Technical note: Coupling infrared gas analysis and cavity ring down spectroscopy for autonomous, high-temporal-resolution measurements of DIC and <i>δ</i><sup>13</sup>C–DIC
A new approach to autonomously determine concentrations of dissolved inorganic carbon (DIC) and its carbon stable isotope ratio (<i>δ</i><sup>13</sup>C–DIC) at high temporal resolution is presented. The simple method requires no customised design. Instead it uses two commerci...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-03-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/14/1305/2017/bg-14-1305-2017.pdf |
| Summary: | A
new approach to autonomously determine concentrations of dissolved inorganic
carbon (DIC) and its carbon stable isotope ratio (<i>δ</i><sup>13</sup>C–DIC) at high
temporal resolution is presented. The simple method requires no customised
design. Instead it uses two commercially available instruments currently used
in aquatic carbon research. An inorganic carbon analyser utilising
non-dispersive infrared detection (NDIR) is coupled to a Cavity Ring-down
Spectrometer (CRDS) to determine DIC and <i>δ</i><sup>13</sup>C–DIC based on the
liberated CO<sub>2</sub> from acidified aliquots of water. Using a small sample
volume of 2 mL, the precision and accuracy of the new method was comparable
to standard isotope ratio mass spectrometry (IRMS) methods. The system
achieved a sampling resolution of 16 min, with a DIC precision of ±1.5
to 2 µmol kg<sup>−1</sup> and <i>δ</i><sup>13</sup>C–DIC precision of
±0.14 ‰ for concentrations spanning 1000 to
3600 µmol kg<sup>−1</sup>. Accuracy of 0.1 ± 0.06 ‰ for
<i>δ</i><sup>13</sup>C–DIC based on DIC concentrations ranging from 2000 to
2230 µmol kg<sup>−1</sup> was achieved during a laboratory-based algal
bloom experiment. The high precision data that can be autonomously obtained
by the system should enable complex carbonate system questions to be explored
in aquatic sciences using high-temporal-resolution observations. |
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| ISSN: | 1726-4170 1726-4189 |