HomeMy WebLinkAboutAQ_GEN_PLNG_20220404_SIP_RH-SIP_AppE2d
Appendix E-2d
Regional Haze Modeling for Southeastern VISTAS II
Regional Haze Analysis Project 2028 CAMx Version
6.32 and 6.40 Comparison Report
Benchmark Run #4
August 17, 2020
This page intentionally left blank.
CAMx Benchmarking Report #4
Regional Haze Modeling for Southeastern
VISTAS II Regional Haze Analysis Project
2028 CAMx Version 6.32 and 6.40 Comparison
Report
Task 6 Benchmark Report #4
Covering Benchmark Run #4
Prepared for:
Southeastern States Air Resource Managers, Inc.
(SESARM)
205 Corporate Center Drive, Suite D
Stockbridge, GA 30281-7383
Under Contract No. V-2018-03-01
Prepared by:
Alpine Geophysics, LLC
387 Pollard Mine Road
Burnsville, NC 28714
and
Eastern Research Group, Inc.
1600 Perimeter Park Dr., Suite 200
Morrisville, NC 27560
Final – August 17, 2020
Alpine Project Number: TS-527
ERG Project Number: 4133.00.006
CAMx Benchmarking Report #4
August 17, 2020 i
This page is intentionally blank.
CAMx Benchmarking Report #4
August 17, 2020 ii
Contents
Page
1.0 INTRODUCTION ............................................................................................................1
1.1 Overview ...............................................................................................................1
1.2 2028 CAMx 6.32 and CAMx 6.40 Comparison ...................................................3
2.0 DIFFERENCES BETWEEN CAMX 6.32 AND 6.40 SIMULATIONS .........................3
2.1 Model Code Differences .......................................................................................3
2.2 Configurations Difference ....................................................................................4
2.3 Emissions Differences ..........................................................................................5
3.0 CONFIRMATION METHODOLOGY ............................................................................5
3.1 CAMx Species Mapping .......................................................................................6
4.0 CAMX 6.32 2028EL AND CAMX 6.40 2028ELV3 COMPARISON ............................7
4.1 Emissions ..............................................................................................................7
4.2 Annual PM2.5 Design Value ................................................................................25
4.3 24-Hour (Daily) PM2.5 Design Value ..................................................................34
4.4 Scatterplots of Ozone and PM Species Concentrations ......................................42
5.0 CONCLUSIONS.............................................................................................................49
CAMx Benchmarking Report #4
August 17, 2020 iii
This page is intentionally blank.
CAMx Benchmarking Report #4
August 17, 2020 iv
TABLES
Table 3-1. Species Mapping from CAMx into Aggregated Species ...............................................6
Table 4-1. Comparison of 2028el CAMx 6.32 and 2028elv2/v3 CAMx 6.40 Annual
Emissions .............................................................................................................................8
Table 4-2. Comparison of 2028el CAMx 6.32 and 2028elv3 CAMx 6.40 Predicted Annual
PM2.5 Design Values (µg/m3) for FRM Monitors in VISTAS States ................................26
Table 4-3. Comparison of CAMx 6.40 2028elv3 and CAMx 6.32 2028el Simulation of Daily
(24-Hour) PM2.5 Design Values (µg/m3) ...........................................................................35
FIGURES
Figure 4-1. Comparison of Elevated NOX Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations ..........................................................................................9
Figure 4-2. Comparison of Elevated VOC Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations ........................................................................................10
Figure 4-3. Comparison of Elevated PEC Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations ........................................................................................12
Figure 4-4. Comparison of Elevated PNH4 Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations ........................................................................................13
Figure 4-5. Comparison of Elevated PNO3 Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations ........................................................................................14
Figure 4-6. Comparison of Elevated POA Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations ........................................................................................15
Figure 4-7. Comparison of Elevated PSO4 Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations ........................................................................................16
Figure 4-8. Comparison of Low Level NOX Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations ........................................................................................17
Figure 4-9. Comparison of Low Level VOC Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations ........................................................................................18
Figure 4-10. Comparison of Low Level SO2 Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations ........................................................................................19
Figure 4-11. Comparison of Low Level PEC Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations ........................................................................................20
Figure 4-12. Comparison of Low Level PNH4 Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations ........................................................................................21
Figure 4-13. Comparison of Low Level PNO3 Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations ........................................................................................22
CAMx Benchmarking Report #4
August 17, 2020 v
Figure 4-14. Comparison of Low Level POA Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations ........................................................................................23
Figure 4-15. Comparison of Low Level PSO4 Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations ........................................................................................24
Figure 4-16. Comparison of Annual PM2.5 Design Values (µg/m3) for CAMx 6.32 2028el and
CAMx 6.40 2028elv3 Simulations ....................................................................................32
Figure 4-17. Scatterplot Comparing Annual Average Predicted PM2.5 Design Values (µg/m3)
at all Monitor Locations for CAMx 6.32 2028el and CAMx 6.40 2028elv3
Simulations Performed by VISTAS (Alpine) ....................................................................33
Figure 4-18. Comparison of Daily PM2.5 Design Values (µg/m3) for CAMx 6.32 2028el and
CAMx 6.40 2028elv3 Simulations ....................................................................................40
Figure 4-19. Comparison of Daily PM2.5 Design Values (µg/m3) for CAMx 6.32 2028el and
CAMx 6.40 2028elv3 Simulations ....................................................................................41
Figure 4-20. Scatterplot Comparing 24-hour Average Predicted Ozone Concentrations (ppb)
for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx 6.40
2028 Simulations Performed by VISTAS (Alpine) ...........................................................42
Figure 4-21. Scatterplot Comparing 24-hour Average Predicted PM2.5 Concentrations (µg/m3)
for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx 6.40
2028 Simulations Performed by VISTAS (Alpine) ...........................................................43
Figure 4-22. Scatterplot Comparing 24-hour Average Predicted PM2.5 Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx
6.40 2028 Simulations Performed by VISTAS (Alpine); Modified Scale ........................44
Figure 4-23. Scatterplot Comparing 24-hour Average Predicted Sulfate Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx
6.40 2028 Simulations Performed by VISTAS (Alpine) ...................................................45
Figure 4-24. Scatterplot Comparing 24-hour Average Predicted Nitrate Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx
6.40 2028 Simulations Performed by VISTAS (Alpine) ...................................................46
Figure 4-25. Scatterplot Comparing 24-hour Average Predicted Organic Carbon
Concentrations (µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx
6.32 and CAMx 6.40 2028 Simulations Performed by VISTAS (Alpine) ........................47
Figure 4-26. Scatterplot Comparing 24-hour Average Predicted Organic Carbon
Concentrations (µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx
6.32 and CAMx 6.40 2028 Simulations Performed by VISTAS (Alpine); Modified
Scale ...................................................................................................................................48
CAMx Benchmarking Report #4
August 17, 2020 vi
Abbreviations/Acronym List
Alpine Alpine Geophysics, LLC
CAMx Comprehensive Air Quality Model with Extensions
dv Deciview
DV Design Value
EGU Electric Generating Unit
EPA Environmental Protection Agency
ERG Eastern Research Group, Inc.
ERTAC Eastern Regional Technical Advisory Committee
FLM Federal Land Manager
FR Federal Register
IPM Integrated Planning Model
km kilometer
µg/m3 microgram per cubic meter
NAAQS National Ambient Air Quality Standard
NOx Oxides of nitrogen
OAQPS Office of Air Quality Planning and Standards
O3 Ozone
OC Organic carbon
OSAT Ozone Source Apportionment Technology
PEC Primary elemental carbon
PM Particulate matter
PM2.5 Fine particle; primary particulate matter less than or equal to 2.5 microns
in aerodynamic diameter
PNH4 Particulate ammonium
PNO3 Particulate nitrate
POA Primary Organic Aerosol
PSAT Particulate Source Apportionment Technology
PSO4 Particulate sulfate
R2 Pearson correlation coefficient squared
RADM-AQ Regional Acid Deposition Model – aqueous chemistry
RHR Regional Haze Rule
SESARM Southeastern States Air Resource Managers, Inc.
SIP State Implementation Plan
SMAT-CE Software for Model Attainment Test – Community Edition
SMOKE Sparse Matrix Operator Kernel Emissions
SO2 Sulfur dioxide
SOA Secondary organic aerosol
SOAP Secondary organic aerosol partitioning
tpy Tons per year
U.S. United States
VISTAS Visibility Improvement – State and Tribal Association of the Southeast
VOC Volatile organic compounds
CAMx Benchmarking Report #4
August 17, 2020 vii
This page is intentionally blank.
CAMx Benchmarking Report #4
August 17, 2020 1
1.0 INTRODUCTION
1.1 Overview
Southeastern States Air Resource Managers, Inc. (SESARM) has been designated by the
United States (U.S.) Environmental Protection Agency (EPA) as the entity responsible for
coordinating regional haze evaluations for the ten Southeastern states of Alabama, Florida,
Georgia, Kentucky, Mississippi, North Carolina, South Carolina, Tennessee, Virginia, and West
Virginia. The Eastern Band of Cherokee Indians and the Knox County, Tennessee local air
pollution control agency are also participating agencies. These parties are collaborating through
the Regional Planning Organization known as Visibility Improvement - State and Tribal
Association of the Southeast (VISTAS) in the technical analyses and planning activities
associated with visibility and related regional air quality issues. VISTAS analyses will support
the VISTAS states in their responsibility to develop, adopt, and implement their State
Implementation Plans (SIPs) for regional haze.
The state and local air pollution control agencies in the Southeast are mandated to protect
human health and the environment from the impacts of air pollutants. They are responsible for
air quality planning and management efforts including the evaluation, development, adoption,
and implementation of strategies controlling and managing all criteria air pollutants including
fine particles and ozone (O3) as well as regional haze. This project will focus on regional haze
and regional haze precursor emissions. Control of regional haze precursor emissions will have
the additional benefit of reducing criteria pollutants as well.
The 1999 Regional Haze Rule (RHR) identified 18 Class I Federal areas (national parks
greater than 6,000 acres and wilderness areas greater than 5,000 acres) in the VISTAS region.
The 1999 RHR required states to define long-term strategies to improve visibility in Federal
Class I national parks and wilderness areas. States were required to establish baseline visibility
conditions for the period 2000-2004, natural visibility conditions in the absence of anthropogenic
influences, and an expected rate of progress to reduce emissions and incrementally improve
visibility to natural conditions by 2064. The original RHR required states to improve visibility on
the 20% most impaired days and protect visibility on the 20% least impaired days.1 The RHR
1 RHR summary data is available at: http://vista.cira.colostate.edu/Improve/rhr-summary-data/
CAMx Benchmarking Report #4
August 17, 2020 2
requires states to evaluate progress toward visibility improvement goals every five years and
submit revised SIPs every ten years.
EPA finalized revisions to various requirements of the RHR in January 2017 (82 FR
3078) that were designed to strengthen, streamline, and clarify certain aspects of the agency’s
regional haze program including:
A. Strengthening the Federal Land Manager (FLM) consultation requirements to ensure
that issues and concerns are brought forward early in the planning process.
B. Updating the SIP submittal deadlines for the second planning period from July 31,
2018 to July 31, 2021 to ensure that they align where applicable with other state
obligations under the Clean Air Act. The end date for the second planning period
remains 2028; that is, the focus of state planning will be to establish reasonable
progress goals for each Class I area against which progress will be measured during
the second planning period. This extension will allow states to incorporate planning
for other Federal programs while conducting their regional haze planning. These
other programs include: the Mercury and Air Toxics Standards, the 2010 1-hour
sulfur dioxide (SO2) National Ambient Air Quality Standards (NAAQS); the 2012
annual fine particle (PM2.5) NAAQS; and the 2008 and 2015 ozone NAAQS.
C. Adjusting interim progress report submission deadlines so that second and subsequent
progress reports will be due by: January 31, 2025; July 31, 2033; and every ten years
thereafter. This means that one progress report will be required midway through each
planning period.
D. Removing the requirement for progress reports to take the form of SIP revisions.
States will be required to consult with FLMs and obtain public comment on their
progress reports before submission to the EPA. EPA will be reviewing but not
formally approving or disapproving these progress reports.
The RHR defines “clearest days” as the 20% of monitored days in a calendar year with
the lowest deciview (dv) index values. “Most impaired days” are defined as the 20% of
CAMx Benchmarking Report #4
August 17, 2020 3
monitored days in a calendar year with the highest amounts of anthropogenic visibility
impairment. The long-term strategy and the reasonable progress goals must provide for an
improvement in visibility for the most impaired days since the baseline period and ensure no
degradation in visibility for the clearest days since the baseline period.
1.2 2028 CAMx 6.32 and CAMx 6.40 Comparison
Recent EPA 2011el and 2028el platform simulations were performed with the
Comprehensive Air Quality Model with Extensions (CAMx) version 6.32. Since that time the
CAMx model has been updated to include better physical treatment, and to correct any model
flaws that were discovered after the release of 6.32.
Under subcontract to Eastern Research Group, Inc, (ERG), Alpine Geophysics, LLC
(Alpine) has executed two air quality simulations for the 2028el projection year modeling
platform; one run with CAMx 6.32 and one with CAMx 6.40. We note that CAMx 6.50 has now
been released, however that model release was too late to be included with sufficient certainty in
the VISTAS II project schedule.
This comparison is to document the differences in model estimates between 2028el
simulated with CAMx 6.32 and 2028elv3 CAMx 6.40 as is discussed in the VISTAS II
Modeling Protocol 2 in Section 6.5.2 model comparison number 4.
2.0 DIFFERENCES BETWEEN CAMX 6.32 AND 6.40 SIMULATIONS
Differences in modeled output concentrations between the 2028el CAMx 6.32 and
2028elv3 6.40 simulations were as a result both of changes to the CAMx model code, changes to
the model configuration and changes to the emissions inventory.
2.1 Model Code Differences
Many updates to the CAMx model were implemented between the 6.32 and 6.40 release.
According to the CAMx 6.40 release notes, the significant changes included:
2 “Regional Haze Modeling for Southeastern VISTAS II Region Haze Analysis Project, Final Modeling Protocol.” Prepared
for SESARM under Contract No. V-2018-03-01. Prepared by Alpine Geophysics, LLC and Eastern Research Group, Inc.
June 27, 2018.
CAMx Benchmarking Report #4
August 17, 2020 4
1. Updates to the chemistry to include a condensed halogen mechanism for ocean-borne
inorganic reactive iodine, hydrolysis of isoprene-derived organic nitrate and SO2
oxidation on primary crustal fine particulate matter (PM). This update includes the
changes to the Ozone and Particulate Source Apportionment Technology
(OSAT/PSAT) algorithms;
2. Inclusion of in-line inorganic iodine emissions to support halogen chemical
mechanisms;
3. A major revision to the secondary organic aerosol partitioning (SOAP) secondary
algorithm;
4. Updates to the Regional Acid Deposition Model – aqueous chemistry (RADM-AQ)
algorithm; and
5. A major revision to the wet deposition algorithm to identify assumptions or processes
that were unintentionally or otherwise unreasonably limiting gas and PM update into
precipitation. The wet deposition algorithm was simplified and improved in several
ways, resulting in the increased scavenging of gases and PM.
2.2 Configurations Difference
In addition to the model version, the CAMx 6.32 and 6.40 simulations contained
differences in the EPA modeling platform that had been made subsequent to the 2011el/2028el
model release. In the most current 2023en simulation, EPA developed new photolysis rates and
ozone column data. These updates were included in the updated modeling platform and resulting
CAMx 6.40 simulation and were consistent with those used in the VISTAS II 2011el
simulations.
Another configuration difference is how the boundary conditions were mapped for
speciation in the two versions of the model. EPA and the VISTAS CAMx 6.32 and 6.40
simulations all used the same boundary condition files. However, when CAMx was updated
from 6.32 to 6.40 the species in the secondary organic aerosol (SOA) scheme changed. The
SOA5, SOA6, and SOA7 were removed and SOA3 and SOA4 were redefined. Neither EPA nor
CAMx Benchmarking Report #4
August 17, 2020 5
this study remapped the boundary conditions to account for this change. EPA examined the
regional haze summary data for all Class I areas and found the total organic carbon (OC) species
(not just SOA) accounted for 1-5% of the boundary condition impairment at the Southeastern
Class I areas.3 This is a small impact on regional haze and the impact of SOA on regional haze is
even smaller.
2.3 Emissions Differences
Finally, there are notable emissions inventory differences used in the modeling by
SESARM compared to EPA’s 2028el modeling platform. SESARM updated the 2028 emissions
inventory used in this analysis (2028elv2) with changes to both electric generating unit (EGU)
and non-EGU point source emissions. A summary of the emission differences are presented in
the Task 2 emissions inventory report 4 for this study and summarized in Section 4.1.
3.0 CONFIRMATION METHODOLOGY
The presented comparison of model simulations are based on annual and 24-hour PM2.5
design values as generated from the output of the two 12US2-based simulations; CAMx 6.32
with 2028el and CAMx 6.40 with 2028elv2 emissions. This report does not compare hourly
concentrations for each PM species as the model version, platform configuration and processing
methods, and the underlying projection year emissions inventories differ significantly between
the two model runs making it difficult, if not impossible, to determine the cause of any
differences seen in concentrations. We also provide a comparison of gridded 12-kilometer (km)
annual elevated and low level emissions for the domain. The metric for comparison of the design
values are the absolute difference (Equation 1) and percent difference (Equation 2) defined as:
(Equation 1) (𝐶𝐶6.40 −𝐶𝐶6.32 )
(Equation 2) (𝐶𝐶6.40−𝐶𝐶6.32 )(𝐶𝐶6.32 )
Where C6.40 is the design value at each receptor for the CAMx 6.40 simulation and C6.32
is the design value at each receptor for the CAMx 6.32 simulation. The order of the comparison
3 Brian Timin, EPA Office of Air Quality Planning and Standards (OAQPS) personal communication October 11, 2018.
4 Southeastern States Air Resource Managers, Inc. "Southeastern VISTAS II Regional Haze Analysis Project - Task 2
Emission Inventory Report." Prepared by Eastern Research Group, Inc. under Contract V-2018-03-01. Revised Final. August
28, 2018.
CAMx Benchmarking Report #4
August 17, 2020 6
variables differs from earlier benchmark reports as the intention of this report is to confirm
appropriate use of the CAMx 6.40 configuration as compared to the CAMx 6.32 configuration
and therefore by using the switched order, we give more weight to the CAMx 6.40 run. For the
emission comparison plots, only Equation 1 results were calculated for each grid cell and plotted
for review.
The results are presented for each receptor in the VISTAS states within the larger 12US2
domain for each of the two design values. Spatial maps are presented for the domain as a whole.
On each spatial emissions difference plot presented, the maximum positive and negative values,
along with the grid cell in which these occur, are presented at the top of the graphic. The
coordinates refer to the row and columns of the cell referenced to the cell coordinates on the
bottom (column) and left (row) of the graphic.
Scatterplots of the daily average concentrations of ozone and the various calculated PM
species in local standard time at the Interagency Monitoring for Protected Visual Environment
(IMPROVE) monitors across all modeled days are also presented with the CAMx 6.40 results
plotted on the x-axis and the CAMx 6.32 results plotted on the y-axis.
3.1 CAMx Species Mapping
Updates to the CAMx model between version 6.32 and 6.40 necessitated making changes
to how the individual CAMx species were aggregated to the presented species. The CAMx
species mapping between the two compared versions are presented in Table 3-1.
Table 3-1. Species Mapping from CAMx into Aggregated Species
Aggregated
Species CAMx 6.32 Species CAMx 6.40 Species
Ozone O3 O3
PM2.5
PSO4+PNO3+PNH4+SOA1+SOA2+SOA3
+SOA4+SOA5+SOA6+SOA7+SOPA+SOP
B+POA+PEC+FPRM+FCRS+NA+PCL
PSO4+PNO3+PNH4+SOA1+SOA2
+SOA3+SOA4+SOPA+SOPB+POA
+PEC+FPRM+FCRS+NA+PCL
Sulfate PSO4 PSO4
Nitrate PNO3 PNO3
Organic
Matter (OM)
SOA1+SOA2+SOA3+SOA4+SOA5+SOA6
+SOA7+SOPA+SOPB+POA1
SOA1+SOA2+SOA3+SOA4+SOPA
+SOPB+POA
1 SOAH was not included in the 6.32 comparison since it was not included as an output species in the EPA
simulation.
CAMx Benchmarking Report #4
August 17, 2020 7
4.0 CAMX 6.32 2028EL AND CAMX 6.40 2028ELV3 COMPARISON
This section presents comparisons of the simulations using CAMx 6.32 2028el and
CAMx 6.40 2028elv3 performed on the Alpine computer system. Emissions presented are the
post-processed results of the Sparse Matrix Operator Kernel Emissions (SMOKE) emissions
tool, including oxides of nitrogen (NOX), volatile organic compounds (VOC), and speciated
PM2.5 components (e.g., particulate nitrate (PNO3), particulate sulfate (PSO4), etc.) for elevated
and low level sources. Annual and 24-Hour PM2.5 design values are the result of running each of
the model platforms through the Software for the Modeled Attainment Test - Community Edition
(SMAT-CE) tool to generate receptor-level values.
4.1 Emissions
Annual emission summaries have been prepared from the model-ready input files for
both elevated and low level sources. Elevated sources include all CEM-based emissions in the
modeling platform, non-EGU point sources with explicit latitude and longitude release
coordinates and calculated plume rise greater than or equal to twenty (20) meters, emissions
from wildfires, and international commercial marine emissions not otherwise associated with
specific U.S. states. Low-level sources are comprised of all other anthropogenic source types
including non-EGU point sources with a calculated plume rise of less than twenty (20) meters,
agricultural and prescribed fires, biogenic and other natural source emissions, and commercial
marine emissions associated with sources assigned to specific U.S. states. Results presented
include maps of the 12US2 domain with annual emissions (tons per year) and emission
differences by grid cell and pollutant. Table 4-1 presents summary results by pollutant over the
entire 12US2 domain for elevated and low level comparisons. Figures 4-1 through 4-7 present
the annual emissions and emission differences for elevated sources by pollutant in the 12US2
modeling domain. Figures 4-8 through 4-15 present annual emissions and emission differences
for low level sources, by pollutant, in the 12US2 modeling domain.
As expected with the changes in emission inventories between the EPA 2028el and
SESARM 2028elv2 platforms, we see the largest changes in elevated (point source) emissions
largely concentrated in the southeastern sector of the modeling domain with scattered differences
in other regions. These changes are related to the replacement of 2028 Integrated Planning
Model (IPM) EGU emissions with 2028 Eastern Regional Technical Advisory Committee
CAMx Benchmarking Report #4
August 17, 2020 8
(ERTAC) EGU emissions in the 2028elv2 emissions platform. These differences are consistent
with the emission inventory changes documented4 for this project. Low-level emission changes
are also seen predominantly in the VISTAS states for areas where emission inventory
modifications were applied for this analysis with scattered changes elsewhere due to the
replacement of IPM with ERTAC as noted above. Note that as a result of reprocessing the
2028elv2 elevated emissions to correct an earlier omission, results are reported in this document
2028elv3 where appropriate.
Table 4-1. Comparison of 2028el CAMx 6.32 and 2028elv2/v3 CAMx 6.40 Annual Emissions
Source Type Pollutant
2028 Annual Emissions
CAMx 6.40 6.40 - 6.32 Domain Wide Individual Grid Cell
Total Tons Total Change % Change Max Increase Max Decrease
Elevated NOX 4,512,000 489,300 10.84% 25,810 -25,250
Elevated VOCa 4,707,000 -8,096 -0.17% 2,046 -2,615
Elevated SO2 3,977,000 795,000 19.99% 54,910 -38,780
Elevated PEC 261,300 16,620 6.36% 358 -126
Elevated PNH4b 14,690 3.47E+01 0.24% 32 -15
Elevated PNO3 15,460 8.64E+02 5.59% 20 -25
Elevated POA 1,734,000 12,240 0.71% 323 -1,269
Elevated PSO4 83,570 1,814 2.17% 388 -298
Low Level NOX 7,302,000 5,788 0.08% 632 -1,695
Low Level VOC 60,670,000 45,170 0.07% 2,615 -861
Low Level SO2 321,500 2,623 0.82% 1,487 -501
Low Level PEC 151,900 324 0.21% 77 -9
Low Level PNH4b 6,696 13 0.20% 6 -3
Low Level PNO3 4,671 44 0.95% 12 -5
Low Level POA 909,600 -2,630 -0.29% 54 -87
Low Level PSO4 198,300 1,223 0.62% 82 -19
a VOC emissions are approximate since calculated from CB6 speciated emissions.
b PNH4 = Particulate ammonium
CAMx Benchmarking Report #4
August 17, 2020 9
Annual NOX Emissions – Elevated Sources
2028elv3
Difference (2028elv3 - 2028el)
Figure 4-1. Comparison of Elevated NOX Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 10
Annual VOC Emissions – Elevated Sources
2028elv3
Difference (2028elv3 - 2028el)
Figure 4-2. Comparison of Elevated VOC Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 11
Annual SO2 Emissions – Elevated Sources
2028elv3
Difference (2028elv3 - 2028el)
Figure 4-3. Comparison of Elevated SO2 Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 12
Annual PEC Emissions – Elevated Sources
2028elv3
Difference (2028elv3 - 2028el)
Figure 4-3. Comparison of Elevated PEC Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 13
Annual PNH4 Emissions – Elevated Sources
2028elv3
Difference (2028elv3 - 2028el)
Figure 4-4. Comparison of Elevated PNH4 Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 14
Annual PNO3 Emissions – Elevated Sources
2028elv3
Difference (2028elv3 - 2028el)
Figure 4-5. Comparison of Elevated PNO3 Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 15
Annual POA Emissions – Elevated Sources
2028elv3
Difference (2028elv3 - 2028el)
Figure 4-6. Comparison of Elevated POA Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 16
Annual PSO4 Emissions – Elevated Sources
2028elv3
Difference (2028elv3 - 2028el)
Figure 4-7. Comparison of Elevated PSO4 Emissions (tpy) for CAMx 6.40 2028elv3 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 17
Annual NOX Emissions – Low Level Sources
2028elv2
Difference (2028elv2 - 2028el)
Figure 4-8. Comparison of Low Level NOX Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 18
Annual VOC Emissions – Low Level Sources
2028elv2
Difference (2028elv2 - 2028el)
Figure 4-9. Comparison of Low Level VOC Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 19
Annual SO2 Emissions – Low Level Sources
2028elv2
Difference (2028elv2 - 2028el)
Figure 4-10. Comparison of Low Level SO2 Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 20
Annual PEC Emissions – Low Level Sources
2028elv2
Difference (2028elv2 - 2028el)
Figure 4-11. Comparison of Low Level PEC Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 21
Annual PNH4 Emissions – Low Level Sources
2028elv2
Difference (2028elv2 - 2028el)
Figure 4-12. Comparison of Low Level PNH4 Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 22
Annual PNO3 Emissions – Low Level Sources
2028elv2
Difference (2028elv2 - 2028el)
Figure 4-13. Comparison of Low Level PNO3 Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 23
Annual POA Emissions – Low Level Sources
2028elv2
Difference (2028elv2 - 2028el)
Figure 4-14. Comparison of Low Level POA Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 24
Annual PSO4 Emissions – Low Level Sources
2028elv2
Difference (2028elv2 - 2028el)
Figure 4-15. Comparison of Low Level PSO4 Emissions (tpy) for CAMx 6.40 2028elv2 and
CAMx 6.32 2028el Simulations
CAMx Benchmarking Report #4
August 17, 2020 25
4.2 Annual PM2.5 Design Value
Annual PM2.5 design values were generated using the results of each individual CAMx
simulation (version 6.32 with EPA’s 2028el platform and version 6.40 with SESARM’s
2028elv3 emissions platform) and the SMAT-CE tool. Results for each individual receptor in the
VISTAS states are presented in tabular format in Table 4-2 along with the absolute difference
and percent difference in design value.
The maximum calculated increase is 0.51 µg/m3 at monitor 510590030 in Fairfax,
Virginia (7% increase between 6.32 and 6.40) and maximum decrease is 0.43 µg/m3 at monitor
210290006 in Bullitt County, Kentucky (4% decrease going from 6.32 to 6.40). The average
change in annual design value for all monitors in the VISTAS states is an increase of 0.20 µg/m3,
with an average annual percent increase of 3% at these same locations.
Geographic distribution of the 6.40 annual PM2.5 design values and differences in design
values compared to the 6.32 simulation is presented in Figure 4-16. In the VISTAS state region,
the largest annual PM2.5 design value fractional change is seen along the Atlantic coast and
through much of North Carolina. The smallest fractional changes seen inside the heart of the
SESARM state domain consistent with significant emission reductions modeled from updated
EGU inventories within these states.
A scatterplot of the annual PM2.5 design values for all FRM monitors in the 12US2
domain is presented in Figure 4-17. The CAMx 6.40 results are plotted on the x-axis and the
CAMx 6.32 results are plotted on the y-axis. The data has a high degree of correlation with a line
of best fit with a slope of 0.9875, an intercept of -0.1058 µg/m3and an R2 of 0.9825. The
agreement between the models is higher at lower concentrations. CAMx 6.40 concentrations
appear to be marginally higher compared to CAMx 6.32 at low and medium concentration
ranges and slightly lower than the CAMx 6.32 results in high concentration ranges.
CAMx Benchmarking Report #4
August 17, 2020 26
Table 4-2. Comparison of 2028el CAMx 6.32 and 2028elv3 CAMx 6.40 Predicted Annual
PM2.5 Design Values (µg/m3) for FRM Monitors in VISTAS States
Monitor State County
2028 Annual PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
010030010 Alabama Baldwin 7.98 8.06 0.08 1%
010270001 Alabama Clay 7.78 7.92 0.14 2%
010331002 Alabama Colbert 8.21 8.37 0.16 2%
010491003 Alabama DeKalb 8.33 8.52 0.19 2%
010550010 Alabama Etowah 8.66 8.84 0.18 2%
010690003 Alabama Houston 8.12 8.25 0.13 2%
010730023 Alabama Jefferson 10.92 11.17 0.25 2%
010731005 Alabama Jefferson 9.25 9.33 0.08 1%
010731009 Alabama Jefferson 8.16 8.24 0.08 1%
010731010 Alabama Jefferson 9.44 9.56 0.12 1%
010732003 Alabama Jefferson 10.14 10.31 0.17 2%
010732006 Alabama Jefferson 9.42 9.50 0.08 1%
010735002 Alabama Jefferson 8.74 8.97 0.23 3%
010735003 Alabama Jefferson 8.55 8.68 0.13 2%
010890014 Alabama Madison 8.94 9.15 0.21 2%
010970003 Alabama Mobile 8.02 8.16 0.14 2%
010972005 Alabama Mobile 7.74 7.83 0.09 1%
011011002 Alabama Montgomery 9.33 9.58 0.25 3%
011030011 Alabama Morgan 8.53 8.73 0.20 2%
011130001 Alabama Russell 9.98 10.17 0.19 2%
011170006 Alabama Shelby 8.11 8.18 0.07 1%
011210002 Alabama Talladega 9.02 9.14 0.12 1%
011250004 Alabama Tuscaloosa 8.60 8.74 0.14 2%
011270002 Alabama Walker 9.00 9.12 0.12 1%
120990008 Florida Palm Beach 6.84 6.94 0.10 1%
120990009 Florida Palm Beach 5.70 5.85 0.15 3%
130210007 Georgia Bibb 10.70 10.60 -0.10 -1%
130210012 Georgia Bibb 8.08 7.95 -0.13 -2%
CAMx Benchmarking Report #4
August 17, 2020 27
Table 4-2. Comparison of 2028el CAMx 6.32 and 2028elv3 CAMx 6.40 Predicted Annual
PM2.5 Design Values (µg/m3) for FRM Monitors in VISTAS States
Monitor State County
2028 Annual PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
130510091 Georgia Chatham 8.57 8.54 -0.03 0%
130590002 Georgia Clarke 8.01 8.13 0.12 1%
130630091 Georgia Clayton 9.30 9.43 0.13 1%
130670004 Georgia Cobb 8.48 8.73 0.25 3%
130890002 Georgia DeKalb 8.60 8.76 0.16 2%
130950007 Georgia Dougherty 10.33 10.41 0.08 1%
131150003 Georgia Floyd 9.31 9.48 0.17 2%
131210039 Georgia Fulton 10.18 10.36 0.18 2%
131390003 Georgia Hall 7.94 8.07 0.13 2%
131530001 Georgia Houston 8.60 8.55 -0.05 -1%
132150001 Georgia Muscogee 10.59 10.78 0.19 2%
132450005 Georgia Richmond 9.53 9.27 -0.26 -3%
132450091 Georgia Richmond 9.87 9.54 -0.33 -3%
132950002 Georgia Walker 7.90 8.02 0.12 2%
133190001 Georgia Wilkinson 10.26 9.97 -0.29 -3%
210130002 Kentucky Bell 8.68 8.80 0.12 1%
210190017 Kentucky Boyd 8.00 8.31 0.31 4%
210290006 Kentucky Bullitt 9.75 9.32 -0.43 -4%
210373002 Kentucky Campbell 7.36 7.61 0.25 3%
210430500 Kentucky Carter 6.57 6.80 0.23 4%
210470006 Kentucky Christian 8.28 8.39 0.11 1%
210590005 Kentucky Daviess 9.11 9.25 0.14 2%
210670012 Kentucky Fayette 7.76 7.97 0.21 3%
210930006 Kentucky Hardin 8.30 8.40 0.10 1%
211010014 Kentucky Henderson 8.68 8.96 0.28 3%
211110067 Kentucky Jefferson 9.53 9.44 -0.09 -1%
211451004 Kentucky McCracken 8.57 8.84 0.27 3%
211510003 Kentucky Madison 6.77 6.97 0.20 3%
CAMx Benchmarking Report #4
August 17, 2020 28
Table 4-2. Comparison of 2028el CAMx 6.32 and 2028elv3 CAMx 6.40 Predicted Annual
PM2.5 Design Values (µg/m3) for FRM Monitors in VISTAS States
Monitor State County
2028 Annual PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
211950002 Kentucky Pike 7.71 8.03 0.32 4%
212270008 Kentucky Warren 8.72 8.83 0.11 1%
280330002 Mississippi DeSoto 8.15 8.36 0.21 3%
280350004 Mississippi Forrest 9.81 9.92 0.11 1%
280430001 Mississippi Grenada 7.81 8.00 0.19 2%
280450003 Mississippi Hancock 8.31 8.23 -0.08 -1%
280470008 Mississippi Harrison 7.99 7.99 0.00 0%
280490010 Mississippi Hinds 9.45 9.58 0.13 1%
280590006 Mississippi Jackson 7.91 7.90 -0.01 0%
280670002 Mississippi Jones 10.01 10.10 0.09 1%
280750003 Mississippi Lauderdale 9.13 9.20 0.07 1%
280810005 Mississippi Lee 9.21 9.36 0.15 2%
370010002 North Carolina Alamance 7.01 7.36 0.35 5%
370210034 North Carolina Buncombe 6.77 6.97 0.20 3%
370330001 North Carolina Caswell 6.22 6.57 0.35 6%
370350004 North Carolina Catawba 7.71 7.98 0.27 4%
370370004 North Carolina Chatham 5.73 6.07 0.34 6%
370510009 North Carolina Cumberland 7.38 7.65 0.27 4%
370570002 North Carolina Davidson 8.14 8.54 0.40 5%
370610002 North Carolina Duplin 6.36 6.48 0.12 2%
370630015 North Carolina Durham 6.69 7.00 0.31 5%
370650004 North Carolina Edgecombe 6.35 6.66 0.31 5%
370670022 North Carolina Forsyth 6.91 7.33 0.42 6%
370670030 North Carolina Forsyth 6.91 7.34 0.43 6%
370710016 North Carolina Gaston 7.52 7.77 0.25 3%
370810013 North Carolina Guilford 6.59 6.97 0.38 6%
370810014 North Carolina Guilford 6.72 7.13 0.41 6%
370870012 North Carolina Haywood 7.84 7.86 0.02 0%
CAMx Benchmarking Report #4
August 17, 2020 29
Table 4-2. Comparison of 2028el CAMx 6.32 and 2028elv3 CAMx 6.40 Predicted Annual
PM2.5 Design Values (µg/m3) for FRM Monitors in VISTAS States
Monitor State County
2028 Annual PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
370990006 North Carolina Jackson 7.06 7.15 0.09 1%
371010002 North Carolina Johnston 6.38 6.70 0.32 5%
371070004 North Carolina Lenoir 6.59 6.85 0.26 4%
371110004 North Carolina McDowell 7.37 7.60 0.23 3%
371170001 North Carolina Martin 6.01 6.38 0.37 6%
371190041 North Carolina Mecklenburg 7.86 8.11 0.25 3%
371190042 North Carolina Mecklenburg 8.21 8.45 0.24 3%
371190043 North Carolina Mecklenburg 7.37 7.64 0.27 4%
371210001 North Carolina Mitchell 7.04 7.19 0.15 2%
371230001 North Carolina Montgomery 6.62 6.95 0.33 5%
371290002 North Carolina New Hanover 5.39 5.61 0.22 4%
371470006 North Carolina Pitt 5.98 6.29 0.31 5%
371550005 North Carolina Robeson 7.29 7.51 0.22 3%
371590021 North Carolina Rowan 7.54 7.84 0.30 4%
371730002 North Carolina Swain 7.40 7.50 0.10 1%
371830014 North Carolina Wake 7.58 7.89 0.31 4%
371830020 North Carolina Wake 6.78 7.09 0.31 5%
371890003 North Carolina Watauga 6.07 6.28 0.21 3%
371910005 North Carolina Wayne 7.14 7.40 0.26 4%
450190048 South Carolina Charleston 6.91 7.11 0.20 3%
450190049 South Carolina Charleston 6.66 6.88 0.22 3%
450250001 South Carolina Chesterfield 7.46 7.69 0.23 3%
450370001 South Carolina Edgefield 8.01 8.03 0.02 0%
450410003 South Carolina Florence 8.45 8.65 0.20 2%
450450009 South Carolina Greenville 8.41 8.65 0.24 3%
450450015 South Carolina Greenville 8.68 8.92 0.24 3%
450630008 South Carolina Lexington 8.57 8.64 0.07 1%
450830011 South Carolina Spartanburg 8.26 8.47 0.21 3%
CAMx Benchmarking Report #4
August 17, 2020 30
Table 4-2. Comparison of 2028el CAMx 6.32 and 2028elv3 CAMx 6.40 Predicted Annual
PM2.5 Design Values (µg/m3) for FRM Monitors in VISTAS States
Monitor State County
2028 Annual PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
470650031 Tennessee Hamilton 8.43 8.55 0.12 1%
470651011 Tennessee Hamilton 8.32 8.45 0.13 2%
470654002 Tennessee Hamilton 8.16 8.30 0.14 2%
510030001 Virginia Albemarle 6.32 6.67 0.35 6%
510360002 Virginia Charles 6.23 6.57 0.34 5%
510410003 Virginia Chesterfield 7.06 7.44 0.38 5%
510590030 Virginia Fairfax 6.87 7.38 0.51 7%
510690010 Virginia Frederick 7.70 8.19 0.49 6%
510870014 Virginia Henrico 6.81 7.17 0.36 5%
510870015 Virginia Henrico 6.38 6.76 0.38 6%
511071005 Virginia Loudoun 7.08 7.57 0.49 7%
511390004 Virginia Page 6.77 7.13 0.36 5%
511650003 Virginia Rockingham 7.56 7.89 0.33 4%
515200006 Virginia Bristol City 7.53 7.73 0.20 3%
516500008 Virginia Hampton City 5.65 5.93 0.28 5%
516800015 Virginia Lynchburg City 6.24 6.52 0.28 4%
517100024 Virginia Norfolk City 6.77 7.04 0.27 4%
517700015 Virginia Roanoke City 7.47 7.73 0.26 3%
517750011 Virginia Salem City 7.24 7.50 0.26 4%
518100008 Virginia
Virginia Beach
City 6.71 6.98 0.27 4%
540030003 West Virginia Berkeley 8.90 9.38 0.48 5%
540090005 West Virginia Brooke 9.10 9.59 0.49 5%
540110006 West Virginia Cabell 8.81 9.09 0.28 3%
540291004 West Virginia Hancock 8.27 8.73 0.46 6%
540390010 West Virginia Kanawha 7.84 8.14 0.30 4%
540391005 West Virginia Kanawha 8.97 9.27 0.30 3%
540490006 West Virginia Marion 8.75 9.21 0.46 5%
540511002 West Virginia Marshall 9.85 10.03 0.18 2%
CAMx Benchmarking Report #4
August 17, 2020 31
Table 4-2. Comparison of 2028el CAMx 6.32 and 2028elv3 CAMx 6.40 Predicted Annual
PM2.5 Design Values (µg/m3) for FRM Monitors in VISTAS States
Monitor State County
2028 Annual PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
540610003 West Virginia Monongalia 7.57 8.07 0.50 7%
540690010 West Virginia Ohio 8.37 8.72 0.35 4%
540810002 West Virginia Raleigh 6.68 6.99 0.31 5%
541071002 West Virginia Wood 8.91 9.12 0.21 2%
CAMx Benchmarking Report #4
August 17, 2020 32
Annual PM2.5 Design Value – 12US2 Domain
CAMx 6.40
Percent Difference (CAMx 6.40 - CAMx 6.32) / CAMx 6.32
Figure 4-16. Comparison of Annual PM2.5 Design Values (µg/m3) for CAMx 6.32 2028el
and CAMx 6.40 2028elv3 Simulations
CAMx Benchmarking Report #4
August 17, 2020 33
Figure 4-17. Scatterplot Comparing Annual Average Predicted PM2.5 Design Values
(µg/m3) at all Monitor Locations for CAMx 6.32 2028el and CAMx 6.40 2028elv3
Simulations Performed by VISTAS (Alpine)
CAMx Benchmarking Report #4
August 17, 2020 34
4.3 24-Hour (Daily) PM2.5 Design Value
Daily PM2.5 design values were generated using the results of each individual CAMx
simulation (version 6.32 with EPA’s 2028el platform and version 6.40 with SESARM’s
2028elv3 platform) and the SMAT-CE tool. Results for each individual receptor in the VISTAS
states are presented in tabular format in Table 4-3 along with the absolute difference and percent
difference in design value.
The maximum calculated increase is 1.1 µg/m3 at monitor 510030001 in Albemarle,
Virginia (9% increase going from CAMx 6.32 to 6.40) and maximum calculated decrease is
0.7 µg/m3 at monitor 130210007 in Bibb, Georgia (3% decrease going from CAMx 6.32 to
6.40). The average change in daily design value for all monitors in the VISTAS states is
0.20 µg/m3, with an average daily percent difference of 2% at these same locations.
Geographic distribution of the 6.40 daily PM2.5 design values and differences in design
values compared to the 6.32 simulation is presented in Figure 4-18. As similarly seen in the
annual PM2.5 design values, daily PM2.5 design values have the smallest fractional change within
the middle of the VISTAS state domain and the largest daily design value fractional changes are
seen across much of the central states region, running north to south along the western border of
the VISTAS domain and along the northeastern boundary of the VISTAS domain, adjacent to
MARAMA state boundaries.
A scatterplot of the daily PM2.5 design values for all FRM monitors in the 12US2 domain
is presented in Figure 4-19. The CAMx 6.40 results are plotted on the x-axis and the CAMx 6.32
results are plotted on the y-axis. The data has a high degree of correlation with a line of best fit
with a slope of 1.0395, an intercept of -1.1381 µg/m3 and an R2 of 0.9895. CAMx 6.40
concentrations appear to be marginally higher compared to CAMx 6.32 at low concentration
ranges and slightly lower than the CAMx 6.32 results in medium to high concentration ranges.
CAMx Benchmarking Report #4
August 17, 2020 35
Table 4-3. Comparison of CAMx 6.40 2028elv3 and CAMx 6.32 2028el Simulation of
Daily (24-Hour) PM2.5 Design Values (µg/m3)
Monitor State County
2028 Daily (24-Hr) PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
010030010 Alabama Baldwin 15.8 15.9 0.1 1%
010270001 Alabama Clay 17.1 17.2 0.1 1%
010331002 Alabama Colbert 16.4 16.2 -0.2 -1%
010491003 Alabama DeKalb 16.9 17.1 0.2 1%
010550010 Alabama Etowah 17.8 17.7 -0.1 -1%
010690003 Alabama Houston 17.0 17.0 0.0 0%
010730023 Alabama Jefferson 22.8 22.9 0.1 0%
010731005 Alabama Jefferson 18.0 17.8 -0.2 -1%
010731009 Alabama Jefferson 17.8 17.8 0.0 0%
010731010 Alabama Jefferson 18.2 18.3 0.1 1%
010732003 Alabama Jefferson 20.9 21.2 0.3 1%
010732006 Alabama Jefferson 18.6 18.6 0.0 0%
010735002 Alabama Jefferson 17.6 17.4 -0.2 -1%
010735003 Alabama Jefferson 17.8 17.7 -0.1 -1%
010890014 Alabama Madison 18.5 18.6 0.1 1%
010970003 Alabama Mobile 16.0 16.1 0.1 1%
010972005 Alabama Mobile 16.6 16.7 0.1 1%
011011002 Alabama Montgomery 19.9 19.9 0.0 0%
011030011 Alabama Morgan 16.5 16.5 0.0 0%
011130001 Alabama Russell 23.3 23.4 0.1 0%
011170006 Alabama Shelby 15.8 15.8 0.0 0%
011210002 Alabama Talladega 18.5 18.5 0.0 0%
011250004 Alabama Tuscaloosa 18.9 19.0 0.1 1%
011270002 Alabama Walker 17.8 17.8 0.0 0%
120990008 Florida Palm Beach 15.6 15.7 0.1 1%
120990009 Florida Palm Beach 13.5 13.6 0.1 1%
130210007 Georgia Bibb 22.8 22.1 -0.7 -3%
130210012 Georgia Bibb 18.3 17.9 -0.4 -2%
CAMx Benchmarking Report #4
August 17, 2020 36
Table 4-3. Comparison of CAMx 6.40 2028elv3 and CAMx 6.32 2028el Simulation of
Daily (24-Hour) PM2.5 Design Values (µg/m3)
Monitor State County
2028 Daily (24-Hr) PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
130510017 Georgia Chatham 24.7 24.3 -0.4 -2%
130510091 Georgia Chatham 24.3 24.4 0.1 0%
130590002 Georgia Clarke 17.4 17.6 0.2 1%
130670004 Georgia Cobb 16.9 17.1 0.2 1%
130890002 Georgia DeKalb 17.1 17.2 0.1 1%
130950007 Georgia Dougherty 24.4 24.3 -0.1 0%
131390003 Georgia Hall 16.3 16.5 0.2 1%
131530001 Georgia Houston 19.7 19.5 -0.2 -1%
132950002 Georgia Walker 17.5 17.2 -0.3 -2%
133190001 Georgia Wilkinson 20.5 20.2 -0.3 -1%
280330002 Mississippi DeSoto 15.6 15.9 0.3 2%
280350004 Mississippi Forrest 19.5 19.5 0.0 0%
280430001 Mississippi Grenada 15.5 15.8 0.3 2%
280450003 Mississippi Hancock 18.4 18.3 -0.1 -1%
280470008 Mississippi Harrison 15.3 15.1 -0.2 -1%
280490010 Mississippi Hinds 18.1 18.5 0.4 2%
280590006 Mississippi Jackson 17.7 17.6 -0.1 -1%
280670002 Mississippi Jones 20.1 20.3 0.2 1%
280750003 Mississippi Lauderdale 18.5 18.6 0.1 1%
280810005 Mississippi Lee 17.0 17.4 0.4 2%
370010002 North Carolina Alamance 14.7 15.2 0.5 3%
370210034 North Carolina Buncombe 13.0 13.5 0.5 4%
370330001 North Carolina Caswell 12.7 12.8 0.1 1%
370350004 North Carolina Catawba 16.3 16.4 0.1 1%
370370004 North Carolina Chatham 12.6 13.0 0.4 3%
370510009 North Carolina Cumberland 16.6 17.0 0.4 2%
370570002 North Carolina Davidson 15.4 15.9 0.5 3%
370610002 North Carolina Duplin 14.2 14.4 0.2 1%
CAMx Benchmarking Report #4
August 17, 2020 37
Table 4-3. Comparison of CAMx 6.40 2028elv3 and CAMx 6.32 2028el Simulation of
Daily (24-Hour) PM2.5 Design Values (µg/m3)
Monitor State County
2028 Daily (24-Hr) PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
370630015 North Carolina Durham 13.6 13.9 0.3 2%
370650004 North Carolina Edgecombe 14.3 14.7 0.4 3%
370670022 North Carolina Forsyth 14.9 15.3 0.4 3%
370670030 North Carolina Forsyth 14.4 14.8 0.4 3%
370710016 North Carolina Gaston 16.2 16.4 0.2 1%
370810013 North Carolina Guilford 15.5 16.1 0.6 4%
370810014 North Carolina Guilford 13.5 14.4 0.9 7%
370870012 North Carolina Haywood 18.7 18.8 0.1 1%
370990006 North Carolina Jackson 13.9 13.8 -0.1 -1%
371010002 North Carolina Johnston 13.8 14.1 0.3 2%
371070004 North Carolina Lenoir 15.3 15.8 0.5 3%
371110004 North Carolina McDowell 15.1 15.4 0.3 2%
371170001 North Carolina Martin 16.5 17.3 0.8 5%
371190041 North Carolina Mecklenburg 17.2 17.5 0.3 2%
371190042 North Carolina Mecklenburg 17.7 17.9 0.2 1%
371190043 North Carolina Mecklenburg 15.0 15.2 0.2 1%
371210001 North Carolina Mitchell 13.8 13.8 0.0 0%
371230001 North Carolina Montgomery 14.5 14.9 0.4 3%
371290002 North Carolina New Hanover 15.6 15.9 0.3 2%
371470006 North Carolina Pitt 14.8 15.4 0.6 4%
371550005 North Carolina Robeson 16.3 16.9 0.6 4%
371590021 North Carolina Rowan 14.9 15.3 0.4 3%
371730002 North Carolina Swain 15.5 15.6 0.1 1%
371830014 North Carolina Wake 16.9 17.4 0.5 3%
371830020 North Carolina Wake 14.1 14.4 0.3 2%
371890003 North Carolina Watauga 12.6 13.0 0.4 3%
371910005 North Carolina Wayne 15.3 15.8 0.5 3%
450190048 South Carolina Charleston 16.2 16.3 0.1 1%
CAMx Benchmarking Report #4
August 17, 2020 38
Table 4-3. Comparison of CAMx 6.40 2028elv3 and CAMx 6.32 2028el Simulation of
Daily (24-Hour) PM2.5 Design Values (µg/m3)
Monitor State County
2028 Daily (24-Hr) PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
450190049 South Carolina Charleston 15.6 15.9 0.3 2%
450250001 South Carolina Chesterfield 15.5 15.5 0.0 0%
450370001 South Carolina Edgefield 17.0 16.9 -0.1 -1%
450410003 South Carolina Florence 18.2 18.4 0.2 1%
450450009 South Carolina Greenville 17.9 18.1 0.2 1%
450450015 South Carolina Greenville 19.2 19.3 0.1 1%
450630008 South Carolina Lexington 18.9 19.0 0.1 1%
450790019 South Carolina Richland 19.5 19.4 -0.1 -1%
450830011 South Carolina Spartanburg 17.2 17.4 0.2 1%
470650031 Tennessee Hamilton 18.6 18.6 0.0 0%
470651011 Tennessee Hamilton 17.3 17.0 -0.3 -2%
470654002 Tennessee Hamilton 17.0 16.7 -0.3 -2%
510030001 Virginia Albemarle 12.7 13.8 1.1 9%
510360002 Virginia Charles 13.2 13.9 0.7 5%
510410003 Virginia Chesterfield 14.7 15.5 0.8 5%
510590030 Virginia Fairfax 17.3 18.0 0.7 4%
510690010 Virginia Frederick 18.1 18.6 0.5 3%
510870014 Virginia Henrico 15.4 16.1 0.7 5%
510870015 Virginia Henrico 13.1 14.1 1.0 8%
511071005 Virginia Loudoun 16.1 16.5 0.4 2%
511390004 Virginia Page 15.2 16.1 0.9 6%
511650003 Virginia Rockingham 17.1 17.7 0.6 4%
515200006 Virginia Bristol City 15.7 16.2 0.5 3%
516500008 Virginia Hampton City 14.1 14.9 0.8 6%
516800015 Virginia Lynchburg City 13.4 13.9 0.5 4%
517100024 Virginia Norfolk City 15.0 15.7 0.7 5%
517700015 Virginia Roanoke City 16.4 16.9 0.5 3%
517750011 Virginia Salem City 14.6 15.0 0.4 3%
CAMx Benchmarking Report #4
August 17, 2020 39
Table 4-3. Comparison of CAMx 6.40 2028elv3 and CAMx 6.32 2028el Simulation of
Daily (24-Hour) PM2.5 Design Values (µg/m3)
Monitor State County
2028 Daily (24-Hr) PM2.5 Design Value (µg/m3)
6.32
2028el
6.40
2028elv3 Difference Percent
Difference
518100008 Virginia
Virginia Beach
City 16.4 16.8 0.4 2%
540030003 West Virginia Berkeley 22.8 23.5 0.7 3%
540090005 West Virginia Brooke 18.9 19.2 0.3 2%
540110006 West Virginia Cabell 17.9 18.8 0.9 5%
540291004 West Virginia Hancock 19.6 20.5 0.9 5%
540390010 West Virginia Kanawha 16.1 17.0 0.9 6%
540391005 West Virginia Kanawha 18.2 18.6 0.4 2%
540490006 West Virginia Marion 19.1 19.3 0.2 1%
540511002 West Virginia Marshall 23.1 23.3 0.2 1%
540610003 West Virginia Monongalia 16.2 17.1 0.9 6%
540690010 West Virginia Ohio 17.7 17.9 0.2 1%
540810002 West Virginia Raleigh 13.9 14.3 0.4 3%
541071002 West Virginia Wood 18.6 18.6 0.0 0%
CAMx Benchmarking Report #4
August 17, 2020 40
Daily PM2.5 Design Value – 12US2 Domain
CAMx 6.40
Percent Difference (CAMx 6.40 – CAMx 6.32) / CAMx 6.32
Figure 4-18. Comparison of Daily PM2.5 Design Values (µg/m3) for CAMx 6.32 2028el and
CAMx 6.40 2028elv3 Simulations
CAMx Benchmarking Report #4
August 17, 2020 41
Figure 4-19. Comparison of Daily PM2.5 Design Values (µg/m3) for CAMx 6.32 2028el and
CAMx 6.40 2028elv3 Simulations
CAMx Benchmarking Report #4
August 17, 2020 42
4.4 Scatterplots of Ozone and PM Species Concentrations
Scatterplots of the daily average concentrations of ozone and the various calculated PM
species in local standard time at the Interagency Monitoring for Protected Visual Environment
(IMPROVE) monitors across all modeled days are presented in Figures 4-20 through 4-26. The
CAMx 6.40 results are plotted on the x-axis and the CAMx 6.32 results are plotted on the y-axis.
Figure 4-20 exhibits concentrations for ozone have a high degree of correlation with a
line of best fit with a slope of 0.9754, an intercept of 0.5203 ppb and an R2 of 0.9974. Results are
scattered both above and below the 1:1 line, with marginally higher concentrations estimated by
CAMx 6.40 across the concentration range.
Figure 4-20. Scatterplot Comparing 24-hour Average Predicted Ozone Concentrations
(ppb) for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx 6.40
2028 Simulations Performed by VISTAS (Alpine)
CAMx Benchmarking Report #4
August 17, 2020 43
Scatterplots of the daily average PM2.5 concentrations in local standard time at the
IMPROVE monitors are presented in Figures 4-21 and 4-22 with different axis scaling to
facilitate analysis over the full range of concentrations. The CAMx 6.40 results are plotted on the
x-axis and the CAMx 6.32 results are plotted on the y-axis. The data has a high degree of
correlation with a line of best fit with a slope of 0.9973, an intercept of 0.3731 µg/m3and an R2
of 0.9845. The agreement between the models is higher at higher concentrations. At lower
concentrations the CAMx 6.32 results are slightly higher than the CAMx 6.40 results.
Figure 4-21. Scatterplot Comparing 24-hour Average Predicted PM2.5 Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx 6.40
2028 Simulations Performed by VISTAS (Alpine)
CAMx Benchmarking Report #4
August 17, 2020 44
Figure 4-22. Scatterplot Comparing 24-hour Average Predicted PM2.5 Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx 6.40
2028 Simulations Performed by VISTAS (Alpine); Modified Scale
Scatterplots of the daily average sulfate concentrations in local standard time at the
IMPROVE monitors are presented in Figure 4-23. The CAMx 6.40 results are plotted on the
x-axis and the CAMx 6.32 results are plotted on the y-axis. The data has considerably more
scatter than the ozone or PM2.5 results with a line of best fit with a slope of 0.9057, an intercept
of 0.0.092 µg/m3 and an R2 of 0.8566. The vast majority of the points at low concentrations are
above the 1:1 line, meaning that the CAMx 6.32 modeled values are higher than the CAMx 6.40
results. The reverse is true at medium and high concentrations where CAMx 6.40 tends to
estimate higher concentrations than CAMx 6.32. These are likely a result of the changes in the
wet deposition algorithms and the oxidation of SO2 on primary crustal particles and updates to
the RADM aqueous chemistry algorithm in addition to the changes in the elevated SO2
emissions.
CAMx Benchmarking Report #4
August 17, 2020 45
Figure 4-23. Scatterplot Comparing 24-hour Average Predicted Sulfate Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx 6.40
2028 Simulations Performed by VISTAS (Alpine)
Scatterplots of the daily average nitrate concentrations in local standard time at the
IMPROVE monitors are presented in Figure 4-24. The CAMx 6.40 results are plotted on the
x-axis and the CAMx 6.32 results are plotted on the y-axis. The data has slightly more scatter
than the ozone or PM2.5 results with a line of best fit with a slope of 0.9266, an intercept of
0.0009 µg/m3 and an R2 of 0.9743. Unlike the sulfate results which showed more uniform scatter
around the 1:1 line, the CAMx 6.40 nitrate results are marginally higher than CAMx 6.32 except
at low concentrations.
CAMx Benchmarking Report #4
August 17, 2020 46
Figure 4-24. Scatterplot Comparing 24-hour Average Predicted Nitrate Concentrations
(µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32 and CAMx 6.40
2028 Simulations Performed by VISTAS (Alpine)
Scatterplots of the daily average organic carbon concentrations in local standard time at
the IMPROVE monitors are presented in Figures 4-24 and 4-25 with different axis scaling to
facilitate analysis over the full range of concentrations. The CAMx 6.40 results are plotted on the
x-axis and the CAMx 6.32 results are plotted on the y-axis. The data has a high degree of
correlation with a line of best fit with a slope of 1.0146, an intercept of 0.3025 ppb and an R2 of
0.9837. The CAMx 6.40 results are slightly lower than CAMx 6.32 across the concentration
range.
CAMx Benchmarking Report #4
August 17, 2020 47
Figure 4-25. Scatterplot Comparing 24-hour Average Predicted Organic Carbon
Concentrations (µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32
and CAMx 6.40 2028 Simulations Performed by VISTAS (Alpine)
CAMx Benchmarking Report #4
August 17, 2020 48
Figure 4-26. Scatterplot Comparing 24-hour Average Predicted Organic Carbon
Concentrations (µg/m3) for All Days at all IMPROVE Monitor Locations for CAMx 6.32
and CAMx 6.40 2028 Simulations Performed by VISTAS (Alpine); Modified Scale
CAMx Benchmarking Report #4
August 17, 2020 49
5.0 CONCLUSIONS
A comparison has been made between CAMx 6.32 and CAMx 6.40 simulations using
EPA’s 2028el and SESARM’s 2028elv3 modeling platform as performed on the Alpine
Geophysics computer system. The comparison was conducted for PM2.5 and included an
examination both of annual emissions for elevated and low level sources and annual and daily
future year design values at monitors in the modeling domain.
The annual emissions comparisons showed areas of differences across the domain that
are consistent with documented changes in the 2028 emissions inventories used by SESARM for
this analysis. A comparison of the annual and daily PM2.5 design values at the monitors in the
12US2 modeling domain showed a systematic increase for the majority of FRM monitors for
both values between the CAMx 6.32 and CAMx 6.40 platform. The greatest change in design
values are seen in and around boundaries of VISTAS states and other outside regions (e.g., OTC
and CENRAP) with smallest change noted centrally within the VISTAS state domain itself.
A comparison of the daily average concentrations at the IMPROVE monitors showed
fairly small differences for ozone between the two simulations with CAMx 6.40 estimating
slightly larger values in the high concentration range. Organic Carbon was estimated as slightly
lower across all concentration ranges using CAMx 6.40 compared to CAMx 6.32. For sulfate,
the CAMx 6.40 results were generally higher than CAMx 6.32, especially across the medium
and high concentration ranges. This is likely a result of the changes in the wet deposition
algorithms, the oxidation of SO2 on primary crustal particles, and updates to the RADM aqueous
chemistry algorithm and changes in SO2 emissions. For nitrate, the CAMx 6.40 results were
consistently higher across all ranges compared to CAMx 6.32 except at very low concentrations.
The PM2.5 results generally showed lower CAMx 6.40 concentrations compared to CAMx 6.32
at low concentration levels.
The comparison of CAMx 6.32 and 6.40 showed differences in both annual and daily
PM2.5 design values as well as in daily concentrations of various PM2.5 species. This is to be
expected given the changes to the model from the inclusion of new science into CAMx 6.40 over
that which was included in CAMx 6.32 and the changes made in the 2028 projection emission
inventory across the modeling domain. Alpine Geophysics does not see any features in the
CAMx Benchmarking Report #4
August 17, 2020 50
modeling that would preclude the use of the better science and updated emission inventories in
CAMx 6.40 for use in the VISTAS air quality planning.