Near-Infrared Mobile Cloud OA-ICOS Sensor System for Atmospheric Carbon Dioxide Monitoring

Based on near-infrared off-axis integrated cavity output spectroscopy (OA-ICOS), a portable carbon dioxide (CO₂) sensor system capable of atmosphere monitoring is proposed by targeting the CO₂ absorption lines at 2.004 μm. To address the comprehensive issues of complex light-adjustment structures, poor sealing, and slow gas replacement, an effective optimization scheme is introduced, combining fluid dynamics to produce a stable optical resonant cavity with an optical path length of 891 m and a physical length of 30 cm. The sensor system boasts a wide dynamic range of 0.011-800 parts per million (ppm), with a limit of detection (LoD) of 11 parts per billion (ppb) at an averaging time of 0.5 s. To address the issues of long monitoring time and cumbersome data supervision, a cloud monitoring system was developed based on a master control module, a cloud server, and a portable monitoring terminal. Field mobile monitoring of urban CO₂ was conducted over a large area in Changchun city, along with a 7-day fixed-point detection on the campus of Jilin University, verifying the reliability and application potential of the mobile CO₂ monitoring system in field applications.