TOPIC III "Aerosol Physics"

Study of the dynamic behaviour of hazardous semi-volatile multi-component aerosols and impact on workplace sampling (SEVOMEGA)

The aim of the project is to study the dynamics of gas-particle partitioning of SVOC workplace aerosols both theoretically and experimentally. Conventional off-line personal samplers are compared to reference direct-reading instruments and evaluated for measurement- and sampling errors. Building on the previous work of project FP0299, experiments are taken closer to actual workplace aerosols by focusing on polar compounds as well as mixtures of two or more substances. An important aspect of the project is the further development of aerosol generation and sampling systems coupled with the integration of mass spectrometric analysis of mixed aerosols.

Our previous studies showed that semi-volatile aerosols are highly dynamic and that it is difficult to accurately distinguish particles from vapours. Therefore, development of systems that can separate particles from vapours without sampling artefacts will be further pursued.

Scientists involved: George Dragan, Vesta Kohlmeier

Intercomparison of black carbon (BC) measurement devices

The international project deals with the intercomparison of different analysers and techniques to determine the black carbon (BC) content of combustion sources. The measurement campaign took place in 2017 at the Department of Atmospheric Chemistry at the Leibniz - Institut für Troposphärenforschung at Leipzig, Germany (contact Dr. Böge). Main focus was on the characterization of wheat straw exhaust gases in the aerosol aging chamber LEAK (Leipzig Aerosol Kammer). CMA participated with the BC measurement device Aethalometer (AE33, Magee scientific). The final report and publication is expected for 2018.

Scientists involved: Dr. Gert Jakobi

How does exhaust gas treatment affect the particle emission analysis at a wood pellet stove?

A project of the Oel-Wärme-Institute (OWI), Aachen, Germany, supported by the the AIF programme of the Federal Ministry of Economics and Energy was supported by our group with online- and offline-analytical equipment. Background for the campaign was the change in emission limit values in the Federal Immission Protection Ordinance (BImSchV) for exhaust particulate concentration. As filter sampling is no longer mandantory for emission documentation, new appropriate methods are to be developed and certified.

Online analytical techniques like electrical low pressure impactors, particle counters, mobility analysers and conventional filter samplers were used at various sampling sites along the emission line. To determine the new 20 mg m-3 threshold on the basis of identical gravimetry samples as for the old 150 mg m-3 analyses, sampling time has to be prolonged (113 min instead of 15 min) or sample volume increased (34 ltr min-1 instead of 4.5 ltr min-1) substantially.

Particle size distribution is mainly influenced by heating power level and fire control and, additionally, by the exhaust line conditions. During the start-up process (Fig 1), the system emits about 10 times higher particle concentration at almost all particle diameters than during the subsequent steady–state combustion. The analysis of the cross sectional temperature variation and the flow regime inside the emission tube (Fig 2) clearly shows the formation of flow threads in the hot part (Fig 2a) and the formation of stratified layers (Fig 2b) when the wall cools down; both should be known and taken into account when sampling from the exhaust line. A bend forms almost isotropic conditions in the pipe’s cross section by turbulence (Fig 2c).

The highly sensitive particle counters may be considered as an alternative method for future exhaust gas measurement. Another real-time method may be the Aethalometer which analyses carbon concentration by a similar principle as the traditional filter absorption method ("smoke number") and which is meanwhile available as a handheld instrument. Finally, a measurement procedure based on micro-cantilever vibration to analyse the mass concentration of nanoparticles in the surrounding air was found by literature search (Wasisto, H. S. et al., 2013).

Fig 1: Color contour plot (blue: low concentration; red: high concentration) of time (ordinate bottom to top) and particle size (abscissa left to right) during start and constant flame phase.

Fig 2: Cross sectional temperature profiles (a) at the outlet of the stove (left), (b) at 1.8 m Distance (center) and (c) after a 90° bend (right).

Scientists involved: Erwin Karg

Lung Deposition Model

The HPLDB Model of George A. Ferron is available to calculate the deposition of aerosol particles in different regions of the human lung,

In Preparation: Regional deposition in the lung of a rat

Disclaimer:

  • The software used here is developed and tested as a scientific computer model. It bases on the publications listed below
  • The calculated results are not readily and in all cases the real world
  • The Helmholtz Zentrum München does not guarantee the correctness of the calculation results and is not responsible for errors arising from using them
  • The calculated results are intended for scientific and private use only. Any commercial use is permitted only with the consent of the Helmholtz Zentrum München

References

  • Ferron, G. A., Upadhyay, S., Zimmermann, R. and Karg, E.: Model of the Deposition of Aerosol Particles in the Respiratory Tract of the Rat. II. Hygroscopic Particle Deposition. Journal of Aerosol Medicine and Pulmonary Drug Delivery 26, pp 101-119 (2013).  Read more at the publisher 
  • Schmid, O., Bolle, I., Harder, V., Karg, E., Takenaka, S., Schulz, H. and Ferron, G. A.: Model for the Deposition of Aerosol Particles in the Respiratory Tract of the Rat. I. Nonhygroscopic Particle Deposition. Journal of Aerosol Medicine and Pulmonary Drug Delivery 21, pp 291-308 (2008). Read more at the publisher
  • Ferron, G. A.: Aerosol properties and lung deposition. European Respiratory Journal7, pp 1392-1394 (1994). Read more at the publisher  
  • Ferron, G. A., Karg, E. and Peter, J. E.: Estimation of deposition of polydisperse hygroscopic aerosols in the human respiratory tract. Journal of Aerosol Science 24, pp 655-670 (1993). Read more at the publisher
  • Ferron, G. A., Kreyling, W. G. and Haider, B.: Inhalation of salt aerosol particles — II. Growth and deposition in the human respiratory tract. Journal of Aerosol Science 19, pp 611-631 (1988).   
    Read more at the publisher  
  • Ferron, G. A., Haider, B. and Kreyling, W. G.: Inhalation of salt aerosol particles — I. Estimation of the temperature and relative humidity of the air in the human upper airways. Journal of Aerosol Science 19, pp 343-363 (1988).  
    Read more at the publisher

 Scientists involved: Erwin Karg, George Ferron

Modeling the Evaporation of Semi-Volatile Particles

At the workplace numerous semi volatile organic compounds (SVOCs) are ubiquitously used as solvents, diluents or lubricants. They can be deliberately or unintendedly released in the workplace air, forming thereby an aerosol of both vapour- and particle-phase. When particles from SVOCs are dispersed in the ambient air they evaporate during transport and dilution depending on their temperature and vapour pressure (Karg, 2015). The lifetime of a SVOC particle depends on its size, composition and the thermodynamic properties of its components. Particle lifetime is a fundamental parameter with respect to workplace particle sampling and inhalation.

SVOCs are defined as organic material with a boiling point between 180 and 350 °C (EN 13936) forming thereby aerosols partitioned between particle- and vapor phases. Mass transport of SVOC particles is described by an equation derived from the first Law of Fick assuming quasi-stationary transport conditions (Fick, 1859; Fuchs, 1959). A particle containing a mixture of SVOCs obeys the Law of Raoult.

Within the Projects FP299 and FP371, granted by the German Social Accident Insurance, a computer program has been developed (Ferron, 1977; Ferron, 1989; Dragan, 2014) for alkane particles to serve as a model for SVOC aerosol particles. Please note: the model presented here neglects the effects by the evaporation heat, and the corrections for submicron particles such as the Kelvin effect (surface tension) and the Cunningham (or slip) correction.

Find here a computer model for the lifetime of particles consisting of a mixture of two alcanes.

Disclaimer

The software used here is developed and tested as a scientific computer model. It bases on the publications listed below.

The calculated results are not readily and in all cases the real world.

The Helmholtz Zentrum München does not guarantee the correctness of the calculation results and is not responsible for errors arising from using them.

The calculated results are intended for scientific and private use only. Any commercial use is permitted only with the consent of the Helmholtz Zentrum München.

References

Dragan, G.-C. ; Breuer, D. ; Blaskowitz, M. ; Karg, E.W. ; Schnelle-Kreis, J. ; Arteaga-Salas, J.M. ; Nordsieck, H. ; Zimmermann, R.: „An evaluation of the "GGP" personal samplers under semi-volatile aerosols: Sampling losses and their implication on occupational risk assessment.” Environ. Sci. Process Impacts 17, 270-277 (2015)Read more at the publisher

Dragan GC, Karg EW, Nordsieck H, Schnelle K, J., Breuer D, Arteaga-Salas JM, et al.: Short-term evaporation of semi-volatile N-alkane aerosol particles: Experimental and computational approach. Environ Eng Manag J. 2014;13(7):1775-85. Read more at the publisher

Ferron GA, Soderholm SC.: Estimation of the times for evaporation of pure water droplets and for stabilization of salt solution particles. J Aerosol Sci. 1990;21(3):415-29. Read more at the publisher

Ferron GA.: The size of soluble aerosol particles as a function of the humidity of the air. application to the human respiratory tract. J Aerosol Sci. 1977;8(A):251 - 67. Read more at the publisher

Fick A. Ueber Diffusion. Annalen der Physik (Leipzig). 1855;94:59-86.

Fuchs NA. Evaporation and droplet growth in gaseous media. (Edited by Bradley RS) Oxford: Pergamon Press, 1959

Karg, E.W. ; Dragan, G.-C. ; Ferron, G.A. ; Nordsieck, H. ; Blaskowitz, M. ; Friedrich, C. ; Kohlmeier, V. ; Moehlmann, C. ; Schnelle-Kreis, J. ; Stanglmaier, S. ; Zimmermann, R. ; Breuer, D.: „Dynamisches Verhalten von Aerosolen aus semivolatilen Komponenten.“ Gefahrstoffe Reinhalt. Luft 75, 265-274 (2015)Read more at the publisher

Scientists involved: Erwin Karg, George Ferron, George Dragan, Vesta Kohlmeier

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