Applications of Cavity Ring-Down Spectroscopy (CRDS) to Analysis of Carbon Stable Isotope Composition of Groundwater

Carbon Capture and Storage (CCS) has been considered as an effective strategy to reduce atmospheric carbon dioxide (CO₂) concentration. However, unintended leakage of CO₂ leakage from storage sites could occur through highly permeable conduits such as fractures in low-K formations during the injection and storage of SCCO₂ (supercritical phase CO₂). Therefore, prediction and detection of CO₂ leakage and relevant analysis of carbon isotope are crucial to assure environmental and public safety.

Until recently, Isotope Ratio Mass Spectrometry (IRMS) has been utilized to measure the stable isotope ratio of water. However, IRMS is time-consuming operation due to complicated pretreatment, and thus not a practical methodology under field conditions.

Carbon Isotope Analyzer (CCIA), which is a kind of Cavity Ring-Down Spectroscopy (CRDS) and has a wide measurement range from 300 to 25000 ppmv, can facilitate the rate of measurements up to 1 Hz by using continuous flow method so that it can be readily applied to field. In this study, carbon stable isotope ratio of groundwater will be analyzed using CCIA. Then, the CCIA results will be compared with IRMS to validate its accuracy and stability. This research will provide an appropriate method for analyzing carbon stable isotope in groundwater, using a continuous flow mode.