Low Power Instrumentation for Measurement of Greenhouse Gas Emissions in Terrestrial-Aquatic Interfaces

Nitrous oxide is the third most important greenhouse trace gas after carbon dioxide and methane and is a dominant ozone depleting substance. Its emissions to the atmosphere are extremely heterogeneous in space and time. Novel approaches to characterize such heterogeneity for incorporation into models and to identify effective mitigation strategies are greatly needed. Commercial instruments for flux measurement of methane are available, however, similar instruments for nitrous oxide are lacking, as it presents greater measurement challenges. Southwest Sciences, Inc. is addressing this need through an intensive program of further development, field testing, and commercialization of low power laser-based systems that measure nitrous oxide emissions, along with either water vapor or carbon dioxide. The instruments developed in this project will allow accurate, simultaneous measurements of greenhouse gas emissions at unprecedented spatial and temporal scales in a robust, low-power field package. The Phase I effort demonstrated that our nitrous oxide gas analyzer technology can be packaged into a compact, low power, light weight system that can run on battery power for extended times for use at remote study sites. Field tests demonstrated that the gas analyzer performance provides the speed and resolution required for eddy covariance flux determinations and, when combined with a sonic anemometer, provides data that can be processed to provide meaningful flux values by eddy covariance techniques. The Phase II research and development has included extensive field testing of prototype instruments in agricultural settings in collaboration with researchers at the University of Illinois and the Lawrence Berkeley National Laboratory. In Phase IIB, design improvements will be implemented that improve the operational performance and field ruggedness of the instruments, and detailed covariance calculations performed by LBNL researchers under subcontract will include relevant correction terms to account for spectroscopic effects, changes in air density, and high-frequency signal attenuation to strengthen the robustness of measurements using this groundbreaking instrumentation. Commercial instruments for measuring nitrous oxide fluxes (simultaneously with either water or carbon dioxide) will be developed. The technology could be widely applied across existing and future FLUXNET, AmeriFlux, ARM and other atmospheric science networks. The instrument will allow researchers, regulators, and environmental consultants to accurately and effectively measure emissions at unprecedented spatial and temporal scales in a quick, efficient, and easy manner.