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Design Sciences

Faculty of Engineering, LTH

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Measurement technology

We have a large set of measurement techniques for determining the physical and chemical properties of aerosol particles. Instruments are available for both online measurement and collection for later analysis:


Size distribution and concentration
Instruments are available to measure particle size distribution in air from about 5 nm to several hundred μm. The fastest instruments have time resolutions down to milliseconds. Among the more important technologies are several SMPS systems (scanning mobility particle sizers, size range 5-1000 nm, time resolution max about 1 minute), APS:s (aerodynamic particle sizers, size range 0.5-20 μm, time resolution of a few seconds), DMS (particles in the range 0.005-2.5 μm with time resolution down to 200 ms), droplet size distribution (0.5-1000 μm second level based on laser diffraction), optical particle counters and impactors for size-separated particulate collection on filters.

Chemical composition
The most advanced technology in the aerosol lab for online chemical aerosol analysis is aerosol mass spectrometry (AMS), which provides chemical composition for particles in the range of 50-1000 nm with time resolution of seconds. Instruments are also available for determination of elemental and organic carbon and salt fraction.

Mass
Particle mass can be measured both online and afterwards by weighing collected aerosol material. A standard technique for determining particle mass in real-time is TEOM (tapered element oscillating microbalance). The instruments can be combined with cyclones or impactors to measure particulate mass in a specific size range.

Water absorption (hygroscopicity, drip formation)
The ability of the particles to absorb water at different atmospheric pressures can be measured by an H-TDMA (for relative humidity up to about 90% and particles in the range of 10-300 nm) or CCN counters (for supersaturated air).

Density
Different methods exist for detection of particle density. Among other things, we have access to an APM (aerosol particle mass analyzer) that "weighs" the particles by balancing them between an electric field and centrifugal force.

Biological properties
We can detect biological particles based on their fluorescence using a BioTrak. Methods are also available for collecting particles on nutrient plates or in liquid for microbiological analysis. The Aerosol laboratory has a room for handling microbiological materials, including -80 ° C freezer, clean bench, centrifuge, autoclave and incubator.

Particle collection for later analysis
Aerosol particles collected on filters or in liquid, for example, can be analyzed by a wide range of techniques in the aerosol laboratory and with instruments located elsewhere. The collection method must be adapted to the type of analysis to be performed. We have equipment that allows well-controlled collection with high efficiency (airflows up to several cubic meters per minute), in different particle sizes (for example by impactors), on different types of filters or directly in liquid.

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