Compact, Autonomous 13CO2 Flux Monitor Using Pulsed Difference Frequency

75422-The increase of atmospheric CO2 from fossil fuel combustion is a major contributor to global warming and climate change. Improved measurement technology for directly determining the exchange fluxes of the stable isotopes of CO2 is crucial to understanding the natural carbon cycle, which transforms atmospheric CO2 into biological carbon, and to develop strategies to mitigate the problem. Based on recent advances in infrared laser technology, this project will develop a field-portable instrument for the direct measurement of the stable isotopes of CO2. The instrument will have sufficient precision and time response to directly measure 13CO2 fluxes from terrestrial ecosystems using the eddy covariance technique. It will be capable of continuous, unattended operation at remote field sites with minimal consumable supplies and without reliance on cryogenic cooling of light source or detector. Phase I will demonstrate feasibility and explore pump sources for a compact, robust, pulsed difference frequency generation (DFG) light source at a wavelength of 4.3 micrometers using periodically poled lithium niobate (PPLN). Other critical system components, including a dual-path length multiple pass absorption cell and a thermal electric cooled detector, will be optimized and demonstrated. Signal processing algorithms for maximizing measurement precision when using a pulsed laser light sources will be designed and demonstrated. Commercial Applications and Other Benefits as described by the awardee: The direct measurement of 13CO2 fluxes can be used to differentiate carbon exchange mechanisms of photosynthesis and respiration, and to assess the relative importance of vegetation types (C3 vs C4 plants) for carbon sequestration. The instrument would provide a simpler and more compact alternative to presently available isotope ratio mass spectrometer systems. A potentially larger market exists in medical research where stable isotope metabolic tracers can be used to monitor the isotopic ratio in exhaled breath.