Near-infrared Tunable Diode Lasers have recently found increased usage in atmospheric chemistry and air monitoring research, but applications in Volcanology are still limited to a few examples. The Tunable Diode Laser Spectroscopy technique (TDLS) relies on measuring the absorbance at specific wavelengths due to the absorption of IR radiation by a target gas. Here, we report on the application of the GasFinder 2.0, a commercial infrared laser-receiver unit operating in the 1.3-1.7 m wavelength range, to measuring CO2 concentrations and fluxes in volcanic gas emissions. Our field tests were conducted at Campi Flegrei volcano (near Pozzuoli, Southern Italy), where the GasFinder was used (during three campaigns in October 2012, January 2013 and May 2013) to repeatedly measure the path-integrated concentrations of CO2 along cross-sections of the atmospheric plumes of the two main fumarolic fields in the area (Solfatara and Pisciarelli). At each site, we used an adhoc designed measurement geometry, using the GasFinder unit and several retro-reflector mirrors, to scan the plumes from different angles and distances. The laser unit and retro-reflectors positions were chosen so to have the target fumarolic plumes in between the GasFinder and retro-reflectors, and to allow for complete coverage of the degassing area. From post-processing of the data, by using a tomographic Matlab routine, we resolved, for each of the two manifestations, the contour maps of CO2 concentrations in their atmospheric plumes and, from their integration (and after multiplication by the plumes ? transport speeds) we evaluated the CO2 fluxes. The so-calculated fluxes average at 490 tons/day, supporting a significant contribution of fumaroles to the total CO2 budget at Campi Flegrei. The application of lasers to volcanic gas studies is still an emerging (though intriguing) research field, and requires more testing and validation experiments. We conclude that TDLS technique may valuably assist CO2 flux quantification at a number of volcanic targets worldwide.
Pedone, M., Aiuppa, A., & Giudice, G. (2014). Real-time measurements of Volcanic Gases based by Infrared Spectroscopy [Esposizione].
|Citazione:||Pedone, M., Aiuppa, A., & Giudice, G. (2014). Real-time measurements of Volcanic Gases based by Infrared Spectroscopy [Esposizione].|
|Data di pubblicazione:||2014|
|Appare nelle tipologie:||9.1 Altro|