 |
| Titel |
Comparison of different real time VOC measurement techniques in a ponderosa pine forest |
| VerfasserIn |
L. Kaser, T. Karl, R. Schnitzhofer, M. Graus, I. S. Herdlinger-Blatt, J. P. DiGangi, B. Sive, A. Turnipseed, R. S. Hornbrook, W. Zheng, F. M. Flocke, A. Guenther, F. N. Keutsch, E. Apel, A. Hansel |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 13, no. 5 ; Nr. 13, no. 5 (2013-03-11), S.2893-2906 |
| Datensatznummer |
250018488
|
| Publikation (Nr.) |
 copernicus.org/acp-13-2893-2013.pdf |
|
|
|
|
|
| Zusammenfassung |
| Volatile organic compound (VOC) mixing ratios measured by five independent
instruments are compared at a forested site dominated by ponderosa pine
(Pinus Ponderosa) during the BEACHON-ROCS field study in summer 2010. The instruments
included a Proton Transfer Reaction Time of Flight Mass Spectrometer
(PTR-TOF-MS), a Proton Transfer Reaction Quadrupole Mass Spectrometer
(PTR-MS), a Fast Online Gas-Chromatograph coupled to a Mass Spectrometer
(GC/MS; TOGA), a Thermal Dissociation Chemical Ionization Mass Spectrometer
(PAN-CIMS) and a Fiber Laser-Induced Fluorescence Instrument (FILIF). The
species discussed in this comparison include the most important biogenic
VOCs and a selected suite of oxygenated VOCs that are thought to dominate
the VOC reactivity at this particular site as well as typical anthropogenic
VOCs that showed low mixing ratios at this site. Good agreement was observed
for methanol, the sum of the oxygenated hemiterpene 2-methyl-3-buten-2-ol
(MBO) and the hemiterpene isoprene, acetaldehyde, the sum of acetone and
propanal, benzene and the sum of methyl ethyl ketone (MEK) and butanal.
Measurements of the above VOCs conducted by different instruments agree
within 20%. The ability to differentiate the presence of toluene and
cymene by PTR-TOF-MS is tested based on a comparison with GC-MS
measurements, suggesting a study-average relative contribution of 74% for
toluene and 26% for cymene. Similarly, 2-hydroxy-2-methylpropanal (HMPR)
is found to interfere with the sum of methyl vinyl ketone and methacrolein
(MVK + MAC) using PTR-(TOF)-MS at this site. A study-average relative
contribution of 85% for MVK + MAC and 15% for HMPR was determined. The
sum of monoterpenes measured by PTR-MS and PTR-TOF-MS was generally
20–25% higher than the sum of speciated monoterpenes measured by TOGA, which
included α-pinene, β-pinene, camphene, carene, myrcene,
limonene, cineole as well as other terpenes. However, this difference is
consistent throughout the study, and likely points to an offset in
calibration, rather than a difference in the ability to measure the sum of
terpenes. The contribution of isoprene relative to MBO inferred from PTR-MS
and PTR-TOF-MS was smaller than 12% while GC-MS data suggested an
average of 21% of isoprene relative to MBO. This comparison demonstrates
that the current capability of VOC measurements to account for OH reactivity
associated with the measured VOCs is within 20%. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|