1,1,2- 1Anhui Institute of Optics and Fine Mechanics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, China (zhoujch@aiofm.ac.cn)
- 2Laboratoire de Physicochimie de l’Atmosphère, Université du Littoral Côte d’Opale, Dunkerque, France
Nitrogen oxides (NOx) including nitric oxide (NO) and nitrogen dioxide (NO2), are significant reactive nitrogen compounds in the tropospheric atmosphere. The circulation of NOx and free radicals are coupled and interacted with each other, which has an important influence on atmospheric oxidation capacity and the formation of air pollution. Emissions from agricultural sources are the main source of atmospheric NOx. However, due to the limitations of high-precision measurement method of NOx and its flux measurement technique, the flux intensity of NOx emissions from agricultural sources and their effects on atmospheric oxidation are still unclear.
In this presentation, we will report the latest development of amplitude-modulated cavity-enhanced absorption spectroscopy (AM-CEAS) and its application to NOx flux measurement using eddy covariance (EC) method.
The new AM-CEAS based instrument was operated at 406 nm and TTL-modulated at 5 kHz, using phase-sensitive detection for ultra-sensitive absorption measurement. The detection precisions of the instrument were 78 pptv and 30 pptv, respectively, in 0.1 s and 1 s data acquisition time, for NO2 measurement. Combining with Cavity Ring-Down Spectroscopy (CRDS), the AM-CEAS method can eliminate the calibration process of mirror reflectivity, thus realizing NO2 absolute concentration measurements. Building upon single-channel system, a dual-channel NO2 detector has been developed. It utilizes ozone titration in one channel to convert NO to NO₂, allowing for NOx measurement by calculating the difference between the channels.
Using the NOx analyzer, an EC NOx flux observation system was constructed at a wheat field of Shouxian county, and was used for measuring the atmospheric NOx and its flux intensity in summer when ozone pollution is severe. The performance of the flux observation system was evaluated and the resulting NOx fluxes were also analyzed. Based on the advantages of high sensitivity, and minimal maintenance of AM-CEAS, the flux observation system demonstrated good performance, and provided the potential for investigating NOx flux using the EC method across diverse temporal scales.
How to cite: Zhou, J., Zhao, W., Ni, S., Du, Q., Zhang, W., and Chen, W.: Development of an amplitude-modulated cavity-enhanced NOx analyzer and its application for flux measurement in a wheat field, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8501, https://doi.org/10.5194/egusphere-egu26-8501, 2026.
