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| Titel |
Hygroscopicity and CCN activity of CaCO3 and Ca(HCO3)2 aerosols |
| VerfasserIn |
Defeng Zhao, Angela Buchholz, Thomas F. Mentel, Klaus-Peter Müller, Astrid Kiendler-Scharr, Christian Spindler, Ralf Tillmann, Achim Trimborn, Andreas Wahner, Tong Zhu |
| 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 |
250042489
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| Zusammenfassung |
| Calcium carbonate (CaCO3) is an important component of mineral dust. It also is one of its
most reactive components. In the atmosphere it can react with acids (e.g. H2SO4 and HNO3)
forming the corresponding salts.
First we investigated freshly produced CaCO3 and calcium bicarbonate (Ca(HCO3)2)
aerosol. The chemical composition was characterized with a quadrupole aerosol mass
spectrometer. Hygroscopic growth factors (GF) were measured with a humidity tandem
differential mobility analyzer (HTDMA) for 150nm particles at RH = 2 - 97%. Cloud
condensation nuclei (CCN) activation was studied with a continuous flow CCN counter
(DMT).
Fresh Ca(HCO3)2 aerosol is more hygroscopic than CaCO3 although both of them do not
exhibit high GF (GF(95%) = 1.02 and 1.01, respectively). The CCN activity of Ca(HCO3)2
aerosol is remarkably higher than that of CaCO3 aerosol and not much less than calcium
nitrate (Ca(NO3)2) or ammonium sulfate (critical SS for 150nm particles: 0.175% for
Ca(HCO3)2 and 0.85% for CaCO3).
Experiments in the Large Jülich Aerosol Chamber show that Ca(HCO3)2 can exist for
longer time periods under dry atmospheric conditions which is in contrast to the current
believe that Ca(HCO3)2 is generally unstable in the atmosphere. Under humid condition in
the presence of NOy the fresh aerosol is converted into Ca(NO3)2 which has an even higher
hygroscopicity (GF(95%) = 1.92) and is more CCN active than the bicarbonate (critical SS
0.2% for 92nm particles). |
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