b) The same as (a), but for the CSN. The color of the upward-pointing triangle refers to the season with the maximum monthly mean concentration, and the downward-pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration.... S-15 Figure S.4.5. (a) Seasonal variability for monthly mean IMPROVE fine soil mass concentrations. (b) The same as (a), but for the CSN. The color of the upward-pointing triangle refers to the season with the maximum monthly mean concentration, and the downward-pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration.... S-16 Figure S.4.6. (a) Seasonal variability for monthly mean IMPROVE PM 2.5 gravimetric fine mass (FM) concentrations. (b) The same as (a), but for the CSN. The color of the upward-pointing triangle refers to the season with the maximum monthly mean concentration, and the downward-pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration.... S-17 Figure S.5.1a. Annual mean PM 2.5 deciview (dv) for for rural IMPROVE sites. Wavelength corresponds to 550 nm.... S-20 Figure S.5.1b. Seasonal variability for monthly mean IMPROVE deciview (dv) light extinction coefficient (b ext ). The color of the upward-pointing triangle refers to the season with the maximum monthly mean concentration, and the downward-pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration.... S-20 Figure S IMPROVE regional monthly mean ( ) PM 2.5 light extinction coefficient (b ext ) fractions for Hawaii, Alaska, and the Virgin Islands. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) is in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites, shown as dots.... S-21 Figure S IMPROVE regional monthly mean ( ) PM 2.5 light extinction coefficient (b ext ) fractions for the eastern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) is in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites, shown as dots.... S-22 Figure S IMPROVE regional monthly mean ( ) PM 2.5 light extinction coefficient (b ext ) fractions for the southwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) is in ix

13 yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites, shown as dots.... S-23 Figure S IMPROVE regional monthly mean ( ) PM 2.5 light extinction coefficient (b ext ) fractions for the northwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) is in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites, shown as dots.... S-23 Figure S Long-term ( ) trends (% yr -1 ) in average winter sulfate ion mass concentrations. Sites with statistically significant trends (p 0.05) are designated by filled red (increasing) and blue (decreasing) triangles. Insignificant trends (p>0.15) are designated by filled black triangles.... S-26 Figure S Short-term ( ) trends (% yr -1 ) in average spring sulfate ion mass concentrations. Sites with statistically significant trends (p 0.05) are designated by filled red (increasing) and blue (decreasing) triangles. Insignificant trends (p>0.15) are designated by filled black triangles.... S-27 Figure S Short-term ( ) trends (% yr -1 ) in 10 th percentile nitrate ion mass concentrations. Sites with statistically significant trends (p 0.05) are designated by filled red (increasing) and blue (decreasing) triangles. Insignificant trends (p>0.15) are designated by filled black triangles.... S-28 Figure S Short-term ( ) trends (% yr -1 ) in 50 th percentile nitrate ion mass concentrations. Sites with statistically significant trends (p 0.05) are designated by filled red (increasing) and blue (decreasing) triangles. Insignificant trends (p>0.15) are designated by filled black triangles.... S-29 Figure S Long-term ( ) trends (% yr -1 ) in 10 th percentile total carbon (TC = organic carbon + light absorbing carbon) mass concentrations. Sites with statistically significant trends (p 0.05) are designated by filled red (increasing) and blue (decreasing) triangles. Insignificant trends (p>0.15) are designated by filled black triangles.... S-30 Figure S Long-term ( ) trends (% yr -1 ) in 10 th percentile PM 2.5 gravimetric fine mass (FM) concentrations. Sites with statistically significant trends (p 0.05) are designated by filled red (increasing) and blue (decreasing) triangles. Insignificant trends (p>0.15) are designated by filled black triangles.... S-31 Figure 1.1. Class I areas of the contiguous United States. The shade coding identifies the managing agency of each Class I area Figure 1.2. Locations of IMPROVE and IMPROVE protocol sites are shown for all discontinued and current sites as of December The IMPROVE regions used for grouping the sites are indicated by shading and bold text. Urban sites included in the IMPROVE network for quality assurance purposes are identified by stars 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 x

14 Figure 1.4. Schematic of the version II IMPROVE sampler PM 2.5 module Figure 1.5. Detached screen cassette Figure 1.6. Attached screen cassette Figure 1.7. Filter sample collected using attached screen cassette Figure 1.8. Filter sample collected using detached screen cassette Figure 1.9. Current and discontinued Chemical Speciation Network (CSN) sites (grey and orange) operated by the Environmental Protection Agency. Regions are shown as shaded areas and bold text. The sites included in the analyses in this report are shown as orange circles Figure Comparisons of aerosol mass concentration data (μg m -3 ) for seven collocated IMPROVE and CSN sites (see text) for adjusted organic carbon (OC), adjusted light absorbing carbon (LAC), ammonium sulfate (AS), ammonium nitrate (AN), soil, sea salt (SS), PM 2.5 gravimetric fine mass (FM), and PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.1a. IMPROVE (rural) PM 2.5 ammonium sulfate (AS) annual mean mass concentrations (μg m -3 ) Figure 2.2.1b. IMPROVE and CSN PM 2.5 ammonium sulfate (AS) annual mean mass concentrations (μg m -3 ) Figure 2.2.1c. IMPROVE (rural) annual mean percent (%) contributions of ammonium sulfate (AS) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.1d. IMPROVE and CSN annual mean percent (%) contributions of ammonium sulfate (AS) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.2a. IMPROVE (rural) PM 2.5 ammonium nitrate (AN) annual mean mass concentrations (μg m -3 ) Figure 2.2.2b. IMPROVE and CSN PM 2.5 ammonium nitrate (AN) annual mean mass concentrations (μg m -3 ) Figure 2.2.2c. IMPROVE (rural) annual mean percent (%) contributions of ammonium nitrate (AN) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.2d. IMPROVE and CSN annual mean percent (%) contributions of ammonium nitrate (AN) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.3a. IMPROVE (rural) PM 2.5 particulate organic matter (POM) annual mean mass concentrations (μg m -3 ) Figure 2.2.3b. IMPROVE and CSN PM 2.5 particulate organic matter (POM) annual mean mass concentrations (μg m -3 ) Figure 2.2.3c. IMPROVE (rural) annual mean percent (%) contributions of particulate organic matter (POM) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.3d. IMPROVE and CSN annual mean percent (%) contributions of particulate organic matter (POM) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.4a. IMPROVE (rural) PM 2.5 light absorbing carbon (LAC) annual mean mass concentrations (μg m -3 ) xi

15 Figure 2.2.4b. IMPROVE and CSN PM 2.5 light absorbing carbon (LAC) annual mean mass concentrations (μg m -3 ) Figure 2.2.4c. IMPROVE (rural) annual mean percent (%) contributions of light absorbing carbon (LAC) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.4d. IMPROVE and CSN annual mean percent (%) contributions of light absorbing carbon (LAC) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.5a. IMPROVE (rural) PM 2.5 soil annual mean mass concentrations (μg m -3 ) Figure 2.2.5b. IMPROVE and CSN PM 2.5 soil annual mean mass concentrations (μg m -3 ) Figure 2.2.5c. IMPROVE (rural) annual mean percent (%) contributions of soil to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.5d. IMPROVE and CSN annual mean percent (%) contributions of soil to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.6a. IMPROVE (rural) PM 2.5 sea salt (SS) annual mean mass concentrations (μg m -3 ) Figure 2.2.6b. IMPROVE and CSN PM 2.5 sea salt (SS) annual mean mass concentrations (μg m -3 ) Figure 2.2.6c. IMPROVE (rural) annual mean percent (%) contributions of sea salt to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.6d. IMPROVE and CSN annual mean percent (%) contributions of sea salt (SS) to PM 2.5 reconstructed fine mass (RCFM) Figure 2.2.7a. IMPROVE (rural) PM 2.5 annual mean gravimetric fine mass (FM) concentrations (μg m -3 ) Figure 2.2.7b. IMPROVE and CSN PM 2.5 annual mean gravimetric fine mass (FM) concentrations (μg m -3 ) Figure 2.2.8a. IMPROVE (rural) PM 2.5 annual mean reconstructed fine mass (RCFM) concentrations (μg m -3 ) Figure b. IMPROVE and CSN PM 2.5 annual mean reconstructed fine mass (RCFM) concentrations (μg m -3 ) Figure 2.2.9a. IMPROVE (rural) PM 2.5 annual mean mass difference (dm = FM - RCFM) between PM 2.5 gravimetric fine mass (FM) and reconstructed fine mass (RCFM) (μg m - 3 ) Figure 2.2.9b. IMPROVE and CSN PM 2.5 annual mean difference (dm = FM - RCFM) between PM 2.5 gravimetric fine mass (FM) and reconstructed fine mass (RCFM) (μg m - 3 ) Figure IMPROVE (rural) annual mean coarse mass (CM = PM 10 - PM 2.5 ) (μg m -3 ) Figure a. IMPROVE (rural) annual mean PM 10 mass (μg m -3 ) xii

16 Figure b. IMPROVE (rural) and EPA annual mean PM 10 mass (μg m -3 ) Figure 3.1. Humidification factor (f(rh)) as a function of relative humidity (RH) A lognormal ammonium sulfate mass size distribution with a geometric mass mean diameter of 0.3 μm and a geometric standard deviation of 2.0 was assumed. A wavelength of 550 nm was used Figure 3.2a. PM 2.5 reconstructed ambient annual mean light extinction coefficient for ammonium sulfate (b ext_as, Mm -1 ) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.2b. PM 2.5 reconstructed ambient annual mean light extinction coefficient for ammonium sulfate (b ext_as, Mm -1 ) for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.2c. Annual mean percent contribution (%) of ambient ammonium sulfate (AS) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.2d. Annual mean percent contribution (%) of ambient ammonium sulfate (AS) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.3a. PM 2.5 reconstructed ambient annual mean light extinction coefficient for ammonium nitrate (b ext_an, Mm -1 ) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.3b. PM 2.5 reconstructed ambient annual mean light extinction coefficient for ammonium nitrate (b ext_an, Mm -1 ) for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.3c. Annual mean percent contribution (%) of ambient ammonium nitrate (AN) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.3d. Annual mean percent contribution (%) of ambient ammonium nitrate (AN) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.4a. PM 2.5 reconstructed ambient annual mean light extinction coefficient for particulate organic matter (POM) (b ext_pom, Mm -1 ) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.4b. PM 2.5 reconstructed ambient annual mean light extinction coefficient for particulate organic matter (POM) (b ext_pom, Mm -1 ) for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm xiii

17 Figure 3.4c. Annual mean percent contribution (%) of ambient particulate organic matter (POM) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.4d. Annual mean percent contribution (%) of ambient particulate organic matter (POM) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.5a. PM 2.5 reconstructed ambient annual mean light extinction coefficient for light absorbing carbon (b ext_lac, Mm -1 ) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.5b. PM 2.5 reconstructed ambient annual mean light extinction coefficient for light absorbing carbon (b ext_lac, Mm -1 ) for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.5c. Annual mean percent contribution (%) of ambient light absorbing carbon (LAC) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.5d. Annual mean percent contribution (%) of ambient light absorbing carbon (LAC) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.6a. PM 2.5 reconstructed ambient annual mean light extinction coefficient for soil (b ext_soil, Mm -1 ) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.6b. PM 2.5 reconstructed ambient annual mean light extinction coefficient for soil (b ext_soil, Mm -1 ) for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.6c. Annual mean percent contribution (%) of ambient soil light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.6d. Annual mean percent contribution (%) of ambient soil light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.7a. PM 2.5 reconstructed ambient annual mean light extinction coefficient for sea salt (b ext_ss, Mm -1 ) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.7b. PM 2.5 reconstructed ambient annual mean light extinction coefficient for sea salt (b ext_ss, Mm -1 ) for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm xiv

18 Figure 3.7c. Annual mean percent contribution (%) of ambient sea salt (SS) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.7d. Annual mean percent contribution (%) of ambient sea salt (SS) light extinction coefficient (b ext ) to PM 2.5 reconstructed aerosol b ext for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.8a. PM 2.5 reconstructed annual mean light extinction coefficient for ambient aerosol (b ext_aer, Mm -1 ) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.8b. PM 2.5 reconstructed annual mean light extinction coefficient for ambient aerosol (b ext_aer, Mm -1 ) for for rural IMPROVE and urban CSN sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.9a. Annual mean light extinction coefficient for coarse mass (b ext_cm, Mm -1 ) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure 3.9b. Annual mean percent contribution (%) of coarse mass (CM) light extinction coefficient to total reconstructed aerosol b ext for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm. Rayleigh scattering was not included in total b ext Figure Annual mean PM 2.5 deciview (dv) for for rural IMPROVE sites. The modified original IMPROVE algorithm was used (see text). Wavelength corresponds to 550 nm Figure IMPROVE regional monthly mean PM 2.5 mass concentrations (μg m -3 ) for the eastern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure IMPROVE regional monthly mean PM 2.5 mass concentrations (μg m - 3 ) for the northwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure IMPROVE regional monthly mean PM 2.5 mass concentrations (μg m - 3 ) for the southwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots xv

19 Figure IMPROVE regional monthly mean PM 2.5 mass concentrations (μg m - 3 ) for Hawaii, Alaska, and the Virgin Islands. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure Seasonal variability for IMPROVE monthly mean ammonium sulfate (AS) mass concentrations. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure CSN regional monthly mean PM 2.5 mass concentrations (μg m -3 ) for the eastern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure CSN regional monthly mean PM 2.5 mass concentrations (μg m -3 ) for the southwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure CSN regional monthly mean PM 2.5 mass concentrations (μg m -3 ) for the northwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure CSN regional monthly mean PM 2.5 mass concentrations (μg m -3 ) for Hawaii and Alaska. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure Seasonal variability for CSN monthly mean ammonium sulfate (AS) mass concentrations. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure IMPROVE regional monthly mean PM 2.5 reconstructed fine mass fractions for the eastern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in xvi

20 red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure IMPROVE regional monthly mean PM 2.5 reconstructed fine mass fractions for the northwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure IMPROVE regional monthly mean PM 2.5 reconstructed fine mass fractions for the southwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure IMPROVE regional monthly mean PM 2.5 reconstructed fine mass fractions for Hawaii, Alaska,and the Virgin Islands. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure Seasonal variability for IMPROVE monthly mean ammonium sulfate (AS) reconstructed fine mass fractions. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure CSN regional monthly mean PM 2.5 reconstructed fine mass fractions for the eastern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure CSN regional monthly mean PM 2.5 reconstructed fine mass fractions for the northwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure CSN regional monthly mean PM 2.5 reconstructed fine mass fractions for the southwestern United States. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, xvii

21 soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure CSN regional monthly mean PM 2.5 reconstructed fine mass fractions for Hawaii and Alaska. The letters on the x-axis correspond to the month and A corresponds to annual mean. Ammonium sulfate (AS) in yellow, ammonium nitrate (AN) in red, particulate organic matter (POM) in green, light absorbing carbon (LAC) in black, soil in brown, and sea salt in blue. The shaded area corresponds to the regions that comprise the sites used in the analysis, shown as dots Figure Seasonal variability for CSN monthly mean ammonium sulfate (AS) reconstructed fine mass fractions. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for IMPROVE monthly mean ammonium nitrate (AN) mass concentrations. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for CSN monthly mean ammonium nitrate (AN) mass concentrations. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for IMPROVE monthly mean ammonium nitrate (AN) reconstructed fine mass fractions. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for CSN monthly mean ammonium nitrate (AN) reconstructed fine mass fractions. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for IMPROVE monthly mean particulate organic matter (POM) mass concentrations. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for CSN monthly mean particulate organic matter (POM) mass concentrations. The color of the upward pointing triangle refers to the season xviii

22 with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for IMPROVE monthly mean particulate organic matter (POM) reconstructed fine mass fractions. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for CSN monthly mean particulate organic matter (POM) reconstructed fine mass fractions. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for IMPROVE monthly mean light absorbing carbon (LAC) mass concentrations. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for CSN monthly mean light absorbing carbon (LAC) mass concentrations. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for IMPROVE monthly mean light absorbing carbon (LAC) reconstructed fine mass fractions. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for CSN monthly mean light absorbing carbon (LAC) reconstructed fine mass fractions. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration Figure Seasonal variability for IMPROVE monthly mean fine soil mass concentrations. The color of the upward pointing triangle refers to the season with the maximum monthly mean concentration and the downward pointing triangle refers to the season with the minimum monthly mean concentration. The size of the triangles refers to the magnitude of the ratio of maximum to minimum monthly mean mass concentration xix