Speaker
Description
Geological storage of CO2 requires monitoring techniques capable of detecting and char-
acterising potential surface leakage. This study evaluates the reliability of carbon isotopic
composition (δ13C) as a leakage indicator using mobile wavelength-scanned cavity ring-
down spectroscopy (WS-CRDS) data collected at the Salt Wash fault system, Utah, an
established natural analogue for geological CO2 leakage. Spatially continuous measure-
ments were acquired across bubbling springs and areas of diffuse seepage, producing a
high-resolution dataset of CO2 concentration and δ13C variability. Atmospheric back-
ground conditions were characterised by relatively stable CO2 concentrations (370 - 420
ppm) and mean δ13C values of −8.49 ‰, providing a baseline for leakage detection. Both
bubbling springs produced repeatable, high-magnitude concentration anomalies confirm-
ing active surface leakage. In contrast, isotopic responses during direct vent encounters
were highly variable. Keeling plot analysis constrained the apparent isotopic composition
of seep-derived CO2 to a narrow range of 0.60 - 2.36 ‰, indicating a source signature
that is isotopically heavier than atmospheric CO2, consistent with measurements of near-
surface dissolved inorganic carbon in waters and interaction with deep carbonate forma-
tions during subsurface migration for the same site. As a result of the proximity of the
isotopic signatures for leaking and atmospheric CO2, Keeling mixing relationships demon-
strate that isotopic discrimination is rapidly lost as leaking CO2 is diluted by atmospheric
air. At concentrations below approximately 700 - 740 ppm, the δ13C values fall within
the natural background range, limiting the effectiveness of δ13C as a stand-alone leakage
detection method. In contrast, CO2 concentration anomalies provide a clear and reliable
indicator of leakage across the survey area. These results highlight the strong site de-
pendence of isotopic monitoring and emphasise the need to integrate concentration-based
detection with complementary approaches in geological CO2 storage monitoring.
| Country | United Kingdom |
|---|---|
| Student Awards | I would like to submit this presentation into the InterPore Journal Student Paper Award. |
| Acceptance of the Terms & Conditions | Click here to agree |
