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| Titel |
Seasonal and diurnal variations of particulate nitrate and organic matter at the IfT research station Melpitz |
| VerfasserIn |
L. Poulain, G. Spindler, W. Birmili, C. Plass-Dülmer, A. Wiedensohler, H. Herrmann |
| 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 ; 11, no. 24 ; Nr. 11, no. 24 (2011-12-15), S.12579-12599 |
| Datensatznummer |
250010266
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| Publikation (Nr.) |
 copernicus.org/acp-11-12579-2011.pdf |
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| Zusammenfassung |
| Ammonium nitrate and several organic compounds such as dicarboxylic acids
(e.g. succinic acid, glutaric acid), some Polycyclic Aromatic Hydrocarbon
(PAHs) or some n-alkanes are semi-volatile. The transition of these
compounds between the gas and particulate phase may significantly change the
aerosol particles radiative properties, the heterogeneous chemical
properties, and, naturally, the total particulate mass concentration. To
better assess these time-dependent effects, three intensive field experiments
were conducted in 2008–2009 at the Central European EMEP research station
Melpitz (Germany) using an Aerodyne Aerosol Mass Spectrometer (AMS). Data
from all seasons highlight organic matter as being the most important
particulate fraction of PM1 in summer (59%) while in winter, the
nitrate fraction was more prevalent (34.4%). The diurnal variation of
nitrate always showed the lowest concentration during the day while its
concentration increased during the night. This night increase of nitrate
concentration was higher in winter (ΔNO3− = 3.6 μg m−3) than in summer (ΔNO3− =
0.7 μg m−3). The variation in particulate nitrate was
inherently linked to the gas-to-particle-phase equilibrium of ammonium
nitrate and the dynamics of the atmosphere during day. The results of this
study suggest that during summer nights, the condensation of HNO3 and
NH3 on pre-existing particles represents the most prevalent source of
nitrate, whereas during winter, nighttime chemistry is the predominant source
of nitrate. During the summer 2008's campaign, a clear diurnal evolution in
the oxidation state of the organic matter became evident (Organic Mass to
Organic Carbon ratio (OM/OC) ranging from 1.65 during night to 1.80
during day and carbon oxidation state (OSc) from −0.66 to −0.4), which
could be correlated to hydroxyl radical (OH) and ozone concentrations,
indicating a photochemical transformation process. In summer, the organic
particulate matter seemed to be heavily influenced by regional secondary
formation and transformation processes, facilitated by photochemical
production processes as well as a diurnal cycling of the substances between
the gas and particulate phase. In winter, these processes were obviously less
pronounced (OM/OC ranging from 1.60 to 1.67 and OSc from −0.8 to
−0.7), so that organic matter apparently originated mainly from aged
particles and long range transport. |
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