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| Titel |
Particle formation from stress-induced BVOC emissions from poplar is inhibited by isoprene |
| VerfasserIn |
Astrid Kiendler-Scharr, Monika Springer, Sebastian Broch, Thomas Mentel, Florian Rubach, Ralf Tillmann, Katja Behnke, Jörg-Peter Schnitzler, Einhard Kleist, Jürgen Wildt |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048295
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| Zusammenfassung |
| We measured the formation of secondary organic aerosols (SOA) from stressed-induced
emissions of biogenic volatile organic compounds (BVOC) emitted from grey poplar
(Populus x canescens). Measurements were conducted in the Juelich plant atmosphere
chamber (JPAC) under controlled conditions. BVOC emitted from poplar plants in a plant
chamber were transferred into a reaction chamber where they were oxidized by ozone and by
OH radicals. Comparing particle formation from BVOC emitted from isoprene emitting wild
type (WT) poplar to particle formation from transgenic poplar lines down-regulated in
isoprene emission (R-lines) enabled characterization of isoprene’s impact on SOA
formation.
In unstressed wild type poplars the emission profile is nearly exclusively dominated by
isoprene while in transgenic isoprene emission-repressed lines the emission rates were
approximately an order of magnitude lower. Using these unstressed plants as BVOC source
for particle formation we found inefficient SOA formation. For WT poplars the
nucleation rates were far below 1 cm-3 s-1. Unstressed R-lines stimulated no particle
formation.
Poplar plants, WT and R-lines, stressed by short ozone pulses showed strong additional
emissions of sesquiterpenes and aromatic volatiles. These emissions increased and decreased
on a time scale of several days allowing to study particle formation under steady state
conditions similar to studies with constitutive emissions. Feeding the BVOC mixes
including sesquiterpenes and aromatic compounds into the reaction chamber and
inducing production of OH radicals by ozone photolysis resulted in very strong SOA
formation events with nucleation rates exceeding 3000 cm-3s-1. Nucleation rates were
depended on the BVOC turnover in the reaction chamber. After normalizing to
the turnover, nucleation rates were generally lower for the isoprene emitting WT
type. This observation confirmed former findings of suppression of nucleation by
isoprene.
Rapid changes in light intensity of the plant chamber caused fast changes of isoprene
emissions whereas the emission rates of the other BVOC more slowly responded to these
changes on a time scale of several hours. Again, inducing particle formation from the
emission mix of WT plants caused a minor SOA formation event compared to R-line
emissions. Switching off the photosynthetic light during the SOA formation event caused a
fast decrease of isoprene emission and hence isoprene concentrations in the reaction chamber.
This decrease was paralleled by an increase of SOA formation and an increase of OH
concentrations. We therefore conclude that suppression of OH concentrations by
isoprene is a major reason for suppression of nucleation from non-isoprene BVOC. |
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