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| Titel |
Chemical and physical characteristics of aerosol particles at a remote coastal location, Mace Head, Ireland, during NAMBLEX |
| VerfasserIn |
H. Coe, J. D. Allan, M. R. Alfarra, K. N. Bower, M. J. Flynn, G. B. McFiggans, D. O. Topping, P. I. Williams, C. D. O'Dowd, M. Dall'Osto, D. C. S. Beddows, R. M. Harrison |
| 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 ; 6, no. 11 ; Nr. 6, no. 11 (2006-08-09), S.3289-3301 |
| Datensatznummer |
250004054
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| Publikation (Nr.) |
 copernicus.org/acp-6-3289-2006.pdf |
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| Zusammenfassung |
| A suite of aerosol physical and chemical measurements were made at
the Mace Head Atmospheric Research Station, Co. Galway, Ireland, a
coastal site on the eastern seaboard of the north Atlantic Ocean
during NAMBLEX. The data have been used in this paper to show that
over a wide range of aerosol sizes there is no impact of the
inter-tidal zone or the surf zone on measurements made at 7 m above
ground level or higher. During the measurement period a range of air
mass types were observed. During anticyclonic periods and conditions
of continental outflow Aitken and accumulation mode were enhanced by
a factor of 5 compared to the marine sector, whilst coarse mode
particles were enhanced during westerly conditions. Baseline marine
conditions were rarely met at Mace Head during NAMBLEX and high wind
speeds were observed for brief periods only.
The NAMBLEX experiment focussed on a detailed assessment of
photochemistry in the marine environment, investigating the linkage
between the HOx and the halogen radical cycles.
Heterogeneous losses are important in both these cycles. In this
paper loss rates of gaseous species to aerosol surfaces were
calculated for a range of uptake coefficients. Even when the
accommodation coefficient is unity, lifetimes due to heterogeneous
loss of less than 10 s were never observed and rarely were they
less than 500 s. Diffusional limitation to mass transfer is
important in most conditions as the coarse mode is always
significant. We calculate a minimum overestimate of 50% in the loss
rate if this is neglected and so it should always be considered when
calculating loss rates of gaseous species to particle surfaces.
HO2 and HOI have accommodation coefficients of around
0.03 and hence we calculate lifetimes due to loss to particle
surfaces of 2000 s or greater under the conditions experienced
during NAMBLEX.
Aerosol composition data collected during this experiment provide
representative information on the input aerosol characteristics to
western Europe. During NAMBLEX the submicron aerosol was
predominately acidified sulphate and organic material, which was
most likely internally mixed. The remaining accumulation mode
aerosol was sea salt. The organic and sulphate fractions were
approximately equally important, though the mass ratio varies
considerably between air masses. Mass spectral fingerprints of the
organic fraction in polluted conditions are similar to those
observed at other locations that are characterised by aged
continental aerosol. In marine conditions, the background input of
both sulphate and organic aerosol into Europe was observed to be
between 0.5 and 1 µg m−3. Key differences in the mass
spectra were observed during the few clean periods but were
insufficient to ascertain whether these changes reflect differences
in the source fingerprint of the organic aerosol. The coarse mode
was composed of sea salt and showed significant displacement of
chloride by nitrate and to a lesser extent sulphate in polluted
conditions. |
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