Particulate matter speciation profiles for light-duty gasoline vehicles in the United States

Figures & data

Table 1. PM_2.5 species included in CMAQv5.0 (Aerosol Module 6), CMAQv4.7.1 (Aerosol Module 5), and CAMx5.4

PM2.5 species	CMAQv5.0 species name	Required in CMAQv4.7.1	Required in CAMx5.4
Primary organic carbon	POC	x	x
Elemental carbon	PEC	x	x
Sulfate	PSO4	x	x
Nitrate	PNO3	x	x
Ammonium	PNH4	x	x
Noncarbon organic matter	PNCOM		x
Iron	PFE
Aluminum	PAL
Silica	PSI
Titanium	PTI
Calcium	PCA
Magnesium	PMG
Potassium	PK
Manganese	PMN
Sodium	PNA		x
Chloride	PCL		x
Water	PH2O		x
Primary unspeciated PM2.5	PMOTHR	x	x

Note: Sources: Simon (2012) and CAMx (2011).

Table 2. Vehicle sample size in the Kansas City Light Duty Vehicle Emissions Study

Vehicle type ^a	Strata	Model year group	Percent of KC LDGV vehicle population ^a	Percent of KC LDGV vehicle miles traveled (VMT)^b		Summer round sample		Winter round sample
						Full sample	Speciation subset	Full sample	Speciation subset
Truck	1	Pre-1981	1.1%	0.6%		2	2	10	3
	2	1981–1990	3.7%	2.4%		21	4	33	3
	3	1991–1995	7.2%	6.5%		18	6	33	7
	4	1996–2005	28.6%	34.2%		39	8	59	11
Car	5	Pre-1981	1.3%	0.7%		6	5	17	3
	6	1981–1890	7.4%	4.6%		49	4	40	5
	7	91–1995	13.4%	11.2%		39	6	44	9
	8	1996–2005	37.3%	39.8%		87	14	41	9
		Sum =	100%	100%		261	49	277	50

Notes: ^aThe definition for car and truck, and the population percentages, are estimated from the 2004 Kansas City Travel Behavior Survey (U.S. EPA, 2008): Passenger cars are defined as coups, sedans, and wagons, trucks are defined as minivans, sport-utility vehicles, and pickups.

^bThe VMT contribution by strata is calculated based on the population percentages combined with annual VMT by vehicle age estimated from the 2001 National Household Travel Survey (NHTSA, 2006).

Table 3. Levels of PM characterization conducted on vehicles tested in Kansas City

	Level 1: Full sample	Level 2: Speciation subsample	Level 3: Speciation composites
Vehicles	496 vehicles	98 vehicles	98 vehicles (same as Level 2)
Measurements	<555 vehicle tests × 3 bags	102 vehicle tests × 3 bags	52 composite samples
Individual vehicle tests	Yes	Yes	Individual vehicle samples for pre-1990 model years vehicles;
			sample composites of one to five vehicles for 1990 and newer model years vehicles
Phase (Bag)-specific measurements?	Yes	Yes	No (composite average of 3-bag LA-92)
Measurements	Gravimetric mass (Teflon filters), CO2, CO, HC, NOx; BC (photoacoustic analyzer); indirect continuous PM (DustTrak, DataRam, quartz crystal microbalance)	Elemental carbon, organic carbon (TOR-IMPROVE, Quartz filters); 49 elements (XRF, Teflon filters)	Sulfate and nitrate (ion chromatography from the sample extracted from the quartz filters). Seven elements (ICP/MS from the sample extracted from the Teflon filters); 293 particle-phase and semivolatile organic species (separate sample train GC/MS, TIGF/XAD).

Table 4. Significance test results of species measurements from the KCVES program

Type I error	Measurements observed above the measurement uncertainty	Species
3.0E-15	52	PM mass, EC, OC Ca, Fe, S, Zn, SO4 Cr-ICP, Mn-ICP, Zn-ICP Pb-ICP
3.0E-15	51	Si
3.0E-15	50	Cu-ICP
3.0E-15	48	Cu
3.0E-15	47	P
3.0E-15	39	Cr
3.0E-15	35	Cl	 ← Significant →
4.3E-15	33	Ni, Pb
1.6E-14	32	Br
2.0E-09	26	K
5.2E-06	21	Al, NO3
7.1E-05	19	Na
0.0021	16	As-ICP
0.0054	15	Mo
0.013	14	Mn
0.059	12	Ti
0.31	9	Mg, Zr, Hg-ICP
0.74	6	Ba	← Insignif cant →
0.85	5	Ga
0.93	4	Sr
0.97	3	Sn, Tl
0.99	2	V, As, Rb, Pd, Ag, Hg
1.00	1	Se, Y, Sb, La, Au, U
1.00	0	Co, Cd, In

Note: Elements measurements are made from XRF (x-ray fluorescence) unless noted by ICP-MS (inductively coupled plasma–mass spectrometry).

Figure 1. Comparison of mass-balanced corrected organic matter emission rates with measured organic carbon emission rates.

Figure 2. Average reconstructed PM_2.5 composition of cold start emissions.

Table 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	Na2O			1.35
Mg	Mg			1.0
Al	Al2O3			1.89
Si	SiO2			2.14
P	PO4			3.07
Cl	Cl			1.0
K	K20			1.20
Ca	Ca			1.0
Ti	TiO2			1.67
Cr	Cr2O3	CrO3		1.69
Mn	MnO	MnO2	Mn2O7	1.63
Fe	FeO	Fe2O3		1.36
Ni	NiO			1.27
Cu	CuO			1.25
Zn	Zn			1.0
Br	Br			1.0
Mo	MoO2	MoO3		1.42
Pb	PbO	PbO2		1.12

Figure 3. Average PM_2.5 fraction of each measured species for cold start emissions by model-year group, accompanying 95% confidence intervals.

Table 6. Mass-balance OM compared to measured OC

Bag	Model group	n	Ratio of mass-balance OM to measured OC	Standard error	Lower 95% confidence interval	Upper 95% confidence interval
Bag 1	Pre-1981	14	1.16	0.04	1.07	1.26
	1981–1990	17	1.25	0.06	1.13	1.37
	1991–1995	27	1.17	0.08	1.01	1.34
	1996–2005	37	1.09	0.09	0.90	1.27
Bag 2	Pre-1981	14	1.05	0.15	0.74	1.37
	1981–1990	15	1.14	0.07	1.00	1.28
	1991–1995	28	1.22	0.09	1.03	1.40
	1996–2005	42	1.20	0.08	1.03	1.37
Bag 3	Pre-1981	12	0.98	0.29	0.35	1.61
	1981–1990	14	1.16	0.09	0.97	1.36
	1991–1995	22	0.60	0.12	0.36	0.84
	1996–2005	27	0.73	0.14	0.44	1.01

Figure 4. Average reconstructed PM_2.5 composition of Bag 2 emissions.

Figure 5. Average PM_2.5 fraction of each measured species for hot stabilized running emissions by model-year group, accompanying 95% confidence intervals.

Table 7. PM_2.5 profile for cold start and hot stabilized running emissions, with weighted average using vehicle miles traveled (VMT)

	Start				Running				Measurement/source
PM species	n	Mean ratio ± 95% CI			n	Mean ratio ± 95% CI
Elemental carbon (EC)	484	443.69	±	42.96	531	140.00	±	26.79	BC measured by photoacoustic analyzer. Used to represent CMAQ5.0 EC.
Organic carbon (OC)	66	426.39	±	66.33	99	557.00	±	40.18	5/6 of organic matter, calculated by mass balance of each sample
Noncarbon organic matter (NCOM)	66	85.28	±	13.27	99	111.40	±	8.04	1/6 of organic matter
SO4	66	9.45	±	2.43	99	71.87	±	19.03	Ion chromatography
NO3	66	2.63	±	0.82	99	2.89	±	0.78	Composite measurements allocated to bag by mass fraction
NH4	66	4.31	±	1.02	99	27.79	±	7.25	Imputed assuming ammonium sulfate and ammonium nitrate
Fe	66	3.07	±	2.14	99	18.28	±	5.26	XRF
Al			±		99	3.24	±	0.98	XRF
Si			±		99	3.24	±	0.98	Imputed from Al based on Schauer et al. (2002)
Ti			±		99	0.34	±	0.14	XRF
Ca	66	3.88	±	1.43	99	14.43	±	2.58	XRF
Mg	66	0.19	±	0.18	99	1.45	±	0.25	Imputed from ratio to Zn based on Schauer et al. (2006)
K			±		99	0.85	±	0.26	XRF
Mn			±		99	0.24	±	0.15	XRF/ICP (composite ICP measurements allocated to bag with XRF)
Na	66	0.05	±	0.05	99	0.39	±	0.07	Imputed from ratio to Zn based on Schauer et al. (2006)
Cl	66	0.21	±	0.12	98	1.04	±	0.42	XRF
P	66	1.51	±	0.51	99	4.34	±	0.79	XRF
Cr	66	0.20	±	0.11	99	0.73	±	0.20	XRF
Ni	66	0.08	±	0.05	99	0.27	±	0.11	XRF
Cu			±		99	0.96	±	0.24	XRF
Zn	66	0.78	±	0.72	99	5.93	±	1.02	XRF
Br			±		99	0.22	±	0.08	XRF
Mo			±		99	0.21	±	0.06	XRF
Pb	66	0.26	±	0.11	99	0.48	±	0.14	XRF
Metal-bound oxygen (MBO)	66	4.06	±	2.33	99	26.80	±	5.20	Assumed metal oxide states
KCVES unspeciated	66	13.95	±	18.22	99	5.63	±	6.77	Remainder
CMAQ5.0 AE6 unspeciated (PMOTHR)	66	20.85	±	17.54	99	45.57	±	10.96	Remainder + elements not included by AE6 CMAQ5.0

Note: Ratio values are in mass per total PM_2.5 (mg/g).

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