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| Titel |
Emissions of biogenic volatile organic compounds and subsequent formation of secondary organic aerosols in a Larix kaempferi forest |
| VerfasserIn |
T. Mochizuki, Y. Miyazaki, K. Ono, R. Wada, Y. Takahashi, N. Saigusa, K. Kawamura, A. Tani |
| 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 ; 15, no. 20 ; Nr. 15, no. 20 (2015-10-29), S.12029-12041 |
| Datensatznummer |
250120130
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| Publikation (Nr.) |
 copernicus.org/acp-15-12029-2015.pdf |
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| Zusammenfassung |
| We conducted
simultaneous measurements of concentrations and above-canopy fluxes of
isoprene and α-pinene, along with their oxidation products in aerosols
in a Larix kaempferi (Japanese larch) forest in summer 2012.
Vertical profiles of isoprene showed the maximum concentration near the
forest floor with a peak around noon, whereas oxidation products of isoprene,
i.e., methacrolein (MACR) and methyl vinyl ketone (MVK), showed higher
concentrations near the canopy level of the forest. The vertical profile
suggests large emissions of isoprene near the forest floor, likely due to
Dryopteris crassirhizoma (a fern species), and the subsequent
reaction within the canopy. The concentrations of α-pinene also showed
highest values near the forest floor, with maximums in the early morning and
late afternoon. The vertical profiles of α-pinene suggest its large
emissions from soil and litter in addition to emissions from L.
kaempferi leaves at the forest site. Isoprene and its oxidation products in
aerosols exhibited similar diurnal variations within the forest canopy,
providing evidence of secondary organic aerosol (SOA) formation via oxidation
of isoprene most likely emitted from the forest floor. Although high
abundance of α-pinene was observed in the morning, its oxidation
products in aerosols showed peaks in daytime, due to a time lag between the
emission and atmospheric reactions of α-pinene to form SOA. Positive
matrix factorization (PMF) analysis indicated that anthropogenic influence is
the most important factor contributing to the elevated concentrations of
molecular oxidation products of isoprene- (> 64 %) and
α-pinene-derived SOA (> 57 %). The combination of the measured
fluxes and vertical profiles of biogenic volatile organic compounds (BVOCs)
suggests that the inflow of anthropogenic precursors/aerosols likely enhanced
the formation of both isoprene SOA and α-pinene SOA within the forest
canopy even when the BVOC flux was relatively low. This study highlights the
importance of intra-canopy processes that promote biogenic SOA formation in
the presence of significant inflow of oxidants together with anthropogenic
aerosols and their precursors. |
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