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Continuous observations of particle size distributions at the
Frohnau Tower in Berlin with an altitude of 320 m
Markus Pesch, Stefan Hartstock and Daniel Oderbolz
v
Senatsverwaltung für Gesundheit,
Umwelt und Verbraucherschutz
Introduction
The department of environmental engineering of the TU-Berlin carries out a
1-year PM2.5 measurement campaign (01.12.06 - 30.11.07) which is
granted by the Senate of Berlin. The measurements were taken at four
different sites to determine local, urban and regional sources of fine
particulate matter in Berlin. One measurement site is the “Frohnau tower”,
a tower at the northern outskirt of the city with an altitude of 345 m over
ground. At the height of 320 m a measurement cabin was equipped with a
filter sampler for daily gravimetric PM2.5-measurements, a continuous
measurement device and a Scanning Mobility Particle Sizer (SMPS+C,
type Vienna-DMA, GRIMM Aerosol Technik GmbH). The SMPS in
combination with an aerosol spectrometer (EDM190) allows the detection
of wide range particle size distributions from 5 nm to 32 μm. The tower
cabin at 320 m equipped with different aerosol samplers is shown in
figure 1.
Frohnau tower (345 m)
DMA+CPC and EDM190
(GRIMM Aerosol Technik)
Probe inlet
Cabin at the tower plat-
form with PM-equipment
(GRIMM, Thermo, Leckel)
Frohnau tower (345 m)
DMA+CPC and EDM190
(GRIMM Aerosol Technik)
Probe inlet
Cabin at the tower plat-
form with PM-equipment
(GRIMM, Thermo, Leckel)
Figure 1: Measurement site “Frohnau tower”
Results
The measurements of particle size distributions at the Frohnau tower show that even at an altitude of 320 m high numbers of ultra fine particles occur.
Figure 2 shows an example of the 25
th
of June 2007.
On some days, a good correlation between the total number of particles and the PM2.5 concentration over time was observed (figure 3). There are also days,
where a high number of ultra fine particles were measured, but the level of PM2.5 was relatively low. Depending on the atmospheric turbulences above Berlin
fine particles might be mixed up and down. Sources for ultra fine particles are combustion processes, e.g. soot emissions caused by traffic and power plants
and organic components formed by photochemical reactions. The interesting question is, whether fine particles are emitted from the urban agglomeration or
from sources outside of the city. The measurement site Frohnau tower is in certain weather conditions (often during a clear night) above the stable
atmospheric boundary layer. With sunrise the mixing layer increases and aerosols from the urban agglomeration are mixed up as shown in figure 4. High
number of particles as well as PM2.5 concentrations were observed on June, 7
th
2007, see figure 5. The calculated 2-dimensional backward trajectories of
this day show that the air masses came from the East and crossed over several large power plants in Poland (figure 6). Sulphate as a secondary aerosol is a
suitable tracer for combustion processes, especially for coal combustion of power plants. Air masses transporting high loadings of sulphate mainly come from
Eastern and South Eastern directions to Berlin (figure 7). In these directions judge power plants fuelled with coal in Poland and Czech Republic emit high
levels of SO
2
and particulate matter. Figure 2 shows an example of the wide range measurements for the June, 25
th
2007. High numbers of ultra fine particles
(dp smaller 0,1 μm) could be detected. This example demonstrates that even at an altitude of 320 m high densities of fine particles are transported and
mixed.
Figure 2: Particle size distribution on 25.06.2007
Figure 6: 2-dimensional backward
trajectories, 07.06.2007
Outlook
The aim of further research is to determine the main sources and
meteorological parameters leading to high particle concentrations over
Berlin. Therefore we will add the results of simultaneous NO
x
, SO
2
and
ozone measurements at the Frohnau tower.
The correlation of elastic backscatter Lidar data with ultra fine particle
concentrations considering relative humidity, diurnal as well as annual
variations will be investigated as well.
It is also aimed to investigate whether the traffic restrictions set by the
Berlin government starting at January, 1
st
2008 will significantly reduce
the number of ultra fine particles in down town Berlin.
References
Baron, P. A.; Willeke, K. (2001): Aerosol measurement: principles, techniques and
applications, John Wiley & Sons Ltd., New York, NY (US).
Hinds, W. C. (1999): Aerosol Technology: Properties, Behavior, and Measurement of
Airborne Particles, Wiley New York.
Mehnert, Jan; Pesch, Markus (2007): Locating the mixing layer: algorithms to identify the
mixing layer height using lidar signals. Proceedings of SPIE 6750.
Pesch, Markus; Oderbolz, Daniel (2007): Calibrating a ground based backscatter Lidar
for continuous measurements of PM2.5. Proceedings of SPIE 6750.
Senatsverwaltung für Gesundheit, Umwelt und Verbraucherschutz Luftreinhalte- und
Aktionsplan für Berlin 2005 – 2010
Figure 4: Increasing of the mixing layer and fine particles
Figure 3: Total counts and PM2.5 on 21.06.2007
Figure 5:
High concentration of particle number
and PM2.5, 07.06.2007
Figure 7: Origin of high sulphate transported
to Berlin, 01.12.2006-31.05.2007