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| Titel |
Characterisation and first application of a cavity ring-down instrument for measurements of NO3 and N2O5 |
| VerfasserIn |
Stephanie Schrade, Mathias Bachner, Kamil Kubik, Hendrik Fuchs |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094742
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| Publikation (Nr.) |
 EGU/EGU2014-10173.pdf |
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| Zusammenfassung |
| A new instrument was built for atmospheric measurements using the cavity ringdown
technique for a simultaneous measurement of nitrate radicals (NO3) and dinitrogen pentoxide
(N2O5) using a red laser diode at 662 nm. The instrument consists of two channels: The inlet
and the cavity of the first one is heated up to 120 °C to force the thermal equlibrium of N2O5
and NO3 to the side of NO3, so that this channel measures the sum NO3 and N2O5. The other
channel stays at ambient temperature to measure NO3 only. To prevent aerosol
extinction, a filter is installed upstream of the cavities. The detection limit is within the
range of a few ppt at 1 s time resolution. Measurements have an accuracy of 15 %.
Instrument losses were characterized by a titration method using the conversion
of NO3 to NO2 by adding NO. Two addition points where chosen, right before
and after the NO3 intrument.The NO2 concentration was measured downstream of
the instrument with another CRDS intrument using a blue laser diode at 405 nm.
Estimated losses are within the range of 40 % due two a high point loss on the used
filter housing. First application took place at the SAPHIR simulation chamber at
Forschungszentrum Jülich GmbH. Experiments were made by injecting known
concentrations of NO2 and ozone into the dark chamber filled with pure synthetic air to
analyse the behavior of NO3 and N2O5 in the clean chamber. Possible losses were estimated
from the steady-state lifetime of NO3, which can be calculated from measured NO3,
NO2 and ozone concentrations. Estimated lifetimes of NO3 and N2O5 were within
the range of 19 min and 44 min, respetively. During futher experiments organic
compounds (isoprene, β-pinene, limonene) were additionally injected, in order to test the
applicability of chamber experiments for the invertigation of oxidation processes by NO3. |
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