A Thermophoretic Precipitator for the Representative Collection of Atmospheric Ultrafine Particles for Microscopic Analysis |
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| Authors: | R Lorenzo R Kaegi R Gehrig L Scherrer B Grobéty H Burtscher |
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| Affiliation: | 1. Empa, Materials Science &2. Technology, Laboratory for Air Pollution &3. Environmental Technology , Dübendorf, Switzerland;4. Institute for Mineralogy and Petrography , University of Fribourg , Fribourg, Switzerland;5. Eawag, Swiss Federal Institute for Aquatic Science and Technology, Urban Water Management , Dübendorf, Switzerland;6. Environmental Technology , Dübendorf, Switzerland;7. ETH Zürich, Solid State Physics , Zürich, Switzerland;8. Institute for Mineralogy and Petrography , University of Fribourg , Fribourg, Switzerland;9. Institute for Aerosol and Sensor Technology , University for Applied Sciences of Northwestern Switzerland , Windisch, Switzerland |
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| Abstract: | In this article, the potential of a thermophoretic sampling device to derive quantitative particle size distributions and number concentrations of aerosols based on microscopic single particle analysis is explored. For that purpose a plate-to-plate thermophoretic precipitator to collect ultrafine atmospheric particles for TEM (transmission electron microscopy) analysis has been calibrated and characterized. The representativeness of the samples has been verified in a series of experiments. Results show that, for particles with diameters of 15 nm to 300 nm, the precipitator's collection efficiency is independent of size, shape, and composition of the particles. Hence, its samples accurately represent the original aerosol. A numerical model of thermophoretic deposition within the device has been developed and tailored to the specifications of the precipitator. The model has been used to derive the particle number density and size distribution of several calibration aerosols using the TEM analysis of the samples taken with the thermophoretic precipitator as input parameters. The results agree very well with the on-line measurements of the calibration aerosols. This work demonstrates that our thermophoretic sampling device can be used to derive quantitative particle size distributions and number concentrations of ultrafine particles based on microscopic single particle analysis. |
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