The interpretation of volcanic gas datasets offers key information to build/validate geological models relevant to a variety of volcanic processes and behaviours, including eruptions. Major efforts have therefore been spent in recent years to improve our ability to measure volcanic gas compositions and fluxes. In the last decades, near-infrared room-temperature diode lasers, though in an experimental phase, are finding applications in volcanic gas studies. In this PhD dissertation, I use the GasFinder 2.0, a commercial tunable diode infrared laser transmitter-receiver unit, operating in the 1.3-1.7 m wavelength range, in the attempt to measure CO2 mixing ratios and fluxes in volcanic gas emissions. I initially report on the first field tests conducted at Campi Flegrei volcano (near Pozzuoli, Southern Italy). In later sections, I then focus on observations performed at other degassing systems (Nea Kameni volcano, Greece; Hekla Volcano and Krýsuvík hydrothermal area, Iceland; Furnas volcano, Azores; Vulcano summit crater and Paternò area, Italy). In all such systems, the GasFinder was used to repeatedly measure the path-integrated mixing ratios of CO2 along cross-sections of the atmospheric plumes of the main fumarolic fields. At each site, an ad-hoc designed measurement geometry was used, using the GasFinder unit and several retro-reflector mirrors, to scan the plumes from different angles and distances. From post-processing of the data using a tomographic Matlab routine, the contour maps of CO2 mixing ratios in the fumaroles' atmospheric plumes were resolved for each of the manifestations. From their integration (and after multiplication by the plumes’ transport speeds), the CO2 fluxes were evaluated. The so-calculated fluxes range from 5.7 ± 0.9 (Krýsuvík) to 524 ± 108 (Vulcano) tons/day, supporting a significant contribution of fumaroles to the global CO2 budget. Overall, the results presented in this study contribute to improve understanding of the rates of CO2 release from sub-aerial volcanism. Our observations suggest, in particular, that the cumulative CO2 contribution from weakly degassing volcanoes in hydrothermal stage may more significant at global scale. Than previously thought.
Pedone, M.REAL-TIME MEASUREMENT OF VOLCANIC GASES BASED ON INFRARED SPECTROSCOPY.
|Titolo:||REAL-TIME MEASUREMENT OF VOLCANIC GASES BASED ON INFRARED SPECTROSCOPY|
|Citazione:||Pedone, M.REAL-TIME MEASUREMENT OF VOLCANIC GASES BASED ON INFRARED SPECTROSCOPY.|
|Appare nelle tipologie:||4.2 Tesi di dottorato|