Dual Laser Isotopic Flux Monitor for Carbon Dioxide and Water Vapor

The increase of carbon dioxide (CO2) in the Earth¿s atmosphere is the most important driver of global warming. In order to predict future carbon dioxide concentrations under various mitigation strategies, a better quantitative understanding of the sources and sinks of atmospheric carbon dioxide is required. The ratios of the stable isotopes of CO2 has long been recognized as markers for identifying these sources and sinks. However, the wider use of stable isotopes in ecosystem exchange studies has been impeded by the difficulty of making these measurements at the requisite precision (better than 0.2 ¿). As a further complication, existing instrumentation using isotope-ratio mass spectrometry requires samples to be collected in flasks and returned to the laboratory for analysis. This project will develop an advanced laser-based instrument for simultaneous real-time measurement of isotopologues of CO2 and H2O. The instrument will be suitable for field-measurement of isotopic fluxes by eddy covariance, which will allow (1) the determination of wide area emission and deposition of CO2, and (2) a partitioning between plant photosynthesis and respiration fluxes. The instrument also will be suitable for high precision measurements of CO2 concentration. In Phase I, an existing pulsed quantum cascade laser will be upgraded to a continuous wave (CW) quantum cascade laser. During Phase II, a second laser will be added for the measurement of isotopologues of H2O (H216O, H218O, HD16O), which will allow a more complete understanding of the fluxes of these gases where there is rapid exchange of oxygen isotopomers. Commercial Applications and other Benefits as described by the awardee: This instrument has the potential to significantly benefit human health and well being by improving our understanding of the sources and sinks of atmospheric CO2. The primary market for this instrument will be atmospheric research groups at universities and national laboratories. Additional markets include the atmospheric science and the environmental pollution research and development communities.