Global Modeling of Organic PM: State of the Science and Major Gaps

1
Global Modeling of Organic PM State of the
Science and Major Gaps
Daniel J. Jacob
with Rokjin J. Park1, Colette L. Heald2 Tzung-May
Fu3, Hong Liao4
and funding from EPRI, EPA, NSF
1 now asst. prof. at Seoul National University 2
now asst. prof. at Colorado State University 3
now asst. prof. at Hong Kong Polytechnic
University 4 Caltech, now at Chinese Academy of
Sciences
2
ORGANIC PM IN STANDARD GEOS-Chem MODEL
Global sources in Tg C y-1
20
K
OH, O3,NO3
SOG
SOA
VOC
secondary formation
POA
isoprene terpenes oxygenates
alkenes aromatics oxygenates
alkanes alkenes aromatics
20
100
30
700
50
fuel/industry open fires
vegetation fuel/industry open fires
VOC EMISSION
PRIMARY EMISSION
3
TOP-DOWN CONSTRAINTS ON U.S. SOURCES
Fit GEOS-Chem sources of organic PM to monthly
1998 data at IMPROVE sites
annual
Park et al. JGR 2003
4
IMPROVED MODEL WITH 1ox1o RESOLUTION,SOA
FORMATION BY PANKOW/SEINFELD MECHANISM
IMPROVE
(2001, annual)
Park et al. AE 2006
mg m-3
5
SENSITIVITY OF NATURAL OC PM CONCENTRATIONSTO
PRE-EXISTING POA AVAILABILITY
Is SOA formation limited by availability of
primaryorganic aerosol (POA)?
YES
NO
Major implications for natural visibility
objective of the Regional Haze Rule
Park et al. AE 2006
6
QUANTIFYING THE BIOMASS BURNING SOURCE OF PM2.5
FROM CORRELATION OF TOTAL CARBON (TC) WITH
NON-SOIL KAT IMPROVE SITES
Non-soil K West summer max, low
background East winter and summer maxes, high
background
use TC vs. ns-K linear regression together
w/satellite data to quantify TC from open fires
Background ns-K (traces industrial biofuel)
dTC/dns-K
Park et al. AE 2007
7
FIRE AND BIOFUEL CONTRIBUTIONS TO TC PM2.5
Annual mean C concentrations, 2001-2004 Mean
values for W and E at top of plot
Park et al. AE 2007
8
IMPLICATIONS FOR AQ STANDARDS AND EMISSION
INVENTORIES
Emissions for contiguous U.S. (climatological
estimate for fires)
Source attribution at IMPROVE sites (annual means)
Park et al. AE 2007
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FIRST MASS CONCENTRATION MEASUREMENTSOF OC
AEROSOLS IN FREE TROPOSPHERE
ACE-Asia aircraft data over Japan (April-May 2001)
Observed (Russell)
Chung and Seinfeld scheme
OC/sulfate ratio

• Observations show 1-3 mg m-3 background
• model too low by factor 10-100

Heald et al. GRL 2005
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LITTLE TRANSPACIFIC INFLUENCE OF ASIAN ORGANIC
PMON U.S. SURFACE AIR
Spring 2001 IMPROVE sulfate data
Mean PM concentrations observed in NW U.S. (mg
m-3)
Days of max Asian influence (diagnosed by
GEOS-Chem)
Other studies (Randall Martin, Rodney Weber)
find no OC enhancement in transpacific Asian
plumes sampled from aircraft
Heald et al., JGR 2006a
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ITCT-2K4 AIRCRAFT CAMPAIGN OVER EASTERN U.S. IN
JULY-AUGUST 2004
water-soluble organic carbon (WSOC) aerosol
measurements by Rodney J. Weber (Georgia Tech)
Alaska fire plumes
2-6 km altitude
Heald et al. JGR 2006b
Values 2x lower than observed in ACE-Asia
excluding fire plumes gives mean of 1.0 mgC m-3
(3x lower than ACE-Asia)
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MODEL OC AEROSOL SOURCES DURING ITCT-2K4
Large fires in Alaska and NW Canada 60 of fire
emissions released above 2 km (pyro-convection)
Heald et al., JGR 2006b
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ITCT-2K4 OC AEROSOL VERTICAL PROFILES
Total Biomass burning Anthropogenic Biogenic SOA
Observations Model
hydro- phobic
SOx SO2 SO42- efficient scavenging during
boundary layer ventilation
Data filtered against fire plumes (solid) and
unfiltered (dotted)
Model source attribution
Heald et al. JGR 2006b
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IRREVERSIBLE DICARBONYL UPTAKE BY AQUEOUS AEROSOL
glyoxal
methylglyoxal
Chamber AMS experiments of glyoxal uptake by
Liggio et al. JGR 2005
Organic aerosol mass growth with time
Inferred reactive uptake coefficient g

• median g 2.9x10-3 observed for aqueous
  surfaces evidence for oligomerization
• similar g observed for methylglyoxal on acidic
  surfaces Zhao et al. EST 2006

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POSSIBLE MECHANISMS FOR DICARBONYL SOA FORMATION
GAS
AQUEOUS
Schweitzer et al. 1998 Kalberer et al.
2004 Liggio et al. 2005a,b Hastings et al.
2005 Zhao et al. 2006 Loeffler et al. 2006
glyoxal
Oligomers
oligomerization
oligomerization
H 105 M atm-1
Altieri et al. 2006, 2008
oxidation
methylglyoxal
OH
Organic acids
Ervens et al. 2004 Crahan et al. 2004 Lim et
al. 2005 Carlton et al. 2006, 2007 Warneck et
al. 2005 Sorooshian et al. 2006, 2007
H 103 M atm-1
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GLYOXAL/METHYLGLYOXAL FORMATION FROM ISOPRENE
6
25
GEOS-Chem mechanism based on MCM v3.1
Fu et al. JGR, in press
molar yields
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GLOBAL GLYOXAL BUDGET IN GEOS-Chem
Including reactive uptake by aq. aerosols
clouds with g 2.9x10-3 Liggio et al., 2005
(biomass burning)
t 2.9 h
Global SOA formation of 6.4 Tg yr-1 (1.0 in clear
sky 5.4 in cloud) compare to 16 Tg yr-1 from
terpenes/isoprene by semivolatile mechanism
Fu et al. JGR, in press
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GLOBAL METHYLGLYOXAL BUDGET IN GEOS-Chem
Including reactive uptake by aerosols and clouds
with g 2.9x10-3
(biomass burning)
t 1.6 h
Global SOA formation of 16 Tg yr-1 (2 in clear
sky 14 in cloud) compare to 16 Tg yr-1 from
terpenes/isoprene by semivolatile mechanism
Fu et al. JGR, in press
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MODEL COMPARISON TO IN SITU OBSERVATIONS
Continental boundary layer (all northern
midlatitudes summer) Continental free
troposphere Marine boundary layer
Glyoxal
Methylglyoxal
Indication of a missing marine source in the model
Fu et al. JGR, in press
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SCIAMACHY SATELLITE OBSERVATION OF GLYOXAL

• General spatial pattern reproduced over land,
  SCIAMACHY is 50 higher than model
• SCIAMACHY sees high values over oceans
  correlated with chlorophyll unidentified marine
  source?

100 pptv glyoxal in marine boundary layer would
yield 1 mg C m-3 SOA could contribute to
observed OC aerosol concentrations in marine air
Fu et al. JGR, in press
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SIMULATION OF WSOC AEROSOL OVER EASTERN U.S.
Water-soluble OC (WSOC) aerosol observations by
Rodney Weber (GIT) from NOAA aircraft during
ICARTT campaign out of Portsmouth, NH (Jul-Aug 04)
Boundary layer data (lt2 km)
biomass burning plumes excluded
Observed
Model w/ dicarbonyl SOA added
Model w/ standard SOA
Model hydrophilic primary OA
Dicarbonyl source in summer is mainly Biogenic
(isoprene)
Fu et al., in prep.
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CORRELATIONS OF FREE TROPOSPHERIC WSOC WITH
OTHER VARIABLES MEASURED ON NOAA AIRCRAFT
Observed Model with dicarbonyl SOA Model without
dicarbonyl SOA

• WSOC is observed to correlate with
• toluene and methanol (anthrobio?)
• sulfate (aqueous-phase production?)
• alkyl nitrates (photochemistry?)
• Model does not reproduce observed WSOC
  variability but does better with correlations,
  particularly when dicarbonyl SOA is included
  (sulfate, alkyl nitrates)

Fu et al., in prep.