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Article

Advances in High-Precision NO2 Measurement by Quantum Cascade Laser Absorption Spectroscopy

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Empa-Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution and Environmental Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland
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Empa-Swiss Federal Laboratories for Materials Science and Technology, Transport at Nanoscale Interfaces, Überlandstrasse 129, 8600 Dübendorf, Switzerland
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METAS-Federal Institute of Metrology, Chemical and Biological Metrology, Lindenweg 50, 3003 Bern-Wabern, Switzerland
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Author to whom correspondence should be addressed.
Academic Editor: Giulio Nicola Cerullo
Appl. Sci. 2021, 11(3), 1222; https://doi.org/10.3390/app11031222
Received: 9 December 2020 / Revised: 13 January 2021 / Accepted: 22 January 2021 / Published: 29 January 2021
Nitrogen dioxide (NO2) is a major tropospheric air pollutant. Its concentration in the atmosphere is most frequently monitored indirectly by chemiluminescence detection or using direct light absorption in the visible range. Both techniques are subject to known biases from other trace gases (including water vapor), making accurate measurements at low concentration very challenging. Selective measurements of NO2 in the mid-infrared have been proposed as a promising alternative, but field deployments and comparisons with established techniques remain sparse. Here, we describe the development and validation of a quantum cascade laser-based spectrometer (QCLAS). It relies on a custom-made astigmatic multipass absorption cell and a recently developed low heat dissipation laser driving and a FPGA based data acquisition approach. We demonstrate a sub-pptv precision (1 σ) for NO2 after 150 s integration time. The instrument performance in terms of long-term stability, linearity and field operation capability was assessed in the laboratory and during a two-week inter-comparison campaign at a suburban air pollution monitoring station. Four NO2 instruments corresponding to three different detection techniques (chemiluminescence detection (CLD), cavity-attenuated phase shift (CAPS) spectroscopy and QCLAS) were deployed after calibrating them with three different referencing methods: gas-phase titration of NO, dynamic high-concentration cylinder dilution and permeation. These measurements show that QCLAS is an attractive alternative for high-precision NO2 monitoring. Used in dual-laser configuration, its capabilities can be extended to NO, thus allowing for unambiguous quantification of nitrogen oxides (NOx), which are of key importance in air quality assessments. View Full-Text
Keywords: air pollution; trace gas; nitrogen dioxide; laser spectroscopy; mid-infrared; quantum cascade laser; selective detection air pollution; trace gas; nitrogen dioxide; laser spectroscopy; mid-infrared; quantum cascade laser; selective detection
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MDPI and ACS Style

Sobanski, N.; Tuzson, B.; Scheidegger, P.; Looser, H.; Kupferschmid, A.; Iturrate, M.; Pascale, C.; Hüglin, C.; Emmenegger, L. Advances in High-Precision NO2 Measurement by Quantum Cascade Laser Absorption Spectroscopy. Appl. Sci. 2021, 11, 1222. https://doi.org/10.3390/app11031222

AMA Style

Sobanski N, Tuzson B, Scheidegger P, Looser H, Kupferschmid A, Iturrate M, Pascale C, Hüglin C, Emmenegger L. Advances in High-Precision NO2 Measurement by Quantum Cascade Laser Absorption Spectroscopy. Applied Sciences. 2021; 11(3):1222. https://doi.org/10.3390/app11031222

Chicago/Turabian Style

Sobanski, Nicolas, Béla Tuzson, Philipp Scheidegger, Herbert Looser, André Kupferschmid, Maitane Iturrate, Céline Pascale, Christoph Hüglin, and Lukas Emmenegger. 2021. "Advances in High-Precision NO2 Measurement by Quantum Cascade Laser Absorption Spectroscopy" Applied Sciences 11, no. 3: 1222. https://doi.org/10.3390/app11031222

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