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首页> 外文会议>AWMA's (Air Waste Management Association) annual conference exhibition >Assessment of Hydrogen Sulfide Minimum Detection Limits of an Open Path Tunable Diode Laser
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Assessment of Hydrogen Sulfide Minimum Detection Limits of an Open Path Tunable Diode Laser

机译：开路可调二极管激光器的硫化氢最小检出限的评估

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During June 2007, U.S. EPA and ARCADIS conducted a feasibility study at an industrial facility in the southeast U.S. to determine whether the EPA OTM 10 measurement approach, also known as Radial Plume Mapping (RPM), was feasible at the site. The two-day campaign used a Boreal open-path tunable diode laser (OP-TDL) to collect path-integrated hydrogen sulfide measurements along single optical paths downwind of suspected H_2S source areas. The data collected during two pre-study calibration experiments, as well as data collected in the field, were used to assess the minimum detection limit (MDL) of the OP-TDL instrumentation. The results of the analysis of the in-field data suggests that the instrument MDL increases considerably when using longer path lengths. This is due to the fact that the instrument light intensity is lower along longer beam paths, and optical noise will increase as the beam diverges with increasing distance, leading to a lower signal-to-noise ratio. For future studies, it is possible to improve the instrument MDL by using larger retro-reflecting mirrors in the field and measuring over shorter path lengths when possible. Qualitatively, it was observed that the OP-TDL instrument was overestimating the actual hydrogen sulfide concentrations, as the levels approached the instrument MDL. This finding was confirmed by the results of pre-deployment calibration experiment. Based on an analysis of the path-integrated concentration (PIC) values collected with a corresponding R~2 value <0.20, a correction factor was developed. This factor was applied to all PIC values from the study with a corresponding R~2 value less than 0.20 to retrieve a more representative PIC value.
机译：在2007年6月期间，美国EPA和ARCADIS在美国东南部的一家工业设施中进行了可行性研究，以确定EPA OTM 10测量方法（也称为径向羽孔图（RPM））在该地点是否可行。历时两天的活动使用了北方开放式可调谐二极管激光器（OP-TDL）沿可疑H_2S源区顺风的单个光路收集了路径积分的硫化氢测量值。在两次研究前校准实验期间收集的数据以及在现场收集的数据用于评估OP-TDL仪器的最低检测限（MDL）。现场数据的分析结果表明，当使用更长的路径长度时，仪器的MDL会大大增加。这是由于以下事实：沿着较长的光束路径，仪器的光强度较低，并且随着光束随着距离的增加而发散，光学噪声将增加，从而导致较低的信噪比。为了将来的研究，可以通过在现场使用较大的后向反射镜并在可能的情况下以较短的路径长度进行测量来改善仪器的MDL。定性地观察到，随着水平接近仪器的MDL，OP-TDL仪器高估了实际的硫化氢浓度。部署前校准实验的结果证实了这一发现。基于对所收集的路径积分浓度（PIC）值（对应的R〜2值<0.20）的分析，得出了校正因子。该因子应用于研究中的所有PIC值，相应的R〜2值小于0.20，以获取更具代表性的PIC值。

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