Thermodenuder

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A thermodenuder is a device that strips off volatile particulate compounds off of aerosol particles in the airborne state. This allows to distinguish different classes of compounds, depending on their volatilisation temperature.

TROPOS has conducted particle size distribution measurements of non-volatile particle cores in a number of atmospheric observation sites since 2003.

Measurement principle

Segregated measurements of the volatile and non-volatile fractions of atmospheric aerosols have recently become increasingly important, partly because non-volatile carbonaceous particles might be linked to respiratory illness. Volatile material is defined as a material that is volatile below temperatures of 250°C, such as sulfate, nitrate, ammonium, and several volatile organic carbon compounds.

Non-volatile material is defined as the material that is only volatile above temperatures of 250°C, such as sea salt, crustal material, trace metals, fly ash, and carbonaceous compounds (e.g., soot). Carbonaceous material represents the dominant fraction of non-volatile submicrometer particles in anthropogenically influenced regions. Therefore, volatility measurements are needed to characterize the fraction of non-volatile carbon in particles.

References

Technical description of the thermodenuder

  • Wehner, B., S. Philippin, and A. Wiedensohler, Design and calibration of an improved thermodenuder to study the volatility fraction of aerosol particles, J. Aerosol Sci., 33, 1087-1093, 2002.

Mass balance of particles at 300°C, using illustrative AMS measurements

  • Poulain, L., Birmili, W., Canonaco, F., Crippa, M., Wu, Z. J., Nordmann, S., Spindler, G., Prévôt, A. S. H., Wiedensohler, A., and Herrmann, H.: Chemical mass balance of 300 °C non-volatile particles at the tropospheric research site Melpitz, Germany, Atmos. Chem. Phys., 14, 10145-10162, 2014. Download from ACP

Non-volatile particles in Augsburg, Germany

  • Birmili, W., Heinke, K., Pitz, M., Matschullat, J., Wiedensohler, A., Cyrys, J., Wichmann, H.-E., and Peters, A.: Particle number size distributions in urban air before and after volatilisation, Atmos. Chem. Phys., 10, 4643-4660, 2010. Download from ACP

Properties of newly formed particles at 300°C

  • Wehner, B., T. Petäjä, M. Boy, C. Engler, W. Bimili, T. Tuch, A. Wiedensohler, M. Kulmala: The contribution of sulfuric acid and non-volatile compounds on the growth of freshly formed atmospheric aerosols. Geophys. Res. Lett., 32, L17810, 2005.

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