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| Titel |
Organic particle types by single-particle measurements using a time-of-flight aerosol mass spectrometer coupled with a light scattering module |
| VerfasserIn |
S. Liu, L. M. Russell, D. T. Sueper, T. B. Onasch |
| 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 ; 6, no. 2 ; Nr. 6, no. 2 (2013-02-01), S.187-197 |
| Datensatznummer |
250017380
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| Publikation (Nr.) |
 copernicus.org/amt-6-187-2013.pdf |
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| Zusammenfassung |
| Chemical and physical properties of individual ambient aerosol particles can
vary greatly, so measuring the chemical composition at the single-particle
level is essential for understanding atmospheric sources and transformations.
Here we describe 46 days of single-particle measurements of atmospheric
particles using a time-of-flight aerosol mass spectrometer coupled with a
light scattering module (LS-ToF-AMS). The light scattering module optically
detects particles larger than 180 nm vacuum aerodynamic diameter (130 nm
geometric diameter) before they arrive at the chemical mass spectrometer and
then triggers the saving of single-particle mass spectra. 271 641 particles
were detected and sampled during 237 h of sampling in single-particle mode.
By comparing timing of the predicted chemical ion signals from the light
scattering measurement with the measured chemical ion signals by the mass
spectrometer for each particle, particle types were classified and their
number fractions determined as follows: prompt vaporization (46%), delayed vaporization
(6%), and null (48%), where null was operationally
defined as less than 6 ions per particle. Prompt and delayed vaporization
particles with sufficient chemical information (i.e., more than 40 ions per
particle) were clustered based on similarity of organic mass spectra (using
k-means algorithm) to result in three major clusters: highly oxidized
particles (dominated by m/z 44), relatively less oxidized particles
(dominated by m/z 43), and particles associated with fresh urban
emissions. Each of the three organic clusters had limited chemical properties
of other clusters, suggesting that all of the sampled organic particle types
were internally mixed to some degree; however, the internal mixing was never
uniform and distinct particle types existed throughout the study.
Furthermore, the single-particle mass spectra and time series of these
clusters agreed well with mass-based components identified (using factor
analysis) from simultaneous ensemble-averaged measurements, supporting the
connection between ensemble-based factors and atmospheric particle sources
and processes. Measurements in this study illustrate that LS-ToF-AMS provides
unique information about organic particle types by number as well as mass. |
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