Speciation of Total Organic Gas and
Particulate Matter Emissions from
Onroad Vehicles in MOVES4
£% United States
Environmental Protect
Agency
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Speciation of Total Organic Gas and
Particulate Matter Emissions from
This technical report does not necessarily represent final EPA decisions
or positions. It is intended to present technical analysis of issues using
data that are currently available. The purpose in the release of such
reports is to facilitate the exchange of technical information and to
inform the public of technical developments.
Onroad Vehicles in MOVES4
Assessment and Standards Division
Office of Transportation and Air Quality
U.S. Environmental Protection Agency
NOTICE
4>EPA
United States
Environmental Protection
Agency
EPA-420-R-23-006
August 2023
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Table of Contents
1 Introduction 3
1.1 Measuring Hydrocarbons and Particulate Matter 3
1.2 MOVES Speciation Approach 4
1.3 Data Uncertainty and Limitations 4
2 Speciation Glossary 6
2.1 General Terms 6
2.2 Organic Gas Terms 6
2.3 Particulate Matter Terms 8
2.4 Databases, Models and Tools 9
3 Organic Gas Aggregations and Ratios 10
3.1 Total Organic Gaseous Calculations 11
3.2 Ratios for Evaporative Emissions and Most Exhaust Emissions 12
3.3 Ratios for 2001 -and-Later Light-Duty Gasoline Exhaust 17
3.4 Ratios for Flex Fuel Vehicles using High Ethanol Blends (E85) 21
3.5 Ratios for CNG Vehicles 22
3.6 CH4 Ratios for 2010-and-Later Heavy-Duty Diesel Vehicles 24
4 Residual TOG Speciation 25
4.1 Overview 25
4.2 Mapping Residual TOG to Speciation Profiles 26
5 PM2.5 Speciation 29
5.1 MOVES PM2.5 Species 29
5.2 PM2.5 Speciation Calculations 30
5.3 PM2.5 Exhaust Speciation Profiles 35
5.4 Brake and Tire Wear Speciation 38
6 Post-processing of residual TOG, residual PM and OM 38
Appendix A Supporting Information for TOG calculations 41
Appendix B CNG CH4/THC and Speciation Constant Parameters for CNG vehicles.... 48
Appendix C TOG Speciation Map 49
Appendix D Comparison of ACES Phase 1 and Phase 2 SPECIATE Profiles 52
Appendix E Development of PM2.5 speciation profiles in MOVES 59
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E. 1 Development of Gasoline Profiles from the Kansas City Light-duty Vehicle Emissions
Study 60
E.2 Development of E55/59 Profile for Pre-2007 Conventional Diesel 63
E.3 Development of the ACES PM2.5 Profile for 2007 and Newer Technology Diesel 68
E.4 Development of the Compressed Natural Gas (CNG) Profile 70
Appendix F PM10/PM2.5 Factors 73
7 References 74
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1 Introduction
The United States Environmental Protection Agency's Motor Vehicle Emission Simulator—
commonly referred to as MOVES—is a set of modeling tools for estimating air pollution
emissions produced by onroad (highway) and nonroad mobile sources. MOVES estimates the
emissions of greenhouse gases (GHGs), criteria pollutants and selected air toxics. The MOVES
model is currently the official model for use for state implementation plan (SIP) submissions to
EPA and for transportation conformity analyses outside of California. The model is also the
primary modeling tool for estimating the impact of mobile source regulations on emission
inventories, and thus, provides important inputs to air quality models.
In MOVES, some pollutant emissions are computed directly, based on measured emission
rates1'2. Other pollutants are estimated as a function of the directly computed emissions. This is
true of many of the air toxics, as described in the MOVES air toxics report7. For air quality
modeling purposes, further chemical characterization of total organic gases (TOG) and
particulate matter (PM) is required. The process of apportioning aggregate organic gases and
particulate matter into sets of separate components is called "speciation."
Note that previous versions of MOVES applied speciation to all onroad sources and processes,
except for brake and tire wear particulate matter emissions as discussed in Section 5.4. For
nonroad, speciation was handled differently. Toxics were estimated in the nonroad portion of the
model, similar to what was done for highway sources, and detailed speciation of TOG and PM2.5
was conducted as part of post-processing of MOVES nonroad results.3 However, since
MOVES3(v3.0.4), all speciation for onroad and nonroad emissions is handled via post-
processing.
1.1 Measuring I ivdrocarbons and Particulate Matter
In addition to estimating emissions of pollutants that are discrete chemical compounds, such as
carbon monoxide (CO) and sulfur dioxide (SO2), MOVES produces emission rates for
aggregates of individual chemical compounds, including total hydrocarbons (THC), volatile
organic compounds (VOC), total organic gases (TOG) and particulate matter (PM). These
pollutants are operationally defined, meaning that their definition depends on the measurement
technique(s) selected. For example, THC is defined as the hydrocarbons measured by a flame
ionization detector (FID). TOG is defined to include all organic gases.4 Because THC
measurements do not respond fully to carbon-oxygen bonds in oxygenated compounds, such as
aldehydes, alcohols, and ketones, these oxygenates need to be measured separately by gas and
liquid chromatography and added to the THC measurements to calculate TOG. Alternatively,
TOG measurements can be made solely with gas and liquid chromatography methods.a
Similarly, particulate matter is operationally defined as the measured mass collected on a filter
using EPA-defined sampling filter media, conditions, and practices.5'6 PM2.5 refers to particulate
matter emissions collected downstream of a cyclone that removes the particles with aerodynamic
a Thus, differences in measurement methods need to be considered when comparing THC to TOG emission
measurements.
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diameter greater than 2.5 microns, while PMio refers to particulate matter emissions with
aerodynamic diameter less than 10 microns.
1.2 MOVES Speciation Approach
MOVES produces emission estimates for a subset of species that contribute to TOG and PM2.5.
These include important organic gaseous toxics (e.g., formaldehyde and benzene), and toxic
particle-phase elements (e.g., nickel and manganese). These also include semi-volatile organic
compounds, such as 15 individual polycyclic aromatic hydrocarbons (e.g., benzo(g;/z/,/)perylene)
that can exist in both the gaseous and particle phases under different measurement conditions.
Individual toxic emission rates are detailed in the toxics report7, but are peripherally discussed in
this report in the context of their use in deriving speciated TOG and PM emissions.
Previous versions of MOVES applied speciation to produce the species needed for air quality
modeling through a combination of estimation, subtraction of known pollutants and allocation of
the remaining emissions based on profiles from EPA's SPECIATE database.8 To facilitate the
use of state-of-the-science speciation profiles and chemical mechanisms without waiting for new
public versions of MOVES that incorporate the latest speciation data, MOVES now speciates
residual TOG, PM and organic matter as a postprocess. This feature was developed specifically
for air quality modelers who wish to translate onroad emissions into chemical mechanism
species. The post-processing of onroad emissions in MOVES is done with a script that is
incorporated in the Tools menu of the MOVES graphical user interface (GUI). This new
capability was first implemented in MOVES3 (v3.0.4) and has been updated in MOVES4 to
incorporate the latest information in SPECIATE profiles and to improve the post-processing
scripts.
MOVES continues to provide the same speciated TOG and PM pollutants and users can continue
selecting these pollutants when building the RunSpec. Compared to MOVES3.0.3 and earlier
versions, the only GUI changes that the user will notice is the addition of two new pollutants
(Total Organic Matter and Residual PM) and the removal of chemical mechanisms options in
favor of a single option to generate Residual TOG (NONHAPTOG). These new pollutants must
be selected if the user desires to perform speciation of onroad emissions as a post-processing
step. We note that the addition of new pollutants did not require changes to model calculations as
MOVES already calculated these quantities implicitly during runtime; the effective changes
simply allow the selection of these pollutants as part of the model output. For further details on
speciation outside of MOVES, see Section 6. For users interested in the previous speciation
process, the technical reports for MOVES3.0.3 and earlier versions are provided in the MOVES
website9.
1.3 Data Uncertainty and Limitations
Speciated emissions are collected in laboratory conditions using laboratory bench instruments
that can analyze bag measurements of volatile organic compounds and can properly handle
particulate matter filters for chemical analysis. Speciated measurements also are based on time-
aggregated bag or filter measurements from engine or chassis dynamometer tests rather than
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time-resolved emission measurements (e.g. second-by-second measurements) that are used to
inform emission rates in MOVES from vehicles operating in different operating modes.
As such, the number of vehicles and the range of vehicle operation conditions from which we
have speciated data are more limited than the vehicle samples and operating conditions used to
estimate emission rates of total hydrocarbon and PM2.5 emission rates as documented in the
emission rate reports.1'2 Thus, the speciation results may be heavily impacted by test-to-test and
vehicle-to-vehicle variability. For example, THC emissions for light-duty gasoline vehicle are
based on hundreds or thousands of vehicles for each model year1, and heavy-duty diesel vehicles
measurements are based on hundreds of vehicles operating in real-world operation.2 On the other
hand, the speciation profile for model year 2001 and later light-duty gasoline vehicles is based on
only three vehicles as discussed in Section 3.3b, and the speciation profiles applied to model year
2010 and later diesel vehicles are based on three heavy-duty engines as discussed in Section 3.2.
In addition, available vehicle exhaust speciated measurements tend to be sampled from relatively
new engines or vehicles. However, speciation likely changes as vehicles age. For example, new
vehicles with fully active catalysts likely have higher CH4/THC ratios than older vehicles due to
the relative effectiveness of newer aftertreatment systems in oxidizing the NMHC species as
comparted to more difficult to oxidize methane. 10'u However, we do not have sufficient data to
model age-varying speciation ratios (CH4/THC, NMOG/NMHC and VOC/NMHC) or speciation
profiles, nor have we designed MOVES to handle varying speciation as vehicle age. Similarly,
speciation testing is often conducted using regulatory cycles, while real-world speciation may
differ. For now, our best approach is to select speciation data that are deemed the most
representative of the vehicle fleet by emission process, fuel type, regulatory class, and model
year.
Additional uncertainty comes from applying speciation profiles to technologies and processes
that differ from what was tested. For example, we apply the diesel speciation profile developed
from heavy heavy-duty engines to light-duty diesel emissions. Also, with the exception of the
light-duty gasoline PM2.5 speciation discussed in Appendix E, the speciation profiles are
developed from vehicles that are properly functioning and with low accumulated mileage, but we
apply them to fleet-average emission rates which include higher emissions due to aged and
deteriorated engine and emission control systems. Similarly, the EPAct light-duty gasoline
speciation profile is based on combined emission of start and running emissions. As a result,
there is no resolution between start and running emissions in the speciation profile.
In addition to small sample sizes and limited testing scope, measurement deficiencies contribute
to the uncertainty of MOVES speciated emission emissions. For example, as discussed in
Section 3.2, the 2010-and-later model year heavy-duty diesel total organic gas speciation profile
was corrected to remove three erroneous measurements artifacts. Speciation profiles also may
not measure pollutants because the concentrations were below the detection limits of the
measurement. As discussed in the toxics report7, many individual species are emitted below
detection limits during hot-running operation.
b As discussed in the Toxics report, many of the key toxics are estimated from the fifteen vehicles tested in the Phase
3 of the Epact program.
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We have attempted to include qualitative discussions of the sources of uncertainty and
application of the speciation data for each of the relevant sections of the report.
2 Speciation Glossary
In the area of "speciation," many terms have multiple meanings. The definitions below provide
the terms as they are used in the context of speciation in MOVES. We have grouped the terms
into General, Organic Gas, Particulate Matter, and Databases, Models and Tools Terms.
2.1 General Terms
• Species: Distinct chemical compounds, ions, groups of compounds, or other chemical
entities. In this report, we distinguish "real species," "aggregate species," "CM species,"
and "intermediate species," as explained below
• Aggregate species: Groups of chemical compounds. These are often defined
operationally or may be defined for modeling purposes. For example, THC, TOG and
VOC are aggregate gaseous species. NonEC is an aggregate particulate matter species.
• Real species: Species in the normal chemical sense—a pure chemical substance. The
word "real" helps distinguish these species from chemical mechanism species or
aggregated species.
• Real speciation profile: ideally, a complete listing of the real species and their quantities
of TOG or Particulate Matter. In practice, these profiles are incomplete; a certain fraction
of the mass is unresolved. Such a profile is produced by laboratory analysis of emissions.
This is not a CM speciation profile and is independent of chemical mechanism. Such a
profile does, however, depend on process, fuel, and technology, since the mix of real
species in TOG or PM is different for different emission processes (e.g. evaporative and
exhaust), for different fuels, and for different technologies. The SPECIATE database is
the EPA repository for these profiles.8
2.2 Organic Gas Terins
• Hydrocarbon (HC): compound containing only carbon and hydrogen12. Because we
cannot precisely measure emissions from combustion emissions using this strict
definition, we often refer to hydrocarbon (HC) emissions synonymously with total
hydrocarbon (THC) emissions which is a defined by the measurement method. For
example, the National Emissions Inventory reports MOVES total hydrocarbon emissions
(THC) as hydrocarbon (HC) emissions. At other times, we also use the term hydrocarbon
more generally to include multiple measurements and definitions of organic gases that are
primarily composed of hydrocarbons, including: non-methane hydrocarbons (NMHC),
non-methane organic gases (NMOG), and total organic gases (TOG). When discussing
HC emission in the MOVES technical reports, we typically only refer to gaseous HC
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emissions, and not HC emissions in the particulate phase, which is measured as organic
carbon (OC) and non-carbon organic matter (NCOM).
• Total Hydrocarbons (THC): "THC is the measured hydrocarbon emissions using a Flame
Ionization Detector (FID) calibrated with propane. The FID is assumed to respond to all
hydrocarbons identically as it responds to propane in determining the concentration of
carbon atoms in a gas sample. Most hydrocarbons respond nearly identically as propane
with notable exceptions being oxygenated hydrocarbons such as alcohols and aldehydes
commonly found in engine exhaust."4 In MOVES, THC is often used synonymously with
hydrocarbon (HC) emissions.
• Non-Methane Hydrocarbons (NMHC): NMHC = THC - CH4 (methane).
• Non-Methane Organic Gases (NMOG): NMOG = TOG - CH4 (methane).
• Total Organic Gases (TOG): Total hydrocarbon (THC) emissions plus oxygenated
hydrocarbons such as alcohols and aldehydes.4
• Volatile Organic Compounds (VOC): EPA defines VOC as any compound of carbon
(excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or
carbonates, and ammonium carbonate) which participates in atmospheric photochemical
reactions, except those designated by EPA as having negligible photochemical
reactivity.13 In mobile source testing, typically only a few compounds with negligible
photochemical reactivity are measured in significant quantities. For use in MOVES in
defining emission rates and application of speciation profiles, VOC is defined as TOG
minus methane, ethane, and acetone (Equation 9).
• Integrated species: Real species for which MOVES produces emissions that are
subtracted from TOG emissions to calculate "Residual TOG." MOVES integrates the 15
species shown in Table 2-2. The integrated species include all the organic gases estimated
by MOVES, including naphthalene gas, but excepting all other polycyclic aromatic
hydrocarbons.
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Table 2-1 Integrated MOVES Pollutants
pollutantID
Pollutant Name
5
Methane (CH4)
20
Benzene
21
Ethanol
24
1,3-Butadiene
25
Formaldehyde
26
Acetaldehyde
27
Acrolein
40
2,2,4-Trimethylpentane
41
Ethyl Benzene
42
Hexane
43
Propionaldehyde
44
Styrene
45
Toluene
46
Xylene
185
Naphthalene gas
• Residual TOG or NonHAPTOG: TOG that remains after subtracting integrated species.
MOVES reports emission rates of residual TOG as NonHAPTOG with pollutantID 88.
The speciation of Residual TOG into chemical mechanism species is done via
postprocessing (see Section 6).
2.3 Particulate Matter Tenns
• Primary Exhaust PM2.5 - Total (PM2.5). Primary particulate matter emissions from vehicle
exhaust collected using a filter, measured downstream of a cyclone that removes particles
with mean aerodynamic diameters greater than 2.5 microns. PM2.5 = EC + nonECPM.
• Primary Exhaust PM10 - Total (PM2.5). Primary particulate matter emissions from vehicle
exhaust collected using a filter, measured downstream of a cyclone that removes particles
with mean aerodynamic diameters greater than 10 microns.
• Intermediate PM2.5 species: Groups of PM2.5 species used to simplify calculations,
improve computation time, and to reduce the size of the emission rate tables. They
include the aggregate species: "non-elemental carbon particulate matter" (NonECPM)
and "non-elemental carbon non-sulfate particulate matter" (NonECnonS04PM),
elemental carbon (EC), sulfate (SO4) and particulate water (H2O). They are used to
compute total PM2.5 emissions and speciated PM2.5 emissions. The EC, nonECPM, SO4,
and H2O species are reported as MOVES outputs.
• Elemental Carbon (EC): "A descriptive term for carbonaceous particles based on
chemical composition rather than light-absorbing characteristics. This term is often used
as a synonym for black carbon."14 Elemental carbon is measured through thermal optical
techniques as particle-phase carbon that does not volatize at high temperatures in an
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oxygen-free environment.15 In tailpipe exhaust, EC is one measure of carbonaceous soot
formed from fuel pyrolysis occurring during combustion.16
• Organic Carbon (OC): "The mix of compounds containing carbon bound with other
elements, e.g., hydrogen and oxygen. Organic carbon may be a product of incomplete
combustion or formed through the oxidation of VOCs in the atmosphere." Organic
carbon is measured using thermal-optical methods as the particle-phase carbon collected
on a filter that volatizes at high temperatures in an oxygen-free environment.
• Total Organic Matter (TOM): Particle-phase organic matter. The mass of the organic
material in particulate: TOM = organic carbon (OC) + non-carbon organic matter
(NCOM).
• Non-Carbon Organic Matter (NCOM): the mass of the oxygen, hydrogen, nitrogen and
other elements present in particle-phase organic matter. OC and NCOM are modeled
separately in air quality models in order to model the degree of oxidation of organic
matter, which depends on the emission source and the chemical transformation in the
atmosphere.17
• Non-Elemental Carbon Particulate Matter (nonECPM): The PM2.5 that is not elemental
carbon. This is typically calculated as the difference between PM2.5 mass filter-based
measurements and elemental carbon measurements made using thermal optical
measurements, or surrogate elemental carbon measurements such as photoacoustic
sensors. nonECPM = nonECnonS04PM + SO4 + H2O.
• Non-Elemental Carbon, Non-Sulfate Particulate Matter (nonECnonS04PM): MOVES
intermediate species used to represent the PM2.5 mass other than elemental carbon,
sulfate, and associated water. NonECnonS04PM includes organic matter, elements, and
ions. NonECnonS04PM is adjusted for fuel and temperature effects prior to speciation
due to limited data on temperature and fuel effects on individual PM2.5 species in the
exhaust, and to improve computational time.
• Residual PM (nonECnonS04nonOM PM): Similar to nonECnonS04 PM but further
subtracts total organic matter (TOM) leaving elements and ions.
2.4 Databases, Models and Tools
• CMAQ: The Community Multiscale Air Quality system (CMAQ) is a photochemical and
transport air quality model. CMAQ is an open-source development project sponsored by
the US EPA Atmospheric Science Modeling Division
(https://www.cmascenter.org/cmaq/).
• SPECIATE: EPA's repository of organic gas and particulate matter (PM) speciation
profiles from air pollution sources.8 The SPECIATE database contains a record of each
profile including its referenced source, testing methods, a subjective rating of the quality
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of the data, and other detailed data that allow researchers to decide which profile is most
suitable for model input (https://www.epa.gov/air-emissions-modeling/speciate)
• Speciation Tool: Estimates "split-factors" to translate inventory pollutants such as VOC
to chemical mechanisms species. The Speciation Tool creates the mapping of
NONHAPTOG emissions from MOVES to the chemical mechanism species, using the
relevant speciation profiles from SPECIATE, re-normalized without the integrated
1 8
species.
• SMOKE: Sparse Matrix Operator Kernel Emissions is a computer program used to
provide model-ready inputs into CMAQ. SMOKE produces gridded, speciated, and
hourly emissions input for use in CMAQ and other air-quality models. For onroad
emissions, MOVES provides the emissions already speciated into the chemical
mechanism species, (https://www.cmascenter.org/smoke/)
• SMOKE-MOVES: "A set of methodologies and software tools to help use output from
MOVES as inputs to SMOKE."19 MOVES is run in rates-mode to produce emission rates
for different meteorological conditions, vehicle speeds (for running emissions), emission
processes, road types, fuel types, and source types at different temporal and geographical
domains to account for local differences in emissions. SMOKE-MOVES combines
MOVES emission rates with respective vehicle activity to estimate emissions that are
input into SMOKE.
3 Organic Gas Aggregations and Ratios
o est? o
MOVES provides estimates of organic gas emissions in a number of different aggregations.
Table 3-1 shows the composition of various organic gas aggregate classes in MOVES. As the
table shows, the organic gas aggregations differ based on the presence or absence of methane,
ethane, alcohols, and aldehydes. Definitions of these species are also included in the glossary. In
MOVES, total hydrocarbons (THC) is defined as hydrocarbons measured with a Flame
Ionization Detector and includes methane and ethane. MOVES calculates emissions of total
organic gases (TOG), non-methane organic gases (NMOG) and volatile organic compounds
(VOC) using information regarding the organic gas speciation of emissions.
Table 3-1 Relationships among C
rganic Gas Aggregations in MOVES
pollutantID
pollutantName
Acronym
nu-
nc
Methane
Ethane
Acetone
Alcohols
Aldehydes
1
Total
Hydrocarbons
THC
Yes
Yes
Yes
No
No
No
79
Non-Methane
Hydrocarbons
NMHC
Yes
No
Yes
No
No
No
87
Volatile
Organic
Compounds
VOC
Yes
No
No
No
Yes
Yes
86
Total Organic
Gases
TOG
Yes
Yes
Yes
Yes
Yes
Yes
80
Non-Methane
Organic Gases
NMOG
Yes
No
Yes
Yes
Yes
Yes
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In MOVES, THC emission rates are the base organic gas emission rates as documented in the
MOVES light-duty exhaust1, heavy-duty exhaust2, and evaporative20 emission rate report from
which each of the other organic emissions are estimated using the calculations documented in the
following section. Gas-phase organic air toxics are calculated from VOC emissions as discussed
in the MOVES air toxics report
3.1 Total Organic Gaseous Calculations
Exhaust regulations for organic gases are often expressed in terms of non-methane hydrocarbons
(NMHC). MOVES calculates both methane and NMHC from the THC emissions using methane-
to-total hydrocarbon ratios (recorded in the CH4THCRatio field of the MOVES
MethaneTHCRatio table) as shown in Equation 1 and Equation 2.
CH4
- THC x Equation 1
V THC)
CH \
NMHC = THCX(1 - 4 *
Equation 2
Following the calculation of NMHC, the MOVES algorithm calculates NMOG, VOC and TOG
as shown in Equation 3 through Equation 5.
NMOG
NMOG = NMHC X NMHC Equation 3
voc ^ ,
VOC = NMHC X NMHC Equation 4
TOG = NMOG + CH4 Equation 5
In early versions of MOVES, the data used to calculate CHVTHC was not consistent with the
data used to calculate ratios of organic aggregates.21 Beginning in MOVES3, for many of the
vehicles and emission processes, we determined CHVTHC ratios from the SPECIATE profiles
that are currently used in the model. The CHVTHC ratios stored in the Methane THC "Ratio table
in MOVES vary by emission process, regulatory class, fuel subtype, and model year. The
methodology to calculate CHVTHC ratios from SPECIATE data is presented in Section 3.2 and
the calculated ratios for each profile are presented in Table 3-2.
Within MOVES, the NMOG/NMHC and VOC/NMHC ratios shown in Equation 3 and Equation
4 are called "speciation constants." Speciation constants were calculated for each SPECIATE
profile used in MOVES in order to be consistent with the updated CHVTHC ratios and with the
TOG calculation chain.0 These ratios continue to be stored in the HCSpeciation table which now
0 Previous to MOVES3, the speciation constant parameters were calculated using either of two methods. The first
method was based on the relative carbon fraction of each species and was first developed for MOBILE4.1. The
second method was based on Equation 1066.635-1 of the CFR. For further details, the reader is directed to the
MOVES2014 speciation report33.
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also includes the key fields regulatory class and fuel subtype. The new speciation constant
parameters are also presented in Table 3-2.
The calculation of NMOG and VOC in previous MOVES versions included additional terms that
represented adjustments to correct for the oxygenated volume in the fuel (oxySpeciation,
volToWtPercentOxy and oxyVolume parameters). Since MOVES3, different speciation
constants are provided for fuel subtypes for different fractions of ethanol in gasoline (EO, E5, E8,
E10, E15, E85), and the previous adjustments made to correct for oxygenated volume in the fuel
were removed, simplifying the equations as shown in Equation 3 and Equation 4. The new
methodology removes the capability of MOVES to adjust NMOG and VOC according to other
oxygenated compounds such as methyl tert-butyl ether (MTBE), ethyl tert-butyl ether (ETBE)
and tert-amyl methyl ether (TAME). However, fuel market projections indicate that additives
other than ethanol are unlikely to return to the market, supporting the removal of these
parameters from the model.
3.2 Ratios for Evaporative Emissions and Most Exhaust Emissions
We use SPECIATE profiles to derive CH4/THC, NMOG/NMHC and VOC/NMHC for all
emissions processes and vehicle classes except exhaust emissions from 2001-and-later light-duty
gasoline vehicles, exhaust emissions from flex-fuel vehicles using E85 fuel, CNG exhaust, and
the CHVTHC fractions for 2010-and-later heavy-duty diesel exhaust, as discussed in the
following subsections.
The speciation profiles in MOVES were obtained from the SPECIATE database8. Each profile
has a detailed list of measured compounds and reports their weight as percentage of TOG. The
calculation of NMOG for each profile was done by simply subtracting CH4 from TOG as shown
in Equation 6.
NMOG = TOG — CH4 Equation 6
The calculation of NMHC is based on Equation 1066.635-1 in the Code of Federal Regulations.
The equation provided in the CFR was rearranged as shown in Equation 7 to solve for NMHC
using NMOG calculated in the previous step as an input.
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X ^^OHCi\THC-F!D\
^ mOCHi
i=l
N
Equation 7
mNMOG = mass of NMOG in the exhaust.
mNHMC = mass of NMHC in the exhaust.
Pnmhc = 576.816 g/m3 which is the effective Cl-equivalent density of NMHC as specified in
§1066.1005(f).
moHCi = mass of oxygenated species i in the exhaust.
poHCi = Cl-equivalent density of oxygenated species i as specified in 40 CFR 1066.605-1. For
methanol, the density is 1332.02 g/m3; for ethanol, the density is 957.559 g/m3; for acetaldehyde,
the density is 915.658 g/m3; for formaldehyde, the density is 1248.21 g/m3; and for propanol, the
density is 832.74 g/m3.
RFoHCi[THc-FiD] = response factor of a THC-FID to oxygenated species i relative to propane on a
Cl-equivalent basis as determined in 40 CFR 1065.845. The RF for acetaldehyde is 0.5; for
formaldehyde is 0; for ethanol is 0.75; for methanol is 0.63 and for propanol is 0.85.
After NMHC and NMOG are calculated, the calculation of THC is done as shown in Equation 8.
Once THC is calculated, the CHVTHC can then be determined.
Finally, VOC is calculated following the definition used in MOVES, where methane (CH4),
ethane (C2H2) and acetone (C3H5O) are subtracted from TOG emissions as shown in Equation 9.
Table 3-2 presents the ratios determined for each SPECIATE composite profile. Information on
the data behind each SPECIATE profile is provided in more detail in Appendix A.
Table 3-2 notes the assignment of the derived speciation ratios to different model years,
processes, fuel subtypes, and regulatory classes. For gasoline exhaust, we use profiles 8750a and
8751a to represent gasoline exhaust for 2000 and earlier light-duty vehicles. For other gasoline
regulatory classes (motorcycles and heavy-duty vehicles), the same profiles were used for all
model years.
THC = NMOG X
Equation 8
VOC = TOG — CH4 — C2H2 — C3HeO
Equation 9
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Table 3-2 Updated CH4/THC and Speciation Constant Parameters from SPECIATE Profiles for MOVES4
Profile
Number
Profile
Description
Emission Process
Fuel
Subtype
Vehicles
CH4/THC
Ratio
NMOG/NMHC
Ratio
VOC/NMH
C Ratio
95120cd
Liquid diesel
Refueling Spillage
Diesel,
biodiesel
All diesel
0
1
1
8750a
Pre-Tier 2 E0
exhaust
Running, starts exhaust and
crankcase
Conventional
Gasoline
Pre-2001 LD gasoline
All MC and non-LD
gasoline
0.142
1.024
0.996
8751a
Pre-Tier 2
E10 exhaust
Running, starts exhaust and
crankcase
RFG, E10, E8,
E5
Pre-2001 LD gasoline
All MC and non-LD
gasoline
0.146
1.037
1.008
8753
E0 Evap
Evaporative (vapors, leaks,
refueling spillage)
Conventional
Gasoline
All gasoline
0
1
1
8754
E10 Evap
Evaporative (vapors, leaks,
refueling spillage)
E10, E8, E5
All gasoline
0
1.071
1.071
8766
E0 Evap
perm
Evaporative Permeation
Conventional
Gasoline
All gasoline
0
1
1
8769
E10 Evap
perm
Evaporative Permeation
E10, E8, E5
All gasoline
0
1.129
1.129
8770
E15 Evap
perm
Evaporative Permeation
E15
All gasoline
0
1.175
1.175
8774
Pre-2007 MY
HDD exhaust
Running, starts, extended
idle exhaust and crankcase
Diesel,
Biodiesel
Pre-2007 diesel
0
1.145
1.124
APU
Pre-2024 APU
Running, starts exhaust and
crankcase
Pre-2007 LD diesel
8775
2007-2009
HDD exhaust
Running, starts exhaust and
crankcase
Diesel,
Biodiesel
2007+ LD diesel
0.589
1.343
1.285
APU
2024+ APU
Running, starts, extended
idle exhaust and crankcase
2007+ HD diesel
95335a
2010+ HDD
exhaust
Running, starts exhaust and
crankcase
Diesel,
Biodiesel
2010+ LD diesel
0, Not
Used6
1.085
0.965
Running, starts, extended
idle exhaust and crankcase
2010+HD diesel
14
-------
Table 3-2 (continued)
Profile
Number
Profile
Description
Emission Process
Fuel Subtype
vehicles
ch4/thc
Ratio
NMOG/NMHC
Ratio
VOC/NMHC
Ratio
8869
E0 Headspace
Refueling displacement
vapor loss
Conventional
Gasoline
All gasoline
0
1
1
8870
E10
Headspace
Refueling displacement
vapor loss
E10, E8, E5
All gasoline
0
1.037
1.037
8871
E15
Headspace
Refueling displacement
vapor loss
E15
All gasoline
0
1.175
1.175
8872
El5 Evap
Evaporative (vapors,
leaks, refueling spillage)
E15
All gasoline
0
1.118
1.118
8934
E85 Evap
Evaporative permeation
E85, E70
All gasoline
vehicles running
on high ethanol
blends
0
1.501
1.501
Evaporative (vapors,
leaks), refueling
displacement and
spillage losses
All gasoline
vehicles running
on high ethanol
blends
d Profile 95120 is based on NMOG and we assume that there is no methane in liquid diesel fuel. In addition, no oxygenated species are measured in the profile
(formaldehyde, acetaldehyde, or ethanol), nor any non-volatile organic compounds (ethane, and acetone), thus the CH4/THC, NMOG/NMHC and VOC/NMHC values
are 0, 1, and 1, respectively.
e MOVES uses a 0.38 CH4/THC ratio based on a literature review discussed in Section 3.6
15
-------
For vapor venting, fuel leaks, and fuel spillage loss emissions from EO and E10, the speciation
constants are based on SPECIATE profiles from the Auto/Oil Air Quality Improvement
Research Program (profiles 8753 and 8754).f The speciation profiles for refueling displacement
vapor loss (profiles 8869, 8870, and 8871) for EO, E10, and E15 fuels were based on
measurements conducted by EPA.22 ) Profile 8872 used for vapor venting, leaks, and refueling
spillage for El 5 fuels is based on SPECIATE profile 8754 (a composite profile developed from
the Auto/Oil Air Quality Improvement Research Program) and data collected in the EPAct/V2/E-
89 program on E10 and E15 fuels. For evaporative permeation emissions, MOVES uses
speciation constants developed from three ethanol blend levels (EO, E10, El 5) from the CRC E-
77 program (profiles 8766, 8769, 8770).23 In the CRC E-77 programs the test procedure
specifically separated the evaporative emissions mechanisms, therefore there was an apparent
ethanol effect on permeation but not a clear RVP effect.
The speciation constants for all evaporative emission processes from E85-fueled vehicles are
calculated from SPECIATE profile 8934 developed from the CRC E-80 report.24 The speciation
profile used for diesel refueling emissions, (which only include liquid diesel spillage loss in
MOVES20) was updated in MOVES3 to be based on a liquid diesel SPECIATE profile 95120.d
For pre-2007 diesel emissions (both light-duty and heavy-duty), MOVES uses speciation profile
8774, which is based on a review of speciated diesel emissions on pre-2007 model year engine
technologies. MOVES uses the pre-2007 NMOG/NMHC value for diesel auxiliary power units
(APUs; processID 91) for all model years prior to 2024 because they are not subject to the same
control as on-highway diesel engines. For 2007 to 2009 model year light-duty and heavy-duty
diesel vehicles, MOVES uses speciation profile (8775) based on data from Phase 1 of the
Advanced Collaborative Emissions Study (ACES)25, which includes diesel engines equipped
with diesel particulate filter, and is the technology used to meet the heavy-duty 2007 diesel
standards.26 MOVES also applies the ACES Phase 1 speciation profile to 2024 and later
auxiliary power units because it is anticipated they would use diesel particulate filters to meet the
APU PM standards promulgated as part of the Phase 2 medium and heavy-duty greenhouse gas
regulation.27
Beginning in MOVES3, we incorporated a new speciation profile (95335a) to 2010 and later
diesel vehicles based the ACES Phase 2 test program.28 This program tested three heavy heavy-
duty 2011 model year engines equipped with diesel particulate filters and selective catalytic
reduction systems that are representative of current diesel technologies used to achieve the 2010
heavy-duty emission standards. The engines and aftertreatments were tested new, and the
emissions of NMHC were over 99% below the 2010 emission standards. Furthermore, emissions
of the majority of individual organic compounds were below the levels measured from the ACES
Phase 1 program, including methane emissions, which were below the detection limit in ACES
Phase 2, but which contributed over 50% of the TOG emissions in the ACES Phase 1 program.29
f The CRC E-77 program23 observed a significant effect for both RVP and ethanol in the diurnal emissions data
largely due to the vapor venting breakthrough emissions which were vented outside of the SHED using special
procedures as defined in the individual study reports. As noted in the 2017 peer-review58, there is likely an
accompanying effect of RVP on vapor venting emissions (from both vapor venting and fuel displacement venting),
and both RVP and ethanol content should be considered as factors when developing updated vapor venting
speciation profiles in future test programs.
16
-------
Due to the low level of TOG emissions, the relative error of the speciation fractions of TOG is
high in the ACES Phase 2 program. We have developed methane fractions from a literature
review of emission studies on MY 2010-and-later heavy-duty diesel engines as discussed in
Section 3.6. In addition, we removed alcohol species from the original profile (95335) that are
likely measurement artifacts as documented in Appendix D. In addition, many of the
measurements were near detection limits, and individual species measurements showed
inconsistencies when compared to the emission trends of groups of gaseous hydrocarbons from
ACES Phase 1 (see Appendix D). Given the limited number of tests and low emission levels
measured, it is not possible to determine whether these inconsistencies represent real differences,
test to test variability, or measurement uncertainties.
Despite the uncertainties regarding the Phase 2 speciation profile, we have incorporated it into
MOVES (including the NMOG/NMHC and VOV/NMHC ratios) because it is the most
comprehensive chemical sampling program available for exhaust from MY 2010 and later
heavy-duty diesel technology. We recommend further speciated measurements of modern heavy-
duty diesel engine exhaust, including vehicles with aged and deteriorated aftertreatment systems
that likely emit higher concentrations of organic gas and particulate matter emissions.
3.3 Ratios for 2001-and-Lalcr! mhi-l Mity Gasoline Exhaust
aj
We determined ratios of CHVTHC, NMOG/NMHC and VOC/NMHC for exhaust emissions
from Tier 2 (model year 2001-and-later) vehicles running on gasoline-ethanol blends (0 percent -
15 percent ethanol) using bag-specific data from the EPAct Phase 1 program30 In contrast, the
SPECIATE profiles (8756, 8757, and 8758) developed from the EPACT/V2/E-89 program
combined the start and running emissions (Table 4-1). As presented in this section, the speciation
constants varied significantly by bag, and we determined that it was preferable to use the
resolved speciation constants based on the bag data from the same data set used to derive the
SPECIATE profiles.
EPAct Phase 1 was designed to collect data from light-duty vehicles running on low-level
ethanol blends. Three vehicles (MY 2008) were tested to generate data for the three bags
required to create speciated composite profiles. The tests involved 9 runs using fuel with 0
percent ethanol, 6 runs using fuel with 10 percent ethanol and 7 runs using fuel with 15 percent
ethanol. Further information on vehicles, fuels and testing is detailed in the EPAct Phase I
report.30 The data corresponding to the runs used for this analysis is listed in Appendix A.
For ethanol levels between 0-15 percent, the average CH4 and THC emissions were calculated
and subsequently a ratio of means was determined (i.e., CFUavg/THCavg). To verify if there was
a statistically significant trend with ethanol composition, a linear regression between these ratios
and ethanol composition was performed (Figure 3-1). The regression analysis indicated that the
slope was statistically significant (significance level < 0.05) for start emissions but not for
running emissions. Therefore, CH4/THC for starts are specific for each ethanol composition, but
for running an average CH4/THC across all low-level ethanol blends is used. The linear fit for
starts was used to interpolate CH4/THC values for E5 and E8 fuel compositions, for which no
SPECIATE profiles are available.
17
-------
¦©- running ~starts
Figure 3-1 Relationship between CH4/THC Ratios and Ethanol Composition for Tier 2 Vehicles using Low-
Level Ethanol Blends
The speciated data used to determine NMOG/NMHC and VOC/NMHC for Tier 2 vehicles
corresponds to the same EPAct Phase 1 runs referred to in the determination of CH4/THC ratios
for these vehicles. Data from Bag 3 was subtracted from Bag 1 to determine cold start emissions.
NMOG, VOC and NMHC were calculated for each test following the methodology described in
Section 3.1. The reported speciation constant parameters were determined as a ratio of means
(i.e., NMOGavg/NMHCavg or VOCavg/NMHCavg) for each ethanol composition. The linear
relationship between speciation constant parameters and ethanol composition was statistically
significant for starts (a < 0.05), but not for running emissions (Figure 3-2). Therefore, like the
CH4/THC ratios, we report speciation constant parameters for start emissions (Table 3-3) at each
ethanol composition analyzed, whereas for running emissions (Table 3-4) we report an average
across the ethanol compositions. This approach is supported by a previous study performed by
the Oak Ridge National Laboratory (ORNL)31 which focused on the estimation of NMOG
emissions from 68 vehicles using mid-level ethanol blends. The ORNL study found that given
very low emissions normally measured in bag 2 and the level of scatter associated with them, the
recommended approach was to use a constant NMOG/NMHC ratio across ethanol compositions.
We apply the resulting EPAct Phase 1 speciation constant values for all light-duty gasoline
vehicles in model year 2001 and later. As we note in the discussion of the light-duty PM2.5
speciation profile (Appendix E.l), modern gasoline direct injection vehicles have significantly
different composition of particulate matter emissions. We anticipate that there are also
significant differences in the organic gas speciation. We plan to incorporate light-duty gasoline
organic gas speciation profiles and constants in MOVES and SPECIATE as such data on
representative, in-use vehicles become available.
18
-------
¦©¦ running starts
running starts
1 10-
105-
1 00"
095-
y = 0.0036X + 1.0135
R2 = 0.9919
p-value = 0.057
V = 0.0011x+ 1.0365
R2 = 0.0605
p-value = 0.841
10
1 10-
1 05-
1 00*
y = 0.0033X + 0.9808
R2 = 1
p-value = 0.003
V = -0.0005x + 0.9832
R2 = 0.0127
p-value = 0.928
095-
15
10
15
Ethanol (%) Ethanol (%)
Figure 3-2 Relationship between Speciation Constant Parameters and Ethanol Composition for Tier 2
Vehicles using Low-Level Ethanol Blends
Furthermore, the reported NMOG/NMHC ratio for 0 percent ethanol level in the ORNL study
was 1.0302 which corresponds to the intercept of the best-fit line for the current analysis. For
comparison purposes, we also determined the NMOG/NMHC ratio for the SPECIATE running
profile 8756 (Tier 2 E0 exhaust) using the methodology described in this report. The
NMOG/NMFIC ratio we estimated was 1.038, showing reasonable agreement with the value
determined by the ORNL study.
19
-------
Table 3-3 CH4/THC and Speciation Constant Parameters for Start Emissions from Tier 2
Vehicles
Bag data
from
profile
Profile
description
Emission
process
Fuel Subtype
Affected
vehicles
ch4/thc
Ratio
NMOG/NMH
CRatio
VOC/NMHC
Ratio
8756
Tier 2 E0
exhaust
Start
exhaust and
crankcase
Conventional
Gasoline
2001+LD
gasoline
0.091
1.014
0.981
N/A
Tier 2 E5
exhaust
Start
exhaust and
crankcase
E5
2001+LD
gasoline
0.098
1.031
0.997
N/A
Tier 2 E8
exhaust
Start
exhaust and
crankcase
E8
2001+LD
gasoline
0.102
1.042
1.007
8757
Tier 2 E10
exhaust
Start
exhaust and
crankcase
E10
2001+LD
gasoline
0.105
1.046
1.014
8758
Tier 2 E15
exhaust
Start
exhaust and
crankcase
E15
2001+LD
gasoline
0.112
1.069
1.030
8855
Tier 2 E85
exhaust
Start
exhaust and
crankcase
E85, E70
Pre-2001 MY
flex-fuel
vehicles
running on high
ethanol blends
0.273
1.511
1.454
8855
Tier 2 E85
exhaust
Start
exhaust and
crankcase
E85, E70
MY 2001+
flex-fuel
vehicles
running on high
ethanol blends
0.273
Not Useda
Not Useda
a MY 2001 and later E85 fueled vehicles use the Tier 2 E10 NMOG/NMHC and VOC/NMHC ratios as discussed in Section 3.4
20
-------
Table 3-4 CH4/THC and Speciation Constant Parameters for Running Emissions from Tier
2 Vehicles
Bag data
from
profile
Profile
Emission
Fuel Subtype
Affected
CH4/TH
NMOG/NMHC
VOC/NMH
description
Process
vehicles
CRatio
Ratio
L
Ratio
8756
Tier 2 E0
exhaust
Running
exhaust and
crankcase
Conventional
Gasoline
2001+LD
gasoline
0.338
1.038
0.974
N/A
Tier 2 E5
exhaust
Running
exhaust and
crankcase
E5
2001+LD
gasoline
0.338
1.038
0.974
N/A
Tier 2 E8
exhaust
Running
exhaust and
crankcase
E8
2001+LD
gasoline
0.338
1.038
0.974
8757
Tier 2 E10
exhaust
Running
exhaust and
crankcase
E10
2001+LD
gasoline
0.338
1.038
0.974
8758
Tier 2 E15
exhaust
Running
exhaust and
crankcase
E15
2001+LD
gasoline
0.338
1.038
0.974
Pre-2001 MY
8855
Tier 2 E85
exhaust
Running
exhaust and
crankcase
E85, E70
flex-fuel
vehicles
running on
high ethanol
blends
0.822
1.234
0.934
MY 2001+
8855
Tier 2 E85
exhaust
Running
exhaust and
E85, E70
vehicles
running on
0.822
Not Usedb
Not Usedb
crankcase
high ethanol
blends
bMY 2001 and later E85 fueled vehicles use the Tier 2 E10 NMOG/NMHC and VOC/NMHC ratios as discussed in Section 3.4
3.4 Ratios for Flex Fuel Vehicles usinu I huh bihanol Blench i!
The CHVTHC ratios and speciation constants used for high-level ethanol blends (E70 and E85),
shown in Table 3-3, were developed from three high-level ethanol fueled vehicles tested as part
of the EPAct/V2/E-89 program.32 The CH4/THC, NMOG/NMHC and VOC/NMHC ratios are
used to estimate CH4, NMHC, NMOG, VOC, and TOG emissions for pre-2001 model year E85
vehicles. The CH4/THC ratios are also used to estimate CH4 and NMHC emissions for 2001 and
later model year vehicles.
The NMOG and VOC emissions from high-level ethanol fueled vehicles for 2001 and later
model year vehicles in MOVES are calculated differently. As discussed in the fuel effects
report46, NMOG and VOC emission rates for high-level ethanol exhaust emissions are based on
the EPAct/V2/E-89 data, plus data from three other testing programs with a total of 19 Tier 2
FFV vehicles tested on both E10 gasoline and E85 fuels. No significant differences were
observed in the NMOG emissions between the Tier 2 vehicles tested on E10 and E85 fuels. As
such, MOVES calculates NMOG and VOC emissions from NMHC emissions calculated using
21
-------
E10 CH4/NMHC ratios, and fuel effects primarily using E10 fuel properties.g NMOG and VOC
emissions for E85-fueled vehicles are then calculated using the NMOG/NMHC and
VOC/NMHC ratios from the Tier 2 E10 Profile (8757). We recognize this approach can result in
discrepancies between NMHC and VOC emissions from E85-fueled vehicles particularly if the
methane ratios are significantly different between ratios between the EPAct/V2/E-89 study (3
vehicles), and the larger 19-vehicle dataset.11 One of the reasons this approach was taken was due
to the limited data on E85 emissions; it reflects the need for further research on E85 emissions. A
more detailed discussion of NMOG and VOC emissions from high ethanol blend fueled vehicles
is included in the MOVES Fuel Effects Report.46
3.5 Ratios for CNG Vehicles
The speciation values for compressed natural gas (CNG) exhaust are derived from a study
conducted by the California Air Resources Board on a CNG lean-burn transit bus with and
without an oxidation catalyst (Ayala et al. 20 0338). The derivation of the CNG methane and
speciation constants are documented in Appendix B. In MOVES, we apply the speciation values
from the "without control" tests to pre-2002 model year CNG vehicles, and the values "with the
oxidation catalyst" to 2002 and later vehicles as shown in Table 3-5. The data used to develop
the speciation constants was not complete enough to develop full speciation profiles. In the
absence of mobile-source CNG speciation profile, we use SPECIATE profile 10011 to speciate
the residual TOG (Table 4-1).
Table 3-5 C
14/THC and Speciation Constant Parameters for CNG Exhaust
Profile
Description
Model
Years
affected
Emission
process
CH4/THC
Ratio
NMOG/NMHC
Ratio
VOC/NMHC
Ratio
CNG lean-
burn
1960-2001
Starts and
running
exhaust
and
crankcase
0.886
1.9
1.68
CNG lean-
burn
oxidation
catalyst
2002-2060
Starts and
running
exhaust
and
crankcase
0.959
1.24
0.93
The peer-reviewers of the MOVES2014 Speciation report33 recommended we consider using
more recent studies of CNG vehicles. In response, we compared the CHVTHC, NMOG/NMHC,
and VOC/NMHC developed from Ayala et al. (20 03)38, to more recent studies including data on
stoichiometric three-way catalyst (TWC) technology engines as shown in Table 3-6. The
MOVES CHVTHC value falls within the range of recent studies. Larger differences between
g With the exception of sulfur level, see the discussion in the MOVES fuel effects report46
h Only a fraction of the vehicles tested in the 19 vehicle-test sample reported methane measurements. If the methane
fraction is significantly different in the EPAct/V2/E-89 program compared to the 19 vehicle-test sample compared to
the EPAct/V2/E-89 program used to derive the NMOG rates, this could create the observed inconsistency in the
NMOG/NMHC and VOC/NMHC ratios.
1 As shown in Table A-4, Speciate profile 1001 is based on a measurements from a stationary CNG engine
22
-------
studies are observed for the NMOG/NMHC and VOC/NMHC ratios, particularly for the
uncontrolled lean-burn values. The differences can be explained by the fact that the CNG
exhaust from Ayala et al. (20 03)38 used in MOVES contain high formaldehyde emissions,
particularly for uncontrolled lean-burn buses, which causes high NMOG/NMHC ratios. The
large variation in these values may also be due to differences in measurement methods,
particularly because non-methane hydrocarbons constitute a small fraction of the total organic
gas emissions from CNG buses.
The MOVES speciation value for the catalyst -equipped engines used for MY 2001 and later, are
slightly outside the range of values obtained in other studies, but still compare relatively well
considering the variability among the different studies. As such, we have maintained the use of
them in MOVES. The variation among the different values could be used to assess the relative
uncertainty of the methane, NMOG, and VOC emissions estimated in MOVES.
Table 3-6 Comparison of CH4/THC and Speciation Constant Parameters for CNG Engines
from several studies
Study
Technology
Model
year
Cycles
tested
CH4/THC
Ratio
NMOG/NMHC
Ratio
VOC/NMHC
Ratio
CEC-201534
Lean-burn
2005
CBDa
0.853
1.062
1.062
Stoichiometric
TWC
2011-2013
CBD
0.881
1.183
1.183
Thiruvengadam
et al.35,36
Stoichiometric
TWC
2008-2009,
2011
UDDSb
0.982
1.096
1.096
Dual-Fuel
High-Pressure
Direct
Injection
(HPDI)
2011
UDDS
0.683
1.031
1.031
CE-CERT37
Stoichiometric
TWC°
2014
UDDS
0.941
NDd
ND
Stoichiometric
TWC
2014
CBD
0.719
ND
ND
Ayala et al.38
(MOVES)
Lean-burn, no
control
2000
CBD
0.886
1.9
1.68
Lean-burn,
Oxidation
catalyst
2000
CBD
0.959
1.24
0.93
Notes:
a Central Business District
b Urban Dynamometer Driving Schedule
0 TWC= Three-way catalyst
d ND: Not Determined
Currently, we do not estimate evaporative or refueling emissions from CNG vehicles in MOVES
and thus, have no CH4/THC, NMOG/NMHC, and VOC/NMHC ratios for these processes. This
is an area for future research.
23
-------
3.6 CH4 Ratios for 2010-and-Later Heavy-Duty Diesel Vehicles
The pre-2007, 2007-2009, and 2010-and-later model years, CH4/THC ratios for heavy-duty
diesel based on the assigned speciation profiles in Table 3-2 are 0%, 58%, and 0%. The 2010-
and-later speciation profiles (95335a) is developed from the ACES Phase 2 program, where
methane emissions were below the detection limit.29 Methane and NMHC emissions below the
detection limit has also been reported in other studies that measured emissions from MY 2010
and later heavy-duty vehicles.39'85
However, due to the large inconsistency in the methane fractions between the 2007-2009 and
2010-and-later model years, and our relative uncertainty regarding the methane fraction from the
Phase 2 profiles (See Appendix D), we conducted a literature review on methane emissions from
MY 2010 and later heavy-duty diesel trucks. Three different studies from the literature and EPA
certification data reported significant CH4/THC ratios from MY 2010+ heavy-duty exhaust as
shown in Table 3-7. From the reported values, we calculated an average CH4/THC ratio of 38%,
which we use in MOVES for all MY 2010 and later diesel-fueled vehicles.
We recognize there is uncertainty regarding representative driving conditions and vehicles.
Quiros et a/.(2016,2017)40'41 showed that methane fractions varied by driving cycle, but there
was not a consistent trend in the methane ratios from low to higher load operation. Due to the
wide variety of results, we decided to take an average of each of the cycle-average values from
each of the studies shown in Table 3-7, except for the local drayage value from Quiros et a/.40'41
which was deemed an outlier value (90% methane). This approach was deemed the most
reasonable to yield a representative methane fraction for in-use driving.
The vehicles sampled also tended to be vehicles with low mileage accumulation. The reported
odometer readings that were available were relatively low for heavy-duty diesel trucks (less than
200,000 miles). The EPA certification data are obtained from test-engines with fully functioning
aftertreatment systems that have not been applied in-use. In theory, the CH4/THC ratios are
likely to decrease as vehicles age, as the aftertreatment system becomes less efficient at
oxidizing NMHC. However, we don't have the data nor the MOVES structure to support this,
and we are using the methane fraction to represent all vehicle ages for MY 2010-and-later diesel
vehicles.
As discussed in Section 3.2, we are continuing to use the ACES Phase 2 speciation program for
the speciation factors for NMHC from 2010-and-later exhaust (i.e. NMOG/NMHC and
VOC/NMHC ratios, and the speciation profile to estimate the chemical mechanism species from
the integrated species and NONHAPTOG). Most of the studies evaluated did not provide
sufficient speciation measurements from which to develop speciation profiles or even speciation
factors beyond the methane ratios. Future work could develop updated speciation ratios and
profiles from Hays et al.{2017)42 and other relevant studies.
24
-------
fable 3-7 CH4/TH<
C Ratios for MY 2010+ Heavy-Duty Diesel Trucks
Source
Vehicle
#
Reg
Class
Model
Year
Technology
Odometer
Cycle
CH4/THC
(%)
Hill Climb
18%
Quiros et al
201640
Interstate
25%
4
HHD
2013-2014
DOC+DPF+SCR
40K to
Regional
20%
Quiros et al
201741
186K
Local Drayage
90%
Near Dock
22%
Urban
33%
Hays et al
201742
3
LHD2b3,
LHD45,
MHD
2011
LHD2b3:
DOC+NAC+DPF
LHD45 & MHD:
4K to 35K
CARBMHD
UDDS and
HD-UDDS
42%
DOC+SCR+DPF
Karavalakis
UDDS
68%
1
HHD
2014
DOC+DPF+SCR
NA
et al 2016 43
HHDDT
55%
Transient
9
engine
families
LHD
47%
EPA
Certification
Data44-3
16
engine
families
MHD
2016-2019
DOC+DPF+SCR
NA
Transient (TR)
Comb Adj
39%
10
engine
families
HHD
46%
Average =
(excluding the Local Drayage from Quiros et al.)
38%
Note: DOC-Diesel Oxidation Catalyst, DPF-Diesel Particulate Filter, NAC-NOx Adsorber Catalyst, SCR-Selective
Catalytic Reduction
a The methane fractions from the EPA certification data were calculated as average of ratios from each engine
family, rather than a ratio of averages, which would yield lower methane fractions.
4 Residual TOG Speciation
4.1 Overview
As introduced in Section 2.2, MOVES estimates emissions for a subset of 15 species that
contribute to TOG known as "integrated species" (Table 2-2). MOVES contains algorithms and
information on fuel properties and temperature dependencies that allows estimating these species
with more detail than available from speciation profiles. For example, the benzene fraction
estimated by MOVES for light-duty gasoline vehicles accounts for the benzene content in the
gasoline fuel, whereas the benzene fraction estimated in the TOG speciation profiles is based on
the benzene level in the tests conducted for the speciation measurements. After subtracting the
integrated species from the total organic gas estimates, the remaining emissions are referred to as
Residual TOG or NONHAPTOG.
25
-------
Residual TOG = TOG - MOVES gaseous integrated species
Equation 10
MOVES also computes a select list of PAHs, dioxins, and furans which are not integrated except
for one PAH species, naphthalene. The other PAHs, dioxins and furans are not included in the
integrated species in part because they compose a small percentage of the Residual TOG
emissions; incorporating them into the integrated species would require additional data
processing without a significant impact on the Residual TOG estimates.
4.2 Mapping Residual TOG to Speciation Profiles
A real speciation profile is, in principle, a complete listing of all the real species and their
quantities that make up an aggregate species such as TOG. Of course, the hundred or so
compounds listed in these profiles are not a complete listing, which would likely include
thousands of species. However, these profiles contain the major species by mass and reactivity.
Such profiles are produced by laboratory analysis of emissions and are independent of chemical
mechanism.
MOVES3.0.3 and earlier versions used speciation profiles to translate Residual TOG emissions
estimates directly into chemical mechanism species. However, in MOVES3.0.4 and later, we
removed this capability from the model in favor of a postprocessing step that could facilitate
speciating MOVES output into any chemical mechanism without the need of re-running
MOVES. The details for the post-process are discussed in Section 6, but the mapping of onroad
emissions to specific speciation profiles is discussed below.
Table 4-1 summarizes the speciation profiles used in MOVES and hosted on SPECIATE,
together with the fuels, affected vehicles, and MOVES emission processes to which they apply.
Table A-4 lists the referenced sources for each of the real speciation profiles.
The mapping of speciation profiles to onroad emissions is done by model year, fuel subtype,
regulatory class, and emission process; Appendix C provides the assignment at this level.
Appendix C also provides the SPECIATE codes for the corresponding volatility-based profiles^
to provide speciation under the Reactive Organic Carbon framework (see Section 6). Fuel
subtype refers to fuel groupings within the larger fuel types of gasoline, diesel, CNG and E85 as
detailed in Table C-3. Regulatory class refers to vehicle type as defined in Table C-2. Emission
process refers to the emission's physical mechanism. As listed in Table C-l, MOVES has twelve
emission processes that are relevant for TOG speciation. Note that different TOG and PM
speciation profiles can be applied to different emission processes, but not to individual operating
modes (e.g., idling).
J Organic emissions, both gaseous and particulate, are made up of individual organic components. These components
feature different physiochemical properties, including volatility. The volatility profile of emissions can be quantified
using the effective saturation concentration (C*) of all organics, with a higher volatility corresponding to a higher
C*. In general, volatility profiles are defined for condensable reactive organic carbon (CROC) associated with OM
speciation and containing compounds with C* less than 320 |ig m 3; and gaseous reactive organic carbon (GROC)
associated with NMOG speciation and compounds with C* greater than 320 |ig m 3.
26
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Table 4-1 Speciation Profiles Used for Onroad TOG Emissions'4
Profile
Profile
Description
Fuel
Affected Vehicles
Emission Process
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust,
1001
CNG Exhaust
CNG
All CNG Transit Buses
Crankcase Start Exhaust
95120c1
Liquid Diesel
Diesel
All Diesel
Refueling Spillage Loss
8753
E0 Evap
E0
All Gas
Evap Fuel Vapor Venting, Evap Fuel
Leaks, Refueling Spillage Loss
8754
E10 Evap
E10
All Gas
Evap Fuel Vapor Venting, Evap Fuel
Leaks, Refueling Spillage Loss
Running Exhaust, Start Exhaust,
Tier 2 E0
Crankcase Running Exhaust,
8756
Exhaust
E0
2001+LD Gas
Crankcase Start Exhaust
Running Exhaust, Start Exhaust,
Tier 2 E10
Crankcase Running Exhaust,
8757
Exhaust
E10
2001+LD Gas
Crankcase Start Exhaust
Running Exhaust, Start Exhaust,
Tier 2 E15
Crankcase Running Exhaust,
8758
Exhaust
E15
All Gas
Crankcase Start Exhaust
8766
E0 Evap
Permeation
E0
All Gas
Evap Permeation
8769
E10 Evap
Permeation
E10
All Gas
Evap Permeation
8770
El5 Evap
Permeation
E15
All Gas
Evap Permeation
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust,
Crankcase Start Exhaust, Crankcase
Pre-2007 MY
Extended Idle Exhaust, Extended Idle
8774
HDD Exhaust
Diesel
Pre-2007 HD Diesel
Exhaust
Pre-2007 MY
8774
HDD Exhaust
Diesel
Pre-2024 APU
Auxiliary Power Exhaust
Running Exhaust, Start Exhaust,
Pre-2007 MY
Crankcase Running Exhaust,
8774
HDD Exhaust
Diesel
Pre-2007 LD Diesel
Crankcase Start Exhaust
Running Exhaust, Start Exhaust,
2007-2009
Crankcase Running Exhaust,
8775
HDD Exhaust
Diesel
2007-2009 LD Diesel
Crankcase Start Exhaust
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust,
Crankcase Start Exhaust, Crankcase
2007-2009
Extended Idle Exhaust, Extended Idle
8775
HDD Exhaust
Diesel
2007-2009 HD Diesel
Exhaust
k Appendix C provides a complete mapping of the TOG speciation profiles to modelYearGroupID, processID,
fuelSubTypelD, and regClassID.
1 While MOVES maps the liquid diesel profile to several processes, MOVES only estimates emissions from
refueling spillage loss. The other evaporative and refueling processes from diesel vehicles have zero emissions.
27
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Table 4-1 (continued)
Profile
Profile
Description
Fuel
Affected Vehicles
Emission Process
8775
2007-2009
HDD Exhaust
Diesel
2024+ APU
Auxiliary Power Exhaust
95335a
2011 HDD
Exhaust
Diesel
2010+ LD Diesel
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust, Crankcase
Start Exhaust
95335a
2011 HDD
Exhaust
Diesel
2010+ HD Diesel
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust, Crankcase
Start Exhaust, Crankcase Extended Idle
Exhaust, Extended Idle Exhaust
8855
Tier 2 E85
Exhaust
E70, E85
E70, E85
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust, Crankcase
Start Exhaust
8869
E0 Headspace
EO
All Gas
Refueling Displacement Vapor Loss
8870
E10
Headspace
E10
All Gas
Refueling Displacement Vapor Loss
8871
E15
Headspace
E15
All Gas
Refueling Displacement Vapor Loss
8872
E15 Evap
E15
All Gas
Evap Fuel Vapor Venting, Evap Fuel
Leaks, Refueling Spillage Loss
8934
E85 Evap
E70, E85
E70, E85
Evap Permeation, Evap Fuel Vapor
Venting, Evap Fuel Leaks, Refueling
Displacement Vapor Loss, Refueling
Spillage Loss
8750a
Pre-Tier 2 E0
Exhaust
EO
Pre-2001 LD Gas
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust, Crankcase
Start Exhaust
8750a
Pre-Tier 2 EO
Exhaust
EO
All MC and non-LD Gas
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust, Crankcase
Start Exhaust
8751a
Pre-Tier 2
E10 Exhaust
RFG, E10
Pre-2001 LD Gas
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust, Crankcase
Start Exhaust
8751a
Pre-Tier 2
E10 Exhaust
RFG, E10
All MC and Non-LD Gas
Running Exhaust, Start Exhaust,
Crankcase Running Exhaust, Crankcase
Start Exhaust
28
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5 PM2.5 Speciation
5/1 MOVES PM2.5 Species
MOVES estimates the 18 PM2.5 species outlined in Table 5-1.
Table 5-1 AE6 Chemical Mechanism PM2.5 Species
PM2 5 Species
AE6 Species
Name
Primary organic carbon
POC
Elemental carbon
PEC
Sulfate
PS04
Nitrate
PN03
Ammonium
PNH4
Non-carbon organic matter
PNCOM
Iron
PFE
Aluminum
PAL
Silicon
PSI
Titanium
PTI
Calcium
PCA
Magnesium
PMG
Potassium
PK
Manganese
PMN
Sodium
PNA
Chloride
PCL
Particulate water
PH20
Primary unspeciated PM2 5m
PMOTHR
Similar to the methods used to speciate total organic gases, MOVES uses speciation profiles to
estimate individual PM2.5 species. The PM2.5 Speciation profiles were developed to directly
estimate the species used for the CMAQ Aerosol Module, version 6, or "AE6;"18 all other
measured PM2.5 species are aggregated into PMOTHER m If needed, post-processing can be
used to aggregate the AE6 species into the PM2.5 species used with the Comprehensive Air
Quality Model with Extensions (CAMx).18
m Primary unspeciated PM2.5 (PMOTHR) is calculated as 1- sum(AE6 species fractions) and can include both
unspeciated PM2 5 mass as well as measurements of other PM2 5 species that are not included in the AE6 chemical
mechanism species.
29
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5.2 PM25 Speciation Calculations
Figure 5-1 and Figure 5-2 provide an overview of the algorithm used to calculate speciated and
total exhaust PM emission rates in MOVES. The steps used to calculate PM2.5 emissions and
PM2.5 speciation are outlined in nine steps below. Steps 1 - 4 are outlined in Figure 5-1.
Base EC and
NonECPM
exhaust emission
rates
at 72°
by polProcessID,
OpModelD,
ageGroupID,
SourceBinID
EC, NonECS04PM, S04, and
H20 exhaust emissions
adjusted by fuel and
temperature effects. Effects
differ by polProcessID
SourceType,fuelTypelD,
modelYearRangelD
NonEC
nonS04
PM
S04 fraction
by polProcessID,
SourceType,
fuelTypelD,
modelYearRangelD
Figure 5-1 Flow Chart of Calculation of the Intermediate PM2.5 Emission Rates
Step 1. MOVES stores PM2.5 exhaust emission rates in the emissionRateByAge table by
pollutant process (start, running, extended idle), operating mode, sourcebin (fuelType, engine
technology, regulatory class, model year), and vehicle age. MOVES stores the base exhaust rates
for PM2.5 in two primary components (EC and nonECPM), so that the EC/PM2.5 ratio can vary
across operating modes.11-2
n Within MOVES, modal EC/PM ratios are developed for conventional diesel vehicles (pre-2007) as documented in
the heavy-duty exhaust report.2 Modal EC/PM2 5 ratios have not been developed for other vehicle types (gasoline,
CNG, ethanol, and 2007+ diesel), and the EC and NonECPM emission rates for these sourcetypes and fuels have a
constant ratio across operating modes.
30
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Step 2. MOVES calculates sulfate (SO4) and particulate water (H2O) emissions as a fraction of
nonECPM. The sulfate to nonECPM fraction (SulfatenonECPMFraction) used in MOVES is
derived from the PM2.5 speciation profiles documented in Table 5-5. MOVES stores this value in
the sulfateFraction MOVES table. The sulfate calculator, documented in the MOVES fuel effects
report,46 adjusts the sulfate fraction based on the default or user-supplied fuel sulfur level. The
remaining nonECPM is renamed nonECnonS04PM. This intermediate species contains organic
matter, elements, ions, and the unspeciated portion of PM2.5.
Step 3. The intermediate PM species are adjusted for ambient temperature effects such as
inefficient oxidation of emissions at cool catalyst temperatures and additional fuel needed to start
an engine at cold temperatures. The temperature effects can differ by intermediate species, model
year groups, and fuel type. Currently, temperature effects only apply to gasoline and ethanol-
blend fueled vehicles for start emissions. EC, nonECnonS04PM, SO4, and H2O emissions are
each adjusted using the same temperature adjustments, because our data does not support
individual temperature adjustments.59 The temperature effects are documented in the Emission
Adjustments report.45
Step 4. MOVES adjusts the intermediate species (EC and NonECnonS04PM) according to fuel
properties and the applicable fuel effects (e.g., EPAct fuel effects model for 2001 and later light-
duty gasoline). The fuel adjustments and calculators are described in the Fuel Effects Report.46
Steps 5 - 8 are outlined in Figure 5-2.
31
-------
Exhaust and crankcase
intermediate PM2.5 species.
Individual Ratios for EC,
NonECnonS04PM, S04 and
H20 ratios differ by
polProcessID, sourceTypelD,
fuelTypelD,
modelYearRangelD
Speciated PM2 5 emissions by processID
(start/running/extended idle exhaust
and start/running/extended idle
crankcase emissions), sourceTypelD,
fuelTypelD, modelYearRangelD
PM10 calculated from
total PMJ5. PM10/PMj5
factors by processID,
sourceTypelD, fuelTypelD,
modelYearRangelD
species to output
Total PM,,
Total Crankcase '
>1 _ _ 1
Figure 5-2 Flow Chart of Calculation of Exhaust and Crankcase PM2.5 and PM10 Emission Rates, and PM2.5
Exhaust and Crankcase Speciation
Step 5. Exhaust and crankcase emissions are calculated from the intermediate exhaust PM2.5
species (EC, NonECnonS04PM, SO4, and H2O), after the intermediate exhaust species have been
adjusted for fuel effects and temperature effects. The exhaust and crankcase emissions are
calculated from the intermediate exhaust rates with exhaust and crankcase ratios that can vary
32
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according to pollutant, process, regulatory class, fuel type, and model year range. Example
crankcase ratios for heavy-duty diesel vehicle are shown in Table 5-2.
For most vehicle types (including pre-2007 and 2010+ heavy-duty diesel, gasoline, and CNG
vehicles), this step accounts for the PM crankcase emissions that are not measured in the exhaust
emission rates (i.e., the exhaust and crankcase ratios sum to greater than one for each PM
subspecies). The exhaust emissions remain constant in this step.
For 2007-2009 MY heavy-duty diesel engines, crankcase emissions are assumed to be included
in the tailpipe exhaust emissions in the certification data. The exhaust and crankcase emission
ratios are used to split the PM rates into exhaust and crankcase emissions. For 2007-2009 heavy-
duty diesel, the exhaust and crankcase ratios sum to one for each PM subspecies.
The exhaust and crankcase ratios are applied by intermediate subspecies, to account for
differences in PM2.5 speciation between crankcase and tailpipe particulate matter emissions. For
example, MOVES models higher EC/PM composition for exhaust than for crankcase emissions
for pre-2007 conventional0 diesel, using the exhaust and crankcase ratios as shown in Table 5-2.
For MY 2007-2009 heavy-duty diesel vehicles, the exhaust and crankcase ratios are the same
across intermediate PM2.5 species, yielding the same PM2.5 composition for exhaust and
crankcase emissions. This is intended because the PM2.5 speciation profile is estimated from
measurements that contained both tailpipe exhaust and crankcase exhaust emissions.2
The sources of the crankcase emission factors are documented in the light-duty exhaust1 and
heavy-duty exhaust emissions rates reports.2
0 We use the term "conventional diesel" here to refer to diesel trucks which lack exhaust aftertreatment systems such
as diesel particulate filters (DPF), diesel oxidation catalysts (DOC), and selective catalytic reduction systems (SCR)
that modern diesel trucks use to meet the EPA 2007/2010 heavy-duty emission standards.
33
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Table 5-2 Heavy-duty Diesel Crankcase Ratios" by Pollutant, Process, Model Year Group,
and Regulatory Class
Reg.
Classb
1960-2006
2007-2009°
2010-2013°
2014-2026°'d
Pollutant
Start
Running
Extended
Idle
Running
Running
Running
46
0.039
0.237
0.292
EC
47
0.007
0.004
0.007
0.029
0.174
0.215
48
nonECnonS04
PM
46
0.039
0.237
0.292
47
0.367
0.937
0.367
0.029
0.174
0.215
48
46
0.039
0.237
0.292
S04
47
48
0.367
0.937
0.367
0.029
0.174
0.215
46
0.039
0.237
0.292
H20
47
0.367
0.937
0.367
0.029
0.174
0.215
48
aExhaust ratios not shown here, but they are equal to 1 for all cases
bRegulatory class 49 (Gliders) not shown but has similar start and running crankcase ratios than 1960-2006 Class 8 trucks,
and an extended idle crankcase ratio of 1
Tor all regulatory classes in these model year groups, crankcase ratios for start are 0 and for extended idle are 1
dFor MY2027+, all HD vehicles have closed crankcase, thus all crankcase ratios are 0.
Step 6. The exhaust intermediate species and the crankcase intermediate species are summed to
calculate primary exhaust PM2.5 emissions. The intermediate species are used instead of the fully
speciated PM2.5 emissions to save computational time during MOVES runs.
Step 7. MOVES calculates primary exhaust and crankcase PM10 emissions from the primary
PM2.5 emissions using PM10/PM2.5 ratios. The PM10/PM2.5 ratio used for primary exhaust and
crankcase emissions are listed in Table 5-3. MOVES has the capability to apply separate ratios
by source type, emission process, and model year. At present, a single value of the PM10/PM2.5
ratio is used for all source types, emission processes, and model years for primary exhaust and
crankcase emissions. No speciation is conducted within MOVES for PM10 emissions because it
is not needed for air quality modeling purposes.p'47 The derivation of the PM10/PM2.5 ratio is
presented in Appendix F.
Table 5-3 PM10/PM2.5 Ratios for Primary Exhaust and Crankcase Emissions
PM10/PM2.5
gasoline
1.130
diesel
1.087
p Within CMAQ, the US EPA assumes a single speciation profile for all anthropogenic coarse PM.47
34
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Step 8. MOVES calculates the remaining PM2.5 species, by applying speciation profiles to the
adjusted nonECnonSC>4 fraction. The nonECnonS04 speciation profiles are calculated from the
PM2.5 profiles in Table 5-5, by removing EC, SO4, and H2O and then renormalizing the
remaining species. These values are stored in the MOVES pmSpeciation tables, with a column
key 'inputPollutantID' specifying that the PM speciation profile is based on nonECnonS04
(pollutantID 120). Residual PM (nonECnonS04nonOM PM, pollutantID = 124) is calculated
after subtracting pollutantID 123 (TOM = OM+NCOM) from nonECnonS04 PM. The data
sources and derivation for the PM2.5 profiles are documented in Appendix E.
Step 9. Although not shown in Figure 5-1 or Figure 5-2, MOVES can calculate additional
particulate-phase species, required for the National Emission Inventory (NEI) and National Air
Toxics Assessment (NATA). Listed in Table 5-4, these include: manganese, nickel, chromium,
arsenic, and particulate mercury. The metals are emitted in exhaust as PM2.5, but they are
calculated with a separate calculator than the other PM2.5 species. The emission rates for these
metals are not chained from NonECS04PM, but are independent mass/distance rates as
documented in the Air Toxic Emissions Report.7 The mass of these compounds is not used in the
summation to calculate PM2.5 due to the very small mass, but they are important PM2.5 exhaust
species from a health effects perspective. Of the toxic metals, CMAQv5.1 only requires
manganese as a required PM2.5 species. By default, MOVES calculates manganese emission rates
when the user requests PM2.5 speciation. Chromium, nickel, arsenic, and particulate mercury
emission rates are produced when requested by the user.
Table 5-4 Metal Particulate Air Toxics Produced by MOVES
Pollutant
Chromium 6+
Manganese
Nickel
Particulate Hg
Arsenic
5.3 PM2.5 Exhaust Speciation Profiles
Table 5-5 lists the PM2.5 speciation profiles used in MOVES with the SPECIATE database
profilelD. As discussed earlier, these profiles only estimate the AE6 Chemical Mechanism PM2.5
species, with the other measured species and unspeciated mass being considered as part of the
unspeciated PM2.5 species (PMOTHR).
35
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Table 5-5 Mi
3VES PM2.5 Exhaust Speciation Profiles
Profile ID
Profile Name
Source Data
8992
Light-duty
Gasoline Exhaust
- Start
Kansas City PM characterization Study. Final Report. EPA 420-R-
08-009. U.S. EPA, April 2008. Available at:
http://www.epa.gov/oms/emission-factors-research/index.htm.
8993
Light-duty
Gasoline Exhaust-
Hot Stabilized
Running
Kansas City PM characterization Study. Final Report. EPA 420-R-
08-009. U.S. EPA, April 2008. Available at:
http://www.epa.gov/oms/emission-factors-research/index.htm.
8994
Conventional
HDD - Idle
Clark, N.N. and Gautam, M. HEAVY-DUTY Vehicle Chassis
Dynamometer Testing for Emissions Inventory, Air Quality
Modeling, Source Apportionment and Air Toxics Emissions
Inventory. August 2007. CRC Report. No. E55/59
8995
Conventional
HDD - Hot
Stabilized
Running
Clark, N.N. and Gautam, M. HEAVY-DUTY Vehicle Chassis
Dynamometer Testing for Emissions Inventory, Air Quality
Modeling, Source Apportionment and Air Toxics Emissions
Inventory. August 2007. CRC Report. No. E55/59
8996
2007 and Newer
Diesel Exhaust
Composite
Khalek, I. A.; Bougher, T. L; Merrit, P. M.; Phase 1 of the
Advanced Collaborative Emissions Study. CRC Report: ACES
Phase 1, June 2009.
95219a
CNG transit bus
exhaust from a
lean-burn engine -
no aftertreatment
Okamoto, R. A.; Kado, N. Y.; Ayala, A.; Gebel, M.; Rieger, P.;
Kuzmicky, P. A.; Kobayashi, R.; Chemical and Bioassay Analyses
of Emissions from Two CNG Buses with Oxidation Catalyst.
http://www.arb.ca.gov/research/veh-emissions/cng-diesel/cng-
diesel.htm.
95220a
CNG transit bus
exhaust from a
lean-burn engine
- oxidation
catalyst
Okamoto, R. A.; Kado, N. Y.; Ayala, A.; Gebel, M.; Rieger, P.;
Kuzmicky, P. A.; Kobayashi, R.; Chemical and Bioassay Analyses
of Emissions from Two CNG Buses with Oxidation Catalyst.
http://www.arb.ca.gov/research/veh-emissions/cng-diesel/cng-
diesel.htm.
The PM2.5 profiles used for the applicable source type, fuel, pollutant process, and model year
ranges are described in Table 5-6 and detailed in Table E-l. Table 5-6 also displays the
corresponding volatility-based profiles derived based on the reference listed in Table A-4.
36
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Table 5-6 Application of MC
)VES PM2.5 Speciation Profiles
Profile
ID
Description
Fuel
Affected
Vehicles
Emission Process
8992/
IOOCROC
Light-duty Gasoline
Exhaust - Start
All
gasoline
vehicles
(E0 to
E85)
All model years
Start exhaust; crankcase start
exhaust.
8993/
101 CROC
Light-duty Gasoline
Exhaust- Hot Stabilized
Running
All
gasoline
vehicles
(E0 to
E85)
All model years
Running exhaust; crankcase
running exhaust.
8994/
102CROC
Conventional HDD - Idle
Diesel
Pre-2007 and all
MY auxiliary
power units
Running exhaust; crankcase
running and extended idle
exhaust; auxiliary power unit
8995/
103 CROC
Conventional HDD - Hot
Stabilized Running
Diesel
Pre-2007
Start exhaust; crankcase start
exhaust.
8996/
104CROC
2007 and Newer Diesel
Exhaust Composite
Diesel
2007+
Start exhaust; crankcase start
exhaust. Running exhaust;
crankcase running and
extended idle exhaust;
auxiliary power unit
95219a/
105 CROC
CNG transit bus exhaust
from a lean-burn engine -
no aftertreatment
CNG
pre-2002 model
year
Start exhaust; crankcase start
exhaust. Running exhaust;
crankcase running and
extended idle exhaust;
auxiliary power unit
95220a/
106CROC
CNG transit bus exhaust
from a lean-burn engine
- oxidation catalyst
CNG
2002+ model
year
Start exhaust; crankcase start
exhaust. Running exhaust;
crankcase running and
extended idle exhaust;
auxiliary power unit
MOVES uses two light-duty gasoline profiles to characterize PM2.5 emissions from all gasoline
vehicles, including motorcycles, light-duty passenger cars and trucks, and medium and heavy-
duty gasoline trucks and buses.
The pre-2007 diesel profiles are used to represent all pre-2007 on-highway diesel vehicles in
MOVES, including light-duty passenger cars and trucks, medium, and heavy-duty trucks, and
diesel buses. Tailpipe exhaust and crankcase nonECnonS04 emissions emitted during extended
idle and start are speciated using the Idle Profile (8994). Tailpipe exhaust and crankcase
nonECnonS04 emissions emitted during running operation are speciated using the running
profile (8995). In addition, the idle profile (8994) is used to characterize nonECnonS04
emissions from diesel-powered auxiliary power units used on heavy-duty diesel trucks.
The ACES Phase 1 profile (8996) is used for all 2007-and-later diesel sources, including light-
duty passenger cars and trucks, medium- and heavy-duty trucks and diesel buses. The ACES
37
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Phase 1 16-hour cycle is used to develop the profile, which includes both exhaust and crankcase
emissions, as well as start, extended idle and running emission processes. For this reason, the
composite profile is also used to speciate all emission processes for 2007-and-later diesel
engines. It should be noted that while PM speciation data for 2010 and later diesel engines is
available from the ACES Phase 2 test program, we did not update PM speciation to incorporate
these data because the ACES Phase 2 emissions data did not collect any active regeneration
events, and thus, had minimal sulfate emissions. Testing done by California Air Resources
Board48 has shown active regeneration events occur on 2010+ technology on-highway diesel
trucks, but at a lower frequency than 2007-2009 model year trucks. During active regeneration,
fuel is injected into the aftertreatment system to raise the temperature to burn off the soot
collected in the diesel particulate filter, which increases emissions of particulate matter (mostly
sulfate). Thus it is important that sulfate emissions be represented in the PM2.5 profile to
represent real-world regeneration events.49
The CNG compression ignition profile is applied to the pre-2002 model CNG heavy-duty
vehicles, and the CNG profile with oxidation catalyst profile is applied to the 2002+ model year
CNG heavy-duty vehicles.
5.4 Brake and Tire Wear Speciation
Brake and tire wear PM2.5 are not speciated within MOVES. For developing the emissions
modeling platform, SPECIATE Profiles 95462 and profile 95460 developed from Schauer et al.
200665 are applied to brake wear and tire wear PM2.5 emissions in the moves2smk postprocessor
that prepares the emission factors for processing in SMOKE.50
6 Post-processing of rcsiduttl TOG, rcsiduttl PM and OM
Post-processing of onroad emissions to speciate residual TOG, residual PM and total OM
requires the selection of these pollutants when creating the MOVES RunSpec. As discussed in
section 4, residual TOG (NONHAPTOG, pollutantID = 88) corresponds to the remaining TOG
mass after MOVES has applied fuel and temperature effects to calculate gaseous integrated
species. Similarly, Residual PM (nonECnonS04nonOM, pollutantID = 124) corresponds to the
remaining PM mass after MOVES has applied fuel and temperature adjustments, and has
calculated particulate integrated species: EC, H2O, nonECnonS04 PM, SO4 and total organic
matter. Total Organic Matter (TOM, pollutantID = 123) is the sum of two other MOVES
pollutants: NCOM and OC. MOVES aggregates these species as a separate pollutant to facilitate
the speciation of organic matter under the Reactive Organic Carbon framework51 during post-
processing downstream from MOVES.
During the speciation step within previous versions of MOVES, residual TOG and PM were
matched to specific speciation profiles by fuel subtype, emission process, regulatory class and
model year. To mimic this step during postprocessing outside of MOVES, we have added a new
table (rocSpeciation) to the MOVES default database that records the latest mapping of
emissions to traditional speciation profiles, as well as mapping to volatility profiles and new
parameters for the speciation of organic matter within the ROC framework. The rocSpeciation
table contains the following columns: fuelSubtypelD, regClassID, processID, minModelYearlD,
38
-------
maxModelYearlD, pmSpeciationProfilelD, CROCCode, CROCOMratio,
togSpeciationProfilelD, GROCCode and GROCNMOGratio. The first five columns characterize
the vehicle emission source; togSpeciationProfilelD and pmSpeciationProfilelD indicate the
traditional speciation profiles8 associated with each vehicle emission source; the "Code" columns
specify the ROC speciation profiles52 (listed in EPA's SPECIATE database8) associated with a
given vehicle emission source and the "Ratio" columns contain adjustment factors applied within
the post-processing script to generate Condensable Reactive Organic Carbon (CROC) mass and
Gaseous Reactive Organic Carbon (GROC) mass.
MOVES does not use the new rocSpeciation table at runtime. Instead, it is used by the post-
processing script. For modelers planning to speciate onroad emissions outside of MOVES, in
addition to selecting the appropriate pollutants, they must also specify output by SCC, regulatory
class, fuel type, emission process and model year for the postprocessing script to run.
The post-processing script generates a SQL database with NONHAPTOG, Residual PM and
TOM speciated emissions. The speciated emissions are grouped into SMOKE SCCs to facilitate
the combination with vehicle activity within SMOKE-MOVES. A diagram of the new workflow
for the post-process is shown in Figure 6-1. Further details on how to generate appropriate
MOVES output, run the script and how to use the script output are provided in the instructions
associated with the post-processing speciation script included in the MOVES GUI.
39
-------
MOVES
inputs
MOVES
TOM
Residual PM
NONHAPTOG
MOVES Output:
Emissions
per SCC
rocSpeciation
table
I
Profile
Weighting
Script
Generates
profile % per
SCC
(GSREF-COMBO)
SPECIATE
Speciation
Profiles
I
Explicit
Compound
Profiles
Speciation
Tool
Transforms
explicit
compound
profiles into
chemical
mechanism
species (GSPRO)
SMOKE-
MOVES
Gridded
emissions of
chemical
mechanism
species
Figure 6-1. Diagram showing the new workflow to post-process the speciation of onroad emissions into
chemical mechanism species and how it interacts with other modeling platform tools.
40
-------
Appendix A Supporting Information for TOG calculations
Table A-l and Table A-2 summarize the data53 used to generate CH4/THC ratios for Tier 2
vehicles running on low-level ethanol blends as described in Section 3.3. In Table A-2, "cold
start" refers to the difference between Bags 1 and 3. Running data corresponds to stabilized
emissions from Bag 2. In the particular case of running emissions, seven tests (shown in grey in
Table A-l and Table A-2) were not considered in the analysis because the reported CH4 emissions
were higher than the reported THC emissions, possibly because measurements were close to the
detection limit of the instrument.
Table A-l Data53 Used to Generate CH4/THC Ratios for Tier 2 Vehicles Running on Low-
Level Ethanol Blends
Bag data
from
profile
Run
Number
EPAct
Phase 1
Ethanol
(%)
Bagl - Bag 3
Bag 2
CH4
(g/mi)
THC
(g/mi)
CH4
(g/mi)
THC
(g/mi)
8756
3162
0
0.048
0.427
0.006
0.016
3169
0
0.050
0.570
0.006
0.017
3179
0
0.024
0.299
0.001
I) ()()()
3190
0
0.027
0.355
I) DO I
I) ODD
3205
0
0.042
0.369
(J.IP4
3215
0
0.043
0.430
0.006
0.026
3223
0
0.019
0.236
0.001
0.002
3231
0
0.017
0.211
0.001
0.004
3239
0
0.030
0.382
I) DO I
I) ()()()
8757
3280
10
0.031
0.351
0.001
I) ODD
3291
10
0.029
0.343
0.001
0.001
3302
10
0.045
0.362
0.005
0.014
3313
10
0.049
0.382
0.006
0.021
3326
10
0.016
0.163
0.001
0.004
3339
10
0.016
0.165
0.001
0.003
8758
3480
15
0.058
0.448
0.007
0.018
3492
15
0.053
0.424
0.007
0.014
3508
15
0.017
0.141
0.001
0.002
3516
15
0.017
0.209
1
3542
15
0.052
0.494
I) DO I
I) ODD
3553
15
0.043
0.379
I) DO I
0 odd
3568
15
0.022
0.248
<).()() 1
o.ooo
41
-------
Table A-2. Data53 Used to Generate Speciation Constant Parameters for Tier 2 Vehicles
Running on Low-Level Ethanol Blends
Bag data
from
profile
Run
Number
EPAct
Phase 1
Ethanol
(%)
Cold
Start
NMOG
(g/mi)
Cold
Start
voc
(g/mi)
Cold
Start
NMHC
(g/mi)
Running
NMOG
(g/mi)
Running
VOC
(g/mi)
Running
NMHC
(g/mi)
8756
3162
0
0.345
0.332
0.338
0.009
0.008
0.008
3169
0
0.468
0.453
0.458
0.010
0.010
0.010
3179
0
0.256
0.250
0.255
0.001
0.001
0.001
3190
0
0.284
0.276
0.282
0.001
0.001
0.001
3205
0
0.314
0.301
0.306
0.013
0.012
0.013
3215
0
0.360
0.346
0.353
0.013
0.012
0.013
3223
0
0.197
0.190
0.196
0.001
0.001
0.001
3231
0
0.168
0.162
0.165
0.004
0.004
0.004
3239
0
0.295
0.287
0.294
0.001
0.001
0.001
8757
3280
10
0.312
0.305
0.301
0.001
0.001
0.001
3291
10
0.315
0.306
0.301
0.000
0.000
0.000
3302
10
0.331
0.320
0.317
0.007
0.006
0.006
3313
10
0.345
0.332
0.327
0.008
0.007
0.007
3326
10
0.144
0.139
0.137
0.000
0.000
0.000
3339
10
0.159
0.154
0.151
0.000
0.000
0.000
8758
3480
15
0.390
0.372
0.363
0.012
0.011
0.012
3492
15
0.371
0.354
0.348
0.012
0.011
0.012
3508
15
0.143
0.137
0.133
0.001
0.001
0.001
3516
15
0.188
0.182
0.172
0.000
0.000
0.000
3542
15
0.433
0.420
0.410
0.000
0.000
0.000
3553
15
0.328
0.317
0.310
0.000
0.000
0.000
3568
15
0.239
0.232
0.221
0.000
0.000
0.000
Table A-3. documents the CHVTHC and speciation constant parameters for all the sources in
MOVES (by including the data from Table 3-2, Table 3-3, Table 3-4, and Table 3-5 ). In
addition, it specifies the MOVES variables that are used to define the CHVTHC and
speciationConstants within the MethaneTHCRatio and HcSpeciation tables, respectively.
42
-------
Table A-3 CH4/TB
C and Speciation Constant Parameters and Their
Relationship to MOVES Variables
Profile
number
Profile
description
modelYear
-GroupID
processID
fuelSubTyp
elD
regClassID
CH4/THC
NMOG/NMH
C
VOC/NMHC
95120c
Liquid
Diesel
1960-2060
11
20,21,22
0
0
1
1
12,13,18,19
20,21,22
10,20,30,41,42,
46,47,48
0
8750a
Pre-Tier 2
E0 exhaust
1960-2000
1,2,15,16
10
20,30
0.142
1.024
0.996
1960-2060
10,41,42,46,47,
48
8751a
Pre-Tier 2
E10 exhaust
1960-2000
1,2,15,16
11,12,13,14
20,30
0.146
1.037
1.008
1960-2060
10,41,42,46,47,
48
8753
E0 Evap
1960-2060
12,13,19
10
10,20,30,41,42,
46,47,48
0
1
1
8754
E10 Evap
1960-2060
12,13,19
12,13,14
10,20,30,41,42,
46,47,48
0
1.071
1.071
8766
E0 Evap
perm
1960-2060
11
10
0
0
1
1
8769
E10 Evap
perm
1960-2060
11
12,13,14
0
0
1.129
1.129
8770
El5 Evap
perm
1960-2060
11
15,18
0
0
1.175
1.175
8774
Pre-2007
MY HDD
exhaust
1960-2006
1,2,15,16,1
7,90
20,21,22
41,42,46,47,48
0
1.145
1.124
1960-2023
91
46,47
1960-2006
1,2,15,16
20,30
8775
2007-2009
HDD
exhaust
2007-2009
1,2,15,16
20,21,22
20,30
0.589
1.343
1.285
2024-2060
91
46,47
2007-2009
1,2,15,16,1
7,90
41,42,46,47,48
95335a
2010+HDD
exhaust
2010-2060
1,2,15,16
20,21,22
20,30
0
1.085
0.965
1,2,15,16,1
7,90
41,42,46,47,48
43
-------
Table A-3 (continued)
Profile
number
Profile
description
modelYear
GroupID
processID
fuelSubTy
pelD
regClassID
ch4/thc
NMOG/NMH
C
VOC/NMH
C
8869
E0
Headspace
1960-2060
18
10
10,20,30,41,42,
46,47,48
0
1
1
8870
E10
Headspace
1960-2060
18
12,13,14
10,20,30,41,42,
46,47,48
0
1.037
1.037
8871
E15
Headspace
1960-2060
18
15,18
10,20,30,41,42,
46,47,48
0
1.175
1.175
8872
E15 Evap
1960-2060
12,13,19
15,18
10,20,30,41,42,
46,47,48
0
1.118
1.118
8934
E85 Evap
1960-2060
11
50,51,52
10,20,30
0
1.501
1.501
12,13,18,19
10,20,30
44
-------
Table A-4 Data Sources for the SPECIATE8 Profiles used in MOVES
Profile
ID
Profile
Name
Source Data
Additional Documentation
1001
Internal
Combustion
Engine -
Natural Gas
Oliver, W. R. and S. H. Peoples, Improvement of the
Emission Inventory for Reactive Organic Gases and
Oxides of Nitrogen in the South Coast Air Basin,
Volumes I and II, Final Report (Prepared for California
Air Resources Board), May 1985.
95120
Liquid Diesel
- California
composite
Gentner, Drew R, Gabriel Isaacman, David R Worton,
Arthur WH Chan, Timothy R Dallmann, Laura Davis,
Shang Liu, et al. "Elucidating Secondary Organic
Aerosol from Diesel and Gasoline Vehicles through
Detailed Characterization of Organic Carbon
Emissions." Proceedings of the National Academy of
Sciences 109, no. 45 (2012): 18318-23. DOI:
10.1073/pnas. 1212272109
8750a
Gasoline
Exhaust -
Reformulated
gasoline (pre-
Tier 2)
Kansas City PM characterization Study. Final Report.
EPA 420-R-08-009. U.S. EPA, April 2008. Available
at: http://www.epa.gov/oms/emission-factors-
research/index.htm.
Emission Profiles for EPA SPECIATE Database.
EPA Contract No. EP-C-06-094. Environ
Corporation, January 2008. Available at:
http://www.regulations.gov. Docket ID: EPA-
HQ-OAR-2005-0161, Document ID: EPA-HQ-
OAR-2005-0161-2710.
8751a
Gasoline
Exhaust - E10
ethanol
gasoline (pre-
Tier 2)
Kansas City PM characterization Study. Final Report.
EPA 420-R-08-009. U.S. EPA, April 2008. Available
at: http://www.epa.gov/oms/emission-factors-
research/index.htm.
Emission Profiles for EPA SPECIATE Database.
EPA Contract No. EP-C-06-094. Environ
Corporation, January 2008. Available at:
http://www.regulations.gov. Docket ID: EPA-
HQ-OAR-2005-0161, Document ID: EPA-HQ-
OAR-2005-0161-2710.
8753
Gasoline
Vehicle -
Evaporative
emission -
Reformulated
gasoline
Auto/Oil Air Quality Improvement Research Program.
Coordinating Research Council, 1990-1997. List of
reports at: http://www.crcao.com/reports/auto-
oil/default.htm
Emission Profiles for EPA SPECIATE Database.
EPA Contract No. EP-C-06-094. Environ
Corporation, January 2008. Available at:
http://www.regulations.gov. Docket ID: EPA-
HQ-OAR-2005-0161, Document ID: EPA-HQ-
OAR-2005-0161-2710.
8754
Gasoline
Vehicle -
Evaporative
emission -
E10 ethanol
gasoline
Auto/Oil Air Quality Improvement Research Program.
Coordinating Research Council, 1990-1997. List of
reports at: http://www.crcao.com/reports/auto-
oil/default.htm
Emission Profiles for EPA SPECIATE Database.
EPA Contract No. EP-C-06-094. Environ
Corporation, January 2008. Available at:
http://www.regulations.gov. Docket ID: EPA-
HQ-OAR-2005-0161, Document ID: EPA-HQ-
OAR-2005-0161-2710.
8756
Gasoline
Exhaust - Tier
2 light-duty
vehicles using
0% Ethanol -
Composite
Profile
Data Collected in EPAct Fuel Effects Study Pilot
Phases 1 and 2. Memorandum to the Tier 3 Docket.
U.S. EPA, 2013 Available at:
http://www.regulations.gov. Docket ID: EPA-HQ-
OAR-2011-0135.
Exhaust Emission Profiles for EPA SPECIATE
Database: Energy Policy Act (EPAct) Low-Level
Ethanol Fuel Blends and Tier 2 Light-Duty
Vehicles. EPA Report No. EPA-420-R-09-002.
U.S. EPA, 2009. Available at:
http://www.regulations.gov. Docket ID: EPA-
HQ-OAR-2005-0161, Document ID: EPA-HQ-
OAR-2005-0161-2711.
8757
Gasoline
Exhaust - Tier
2 light-duty
vehicles using
10% Ethanol -
Composite
Profile
Data Collected in EPAct Fuel Effects Study Pilot
Phases 1 and 2. Memorandum to the Tier 3 Docket.
U.S. EPA, 2013 Available at:
http://www.regulations.gov. Docket ID: EPA-HQ-
OAR-2011-0135.
Exhaust Emission Profiles for EPA SPECIATE
Database: Energy Policy Act (EPAct) Low-Level
Ethanol Fuel Blends and Tier 2 Light-Duty
Vehicles. EPA Report No. EPA-420-R-09-002.
U.S. EPA, 2009. Available at:
http://www.regulations.gov. Docket ID: EPA-
HQ-OAR-2005-0161, Document ID: EPA-HQ-
OAR-2005-0161-2711.
8758
Gasoline
Exhaust - Tier
2 light-duty
vehicles using
15% Ethanol -
Composite
Profile
Data Collected in EPAct Fuel Effects Study Pilot
Phases 1 and 2. Memorandum to the Tier 3 Docket.
U.S. EPA, 2013 Available at:
http://www.regulations.gov. Docket ID: EPA-HQ-
OAR-2011-0135.
Exhaust Emission Profiles for EPA SPECIATE
Database: Energy Policy Act (EPAct) Low-Level
Ethanol Fuel Blends and Tier 2 Light-Duty
Vehicles. EPA Report No. EPA-420-R-09-002.
U.S. EPA, 2009. Available at:
http://www.regulations.gov. Docket ID: EPA-
HQ-OAR-2005-0161, Document ID: EPA-HQ-
OAR-2005-0161-2711.
45
-------
Table A-4 (continued)
Profile
ID
Profile
Name
Source Data
Additional Documentation
8766
Diurnal
Permeation
Evaporative
Emissions
from Gasoline
Vehicles
using 0%
Ethanol-
Combined -
Composite
Profile
Evaporative Emissions from In-use Vehicles: Test Fleet
Expansion. CRC E-77-2b. SWRI Project No.
03.14936.05. Final report. Available at:
http://www.epa.gov/otaq/emission-factors-research/
8769
Diurnal
Permeation
Evaporative
Emissions
from Gasoline
Vehicles
using 10%
Ethanol-
Combined -
Composite
Profile
Evaporative Emissions from In-use Vehicles: Test Fleet
Expansion. CRC E-77-2b. SWRI Project No.
03.14936.05. Final report. Available at:
http://www.epa.gov/otaq/emission-factors-research/
8770
Diurnal
Permeation
Evaporative
Emissions
from Gasoline
Vehicles
using 15%
Ethanol-
Combined
Evaporative Emissions from In-use Vehicles: Test Fleet
Expansion. CRC E-77-2b. SWRI Project No.
03.14936.05. Final report. Available at:
http://www.epa.gov/otaq/emission-factors-research/
8774
Diesel
Exhaust
Emissions
from Pre-
2007 Model
Year Heavy-
Duty Diesel
Trucks
Heavy-duty Vehicle Chassis Dynamometer Testing for
Emissions Inventory, Air Quality Modeling, Source
Appointment and Air Toxics Emissions Inventory. CRC
Project No. E-55/E-59, Phase II Final Report.
Coordinating Research Council, July 2005. Available at:
http://www.crcao.com/publications/emissions/index.html
8775
Diesel
Exhaust
Emissions
from 2007
Model Year
Heavy-Duty
Diesel
Engines with
Controls
Phase 1 of the Advanced Collaborative Emissions Study.
Coordinating Research Council, July 2009. Available at:
http://www.crcao.com/publications/emissions/index.html
8855
Gasoline
Exhaust - Tier
2 light-duty
vehicles using
85% Ethanol -
Composite
Profile
EPAct/V2/E-89: Assessing the Effect of Five Gasoline
Properties on Exhaust Emissions from Light-Duty
Vehicles Certified to Tier-2 Standards: Final Report on
Program Design and Data Collection. EPA-420-R-13-
004. U.S. EPA, April 2013. Available at:
http://www.epa.gov/otaq/models/moves/epact.htm.
8869
Gasoline
Headspace
Vapor - 0%
Ethanol (E0)
Combined -
EPAct/V2/E-
89 Program
Hydrocarbon Composition of Gasoline Vapor Emissions
from Enclosed Fuel Tanks, Report No. 420-R-l 1-018.
U.S. EPA, December 2011. Available at:
http://www.regulations.gov, Docket ID: EPA-HQ-OAR-
2011-0135, Document ID: EPA-HQ-OAR-2011-0135-
0027.
Mobile Source Hydrocarbon Speciation Profiles
for the Tier 3 Rule NPRM and Anti-backsliding
Study Air Quality Modeling. Memorandum to
the Docket. U.S. EPA, 2013. Available at:
http://www.regulations.gov. Docket ID: EPA-
HQ-OAR-2011-0135, Document ID: EPA-HQ-
OAR-2011-0135-0089.
46
-------
Table A-4 (continued)
Profile ID
Profile
Name
Source Data
Additional Documentation
8870
Gasoline
Headspace
Vapor - 10%
Ethanol (E10)
Combined -
EPAct/V2/E-
89 Program
Hydrocarbon Composition of Gasoline Vapor Emissions
from Enclosed Fuel Tanks, Report No. 420-R-11-018.
U.S. EPA, December 2011. Available at:
http://www.regulations.gov, Docket ID: EPA-HQ-OAR-
2011-0135, Document ID: EPA-HQ-OAR-2011-0135-
0027.
Mobile Source Hydrocarbon Speciation
Profiles for the Tier 3 Rule NPRM and Anti-
backsliding Study Air Quality Modeling.
Memorandum to the Docket. U.S. EPA,
2013. Available at:
http://www.regulations.gov. Docket ID:
EPA-HQ-OAR-2011-0135, Document ID:
EPA-HQ-OAR-2011-0135-0089.
8871
Gasoline
Headspace
Vapor - 15%
Ethanol (El 5)
Combined -
EPAct/V2/E-
89 Program
Hydrocarbon Composition of Gasoline Vapor Emissions
from Enclosed Fuel Tanks, Report No. 420-R-11-018.
U.S. EPA, December 2011. Available at:
http://www.regulations.gov, Docket ID: EPA-HQ-OAR-
2011-0135, Document ID: EPA-HQ-OAR-2011-0135-
0027.
Mobile Source Hydrocarbon Speciation
Profiles for the Tier 3 Rule NPRM and Anti-
backsliding Study Air Quality Modeling.
Memorandum to the Docket. U.S. EPA,
2013. Available at:
http://www.regulations.gov. Docket ID:
EPA-HQ-OAR-2011-0135, Document ID:
EPA-HQ-OAR-2011-0135-0089.
8872
Gasoline
Vehicle -
Evaporative
emission -
E15 ethanol
gasoline -
Calculated
Auto/Oil Air Quality Improvement Research Program.
Coordinating Research Council, 1990-1997. List of
reports at: http://www.crcao.com/reports/auto-
oil/default.htm
EPAct/V2/E-89: Assessing the Effect of Five Gasoline
Properties on Exhaust Emissions from Light-Duty
Vehicles Certified to Tier-2 Standards: Final Report on
Program Design and Data Collection. EPA-420-R-13-
004. U.S. EPA, April 2013. Available at:
http://www.epa.gov/otaq/models/moves/epact.htm.
Mobile Source Hydrocarbon Speciation
Profiles for the Tier 3 Rule NPRM and Anti-
backsliding Study Air Quality Modeling.
Memorandum to the Docket. U.S. EPA,
2013. Available at:
http://www.regulations.gov. Docket ID:
EPA-HQ-OAR-2011-0135, Document ID:
EPA-HQ-OAR-2011-0135-0089.
8934
Evaporative
Emissions
from
Flexible-Fuel
Gasoline
Vehicles
using 85%
Ethanol
Exhaust and Evaporative Emissions Testing of Flexible-
Fuel Vehicles. Final report. CRC Report CRC-E-80.
Coordinating Research Council, Inc. August 2011.
Report and program data available at
http://www.crcao.org/publications/emissions/index.html
95335
Diesel
Exhaust -
Heavy-heavy
duty truck -
2011 model
year
Khalek, I., Blanks, M., and Merritt, P. M. (2013).
Phase 2 of the Advanced Collaborative Emissions
Study. Prepared by Southwest Research Institute for the
Coordinating Research Council and the Health Effects
Institute, November 2013. Available at www.crcao.org.
CROC/GROC
Multiple
profiles
All existing SPECIATE profiles listed above were
translated to volatility-based profiles for use in Murphy,
B. N., Sonntag, D., Seltzer, K. M., Pye, H. O. T., Allen,
C., Murray, E., Toro, C., Gentner, D. R., Huang, C.,
Jathar, S. H., Li, L., May, A. A., and Robinson, A. L.:
Reactive Organic Carbon Air Emissions from Mobile
Sources in the United States, EGUsphere [preprint],
https://doi.org/10.5194/egusphere-2023-855, 2023
47
-------
Appendix B CNG CH4/THC and Speciation Constant
Parameters for CNG vehicles
SPECIATE 5.18 does not contain a TOG speciation profile from modern CNG exhaust
emissions. We used hydrocarbon speciation data from Ayala et al. that measured a 2000 MY
transit bus with a Detroit Diesel Series 50G engine with and without an oxidation catalyst
collected on the CBD cycle.38 This data allows us to isolate the impact of the oxidation catalyst.
Studies have shown that the speciation of hydrocarbon can be drastically different between
uncontrolled CNG buses and CNG buses with oxidation catalysts. For example, formaldehyde
emissions can be quite large from uncontrolled CNG buses54'55, but are significantly reduced
with oxidation catalysts.38 Large formaldehyde emissions have a large impact on the NMOG
and VOC emissions estimated from THC emissions from CNG buses because THC-FID
measurements have a small response to formaldehyde concentrations.56
We used the CBD test cycle to be consistent with our analysis of the criteria emission rates
documented in the heavy-duty emission rate report.2 NMOG and VOC conversion factors are
listed in Table B-l. The NMOG values are calculated using Equation 7. The VOC emissions are
calculated from subtracting the ethane and acetone from the NMOG values. The emissions of
hazardous air pollutants, including formaldehyde and acetaldehyde, are also estimated from this
study as documented in the MOVES Toxics Emissions Report.7
Table B-l Hydrocarbon Speciation Values for CNG Transit Emissions with No Control
and with Oxidation Cata
yst from Ayala et al. (2003)38
Measured values
(mg/mile)
No Control
Oxidation
Catalyst
THC
8660
6150
CH4
7670
5900
C2H6
217
72.2
Formaldehyde
860
38.4
Acetaldehyde
50.7
32.6
Calculated values (mg/mile)
NMHC
990
250
NMOG
1881.0
309.0
VOC
1658.5
232.1
Ratios
NMOG/NMHC
1.90
1.24
VOC/NMHC
1.68
0.93
48
-------
Appendix C TOG Speciation Map
Table C-4 provides a speciation map between MOVES TOG profiles and the distinguishing
factors used in MOVES. To help interpret this table, we have also provided tables that describe
the MOVES processes, fuel subtypes, and regulatory classes and list their id codes.
Model YearGroupID is simply the first model year of the group, followed by the last model
year.
Table C-l MOVES Processes Relevant for Speciation Profiles'11
processID
Process Name
1
Running Exhaust
Exhaust emissions from a running vehicle
2
Start Exhaust
Exhaust emissions that occur at engine start
11
Evap Permeation
migration of hydrocarbons through materials in the fuel
system
12
Evap Fuel Vapor Venting
Escape of vapors that are generated through heating of
gasoline fuel system
13
Evap Fuel Leaks
Fuels escaping gasoline fuel system in a non-vapor form
15
Crankcase Running Exhaust
Combustion products and oil droplets from compression
ignition engines that are vented to the atmosphere rather
than routed through the exhaust
16
Crankcase Start Exhaust
17
Crankcase Extended Idle Exhaust
18
Refueling Displacement Vapor Loss
Displaced fuel vapors when liquid fuel is added to the
vehicle tank
19
Refueling Spillage Loss
Vapor emissions from any liquid fuel that is spilled during
refueling
90
Extended Idle Exhaust
Idle emissions during "hotelling" of long-haul combination
trucks
91
Auxiliary Power Exhaust
Auxiliary power unit emissions during hotelling of long-
haul combination trucks
q Not a complete list of MOVES emission processes.
49
-------
Table C-2 Regulatory Classes in MOVES
regClassID
Regulatory Class Name
Description
0
Doesn't Matter
Doesn't Matter
10
MC
Motorcycles
20
LDV
Light-Duty Vehicles
30
LDT
Light-Duty Trucks
41
LHD2b3
Class 2b and 3 Trucks (8,500 lbs < GVWR <= 14,000
lbs)
42
LHD45
Class 4 and 5 Trucks (14,00 lbs. < GVWR <= 19,500
lbs.)
46
MHD
Class 6 and 7 Trucks (19,500 lbs. < GVWR < =33,000
lbs.)
47
HHD
Class 8a and 8b Trucks (GVWR > 33,000 lbs.)
48
Urban Bus
Urban Bus (see CFR Sec. 86.091 2)
49
Gliders
Glider Vehicles57
Table C-3 Fuel Subtypes in MOVES
fuelSubtypelD
fuelTypelD
fuelSubtypeDesc
10
1
Conventional Gasoline
11
1
Reformulated Gasoline (RFG)
12
1
Gasohol (E10)
13
1
Gasohol (E8)
14
1
Gasohol (E5)
15
1
Gasohol (El5)
20
2
Conventional Diesel Fuel
21
2
Biodiesel (BD20)
22
2
Fischer-Tropsch Diesel (FTD100)
30
3
Compressed Natural Gas (CNG)
40
4
Liquefied Petroleum Gas (LPG)
50
5
Ethanol
51
5
Ethanol (E85)
52
5
Ethanol (E70)
90
9
Electricity
50
-------
Table C-4 Residual TOG Speciation Map
Profile
Profile Description
modelYear-
GroupID
processID
fuelSubTypelD
regClassID
1001/
107GROC
CNG Exhaust
19602060
1,2,15,16
30
47,48
95120c1
Liquid Diesel
19602060
11
20,21,22
0
95120c1
Liquid Diesel
19602060
12,13,18,19
20,21,22
10,20,30,41,42,46,47,48
8753
E0 Evap
19602060
12,13,19
10
10,20,30,41,42,46,47,48
8754
E10 Evap
19602060
12,13,19
12,13,14
10,20,30,41,42,46,47,48
8756
Tier 2 E0 Exhaust
20012060
1,2,15,16
10
20,30
8757/
103GROC
Tier 2 El 0 Exhaust
20012060
1, 15
12,13,14
20,30
8757/
101GROC
Tier 2 El 0 Exhaust
20012060
2,16
12,13,14
20,30
8758
Tier 2 El 5 Exhaust
19602060
1,2,15,16
15,18
10,20,30,41,42,46,47,48
8766
E0 evap permeation
19602060
11
10
0
8769
E10 evap permeation
19602060
11
12,13,14
0
8770
El 5 evap permeation
19602060
11
15,18
0
8774/
104GROC
Pre-2007 MY HDD
exhaust
19602006
1,2,15,16,17,90
20,21,22
41,42,46,47,48,49
8774/
104GROC
Pre-2007 MY HDD
exhaust
19602060
91
20,21,22
46,47,49
8774/
104GROC
Pre-2007 MY HDD
exhaust
19602006
1,2,15,16
20,21,22
20,30
8775/
105GROC
2007+ MY HDD exhaust
20072009
1,2,15,16
20,21,22
20,30
8775/
105GROC
2007+ MY HDD exhaust
20072009
1,2,15,16,17,90
20,21,22
41,42,46,47,48,49
95335a/
106GROC
2010+ MY HDD exhaust
20102060
1,2,15,16
20,21,22
20,30
95335a/
106GROC
2010+ MY HDD exhaust
20102060
1,2,15,16,17,90
20,21,22
41,42,46,47,48,49
8855/
108GROC
Tier 2 E85 Exhaust
19602060
2,16
50,51,52
10,20,30,41,42,46,47,48
8855/
109GROC
Tier 2 E85 Exhaust
19602060
1,15
50,51,52
10,20,30,41,42,46,47,48
8869
E0 Headspace
19602060
18
10
10,20,30,41,42,46,47,48
8870
E10 Headspace
19602060
18
12,13,14
10,20,30,41,42,46,47,48
8871
El 5 Headspace
19602060
18
15,18
10,20,30,41,42,46,47,48
8872
El 5 Evap
19602060
12,13,19
15,18
10,20,30,41,42,46,47,48
8934
E85 Evap
19602060
11
50,51,52
0
8934
E85 Evap
19602060
12,13,18,19
50,51,52
20,30
8750a
Pre-Tier 2 E0 exhaust
19602000
1,2,15,16
10
20,30
8750a
Pre-Tier 2 E0 exhaust
19602060
1,2,15,16
10
10,41,42,46,47,48
8751a/
100GROC
Pre-Tier 2 E10 exhaust
19602000
2,16
11,12,13,14
20,30
8751a/
102GROC
Pre-Tier 2 E10 exhaust
19602000
1,15
11,12,13,14
20,30
8751a/
100GROC
Pre-Tier 2 E10 exhaust
19602060
2,16
11,12,13,14
10,41,42,46,47,48
8751a/
102GROC
Pre-Tier 2 E10 exhaust
19602060
1,15
11,12,13,14
10,41,42,46,47,48
51
-------
Appendix D Comparison of ACES Phase 1 and Phase 2
SPECIATE Profiles
We initially developed profile 95335 from the ACES Phase 2 profile as recommended by the
MOVES2014 peer-reviewers.33 However, there are inconsistencies between the ACES Phase 1
and 2 profiles. For example, ACES Phase 1 is composed of over 50% percent methane, while
the ACES Phase 2 profile has zero percent methane (Updated in Section 3.6). Other anomalies
in the ACES Phase II profile included benzene is not detected (ND) in the ACES Phase II
profile (from which we then assumed benzene=0), while ethanol comprises over 3% of the TOG
emissions. As suggested by one of the 2017 peer-reviews,58 to better understand the consistency
of these changes, we compared emission trends among different groups of gaseous
hydrocarbons (Tables D-5) and individual compounds (Table D-6 through D-10) between the
ACES Phase 1 and Phase 2 profiles.
While relative amounts of olefins and aromatics substantially increased in the Phase 2 profile
relative to Phase 1, paraffins, aldehydes and ketones decreased. However, there was
inconsistency in emission changes among individual compounds in all chemical groups. For
example, propane increased by more than a factor of four from ACES Phase 1 to ACES Phase
2, but hexane decreased by 69%. Similarly, while the total weight percentage of olefins
decreased, both ethene and propene increased as a proportion of total organic emissions.
Carbonyl compounds consistently decreased with the exception of acetaldehyde which
increased by 3%.
We did not attempt to impute minimum values in the cases where the species were not detected
in one of the profiles. Our speciation profiles consist of the weight percentage of total organic
emissions for each detected species as opposed to an absolute emissions value (in mg/mi or
similar unit); therefore, it is not straightforward to apply a below detection limit value to not
measured species
Within SPECIATE profile 95335, the mass fraction of three alcohol species, ethyl alcohol
(ethanol), isopropyl alcohol (2-propanol), methyl alcohol (methanol), sum to 7% of the total
TOG emissions. We do not believe these alcohol species are produced in modern heavy-duty
exhaust; instead they are likely an artifact of measurement during sampling or analysis in the
laboratory. With agreement from one of the 2017 peer-reviewers58, we created a new profile
(95335a) from 95335 where the mass fractions for the alcohol species are set to zero and we re-
weighted the remaining non-alcohol species.
While it is difficult to predict how complex emission control systems may affect individual
compounds, the inconsistent pattern of hydrocarbon measurements suggests that there are
potential significant uncertainties in the measurements. Additional sources of uncertainty in the
ACES phase 2 profile are due to the small number of engines tested (three), the low
concentrations of organic gas emitted with new 2010-compliant engines and aftertreatment
systems causing many measurements to be near the detection limits. Although ACES Phase 2 is
currently our best data source for the speciation of advanced technology diesels, the data should
52
-------
still be interpreted with caution. As we discussed in the main text, we recommend further work
to improve the confidence of speciation of exhaust from modern heavy-duty diesel engines,
including from engines with aged and deteriorated aftertreatment systems.
Table D-5 Comparison of Groups of Compounds from diesel exhaust speciation from
ACES Phase 1 and ACES Phase 2).
Compound Group
ACES Phase 1
(Weight %)
ACES Phase II
(Weight %)
% Change:
Phase I to
Phase II
Paraffins (total)
67.09
33.07
-51%
Olefins (total)
6.13
33.09
440%
Aromatics (total)
5.77
17.37
201%
Aldehydes/Ketones (total)
16.66
7.83
-53%
Unknown
4.35
1.56
-64%
Other
7.07
53
-------
Table D-6 Comparison of Individual Compounds from diesel exhaust speciation from
ACES Phase 1 and ACES Phase 2): Parafins
ACES Phase
ACES
% Change:
CAS
Name
1 (Weight
Phase II
Phase I to
%)
(Weight %)
Phase II
74-82-8
methane
51.64r
74-84-0
Ethane
1.34
10.11
655%
96-37-7
methylcyclopentane
0.02
112-40-3
dodecane
2.34
0.36
-84%
1120-21-4
undecane
1.75
106-97-8
N-butane
1.10
0.17
-85%
109-66-0
N-pentane
1.01
3.06
201%
78-78-4
Isopentane (2-Methylbutane)
0.88
124-18-5
decane
0.38
0.12
-68%
111-84-2
nonane
0.28
2.72
873%
74-98-6
Propane
0.51
2.75
441%
75-28-5
Isobutane
0.50
1.03
108%
3522-94-9
2,2,5 -trimethy lhexane
0.04
590-73-8
2,2-dimethylhexane
0.66
589-43-5
2,4-dimethy lhexane
0.42
589-34-4
3-methy lhexane
0.15
0.26
76%
108-87-2
methylcyclohexane
0.89
0.77
-13%
619-99-8
3-ethy lhexane
0.08
110-54-3
n-hexane
0.24
0.07
-69%
96-14-0
3-methylpentane
0.14
107-83-5
2-methylpentane
0.13
0.59
336%
79-29-8
2,3 -dimethy lbutane
0.09
15869-87-1
2,2-dimethyloctane
0.00
0.30
26037%
111-65-9
octane
0.20
0.36
80%
565-75-3
2,3,4-trimethy lpentane
0.54
560-21-4
2,3,3 -trimethy lpentane
0.52
540-84-1
2,2,4-trimethylpentane
0.37
0.37
-1%
565-59-3
2,3 -dimethy lpentane
0.35
562-49-2
3,3 -dimethy lpentane
0.00
590-35-2
2,2-dimethylpentane
0.02
1068-19-5
4,4-dimethy lheptane
0.16
1072-05-5
2,6-dimethylheptane
0.20
0.82
303%
589-81-1
3-methy lheptane
0.07
592-27-8
2-methy lheptane
142-82-5
heptane
0.28
0.09
-66%
463-82-1
2,2-dimethylpropane
0.68
75-83-2
2,2-dimethy lbutane
2.40
r This differs from the 58% CH4/THC reported in Table 3-2 because the 51% reports the fraction of methane/TOG.
We calculated THC from TOG using the methods described in Section 3.2
54
-------
Table D-6 (Continued)
ACES Phase
ACES
% Change:
CAS
Name
1 (Weight
Phase II
Phase I to
%)
(Weight %)
Phase II
767-58-8
1-methy lindane
2216-33-3
3-methyloctane
0.16
584-94-1
2,3 -dimethy lhexane
108-08-7
2,4-dimethylpentane
1.45
591-76-4
2-methy lhexane
0.41
124-11-8
1-nonene
0.06
2213-23-2
2,4-dimethylheptane
0.61
4032-94-4
2,4-dimethyloctane
0.63
3221-61-2
2-methyloctane
0.19
583-48-2
3,4 -dimethy lhexane
0.22
90622-57-4
C9-cl2 isoalkanes
1.51
2532-58-3
Cis-1,3 -dimethy lcyclopentane
0.46
Cis-l,trans-2,4-
16883-48-0
trimethylcyclopentane
0.06
1759-58-6
Trans-1,3 -dimethy lcyclopentane
0.07
55
-------
Table D-7 Comparison of Individual Compounds from diesel exhaust speciation from
ACES Phase 1 and ACES Phase 2): Olefins
CAS
Name
ACES Phase 1
(Weight %)
ACES Phase
II (Weight
%)
% Change:
Phase I to
Phase II
74-85-1
ethene
3.07
9.55
212%
763-29-1
2-methy 1-1 -pentene
0.01
115-07-1
propene
0.94
4.31
359%
74-86-2
acetylene
0.58
0.82
42%
115-11-7
2-methy lpropene
0.97
13.33
1268%
106-99-0
1,3-butadiene
0.04
590-19-2
1,2-butadiene
592-41-6
1-hexene
0.01
7688-21-3
Cis-2-hexene
4050-45-7
Trans-2-hexene
106-98-9
1-butene
0.03
590-18-1
cis-2-butene
0.53
624-64-6
trans-2-butene
513-35-9
2-methyl-2-butene
3.01
691-37-2
4-methy 1-1 -pentene
0.06
625-27-4
2-methyl-2-pentene
0.03
7385-78-6
3,4-dimethyl-1 -pentene
0.07
107-40-4
2,2,4-trimethyl-2-pentene
0.04
142-29-0
cyclopentene
0.01
816-79-5
3-ethyl-2-pentene
0.01
0.50
4963%
107-00-6
1-butyne
0.25
542-92-7
cyclopentadiene
0.02
627-20-3
Cis-2-pentene
0.17
110-83-8
Cyclohexene
0.87
56
-------
Table D-8 Comparison of Individual Compounds from diesel exhaust speciation from
ACES Phase 1 and ACES Phase 2): Aromatics
CAS
Name
ACES Phase 1
(Weight %)
ACES Phase
II (Weight
%)
% Change:
Phase I to
Phase II
71-43-2
benzene
0.61
108-88-3
toluene
1.24
1.52
22%
95-47-6
o-xylene
0.65
0.37
-44%
108-38-3; 106-42-3
m/p-xylenes
1.04
6.65
539%
527-53-7
1,2,3,5-tetramethylbenzene
0.16
95-93-2
1,2,4,5-tetramethylbenzene
0.08
1.25
1526%
95-63-6
1,2,4-trimethylbenzene
0.75
0.18
-76%
25551-13-7
trimethylbenzene
526-73-8
1,2,3-trimethylbenzene
0.06
4.54
7737%
108-67-8
1,3,5 -trimethylbenzene
1758-88-9
l,4-dimethyl-2-ethylbenzene
0.12
620-14-4
1 -Methy 1-3 -ethylbenzene
0.08
622-96-8
1 -Methy 1-4-ethylbenzene
611-14-3
1 -methyl-2-ethylbenzene
0.05
0.02
-56%
103-65-1
Propylbenzene
0.72
100-41-4
ethylbenzene
0.31
0.92
194%
98-19-1
tert-butyl-m-xylene
0.13
100-42-5
styrene
98-82-8
isopropylbenzene
0.52
538-93-2
(2 -methy lpropy l)benzene
0.20
0.12
-43%
535-77-3
1 -Methy 1-3 -isopropylbenzene
0.05
527-84-4
1 -methyl-2-isopropylbenzene
0.06
1074-43-7
1 -Methy 1-3 -propylbenzene
0.02
03968-85-2
2-methyl-butyl-benzene
0.05
1074-92-6
t-1 -Butyl-2-Methy lbenzene
0.03
91-20-3
Naphthalene
0.07
141-93-5
1,3-diethylbenzene (meta)
105-05-5
1,4-diethylbenzene (para)
0
Isomers of diethylbenzene
104-51-8
buty lbenzene
1,2,4-trimethylbenzene
25155-15-1
Isopropyltoluene
28729-54-6
Propyltoluene
7364-19-4
1 -tert-butyl-4-ethy lbenzene
0.56
57
-------
Table D-9 Comparison of Individual Compounds from diesel exhaust speciation from
ACES Phase 1 and ACES Phase 2): Aldehydes/Ketones
CAS
Name
ACES Phase 1
(Weight %)
ACES Phase
II (Weight
%)
% Change:
Phase I to
Phase II
50-00-0
formaldehyde
10.05
2.20
-78%
75-07-0
acetaldehyde
3.36
3.45
3%
107-02-8
acrolein
0.50
0.30
-41%
67-64-1
acetone
0.76
1.01
34%
100-52-7
benzaldehyde
0.79
0.03
-96%
123-38-6
propionaldehyde
0.15
0.24
58%
78-93-3
Methyl ethyl ketone (2-butanone)
0.16
0.08
-50%
123-72-8
butyraldehyde
0.16
0.11
-30%
66-25-1
hexanaldehyde
0.11
0.04
-64%
590-86-3
isovaleraldehyde
0.08
0.03
-69%
104-27-0
M- & p-tolualdehyde
0.49
0.13
-75%
110-62-3
valeraldehyde
0.05
0.14
208%
4170-30-3
Crotonaldehyde
0.02
28351-09-9
Dimethylbenzaldehyde
0.02
529-20-4
o-Tolualdehyde
0.04
Table D-10 Comparison of Individual Compounds from diesel exhaust speciation from
ACES Phase 1 and ACES Phase 2): Other/Un
mown
CAS
Name
ACES Phase 1
(Weight %)
ACES Phase
II (Weight
%)
% Change:
Phase I to
Phase II
64-17-5
Ethyl alcohol (ethanol)
3.19
67-63-0
Isopropyl alcohol (2-Propanol)
1.74
67-56-1
Methyl alcohol (methanol)
2.14
N/A
C-6 Compounds
1.42
N/A
C-8 Compounds
0.14
N/A
Unknown
4.35
58
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Appendix E Development of PM2.5 speciation profiles in
MOVES
This report includes the derivation of each PM2.5 profiles used in MOVES to estimate AE6
chemical mechanism PM2.5 species.
For comparison purposes, the seven PM2.5 profiles developed for MOVES are presented in
Table E-l. The remainder of this appendix explains how each profile was derived.
Table E-l PJVh.s Profiles developed for MOVES
Light-duty Gasoline
Exhaust - Start (8992)
Light-duty Gasoline
Exhaust- Hot Stabilized
(8993)
Conventional HDD- Idle
(8994)
Conventional HDD- Hot
Stabilized Running (8995)
2007 and Newer Diesel
Exhaust Composite (8996)
CNG transit bus exhaust
from a lean-burn engine -
no aftertreatment (95219a)
CNG transit bus exhaust
from a lean-burn engine -
aftertreatment (95220a)
Elemental Carbon
(EC)
44.37%
14.00%
46.40%
78.97%
9.98%
9.25%
11.12%
Organic Carbon (OC)
42.64%
55.70%
34.74%
14.52%
22.33%
36.99%
37.45%
Non-carbon Organic
Matter (NCOM)
8.53%
11.14%
6.95%
2.90%
4.47%
7.40%
7.49%
S04
0.95%
7.19%
5.27%
1.03%
59.91%
0.64%
1.04%
N03
0.26%
0.29%
1.25%
0.18%
0.00%
NH4
0.43%
2.78%
1.74%
0.36%
0.00%
Fe
0.31%
1.83%
0.34%
0.13%
0.64%
0.25%
0.25%
A1
0.32%
0.06%
0.06%
0.11%
0.89%
0.89%
Si
0.32%
0.30%
0.22%
0.09%
0.46%
0.59%
Ti
0.03%
0.01%
0.01%
0.02%
Ca
0.39%
1.44%
0.58%
0.35%
0.47%
0.21%
0.44%
Mg
0.02%
0.14%
0.13%
0.01%
0.14%
K
0.09%
0.26%
0.02%
0.05%
Na
0.01%
0.04%
0.31%
0.03%
0.99%
CI
0.02%
0.10%
0.38%
0.13%
0.04%
unspeciated
(PMOTHR)
2.09%
4.58%
1.28%
1.09%
0.78%
43.90%
40.74%
59
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E.l Development of Gasoline Profiles from the Kansas City
Light-duty Vehicle Emissions Study
The Kansas City Light-duty Vehicle Emissions Study (KCVES) is the primary source of PM2.5
emission rates for light-duty vehicles in MOVES.1 The KCVES sampled PM2.5 emissions from
496 vehicles recruited in a stratified random sample. The KCVES also measured speciated
PM2.5 on a subset of 99 of these vehicles. An overview of the vehicles included in this
"chemical subset" is included in Table E-2.
Table E-2 Vehicle Sample Size in the Kansas City Light Duty Vehicle Emissions Study
Vehicle
Type1
Strata
Model
Year
Group
% of KC
LDGV
Vehicle
Population
% of KC
LDGV
Vehicle
Miles
Traveled
(VMT)
Summer Round
Sample
Winter Round
Sample
Full
Sample
Chemical
Subset
Full
Sample
Chemical
Subset
Truck
1
pre-1981
1.1%
0.6%
2
2
10
3
2
81-90
3.7%
2.4%
21
4
33
3
3
91-95
7.2%
6.5%
18
6
33
7
4
96-2005
28.6%
34.2%
39
8
59
11
Car
5
pre-1981
1.3%
0.7%
6
5
17
3
6
81-90
7.4%
4.6%
49
4
40
5
7
91-95
13.4%
11.2%
39
6
44
9
8
96-2005
37.3%
39.8%
87
14
41
9
Sum =
100%
100%
261
49
277
50
The derivation of the PM2.5 gasoline profile for MOVES is documented in Sonntag el al.
(2013).59 A summary of the speciation derivation is included in this report, as well as a
discussion on implementing the profile into the MOVES framework. Two gasoline profiles are
developed to maintain differences between start and running processes. Minor differences were
detected between the PM2.5 compositions between seasons, which were confounded by the
different vehicles tested in each season. The analysis used equally weighted data from the
summer and winter tests to calculate a profile that incorporates data from both seasons.
We discovered high concentrations of silicon in some of the PM2.5 measurements— likely due to
contamination from silicone rubber couplers used in KCVES. The silicone contamination
occurred primarily on bag 2 of the LA-92 drive cycle which was used for developing the
running PM2.5 speciation profile and emission rates. The silicone contamination was larger for
trucks than cars due to their higher exhaust temperatures. The effect of the silicone
contamination was removed from the developed profile using the silicon emissions
measurement by X-ray florescence. The primary exhaust PM2.5 emission rates were corrected in
MOVES to account for the silicone contamination.1 After removing the silicone contamination
from the speciated data, no significant differences were detected between passenger cars and
light-duty trucks, and the data from the cars and trucks were pooled to develop single start and
running PM2.5 speciation profiles for all light-duty gasoline vehicles.
60
-------
While differences in the PM2.5 compositions were detected among model year groups, the
speciation sample size was deemed too limited to accurately capture the impact of deterioration
and high-emitting vehicles within each model-year group. Instead fleet-average profiles were
calculated to better capture the impact of deterioration within all model year groups and to avoid
over-fitting the data to model year group trends. Malfunctioning high-emitting vehicles are
known to contribute a significant share of in-use PM emissions from light-duty
vehicles.60'61'62'63 High-emitting gasoline emissions have a highly variable PM composition due
to failed emission control systems, excessive oil consumption, and poor fuel control. Previous
analysis of the KCVES suggested that the speciation subsample (102 tests) provides a
reasonable estimate of the total PM mass compared to the full sample (522 tests), but the
speciation sample underestimated the high emitting vehicles in the newer model year groups.64
Other test programs have confirmed that high emitting gasoline vehicles also occur in vehicle
fleets such as 1990-era vehicles with electronic fuel injection.60'61'62 By using all the data in a
fleet-average approach, we incorporated the impact of deteriorated vehicles on the fleet-average
PM2.5 emissions.
The fleet-average PM speciation profiles are calculated using seasonal, vehicle-miles-traveled
(VMT), and PM mass-weighting. The PM profile is calculated using the ratio of the means, also
referred to as a mass-normalized emission profile.65 The ratio of means is calculated by first
calculating the mean emission rate of the total PM2.5, and the mean emission rate of each PM
species (EC, OC, Fe, etc.). Then the speciation profile is calculated, by calculating the ratio of
the mean emission rate from each species, to the mean PM2.5 emission rate, e.g., mean
(EC)/mean(PM). The vehicle tests from each season are equally weighted, and averaged
according to the calculated contribution to annual VMT in the Kansas City MSA (Table E-2).
By using VMT and mass weighting, the profile scales up the contribution of older and higher
emitting vehicles according to their high PM emissions, but also scales their down their
contribution based on the relatively small number of vehicle miles traveled associated with
these vehicles. For application in MOVES, the fleet-average profile is used to characterize
PM2.5 emissions across all model year groups, and all ages of vehicles used to represent
deterioration.
Because the PM2.5 speciation varied significantly by model year group,59 the fleet average
speciation profile is sensitive to the averaging assumptions. As mentioned above, we did not
maintain the difference in speciation in model year groups, due to concern that the model-year
groups would not be representative of the PM emissions as the vehicles aged. Given the
uncertainty of the PM speciation profiles, we thought it would be unreasonable to model
differences in PM speciation according to different ages of vehicle fleets in different areas in the
US. For simplicity, we assume that the fleet-average PM2.5 profile from Kansas City to be
representative of the US gasoline fleet.
We recognize the need to incorporate speciation data on newer vehicles. For the next generation
of vehicles, the composition of PM is expected to become increasingly dominated by black
carbon emissions from both low-emitting port-fuel injected vehicles60'66'67'68 and gasoline-direct
injection (GDI) vehicles.69'70'71 We plan on incorporating light-duty gasoline PM profiles to
MOVES and SPECIATE as such data on representative, in-use vehicles become available.
61
-------
The developed PM2.5 profiles used in MOVES for gasoline exhaust are included in Table E-3..
The number of samples for each PM2.5 species are also shown. EC was measured on each
vehicle test and has a much greater sample size than the other species. The EC and nonECPM
emission rates in MOVES are consistent with the EC fractions listed here.
For application in MOVES, only the PM2.5 species required by CMAQv5.1 are reported. Metal
emission rates for Mn, Cr, and Ni for gasoline vehicles based on the KCVES are provided in the
Air Toxics Report.7 The PM2.5 ratios that were not significantly greater than 0 at the 95 percent
confidence intervals were reported as 0, which removed five PM2.5 species pollutants from the
start profile. Fuel samples analyzed for 171 of the vehicles tested in KCVES yielded an average
fuel sulfur content of 161.2 ppm. Fuel sulfur content in the US is now much lower after
implementation of the Tier 2 72 and Tier 3 73 Gasoline Sulfur Standards (30 ppm beginning 2006-
2008, and 10 ppm in 2020). In MOVES, the baseline sulfate emissions estimated from the PM2.5
profile are adjusted according to the fuel sulfur content as discussed in the fuel effects report.46
Details on the data, quality control measures, and statistical methods used to develop the profile
are documented in the Sonntag et al. (2013).59 The paper also introduces methods to identify
significant measurements, correct for organic carbon positive artifact, control for contamination
from the testing environment on the PM2.5 speciation profiles, and impute missing PM2.5 species
in the KCVES measurements from other light-duty gasoline PM emission studies. Speciation
factors for additional PM2.5 species (P, Cu, Zn, Br, Mo, and Pb) that are not included in
MOVES are also presented.
Table E-3 Gasoline PM2.5 Profile for Start and Running Emissions Weighted Average
using Vehicle Miles Traveled (VMT)
PM Species
Start (8992)
Running (8993)
n
mean ratio +/- 95% CI
n
mean ratio +/- 95% CI
Elemental Carbon (EC)
484
44.37%
+/- 4.30%
531
14.00%
+/- 2.68%
Organic Carbon (OC)
66
42.64%
+/- 6.63%
99
55.70%
+/- 4.02%
Non-carbon Organic Matter (NCOM)
66
8.53%
+/- 1.33%
99
11.14%
+/- 0.80%
S04
66
0.95%
+/- 0.24%
99
7.19%
+/- 1.90%
N03
66
0.26%
+/- 0.08%
99
0.29%
+/- 0.08%
NH4
66
0.43%
+/- 0.10%
99
2.78%
+/- 0.73%
Fe
66
0.31%
+/- 0.21%
99
1.83%
+/- 0.53%
Al
99
0.32%
+/- 0.10%
Si
99
0.32%
+/- 0.10%
Ti
99
0.03%
+/- 0.01%
Ca
66
0.39%
+/- 0.14%
99
1.44%
+/- 0.26%
Mg
66
0.02%
+/- 0.02%
99
0.14%
+/- 0.02%
K
99
0.09%
+/- 0.03%
Mn
99
0.02%
+/- 0.02%
Na
66
0.01%
+/- 0.00%
99
0.04%
+/- 0.01%
CI
66
0.02%
+/- 0.01%
98
0.10%
+/- 0.04%
Unspeciated (PMOTHR)
66
2.09%
+/- 1.75%
99
4.56%
+/- 1.10%
62
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E.2 Development of E55/59 Profile for Pre-2007
Conventional Diesel
An PM2.5 profile for pre-2007 conventional0 diesel trucks was developed from the CRC E55/59
Study: Heavy-Duty Vehicle Chassis Dyno Testing for Emissions Inventory.74 The E55/59
program is the current source for PM2.5 emission rates for medium- and heavy-duty pre-2007
model year conventional diesel trucks in MOVES, and is the source of the conventional pre-
2007 diesel TOG speciation profiles. By using the E55/59 study for PM2.5 speciation profiles,
we are using consistent data with both the PM2.5 emission rates and the TOG speciation profiles
in MOVES.
The E55/59 PM2.5 profile includes measurements from eight heavy-duty trucks, ranging from
1985 to 2004 model year as shown in Table D-4. The E55/59 average sulfur content is 172 ppm.
The CRC E55/59 study was conducted from 2001-2005 in several phases. Chemical
characterization of PM2.5 emissions was conducted for nine of the 75 trucks tested in the E55/59
study, ranging from 1985 to 2004 model year.
Table
£-4 Vehicle Information from t
ie Speciated E55/59 Trucks
Phase
ID
Medium/
Heavy-
Duty
Vehicle
Model
Year
Vehicle
Manufacturer
Engine
Model
Year
Engine
Model
Engine
Power
(hp)
Engine
Disp.
(Liter)
Engine
Manufacturer
Odometer
Reading
(mi)
1
1
H
1994
Freightliner
1994
Series
60
470
12.7
Detroit
639105
1
2
H
1995
Freightliner
1995
3406B
375
14.6
Caterpillar
241843
1
3
H
1985
International
1985
NTCC-
300
300
14
Cummins
501586
2
39
H
2004
Volvo
2003
ISX
530
14.9
Cummins
45
2
40
H
2004
Freightliner
2003
Series
60
500
14
Detroit
8916
2
41
M
1998
Ford
1997
B5.9
210
5.9
Cummins
13029
2
42
H
2000
Freightliner
1999
3406
435
14.6
Caterpillar
576998
2
43
H
1995
Peterbilt
1994
Series
60
470
12.7
Detroit
899582
2
44
H
1989
Volvo
1989
3406
300 (est.)
14.6
Caterpillar
811202
In all, 65 tests were conducted on the nine trucks selected for PM speciation. Phase 1 tested
three heavy heavy-duty diesel trucks (HHDDTs) for PM speciation on four modes of the Urban
Dynamometer Driving Schedule (UDDS), including: idle, creep, transient and cruise. Phase 2
tested six additional heavy heavy-duty diesel trucks, and one medium heavy-duty diesel truck
(MHDDT). In Phase 2, the HHDDTs were also tested on the UDDS, as well as a high-speed
cruise mode added after Phase 1. The MHDDT was tested on MHDDT schedule developed by
the California Air Resources Board that included two transient modes and a cruise mode. For
chemical speciation, some tests were repeated in sequence to collect additional mass on the
63
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filter, including extended idle and extended creep. In Phase 2, the speciation data was not
collected for the creep mode.74
The total and speciated PM2.5 emissions data from the E55/59 study was compiled from the
speciation database compiled in CRC Report No. E75-2: Diesel Unregulated Emission
Characterization Report75 and from Table 17 of the E55/59 Phase 1 report.76 The data reduction
steps used to develop a PM2.5 speciation profile from the E55/59 speciated data are outlined in
the following Steps: 1-4.
Step 1. We first calculated the average PM2.5 profile for each individual truck and four generic
classifications of test cycle, namely: idle, creep, cruise, and transient. The composite UDDS
cycle is classified as a transient cycle, similar to the classification conducted of speciation
profiles by E75-2.74 The truck and test cycle average PM profiles are calculated as ratios of the
means, also called a PM mass-weighted profile. In this manner, idle tests that contain three
repeat idle cycles contribute more to the average than tests that include only one idle cycle. The
average profile for each vehicle/test cycle classification is shown in Figure D-l. Thirty average
speciation profiles were calculated from the 65 tests as shown in Figure D-l. Typically, each
truck/cycle average contains two tests.
t
~3)
o
a)
T3
o
E
~3)
af
ro
Q1
c
o
'(/)
CO
'E
LD
31
31
21
21
11
11
CK
0:1
6"
5-
4-
3-
2-
1-
0-
1-
11
1r<
01
0^
0^
0:
01.
3^
3^
2:
21
I
II
0:
0:1
¦-
M R
n r
M R
h
h
39
40
MR MR
n r
M R
41
42
m-
43
44
I
I
Pollutant. ID
PM2.5
Elemental carbon
Organic carbon
| ions
| S04-2
I elements
MR MR MR MR
Figure D-l Average PM2.5 Speciation Profiles by Truck and Test Cycle from the E55/59
Program. M = Measured total PM2.5, R = Reconstructed Total PM2.5 from the Speciated
Measurements
Step 2. We removed the average PM2.5 profiles with suspect data. As shown in Figure D-l, the
MMHDT truck (Truck 41) had very low PM emissions on the transient cycle, and a very large
64
-------
contribution of ammonium to the idle cycle. This PM composition does not compare well with
previous data in the literature77, so the medium-duty truck was removed from further analysis.
Step 3. We calculated a median PM profile using the individual truck/test-cycle PM profiles
calculated in steps 1 and 2. The median is used rather than the mean due to the small sample
(eight trucks), in contrast to the variety of truck technologies, exhaust control systems, and ages
of the trucks in the real-world fleet. A mass-weighted mean would have been dominated by the
results for Truck 3 and Truck 44, which had the highest PM emission rates. Instead we
calculated the median of the PM fractions, and not a fraction of the median emission rates. In
this manner, the final PM speciation profile is not overly dependent on any one vehicle.
Additionally, there may be systematic differences between the Phase 1 and Phase 2
measurements that could impact a mass-weighted profile. By calculating the PM2.5 species
fraction before computing the median, any differences impacted the absolute PM2.5 emission
rates between phases do not impact the resulting speciation profile.
Step 4. We adjust the median profile to account for unmeasured PM2.5 species including metal-
bound oxygen and non-carbon organic matter. The additional oxygen mass associated with the
metal oxides are calculated using the oxide state assumptions in Sonntag et al. (2013)59
reproduced in Table E-5.
Table E-5 Oxide States Assumed for Calculation of Metal-Bound Oxygen
Element
Oxide Form 1
Oxide Form 2
Oxide Form 3
Oxide/Element
Mass Ratio
Na
Na20
1.35
Mg
Mg
1.0
Al
AI2O3
1.89
Si
Si02
2.14
P
P04
3.07
CI
CI
1.0
K
K20
1.20
Ca
Ca
1.0
Ti
Ti02
1.67
Cr
Cr203
Cr03
1.69
Mn
MnO
Mn02
\111O
1.63
Fe
FeO
Fe203
1.36
Ni
NiO
1.27
Cu
CuO
1.25
Zn
Zn
1.0
Rb
Rb20
1.09
Br
Br
1.0
Mo
M0O2
M0O3
1.42
Pb
PbO
Pb02
1.12
65
-------
For the Phase 1 samples, the molar concentration of ammonium balances within 5 percent of the
molar concentrations of 2*SC>4 + NO3. This is what would be expected if the ammonium exists
as ammonium sulfate [NH4]2S04 and ammonium nitrate, NH4NO3. For the Phase 2 samples,
ammonium balances within 25 percent of the molar concentrations of 2*SC>4 + NO3. Due to the
relatively good agreement between the measurements, it appears that the sulfate on the filter
exists as ammonium sulfate. As such, we did not account for sulfate-bound water contributing
to filter mass.
The sum of the PM fractions from the median profiles is greater than one. To achieve mass
balance, we are scaled down the organic carbon fraction to correct for positive artifact inherent
in organic carbon (OC) filter measurements, as was done in previous work including for the
light-duty gasoline profile59 and analysis of emissions from other combustion sources.78 We
calculated the organic matter (OM) as the remainder of the PM2.5 using Equation 11.
OM% = 100 — EC% — elements% — metal bound oxygen% — ions% Equation
Then, we split the OM into OC and non-carbon organic matter (NCOM) using the following
relationship: OM = 1.2 * OC used by Kleeman etal. (2000)79 and developed from work
conducted on medium-duty diesel emissions77, as shown in Equation 12 and Equation 13.
OC% = OM%
NCOM% = Q OM%
The initial and corrected OC/PM factors are shown in Table E-6. The adjusted OC speciation
factors are smaller than the initially measured OC/PM fraction, which is expected due to the
higher affinity for OC artifact to collect on the quartz fiber filters, as compared to the Teflon
filters used to measure PM2.5 mass.80
Table E-6 Impact of Mass-Balance Correction on Organic Carbon and Organic Matter
Emission Rates
PM factors
IDLE
CRUISE
TRANSIENT
Initial OC/PM factor
54.1%
36.3%
30.1%
Mass-balance OM/PM factor
41.7%
36.1%
17.4%
Corrected OC/PM factor
34.7%
30.1%
14.5%
The resulting profiles for the PM2.5 species are located in Table E-7. The Start/Extended Idle
profile is based on the idle test cycles, and the running emissions are based on the transient
cycles. These cycles are selected for use for modeling these emission processes because they
have similar PM characteristics (EC/PM) ratio as the PM2.5 MOVES emission rates for
conventional diesel as discussed next.
Equation
12
Equation
13
66
-------
Table E-7 PM2.5 Profiles for Pre-2007 Diesel Exhaust Developed for MOVES2014
Idle (Profile
8994)
Running
(Profile
8995)
Elemental Carbon
46.40%
78.97%
Organic Carbon
34.74%
14.52%
NonCarbon OM
6.95%
2.90%
S04
5.27%
1.03%
N03
1.25%
0.18%
NH4
1.74%
0.36%
Fe
0.34%
0.13%
Al
0.06%
0.06%
Si
0.30%
0.22%
Ti
0.01%
0.01%
Ca
0.58%
0.35%
Mg
0.13%
0.01%
K
0.26%
0.02%
Na
0.31%
0.03%
CI
0.38%
0.13%
CMAQ5.0 unspeciated
1.28%
1.09%
In MOVES, the EC/PM fraction from the Idle profile (8994) is used for idle emissions from
running (opModelD 1, processID 1) and extended idle (processID 90). It is also used to speciate
the PM from start emissions (processID 2) and auxiliary power emissions (processID 91). The
running profile is used to speciate the PM from all other operating modes from running
emissions (processID 1).
Table E-8 compares the profiles developed from the E-55/59 study to measurements made at
CE-CERT (Shah et al. (2004)81), a composite profile developed by Schauer et al. (2006)65 from
the DOE Gasoline/Diesel PM Split Study, and the NFRAQS heavy-duty diesel profile
(SPECIATE Profile 91106). The EC/PM fraction from the E55/59 transient cycle compares
well to both the composite profiles. The E55/59 idle profile has a substantially lower EC/PM
fraction than the composite profiles, with a corresponding higher fraction of organic matter. The
cold/start idle profile from CE-CERT (Shah et al. (2004)) also shows an even lower EC/PM
fraction during idle than high load conditions. The MOVES sulfate fractions appear to be more
aligned with the DOE Split study, which could be due to newer technology diesel and lower
altitude testing. Elements and ion emission rates compare well to the DOE gasoline/diesel PM
split study.
67
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Table E-8 Comparison of MOVES Conventional Pre-2007 Diesel Profiles with other PM2.:
Conventional Diesel Profiles
MOVES
E-55/59
CE-CERT 2004a
DOE
Gasoline/
Diesel PM
Split Study
Northern
Front Range
Air Quality
Study
Idle (8994)
Running
(8995)
Cold
start/Idle
Running
(Transient)
Composite
Composite
(91106)
Elemental carbon
46.4%
79.0%
13.3%
68.0%
72.7%
77.1%
Organic matter
41.7%
17.4%
81.4%
33.5%
24.1%
17.6%
SO4-2
5.3%
1.0%
1.3%
0.3%
CI + NH4 + N03
3.4%
0.7%
0.4%
0.1%
Elements
2.1%
1.1%
1.5%
0.5%
Note:
a. Organic matter estimated using the 1.2 * OC, other components not measured.
E.3 Development of the ACES PM2.5 Profile for 2007 and
Newer Technology Diesel
The PM2.5 speciation profile for 2007-and-later technology is based on Phase 1 of the Advanced
Collaborative Emissions Study (ACES) Report.25 The purpose of the ACES report was to
characterize criteria and toxic emissions from advanced technology diesel engines and control
systems. Phase 1 of ACES tested four heavy-duty diesel engines each equipped with a catalyzed
diesel particulate filter (C-DPF). The PM2.5 profile is based on a 16-hour cycle which is
composed of FTP and CARB 5-Modes, developed specifically to gain sufficient PM mass to
measure the emission rates of trace metals and toxics and to capture diesel particulate filter
regeneration events. The PM2.5 measurements from the 16-hour cycle include the exhaust
measurements downstream of the C-DPF and crankcase blow-by emissions. Crankcase blow-by
emissions contributed 38 percent of the combined crankcase and tailpipe PM2.5 emissions on the
FTP cycle.
The SPECIATE contractor (Abt Associates) developed the PM2.5 profile from the ACES
program Phase 1 with input from the US EPA, with the intent of maintaining consistency with
the summarized results in the ACES Phase 1 report. The 16-hour results yielded the most
accurate measurements at the low levels of PM2.5 and are used to represent all PM2.5 emission
processes from 2007-and-newer on-highway diesel vehicles.
The following decisions were made to develop a profile to be consistent with the results in the
ACES Phase 1 report.
1. The original measurements were used rather than background or tunnel corrected
measurements. EC and OC were not corrected for background, or backup quartz filters.
Background correcting the EC/OC filters caused negative EC/OC emission rates on
three of the four engines. The ACES researchers did not report OC corrected by a
backup-quartz filter because of concern of under-representing OC emissions.82
Similarly, species for elements and ions were not corrected for tunnel blanks. Using
68
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uncorrected OC measurements likely contributed to the mass of the sum of the speciated
measurements being higher than Teflon filter measurements.83 By using the original
measurements, rather than the background or tunnel corrected measures, we are likely
overestimating the emissions from some of the individual species that are subject to
positive artifact like OC. The ACES researchers discuss possible approaches for
correcting the measured OC emission rates and mention this as an area for future work
for 2007-and-later diesel engines.
2. Unmeasured species that likely contribute to particulate matter were not included in the
profile, including sulfate-bound water and metal-bound oxygen from the profile. The
PM collected on the filter were analyzed for nitrate and ammonium, however no
ammonium or nitrate was detected.25 In the absence of these species, the sulfate is
expected to exist as hydrated sulfuric acid. Khalek et al. 201182 reported that accounting
for the water-bound sulfate would increase the summed mass of the individual species
37 percent beyond the measured filter mass. Rather than lowering the factors for other
species by including the sulfate-bound water, it was excluded from the profile.
Converting the measured organic carbon to organic matter and accounting for the oxide
state of the elements was considered by Khalek et al. (2011)82, but was not conducted
due to the uncertainty of reconciling the filter mass and the sum of the measured species.
3. According to the SPECIATE database, the profile was normalized to the gravimetric
mass of PM. Gaseous and particulate phase sulfate are combined in the PM profile.
More information on the profile itself can be found in the SPECIATE database, and the
database's supporting documentation outlines specific procedures for creating PM
profiles.84
The ACES Profile is included in the SPECIATE database as profile #5680. This profile is the
basis of SPECIATE profile 8996 used in MOVES with one adjustment. MOVES needs organic
matter reported as OC and non-carbon organic matter (NCOM). We treated the reported OC in
the SPECIATE profile 5680 as OM, and calculate OC and NCOM using the same split
(Equation 12) as used for pre-2007 diesel and light-duty gasoline. The species not needed by
MOVES from the ACES Phase 1 profile are summed into the unspeciated fraction. The
speciation values are presented in Table D-9. Metal emission rates for manganese, chromium,
and nickel from MOVES are derived from the ACES Phase 1 data.7 They are estimated using
the metals calculator with mass/distance emission rates, and are not reported in the SPECIATE
profiles.
69
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Table E-9 SPECIATE PM2.5 Profile 8996 Developed from the 16-hour Cycle from Four
Heavy-duty Diese
Engines with Catalyzed-DPFs in the ACES Phase 1 Program
Weight %
Elemental Carbon
9.98%
Organic Carbon
22.33%
Non Carbon Organic Matter
4.47%
Sulfate
59.91%
Nitrate
0.00%
Ammonium
0.00%
Iron
0.64%
Aluminum
0.11%
Silicon
0.09%
Titanium
0.02%
Calcium
0.47%
Magnesium
0.14%
Potassium
0.05%
Sodium
0.99%
Chlorine
0.04%
Unspeciated
0.78%
The ACES Phase 1 derived EC fraction of 9.9% falls within the range of EC fraction of total
carbon emissions (2 to 20%) reported from Thiruvengadam et al. 2016.85
E.4 Development of the Compressed Natural Gas (CNG)
Profile
The California Air Resource Board (CARB) conducted several emission characterization
studies on compressed natural gas vehicles. In our profile development, we used only the data
reported by CARB for a CNG New Flyer bus with a 2000 MY Detroit Diesel (DDC) Series 50G
engine, equipped with and without an oxidation catalyst. Using a single profile provides
consistency in the PM characterization estimates and assures that the organic carbon emissions
are reduced with implementation of oxidation catalyst controls. CARB also conducted tests on a
CNG bus with a 2001 Cummins Westport engine. Other studies that reported EC/OC did not
measure emission rates for elements.86
We developed the profiles shown in Table E-10 with and without catalyst to estimate the impact
of oxidation catalyst control. CARB characterized the PM emissions on a steady-state cycle,
and a central business district cycle (CBD). We used the CBD data, which was consistent with
the criteria pollutant analysis in the heavy-duty emissions report2 and was considered more
70
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representative of typical transit bus behavior.s'87 The PAH/OC ratios documented in the
MOVES toxics report7 were also developed from the CARB measurements on the DDC 50G.
Table E-10 PM2.5 Speciation Profiles for CNG Compressed Ignition Transit Bus Exhaust
Pollutant
Uncontrolled
(95219)
Oxidation
Catalyst
(95220)
Elemental Carbon (EC)
9.25%
11.12%
Organic Carbon (OC)
36.99%
37.45%
Non-carbon Organic Matter (NCOM)
7.40%
7.49%
S04
0.64%
1.04%
aluminum
0.89%
0.89%
calcium
0.21%
0.44%
chromium
0.25%
0.25%
cobalt
0.39%
0.40%
iron
0.25%
0.25%
nickel
0.04%
0.00%
phosphorus
0.04%
0.15%
silicon
0.46%
0.59%
zinc
0.14%
0.20%
Unspeciated PM2 5
43.04%
39.74%
We used PM, EC, OC, and element emission rates for two repeat tests both with and without the
oxidation catalyst.88'89 CARB measured 13 elements by X-ray fluorescence but no ions (sulfate,
ammonium, or nitrate) were measured. The sulfate emissions were estimated by assuming that
all elemental sulfur is in the form of sulfate. This assumption is consistent with sulfate and
elemental sulfur measurements reported for natural gas combustion in the speciate database
(SPECIATE 91112). We assume that the missing ammonium and nitrate emissions are zero,
based on the negligible ammonium and nitrate measurements from modern spark-ignition CNG
buses equipped with three-way catalysts.90 Sodium and magnesium were the largest elements
measured (sodium was over 7 percent of the PM2.5 measured in the uncontrolled test), which is
likely due to known measurement artifact for XRF measurements of sodium and magnesium.
As such the sodium and magnesium emission rates are reported as zero.
The use of the oxidation catalyst reduced the PM2.5 emission rates from 28 mg/mile to 20.3
mg/mile on the CBD cycle (a 27.5 percent decrease). As shown in Table E-10, the composition
of the PM2.5 stayed fairly constant. The EC and OC fractions between the two control conditions
are not statistically different. Both profiles contain a large amount of unspeciated PM2.5
emissions. The source of the large unspeciated PM2.5 emissions is unknown but may be
attributed to the different sampling media for the total and speciated PM2.5 emissions, which is
amplified at the low PM2.5 concentrations measured from CNG exhaust. The absence of ion
measurements may also be a contributing factor.
s The CNG profile was developed for MOVES2014, where transit buses were the only source type that were run on
CNG fuels. In later versions of MOVES, CNG is modeled for other heavy-duty source types as documented in the
population and activity report.87
71
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The real-world variability in the PM2.5 composition is larger than the developed profiles suggest.
The OC/PM fraction for the 2001 Cummins Westport with oxidation catalyst was 61.9 percent,
which is much larger than that measured on the 2000 Detroit diesel engine. Lanni et al. (2003)86
reported that the OC/PM fraction on three CNG transit buses with DDC Series 50G engines
ranged from 29 percent to 74 percent of the PM2.5. The EC emissions measured by Lanni el al.
(2003)86 were below the detection limit, but the presented results compare well with the 2001
Cummins Westport measured by CARB (12.7 percent EC/PM). The sulfate fraction for the
oxidation catalyst presented in compares well with the sulfate fraction reported for the 2001
Cummins Westport by CARB89 (2.8 percent), and by Lanni et al. (2003)86 (1.5 percent to 2.4
percent).
72
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Appendix F PM10/PM2.5 Factors
The gasoline PM10/PM2.5 factor is based on measurements of 1991-1997 model year vehicles
tested by Norbeck et al. (1998).91 This ratio estimates that roughly 10 percent of the PM emitted
from gasoline vehicles is in the coarse range, which agrees with the size-distributions reported
from cascade impactor measurements on light-duty gasoline exhaust from Schauer et al.
(2008).92
The diesel PM10/PM2.5 factor is based on a 1985 EPA report93, which reports that 92 percent of
particulate mass is measured below a 2.5 |im cut-off. Although derived from measurements on
older technologies, the diesel PM10/PM2.5 ratio compares well with observations of the particle
size distribution of diesel exhaust by Kittelson et al. (1998)94, who states that the coarse mode
contains 5-20 percent of the total aerosol mass. Unfiltered crankcase emissions published by
Donaldson Company Inc. (2011)95 have similar reported mass distributions with ~ 93 to 97
percent of the cumulative mass particles smaller than 2.5 |im. In contrast, Tatli and Clark
(2008)96 report that the particle mass size distribution is significantly different from crankcase
and tailpipe diesel emissions for particles below 1 |im. Due to the limited information on
coarse-mode crankcase particulate emissions, we assume the same PM10/PM2.5 fraction for
diesel crankcase emissions.
Filtered diesel crankcase and exhaust emissions are expected to have smaller PM10/PM2.5 ratios,
due to the higher filter capture efficiency of coarse mode particles.95'97 However, the same
PM10/PM2.5 ratios are used for the later model year groups, due to limited coarse mode
particulate exhaust measurements, and limited information on the failure rates of these
technologies in real-world use.
No information was available on the PM10/PM2.5 ratios for CNG emissions, and the gasoline
ratio is used for CNG emissions. Table F-l contains the selected exhaust PM10/PM2.5 ratios used
in MOVES.
Table F-l PM10/PM2.5 Ratios for Primary Exhaust and Crankcase Emissions by Fuel Type
Fuel
PM10/PM2.5
Gasoline, E85, CNG
1.130
Diesel
1.087
73
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