Instrumentation

Transcrição

Instrumentation

Cite abstract as Author(s) (2009), Title, European Aerosol Conference 2009, Karlsruhe, Abstract T023A01
Development of an Aircraft-based Laser Ablation Aerosol Mass Spectrometer
(ALABAMA)
M. Brands1,2, M. Kamphus1,3, J. Schneider2, C. Voigt4, F. Drewnick2 and S. Borrmann1,2
1
2
Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
3
now at: EMERSON Process Management, Hasselroth, Germany
4
Institute of Atmospheric Physics, German Aerospace Center, Wessling, Germany
Keywords: Aerosol mass spectrometry, Single particle analysis, Laser ablation, Aircraft measurements.
We present here the development of a novel
Aircraft-based single particle Laser ABlation timeof-flight MAss spectrometer (ALABAMA), which is
capable of measuring the chemical composition and
size of ambient aerosol particles in the size range
between 200 and 900 nm.
The aerosol particles are sampled from ambient air
through a pressure-regulated Liu type aerodynamic
lens system and focused to a narrow beam into the
vacuum of a sizing chamber. By travelling through
two orthogonally aligned 532 nm continuous wave
laser beams, particles generate scattered light that is
focused onto photomultipliers by means of two
elliptical mirrors.
After deriving the aerodynamic size of the particles
from their individual flight time, a 266 nm Nd:YAG
laser (τ = 5 ns, E = 8 mJ/pulse) is triggered to
vaporize and ionize the particles in the extraction
region of the mass spectrometer.
The bi-polar Z-shaped time-of-flight mass
spectrometer (TOFWERK AG, Thun, Switzerland)
generates a complete mass spectrum with a resolution
of m/∆m ~450 in the m/z range from 10-300.
All components fit in a 19’’ aircraft-compatible rack
of approximately 1,60m height, not exceeding a total
weight of 150kg. The instrument will be suitable and
certified for the new german HALO high altitude and
long range research aircraft.
Extensive lab characterizations have been performed,
providing detailed information on the instruments
performance and limitations.
The lower detection limit is given by the amount of
light scattered by the particles and the upper
detection limit by the transmission properties of the
inlet system.
Detection and ablation efficiencies for polystyrene
latex (PSL) monospheres as a function of particle
size are shown in Figure 1.
Measurements for different particle shapes and sizes
show a decrease in detection efficiency by ~85% for
NaCl and even >95% for soot particles, due to a
widening and misalignment of the particle beam as
well as different optical properties of the particles.
Ablation efficiency varies strongly (up to -60% for
mineral dust) due to changes in absorption- and
ionization properties for different particle types, as
well as decreasing hitrate due to the widening and
misalignment of the particle beam.
Figure 1. Detection and ablation efficiency of PSL
microspheres as a function of size.
Furthermore ALABAMA has been deployed during a
four week measurement campaign at the AIDA
chamber (Aerosol and Heterogeneous Chemistry in
the Atmosphere) at the Research Center in
Karlsruhe/Germany. This project focused on ice
nuclei and ice formation efficiencies of different
particle types and atmospheric conditions and offered
excellent opportunity to test the instrument under
atmospheric
conditions.
Additionally
an
intercomparison with instruments operating on
similar methodologies has been performed.
In summer 2009 ALABAMA will be operated on a
research aircraft during the MEGAPOLI campaign to
perform measurements on urban pollution aerosols
within and above the boundary layer above and
downwind of large metropolitan areas.
Results on the instruments performance under
various pressure and ambient conditions, as well as
single particle composition data of the field and
laboratory measurements will be presented.
This work is financed by the State Excellence Cluster
“Geocycles” of Rheinland Pfalz, the Priority Program
1294 “Atmospheric and earth system research with
the ‘High Altitude Long Research Aircraft’ (HALO)”
of the German Science Foundation (DFG), the
Collaborative Research Center 641 (SFB 641) “The
Tropospheric Ice Phase – TROPEIS” and internal
funding of the Max Planck Institute for Chemistry.
Performance comparison of two different Laser Ablation Time-of-Flight Mass
Spectrometers
T. Klimach2, M. Brands1,2, F. Drewnick2, J. Schneider2, M. Kamphus1, and S. Borrmann1,2
1
Institute for Atmospheric Physics, Johannes Gutenberg University, Mainz, Germany
Particle Chemistry Department, Max Planck Institute for Chemistry, Mainz, Germany
2
Keywords: Aerosol mass spectrometry, Single particle analysis, Laser ablation
We present extensive intercomparison
measurements between two different single particle
laser ablation time-of-flight aerosol mass spectrometers utilizing similar working principles with
differences in the inlet and particle detection design
and in the ablation laser wavelength: the Single
Particle Laser Ablation Time-of-flight aerosol mass
spectrometer (SPLAT, Kamphus et al., 2008) and
the Aircraft-based Laser Ablation Aerosol Mass
spectrometer (ALABAMA).
The general setup of both instruments is as
follows. Ambient aerosol is focused by an
aerodynamic lens system to a narrow beam. Two
orthogonal CW laser beams are used to determine
the aerodynamic diameter of the aerosol particles
and to trigger the ablation laser. The ablation,
which vaporizes and ionizes the particles, takes
place in the extraction region of a bi-polar time-offlight mass spectrometer, resulting in detailed information on the chemical composition of the
individual particles.
For comparison of the inlet and particle
detection systems of the two instruments detection
and ablation efficiencies for different types of
aerosol particles, namely PSL (Fig. 1) and glass
spheres, broken glass, soot and PAH, were
determined as a function of particle size, SPLAT
was operated with both, a Schreiner type
aerodynamic lens (Schreiner, 1999) focusing
particles in a size range between 0.2 and 3 μm and
with a Liu type lens with a size range from 50 to
800 nm detecting the forward scattered light with
an optical lens assembly and a photomultiplier.
ALABAMA was operated with the Liu type
aerodynamic lens only, using elliptical mirrors to
collect the scattered light.
Due to its elliptical mirrors ALABAMA is
able to detect smaller particles than SPLAT, which
on the other hand detects larger particles more
efficiently.
For investigation of the influence of the
ablation laser wavelength onto the ion fragmentation a variety of identical aerosol particles has
been measured with the two instruments. SPLAT
uses an excimer laser for particle ablation, which
can be operated at 193 nm and 308 nm, depending
on the laser gas; ALABAMA uses a frequency
quadrupled Nd:YAG laser, operating at 266 nm.
The higher energy of the 193 nm ablation laser is
supposed to result in a stronger fragmentation of the
vaporized molecules. This was also observed in the
mass spectra of Arizona Test Dust particles (Fig. 2).
Figure 2: Averaged mass spectra of Arizona Test Dust
obtained with SPLAT and ALABAMA.
Further experiments with different mineral
dusts and organic substances are conducted to
investigate the influence of the ablation wavelength
on single-particle mass spectra and to get a better
understanding of the underlying laser desorption
and ionisation effects.
Kamphus M., et al. (2008), Aerosol Science and
Technology, 42:11, pp.970-980
Schreiner J., et al. (1999), Aerosol Science and
Technology, 31, pp. 373-382
Liu P., et al (1995), Aerosol Science and
Technology, 22, pp. 314-324
Figure 1: PSL Detection efficiencies of SPLAT and
ALABAMA. Both devices equipped with a Liu type lens.
Efficient Sampling and Collection of Atmospheric Aerosols with a Novel Particle
Concentrator – Electrostatic Precipitator System
B. Han1, N. Hudda2, Z. Ning2, Y. J. Kim1, C. Sioutas2
1
Eco-machinery Research Division, Korea Institute of Machinery and Materials, Daejeon 305-343, South Korea
2
Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA
90089, USA
Keywords: Charging, Concentrator, Ambient aerosol, Electrostatic Precipitator(ESP), Ozone, VACES
A novel particle sampling methodology,
combining a versatile aerosol concentrator
enrichment system (VACES) and carbon fiber
charger developed by our lab (Han et al. 2008) was
extended to develop prototype electrostatic
precipitators (ESP) for the collection of particles on
substrate (Particulate Matter-ESP) and direct cell
exposure (Cell-ESP) for toxicological analysis.
In our system, particles grown to supermicron droplets via condensation of ultrapure
deionized water were concentrated by virtual
impaction in VACES and then droplets were
charged in a carbon fiber charger with negligible
ozone generation, and subsequently diffusion-dried
to their original particle size, while preserving the
acquired charges. The charged particles were then
collected on suitable substrates in two different
ESP prototypes for chemical and toxicological
analysis.
To minimize possible chemical reactions
between sampled particles and ions or negligible
amount of ozone generated in the corona region,
our previous carbon fiber charger was modified, by
separating the charging zone from the ionization
zone. Number of charges per particle was about 50
per particle, which was higher than comparative
studies (Biskos et al, 2005). These charged
particles had removal efficiencies (the fraction of
particles not penetrating the ESP of the total
incoming; based on particle number concentration
before and after ESP) greater than 90% for particle
sizes smaller than 200 nm, and about 80-90% for
particles larger than 200 nm in the PM-ESP at 3
l/min, whereas more than 95% removal was
achieved for particles smaller than 200 nm in CellESP at 1.5 l/min. These results imply that ultrafine
particles (smaller than 100 nm), which have been
traditionally difficult to charge by means of
conventional charging techniques, can be
effectively charged and removed in both
concentrator-ESP systems.
ESPs were further investigated to establish
the collection efficiency, i.e., fraction of particles
deposited on the target surface from that removed
in ESP. Difference between removal and collection
efficiency represent losses to tubing and the
insulating parts of ESP. Based on the test done on
lab generated PSL particles of 100 nm, NaCl and
atmospheric aerosol the gravimetric agreement
between the parallel filter line and ESP collection
substrate was about 80%.
Field test were also conducted to establish
the performance of the PM-ESP prototype by
comparing the mass and chemical compositions to
a filter in a parallel reference line. Samples were
composited and offline chemical analyses on the
filters/substrates included ion chromatography (IC)
for the analysis of inorganic ions (chloride, nitrate,
phosphate, ammonium and sulfate), selected trace
elements measured via inductively coupled plasmamass spectroscopy (ICP-MS), and water soluble
organic carbon (WSOC). These test results had a
concentration agreement for various elements
(0.81) and inorganic ions (0.83) similar to the
gravimetric agreement or the collection efficiency.
The consistent agreement across a variety of PM
species indicates that the particle concentratorelectrostatic precipitator system is efficient in
collecting ambient aerosols while preserving their
chemical composition.
This work was supported in part by the
Southern California Particle Center (SCPC),
funded by EPA under the STAR program through
Grant RD-8324- 1301-0 and BasicResearch Fund
(NK134B) of the Korea Institute of Machinery and
Materials and the Korea Research Foundation
Grant funded by the Korean Government
(MOEHRD)"(KRF-2007-611-D00003).
Biskos G., Reavell, K., and Collings, N. (2005).
Unipolar Diffusion Charging of Aerosol Particles
in the Transition Regime. J. Aerosol Sci., 36:247265.
Han, B., Hudda, N., Ning, Z., and Sioutas, C.
(2008a) Enhanced Unipolar Charging of
Concentration-Enriched Particles using Waterbased Condensation Growth. J. Aerosol Sci.,
39:770-784.
Concentrated atmospheric nanoparticle beams in vacuum
for X-ray and optical spectroscopy.
J. Meinen1,2, S. Khasminskaya1 and T. Leisner1,2
1
Institute for Meteorology and Climate Research, Aerosols and Heterogeneous Chemistry in the Atmosphere
(IMK-AAF), Forschungszentrum Karlsruhe GmbH, Germany
2
Institute for Environmental Physics (IUP), Atmosphere and Remote Sensing, Ruprecht-Karls-Universität
Heidelberg, Germany
Keywords: Atmospheric Nanoparticles, Charge Reversal Spectroscopy, Aerodynamic Lens
The IPCC AR4 points out the important role
of aerosol in the radiation budget of the earth. In the
model prediction, direct and indirect contribution of
the atmospheric aerosol causes a net cooling of the
earth. Understanding the fundamental physical and
chemical processes of heterogeneous nucleation of
water on nanoparticles could help improving the
models.
On our poster we present the first stage of the
TRAPS apparatus (Trapped Reactive Atmospheric
Particle Spectrometer). The apparatus comprises as
nanoparticle sources atomizers, electrospray and
plasma reactors in order to produce nanoparticle sizes
from 20-50nm, 10-20nm and 5-10nm respectively.
The nanoparticles are dispersed in helium as carrier
gas at high pressure. After passing a critical orifice
into rough vacuum a tuneable aerodynamic lens is
used to focus the particles into a differential pumping
stage. We put high effort in optimizing the
aerodynamic lens for particle beams close to the
diffusion limit by CFD calculations. Downstream the
differential pumping the particle beam is used to
continuously refill a linear ion trap. For the trapping
of particles in the size range of several kDa to MDa,
a radio frequency from 10-150 kHz is. In contrast to
the work of other groups, which are using digital ion
traps, we developed an amplifier capable to provide
an appropriate sinusoidal voltage with amplitude up
to 3kV.
This assembly is capable to inject
nanoparticles into vacuum chambers in a highly
efficient way. The dilution of the particle number
concentration arising from the gas expansion from
room pressure into vacuum is compensated by
concentrating the particles in a small cylindrical
volume by electrodynamic trapping. The enlargement
of the target density compared to a free molecular
beam provides a tool for various techniques of
spectroscopy used on smaller ions by routine.
In-situ Small Angle X-Ray Scattering (SAXS) Characterization of SiO2 Nanoparticles
Synthesized in a Microwave-Plasma Reactor
V. Goertz1, A. Abdali2, H. Wiggers2, C. Schulz2 and H. Nirschl1
1
Institut f. Mechanische Verfahrenstechnik u. Mechanik, Universität Karlsruhe (TH), 76131 Karlsruhe, Germany
2
Institut f. Verbrennung u. Gasdynamik, Universität Duisburg-Essen and CeNIDE, Center for NanoIntegration
Duisburg-Essen, 47057 Duisburg, Germany
Keywords: In-situ measurements, Microwave-plasma reactor, Nanoparticle characterization, SiO2, SAXS
Optical, mechanical, thermal or handling
properties of coatings as well as bulk materials can
be improved by using nanomaterials and
nanocomposites containing nanoparticles. Depending
on the application, specific properties of the
nanomaterials are required. For example if a high
transparency of coatings with high mechanical and
chemical resistance is demanded, SiO2 nanoparticles
with a specific size, morphology and surface coating
are particularly suitable. Thus, a detailed
characterization of the nanoparticles and also an
exact knowledge concerning the particle formation
and particle growth is indispensable.
An adequate measuring method is the smallangle X-ray scattering (SAXS), which can be used
for in-situ measurements of aerosols as well as
suspensions. The technique can determine the
particle size and size distribution, the specific surface
area, the fractal dimension and the aggregate number
within one measurement (Beaucage et al., 2004).
Besides the multiplicity of particle describing
parameters within a single measurement, the
technique offers the opportunity to measure in-situ.
However, laboratory X-ray scattering
equipment like Kratky and pinhole cameras has a low
scattering intensity and as a consequence, the
measurement takes several hours (8h+). To overcome
this constraint a Kratky compact camera was
modified using a multilayer X-ray mirror (Göbel
mirror). The mirror converts a divergent, incoming
X-ray beam into a parallel one and was established
inside the camera. Additionally, a two-dimensional
imaging plate detector replaced the one-dimensional,
gas-filled detector. Owing to these changes, intensity
and image quality are increased and the required
measurement time is decreased by a factor of 20. Due
to this, the camera can be used now for in-situ
measurements during particle formation.
In order to validate the in-situ measurement
technique the synthesis of SiO2 nanoparticles in a
microwave-plasma reactor is observed. Inside the
plasma a gas mixture including TEOS vapour,
oxygen, argon, and nitrogen is decomposed within a
few microseconds followed by the formation of silica
nanoparticles.
With respect to the reactor design, the SAXS
camera body is split in two parts to integrate the
reaction chamber into the measurement section and
to operate the camera in the particle formation zone.
In Figure 1 the in-situ measurement setup is
represented.
Figure 1. Schematic representation of the in-situ
SAXS measurement setup
The in-situ SAXS results are compared with
online particle mass spectrometry and TEM
measurements (Janzen et al., 2001). For the TEM
measurements, particles collected from the PMS
molecular beam and through thermophoretic
sampling of nanoparticles from the reaction chamber
were investigated. The results show a good match
between the different measurement techniques and
qualify the SAXS method as a non-intrusive
possibility for the in-situ characterization of
nanoparticle properties.
This work is supported by the German Research
Foundation under grant PAK 75/2 “Gasdynamically
induced nanoparticle synthesis”.
Beaucage G., Kammler H.K., Mueller R., Strobler
R., Agashe N., Pratsinis S.E., Narayanan T.
(2004). Nat. Mater., 6, 370-374.
Beaucage G., Kammler H.K., Pratsinis S.E. (2004).
J. Appl. Cryst., 37, 523-535.
Janzen C., Wiggers H., Knipping J., Roth P. (2001).
J. Nanosci. Nanotech., 1, 221-225.
Source apportionment of particle number and PM10 concentration
E. Cuccia1, F. Mazzei1, V. Bernardoni2, P. Prati1, G. Valli2, R. Vecchi2
1
Department of Physics, University of Genova and I.N.F.N., Via Dodecaneso 33, 16146, Genova, Italy
2
Department of Physics, University of Milano and I.N.F.N.,Via Celoria 16, 20133, Milano, Italy
Keywords: optical counter, PMF, ED-XRF, size-segregated source apportionment, urban aerosol
number in several size classes by receptor models
(Gordon, 1988) fed with high time resolution series
of elemental concentration values.
In this work the same approach is tested on a
set of PM10 daily samples collected in the city of
Genoa, during a campaign carried out in the harbour
area. Elemental concentrations from Na to Pb were
obtained through Energy Dispersive X-Ray
Fluorescence (ED-XRF), and the contribution of
specific sources to particulate matter (PM)
concentration were apportioned by Positive Matrix
Factorization, PMF (Paatero and Tapper, 1994).
During the PM10 sampling, size segregated particles
number distribution was measured by a Grimm 1.108
optical counter (OPC). This device counts
atmospheric particles, with diameter, Dp, between
0.25 µm and 32 µm, in 31 size bins. The number of
particles in each size bin was apportioned versus the
time trends of PM10 sources resolved by PMF, using
a multi-linear regression. The result is shown in
Figure 1. On average, an absolute uncertainty of ±
5%, must be added to each value reported in Figure
1. As expected, natural sources as “sea salt” and “resuspended soil” show larger contributions in the
coarse fraction, unlike “secondary” compounds that
are mainly concentrated in the fine fraction. Traffic
emissions contribute to all size bins even if with a
smaller contributions between 0.6 µm and 2 µm.
Heavy oil combustion shows a flat distribution up to
3 µm but it should be reminded that very fine
particles (i.e. with Dp < 0.25µm) are not detected by
the OPC. Finally, we could identify a “local source”,
concentrated in particles with Dp > 0.5 µm, which,
according to its profile, looks linked to harbour
activities.
The apportionment in Figure 1 can be partially tested
assuming all particles with the same density and
deducing, for each size bin, the corresponding mass
concentration apportionment. Summing on all the
size bins, a new apportionment of PM10 can be
obtained and compared with the standard result based
on daily elemental concentration values. Results are
presented in Figure 2 where the good agreement of
the two methods can be appreciated. This study
shows that the contemporary use of daily PM
samplers and OPC can give the apportionment of
both PM and size-segregated number of particles,
provided that the elemental/chemical composition of
PM samples is deduced by proper laboratory analysis
and used as input of a receptor model as PMF.
Oil combustion
Traffic
Secondary
Re‐suspended soil
Sea salt
Local source
120%
100%
80%
60%
40%
20%
0%
0.
25
‐
0. 0.2
28 8
‐
0. 0.3
30 0
‐
0. 0.3
35 5
‐
0. 0.4
40 0
‐
0. 0.4
45 5
‐
0. 0.5
50 0
‐
0. 0.5
58 8
‐
0. 0.6
65 5
‐
0. 0.7
70 0
‐ 0.
8
0. 0
80
‐ 1
1 ‐ 1
1. .3
3 ‐ 1
.6
1.
6 ‐ 2
2 ‐ 2
.5
2.
5 ‐ 3
3 ‐ 3
.5
3.
5 ‐ 4
4 ‐ 5
5 ‐ 6
6. .5
5 ‐ 7
7. .5
5 ‐ 8
.
8. 5
5 ‐ 1
0
In a previous work (Mazzei et al., 2007), we
described a methodology to apportion particles
dimensional classes (µm)
Figure 1: Apportionment of particles number in each size
bin versus the PM sources identified by PMF
40%
35%
30%
25%
20%
15%
10%
5%
0%
Oil combustion
Traffic
Secondary
Re‐suspended
soil
Sea salt
Local source
Sources
Figure 2: Comparison between “standard” apportionment
of PM10 obtained by time series of elemental
concentration values measured on daily basis plus PMF
analysis (black bars) and the PM10 apportionment deduced
with the methodology proposed in this work (white bars)
This work has been partly supported by
Amministrazione Provinciale di Genova, we
acknowledge Dr. E. Daminelli for his precious
collaboration.
Mazzei, F., Lucarelli, F., Nava, S., Prati, P., Valli, G.,
Vecchi, R. (2007). Atmos. Environ., 41, 5525-5535.
Gordon, GE., (1988). Environ. Sci. Technol., 22,
1132–1142.
Paatero, P, Tapper, U., (1994). Environmetrics, 5,
11–126.
A new calibration method for optical particle counters in the size range of 0.2 to 8 m
M. Weiß, L. Mölter1
1
Palas GmbH, 76229, Karlsruhe, Germany
Keywords: optical aerosol spectrometer, calibration, size resolution, monodisperse aerosol generator.
Several papers about the calibration of lightscattering aerosol spectrometers (e.g. Friehmelt,
2000, Heim et al., 2008) already exist. However, the
calibration of the Optical Aerosol Spectrometers
(OAS) is still extensively discussed and issue of
standardization committees (e.g. ISO/FDIS 21501-1).
There are three significant reasons for this: 1.) An
OAS has to be calibrated with respect to its counting
efficiency and its size resolution. 2.) There is still no
unique procedure available to calibrate optical
particle counters in an expanded size range. A
calibration related to the counting efficiency is often
limited to a maximum size range of about 800 nm,
the maximum mobility diameter that can be classified
by commonly used Different Mobility Analysers
(DMA). 3.) The effort which is necessary in order to
calibrate OAS is large and time-consuming and
therefore routinely not applicable for a quality
control standard.
For this reason a calibration method has been
developed that can be used to calibrate OAS with
respect to the counting efficiency and the size
resolution (see Fig. 1). The method is based on an
improved aerosol generator for DEHS (MAG 3000)
which produces monodisperse droplets in the size
range of 0.2 to 8 m. Additionally, the generator is
able to keep the concentration constant which makes
it suitable for reliable and reproducible
measurements. In order to calibrate OAS, the aerosol
of the generator is diluted into a channel with clean
air to reduce the concentration, to avoid coincidence
problems and to enable isokinetic sampling for the
OAS. In contrast to a calibration procedure with a
DMA as classifier for a monodisperse aerosol (Heim
et al, 2008), the method with the MAG 3000 as a
constantly producing monodisperse aerosol generator
makes the calibration of OAS possible up to 8 m.
Moreover, this method is much cheaper in terms of
technical requirements and less time-consuming
which makes it applicable for quality standard
controls.
The procedures to evaluate the measured
distributions in order to characterize the size
resolution and to measure the counting efficiency
with a reference device are discussed. It is also
shown that the described method is suitable for the
calibration of OAS and the results are comparable to
a calibration method with a DMA as a classifier for a
monodisperse aerosol.
The above-described method has been used to
characterize the size resolution and to measure the
counting efficiency of the newly developed white
light aerosol spectrometer welas® digital 2000 in the
size range of 0.2 to 8 m. In contrast to the
predecessor welas® 2000 the welas® digital 2000 has
a digital signal processing and a logarithmic A/Dconverter (the former welas® had an analog signal
processing and a linear A/D-converter). This
improvement enhances the counting efficiency of the
welas® digital and improves the size resolution for
particles smaller than 1 m. Additionally, the method
has also been used to characterize the LAS-X II®
(PMS) and to compare its size resolution and the
counting efficiency with the welas® digital 2000. As
the welas® digital 2000 can be equipped with five
different sensors for concentrations from 1 P/cm³ to
106 P/cm³, it is further shown that all sensors can be
calibrated with the described procedure.
Since this calibration method is an accurate
and cost-efficient method to calibrate OAS, it is now
used as a quality control for all welas® digital
systems.
Figure 1. Set-up to calibrate light scattering aerosol
spectrometers with a constantly producing
monodisperse aerosol generator (MAG 3000).
Different OAS are measured consecutively.
Friehmelt,
R.
(2000).
Aerosol-Meßsysteme,
Vergleichbarkeit und Kombination ausgewählter oline Verfahren, Universität Kaiserslautern, ISBN 3925178-47-3
Heim M., Mullins, B.J. Umhauer, H., Kasper, G.
(2008). J. Aerosol Science, 39, 1019-1031
Fluorescent test particles for the determination of
protection factor of safety work benches
S. Opiolka1, A. Bankodad1, S. Haep1, M. Abele2 and L. Mölter2
1
Institut für Energie- und Umwelttechnk e.V., Bliersheimer Strasse 60, 47229, Duisburg, Germany
2
Palas GmbH, Greschbachstrasse 3b, 76229, Karlsruhe, Germany
Keywords: fluorescence particle generation, fluorescence particle detection.
For the handling of dangerous materials in
micro-biological and biotechnological laboratories as
well as in medical institutions, safety work benches
according to EN 12469 and cytostatics work benches
according to DIN 12980 are used for the personal,
product and diversion protection. In order to
guarantee these security functions officially
prescribed tests are described in the mentioned
standards.
From point of view of the personal protection
the examination of the protection factor on the
working aperture of the safety work bench is of
particular importance. Objective of the test is the
evaluation of the number of test particles which enter
the work bench’ location under overcoming of the air
flow on the working aperture.
In addition to the test particles released during
the examination, there are also other, naturally
existing particles like e. g. dust, abrasion from
clothes and devices, danders, etc., within the safety
work bench’ location. The number of the naturally
existing particles in the ambient air normally exceeds
the number of the test particles released. A nonselective proof of the test particles by, e. g. optical
particle counters supplies, in this case, a number
concentration from the sum of the naturally existing
particles and the test particles in the ambient air.
Thus, the evaluation of the measuring result for the
calculation of the protection factor of the work bench
is not possible. For this reason, time-consuming
micro-biological and chemical procedures with
principal disadvantages are currently used for the test
described to get the selective proof of the test
particles.
New verification procedures for the
determination of the protection factor on the working
aperture of the safety work benches should comply
with particular requirements (EN 12469). The
number of released test particles N should not be
smaller than 3 x 108 and the suction rate s not smaller
than 20 l/min. The number of detected test particles n
should not be higher than 4. A protection factor Apf
of at least 1,5 x 105 can be verified with these values.
Thereby, the protection factor is calculated with:
Apf = (N x s) / (104 x n)
A new verification procedure which complies
with these conditions uses fluorescent test particles.
These are released within the safety work bench and
collected out of the work bench with impactors used
as samplers. The plates of the impactors are
evaluated under a fluorescence microscope after the
test. In the dark field mode all particles collected are
visible, in the fluorescence mode exclusively the
fluorescent test particles.
Figure 1. Microscope in the dark field mode (left)
and fluorescent mode (right).
Another new verification procedure uses also
fluorescent test particles. These are directly detected
by an optical particle counter. Exclusive the
fluorescence light of the test particles is detected by
the selection of suitable light sources, optical filters
and photomultipliers. All other particles existing in
the ambient air are faded out. A functional prototype
of the new particle monitor for fluorescent test
particles is introduced.
This work was supported by the German Federal
Ministry for Economy and Technology. Parts of the
work were accomplished in co-operation with the
company Palas® GmbH, Karlsruhe.
DIN 12980 Laboratory furniture - Cabinets for
handling cytotoxic drugs - Requirements, testing.
EN 12469 Biotechnology - Performance criteria for
microbiological safety cabinets.
New data of dry deposition velocity of sub-micron aerosol on several rural substrates
and comparison with models.
P. E. Damay1, D. Maro1, A. Coppalle2, E. Lamaud3, O. Connan1, D. Hébert1 and M. Talbaut2
1
2
Institut de Radioprotection et de Sûreté Nucléaire, DEI/SECRE/LRC, 50130 Cherbourg Octeville, France
COmplexe de Recherche Interprofessionnel en Aérothermochimie, 76801 Saint Etienne du Rouvray, France
3
Institut National de la Recherche Agronomique, 33883 Villenave d’Ornon, France
Key words: Dry deposition, ELPI, Atmospheric aerosols
10
1
Vd/U *
INTRODUCTION
Dry deposition flux is the quantity of particles
deposited per unit surface and time. The dry
deposition velocity is obtained by dividing the
deposit flux by the aerosol concentration measured in
the air. The lack of experimental data on dry
deposition velocities of sub-micron aerosols in a
prairie creates uncertainties larger than one order of
magnitude for operational models. In this work we
present the new results on several substrates and
quantified them as a function of aerosol sizes and
atmospheric turbulence parameters.
MATERIAL AND METHODS
Dry deposition flux can be calculated from the
covariance between fluctuations of the vertical wind
velocity and fluctuations of the atmospheric aerosol
concentration. The aerosol concentration was
measured with an Electrical Low Pressure Impactor
(ELPI, Dekati, Inc.) and the wind by an ultrasonic
anemometer for 30 minutes at high frequency. The
vertical calibration of parameters to validate
measurements (stationarity, integral characteristic of
turbulence, Foken & Wichura, 1996), then spectral
analysis and the calculation of fluxes were done.
Three experimental campaigns were conducted in
southwestern France in order to carry out the
methodology on several substrates (maize, grass and
bare soil).
RESULTS
Measurement provided values of dry
deposition velocities (Vd) of sub-micron aerosols.
The friction velocity (U*) and the heat sensible flux
(H) have simultaneous effect on the deposit
phenomena, because they influence the atmospheric
turbulence These effects can be taken into account
simultaneously by parameterizing Vd/U* as a
function of the inverse of Monin-Obukov length
(Wesely, 1985).
For neutral and stable atmospheric conditions,
the dry deposition velocities are shown on the
figure1. Vd is plotted as a function of the aerosol size
and normalized by U*. Operational models (Slinn
1982, and Zhang et al. 2002) are also plotted on the
same graph. Vd/U* results are very close for every
substrates. Furthermore, a discrepancy between
models and measurements is observed for aerosol
greater than 0.5 µm.
Slinn Maize
Slinn Bare soil
Slinn Grass
Zhang et al. Maïze
Zhange et al. Grass
Zhang et al. Bare soil
Maize
Grass
Bare soil
0.1
0.01
0.001
0.0001
0.001
0.01
0.1
1
10
100
Aerodynamic Diameter of aerosol (µm)
Figure 2. Dry deposition velocity measurements and
models on different rural canopies
CONCLUSION
We present our results: discuss the impact of
micrometeorological parameters and particle size on
the dry deposition velocity. The perspective of work
is to apply this method on other substrates: urban,
forest or other rural substrates.
Foken Th., & Wichura, B. (1996). Tools for Quality
assessment of surface-based flux measurement.
Agricultural and Forest Meteorology, 78, 83-105
Kaimal J. C. & Finnigan J. J. (1994). Spectra and
cospectra over flat uniform terrain. In: Oxford
University Press (Eds), Atmospheric Boundary
Layer Flows, New York, pp. 32-66.
Wesely, M. L., Cook, D. R. et Hart, R. L. (1985)
Measurements and parameterization of particulate
sulfur dry deposition over grass. Journal of.
Geophysical Research 90, 2131-2143.
Slinn W. G. N. (1982). Prediction for particle
deposition to vegetative canopies. Atmospheric
Environment 16, 1785-1794.
Zhang L., Gong S., Padro J., Barrie L. (2001). A
size-segregated particle dry deposition scheme for
an atmospheric aerosol module. Atmospheric
Measurement of Nanoparticle Agglomerates by Combined Measurement of Electrical
Mobility and Charging Properties
D.Y.H. Pui1, H. Fissan2, J. Wang1, W.G. Shin1, M. Mertler3 and B. Sachweh3
1
Particle Technology Laboratory, Department of Mechanical Engineering, University of Minnesota,
Minneapolis, MN, USA, 55455
2
Institute of Energy and Environmental Technology e. V. (IUTA), Bhersheimer Strasse 60,
47229, Duisburg, Germany
3
BASF SE, Fine Particle Technology and Particle Characterization, GCT/P - L540, 67056,
Ludwigshafen, Germany
Keywords: agglomerates, measurements, instrument development, NSAM.
surface area and electrical capacitance of particle are
two important parameters to determine mean charge
of non-spherical particles. Our analysis shows that
the electrical capacitance of loose agglomerates is
larger than that of spherical particles with the same
mobility. Therefore loose agglomerates can gain
more charges in a charger, which in turn gives rise to
higher values of UNPA sensitivity.
0.06
Room Temperature
200 C
0.05
600 C
3
UNPA sensitivityS (fA cm )
Nanoparticle agglomerates are pervasive in
atmospheric sciences, air pollution, and material
manufacturing. Combustion processes are used to
manufacture a variety of materials in agglomerate
form including fumed silica, titanium dioxide, and
carbon black. Measurement of agglomerates is of
great importance to many applications.
Agglomerates may possess complicated
structures, which makes measurement of them a
difficult task. One of the most common methods for
agglomerate measurement is electron micrograph,
which can provide direct measurement of the
structural properties (Shin et al. 2009). However,
taking electrical micrographs and performing image
analysis can be time consuming and expensive. In
addition, interpretation of the 2D images for 3D
results may rely on assumptions and cause
inaccuracy. Fast and online measurement for
agglomerates is required in many scenarios including
measuring fast changing agglomerates, quality
control for material manufacturing, monitoring toxic
air-borne agglomerates, etc. Most of the current
aerosol instruments are designed for spherical
particles. Therefore, there is a need for instruments
capable of fast and online measurement of gas-borne
nanoparticle agglomerates.
We have developed an instrument, Universal
NanoParticle Analyzer (UNPA), for online
measurement of gas-borne nanoparticle agglomerates.
UNPA utilizes Differential Mobility Analyzer
(DMA), Condensation Particle Counter (CPC) and
Nanoparticle Surface Area Monitor (NSAM) to
characterize airborne nanoparticle morphology and
measure the number, surface area and volume
distributions of airborne nanoparticles. The key
parameter measured is the UNPA sensitivity, which
is defined as the current (fA) measured by the NSAM
divided by the number concentration measured
(#/cm3)
S = I/N (fA cm3).
Experimental data (Figure 1) have shown that the
UNPA sensitivity S depends on the particle
morphology. S is larger for loose agglomerates than
for spheres at a fixed mobility diameter.
Charging theories of Chang (1981) for aerosol
particles of arbitrary shape indicates that geometric
S = 9E-05d m
0.04
S = 1E-04d m
1.1915
2
1.2085
R = 0.9974
2
R = 0.9908
0.03
S = 0.0001d m
0.02
1.0815
2
R = 0.9961
0.01
0
50
70
90
110
130
150
170
190
d m (nm)
Figure 1. UNPA sensitivity as a function of the
mobility size for particles of different morphologies.
UNPA measures the sensitivity S at a
specified mobility size, compares it to the values of
the loose agglomerates and spheres from calibration
to determine the morphology. Agglomerates are
modeled as clusters of spherical primary particles.
From UNPA sensitivities, the primary particle size is
determined using a fitting procedure. Using the
models of Lall and Friedlander (2006) for loose
agglomerates, the number of primary particles in
agglomerates can be computed. Then the surface area
and volume of agglomerates can be obtained.
Operated under the scanning mode, UNPA can
provide the number, surface area and volume
distributions of loose agglomerates in the range of 50
– 800 nm in several minutes.
Shin, W-G, Wang, J., Mertler, M., Sachweh, B.,
Fissan, H., Pui, D.Y.H. (2009), J. Nanoparticle
Research. 11, 163 – 173.
Chang, J.-S. (1981). J. Aerosol Science, 12, 19-26.
Lall, A. A. & Friedlander, S. K. (2006) J. Aerosol
Science. 37, 260-271.
Experimental study on collision efficiency for aerosol particles scavenged by cloud drops
L. Ladino1, O. Stetzer1, U. Lohmann1 and B. Hattendorf2
1
Institute for Atmospheric and Climate Science, ETH Zürich, 8092, Zürich, Switzerland
2
Department of Chemistry, ETH Zürich, 8093, Zürich, Switzerland
Keywords: Brownian Diffusion, Collection efficiency, Inertial Impaction, Thermophoresis
Cloud formation is an important issue in atmospheric
and climate science. For example the impact of the
anthropogenic aerosols on clouds it is still unknown.
Aerosol particles can activate as cloud condensation
and ice nuclei. In addition, aerosol particles colliding
with droplets can be removed from the atmosphere
by wet deposition. Collisions below 0°C can initiate
freezing of droplets by contact freezing. Therefore,
this process can influence cold clouds and hence the
global radiation budget and the hydrological cycle.
There are some instruments available to measure the
collision efficiency between droplets and aerosol
particles. In most of them is not possible to work
with small drops. Only few experimental data are
available on collision efficiencies and the majority of
all experiments were done with particles smaller than
0.4 m and raindrops (Dd>100 m).
In figure 1 we can see that all previous experiments
were done mainly for rain drops (> 100 m) with a
constant particle diameter and changing drop sizes.
Collision efficiencies for varying particle sizes are
not well known.
In this study, collision efficiencies are measured with
a new experimental setup. Aerosol particles of a
known size and concentration can interact with small
droplets produced with a piezo droplet generator in a
chamber of variable length. The droplets are then
collected with a cup impactor. The collected solution
is then analyzed for the scavenged aerosol mass by
Inductively Coupled Plasma-Mass Spectrometry
(ICP-MS).
From this data, collision efficiencies can be derived.
We report the first results with particles of LiBO2
(with diameters between 0.4 μm and 0.6 μm) and
droplets with a diameter of 32 μm. Our data is then
compared to theoretical model calculations (Park et
al. (2005) and Tinsley et al. (2006)) and literature
data.
The forces included in our calculation are Brownian
diffusion, interception, inertial impaction and
thermophoresis.
Figure 1. Comparison of theoretical collision
efficiencies with experimental data from the
literature and with our laboratory experiments.
The theoretical results show that by increasing the
droplet diameter the collision efficiency decreases
(confirmed experimentally by Vohl et al. (2001)). If
the model is right previous experimental data
drastically overestimate the collision efficieny.
Our data also differ from theory but lie in the range
of other experimental data. With some modifications
to the experimental setup we expect to get better
results in future.
This work was supported by the Swiss National
Foundation Project 200021-107663/1.
Tinsley B.; Zhou L.; Plemmons A. (2006)
“Changes in scavenging of particles by droplets due
to weak electrification in clouds”. Atmos. Res., 79,
266-295.
Park S.; Jung C.; Jung K.; Lee B.; Lee k. (2005)
“Wet scrubbing of polydisperse aerosols by freely
falling droplets”. Aerosol Sci. 36, 1444–1458.
Vohl O.; Mitra S.; Diehl K.;Huber G.; Wurzler S.;
Kratz K.; Pruppacher H. (2001) “A wind tunnel of
turbulence effect on the scavenging of aersolos
particles by water drops”. J. Atmos. Sci. 58, 30643072.
Evaporation kinetics of a non-spherical, levitated aerosol particle using optical
resonance spectroscopy for precision sizing
Ulrich K. Krieger1, and Alessandro A. Zardini2
1
Institute for Atmospheric and Climate Science, ETH Zurich, 8092 Zurich, Switzerland
2
Department of Chemistry, University of Copenhagen, 2100 Copenhagen, Denmark
Keywords: Aerosol Spectrometry, Single Particle Analysis, Size Measurement, Vapour Pressure.
In atmospheric and climate science there is
considerable interest in understanding the partitioning between gas and particle phase of chemical species. In particular, for semi-volatile substances like
ammonium nitrate or certain organic species, the
partitioning will strongly influence the particulate
matter burden in the troposphere, the radiative properties of the aerosol, the cloud processing and the
heterogeneous chemistry. In order to predict this partitioning, it is crucial to know the vapour pressure of
the compounds under ambient conditions, whereas
most established methods rely on high temperatures
to achieve detectable vapour pressures. In the present
work we use optical resonance spectroscopy (Zardini
et al., 2006) to size solid, non-spherical particles during evaporation with a precision superior to direct
imaging and mass change monitoring.
tensity). The intensity of each spectrum is normalized
to the same maxima and minima in panel (b). In
panel (c) the data of panel (b) are normalized with
the mean spectrum of the complete time series. Panel
(d) show the radius deduced from panel (c). A linear
fit to the data yields: dr/dt = −1.9×10−6 μm/s at T =
283 K.
In contrast to evaporating liquid particles, raw resonance spectra do not allow easily to discern a shift in
the resonance position, which is related to a size
change. To make the size change of an evaporating,
non-spherical particle visible in its resonance spectra
we proceed as shown in Fig. 1. Panel (a) shows the
times series of raw spectra (grey scale coded intensity). Each single spectrum is separately normalized
to its own maximum and minimum and the result is
plotted in panel (b). The most prominent features
here are intensity extrema at certain wavelength
(roughly regularly spaced) which are not time dependent and originate from etaloning of the CCD.
Therefore, further normalization is performed in
panel (c) by dividing each spectrum of panel (b) by
the mean spectrum of the complete times series. The
non time dependent features are suppressed and optical resonances shifting with time become visible,
although not nearly as distinct as in the case of an
evaporating liquid, i.e. spherical particle. To deduce
quantitative information about the radius change with
time, we associate one of the optical resonances with
a specific size parameter x0 =2π·r0/λ0. If we know the
initial radius, r0, we may follow its temporal evolution by measuring the wavelength, λ(t), of the time
shifting resonance through r(t) = x0·λ(t)/2π. For retrieval of the particle radius from the resonance spectra shift of Fig. 1(c) we use visual inspection, i.e. a
prominent resonance feature is tracked down as indicated by the black dots. If it leaves the wavelength
domain or becomes less distinct with time, we switch
to another resonance feature as illustrated in Fig. 1(c)
at t ≈ 40000 s.
The vapour pressures deduced from these experiments compare favourably with high temperature
effusion measurements of ammonium nitrate.
Figure 1. Panel (a) shows the raw spectra of an
evaporating ammonium nitrate solid particle versus
time (wavelength on vertical axis, colour coded in-
Zardini, A. A., Krieger, U. K., and Marcolli, C.
(2006), Opt. Express, 14, 6951–6962.
Laser-induced breakdown spectroscopy for on-line measurements of particle
composition
C. Fricke-Begemann1, N. Strauß2 and R. Noll1
1
Fraunhofer-Institut für Lasertechnik, Aachen, Germany
Chair for Laser Technology, RWTH Aachen University, Aachen, Germany
2
Keywords: chemical analysis, elemental composition, on-line measurements, optical instrumentation, DMA.
For the analysis of particle composition, a
measurement technique has been developed using
laser-induced breakdown spectroscopy (LIBS). It
offers favourable characteristics for applications from
emission monitoring to industrial process control.
LIBS is a measurement technology for
chemical analysis which uses a focussed pulsed laser
beam that evaporates and thermally excites a small
portion of material. The radiation emitted from the
excited material is measured with a spectrometer and
because of the characteristic spectral lines of the
elements, the signal allows to determine the
composition of the material under investigation. The
concentrations of practically all elements can be
determined.
LIBS can directly be applied to solids, liquids
and gases, and is used today in a wide range of
applications. In industrial applications LIBS
measurement systems have been proven to be suited
for routine automated analytical purposes. For the
analysis of aerosol, this technique has been applied
before for the elemental analysis of particles
deposited on filter substrates with size-classification
(Kuhlen et al., 2008).
When applied to an aerosol stream, LIBS can
be used to measure the composition of particles in a
large size-range from a few nanometers up to the
upper micrometer range. Due to the complete
dissociation of chemical compounds, the technique
can be applied to all types of particles including
industrial nanoparticles of metallic oxides.
To measure the composition of particles using
LIBS, we demonstrate the realisation of a
measurement which transfers an aerosol containing
gas stream into a measurement chamber where the
particles are evaporated into a laser-induced plasma.
The system is characterised and calibration examples
are given for some elements. The short response time
of the instrument allows measurements with a time
resolution below one second. Direct data processing
immediately provides analytical results as required
for online applications.
Into the measurement system a DMA has been
included. When the aerosol gas stream is previously
guided through the electrostatic classifier, the particle
composition can be determined with respect to the
particle size.
Kuhlen, T., Fricke-Begemann C., Strauss N., Noll R.
(2008), Analysis of size-classified fine and
ultrafine particulate matter on substrates with
laser-induced
breakdown
spectroscopy,
Spectrochimica Acta Part B, 63, 1171–1176
A Synchronized Hybrid Real-Time Particulate Monitor
K.J. Goohs1, P. Lilienfeld1, and J. Wilbertz2
1
Department of Research, Thermo Fisher Scientific, Massachusetts, 27 Forge Parkway, 02038, Franklin, USA
2
Engineering Department, Thermo Electron GmbH, Frauenauracher Strasse 96, 91056 Erlangen, Germany
Keywords: Aerosol Instrumentation, Light Scattering, Beta Attenuation, Hybrid Methodology
The SHARP monitor incorporates a “dynamic
heater” system designed to maintain the relative
humidity of the air passing through the filter tape of
the radiometric stage well below the point at which
the collected particles accrete and retain liquid water.
This heating system minimizes the internal
temperature rise ensuring negligible loss of semivolatiles from the collected sample. The SHARP
monitor is operable at ambient temperatures and
features an adjustable filter change cycle and relative
humidity set point to mitigate aerosol artifacts or
more closely match the measurements of gravimetric
reference methods.
Transformed field test data from four test sites
with varied season, geography and chemical
composition indicate that the SHARP monitor
provides PM short-term, i.e., one hour-resolved
measurements with a precision of better than ±1.0
μg/m3. Yearlong field tests indicate acceptable daily
accuracy (1.0 + 0.1) and correlation > 0.97 compared
against PM2.5 reference samplers.
Hourly Collocated SHARP PM2.5 - St. Louis Supersite
April 23, 2005 through January 29, 2006
300
40.0
SHARP 1
250
SHARP 2
Stdev (ug/m3)
Targeted Precision
91% of the hourly values meet the precision target of 2 μg/m
3
86% of the hourly values have a precision of 1 μg/m
3
30.0
20.0
10.0
150
0.0
-10.0
100
-20.0
50
-30.0
-40.0
5/
6/
20
05
5/
20
/2
00
5
6/
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20
0
6/
17 5
/2
00
5
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1/
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00
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5
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/2
00
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5
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00
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5
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00
5
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00
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5
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00
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5
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20
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0
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05
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05
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05
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00
1/
6
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/2
00
6
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22
/2
00
5
0
Sample Date (mm/dd/yyyy)
Figure 1. Collocated precision field data
Precision (μg/m3)
PM2.5 SHARP Conc. (ug/m3)
200
SHARP @ 35% RH Control vs. USEPA Reference Method
Integrated Results From Four Monitoring Locations
80.0
70.0
60.0
50.0
SHARP
A
hybrid
nephelometric/radiometric
particulate mass monitor capable of providing realtime measurements is described. The SHARP
(Synchronized
Hybrid
Ambient
Real-time
Particulate) monitor incorporates a light scattering
photometer whose output signal is continuously
referenced to the time-averaged measurements of an
integral beta attenuation mass sensor. This system
achieves improved short-term precision and accuracy
of both PM10 and PM2.5 determinations. The SHARP
monitor incorporates advanced firmware to optimize
the continuous mass calibration of the nephelometric
signal, ensuring that the measured mass
concentration remains independent of changes in the
particle population being sampled.
40.0
y = 1.005x + 0.321
R2 = 0.973
30.0
20.0
10.0
0.0
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
PM2.5 FRM (μg/m3)
SHARP
Linear (SHARP)
Figure 2. Scatter plot of SHARP Monitor data versus
EPA reference method. Data is integrated across
four regional monitoring locations of varied chemical
composition that include winter and summer testing
periods.
Babich, P., Wang, P.-Y., Allen, G., Sioutas, C.,
Koutrakis, P. (2000). Development and
evaluation of a continuous ambient PM2.5
mass monitor. Aerosol Science and
Technology 32, 309-324.
Chang, C. T. and Tsai, C. J. (2003). A model for the
relative humidity effect on the readings of the
PM10 beta-gauge monitor. Journal of Aerosol
Science 34, 1685-1698.
Charron, A., Harrison, R. M., Moorcroft, S., Booker,
J. (2004). Quantitative interpretation of
divergence between PM10 and PM2.5 mass
measurements by TEOM and gravimetric
(Partisol) instruments. Atmospheric
Chung, A., Chang, D. P. Y., Kleeman, M. J., Perry,
K. D., Cahill, T. A., Dutcher, D., McDougall,
E. M., Stroud, K. (2001). Comparison of realtime instruments used to monitor airborne
particulate matter. Journal of the Air and
Waste Management Association 51, 109-120.
Dresia, H., Fischotter, P., Felden, G. (1964).
Kontinuierliches Messen des Staubgehaltes in
Luft und Abgasen mit Betastrahlen
(Continuous measurement of the dust
concentration in air and in exhausts by means
of beta radiation). VDI-Z. 106, 1191-1195.
Gebhart, J. (2001). Optical direct-reading
techniques. Aerosol Measurement, 2nd
edition, Baron, P. A., Willeke, K., editors.
(Wiley- Interscience). Chapter 15.
miniDiSC for personal monitoring and high-resolution monitoring networks
M. Fierz, P. Steigmeier, C. Houle and H. Burtscher
University of Applied Sciences Northwestern Switzerland, 5210 Windisch, Switzerland
Keywords: ambient air pollution, diffusion battery, field measurements, instrumentation, personal sampling.
Current aerosol instruments capable of
measuring ultrafine particles are mostly large, heavy,
expensive, which complicates many applications of
these instruments. Recently, we introduced the
diffusion size classifier (DiSC, Fierz et al., 2007) as a
simple instrument capable of simultaneously
measuring particle number concentration and mean
particle diameter with a time resolution of one
second. Since the DiSC is based on a unipolar
diffusion charger followed by current detection in
two electrometers, it can also measure the total
aerosol length or the lung-deposited surface area like
the TSI NSAM (Fissan et al., 2006) – a parameter
that is likely to be health relevant.
We have now developed a miniaturized
version of the DiSC (see Figure 1), which is nearly
ten times smaller and lighter than the original
instrument – it is truly handheld and weighs less than
1 kg. The entire instrument was also optimized to
reduce the number of necessary parts to lower the
instrument cost.
Another potential area of application for the
new instrument is in monitoring networks. Currently,
most monitoring networks consist of a limited
number of stations containing bulky and expensive
instruments. An alternative approach is to use a much
larger number of inexpensive instruments which
operate autonomously over extended periods of time,
and which transmit their measurements and the
instrument status over wireless communications
networks. This type of measurement network can be
set up with minimal effort on either a very local scale
(e.g. to measure transport properties close to an
aerosol source) or on a slightly larger scale, e.g. to
monitor the temporal and spatial variation of air
pollution in a city with very high resolution. Since
the miniDiSC is inexpensive and requires very little
maintenance, we are working on this type of
monitoring network, and the direct integration of
results in Google Earth (Figure 2).
Figure 2. Integration of monitoring network data into
Google Earth.
Figure 1: an image of the miniaturized diffusion size
classifier (miniDiSC) compared to a CPC.
It has often been suggested that particulate
mass (proportional to diameter d3) may not be the
most health relevant parameter to measure (e.g.
Maynard 2007), and that particle surface area (~d2)
or number (~d0) might be just as relevant. The
miniDiSC is small and simple enough to allow
personal exposure monitoring. It will allow studies
linking particle number concentration and lungdeposited surface area to acute health effects to test
the hypothesis that these parameters are highly
health-relevant.
Fierz M., Burtscher H., Steigmeier P. and Kasper M.
2007. Field measurement of particle size and
number concentration with the Diffusion Size
Classifier (DiSC), SAE 08PFL-484
Fissan H., Neumann S., Trampe A., Pui D.Y.H. and
Shin W.G. 2006. Rationale and principle of an
instrument
measuring
lung
deposited
nanoparticle surface area. J. Nanoparticle
Research 9:53-59.
Maynard A.D. 2007. Nanotechnology: The Next Big
Thing, or Much Ado about Nothing? Ann. Occup.
Hyg. 51:1-12.
Probing Nanoparticles Deposited on Flat Surfaces by X-ray Spectrometry at Grazing
Incidence
Falk Reinhardt1, Burkhard Beckhoff1, Harald Bresch2 und Stefan Seeger2
1
2
Physikalisch-Technische Bundesanstalt, Abbestr. 2-12, 10587 Berlin
Bundesanstalt für Materialforschung und -prüfung, Unter den Eichen 87, IV.24, 12205 Berlin
Keywords: Aerosol characterization, Cascade impactor, Elemental composition,
Particle size distribution, XRF
The strive for advancement in quantitative and
qualitative nanoparticle analysis is motivated by
multiple questions about potential risks caused by
handling of or exposition to nanoscaled particles
(interaction with the environment). Among those
questions the verification and quantification of the
dose-response relationship is a prominent one.
Furthermore, improved knowledge of the interactions
of nanoparticles with all kind of material surfaces is
necessary for evaluating the use of the particle’s
properties. To answer those questions analysis of
nanoparticles has to be developed further with
respect to both sampling procedures and analytic
techniques aiming on elemental compositions.
The further development of analytic
techniques also involves the examination of
deposited nanoparticles with synchrotron radiation.
Depending on the particle number concentration,
size-preselected nanoparticles were sampled on clean
and flat silicon wafers either by use of a cascade
impactor or by use of an electrostatic sampler. The
deposition density on the wafer was approximately
105 particles/mm2 or less. Deposition with the
electrostatic sampler led to an approximately evenly
distributed deposition.
PTB employs monochromatized synchrotron
radiation of well-characterized beamlines, reliable Xray spectrometry (XRS) instrumentation and
absolutely calibrated X-ray detectors for the nondestructive investigation of bulk and layered samples
in its laboratory at BESSY II (Beckhoff, 2008).
surfaces with respect to elemental compositions, and
potentially even depth profiles. Based on totalreflection X-ray fluorescence analysis (TXRF),
which offers lower levels of detection in the pg to fg
range, in GIXRF the incident angle of the excitation
radiation is tuned between 0° and about threefold the
critical angle of total-reflection. Therewith the
intensity of the X-ray standing wave field (XSW) at a
given height above the surface is modified. A particle
of a given diameter deposited on the flat surface will
be affected by the intensity of excitation radiation
varying with the angle of incidence and hence yields
a correspondingly varying X-ray fluorescence signal.
Thus, in addition to information on the
elementary composition of the particles, which is
inherent to XRF, information on the deposited size
fraction can be obtained (Fig. 2).
Figure 2: Angular dependence of detected
fluorescence radiation dependent on incident angle.
Different specimens were prepared by
depositing Zn compounds and NaCl particles with
size fractions down to 10 nm on silicon wafer
substrates by use of a differential mobility analyzer
(DMA). Those particles serve as model systems for
current and future reference-free quantitative analysis
of size fractioned aerosol particles.
Figure 1: Sketch of grazing incidence XRS beam
geometry
Grazing incidence X-ray fluorescence analysis
(GIXRF) has the potential to effectively contribute to
the characterization of nanoparticles deposited on flat
The financial support of this research activity within
the frame of the ProFiT project “Nanoparticle X-ray
Analysis” supported by the Investitionsbank Berlin is
gratefully acknowledged.
Beckhoff, B. (2008). J. Anal. At. Spectrom. 23, 845.
Quantification of carbonate carbon in atmospheric aerosol by means of ATR
(Attenuated Total Reflection) spectroscopy and a multivariate calibration method
P. Fermo1 , A. Piazzalunga1,* F. Tuccillo1, L. Brambilla1 , F. Mazzei2, P. Prati2
1
Dep. Inorganic, Metallorganic and Analytical Chem., University of Milan, Via Venezian 21, 20133, Milan, Italy
*
Now: Dep. of Environmental Sciences, University of Milano-Bicocca, Piazza della Scienza 1, 20126, Milan,
Italy
2
Dipartimento di Fisica and INFN, University of Genova, via Dodecaneso 33, 16146, Genova, ITaly
Key words: particulate matter, carbonate, FT-IR, ATR, XRF
Particulate matter (PM) carbonaceous fraction
contains organic carbon (OC), elemental carbon (EC)
as well as carbonate carbon (CC). The contribution of
inorganic carbon is often neglected because its
concentration is generally low and, moreover, there is
not a reference analytical method for its
quantification. Nevertheless in same cases, where a
specific source of carbonate is present (mineral dust,
street dust re-suspension, concrete plant, etc.), this
fraction must be determined (Jankowski et al.,
2008).
PM10 atmospheric aerosol samples came from
Massa Carrara, one of the most famous place in Italy
where marble is quarried. The samples were
collected on a daily basis (24 hours) along the road
followed by the trucks transporting marble rocks
form the pit to the sea. PTFE filters were used and
characterized for their elemental composition by
means of ED-XRF. PM10 concentration on average
was 34.6 µg/m3 and calcium showed quite high
values being on average 17.3 µg/m3 . Therefore a
contribution of the marble pit and/or marble
transportation as significant PM sources cannot be
ruled out.
In this work CaCO3 was determined by infrared
spectroscopy in ATR (Attenuated Total Reflection)
mode. This approach, more effective than IR
spectroscopy in transmission mode, has already been
used in the literature for the quantification of PM
organic fraction (Ghauch et al., 2006).
In order to quantify CaCO3 amount by ATR
technique, a multivariate calibration method has been
employed. For this purpose the program TQ
ANALYST 8.0 by Thermo Fisher Scientific was
employed. The regression algorithm is PLS (Partial
Least Square). The use of chemometric techniques
for quantification of some species in PM samples by
IR spectroscopy has been already used (Coury et al.,
2008) but not for the determination of carbonate
content since CaCO3 infrared most intense absorption
(at about 1420 cm-1 and due to CO32- stretching
mode) is interfered by the presence of both
ammonium sulphate and nitrate. Because of this
superposition we investigated only the region center
at 871 cm-1 which correspond to CO32- bending.
Suitable standards were prepared mixing known
quantities of calcium carbonate with nujol, which is
normally used as a diluting matrix when IR spectra
are acquired. In order to obtain for the standard
mixtures ATR spectra comparable with those
registered for PM samples, the standards were
deposited on the diamond crystal, covered with a
PTFE filter and then pressurized and scanned as for
the ambient samples.
The calibration curve, obtained analyzing 15
standards, has a fit of R2=0.99 and a RMSEC (root
mean square error of calibration) of 0.69. Since the
model efficiency is based on its performance in
prediction (in this case the ability to estimate
unknown CaCO3 concentrations in aerosol samples),
a validation procedure was applied giving a model
Performance Index of 91.3%.
In order to validate the method based on ATR-FTIR,
portions of the same PM10 samples have been
analyzed by means of IC (Ion Chromatography)
following a procedure recently suggested in the
literature (Jankowski et al., 2008).
A very good agreement between the two methods has
been obtained. Furthermore it has been demonstrated
that there is a contribution to PM due to the marble
caves even if calcium is not present only as calcium
carbonate (on average 50% of Ca is in the form of
CaCO3). This evidence has been confirmed also by
SEM-EDX (Scanning Electon Microscopy – Energy
Dispersion X-ray spectroscopy) analyses carried out
on some of the filters where the presence of calcium
carbonate together with calcium silicates and calcium
sulphate has been pointed out.
In conclusion the method here proposed is an
alternative to IC analysis and offers an advantage
since it allows to analyze directly carbonate content
which is not indirectly derived from the ions balance.
Jankowski, N., Schmidl, C., Marr, I. L., Bauer, H.,
Puxbaum, H., (2008). Atmos. Env., 42, 8055 – 8064.
Ghauch, A., Deveau, P.A., Jacob, V., Baussand, P.
(2006). Talanta, 68, 1294 – 1302.
Coury, C., Dillner, A. M., (2008). Atmos. Env., 42,
5923 – 5932.
A Miniature Collector for the Concentrated Collection of Fine Airborne Particles
S. V. Hering1 and G. S. Lewis1
1
Aerosol Dynamics Inc., 935 Grayson Street, Berkeley, CA 94710, USA
Keywords: water-condensation particle counter, PM2.5 sampling
find that the water coating eliminates particle
rebound, and indeed tests with 1.4 µm PSL showed
that it is possible to form a “stack” of particles twice
as high as it is wide. Ambient particles can also be
collected into <80 µL volume of water.
Size dependent collection efficiencies are
shown in Figure 3 for two types of aerosols,
ammonium sulfate and oleic acid. We find high
collection efficiency for all particles at sizes above 10
nm in diameter. This was found for both hygroscopic
and hydrophilic particles. The efficiency was also
tested as a function of particle concentrations. For
this system, which was explicitly designed to
minimize concentration effects, the collection
efficiency remained high at the highest concentration
tested of 105cm-3.
8
OUTPUT DROPLET SIZE
Output
Output
Output
Output
Output
INPUT PARITCLE SIZE
dN/dLogDp
6
for 30nm, Eff=96%
for 70nm, Eff=86%
for 100nm. Eff=100%
for 120nm, Eff=100%
for 200nm, Eff=99%
4
2
0
0.1
1
Diameter (µm)
10
Figure 2. Size distribution of droplets formed for
varying input particle sizes.
1.0
Collection Efficiency
Over the last decade several types of real-time
instruments have evolved that provide in-situ
chemical characterization of ambient aerosols, yet
because of their cost and operational demands, these
instruments have not replaced the filter sampling for
routine monitoring. Measurements in multiple
locations, especially in remote regions, require small,
low-cost, low-power instruments. Similarly microenvironmental and personal sampling demand small,
light-weight, low-cost monitors. We seek here to
develop a method that provides a concentrated,
ready-to-analyze aerosol sample that takes advantage
of low detection limits of many analytical methods,
and yet has few operational demands.
As a first step in the development of such a
monitor, we present here a miniature collector that
provides a concentrated particulate sample. As in the
water-based condensation particle counters (Hering
and Stolzenburg, 2005), ambient particles are
enlarged through water condensation using a laminar,
thermally diffusive flow. Once enlarged the droplets
are collected by impaction onto a solid surface, or
into a small water reservoir.
This miniature collector, shown in Figure 1,
utilizes a single, wet-walled tube, 4 mm ID, with an
active length of 120mm. An annular thermal electric
device mounted between the preconditioner and
condenser acts as a heat pump to create a region of
supersaturation for condensational growth. Cooling
fins equipped with small fans are used to regulate the
temperature of the condenser region. Typically, the
system is operated with a preconditioner temperature
of 5°-10°C, a condenser temperature of 30°-37°C and
an air sampling rate of 0.4 L/min.
The droplets formed from this system are
uniformly sized at approximately 2 µm in diameter,
independent of the input particle size, as shown by
measurements with an aerodynamic particle sizer in
Figure 2. Once enlarged, the particles are deposited
within a 300-µm spot by means of impaction. We
0.8
0.6
Personal Sampler
400 cm3/min, 0.6 mm Nozzle
0.4
o
T = 25 C
Amonium Sulfate
Oleic Acid
0.2
0.0
4 5 6 7
2
10
3
4 5 6 7
2
100
Dp (nm)
3
4 5 6 7
2
1000
Figure 3. Size-dependent collection efficiency.
120 mm
This work was supported by the National Institute for
Environmental Health under SBIR grant R44 ES014997
Figure 1. Miniature particle collector
Hering, S. V., Stolzenburg, M. R. (2005), Aerosol
Science and Technology, 39: 428-436
3
Retrieval of Aerosol Profiles using
Multi Axis Differential Absorption Spectroscopy (MAX-DOAS)
S. Yilmaz1, U. Frieß1, A. Apituley2, G. de Leeuw3,4,5 and U. Platt1
1
2
Institute of Environmental Physics, University of Heidelberg, Germany
National Institute for Public Health and the Environment, Bilthoven, The Netherlands
3
Finnish Meteorological Institute, Helsinki, Finland
4
Department of Physics, University of Helsinki, Finland
5
TNO, Utrecht, The Netherlands
Keywords: Remote sensing, atmospheric aerosols, optical properties, instrument development.
Multi
Axis
Differential
Absorption
Spectroscopy (MAX-DOAS) is a well established
measurement technique to derive atmospheric trace
gas profiles by collecting scattered light spectra at
diﬀerent elevation angles and subsequent inverse
modelling of the radiative transfer (Hönninger et al.,
2004). Since aerosol particles are significantly
involved in the scattering of the detected light,
information about their distribution in the atmosphere
is vitally important for the modelling procedure.
Through MAX-DOAS measurements of trace gases
with an already known vertical distribution, like the
oxygen dimer O4, it is possible to retrieve
information on atmospheric aerosols (Wagner et al.,
2004). Based on the optimal estimation method, we
have developed an algorithm (Frieß et al., 2006)
which fits simultaneously measured O4 optical
densities at several wavelengths and elevation angles
to values simulated by a radiative transfer model.
Retrieval parameters are aerosol extinction profile
and optical properties like single scattering albedo,
phase function and Angström exponent.
In May 2008, an intercomparison campaign
with established aerosol measurement techniques
took place in Cabauw/Netherlands, where
simultaneous DOAS, Lidar, Sun photometer and
Nephelometer measurements were performed.
We present first results of selected days from
this period (Figure 2). The optical properties of
aerosols retrieved by the DOAS technique show
qualitative agreement with the established
measurement techniques demonstrating the progress
towards our goal of establishing the MAX-DOAS
technique for retrieving optical properties of
atmospheric aerosols. Quantitative comparison is
ongoing.
Figure 2. Profiles of aerosol optical properties retrieved
from an intercomparison performed in
Cabauw/Netherlands on 09.05.2008. Top: range
corrected lidar signal. Bottom: aerosol extinction from
MAX-DOAS.
Figure 1. MAX-DOAS instrument with spectrometer (left)
and telescope unit (right)
In the scope of a joint research activity of the
EU funded project EUSAAR (European Supersites
for Atmospheric Aerosol Research) we have
developed a new type of DOAS instrument, which
uses three miniature spectrometers to cover the near
ultraviolet to visible wavelength range (290–790nm),
enabling to capture all absorption bands of the
oxygen-dimer O4. Additionally, it is possible to point
to any direction in the sky with a 2D telescope unit
which is connected to the spectrometers via fibre
optics (Figure 1).
This work was supported by the EU Research
Infrastructures Project I3 EUSAAR (contract
026140).
Hönninger, G., v. Friedburg, C., & Platt, U. (2004). Multi Axis
Diﬀerential Absorption Spectroscopy (MAX-DOAS).
Atmospheric Chemistry and Physics, 4(231-254).
Wagner, T., Dix, B., v. Friedeburg, C., Frieß, U., Sanghavi, S.,
Sinreich, R., & Platt, U. (2004). MAX-DOAS O4
measurements: A new technique to derive information on
atmospheric aerosols - Principles and information content.
Journal of Geophysical Research, 109(D22205)
(doi:10.1029/2004JD004904).
Frieß, U., Monks, P.S., Remedios, J.J., Rozanov, A., Sinreich, R.,
Wagner, T., & Platt, U. (2006). MAX-DOAS O4
measurements: A new technique to derive information on
atmospheric aerosols. (II) Modelling studies. Journal of
Geophysical Research, 111(D14203)
(doi:10.1029/2005JD006618).
NanoCheck, a Valuable Tool for Size Range Expansions of Optical Particle Counters for
Environmental Applications
Markus Pesch, Hans Grimm, Roland Hagler and Xiaoai Guo
GRIMM Aerosol Technik GmbH & Co. KG, Dorfstrasse 9, D-83404 Ainring, Bayern, Germany
Email: [email protected]
Keywords: Aerosol instrumentation, Nanoparticles, Number concentration, Optical particle counter, PM measurements
A series of GRIMM optical particle counters can be
used for continuous measurement of aerosol particles,
which can be reported for the various particle size channels
down to sub-micron range in various modes, like particle
counts in [#/liter] and environmental dust mass distribution
in [µg/m³]. These environmental instruments work using
the principle of light scattering technology, as shown in
Fig.1. A semiconductor laser serves as light source. The
signal scattered from the particle passing the laser beam is
collected at ca. 90° by a mirror and transferred to a
recipient-diode. The signal of the diode passes a multichannel size classifier after a corresponding amplification.
A pulse height analyzer then classifies the signal
transmitted in each channel. These counts can be converted
to a mass distribution from which different PM values
derive.
1 shows that on Friday afternoon more people go back
home by car and hold a dinner party or celebration nearby
and the high peak is due to the fog and drizzle. Peak 2 and
3 result from traffic on Saturday and house heating by
burning wood, respectively. On Sunday people go to
church and then in about 1 hour they go back home, as
illustrated in Peak 4. Thus, by monitoring PM values one
can indentify and study the aerosol sources resulting from
human activities, nearby traffic, meteorological effect like
fog and drizzle, and so on.
A comparison of the outdoor aerosol number
concentrations measured with NanoCheck 1320 and EDM
365 is made in Fig.3b. The difference between two
measurements gives the particle number concentration in
the size range of 25nm-0.25µm. EDM365 data multiplied
by a factor fit well to Nanocheck data and the trend of both
measurements seems to be the same. It shows that
NanoCheck 1320 is a valuable addition to EDM 365,
greatly expanding the size range of optical particle
counters.
110
100
GRIMM EDM 365
Fig.2 GRIMM NanoCheck
1.320 Sensor.
80
100
PM-10
1
[µg/m³]
50
80
PM-1.0
70
Temp.:(°C)
70
Humidity(%rH)
60
2
60
3
4
50
40
40
30
30
20
20
10
0
0
07
.1
07 1.2
.1 0
07 1.2 08
.1 0 16
07 1.2 08 :37
.1 0 18
07 1.2 08 :22
.1 0 20
08 1.2 08 :07
.1 0 21
08 1.2 08 :52
.1 0 23
08 1.2 08 :37
.1 0 01
08 1.2 08 :22
.1 0 03
08 1.2 08 :07
.1 0 04
08 1.2 08 :52
.1 0 06
08 1.2 08 :37
.1 0 08
08 1.2 08 :22
.1 0 10
08 1.2 08 :07
.1 0 11
08 1.2 08 :52
.1 0 13
08 1.2 08 :37
.1 0 15
08 1.2 08 :22
.1 0 17
08 1.2 08 :07
.1 0 18
09 1.2 08 :52
.1 0 20
09 1.2 08 :37
.1 0 22
09 1.2 08 :22
.1 0 00
09 1.2 08 :07
.1 0 01
09 1.2 08 :52
.1 0 03
09 1.2 08 :37
.1 0 05
09 1.2 08 :22
.1 0 07
09 1.2 08 :07
.1 0 08
09 1.2 08 :52
.1 0 10
09 1.2 08 :37
.1 00 12
1. 8 :2
20 1 2
08 4:0
15 7
:5
2
10
100000
b)
10000
Number Concentration [#/cm³]
Since the intensity of the scattered light decreases
with the sixth power of the particle size, optical light
scattering systems can’t detect particles below about
0.1µm. As displayed in Fig.2, a GRIMM patented portable
NanoCheckTM 1.320 sensor, which combines a unipolar
diffusion charger, a time multiplexed electrical
conductivity measurement and an aerosol faraday cup
electrometer, can measure the total number concentration
in the range of about 30nm to 400nm and the mean
diameter of the aerosol number distribution in real time and
continuously. This new portable NanoCheckTM 1.320
Sensor can work with any GRIMM aerosol spectrometer,
getting the sample directly from the spectrometer. In this
way the combination of both instruments makes it possible
to monitor the full aerosol size range from a few
nanometers up to 30µm in different size channels. This
compactly designed detector can be used as an exposure
monitor for indoor and outdoor aerosol nanoparticles.
In this work, by using a GRIMM environmental
dust monitor (EDM 365) and a NanoCheckTM 1.320
Sensor, various measurements were carried out in a
resident’s garden in Ainring in Germany and in a traffic
measuring station in Salzburg in Austria. EDM 365 reports
PM10, PM2.5, PM1.0, particle counts as well as
meteorological parameters such as temperature and relative
humidity. Fig.3a illustrates the measured PM values of
outdoor aerosols in a resident’s garden in Ainring in
Germany. There appear some peaks in the PM curves. Peak
90
PM-2.5
Temperature [°C] and Humidity [%rH]
a)
Fig.1 Measurement Principle
of GRIMM Spectrometer.
90
1000
100
10
EDM 365 Counts Size range: 0.25-0.40µm
NanoCheck1320 N-AVG Size range:0.025-0.40µm
EDM 365 Counts*factor
1
23.12.2008 24.12.2008 24.12.2008 24.12.2008 24.12.2008 24.12.2008 25.12.2008 25.12.2008
19:12
00:00
04:48
09:36
14:24
19:12
00:00
04:48
Fig.3 a) Results measured by GRIMM EDM 365; b)
Comparison of the outdoor aerosol number concentrations
measured with EDM 365 and NanoCheck.
Application of Computer Software for Airborne Particles Counting
B. Trivuncevic1, G. Jereb1,4, B. Poljšak1, M. Bizjak1,2 and S. A. Katz3,4
1
University of Ljubljana, College of Health Studies, Poljanska 26 a, 1000 Ljubljana, Slovenia
Environmental Agency of the Republic of Slovenia, Vojkova 1b, 1000 Ljubljana, Slovenia
3
Rutgers University, Department of Chemistry, Camden, NJ 08102-1411, USA
4
University of Nova Gorica, School of Environmental Sciences, Vipavska 13, Nova Gorica, Slovenia
2
Keywords: air pollution, TSP, alternative deposition method, particle counting
Dust emissions from various anthropogenic
sources such us ore depots, coal pits or even quarries
represent nuisance sources in residential areas. The
inhabitants of the residential area Rožnik and
Ankaran city are located near the Port of Koper have
complained for several years now about dust
emissions, which they observe in their living
environment, on the vegetables, fruits, etc. and
attribute to some of the activities at the port.
Particulate matter deposition is usually a
complex mixture of particles of different origin, size
and chemical composition. Sources of particles can
vary; some of anthropogenic and some of terrestrial
origin. For that reason simple alternative
measurement device for quick estimation of direction
and quantity of particulate matter, based on
deposition and/or adhesion was developed (1). Two
types of sampling devices were constructed. Both of
them collect particulate matter from air on adhesive
material (medical Vaseline) and enable collection in
both the horizontal and vertical directions.
Plastic ball of 20 cm diameter, covered with
Vaseline was used for sampling device 1. For
sampling device 2 specially designed octagonal
prisms in which nine glass plates covered with
Vaseline were assembled in a way that collects
particles coming from different directions on the
adhesive surface (Figure 1). Sampling devices were
located around the coal and iron ore depot in Port of
Koper (Slovenia).
devices, especially the cost of type 1, is relatively
low, many such devices could be used for quick
screening of environment in order to find the most
representative locations for later placement of more
sophisticated, accurate and expensive devices for air
monitoring.
Since both methods are not sensitive enough
for quantification of particulate mass by
gravimetrical analysis counting of particles was used
as an alternative method. Samples were analyzed
using two different approaches: I) Particles were
counted manually by visual approach using
magnifying lens. On each side of the ball particles
were counted according to template model on total
surface of 5 cm2 (Figure 2). II) From each ball or
plate from octagonal sampler digital pictures were
made and on them particles on 5 cm2 surface were
analyzed and counted by use of computer software.
Figure 2. Appearance of template model for particles
counting
Figure 3. Sampling device 1 after 1 month exposure
The aim of this experiment was to compare
visual counting with computer counting in order to
evaluate the ease and accuracy with which the
particles on the sampling device could be
determined. In future we will try to correlate number
of particles on surface with other standard methods
(VDI, 1996) in order to extrapolate data collected in
this manner with regulatory limits.
Figure 1. Appearance of sampling device 1 and 2
References
Previous study (Goličnik et al., 2008) already
revealed that these new sampling devices are suitable
for rapidly estimating the flow direction of major
particulate matter sources. Particulate matter
samples, collected in this way could also be analyzed
qualitatively. Since the cost of both sampling
Goličnik B., Jereb G, Poljšak B, Planinšek A., Katz S.A. and
Bizjak M. Alternative method for quick estimation of direction
and quantity of particulate matter by its deposition. EAC 2008,
Thessaloniki.
VDI und DIN Guideline VDI 2119 part 2 (1996) - Measurement of
Particulate Precipitations – Determination of dust
precipitation with collecting pots made of glass.
Program controlled gear complex for aerosol monitoring
T. E. Ovchinnikova1, A. M. Baklanov2, S. N. Dubtsov2, I. V. Melekhov2
1 Institute for Water and Environmental Problems SB RAS, Morskoy pr. 2, IWEP, 630090 Novosibirsk, Russia
2
Institute of Chemical Kinetics and Combustion SB RAS, Institutskaya, 3, 630090, Novosibirsk, Russia
Keywords: atmospheric aerosols, diffusion battery, optical particle counter, particle size distribution
A complex of two devices for atmospheric aerosol monitoring was developed in the Institute of
Chemical Kinetics and Combustion. First of them is the
diffusion spectrometer of aerosol DSA, or diffusion
battery created in the institute. It was used for a long
time for the analysis of concentrations and particle size
distributions. The other one is optical particle counter
AZ6. DSA is meant for the analysis of aerosol structure
with particle sizes in the range from 3 to 200 nm, and
AZ6 is used for aerosols with particle sizes from 200 to
1200 nm.
A specially developed computer program
DSA09 controls the complex (separately or together).
The program allows to set up measurements regimes, to
accept and process data and to save them as files.
Diffusion battery penetration data are obtained
as m measured concentration values ci (m is the total
concentration, (left upper widow); a dashed line
represents data reconstructed from calculated distribution;
calculated particle size distribution (left lower window).
Data obtained with AZ6 include:
time of measurement beginning, mean values, total
concentration, (right upper widow);
particle concentrations diagram (right lower window).
A panel View Progress is assigned for measurements review (subsequently or in random order).
The data represented on the figure are the result
of laboratory experiment.
number of battery ports)
To obtain particle size distribution f(r) one
needs to solve the set of integral equations
ci + ei =
r max
∫ f (r ) pi (r ) dr ,
r min
i = 1...m ,
where ci is measured concentration value, ei is unknown measurement error and p i ( r ) is the penetration function for i-th port of a battery. The method of
use is based on the idea that as set of solutions is convex and error distribution is known, resulting solution
may be represented as approximate sum of all possible
solutions multiplied by their statistical weights.
(Ovchinnikova et all, 2006).
As the data error is estimated during measurements particle size distribution can be obtained even
under sharp fluctuations of aerosol concentrations resulting to nonmonotonic data.
Graphic interface lets to watch concentrations
and structure of aerosol dynamics. On the Fig. 1 the
main window of the program of data view and process
with the data of one measurements is shown.
Data obtained with DSA include:
counts values (panel "Counts");
graph of measured counts, time of measurement
beginning, mean values, error assessment, total
Figure 1. Laboratory experiment data.
Ovchinnikova, Т. Е., Eremenko, S .I. & Baklanov, A.M
(2006). in Proc. 7th Int. Aerosol Conf. St.Paul, Minnesota, 497-498.
Validation of a new Atmospheric Pressure Interface Time-of-Flight mass spectrometer
(API-TOF) to measure the composition of sub-2 nm aerosol particles
M. Ehn1, H. Junninen1, K. Neitola1, M. Sipilä1, H. Manninen1, T. Petäjä1, K. Fuhrer2, M. Gonin2, U. Rohner2, S.
Graf2, M. Kulmala1, and D.R. Worsnop1,3
1
Department of Physics, University of Helsinki, P.O.Box 64, 00014, Helsinki, Finland
2
Tofwerk AG, Switzerland
3
Aerodyne Research Inc., Billerica, MA, USA
Keywords: Cluster ions, mass spectrometry, ion mobility, instrumentation
The lower size limit for aerosol particle
detection has long been 3 nm. During recent years,
new methods of detection and, also indirect
composition measurements, have been presented
(e.g. Kulmala et al., 2007). Now, a new Atmospheric
Pressure Interface Time-of-Flight mass spectrometer
(API-TOF) is being developed at Tofwerk AG, Thun,
Switzerland. This instrument will give new insight
into particle chemical composition in the range 03000 Da, which corresponds roughly to a particle
size range up to 2.5 nm in diameter. These are the
sizes where atmospheric nucleation takes place, and
is therefore of great interest. The API-TOF is
currently being tested in the laboratory at the
department of physics at University of Helsinki,
through comparison with a high resolution Herrmann
differential mobility analyzer (HDMA, Herrmann et
al., 2000) and a neutral cluster and air ion
spectrometer (NAIS).
The API-TOF samples 0.9 L/min of air
(through a 300 µm orifice), directly from ambient
pressure. Two quadrupoles then guide ions as the gas
is pumped away. Finally, an ion lens focuses the ions
into the TOFMS extraction region. The TOFMS
operates in two modes, V or W, where the letter
signifies the flight path of the ions in the TOFMS;
i.e. there are one or two reflections in the V and W
modes, typical m/Q resolving power of roughly 3000
or 5000, respectively.
The NAIS and HDMA both measure cluster
ion mobility. The relationship between ion mobility
and mass are somewhat uncertain. Here we have used
the empirical fit described in Mäkelä et al, 1996.
Both the NAIS and HDMA measure the distributions
at ambient pressure whereas the API-TOF pressure is
reduced to 10-6 mbar. Therefore the cluster
distribution can be perturbed both due to evaporation
at low pressure, and fragmentation in the quadrupole
ion guides.
One of the first experiments generated ions by
passing laboratory air through a corona charger,
measuring the output with all three instruments in
parallel. Preliminary results are plotted in Fig. 1. The
top panel shows the cluster distribution as measured
by the NAIS and HDMA. It is evident that the
HDMA has superior resolution compared to the
NAIS, but nevertheless, there is an agreement
between the instruments. The bottom graph shows an
average mass spectrum measured simultaneously by
the API-TOF. The pattern of peaks at higher masses,
the largest at 610 Th (~1.6 nm), result from a short
piece of conductive silicone tubing in the inlet,
showing how sensitive the system is to
contamination. The mobility spectra and the mass
spectrum are not an exact match, but as mentioned,
this was not expected.
High resolution analysis of the mass scale and
isotope patterns should allow for identification of
more peaks in Fig. 1. The detailed analysis of the
spectra obtained so far has only begun, and more
experiments will be performed during a 3 week
intensive. The goal is to use API-TOF to measure
aerosol clusters in ambient air, at orders of magnitude
lower concentrations.
Figure 1. Size distributions of positive ions produced
by a corona charger, measured with three different
instruments.
Herrmann,W., Eichler, T., Bernardo, N., and
Fernandez de la Mora, J. (2000). Abstract to the
annual conference of the AAAR, St. Louis, MO.
Kulmala, M., Riipinen, I., Sipilä, M., Manninen, H.
Petäjä, T., Junninen, H., Dal Maso, M., Mordas,
G. Mirme, A., Vana, M., Hirsikko, A., Laakso, L.,
Harrison, R., Hanson, I., Leung, C., Lehtinen, K.,
Kerminen, V-M. (2007). Science, Vol. 318. No.
5847, pp. 89 - 92.
Mäkelä, J., Jokinen, V., Mattila, T., Ukkonen, A. and
Keskinen, J. (1996). J. Aerosol Sci., Vol. 27, No.
2, pp. 175 - 190.
Parallel-DMA (PDMA) – a tool for characterization and enrichment of aerosol
nanoparticles
Anne Maißer1, Günter Allmaier2 and Wladyslaw W. Szymanski1
1
2
Faculty of Physics, University of Vienna, 1090, Vienna, Austria
Institute of Chemical Technology and Analytics, Vienna University of Technology, 1060, Vienna, Austria
Keywords: nanoparticles, bioaerosols, collection efficiency, characterization
Electrostatic methods provide numerous
options for the characterization and investigation of
aerosol nanoparticles. Differential mobility analysis
(DMA) has proven its ability to characterize
according to size and separate inorganic particles as
well as aerosol particles of biological origin such as
proteins or viruses. Because it operates under
atmospheric pressure it offers an opportunity also to
utilize this technique for micro-preparative
applications. For that reason a parallel-DMA
(PDMA) system was constructed and has proven its
feasibility to simultaneously monitor the size
distribution of aerosolized nanoparticles and to select
one specific fraction particle size fraction (Allmaier
et al. 2008). PDMA contains of two identical DMAs
working in parallel. The scanning nano-DMA1
delivers the complete size spectrum of the
aerosolized particles. The nanoDMA1 is combined
with an electrical aerosol detection device working
on the Faraday cup principle. An identical separation
unit – the nano-DMA2 - running parallel with the
nano-DMA1 operates at one given voltage setting
(separation) and can be used for sampling or
enrichment (collection) of the one selected size class
of nanoparticles..
For further physical or chemical investigation
of this specific classified size fraction it is necessary
to remove the nanoparticles from the gas phase after
nano-DMA2 separation. Thus the PDMA was used in
combination with an electrostatic nano-sampler
(ENS). The ENS was designed specifically for the
usage on bionanoaerosol particles but it works
equally well for inorganic particles. It uses
electrostatic force to collect charged particles exiting
the nanoDMA2. The ENS is a kind of an impinger
using a liquid as collecting media to provide “soft
landing” to the particles. Between the nozzle outlet
and the liquid surface an electrostatic field is applied.
The appropriate choice of liquid offers both the
conductivity and if needed an appropriate
environment to preserve biological activity of
particles impacted and captured on its surface.
Several proteins, dendrimers and silica particles
covering equivalent mobility diameters from 5 to 30
nm were chosen to evaluate the collection efficiency
of the ENS.
It was shown that the appropriate voltage applied to
the liquid could increase the collection efficiency of
the ENS up to 100 % for all investigated particles.
The ultimate verification of the feasibility of the
PDMA-ENS system is to prove the presence and, in
the case of bioaerosols, the biological viability of the
size-selected nanoparticles in the ENS liquid.
Various nanoparticles were classified and
sampled on liquid surface in the ENS over periods of
up to 50 hours. The sample was consequently reinjected to the Electrospray Aerosol Generator (Mod.
3480, TSI, Inc.) and again analyzed with the PDMA.
Fig.1 shows the size distributions for HS-30 silica
particles (Sigma Aldrich). The exactly same location
of measured peaks for the stock suspension and in the
liquid sampled silica particles proves the feasibility
of the approach.
Figure 1. PDMA size distributions of silica particles.
An enzyme activity of the sampled enzyme
was tested to answer the question on the preservation
of the biological function after the aerosolization,
charging, separation and sampling step. The
bioactivity of the enzyme β-galactosidase (equivalent
mobility diameter 8 nm) was measured before and
after the sampling process. The enzyme activity test
revealed the existence of activity in the enzyme after
the sampling process. This is an evidence for a
successful effort combining electrospraying and
DMA-technique with “soft landing” collection and
enrichment of biological nanoparticles.
This work was supported in part by a grant of the
Austrian Science Foundation (Project P16185-N02).
Allmaier, G. et al. (2008), Journal of the American
Society of Mass Spectrometry 19, 1062-1068.
Diffusion based nanoparticle monitor using QCM-technology
J. Leskinen1, J. Joutsensaari3, A. Jakorinne4, M. Laasanen4, J. Jokiniemi1,2
1
Univ. of Kuopio, Department of Environmental Science, P.O. Box 1627, FI-70211 Kuopio, Finland.
2
VTT Technical Research Centre of Finland, P.O. Box 1602, 02044 VTT, Espoo, Finland
3
Univ. of Kuopio, Department of physics, P.O. Box 1627, FI-70211 Kuopio, Finland.
4
Savonia Univ. of Appl. Sci., Information Technology R&D Unit, P.O. Box 6, FI 70201 Kuopio, Finland
Keywords: Diffusion, Deposition, Nanoparticles, Indoor air quality, Real-time detection
The aerosol flow rate can be varied from 0 to
around 1.5 lpm. Calculations using particle
diffusion equations (Hinds, 1999) predict that the
greater the flow rate, the more mass will be
deposited on the crystals. The 0.2 mm spacing is
quite narrow and turbulence would not increase
the deposition rate.
A sample aerosol was produced using a
constant output atomizer (TSI) with ammonium
sulfate-water-solution and was diluted with dry
pressured air. The particle distribution was
measured by SMPS at the beginning of the test
period to get number concentration around 106
#/cm3 and the mode around 50 nm.
The sample aerosol guided to the nanoparticle
monitor was dried to remove moisture from the
particles. A preimpactor was used to remove large
particles. Particle exposure gave a clear response
when the impactor’s cut 50 % diameter was as
low as 355 nm.
70
60
Deposited mass (ng)
The use of nanoparticles has increased rapidly
over the past decade. Therefore health effects of
these ultra fine particles are of public concern and
it has become important to monitor
concentrations of nanoparticles in the air at
workplaces where nanoparticles are handled.
We have developed an inexpensive method
and device called nanoparticle monitor to monitor
nanoparticle concentrations in the air surrounding
employees. At the moment we are in a testing
phase, a prototype has been constructed and the
device gives a response for high nanoparticle
concentrations.
The device is based on two vibrating quartz
crystals (QCM) which detect particle mass
deposited on them (Ho, 1984). In our current
prototype, characteristic frequency of the crystals
is around 5 MHz and the frequency change,
caused by the deposited mass is detected with a
precision of 0.1 Hz. This enables a theoretical
mass sensing limit of around 2.2 ng. The crystals
are placed between two polyoxymethylene-plastic
blocks. The blocks are put together, with the
crystals facing each other (fig1). The crystals are
separated from each other with a spacer plate.
The plate is hollow in the middle and the distance
between the crystals can be changed by using
spacers with demanded thickness. In the present
study, a 0.2 mm foil was used as a spacer. The
sample aerosol flows through the device and a
fraction of the particles is deposited on the
crystals via diffusion.
50
40
30
Crystal 0
20
Crystal 1
10
0
0
200
400
600
800
1 000
1 200
1 400
Time (s)
Figure 2. Nanoparticle mass deposited on the
crystals with flow rate 1.5 lpm and
preimpactor cut 50 % diameter 355 nm.
The nanoparticle monitor will be further
developed to enhance the particle deposition. In
addition different methods will be tested to
prevent larger particles from depositing on the
crystal surfaces.
This work is supported by the Finnish Funding
Agency for Technology and Innovation,
Sachtleben Pigments Oy, Beneq Oy (fin), Amroy
and Teknologiateollisuus ry.
Figure 1. Schematic drawing of the prototype.
1) spacer plate, 2) plastic block, 3)
aerosol in, 4) aerosol out and 5) crystal
holder.
M. H. Ho (1984). Application of Quartz
Microbalances in Aerosol Mass
Measurements. Application of Piezoelectric
Quartz Crystal Microbalances, Elsevier
Science Publishers.
Hinds W. C. (1999). Aerosol technology.
A Wiley-interscience publication.
Determination of particulate ammonium (NH4+) by thermal dissociation and detection of
the generated gaseous ammonia
1
Ch. Hueglin1, H. Burtscher2, P. Graf1, C. Houle2, D. Meier2 and E. Rochat3
Empa, Swiss Federal Laboratories for Materials Testing and Research, 8600 Duebendorf, Switzerland
2
University of Applied Sciences Northwestern Switzerland, 5210 Windisch, Switzerland
3
Omnisens SA, 1110 Morges, Switzerland
Keywords: Ammonia, ammonium nitrate, ammonium sulfate, inorganics, thermal decomposition.
200
200
A prototype sampler and thermal dissociation
unit was built and tests of the thermal dissociation of
ammonium salt test aerosols (ammonium nitrate,
ammonium sulfate and ammonium bisulfate) and
ambient aerosols were performed. We found that the
used technique is feasible for automated semicontinuous determination of NH4+. A major problem
was the high adsorptivity and reactivity of NH3. This
requires a very careful selection of materials which
are in contact with ammonia. In addition, a trap for
acids (i.e. nitric acid and sulfuric acid), which are
formed during the dissociation, had to be installed.
Otherwise, the formed acids may deposit on available
surfaces and act as a sink for NH3. Some other
technical problems still have to be solved. Figure 1
shows results for a laboratory sample (left) and a
sample from outdoor aerosol. In both cases the
sulfate and the nitrate peak can clearly be resolved.
0 100
300
500
700
Time (sec)
900
1100
140
100
80
20
0
0
0
20
40
40
50
60
Temperature (°C)
100
100
80
50
60
NH3 (ppb)
140
150
NH3
Temp measured
Temp setpoint
Temperature (°C)
100
NH3 (ppb)
150
NH3
Temp measured
Temp setpoint
0
In the continental boundary layer, inorganic
salts are main constituents of the atmospheric
aerosol. They mainly consist of ammonium (NH4+),
sulfate (SO42-), nitrate (NO3-) and small amounts of
sodium (Na+) and chloride (Cl-) (Putaud et al., 2004).
NH4+ exists preferably as ammonium sulfate
((NH4)2SO4) and semi-volatile ammonium nitrate
(NH4NO3).
Because ammonium is of considerable environmental importance, a variety of measurement
techniques have been developed during the past.
These include filter-based methods, continuous
particle collection systems with subsequent analysis
by ion chromatography (IC), as well as aerosol mass
spectrometry. However, simple and reliable
techniques for time-resolved long-term measurement
of ammonium are not readily available.
As mentioned above, NH4NO3 is semivolatile and easily dissociates at ambient conditions,
contributing to the well known volatilisation losses
often encountered in measurements of ambient
particulate matter (PM). In contrast, (NH4)2SO4 is
non-volatile at atmospheric conditions. To our
knowledge, there is no conclusive information about
the thermal decomposition mechanism available in
the literature. Halstead (1970) studied the thermal
dissociation of ammonium sulfate at 400°C and
found that volatilisation occurs in two distinct sets of
reactions. First, ammonium pyrosulfate (NH4)2S2O7
and NH3 is formed, in a second stage ammonium
pyrosulfate is decomposed forming NH3, SO2 and N2.
Kiyoura & Urano (1970) proposed a more complex
thermal dissociation process involving ammonium
triammonium
sulfate
bisulfate
(NH4HSO4),
((NH4)3HSO4)2), ammonium pyrosulfate and
sulfamic acid (NH2SO3H) as intermediates.
In this study, we investigate the potential of a
novel approach for quantitative determination of
NH4+ based on thermal dissociation of ammonium
compounds. Our technique is conceptually similar to
methods developed for analysis of nitrate in aerosol
particles (Yamamoto & Kosaka, 1994). It is based on
the collection of dried ambient aerosols on a cold
sampling filter maintained at 4°C, followed by
controlled thermal dissociation of the collected
ammonium compounds and finally, by time resolved
detection of gaseous ammonia that results from
thermal dissociation.
0 100
300
500
700
900
1100
Time (sec)
Figure 1. Thermal dissociation of mixed NH4NO3
and (NH4)2SO4 aerosols generated by atomising an
aqueous solution of the two salts (left). Right graph:
NH3 signal from thermal dissociation of ambient
aerosol particles collected during 2.5h on a summer
afternoon with obviously low NH4NO3 concentration
(July 24 2008, outdoor temperature = 24°C).
This work was supported by the technology
promotion fund of the Swiss Federal Office for the
Environment (FOEN).
Halstead, W.D. (1970). J. appl. Chem., 20, 129-132.
Kiyoura R., Urano K. (1970). Ind. Eng. Chem.
Process Des. Develop., 9, 489-494.
Putaud, J.P. et al. (2004). Atmos. Environ., 38, 25792595.
Yamamoto, M., Kosaka, H. (1994). Anal. Chem., 66,
362-367.
Characterization of the Hermann and Attoui DMA in the super 3 nm range.
M. ATTOUI
Physical Department, University Paris XII France
Keywords: DMA, mobility, transfer function, nano particles.
The particles leaving the atomizer at 3
lmin-1 are dried in diffusion dryer and
neutralized in Kr 85 TSI neutralizer before
their introduction in the first DMA. The
particles produced with the wire generator
are not neutralized since they are self
singly charged. A home-made Faraday
cup electrometer (FCE) or CPC is used as
a detector for the monodisperse aerosol.
The sheath flow rate in the both DMAs is
measured with TSI mass flowmeters. The
both DMAs run in open loop. The first one
runs over pressure by pushing clean air
with a blower through a TSI mass
flowmeter. The second DMA runs
underpressure by sucking with a second
blower and second TSI mass flowmeter. A
laminar flowmeter is used in the aerosol
flow between the two DMAs. The
polydisperse aerosol is introduced at 3
lmin in the first DMA. The monodisperse
aerosols is sucked at 3 lmin.
Fig 1 gives the results for the ADMA
running at different flowrates from 80 to
800 l min-1.
0,28
200 lmin
EM Signal
Juan Fernandez de la Mora with various
collaborators and colleagues at Yale
University (CT. USA) introduced last few
decades high resolution DMAs (Hermann,
Rosser, Attoui DMAs) for ions and
particles in the sub 3 nm range. These
DMAs work at high sheath flowrates
(around 1000 lmin-1 for the HDMA and
4 000 lmin-1 for the ADMA for example)
to minimize diffusion losses and increase
the resolution in terms of mobility
diameters. All these DMAs have been
tested with standard positive ions (tetraalkyl ammonium halides) in the sub 3 nm
range, produced with electrospray method.
This
paper
presents
experimental
measurement results of the transfer
function of the HDMA and ADMA
running at sheath flowrates ranging from
50 to 1 000 l min-1 with particles larger
than 3 nm. The super 3 nm particles are
produced with a hot wire generator and/or
atomizer. A hot wire generator is used for
the production of singly charged particles
from 3 to 20 nm. Two identical ADMA are
used in serial to measure the transfer
function
with
‘large’ particles.
Unfortunately it was not possible to loan a
second HDMA for this study. An ADMA
is used as a generator for the HDMA
transfer function measurement. Atomizer
(for deionised and tape water, polystyrene
spheres in clean water and diethyl sebacate
in ethanol) is used for particles larger than
20 nm. The first DMA (Attoui type) is
used as a generator of monomobile
particles at a constant voltage while the
voltage of the second (tested) DMA is
scanned from 0 to 6 kV.
0,23
100 lmin
80 lmin
0,18
0,13
0,08
0,03
0
2
4
Vdma 6
Fig 1 Transfer functionoftheADMAat 3
sheath air flowrates.
Challenges and Barriers for the Development of SiC Nanoparticle Measurement
Technology in Laser Pyrolysis Reactors
A. Asimakopoulou1, M. Kostoglou1,2 and A.G. Konstandopoulos1,3
1
Aerosol & Particle Technology Laboratory, CERTH/CPERI, P.O. Box 60361, 57001, Thessaloniki, Greece
2
Department of Chemistry, Aristotle University, Univ. Box 116, 54124, Thessaloniki, Greece.
3
Department of Chemical Engineering, Aristotle University, PO. Box 1517, 54006, Thessaloniki, Greece
Keywords: silicon carbide, laser pyrolysis, fractal aggregates, on-line measurements, nanoparticles.
The on-line monitoring of aerosol size
distribution has proven to be a valuable tool in
various applications concerning atmospheric
pollution, health effects or industrial nanoparticles
production. For the last case, an on-line monitoring
system could greatly enhance the process
optimization, the constant product quality and the
achievement of safe operational conditions.
However, several issues must be addressed regarding
the aerosol sample handling, the design and location
of sampling ports, etc. The aim of the present study is
to deal with the challenges that appear during on-line
measurements (such as the level and the kind of
dilution, particle losses, etc.) in order to proceed with
in-situ measurements during the synthesis of SiC
nanoparticles by laser pyrolysis.
Proper aerosol sampling procedures presented
in the literature (e.g. Burtscher, 2001), alert to the
challenges that must be addressed in order not to
affect the resulting particle size distribution. Particle
losses may occur in the sampling path due to
diffusion, impaction, thermophoresis, or even
internally in the monitoring instrument. Among
them, diffusion losses are more prevalent for smaller
particles and, thus, it is important to quantify
accurately the nanoparticle losses when sizing
aerosol particles on-line. For high concentration
aerosols (the case of laser pyrolysis nanoparticle
production), care must be taken to properly dilute the
sample to minimize any effects of condensible
species and coagulation and to effectively “freeze”
the size distribution as it is in the process stream. All
these factors must be examined before building up an
on-line aerosol sampling and measuring system.
In order to study where and how to place
sampling ports in a SiC laser pyrolysis reactor, it is
necessary to understand the transformations of the
particle size distribution caused by the physical and
chemical phenomena that occur inside the reactor.
For this reason, a theoretical consideration of the
laser pyrolysis process is performed. The key feature
of the process is the excitation of silane by a CO2
laser. The resulting species are very reactive and
produce solid silica on which acetylene reacts leading
to aggregate generation with primary particles
consisting of Si and SiC. The above phenomena
occur very fast (along few mm of the reactor). In the
rest of the reactor only coagulation takes place
(irreversibly due to the partial sintering at the necks
between the primary particles). A fractal aggregation
model is developed to describe the particle dynamics
in the second part of the reactor in order to
understand better the measured aggregate size
distributions.
Apart from the theoretical approach, the
aforementioned barriers in on-line aerosol sampling
and measuring are examined here, also, in practice.
Therefore, for the development of appropriate SiC
aggregate nanoparticle measurement methods, an
experimental set-up for ex-situ measurements has
been created. In this set-up, an aerosol stream of SiC
nanoparticles synthesized by laser pyrolysis is
generated and, afterwards, properly diluted. An
SMPS (TSI Inc. SMPS 3936) is recording several
nanoparticle size distributions and useful information
is obtained regarding the type of size distribution
(unimodal or multimodal), the mean diameter and the
standard deviation of each peak. Results obtained
with the SMPS are compared with ex-situ
characterization techniques (BET, XRD, SEM,
TEM). The above set-up forms the basis for a
monitoring system (see Figure 1) which will allow
the on-line qualitative and quantitative analysis of
crucial characteristics of silicon carbide nanoparticles
in a laser pyrolysis reactor process.
Production
Process
Sampling
System
Sampling
System
Process
step
Characterization
instruments
Characterization
instruments
Sampling
System
Characterization
instruments
…. Process
product
step
Process monitoring
and simulation
Off-line
characterization
Figure 1. Lay out for SiC nanoparticles measurement.
This work was partially funded by the European
Commission within the Project SAPHIR (NMP3-CT2006-026666-2). We would like to thank Mr. Tsakis
and Mr. Daskalos for their assistance in the tests.
Burtscher, H.,
Measurement
March 2001.
2001., Report for Particle
Programme, BUWAL/GRPE,
Thermal desorption/laser photo-ionisation aerosol mass spectrometry for on-line
monitoring of molecular organic compounds from individual aerosol particles
M.Bente1,2, M.Sklorz1,2, T.Streibel1,2 and R.Zimmermann1,2,3
1
Institute of Ecological Chemistry, Helmholtz Zentrum München, D-85764, Oberschleißheim, Germany
2
Chair of Analytical Chemistry, University of Rostock, D- 18051, Rostock, Germany
3
bifa-Umweltinstitut, D-86167, Augsburg, Germany
Keywords: Aerosol mass spectrometry, Single particle analysis, Polycyclic aromatic compounds, Source identification
Within the last decade, aerosol mass spectrometry
has evolved to a versatile tool for applied and
fundamental aerosol research. Up to now, however,
the detection of molecular organic species by aerosol
mass spectrometry is very difficult. Recently a new
single particle laser ionisation mass spectrometer,
using a two-step laser-desorption photo-ionization
approach for detection of aromatic molecular
compounds on individual particles was developed
and successfully tested (Bente 08). Tracked and sized
individual single particles (SP) herein firstly are laser
desorbed (LD) on the fly within the ion source of the
mass spectrometer by a IR-laser pulse (CO2-laser,
10.2 µm). After some microseconds the released
aromatic molecules are selectively ionized by an
intense UV-laser pulse (ArF excimer, 248 nm) in a
resonance enhanced multiphoton ionisation process
(REMPI). The ions are detected in a time of flight
mass spectrometer (TOFMS). With this setup (i.e.
laser desorption –REMPI-ionisation – single particle
– Time-of-flight mass spectrometry or LD-REMPISP-TOFMS) it is possible to detect profiles of
polycyclic aromatic hydrocarbons (PAH) and their
derivatives which are predominantly bound to the
ambient fine particulate matter (PM). It could be
shown, that source specific molecular indicators for
diesel car emissions, gasoline car emissions as well
as for biomass burning (soft/hard wood) are
detectable. As PAH and their derivatives may show
both, chronic toxicity (i.e. many PAH are potent
carcinogens) as well as acute toxicity (i.e.
inflammatory effects due to oxidative stress) and are
discussed to be relevant for the observed health
effects of ambient PM, a better understanding of the
occurrence, dynamics and particle size dependence of
particle bound-PAH is of particular interest. In this
context it was decided to make the LD-REMPI-SPTOFMS aerosol mass spectrometric technology for
organic monitoring more suited for field
measurements. For this purpose the laser desorption
step (LD) is substituted by a thermal desorption (TD)
step, similar as in case of the Aerodyne AMS
technology (Bente 2009). However, due to the
features of the pulsed REMPI photo-ionisation a
single particle detection of molecular organic
compounds remains possible. With the current
aerosol inlet system particles from about 400 nm to
10 µm are accessible. The novel thermal desorption –
REMPI-ionisation – single particle – Time-of-flight
mass spectrometry approach (TD-REMPI-SPTOFMS) was tested with standard aerosol in the
laboratory (re-dispersed wood ash). Furthermore
real-world combustion aerosols were investigated
(diesel/gasoline car emissions). Finally ambient
measurements were performed using a virtual
impactor enrichment unit to increase the detection
frequency of ambient particles in the covered size
range. It was possible to find distinct differences in
the pattern of PAH and PAH derivatives in the single
particle mass spectra from different sources (e.g.
gasoline, wood combustion and diesel emissions). In
Figure 1 a TD-REMPI-SP-TOFMS mass spectrum
from ambient air (winter) is shown.
Figure 1: TD-REMPI-SP-TOFMS mass spectrum from
ambient air in winter 2008 (50 single particle mass spectra
averaged, Oberschleißheim, Germany). Beside several
prominent PAH masses, the peak at 234 m/z can be
assigned to retene, a wood combustion tracer.
The results obtained with the novel on-line thermal
desorption method are comparable to the ones
obtained by the earlier, more sophisticated two lasertechnology. In conclusion, on-line thermal desorption
laser photo-ionization single particle mass
spectrometry (TD-RTEMPI-SP-TOFMS) represents
a promising technology for field measurements and
source apportionment studies based on single particle
organic analysis. It is planned to apply the
technology at the Augsburg aerosol monitoring
super-site of the Helmholtz-Zentrum München.
Bente, M., Sklorz, M., Streibel, T., Zimmermann, R.
Anal. Chem. 80 (2008) 8991–9004
Bente, M., Sklorz, M., Streibel, T., Zimmermann, R.
Anal. Chem. 81 (2009) in press
Monitoring of growth of cloud droplets ensembles with soot and salt condensation nuclei
L. Vámos, P. Jani
Research Institute for Solid State Physics and Optics, Konkoly-Thege str. 29-33. H-1121. Budapest, Hungary
Keywords: optical instrumentation, condensation monitoring, particle growth, Mie scattering
In a simple experiment the scattered intensity
of an ensemble of particles is easily collected during
an appropriately short time of the condensation
process. While the steady state is reached according
to the thermo dynamical conditions the scattered data
can be collected in a few milliseconds. This gives an
adequately accurate estimate for the mean intensity
and the variance intensity.
In an earlier work (Jani et al, 2002) we have
shown that the ratio of the mean intensity, I , to its
standard deviation, σ I , on the particle ensemble is a
constant, depending on the number of the scattering
particles:
I
I1
,
(1)
= N
2
σI
2
σ I1 + I 1
where
200nm and the relative coat radius up to three times
of the core.
Ensemble data were generated from 1000
particle in average by Monte Carlo method according
to the Poissonian distribution. The lognormal drop
size distribution was generated for fixed 200nm salt
and soot core size. The illumination pulse train
consists of 1000 pulses at 1064nm. As the
monodispersity is assumed the I / σ ratio gives
directly the square root of the average particle
diameter independent of the size and material
(refractive index) of the particle or the illumination
wavelength.
I 1 the mean value and σ I1 is the standard
deviation of intensity scattered on single particles.
If we assume that the number of particles in a
sensing volume changes according to the Poissonian
statistics with constant mean number and deviation,
then the change of the scattered intensity can be
directly attributed to the condensation/evaporation of
the coated water layer. The purpose of this paper is to
extract the scattering data from ensemble of particles
which can be attributed to the change of the particle
radius.
We now consider the scattering properties of
single coated soot (n=1.96+i0.66) and salt (n=1.54)
particles by Mie computation based on our earlier
study in [Jani, P. & Vámos, L., 2006]. The scattered
intensity ratio relative to homogenous water droplets
is shown in Figure 1. The core size was varied up to
Figure 2. Average scattered intensity for cloud
droplets with soot and salt nuclei (top) and the ratio
of the average scattered intensity to its standard
deviation as a function of the relative radius.
The average scattered intensity has a dynamic range
of three orders of magnitude meanwhile the average
particle number and so the I / σ doesn’t change.
The result gives the possibility of a simple
measurement of the layer thickness from the statistics
of the scattered intensities. By the way the constant
I / σ ratio gives the average particle number in the
sensing volume for monodisperse particles. A nonintrusive optical method was suggested for the online
monitoring of the condensation process.
The authors thankfully acknowledge the financial
support of MAG Zrt. under the grant KMOP-1.1.107/1-2008-0056.
Figure 1. Scattered intensity of cloud droplets with
salt nuclei relative to pure water droplets as a
function of the core radius and the relative water
layer thickness radius.
Jani P. et al (2002), J. Aerosol Science, 33, 694-707.
Jani, P. & Vámos, L. (2006), in Proc. 7th
International Aerosol Conference IAC2006 St.
Paul, Minnesota, USA, 10-15 Sept., 490p.
Application of on-line time-of-flight aerosol mass spectrometry for the determination of
molecular iodine
M. Kundel, M. Schott, M. Ries and T. Hoffmann
1
Department of Inorganic and Analytical Chemistry, Johannes Gutenberg-University, Duesbergweg 10-14,
55128, Mainz, Germany
Keywords:
aerosol mass spectrometry, on-line measurements, molecular iodine, MBL
In the last few years, there has been increasing
evidence that iodine species do have an important
influence on the marine atmospheric chemistry.
Recent studies show that iodine species are involved
in the tropospheric ozone depletion, the formation of
new particles in the marine boundary layer (MBL)
and the enrichment of iodine in the marine aerosol.
Numerous laboratory and tropospheric field
measurements show that molecular iodine (I2) and
biogenic volatile organoiodine compounds (e.g.
CH3I, CH2I2), which are released into marine
atmosphere by algae and phytoplankton, are
suggested to be the most important precursors for
reactive iodine in the MBL (O´Dowd & Hoffmann
2005). During daylight these compounds are rapidly
photolyzed to I atoms because of their photochemical
instability. Their major fate is the reaction with ozone
forming the iodine monoxide radical (IO). Further
reactions of IO lead to the formation of higher iodine
oxides (Hoffmann et al. 2001), which finally nucleate
and form new particles. Natural new particle
conversion via gas-to-particle is an important process
determining the concentration of atmospheric
aerosols. In their evolution aerosols can act as cloud
condensation nuclei. Thus aerosols have an indirect
effect on the Earth´s radiative budget and
consequently on the Earth´s climate.
However,
the
identification
and
quantification of reactive iodine containing
compounds is still an analytical challenge. This work
presents the development of an on-line method for
the determination of molecular I2 using time-of-flight
aerosol mass spectrometry (ToF-AMS). Aerosol
mass spectrometry (AMS) provides a real-time
analysis of the particle size, the particle mass and the
chemical composition of non-refractory aerosols.
A direct measurement of gaseous I2 by ToFAMS is not possible. Therefore molecular iodine has
to be transferred from the gas phase to the particle
phase before entering the ToF-AMS. For this purpose
-cyclodextrin was used as a derivatization agent. cyclodextrin molecules consist of a hydrophilic
surface and a hydrophobic cavity. Due to its hollow
cone structure -cyclodextrin is capable of forming
an inclusion complex with I2.
The derivatization reaction was carried out in
a 10L reaction chamber made of glass. A fine spray
of -cyclodextrin, which had been generated by an
atomizer, was continuously introduced into the
reaction chamber. Gaseous I2 was added into
chamber by using a temperature controlled and
nitrogen flushed test gas source, which was based on
an open tube diffusion technique. After exiting the
reaction chamber, the aerosol was analysed by ToFAMS.
This work was supported by the German Research
Foundation (Deutsche Forschungsgemeinschaft,
DFG) within the graduate program 826 “Trace
Analysis of Elemental Species: Development of
Methods and Applications”.
Hoffmann, T., et al. (2001). Geophysical Research
Letters, 28, 1949-1952.
O´Dowd, C.D., & Hoffmann, T. (2005).
Environmental Chemistry, 2, 245-255
Preview on Nanoparticle Monitors
A. Dahl, A. Gudmundsson and M. Bohgard
Ergonomics and Aerosol Technology, Lund University, SE-22100, Lund, Sweden
Keywords: MiniDiSC, NanoCheck, NanoTracer, Indoor Air Quality
MiniDiSC (University of Applied Sciences,
Windisch, CH), NanoCheck (Grimm Aerosol) and
NanoTracer (Philips Research) are new, light weight,
battery powered aerosol instruments that are based on
electrical measurement techniques. The MiniDiSC is
a handheld version of the DiSC (Fierz et al. 2007).
The handheld NanoTracer (Marra 2008) and the
portable NanoCheck (Schneider 2009) are based on
similar measuring principle. These instruments are
developed for measuring nanoparticles and are able
give fair estimates on number concentration and
particle mean diameter. In this study the instruments
were tested on candle smoke.
The NanoTracer and the MiniDiSC was at the
time of the study in the final stages of development.
The results are, therefore, not necessary
representative for the final products.
The three instruments were calibrated by the
manufacturers with salt aerosols. During the tests
the instruments where run in parallel with a uCPC
(model 3025, TSI) and an SMPS-system consisting
of a Vienna DMA and a 3760A CPC (TSI). The
candle smoke was generated by ten candles and the
smoke was then led to a 22m3 chamber were the
instruments were placed. After reaching a mass
concentration of 200µg/m3 the candles were
extinguished. The chamber was continuously
ventilated with particle free at an air exchange ratio
of 5h-1.
less than 2%, while NanoTracer and the MiniDiSC
overestimated the number concentration by an
average of 34% and 45% respectively.
Neither of the instruments was calibrated for
the aerosol used in this study and errors are expected
and since the errors show fairly monotonic
relationship, proper calibration would suppress these
errors.
Figure 2. Concentration correlation between uCPC
and the studied instruments. 60s average. (At
400 000 #/cm3 the SMPS was used as reference.)
The SMPS system is the most frequently used
instrument for nanoparticles, but the complexity
makes field work challenging. Although the
instruments in this study provide less accurate data,
the simplicity and the battery powered design give
them potential to be used extensively in field work.
Acknowledgements: This work has been supported
by the Development Fund of the Swedish
Construction Industry (SBUF) and The Swedish
Research Council for Environment, Agricultural
Sciences and Spatial Planning (FORMAS).
Special thanks to: Martin Fierz, Grimm Aerosol and
Philips Aerasense
Figure 1. Diameter correlation between SMPS
system and the studied instruments. 60s average.
As shown in figure 1, the NanoTracer
correlates well with the particle diameter as measured
with SMPS (average of 2.5% error). The MiniDiSC
and the NanoCheck underestimated the diameter with
an average of 19% and 25% respectively. On the
other hand as indicated in figure 2, the average error
in the NanoCheck particle number concentration is
Fierz M., Burtscher H., Steigmeier P. and Kasper M.
(2007). Field measurement of particle size and
number concentration with the Diffusion Size
Classifier (DiSC). /SAE 2007-08PFL-484/
Marra J. (2008). Ultra-fine particle sensors for
indoor air pollution monitoring and control.
Proc., Indoor Air, Copenhagen, Denmark.
Schneider F. (2009). New insights in aerosol particle
Detection - NanoCheck and Wide Range
Aerosol Spectrometer. Proc. 18th Symposium
of the NVvA, Zeist, Netherlands.
Nanoparticles Sampling Techniques for
an Aerosol- / Particle Mass Spectrometer
J. Meinen1,2, W. Baumann3, H.-R. Paur3 and T. Leisner1,2
1
Institute for Meteorology and Climate Research, Aerosols and Heterogeneous Chemistry in the Atmosphere
(IMK-AAF), Forschungszentrum Karlsruhe GmbH, Germany
2
Institute for Environmental Physics (IUP), Atmosphere and Remote Sensing, Ruprecht-Karls-Universität
Heidelberg, Germany
3
Institute for Technical Chemistry, Thermal Waste Treatment (ITC-TAB), Forschungszentrum Karlsruhe
GmbH, Germany
Keywords: Aerosol Mass Spectrometry, Aerodynamic Lens, Microwave Plasma Reactor, CFD
For the measurement of the particle formation
kinetics in technical processes, the Research Centre
in Karlsruhe developed a particle mass spectrometer
(PMS) specifically for the measurement of the size
distribution of primary particles in the flames and
plasmas with very high concentrations of particle
numbers in the range of 108 to 1012 cm-3. Therefore,
an intact sampling technique is needed which is
suitable for particles in the size range of a few nm.
The particle mass spectrometer uses a classic
molecular beam sampling technique with an inlet
nozzle and a second nozzle as a skimmer. The system
has been tested successfully covering different
nanoparticle sources, such as microwave plasma
synthesis, a low-pressure flame and a spark
generator. These particles sources are characterized
by very small primary particles of a size range from 3
to 10 nm and they generate a very high number
concentration, which is difficult to measure online
with other measurement methods. The molecular
beam technique, as a sampling method, offers the
following advantage: Due to the supercritical
expansion, the incoming gas is frozen very quickly;
furthermore, all interactions between the particles or
interactions between particles and gas molecules are
blocked within the shortest possible time (ms). On
the other hand the disadvantages of this sampling
technique are bad particle transmission into the
measurement chamber and a very high pumping
capacity, which has to be provided for supercritical
expansion into the molecular range.
For sampling purpose other Aerosol- / Particle
Mass Spectrometers use almost exclusively an
aerodynamic lens. The first generation of these lenses
was designed for a minimum particle size of 300 nm
and a second generation of commercially designed
lenses are now available down to 30 nm, which are
used in the AMS (Aerodyne) and the ATOFMS
(TSI). McMurry has designed and tested an
aerodynamic lens for particles smaller then 10 nm.
An optimized aerodynamic lens system arisen from
CFD-Simulations combines the advantage of a
supercritical expansion through a critical nozzle and
forms a well-defined beam through a multilevel
aerodynamic lens, especially for nanoparticles.
The measurement principle of PMS is based
on the deflection of a charged nanoparticle beam by a
homogeneous field of a capacitor. The deflection
capacitor separates the incoming particles according
to their polarity in a negative and a positive charged
fraction. The deflection voltage is proportional to the
ratio of the kinetic particle energy to its charge (U ~
½ m v² / z). By varying the deflection voltage,
particles of different energy-to-charge ratio are
collected at the faraday cups, which are located
symmetrically to the left and right of the centre line
at the end of the detection chamber. The current
generated at the faraday cup is proportional to the
incoming number of particles times their total charge
and it is measured with a highly sensitive amplifier.
The amplification is 1010 V/A with an ultra-low-noise
3-dB bandwidth of 7 kHz. The results can be
translated to retrieve the ratio of the kinetic particle
energy to the number of charges (½ m v² / z). To
convert this energy spectrum into the particle size
distribution, the number of charges (z), the particle
velocity and the material density must be known. For
an accurate measurement, detailed knowledge of the
molecular beam and of the particles included is
necessary. Furthermore, the particle speed in the
molecular beam, the charge number per particle and
the ratio of charged to uncharged particles is also
needed.
The quality and the particles transfer of the
molecular beam sampling technique were measured
with SiO2 - nanoparticles from the microwave
plasma synthesis; and the absolute particle mass was
detected with a quartz crystal microbalance (QCM)
installed in the molecular beam.
Design and performance of an automatic regenerating adsorption aerosol dryer for
continuous operation at monitoring sites
Th. M. Tuch, A. Haudek, Th. Müller, A. Nowak, H. Wex, A. Wiedensohler
Leibniz Institute for Tropospheric Research, Leipzig, Germany
Keywords: Aerosol instrumentation, Monitoring.
Physical and optical properties of aerosol
particles depend on the relative humidity of their
carrier gas. To achieve comparability of
measurements from different aerosol monitoring
sites, networks usually require that the aerosol is
dried to a relative humidity below 50% r.H..
Commercially available aerosol dryers are often not
suitable for remote monitoring sites. Diffusion dryers
need to be regenerated frequently, Nafion dryers are
not designed for high aerosol flow rates. We have
developed automatic regenerating adsorption aerosol
dryers for a design flow rate of 1 m³/h (figure 1).
Particle transmission efficiency has been measured
during a 3 weeks experiment. The lower 50%
transmission efficiency was found to be below 3 nm
at this flow rate. Operated at the design flow rate, the
aerosol transmission efficiency exceeds 92% in the
size range from 10 nm to 800 nm. Measured
transmission efficiencies (dots) are in good
agreement with theoretical calculations line (figure
2.).
1.2
1.1
1.0
0.9
transmission
0.8
0.7
0.6
0.5
0.4
0.3
0.2
experimental data
calculated transmission
0.1
0.0
1
10
diameter [nm]
100
1000
Figure 2: Size dependent transmission of the aerosol
dryer (measured and calculated) at 16.7 l/min.
So far seven dryers have been deployed worldwide.
The most challenging site for such a dryer is located
in the rainforest of the Amazonas river basin about
50 km off the city of Manaus.
Monthly average temperatures at this site range from
24 to 33 deg. C with a daily average humidity of up
to 90% r.H.. From February 2008 through August
2008 we measured an average ambient temperature
of 30.3 +/- 2.3 deg. C with a relative humidity of 78.5
+/- 3.9%. During the experiment average relative
humidity of the dried aerosol was 27.1 +/- 7.5 % r.H.
Figure 1: Schematic view of the aerosol dryer
We demonstrated that the new automatic
regenerating aerosol dryer performs well under
adverse environmental conditions. Relative humidity
of the aerosol at the most challenging site never
exceeded design values. Operational parameters of
the system need, however, to be set according to site
requirements. Routine maintenance of the system did
require little effort which makes these dryers suitable
to be operated at remote continuous monitoring sites.
A new personal thermophoretic sampler with simplified analysis routines for
nanoparticle exposure studies
Nkwenti Azong-Wara1, Christof Asbach1, Burkhard Stahlmecke1, Heinz Fissan1,
Heinz Kaminski1, Sabine Plitzko2, Thomas A.J. Kuhlbusch1
1
Institute of Energy and Environmental Technology (IUTA), Air Quality & Sustainable Nanotechnology Unit,
Bliersheimer Str. 60, Duisburg, Germany
2
Federal Institute for Occupational Safety and Health (BAuA), Nölderstrasse 40-42, Berlin, Germany
Keywords: thermophoresis, CFD, modelling, nanoparticles, personal sampling.
deviation of the orientation-dependent deposition
rates.
6
% total number of particles
deposited per mm
Assessing
the
exposure
to
airborne
nanoparticles, e.g. at workplaces during nanoparticle
production, is an important step towards a sustainable
nanotechnology. Personal exposure assessments of
fine and coarse particles have been predominantly
carried out by the use of mass based personal particle
samplers. Most common versions of these personal
particle samplers consist of a miniaturized impactor
with a defined cut off size followed by a filter (e.g.
Sioutas et al., 1999). This approach is undesirable for
assessing the exposure of nanoparticles where the
mass is not a very prominent factor. One suitable
way of sampling nanoparticles is by employing the
principle of thermophoresis defined as the directed
thermal diffusion of aerosol particles that occurs
when a temperature gradient is established in the gas.
A new thermophoretic personal sampler, also
known as Thermal Precipitator (TP), was developed
with the objective to uniformly deposit particles on a
substrate, in order to simplify the microscopic
analysis e.g. by Scanning Electron Microscopy
(SEM). The development builds on an old TP
developed by the German Federal Institute for
Occupational Safety and Health (BAuA). The nonuniform deposition pattern of this old TP was found
to be due to its non-uniform temperature gradient
caused by two centrally placed tiny heating coils in
the middle of the TP. A uniform temperature gradient
is created in the new TP by introducing two plates
with different but uniform temperatures with the
colder plate acting as the substrate for particle
deposition. Analytical calculations were done,
considering the interaction and effectiveness of the
various forces acting on particles in the TP, assuming
a plug flow velocity of 5.5 mm/s (inlet velocity in old
TP) and a substrate length of 20 mm. The
calculations showed an optimum at a gap distance of
1 mm and temperature gradient of 15 K/mm in order
to achieve a uniform deposition of particles. These
results set the basis for more complex numerical
simulations. The simulations were carried out with
the CFD software FLUENT in connection with the
Fine Particle Model (FPM). Fig. 1 illustrates the
homogeneous particle deposition as a function of
particle size for three typical orientations of the TP
between 1.5 mm and 8 mm from the start of the
substrate. The deposition is fairly homogeneous up to
a particle size limit of about 300 nm independent of
the orientation. Above 300 nm, gravity causes a
4
2
Default vertical orientation
Horizontal orientation; substrate at the bottom
Horizontal orientation; substrate on top
0
10
100
1000
Particle size (nm)
Fig. 1 Particle deposition for three orientation cases
of the TP with a temperature gradient of 15 K/mm
The modelling results affirmed that during an
eight hour sampling period (standard working shift)
sufficient particles will be deposited for SEM
analysis.
The new TP was designed based on the
modelling results and a first prototype built. Peltier
elements were employed on both plates in the TP to
create a temperature gradient which is kept constant
by a temperature regulation element. The new TP has
the dimensions of 4.1 x 4.5 x 9.7 cm³ and weighs
approximately 130 grams, and can therefore be
comfortably carried by a worker. Fig 2 shows the
design of the first prototype. Modelling results and
the design of the new TP will be presented.
Body
Warmer
Plate
Substrate
Substrate insertion
unit with inlet slit.
Peltier elements
Fan
Heat sinks
Fig. 2 Design of the new Thermal Precipitator
Reference:
Sioutas et al. J. Aerosol Sci. 6: 693-707, 1999
A miniature impactor for aerosol collection with emphasis on single particle analysis
K. Kandler1
1
Institut für Physik der Atmosphäre, Universität Mainz;
now at: Angewandte Geowissenschaften, Technische Universität Darmstadt, Germany
Keywords: aerosol sampling, impactor, SEM/EDX, single particle analysis
The collection of samples for individual
particle analysis differs from those of for example
bulk-chemical methods. The particles need to be
isolated on the substrate, which should provide as
much (chemical or morphological) contrast to the
particles as possible. In this work, a micro inertial
impactor (MINI) is described, a cascade impactor
with single round nozzles designed for a versatile
operation for the collection of single particle
analysis. Most attention was paid to the small
instrument size, ease of use, interchangeability of
different substrates, and a collection size range
suitable for electron-microscopic particle analysis.
The MINI follows the design of Mercer et al.
(1970), but for ease of use each single stage is split
into a nozzle and a substrate holder. The MINI outer
shell consists of a tube with interior and exterior
diameters of 10 mm and 18 mm, respectively and an
inner length of 40 mm. It features o-ring fittings at
the top and bottom to seal the threads. Construction
material is stainless steel.
The split design of the single stages (see
Fig. 1) allows the use of nozzles and substrate
holders in any combination. O-rings around the
nozzles ensure the sealing of the single stages and
hold the stages in position through friction. Nozzles
from 0.2 to 1.5 mm were constructed with a small
interval. The nozzle construction followed the design
criteria given by Newton et al. (1977).
The flow rate is usually set by keeping one of
the nozzles in critical condition. When the 0.25 mm
nozzle is used as critical orifice, a flow of
approximately 0.5 l/min is reached. Nozzle diameters
and the corresponding approximate cut-off sizes for
this case can easily be calculated (e. g., Raabe et al.,
1988). Alternatively, the MINI can be used in lowpressure mode. Behind a drop in the pressure on the
critical nozzle of significantly more than half of the
inlet pressure, particles smaller than 30 nm can be
collected. However, the maintenance of the necessary
vacuum (typically 50 to 100 hPa at a strongly
increased air volume flow) on the impactor outlet
requires rather large vacuum pumps.
For each type of substrate the substrate holder
needs to be adapted to place the surface of the
sampling substrate at the reference height h0 (Fig. 1)
with exactness better than the nozzle diameter w to
yield the target cut-off size. The substrate holders can
feature magnets to securely hold substrates like
transmission electron microscopy grids or nickel
plates commonly used in electron microscopy. The
criter.
s/w
l/w
ws/s
α
Dt
Ds
Df
Dc
fd
fh
O-ring
value
1.3
1 for w > 0.5 mm,
else 0.5 mm
3 for w > 0.5 mm,
else 1.5 mm
45°
10.0 mm
9.95 mm
7.0 mm
4.0 mm
0.9 mm
1.2 mm
8 mm x 1 mm
fd
fh
ws
α
w
l
s
h0
Fig. 1 (right): Design criteria,
measures, and schematic drawing
Dc
Df
Ds
Dt
Fig. 2 (below): Substrate holders for
3.05 mm diameter TEM grids with
edge to prevent slipping (left), for
4 mm diameter metal discs with or
without coating (center), and for
5 mm square silicon plates (right)
maximum usable substrate size is about 5 mm in
square (see Fig 2 for examples).
To facilitate the assembly of the MINI it is
recommended to create a rod with two different tips
from a softer material (e. g., PTFE) to push the stages
in and out. As the nozzles are susceptible to
mechanical damage, an annular tip should be used
with an outer diameter of 6.5 mm and an inner
diameter of 4.5 mm. The other tip used for pushing
into the inlet cone of the nozzles should be spherical
or tapered. A cap should be built which holds the
stages safely while pushing them out of the impactor
tube with an inner diameter of 11 mm and a length of
40 mm. An end-to-end slot in the cap facilitates
taking out the nozzles and substrate holders with
tweezers.
Mercer, T. T., Tillery, M. I., Newton, G. J. (1970). J.
Aerosol Sci., 1, 15.
Newton, G. J., Raabe, O. G., Mokler, B. V. (1977). J.
Aerosol Sci., 8, 339-347.
Raabe, O. G., Braaten, D. A., Axelbaum, R. L.,
Teague, S. V., Cahill, T. A. (1988). J. Aerosol
Sci., 19, 183-195.
Development of new instrumentation for aerosol angular light scattering
and spectral absorption measurements
G. Dolgos1, J.V. Martins1,2, L.A. Remer2 and A.L. Correia2
1
Dep. of Physics, University of Maryland, Baltimore County, 1000 Hilltop Circle, 21250, Baltimore MD, USA
2
NASA Goddard Space Flight Center, Code 613.2, 20771, Greenbelt MD, USA
Keywords: Light absorption, Chemical composition, Scattering matrix, Hygroscopicity.
In order to quantify the effects of aerosols on
the atmospheric radiation budget, absorption and
scattering properties of many different aerosol types
have to be mapped with considerable accuracy.
Remote sensing of aerosol properties from space with
current satellite sensors requires knowledge of
aerosol optical properties, including phase function
(the directional distribution of scattered light), in
order to quantify aerosol loading (Mishchenko et al.,
2004). Black carbon is the main anthropogenic
absorber; its warming effect can be comparable to
that of carbon dioxide (Ramanathan & Carmichael,
2008). Other absorbers (mainly organic materials and
dust) are also important, and have distinct spectral
dependence over the solar spectrum.
We designed, built and calibrated a novel
device for aerosol phase function measurements. This
device is an imaging nephelometer called I-Neph that
is capable of measuring the phase function close to
the extreme directions, i.e. from 1.5° to 178.5° in the
present configuration. The broad range is crucial for
particle size retrievals. The current resolution is less
than 1° near the extreme directions, and the angular
range and resolution can be improved.
next effort to improve the I-Neph. Aerosol phase
functions can be measured already as a function of
humidity. The I-Neph has no moving parts, measures
in a few seconds and is suitable for the laboratory
and the field. We will upgrade the I-Neph to measure
polarization and the full phase matrix.
Our goal has been to measure the absorption
spectra of black carbon and other aerosols from 200
nm to 2500 nm, using sampled filters. Although the
deep UV measurements are not important for the
atmospheric radiative balance, they contain important
information about the chemical composition of the
sample. Measuring the decrease in filter reflectance
permits the calculation of spectral absorption cross
section of the aerosol particles. We implement
multiple ways to measure reflectance (including a
stable novel integrating sphere) in order to eliminate
systematic errors due to its directional distribution.
Preliminary results of spectral aerosol optical depth
(AOD) are shown in Figure 2, mass measurements
will be carried out in the upcoming months in order
to obtain mass absorption coefficient.
Figure 2. Relative spectral mass absorption
coefficient of various aerosols.
Figure 1. Raw data of direct measurements at 532 nm
with the current I-Neph prototype at UMBC. Pure N2
and CO2 data are compared with their corresponding
theoretical calculations and ambient aerosol data.
The aerosol phase function in Figure 1 has not
been corrected for the Rayleigh contribution from air.
The angle dependent sensitivity of the system causes
the small discrepancy between raw data and Rayleigh
theory. We located the cause of the current high
frequency noise and it will be eliminated during our
This research was supported in part by the NASA
Atmospheric Composition program (grant number
NNX07AT47G), and by the NASA Interdisciplinary
Science Program (grant number NNX07AI49G).
Mishchenko, M., B. Cairns, J. E. Hansen, L. D.
Travis, R. Burg, Y. J. Kaufman, J. V. Martins, E. P.
Shettle (2004), JQSRT, 88, 149–161
Ramanathan, V. and G. Carmichael (2008), nature
geoscience, 1, 221-227
Response of the DustTrak DRX to Aerosols of Different Materials
X. L. Wang, A. Hase, G. Olson, A. Sreenath, J. Agarwal
TSI Inc., St Paul, MN 55126, USA
Keywords: PM Measurement, Aerosol Photometer Method, Mass Concentration, Optical Instrumentation, Mie
Scattering
measure very low concentrations (<0.1 µg/m3), it
suffered coincidence losses at relatively low
concentrations (~10 µg/m3). On the other hand, the
DRX was not so accurate at very low concentrations
(<1 µg/m3) due to low signal-to-noise ratio, it can
measure high concentrations without coincidence
losses. Therefore the DRX is suitable for dusty
environments.
In summary, we measured the DustTrak DRX
response to different aerosols. It is shown that the
DRX could not accurately measure mass
concentration if the aerosol of interest is different
from the calibration aerosol. However, once
calibrated with the measurement aerosol, the DRX
can measure size segregated mass concentrations
quite accurately. Comparing to a simple photometer,
the DRX not only provides particle size information,
but also is more accurate for PM10 measurement and
less sensitive to particle size distribution shift.
Comparing an OPC, the DRX can measure higher
concentrations, and is more suitable to dusty
environment.
18
3
Petroleum Coke Concentration (mg/m )
The DustTrak DRX is a real-time monitor for
size segregated aerosol mass concentrations. It
combines photometry with single particle sizing to
measure PM1, PM2.5, PM4 and PM10. Since this
instrument works on the principle of light scattering,
its response depends on aerosol properties, such as
particle shape, refractive index, size distribution and
density. In this paper, we report the results from four
sets of experiments using the DRX to measure
different aerosols. Its comparison with a photometer
and an optical particle counter (OPC) will be
discussed, and its advantages and limitations will be
addressed.
The first experiment investigates the DRX
photometric response to different aerosols. The DRX
was challenged with ultrafine Arizona Road Dust
(A1 dust), ammonium sulfate, sodium chloride and
Emery oil. The result showed that the DRX
photometric response for unit aerosol mass is
approximately inversely proportional to the particle
density for the aerosols investigated.
The second experiment uses the DRX to
measure four different aerosols: ultrafine Arizona
Road Dust, coarse Arizona Road Dust (A4 dust),
hematite and petroleum coke. The result showed that
when the aerosol under measurement is different
from the calibration aerosol, the DRX could not
predict mass concentrations accurately. This
experiment also showed that once calibrated with the
aerosol of interest, the DRX can measure mass
concentrations quite accurately. An example
comparison between the DRX and the Tapered
Element Oscillating Microbalance (TEOM) for
measuring the light absorbing petroleum coke is
shown in Figure 1.
The third experiment compares the DRX with
a simple photometer, the TSI DustTrak 8520, for
their sensitivities to size distribution change. Both
instruments were calibrated with A1 dust. Then they
were used to measure A4 dusts. It was shown that the
DRX underestimated PM10 concentration by 7%,
while the DustTrak 8520 underestimated 31%.
Therefore the DRX PM10 measurement is less
sensitive to size distribution change than a
photometer due to its single particle measurement
feature.
The forth experiment compares the DRX with
the TSI 8220 OPC for measuring monodisperse
Emery oil particles at various concentrations. The
result showed that while the OPC can accurately
16
PM 10
TEOM
DRX
14
12
10
8
6
4
2
0
15:53
15:56
15:59
16:01
16:04
16:07
16:10
16:13
16:16
Time
Figure 1. PM10 mass concentrations of petroleum
coke dust measured by TEOM and DRX. The TEOM
had a PM10 impactor on it inlet, while the DRX did
not have an impactor. The DRX simultaneously
measured PM1, PM2.5, PM4, PM10 and TPM. Only
PM10 is plotted for the sake of clarity.
Development of an optical particle counter for in-situ detection of single ice particles in
LACIS
T. Clauß, A. Kiselev, D. Niedermeier, S. Hartmann, H. Wex and F. Stratmann
Leibniz-Institute for Tropospheric Research, 04318 Leipzig, Germany
Keywords: Depolarization, Instrumentation/physical char., Instrument development, Optical counter
Ice particles influence radiation properties and
precipitation mechanisms in atmospheric clouds.
Therefore the investigation of the freezing behaviour
of different aerosol particles which act as ice nuclei
(IN) is important and still poses unresolved
questions.
The Leipzig Aerosol Cloud Interaction
Simulator (LACIS, Stratmann et al., 2004) is used to
investigate the IN activity of different natural and
artificial aerosol particles, and to learn more about
homogenous and different heterogeneous freezing
processes.
To support these measurements, a particle
detection method able to differentiate between ice
particles and droplets in LACIS is needed. The main
goal is to determine the fraction of frozen and
unfrozen particles in mixed water and ice aerosol
systems under different thermodynamic conditions.
An Optical Particle Counter (OPC) was built
to detect single particles downstream of the LACIS
tube to measure not only a size distribution but also
the rotation of the main polarization plane of the
backscattered light. The principle is based on the
difference in depolarization of particles with different
shape.
Figure 1. Optical layout of the OPC for the detection
of ice particles (top view).
The configuration of the OPC is shown in
Figure 1. The vertically polarized laser light at
532 nm is focused on the measuring volume situated
downstream of the LACIS tube. The light scattered
by a single particle crossing the measuring volume
into the near forward direction is detected by two
photomultiplier tubes (PMT) "A" and "B". The
detected signal of PMT "A" is then used to determine
the particle size, whereas the signal of PMT "B" is
used to ensure that the particle is crossing the
measuring volume exactly in the focal point of the
illuminating optics. The backscattered light is filtered
by a polarizer and detected by PMT "C". By rotating
the polarizer, it is possible to distinguish between
different polarization states.
In case of spherical particles, the polarization
state of the scattered light can be analytically
described by Lorenz-Mie theory. Figure 2 shows an
example of a backward scattering pattern for a 5 µm
water droplet. It can be clearly seen, that there exist
special angular ranges where the parallel polarization
component dominates.
Figure 2. The parallel (a) and perpendicular (b)
polarization components normalized to the total
scattering intensity and mapped onto the backward
scattering detector plane. The zero of the XYcoordinate frame corresponds to the 180° scattering
direction. The scattering pattern is calculated by
Lorenz-Mie theory for a 5 µm spherical water
droplet.
In general, ice particles are not spherical, so
that the backscattering patterns of both polarization
components are much more complicated. With a
mask installed in the backscattering channel it is
possible to limit the field of view of the PMT "C", so
that the perpendicular component of light scattered
by a spherical particle almost vanishes. Thus it is
possible to exclude spherical particle from
registration. The appearance of this mask is defined
by the calculations.
First test measurements of immersion freezing
on Arizona Test Dust particles (ATD) were
performed with the new OPC. In these experiments it
was shown for the first time that an in-situ
discrimination of single frozen and unfrozen water
droplets is possible.
Stratmann, F. et al. (2004). J. Atmos. Oceanic
Technol., 21, 876-887.
Novel Photoacoustic Aerosol Monitor for Optical Absorption Coefficient Determination.
Laboratory and Field Test.
T.Ajtai1, M. Schnaiter2, C. Linke2, M. Vragel2, Á. Filep1, L. Födi1, G. Motika 4, Z. Bozóki3, G. Szabó1
1
Department of Optics and Quantum Electronics, University of Szeged, Hungary
Institute of Meteorology and Climate Research, forschungszentrum Karlsruhe
3
Research Group on Laser Physics of the Hungarian Academy of Science, University of Szeged, Hungary
4
Lower Tisza Valley Environmental Inspectorate, Szeged, Hungary.
2
Keywords: Absorption coefficients, Aerosol instrumentation, Absorption, Aerosol characterisation,
Carbonasceous aerosol.
Table 1. Wasul-MuWaPaS system performance
Wavelength
(nm)
1064
532
355
266
Power
(mW)
360
90
12
6
MDOA
(Mm-1)
0,6
1,2
9,6
9,5
The spectral PA response of different type of
artificially generated soot and dusts were measured.
As a reference the extinction spectrometer and TSI;
3653 Nephelometer was used. From the extinction
and scattering measurement the absorption
coefficient can be calculated. Good agreement was
found between the PA and the reference response.
Figure 1.
The WaSul-MuWaPas was deployed at the EMEPGAW regional station of JRC Ispra and operated
parallel with the instrumentation used at the site
photoacoustic babs 532nm 1/m
including Nephelometer,
DMPS.
Aethalometer,
MAAP,
0.0030
soot mini-cast C/O 0.29
slope 1.07 ±0.01
0.0025
0.0020
0.0015
0.0010
0.0005
0.0000
0.0000
0.0005
0.0010
0.0015
0.0020
0.0025
0.0030
Reference method babs 532nm550nm 1/m
Figure 1: Correlation between the PA and the
reference spectral response of CAST soot at 532nm
wavelength.
Despite the low EBC mass concentration
(below 1μg/m3) occurred at the field station during
the experiments excellent agreement was found
between the PA and the corrected aethalometer
response.
PA response @ 532 nm [nV]
There is an increasing concern for novel
methods to determine the optical absorption
coefficients of atmospheric aerosol. The available online instruments like MAAP (Multi Angle
Absorption Photometer) and PS2 (Single Particle
Soot Photometer) has weakness of spectral resolution
or the sampling artifact of filter matrix. These
methods neither suitable for direct determination of
light absorption by aerosol nor dispose the capability
of the source apportionment. Photoacoustic
measurement technique is one of the highly
promising method for analysis of aerosols, as it can
determine directly the amount of light absorption by
aerosols while being largely insensitive to
uncharacteristic light scattering.
The Multi Wavelength Photoacoustic System
(WaSul-MuWaPas) operating at four different
wavelength in wide wavelength range (266nm,
355nm, 532nm, 1064nm) for optical characterisation
of artificially generated and atmospheric aerosol was
developed.
The system characteristic performances are
shown at table 1. (MDOA: Minimum Detectable
Optical Absorption Coefficient)
4000
3500
3000
2500
2000
1500
1000
500
0
0.0
-6
5.0x10
-5
1.0x10
-5
1.5x10
-5
2.0x10
-5
2.5x10
Aethalometer data [1/m]
Figure 2. Correlation between the PA response
These
researchesaethalometer
were funded data
by Hungarian
and the
corrigated
at 532nm
wavelength during the one week measurement
period.
The research were founded by Ministry of Economy
and Transport NKFP_07_A4_AEROS_EU.
Monitoring of indoor air quality and workplace aerosols - one compact portable system
for dust mass, number concentration and Nano particles
F. Schneider, R. Hagler and H. Grimm
Grimm Aerosol Technik GmbH, 83404 Ainring, Germany
Keywords: indoor air quality, Nanoparticles characterization, occupational health, mass concentration, aerosol
measurement, aerosol size distribution,
Laser aerosol spectrometry is a well-proofed
techniques for online particle monitoring with very
good time and size resolution. Battery powered
systems even are suitable portable measurements.
One limitation of optical light scattering technique is
the limit of particle size detection, due to the strong
decrease of scattering intensity with decreasing
particle size. A new sensor attachment now enables
to measure down to 25nm with high time resolution,
and displaying particle concentration and mean
particle diameter of Nano sized aerosol particles and
keeping all the advantages of laser aerosol
spectrometer.
Portable Nano attachment NanoCheck 1320 with
adapter 1320-HLX and laser aerosol spectrometer
The sensor attachment exists of a faraday cup
electrometer, combined with a charger and a time
multiplexed electrode for conductivity measurement.
This unique patent pending setup is sensitive to about
10fA, which correlates to an minimum concentration
of 5000 particles/ccm and can measure up to about 5
* 10^6 particles/ccm. In addition one can determine
the mean particle diameter also and the active surface
area of the measured nano sized aerosol.
Indoor air quality and workplace monitoring
are historically based on measurements of particles
mass fractions according to their penetration depth
into the lung. So this system keeps the link to the
past, by data output according to the European
standard EN 481. Particle mass only has limited
significance characterizing health effects due to
inhaled particles emitted e.g. by combustion, Nano
particle processing or welding.
This setup is unique for monitoring the risk
potential of aerosol particles and nano particles in
particular, which will become more and more
important for indoor air quality and the monitoring of
workplace aerosols. The compact and lightweight
design of this new device will enable necessary
mobile measurements for work place monitoring,
inhalation studies, occupational health studies and
production inspection.
This contribution reports on a new technique
for determination of particle number concentration
and mean particle diameter in a size range 25nm up
to 300nm in combination with complete
characterization number, size can mass distribution
of the aerosol particles up to 32µm. Examples of
measurements at different indoor environments will
be presented in detail, also the possibility to
comparisons of indoor and outdoor measurements,
e.g. for the fast determination of background
concentrations levels.
First Steps Towards a Photophoretic Mobility Analyzer
C. Haisch, L. Opilik, M. Oster, and R. Niessner
Chair for Analytical Chemistry, Technische Universität München, D-81377, Munich, Germany
Keywords: photophoresis, optical properties, particle characterization, separation.
Photophoresis (PP), or more precisely photothermophoresis (PTP), occurs when an aerosol
particle is illuminated by a strong light from one side,
which leads to locally inhomogeneous warming. The
heat is transferred to the surrounding gas atmosphere,
which gets heated as well. In consequence, the
collision rate of the gas molecules with the particle
increases, which results in a net force acting on the
particle. It reaches an equilibrium velocity, governed
by the PP force on the one hand and the Stoke’s flow
resistance on the other. For semitransparent particles,
the PTP force can even act towards the light source,
if the light gets focused behind the particle, leading
to local warming on the particle’s backside. The PTP
force depends on the light intensity, on thermal
properties of the gas medium and on the geometrical,
optical and thermal properties of the particle. As we
presented, the evaluation of the PP velocities of
different particles can reveal information on their
optical and thermal properties, when the gas’s
properties are known (Haisch et al., 2008).
Additionally, direct PP forces act on the particles,
which are caused by the momentum transfer of
photons being scattered on the particle. Generally,
these forces are considered negligible compared to
the PTP force, but for certain, highly scattering
particles this may not hold true.
We are designing an instrument which
employs PTP and PP forces for aerosol
characterization and
fractionation.
As
the
fundamental operating is similar to the one of a
Differential Mobility Analyzer, we chose the name
PP Mobility Analyzer for the new instrument. Two
similar designs are currently under comparison. Both
are based on two coaxial gas flows, the inner one
(diameter ~100 µm) containing the particles, the
outer one acting as sheath air. Both laminar flows are
adjusted to the same flow velocity of few 100 µm s-1.
Without the influence of the PP force, particles move
with the flow trajectories. Opposite to the aerosol
inlet, there is either a narrow wall, splitting the flow
into two separate channels. Depending on the flows
in these two channels, which are maintained by
pumps, the flow trajectories in before the wall are
influenced in a way that all particles end in one of the
two channels (see Fig. 1). The PP force pushes
particles with high PP efficiency into other flow
trajectories. If the PP force is sufficiently strong, they
end up in the other channel, where they can be
counted. Depending on the flow ratio of the two
channels, more or less PP force is necessary to push
particles into the second channel. As alternative
configuration we replaced the separation wall by a
second capillary, which is experimentally simpler,
but not suitable for the separation of particles
exhibiting negative PP.
Figure 1 Principle of the PP Mobility Analyzer.
The proposed PPMA system will reveal new
information on optical and thermodynamic properties
of aerosol particles and will find its way to routine
application. The PP velocimetric measurements
carried out in parallel indicate, that the PP effect
allows distinguishing between particles of identical
chemical composition, but different microstructure.
One example are the significantly different velocities
of NaCl particles generated either by condensation
from the gas phase or by drying of nebulised salt
solution. We present results of our optimized PP
velocimetry setup, which now allows online data
evaluation, which means that a continuous
monitoring of PP properties is possible.
All PP systems presented here are now
coupled to the outlet of a Differential Mobility
Analyzer in order to distinguish between the
influence of particle’s size and opto-thermal
properties on the PP force. The PP measurements are
carried out only on a limited size fraction of the
particles, which can be varied stepwise.
Haisch, C., Kykal, C., & Niessner, R. (2008), Anal.
Chem. 80, 1546-1551.
Measurement of the wavelength dependence of the extinction coefficient for studying the
aerosol contamination of the atmosphere
A. Czitrovszky, A. Nagy, A. Kerekes
Research Institute for Solid State Physics and Optics, Konkoly Thege Miklós st. 29-33.
1121 Budapest, Hungary
Envi-Tech Ltd., , Konkoly Thege M. st. 29-33., 1121 Budapest, Hungary
Keywords: remote sensing, radiation measurement, radiometry,
size distribution, extinction coefficient
Remote sensing of aerosols, retrieval of
optical depth and aerosol size distribution in the
atmosphere by means of sun photometry has long
history and is in the focus of the scientific interest
continuously. The relationship between the aerosol
contamination of the atmosphere and wavelength
dependence of the extinction coefficient has been
studied theoretically than experimentally by a
number of groups (King et al. 1978, Liu et al. 1999,
Schmid et al. 1997 etc.). From spectral attenuation
measurements the size distribution and the
concentration of aerosol can be determined.
Our aim was to develop a multi channel
radiometer for the measurement of the extinction
coefficient at different wavelengths. The system
consists of a three channel detection system with
wide spectral range (from UV to IR) in which the
selection of the wavelengths can be made using
narrow band filters. The central wavelength of the
filters was fitted to the characteristic spectral lines
corresponding to certain materials.
The system has three detection channels. Two
of them has narrow band interference filter holder,
for selecting the proper wavelengths. In the third
detection channel the incoming light is reflecting
from four mirrors which have high reflectivity only
in a narrow band around a certain UV line. This four
mirror increases the wavelength selectivity by four
orders of magnitudes. So this device combines the
benefits of the UV radiometer and a wide range
spectrometer for the determination of the wavelength
dependence of the extinction coefficient.
In addition to the commonly used data
retrieval process for the determination the size
distribution and concentration of atmospheric
aerosols (Liu et al. 1999, Schmid et al. 1997, King et
al. 1978, Pearson et al. 2007, etc.), an evaluation
method based on the ratio of the signals obtained in
different channels is introduced. This method is
independent of the absolute intensity which is
varying with the cloud density or meteorological
conditions.
After the calibration of the device we made
several measurement campaigns at different optical
conditions. The measurement results are under
evaluation.
Figure 1. The multichannel radiometer device
This work was supported by the GVOP TST
Programme under grant No 0119/2005.
King M.D., Byrne D.M., Herman B.M., Reagan J.A.,
(1978) Aerosol size distributions obtained by
inversion of spectral optical depth measurements,
J. Atmos. Sci., 35, 2153-2167.
Liu Y, Arnott W.P., Hallett H., (1999) Particle size
distribution retrieval from multispectral optical
depth: influences of particle non-sphericity and
refractive index, J. Geophys. Res., 104, 3175331762.
Schmid, B., Matzler, C., Heimo, A., Kampfer, N.,
(1997) Retrieval of optical depth and particle size
distribution of tropospheric and stratospheric
aerosols by means of Sun photometry,
Geoscience and Remote Sensing, IEEE
Transactions on Volume 35, Issue 1, 172 – 182.
Pearson R., Fitzgerald R.M., Polanco J., (2007) An
inverse reconstruction model to retrieve aerosol
size distribution from optical depth data, J. Opt.
A: Pure Appl. Opt. 9 56-59.
Dependence of the performance of condensation particle counter (CPC) on particle
number concentration
Z.Z. Zhang
Institute of Nuclear and New Energy Technology, Tsinghua University, 100084, Beijing, P.R.China
Keywords: CPC, counting efficiency, number concentration, particle growth.
The condensation particle counter (CPC) is a
widely used instrument for measuring the number
concentration of submicrometer and nanometer
airborne particles. The instrument operates by
producing a supersaturated vapour in the saturator
and then condensing on the particles to grow them to
a large, detectable size.
The simulated condenser in this paper is that
of TSI model 3020 CPC, the length of condenser is
8cm and the diameter is 4mm, the working fluid is nbutyl alcohol, the saturator and condenser
temperatures are 35 ℃ and 10 ℃ separately, the
sample flow rate is 5cm3/s (Zhang & Liu, 1990).
The equations of continuity, momentum,
particle diffusion, heat and mass transfer are used.
Especially, the heat and mass source terms are
considered based on the heat release of vapor
condensation and the vapor depletion (Barret &
Baldwin, 2000; Varghese & Gangamma, 2007).
⎡ ∂ 2T 1 ∂ ⎛ ∂T ⎞⎤
∂T ⎞
⎛ ∂T
+
C ρ⎜u
+v
⎜r
⎟⎥ + Lm&
⎟ = k⎢
p ⎝ ∂x
∂r ⎠
⎢⎣ ∂x 2 r ∂r ⎝ ∂r ⎠⎥⎦
u
0.5μm, and the photodector of CPC cannot detect
any particles.
The results above are also applicable to the
particles whose diameter is different from 100nm.
Figure 1. Particle diameter along the condenser axis
at different number concentrations.
⎡ ∂ 2 n 1 ∂ ⎛ ∂n ⎞⎤
∂n
∂n
+v
= D⎢ 2 +
⎜ r ⎟ − m&
∂x
∂r
r ∂r ⎝ ∂r ⎠⎥⎦
⎣ ∂x
In this paper, the simulated particles are of
100nm diameter and the number concentrations are
from 10#/cm3 to 107#/cm3.
As shown in Figure 1 and Figure 2, when the
number concentrations are smaller than 104#/cm3, the
particles growth would be not affected by the particle
concentrations. But for the concentration of about
105#/cm3, the growth has a litter different. Because
the photodetector of CPC can detect the particles
larger than 0.5μm by counting method, the counting
efficiency would be equal to that of concentrations
smaller than 104#/cm3.
For the concentration of about 106#/cm3, the
vapor in the tube isn’t enough to grow all of the
particles freely following the particle growth law. At
the outside of the condenser, the particle size would
be smaller than 0.5μm near the condenser wall, so
the CPC counting efficiency would be smaller than
100%.
For the concentration of about 107#/cm3, the
vapor is so little that the particles wouldn’t grow to
Figure 2. Size distribution of particles at the outside
of the condenser at different number concentrations.
This work was supported by the National Natural
Science Foundation of China (No.50608044).
Barrett, J. C., & Baldwin, T. J. (2000). Journal of
Aerosol Science, 31, 633-650.
Varghese, S. K., & Gangamma, S. (2007). Aerosol
and Air Quality Research. 7, 46-66.
Zhang, Z. Q., & Liu, B. Y. H. (1990). Aerosol
Science and Technology, 13, 493-504.
Method for the characterization of nanoparticle release from surface coatings
M. Vorbau, L. Hillemann, D. Göhler, M. Stintz
Institute of Process Engineering and Environmental Technology, TU Dresden, 01062 Dresden, Germany
Keywords: abrasion, particle release, surface coating
Surface coatings are widely used in industry
as well as domestically. Nanoparticles are considered
to enhance substantially certain properties of such
coatings, e.g. its resistance to mechanical stress or
UV-light. Thus they are increasingly employed as
additives. The usage of these coatings is subject to
investigations regarding the release of nanoparticles
into air, which may cause adverse health effects /
have an impact on human health. However, suitable
methods for the quantification of nanoparticle release
have not been established yet.
Investigations in the field of wear resistance
were normally made in the area of material science
either in dry and in wet environments. One of the
most common tests for simulating the abrasive
damage during the service life of components is the
so called Taber test (see Figure 1).
microscopic analysis. The mass loss resulting of the
abrasion process is determined gravimetrically.
Figure 2. Schematic test rig with aerosol generation
(Taber Abraser) and measurement setup (CPC,
SMPS and ESP).
Figure 1. Abrasion scheme of a Taber Abraser with
test piece (sample), abraded area, abrasion wheels
and the direction of rotation (marked with arrows)
The stress of the Taber test corresponds to the
typical stress applied to surface coatings in a
domestic scenario, e.g. when walking with sandy
shoes on a floor surface coating. With this method an
area of 30 cm2 per revolution is stressed with both
wheels. The parameters which have to be specified
for the testing method are the material of the abrasion
wheels, the normal force and the number of abrasive
cycles (number of turntable revolutions).
The Taber test ensures a reproducible and
standardized stress of the sample which is important
for reproducible measurement results.
The employed test rig bases on an abrasion
section and a measurement section. The released
particle concentration of the aerosol, generated by the
Taber Abraser, is determined by CPC. Also the
particle size distribution of the aerosol is measured
by SMPS. An Electrostatic Precipitator (ESP) is used
for deposition of nanoparticles for subsequent
In preliminary tests the optimal adjustments
of the abrasion tool were determined.
The measured data delivers the mass loss of
the sample and the size distribution of the released
particles. This enables the specification of the
number concentration of the released particles in
defined size fractions (< 100 nm, < 625 nm and total)
per mass unit of the coating material.
The contribution will explain the developed
method in detail and present first data for different
coating types. More information are given in Vorbau
et al., 2008.
M. Vorbau, L. Hillemann, M. Stintz. Method for the
characterization of the abrasion induced
nanoparticle release into air from surface
coatings. J Aerosol Science, (2008), doi:
10.1016/j.jaerosci.2008.10.006
Characterization of a Newly Developed Particle Detector, NanoCheck 1320
Jaejung Seo1, Hagler Roland2, Myungjoon Kim1 and Taesung Kim1
1
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan Universiry, Cheoncheon-dong, 440746, Suwon, Korea
2
Grimm Aerosol Technik GmbH & Co. KG, DorfstraBe 9 D-83404, Ainring, Germany
Keywords: nanoparticle, calibration, particle detector
Since the scatter intensity decreases with the
sixth power of the particle size, it is difficult for an
optical light scattering system to detect particles
below about 0.1 μm. For this reason, developing the
nanoparticle instrumentation with various methods
has been attempted for many years.
Recently, Grimm Aerosol Technik developed
a new particle detector for aerosol exposure
monitoring, which covers nanoparticles and the dust
in one portable unit. This particle detector is
composed of a unipolar diffusion charger, a new
conductivity measurement tool and an aerosol
electrometer. The use of an ion attachment by
diffusion from an electrical charger with the
detection of the total charge is a well known
technique for measuring the so-called active surface
area. The current is nearly proportional to the particle
concentration and mean diameter. In addition, a new
method of conductivity measurement is implemented
in the sensor. Conductivity measurement combined
with the diffusion charging, the current of the aerosol
electrometer and calibration factors enable obtaining
the total number concentration in the range of
20nm~400nm and the mean diameter of the aerosol
number distribution function in real time.
mean particle diameter Dp and the Dp with the
measured current Itot is used to calculate the particle
number concentration. Hence, by knowing the
efficiency curve of the diffusion charger and the
particle diameter, the particle concentration can be
determined. However, due to the different charging
characteristics of particles, the detector response
might be different where different correction factor
has to be incorporated in the particle detector.
In this study, characterization of NanoCheck
was performed with a scanning mobility particle sizer
(SMPS), which consists of differential mobility
analyzer (DMA) and condensation particle counter
(CPC). To obtain the optimum setup for a new
particle detector, we first characterized the NaCl
particles along with different types of DMA and flow
rate were carried out. From this experiment, we
found out that the best results were obtained with
1.5l/min of sample flow along with middle DMA for
5lpm of sheath air flow. In addition, different types
of aerosols such as indoor and outdoor aerosols were
also used for further verification. The routine Itot was
measured and knowing the flow rate and the particle
concentration measured by a CPC to determine the
elementary charge per particle size.
In conclusion, a new particle detector,
NanoCheck developed by GRIMM Aerosol Technik
showed that the measurement performed in the range
of 20nm~ 400nm with correction factor of 1.1 for
NaCl, 1.7 for indoor and 1.9 for outdoor aerosol.
This work was supported by the Korea Science and
Engineering Foundation and German Academic
Exchange Service.
Jan DL, Sharpiro AH, Kamm R. (1989). Journal of
Applied Physics, 67, 147-159.
W.G. Shin, D.Y.H.Pui, H. Fissan, S. Neumann and A.
Trampe. (2006). Journal of Nanoparticle Research, 9,
61-69.
Figure 1. Comparison of experimental results with
the ideal
The detector measures two currents Itot and IwE
sequentially, from which ∆I = Itot – IwE can be
calculated. These raw data are used to determine a
DMA-FMPS aerosol spectrometers laboratory intercomparison
F.Belosi1, V. Poluzzi3, S. Ferrari3, G. Santachiara1, F. Scotto3, A. Trentini3, F. Prodi1,2
1
Institute ISAC-CNR, Bologna, Italy
Physics Department, University of Ferrara, Italy
3
Regional Agency for Prevention and Environment (ARPA), Bologna Department, Italy
2
Keywords: ultrafine particles, DMA, FMPS.
dN/dLn(dp), #/cm-3
120000
2500
Fe2O3
H2OM-Q
Indoor
80000
2000
1500
1000
40000
500
0
10
0
1000
100
Indoor dN/dLn(dp), #/cm-3
100% and tend to increase with aerosol size (dp >
100 nm). Further research on the performance of the
new FMPS against the traditional sampler should be
encouraged in order to better understand eventual
behaviour differences.
Diameter, nm
Figure 1. Grimm-DMA aerosol size distribution
60000
1600
Fe2O3
dN/dln(Dp), #/cm3
1200
Indoor
40000
1000
800
600
20000
400
200
0
10
0
1000
100
Diameter, nm
Figure 2. TSI-FMPS aerosol size distribution
TSI-Grimm Comparison
150
100
50
0
-50 10
100
1000
-100
H2OM-Q
Fe2O3
Indoor
-150
-200
-250
Diameter (nm)
Figure 3. Relative difference results
Indoor, dN/dln(Dp) #/cm3
1400
H2OM-Q
(Grimm-TSI)/Grimm
Ultrafine particles could have a strong impact
on human health, as several works show. Therefore
the need to characterize the aerosol size distribution
up to a few nanometers, also in air quality studies,
has increased considerable increased over recent
years. The most common sampling technique is
based on a DMA column coupled with a CPC. The
Differential Mobility Analyzer (DMA) technique
requires radioactive sources to bring the sampled
particles to the Boltzmann equilibrium charge
condition. Current regulations, at least in European
countries, pose restrictions on the transport and
detection of radioactive materials (European
Directive 1493/93) even for sealed radionuclide
sources, making difficult to perform field DMA
measurements or ultrafine primary aerosol emission
characterisation at chimneys. TSI has developed a
Fast Mobility Particle Sizer Spectrometer (FMPS)
whose measurement principle is based on a particle
unipolar charger and an electrometer analyzer
consisting of a series of electrometers thus avoiding
a radioactive source and shortening the sampling
time.
This study will present the results of a
laboratory comparison between a DMA system
(Grimm, DMA Mod. 5.500 and CPC Mod. 5.403)
and a FMPS (TSI, Model 3091). The Grimm DMA
column is capable of measuring aerosol size
distribution in the range from 11 nm up to 1000 nm,
while the FMPSS works in the range from 5.6 nm to
560 nm. Therefore, a wide size spectrum overlaps
between the instruments. The exercise consists of a
simultaneous sampling by the two devices of three
different kinds of aerosols generated in the
laboratory: Milli-Q water and a Fe2O3 colloidal
solution, both nebulized in a Collison type atomizer,
and indoor particles.
Fig. 1 and 2 show respectively the size
distribution obtained with the Grimm-DMA and TSIFMPS of the three tested aerosols: the Milli-Q water
has the lowest particle size distribution (which can
not be resolved by DMA ), the Fe2O3 particles have
a maximum at about 30 nm, and indoor particles at
about 100 nm. Each aerosol type test consists of 3
replicas of simultaneous samplings (DMA was run in
fast mode so that both instruments almost the same
sampling time). Fig. 3 shows the relative difference
between Grimm and TSI, against the particle
diameter. Relative differences are of the order of
Intercomparison of two types of portable optical particle counters (Grimm model 1.109
and 1.108) at an urban aerosol measurement station
J. Burkart1, H. Moshammer2, M. Neuberger2, G. Steiner1, G. Reischl1 and R. Hitzenberger1
1
University of Vienna
Faculty of Physics, Aerosol, Bio- and Environmental Physics, Boltzmanng. 5, A-1090 Vienna, Austria
2
Medical University of Vienna
Institute of Environmental Health, Kinderspitalgasse 15, A-1090 Vienna, Austria
Keywords: optical particle counter, urban aerosol
In Figure 1 the total particle concentration as
obtained by integration over the whole DMA size
distribution is plotted as well. It can be seen that the
total particle concentration can be over 20 times
larger than the particle concentration obtained by the
OPCs. (Please note that there is a factor of ten
between the scale on the left y-axis and the scale on
the right y-axis. Only total particle concentration
(DMA) refers to the left axis.) The total particle
concentration does not even follow the pattern of the
particle concentrations received by OPC1 and OPC2
and the factor of difference is not constant.
Our comparison shows that using OPCs for
estimating particle number concentration can be very
misleading and in general underestimates particle
number concentration quite severely. Even a slight
difference in the lower cut-off diameter can lead to
considerable differences in measured particle
concentrations.
Comparison of the total particle concentration measured by a DMA and
two optical particle counters (OPC 1, OPC 2)
7,00E+05
DMA-total
DMA->300nm
DMA->250nm
OPC 2->300nm
OPC 1->250nm
6,00E+06
6,00E+05
5,00E+06
5,00E+05
4,00E+06
4,00E+05
3,00E+06
3,00E+05
2,00E+06
2,00E+05
1,00E+06
1,00E+05
0,00E+00
04:48:00
06:00:00
07:12:00
08:24:00
09:36:00
10:48:00
total particle concentration
measured by OPC 1 and OPC 2
and DMA fraction [1/liter]
7,00E+06
total particle concentration
(DMA) [1/liter]
Optical particle counters (OPC) are used
frequently as online instruments in order to get a
quick overview of aerosol parameters such as mass
concentration (e.g. PM10 or PM2.5) or number
concentration.
In our study the focus was on testing the
performance of two different types of optical particle
counters when measuring particle number
concentration and number size distribution of
atmospheric urban aerosols.
Optical particle counters measure the intensity
of the light scattered by single particles passing a
laser beam. The resulting electrical signal is analysed
and particles are classified into different size
channels according to the height of the electrical
impulse, and a number size distribution is obtained.
Scattered light intensity is assumed to be a
monotonic function of particle size.
Both OPCs used in this study are produced by
Grimm, Ainring, Germany. Model 1.108 (OPC2) has
15 size channels and a lower and upper cut-off
diameter of 0.3 and 20µm, respectively. Model 1.109
(OPC1) has 31 size channels and a lower and upper
cut-off diameter of 0.25 and 32µm, respectively. The
OPCs were connected with a Y-piece to the same
inlet tube and sampled atmospheric aerosol with a
flowrate of 1.2 L/min. In addition to the OPCs a
Vienna type DMA and a TSI CPC were operated to
obtain information on the number size distribution in
the size range from 10 to 1000nm (DMA) and the
total
particle
concentration
(CPC).
The
measurements were performed at the urban aerosol
measurement station at the roof laboratory of the
University of Vienna in December 2007 and January
2008.
When comparing total particle concentration
measured by OPC1 and OPC2, an average difference
of a factor of 2.5 can be found. In all the cases OPC1
could detect more particles than OPC2. A
comparison with the DMA data confirms that this is
due to the slight difference in the lower cut-off
diameter of the two instruments. As illustrated in
Figure 1 the concentrations obtained by integration of
the DMA size distribution from the upper cut-off
diameter to 250 and 300nm agree within 15% to the
concentrations measured with the OPCs.
0,00E+00
12:00:00
time [10 minutes]
Figure 1 Comparison of the total particle
concentration measured by a DMA and two different
optical particle counters
This work was supported by the Austrian Science
Fund (FWF) under grant P19515-N20 and the Clean
Air Commission of the Austrian Academy of the
Sciences (ÖAW).
Mass concentration of PM2.5, nitrate and sulfate measured by automatic instruments
and manual sampler during various meteorological conditions
J.H. Tsai1, C.H. Lin1, C.C. Liu2, W.F. Lai1 and Y.C. Yao1
Department of Environmental Engineering, National Cheng Kung University, Tainan, 701, Taiwan, Republic
of China
2
Taiwan Environmental Protection Administration, Taipei, 100, Taiwan, Republic of China
Keywords:
fine particulate matter, nitrate, sulfate, TEOM, MOUDI.
In order to characterize of fine particulate
matter,
Taiwan
Environmental
Protection
Administration (TEPA) has established an air
quality monitoring network (aka supersite) in
southern Taiwan. Those particulate concentrations
are measured by analyzers automatically and
continuously in stations, as said TEOM method.
This study was undertaken to evaluate the data
difference between the automatic monitoring
instrument and manual sampler under various
meteorological conditions, i.e. temperature and
relative humidity, and to understand the accuracy of
the automatic monitoring instrument. The
instruments are presented in Table 1.
Table1. The sampling instrument of ambient fine
PM used at this study.
Automatic
Item
PM2.5 mass
concentration
particulate
nitrate in PM2.5
particulate
sulfate in PM2.5
Instrument
R&P
1400
R&P
8400N
R&P
8400S
manual
Data
collection
period
Instrument
Data
collection
period
10 min
MOUDI
24 hour
30 min
MOUDI
24 hour
30 min
MOUDI
24 hour
The airborne particulate matter and their
precursor gases were collected by MOUDI samplers
at an air quality monitoring station located near the
supersite during October 2005 to December 2007.
This station was one of the stations with highly
frequent occurrences of poor air quality days in
Taiwan. The NO3- and SO42- contained in PM2.5
particulate were detected by ion chromatography.
Totally were 23 sets of daily concentration data
measured by manually MOUDI samples, and by
automatically measurements (R&P analyzers).
In general, the result of whole data shows that
the PM2.5 mass concentration by MOUDI sampler is
larger than that by R&P automatic analyzers
significantly (p value < 0.05 by t-test); the mean
concentrations are 53.6 and 38.6 μg/m3, respectively.
Moreover, the R&P 1400 data were related to
MOUDI data with a high correlation coefficient (r =
0.89).
The NO3- in PM2.5 by MOUDI sampler is
larger than that by R&P 8400N, however, without
statistical significance. The correlation result shows
a medium correlation between the data measured by
R&P 8400N and MOUDI. The SO42- in PM2.5 by
MOUDI sampler is close to that by R&P automatic
analyzers. The correlation coefficient is 0.73.
At ambient temperature lower than 25 oC, the
mean PM2.5 mass concentration by MOUDI sampler
(79.4 μg/m3) is larger than that by R&P automatic
analyzers (52.7 μg/m3) significantly (p<0.05),
however, the mean value are close at temperature
higher than 25 oC (25.4 μg/m3 for MOUDI and 23.3
μg/m3 for R&P 1400). In contrast, the PM2.5 mass
concentrations by MOUDI were larger than that by
R&P 1400 significantly (p<0.05) regardless of RH
condition (lower or higher than 70%). The result
also indicated that the R&P 1400 data were related
to MOUDI data with a high correlation coefficient,
the r value is 0.97 (RH<70%), and 0.82 (RH>70%).
Figure 1 illustrated the relative of PM2.5 mass
concentration measured by automatic instruments
and manual sampler at different RH condition.
PM2 5 by automatic R&P 1400 (μg/m3)
1
PM2.5 by manual MOUDI (μg/m3)
Figure 1. The relative of automatic instruments and
manual sampler at different RH condition (at RH
< 70%, at RH > 70%).
In brief, the study showed that the automatic
instruments and manual sampler instruments for fine
particulate measurement shall have different result,
to some extent. The study would be helpful to
develop or evaluated the fine particulate monitoring
instrument or method.
This work was supported by the National Science
Council and the Environmental Protection
Administration, Taiwan, Republic of China under
grant NSC95-2221-E-006 -287.
Performance of a New Condensation Particle Counter
Hojoong Kim1, Juergen Spielvogel2, Soohyun Ha1, and Taesung Kim1
1
SKKU Advanced Institute of Nanotechnology (SAINT), Sungkyunkwan Universiry, Cheoncheon-dong, 440746, Suwon, Korea
2
Grimm Aerosol Technik, Dorfstrasse 9, D-83404, Ainring, Germany
Keywords: CPC, aerosol instrumentation, nanoparticles, measurements
With the increase of submicron or ultrafine
particle researches on either atmospheric or
nanoscience field, the scanning mobility particle sizer
(SMPS) which mainly consists of differential
mobility analyzer (DMA) and condensation particle
counter (CPC), is one of the most commonly used
instruments. As the particle number concentration in
a unit aerosol volume is counted by the CPC, its
counting efficiency determines overall performance
of the SMPS instrument.
From the invention of continuous-flow CPC, a
number of CPC measurement methods characterizing
performance of the CPC have been carried out, such
as the work of Wiedensohler et al. (1997) or S
Mertes et al. (1995). Although, there are a lot of
studies related to the CPC measurements, new
studies are still performed due to its importance in
ultrafine particle research.
Grimm Aerosol Technik, an aerosol
instrumentation company in Germany, has recently
developed new CPC instrument which has improved
performance compared to previously developed
CPCs of the company. The instrument has smaller
optical volume than that of previous instruments so
that higher limit of single particle count per time can
be achieved due to less coincidence effect. Larger
The experimental setup was composed of new CPC,
Grimm 5.403 CPC, and faraday cup electrometer
(FCE) unit. The FCE unit was considered as a
reference to calibrate the prototype and Grimm 5.403
CPCs.
Linearity
and
square
wave
input
measurements were performed to confirm calibration
status of 2 CPCs used in this study. Figure 1 shows
the result of linearity measurement of the CPCs. For
counting efficiency measurements, we used different
conditions of atmospheric pressure, low pressure
down to 800 mbar, different ΔT, and particles made
of different materials.
The experimental results of efficiency
measurement showed that new CPC has smaller d50
and higher counting efficiency for ultrafine particles
than Grimm 5.403 CPC. Similarly, other
experimental results also showed better results than
those of Grimm 5.403 CPC.
In conclusion, new CPC showed that it has
improved performance than the previously developed
CPC.
temperature difference (ΔT) between condenser and
saturator, and internal coincidence effect correction
function also contribute to the improved performance.
In this study, calibration and characterization
were performed with a prototype model of new CPC.
List of the measurements is shown in Table 1.
Table 1. List of the measurements.
Name of
measurement
Used instruments
Linearity
New CPC, Grimm 5.403, FCE
Square wave
input response
New CPC , Grimm 5.403,
FCE
Ramp input
response
New CPC , Grimm 5.403
Counting
efficiency
New CPC , Grimm 5.403
Figure 1. The result from linearity measurement
Wiedensohlet, A., Orsini, D., Covert, D. S.,
Coffmann, D., Cantrell, W., Havlicek, M.,
Brechtel, F. J., Russell, L. M., Weber, R. J., Gras,
J., Hudson, J. G., & Litchy, M. (1997). Aerosol
Science and Technology, 27, 224-242.
Mertes, S., Schroder, F., & Wiedensohler, A. (1995).
Aerosol Science and Technology, 23, 257-261.
Comparison of the Thermo Scientific TEOM 1405-DF monitor to Reference Method
Sampling Results for the Measurement of PM2.5
J.L. Ambs1
1
Thermo Fisher Scientific, Franklin, Massachusetts, 02038, United States of America
Keywords: TEOM, FDMS, PM2.5, Ambient PM
Thermo Scientific recently conducted PM2.5
equivalency testing on the new TEOM 1405-DF
Dichotomous Ambient Particulate Monitor with
FDMS (TEOM 1405-DF) The TEOM 1405-DF was
compared to the US EPA PM2.5 reference method and
the European reference methods at locations in both
the US and Europe.
The TEOM 1405-DF is a dichotomous
sampler configured as a dual filter sampler for the
simultaneous measurement of both fine (PM2.5) and
coarse (PM10-2.5) particles in PM10. A virtual impactor
is used to separate the fine and coarse PM into two
samples for collection and measurement on two
sample filters in the TEOM 1405-DF. The two
samples pass through two FDMS modules before
being captured and measured by the two inertial
micro-balances in the TEOM mass sensor.
The FDMS was designed to take advantage of
the TEOM real-time mass measurement system to
address these issues by characterizing the semivolatile and non-volatile portions of ambient PM2.5 as
present in the atmosphere at the time of collection.
When sampling ambient aerosol, the sample filter in
the TEOM monitor collects the incoming ambient
aerosol, which includes both the non-volatile as well
as semi-volatile material. Because of the selfreferencing nature of the FDMS equipped TEOM
monitors, the FDMS equipped TEOM monitors are
able to measure and correct for the presence of semivolatile material present in the collected sample.
for these switch periods at the end of each successive
measurement.
The reference mass concentration is then
subtracted from the base mass concentration to
determine the near real-time ambient mass
concentration. In this way the FDMS system
determines the total atmospheric aerosol mass
concentration including volatile and semi-volatile
components as they exist in the atmosphere at the
time of collection. The system then subtracts the
calculated reference concentration from the
calculated base mass concentration giving a net
ambient aerosol mass concentration which represents
the mass concentration of ambient aerosol as it exists
at the time of sample collection.
During this sample study, multiple reference
samplers and multiple TEOM 1405-DF monitors
were operated simultaneously at each of
the
sampling locations. The reference sampler filters
were sampled for 23-hour periods and collected
daily. The test program provided for a wide range of
sampling conditions over multiple seasons of the
year, and widely varying environmental conditions.
The results presented in Figure 1 are representative
of the results obtained over the test program.
80
70
TEOM 1405-DF MC ug/m3
60
During operation, the FDMS equipped TEOM
monitors alternately sample ambient aerosol and then
sample through a chilled reference filter for equal
time periods. During normal sampling, or the base
period, the TEOM sample filter is measuring mass
increase from the ambient aerosol as well as any
mass changes of collected the semi-volatile material.
During the reference period of sampling, the sampled
ambient aerosol is filtered in the chilled filter
conditioner and no incoming ambient aerosol is
measured by the mass sensor and only changes to the
amounts of semi-volatile material previously
collected on the sample filter are measured. The
switch between the base and reference measurement
periods occurs every six minutes and the monitor
calculates the base and reference mass concentrations
23-Hour Samples
PM-2.5
50
y = 1.004x + 1.464
2
R = 0.991
40
30
20
10
0
0
10
20
30
40
50
60
70
80
Reference Method MC ug/m3
Figure 1. Comparison between the TEOM 1405-DF
Dichotomous Ambient Particulate Monitor with
FDMS and Reference Method samplers in multiple
locations and multiple seasons.
Comparison of the performance of the Thermo Scientific TEOM 1400a with 8500C
FDMS and the TEOM 1400a with 8500B FDMS monitors for the measurement of PM2.5
J.L. Ambs1
1
Thermo Fisher Scientific, Inc., Franklin, Massachusetts, 02038, United States Of America
Keywords: TEOM, FDMS, PM2.5, Ambient PM
PM2.5 is a complex mixture of chemical
species in a range of physical sizes that varies
significantly with season and location and can
include both non-volatile and semi-volatile materials.
Ammonium nitrate, semi-volatile organic material,
and water are semi-volatile materials, while other
components are non-volatile in the context of
ambient PM measurements. Many studies show that
there is a loss of semi-volatile material from the
collected samples using some continuous monitors as
well single event filter samples, including the US
EPA PM2.5 reference method.
The FDMS was designed to take advantage of
the TEOM real-time mass measurement system to
address these issues by characterizing the semivolatile and non-volatile portions of ambient PM2.5 as
present in the atmosphere at the time of collection.
When sampling ambient aerosol, the sample filter in
the TEOM monitor collects the incoming ambient
aerosol, which includes both the non-volatile as well
as semi-volatile material.
Because of the
self-referencing nature of the FDMS equipped
TEOM monitors, the monitors are able to measure
and correct for the presence of semi-volatile material
present in the collected sample.
During operation, the FDMS equipped TEOM
monitors alternately sample ambient aerosol and then
sample through a chilled reference filter for equal
time periods. During normal sampling, or the base
period, the TEOM sample filter is measuring mass
increase from the ambient aerosol as well as any
mass changes of collected the semi-volatile material.
During the reference period of sampling, the sampled
ambient aerosol is filtered in the chilled filter
conditioner and no incoming ambient aerosol is
measured by the mass sensor and only changes to the
amounts of semi-volatile material previously
collected on the sample filter are measured. The
switch between the base and reference measurement
periods occurs every six minutes and the monitor
calculates the base and reference mass concentrations
for these switch periods at the end of each successive
measurement.
The reference mass concentration is then
subtracted from the base mass concentration to
determine the near real-time ambient mass
concentration. In this way the FDMS system
determines the total atmospheric aerosol mass
concentration including volatile and semi-volatile
components as they exist in the atmosphere at the
time of collection. The system then subtracts the
calculated reference concentration from the
calculated base mass concentration giving a net
ambient aerosol mass concentration which represents
the mass concentration of ambient aerosol as it exists
at the time of sample collection.
Field comparisons of the two FDMS systems
were performed in multiple locations and over
multiple seasons to evaluate the effect of the
improved dryer on the performance of the FDMS
equipped TEOM monitors. Collocated monitors were
compared over 24 hour test periods and compared to
the results collected from collocated reference
samplers. Comparative results from the collocated
FDMS equipped TEOM monitors are presented in
Figure 1.
80
FDMS 8500B vs FDMS 8500C
Regression Statistics
y = 0.975x + 1.197
2
R = 0.998
70
8500B FDMS Mass Concentration (ug/m3)
Thermo Scientific released the first Filter
Dynamics Measurement System (FDMS) for the
TEOM monitor in 2002. The Thermo Scientific
TEOM 1400a with 8500C FDMS (8500C FDMS) is
the current version of the 8500 FDMS equipped line
of TEOM 1400a ambient PM monitors. The “C”
version of the FDMS utilizes a more efficient dryer
for better performance. This work explored the
performance differences between, TEOM monitors
using the current version of the dryer with older
dryers.
60
50
40
30
20
10
0
0
10
20
30
40
50
60
70
80
8500C FDMS Mass Concentration (ug/m3)
Figure 1. Comparison of FDMS systems with the “B”
and “C” types of dryers installed.
Integrated water vapor (IWV) climatology with RIMA-AERONET sunphotometers,
GPS and Radiosondes in the Southwestern of Spain
B. Torres1, V. E. Cachorro1, C. Toledano1, J. P. Ortiz de Galisteo2, A. Berjón1, A. M. de Frutos1
1
2
Group of Atmospheric Optics, University of Valladolid, Spain.
Spanish Meteorology Agency (AEMET), Delegación Territoral de Castilla y León, Spain
Keywords: Precipitable water vapor, Sun-Photometer, GPS, Radiosonde, RIMA-AERONET.
Abstract
Column integrated water vapor (IWV) data in the
Southwestern of Spain are analyzed during 2001 to
2005 with two aims: 1) to establish the climatology
over this area using three different techniques, such
as Sun-Photometer (SP), Global Position System
(GPS) and Radiosondes, and 2) to take advantage of
this comparative process to assess the quality of
radiometric IWV data collected at the RIMAAERONET station. The 5 years of climatological
series gives a mean value of about 2 cm (STD=0.72)
and a clear seasonal behavior as a general feature,
with the highest values in summer and the lowest in
winter. In the multi-annual monthly means basis, the
highest values are reached in August-September,
with a mean value of 2.5-2.6 cm, whereas the lowest
are obtained in January-February, with an average of
1.4-1.5. However the most relevant results for this
area is the observed local minimum in July, occurring
during the maximum of desert dust intrusions in the
southern Iberian Peninsula.
varies from summer with 2% to winter with -8% and
between SP and GPS values from 3% in summer to
–14% in winter.
a) SP#45
b) SP#114
Figure 2. Relative bias values between SPGPS and the regression line of tendency for a) SP
#114 (bad behavior) and b) SP #45(good behavior).
Figure 1. The time series of monthly means of IWV
during 2001-2005, for data collected by GPS, SP and
Radiosondes. Arrows indicate a change of SP.
A comparison process allows us to evaluate
the agreement of IWV data sets between these three
different techniques at different temporal scales
because of different time sampling. On a daily basis
and taking GPS as the reference value (Bokoye et al.,
2006) we have a bias or difference between
Radiosonde and GPS measurements for the entire
data base of 0.07 cm (relative bias of 3%) and RMSE
of 0.33. For SP-GPS we have a bias of 0.14 cm
(about 7%) and RMSE of 0.37. On a monthly basis
the differences between Radiosonde and GPS values
The observed bias between GPS and SP varies during
each SP operational period, with lower values at the
beginning of the measurements and increasing until
the end of its measurement term and with the bias
values being quite dependent on each individual SP.
The observed differences highlight the importance of
drift in each Sun-Photometer, because of filter aging
or other calibration problems. Hence the comparison
with GPS appears to be a powerful tool to asses the
quality of Sun-Photometer for IWV retrieval.
Boyoke, A.I., Royer, A., Cliche, P., & O’Neill, N.
(2006). Calibration of Sun Radiometer-Based
Atmospheric Water Vapor Retrievals Using
GPS Meteorology. Journal of Atmospheric
and Oceanic Technology, 24, 964-979.
Ion-induced solvation and nucleation studies in a sonic DMA
M. Attoui1 J. Fernandez de la Mora2
1
Physic Department, Paris XII University France 2Mechanical Department Yale University USA
Key words: DMA, Mobility, ion induced nucleation
measure the mobility of these ions as a
function of vapour concentration and Mach
number. In preliminary experiments with
no vapour addition we confirm that sonic
conditions are achieved by observing that,
above a critical pump power, further
increases in power lead to no increase in
the voltage VDMA at which the peak of the
(dry) ion appears. Figure 1 shows the
evolution of VDMA as the methanol
concentration is changed at M = 1. The
shift in voltage (inverse mobility) is due in
part to the increased ion drag associated to
the change in composition of the gas, and
in part also to growth of the ion by
solvation. Only the latter effect provides
information on IISN. We plan to isolate the
first effect in experiments at low M and
higher temperature, to then study
quantitatively the second in sonic
experiments at lower temperatures.
800
700
600
S=0%
EM signal
Fernandez de la Mora has recently
introduced the HalfMini DMA, a miniature
high resolution DMA reaching sonic
conditions (Mach number = M = 1) at a
flow rate of sheath gas of only Q~740
lit/min. Due to an efficient diffuser and a
negligible flow resistance at the DMA
outlet, sonic flow is readily achieved with
one or two conventional vacuum cleaner
pumps. Our goal is to study ion induced
solvation and nucleation (IISN) by running
this DMA sonically with a gas containing a
vapour. The vapour is below saturation
conditions at stagnation conditions, but
substantial supersaturation is achieved in
the sonic working section by expansion
cooling. In order to control gas
composition without consuming 750 lpm
of purified gas, we operate the sheath flow
under closed loop, so that its composition
is that of the inlet aerosol. Since the pumps
introduce ~ 1 kW into the gas, the main
challenge is to cool the circuit such as to
achieve a steady state operation with a
temperature as uniform as possible (to
avoid condensation on cold circuit parts)
and as low as possible (to favour IISN over
homogeneous nucleation). This we have
achieved by closing the flow circuit with a
long line of corrugated SS tubing
immersed in a slightly cooled water bath at
10°C witch gives sheath air temperature
between 18 to 22 °C. The working gas is
typically CO2 into which controlled
quantities
of
alcohol
are
added
continuously at the aerosol inlet, with a
syringe pump and in a heated loop,
ensuring complete vaporization of the
alcohol. This vapour-laden gas is then
introduced into an electrospray chamber
where tetraheptyl ammonium (THA+) ions
are added, and then enters the DMA. We
S=11%
S=16%
S=22%
500
400
300
200
100
0
1.38
1.58
1.78
Dp(nm) 1.98
Figure 1 : THA+ size distribution of
THABr at different supersaturation with
methanol. The second peak is the dimer
ion (THA+Br-)THA+
Construction of a Biofluorescence Optical Particle Counter
Russell Greaney1, Oliver Ryan1, S. Gerard Jennings,1 Colin D. O’Dowd,1
1
School of Physics & Centre for Climate and Air Pollution Studies, Environmental Change Institute,
National University of Ireland, Galway, University Road, Galway, Ireland.
Keywords: Fluorescence, Optical particle counter, Primary marine aerosols, Real time detection, Size-segregated
aerosols.
O’Dowd et al. (2004) found that submicrometer
marine spray aerosol contained a significant fraction
of organic matter and is associated with the
seasonality of plankton biological activity as
determined from satellite ocean-colour products.
Laser induced fluorescence will probe the organic
content of marine aerosols through excitation of
fluorescence of chlorophyll-a contained in the
phytoplankton. The fluorescence quantum yield is
very low for chlorophyll-a in phytoplankton, ranging
from 2% to 7% (Lizotte & Priscu, 1994). The
fluorescence signature also has a very short lifetime
on the order of nanoseconds making the fluorescence
output almost simultaneous to the elastic scattered
light signal. This necessitates the use of highly
sensitive photomultiplier tubes (PMTs) to maximise
data signal-to-noise.
wavelength of 500 nm, passing the scattered light to
photodiodes, and the weaker fluorescent emission to
highly sensitive Hamamatsu PMTs.
Calibration and testing of the instrument is currently
underway and is producing both sizing and
fluorescence measurements. The LIF-OPC has sized
particles (ammonium sulphate) as low as 167 nm in
diameter and also detected fluorescence from 3 µm
PSL spheres (Green 510 from Duke Scientific).
Chlorophyll-a powder will be used with the aerosol
generator (TSI atomizer and classifier) to produce
chlorophyll particles of known diameter to calibrate
the PMT fluorescence signal output. A phytoplankton
breeding tank will be created to allow in-house
measurements of bubble mediated aerosol from
seawater enriched with phytoplankton cultures. After
validation the instrument will be brought for flux
measurements and bioaerosol chlorophyll detection
trials on the Atlantic coast at the Mace Head
atmospheric research station.
Thanks to Paul Kaye for his help with the nozzle cap
design and very helpful discussions. This project
(05/RF/GEO009) is funded through the Research
Frontiers Programme of Science Foundation Ireland
(SFI).
Figure 1: A schematic layout of the instrument.
Figure 1 depicts the layout of the laser induced
fluorescence optical particle counter (LIF-OPC)
instrument. All flow rates in and out of the chamber
are balanced to allow a smooth non-turbulent hydrodynamically focused air flow. The ellipsoid reflector
has a protected silver coating to maximize collection
of the scattered 405 nm laser light as well as having
high collection efficiency for the chlorophyll-a
fluorescence. High efficiency dichroic (long pass)
mirrors split the collimated beam at an edge
C.D. O’Dowd, M.C. Facchini, F. Cavalli, D.
Ceburnis, M. Mircea, S. Decesari, S. Fuzzi, Y.J.
Yoon, and J-P. Putaud, “Biogenically-driven organic
contribution to marine aerosol”, Nature 431, 676-680,
2004.
M.P. Lizotte, and J.C. Priscu, “Natural fluorescence
and quantum yields in vertically stationary
phytoplankton from perennially ice-covered lakes,
Limno”. Oceanogr. 39(6), 1399-1410, 1994.
P. H. Kaye, J. E. Barton, E. Hirst, and J. M. Clark,
“Simultaneous light scattering and intrinsic
fluorescence measurement for the classification of
airborne particles”, Applied Optics, 39, 3738-3745,
2000.
Design and Characterization of the Screw-Assisted Rotary Feeder
with Ultra Low Feeding Rate
K.S. Lee1, J.H. Jung1 and S.S. Kim1
1
Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology (KAIST),
Guseong-dong, Yuseong-gu, Daejeon 305-701, Republic of Korea
Keywords: O2/CO2 combustion, In-furnace desulfurization, Feeder, Number concentration, Rotation speed.
Recently, as the regulation about the emission of
the GHG (Green House Gas), such as CO2 or CH4,
has become more severe, the O2/CO2 combustion
system, which enables the easy CO2 recovery from
the high concentration of the CO2 in combustion
chamber by the EGR (Exhaust Gas Recirculation),
was introduced as one of the promising combustion
systems. Furthermore, In-furnace desulfurization
technique, which need not additional chamber for the
desulfurization, can be applied to the O2/CO2
combustion system despite of its low desulfurization
efficiency. The O2/CO2 combustion system is able to
store the exhaust gas using the storage facilities
instead of emitting it to the atmosphere. This process
is conducted using calcium carbonate (CaCO3)
sorbent particles which have wide size range.
In previous studies, various feeding methods, such
as rotary feeder, screw feeder, vibration feeder, and
turntable feeder, have been used to transport the
sorbent particles into the combustion chamber.
However, most of these feeders have several
drawbacks, such as high feeding rate and the usage of
high carrier gas volume rate, when they are applied
to the lab-scale researches (Reist et al., 2000;
Gundogdu, 2004).
In this study, we investigated the screw-assisted
rotary feeder which enables transport small quantity
of sorbent. The generation characteristics, such as
uniformity and stability, were verified using CPC
(Condensation Particle Counter 3022A, TSI Inc.,
USA), APS (Aerodynamic Particle Sizer 3321, TSI
Inc., USA), and SMPS (Scanning Mobility Particle
Sizer, TSI Inc., USA) systems. Two rotors which
have different number of groove (4- and 12- grooved
rotors) were constructed and examined in various
rotation speeds (3, 6, 9, 18, and 27 rpm) with
constant air flow rate (23 L/min).
Figure 1 shows the variance of the particle number
concentration of 4-grooved rotor at the experimental
conditions from 3 to 27 rpm of rotation speed. From
real-time method using CPC, the screw-assisted
rotary feeder has the pulse-shaped particle generation
characteristics
repeating
on-off
operations
periodically. As the rotation speed increased, the
frequency of discharging sorbent particles increased.
At the same time, the amplitudes of the number
concentration data decreased.
Table 1. Mean number concentrations (#/cm3) and
COVs of two different grooved rotors in
various rotation speeds
4-grooved
rotor
12-grooved
rotor
Mean
COV
Mean
COV
3 rpm
0.13E6
0.358
0.29E6
0.127
9 rpm
1.1E6
0.127
0.61E6
0.075
27 rpm
1.6E6
0.082
0.39E6
0.312
Table 1 shows the mean of number concentrations
and the COVs (Coefficient of Variance) of two
different grooved rotors in various rotation speed
conditions. For the 4-grooved rotor, both number
concentration and COV decreased with increased
rotation speed. For 12-grooved rotor, however, they
decreased with variance of rotation speed from 9 to
27 rpm. We think that this variance of mean and
COV may be caused of the lack of filling time of
sorbent particles into the groove.
From this study, the particle generation condition
with high uniformity and stability can be established
from the screw-assisted rotary feeder. Also, we can
control the feeding rates of sorbent particles by
adjusting the rotation speeds of the grooved rotor.
This work was supported by Energy Resources
Technology Development Project of the Korea
Energy Management Corporation (2007-C-CD27-P02-1-000) and by BK21 Program of the South Korea
Ministry of Education, Science, and Technology.
Reist, P. C., & Taylor, L. (2000). Powder Technol.,
107, 36-42.
Gundogdu, M. Y. (2004). Powder Technol., 139, 7680.
Figure 1. Number concentration of 4-grooved rotor in
rotation speeds from 3 to 27 rpm in real time.
Density analyzing method of atmospheric particles: reliability and limitations using a
new ELPI stage
J. Kannosto, J. Yli-Ojanperä, M. Marjamäki, A. Virtanen, J. Keskinen
Aerosol Physics Laboratory, Department of Physics, Tampere University of Technology, P. O. Box 692, FIN33101 Tampere, Finland
Keywords: particle density, nanoparticles composition, nucleation mode, atmospheric aerosols,
ELPI.
The assessment of climatic and health effects of
atmospheric aerosol particles requires detailed
information on the particle properties. In addition, the
particle chemical composition and other chemical
and physical properties carry information concerning
sources and formation mechanisms of the particles.
Nucleation bursts observed in different environments
are producing nucleation mode particles in the
atmosphere. There have been intensive and
successful efforts to identify different nucleation
mechanisms. Regardless of the progress, there are
still gaps in the general understanding of the new
particle formation.
Our method is based on a simultaneous
(“parallel”) distribution measurement with an ELPI
and a SMPS/DMPS and, further, on the relationship
between the aerodynamic size, the mobility size and
the effective density of the particles (Ristimäki et al.
2002). We have studied density of boreal forest
particles and found the density values for nucleation,
Aitken and accumulation modes (Kannosto et al.
2008). Measurements in Kannosto et al. 2008 have
been made using normal ELPI impactor with the
filter stage. After these measurements, we have
developed a new ELPI stage with a lower cut point
(Yli-Ojanperä et al. 2009). And we have performed
calibration measurements in the laboratory and
simulations to clarify the lowest size limits and
reliability of the density analyzing method using the
old and the new ELPI impactors.
We simulated particle distribution modes with
different GMD, GSD and concentration. ELPI
currents were calculated using the simulated modes
and specific density values. 5% random error was
added to these ELPI currents. Density value of each
mode was calculated 50 times. Laboratory tests of the
density analyzing method were taken using di-octyl
sebacate (DOS, density 0.912 g/cm3) and
evaporation-condensation generator to produce
polydisperse aerosol distribution. Geometric mean
diameter of the particles size distribution varied
between 8 nm – 40 nm and the distributions were
very narrow.
Results of the reliability simulations show
differences between the new and the old impactor
setup. The density analyzing method produces
densities close to the initial value at high GMD
values. With smaller GMD than 15 nm, the density
analyses resulted in different values depending on the
impactor type. Density values under 15 nm analyzed
using the old impactor increases as GMD decreases
and variation is very high. Between 8 nm – 15 nm the
new impactor setup gives the density values very
close to the initial values, indicating lower size limit
for density analysis. Also, the variation of the density
values was much smaller with the new impactor.
Lowest detection limit for the new impactor setup is
about 10 nm and for the old setup about 15 nm.
These limits are in aerodynamic diameters and they
are affected by the particle density.
Results of the laboratory test agree with the
results of simulations. The density value of DOS
particle distributions calculated with the density
analyzing method is very close to bulk density of
DOS. The new impactor setup produces the correct
result down to about 10 nm when the old impactor
setup reaches 15 nm.
Kannosto J., Virtanen A., Lemmetty M., Mäkelä
J.M., Keskinen J., Junninen H., Hussein T., Aalto
P., Kulmala M. (2008), Mode resolved density of
atmospheric aerosol particle, Atmospheric
Chemistry and Physics 8, 5327-5337
Ristimäki, J., Virtanen, A., Marjamäki, M., Rostedt,
A., Keskinen J. (2002): On-line measurement of
size distribution and effective density of
submicron aerosol particles. J. Aerosol Sci., 33,
1541-1557
Yli-Ojanperä J., Kannosto J., Marjamäki M.
Keskinen J. (2009), Improving the nanoparticle
resolution of the ELPI, Manuscript in
preparation/submitted
First tests of thermophoretic trap in short duration microgravity conditions
A.A. Vedernikov1, A.M. Markovich1, A.V. Kokoreva1, N. Bastin1, P. Queeckers1, N.V. Kozlov2,
J. Blum3, I. von Borstel3, R. Schräpler3
1
Microgravity Research Centre, Université Libre de Bruxelles, 50, av. F.D. Roosevelt, 1050, Brussels, Belgium
2
Perm State Pedagogical University, Perm, 614990, Russia
3
Institut für Geophysik und Extraterrestrische Physik, Technische Universität zu Braunschweig, 38106, Germany
Keywords: aerosol dynamics, cloud dust, dynamic balancing, instrument development, microgravity
electrodynamic balancing. Mean particle velocity in a
thermophoretic trap is convenient to express as
2
⎡ vref Cz Pref ωref Tac (ωref ) ⎤
vsq = vT t = −
⎢
⎥ z
1 + (ωτ p )2 ⎢⎣ ω ⋅ (∇T )ref ⋅ P
⎥⎦
where τp particle relaxation time; ω angular
frequency (2-10 Hz); νref is the value of the particle
2τ p
thermophoretic velocity at known temperature
gradient (ΔT)ref and reference pressure Pref; Cz
proportionality coefficient in the temperature profile
fit T=T0+Cz*T2 around equilibrium trap point; Tac is
the temperature variation amplitude on heaters at
reference frequency ωref (Tac was 4.2 K for 10 Hz); z
mean particle axial coordinate.
First tests in microgravity conditions of the
Bremen drop tower (microgravity duration 4.7 s)
were performed in a prototype chamber of the ICAPS
project that imposed certain geometrical limitations
on the trap (two coils, diameter 62 mm separated by
10 mm). Measured motion parameters were in
agreement with the theoretical model.
254
axial coordinate Z, pixel
The European Space Agency’s scientific
program Interactions in Cosmic and Atmospheric
Particle Systems (ICAPS) is aimed at increasing our
knowledge about dust agglomeration in astrophysical
processes mostly related to proto-planetary matter
formation (Blum et al., 2008). Microgravity
conditions are needed to suppress sedimentation,
which in the laboratory considerably reduces the
experimentation time, thus Brownian motion driven
agglomeration can be performed over a muchextended period of time. However, grain diffusion to
the walls (at which all dust grains inevitably stick)
and residual forces, like e.g. thermophoresis, impose
limits to the maximum achievable agglomerate size
and the agglomeration rate. The reduction of these
adverse effects demands an efficient trapping
mechanism for dust ensembles with the following
requirements: particle sizes – from monomers of
~1μm to agglomerates of up to ~1mm; particle
concentration up to 106-107 cm-3; fixed pressure in
the range 0.1 -10 mbar; room temperature (about
300K); cloud volume in the ‘area of interest” – 1 to
40 cm3; total chamber volume about 1 liter.
Prevention of grain diffusion or drift to the walls of
the experiment chamber allows long-duration
agglomeration studies for the investigation of
aggregate morphologies, aggregation rate, aggregate
mass distribution, and temporal behavior of the mean
aggregate mass for a variety of grain sizes, shapes,
compositions and gas pressures.
To meet the requirements of the project, the
experimental instrumentation should provide 1)
squeezing of such a dense cloud (mostly to
compensate particle number lowering due to
Brownian agglomeration) and 2) counterbalancing
external cloud perturbations. Traditional approach
would be using electrodynamic balancing (EDB or
Paul trap) taking into account the fact that particles
are naturally charged by cog wheel injection.
However, this technique has principal disadvantages
coming from presence of opposite charges on the
particles. Among other drawbacks it leads to quick
reduction of the total charge-to-mass ratio of growing
agglomerates, lowering of the ‘trapping strength’
followed by loosing the agglomerates - the most
interesting objects of investigation. The use of the
thermophoretic force (Vedernikov et al., 2007)
should remove most disadvantages of the
252
250
248
traj_119, drop702
246
0
0.5
1
1.5
2
time, s
Figure 1. Typical particle trajectory.
The tests allowed identifying 1) necessary
modifications in the trap’s geometry and heater’s
functioning to visualize squeezing effect of the dust
cloud in short duration experiments and 2) potentials
of laboratory use of the thermophoretic trap.
ESA PRODEX program and the Belgian Federal
Science Policy Office are greatly acknowledged.
Blum, J. et al. (2008). Europhysicsnews, 39/3, 27-29.
Vedernikov, A. A., Markovich, A. V., & Blum, J.
(2007). In European Aerosol Conference,
Salzburg (Austria), Abstracts, LP35.
ISO 15900 – A new international standard for differential electrical mobility analysis
H.-G. Horn, K. Ehara, N. Fukushima, K. Ichijo, I. Marshal, Y. Otani, M. Owen, C. Peters, P. Quincey,
H. Sakurai, J. Schlatter, G.J. Sem, J. Spielvogel, C. Tsunoda, J. Vasiliou
ISO TC 24/SC 4/WG 12
Keywords: Aerosol measurement, Measurement errors, SMPS, DMPS, Electrical Mobility.
Differential electrical mobility analysis is a
well established and widely used tool to measure
submicrometer
particle
size
distributions.
Measurements are made with quite a variety of
electrical mobility spectrometers, ranging from
several commercial systems and their multiple
variations to self built equipment. A new
International Standard ISO/DIS 15900 (2008) covers
measurements with such devices.
All electrical mobility spectrometers are based
on the measurement of particle migration in a gas due
to an external electrical force and due to the drag
force. Data inversion routines are necessary to
convert the raw data (either particle count versus
differential electrical mobility classifier voltage or
particle count versus time) into particle number as a
function of particle size. Several parameters
influence the precision of the measurement and of the
data inversion; most important are:
- Applied particle charge distribution model
- Applied transfer function model
- Slip correction coefficients
- Correction of particle losses and detector
efficiency
- Precision of operating parameters like flow
rates, voltages etc.
- Data inversion algorithms
Thus, the comparison of results obtained from
measurements with different spectrometers may
become less simple than originally expected.
For example, recent comparison measurements of electrical mobility spectrometers by Helsper
et al. (2008) have shown that the number
concentration - integrated from 40 nm to 350 nm obtained from measurements with five systems (four
commercial systems from two manufacturers and a
self built system by IfT Leipzig) agreed within 12%.
In the size range from 20 nm to 200 nm, all number
size distributions compared within 20%. However,
deviations increase below and above these size
ranges. The authors conclude that the reasons for
these differences might be uncertainties from
correction functions for particle losses, counting
statistics, bipolar charge distributions used in the
individual inversion routines, and the size dependent
particle losses of the different sampling inlets.
Much higher transparency, especially of the
parameters and algorithms used for data inversion,
would have been necessary to allow in depth analysis
of the reasons for the deviations in the above
mentioned study. ISO 15900 intends to deliver such
transparency: For example, standardized common
values and calculation algorithms are provided for
slip correction and for particle size-dependent
equilibrium charge distributions. Use of different
values and algorithms is - of course - allowed, but
must be reported together with the results to make a
measurement ISO compliant.
The key purpose of ISO 15900 is to provide
user guidance and thus to improve measurement
quality and comparability. The standard does not
address the specific instrument design, or the specific
requirements
of
particle
size
distribution
measurement for different applications, but includes
the calculation method of uncertainty, in accordance
with the guideline given in the ISO/IEC Guide to the
expression of uncertainty in measurement.
To support the user and to further improve
comparability and quality of results, ISO 15900
offers a general description of electrical mobility
spectrometry and the underlying physical principles.
It also describes proven measurement procedures,
and recommends periodic test procedures and
calibrations. Annexes add information about particle
chargers and charge distributions, particle detectors,
the slip correction factor, data inversion, systems
with cylindrical differential electrical mobility
classifier, calibration with particle size standards,
uncertainty of measurement, and a detailed
bibliography.
The new standard ISO 15900 is actually
available as Draft International Standard (DIS). It
will very soon be published as Final Draft
International Standard (FDIS).
ISO/DIS 15900 (2008), Determination of particle
size distribution – Differential electrical mobility
analysis for aerosol particles. ISO/TC 24/SC
4/WG12 (Beuth, Berlin)
Helsper, C., Horn, H.-G., Schneider, F., Wehner, B.
& Wiedensohler, A. (2008). Intercomparison of
five mobility size spectrometers for measureing
atmospheric submicrometer aerosol particles.
Gefahrstoffe - Reinhaltung der Luft 68(2008) Nr.
11/12 (Springer-VDI, Düsseldorf), 475-481.
ISO/IEC Guide 98-3:2008-09. Uncertainty of
Measurement – Part 3: Guide to the expression of
uncertainty in measurement (GUM). (Beuth,
Berlin)
Distortions of the DMA transfer function due to geometrical and flow pattern nonideality and gravity
E. Tamm and J. Uin
Laboratory of Environmental Physics, Institute of Physics, University of Tartu, Ülikooli 18, 50090, Tartu,
Estonia
Keywords: Aerosol instrumentation, DMA, Instrument development, Modelling, Transfer function.
The aim of this work was to investigate the
influences of non-ideal properties of the DMA and
also gravity on the transfer function (TF) of a DMA.
The probability for these effects occurring and the
magnitude of their influence increase with the increasing dimensions of the DMA and thus particle
size being used. The main motivation for this work
comes because of the very long DMA (active length
> 1m) that was built by this workgroup. With such
dimensions any non-idealities of the construction are
more clearly visible.
To investigate the possible effects that the
non-ideal geometrical properties of the DMA construction may have on the DMA TF, a series of computer simulations was conducted. As a base model,
the above-mentioned very long DMA was used with
specific construction and working parameters (i.e.
flow rates, voltage etc.). Mainly two problems were
investigated – first, the effect of shift between the
axes of the cylindrical DMA electrodes and second,
the effect of non-uniformly distributed aerosol flow
along the perimeter of the DMA inlet. Uniformity of
the sheath air along the perimeter is better guaranteed
by the construction.
To calculate the DMA TF, the space between
the electrodes was divided into vertical sections so
that the cross section of the outer was comprised of
sectors with equal central angles. The overall TF was
calculated as an average of TFs of individual sections. The limiting mobilities and TFs were calculated according to Tammet (1970) and Stolzenburg
(1988). This was possible because according to
Tammet, the general theory developed for cylindrical
aspiration capacitor is applicable to the sector of the
cylindrical capacitor as well as to the parallel-plate
capacitor. The flow rates in the section were taken to
be proportional to the area of its cross section. For
finding the capacitance of the section, the corresponding parts of the inner and outer electrode were
taken to form a parallel-plate capacitor. The nonuniform aerosol flow was roughly simulated by using
3 periods of a sine function (the DMA has 3 inlets for
aerosol flow).
The results of the calculations show that the
shift between the DMA cylinders has the effect of
widening and lowering the TF (Fig. 1). It can be seen
that the TF is already significantly lower with shifts
below 0.5 mm. With the increasing shift, the TF deteriorates even further with a second peak appearing
around 0.8 mm. The effect of the non-uniform aerosol flow is also to “soften” the TF, especially the
edges of the function while the peak area remains
practically unchanged. In such a case where both of
described non-idealities are present their effects
would combine, with the second one being much less
pronounced.
Figure 1. DMA transfer functions in case of different
shifts Δr = 0, 0.2, …, 1.4 mm between the axes of the
DMA cylindrical electrodes.
The calculations on the effects of gravity
show that in case of big particles (d ≥ 1 μm), when
particle settling velocity due to gravity is comparable
with its drift velocity in the electric field of the capacitor, the gravity causes shift of the TF in direction
of the bigger mobilities (smaller particles) conserving
its general shape (triangle). In case of the mentioned
very long DMA, the peak mobility of the TF will be
shifted up to 20% for particles with d = 10 μm.
This work was supported by Estonian Science Foundation grant No. 6988 and by the Estonian Research
Council Targeted Financing Project SF0180043s08.
Stolzenburg, M.R. (1988). An ultrafine aerosol size
distribution measuring system. PhD Thesis, University of Minnesota.
Tammet, H.(1970). The aspiration method for the determination of atmospheric ion-spectra. Israel Program for Scientific Translations, Jerusalem.
Best practices in European aerosol monitoring:
the EUSAAR ground-based observation network
P. Laj (1), S. Philippin (1), A. Wiedensohler (2), U. Baltensperger (3), G. de Leeuw (4, 5),
J.-P. Putaud (6), A.M. Fjaeraa (7), M. Fiebig (7), U. Platt (8)
(1) Laboratoire de Météorologie Physique, Université Blaise Pascal, FR-63177 Clermont-Ferrand, France
(2) Leibniz Institute for Tropospheric Research, DE-04318 Leipzig, Germany
(3) Laboratory of Atmospheric Chemistry, CH-5232 Paul Scherrer Institut, Villigen, Switzerland
(4) Netherlands Organisation for Applied Scientific Research, NL-2597 Den Haag, The Netherlands
(5) Finnish Meteorological Institute, FI-00014 Helsinki, Finnland
(6) Climate Change Unit, Joint Research Centre, IT-21020 Ispra, Italy
(7) Norwegian Institute for Air Research, NO-2027Kjeller, Norway
8) University of Heidelberg, DE-69120 Heidelberg, Germany
Keywords: In-situ measurements, Air quality network, Monitoring standard
The
EU-funded
project
EUSAAR
(EUropean Supersites for Atmospheric Aerosol
Research) aims at integrating measurements of
atmospheric aerosol properties from a distributed
network of 20 high-quality European ground-based
stations. The objective is to ensure harmonization,
validation and data diffusion of current
measurements of physical, chemical, and optical
properties being critical for quantifying the key
processes and the impact of aerosols on climate and
air quality. The achievements within the researchbased EUSAAR permit to improve the
comparability of measurements for data users and
to adopt best practices in aerosol monitoring
procedures.
evaluation, and quality control (Wiedensohler et al.,
2009); (2) HTDMAs (Hygroscopicity Tandem
Differential Mobility Analysers) coupled with a
standardized inversion scheme to ensure qualityassured measurements of water uptake of aerosol
particles (Duplissy et al., 2008 Gysel et al., 2009);
(3) Three different commercially available
integrating nephelometers with improved correction
mechanisms to account for the non-ideal
illumination due to truncation of the sensing
volumes and for non-Lambertian illumination from
the light sources (Müller et al., 2008); and (4)
Standardized procedures for improved thermaloptical discrimination between organic and
elemental carbon and for assessing and mitigating
major positive and negative biases of different
types of carbonaceous particulate matter
encountered across Europe (Putaud et al., 2008).
With an increasing number of measurement
sites and institutions involved in measuring aerosol
parameters, the need for technical standardization
and data harmonization of atmospheric aerosols has
become a key issue.
We acknowledge the support of the EC
under Contract N° RII3-CT-2006-026140.
Duplissy, J. et al. (2008). Intercomparison study of
six HTDMAs: results and general recommendations for
HTDMA operation, Atm. Meas. Tech. Disc., 1, 1-507.
Gysel, M. et al. (2009). Inversion of tandem
differential mobility analyser (TDMA) measurements, J.
Figure 1. Map of Europe with the distribution of all
EUSAAR ground-based stations.
Within the network, initiatives were taken to
publish recommendations for long-term and routine
measurements, operational data analysis, and data
structure for the newly developed aerosol
observation database EBAS related to the following
instruments / techniques: (1) Standard particle
mobility
size
spectrometers
(commercially
available and custom-made SMPS, DMPS), still
associated with large uncertainties due to lack of
generally accepted technical standards with respect
to instrumental set-up, measurement mode, data
Atm. Sci., 40, 2, 134-151.
Müller, T. et al. (2008). Performance Characteristics of three Different Integrating Nephelo-meters:
Angular Illumination, Empirical and Size-Based
Corrections, Atm. Sci. Tech., submitted.
Putaud, J.-P. et al. (2008). Toward a standardized
thermal-optical protocol for measuring atmospheric
organic and elemental carbon: The EUSAAR protocol,
Env. Sci. Tech., submitted.
Wiedensohler, A. et al. (2009). Particle Mobility Size
Spectrometers: Harmonization of Technical Standards
and Data Structure to Facilitate High Quality Long-term
Observations of Atmospheric Particle Size Distributions,
Atm. Meas. Tech., submitted.
Effect of size dispersion on the lattice parameters of two-dimensional particle arrays:
A possible uncertainty source in AFM size measurement of monodisperse particles
Katsuhiro Shirono and Kensei Ehara
National Institute of Advanced Industrial Science and Technology
Tsukuba, Ibaraki 305-8563, Japan
Keywords: size measurement, particle size, measurement errors, atomic force microscopy.
Atomic force microscopy (AFM) is a possible
candidate for an accurate method of sizing
monodisperse particles for developing nanoparticle
size standards (APEC ISTWG Project, 2006). In the
AFM method, monodisperse particles such as
polystyrene latex spheres are arranged in a twodimensional closed pack array on a solid surface, and
the average particle diameter is determined by
measuring the lattice parameter. A systematic bias in
the measurement may occur due to the size
dispersion of the particles, but this effect has not
been studied in detail so far. In the present study, a
theoretical simulation of particle arrangement in a
two dimensional array was carried out to investigate
this effect.
In the simulation, seventy-two particles
sampled randomly from a normal size distribution
with mean diameter 100 nm and a standard deviation
σ were placed onto a 2000 nm × 2000 nm area. The
values of σ were set at 0, 2, 4, and 8 nm. The Markov
chain Monte Carlo method was employed to
determine possible arrangements of the particles,
with assuming that the interparticle potential is given
by the sum of van der Waals potential and a hard
core repulsive potential. Simulation was carried out
more than five times for a specified value of σ.
Examples of particle arrangement obtained in
this way are shown in Figure 1. The ideal closed
packing is realized for σ = 0 nm, while a regular
periodic structure is barely discernible for σ = 8 nm.
In the intermediate cases of σ = 2 nm, and 4 nm, it is
seen that a local regularity is retained.
For each pair of two adjacent particles i and j,
the gap was calculated from
(1)
g ij = lij − ( Di + D j ) 2 ,
where lij is the distance between the centre of the
particles, and Di and Dj are the particle diameters. It
is found that except for the case of σ = 0 nm,
particles in approximately 75 to 80 % pairs are in
direct contact (i.e., gij = 0) irrespective of the value of
σ. Considering the finite resolution of AFM images,
we may assume that in practical AFM measurements
the mean particle diameter is determined from
D=
l ij
1,
(2)
∑
( g ij ≤ g )
∑
( g ij ≤ g )
where g represents a threshold gap indicating that
pairs with gij > g are excluded from measurement.
Figure 2 shows D as a function of g. Even
for g = 0, a bias in D is observed. This occurs
because larger particles have higher probability of
having adjacent particles in direct contact than
smaller particles. Because a sizing error in the order
of 0.5 % is considered not negligible in developing
particle size standards, the result shown in Figure 2
indicates that the size dispersion can be a nonnegligible uncertainty source in particle sizing by
AFM.
(a) σ = 0 nm
(b) σ = 2 nm
(c) σ = 4 nm
(d) σ = 8 nm
Figure 1. Typical two dimensional arrangements of
100 nm nearly-monodisperse particles with
(a) σ = 0 nm, (b) 2 nm, (c) 4 nm, and (d) 8 nm.
Figure 2. Average diameter D as a function of the
resolution limit g.
APEC ISTWG Project (2006), Interlaboratory
Comparison on Nanoparticle Size Characterization,
Report on measurement results.

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