Gas studies add information for the interpretation of fluid circulation
dynamics at dormant volcanoes and can contribute to eruption
forecasting. Direct in-situ and remote-sensing techniques were used in
order to improve volcanic gas monitoring, essential for hazard
assessment. In the last decades, near-infrared diode lasers have
increasingly been used in atmospheric research and, though in an
experimental phase, are now finding applications in volcanic gas
studies. 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, an infrared laser unit operating in the
1.3-1.7 μm wavelength range, to measuring CO2 mixing ratios in
volcanic gas emissions. Three different campaigns were carried out at
Campi Flegrei volcano (near Pozzuoli, Southern Italy) in the attempt to
obtain novel information on the current degassing unrest of Solfatara
and Pisciarelli fumarolic fields. At each site, we used the GasFinder
unit and several retro-reflector mirrors, to scan the plumes from
different angles and distances. From post-processing of the data, by
using a tomographic Matlab routine, we resolved, for each of the
manifestations, the contour maps of CO2 mixing ratios in their
atmospheric plumes. From their integration (and after multiplication
by the plumes’ transport speeds) we evaluated the CO2 fluxes. The
so-calculated flux (about 490 Mg/day) supports a significant
contribution of fumaroles to the global CO2 budget. The cumulative
(fumaroles [this study] +soil [1]) CO2 output from Campi Flegrei is
finally evaluated at 1600 Mg/day. The application of lasers to volcanic
gas studies is still an emerging (though intriguing) research field, and
requires more testing and validation experiments