The last ten years have assisted to a growing involvement of the CCVG community into in-situ (near-vent) real-time observations of volcanic gas plume compositions. This renovated interest toward in-plume measurements has been motivated by the advent of a new generation of more compact, robust and relatively cheap gas sensors, which have allowed miniaturising and automating the hardware traditionally used by geochemists for airborne profiling of volcanic gas plume compositions. The advent of the Multi-component Gas Analyser System (Multi-GAS), first conceived in the mid-2000s in Japan (Shinohara, 2005) and Italy (Aiuppa et al., 2005), has greatly expanded our ability to resolve, in nearly real-time, the major element composition (CO2, H2O, SO2, H2S, H2) of volcanic gas plumes, using a combination of near-dispersive infrared and electrochemical sensors. In light of its reasonable cost (<< 20 k$), compact configuration (< 2 kg; typically 40x20x15 cm), robustness (the instrument has been designed to resist long-term exposure to corrosive, harsh volcanic environments), and relatively high acquisition frequency (up to 1 Hz), the Multi-GAS has revealed ideal for expedite gas surveys. The most substantial advance has arisen, however, from the development of fully automated, permanent instruments, adapted for long-term, nearly continuous observation of volcanic gas plumes (Aiuppa et al., 2007, 2009). The permanent Multi-GAS(es) have allowed acquiring time-series of volcanic gas compositions of unprecedented detail, duration and temporal resolution, and therefore to capture precursory changes of the volcanic gas plume CO2/SO2 ratio prior to eruption at Italian volcanoes (Etna, Stromboli) and, more recently, at other volcanoes including Poas, Turrialba and Villarrica. The launch of the DECADE research initiative of the Deep Carbon Observatory is now contributing to instrument new volcanoes, putting the seeds for a first global Multi-GAS network (today counting ~ 15 volcanoes already instrumented, in collaboration with local volcano observatories). Multi-GAS instruments are now being assembled by several distinct research teams worldwide (including UniPa-INGV, GSJ and USGS-VDAP), and it is expected the technique will become of routine (standard) use at volcano observatories in the years to come. Likely future developments of the Multi-GAS will include more refined automation, tools for real-time data processing, improved data quality check via auto-calibrating systems, and implementation to measurement of additional gas species (e.g., CO and HCl). The combination of simultaneously measured CO2/SO2 ratios (by Multi-GAS) and SO2 fluxes (by UV spectroscopy) will also help obtaining unprecedented long time-series of the volcanic CO2 flux, therefore contributing to refined global volcanic CO2 flux inventories.
References:
Aiuppa, A., Federico, C., Giudice, G., Gurrieri, S. 2005, Chemical mapping of a fumarolic field: La Fossa Crater, Vulcano Island (Aeolian Islands, Italy), Geophysical Research Letters 32 (13) , pp. 1-4
Aiuppa A., Moretti R., Federico C., Giudice G., Gurrieri S., Liuzzo M., Papale P., Shinohara H., Valenza M., Forecasting Etna eruptions by real-time observation of volcanic gas composition, Geology, December 2007; v. 35; no. 12; p. 1115–1118; doi: 10.1130/G24149A.
Aiuppa, A., G. Giudice, S. Gurrieri, M. Liuzzo, M. Burton, T. Caltabiano, A. J. S. McGonigle, Aiuppa, A., Federico, C., Giudice, G., Giuffrida, G., Guida, R., Gurrieri, S., Liuzzo, M., Moretti, R., Papale, P. (2009) The 2007 eruption of Stromboli volcano: Insights from real-time measurement of the volcanic gas plume CO2/SO2 ratio Journal of Volcanology and Geothermal Research, 182, 221–230, doi:10.1016/j.jvolgeores.2008.09.013
Shinohara, H. 2005, A new technique to estimate volcanic gas composition: Plume measurements with a portable multi-sensor system, J. Volcanol. Geotherm. Res. 143 (4), pp. 319-333