Isotopic Carbon Dioxide Analyzer for Flux Measurements

A detailed understanding of carbon cycle is limited by the availability of rapid, accurate, and easy-to-use isotope analyzers. Researchers use stable isotope data to study: 1) recycling of CO2 within forests; 2) water use efficiency; 3) partitioning carbon exchange into its components; and 4) identify and quantify the distribution and contributions of C3 and C4 species to global productivity. Los Gatos Research proposes to develop a rugged, field-deployable, Off-Axis Integrated Cavity Output Spectroscopy (Off-Axis ICOS) instrument for eddy flux and chamber flux measurements of CO2 concentration and isotope ratios (13C, 18O, and 17O) in ambient air. LGR demonstrated technical feasibility by fabricating an Off-Axis ICOS instrument that measured CO2 concentration, 13C, 18O, and 17O to better than 0.022 ppm, 0.084 , 0.093 , and 0.186 respectively (1, 100s) on both ambient air and syringe-injected samples. Moreover, the instrument provided a measurement rate of 9.1 Hz for eddy correlation flux measurements. The [CO2] and 13C accuracy of analyzer was better than 0.30 ppm and 0.16 respectively over a wide dynamic range of CO2 concentrations (271 - 2961 ppm). The instrument was interfaced to a soil-gas sampler to record the isotope flux from soils. LGR then worked with Professor Dennis Baldocchi (UC Berkeley) to deploy the instrument at a DOE Amerflux site in Sherman Island, California. Finally, the Phase I instrument was also used to provide mobile monitoring data for the development of Isoscapes. In Phase II, LGR will refine the instrument to increase its accuracy, precision, dynamic range, and stability. A calibration scheme will help optimize precision and minimize concentration dependences. The instrument will be interfaced to other analyzers and a gas injection system. The analyzer will be tested at LGR before delivery to Professor Ralph Keeling (Scripps) for independent verification on calibrated samples and ambient air. Subsequently, LGR will fabricate additional units and work with Professor Chris Still (UC Santa Barbara) and Professor Dennis Baldocchi (UC Berkeley) to deploy the instruments at an Experiment Forest and to study the carbon water cycle interactions and the Sherman Island DOE Ameriflux site for long-term monitoring of CO2 isotope fluxes. Finally, LGR will evaluate using the technology to quantify 14CO2 and 13C18O16O (clumped isotopes). Additionally, LGR is providing a Phase II Funding Commitment to interface a combustion front-end unit to the analyzer. Commercial Applications and Other Benefits: The proposed SBIR analyzer has significant commercial potential for environmental research, medical diagnostics, and other isotope applications (e.g. mining, food verification)