Atmospheric New Particle Formation: What compounds are responsible for their formation and growth and why should we care? Amar Hamed Department of Applied Physics University of Eastern Finland Kuopio, Finland [email protected]

PART 1 Atmospheric New Particle Formation (NPF): ULTRAFINE PARTICLES, What are they? What compounds are responsible for NPF growth? and why should we care? PART 2 Overview of the current status of knowledge of nucleation and NPF PART 3 Some work performed at SPC station related to nucleation and NPF

With every breath, Tiny particles smaller than 100 nanometer or so called “Ultrafine Particles” are inhaled into our body. They are invisible to our eyes , however, if they remain in our lung, they may have an impact on our health.

The particles with diameters in the range of 1 to 50 nm => Particles of this size have very different properties than bulk phase materials have lifetimes in the atmosphere of minutes to an hour. =>This makes them an effective means of measuring local heterogeneous processes … if you can measure them on that timescale!

How do nanoparticles form? Nanoparticles form in the atmosphere by condensation to stable clusters formed by nucleation. They can also be emitted directly, e.g., by diesel engines. So how are stable clusters formed in the atmosphere? The formation of stable clusters from low vapor pressure atmospheric species is known as homogeneous nucleation. random collisions and intermolecular forces cause molecules to form and break apart

cluster grows indefinitely by condensation and coagulation until it becomes a particle

energy

(a particle)

Slide from Prof. James Smith

a stable "critical cluster" forms!

cluster or particle size

minimum detectable diameter by particle instrumentation

~3 nm

What is the main process concerning secondary aerosol formation ?

Nucleation !

Condensational growth !

We suggest that the growth of clusters to a detectable size is restricted by the availability of condensable vapour. Observations of atmospheric particle formation and growth from a continental and a coastal site support this hypothesis, including that a growth process including ternary nucleation is likely to be responsible for the formation of CCN.

Kulmala et al., Nature 2000

How do New Particle Formation form? This schematic shows an example of the nucleation and subsequent growth process for atmospheric binary homogeneous nucleation of H2SO4 and H2O.

J. Curtius / Eur. Phys. J. Conferences 1, 199–209 (2009)

Why are NPF important?

By growing to diameters of 80 nm and greater, NPF can indirectly influence climate by increasing cloud condensation nuclei concentrations.

Laaksonen et al.,GRL, 2005.

Sneak preview of the next hour …  Field measurements: Laaksonen et al.,2005, Polluted PoValley; Hamed et al,2010, rural areas Germany; Kerminen et al., 2005, Clean, Finland)  New particle formation (NPF) can account for a significant amount of the global population of cloud condensation nuclei (CCN). 

Model studies:

Pierce and Adams, ACP, 2007 => suggest that NPF can contribute up to 40% of the CCN at the boundary layer, and 90% in the remote troposphere. Spracklen et al., ACP, 2006 => estimate that NPF can add as much as a 8 times more particles to the remote southern ocean atmosphere than anthropogenic primary particles.

The growth rate of newly formed particles is key to assessing the impact of NPF on CCN populations. How far/close we are to understand the species and mechanisms by which particles grow??

Motivation: We still cannot adequately quantify the impact of aerosols on climate

Part 1

(Intergovernmental Panel on Climate Change “IPCC” 2007)

PART 2 OVERVIEW OF THE CURRENT STATUS OF KNOWLEDGE OF NUCLEATION AND NEW PARTICLE FORMATION

New particle formation happens just about everywhere we look!

• More than 100 individual investigations as of 2003 • NPF form at rates as high as 104 – 105 cm-3 s-1 during nucleation events, then grow at rates of 1-30 nm hr-1.

Kulmala et al., J. Aerosol Sci, 2003

Evidence of The role of sulphuric acid on nucleation & NPF Lab measurement

Jnuc = K [H2SO4] p

Nucleation mechanisms

Jnuc = K [H2SO4] p Jnucl is the atmospheric nucleation rate, [H2SO4] is the sulphuric acid concentration , K is the prefactor that provides insight into the chemistry and physics of the nucleation mechanism (activation and kinetic mechanism, respectively). p = 1 cluster activation mechanism(Critical clusters contain 1 H2SO4 molecule, these clusters are activated for further growth)

p=2 kinetic mechanism (Critical clusters formed in collisions of 2

molecules containing H2SO4, e.g. ammonium bisulphate molecules)

Evidence of The role of sulphuric acid on nucleation & NPF Field measurement

P=2 kinetic mechanism (critical cluster are formed comprising 2 sulfuric acid molecules through a kinetically controlled nucleation process).

Kuang et al., JGR, 2008

Evidence of The role of sulphuric acid on nucleation & NPF Modelling

The model reproduced the observed secondary aerosol concentrations and the occurrence of new particle formation with good accuracy, proving that this kind of a simple parameterization has the potential to predict the occurrence of particle formation, at least in the boreal forest boundary layer.

Sihto et al., ACP, 2009

Lab measurments

At a given nucleation rate, J1.5, can be sustained at lower H2SO4 levels if there is more organic vapor, and vice versa..

Data are color coded with the amount of NucOrg

=>indicating that both species contribute to nucleation in a kinetically limited process.

Modelling

GLOMAP shows simulated surface mean particle number concentrations for different simulations during spring-time BHN

kinetic mechanism

Activation mechanism

kinetic nucleation involving organics

Authors captured the new particle formation days very nicely when they used the combined organo-sulfate formation mechanism…

The general lack of nucleation in oceanic regions is, however, captured by the new organic activation mechanism, due to a low concentration of organics and subsequently slow nucleation rates.

EVIDENCE of the role of organic vapours on nucleation & NPF FIELD MEASUREMENT Filed measurement

Modeled growth due to sulfuric acid shows that sulfuric only accounts for 10% of observed growth. Smith et al., GRL, 2008

TDCIMS measurements of 8-10 nm particles during March 21, 2006 TDCIMS positive ion mass spectrum 200°C filament temp. 37*

ME+

*: reagent 32

19*

46

DME+

Amines in particles formed from nucleation during MILAGRO

Motivation: nucleation mechanisms and vapours participating in the particle formation& growth are still uncertain and poorly understood.

It is essential that new particle formation is sufficiently well understood since global climate models require accurate prediction of atmospheric new particle formation in order to realistically capture aerosol radiative effects.

PART 3 SOME WORK PERFROMED AT SPC STATION RELATED TO NUCLEATION AND NEW PARTICLE FORMATION

Twin DMA Setup SPC Sample Aerosol Ex. Nafion Dryer

CPC

TSI 3025 UF-CPC

1 l/min

Excess Air

DMA

Pump Sheath Air Diffusion Dryer

Excess Air

~2.5 l/min

CO

1.5 l/min 10 l/min

NL

P 6.6 l/min

CO

1.5 l/min 10 l/min P

TSI 3010

DMA

Pump

1 l/min 6.6 l/min

Sheath Air Diffusion Dryer

CPC: Counter CO: DMA: Analyzer Ex. NL: P: UF-CPC Vac.

DMA-1: Number Size Distribution ~3- 15 nm

DMA-2: Number Size Distribution ~15 - 600 nm

Condensation Particle Critical Orifice Differential Mobility Excess Bipolar Neutralizer Pressure Gauge Ultrafine Condensation Particle Counter Vacuum (pump) HEPA filter

Table . Summary of measured gas , meteorological parameters and Aerosol, instruments, measuring ranges and detection limits.

Parameter SO2 NOx O3 Temperature RH Wind direction Wind speed Global radiation

Instrument Monitor Labs model 8850 API model 200A API model 400A Vaisala HMP45D Vaisala HMP45D Vaisala WAV151 Vaisala WAA151 anemometer Kipp&Zonen CM6B

Precipitation

SIAP-UM7525

Pressure Aerosol

Milos board DPA50 TDMPS

Measuring ranges

Detection limit

0-50 pp/0-20 ppm 0-100 ppb/0-10 ppm -40 - +60 °C 0 - 100 % 0 - 360° 0.4 -75 m/s 2000 W/m2 (305 - 2800 nm)

0.5 ppb RMS < 0.6 ppb

500 - 1100 hPa 3-600 nm

± 0.1 mm < 5 mm/h) ± 2% (> 5 mm/h) 3 nm

Source: ARPA Servizio Idro Meteo, Italy.

When YOU can consider a day as a nucleation event day??? In practice, new particle formation event can be seen as: An increase of the particle concentrations in the smallest • channels of the DMPS system. • After some time, these newly formed particles have shown subsequent growth that can be seen typically at a rate of few nanometres per hour during the rest of the day. 1. if the formation of new aerosol particles starts in the nucleation mode size range 2. Nucleation mode is observed over a period of several hours 3. showing signs of growth. If the aerosol size distribution from a given day exhibits these signs, the day can be selected as a typical new particle formation day (event day).

An example of a NPF day at the SPC station, Italy.

An example of a non- NPF day at the SPC station, Italy.

An example of a undefined day (Not sure whether it is event or non-event) at the SPC station, Italy.

Table summarizes the number of nucleation event, Non-Event days (NE), Undefined days and Missing Data (MD) throughout the 10 years measurements at the SPC station. Month 1 2 3 4 5 6 7 8 9 10 11 12

AllOkDays 225 200 240 222 185 138 188 166 144 141 144 185

Nucleation event Days 18 41 62 88 123 86 130 83 44 27 9 14

Non-Nucleation event Days 138 69 73 56 21 19 18 41 41 40 94 111

Undefind Days 69 90 105 78 41 33 40 42 59 74 41 60

Sum

2178

725

721

732

Event days: 33.2% Non-events 33.1% of the data 33.6% are such that an event may or may not have taken place what so called Undefined Days.

Unpublished data

No-data Bad-data 72 13 69 14 64 14 49 36 76 49 94 68 97 25 140 4 142 14 107 62 118 38 112 13 1140

350

Unpublished data

Particle formation rate and growth rate (FR & GR)

Formation rate (the rate of appearance of new particles > 3 nm)

An example of a NPF day (class 1 event on 28.8.2011 at the SPC station, Italy). The thin red and green vertical lines show the start and end of the particle bursts above the detection limit of 3 nm. The thin blue line is the fitted curve for the constant growth rate of the nucleation mode.

On this day, the estimated growth rate (GR) was 5.8 nm h−1. formation rate (J3) was 3 cm−3 s−1 Unpublished data

The nucleation rate, J1 (cm-3 s-1), estimated from particle measurements, versus the sulfuric acid concentration measured at SPC station during campaign from June 26th to July 12th 2009. Black line shows the

best linear fit, n=2.2± 0.02. Unpublished data

We calcaute CCN production for more than 2 years than our earlier paper by Laaksonen et al., 2005

Particle Diameter (nm)

(1). We calculated the increases in concentrations of particles in the 50-600 nm, 100-600 nm, and 200600 nm size ranges on nucleation event days.

10

10

10

10

2

1

0

00:00

06:00

12:00 Time (h)

18:00

24:00

dn/dlogDp (cm-3)

100

10

Particle Concentration (cm -3)

•The concentration increases in the given size ranges were simply determined from the differences at the minima (visual determined where the banana reaches lower limit of the given size range) and at the maxima (the end point is where maximum or mid nigh, whichever, come first), as depicted in the bottom graph.

San Pietro Capofiume: 25-03-2002

3

10

10

10

1000

10000

100000

5 3-600 nm 20-600 nm 50-600 nm 100-600 nm 200-600 nm

4

3

2

00:00

06:00

12:00 Time (h)

18:00

24:00

Size Range (nm)

50-600

100-600

200-600

Annual Production/ cc

2.22E+05

8.05E+04

1.54E+04

Average Concentration/cc

5.83E+03

3.09E+03

8.51E+02

Average Production/Event

8.23E+03

2.98E+03

5.71E+02

(2) For further importance of nucleation events • We estimated the Average Production/Event

Even though the SPC region is characterized by strong anthropogenic activities, and thus it is quite possible that the CCN budget is governed by sources other than nucleation, Surprisingly NPF events are quite intense and frequent, suggesting that they are an important source of CCN in spite of the polluted nature of the region Unpublished data

Conclusions  New particle formation happens at SPC very frequent and not like any other stations ,up to our knowledge, that summer times are the most frequent months for NPF to occur (High T, High Radiation, High SO2, etc… also high O3)  Nucleation at SPC station is more governed by Kinetic mechanism (Critical clusters formed in collisions of 2 molecules containing H2SO4, e.g. ammonium bisulphate molecules)

Nucleation events in SPC are significant sources of CCN production

Acknowledgements C.N.R • Claudio Carbon • Leone Tarozzi • Stefano Decesari • Cristina Facchini University of Eastern Finland •Pasi Mitettinen •Jorma Joutsensaari •Ari Laaksonen

Thank you for your attention!