Contact person: E. Swietlicki, A. Massling

NMR – Nordic Aerosol Project 2004-2006

DMPS/SMPS Intercomparison

Division of Nuclear Physics, Lund University, Lund, Sweden

@mail: Erik.Swietlicki@nuclear.lu.se, massling@tropos.de

General Information

Within the NMR project, an intercomparison of all continuously operated Differential/Scanning Mobility Particle Sizers (DMPS/SMPS) will be done.

The Lund University provides the equipment for a set up that can be applied to each system to generate defined particle number size distributions of monodisperse particles. The size and the number concentration of the generated particles should be determined with your DMPS/SMPS and results will be compared.

Please do not move your system, you can easily provide our set up in your lab where the system is located.

For the intercomparison it is crucial to make the set up as detailed as it is explained on the next slides.

Preparing the set-up

Things you have to prepare:Dry, particle and oilfree, pressurized air at 3 hPaDeionized waterA computer with a serial port

Things we have prepared:A program to log the CPC 3022A dilution chamberTwo nebulizers (both for spheres)Two needle valvesTwo three way valvesTwo filtersOne CPC 3022 (Condensation Particle Counter)Three small flasks containing latex spheres (Dp = 101nm, 277nm, and 420nm)

Additional information

It is recommended to do the following work before starting any measurements.

1. Be sure that your system is leaktide.

2. Be sure that your flows within the systems are calibrated nicely.

3. Be sure that the high voltage supply is calibrated.

4. Be sure that the relative humidity in the system is as low as possible (aerosol inlet RH before charger and sheath air RH).

• Please provide the set up exactly how it is shown in the sketch on the next slide. The set up is thought to investigate the sizing of your DMPS/SMPS system.

• Please use dry, particle and oilfree, pressurized air for the set up.

• The following flowrates should be adjusted:

• Nebulizer: 2.0 lpm

• Dilution air: 2.0 - 4.0 lpm

• CPC 3022: 2.0 lpm

• Please note: The dilution rate depends on the aerosol flowrate of your system since all other flows are defined. The dilution chamber must have slightly overpressure in comparison to atmosphere.

Preparing the set up (sizing experiment)

DMPS/SMPS intercomparison set up

Mixing Chamber

DMA

Micro-NebNebulizer

CPCCPC

Reference2.0 lpm

Pressurized Air

Supplied by Lund

PSL monodisperse particles

BipolarCharger

Drier

Your system operated at defined

flowrates

One inlet open toatmosphere

(additional inlets closed)

Needlevalve

Three wayvalve

Filter2.0 – 4.0 lpm

2.0 lpm

The intercomparison will include two different experiments comparing size and number concentration of particles measured by your DMPS/SMPS. The first experiment will give information about the sizing of your system. Please be sure that you also log the data of the CPC.

Experiment 1a (101nm spheres):Prepare a solution of four to eight droplets of 101nm latex spheres and 20ml of deionized water. Use the nebulizer to spray the particles. Measure the particle number size distribution with your DMPS/SMPS and log the data for at least four scans.

Run 1a:Sizing of 101nm latex spheres: You will see a high noise level below the particle number size distribution. You have to adjust the mixture (droplets of latex solution and deionized water) so that you can at least see the peak of the spheres around 101nm on top of the noisy distribution.

Measurement and preparation

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Dp in nm

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101nm spheres

Example: size calibration with latex spheres (Dp = 101nm)

This experiment is the same as the last one. This time you will investigate 277nm spheres with your DMPS/SMPS system. Please clean the nebulizer carefully with deionized water before you start Run 1b. Please be sure that you also log the data of the CPC 3022.

Experiment 1b (277nm spheres):Prepare a solution of four to eight droplets of 277nm spheres and 20ml of deionized water. Use the nebulizer to spray the particles. Measure the particle number size distribution with your DMPS/SMPS and log the data for at least four scans.

Run 1b:Sizing of 277nm latex spheres: You will see a small noise level below the particle number size distribution. You have to adjust the mixture (droplets of latex solution and deionized water) so that the signal to noise ratio is best. You should be able to identify the singly, doubly, and triply charged particles in the raw (non-inverted) particle distribution.

Measurement and preparation

Example: size calibration with latex spheres (Dp = 277nm)

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Dp in nm

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277nm spheres

This experiment is the same as the last one. This time you will investigate 420nm spheres with your DMPS/SMPS system. Please clean the nebulizer carefully with deionized water before you start Run 1c. Please be sure that you also log the data of the CPC 3022.

Experiment 1c (420nm spheres):Prepare a solution of four to eight droplets of 420nm spheres and 20ml of deionized water. Use the nebulizer to spray the particles. Measure the particle number size distribution with your DMPS/SMPS and log the data for at least four scans.

Run 1c:Sizing of 420nm latex spheres: You will see a small noise level below the particle number size distribution. You have to adjust the mixture (droplets of latex solution and deionized water) so that the signal to noise ratio is best. You should be able to identify the singly, doubly, and triply charged particles in the raw (non-inverted) particle distribution.

Measurement and preparation

Example: size calibration with latex spheres (Dp = 420nm)

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20

40

60

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100

0 100 200 300 400 500

Dp in nm

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420nm spheres

• Please provide the set up exactly how it is shown in the sketch on the next slide. The set up is thought to make a comparison of the measured number concentration of atmospheric particles between your system and the CPC 3022 with well-known efficiency.

• You can use the inlet system that is used for your continuous measurements also.

• Plug your inlet for atmospheric particles to the dilution chamber and close all inlet connections of the dilution chamber.

• Connect your DMPS/SMPS together with the CPC 3022 to the dilution chamber.

Preparing the set up (number concentration)

DMPS/SMPS intercomparison set up

Mixing Chamber

DMA

CPCCPC

Reference2.0 lpm

Supplied by Lund

BipolarCharger

Drier

c

Your system operated at defined

flowrates

Flowrate = DMPS/SMPS + CPC

Aerosol inlet for atmospheric

particles

All inlets closed

c

Your aerosol inlet

The following experiment will give information about the number concentration your system is measuring. Please be sure that you also log the data of the CPC.

Experiment 2:Measure the particle number size distribution with your DMPS/SMPS and log the data over a period of at least two days.

Run 2:A typical particle number size distribution is shown for atmospheric aerosols. The calculated total particle number after inversion should match the measured value of the CPC 3022 for periods when the particle number beyond the size range of your system and the CPC 3022 (7nm – 10μm) is negligible small.

Measurement and preparation

Please prepare two EXCEL files for each run. One file should contain the raw data giving the measured concentration for each mobility channel. The second file should contain the inverted particle number size distribution in dN/dlogdp.

Please provide the data format as shown in the example files.

Please provide one info file for the raw data (which corrections are already done?) and one info file for the inverted data (which corrections are finally done?).

Additionally, please fill in the provided excel sheet giving the system parameters like size range, scan time, etc.

So far, so good. Have fun with our fictive intercomparison DMPS/SMPS workshop!

Data format