Institute of Atmospheric Research and Development of Nitric Oxide Turbulent Flux Observation System

[ Instrument R & D of Instrument Network ] The vortex correlation method based on the turbulence theory is an ideal method for measuring the carbon-nitrogen gas exchange flux of geogas. Because the concentration of nitric oxide (NO) in the atmosphere is very low, there has been very little research on measuring the turbulent flux of NO based on this method for a long time. The carbon and nitrogen cycle team of Wang Kai and Zheng Xunhua, Institute of Atmospheric Physics, Chinese Academy of Sciences, adopted a closed-loop mid-infrared quantum cascade laser (QCL) gas analyzer to develop a set of NO turbulence flux observation system based on eddy correlation method , And carry out observation studies in a typical subtropical farmland ecosystem to evaluate the operating performance of the observation system under field conditions and its applicability for measuring farmland NO turbulence.

The observation system operates stably under field conditions, with a detection accuracy of 1038 NO concentration of 0.338 ppbv and a half-hour NO flux detection limit of 5.6 μg N m-2 h-1 (95% confidence), which is effective Obtain the NO turbulent flux during the low emission period (without fertilization effect). The study did not consider the underestimation of the flux caused by the photochemical reaction during the transfer of NO from the soil surface to the observation height. To obtain the NO emission flux from the soil surface, this systematic error needs to be considered.

The research results show that the NO turbulence flux observation system based on QCL laser detection technology has advantages in stability, measurement response speed, maintenance workload, etc. It is a long-period in-situ observation of NO turbulence exchange flux between the ecosystem and the atmosphere A new method option is provided. In addition, the study also proposed a concentration pulse delay correction scheme suitable for low signal-to-noise ratio gas (such as NO, N2O) and an error evaluation method for turbulent flux, providing a method reference for similar observation studies.