CLEEN's MMEA program organised an international seminar on cleaner air - Outdoor and indoor air quality together with Zhejiang University and assistant organizer Insigma group. This is one of the presentations in the seminar. More info in www.mmea.fi The cleantech field is expanding rapidly and Finnish companies are committed to working for a better environment in the fields of energy efficiency, air quality and monitoring. The world-class Cleantech know-how from Finland and the cooperation with Chinese partners and the results were highlighted in the MMEA seminar. Some of the leading Finnish cleantech companies together with Finnish and Chinese research institutions were present at the event. The seminars focused on cooperation between Finland and China concerning indoor and outdoor air quality and solutions to make them better.

1. Measuring megacity air
Miikka Dal Maso1, Anssi Järvinen1, Antti Rosted1, Jian
Gao2, Topi Rönkkö1
1Tampere University of Technology, Tampere, Finland
2CRAES, Beijing, China

2. Improving urban air quality – a challenge
on many fronts
2015 - Miikka Dal Maso
Understanding and improving urban air quality requires a holistic approach in
which all critical aspects are taken into account.
At TUT, our focus is measuring emissions and concentrations and
modeling transformation at high scientific quality.
6/10/2015
TUT FOCUS TUT FOCUS
Roadmap to Beautiful Beijing/Beautiful China
2

3. Challenges of measuring aerosol in
(mega)cities
Particle Diameter (nm)
1 10 100 1000
107
105
103
101
10000
Sulfuric Acid
Organic
Nitrate
Carbonaceous
Sulfate
Sea Sal
Mineral
2015 - Miikka Dal Maso
Urban PM, with multiple source components, also
exhibits high physical and chemical complexity
6/10/2015
Example of urban aerosol complexity:
Beijing size distribution data shows six
different typical size distributions.
Half the time, more than 50% of
particles are <50 nm.
Beijing
Particle size
Particlenumber(norm.)
Gao, Dal Maso et al, in prep.
3

4. TUT researches city aerosol on several
fronts
6/10/20152015 - Miikka Dal Maso
1. Targeted urban measurements 2. Instrument development
4. Process studies - modeling3. Fresh and aged emission
measurements
4

5. MMEA (Measurement, Monitoring and
Environmental Efficiency Assessment) aerosol
reseach environment
5
• Measurement methods, instrument
development
• Calibrations, field tests
• Emission studies
• Data intercomparisons
• Air quality studies
6/10/20152015 - Miikka Dal Maso

6. What is needed for urban aersol
measurement?
2015 - Miikka Dal Maso
Requirements for urban aerosol
physical characterization:
• small and large particles,
number and volume (mass)
• high time resolution
• high spatial density of
measurement sites – low price
• low maintenance
Understanding of physics and
chemistry, and sources
Gathering and analysis of
heterogeneous urban-scale
data
6/10/2015
Image: ENFUSER example
In urban areas, pollutants are not
distributed evenly, and concentrations
depend on source proximity
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7. China Testbed instrument: Pegasor PPS-
M sensor
6/10/20152015 - Miikka Dal Maso
Diffusion charger based aerosol
sensors (e.g. Pegasor PPS-M) are
good fit for presented requirements:
• Affordable, small, robust,
repeatable, easy to use
• potential for extracting size-
dependency information
• number and mass
• can cover wide size range
7

8. • Overview
– Diffusion charging
+ electrical detection
– Non-collective instrument
– Applications: Emissions,
air quality, portable systems...
• Components
– Pre-cut cyclone
– Ion source
– Charging region
– Ejector pump
– Mobility analyser
8
PPS-M sensor
Sample inlet
Sensor exhaust
Pressurized
air inlet
6/10/20152015 - Miikka Dal Maso

9. Calibration of PPS-M at TUT
2015 - Miikka Dal Maso 9
Aim of calibration is to find response function by particle size and
mobility analyser voltage
CPC is the reference
instrument which
has been calibrated
electrically
CPC is used
because neutral
particles are
preferred in charger
calibrations
Rostedt et al. 2014
Electrically neutral
particles
6/10/2015

10. Developed PPS-M response function
6/10/20152015 - Miikka Dal Maso
Overall response Polydisperse test
   Out p p pS R d N d dd 
Rostedt et al., 2014
Optimal size response for combustion
originating particles
Charging efficiency, mobility analyzer,
diffusion, inertial losses
         , , ,p ma ch p ma ma p ma d p i pR d V E d V P d V P d P d
10

11. Field measurements with PPS-M in
Finland
6/10/20152015 - Miikka Dal Maso
Number
concentration
PPS-M shows good correlations with PM2.5 in residential area and roadside,
and also good number correlations.
China testbed research question: Can we get more information?
Järvinen et al, 2014
PM2.5 Mass
concentration
11

12. Field measurements with PPS-M in China
6/10/20152015 - Miikka Dal Maso
Server in
China
Server in
Finland
Pressurized airDroplet separation
PPS
internal
heating
Insulation
Inlet heating
• PPS-M sensor installed at the CRAES
measurement station
• Continuous measurements from Feb-
Nov 2014
• Comparisons with long-term
observations of performed at CRAES
• Data logged locally and transferred via
network
• Data covers many different situations of
polluted urban air
Gao, Dal Maso et al.,
2015 (in prep)

13. PPS-M Number and Mass response in
highly polluted air
6/10/20152015 - Miikka Dal Maso
PPS-M response dependency on
mobility analyser voltage can be used
to gain information on the mass-
number relationship.
We have used measurements in
Beijing to test the mobility analyser in
real polluted megacity air.
Signal ratio
Mass/Numberratio
Reference
PPS-M fit w/
mobility analyser
voltage cycling
VolumeNumber
Gao, Dal Maso et al., 2015 (in prep)

14. Summary
• We need good concentration
measurements covering urban city
environment
• Diffusion charging based sensors such as
PPS-M fulfill many requirements for
sensors
• We have developed a sensor response
model for size and mobility analyzer
dependence which has been verified by
laboratory measurements
• In outdoor measurements in Finland and
China we could get both mass and number
information. Mobility analysis was added
for measurements in China
6/10/20152015 - Miikka Dal Maso 14

15. Thank you for your attention
6/10/20152015 - Miikka Dal Maso
1. Rostedt, A., Arffman, A., Janka, K., Yli-Ojanperä, J. &
Keskinen, J. (2014) Characterization and Response
Model of the PPS-M Aerosol Sensor, Aerosol Science and
Technology, 48(10), p. 1022-1030, DOI:
10.1080/02786826.2014.951023
2. Järvinen A., Kuuluvainen H., Niemi J.V., Saari S., Dal Maso
M., Pirjola L., Hillamo R., Janka K., Keskinen J., Rönkkö T.
(2014). Monitoring urban air quality with a diffusion charger
based electrical particle sensor, Urban Climate 10,
doi:10.1016/j.uclim.2014.10.002
3. Gao, J,., Järvinen, A., Hui, L., Luo, D., Rönkkö, T., and Dal
Maso, M. (2015): Urban air quality measurements in
Beijing using a diffusion charger based electrical particle
sensor, in preparation
References
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