Deployment of a Carbon Isotope Ratiometer for the Monitoring of CO₂ Sequestration Leakage

Abstract

In an effort to monitor leakage from underground CO(2) storage, a field-deployable analyzer capable of rapidly measuring the CO(2) mixing ratio and δ(13)C values (±0.05 ppm(v) ± 0.2‰, 60 s) was deployed to distinguish between biogenic and fossil CO(2) sources. The analyzer was interfaced with a multiport inlet unit to allow autonomous sampling from multiple locations. The instrument and inlet interface were deployed at the Zero Emissions Research and Technology (ZERT) site (Bozeman, Montana, July 14-22, 2009) during a controlled, subsurface release of CO(2) depleted in (13)C. A biogenic diurnal cycle was observed far from the release, and the associated Keeling plot suggested a CO(2) source (δ(13)C = -27.0 ± 0.5‰) consistent with local C(3) vegetation. Inlets near the leak showed large CO(2) mixing ratios (388/>40 000 ppm(v)) whose predominant source was the release CO(2) (inferred δ(13)C = -58.2 ± 0.7‰). Measurements 3 m from the source showed diurnal CO(2) cycles (382-2400 ppm(v)) influenced by leaked CO(2), possibly due to diel air mixing. Finally, the data from all of the sampling inlets was combined to spatially localize the leak position.

Evaluation of a cavity ring-down spectrometer for in situ observations of <sup>13</sup>CO<sub>2</sub>

“…35 mL min −1 ) compared to other in situ instruments that need flows of 400 mL min −1 to 1000 mL min −1 (cf. McAlexander et al, 2011;Tuzson et al, 2011;Hammer et al, 2012;Griffith et al, 2012). The consumption, however, is still not comparable to the minimal amounts needed for our classical IRMS systems (Huang et al, 2012), that allows to measure smaller samples.…”

“…For 2 min averages (at a flow of 0.4 L min −1 ) they report it to be better than 0.2 ‰. For an off-axis integrated cavity output spectroscopy (ICOS) instrument, McAlexander et al (2011) report a long-term precision of 0.11 ‰ for 35 min integrals (at a flow of 0.5 L min −1 ). A detailed description and thorough calibration strategy for a Fourier-transform infrared spectroscopy (FTIR) instrument was given by and Hammer et al (2012).…”

Evaluating calibration strategies for isotope ratio infrared spectroscopy for atmospheric <sup>13</sup>CO<sub>2</sub> / <sup>12</sup>CO<sub>2</sub> measurement

“…Vogel et al (2013) found a precision 0.2 ‰ with 5 min averaging intervals for a model G1101-i analyzer from Picarro. Guillon et al (2012) and McAlexander et al (2011) found a precision of 0.05 ‰ and 0.15 ‰ with 60 s averaging for two model DLT-100 analyzers from Los Gatos. Bowling et al (2003) showed a precision of 0.25 ‰ with a 2 min sampling interval for a model TGA100 from Campbell Scientific.…”

“…However, in comparison to IRMS, whose operational procedures are mature, IRIS is a relatively immature technology still subject to a number of artifacts some users may not be fully aware of (Griffith et al, 2012;Werner et al, 2012). Sensitivity to changing environmental conditions (e.g., temperature dependence; Guillon et al, 2012) and dependence of δ 13 C on CO 2 concentration are the two main sources of error affecting the IRIS measurements (Wada et al, 2011;McAlexander et al, 2011;Guillon et al, 2012). Proper calibration is necessary to ensure accurate measurements Kammer et al, 2011;Guillon et al, 2012;Hammer et al, 2013;Vogel et al, 2013).…”

Using cavity ringdown spectroscopy for continuous monitoring of δ13C(CO2) and ƒCO2 in the surface ocean

“…This combination of long effective absorption pathlength, immunity to light intensity noise, as well as the possibility to measure spectra in high spectral resolution makes CRDS an ultrasensitive detection method for all sorts of stable and transient molecules, including CO 2 (Friedrichs 2008;Kerstel and Gianfrani 2008). Recently, easy-to-handle and robust isotope ratio CRDS as well as cavity-enhanced absorption spectroscopy (CEAS) instruments entered the market and have been successfully used to perform isotope selective field measurements on land (Graham et al 2010;Gupta et al 2009;Krevor et al 2010;McAlexander et al 2011) and in coral reefs (Bass et al 2012).…”