New Techniques for real-time volcanic gas measurements: the UV camera

Risultato della ricerca: Other contribution

Abstract

In this study, I take advantage of a novel technique - the UV camera - to image SO2 emissions from the Italian volcanoes with improved high temporal resolution. Here, this technique has been updated to a new configuration (dual-camera system), which combines higher temporal resolution (0.5-1.2 Hz) and improved accuracy relative to the single-camera setup. The methodology has been extensively tested and improved, whilst developing a user-friendly control software (Vulcamera) and a calibration technique (in tandem DOAS-SO2 quartz cells calibration), which simplify instrument deployment, acquisition and data analysis. A first application was focused on SO2 gas flux measurements at individual fumaroles from the La Fossa crater (Vulcano island, Italy) fumarolic field. There, the dual UV camera technique, in tandem with MultiGAS, allowed the simultaneous imaging of multiple-source emissions, deriving gas/SO2 molar ratios to accurately assess also CO2, H2O, and H2S fluxes. Results highlight a factor 2 increase in CO2 and H2O degassing during the La Fossa crater degassing/heating unrest event of November-December 2009. On Stromboli, the UV camera-derived data allowed the first simultaneous estimate of the SO2 flux contribution from the three main forms of degassing at Stromboli (passive degassing, 84-92 % ; explosive degassing, 5-8 % ; puffing, 3-8 %). The obtained high frequency SO2 flux time-series also revealed the existence of a periodic SO2 degassing pattern over timescales of minutes, modulated by rhythmic strombolian explosions. Also I report on systematic in tandem UV camera-geophysical observations providing experimental evidence for a positive correlation between seismic (very-long period ; VLP), thermal, and gas (eruptive SO2 mass) signals irradiated by individual Strombolian explosions. At Mount Etna, the pulsate gas emissions (gas puffing) from the North-east crater have been studied. The > 10 hour acquired SO2 flux time series highlighted a periodic degassing behaviour for this vent, with characteristic periods in the 60-250 s range. This allows deriving new constraints on model gas bubble distribution in a magmatic conduit. The data obtained here support a process of gas packaging into trains of discrete bubble-rich layers. This, coupled with time variations in ascent rate of individual gas bubble layers, may well account for the time-dependent periodicity of observed volcanic SO2 flux emissions.
Lingua originaleEnglish
Stato di pubblicazionePublished - 2012

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