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| Titel |
Source identification and budget analysis on elevated levels of formaldehyde within the ship plumes: a ship-plume photochemical/dynamic model analysis |
| VerfasserIn |
C. H. Song, H. S. Kim, R. Glasow, P. Brimblecombe, J. Kim, R. J. Park, J. H. Woo, Y. H. Kim |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 10, no. 23 ; Nr. 10, no. 23 (2010-12-15), S.11969-11985 |
| Datensatznummer |
250008964
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| Publikation (Nr.) |
 copernicus.org/acp-10-11969-2010.pdf |
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| Zusammenfassung |
| Elevated levels of formaldehyde (HCHO) along the ship corridors have been
observed by satellite sensors, such as ESA/ERS-2 GOME (Global Ozone
Monitoring Experiment), and were also simulated by global 3-D
chemistry-transport models. In this study, three likely sources of the
elevated HCHO levels in the ship plumes as well as their contributions to
the elevated HCHO levels (budget) were investigated using a newly-developed
ship-plume photochemical/dynamic model: (1) primary HCHO emission from
ships; (2) secondary HCHO production via the atmospheric oxidation of
non-methane volatile organic compounds (NMVOCs) emitted from ships; and (3)
atmospheric oxidation of CH4 within the ship plumes. For this
ship-plume modelling study, the ITCT 2K2 (Intercontinental Transport and
Chemical Transformation 2002) ship-plume experiment, which was carried out
about 100 km off the coast of California on 8 May 2002 (11:00 local
standard time), was chosen as a base study case because it is the best
defined in terms of (1) meteorological data, (2) in-plume chemical
composition, and (3) background chemical composition. From multiple
ship-plume model simulations for the ITCT 2K2 ship-plume experiment case,
CH4 oxidation by elevated levels of in-plume OH radicals was found to
be the main factor responsible for the elevated levels of HCHO in the ITCT
2K2 ship-plume. More than ~88% of the HCHO for the ITCT 2K2
ship-plume is produced by this atmospheric chemical process, except in the
areas close to the ship stacks where the main source of the elevated HCHO
levels would be primary HCHO from the ships (due to the deactivation of
CH4 oxidation from the depletion of in-plume OH radicals). Because of
active CH4 oxidation by OH radicals, the instantaneous chemical
lifetime of CH4 (τCH4) decreased to ~0.45 yr inside the ship
plume, which is in contrast to τCH4 of ~1.1 yr in the background
(up to ~41% decrease) for the ITCT 2K2 ship-plume case. A variety
of likely ship-plume situations at three different latitudinal locations
within the global ship corridors was also studied to determine the
enhancements in the HCHO levels in the marine boundary layer (MBL)
influenced by ship emissions. It was found that the ship-plume HCHO levels
could be 19.9–424.9 pptv higher than the background HCHO levels depending on
the latitudinal locations of the ship plumes (i.e., intensity of solar
radiation and temperature), MBL stability and NOx emission rates. On
the other hand, NMVOC emissions from ships were not found to be a primary
source of photochemical HCHO production inside ship plumes due to their
rapid and individual dilution. However, the diluted NMVOCs would contribute
to the HCHO productions in the background air. |
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