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| Titel |
Measurements of particle masses of inorganic salt particles for calibration of cloud condensation nuclei counters |
| VerfasserIn |
M. Kuwata, Y. Kondo |
| 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 ; 9, no. 16 ; Nr. 9, no. 16 (2009-08-19), S.5921-5932 |
| Datensatznummer |
250007577
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| Publikation (Nr.) |
 copernicus.org/acp-9-5921-2009.pdf |
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| Zusammenfassung |
| We measured the mobility equivalent critical dry diameter for cloud
condensation nuclei (CCN) activation (dc_me) and the particle mass of
size-selected (NH4)2SO4 and NaCl particles to calibrate a CCN
counter (CCNC) precisely. The CCNC was operated downstream of a differential
mobility analyzer (DMA) for the measurement of dc_me. The particle mass
was measured using an aerosol particle mass analyzer (APM) operated
downstream of the DMA. The measurement of particle mass was conducted for
50–150-nm particles. Effective densities (ρeff) of
(NH4)2SO4 particles were 1.67–1.75 g cm−3, which
correspond to dynamic shape factors (χ) of 1.01–1.04. This shows
that (NH4)2SO4 particles are not completely spherical. In the
case of NaCl particles, ρeff was 1.75–1.99 g cm−3
and χ was 1.05–1.14, demonstrating that the particle shape was
non-spherical. Using these experimental data, the volume equivalent critical
dry diameter (dc_ve) was calculated, and it was used as an input
parameter for calculations of critical supersaturation (S). Several
thermodynamics models were used for the calculation of water activity. When
the Pitzer model was employed for the calculations, the critical S calculated
for (NH4)2SO4 and NaCl agreed to well within the uncertainty
of 2% (relative). This result demonstrates that the use of the Pitzer
model for the calibration of CCNCs gives the most accurate value of S. |
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