How Particles Nucleate and Grow

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How Particles Nucleate and Grow

• Markku Kulmala

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Recently we have shown

• Continuous measurements are powerful
• Atmospheric particle formation has global
  importance
• growth of new particles to cloud droplets
• health effects of ultrafine particles
• Boreal forests act as aerosol sources
• Couple of connections between biosphere-atmospher
  e e.g. biology-physics chemistry and
  meterorology of aerosol formation

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Aerosol Formation
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Approach to study aerosol formation and growth

• experimental
• laboratory
• field (continuous and campaigns)
• development of novel instrumental techniques
• theoretical
• basic theories
• simulations
• model development

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• The dots indicate observation sizes, the
  dashed lines and rectangles indicate regions
  where airborne or ship observations have been
  made. (Kulmala et al, 2004)

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Nucleation ModeFormation and Growth Rates

• From size distribution data
• Formation rates (J3)
• Growth rates
• Condensation sinks
• Coagulation sinks
• can be estimated

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• Mean size versus time of day during a
  regional nucleation event in St. Louis on
  September 1, 2001 (Shi, 2003).

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Summary Formation of Nucleation Mode aerosols

• During last 10 years a lot of observations
• Our recent review (Kulmala et al., 2004)
• more than 100 papers published on the topic
• some support to ternary water-sulphuric-ammonia
  nucleation
• Condensation growth in continental BL (Boy et
  al., 2003)
• 10-40 by sulphuric acids
• 20-40 by dicarboxyl acids
• 10-20 by oxidation products of sesquiterpenes
• More recently (Boy et al., 2004) by sulphuric
  acid
• 5-15 in clean air masses
• 10-40 in polluted air masses

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Formation and Growth ratesObserved values

• J3
• Regional background
• 0.01 10 cm-3s-1
• Urban areas 10 100 cm-3s-1
• Coastal zones 1000 1 000 000 cm-3s-1
• GR
• 1 20 nm/h
• 0.1 nm/h (Arctic areas)

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So far our analysis

• Based mainly on DMPS/SMPS data
• smallest size 3 nm
• what happens below that
• new instrumentation needed
• dynamical behaviour of cluster
• to test and verify hypothesis

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Size evolution from Ion Spectrometer
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Ion spectrometer measurements in Hyytiälä, Finland

• Ion sepctrometers developed By University of
  Tarto
• Accroding to the the analysis of 20 particle
  formation days ion induced nucleation seems to
  be less important or unlikely

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Processes

• Nucleation
• Ternary/Kinetic Nucleation
• H2SO4-NH3-(H2O)
• Initial steps of the growth
• Nano-Kohler
• Heterogeneous Nucleation
• Growth
• Organic vapours
• Aerosol dynamics
• competition between processes

Kulmala Science 302, 1000-1001, 2003
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Open Questions (November 2003)

• Is TSC Nano-Kohler hypothesis valid ?
• Is there neutral clusters ?
• Ion clusters are anyhow around
• Model calculations shows that there is also
  neutral
• The composition of nucleation mode aerosol
  particles ?
• Related thermodynamics ??
• saturation concentration of condensing vapours
  seems to be 3 x 106 cm-3

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Try to Answer

• First two open questions
• Existence of Neutral clusters (TSCs) as predicted
  by Kulmala et al., (Nature, 404, 66-69, 2000)
• size dependent growth as predicted by Kulmala et
  al. (JGR, 2004)
• Using observations and laboratory experiments
  (DMPS/AIS/BSMA) and nucleation inside CPC
• Theoretical understaning why?

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Growth as a function of size

• From DMPS and ion spectrometer data growth rate
  non-constant
• To test different hypothesis of initial steps of
  the growth

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Organic growth rate / 2-10 nm

• Homogeneous nucleation
• at the begining rapid increase then relatively
  constant
• Nano-Kohler
• slow increase of the growth as a function of size
• Condensation enhanced by ions
• decreasing as a function of size

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Nucleation inside CPC


Kulmala et al., 2004
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Neutral clusters concentrations
Kulmala et al., 2004
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Experiment with indoor aerosol
room1
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After shifting
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On Ammoniumbisulphate Clusters

• According to thermodynamics practically every
  sulphuric acid molecule is bound to stable
  ammonium bisulphate cluster in atmospheric
  conditions
• Quantum mechanical calculations show no ammonium
  bisulphate formation
• QM does not predict observed sulphuric acid
  hydrates either
• ammonia affects H2SO4-H2O nucleation according to
  laboratory and atmospehric measurements, but QM
  results say it does not

Vehkamäki et al., 2004
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Open Questions and Recent Answers

• Is TSC Nano-Kohler hypothesis valid ?
• YES
• The growth is size dependent
• Is there neutral clusters ?
• yes
• better confirmation needed
• new and more excat experimental methods needed
• Model calculations shows that there is
• Experimental data shown here gives some
  indications
• composition of clusters ?
• maybe ammoniumbisulphate

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Summary/ Aerosol Formation

• In Continental Boundary layer particularly in
  Boreal Forest
• nucleation sulphuric acid ammonia (water) or
  sulphuric acid di/trimethylamine
• kinetic
• growth by oxidation products of mono- and
  sesquiterepenes
• seasonal variation (particularly growth) related
  photorespiration
• Clear observed coupling between aerosol
  production and carbon sink

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Summary II

• Nucleation mode organic aerosols will form much
  easier on the surface of existing TSCs than form
  new particles
• Coagulation - condensation competition is a key
  ions will affect on that competition
• This explains why we do not see aerosol formation
  in all those cases when predicted by nucleation

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How aerosol particles nucleate and grow

• Typically in troposphere
• kinetic nucleation (H2SO4 NH3(?) H2O)
• formation of stable clusters (ammoniumbisulphate?)
  
• growth by organic vapours
• Also
• A) In polluted areas
• growth also by sulphuric acid
• B) in Coastal areas
• Iodide compounds
• C) Inside clouds and cloud outflows
• insoluble organic compounds

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In Near (?) Future

• Regional and Global Models
• From processes/box to 3D
• Thermodynamics
• vapour pressures, activities
• uptake coefficients
• Field measurements vs modelling
• use of whole BACI network
• Lagrangian and regional modelling

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Team

• University of Helsinki
• Kari E.J. Lehtinen, Hanna Vehkamäki, Kaarle
  Hämeri, Ullar Rannik, Ismo Napari, Pasi P. Aalto,
  Miikka Dal Maso, Genrik Mordas,Michael Boy, Anca
  Gaman, Ismo K. Koponen, Lauri Laakso, Antti
  Lauri, Tanja Suni, Anni Reissel, Jaana Bäck,
  Tuulia Hyötyläinen, Marja-Liisa Riekkola, Pertti
  Hari, Timo Vesala, Alex Lushnikov
• University of Kuopio
• Ari Laaksonen, Jorma Joutsensaari
• Finnish Meteorological Institute
• Veli-Matti Kerminen, Tatu Anttila, Hannele
  Korhonen, Jussi Paatero, Hannele Hakola, Heikki
  Lihavainen, Mika Komppula, Yrjö Viisanen
• University of Tartu, Estonia
• Madis Noppel, Urmas Hörrak, Marko Vana, Hannes
  Tammet, Aadu Mirme
• University of Stockholm, Sweden
• E. Douglas Nilsson, Peter Tunveed, H.-C.
  Hansson, Robert Janson
• National University of Ireland, Galway
• Colin ODowd
• Tampere University of Technology
• Jyrki M. Mäkelä
• MPI Heidelberg, Germany
• Frank Arnold, Markus Hanke
• University of Oslo, Norway
• Alf Grini