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| Titel |
Characterization of a customized calibration unit for continuous measurements of the isotopic composition of water vapor |
| VerfasserIn |
Giovanni Moro, Daniele Zannoni, Giuliano Dreossi, Barbara Stenni |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141632
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| Publikation (Nr.) |
 EGU/EGU2017-5165.pdf |
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| Zusammenfassung |
| The objective of this work is the development, standardization and creation of a
method to carry out continuous measurement of oxygen and hydrogen isotopic
composition of the atmospheric water vapor using a wavelength-scanned cavity
ring down spectroscopy (WS-CRDS) instrument produced by Picarro, L1102-i
model.
Some technical improvements of the standard instrument configuration have been made to
create three different inlet gas lines: a “standard” line, a calibration line and a line connected
with the external sampler.
The calibration line is composed of a syringe-pump that continuously injects standard water
into a steel tee heated at the temperature of 170∘C and flushed with dry nitrogen gas. In this
way, instantaneous and complete vaporization of the standard water takes place.
The resulting steam is characterized by a well-defined composition in δD e δ18O
values.
To allow comparison with other international data, we have characterized the individual
instrumental response to variation of the isotopic composition of the water vapor. Several
humidity-isotope response functions (6000-26000 ppmv) have been estimated with three
different internal standards (0.35‰ -8.75‰ -29.11‰ and -40.28‰ for δ18O; 2.31‰
-58.91‰ -222.19‰ and -317.78‰ for δD).
Moreover, we have measured the instrumental drift at regular time intervals to apply the
opportune corrections to instrument data.
The setup has been tested using a 3.5 day continuous measurements carried out with
the Picarro sampling the water vapor outside our campus in Venice and parallel
sampling using the classical cryogenic trapping procedure, obtaining excellent results.
Furthermore, our analysis technique has given good results for the standards with values
which are similar to those obtained with the isotope ratio mass spectrometry (IRMS)
technique. |
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