Prakash V. Bhave, Ph.D. Physical Scientist EMEP Workshop – PM Measurement & Modeling April 22,...
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Prakash V. Bhave, Ph.D.Physical Scientist
EMEP Workshop – PM Measurement & Modeling April 22, 2004
Measurement Needs for Evaluating Model Calculations
of Carbonaceous Aerosol
Policy-Relevant Questions*• What fraction of PM2.5 mass is carbonaceous?• What fraction of carbonaceous aerosol is primary
vs. secondary?• What are the source contributions to primary
carbon?• What fraction of secondary organic aerosol is
anthropogenic vs. biogenic?• What fraction of carbon in urban areas is
transported from upwind locations?
Existing models can answer these questions, but we need measurements to evaluate the answers
* NCEA Carbonaceous PM Workshop Series - 2004
• Reconstruction of carbonaceous mass Organic mass contains C, H, O, and N atoms Carbon is measured; rest is estimated OM/OC ratios of 1.2 – 2.5 have been proposed Ratio increases with age of aerosol
[Turpin & Lim, 2001] Speciated or FTIR measurements can help
• Evaluation approach In model formulation, OM/OC ratios are known Convert model predictions to OC, and evaluate
against carbon measurements
Carbonaceous Fraction of PM2.5
Carbonaceous Fraction of PM2.5
CMAQ Model Results – Average of 2001 Annual Simulation (TC/PM2.5,dry)
Annual Average PM 2.5 Specia tion P rofiles for U rban S ites(April 2002 through M arch 2003 D ata)
Sulfate
Am m onium
N itrate
TCM
Crusta l
6.41 18.85 31.29
Carbonaceous Fraction of PM2.5
STN data averaged from April ’02 – March ’03* Courtesy of Joann Rice, EPA/OAQPS
OC/EC inter-network inconsistencies (STN vs. IMPROVE) - STN OC data are not blank-corrected - Different thermal-optical protocols
Primary vs. SecondaryCMAQ–2001 Annual Average (Primary Carbon / Total Carbon)
• OCpri & OCsec cannot be measured directly
• Several indirect estimation methods exist• EC tracer method
Primary vs. Secondary
prisec
pripri
EC
OCECOCOC
EC
OCECOC
Estimate (OC/EC)pri from emissions/transport model[S.Yu, et al., 2004]
Make use of the plentiful, ambient OC and EC data
• OC/EC in source profiles must be consistent with the ambient monitors
• Semi-continuous OC/EC data are needed to check model predictions of diurnal OCsec
patterns Most models predict the OCsec peak at nighttime [Pun et al., 2003]
OC & EC data from SEARCH network (IMPROVE TOR method)
Primary vs. Secondary
OC/EC splits in the inventory inconsistent with ambient sampling protocols
Primary vs. Secondary
PM2.5 Weight %
1999 EmissionsTC (tons)
PrimaryOC/EC
SamplingProtocolNEI99 Source Profile OC EC
Non-road Diesel Exhaust 18.70% 74.11% 86,966 0.25 TOR
Agricultural Burning 53.24% 7.50% 73,052 7.10 various
Heavy-duty Diesel Exhaust 18.93% 75.00% 38,375 0.25 TOR
Non-road Gasoline Exhaust 65.50% 8.01% 17,076 8.18 TOT
Light-duty Gasoline Exhaust 47.35% 19.01% 10,535 2.49 TOR
Soil Dust 4.54% 0.37% 8,356 12.27 various
Paved Road Dust 14.73% 1.12% 6,641 13.15 TOR
Jet Fuel Combustion 24.34% 65.87% 6,350 0.37 unknown
Wood Waste Boilers 9.81% 20.19% 4,214 0.49 thermal
Natural Gas Combustion 50.00% 0.00% 3,865 - N/A
Solid Waste Combustion 0.57% 3.50% 2,954 0.16 TOR
Residual Oil Combustion 19.93% 19.33% 2,437 1.03 TOR
Wood Products - Drying 65.83% 4.39% 1,612 15.00 various
Fiberglass Manufacturing 28.00% 2.00% 1,474 14.00 thermal
Food & Agriculture Handling 30.00% 0.00% 1,353 - N/A
Other Sources N/A N/A 10,880 3.59 various
- CMAQ results using source apportionment capability (Aug. 1, 1999)
- Evaluations will provide direct feedback to emission inventory improvement
- Validated results can support control strategy development
Apportionment of Primary CarbonDiesel exhaust fraction Biomass combustion fraction
Needs for Model Evaluation• Data types
Source-specific organic tracers (e.g., levoglucosan, hopanes, cholesterol, etc.) [Schauer, et al.]
Primary biogenic carbon (e.g., carbohydrates, vegetative detritus) [M. Hernandez; W. Rogge, et al.]
Semi-continuous wood smoke source tracers?• Spatial resolution
Several urban sites (e.g., each Supersite) Some representative rural sites
• Temporal resolution 24h data at urban sites for ~1 month per season 2-6h composites at urban sites to check diurnal variation Monthly composites at rural sites to check seasonality
Apportionment of Primary Carbon
SOA: Biogenic vs. Anthropogenic
• What fraction of SOA is anthropogenic? Great uncertainty within model
parameterizations Nashville: July 16-18,1995 model
inter-comparison yields values of 10% - 40% [Pun et al., 2003]
• Uncertainties too large to justify controls directed specifically at anthropogenic SOA
Needs for Model Evaluation• Data types
14C can help provide a measure of biogenic SOA;need collocated wood smoke & vegetative detritus data
Source-specific SOA tracers [Edney et al.]
SOA: Biogenic vs. Anthropogenic
Reprinted from: Edney & KleindeinstOAQPS Model Eval Workshop, Chapel
Hill, Feb.10, 2004
CMAQ–2001 Annual Average (Anthropogenic fraction of OCsec)
SOA: Biogenic vs. Anthropogenic
Carbon fraction of PM2.5
• OC, EC data are plentiful; some network inconsistencies
• OM/OC uncertain, but not essential for model evaluation
Primary vs. secondary?
• Consistent definition of OC and EC across ambient networks and source data
• Semi-continuous OC & EC
Primary source apportionment
• Source-specific tracers
• Increase spatial & temporal resolution of organic tracer measurements
Anthropogenic vs. biogenic SOA
• Tracers for aromatic and monoterpene oxidation
• 14C collocated with wood smoke & detritus markers
Summary of Measurement Needs
Acknowledgements
• Atmospheric Modeling Division (NOAA/EPA)
• Emissions Monitoring & Analysis Division – Air Quality Modeling Group (OAQPS)
• Computer Sciences Corporation
Disclaimer Notice:This work has been funded wholly by the United States Environmental Protection Agency. It has been subjected to Agency review and approved for presentation.
Carbonaceous Fraction of PM2.5
17%
19%
6%6%
Carbon
Sulfate
Nitrate
Ammonium
Other
Urban Network (STN)PM2.5 = 10.5 g/m3
19%
17%
5%9%
Carbon
Sulfate
Nitrate
Ammonium
Other
CMAQ ModelPM2.5 = 11.5 g/m3
2001 Network Median Values (~7000 observations)Carbon Value is “blank-corrected” by 1 g/m3
Apportionment of Primary CarbonGasoline exhaust fraction Coal combustion fraction
- CMAQ results using source apportionment capability (Aug. 1, 1999)
Apportionment of Primary CarbonOil combustion fraction Natural gas combustion fraction
- CMAQ results using source apportionment capability (Aug. 1, 1999)
Apportionment of Primary CarbonFood cooking fraction Paved road dust fraction
- CMAQ results using source apportionment capability (Aug. 1, 1999)
Apportionment of Primary CarbonCrustal material fraction Miscellaneous source fraction
- CMAQ results using source apportionment capability (Aug. 1, 1999)
Fresno IndyS.L.
Tulsa
Missoula
SLC Bronx
Charlotte
Baltimore
Atlanta
Cleveland
Richmond
Birmingham
16 rural IMPROVE sites
13 urban STN sites
Local vs. Regional Contribution
Reprinted from: N. FrankOAQPS Model Eval Workshop, Chapel
Hill, Feb.10, 2004
Differences between urban (STN) and paired rural site (IMPROVE)
Fresno
Missoula
SLC
Tulsa
Birmingham
Indy
Cleveland
Charlotte
Richmond
Baltimore
Bronx
St Louis
Atlanta
Sulfa te :
0 .0 0.4 0.9
Am m onium :
0.0 0.9 1.9
N itra te :
0 .4 3.5 6.5
TC M (k=1.8):
2 .9 8.1 13.2
C rusta l:
0 .0 0.4 0.8
Differences between urban and paired rural site(s) - Carbonaceous mass dominates the “urban excess”
Local vs. Regional Contribution
Reprinted from: N. FrankOAQPS Model Eval Workshop, Chapel
Hill, Feb.10, 2004
CMAQ Results at 1km resolution (OC+EC)Along Pennsylvania - New Jersey border
Local vs. Regional Contribution
Urban contribution 5.4 g/m3
Urban contribution 10.1 g/m3