1 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

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

3 Nucleation Nucleation is the onset of a phase transition in a small region. Nucleation is the onset of a phase transition in a small region.phase transitionphase transition 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. 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. bubblecrystalliquiddropletsvaporbubbleliquid bubblecrystalliquiddropletsvaporbubbleliquid

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

5 How important are they? Particles Air quality Visibility Global climate Health effects 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 of cloud condensation nuclei (CCN), and may change the extent of cloud cover [Laaksonen et al., 2005]. 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. 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. Introduction: New particle formation and growth. Experimental: Measurements performed at Melpitz, Germany Experimental: Measurements performed at Melpitz, Germany Case study: Growth rate and condensable vapor concentration Case study: Growth rate and condensable vapor concentration Summary Summary

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

9 Measurements ---instruments Twin Differential Mobility Particle Sizer (with and without Thermodenuder): (3-800 nm) Twin Differential Mobility Particle Sizer (with and without Thermodenuder): (3-800 nm) Kr nm nm

10 Measurements ---instruments Atmospheric Pressure Chemical Ionisation Mass Spectrometry: H 2 SO 4 Atmospheric Pressure Chemical Ionisation Mass Spectrometry: H 2 SO 4 Air Ion Spectrometer: Air ion mobility distribution Air Ion Spectrometer: Air ion mobility distribution Hydroxyl radical (OH), Ozone Hydroxyl radical (OH), Ozone VOCs VOCs Meteorological parameters Meteorological parameters et al. et al.

11 New particle formation event at Melpitz New particle formation event at Melpitz

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

13 Condensational growth D p : particle diameter; m v : molecular mass of condensable vapor; D : the diffusion coefficient; C : the condensable vapor concentration;  : particle density;  M : transitional correction factor for the mass flux; GR= Sulfuric acid

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

15 Results from the calculation Observed Growth Rate=4.9 nm h -1 condensable vapor conc. = 6.8  10 7 molec. cm -3 H 2 SO 4 available H 2 SO 4 conc. = 2.3  10 7 molec. cm -3

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

17 Potential candidates (1) Non-volatile compounds (at 300  C) GR=1.2 nm h -1 C=1.7  10 7 molec. cm -3 H 2 SO 4 conc. = 2.3  10 7 molec. cm -3 (Observed) Growth Rate=4.9 nm h -1 condensablevapor conc. = 6.8  10 7 molec. cm -3 condensable vapor conc. = 6.8  10 7 molec. cm -3 Coagulation growth < 5% (Wehner et al., 2005 Coagulation growth < 5% (Wehner et al., 2005 )

18 Potential candidates (2) Semi-volatile compounds: oxidation products of Biogenic VOC Semi-volatile compounds: oxidation products of Biogenic VOC VOC, OH, O 3 : Production rate of semi- volatile organic compounds. VOC, OH, O 3 : 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 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. 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 important source of CCN. NPF events constitute an important source of CCN. H 2 SO 4 concentration can only explain part of the growth rate of newly formed particles. H 2 SO 4 concentration can only explain part of the growth rate of newly formed particles. Non-volatile compounds contribute the growth of newly formed particle. 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