The Atmospheric Institute has successfully developed a nitric oxide turbulence flux observation syst

2024-01-08

The eddy correlation method based on turbulence theory is an ideal method for measuring the exchange flux of carbon and nitrogen gases in the atmosphere. Due to the extremely low concentration of nitric oxide (NO) in the atmosphere, there has been a lack of research on measuring NO turbulent flux based on this method for a long time. The carbon nitrogen cycle team of Wang Kai and Zheng Xunhua from the Institute of Atmospheric Physics of the Chinese Academy of Sciences has developed a set of NO turbulent flux observation system based on eddy correlation method by using a closed circuit mid infrared quantum cascade laser (QCL) gas analysis, and carried out observation research in a typical subtropical farmland ecosystem to evaluate the operation performance of the observation system under field conditions and the applicability of measuring farmland NO turbulent flux.

The observation system operates stably under field conditions, with a detection accuracy of 0.338 ppbv for 10 Hz NO concentration and a detection limit of 5.6 for half hour NO flux μ G N m-2 h-1 (95% confidence) can effectively obtain the NO turbulent flux during the low emission period (without fertilization effect). This study did not consider the underestimation of NO flux caused by photochemical reactions during the transfer of NO from the soil surface to the observation height. To obtain the NO emission flux on the soil surface, this systematic error needs to be considered.

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

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