基于激光吸收光谱开放式大气CO2的在线监测

Open-Path Online Monitoring of Ambient Atmospheric CO_2 Based on Laser Absorption Spectrum

二氧化碳(CO2)作为最主要的温室气体,引发的气候变化和生态环境问题已经成为世界关注的焦点,因此在线监测环境大气中CO2浓度,分析生态系统的CO2通量是重要任务。将可调谐半导体激光吸收光谱(TDLAS)技术与开放式长光程技术相结合设计了大范围CO2监测仪,系统选择CO2在近红外1.57μm附近的吸收线,以30 s的时间分辨率对城郊大气CO2浓度进行了连续测量,得出日变化和连续监测结果。结果表明在无污染排放源的城市郊区,大气中的CO2具有明显的日变化周期性,基本特点是白天浓度低,夜间浓度高。监测仪不需要气体采样、具有高灵敏度、高分辨性、可快速在线监测、调校简单等优点,检测限可以达到4.2×10-7。为生态系统中的温室气体大范围通量监测提供了有效的方法。

With the conjunction of tunable diode laser absorption spectroscopy technology（TDLAS） and the open long optical path technology,the system designing scheme of CO2 on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail,and the instrument for large-range measurement was set up.By choosing the infrared absorption line of CO2 at 1.57 μm whose line strength is strong and suitable for measurement,the ambient atmospheric CO2 was measured continuously with a 30 s temporal resolution at an suburb site in the autumn of 2007.The diurnal atmospheric variations of CO2 and continuous monitoring results were presented.The results show that the variation in CO2 concentration has an obvious diurnal periodicity in suburb where the air is free of interference and contamination.The general characteristic of diurnal variation is that the concentration is low in the daytime and high at night,so it matches the photosynthesis trend.The instrument can detect gas concentration online with high resolution,high sensitivity,high precision,short response time and many other advantages, the monitoring requires no gas sampling,the calibration is easy,and the detection limit is about 4.2×10-7.It has been proved that the system and measurement project are feasible,so it is an effective method for gas flux continuous online monitoring of large range in ecosystem based on TDLAS technology.