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| Titel |
Characterization of aerosol photooxidation flow reactors: heterogeneous oxidation, secondary organic aerosol formation and cloud condensation nuclei activity measurements |
| VerfasserIn |
A. T. Lambe, A. T. Ahern, L. R. Williams, J. G. Slowik, J. P. S. Wong, J. P. D. Abbatt, W. H. Brune, N. L. Ng, J. P. Wright, D. R. Croasdale, D. R. Worsnop, P. Davidovits, 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 ; 4, no. 3 ; Nr. 4, no. 3 (2011-03-04), S.445-461 |
| Datensatznummer |
250001795
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| Publikation (Nr.) |
 copernicus.org/amt-4-445-2011.pdf |
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| Zusammenfassung |
| Motivated by the need to develop instrumental techniques for
characterizing organic aerosol aging, we report on the
performance of the Toronto Photo-Oxidation Tube (TPOT) and
Potential Aerosol Mass (PAM) flow tube reactors under
a variety of experimental conditions. The PAM system was designed with lower surface-area-to-volume (SA/V) ratio to
minimize wall effects; the TPOT reactor was designed
to study heterogeneous aerosol chemistry where wall loss can be independently measured. The following
studies were performed: (1) transmission efficiency
measurements for CO2, SO2, and bis(2-ethylhexyl)
sebacate (BES) particles, (2) H2SO4 yield
measurements from the oxidation of SO2, (3) residence
time distribution (RTD) measurements for CO2, SO2,
and BES particles, (4) aerosol mass spectra, O/C and H/C ratios, and cloud
condensation nuclei (CCN) activity measurements of BES
particles exposed to OH radicals, and (5) aerosol mass spectra, O/C and H/C ratios, CCN activity, and yield measurements of secondary
organic aerosol (SOA) generated from gas-phase OH oxidation of
m-xylene and α-pinene. OH exposures ranged from
(2.0 ± 1.0) × 1010 to (1.8 ± 0.3) × 1012 molec cm−3 s. Where applicable, data from the flow tube
reactors are compared with published results from the Caltech
smog chamber. The TPOT yielded narrower RTDs. However, its
transmission efficiency for SO2 was lower than that for
the PAM. Transmission efficiency for BES and H2SO4
particles was size-dependent and was similar for the two flow
tube designs. Oxidized BES particles had similar O/C and H/C ratios and CCN activity at OH exposures greater than
1011 molec cm−3 s, but different CCN activity at
lower OH exposures. The O/C ratio, H/C ratio, and yield of m-xylene and
α-pinene SOA was strongly affected by reactor design
and operating conditions, with wall interactions seemingly
having the strongest influence on SOA yield. At comparable OH
exposures, flow tube SOA was more oxidized than smog chamber
SOA, possibly because of faster gas-phase oxidation relative to particle
nucleation. SOA yields were lower in the TPOT than in the PAM,
but CCN activity of flow-tube-generated SOA particles was
similar. For comparable OH exposures, α-pinene SOA
yields were similar in the PAM and Caltech chambers, but
m-xylene SOA yields were much lower in the PAM compared to the
Caltech chamber. |
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