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SO2 and aerosol evolution over the very clear atmosphere at the Argentinean Andes range sites of San Antonio de los Cobres and El Leoncito
1 , 1, 2 , 1 , 3, 4 , * 1, 5
1  Instituto de Física Rosario (IFIR) CONICET/UNR, Rosario-Argentina
2  Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Rosario-Argentina
3  Instituto de Tecnologías y Detección de Astropartículas (CNEA-CONICET-UNSAM)
4  Universidad Tecnológica Nacional, Facultad Mendoza, Lab. Pierre Auger
5  Facultad de Ciencias Exactas, Ingenieria y Agrimensura (UNR), Rosario-Argentina


 The atmosphere at North-Central Argentinean Andes range is exceptionally clear and well adapted for the placement of astrophysical/astronomical/solar observatories (Piacentini et al, Advances Space Research, 2016). However, this region is part of the Pacific fire belt, due to the large number of active volcanoes. Consequently, it exists the possibility of strong sporadic emissions of different gases and aerosols. In the present work, we analyze in particular the SO2 trace gas, since it can affect significantly the solar UVB (280-320 nm) radiation. Also, particulate matter can attenuate this radiation in the UV-visible ranges. One of the most significant contributions to volcanic eruptions that could arrive at the selected San Antonio de los Cobres(SAC) location is the near Lascar volcano. We used satellite images form the OMI/KMNI/Aura/NASA satellite instrument, for deriving the intensity of the eruption at the SAC geographical point. An important eruption was that of the Puyehue/Cordón Caulle volcanic complex at Chileean Patagonia, in June 2011. No significant influence on the other selected El Leoncito(LEO) location was registered.   We present aerosol optical depth (AOD550) satellite data (analyzed with the Deep Blue algorithm) taken by the SeaWiFS/SeaStar/NASA satellite  instrument for SAC and LEO  places, showing that AOD550 for the whole period is extremely low (0.026 for SAC and  0.030 for LEO). We also present ground atmospheric aerosol concentration measurements as function of aerosol diameter with a high quality GRIMM laser instrument in typical days. In conclusion, our results show that the proposed SAC and LEO sites are of high quality for Southern Hemisphere night (astrophysical/astronomical) and day (solar) observations, even if they are placed in a mountain range with active volcanoes. Also, the results are of importance for the evaluation of the Visibility quality of the region and its possible future evolution, due to the increase in atmospheric contamination.

Keywords: SO2, atmospheric aerosols, clear atmosphere, Argentinean Andes