First portable scanning-DOAS system developed in Latin America for volcanic SO2 monitoring

Abstract Due to the extreme conditions in volcanic environments, in-situ sampling of gases is considered a very dangerous task. For this reason, the implementation of new remote sensing techniques and instruments has become a fundamental tool for monitoring volcanic activity. This work presents the design and development of a system - known as scanning-DOAS - that allows to remotely monitor (from a safe distance) the sulfur dioxide (SO2) concentration of a volcanic plume. The instrument measures the solar radiation that reaches its CCD (Charge-Coupled Device) detector after passing through the plume. The spectral signals are recorded by a spectrometer and then processed using an inversion algorithm based on the DOAS technique (Differential Optical Absorption Spectroscopy). As a result of the analysis, the SO2 concentration in the cross section of the plume is obtained. Knowing the plume's height, speed and direction of propagation it is possible to calculate the gas flux. This work describes the constructive characteristics of a new prototype, which incorporates improvements based on the results obtained from a first prototype that was tested during a monitoring campaign carried out at Planchon-Peteroa Volcanic Complex (Malargue, Mendoza province, Argentina) in the year 2017.