Time-resolved analysis of carbon monoxide emissions from vehicles using a quartz-enhanced photoacoustic sensor

Low-cost sensors networks hold the promise of dense spatial mapping over wide areas, through a combination of its price point and transportability, with a fine spatial reconstruction of the pollutants. Their reliability and the limited performance, particularly at finer temporal resolutions, represents the other side of coin. These shortcomings in dynamic environments pose serious challenges for their use in exposure studies and mobile applications. A recommendation for careful calibration, strategic experimental design, and an emphasis on high temporal resolution use cases are essential for guiding future technological development without losing key features, such as portability and compactness. In this work, we used a Quartz-Enhanced Photoacoustic Spectroscopy (QEPAS)-based sensor for sequentially measuring carbon monoxide (CO), nitrous oxide (N2O), and water vapor emissions near vehicle exhaust pipes. With detection limits of 150 ppb for N2O and 91 ppb for CO, this sensor allows for precise emission measurements. Moreover, the 300 ms temporal resolution enables real-time tracking of emission variations with a detailed temporal analysis. Field tests at the University of Bari Campus parking area confirmed the sensor capability to capture CO concentration fluctuations from both idling and moving vehicles.