organic carbon aerosol: an overview (and insight from recent field campaigns) colette l. heald noaa...
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Organic Carbon Aerosol:An Overview
(and Insight from Recent Field Campaigns)
Colette L. HealdNOAA Climate and Global Change Postdoctoral Fellow
*New Affiliation as of Jan 2008*Colorado State University
GEOS-Chem User’s MeetingApril 12, 2007
ORGANIC CARBON AEROSOL
Semi-Volatiles
Oxidation by OH, O3, NO3
Direct Emission
Fossil Fuel Biomass Burning
Terpenes
Nucleation or Condensation
Aromatics
ANTHROPOGENIC SOURCESBIOGENIC SOURCES
Isoprene
Secondary
Organic
Aerosol
Primary
Organic
Aerosol
GEOS-CHEM OC AEROSOL SIMULATION
Semi-Volatiles
Fossil Fuel BiomassBurning
Monoterpenes Aromatics
ANTHROPOGENIC SOURCESBIOGENIC SOURCES
Isoprene
Semi-Volatiles
Fossil Fuel BiomassBurning
Monoterpenes Aromatics
ANTHROPOGENIC SOURCESBIOGENIC SOURCES
Isoprene
Primary Organic Aerosol [Rokjin Park]
FF: Cooke / BondBF: Logan & YevichBB: Duncan
50% hydrophobic, 50% hydrophillic
Secondary Organic Aerosol [Rokjin Park, Hong Liao, Daven Henze]
Terpenes: Chung and Seinfeld [2002]Isoprene: Henze and Seinfeld [2006] (v7.04.05)Aromatics: new smog chamber data (Henze)Heterogeneous Chemistry: glyoxal (May Fu)
SOA treated as hydrophilic, semi-volatile gases are soluble
Empirical parameterization: 2-product model fit to smog chamber studies
VOC + Oxidant α1 P1 + α2 P2
Equilibrium Partitioning Depends on T, [OC]
k1 k2
GLOBAL OC BUDGET IN GEOS-CHEM
SOURCE TgC/yr
Fossil Fuel 10.6
Biofuel 7.6
Biomass Burning ~25
Terpene SOA 9
Isoprene SOA 5.5
Aromatic SOA ~4
Glyoxal/methylglyoxal uptake May’s talk!
[Park et al., 2003; Henze and Seinfeld, 2006]
ORGANIC CARBON AEROSOL: AT THE SURFACE
Organic carbon constitutes 10-70% of aerosol mass at surface.ISSUE: Measurements do not differentiate POA and SOA
2004 NARSTO Assessment
ACE-ASIA: FIRST OC AEROSOL MEASUREMENTS IN THE FREE TROPOSPHERE
Mean ObservationsMean SimulationObservations+
Concentrations of OC in the FT were under-predicted by a factor of 10-100!We conclude this is missing SOA
(ACE-Asia aircraft campaign conducted off of Japan during April/May 2001)
v7.01.02(only terpene SOA)
[Heald et al., 2005]
[Mader et al., 2002] [Huebert et al., 2003] [Maria et al., 2003]
SEVERAL STUDIES SUGGESTING UNDERESTIMATE OF SOA
[Volkamer et al., 2006]
Global underestimate in SOA?
WHAT CONTRIBUTES TO OC AEROSOL OVER NORTH AMERICA?
NOAA WP-3 Flight tracks
OC concentrations in the FT doubled as a result of Alaskan boreal fires.
Observed boreal fireInfluence down-wind
BB filtered using CH3CN
2004: worst fire season on record in Alaska
DO WE UNDERSTAND OC AEROSOL OVER NORTH AMERICA?
Note: biomass burning plumes were removed
OC aerosol concentrations 4x lower than observed off of Asia, model within 25%
BUT we cannot simulate variability in observations (R=0.21) incomplete understanding of formation.
[Heald et al., 2006]
Sulfur Oxides (SOx)Water soluble
OC Aerosol (WSOC)Simulated source
attribution
ObservedSimulated
v7.02.04(includes isoprene SOA)
WHAT DON’T WE UNDERSTAND ABOUT SOA FORMATION?
SVOC
Oxidation by OH, O3, NO3
Direct Emission
Terpenes
Nucleation or Condensation
Aromatics
OC
Isoprene
CloudProcessing
FF: 45-80 TgC/yrBB: 10-30 TgC/yr
SOA: ?? TgC/yr
Fossil Fuel Biomass Burning
ANTHROPOGENIC SOURCESBIOGENIC SOURCES
Heterogeneous ReactionsPRECURSORS
CHEMISTRY1. NOx, SO2/acidity2. Multi-step oxidation
FORMATION PATHWAYS
MODELING OC AEROSOL: FUTURE?
• Better constraints on role of NOx, seed particles, T, RH, and radiative properties
• CMAQ (A. Carlton)
• Example: Donahue volatility basis sets
• Robinson and Donahue suggest
primary aerosol emission is
misconception…
Implementation of smog-chamber results
In-cloud SOA formation
New SOA Schemes?
Semi-volatile primary emissions?