Volcanic CO2 measurements at Campi Flegrei by Infrared Tunable Diode Laser absorption Spectroscopy

Risultato della ricerca: Other contribution

Abstract

Gas studies add information for the interpretation of fluid circulationdynamics at dormant volcanoes and can contribute to eruptionforecasting. Direct in-situ and remote-sensing techniques were used inorder to improve volcanic gas monitoring, essential for hazardassessment. In the last decades, near-infrared diode lasers haveincreasingly been used in atmospheric research and, though in anexperimental phase, are now finding applications in volcanic gasstudies. The Tunable Diode Laser Spectroscopy technique (TDLS)relies on measuring the absorbance at specific wavelengths due to theabsorption of IR radiation by a target gas. Here, we report on theapplication of the GasFinder 2.0, an infrared laser unit operating in the1.3-1.7 μm wavelength range, to measuring CO2 mixing ratios involcanic gas emissions. Three different campaigns were carried out atCampi Flegrei volcano (near Pozzuoli, Southern Italy) in the attempt toobtain novel information on the current degassing unrest of Solfataraand Pisciarelli fumarolic fields. At each site, we used the GasFinderunit and several retro-reflector mirrors, to scan the plumes fromdifferent angles and distances. From post-processing of the data, byusing a tomographic Matlab routine, we resolved, for each of themanifestations, the contour maps of CO2 mixing ratios in theiratmospheric plumes. From their integration (and after multiplicationby the plumes’ transport speeds) we evaluated the CO2 fluxes. Theso-calculated flux (about 490 Mg/day) supports a significantcontribution of fumaroles to the global CO2 budget. The cumulative(fumaroles [this study] +soil [1]) CO2 output from Campi Flegrei isfinally evaluated at 1600 Mg/day. The application of lasers to volcanicgas studies is still an emerging (though intriguing) research field, andrequires more testing and validation experiments.
Lingua originaleEnglish
Numero di pagine1
Stato di pubblicazionePublished - 2014

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