A new method of gas analysis, in real time, indicates the state of evolution of the Campi Flegrei. It was designed by a team of experts from INGV, the University of Campania 'Luigi Vanvitelli' and Geo Forschung Zenter of Potsdam
The real-time monitoring of volcanic gases, one of the most important eruption indicators, was tested on one of the most active fumarole and ground degassing areas of Campi Flegrei (Pisciarelli area - Naples). The new method was developed by a team of researchers from the National Institute of Geophysics and Volcanology (INGV) in collaboration with the University of Campania 'Luigi Vanvitelli', with the GFZ (Geo Forschung Zentrum) of Potsdam (Germany). The work was published in the International Journal of Mass Spectrometry.
“The method”, explains Alessandro Fedele, research fellow at INGV, “allows the continuous sampling and analysis of fumarolic gases through a quadrupole mass spectrometer, installed near the volcanic gas emission zone of the Campi Flegrei fumaroles , determining the concentrations of the chemical species of greatest interest in real time”.
The analyzes will then be transmitted, via radio or wi-fi, directly to a Monitoring Centre, which can also be located tens or hundreds of kilometers from the monitored fumaroles. “This makes it possible”, continues Fedele, “to acquire and analyze in real time a large amount of data concerning the geochemical composition of the gases emitted and represents a great step forward compared to the more complex and risky system, normally used, of manually sampling the fumarolic gases, transport them to the laboratory and only then analyze them”.
The system, developed using a portable mass spectrometer, was tested in the fumarolic area of Pisciarelli in the period between 2009 and 2012, in which the emission was more intense and evident.
“The data collected in this period”, explains Renato Somma, INGV researcher, “show the short-term variations in the concentrations of chemical species present in the fumarolic emissions, which have never been highlighted by the usual technique of periodic manual sampling and subsequent analysis in laboratory".
In fact, these withdrawals, in addition to causing great delays in the analyses, are carried out more or less monthly.
"With this new methodology", concludes Somma, "it will finally be possible to jointly interpret the geochemical and geophysical data (the latter already recorded in almost real time), with a great improvement in the forecasting capacity of a possible eruption".
The research carried out has an essentially scientific value, with no immediate implications regarding the aspects of civil protection at the moment. It should be remembered that since December 2012 the Campi Flegrei, which are continuously monitored and studied by INGV, have been on a "yellow" alert level (attention).
Photo 1 - Degassing field in Pisciarelli (NA)
Photo 2 – Detail of the maximum degassing area in Pisciarelli (NA)
Extended
Volcanic gas sampling and post-collection chemical determination in a laboratory may preclude any real-time continuous monitoring of volcanic activity. We describe the development, and show the advantages, of a system used for the continuous monitoring of fumarolic gases discharged from the Pisciarelli site (Campi Flegrei, Southern Italy) based on a commercial quadrupole mass spectrometer (QMS-301 Omnistar™). Although numerous technical problems were addressed due to the ephemeral nature of the emission point and the harsh environment, we also report measurements of the chemical composition of the major gas species emitted from the fumarole for two different periods (in 2009 and 2012). The CO2/H2S, H2S/H2, He/CO2 and CH4/CO2 molar ratios were investigated in order to detect magmatic and/or hydrothermal components in the system, while the N2/O2 ratio was adopted to infer other non-volcanic processes, such as air contamination and mixing with polluted surface waters. The presented methodology allows continuous gas sampling and provides the first evidence of short-term gas variations not available by direct sampling, which is often impractical and hazardous. Compared to the current techniques that are used worldwide for the full characterization of gaseous emissions, ie chemical analysis of traditional soda-filled under-vacuum bottles and MultiGAS surveys (laboratory-based and in situ, respectively), QMS-based monitoring is complementary and , in prospect, an alternative. With our method, the geochemical monitoring benefits of the real-time analysis for high sampling rates that can be made comparable to the continuous measurements of geophysical networks. This allows a better understanding of hydrothermal features, particularly of chemical fluctuations occurring on the very short-term, which is fundamental for the evaluation of the evolution of unrest episodes at Campi Flegrei, one of the most hazardous volcanic areas in the world.