BIOCOMPLEXITY: High-Precision 13CO2/12CO2 Ratio Measurements Using an Optical Fiber Based Difference Frequency Generation Laser Source

University Corporation For Atmospheric Res, Boulder CO

Investigators

Abstract

This project entails the development, test, validation, and deployment of a mid-infrared laser based gas sensor system for continuous in-situ measurements of the isotopic composition of atmospheric carbon dioxide (13CO2/12CO2 ratio) with a precision equal to or better than 0.1 per mil. A science team from the National Center for Atmospheric Research, Rice University, and the University of Colorado will utilize the latest developments in optical fiber technology, recent advances in difference frequency generation (DFG), and multi-year experience in carbon cycle research. The proposed DFG instrument will employ commercially available telecommunication lasers which operate at room temperature. Such a laser source presents significant advantages over more traditional laser systems for achieving high measurement precision. The instrument will be used to acquire high precision atmospheric measurements of 13CO2/12CO2 ratios - a measurement currently accomplished by a network of flask samples followed by mass spectrometric analysis. These data are crucial for understanding terrestrial and oceanic carbon sinks which requires an understanding of the distribution, contribution, and evolution of regional and local CO2 source and sink processes. High precision continuous measurements are needed to provide broad temporal and spatial coverage, even though the isotopic precision is inferior to the flask method (0.012 per mil) At present there does not exist a robust field-deployable instrument capable of continuous 13CO2/12CO2 measurements with a precision of 0.1 per mil or better with verifiable accuracy. The first phase of this effort will focus on extensive laboratory testing to identify and implement optimal experimental conditions and data acquisition and retrieval routines. The next phase will focus on optimal packaging for field measurements, and this will be followed by an extensive set of side-by-side comparisons with state-of-the-art flask sample/mass spectrometric measurements carried out in the field at the University of Colorado's Niwot Ridge Observatory site. Co-located measurements will be carried out on both the ground and the University of Colorado tower facility. The new continuous measurements will provide the foundation for a long-term database from the Niwot Ridge site as well as the necessary experience to further extend these new measurements to other venues and platforms. This project has potential broad impacts in the area of carbon cycle research. In addition, the new instrument and associated new approaches can be adapted to other new research problems requiring ultra high measurement precision. Moreover, a multifaceted educational program with graduate and undergraduate students, high school students and teachers, will transfer the understanding and use of this new laser and fiber optic technology to a broader scientific community. The students will be introduced to 1) the potential of optical fiber technologies and its applications; 2) an overview of the carbon cycle; and 3) the challenges of, and information content offered by, high precision isotopic ratio measurements of CO2.