Kein Folientitel

1
Physical Chemical Transformation of Combustion
Biological Aerosol Particles
Ulrich Pöschl Technical University of Munich,
Institute of Hydrochemistry Marchioninistr. 17,
D-81377 München ulrich.poeschl_at_ch.tum.de www.ch.tu
m.de/wasser/aerosol
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• Introduction
• Substances processes
• Chemical Transformation
• Field, laboratory model studies
• Physical Transformation
• Water vapor droplet interactions
• Gas-particle partitioning
• Outlook
• Research needs scientific approach

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Atmosphere Climate

• clouds precipitation
• trace gases
• radiation

quantitative description human influence ?

• allergic, respiratory cardiovascular
  diseases
• spread of organisms

Biosphere Human Health
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Traditional Classification
Molecular Structures

• operational definitions (optical
  thermochemical)
• deviations gt 100

• complex mixture (exploded pharmacy)
• gt 60 unidentified

Physico-Chemical Properties Atmospheric Effects
determined by molecular structures many
speculations, few measurement data
? development, validation application of
powerful efficient measurement techniques
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Hydrocarbons Derivatives
Biopolymers

• Reaction
• Kinetics
• Products ?

Oxidation, Photolysis, Hydrolysis
Oxidation, Photolysis, Hydrolysis
Humic-Like Substances
MultifunctionalHC-Derivatives
Polymerisation
Optical Properties Bio-Activity
CCN IN Activity
? kinetic model master mechanism for
aerosol chemistry particle aging
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• Mass Transport Phase Transitions
• gas-liquid-solid surface-bulk
• adsorption absorption
• surface bulk diffusion
• condensation (nucleation) evaporation
• crystallisation (nucleation) dissolution
• deliquescence efflorescence
• Chemical Reactions
• surface, bulk
• photolysis, hydrolysis
• acid/base, redox reactions

? kinetic model framework for aerosol cloud
chemistry physics consistent universally
applicable formalism, rate coefficients
terminology
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Urban (LKP)
Rural (MOHp)
Fine Particulates (PM2.5) 2-20 ?g m-3 Carbon
Content (TC) 10-50 EC/TC Protein/TC Urban
60 4 Rural 30 30 Alpine
30 15
Alpine (UFS)
? high abundance of primary biological
combustion particles
T. Franze, 2003
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PAH on Soot
Proteins in Birch Pollen
Oxidation of BaP other PAH in urban PM2.5
filter samples
Nitration of proteins (tyrosine) in syringe
filter samples
? enhanced hydrophilicity, analytical artefacts
up to 100
? modified bio-activity, enhanced allergenicity
Schauer et al., Environ. Sci. Technol., 2003
Franze et al., Analyst, 2003
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• Soot/Benzoapyrene (BaP) O3/NO2/H2O
• reversible competitive adsorption,
  rate-limiting surface reaction

? deconvolution of elementary processes rate
coefficients ? Langmuir-Hinshelwood mechanism
Pöschl et al., J. Phys. Chem., 2001 Pöschl, J.
Aerosol Med., 2002Ammann et al., Phys. Chem.
Chem. Phys., 2003
S0,X ? 10-3
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Adsorption
Reaction 1
Reaction 2
Reaction 3
Time-dependence of surface composition gas
uptake coefficient (1 ppmv O3) double-layer
surface model, reversible adsorption, BaP surface
oxidation
? limitation of linear extrapolations
steady-state assumptions ? consistent
universally applicable flux formalism
terminology
Pöschl et al., Atmos. Chem. Phys., to be submitted
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Ozone net uptake chemical aging of soot (100
ppbv O3) reversible adsorption, graphene surface
oxidation catalytic self-reaction
Kinetic model framework for aerosol cloud
chemistry physics chemical reactions
elementary multistep, surface bulk mass
transport gas-surface surface-bulk
(deconvolute mass accommodation), adsorption
desorption, condensation evaporation flux
formalism compatible with traditional
resistance formalism (steady state)
Pöschl et al., Atmos. Chem. Phys., to be
submitted
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Salt (NaCl)
Protein (BSA)
Phase transitions deliquescence
efflorescence hysteresis (NaCl, not BSA) Droplet
growth Köhler theory with semi-empirical
ion-interaction model (NaCl) volume additivity
model with novel parameterisation of
macromolecular osmotic coefficient (solid sphere
approximation, BSA) Dry particle shape compact
spheres or cubes
Mikhailov et al., Atmos. Chem. Phys., 2004
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Hydration Dehydration
Hydration or Dehydration
restructuringporosity shape
Phase transitions hysteresis Droplet growth
separate solute volume additivity Dry particle
shape porous agglomerate, fractal salt core
protein envelope, electric charge effects
upon nebulisation of organic-salt mix,
restructuring by capillary condensation (?V 50 )
Mikhailov et al., Atmos. Chem. Phys., 2004
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• NaCl Particles
• twin peaks stepwise transition

• BSA-NaCl Particles (10 BSA)
• single peak continuous transition

? barrier-free nucleation kinetically
limited growth
? structurally limited nucleation
near-instantaneous growth
E. Mikhailov, 2004
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Hydration Dehydration
restructuring evaporation
evaporation

• BSA-NH4NO3 Particles (50 BSA)
• max. evaporation restructuring at high RH (?V
  30-50 , dep. on neutralization) reduced
  evaporation at medium RH

• NH4NO3 Particles
• max. evaporation at medium RH (?V 30 , conc.
  solution), reduced evaporation at low high RH
  (dry particles dilute droplets)

? interaction of electric charge, organic
inorganic components
? rapid evaporation strong humidity
dependence
E. Mikhailov, 2004
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• Research Needs
• physical chemical properties processes
• trace gases, water vapor, clouds,
  precipitation
• radiation electricity

Composition
Aerosol
Interaction
Transformation

• Scientific Approach
• experimental aerosol cloud process studies
  (field lab)
• development validation of measurement
  techniques (field, lab, remote)
• development validation of detailed master
  mechanism process models (consistent
  universally applicable formalism terminology
  for aerosol cloud processes)
• derivation application of simplified
  parameterisations atmospheric models (lumping
  of species processes, local global)