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| Titel |
Long-term observations of cluster ion concentration, sources and sinks in clear sky conditions at the high-altitude site of the Puy de Dôme, France |
| VerfasserIn |
C. Rose, J. Boulon, M. Hervo, H. Holmgren, E. Asmi, M. Ramonet, P. Laj, K. Sellegri |
| 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 ; 13, no. 22 ; Nr. 13, no. 22 (2013-11-28), S.11573-11594 |
| Datensatznummer |
250085843
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| Publikation (Nr.) |
 copernicus.org/acp-13-11573-2013.pdf |
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| Zusammenfassung |
| Cluster particles (0.8–1.9 nm) are key entities involved in nucleation and
new particle formation processes in the atmosphere. Cluster ions were
characterized in clear sky conditions at the Puy de Dôme station
(1465 m a.s.l.). The studied data set spread over five years (February
2007–February 2012), which provided a unique chance to observe seasonal
variations of cluster ion properties at high altitude. Statistical values of
the cluster ion concentrations and diameters are reported for both positive
and negative polarities. Cluster ions were found to be ubiquitous at the Puy
de Dôme and displayed an annual variation with lower concentrations in
spring. Positive cluster ions were less numerous than negative, but were
larger in diameter. Negative cluster ion properties were not sensitive to the
occurrence of a new particle formation (NPF) event, while positive cluster
ions appeared to be significantly more numerous and larger on event days. The
parameters of the balance equation for the positive cluster concentration are
reported separately for the different seasons and for the NPF event days and
non-event days. The steady-state assumption suggests that the ionization rate
is balanced with two sinks: the ion recombination and the attachment onto
background aerosol particles, referred to as "aerosol ion sink". The
aerosol ion sink was predominant compared to the recombination sink. The
positive ionization rates derived from the balance equation
(Qcalc) were well correlated with the ionization rates obtained
from radon measurement (Qmeas). When ignoring the gamma radiation
contribution to the ion production, Qcalc is on average higher
than Qmeas during the warm season. In contrast, when a seasonal
gamma contribution is taken into account, Qmeas always exceeds
Qcalc. We found that neither the aerosol ion sink nor the
ionization rate (calculated or measured, with or without the gamma
contribution) were significantly different on event days compared to
non-event days, and thus, they were not able to explain the different
positive cluster concentrations between event and non-event days. Hence, the
excess of positive small ions on event days may derive from an additional
constant source of ions leading to a non-steady state. |
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