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| Titel |
Instrument intercomparison of glyoxal, methyl glyoxal and NO2 under simulated atmospheric conditions |
| VerfasserIn |
R. Thalman, M. T. Baeza-Romero, S. M. Ball, E. Borrás, M. J. S. Daniels, I. C. A. Goodall, S. B. Henry, T. Karl, F. N. Keutsch, S. Kim, J. Mak, P. S. Monks, A. Muñoz, J. Orlando, S. Peppe, A. R. Rickard, M. Ródenas, P. Sanchez, R. Seco, L. Su, G. Tyndall, M. Vázquez, T. Vera, E. Waxman, R. Volkamer |
| 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. 4 ; Nr. 8, no. 4 (2015-04-23), S.1835-1862 |
| Datensatznummer |
250116303
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| Publikation (Nr.) |
 copernicus.org/amt-8-1835-2015.pdf |
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| Zusammenfassung |
| The α-dicarbonyl compounds glyoxal (CHOCHO) and methyl glyoxal
(CH3C(O)CHO) are produced in the atmosphere by the oxidation of
hydrocarbons and emitted directly from pyrogenic sources. Measurements of
ambient concentrations inform about the rate of hydrocarbon oxidation,
oxidative capacity, and secondary organic aerosol (SOA) formation. We
present results from a comprehensive instrument comparison effort at two
simulation chamber facilities in the US and Europe that included nine
instruments, and seven different measurement techniques: broadband cavity
enhanced absorption spectroscopy (BBCEAS), cavity-enhanced differential
optical absorption spectroscopy (CE-DOAS), white-cell DOAS, Fourier
transform infrared spectroscopy (FTIR, two separate instruments), laser-induced
phosphorescence (LIP), solid-phase micro extraction (SPME), and
proton transfer reaction mass spectrometry (PTR-ToF-MS, two separate
instruments; for methyl glyoxal only because no significant response was
observed for glyoxal). Experiments at the National Center for Atmospheric
Research (NCAR) compare three independent sources of calibration as a function
of temperature (293–330 K). Calibrations from absorption cross-section
spectra at UV-visible and IR wavelengths are found to agree within 2% for
glyoxal, and 4% for methyl glyoxal at all temperatures; further
calibrations based on ion–molecule rate constant calculations agreed within
5% for methyl glyoxal at all temperatures. At the European Photoreactor
(EUPHORE) all measurements are calibrated from the same UV-visible spectra
(either directly or indirectly), thus minimizing potential systematic bias.
We find excellent linearity under idealized conditions (pure glyoxal or
methyl glyoxal, R2 > 0.96), and in complex gas mixtures
characteristic of dry photochemical smog systems (o-xylene/NOx and
isoprene/NOx, R2 > 0.95; R2 ∼ 0.65
for offline SPME measurements of methyl glyoxal). The correlations are more
variable in humid ambient air mixtures (RH > 45%) for methyl
glyoxal (0.58 < R2 < 0.68) than for glyoxal (0.79 < R2 < 0.99). The intercepts of correlations were
insignificant for the most part (below the instruments' experimentally
determined detection limits); slopes further varied by less than 5% for
instruments that could also simultaneously measure NO2. For glyoxal and
methyl glyoxal the slopes varied by less than 12 and 17% (both
3-σ) between direct absorption techniques (i.e., calibration from
knowledge of the absorption cross section). We find a larger variability
among in situ techniques that employ external calibration sources (75–90%,
3-σ), and/or techniques that employ offline analysis. Our
intercomparison reveals existing differences in reports about precision and
detection limits in the literature, and enables comparison on a common basis
by observing a common air mass. Finally, we evaluate the influence of
interfering species (e.g., NO2, O3 and H2O) of relevance in
field and laboratory applications. Techniques now exist to conduct fast and
accurate measurements of glyoxal at ambient concentrations, and methyl
glyoxal under simulated conditions. However, techniques to measure methyl
glyoxal at ambient concentrations remain a challenge, and would be
desirable. |
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