Organic Carbon in the Troposphere

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Organic Carbon in the Troposphere
Colette L. Heald (heald_at_atmos.colostate.edu)
With acknowledgements to many people at the end!
NOAA Seminar June 11, 2008
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CARBON IN THE ATMOSPHERE
CO2 (820 PgC)
Organic Carbon (10s TgC)

CO (150 TgC)
CH4 (4 PgC)

• Short-lived (reactive)
• BUT important climate role
• direct aerosol radiative forcing
• indirect via CCN
• oxidant chemistry (O3, CH4, )

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RECONCILING THE ORGANIC AEROSOL BUDGET
SOA measured/modeled 4-100! Volkamer et al.,
2006
Good agreement between global model and IMPROVE
observations for OC aerosol concentrations in the
US Park et al., 2003
Global measurements (surface 0.5-32 µgm-3) Zhang
et al., 2007
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GAS-PHASE CARBON MASS CLOSURE?
2847 organic compounds identified in the
atmosphere Graedel et al., 1986 104 compounds
estimated to be present Goldstein and Galbally,
2006 30-100 compounds quantified in typical
measurement campaigns
Chebogue Pt, 1993 (NARE)
UCLA, 1999-2000
Roberts et al., 1998
Chung et al., 2003
WINTER
T/S 1
T/S 1
SUMMER
T/S 1.4-2.2
SC2-C7 agree with total measured within
measurement uncertainty
Suggest that 20-45 NMOC unmeasured in
photochemically aged airmasses
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TOPICS FOR TODAY

• Total Observed Organic Carbon Concept and Field
  Observations
• Isoprene Emissions Global Budgets and
  Predictions
• Primary Biological Aerosol Particles and AMAZE-08

• Total Observed Organic Carbon Concept and Field
  Observations

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PHASES OF ORGANIC CARBON GENERALLY CONSIDERED
SEPARATELY OR ONE-WAY
Oxidation to CO/CO2
Oxidation Condensation
SOA
POA
Deposition
Deposition
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CONSIDER TOTAL ORGANIC CARBON (TOC)
Oxidation to CO/CO2
TOC
Oxidation Condensation
SEMI-VOLATILES
Oxidation Re-volatization
CH4 Oxidation
Deposition
Note Similar to defining nitrogen family (NOy)
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FIELD SITES AND CAMPAIGNS
Eleven datasets upwind/over/downwind of North
America with simultaneous observations of gas
phase and particle phase OC. (Over 130 organic
compounds measured)
TOC Sgas-phase OC aerosol-phase OC TOOC
Total Observed Organic Carbon µgCm-3 _at_ STP
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MEAN DAYTIME TOOC OVER NORTH AMERICA
Increasing age
Mean TOOC ranges from 4.0 µgCm-3 (Trinidad Head,
cleanest) to 456 µgCm-3 (Mexico City, polluted)
and generally decreases with age. Aerosol makes
up 3-17 of TOOC.
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ORGANIC AEROSOL VS SULFATE OVER NORTH AMERICA
Mean POM ranges from lt 1 to 24 µgm-3 OC aerosol
equal/dominates sulfate at all sites, consistent
with NH picture of Zhang et al. 2007. No
discernable trend with age.
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VARIABILITY OF TOOC OVER NORTH AMERICA
Organic carbon concentrations span 2 orders of
magnitude. Minimum of 2 µgCm-3 observed at any
site. OC aerosol never makes up more than 50
of TOOC. Clean marine sites similar (IPX,
BAE) Similar variability for platforms in the NE
(RHB, TF, WP3)
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WHAT CONTROLS THE VARIABILITY OF TOOC AND ORGANIC
AEROSOL?
Gas-phase gt particle-phase in ALL air masses,
highest in NE US
CO is a good predictor for TOOC (46-86 of
variability), but could be of biogenic or
anthropogenic origin in US
Sulfate / Aerosol OC relationship driven by
sources, oxidants, loss?
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BIOGENIC CONTROL ON TOOC? (SOA?)
Anthro sources
HCHO
Isoprene
MVK/MACR
Isoprene oxidation products predict some of
TOOC variability (but not OC aerosol) Methanol is
best correlated tracer, with longest lifetime
(7days), but not solely biogenic
Conundrum No strong indication of biogenic
source of OC aerosol from observations, but 14C
indicates most OC aerosol is modern (SOA?).
Biogenic tracers too short-lived? Need an
anthropogenic trigger for aerosol formation?
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QUESTIONS RAISED?

• How much of TOC is accounted for in TOOC? (key
  missing compounds?)
• How representative are these observations of the
  atmosphere?

WHAT DO WE NEED?

• More routine total NMVOC measurements alongside
  speciated measurements, and semi-volatiles
• More ambient sampling in diverse environments
  (tropics, Asia, polar)
• Time-resolved 14C observations (with aerosol and
  gas-phase measurements)

Heald et al., ACP, 2008
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TOPICS FOR TODAY

• Total Observed Organic Carbon Concept and Field
  Observations
• Isoprene Emissions Global Budgets and
  Predictions
• Primary Biological Aerosol Particles and AMAZE-08

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ISOPRENE CONTROLLING AIR QUALITY AND CLIMATE
C5 H8 Reactive hydrocarbon emitted from plants
(primarily broadleaf trees) Annual global
emissions equivalent to methane emissions
CLIMATE
Depletes OH ? CH4 lifetime
OH
O3
AIR QUALITY
Beijing
IPCC, 2007
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METEOROLOGICAL AND PHENOLOGICAL VARIABLES
CONTROLLING ISOPRENE EMISSION

• LIGHT
• Diffuse and direct radiation
• Instantaneous and accumulated
• (24 hrs and 10 days)

• TEMPERATURE (Leaf-level)
• instantaneous and accumulated
• (24 hrs, 10 days)

?T
?L
T
PAR
AMOUNT OF VEGETATION ? Leaf area index (LAI)

• LEAF AGE
• Max emission mature
• Zero emission new

LAI
SUMMER
Month
SOIL MOISTURE ? suppressed under drought
Guenther et al., 2006
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ISOPRENE IN THE FUTURE
NPP ? Temperature?
2000
2100
Methane lifetime increases Shindell et al., 2007
SOA burden ? gt 20 Heald et al., 2008
Surface O3 ? 10-30 ppb Sanderson et al., 2003
Isoprene emissions projected to increase
substantially due to warmer climate and
increasing vegetation density. ? LARGE impact on
oxidant chemistry and climate ?
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A MISSING FACTOR ISOPRENE EMISSION INHIBITION BY
CO2
Long-Term growth environment gene
adaptation Dependent on ambient CO2
Short-term exposure changes in metabolite pools
and enzyme activity Dependent on intercellular
CO2 (varies with photosynthesis and stomatal
resistance)
Mick Wilkinson and Russ Monson (UC Boulder)
investigated these separately for 4 plant species
and developed an empirical parameterization
Wilkinson et al., submitted
To what degree does this CO2 inhibition
counteract predicted increases in isoprene (due
to T and NPP)?
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MODELING FRAMEWORK
Community Land Model (CLM3) Datasets Lawrence
and Chase 2007 LAI (MODIS) Plant Functional
Types Soil moisture Vegetation Temperature
BVOC Algorithms Guenther et al., 1995
2006 Monterpenes GEIA Isoprene MEGAN
Vegetation Meteorology
BVOC Emissions
Radiation Precipitation
Community Atmospheric Model (CAM3) Chemistry Tra
nsport Radiation
Anthropogenic Emissions, GHG concentrations, SST
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2100 (A1B) CO2 INHIBITION COMPENSATES FOR
TEMPERATURE INCREASE
Future projected emissions drop from 696 TgC/yr
to 479TgC/yr
Dotted2000 Solid2100
See that ?in T activity factor compensated by ?
in CO2 activity factor
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CONCLUSION ISOPRENE EMISSIONS PREDICTED TO
REMAIN CONSTANT
With fixed vegetation
Important implications for oxidative environment
of the troposphere
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UNLESSCO2 FERTILIZATION IS STRONG

• CLM DGVM projects a 3x increase in LAI associated
  with NPP and a northward expansion of vegetation.
• Alo and Wang, 2008
• Isoprene emissions more than double! (1242
  TgCyr-1)
• BUT, recent work suggests that NPP increases may
  be overestimated by 74 when neglecting the role
  of nutrient limitation
• Thornton et al., 2007

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IMPLICATIONS FOR THE PAST?
VOSTOK ICE CORE RECORD
Vostok data source Petit et al. 1999
While the balance between T and CO2 is critical
to future predictions of isoprene, the large T
fluctuations over the last 400 thousand year
remain the primary control on isoprene emission
in the recent geological past.
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TOPICS FOR TODAY

• Total Observed Organic Carbon Concept and Field
  Observations
• Isoprene Emissions Global Budgets and
  Predictions
• Primary Biological Aerosol Particles and AMAZE-08

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PRIMARY BIOLOGICAL AEROSOL PARTICLES (PBAP)
LARGE particles (gt 10 µm)
Jaenicke 2005 suggests may be as large a source
as dust/sea salt (1000s Tg/yr) Elbert et al.
2007 suggest emission of fungal spores 50
Tg/yr
How much does this source contribute to
sub-micron OC?
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ANY INDICATION OF PBAP IN AMAZE-08?
Field site close to Manaus, Brazil (in
Amazonia), Feb-Mar
SIMULATED OC
Observations 1-4 µg/m3
Early Feb observe significantly more organic
aerosol than simulated (rain ends this period).
PBAP?
PRELIMINARY AMS obs Scot Martin, Qi Chen
(Harvard). Jose Jimenez, Delphine Farmer (CU
Boulder)
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OR A ANOTHER EXPLANATION?
Consistent air flow throughout campaign
Feb 1-9
Feb 21-29
MODIS fire counts http//maps.geog.umd.edu/firms/
maps.asp
Fires in the region during early Feb. These are
not reflected in model emission inventories.
Acetonitrile concentrations are also elevated
early in the campaign but so is isoprene
No obvious indication of an important sub-micron
PBAP in the pristine Amazon at this early stage
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ACKNOWLEDGEMENTS
Measurement Teams for ICARTT, PAQS, MILAGRO,
IMPEX, ITCT-2K2 James D. Allan, Allison C.
Aiken, Eric Apel, Elliot L. Atlas, Angela K.
Baker, Timothy S. Bates, Andreas J. Beyersdorf,
Donald R. Blake, Teresa Campos, Hugh Coe, John D.
Crounse, Peter F. DeCarlo, Joost A. de Gouw,
Edward J. Dunlea, Frank M. Flocke, Alan Fried,
Paul Goldan, Robert J. Griffin, Scott C. Herndon,
John S. Holloway, Rupert Holzinger, Jose L.
Jimenez, Wolfgang Junkermann, William C. Kuster,
Alastair C. Lewis, Simone Meinardi, Dylan B.
Millet, Timothy Onasch, Andrea Polidori, Patricia
K. Quinn, Daniel D. Riemer James M. Roberts, Dara
Salcedo, Barkley Sive, Aaron L. Swanson, Robert
Talbot, Carsten Warneke, Rodney J. Weber, Petter
Weibring, Paul O. Wennberg, Douglas R. Worsnop,
Ann E. Wittig, Renyi Zhang, Jun Zheng, Wengang
Zheng NSF, NOAA, NASA Funding for TOOC
Measurements NOAA Climate and Global Change
Postdoctoral Fellowship CO2 Isoprene work
Mick Wilkinson, Russ Monson, Clement Alo,
Guiling Wang, Alex Guenther AMAZE-08 work Qi
Chen, Scot Martin, Delphine Farmer, Jose Jimenez,
Andi Andreae