contribution of soa to ambient pm2.5 organic carbon in ... for the study • find tracer compounds...
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Tadeusz E. Kleindienst 1, Edward O. Edney 1, Michael Lewandowski 1,John H. Offenberg 1, and Mohammed Jaoui 2
1 National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina USA
2 Alion Science and Technology, Research Triangle Park, North Carolina USA
Contribution of SOA to Ambient PM2.5 Organic Carbon in Eastern United States Locations
MANE-VU/Midwest RPO Regional Haze Science MeetingBaltimore, Maryland
July 10, 2007
Background• Condensable material formed from gas-phase reactions of
hydrocarbons produce secondary organic aerosol (SOA) that comprises part of the organic carbon (OC) in PM2.5.
• SOA typically contains organic compounds more highly polar than those from primary emissions and can be semivolatile or nonvolatile.
• Recent data indicates SOA can be a significant summer component of PM2.5 in the eastern U.S.
• Laboratory experiments indicate that organic products in field samples can be associated with specific hydrocarbon precursors (Edney et al. Atmos. Environ., 2003).
• Organic tracer technique for SOA has recently been described (Kleindienst et al., Atmos. Environ., in press)
Other Approaches for Evaluating Ambient SOA(SOA/OC)
● Deficit in chemical mass balance between measured OC and primary organic aerosol (POA) from CMB analysis
(Schauer et al., 2002; Zheng et al., 2002)
● Contribution of SOA to PM2.5 from OC/EC ratio(Turpin and Huntzicker 1995)
● Relative contributions of anthropogenic and biogenic HCs to SOA based on a combined 14C and source-receptor method
(e.g. Lewis et al., 2004)
Simplified View of Ambient Primary and Secondary Carbon
Organic Aerosol Component of PM
PrimarySources
SecondarySources
Distribution of Source Contributions Changes with Season
General Description of SOA from Individual Source
Tracercompounds
Polar multifunctional oxygenates that may include oligomers and other high
molecular-weight compounds
SOA component from α-pinene reactions with OH, O3, NO3 followed
by secondary and higher order aerosol-forming processes
α-P SOA
Objectives for the Study• Find tracer compounds representative of the major SOA precursors from laboratory studies.
Identify tracer compounds found both in the laboratory and field.Estimate the mass fraction of tracers to the formed SOAFocus on isoprene, α-pinene, β-caryophyllene, toluene
• Determine major sources of SOA in PM2.5 in RTP, NC, Detroit, MI, and other locations using the tracer compounds.
• What fraction of the OC represented by SOC.
• Compare biogenic vs. anthropogenic contribution.
• Examine seasonal dependencies.
• Compare differences in location using the same analysis.
NERL Dynamic Photochemical Reaction Simulator
Volume = 14.5 m3
40 L min-1 (τ = 6 h)
Ozone, SO2 and NO/NOx
Analyzers
Scanning Mobility Particle Sizer
(SMPS)
Hygrometer
Inlet Manifold
Gas Chromatography -Flame Ionization
Detector (GC-FID)Other Sampling
Gas Phase Carbonyl Product Measurements
Chemical Composition
LC-ESI ESIMALDIIC
Inorganic
Mass Measurement
Gravimetric Mass
Experimental System for Laboratory Studies
• Experiments conducted in a dynamic mode to operate at relatively low reactant concentrations and to collect sufficient aerosol for analysis.
• Analyze tracer compounds by GC/ITMS and OA and OC by standard methods.
Organic
GC-MS
SemicontinuousOrganic Carbon
MeasurementFilter Sampling
Devices forChamber Aerosol
SOCMsmt
SOAMsmt
Reactive Systems Contributing to SOA Studied Here
Isoprene PhotooxidationRole of acid catalysis (H2SO4 acidic seed; in presence of SO2)
α-Pinene OxidationPhotooxidationOzone reactionRole of acid catalysis
Toluene Photooxidation
β-Caryophyllene OxidationPhotooxidationOzone reaction
Tracer Compounds for the Source Categories
Isoprene SOA Tracers2-Methylglyceric acid
2-Methylerythritol
2-Methylthreitol
Toluene SOA Tracer2,3-Dihydroxy-4-oxopentanoic acid
β-Caryophyllene SOA Tracerβ-Caryophyllinic acid (C14H22O4)
α-Pinene SOA TracersPinic acid
Pinonic acid
3-Acetyl pentanedioic acid
3-Acetyl hexanedioic acid
3-(2-Hydroxyethyl)-2,2-dimethylcyclo-butane carboxylic acid
3-Hydroxyglutaric acid
2-Hydroxy-4-isopropyladipic acid
3-Hydroxy-4,4-dimethylglutaric acid
Structures for Selected Tracer Compounds
A–3
OOH
O
HOPinicacid
OHHO
O O OA–2
H O
O O
O H
OA–4
A–5
A–6
I–1
I–2
I–3
C–1
Pinonicacid
α-Pinene tracers
Isoprene tracers
Toluene tracer
β-Caryophyllene tracer
T–3
Laboratory Data for Mass Fractions(e.g., α-pinene photooxidation; OM/OCα-p = 1.37 ± 0.15)
Experiment ID [hco] (ppmC)
[NOX,o](ppm)
[SOA](μg m-3)
Σ [tri](μg m-3) f soa
α-p – 1 2.18 0.186 111.6 10.3 0.092
α-p – 2 4.18 0.450 74.2 11.9 0.160
α-p – 3 4.18 0.450 86.7 12.9 0.148
α-p – 4 2.19 0.272 72.0 5.8 0.081
α-p – 5 2.19 0.250 101.3 31 0.306
α-p – 6 3.13 0.317 128.0 16.7 0.130
α-p – 7 4.95 0.494 333.8 79.3 0.237
α-p – 8 5.27 0.490 298.3 39.4 0.132
α-p – 9 5.27 0.490 271.0 49.1 0.181
α-p – 10 2.43 0.307 80.9 29.8 0.368
α-p – 11 2.28 0.307 269.0 30.6 0.114
α-p – 12 2.32 0.279 65.4 10.3 0.157
α-p – 13 3.97 0.279 165.0 18.9 0.115
α-p – 14 1.04 0.409 9.7 0.99 0.102
α-p – 15 2.20 0.420 102 19.7 0.193
average f soa, α-p 0.168 ± 0.081
average f soc, α-p 0.231 ± 0.111
Research Triangle Park, NC* Summer 2000, 2001
Baltimore, MD* Summer 2001
Philadelphia, PA (NEOPS)* Summer 2001
New York, NY* Summer 2001
Tampa, FL (BRACE) Summer 2002
Research Triangle Park, NC Entire Year 2003
Detroit, MI (DEARS) Summer 2004, 2005
Detroit, MI (DEARS) Winter
PM2.5 Field Measurements
* Qualitative measurements with double derivative, PFBHA/BSTFA
Example of Tracer Compounds from TIC(Detroit, MI, 24 Aug 2004; OC = 3.72 μg m-3)
Sum of Tracer Concentrations as KPAI : Isoprene: 168 ng m-3
A: α-Pinene: 153 ng m-3
B: β-Caryophyllene: 6.8 ng m-3
T : Toluene: 4.4 ng m-3
• Laboratory measurementsIrradiated single component hydrocarbon/NOX mixtures; repeat for other conditionsIdentify tracer compounds and determine concentrations as ketopinic acid Calculate the mass fraction of the tracer compounds to the measured SOC
• Apply to field measurementsMeasure SOC tracers in ambient PM2.5
Apply the mass fraction factor to get the SOC for each precursor typeCompare SOC contributions to the measured OC
• Assumptions and uncertaintiesAssume mass fraction of the tracers is the same in the field as in the laboratory.Other possible of sources of the tracer compounds currently not knownStandard deviation of the mass fraction measurements were on average 35%Extrapolations from single hydrocarbon contributions to compound classes.
• Measurement of ambient OC and the precursor contribution to OC are independent quantities.
Method for Estimating SOC Source Contributions
Contribution of Isoprene SOC to Ambient OC(Using 2-methylglyceric acid and two 2-methyl tetrols; 2003 - RTP, NC USA)
0
1
2
3
4
5
6
7
812 20 27 27 31 41 45 48 55 69 83 90 10
5
118
132
153
160
174
176
209
216
230
237
239
245
253
262
265
279
293
304
321
324
342
363
Julian Date - 2003
ugC
m-3
OCisoprene
Winter Spring Summer Fall
Contribution of Monoterpene SOC to Ambient OC(Nine tracers for α-pinene; 2003 - RTP, NC USA)
0
1
2
3
4
5
6
7
812 20 27 27 31 41 45 48 55 69 83 90 10
5
118
132
153
160
174
176
209
216
230
237
239
245
253
262
265
279
293
304
321
324
342
363
Julian Date - 2003
ugC
m-3
OCa-pinene
Winter Spring Summer Fall
Contribution of Sesquiterpene SOC to Ambient OC(Tracer using β-caryophyllinic acid; 2003 - RTP, NC USA)
0
1
2
3
4
5
6
7
8
12 20 27 27 31 41 45 48 55 69 83 90 105
118
132
153
160
174
176
209
216
230
237
239
245
253
262
265
279
293
304
321
324
342
363
Julian Date - 2003
ugC
m-3
OCb-caryophyllene
Winter Spring Summer Fall
Contribution of Aromatic SOC to Ambient OC(Tracer using 2,3-dihydroxy-4-oxopentanoic acid; 2003 - RTP, NC USA)
0
1
2
3
4
5
6
7
8
12 20 27 27 31 41 45 48 55 69 83 90 105
118
132
153
160
174
176
209
216
230
237
239
245
253
262
265
279
293
304
321
324
342
363
Julian Date - 2003
ugC
m-3
OCtoluene
Winter Spring Summer Fall
0
1
2
3
4
5
6
7
812 20 27 27 31 41 45 48 55 69 83 90 105
118
132
153
160
174
176
209
216
230
237
239
245
253
262
265
279
293
304
321
324
342
363
Julian Date 2003
ug C
m-3
othertolueneb-caryophylleneisoprenea-pinene
SOC Contributions to Ambient OC(2003 – Research Triangle Park, NC)
Winter Spring Summer Fall
Bimonthly Contribution of SOC to Ambient OC(2003 Research Triangle Park, NC)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
Jan-Feb March-April May-June July-August Sept-Oct Nov-Dec
OC
Con
tribu
tions
(ug/
m3)
Isoprene a-Pinene b-Caryophyllene Toluene Other OC
0.21
0.36
0.44
estimated fraction SOC0.68
0.41
0.28
Other OC = OC - Isoprene SOA - Aromatic SOA - Monoterpene SOA - Sesquiterpene SOA
Other OC includes biomass comb, gasoline exhaust, diesel emissions and meat cooking operations
SOC Contributions to Ambient OC(DEARS Ambassador Bridge Site, Detroit, MI, 11 Aug – 1 Sep 2004)
0.0
1.0
2.0
3.0
4.0
5.0
6.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Sample
Org
anic
Car
bon
(ugC
/m3)
Isoprene a-pinene b-Caryophyllene Toluene Other
Avg SOC mass: 1.55 μgC m-3
Avg fraction SOC: 0.474Anthrop SOC/Total SOC: 0.13
Summary of Key Points
• Secondary organic aerosol from isoprene, monoterpenes, sesquiterpenes, and aromatics contributes substantially to organic carbon in PM2.5 in the eastern U.S. mainly during the summer. Other U.S. areas under study.
• Aromatic contribution higher than typically predicated in air quality models.
• Organic carbon in PM2.5 was found to range from 2 – 5 μgC m-3 throughout the year with primary sources dominating in the winter and SOC dominating during the summer. Primary and secondary contributions can be offsetting leading to minor seasonal trends.
• Estimates of SOC contribution from biogenic HC precursors found to be substantially greater than anthropogenic HC precursors in the eastern U.S.
• Results consistent with SOC contributions to the organic carbon measured in laboratory mixtures and with 14C data measured in laboratory experiments and from 14C in field studies.
Next Steps• Conduct studies combining both CMB analysis for primary compounds
and mass fractions for secondary compounds to see the degree of consistency between SOA and “other OC” from the CMB analysis.
• Look at alternative double derivative technique to improve sensitivity of tracers from aromatic hydrocarbons.
• Use information from laboratory and field studies to provide basis for an improved SOA module for CMAQ.
• Determine tracers compounds from other classes of possible SOA producing hydrocarbons, such as, high MW alkanes, etc.
• Determine tracer compounds from additional high volume aromatic hydrocarbons (e.g., m-xylene, 1,2,4-TMB) and sesquiterpenes (e.g., α-humulene, α-farnesene).
• Examine SOA production from complex mixtures.
• Further study role of acid-catalysis on SOA formation and possible tracer compounds produced.
Bibliography• Edney et al., 2003, Polar organic oxygenates in PM2.5 at a southeastern site in the United States, Atmos. Environ. 37,
3947-3965.
• Kleindienst et al., 2004, Determination of secondary organic aerosol products from the photooxidation of toluene and their implications in PM2.5. J. Atmos. Chem. 47, 79-100.
• Jaoui et al, 2004, Identification and quantification of aerosol polar oxygenated compounds bearing carboxylic or hydroxyl groups. 1. Method development. Analyt. Chem. 76, 4765-4778.
• Jaoui et al., 2005, Identification and quantification of aerosol polar oxygenated compounds bearing carboxylic or hydroxyl groups. 2. Organic tracer compounds from monoterpenes, Environ. Sci. Tech. 39, 5661-5673.
• Edney et al., 2005, Formation of 2-methyl tetrols and 2-methylglyceric acid in secondary organic aerosol from laboratory irradiated isoprene/NOX/SO2/air mixtures and their detection in ambient PM2.5 samples collected in the eastern United States, Atmos. Environ. 39, 5281-5289.
• Offenberg et al. 2006, Thermal properties of secondary organic aerosols. Geophys. Res. Lett. 33, L03816
• Claeys et al. 2007, Hydroxydicarboxylic acids: Markers for secondary organic aerosol from the photooxidation of α-pinene. Environ. Sci. Technol. 41, 1628-1634.
• Jaoui et al., 2007, β-caryophyllinic acid: An atmospheric tracer for β-caryophyllene secondary organic aerosol. Geophys. Res. Lett. 34, L05816.
• Surratt et al. 2007, Evidence for organosulfates in secondary organic aerosol. Environ. Sci. Technol. 41, 517-527.
• Lewandowski et al., 2007, Composition of PM2.5 during the summer of 2003 in Research Triangle Park, North Carolina. Atmos. Environ. 47, 4073-4083.
• Offenberg et al. 2007, Contributions of toluene and α-pinene to SOA formed in an irradiated toluene/α-pinene/NOX/air mixture: Comparison of results using 14C content and SOA organic tracer methods. Env. Sci. Technol. 41, 3972-3976.
• Kleindienst et al., 2007, Estimates of the contribution of biogenic and anthropogenic hydrocarbons to secondary organic aerosol at a Southeastern U.S. Location, Atmos. Environ. (in press).