Measuring megacity air by Miikka Dal Maso and Craes
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Transcript of Measuring megacity air by Miikka Dal Maso and Craes
Measuring megacity air
Miikka Dal Maso1, Anssi Järvinen1, Antti Rosted1, Jian Gao2, Topi Rönkkö1
1Tampere University of Technology, Tampere, Finland2CRAES, Beijing, China
04/15/2023 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.
TUT FOCUS TUT FOCUS
Roadmap to Beautiful Beijing/Beautiful China
04/15/2023 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 Salt
Mineral
2015 - Miikka Dal Maso
Urban PM, with multiple source components, also exhibits high physical and chemical complexity
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
Pa
rtic
le n
um
be
r (n
orm
.)
Gao, Dal Maso et al, in prep.
04/15/2023 4
TUT researches city aerosol on several fronts
2015 - Miikka Dal Maso
1. Targeted urban measurements 2. Instrument development
4. Process studies - modeling3. Fresh and aged emissionmeasurements
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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
2015 - 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
04/15/2023
Image: ENFUSER example
In urban areas, pollutants are not distributed evenly, and concentrations depend on source proximity
04/15/2023 7
China Testbed instrument: Pegasor PPS-M sensor
2015 - 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
04/15/2023
• 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
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PPS-M sensor
Sample inlet
Sensor exhaust
Pressurizedair inlet
2015 - Miikka Dal Maso
04/15/2023
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
04/15/2023 10
Developed PPS-M response function
2015 - Miikka Dal Maso
Overall response Polydisperse test
Out p p pS R d N d dd
Rostedt et al., 2014Optimal 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
04/15/2023 11
Field measurements with PPS-M in Finland
2015 - 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
04/15/2023
Field measurements with PPS-M in China
2015 - 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)
04/15/2023
PPS-M Number and Mass response in highly polluted air
2015 - 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
Mas
s/N
umbe
r ra
tio
Reference
PPS-M fit w/ mobility analyservoltage cycling
Vo
lum
eN
um
ber
Gao, Dal Maso et al., 2015 (in prep)
04/15/2023 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
2015 - Miikka Dal Maso
04/15/2023 15
Thank you for your attention
2015 - 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