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| Titel |
High-resolution continuous-flow analysis setup for water isotopic measurement from ice cores using laser spectroscopy |
| VerfasserIn |
B. D. Emanuelsson, W. T. Baisden, N. A. N. Bertler, E. D. Keller, V. Gkinis |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 8, no. 7 ; Nr. 8, no. 7 (2015-07-17), S.2869-2883 |
| Datensatznummer |
250116485
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| Publikation (Nr.) |
 copernicus.org/amt-8-2869-2015.pdf |
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| Zusammenfassung |
Here we present an experimental setup for water stable isotope (δ18O and δD) continuous-flow measurements and provide metrics
defining the performance of the setup during a major ice core measurement
campaign (Roosevelt Island Climate Evolution; RICE). We also use the
metrics to compare alternate systems. Our setup is the first continuous-flow
laser spectroscopy system that is using off-axis integrated cavity output
spectroscopy (OA-ICOS; analyzer manufactured by Los Gatos Research, LGR) in
combination with an evaporation unit to continuously analyze water samples
from an ice core.
A Water Vapor Isotope Standard Source (WVISS) calibration unit,
manufactured by LGR, was modified to (1) enable measurements on several
water standards, (2) increase the temporal resolution by reducing the
response time and (3) reduce the influence from memory effects. While
this setup was designed for the continuous-flow analysis (CFA) of ice cores,
it can also continuously analyze other liquid or vapor sources.
The custom setups provide a shorter response time (~ 54 and
18 s for 2013 and 2014 setup, respectively) compared to the original WVISS
unit (~ 62 s), which is an improvement in measurement
resolution. Another improvement compared to the original WVISS is that the
custom setups have a reduced memory effect.
Stability tests comparing the custom and WVISS setups were performed and
Allan deviations (σAllan) were calculated to determine
precision at different averaging times. For the custom 2013 setup the
precision after integration times of 103 s is
0.060 and 0.070 ‰ for δ18O and δD, respectively. The corresponding σAllan values for the custom 2014 setup are 0.030, 0.060 and 0.043 ‰ for δ18O, δD and δ17O, respectively. For the WVISS
setup the precision is 0.035,
0.070 and 0.042 ‰ after 103 s
for δ18O, δD and δ17O, respectively. Both
the custom setups and WVISS setup are influenced by instrumental drift with
δ18O being more drift sensitive than δD. The σAllan values for δ18O are 0.30 and
0.18 ‰ for the custom 2013 and WVISS setup, respectively,
after averaging times of 104 s (2.78 h). Using response time
tests and stability tests, we show that the custom setups are more responsive
(shorter response time), whereas the University of
Copenhagen (UC) setup is more stable. More broadly,
comparisons of different setups address the challenge of integrating
vaporizer/spectrometer isotope measurement systems into a CFA campaign with
many other analytical instruments. |
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