image
image
image
image
image
UFP Measurements and Modelling
Wolfram Birmili
Leibniz Institute for Tropospheric Research, Leipzig
UFIPOLNET, Dresden, 24/10/2007
K. Weinhold, D. Hinneburg, O. Knoth, B. Wehner, U. Uhrner, S. v. Löwis,
O. Hellmuth, C. Engler, A. Wiedensohler (IfT), Th. Tuch (UfZ), J. Borken (DLR)

Outline
• Size definition of UFPs
• Experimental UFP observations
• UFP processes in the atmosphere
• Exemplary Model simulations

Atmospheric UFPs: Main questions
• Global climate:
– Mechanism of particle nucleation in the atmosphere
– Yield of cloud condensation nuclei (CCN) from
newly formed particles
• Urban climate and exposure
– Emission and formation rates of UFPs
– Lifetime and persistence of UFPs
– Exposure patterns of UFPs
– Health effects of UFPs

On the definition of Ultrafine Particles
• Health-related research:
D
p
< 100 nm
Coarse (2.5 – 10 μm), Fine (0-2.5 μm), Ultrafine (0-0.1 μm)
• „Nanoparticles“:
D
p
< 50 nm
Size range where molecular effects become apparent
• Other definitions:
D
p
< 20 nm
Ultrafine particles ~ Nucleation mode

Particle emission spectrum of traffic
(A100 motorway Berlin)
6
10
100
500
10
11
10
12
10
13
D
g
= 71 nm
σ
= 1.88
E = 5.6*10
12
veh
-1
km
-1
D
g
= 17 nm
σ
= 1.75
E = 1.2*10
13
veh
-1
km
-1
E [particles veh
-1
km
-1
]
Diameter [nm]
Eq. 6
Eq. 8
Eq. 9
100 nm
Cut-off
SOOT

On the definition of Ultrafine Particles
• A size-cut at 100 nm is not very useful
• Size cuts around 50 nm and 200 nm better separate
2 main types of ultrafine particles:
• 50 nm <
D
p
< 200 nm ~ solid particles (soot)
D
p
< 50 nm ~ condensation particles (H
2
SO
4
, OC)

Berlin (BAB100)
Bitterfeld
Leipzig (Listplatz)
Leipzig (Eisenbahnstraße)
Zerbst
Leipzig (Inselstraße)
Dresden-Neustadt
Hettstedt
Erfurt
Leipzig-IfT
Augsburg
Leipzig-Rabet
Berlin-Westend (Am Bf)
Berlin-Westend (Wasserwerk)
Heidelberg
Panitsch
Hohenpeißenberg (Wald)
Collm
Melpitz
Falkenberg
Waldstein
Hohenpeißenberg
Goldlauter
Schauinsland
Zugspitze
0
20000
40000
60000
80000
100000
Median
75 %-tile
99 %-tile
Ambient UFP concentrations in Germany
N
[10;100nm]
in p./cm
3
Birmili, W. and others (2006)
Räum-
lich-zeitliche Verteilung, Eigen-
schaften und Verhalten ultrafeiner
Aerosolpartikel (< 100 nm) in der
Atmosphäre, sowie die Entwicklung
von Empfehlungen zu ihrer system-
atischen Überwachung in Deutsch-
land.
93 S., UBA-Texte, 26, ISSN
1862-4804, available at
http://www.-
umweltdaten.de.

Site characteristic
cm
-3
Continental Background
600 - 1400
Rural
1000 - 5000
Near city
2800 - 6000
Urban background
3500 - 16000
Urban background (Ruhr area)
8000 - 24000
Near roads
5500 - 37000
Typical levels of ambient UFP
concentrations in Germany

image
Sources of UFPs in Saxony (6 months)
Kay Weinhold, Master thesis, University of Leipzig, 10/2007.
Mountain
station
small
differences
Rural background
Roadside sites
Urban background

image
image
Atmospheric processes of UFPs
Planetary
Boundary Layer
Free Troposphere
Entrainment Zone
Direct emissions
Turbulent
fluxes
Advection
Aerosol dynamics
Coagulation, Condensation
Secondary formation

image
Diurnal pattern of UFPs in Saxony
Urban background
Rural background
Mountain site
TRAFFIC
DILUTION
RE-STRATIFICATION
Kay Weinhold, Master thesis, University of Leipzig, 10/2007.

image
image
Long-term observation strategies for UFPs
Germany: 8 sites in 2007
EUSAAR: > 20 sites in 2007

image
image
Process scales
Global
Europe
Region
Synoptic winds
1 City
Surface roughness
Area in 1 city
Street canyon
Hemispheric oscillations
Boundary layer convection
Vehicle-induced turbulence
Tailpipe plume
Non-equilibrium expansion
Particle emission
Processing
(Coagulation,
Condensation,
Particle deposition
Model Scale
Transport phenomena
Obstacle effects
Aerosol particles
Particle mass
Particle number
Size distribution
Chemical composition

Photochemically produced UFPs in the
continental boundary layer (Melpitz)
0
4x10
4
8x10
4
3
10
100
700
200.0 335.7 563.5 945.7 1587 2664 4472 7506 1.26E42.115E43.55E45.958E4 1E5
200
d
N
/ dlog
D
p
, cm
-3
4500
100000
Particle diameter in nm
April 15, 1996
April 16, 1996
April 17, 1996
770 W m
-2
UFP, cm
-3
[SO
2
]
Solar irradiance
UFP
16 ppbV

image
Kulmala, Pirjola, and Mäkelä (2000)
Stable sulphate clusters as a source of new atmospheric
particles
. Nature 404, 66-69.
Box model: Nucleation & growth
The exact nucleation mechanism is subject to many uncertainties.

Coagulation of UFPs
A major determinant of the lifetime of UFPs is the
coagulation with larger particles

Lifetime estimation of UFPs
12 nm particles in a street canyon (Leipzig)
18 nm particles near a motorway in Berlin
Size distribution percentile Numer concentration in cm-3
Dmax
Half-life-time
50
33000
90 nm
61 min
75
43000
103 nm
49 min
95
92000
75 nm
31 min
99
140000
72 nm
22 min
Size distribution percentile Numer concentration in cm-3
Dmax
Half-life-time
50
25000
90 nm
240 min
75
52000
90 nm
120 min
95
110000
91 nm
63 min
99
180000
96 nm
43 min

image
UFP production rate (at 3 nm) from
neutral cluster activation by H
2
SO
4
Makkonen, Asmi, Korhonen, Kokkola, Järvenoja, Räisänen, Lehtinen, Kerminen, Järvinen and
Kulmala (2007) 17
th
International Conference on Nucleation and Atmospheric Aerosols,
13. -17.8.2007, Galway, Ireland
ECHAM5-HAM

image
UFP concentrations resulting from a
nucleation burst (H
2
SO
4
/H
2
O)
Hellmuth, O. (2006) Atmos. Chem. Phys., 6, 4231-4251, 2006.

• Due to computational restrictions, the
representation of aerosol particles is usually
limited to a few modes;
dynamic processes tend to be parametrised
• High uncertainties exist with regard to
– Particle number emissions & formation rates
– Liquid phase and wet scavenging processes
Aerosol transport models

image
Dispersion of motorway emissions (D=0°)
roadside
background
ASAM
(O. Knoth)

image
Dispersion of motorway emissions (D=270°)
roadside
background
ASAM
(O. Knoth)

Size distribution emission factor
610 100 500
10
11
10
12
10
13
D
g
= 71 nm
σ
= 1.88
E = 5.6*10
12
veh
-1
km
-1
D
g
= 17 nm
σ
= 1.75
E = 1.2*10
13
veh
-1
km
-1
E [particles veh
-1
km
-1
]
Diameter [nm]
Eq. 6
Eq. 8
Eq. 9

image
image
Uhrner, Löwis, Vehkamäki, Wehner, Bräsel, Hermann, Stratmann, Kulmala,
Wiedensohler (2007) Atmos. Env., in press.
Tailpipe Measurements of UFPs

image
Tailpipe CFD & aerosol modelling
Uhrner, Löwis, Vehkamäki, Wehner, Bräsel, Hermann, Stratmann, Kulmala,
Wiedensohler (2007) Atmos. Env., in press.
Particle nucleation
within the turbulent
tailpile of a vehicle
FLUENT-
FPM

• Experimental data confirm that besides
secondary formation, traffic is the most
important source of UFPs in Germany.
• Atmospheric models are now handling aerosols
as a dynamic variable at all atmospheric scales
• Qualitative understanding of most processes
• Need to develop transport models for the
intermediate (urban scale)
• More need for model validation experiments
Summary

Birmili, W., K. Schepanski, A. Ansmann, G. Spindler, I. Tegen, B. Wehner, A. Nowak, E. Reimer, I. Mattis, K. Müller, E. Brüggemann, T.
Gnauk, H. Herrmann, A. Wiedensohler, D. Althausen, A. Schladitz, T. Tuch, and G. Löschau (2007) An episode of extremely high PM
concentrations over Central Europe caused by dust emitted over the southern Ukraine.
Atmos. Chem. Phys. Discuss
.
7
:12231-12288.
Voigtländer, J., T. Tuch, W. Birmili, and A. Wiedensohler. Correlation between traffic density and particle size distribution in a street
canyon and the dependence on wind direction.
Atmos. Chem. Phys
.,
6
:4275-4286, 2006.
Kulmala, M., Vehkamäki, H., Petäjä, T., Dal Maso, M., Lauri, A., Kerminen, V.-M., Birmili, W. and McMurry, P. H. Formation and growth
rates of ultrafine atmospheric particles: A review of observations.
J. Aerosol Sci
.,
35
, 143-176, 2004.
Birmili, W., H. Berresheim, C. Plass-Dülmer, T. Elste, S. Gilge, A. Wiedensohler, and U. Uhrner. The Hohenpeissenberg aerosol formation
experiment (HAFEX): a long-term study including size-resolved aerosol, H2SO4, OH, and monoterpenes measurements.
Atmos. Chem.
Phys
.,
3
:361–376, 2003.
Wehner, B., W. Birmili, T. Gnauk, and A. Wiedensohler. Particle number size distributions in a street canyon and their transformation into
the urban background: Measurements and a simple model study.
Atmos. Env
.,
36
:2215–2223, 2002.
Birmili, W., A. Wiedensohler, J. Heintzenberg, and K. Lehmann. Atmospheric particle number size distribution in Central Europe:
Statistical relations to air masses and meteorology.
J. Geophys. Res.
,
D23
:32,005–32,018, 2001.
Birmili, W. and A. Wiedensohler. New particle formation in the continental boundary layer: Meteo-rological and gas phase parameter
influence.
Geophys. Res. Lett
.,
27
:3325–3328, 2000.
Birmili, W., A. Wiedensohler, C. Plass-Dülmer, and H. Berresheim. Evolution of newly formed aerosol particles in the continental
boundary layer: A case study including OH and H2SO4 measurements.
Geophys. Res. Letters
,
27
:2205–2209, 2000.
Birmili, W., F. Stratmann, and A. Wiedensohler. Design of a DMA-based size spectrometer for a large particle size range and stable
operation.
J. Aerosol Sci
.,
30
:549–553, 1999.
Birmili, W., A. Wiedensohler, B. Wehner, T. Tuch, A. Nowak, U. Franck, M. Pitz, J. Heinrich, J. Cyrys, W. Kreyling, A. Peters, and E.
Wichmann.
Räumlich-zeitliche Verteilung, Eigenschaften und Verhalten ultrafeiner Aerosolpartikel (< 100 nm) in der Atmosphäre, sowie
die Entwicklung von Empfehlungen zu ihrer systematischen Überwachung in Deutschland
. 93 S.,
UBA-Texte,
No. 26/06, document
available as
www.umweltdaten.de/publikationen/fpdf-l/3114.pdf
, 2006
.
Lanzendorf, M., W. Birmili, and P. Franke und weitere beitragende Autoren
, Verkehrsbedingte Feinstäube in der Stadt. 92 S., UBA-Texte,
No. 18/06
,
document available as
www.umweltdaten.de/publikationen/fpdf-l/3067.pdf
, 2006
.
Birmili W., D. Hinneburg, A. Sonntag, K. König, B. Alaviippola, B. Wehner, M. Merkel, S. Klose, A. Wiedensohler, O. Knoth, T. Tuch, M.
Schilde, U. Franck.
Konzentration ultrafeiner luftgetragener Partikel (< 100 nm) in städtischen Atmosphären: Validierung von
Messverfahren, experimentelle Bestimmung ihrer raum-zeitlichen Verteilung und mikroskalige Transport- und
Transformationsmodellierung
. 87 S., Abschlussbericht UFOPLAN-Projekt 20442204/03, Umweltbundesamt, Dessau, 11. April 2007.
Birmili W., K. König, A. Sonntag, Y. F. Cheng, T. Tuch, and A. Wiedensohler, Ermittlung des nordhemisphärischen Hintergrunds an der
GAW-Station Zugspitze unter besonderer Berücksichtigung des Ferntransportes von Feinstäuben. 97 S., Abschlussbericht UFOPLAN-
Projekt 20442202/01, Umweltbundesamt, Dessau, 12. Oktober 2007.
Literature