Modeling secondary organic aerosols SOA: current achievements and future challenges

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Modeling secondary organic aerosols
(SOA)current achievements and future challenges

• Kostas Tsigaridis,
• Stelios Myriokefalitakis, Maria Kanakidou

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O3
Gas-phase chemistry
??
POA
AVOC
BVOC
SOA
3
SOA production
gas-phase condensable products
T ?
absorbing aerosol phase
Potential of total evaporation ? Lower limit of
SOA formation
Upper limit of SOA formation
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SOA formation a-pinene O3
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SOA formation 2 product model

• Keep critical information on
• Chemical speciation
• Optical properties
• Hydrophilic/hydrophobic behaviour

Kp,1
a1
G1
A1
VOC
a2
G2
A2
Kp,2
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VOC candidates

• BVOC
• isoprene
• monoterpenes
• sesquiterpenes
• higher terpenoid compounds
• others?
• AVOC
• aromatics
• solvents
• high C-chain hydrocarbons
• others?

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Processes that affect SOA production

• Pre-existing aerosols
• Oxidant levels
• Gas-phase chemical composition (high/low NOx)
• Relative humidity
• UV light
• Evaporated POA
• Aged SOA
• Others?

Kp,1
a1
G1
A1
VOC
a2
G2
A2
Kp,2
a3
Kp,3
G3
A3
a4
G4
A4
Kp,4
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The simulations TM3 model

• FULL (Tsigaridis and Kanakidou, AE, 2007)
• 5 precursors (isoprene, a-pinene, ß-pinene,
  toluene, xylene)
• 4 products per precursor (2 high-NOx, 2 low-NOx)
• LUMPED_NOX_DEP
• 5 precursors (isoprene, a-pinene, ß-pinene,
  toluene, xylene)
• 2 products per precursor (high-NOx or low-NOx,
  depending)
• NO_NOX_DEP
• 5 precursors (isoprene, a-pinene, ß-pinene,
  toluene, xylene)
• 2 products per precursor (low-NOx)
• MINIMUM
• 3 precursors (isoprene, a-pinene, toluene)
• 2 products per precursor (low-NOx)

Preliminary results!
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SOA burden variation
Chemical production 40-70 difference
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SOA surface concentration, annual mean
FULL
LUMPED_NOX_DEP
NO_NOX_DEP
MINIMUM
ug m-3
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Lumped cases difference surface
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SOA zonal mean concentration, annual mean
FULL
LUMPED_NOX_DEP
NO_NOX_DEP
MINIMUM
ug m-3
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Lumped cases difference zonal mean
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Comparison with measurements CARBOSOL
Measurements FULL MINIMUM
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Comparison with measurements
4 CARBOSOL stations
FULL MINIMUM
Units are ugC m-3, OM/OC 1.3
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Perspectives

• Burden differences compared to surface
  concentration changes reveal the importance of
  the free tropospheric SOA.
• Distinction between POA and SOA is important in
  understanding why models and measurements
  (dis)agree. Emissions play a major role. This,
  though, might never happen (POA is semi-volatile
  Donahue et al., 2006 Robinson et al., 2007).
• How should we treat the VOC reactivity?
• Update the SOA formation mechanism by including
  the most recent chamber data of ?H, a and Kp
  (Offenberg et al., 2006 Henze et al., 2007). How
  should we treat sesquiterpenes (NOx dependence)?
• More detailed comparison which will include
  measurements around the globe. If you have data
  available, do not hesitate kostas.tsigaridis_at_cea.
  fr
• Detailed study of all different simulations.

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Ideas

• What POA means?
• What SOA means?
• Should we model POA/SOA, or HOA/OOA? Or something
  else, e.g. volatility groups?
• Contribution of small molecules and cloud
  processing in SOA?

Source 1
POA
Evap. POA
Aged evap. POA
Source 2
SOA
Aged SOA
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Thank you for your attention! kostas.tsigaridis_at_c
ea.fr From March 2008 _at_ NASA/GISS, New York