1. SMPS

2. Inhalt Atmosphärisches Aerosol Messgeräte: SMPS, DMA & CPC,
DMPS, PM10 oh je oh je
Datenauswertung
Ausblick: FOX
I will start with a short outline
I will first give an introduction….

3. Atmosphärisches Aerosol
I will start with a short outline
I will first give an introduction….

5. Atmosphärisches Aerosol
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant

6. Aerosole
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant

7. Wie gross sind Aerosole?

8. Typical Aerosol Particle Size Ranges
Cloud droplets:
~ µm
Fog droplets:
~ µm
From Friedlander: Smoke, Dust and Haze

9. Grössenverteilung
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant

11. Geographische Variation
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant

12. Messinstrumente SMPS, DMA & CPC, DMPS, PM10 oh je oh je
I will start with a short outline
I will first give an introduction….

13. In-situ Grössen & Anzahlmessung
How do we measure particle number and particle size ?
Following techniques have been used to count particles in the past:
microscope (particles collected on a plate)
picture (cloud chamber)
single particle in a continuous flow (most popular in situ aerosol instrument )
Link for
Aerosol Measurement - Principles, Techniques, and Applications (2nd Edition) Edited by: Baron, Paul A.; Willeke, Klaus © 2001 John Wiley & Sons
In-situ: man misst wo die Partikel sind
Ex-situ: man misst von ausserhalb (z.B. Radar)

14. 1. Anzahl: Condensation Particle Counter
Important instruments in aerosol technology are Condensation Particle Counters (CPC).
They are used to measure the particle number concentration down to the nanometer size range.
The particles are enlarged due to supersaturation and a subsequent condensation of a condensable gas (normally Butanol, now also water!). The particles reach a size at which they can be optically detected.
The number concentration is measured for all particle larger than the lower detection diameter.

15. 1. Anzahl: Condensation Particle Counter
CPCs are used to measure the number concentration in the submicrometer size range.
The lower detection diameter is determined by:
the Kelvin diameter (supersaturation)
diffusion coefficient of the condensable gas
the particle material
The upper and lower detection limits are specific for each CPC type.

16. 1.Continuous Flow CPC
Modern CPCs operate with continuous aerosol flows and are able to count each single particle.
Model TSI 3010, 3760, 3762,…:
Principal: continuous flow, single particle counting
Lower detection Buthanol: 10 nm (Model 3025: 3 nm,)
diameter: Water CPC: 5nm
Upper detection
diameter: ca. 3000nm
Concentration
range: ,000 cm-3 (Model 3025: cm-3)
Accuracy: 10% compared to a reference instrument
Aerosol flow: 1.0 l/min

17. 1. Schematic sketch of the CPC models TSI 3010 (also 3760, 3762)
Functioning:
The aerosol flow is saturated with butanol in a slightly heated saturator.
The the temperature of the butanol-aerosol mixture is decreased by 17-27°C in the condenser of the CPC.
Here, the butanol become supersaturated and condenses onto the particles.
The particles grow to droplets of several µm in diameter.
The droplet flow is focused in a nozzle and introduced into a counting optic.
The droplets pass a laser beam, and each single particle creates a light pulse.
Pulses with an amplitude above a certain threshold are counted.
The particle number concentration can be calculated by knowing the aerosol flow rate.

18. 1. Functioning
The aerosol flow is saturated with butanol in a slightly heated saturator.
The the temperature of the butanol-aerosol mixture is decreased by 17-27°C in the condenser of the CPC.
Here, the butanol become supersaturated and condenses onto the particles.
The particles grow to droplets of several µm in diameter.
The droplet flow is focused in a nozzle and introduced into a counting optic.
The droplets pass a laser beam, and each single particle creates a light pulse.
Pulses with an amplitude above a certain threshold are counted.
The particle number concentration can be calculated by knowing the aerosol flow rate
(critical orifice).

19. 1. CPC Data
Teamviewer:
8814

20. Wie misst man die Grösse eines Aerosols?
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant
Unser Massband:
Differential Mobility Analyser

21. Was ist die Grösse eines Aerosols?
Apfel: Durchmesser
Soot: ???
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant

22. Was ist die Grösse eines Aerosols?
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant
Partikel mit gleicher electrical mobility

23. Was ist die Grösse eines Aerosols?
APS
SMPS
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant
Partikel mit gleicher electrical mobility

24. 2. Particle Size - Differential Mobility Analyzer

25. 2.1 Electric Mobility
Electrically charged particles move in an electric field according to their electrical mobility.
The electrical mobility ZP of a particle with a certain electric charge is defined to (given in [cm2/Vs]):
With ve derived analog to the sedimentation velocity
The electrical mobility depends mainly on the particle size and electrical charge.
The smaller the particle the higher is the electrical mobility.
The higher the electrical charge the higher is the electrical mobility.
n = number of charges
e = elementary charge
B = particle mobility (“velocity per unit force”)

26. 2. 2 Funktionsweise Assumption:
All particles carry only one electrical charge.
The electrical mobility is than only a function of the particle size in case of constant temperature and pressure.
Example:
An electrically charged polydisperse aerosol is led through a plate capacitor.
Electrically charged particles are separated and deposited according their size.

27. 2. Particle Size - Differential Mobility Analyzer
Plate mobility analyzer:
aerosol d
sheath air

28. 2.3 Theory of a plate mobility analyzer:
 The most simple mobility analyzer is a plate capacitor.
A laminar particle-free sheath air flow Qsh is led through the capacitor (x-direction). An electric field is put between the plates (z-direction).
The aerosol flow QA (x-direction) is fed into the capacitor close to one plate.  
The total volume flow is 
The particle velocity in x-direction is given to:
The particle velocity in z-direction is defined to:

29.   
with
w = width of the capacitor
d = distance between plates
The electrical mobility for a certain deposition place is given to:
The voltage to select a certain mobility can be calculated by:

30. 2.4 Theory of cylindrical mobility analyzer:

31. 2.4 Theory of cylindrical mobility analyzer:
Folie neu drucken
2.4 Theory of cylindrical mobility analyzer:  :
The theory is analogous to the plate capacitor. The total flow is given to: 
The particle velocity in x-direction is given to: 
The radial velocity due to the electric field is described to: 
with 

32.  
The electrical mobility for a certain deposition place is given to:
The voltage to select a certain electrical mobility incl. the electrical mobility from Stokes‘ law can be calculated to: 
The particle size for a certain deposition place and voltage cannot be analytically solved:

33. 2. Differential Mobility Analyzer
The voltage to select a certain electrical mobility incl. the electrical mobility from Stokes‘ law can be calculated to:
e = elemental charge 1,602·10-19 As
n = number of charges
The particle size for a certain deposition place is:
∆DP= 1 nm or DP =10nm ± 0.5nm

34. 2. Differential Mobility Analyzer
Aerosol particles can be classified due to their electrical mobility in a DMA.
A small volume flow Qs with particles of a defined mobility is taken out of the DMA through a slit at the end of the inner rod.  
The mean mobility of these particles can be calculated to:
The ideal width of the mobility bin is described to:
for 
QA=QS and QA =1/10 QSh

35. 2. Differential Mobility Analyzer
Example:
DP= 10 nm
with ZP = cm/Vs and ∆ ZP = 4.156·10-3 cm/Vs
∆DP= 1 nm or DP =10nm ± 0.5nm
the size resolution is excellent!
The size resolution depends mainly on the ratio of the volume flow rates QA/QSh.
The greater the ratio, the better becomes the size resolution.  

36. 2. 5 Transfer function
The transfer probability over the mobility bin is not unity.
The DMA-transfer function depends on the particle size and sample flow ratio.  
Example: QA= Qs
The transfer function has the form of a symmetric triangle.
The transfer probability of the mean electrical mobility is unity.
The transfer probability of the upper and lower limit of the mobility bin is Zero.
For QA>QS und QA<QS, the transfer function becomes asymmetric. This cases are not discussed, because they are not the standard applications.

37. 2. 5 Transfer function
Ideal transfer function:

38. 2. 5 Transfer function Real transfer function:
In reality, the DMA transfer function depends also on the DMA-design.
The transfer function becomes a function of the particle diameter.
The reasons are:
Diffusion broadening for ultrafine particles
Particle losses in the aerosol inlet and outlet of the DMA.
The transfer function becomes broader and the maximum transfer probability decreases. 

39. 2.6 Generator for Monodisperse Particles
The DMA can select a quasi monodisperse aerosol from a polydisperse aerosol population.
A generator for monodisperse aerosol particles consists of:
a polydisperse aerosol generator (atomizer, tube furnace)
a bipolar diffusion charger
a DMA 
The monodisperse aerosol with the size DP1 can however contain larger particles with the same electrical mobility carrying more elementary charge units.
Example:
DP1 = 100 nm (singly charged)
DP2 = 152 nm (doubly charged)
DP3 = 196 nm (triply charged)

40. 3. DMA + CPC How do we measure particle number and particle size ?
Link for
Aerosol Measurement - Principles, Techniques, and Applications (2nd Edition) Edited by: Baron, Paul A.; Willeke, Klaus © 2001 John Wiley & Sons
How do we measure particle number and particle size ?
Combination of DMA+CPC (most common application
for atmospheric measurements)

41. Electrical Mobility Spectrometer
The DMA can be used to measure the number size distribution of a polydisperse aerosol.
There exist two different principles:
1. The voltage is increased stepwise (DMPS)
2.The voltage is continuously increased (SMPS)
A electrical mobility spectrometer consists of:
a bipolar diffusion charger
a DMA
a CPC

42. Electrical Mobility Spectrometer
A electrical mobility spectrometer can measure a size distribution only for a certain size range.
This size range depends on the DMA-geometry and the sheath air flow rate.
Longer DMA  larger particle diameter
Higher sheath air flow rate  smaller particle diameter

43. Computer inversion routine:
The computer inversion routine calculates the number size distribution out of the mobility distribution.
For a complete inversion routine must be known:
The mobility distribution
The bipolar charge distribution
The size dependent DMA transfer function
The CPC detection efficiency curve

44. Differential Mobility Particle Sizer (DMPS)
A pre-impactor removes all particles larger than the upper diameter of the size range to be measured
The particles are brought in the bipolar charge equilibrium in the bipolar diffusion charger.
A computer program sets stepwise the voltage for each selected mobility bin.
After a certain waiting time, the CPC measures the number concentration for each mobility bin.
The result is a mobility distribution.
The number size distribution must be calculated from the mobility distribution by a computer inversion routine.

45. Scanning Mobility Particle Sizer (SMPS)
The design of the system is identical to the DMPS.
The difference lies in the measurement principle.
The voltage is continuously increased.
There is no waiting time any longer.
The particle concentration is measured as function of time.
The relationship between electrical mobility and time (time between DMA entrance and CPC detection) must be determined for each SMPS system.
The results is again a mobility distribution.
The number size distribution must be calculated from the mobility distribution by a computer inversion routine.

46. Scanning Mobility Particle Sizer (SMPS)
Teamviewer
2272

47. Messinstrumente SMPS, CPC & DMA, DMPS & PM10 ist jetzt klar?
I will start with a short outline
I will first give an introduction….

48. Datenauswertung I will start with a short outline
I will first give an introduction….

49. Scanning Mobility Particle Sizer (SMPS)
Output:
APS
Average
config
Contour
diagnostics
integral
Inverted
Raw
raw long

50. Particle Size Distributions

51. Particle Size Distributions

52. Particle Size Distributions

53. Area, Volume-Mass Distributions
Heterogeneous and multiphase reaction rates depend on surface area or volume, respectively.
Gravitational settling rates depend on mass and air quality standards are mass-based.
Assuming spherical geometry and dDp0
dS(Dp) = Dp2n(Dp)dDp
dV(Dp) = (/6)Dp3n(Dp)dDp

54. Typical Number Distribution for Urban Aerosols
Solid line: what would be observed, composed of 3 modes
Dotted/Dashed lines: Two common parameterizations
Junge Distribution (dashed line) is a power law. Has some useful properties but requires care.
Log-Normal distribution (dotted line) is most often used (see Pruppacher-Klett, chapter for mathematical formulation)

55. Ausblick: FOX I will start with a short outline
I will first give an introduction….

56. Why are we interested in fog?
Aerosol-cloud interaction is poorly known, especially the anthropogenic effect
In our group we do modelling & lab experiments, but it is essentiel that we also measure in the field (comparison to modelled data & lab data)
So the goal of my talk today will be to convince you that measuring in the fog layer in could indeed help to increase our understanding of the anthropogenic role in the aerosol-cloud interaction
Indirect effect of aerosols on climate poorly known – especially the anthropogenic effect

57. Fog in Switzerland Zürich From Jordi 2004
In Wintertimes a persitent low stratus layer can form above the swiss midlands as you can see on this satelite picture
From Jordi 2004

58. Fog in Switzerland Droplets: 5-20mm (Wanner, 1979) Droplets
Image: courtesy of Hanna Herich (adapted)
Droplets: 5-20mm (Wanner, 1979)
Having a closer look to fog: it consists of droplets and interstital aerosols
Droplets can only form due to the presence of aerosols that serve as condensation nuclei (cloud residuals)
-> Fog is „static“
WHY DID I SAY THAT THIS IS A GOOD SYSTEM TO MEASURE ANTHROPOGENIC EFFECTS?
Why is this such an interesting topic to study
Aerosols needed for cloud formation have natural and anthropogenic sources.
By measuring aerosol properties and cloud droplets one can get new inside knowlegde into
Aerosol cloud interaction and the anthropogenic effect on this system
Droplets
Total aerosol
Cloud residuals Interstitial aerosols

59. ? ? Fog in Switzerland Weekly & Daily cycle Industrial snow
Image: courtesy of Hanna Herich (adapted)
Droplets: 5-20mm (Wanner, 1979)
Droplets:
Diurnal / weekly cycle in the droplet concentration?
Total aerosol:
Physical properties CCN activation
Cloud residuals:
Anthropogenic markers
(metals & carbon) ? ?
So coming back to the fog layer,
I will be interested in 3 different things:
Droplets
Physical properties of the total aerosol
Weekly & Daily cycle Industrial snow

60. FOg Characterisation EXperiment
Image: courtesy of Hanna Herich (adapted)
Droplets: 5-20mm (Wanner, 1979)
Droplets:
Diurnal / weekly cycle in the droplet concentration?
Fog Monitor
Total aerosol:
Physical properties CCN activation
SMPS & CCNC
Cloud residuals:
Anthropogenic markers
(metals & carbon)
CVI /Massspectrometer ? ?
How to measure
Weekly & Daily cycle Industrial snow
Additional: PM1, PM10 & gas phase measurements, anemometer (wind), ceilometer

61. Fog in Switzerland
We needed to find an appropriate location where we can measure inside the fog
Using frequency maps from Bachman and Bendix
Satellite observations: distribution & frequency maps (Bachman & Bendix, 1993; Jordi, 2004)

62. FOX garbage incineration plant AMSL
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
Anthropogenic effect: highway and incineration plant
Criteria
-Fog
-Emissions
-reachable
-Power supply

63. Our Trailer CVI inlet: cloud residuals Total Inlet: CVI Dryer
Mass Condensation
Spectrometer Particle
(chemical Counter
Analysis)
Total
Inlet:
Scanning Cloud
Mobility Condensation
Particle Nuclei
Sizer Counter
(Aerosol size
distribution)
Dryer
CVI
Dryer
- The chosen location will be closed to the lake of Zuerich on the „Albis-ridge“
- 735 above mean sey level
- Anthropogenic effect: highway and incineration plant
Droplet measurements:
Fog Monitor

64. I will start with a short outline
I will first give an introduction….

65. Measuring Aerosols: Part 1: How do we measure particle number?
I will start with a short outline
I will first give an introduction….

66. How do we measure particle number?
Following techniques have been used to count particles in the past:
microscope (particles collected on a plate)
picture (cloud chamber)
single particle in a continuous flow (most popular in situ aerosol instrument )
Link for
Aerosol Measurement - Principles, Techniques, and Applications (2nd Edition) Edited by: Baron, Paul A.; Willeke, Klaus © 2001 John Wiley & Sons

67. Condensation Particle Counter…
... Is an important instruments in aerosol
technology
…Is used to measure the particle number
concentration down to the nanometer
size range
Detection in 2 steps:
1. The particles are enlarged due to
supersaturation and a subsequent
condensation of a condensable gas
2. The particles reach a size at which they
can be optically detected.

68. Schematic sketch of the CPC models TSI 3010 (also 3760, 3762)
Functioning:
The aerosol flow is saturated with butanol in a slightly heated saturator.
The the temperature of the butanol-aerosol mixture is decreased by 17-27°C in the condenser of the CPC.
Here, the butanol become supersaturated and condenses onto the particles.
The particles grow to droplets of several µm in diameter.
The droplet flow is focused in a nozzle and introduced into a counting optic.
The droplets pass a laser beam, and each single particle creates a light pulse.
Pulses with an amplitude above a certain threshold are counted.
The particle number concentration can be calculated by knowing the aerosol flow rate.

69. 1. Functioning
The aerosol flow is saturated with butanol in a slightly heated saturator.
The the temperature of the butanol-aerosol mixture is decreased by 17-27°C in the condenser of the CPC.
Here, the butanol become supersaturated and condenses onto the particles.
The particles grow to droplets of several µm in diameter.
The droplet flow is focused in a nozzle and introduced into a counting optic.
The droplets pass a laser beam, and each single particle creates a light pulse.
Pulses with an amplitude above a certain threshold are counted.
The particle number concentration can be calculated by knowing the aerosol flow rate
(critical orifice).

70. CPC - facts
Modern CPCs operate with continuous aerosol flows and are able to count each single particle.
Model TSI 3010, 3760, 3762,…:
Principal: continuous flow, single particle counting
Lower detection Buthanol: 10 nm (Model 3025: 3 nm,)
diameter: Water CPC: 5nm
Upper detection
diameter: ca. 3000nm
Concentration
range: ,000 cm-3 (Model 3025: cm-3)
Accuracy: 10% compared to a reference instrument
Aerosol flow: 1.0 l/min

71. CPC: detection limits The lower detection diameter is determined by:
the Kelvin diameter (supersaturation)
diffusion coefficient of the condensable gas
the particle material
The upper and lower detection limits are specific for each CPC type.

72. I will start with a short outline
I will first give an introduction….

73. 1. CPC Data
Teamviewer:
8814

74. A.2 Aerodynamic Particle Sizer (APS)
The APS measures the aerodynamic particle diameter and can thus determine the aerodynamic particle size distribution.
Aerodynamic diameter:
The aerodynamic particle diameter is defined as:
„Diameter of a spherical particle with the density of One and the same sedimentation velocity of the measured particle".
 = dynamic shape factor
0 = 1g/cm3, e.g. water
The Stokes-Diameter and the Aerodynamic Diameter are so-called equivalent diameters.

75. Specification of the APS:
The APS determines the aerodynamic number size distribution with a high time resolution.
The aerodynamic particle size range of the APS model TSI is between 0.5 and 20 µm.
Solid and non-volatile particles can be measured.

76. Schematic of the APS:
Acceleration nozzle:
The acceleration nozzle consists of an inner and out nozzle.
The inner nozzle focuses the aerosol flow. The aerosol flow is then surrounded by the sheath air flow.
The entire flow is then accelerated through the outer nozzle.
The total flow rate of 5 l/min consists of 1 l/min aerosol flow and 4 l/min particle-free sheath air.
The velocity of the aerosol flow in the center is assumed to be constant.
Due to inertia, particles with a large aerodynamic diameter cannot follow the acceleration.
This means that particle with different aerodynamic diameters have different velocities directly behind the nozzle (calibrated instrument !).
The laser anemometer measures the time-of-flight between two laser beams.
Laser anemometer
The laser beams are positioned directly behind the outer nozzle.
Particles passing the laser beams emit two light pulses.
The time difference between the two pulse maxima is the time-of-flight.
The time-of-flight is a measure for the aerodynamic particle diameter.
The relation between time-of-flight and aerodynamic particle size must be calibrated for each device.
The main part of the APS are the acceleration nozzle and the laser anemometer.

77. Acceleration nozzle:
The acceleration nozzle consists of an inner and out nozzle.
The inner nozzle focuses the aerosol flow. The aerosol flow is then surrounded by the sheath air flow.
The entire flow is then accelerated through the outer nozzle.
The total flow rate of 5 l/min consists of 1 l/min aerosol flow and 4 l/min particle-free sheath air.
The velocity of the aerosol flow in the center is assumed to be constant.
Due to inertia, particles with a large aerodynamic diameter cannot follow the acceleration.
This means that particle with different aerodynamic diameters have different velocities directly behind the nozzle (calibrated instrument !).

78. Laser anemometer:
The laser anemometer measures the time-of-flight between two laser beams.
The laser beams are positioned directly behind the outer nozzle.
Particles passing the laser beams emit two light pulses.
The time difference between the two pulse maxima is the time-of-flight.
The time-of-flight is a measure for the aerodynamic particle diameter.
The relation between time-of-flight and aerodynamic particle size must be calibrated for each device.

79. Optical measurements:
Beside the determination of the aerodynamic particle size, the signal can also be taken to determine the optical diameter (see also Optical Particle Counter OPC).
Each particle is classified in relation to the refractive index of latex spheres.

81. B.3 Applications of DMPS-Systems
B.3.1 Twin Differential Mobility Particle Sizer (TDMPS)
A combination of two electrical mobility spectrometers allows to measure the size distribution of the entire submicrometer size range.

82. B.3.2 Tandem Differential Mobility Analyzer (TDMA)
A TDMA is a system where two DMAs are applied in series.
A TDMA can measure the mixing state of a defined particle size in terms of a certain aerosol parameter.
The first DMA selects a monodisperse aerosol out of the entire aerosol population.
The monodisperse aerosol is modified in a conditioner
The new size spectrum is determined with the second DMA
Applications:
Bipolar charge distribution
Hygroscopicity
Volatility

83. Hygroscopicity-Tandem-Differential-Mobility-Analyzer (HTDMA)

84. Examples of HTDMA measurement
Particle
Number
Concentration
1/cm3
Particle Diameter (nm) 1 10
100
1000
107
105
103
101
10000
Sulfuric Acid
Organic
Nitrate
Carbonaceous
Sulfate
Sea Salt
Mineral
Wet Dp
Dry Dp
Elevated RH