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| Titel |
Laboratory studies of H₂SO₄/H₂O binary homogeneous nucleation from the SO₂+OH reaction: evaluation of the experimental setup and preliminary results |
| VerfasserIn |
L. H. Young, D. R. Benson, F. R. Kameel, J. R. Pierce, H. Junninen, M. Kulmala  , S.-H. Lee |
| 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 ; 8, no. 16 ; Nr. 8, no. 16 (2008-08-28), S.4997-5016 |
| Datensatznummer |
250006347
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| Publikation (Nr.) |
 copernicus.org/acp-8-4997-2008.pdf |
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| Zusammenfassung |
| Binary homogeneous nucleation (BHN) of sulphuric acid and water
(H2SO4/H2O) is one of the most important atmospheric
nucleation processes, but laboratory observations of this nucleation process
are very limited and there are also large discrepancies between different
laboratory studies. The difficulties associated with these experiments
include wall loss of H2SO4 and uncertainties in estimation of
H2SO4 concentration ([H2SO4]) involved in nucleation.
We have developed a new laboratory nucleation setup to study
H2SO4/H2O BHN kinetics and provide relatively constrained
[H2SO4] needed for nucleation. H2SO4 is produced from
the SO2+OH→HSO3 reaction and OH radicals are produced
from water vapor UV absorption. The residual [H2SO4] were measured
at the end of the nucleation reactor with a chemical ionization mass
spectrometer (CIMS). Wall loss factors (WLFs) of H2SO4 were
estimated by assuming that wall loss is diffusion limited and these
calculated WLFs were in good agreement with simultaneous measurements of the
initial and residual [H2SO4] with two CIMSs. The nucleation zone
was estimated from numerical simulations based on the measured aerosol sizes
(particle diameter, Dp) and [H2SO4]. The measured BHN rates
(J) ranged from 0.01–220 cm−3 s−1 at the initial and residual
[H2SO4] from 108−1010 cm−3, a temperature of 288 K
and relative humidity (RH) from 11–23%; J increased with increasing
[H2SO4] and RH. J also showed a power dependence on
[H2SO4] with the exponential power of 3–8. These power dependences
are consistent with other laboratory studies under similar [H2SO4]
and RH, but different from atmospheric field observations which showed that
particle number concentrations are often linearly dependent on
[H2SO4]. These results, together with a higher [H2SO4]
threshold (108–109 cm−3) needed to produce the unit J measured
from the laboratory studies compared to the atmospheric conditions
(106–107 cm−3), imply that H2SO4/H2O BHN
alone is insufficient to explain atmospheric aerosol formation and growth.
Particle growth rates estimated from the measured aerosol size
distributions, residence times (tr), and [H2SO4] were
100–500 nm h−1, much higher than those seen from atmospheric field
observations, because of the higher [H2SO4] used in our study. |
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