The CO flux database is available to the scientific community2 at the Solfatara di Pozzuoli, (in the period 1998-2016), the largest of its kind in the world. It was developed by a team of researchers from INGV, the University of Perugia and the CNR. The study was published in Scientific Reports
Over 13 measurements included in the carbon dioxide flux dataset (CO2) at the Solfatara of Pozzuoli in the period 1998-2016. The database, the largest in the world in terms of number of measurements and time duration, was created by a group of researchers from the Bologna and Naples sections of the National Institute of Geophysics and Volcanology (INGV), the University of Perugia and the Institute of Geosciences and Georesources (IGG) of the National Research Council (CNR). The results of the study, Monitoring diffuse volcanic degassing during volcanic unrests: the case of Campi Flegrei (Italy), have been posted on Scientific Reports (www.nature.com/articles/s41598-017-06941-2)
"In addition to making the dataset information available to the scientific community", says Giovanni Chiodini, research director at INGV, "the changes in CO2 in the last period of the Campi Flegrei crisis (1998-2016), characterized by an increase in geophysical and geochemical signals”.
Volcanoes emit gases through plume volcanic, fumaroles and diffuse degassing from the ground. The CO2 it represents one of the most abundant gaseous species in volcanic gases and can be released from magma already at great depths.
"In volcanoes characterized by the presence of a hydrothermal system, i.e. a hot aquifer interposed between the magma and the surface", explains Carlo Cardellini, professor at the University of Perugia and first author of the work, "the observable phenomenologies (gas emission, seismic activity, ground deformation, etc.) can be caused both by the ascent of magma and by processes that only affect the hydrothermal system. In these systems, the diffuse outgassing of CO2 from the ground can be the main, if not the only, way of releasing CO2 volcanic".
This is the case of the Solfataraof Pozzuoli, located in the caldera (volcanic depression formed following a major eruption) of Campi Flegrei. After the crises that characterized the last part of the past century (1983-84 bradyseism), the Campi Flegrei have been uplifting again since 2005. This process is accompanied by weak seismic crises and strong variations in the composition of the fluids emitted by the volcano. Processes that led the Civil Protection Department (DPC) in 2012 to decree a change in the alert level of the volcano's status from green (quiet) to yellow (scientific attention).
“It is a dataset relating to 30 COXNUMX flow measurement campaigns2 from the ground at the Solfatara di Pozzuoli and in the surrounding areas, with over 13 measurements of diffuse flux of CO2 elaborated with geostatistical methodologies”, continues Cardellini.
The study made it possible to define not only the origin of the carbon dioxide released from the soil, but also to create maps showing the area affected by the release of CO2 volcanic (Figure 1) and to estimate the total amount of CO2 emitted by the volcano.
"In the last 20 years", adds Cardellini, "sectors of the Solfatara area, previously not affected by anomalous degassing activities, have begun to release CO2 volcanic. From 2003 to today, the affected area has had a significant expansion towards Pisciarelli (Figure 2), together with the increase in the total amount of CO2 emitted through diffuse release from soil, rising from about 800 tons of carbon dioxide per day in 2003 to about 2800 in 2015”.
The study also highlights that the average amount of CO2 emitted by the Solfatara of Pozzuoli, through diffuse degassing from the ground, are comparable to the amount of CO2 released into the atmosphere by medium-large active volcanoes.
“If the CO2 emitted by the fumaroles, the Solfatara of Pozzuoli would be in eighth place among the major volcanoes emitting CO2 of the planet. A result that demonstrates how the quantification of the flux of CO2 from volcanic systems in hydrothermal activity, such as the Solfatara of Pozzuoli, can contribute to the improvement of the quantification of global CO emissions2 volcanic atmosphere as well as a greater understanding of the current Phlegraean crisis”, concludes Giovanni Chiodini of INGV.
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).
Extended
In volcanoes with active hydrothermal systems, diffuse CO2 degassing may constitute the primary mode of volcanic degassing. The monitoring of CO2 emissions can provide important clues in understanding the evolution of volcanic activity especially at calderas where the interpretation of unrest signals is often complex. Here, we report eighteen years of CO2 fluxes from the soil at Solfatara of Pozzuoli, located in the restless Campi Flegrei caldera. The entire dataset, one of the largest of diffuse CO2 degassing ever produced, is made available for the scientific community. We show that, from 2003 to 2016, the area releasing deep-sourced CO2 tripled its extent. This expansion was accompanied by an increase of the background CO2 flux, over most of the surveyed area (1.4 km2), with increased contributions from non-biogenic source. Concurrently, the amount of diffusively released CO2 increased up to values typical of persistently degassing active volcanoes (up to 3000 td−1). These variations are consistent with the increase in the flux of magmatic fluids injected into the hydrothermal system, which cause pressure increase and, in turn, condensation within the vapor plume feeding the Solfatara emission.
Figure 1: Diffuse degassing of CO2 from the Solfatara of Pozzuoli and surroundings (period 1998-2016). The map shows the areas (yellow-red colours) which have been affected by CO emissions2 of volcanic origin
Figure 2: The Pisciarelli fumarole on the eastern slopes of the Solfatara. The strong emission was activated in 2009 (photo Carmine Minopoli)