Real-time Nitrous Oxide Isotopologue Instrument for Assessing Soil Emissions

Nitrous oxide, N2O, is one of the most important greenhouse and ozone-depleting gases in the atmosphere, with levels that are increasing in part because of soil emissions and agricultural practices. New, improved instruments are needed to quantify the sources and sinks of nitrous oxide and to better understand the impact of environmental conditions on emissions. Because these sources and sinks have both high temporal and spatial variability, a real time monitor for eddy covariance measurements will benefit researchers. Advanced, compact, low power instruments will also improve the ability of researchers to more readily deploy real-time, fast response, sensitive nitrous oxide monitors. The proposed low power, compact N2O monitor will meet the need for a fast response, sensitive system for quantification of soil emissions. The instrument will be based on a continuous wave quantum cascade laser in a compact fast response instrument, designed for low power consumption. The overall objective is a nitrous oxide instrument with 1 sec precision of 0.04 ppb, averaging to 0.02 ppb in 60 sec, and a reduction in total instrument power to allow it to be provided by solar energy. The Phase I tasks will demonstrate the feasibility of a compact, low-power nitrous oxide monitor for eddy flux or soil chamber measurements, including studies of N2O isotopologue fluxes in chambers. To accomplish this, a low volume multipass cell will be designed to allow fast response with a lower power pump. Low power, light weight electronics will be designed and an improved thermal instrument design will be developed to eliminate the need for water cooling. Sensitive N2O detection in an instrument incorporating these innovative components will be demonstrated. The outline of a comprehensive eddy covariance system capable of deployment with solar energy will be completed. The application of the monitor to measurement of N2O isotopologues emitted into soil chambers will be shown. Commercial Applications and Other Benefits: The proposed instrument would benefit soil scientists, climate change researchers, and ultimately policy makers. By identifying and improving the understanding of microbial production of N2O in soils, better agricultural management practices can be developed. This technology will provide a significant societal benefit through improved understanding and mitigation of global warming and global climate change.