Compact and portable quartz-enhanced photoacoustic spectroscopy sensor for carbon monoxide environmental monitoring in urban areas

Fabrizio Sgobba; Angelo Sampaolo; Pietro Patimisco; Marilena Giglio; Giansergio Menduni; Ada Cristina Ranieri; Christine Hoelzl; Hubert Rossmadl; Christian Brehm; Verena Mackowiak; Dario Assante; Ezio Ranieri; Vincenzo Spagnolo

doi:10.1016/j.pacs.2021.100318

Compact and portable quartz-enhanced photoacoustic spectroscopy sensor for carbon monoxide environmental monitoring in urban areas

Photoacoustics. 2021 Nov 25:25:100318. doi: 10.1016/j.pacs.2021.100318. eCollection 2022 Mar.

Authors

Fabrizio Sgobba¹, Angelo Sampaolo^{1

2}, Pietro Patimisco^{1

2}, Marilena Giglio¹, Giansergio Menduni¹, Ada Cristina Ranieri^{1

3}, Christine Hoelzl⁴, Hubert Rossmadl⁴, Christian Brehm⁴, Verena Mackowiak⁴, Dario Assante³, Ezio Ranieri⁵, Vincenzo Spagnolo^{1

2}

Affiliations

¹ PolySense Lab, Dipartimento Interateneo di Fisica, University and Politecnico of Bari, CNR-IFN, Via Amendola 173, Bari 70126 Italy.
² PolySense Innovations srl, Via Amendola 173, Bari 70126 Italy.
³ Faculty of Engineering, Uninettuno University, 00186 Rome, Italy.
⁴ Thorlabs GmbH, Münchner Weg 1, 85232 Bergkirchen, Germany.
⁵ Biology Department, University of Bari, Via Orabona 4, 70126 Bari, Italy.

Abstract

We report on the realization, calibration, and test outdoor of a 19-inches rack 3-units sized Quartz Enhanced Photoacoustic Spectroscopy (QEPAS) trace gas sensor designed for real-time carbon monoxide monitoring in ambient air. Since CO acts as a slow energy relaxer when excited in the mid-infrared spectral region, its QEPAS signal is affected by the presence of relaxation promoters, such as water vapor, or quenchers like molecular oxygen. We analyzed in detail all the CO relaxation processes with typical collisional partners in an ambient air matrix and used this information to evaluate oxygen and humidity-related effects, allowing the real CO concentration to be retrieved. The sensor was tested outdoor in a trafficked urban area for several hours providing results comparable with the daily averages reported by the local air inspection agency, with spikes in CO concentration correlated to the passages of heavy-duty vehicles.

Keywords: Carbon monoxide; Energy relaxation processes; Environmental monitoring; Gas sensing; QEPAS, Quartz-Enhanced PhotoAcoustic Spectroscopy; Quartz enhanced photoacoustic spectroscopy.