Development of a Volcanic Remote Monitoring System Based on the DOAS Technique

The extreme conditions of the volcanic environment and the high risk associated with measurements in the field make remote sensing techniques an essential tool for gaseous geochemical monitoring. This paper presents the design and development of an optoelectronic system called scanning-DOAS, which allows monitoring the emission of sulfur dioxide (SO
₂
) of volcanic origin, from a safe distance. The instrument performs a scan of the plume, measuring the scattered UV solar radiation that arrives at the detector. From these solar spectra, the SO
₂
concentration in the cross section of the plume is determined, applying the DOAS (Differential Optical Absorption Spectroscopy) technique. If we have information about the plume's altitude and speed, it is possible to determine the SO
₂
flow. There is evidence that an increase in SO
₂
flows could be associated with an increase in volcanic activity, hence the importance of carrying out systematic monitoring. The work highlights the system's constructive characteristics and describes the technique used to obtain the aforementioned data. The system's design incorporates substantial improvements based on the results obtained using a first prototype, during the monitoring campaign carried out in the Planchón-Peteroa volcanic complex, Malargüe, Mendoza province, in January 2017. The SO
₂
flow variability observed during these measurements are in the order of magnitude of what was expected and agrees (very good correlation) with the information provided by the Observatorio Vulcanológico de los Andes del Sur (OVDAS), Servicio Nacional de Geología y Minería de Chile (SERNAGEOMIN), in its reports of volcanic activity. The results obtained indicate a very low SO
₂
emission rate, typical of the activity of this volcanic complex.