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| Titel |
Aerosol mass spectrometry: particle–vaporizer interactions and their consequences for the measurements |
| VerfasserIn |
F. Drewnick, J.-M. Diesch, P. Faber, S. Borrmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 9 ; Nr. 8, no. 9 (2015-09-18), S.3811-3830 |
| Datensatznummer |
250116580
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| Publikation (Nr.) |
 copernicus.org/amt-8-3811-2015.pdf |
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| Zusammenfassung |
The Aerodyne aerosol mass spectrometer (AMS) is a frequently used instrument
for on-line measurement of the ambient sub-micron aerosol composition. With
the help of calibrations and a number of assumptions on the flash
vaporization and electron impact ionization processes, this instrument
provides robust quantitative information on various non-refractory ambient
aerosol components. However, when measuring close to certain anthropogenic
or marine sources of semi-refractory aerosols, several of these assumptions
may not be met and measurement results might easily be incorrectly
interpreted if not carefully analyzed for unique ions, isotope patterns, and
potential slow vaporization associated with semi-refractory species.
Here we discuss various aspects of the interaction of aerosol particles with
the AMS tungsten vaporizer and the consequences for the measurement results:
semi-refractory components – i.e., components that vaporize but do not
flash-vaporize at the vaporizer and ionizer temperatures, like metal halides (e.g.,
chlorides, bromides or iodides of Al, Ba, Cd, Cu, Fe, Hg, K, Na, Pb, Sr, Zn)
– can be measured semi-quantitatively despite their relatively slow
vaporization from the vaporizer. Even though non-refractory components (e.g.,
NH4NO3 or (NH4)2SO4) vaporize quickly, under
certain conditions their differences in vaporization kinetics can result in
undesired biases in ion collection efficiency in thresholded measurements.
Chemical reactions with oxygen from the aerosol flow can have an influence
on the mass spectra for certain components (e.g., organic species). Finally,
chemical reactions of the aerosol with the vaporizer surface can result in
additional signals in the mass spectra (e.g., WO2Cl2-related
signals from particulate Cl) and in conditioning or contamination of the
vaporizer, with potential memory effects influencing the mass spectra of
subsequent measurements.
Laboratory experiments that investigate these particle–vaporizer
interactions are presented and are discussed together with field results,
showing that measurements of typical continental or urban aerosols are not
significantly affected, while measurements of semi-refractory aerosol in the
laboratory, close to anthropogenic sources or in marine environments, can be
biased by these effects. |
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