Development and application of an eddy covariance system based on amplitude-modulated cavity-enhanced absorption spectroscopy for NO2 flux measurement in a wheat field

IF 5.7 1区农林科学 Q1 AGRONOMY

Agricultural and Forest Meteorology Pub Date : 2025-09-06 DOI:10.1016/j.agrformet.2025.110826

Qianqian Du , Jiacheng Zhou , Weixiong Zhao , Shichuan Ni , Chong Zhang , Chunxiang Ye , Weihua Cui , Weijun Zhang , Yanfeng Huo , Yanyu Lu , Zhu Zhu , Yue Liu

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引用次数: 0

Abstract

Long-term measurements of nitrogen dioxide (NO₂) flux are essential for improving understanding of the mechanisms underlying biosphere-atmosphere NO₂ exchange and elucidating its role in secondary pollutant formation. However, accurately quantifying NO₂ flux remains a challenge due to the absence of a robust fast response gas analyzer. In this work, we report the development of an eddy covariance (EC) NO₂ flux observation system based on amplitude-modulated cavity-enhanced absorption spectroscopy (AM-CEAS) technique, along with its application in a wheat field. Based on a NO₂ detection precision of 78 pptv (1σ) at 10 Hz, the NO₂ flux detection limit was estimated to be 4.65 µg N m⁻² h⁻¹. An analysis of spectral damping showed median flux losses of 24.96 % in the high-frequency range and 0.37 % at low frequencies. The median random error was estimated at 39.64 %. During the observation period, the wheat field acted as a net source of atmospheric NO₂, with a median NO₂ flux of 11.47 (−138.59 − 200.75) µg N m⁻² h⁻¹. Relative dominance of fertilizer, soil temperature, and soil moisture in controlling NO₂ emissions shifted competitively with varying soil conditions. This indicated a key gap in current NOₓ estimates, where simplified driver constraints diverge from observed emissions. A strong dependence of NO₂ exchange rates on their atmospheric concentrations was observed, indicating the existence of a compensation point or a similar mechanism. The compensation point was further estimated to range from 4 to 5 ppbv. 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 NO₂ flux using the EC method across diverse temporal scales.

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基于调幅腔增强吸收光谱的涡旋相关系统在麦田NO2通量测量中的开发与应用

长期测量二氧化氮（NO2）通量对于提高对生物圈-大气NO2交换机制的理解以及阐明其在二次污染物形成中的作用至关重要。然而，由于缺乏可靠的快速响应气体分析仪，准确量化NO2通量仍然是一个挑战。在这项工作中，我们报告了基于调幅腔增强吸收光谱（AM-CEAS）技术的涡动相关（EC） NO2通量观测系统的开发及其在麦田中的应用。基于10 Hz下NO2的检测精度为78 pptv (1σ)， NO2通量的检测限为4.65µg N m−2 h−1。频谱阻尼分析表明，高频范围的磁通损失中值为24.96%，低频范围的磁通损失中值为0.37%。随机误差中位数估计为39.64%。在观测期内，麦田是大气NO2的净来源，NO2通量中值为11.47（- 138.59 - 200.75）µg N m−2 h−1。肥料、土壤温度和土壤湿度在控制NO2排放中的相对优势随着土壤条件的变化而竞争性地变化。这表明目前的NOₓ估计存在一个关键差距，即简化的驾驶员约束与观测到的排放存在差异。NO2交换速率对其大气浓度有很强的依赖性，表明补偿点或类似机制的存在。进一步估计补偿点范围为4至5 ppbv。该通量观测系统具有灵敏度高、维护成本低的优点，为利用EC方法在不同时间尺度上研究NO2通量提供了可能。

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来源期刊

Agricultural and Forest Meteorology 农林科学-林学

CiteScore

10.30

自引率

9.70%

发文量

415

审稿时长

69 days

期刊介绍： Agricultural and Forest Meteorology is an international journal for the publication of original articles and reviews on the inter-relationship between meteorology, agriculture, forestry, and natural ecosystems. Emphasis is on basic and applied scientific research relevant to practical problems in the field of plant and soil sciences, ecology and biogeochemistry as affected by weather as well as climate variability and change. Theoretical models should be tested against experimental data. Articles must appeal to an international audience. Special issues devoted to single topics are also published. Typical topics include canopy micrometeorology (e.g. canopy radiation transfer, turbulence near the ground, evapotranspiration, energy balance, fluxes of trace gases), micrometeorological instrumentation (e.g., sensors for trace gases, flux measurement instruments, radiation measurement techniques), aerobiology (e.g. the dispersion of pollen, spores, insects and pesticides), biometeorology (e.g. the effect of weather and climate on plant distribution, crop yield, water-use efficiency, and plant phenology), forest-fire/weather interactions, and feedbacks from vegetation to weather and the climate system.