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| Titel |
Emissions of biogenic volatile organic compounds and subsequent photochemical production of secondary organic aerosol in mesocosm studies of temperate and tropical plant species |
| VerfasserIn |
K. P. Wyche, A. C. Ryan, C. N. Hewitt, M. R. Alfarra, G. McFiggans, T. Carr, P. S. Monks, K. L. Smallbone, G. Capes, J. F. Hamilton, T. A. M. Pugh, A. R. MacKenzie |
| 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 ; 14, no. 23 ; Nr. 14, no. 23 (2014-12-05), S.12781-12801 |
| Datensatznummer |
250119208
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| Publikation (Nr.) |
 copernicus.org/acp-14-12781-2014.pdf |
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| Zusammenfassung |
Silver birch (Betula pendula) and three Southeast Asian tropical
plant species (Ficus cyathistipula, Ficus benjamina and
Caryota millis) from the pantropical fig and palm genera were grown
in a purpose-built and environment-controlled whole-tree chamber. The
volatile organic compounds emitted from these trees were characterised and
fed into a linked photochemical reaction chamber where they underwent
photo-oxidation under a range of controlled conditions (relative humidity or RH ~65–89%,
volatile organic compound-to-NOx or VOC / NOx ~3–9 and NOx ~2 ppbV). Both
the gas phase and the aerosol phase of the reaction chamber were monitored in
detail using a comprehensive suite of on-line and off-line chemical and
physical measurement techniques.
Silver birch was found to be a high monoterpene and sesquiterpene but low
isoprene emitter, and its emissions were observed to produce measurable
amounts of secondary organic aerosol (SOA) via both nucleation and condensation onto pre-existing seed
aerosol (YSOA 26–39%). In contrast, all three tropical
species were found to be high isoprene emitters with trace emissions of
monoterpenes and sesquiterpenes. In tropical plant experiments without seed
aerosol there was no measurable SOA nucleation, but aerosol mass was shown to
increase when seed aerosol was present. Although principally isoprene
emitting, the aerosol mass produced from tropical fig was mostly consistent
(i.e. in 78 out of 120 aerosol mass calculations using plausible parameter
sets of various precursor specific yields) with condensation of
photo-oxidation products of the minor volatile organic compounds (VOCs) co-emitted; no significant aerosol
yield from condensation of isoprene oxidation products was required in the
interpretations of the experimental results. This finding is in line with
previous reports of organic aerosol loadings consistent with production from
minor biogenic VOCs co-emitted with isoprene in principally isoprene-emitting
landscapes in Southeast Asia. Moreover, in general the amount of aerosol mass
produced from the emissions of the principally isoprene-emitting plants was
less than would be expected from published single-VOC experiments, if
co-emitted species were solely responsible for the final SOA mass.
Interpretation of the results obtained from the fig data sets leaves room
for a potential role for isoprene in inhibiting SOA formation under certain
ambient atmospheric conditions, although instrumental and experimental
constraints impose a level of caution in the interpretation of the results.
Concomitant gas- and aerosol-phase composition measurements also provide a
detailed overview of numerous key oxidation mechanisms at work within the
systems studied, and their combined analysis provides insight into the nature
of the SOA formed. |
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