can 3d models explain observed organic aerosols? · national center for atmospheric research...
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![Page 1: Can 3D Models Explain Observed Organic Aerosols? · NATIONAL CENTER FOR ATMOSPHERIC RESEARCH International Workshop on Air Quality Forecasting Research 2-3 Dec. 2009, NOAA, Boulder,](https://reader036.vdocuments.us/reader036/viewer/2022071502/61215c6f17d95676f91d6ae3/html5/thumbnails/1.jpg)
NATIONAL CENTER FOR ATMOSPHERIC RESEARCH
International Workshop on Air Quality Forecasting Research
2-3 Dec. 2009, NOAA, Boulder, Colorado
Can 3D Models Explain Observed Organic Aerosols?
Alma Hodzic, Sasha Madronich, Julia Lee-Taylor, NCAR / ACD
Jose L. Jimenez, University of Colorado
Jerome Fast, Pacific Northwest National Lab.
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(Kiehl, GRL, 2007)
To trust future climate predictions aerosols need to be better constrained (e.g. organics)
Uncertainty in aerosol effects of climate
0.8 W/m2
1.2 W/m2
- Radiative forcing RF (IPCC, 2007)
2/3 (=0.8/1.2) of models’ range in RF
is due to aerosol forcing ~ 0.8 W/m2
~ ½ of the CO2
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Dominance of organic aerosols
Zhang et al., GRL, 2007 Organic Aerosols : 30-70%
AMS measurements: Sulfate Organics
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Semi‐Vola*l Organic Vapors
Oxida*on by OH, O3, NO3
Direct Emission
Biomass Burning
Secondary Organic
Aerosol
Modeling OA : What are the challenges?
Nuclea*on
Cloud Processing
Par**oning
VOCs Isoprene
Monoterpenes Sesquiterpenes
Aroma*cs Alkanes
Forest Traffic Industries
POA
Evapora*on upon dilu*on
Biological Debris
Deposi*on Surface / mul*phase reac*ons
POA
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Modeling OA formation during MILAGRO 2006
• 2 nested domains (35x35 km2 ; 5x5 km2) • simulation from 1-30 March 2006 • Meteorological data: MM5/AVN • Anthropogenic Emissions:
NEI-99 + MCMA 2006 • MEGAN Biogenic emissions • Wildfire emissions (MODIS) • Gas-phase chemistry:
MELCHIOR 44 sp,116 reactions • Aerosol module
8 bins / internal mixing Inorganics (ISORROPIA) SOA scheme (Pun et al., 2006) Dry / wet deposition
Air quality model CHIMERE
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OA measurements during MILAGRO March 2006
- AMS: Aerosol Mass Spectrometer measurements
March 2006: Composition of PM1 particles
Aiken et al., ACP, 2009
T1 T0 - PMF: Positive Matrix Factorization of AMS spectra
surface sites (T0, T1, PTP) aircraft (G-1, C130)
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Model vs. Measurements at the surface
- Mexico City T0, March 2006
- OA underestimated by a factor of 2
- POA reasonably captured
- SOA largely underpredicted Hodzic et al. ACP, 2009
Primary Organics
Biomass burning
Anthrop.
OBS CHIMERE
Total Organics (µg/m3) Secondary Organics
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SOA formation : 2-product approach
• Lump gas oxidation products into high and low volatility • Partition into organic / aqueous phase based on smog chamber data • Pun et al., 2006 parameterization
VOCi + OXIDANTj ai,jG1i,j + βi,jG2i,j Ai,j
Equilibrium Ki,j (organic phase)
Ai,j
Aqueous phase
Contribution of anthropogenic precursors:
G-1 flights – March 2006 Mexico City (T0) Downwind (T1)
Photochemistry
Background?
OBS CHIMERE
1:1
~8 µg/m3
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SOA formation : explicit chemistry
• Provides chemical identity of products (e.g. Master Chemical Mechanism) • Reactions and rates are extrapolated from know chemistry (not measurements).
Chemistry up to C10 : 220,000 species & 1.5 M reactions (Computer generated chemistry)
Predictions of the GECKO model during MIRAGE 2006:
- SOA ~ up to 2.5 μg/m3 (peak)
Courtesy of Julia Lee-Taylor and Sasha Madronich Julia Lee-Taylor, ACD,
19-Nov-2009 Time (hours)
1,2,3 TMB
m-XYL
- Most of aerosol carbon is accounted for by relatively few species ~10 sp. ( -OH, -NO3, -NO2 groups dominates)
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SOA formation : role of biogenic precursors
Isoprene emissions from MEGAN (Tons/km2/day)
BS
OA
(iso)
B
SO
A (m
onot
er)
BS
OA
(all)
• CHIMERE ---- OBS
Biogenic SOA ‐ modeled with MEGAN ‐ es*mated from tracer measurements (Stone et al., 2009) ‐ Biogenic SOA is NOT underes2mated
At T0
Hodzic et al., ACP, 2009
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OBS Anthropogenic Only With Biogenics
Mexico City (T0) Downwind (T1)
SOA formation : contribution of biogenic precursors
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PBL-column integrated mass
Afternoon: 20 Tons over the MCMA
Night: 1.8 Tons
How large is the unexplained SOA mass?
OBS Anthropogenic Only With Biogenics
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Shortcomings of the traditional SOA approach
Hodzic et al., in prep. ACP
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SOA formation: contribution of primary organic vapors
- POA assumed as volatile (instead of inert)
High Temp. Ambient T
Low dilution (10-100) Ambient T
High dilution (1000-10000)
OH
O3
NO3
hv
(Robinson et al., Science, 2007)
SOA
POA
POA=10 µg/m3
Semi-volatile / Intermediate volatility organic vapors ~ 80 µg/m3
volatility
Typical ambient partitioning At T=20C
OH
Aerosol POA
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SOA formation: contribution of primary organic vapors
- Predicted Total Organic Aerosol : 15-30 March 2006
Robinson et al. 2007 Traditional SOA - POA passive - POA volatile
- Oxygen gain of 7.5% - Volatility drop x10
Grieshop et al. 2009 - POA volatile - Oxygen gain of 40% - Volatility drop x100
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SOA formation: contribution of primary organic vapors
SOA - T0
SOA - T1
Robinson et al. 2007 Grieshop et al. 2009 Traditional SOA
OBS
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- Strong increase of OA in urban plumes as a function of photochemical age due to chemistry
Continuous SOA production downwind of the city
Robinson et al. 2007 Grieshop et al. 2009 G-1 aircraft data (AMS)
~ 1 day aged air mass ~ freshly emitted
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Hodzic et al., in prep. ACP
SOA formation: Summary
- Confirm large underprediction of the traditional SOA approach
- With S/IVOC chemistry model predictions are in the range of measured SOA
- Several SOA formation pathways Need for additional experimental constraints
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How can we better constrain model predictions?
• Aerosol optical properties (e.g. lidar, photometer data, spectral absorption)
- Predicted oxidation state during MIRAGE (15-30 March)
• Atomic ratios (O/C, N/C) provided by AMS measurements
CHIMERE : GRIESHOP run
Inconsistencies in the O/C ratios for the Robinson et al., 2007 although the OA mass is modeled correctly.
AMS data Robinson simu. Grieshop simu. O/C ratios at T0 urban site
Inconsistencies between measured / predicted N/C - N/C (AMS) : < 0.02 - N/C (Master Mech.) : ~ 0.16
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Can we further constrain OA predicted by models?
• Atomic ratios (O/C, N/C) provided by AMS measurements
• Aerosol optical properties (e.g. lidar, photometer data, spectral absorption)
• Fraction of fossil / non-fossil organic carbon
Fossil carbon Biogenic carbon
Hodzic et al., in prep.
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Can we further constrain OA predicted by models?
• Atomic ratios (O/C, N/C) provided by AMS measurements
• Aerosol optical properties (e.g. lidar, photometer data, spectral absorption)
• Fraction of fossil / non-fossil organic carbon
Fraction of Non-Fossil Carbon at T0
14C 12h-filters (Marely et al., 2008) 14C 24h-filters PSI CHIMERE: ROB CHIMERE: GRI
Hodzic et al., in prep.
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(T0)
SO
A (µ
g/m
3 )
AMS CHIMERE
% p
artic
ulat
e ph
ase
SOA formation : 2-product approach
- upon dilution of POA and PBL growth - unaccounted in-particle reactions - multiple oxidations of VOCs
Excessive evaporation of freshly formed SOA
Mexico City (T0) Downwind (T1)
Enhanced partitioning into aerosol phase
100x lower vapor pressure
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Fast et al. ACP, 2009
HOA and BBOA well captured by the model in the city
Good agreement for primary organic species
- Surface stations, March 2006
Anthropogenic POA Biomass burning POA
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SOA formation : role of biogenic precursors
Isoprene emissions from MEGAN (Tons/km2/day)
BS
OA
(iso)
B
SO
A (m
onot
er)
BS
OA
(all)
• CHIMERE -- OBS
Biogenic SOA ‐ modeled with MEGAN ‐ es*mated from tracer measurements (Stone et al., 2009) ‐ Biogenic SOA is NOT underes2mated
At T1
Hodzic et al., ACP, 2009
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Model vs. Measurements at the surface
- Mexico City T1, March 2006
- OA underestimated by a factor of 2
- POA reasonably captured
- SOA largely underpredicted Hodzic et al. ACP, 2009
Primary Organics
OBS CHIMERE
Total Organics (µg/m3) Secondary Organics
Anthrop.
Biomass burning
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C130 : March 29th
Robinson et al. 2007 Grieshop et al. 2009 Traditional SOA OBS
Model vs. Measurements in the urban plume
CO
SOA
POA ~2 µg/m3
~15 µg/m3
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SOA formation : explicit chemistry
Julia Lee-Taylor, ACD,
19-Nov-2009
Top 100 species
Courtesy of Julia Lee-Taylor and Sasha Madronich
AR0212 3-methyl-6-nitro-catechol. Precursor: toluene
AR0128 3-methyl-6-nitro-catechol. Precursor: toluene
AR0293 3,5-dimethyl-6-nitro-catechol. Precursor: m-xylene
AR0875 2-methyl-2,3-epoxy-4-hydroxy-5-nitrooxy-6-keto-octanal. Precursor: 3-ethyltoluene
AR0686 2-methyl-2,3-epoxy-4-nitrooxy-5-hydroxy-6-oxo-heptanal. Precursor: 1,2,4-trimethylbenzene
AR0268 2,3-epoxy-4-hydroxy-5-nitrooxy-6-oxo-heptanal. Precursor: m-xylene
Most of aerosol carbon is accounted for by relatively few species ( -OH, -NO3, -NO2 groups dominates)
10 major species (~ 50% mass)
• Provides chemical identity of products (e.g. Master Chemical Mechanism) • Reactions and rates are extrapolated from know chemistry (not measurements).
Predictions of the GECKO model during MIRAGE 2006: