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| Titel |
Some insights into the condensing vapors driving new particle growth to CCN sizes on the basis of hygroscopicity measurements |
| VerfasserIn |
Z. J. Wu, L. Poulain, W. Birmili, J. Gross, N. Niedermeier, Z. B. Wang, H. Herrmann, A. Wiedensohler |
| 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. 22 ; Nr. 15, no. 22 (2015-11-25), S.13071-13083 |
| Datensatznummer |
250120184
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| Publikation (Nr.) |
 copernicus.org/acp-15-13071-2015.pdf |
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| Zusammenfassung |
| New particle formation (NPF) and growth is an important source of cloud
condensation nuclei (CCN). In this study, we investigated the chemical
species driving new particle growth to the CCN sizes on the basis of particle
hygroscopicity measurements carried out at the research station Melpitz,
Germany. Three consecutive NPF events occurred during summertime were chosen
as examples to perform the study. Hygroscopicity measurements showed that the
(NH4)2SO4-equivalent water-soluble fraction accounts for 20 and
16 % of 50 and 75 nm particles, respectively, during the NPF events.
Numerical analysis showed that the ratios of H2SO4 condensational
growth to the observed particle growth were 20 and 13 % for 50 and 75 nm
newly formed particles, respectively. Aerosol mass spectrometer measurements
showed that an enhanced mass fraction of sulfate and ammonium in the newly
formed particles was observed when new particles grew to the sizes larger
than 30 nm shortly after the particle formation period. At a later time, the
secondary organic species played a key role in the particle growth. Both
hygroscopicity and aerosol mass spectrometer (AMS) measurements and numerical
analysis confirmed that organic compounds were major contributors driving
particle growth to CCN sizes. The critical diameters at different
supersaturations estimated using AMS data and κ-Köhler theory
increased significantly during the later course of NPF events. This indicated
that the enhanced organic mass fraction caused a reduction in CCN efficiency
of newly formed particles. Our results implied that the CCN production
associated with atmospheric nucleation may be overestimated if assuming that
newly formed particles can serve as CCN once
they grow to a fixed particle size, an assumption made in some previous
studies, especially for organic-rich
environments. In our study, the enhancement in CCN number concentration
associated with individual NPF events were 63, 66, and 69 % for 0.1, 0.4,
and 0.6 % supersaturation, respectively. |
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