A System of Observation, Analysis and Verification for the Stable Isotopes of Carbon Dioxide

78555S DOE requires rapid, cost-effective methods for measuring the isotopic composition of atmospheric carbon dioxide. For discrete sampling, the [13CO2]/[12CO2] ratio must be measured to a precision of 0.2¿. For continuous monitoring (e.g. a one hour period), a resolution of 10 times less (~3¿) is acceptable. The instrumentation must be robust enough to operate properly for a full range of natural conditions. This project will develop instrumentation and methodology to observe, by continuous and discrete sampling, the isotopic ratio of air for terrestrial ecosystems. Phase I will construct and evaluate two prototypes for continuous in situ monitoring of the isotopic ratio of air. Both prototypes will be based on the NoinDispersive InfraRed technique, easily the most robust and least expensive option for the instrumentation. Verification will be by flask samples analyzed to high precision by mass spectrometry. The possibility of extending the prototypes to the monitoring of the full carbon cycle also will be evaluated. Commercial Applications and Other Benefits as described by the awardee: The instrumentation should provide verifiable, high precision time measurements of the [13CO2]/[12CO2] isotopic ratio for air associated with diverse components of terrestrial ecosystems. In addition, the system should help answer the following two questions: (1) are any important sources or sinks of CO2 missing from the net observed flux of ecosystems, and (2) is any important information missing from models that predict the response of the inventories to climate change?