摘要
摘要:N₂O是主要源自农田的重要温室气体之一，可破坏臭氧层而导致全球增温。目前对N₂O的原位高频观测尚不多。为完善N₂O的观测方法，为华北地区N₂O变化研究提供参考，本研究以华北平原典型农田为研究对象，利用新型的N₂O测定仪器TGA200A，进行实时、自动、昼夜连续地观测中国科学院禹城综合试验站农田大气N₂O的日动态变化。本次观测自2017年6月中旬玉米播种后开始，持续至2017年9月（8月份仪器调试）。结果显示：1）晴朗天气下，农田大气N₂O呈现出夜晚（0：00-6：00、18：00-24：00）高（0.618~1.171 mg·m^-3）、白天（6：00-18：00）低（0.526~1.145 mg·m^-3）的趋势，而白天高温又促进农田N₂O排放，在午后15：00-17：00大多出现1次峰值，表明温度的促进作用存在滞后性。2）降雨天气下，农田N₂O在适当的雨量下逐渐增加（3 h内增加0.033 mg·m^-3），且存在累积效应，但过度淹水后N₂O表现出逐渐降低的趋势。3）大风天气下，N₂O的浓度产生变化，但规律并不明显。研究结果表明，利用TGA200A可以实现对温室气体N₂O的实时、连续、动态的自动观测，观测结果具有较高可信度，可以反映出当前华北地区农田N₂O在不同环境要素（温度、降水及大风）下的动态变化趋势。
关键词:华北平原/
农田生态系统/
N₂O排放/
通量监测/
高频监测
Abstract:Nitrous oxide (N₂O) is one of the primary greenhouse gases, which depletes ozone sphere and results in strong greenhouse effects. Nowadays, a series of studies on greenhouse gases emissions of vegetation-soil-atmosphere system has been carried out domestic and overseas with the measurement method of static chamber/gas chromatograph, in which gas sampling time is concentrated in a fixed period during daytime rather than around the clock. Moreover, its' sampling frequency is usually longer than one minute inducing difficulty to implement a real-time, high-frequency and continuous determination of greenhouse gas emissions in situ for a long time. As an important source of N₂O emission, farmland ecosystem is a human-disturbed system with fast N recycle and large N₂O emission. To improve N₂O emission observation methods and provide a reference for N₂O change study in the North China Plain, we chose a typical farmland ecosystem, a maize field at the Yucheng Comprehensive Experiment Station, Chinese Academy of Sciences, and monitored N₂O concentration change with a new monitor instrument TGA200A (Trace Gas Analyzer 200A) to achieve a automatically real-time monitoring of N₂O emission for day and night. The TGA200A was equipped with a laser launch tube simultaneously controlled by current and temperature and some related measuring devices. When sample and reference gases (with a known concentration) entered the analyzer synchronously, the target gas concentration was determined by through scanning and comparing the linear absorption wavelengths of laser energy between sample and reference gases. The monitoring was from the middle of June 2017 to September 2017. The results showed, firstly, the N₂O emission was higher in night from 0:00 to 6:00 and 18:00 to 24:00 (0.618-1.171 mg·m^-3) than in daytime from 6:00 to 18:00 (0.526-1.145 mg·m^-3) in fine weather. N₂O emission was facilitated under higher atmospheric temperature in daytime, but the emission peak appeared in 15:00 to 17:00 indicating a significant hysteresis of temperature effect. Secondly, in rainy day, maize field N₂O emissions were increased by 0.033 mg·m^-3 in 3 hours with a proper rainfall and presented an accumulative effect. But if the rain was too heavy for a long time, the N₂O emission would be reduced. Thirdly, N₂O emission was affected by strong wind, but this conclusion needed more verification because such result was not regular. This study demonstrated the data determined by the TGA200A was useful and reliable for study on dynamic change of N₂O emission in different weathers. TGA200A was available in an automatically and real-time monitor of N₂O emission for day and night with different environment elements (temperature, rain, wind) and made it possible to reduce human costs and errors in greenhouse gas flux observation.
Key words:North China Plain/
Farmland ecosystem/
Nitrous oxide emission/
Flux observation/
High-frequency observation



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