Supplemental Information
Intercomparisons of mobility size spectrometers and condensation particle counters
in the frame of the Spanish atmospheric observational aerosol network
Francisco J. Gómez-Moreno1,*, Elisabeth Alonso1, Begoña Artíñano1, Vanesa JuncalBello2, Silvia Iglesias-Samitier2, María Piñeiro Iglesias2, Purificación López Mahía2,
Noemí Pérez3, Jorge Pey3#, Anna Ripoll3, Andrés Alastuey3, Benito A. De La Morena4, M.
Isabel García5,6, Sergio Rodríguez5, Mar Sorribas7,8, Gloria Titos7,8, Hassan Lyamani7,8,
Lucas Alados-Arboledas7,8, Enrique Latorre9, Torsten Tritscher10, Oliver F. Bischof10
1
Department of Environment, CIEMAT, Madrid, Spain
Grupo Química Analítica Aplicada, Instituto Universitario de Medio Ambiente (IUMA),
Departamento de Química Analítica, Facultade de Ciencias, Universidade da Coruña, A
Coruña, Spain
3
Institute of Environmental Assessment and Water Research (IDAEA-CSIC), Barcelona,
Spain
4
Atmospheric Sounding Station 'El Arenosillo', INTA, Mazagón-Huelva, Spain
5
Izaña Atmospheric Research Centre, (IARC/CIAI), AEMet, Santa Cruz de Tenerife, Spain
6
Department of Analytical Chemistry, Nutrition and Food Science, University of La
Laguna, Spain
7
Andalusian Institute for Earth System Research, IISTA-CEAMA, University of Granada,
Granada, Spain
8
Applied Physics Department, University of Granada, Granada, Spain
9
Álava Ingenieros, Madrid, Spain
10
TSI GmbH, Aachen, Germany
2
-----------------------------------------------------------------*Corresponding author: CIEMAT, Av. Complutense 40, E-28040 Madrid, Spain.
E-mail: fj.gomez@ciemat.es
#Current address: Laboratory of Environmental Chemistry LCE-IRA, Aix Marseille
University, Marseille, France
January 2015
S1. CPC intercomparisons
During the 2010 intercomparison campaign, five different models of particle counters were
compared. Ambient air was sampled during 14 hours and the results are shown in Figure
S1, presenting the total particle concentration measured as a function of time and the
deviation of each counter from the mean value. Particle concentration was low until
midnight when there was a change in wind direction, increasing the particle levels in the
measurement site from 2000 to 14000 cm-3. During both periods, the TSI-CPC-2B
(3025A), TSI-CPC-2A (3775) and TSI-CPC-5 (3776) measured similar concentrations, the
TSI-CPC-4 (3010) the lowest and the TSI-CPC-3 (3785) the highest. For the TSI-CPC-4
(3010), the difference compared with the TSI-CPC-2A (3775) was -4% during the first
period and -11% during the second period. One main difference between this CPC and the
other CPC models that also use butanol as their working fluid is the lower detection limit
(Hermann et al., 2007). The other three CPCs have a particle size detection limit of around
3 nm, while the model CPC 3010 can only detect particles 10 nm and larger. If the share of
nucleation mode particles below 10 nm increases, this CPC model will report a lower
number concentration. It should also be pointed out that the CPC 3010 is suitable for
monitoring concentrations up to 10,000 particles/cm3. Although it can measure above this
value, the coincidence error begins to get very important. When there was a high
concentration in the nucleation mode, bigger differences between measurements with
different CPC models were observed. In the first period, there was a typical nocturnal
distribution at the site, with very few particles below 10 nm and relatively low
concentration, so differences were small. When the wind direction changed and there was
particle transport from a nearby industrial area, higher concentrations for particles in the
nucleation mode were reached. The corresponding concentrations were above the
coincidence limit for the CPC 3010. In summary, both the less sensitive lower size limit
and the upper concentration limit were the likely reasons for the larger differences during
this last period. The TSI-CPC-3 (3785), which has a 5 nm detection limit, measured
between 10-12% more than the TSI-CPC-2A (3775). The higher concentration measured
only during the second period with air transported from the industrial area, could be
explained by the lower accuracy of the photometric mode calibration for this water-based
CPC. This has since been addressed in the replacement model WCPC (TSI, model 3787) by
the manufacturer, which no longer requires a photometric mode but is still able to detect
concentrations up to 250,000 cm-3.
CPC-2A (3775)
CPC-2B (3025)
CPC-3 (3785)
CPC-4 (3010)
CPC-5 (3776)
-3
Particle number concentration (cm )
16000
14000
12000
10000
8000
6000
4000
2000
0
16:00
04:00
23/04/2010
22:00
22/04/2010
Figure S1a.
Difference with the mean value (%)
20
15
CPC-2A (3775)
CPC-2B (3025)
CPC-3 (3785)
CPC-4 (3010)
CPC-5 (3776)
10
5
0
-5
-10
-15
-20
16:20
20:30
22/04/2010
0:40
04:50
23/04/2010
Figure S1b
Figure S1. CPC intercomparison during the 2010 campaign (a) particle concentration
measurements, (b) difference between each counter and the mean value during the
measurements
During the 2012 intercomparison these procedures were repeated with the counters
available (TSI-CPC-1, TSI-CPC-2A, TSI-CPC-2B, TSI-CPC-3, TSI-CPC-5A and TSICPC-5B, corresponding to 3772, 3775, 3025A, 3785, and two 3776 models). All the
instruments were connected to the external sampling line using tubes with identical length.
Atmospheric aerosol was sampled for 18 hours and the results are shown in Figure S2.
There were two clear groups of measurements, above and below the average value. The
first group consisted of those CPC models that make use of a photometric mode (CPC
models 3775 and 3785). The second group corresponds to those counters with lower
particle size detection limits down to 3 nm. As these CPCs are able to measure a wider
range of sizes, they should measure the same or higher particle concentration, which was
not the case. It is not clear what causes the differences. Some problems in the photometric
mode or in the internal flow issues (especially for the CPC 3776) could contribute with a
slight drift. No problems were observed with the zero level which could explain these
differences.
The TSI-UFPM-3031 was also compared with a TSI-CPC-5A (3776) during this campaign
and the main results obtained can be found in Figure S2c. Three important factors must be
taken into account, the fact that the UFPM is not actually a single particle count instrument,
the different lower size limits and the different kernel matrixes used in the UFPM. The
measurement time had three different periods where two different kernel matrices were
applied. The environmental matrix was used during periods 1 and 3 and the ammonium
sulfate matrix during period 2. During periods 1 and 3 with the environmental matrix
applied, the UFPM frequently measured higher concentrations than the CPC. During period
2 with the ammonium sulfate matrix used, the UFPM measured concentrations below the
TSI-CPC-5A (3776). This seems to indicate that this last matrix might be better suited
under the conditions present during our measurements. Due to the limited number of
measurements further research is needed to better estimate the influence of the kernel
matrix on the particle concentrations measured.
20000
CPC-1 (3772)
CPC-2A (3775)
CPC-2B (3025)
CPC-3 (3785)
CPC-5A (3776)
CPC-5B (3776)
-3
Particle concentration (cm )
18000
16000
14000
12000
10000
8000
6000
4000
2000
0
13:15
19:05
12/11/2012
Figure S2a
0:55
06:45
13/11/2012
CPC-1 (3772)
CPC-2A (3775)
CPC-2B (3025)
CPC-3 (3785)
CPC-5A (3776)
CPC-5B (3776)
Difference with the mean value (%)
60
50
40
30
20
10
0
-10
-20
-30
-40
13:15
19:05
12/11/2012
06:45
13/11/2012
0:55
Environmental Matrix
15000
(NH4)2SO4 Matrix
20000
CPC-5A (3776)
UFP
Environmental Matrix
-3
Particle number concentration (cm )
Figure S2b
10000
Period 1
5000
08:00
09:00
Period 2
10:00
11:00
Period 3
12:00
Time
Figure S2c
Figure S2. CPC and UFPM intercomparison during the 2012 campaign (a) CPC particle
concentration measurements, (b) difference between each counter and the mean value
during the measurements (c) CPC and UFPM concentration measurements
S2. SMPS intercomparison
During the 2010 campaign, the complete SMPS systems were installed after checking of
the CPC behavior. The initial idea was to perform the size distribution measurements using
the same flow rates that every instrument uses at its regular location. Nevertheless, the use
of different flow rates results in different losses for the smallest particles, as diffusion
losses are a function of the particles’ residence time inside the instrument and in the
sampling lines. For this reason the diffusion correction factor in the software (TSI, model
AIM 3936) was selected, as well as the multiple charge correction (Reineking and
Porstendörfer, 1986; Wiedensohler, 1988). No correction was applied for possible
differences in particle losses in the sampling lines. For accumulation mode particles, the
losses must be very similar for all the flow rates used during the comparison. There were
several groups of flow rates during the campaign: (a) three instruments used 0.3 lpm for the
aerosol flow, which correspond to the low flow rate of CPC models 3775 and 3776; (b) an
instrument used 0.6 lpm, which corresponds to the inlet flow of the CPC 3010; (c) and two
instruments used 1 lpm, which corresponds to the inlet flow of CPC models 3772 and 3785.
In all cases, the ratio between the aerosol and the sheath flows in the DMAs was 1:10.
The measurements obtained with three SMPS systems using CPC models 3775 (TSISMPS-2), 3010 (TSI-SMPS-4) and 3776 (TSI-SMPS-5) as their detectors are shown in
Figure S3. All of them used a Nafion dryer for the sample flow and a Nafion or a diffusion
dryer in the sheath flow. The measurements were carried out for almost two days (41 hours)
and during this time air masses of different origins, and hence different types of particles
(Sorribas et al., 2011), reached the sampling point, as was also seen in the meteorological
data measured in situ. In this figure an example of two different particle size distributions
measured is shown. In Figure S3a, only particles in the accumulation mode were observed,
while in Figure S3b a change in the air mass had taken place and a nucleation mode also
appeared. These different size distributions are very interesting for this intercomparison
because particles belonging to each mode have different properties. In both graphs the
particle size corresponding to the modes were very similar in the three instruments. In the
case of the accumulation mode, TSI-SMPS-2 and TSI-SMPS-4 measured almost
indistinguishable particle number concentrations while TSI-SMPS-5 reported slightly lower
values, probably due to losses in the total system. In the case of the nucleation mode
(Figure S3b), the situation is different. TSI-SMPS-2 and TSI-SMPS-5 measured the same
particle concentrations while the TSI-SMPS-4 measured higher values for the nucleation
mode. A possible explanation is that TSI-SMPS-2 and TSI-SMPS-5 worked with aerosol to
sheath flow ratios of 0.3 to 3, while the TSI-SMPS-4 worked with a ratio of 0.6 to 6 by
means of a flow equalizer. In this latter case the higher aerosol flow produces lower losses
in the entire sampling line, so that the measured particle number concentration is also
higher for the smaller sizes that are most affected by diffusion losses (Karlsson and
Martinsson, 2003). At any rate, the concentrations measured were within the +/- 10%
tolerance band and only for the smallest particles they were slightly above this tolerance for
TSI-SMPS-4. TSI-SMPS-3 was later compared with TSI-SMPS-2 and very good results
were obtained, measuring the same diameters and very similar concentrations that were
distinctly within the +/- 10% tolerance.
12000
SMPS-2
SMPS-4
SMPS-5
Average
Average +/-10%
21/04/2010 7:00h
-3
dN/dLog Dp (cm )
10000
8000
6000
4000
2000
0
10
100
1000
Dp (nm)
Figure S3a
21/04/2010 11:00h
SMPS-2
SMPS-4
SMPS-5
Average
Average+/-10%
4000
-3
dN/dLog Dp (cm )
5000
3000
2000
1000
0
10
100
1000
Dp (nm)
Figure S3b
Figure S3. Particle size distributions measured by the SMPSs during the 2010 campaign
During the 2011 intercomparison, the SMPS systems available were the instruments
designated as 1, 2, 3 and 5. It was observed that the TSI-SMPS-1 measured in a similar way
as the other instruments for the smaller particle sizes, but significantly different above 7080 nm, showing lower values of concentration. The reason for this deviation could be the
high-voltage source (Wiedensohler et al., 2012) as the sheath flow was kept constant over
time. This case reinforces the necessity of checking the high voltage during the routine
maintenance. An example of the results obtained with the other three instruments can be
found in Figure S4, where average measurements from 22:00 to 24:00 on October 6, 2011
are shown. The concentrations measured were similar except for the mode of the
distribution, where differences exceeded 10%. Such deviation was larger than the
differences previously observed among the CPCs. These maximum occurred around 100
nm, so diffusion losses in the sampling lines caused by different aerosol flow rates were
discarded as a possible reason.
The TSI-UFPM was also compared with the SMPS systems. The comparison with TSISMPS-5 for four selected times is shown in Figure S4b. The SMPS data were average over
the size bins used in the UFPM (20-30, 30-50, 50-70, 70-100 and 200-450 nm) for
comparison. The kernel matrix used during the measurement was the one for ammonium
sulfate. During most of the time, the shapes of the size distribution were similar in both
instruments, showing the maximum at the same diameter, although the concentrations
measured by the TSI-UFPM were higher. Only for the biggest diameters the concentrations
in the SMPS were above those measured by the UFPM. This seems contradictory to the
comparison with the CPCs when the UFPM measured lower concentrations, but the CPCs
could reach smaller sizes than the UFPM. This is likely due to the fact that the UFPM uses
a unipolar corona charger rather than a bipolar aerosol neutralizer. The diffusion charger
used in the UFPM delivers a mean charge level per particle that is proportional to its
diameter for the size range from 10 to 100 nm (Kaufman et al., 2002), but slightly flattens
out above 100 nm which leads to a higher uncertainty in the reported concentrations of an
electrometer detector for larger particles.
3500
SMPS-2
SMPS-3
SMPS-5
Average
Average +/-10%
2500
-3
dN/dLog Dp (cm )
3000
2000
1500
1000
500
0
10
100
Dp (nm)
Figure S4a
1000
5/10/2012 13:00GMT
SMPS-5
UFP
8000
5/10/2012 21:00GMT
SMPS-5
UFP
6000
-3
dN/dLog Dp (cm )
-3
dN/dLog Dp (cm )
4000
4000
2000
3000
2000
1000
0
0
100
100
Dp (nm)
Dp (nm)
Figure S4b1
7000
6/10/2012 5:00GMT
Figure S4b2
SMPS-5
UFP
25000
SMPS-5
UFP
6/10/2012 11:00GMT
20000
-3
dN/dLog Dp (cm )
-3
dN/dLog Dp (cm )
6000
5000
4000
3000
15000
10000
2000
5000
1000
0
0
100
100
Dp (nm)
Dp (nm)
Figure S4b3
Figure S4b4
Figure S4. Particle size distributions measured by the SMPSs and UFPM during the 2011
campaign
S3. Particle deposition in the dryers
SMPS-B
Flow splitter
Air
Common dryer
Test dryer
SMPS-A
Figure S5. Set-up used during the particle deposition study on dryers
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