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CO2和H2O是大气中两种重要的温室气体,对生态系统中CO2和H2O的浓度进行在线监测可用于分析环境及气候变化。选择CO2和H2O的近红外吸收谱线,利用可调谐半导体激光吸收光谱技术结合自动增益调节技术设计了开放式CO2和H2O在线检测仪。在中国科学院禹城综合试验站进行了1238m光程下,20Hz时间分辨率的连续观测实验,结果表明自动增益调节解决了开放光路检测时探测信号幅度大幅变化问题。监测点的CO2浓度具有白天低,夜间高的日变化周期性。与同场地涡度相关系统的LI-7500对比测量,数据一致性较好。该检测技术灵敏度高、响应速度快、免采样,实现了大尺度区域生态系统中CO2和H2O浓度的稳定、连续、在线检测。
CO2 and H2O are two important greenhouse gases in the atmosphere. Online monitoring of CO2 and H2O concentrations in ecosystems can be used to analyze environmental and climate changes. The CO2 and H2O near-infrared absorption spectra were selected and the open CO2 and H2O on-line detector was designed by using tunable semiconductor laser absorption spectroscopy combined with automatic gain adjustment. The continuous observing experiment of 20Hz temporal resolution at 1238m optical path was carried out at Yucheng Comprehensive Experimental Station of Chinese Academy of Sciences. The results show that the automatic gain adjustment solves the problem of large amplitude change of the detection signal when the open optical path is detected. The CO2 concentration at the monitoring sites has low daytime and high diurnal periodicity of nighttime. LI-7500 contrast measurement with the same place vorticity correlation system, the data consistency is good. The detection technology has the advantages of high sensitivity, fast response and no-sampling, and realizes stable, continuous and on-line detection of CO2 and H2O concentrations in large-scale regional ecosystems.