Laser Isotope Ratio-meter (LIR) Instrument Initiative uri icon

DCO ID 11121/7468-9864-8281-7514-CC


  • Laser Isotope Ratio-meter (LIR) for real time in-situ measurement of 12CO2/13CO2

    Volcanic degassing is the main pathway of carbon release from the Earth’s interior to the atmosphere. To constrain Earth’s deep carbon cycle, we must first quantify the relative contribution from various gas sources of volcanic origin. Quantitative knowledge of the isotopic composition of outgassed CO2 - specifically 12CO2/13CO2 ratio - contributes to identifying carbon sources and therefore to validating degassing models. Understanding these carbon fluxes is critical to the overarching goal of DCO’s Reservoirs & Fluxes Community to identify Earth’s principal deep carbon reservoirs, to determine the mechanisms and rates by which carbon moves among these reservoirs, and to assess the total carbon budget of Earth.

    Achieving these scientific goals requires developing technologies and instrumentation that deliver data at relevant cost, temporal, and spatial scales. Damien Weidmann and colleagues developed a novel concept of real-time monitoring of carbon isotope ratio enabling compact, rugged and portable deployment. High-resolution middle infrared (2-20 µm) laser spectroscopy is used to precisely fingerprint isotopologues, which owing to their slight mass difference, vibrate with different frequencies that can be resolved by lasers. The advantages of this approach include precision, non-contact measurements, large immunity to interferences, limited sample preparation, real time measurements in a compact format, and possibility for absolute concentration measurements.

    Weidmann’s project consists of evolving a laboratory demonstrator into a field deployable instrument and conducting a first sortie to a volcanic field (La Solfatara, Campi Fleigrei). To this end, the instrument was shrunk and ruggedized, without loss of sensitivity. Dedicated field electronics were also designed to allow operation using portable power sources. Lastly, a specific gas handling system was designed and implemented to sustain the chemical mixture expected from the Solfatara’s fumaroles.