Abstract
Abstract. We present the first comparison of carbon monoxide (CO) measurements performed with a portable laser spectrometer that exploits the optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) technique, against a high-performance automated gas chromatograph (GC) with a mercuric oxide reduction gas detector (RGD). First, measurements of atmospheric CO mole fraction were continuously collected in a Paris (France) suburb over 1 week. Both instruments showed an excellent agreement within typically 2 ppb (part per billion in volume), fulfilling the World Meteorological Organization (WMO) recommendation for CO inter-laboratory comparison. The compact size and robustness of the OF-CEAS instrument allowed its operation aboard a small aircraft employed for routine tropospheric air analysis over the French Orléans forest area. Direct OF-CEAS real-time CO measurements in tropospheric air were then compared with later analysis of flask samples by the gas chromatograph. Again, a very good agreement was observed. This work establishes that the OF-CEAS laser spectrometer can run unattended at a very high level of sensitivity ( < 1 ppb) and stability without any periodic calibration.
Highlights
Carbon monoxide (CO) is a reactive trace gas that plays a significant role in global atmospheric chemistry by being a major sink of tropospheric hydroxyl radicals (OH)
In order to further establish for different user communities that optical-feedback cavity-enhanced absorption spectroscopy (OF-CEAS) can become a work horse in many applications of CO analysis, which demand robust and compact instrumentation with ppb sensitivity and a fast response time, this paper reports on the comparison of CO measurements performed by OF-CEAS against those obtained by the well-established gas chromatography technique
The OF-CEAS technique allows for the development of sensitive, compact, robust and reliable instruments to perform in situ trace gas analysis
Summary
Carbon monoxide (CO) is a reactive trace gas that plays a significant role in global atmospheric chemistry by being a major sink of tropospheric hydroxyl radicals (OH). OF-CEAS offers many advantages for quantitative and selective trace gas analysis: it allows real-time absolute measurements with the smallest detectable absorption coefficient in the range of a few 10−10 cm−1 for 1 s acquisition time (Landsberg et al, 2014), it does not require periodic calibrations with certified gas mixtures, its sampling volume is small (20 cm3), its response time can be faster than 1 s, and it enables the development of compact instruments to be operated by nonspecialists Another advantage that follows from the high sensitivity of the OF-CEAS technique is the ability to work in the nearinfrared region (NIR), where widely used optics are commercially available together with room temperature lasers and detectors. All values reported in this paper are dry air mole fractions (expressed in ppm or ppb) but are called “concentrations” as commonly done by the community
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