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| Titel |
Seasonal measurements of total OH reactivity emission rates from Norway spruce in 2011 |
| VerfasserIn |
A. C. Nölscher, E. Bourtsoukidis, B. Bonn, J. Kesselmeier, J. Lelieveld  , J. Williams |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 6 ; Nr. 10, no. 6 (2013-06-26), S.4241-4257 |
| Datensatznummer |
250018310
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| Publikation (Nr.) |
 copernicus.org/bg-10-4241-2013.pdf |
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| Zusammenfassung |
Numerous reactive volatile organic compounds (VOCs) are emitted into
the atmosphere by vegetation. Most biogenic VOCs are highly reactive
towards the atmosphere's most important oxidant, the hydroxyl (OH)
radical. One way to investigate the chemical interplay between
biosphere and atmosphere is through the measurement of total OH
reactivity, the total loss rate of OH radicals. This study presents
the first determination of total OH reactivity emission rates
(measurements via the comparative reactivity method) based on
a branch cuvette enclosure system mounted on a Norway spruce (Picea
abies) throughout spring, summer and autumn 2011. In parallel
VOC emission rates were monitored by a second proton-transfer-reaction mass spectrometer (PTR-MS), and total ozone (O3) loss
rates were obtained inside the cuvette. Total OH reactivity emission
rates were in general temperature and light dependent, showing
strong diel cycles with highest values during daytime. Monoterpene
emissions contributed most, accounting for 56–69% of the
measured total OH reactivity flux in spring and early
summer. However, during late summer and autumn the monoterpene
contribution decreased to 11–16%. At this time, a large
missing fraction of the total OH reactivity emission rate
(70–84%) was found when compared to the VOC budget measured by
PTR-MS. Total OH reactivity and missing total OH reactivity emission
rates reached maximum values in late summer corresponding to the
period of highest temperature. Total O3 loss rates within the
closed cuvette showed similar diel profiles and comparable
seasonality to the total OH reactivity fluxes.
Total OH reactivity fluxes were also compared to emissions from
needle storage pools predicted by a temperature-only-dependent
algorithm. Deviations of total OH reactivity fluxes from the
temperature-only-dependent emission algorithm were observed for
occasions of mechanical and heat stress. While for mechanical
stress, induced by strong wind, measured VOCs could explain total OH
reactivity emissions, during heat stress they could not. The
temperature-driven algorithm matched the diel variation of total OH reactivity emission rates much better in
spring than in summer, indicating a different production and
emission scheme for summer and early autumn. During these times,
unmeasured and possibly unknown primary biogenic emissions
contributed significantly to the observed total OH reactivity flux. |
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