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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 (SO 2) 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 SO 2 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 Planchón-Peteroa Volcanic Complex (Malargüe, Mendoza province, Argentina) in the year 2017. • DOAS technique is a complementary tool to current in-situ sampling techniques. • The data measured with DOAS device allow to improve volcanic eruptions forecasting. • DOAS instrument performe scans of volcanic plumes to retrieve the SO2 concentration. • New portable and autonomous prototype built using 3D printer. • First scanning-DOAS developed in Argentina and Latin America. [ABSTRACT FROM AUTHOR]

The Planchón – Peteroa Volcanic Complex exhibits two active degassing areas: Peteroa crater, PC, and peripheral hydrothermal areas, analyzed in three sampling sites, namely Valle Baños del Azufre, VBA, Valle del Peñón, VP and Valle Valenzuela, VZ. This prospective study was designed to investigate the soil diffuse emissions of CO 2 at this volcanic complex. The survey consisted of 560 measurements of CO 2 soil diffuse flux and temperature carried out at PC, VBA, VP. The results of this work show that diffuse CO 2 is emitted at PC through two well-defined diffuse degassing structures and flux distribution that can be modeled by combining two log-normal populations. Here, the main source of soil CO 2 is a shallow aquifer recharged by steam condensation and meteoric fluids that interact with rising magmatic gases. The carbon isotopic signature reveals that CO 2 diffuse degassing is affected by secondary soil processes during its ascent. The total diffuse CO 2 output at the surveyed area of PC, which covers ̴77,000 m2 around the crater fumarolic field, is 6.49 ± 0.32 t d−1. Soil diffuse emissions at the hydrothermal peripheral sites, VBA and VP, were studied covering a total area of ̴590,000 m2. These emissions are characterized by poorly defined diffuse degassing structures and flux distributions that can be modeled by combining three log-normal populations, which suggest that multiple sources feed CO 2 diffuse emissions. In concordance, the isotopic analysis also suggests a mixed source of CO 2 and degassing affected by secondary processes that modify the original isotope composition. CO 2 soil degassing at VZ shows a clear relation with the vegetated areas of the soil. The minimum endogenous CO 2 output estimation here proposed for the Planchón – Peteroa Volcanic Complex is that of PC, ̴6.5 t d−1. The thermal energy release was computed for PC, and the estimation is 2.57 ± 0.53 MW. • Planchón – Peteroa Volcanic Complex emits over 6 tons per day of volcanic- hydrothermal diffuse carbon dioxide. • Deep CO 2 is emitted through the active crater of Peteroa volcano. The peripheral hydrothermal sites emit mainly biogenic CO 2. • The carbon isotopic composition suggests that secondary processes deeply modify the original isotope composition. • The thermal energy release was estimated by assessing the flux of steam. The heat flux at Peteroa crater is 2.5 MW. [ABSTRACT FROM AUTHOR]