Field validation of gas sensors for urban and volcanic emissions monitoring based on quartz-enhanced photoacoustic spectroscopy

Real-time detection of trace gases is essential for environmental and geochemical monitoring. We present two compact QEPAS-based sensors for the selective detection of CO, N₂O, and H₂S, both sharing a common acoustic architecture based on a T-shaped quartz tuning fork with resonator tubes but differing in the laser source used to target the analytes. The first system employs a mid-IR quantum cascade laser (λ ≈ 4.61μm) for detecting CO and N₂O at ppb levels. The second uses a near-IR DFB diode laser (λ ≈ 2.63μm) for H₂S detection at ppm levels. Field validation was carried out in two distinct scenarios: an open-air university parking area, where the urban sensor intercepted vehicle exhaust plumes, and the Pisciarelli fumarolic field (Campi Flegrei, Italy), where the volcanic sensor tracked rapid H₂S variations. Results confirm the versatility and robustness of the modular QEPAS architecture for autonomous, high-resolution gas monitoring in complex field environments.