介绍了一套基于便携式悬臂梁麦克风光声光谱监测大气环境温室气体浓度的高灵敏系统,采用脉冲红外光源通过窄带光学滤光片,形成中红外区的多个光谱波段,结合光学悬臂梁麦克风技术,具有超高灵敏度,可去除背景气体干扰,实现同时监测多种气体.通过对温室气体浓度的测量,验证了甲烷(CH4)的方法检出限为0.226×10-6,二氧化碳(CO2)的方法检出限为2.624×10-6,其余的温室气体检出限最低为四氟化碳(0.052×10-6),最高为三氟化氮(0.164×10-6).同时验证了长期重复性,CO2的1倍标准偏差为0.405 5,最大漂移量为1.775 6×10-6;CH4的1倍标准偏差为9.162 0,最大漂移量为36.261 1×10-9;该仪器对CO2的最大示值偏差为-0.04×10-6,CH4的最大示值偏差为1.48×10-9.温室气体的相对标准偏差均＜2％;CO2和CH4的平均响应时间均为2 min 40 s;CO2和CH4的决定系数(R2)均＞0.999 9,CO2拟合残差在±0.05×10-6以内,CH4拟合残差在±1×10-6以内.
Performance Test of Portable Cantilever Beam Microphone Photoacoustic Spectrum Green-house Gas Monitoring Instrument
This paper introduces a set of highly sensitive system based on portable cantilever beam microphone photoacoustic spectroscopy to monitor the concentration of greenhouse gases in the atmospheric environment.The pulsed infrared light source is used to form multiple spectral bands in the mid-infrared region through a narrow-band optical filter.Combined with the optical cantilever beam microphone technology,it has ultra-high sensitivity and can remove background gas interference to achieve simultaneous monitoring of multiple gases.By measuring the concentrations of greenhouse gases,it was verified that the method detection limit of CH4 is 0.226×10-6,and the method detection limit of CO2 is 2.624×10-6.The detection limits of other greenhouse gases were as low as CF4(0.052×10-6)and as high as NF3(0.164×10-6).The long-term repeatability was verified,with 1 time the standard deviation of CO2 being 0.405 5 and the maximum drift being 1.775 6×10-6;1 time the standard deviation of CH4 being 9.162 0 and the maximum drift being 36.261 1×10-9.It was verified that the maximum indication deviation of the instrument for CO2 is-0.04×10-6,and for CH4 is 1.48×10-9.The relative standard deviations of greenhouse gases are all＜2％;the average response time of CO2 and CH4 is verified to be 2 min 40 s;the R2 of C02 and CH4 is verified to be＞0.999 9,the CO2 fitting residual is within±0.05×10-6,and the CH4 fitting residual is within±1×10-6.
Greenhouse gasesPhotoacoustic spectrometryEnhanced cantilever beam optical microphoneMultiple gas detection
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