ARB’s Study of Emissions from “Late-model” Diesel and CNG Heavy-duty Transit Buses:
Toxic Compounds and PM Emissions
Alberto Ayala, Norman Kado, Robert Okamoto, and Paul Rieger
Technical Collaborators:
Dr. B. Holmen (UCD), Dr. L. Zafonte, Dr. M. Gebel, H. Porter (CAVTC), K. Stiglitz (CAVTC), F. Gonzalez (CAVTC), P. Kuzmicky (UCD), Reiko Kobayashi (UCD), K. Sahay, G. Gatt, N. Verma,1 C. Maddox, Dr. B. Dharmawardhana, Dr. S. Paulson (UCLA)
Briefing # 2 Content
RESULTS: • Speciation of Gas-Phase Hydrocarbons • Carbonyl Compounds • Organic and Elemental Carbon and Elemental
Composition of PM • Phase distribution of PAH’s • Mutagenicity: Ames Bioassay Analysis • Emission Factors Summary Table
2
Project Update
• Majority of results already in …
• Remaining PAH results expected early ‘02 • Remaining bioassay results expected early ’02 • ELPI results expected Dec ‘01
3
Test Fleet “CNG”
“CNG re-test” “Diesel (OEM)”
“CRT”
Model 2000 DDC Series 50G
1998 DDC Series 50
1998 DDC Series 50
Aftertreatment None OEM Catalyzed
Muffler
CRT
Fuel CNG ECD-1 ECD-1 Odometer 19,629 15,169 15,569
Weight 33,150 lbs 30,510 30,510
• Los Angeles County Metropolitan Transit Authority fleet • 8.5 liter, 4-stroke, turbocharged, 4-cylinder, New Flyer Low 40
passenger transit buses
NOTE: CNG retest fuel sample below specification 4
Toxic Gas-Phase HC’s - Sampling Methodology
Target Analytes - 1,3-Butadiene - Benzene -Toluene -Ethylbenzene -m,p-xylene -o-xylene -Styrene
Tedlar Bag Collection On-site GC-FID’s
5
1,3 Butadiene Vehicle Emission (range of values for multiple tests denoted)
0
2
4
6
8
10
12
Vehi
cle
Emis
sion
(mg/
mile
)
CBD cycle (LOD ~ 0.6)
UDDS cycle (LOD ~ 0.4)
NYC cycle (LOD ~ 2.1)
SS test (LOD ~ 0.1)
CNG Diesel Diesel CNG vehicle OEM w/CRT re-test
Benzene Vehicle Emission (range of values for multiple tests denoted) Total BTEX Vehicle Emission
0
1
2
3
4
5
6
7
8
9
10
Vehi
cle
Emis
sion
(mg/
mile
)
CBD cycle (LOD ~ 0.6)
UDDS cycle (LOD ~ 0.4)
NYC cycle (LOD ~ 2.1)
SS test (LOD ~ 0.1)
CNG Diesel Diesel CNG
(range of values for multiple tests denoted)
0
2
4
6
8
10
12
14
16
18
Vehi
cle
Emis
sion
(mg/
mile
) CBD cycle (LOD ~ 0.6)
UDDS cycle (LOD ~ 0.4)
NYC cycle (LOD ~ 2.1)
SS test (LOD ~ 0.1)
CNG Diesel Diesel CNG
vehicle OEM w/CRT re-test vehicle OEM w/CRT re-test
6
Carbonyl Compounds
Sampling Methodology and Analysis
- Collection on DNPH cartridges - High-precision Liquid Chromatography Analysis
Target Analytes - Formaldehyde - Acetaldehyde - Acetone - Acrolein - Propionaldehyde -Crotonaldehyde - Methyl ethyl ketone - Methacrolein - Butyaldehyde - Benzaldehyde - Valeraldehyde - M-tolualdehyde - Hexanal
Aldehydes Bench
7
Carbonyl Emission for CBD Cycle (range of values for multiple tests denoted)
0
200
400
600
800
1000
1200
Vehi
cle
Emis
sion
(mg/
mile
) Formaldehyde
Acetaldehyde
Total Carbonyls
Carbonyl LOD ~ 0.9
Carbonyl Emission for SS tests CNG Diesel CNG (range of values for multiple tests denoted)
vehicle w/CRT re-test
Veh
icle
Em
issi
on (m
g/m
ile) 100
80
60
40
20
0
Formaldehyde
Acetaldehyde
Total Carbonyls
Carbonyl LOD ~ 0.1
CNG Diesel vehicle w/CRT
e e ein e e e in e de e al n ydn d yd yd d
Hexane
Aceto hy o yy l
Acrol
cro h eh heh htede e de e Kd ald d daal ral l l l
hyl
Crotona a uah
on nz
Valer
Mety
m-TolEt
But eip Blo
thyPr
Me
Additional Carbonyls for CBD Cycle
0
2
4
6
8
10
12
14
16
Vehi
cle
Emis
sion
(mg/
mile
)
CNG vehicle Diesel w/CRT CNG re-test
Carbonyl LOD ~ 0.1
9
EC/OC and Elemental Analysis
EC/OC Procedure • Quartz-Filter Collection of PM
• DRI/IMPROVE Optical/Thermal Analysis
Elemental Analysis • Teflon-Filter Collection of PM
• X-ray Fluorescence
Sampling Probes
Primary Dilution Tunnel
10
11
Average Composition of PM Average Fractions in CNG Exhaust
100%
80%
60%
40%
20%
0% TB IDLE SS CBD NYBC UDDS
EC/TPM OC/TPM Elements/TPM
• OC dominates CNG PM composition across all cycles
• Similar tunnel blank composition
Average Fractions in CNG retest Exhaust
0%
20%
40%
60%
80%
100%
TB SS CBD NYBC UDDS
EC/TPM OC/TPM Elements/TPM
NOTE: TPM=Total PM= EC+OC+Elements
12
Average Composition of PM (cont’d)
• EC/OC fraction in Diesel (OEM) PM shows strong cycle dependence
• OC dominates CRT PM composition across all cycles
Average Fractions in Diesel (OEM) Exhaust
0%
20%
40%
60%
80%
100%
TB IDLE SS NYBC UDDS CBD
EC/TPM OC/TPM Elements/TPM
Average Fractions in CRT Exhaust
0%
20%
40%
60%
80%
100%
TB IDLE SS CBD NYBC UDDS
EC/TPM OC/TPM Elements/TPM
NOTE: TPM=Total PM= EC+OC+Elements
• In general, emissions:
NOTE: Cumulative results per test sequence, not per cycle 13
EC/OC/Elements-Total Emissions
CNG
0
20
40
60
80
100
120
140
TB idle SS TB
CBD
CBD
CBD TB TB
NYBC
NYBC TB
UDDS TB
CBD
g/fil
ter
OC EC TC Elements
CNG retest
0
20
40
60
80
100
120
140
CBD
CBD TB TB
NVBC
NYBC TB TB
UDDS
UDDS
UDDS TB TB SS SS
g/fil
ter
OC EC TC Elements
Diesel (OEM)
0
50
100
150
200
250
300
350
400
TB
IDLE
IDLE SS SS
NYBC TB
UDDS
UDDS TB
CBD
CBD TB
g/fil
ter
OC EC
CRT
g/fil
ter
Diesel (OEM) > CNG > CRT TB ~ Idle < other cycles
TC Elements
0
10 20
30
40 50
60
70
80 90
100
CBD
CBD TB SS SS TB
NYBC
NYBC TB
UDDS IDLE TB
UDDS
UDDS TB
OC EC TC Elements
• EC/OC/Elements fractions show cycle dependence and variability
m
umum se
on n c ne l us n r e u no Tiu k Zifi
anga
ne
hosp
horr ci i ln or om cIc SuSiliNii alm l
ChC hrlu CA M P
Elemental Analysis Results Tunnel Blank
CNG
0
300
600
900
1200
1500
Aluminu
mCalc
ium
Chlorin
e Chro
mium
Coppe
r Cob
alt
Nickel
Manga
nese
Iron
Phos
phoru
s Po
tassiu
mSilic
on
Sulfur
Zinc
ng/fi
lter
TB3(UDDSX2) SS(UDDSX2) CBDX2 CBDX2 CDBX2 CBDX4 TB1(CBDX2) TB2(CBDX2)
CNGS Ca Cu Fe K Al
• Ca, Cl, P, Zn, S are oil components • Fe from engine wear • Si source unknown • Si emissions: Diesel (OEM) >> CNG ~ CRT • In general, TB << SS and CBD
NOTE: Cumulative results per test sequence, not per cycle
14
Diesel (OEM)
8000
9000
SS(UDDSX1) SS(UDDSX1) TB1(UDDSX1) CBDX2 CBDX2 TB(CBDX2)
Diesel (OEM)
Al Si Zn Fe
CNG retest
0
300
600
900
1200
1500
Aluminu
m Calc
ium
Chromium
Chlo
rine
Cobalt
Iron
Phos
phoru
s
Silicon
Sulfur Zinc
ng/fi
lter
SS1 SS2 CBDX4 CBDX4 TB(CDBX4) TB(CBDX4)
CNG retest
S
CRT
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
Aluminu
m
Chlorin
e
Iron
Silicon
Sulfur Zinc
ng/fi
lter
SS1(UDDSX4)
SS2(UDDSX4)
TB1(UDDSX2)
CBDX8
CBDX8
CRT
Si
7000
6000
5000
4000
3000
2000
1000
0
ng/fi
lter
Polycyclic Aromatic Hydrocarbons
Particle Associated OEHHA Unit risk for PAH's cancer by inhalation
per million (ug/m3)E-1
Benz[a]anthracene Chrysene 11
Benzo[b]fluoranthene 110 Benzo[k]fluoranthene 110
Benzo[a]pyrene 1100 Dibenz[ah]anthracene 1200
Expected PAH phase distribution in ambient and CARB diesel exhaust samples
TARG ET PAHS
Partic le Assciated PAHs Benzo[ghi]perylene D ibenz[ah]anthracene Indeno[1,2,3-cd]pryene Perylene Benzo[a]pyrene Benzo[e]pyrene Benzo[k]fluoranthene Benzo[b]fluoranthene Chrysene Benz[a]Anthracene
Sem i-Volatile PAHs Pyrene Fluoranthene M ethyl Phenanthrene Anthracene Phenanthrene Fluorene
Volatile PAHs Dim ethyl naphthalene Acenaphthene Acenaphthylene D im ethyl naphthalene B iphenyl 1-m ethyl naphthalene 2-m ethyl naphthalene Naphthalene
FILTER
PUF
XA D
15
PAH ANALYSIS
GC/MS PUF
GC/MS FIL
FIL PUF XAD
BIOASSAY SAMPLES RANGE FINDING
GC/MS AN
POOL & CON
GC/MS AN
EXTRACT DCM
GC/MS AN
POOL
EXTRACT TOLUENE ECD-WO
FILTER IS
GC/MS AN
EXTRACT ACETONE
PUF IS
GC/MS AN
EXTRACT DCM
XAD IS
PAH SAMPLES
16
*All results not corrected for tunnel blanks and XAD values corrected for background contamination
Partic le As s o c iated PAHs -CBD and S S Cyc les *
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
B(a)
A
Chry
B(b)
F
B(k)
F
B(e)
P
B(a)
P
Per
In(1
,2,3
-cd
)P
DiB(
a ,h)
A
B(g,
h,i)P
ug/m
ile
FILTER CNG-CBD FIL CNG-S S FILTER D OEM-CBD FIL D OEM-S S FILTER D W/CRT-CBD FIL D W/CRT-S S FILTER CNG RT-CBD
Filter and PUF PAHs -CBD and S S Cyc le s *
0.0
5.0
10.0
15.0
20.0
25.0
Phen
1-M
e-Ph
en
Fuor
an Pyr
ug/m
ileCNG-CBD TOTAL CNG-S S F+P D OEM-CBD F+P D OEM-S S F+P D W/CRT-CBD F+P ECD-WT D W/CRT CNG-RT-CBD F+P
PUF and XAD PAHs -CBD and S S Cyc le s *
0.0
100.0
200.0
300.0
400.0
500.0
600.0
Na p
(T)
2-M
e-N
ap
1-M
e-N
ap
ug/ m
ile
CNG-CBD PUF+XAD CNG-SS PUF+XAD D OEM-CBD PUF+XAD D OEM-SS PUF+XAD
D w /CRT-CBD PUF+XAD D w /CRT-SS PUF+XAD CNG R-CBD PUR+XAD
17
P AH
PAH
PAH
18
•CBD and SS Results PAHs in PM –Diesel (OEM)-Most PAHs Detected –CNG CBD - Most PAHs m.w. 252 Not Detected except for BaP –CNG SS- All PAHs m.w. 252 Not Detected –CRT- CBD and SS Only Benz[a]anthrancene and Chrysene Detected
•CBD and SS Semi-volatile PAHs –Diesel (OEM) Generally the Highest Levels –CNG Similar Levels to Diesel OEM –CRT Lowest Levels
•CBD and SS Volatile PAHs –At Similar Levels
•Fluoranthene and Pyrene Phase Distribution –CBD Diesel(OEM)-Primarily in Filter –SS Distributed more evenly between the Filter and PUF –CRT and CNG-Primarily in PUF
P ha s e Dis tributio n o f F lo ura nthe ne a nd P yrene in S S
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
Phen
1-M
e-Ph
en
P AH CNG FIL CNG P UF D OEM FIL D OEM P UF D w/CRT FIL D w/CRT P UF
Phas e Dis tribution o f Fluo ranthe ne and Pyre ne in CBD
0.0
2.0
4.0
6.0
8.0
10.0
12.0
14.0
Fuo
r an
Py
r
P AH
CN G FILTER CNG PUF D OEM FILTER D OEMPUF D w/ CRT FILTER D w/ CRT PUF CNG RT FILTER CNG RT PUF
Bioassay Analysis
Procedure • Collection of PM on Filter
• Collection of vapor-phase on PUF
• Solvent Extraction
•Salmonella/Microsuspension procedure
• TA98 and TA 100 Tester Strains with and w/o +S9 Metabolic Enzymes
192-stage Sampler
CVS Tunnel
ECD CNG.2 ECD
ECD CNG.2 ECD
Mutagenicity Results
CBD Emissions
0 2 4 6 8
10 12 14
CNG.1 CRT
Vehicle Type
Mut
agen
Em
issi
ons
(TA
98 R
ev/m
ile) x
105
(+S9)
(-S9)
Steady State Emissions
0 1 2 3 4 5 6 7
CNG CRT
Vehicle Type
Mut
agen
Em
issi
ons
(TA
98 R
ev/m
ile) x
105
(+S9)
(-S9)
CNG retest
Diesel (OEM)
Diesel (OEM)
CBD Specific Acivity (-S9)
0
20
40
60
80
100
CNG.1 CRT
Vehicle Type
Spec
ific
Mut
agen
icA
ctiv
ity (R
ev/u
g)
Sample
TBlank
Steady State Specific Activity (-S9)
0
20
40
60
80
100
CNG CRT
Vehicle Type
Spec
ific
Mut
agen
icA
ctiv
ity (
Rev/
ug)
Sample
TBlank
Diesel (OEM)
Diesel (OEM)
CNG retest
20
Emission Factor Summary CBD
CNG emission
rate mg/mi
CRT emission
rate mg/mi
Diesel(OEM) emission
rate mg/mi
OEHHA Unit risk for cancer by inhalation
per million (ug/m3)E-1
Total PM Butadiene Benzene
Formaldehyde Acetaldehyde
40.0 3.5 3.2
780.0 90.0
14.0 0.0 0.6 0.0 0.0
119.0 0.0 1.6 ** **
300* 170 29 6
2.7
110
Total PAH's heavy
semi-vol volatile
0.58 0.0004
0.04 0.54
0.78 0.0001
0.02 0.77
0.80 0.0038
0.05 0.75
B[a]a 9.0E-05 4.0E-05 2.7E-04 Chr 2.3E-04 5.0E-05 3.7E-04 11 B[b]f 0 0 4.1E-04 110 B[k]f 0 0 2.0E-04 110 B[a]p *** *** 4.5E-04 1100
Dib[ah]a 0 0 3.5E-04 1200 Spec.Mut. Activity****
((TA98 Rev/mi)X10E5) 9.6/6 1/2.5 2/1.2
* For diesel total PM only from ARB TAC document ** Data not available *** Emission factor under development ****CBD/Steady State
21
Challenges
• Test Low-emission Technologies: CNG and CRT – Current methodologies needed improvement or required modification
• Emissions Testing – Large Test Matrix – Extremely low levels of PM requiring large number of samples to be
collected – Interferences from the Tunnel Background
• Analytical – Low levels of PM and gaseous emissions require lower detection limits
• Logistics – Short Turn-Around Time – Limited Resources
22
Meeting the Challenge
• Developed ARB in-house Expertise • Modified existing sample collection and analysis
methods: – For PAH’s, 1) concentrated samples, 2) required
different solvent to extract samples, and 3) developed a faster method to extract XAD
• Required Pooling of Samples to Obtain sufficient Sample for analysis
23
What Was Learned From This Study?
• Not Routine…Research Effort • Tunnel Background Interferences
– To evaluate accurately low-emission technologies will require new sampling methodologies including different types of dilution tunnels to address tunnel background interferences
• Changes to Sampling Methodology – Need samplers that can collect greater PM mass – Apply what was learned from this study to improve on future
studies
• Analytical Techniques – Methodology for particle number/size characterization is needed – For PAH’s, may need to develop additional clean-up procedures to
eliminate interferences – For PAH’s, automate sample preparation – Develop techniques that lower the Method Detection Limit
24
Final Remarks
Toxic Hydrocarbons and Carbonyl Compounds
• Butadiene was only detected in CNG vehicle exhaust (with 1 exception: Diesel without trap idle test).
• Generally, BTEX concentrations in CVS exhaust samples were close to ambient levels
• Generally, BTEX emission follows the order: CNG > Diesel (OEM) > CRT
• Carbonyl emissions from CNG vehicle were much higher than from CRT-equipped vehicle
• Total carbonyl emissions (by mass) from CNG vehicles are two orders of magnitude higher than BTEX and 1,3 Butadiene emissions
• CNG vehicle carbonyl emissions are dominated (>80%) by formaldehyde
25
Final Remarks (cont’d) Composition of PM • OC dominates CNG PM composition across all cycles • Similar tunnel blank composition • EC/OC fraction in Diesel (EOM) PM shows strong cycle dependence • OC dominates CRT PM composition across all cycles • EC/OC/Elements fractions show cycle dependence and variability • Emission of EC/OC/Elements: Diesel (OEM) > CNG > CRT • Ca, Cl, P, Zn, S are oil components • Fe from engine wear • Si source unknown • Si emissions: Diesel (OEM) >> CNG ~ CRT
26
Final Remarks (cont’d)
PAH’s and Bioassay • Emission rates (ug/mi) for most PAH’s were higher in the CBD than SS • Emission rates for CNG retest were generally higher than CNG • Differences were observed in the properties of PM from CNG, Diesel
(OEM), and CRT • New substrate is needed to replace XAD because of backgrounds of some
PAH’s approach the low PAH levels in tunnel blank and samples • CRT PAH levels are similar levels to TB’s • Generally, CNG and Diesel (OEM) are higher than TB’s • Emissions of mutagenic compounds showed cycle dependence • For CBD, bioassay follows: CNG > Diesel (OEM) > CRT • For SS, bioassay follows: CNG > CRT > Diesel (OEM)
27
“Bottom Line” and Next Step • Thus far, the cumulative results in this study suggest that the “adverse” impact from emissions follows:
Total PM Mass: Diesel(OEM)>CNG>CRT
Secondary PM: CRT>Diesel (OEM)> CNG
Particle Size/Counts: CNG>Diesel(OEM)>CRT ?Toxicity/Mutagenicity: CNG>CRT~Diesel(OEM)
• Results show cycle dependence
• PM is not PM and is not PM !
What is next?
• SCAQMD Briefing
• Finish data analysis and subject it to peer review
• Report back once publications accepted 28
IDEAS FOR FOLLOW-UP STUDY: Investigation of Toxics from Interim and “2007” Heavy-Duty
Emission Controls
Scope Cuts Across Applications:
• Baseline
• CRT and SCRT on bus or truck (in-house)
• DPX and DPX/EGR on bus or truck (in-house)
• SCR/DPF engine tests (piggy back on current work: DOE or EPA)
• NOx Adsorber/DPF engine tests (piggy back on current work: DOE or EPA)
• CNG/Catalyst, “Advanced” CNG, CNG/H2, or CNG/Trap?? bus (in-house)
• Other? (i.e., fuel-borne cat, active PM trap)
Approach:
• Duplicate samples, one fuel, one oil, one or two duty cycles 29
FOLLOW-UP STUDY (cont’d)
Emissions of Concern:
• DPF Ash
• Regulated Emissions
• Elements
• Toxic VOC’s and Carbonyls
• PAH’s and Nitro-PAH’s
• Bioassay Analysis
• Characterization of Particle Number and Size
• Dioxins
• Other? (HONO, N2O, etc.)
Participants:
• Lead Team: RD, SSD, MSCD
• In-house Testing: RD, MSCD
• Analysis: UCD, MLD, NREL, EPA, Private Lab
• Data Reduction: RD, SSD, MSCD
30