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| Titel |
Towards an experiment to investigate N2O5 uptake to aerosol particles at ambient conditions using the radioactive tracer 13N |
| VerfasserIn |
G. Grzinic, T. Bartels-Rausch, M. Birrer, M. Ammann |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250064640
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| Zusammenfassung |
| N2O5 is an atmospheric trace gas which plays an important role as a reactive intermediate in
the nighttime NOx tropospheric chemistry [1]. N2O5 can function in a dual role: as a NO3
radical reservoir and as a sink for NOx species thanks to the reaction of heterogeneous
hydrolysis on aerosol, water and ice surfaces. Therefore N2O5 can have a direct impact on
tropospheric ozone production and the oxidizing capacity of the troposphere [1, 2].
Laboratory studies have also shown that uptake of N2O5 to aerosol particles depends on
meteorological parameters like temperature and relative humidity as well as aerosol
composition [1, 2].
In our experiments we have used the 13N short-lived radioactive tracer technique [3]
developed at the Paul Scherrer Institute coupled to an aerosol flow tube reactor. This method
allows for the study of N2O5 uptake kinetics to aerosols under realistic conditions,
e.g., at ambient pressure and low trace gas concentrations as well as high relative
humidity values. Furthermore it allows to observe behavior in a wide temperature range
(tropospheric conditions) and the influence of concentration effects on uptake (nitrate
effect).
Radioactively labeled 13NO is produced in a gas target attached to the Isotope Production
Station IP2 at a branch of Injector II at Paul Scherrer Institute and mixed with O3 in the
reactor to give 13N2O5. The 13N labeled species formed were monitored by trapping
them in a narrow parallel plate diffusion denuder system that allows for selective
separation of the gaseous species present and observing the radioactive decay of 13N
therein. Activity of N2O5 taken up on aerosol was monitored on a particle filter
positioned at the exit of the denuder system. Several denuder coatings were tested
for N2O5 and citric acid was selected because of lower interference with NO2.
Measurements performed have confirmed formation of 13N labeled N2O5, consistent with
predictions obtained via computer modeling. A preliminary study using a citric
acid aerosol (whose hygroscopic properties are well known) at relative humidities
of 50-80% RH has shown uptake of radioactively labeled N2O5 on the aerosol
particles.
References
1. Chang, W.L., et al., Heterogeneous Atmospheric Chemistry, Ambient Measurements,
and Model Calculations of N(2)O(5): A Review. Aerosol Science and Technology, 2011.
45(6): p. 665-695.
2. Finlayson-Pitts, B.J. and J.N. Pitts, Jr., Chemistry of the upper and lower atmosphere.
2000, San Diego, CA: Academic Press.
3. Ammann, M., Using 13N as tracer in heterogeneous atmospheric chemistry
experiments. Radiochim. Acta, 2001. 89: p. 831-838. |
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