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| Titel |
Evaluation of the performance of a particle concentrator for online instrumentation |
| VerfasserIn |
S. Saarikoski, S. Carbone, M. J. Cubison, R. Hillamo, P. Keronen, C. Sioutas, D. R. Worsnop, J. L. Jimenez |
| 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 ; 7, no. 7 ; Nr. 7, no. 7 (2014-07-15), S.2121-2135 |
| Datensatznummer |
250115847
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| Publikation (Nr.) |
 copernicus.org/amt-7-2121-2014.pdf |
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| Zusammenfassung |
| The performance of the miniature Versatile Aerosol Concentration Enrichment
System (m-VACES; Geller et al., 2005) was investigated in laboratory and
field studies using online instruments. Laboratory tests focused on the
behavior of monodisperse ammonium sulfate (AS) or dioctyl sebacate (DOS)
particles in the m-VACES measured with the aerodynamic particle sizer (APS)
and scanning mobility particle sizer (SMPS). The ambient measurements were
conducted at an urban site in Helsinki, Finland, where the operation of the
m-VACES was explored in conjunction with a Soot Particle Aerosol Mass
Spectrometer (SP-AMS) in addition to the SMPS. In laboratory tests, the
growth of particles in water vapor produced a stable droplet size
distribution independent of the original particle size. However, when the
droplets were dried with the goal of measuring the original size
distribution, a shift to larger particles was observed for small particle
sizes (up to ~ 200 nm in mobility diameter). That growth was
probably caused by water-soluble organic compounds absorbed on the water
droplets from the gas phase, but not evaporated in the drying phase. In
ambient measurements, a similar enrichment was observed for nitrate and
sulfate in the m-VACES whereas the presence of acidic ambient particles
affected the enrichment of ammonium. Gaseous ammonia was likely to be
absorbed on acidic particles in the m-VACES, neutralizing the aerosol. For
organics, the enrichment efficiency was comparable with sulfate and nitrate
but a small positive artifact for hydrocarbons and nitrogen-containing
organic compounds was noticed. Ambient and concentrated organic aerosol (OA)
was analyzed further with positive matrix factorization (PMF). A
three-factor solution was chosen for both of the data sets but the factors
were slightly different for the ambient and concentrated OA, however, the
data set used for the PMF analysis was limited in size (3 days) and
therefore had substantial uncertainty. Overall, the operation of the m-VACES
was not found to lead to any severe sampling artifacts. The effect of
acidity could be an issue in locations where the aerosol is acidic, however,
in those cases the use of a denuder (which was not used in this study) is
recommended. Further ambient tests are needed for the characterization of the
m-VACES as the time period for the ambient measurements was only 5 days
in this study. Especially for OA additional tests are important as the
chemical properties of organics can differ widely depending on time and
location. |
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