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Wu Zhijun Leibniz-Institute for Tropospheric Research (Ift) , Leipzig, Germany

The roles of H 2 SO 4 and organic species in the growth of newly formed particles in the rural environment. Wu Zhijun Leibniz-Institute for Tropospheric Research (Ift) , Leipzig, Germany. Talk outline. Introduction: Nucleation and New particle formation and growth.

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Wu Zhijun Leibniz-Institute for Tropospheric Research (Ift) , Leipzig, Germany

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  1. The roles of H2SO4 and organic species in the growth of newly formed particles in the rural environment Wu Zhijun Leibniz-Institute for Tropospheric Research (Ift), Leipzig, Germany

  2. Talk outline • Introduction: Nucleation and New particle formation and growth. • Experimental: Measurements performed at Melpitz, Germany • Case study: Growth rate and condensable vapor concentration • Summary

  3. Nucleation • Nucleation is the onset of a phase transition in a small region. • The phase transition can be the formation of a bubble or of a crystal from a liquid. Creation of liquid droplets in saturated vapor or the creation of gaseous bubble in a saturated liquid is also characterized by nucleation. Nucleation of crystalline, amorphous, and even vacancy clusters in solid materials is also important.

  4. Theories: (1) Binary (H2SO4+H2O) (2) Ternary (H2SO4+NH3+H2O) (3) Ion-induced nucleation (4) Organics (5)…. NewParticle Formation Condensation Coagulation Subsequent growth CCN What is new particle formation? Condensable Vapors Nucleation Stable clusters 1 nm 3 nm detectable Size Kulmala, Science, (2003); Kulmala, Science, (2004);McMurry et al., JGR, (2005)

  5. How important are they? New particle formation is considered as an important source of particles (e.g. Stanier et al. 2004). In particular: Play an important role in determining the concentration ofcloud condensation nuclei (CCN), and may change the extent of cloud cover [Laaksonen et al., 2005]. Global climate Air quality Visibility Particles Health effects What are the chemical mechanisms controlling nucleation ? What are the vapors causing the particle growth?

  6. Up to now: The mechanisms of new particle formation and growth are still not understood very well. • Several different nucleation theories available, but do not work to all the different geographical locations . • The characteristics of species contributing to particle nucleation and growth are still an open question .

  7. Talk outline • Introduction: New particle formation and growth. • Experimental: Measurements performed at Melpitz, Germany • Case study: Growth rate and condensable vapor concentration • Summary

  8. Measurement site Ift’s research station Field campaign: May, June, 2008 Melpitz

  9. Kr85 20-100 nm 3-20 nm Measurements ---instruments • Twin Differential Mobility Particle Sizer (with and without Thermodenuder): (3-800 nm)

  10. Measurements ---instruments • Atmospheric Pressure Chemical Ionisation Mass Spectrometry: H2SO4 • Air Ion Spectrometer: Air ion mobility distribution • Hydroxyl radical (OH), Ozone • VOCs • Meteorological parameters • et al.

  11. New particle formation event at Melpitz

  12. Growth rate of newly formed particles 2008/05/07 Multiple lognormal function: Dm :Mean geometric diameter of lognormal ultrafine particle mode Growth Rate (GR):

  13. Condensational growth GR= Sulfuric acid • Dp : particle diameter; • mv : molecular mass of condensable vapor; • D : the diffusion coefficient; • C : the condensable vapor concentration; • : particle density; M : transitional correction factor for the mass flux;

  14. Condensable vapor concentration • : The mass accommodation coefficient • : The mean free path of the gas molecules.

  15. Results from the calculation H2SO4 available Observed Growth Rate=4.9 nm h-1 condensable vapor conc. = 6.8107 molec. cm-3 H2SO4 conc. = 2.3 107 molec. cm-3

  16. Without Thermodenuder What are the non-volatile compounds? Polymers (Kalberer et al., 2004); HULIS substances (Limbeck et al., 2003); (Heterogeneous reactions) EC? With Thermodenuder (at 300C) ? Potential candidates (1) • Non-volatile compounds (at 300 C)

  17. H2SO4 conc. = 2.3 107 molec. cm-3 (Observed) Growth Rate=4.9 nm h-1 condensablevapor conc. = 6.8107 molec. cm-3 Potential candidates (1) Non-volatile compounds (at 300 C) GR=1.2 nm h-1 C=1.7 107 molec. cm-3 Coagulation growth < 5% (Wehner et al., 2005)

  18. Potential candidates (2) • Semi-volatile compounds: oxidation products of Biogenic VOC VOC, OH, O3: Production rate of semi-volatile organic compounds.

  19. Summary • The sulphuric acid concentrations are too low to explain particle growth in the rural environment, at least for Melpitz. • The non-volatile compounds contributed to the particle growth, and formed parallel to the growth of newly formed particles.

  20. Three take-home messages • NPF events constitute an importantsource of CCN. • H2SO4 concentration can only explain part of the growth rate of newly formed particles. • Non-volatile compounds contribute the growth of newly formed particle.

  21. Thanks!! Acknowledgments: Dr. Wolfram Birmili Aerosol group in ift EUCAARI project Organizers of summer school

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