Novel Laser Systems for CO2 Source Identification – An Isotope Approach

Los Alamos National Laboratory has engineered three types of laser systems to monitor the carbon isotopes of CO2 in the air for the purpose of tracking seepage from geological CO2 storage reservoirs. Yet, these systems have also been used to monitor the natural fluxes of photosynthesis and respiration in mixed environments, specifically managed agricultural fields in Bozeman, MT, and high altitude Montaigne grassland ecosystems in northern NM. Specifically, we are using a closed-path system, an open-path retroreflection system, and a LIDAR system to monitor the 13CO2 and 12CO2 gases in the canopy. Specifically, we are using frequency modulated spectroscopy (FMS) to direct a tunable diode laser (TDL) through an electro-optical modulator operating in the radio frequency regime producing the original carrier frequency from the TDL (ωc) and evenly spaced sidebands (ωc ± ωm). The 12CO2 and 13CO2 are detected by tuning the TDL and the modulation frequency such that one of the sidebands interacts with a specific spectral feature. Frequency modulated spectroscopy (FMS) is an ultra sensitive means of detecting the stable isotopes of CO2 that is conservatively 100x more sensitive than standard absorption spectroscopy. Through the use of this novel remote sensing approach, we are able to monitor the isotopes of CO2 in real time at both point locations and over a range of space, 250 m column integrated measurements. This type of measurement could be used to advance ecological models, carbon flux measurements, integrated carbon source evaluations, and management impacts to carbon exchange models. These remote sensing systems my transform our approach to measuring stable isotopes of trace gases in the atmosphere.