Roles of H2SO4 and Organic Species in Growth of Newly Formed Particles in Rural Environment

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