Marco Liuzzo

The Total Volatile (TV) flux from Mount Etna volcano has been characterised for the first time, by summing the simultaneously-evaluated fluxes of the three main volcanogenic volatiles: H2O, CO2 and SO2. SO2 flux was determined by routine DOAS traverse measurements, while H2O and CO2 were evaluated by scaling MultiGAS-sensed H2O/SO2 and CO2/SO2 plume ratios to the UV-sensed SO2 flux. The time-averaged TV flux from Etna is evaluated at ~21,000 t.day-1, with a large fraction accounted for by H2O (~13,000 t.day-1). H2O dominates (>=70%) the volatile budget during syn-eruptive degassing, while CO2 and H2O contribute equally to the TV flux during passive degassing. The CO2 flux was observed to be particularly high prior to the 2006 eruption, suggesting that this parameter is a good candidate for eruption prediction at basaltic volcanoes.

The recent eruption of Stromboli in February-April 2007 offered a unique chance to test our current understanding of processes driving the transition from ordinary (persistent Strombolian) to effusive activity, and the ability of instrumental geophysical and geochemical networks to interpret and predict these events. Here, we report on the results of two years of in-situ sensing of the CO 2/SO 2 ratio in Stromboli's volcanic gas plume, in the attempt to put constraints on the trigger mechanisms and dynamics of the eruption. We show that large variations of the plume CO 2/SO 2 ratio (range, 0.9-26) preceded the onset of the eruption (since December 2007), interrupting a period of relatively-steady and low ratios (time-averaged ratio, 4.3) lasting from at least May to November 2006. By contrasting our observations with numerical simulations of volcanic degassing at Stromboli, derived by use of an equilibrium saturation model, we suggest that the pre-eruptive increase of the ratio reflected an enhanced supply of deeply-derived CO 2-rich gas bubbles to the shallow-plumbing system. This larger-than-normal ascent of gas bubbles was likely sourced by a 1-3 km deep gas-melt separation region (probably a magma storage zone), and caused faster convective overturning of magmas in the shallow conduit; an increase in the explosive rate and in seismic tremor, and finally the collapse of the la Sciara del Fuoco sector triggering the effusive phase. The high CO 2/SO 2 ratios (up to 21) observed during the effusive phase, and particularly in the days and hours before a paroxysmal explosion on March 15, 2007, indicate the persistence of the same gas source; and suggest that de-pressurization of the same 1-3 km deep magma storage zone could have been the trigger mechanism for the paroxysm itself.

We report here on the first hydrogen determinations in the volcanic gas plume of Mount Etna, in Italy, which we obtained during periodic field surveys on the volcano's summit area with an upgraded MultiGAS. Using a specific (EZT3HYT) electrochemical sensor, we resolved H2 concentrations in the plume of 1-3 ppm above ambient (background) atmosphere and derived H2-SO2 and H2-H2O plume molar ratios of 0.002-0.044 (mean 0.013) and 0.0001-0.0042 (mean 0.0018), respectively. Taking the above H2-SO2 ratios in combination with a time-averaged SO2 flux of 1600 Gg yr-1, we evaluate that Etna contributes a time-averaged H2 flux of ˜0.65 Gg yr-1, suggesting that the volcanogenic contribution to the global atmospheric H2 budget (70,000-100,000 Gg yr-1) is marginal. We also use our observed H2-H2O ratios to propose that Etna's passive plume composition is (at least partially) representative of a quenched (temperatures between 750°C and 950°C) equilibrium in the gas-magma system, at redox conditions close to the nickel-nickel oxide (NNO) mineral buffer. The positive dependence between H2-SO2, H2-H2O, and CO2-SO2 ratios suggests that H2 is likely supplied (at least in part) by deeply rising CO2-rich gas bubbles, fluxing through a CO2-depleted shallow conduit magma.

It is generally accepted, but not experimentally proven, that a quantitative prediction of volcanic eruptions is possible from the evaluation of volcanic gas data. By discussing the results of two years of real-time observation of H 2 O, CO 2 , and SO 2 in volcanic gases from Mount ...

Active volcanoes are thought to be important contributors to the atmospheric mercury (Hg) budget, and this chemical element is one of the most harmful atmospheric pollutants, owing to its high toxicity and long residence time in ecosystems. There is, however, considerable uncertainty over the magnitude of the global volcanic Hg flux, since the existing data on volcanogenic Hg emissions are sparse and often ambiguous. In an attempt to extend the currently limited dataset on volcanogenic Hg emissions, we summarize the results of Hg flux measurements at seven active open-conduit volcanoes; Stromboli, Asama, Miyakejima, Montserrat, Ambrym, Yasur, and Nyiragongo.. Data from the dome-building Soufriere Hills volcano are also reported. Using our determined mercury to SO2 mass ratios in tandem with the simultaneously-determined SO2 emission rates, we estimate that the 7 volcanoes have Hg emission rates ranging from 0.2 to 18 t yr-1 (corresponding to a total Hg flux of ~41 t·yr-1). Based on our dataset and previous work, we propose that a Hg/SO2 plume ratio ~10-5 is best-representative of gas emissions from quiescent degassing volcanoes. Using this ratio, we infer a global volcanic Hg flux from persistent degassing of ~95 t·yr-1 .

The Total Volatile (TV) flux from Mount Etna volcano has been characterised for the first time, by summing the simultaneously-evaluated fluxes of the three main volcanogenic volatiles: H2O, CO2 and SO2. SO2 flux was determined by routine DOAS traverse measurements, while H2O and CO2 were evaluated by scaling MultiGAS-sensed H2O/SO2 and CO2/SO2 plume ratios to the UV-sensed SO2 flux. The

Measure of CO2fluxes diffused from the soil (φ CO2) released from active volcanoes brings profound insights into our understanding of volcanic processes, as a matter of fact strong CO2 soil flux variations were recorded before and during the last eruptions on Mt. Etna. In order to further our understanding of the volcano dynamics concerning soil's degassing, a network for measuring geochemical parameter (ETNAGAS) stations was installed on the flanks of Mt. Etna. This network contributes to volcano monitoring since December 2002. Today, ETNAGAS consists of 19 automatic stations located close to the main volcanic structures of the Mt. Etna, in areas of the volcano characterized by strong soil CO2emissions. The monitoring stations of the network were entirely developed by the INGV at Palermo; they are able to monitor different parameters, such as CO2 (eventually CH4) soil flux, T, P, rain, Rh, wind speed and wind direction, and data are acquired at hourly intervals. The soil CO2flux measuring system follows the principles proposed by Gurrieri and Valenza (Gurrieri & Valenza 1988) which is based on CO2content in a mixture of air and soil gas (dynamic concentration, Cd). A multi network management software has also been developed in order to allow stations handling and data elaboration. The software was developed for a LINUX environment and consists of several modules for data acquisition, processing, visualization and early warning generation. The remote stations are connected by radio modem and/or GSM modem to the Geochemical monitoring laboratory of the INGV at Palermo, where data are real-time processed and used for surveillance of the volcano. We report here on the very large φ CO2variations recorded by the above network during the last 5 years during eruptive periods, in particular we show the results about the 2004-2005 and 2006 eruptions on Mt. Etna. These results suggest the importance of continuously monitoring the CO2emitted from soil to the surveillance of volcanic activity in this area, and open up an interesting scenario for the surveillance of this volcano.

We report on the first detection of CO2 flux precursors of the till now unforecastable larger than normal ("major") explosions that intermittently occur at Stromboli volcano (Italy). Automated survey of the crater plume emissions in the period 2006-2010, during which 12 such explosions happened, demonstrate that these events are systematically preceded by a brief phase of increasing CO2/SO2 weight ratio (up to >40) and CO2 flux (>1300 t/d) with respect to the time-averaged values of 3.7 and ~500 t/d typical for standard Stromboli's activity. These signals are best explained by the accumulation of CO2-rich gas at a discontinuity of the plumbing system (decreasing CO2 emission at the surface), followed by increasing gas leakage prior to the explosion. Our observations thus support the recent model of Allard (2010) for a CO2-rich gas trigger of recurrent major explosions at Stromboli, and demonstrate the possibility to forecast these events in advance from geochemical precursors. These observations and conclusions have clear implications for monitoring strategies at other open-vent basaltic volcanoes worldwide.

We report on the first detection of CO2 flux precursors of the till now unforecastable "major" explosions that intermittently occur at Strombolivolcano (Italy). An automated survey of the crater plume emissions in the period 2006-2010, during which 12 such explosions happened, demonstrated that these events are systematically preceded by a brief phase of increasing CO2/SO2 weight ratio (up to >40) and CO2 flux (>1300 t d-1) with respect to the time-averaged values of 3.7 and ~500 t d-1 typical for standard Stromboli's activity. These signals are best explained by the accumulation of CO2-rich gas at a discontinuity of the plumbing system (decreasing CO2 emission at the surface), followed by increasing gas leakage prior to the explosion. Our observations thus supports the recent model of Allard (2010) for a CO2-rich gas trigger of recurrent major explosions at Stromboli, and demonstrates the possibility to forecast these events in advance from geochemical precursors. These observations and conclusions have clear implications for monitoring strategies at other open-vent basaltic volcanoes worldwide.

Large variations of the CO2 flux through the soil were observed between November 2002 and January 2006 at Mt. Etna volcano. In many cases, the CO2 flux was strongly influenced by changes in air temperature and atmospheric pressure. A new filtering method was then developed to remove the atmospheric influences on soil CO2 flux and, at the same time, to highlight the variations strictly related to volcanic activity. Successively, the CO2 corrected data were quantitatively compared with the spectral amplitude of the volcanic tremor by cross correlation function, cross-wavelet spectrum and wavelet coherence. These analyses suggested that the soil CO2 flux variations preceded those of volcanic tremor by about 50 days. Given that volcanic tremor is linked to the shallow (a few kilometer) magma dynamics and soil CO2 flux related to the deeper (~12 km b.s.l.) magma dynamics, the “delayed similarity” between the CO2 flux and the volcanic tremor amplitude was used to assess the average speed in the magma uprising into the crust, as about 170–260 m per day. Finally, the large amount of CO2 released before the onset of the 2004–2005 eruption indicated a deep ingression of new magma, which might have triggered such an eruption.

The low-intensity activity of basaltic volcanoes is occasionally interrupted by short-lived but energetic explosions which, whilst frequently observed, are amongst the most enigmatic volcanic events in Nature. The combination of poorly understood and deep, challenging to measure, ...