11

The roles of The roles of HH22SOSO44 and organic and organic speciesspecies

in the growth of newly formed particles in the growth of newly formed particles in the rural environmentin the rural environment

Wu ZhijunWu Zhijun

Leibniz-Institute for Tropospheric ResearchLeibniz-Institute for Tropospheric Research (Ift) (Ift), , Leipzig, GermanyLeipzig, Germany

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Talk outlineTalk outline

• Introduction: Nucleation and New particle Introduction: Nucleation and New particle formation and growth.formation and growth.

• Experimental: Measurements performed Experimental: Measurements performed at Melpitz, Germanyat Melpitz, Germany

• Case study: Growth rate and condensable Case study: Growth rate and condensable vapor concentrationvapor concentration

• SummarySummary

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NucleationNucleation

• NucleationNucleation is the onset of a is the onset of a phase transitionphase transition in a in a small region.small region.

• The phase transition can be the formation of The phase transition can be the formation of a a bubblebubble or of a or of a crystalcrystal from a from a liquidliquid. Creation . Creation of liquid of liquid dropletsdroplets in saturated in saturated vaporvapor or the or the creation of gaseous creation of gaseous bubblebubble in a saturated in a saturated liquidliquid is also characterized by nucleation is also characterized by nucleation. . Nucleation of crystalline, amorphous, and Nucleation of crystalline, amorphous, and even vacancy clusters in solid materials is even vacancy clusters in solid materials is also importantalso important..

44

What is new particle What is new particle formation?formation?

Nucleation

1 nm1 nm 3 nm detectable Size3 nm detectable Size

Condensable Vapors

Kulmala, Science, (2003); Kulmala, Science, (2004); McMurry et al., JGR, (2005)

Theories:Theories:(1) Binary ((1) Binary (HH22SOSO44+H+H22O)O)

(2) Ternary (H(2) Ternary (H22SOSO44+NH+NH33+H+H22O)O)

(3) Ion-induced nucleation(3) Ion-induced nucleation(4) Organics(4) Organics(5)….(5)….

Stable clustersStable clusters

Condensation

Coagulation

New Particle Formation

CCNSubsequent growth

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How important are they?How important are they?

ParticlesParticlesAir qualityVisibility

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?

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Up to now:Up to now: The mechanisms of new particle The mechanisms of new particle formation and growth are still not understood very formation and growth are still not understood very

well.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 . .

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Talk outlineTalk outline

• Introduction: New particle formation and Introduction: New particle formation and growth.growth.

• Experimental: Measurements performed Experimental: Measurements performed at Melpitz, Germanyat Melpitz, Germany

• Case study: Growth rate and condensable Case study: Growth rate and condensable vapor concentrationvapor concentration

• SummarySummary

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Measurement siteMeasurement siteIft’s research station

Melpitz

Field campaign: May, June, 2008

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MeasurementsMeasurements --- ---instrumentsinstruments• TTwin win DDifferential ifferential MMobility obility PParticle article SSizer izer

(with and without Thermodenuder): (3-(with and without Thermodenuder): (3-800 nm)800 nm)

Kr8

Kr8

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3-20 nm 20-100 nm

1010

Measurements Measurements ------instrumentsinstruments• AAtmospheric tmospheric PPressure ressure CChemical hemical

IIonisation onisation MMass ass SSpectrometry: pectrometry: HH22SOSO44

• AAir ir IIon on SSpectrometer: pectrometer: Air ion Air ion mobility distributionmobility distribution

• Hydroxyl radical (OH), OzoneHydroxyl radical (OH), Ozone• VOCsVOCs• Meteorological parametersMeteorological parameters• et al.et al.

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New particle formation event at MelpitzNew particle formation event at Melpitz

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Growth rate of newly formed Growth rate of newly formed particlesparticles

n

i i

i

i

it DpDpN

Dpd

dN

12

2,

)(log2

)log(logexp

log2log

t

DGR m

DmDm :Mean geometric diameter :Mean geometric diameter of lognormal ultrafine particle modeof lognormal ultrafine particle modeGrowth Rate (GR):

Multiple lognormal function:

2008/05/07

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Condensational growthCondensational growth

p

Mvp

D

DCm

dt

dD 4

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;

GR= Sulfuric acid

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Condensable vapor Condensable vapor concentrationconcentration

0,

20,

20,

2

2

2ln623.0312.0

3

2

8 p

ppp

pp

v D

DDD

DD

tDmC

: The mass accommodation coefficient : The mean free path of the gas molecules.

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Results from the Results from the calculationcalculation

Observed Growth Rate=4.9 nm h-1

condensable vapor conc. = 6.8107 molec. cm-3

H2SO4 available

H2SO4 conc. = 2.3 107 molec. cm-3

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Potential candidates (1)Potential candidates (1)• Non-volatile compounds (at 300 Non-volatile compounds (at 300

C)C) Without Thermodenuder

With Thermodenuder (at 300C)What are the non-volatile compounds?Polymers (Kalberer et al., 2004);HULIS substances (Limbeck et al., 2003);(Heterogeneous reactions)EC?

? ?

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Potential candidates (1)Potential candidates (1)

Non-volatile compounds (at 300 Non-volatile compounds (at 300 C)C)GR=1.2 nm hGR=1.2 nm h-1-1

C=1.7 C=1.7 101077 molec. cm molec. cm-3-3

HH22SOSO44 conc. = 2.3 conc. = 2.3 101077 molec. cm molec. cm-3-3

(Observed) Growth Rate=4.9 nm h(Observed) Growth Rate=4.9 nm h-1-1

condensablecondensable vapor conc. = 6.8vapor conc. = 6.8101077 molec. cm molec. cm-3-3

Coagulation growth < 5% (Wehner et al., 2005Coagulation growth < 5% (Wehner et al., 2005)

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Potential candidates (2)Potential candidates (2)

• Semi-volatile compounds: Semi-volatile compounds: oxidation products of Biogenic oxidation products of Biogenic VOCVOC

VOC, OH, OVOC, OH, O33: Production rate of semi-: Production rate of semi-volatile organic compounds. volatile organic compounds.

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SummarySummary

• The sulphuric acid concentrations are The sulphuric acid concentrations are too low to explain particle growth in the too low to explain particle growth in the rural environment, at least for Melpitz. rural environment, at least for Melpitz.

• The non-volatile compounds contributed The non-volatile compounds contributed to the particle growth, and formed to the particle growth, and formed parallel to the growth of newly formed parallel to the growth of newly formed particles. particles.

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Three take-home Three take-home messagesmessages

• NPF events constitute an importantNPF events constitute an important source of CCNsource of CCN..

• HH22SOSO44 concentration can only explain concentration can only explain

part of the growth rate of newly formed part of the growth rate of newly formed particles. particles.

• Non-volatile compounds contribute the Non-volatile compounds contribute the growth of newly formed particle. growth of newly formed particle.

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Thanks!!Thanks!!

Acknowledgments:Acknowledgments:Dr. Wolfram Birmili Dr. Wolfram Birmili Aerosol group in iftAerosol group in iftEUCAARI projectEUCAARI projectOrganizers of summer schoolOrganizers of summer school