Calibrated high-precision <sup>17</sup>O-excess measurements using cavity ring-down spectroscopy with laser-current-tuned cavity resonance
High-precision analysis of the <sup>17</sup>O / <sup>16</sup>O isotope ratio in water and water vapor is of interest in hydrological, paleoclimate, and atmospheric science applications. Of specific interest is the parameter <sup>17</sup>O excess (&Del...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2014-08-01
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| Series: | Atmospheric Measurement Techniques |
| Online Access: | http://www.atmos-meas-tech.net/7/2421/2014/amt-7-2421-2014.pdf |
| Summary: | High-precision analysis of the <sup>17</sup>O / <sup>16</sup>O
isotope ratio in water and water vapor is of interest in
hydrological, paleoclimate, and atmospheric science applications.
Of specific interest is the parameter
<sup>17</sup>O excess (Δ<sup>17</sup>O),
a measure of the deviation from a~linear relationship between
<sup>17</sup>O / <sup>16</sup>O and
<sup>18</sup>O / <sup>16</sup>O ratios. Conventional analyses of
Δ<sup>17</sup>O of water are obtained by fluorination of
H<sub>2</sub>O to O<sub>2</sub> that is analyzed by dual-inlet isotope
ratio mass spectrometry (IRMS). We describe a new laser spectroscopy
instrument for high-precision Δ<sup>17</sup>O
measurements. The new instrument uses cavity ring-down spectroscopy
(CRDS) with laser-current-tuned cavity resonance to achieve reduced measurement
drift compared with previous-generation instruments. Liquid water
and water-vapor samples can be analyzed with a better than 8 per meg
precision for Δ<sup>17</sup>O using integration times of
less than 30 min. Calibration with respect to accepted water
standards demonstrates that both the precision and the accuracy of Δ<sup>17</sup>O
are competitive with conventional IRMS methods. The new instrument also
achieves simultaneous analysis of δ<sup>18</sup>O,
Δ<sup>17</sup>O and δ<i>D</i> with precision of < 0.03‰,
< 0.02 and < 0.2‰, respectively, based on repeated
calibrated measurements. |
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| ISSN: | 1867-1381 1867-8548 |