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| Titel |
CCN activation and hygroscopic growth measurements of secondary organic aerosols from tree emissions |
| VerfasserIn |
Angela Buchholz, Thomas F. Mentel, Astrid Kiendler-Scharr, Christian Spindler, Ralf Tillmann, Einhard Kleist, Juergen Wildt |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039821
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| Zusammenfassung |
| Plant emitted volatile organic compounds (VOCs) are a major precursor of secondary organic
aerosols (SOA), an important constituent of atmospheric aerosols. We used the Juelich Plant
Atmosphere Chamber (JPAC) at the Research Center Juelich to investigate the microphysical
properties of aerosols. SOA particles were produced from the ozonolysis and reaction of OH
radicals with the complex VOC mixture emitted from trees typical for the boreal forest.
Hygroscopic growth factors (GF) were determined with a humidity tandem differential
mobility analyzer (HTDMA) for different particle sizes at RH = 2 - 97%. Cloud condensation
nuclei (CCN) activation was measured with a continuous flow CCN counter (DMT).
Additionally, the chemical composition, size distribution and number concentration
of the particles were measured. The gas phase was monitored with GC-MS and
PTR-MS.
Changing the emission pattern of the trees changed the measured GF and the diameter of
the dry particles that were activated (Dcrit). However, below 80% RH the GF changes are
within the range of the measurement error. The GF (RHÂ =Â 95%) are between 1.11 and 1.19
and the Dcrit(SSÂ =Â 0.4%) in a range of 93 - 100nm.
Koehler theory was applied to achieve closure between CCN activation and GF
measurements. The κ parameter according to Petters and Kreidenweis (2007) was calculated
for all SS (κ(CCN)) and RH (κ(GF)). The κ(GF) decrease with increasing RH but levels off
at RH > 95%. Assuming the surface tension of pure water, κ(GF, RH>95%) would be by a
factor of 2 lower than κ(CCN). Closure between the HTDMA and CCN measurement
requires the use of either a lower surface tension or a limited solubility of the organic
material.
Reference: Petters, M. D. and Kreidenweis, S. M. (2007). Atmos. Chem. Phys., 7,
1961-1971. |
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