Near-infrared Tunable Diode Lasers have recently foundincreased usage in atmospheric chemistry and air monitoringresearch, but applications in Volcanology arestill limited to a few examples. The Tunable Diode LaserSpectroscopy technique (TDLS) relies on measuringthe absorbance at specific wavelengths due to the absorptionof IR radiation by a target gas. Here, we reporton the application of the GasFinder 2.0, a commercialinfrared laser-receiver unit operating in the 1.3-1.7 m wavelength range, to measuring CO2 concentrationsand fluxes in volcanic gas emissions. Our field tests wereconducted at Campi Flegrei volcano (near Pozzuoli, SouthernItaly), where the GasFinder was used (duringthree campaigns in October 2012, January 2013 and May2013) to repeatedly measure the path-integrated concentrationsof CO2 along cross-sections of the atmosphericplumes of the two main fumarolic fields in the area(Solfatara and Pisciarelli). At each site, we used an adhocdesigned measurement geometry, using the GasFinderunit and several retro-reflector mirrors, to scan theplumes from different angles and distances. The laserunit and retro-reflectors positions were chosen so to havethe target fumarolic plumes in between the GasFinderand retro-reflectors, and to allow for complete coverageof 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 mapsof CO2 concentrations in their atmospheric plumes and,from their integration (and after multiplication by theplumes ? transport speeds) we evaluated the CO2 fluxes.The so-calculated fluxes average at 490 tons/day, supportinga significant contribution of fumaroles to the totalCO2 budget at Campi Flegrei. The application of lasersto volcanic gas studies is still an emerging (thoughintriguing) research field, and requires more testing andvalidation experiments. We conclude that TDLS techniquemay valuably assist CO2 flux quantification at anumber of volcanic targets worldwide.
|Number of pages||1|
|Publication status||Published - 2014|