Salvatore Inguaggiato

Sources, size distribution, and downwind grounding of aerosols from Mount Etna

The number concentrations and size distributions of aerosol particles >0.3 mm diameter were measured at the summit of Mount Etna and up to 10 km downwind from the degassing vents during July and August 2004. Aerosol number concentrations reached in excess of 9 106 L1 at summit vents, compared to 4–8 104 L1 in background air. Number concentrations of intermediate size particles were higher in emissions from the Northeast crater compared to other summit crater vents, and chemical composition measurements showed that Northeast crater aerosols contained a higher mineral cation content compared to those from Voragine or Bocca Nuova, attributed to Strombolian or gas puffing activity within the vent. Downwind from the summit the airborne plume was located using zenith sky ultraviolet spectroscopy. Simultaneous measurements indicated a coincidence of elevated ground level aerosol concentrations with overhead SO2, demonstrating rapid downward mixing of the plume onto the lower flanks of the volcano under certain meteorological conditions. At downwind sites the ground level particle number concentrations were elevated in all size fractions, notably in the 2.0–7.5 mm size range. These findings are relevant for assessing human health hazard and suggest that aerosol size distribution measurements may aid volcanic risk management.

The 2014 effusive eruption at Stromboli volcano (Italy): Inferences from soil CO2 flux and 3He/4He ratio in thermal waters

A new eruption started at Stromboli on 6 August 2014, which had been preceded by 2 months of increased Strombolian activity and several lava overflows from the craters. The eruption was characterized by a lava effusion in Sciara del Fuoco from a fracture at 650 m above sea level that lasted until 13–17 November. Here we present the first geochemical observations of this eruption, based on the soil CO2 flux in the summit area and on 3He/4He ratios in the thermal waters near Stromboli village. We infer that this eruption was triggered by the gradual replenishment of the feeding system by a CO2- and 3He-rich magma at the end of 2013 and after June 2014, suggested by the increase in 3He/4He ratio before eruption, which reached its highest value since 2007. We thus infer that this eruption was unusual, and we finally speculate on the evolutionary scenario of posteruption.

Submarine Hydrothermal Vents of the Aeolian Islands: Relationship Between Microbial Communities and Thermal Fluids

The relationship between fluid geochemistry and microbial communities was investigated for shallow (< 25 m) submarine hydrothermal vents in the Aeolian Islands (Southern Italy). Thermal waters, gases, and deposits of white filamentous material were collected from 11 sites. The geochemical analyses showed a magmatic component was present in all sampled fluids. The total microbial abundances, evaluated as direct counts of picoplanktonic cells (ranging from 0.2 to 2 mu m in diameter), were between 1.55 107 and 4.18 108 cells per liter. Picophytoplankton (total autofluorescent cells) ranged from 9.6 105 to 7.88 106 cells per liter. Yellow-orange autofluorescent prokaryotes belonging to the cyanobacteria were more abundant than red autofluorescent eukaryotic cells. Chemolithoautotrophic, sulfur-oxidizing, rod-shaped Bacteria were isolated from venting water samples and identified as Thiobacillus -like. Microscopic examination of the white mat deposits showed the presence of filamentous microorganisms.

Geochemical and hydrogeological characterization of thermal springs in Western Sicily, Italy

Abstract Thermal and cold waters from Castellammare–Alcamo (Western Sicily-Italy) were collected between May 1994 and May 1995 and studied for their chemical and isotopic composition. During the same period, mean monthly samples of meteoric water were also collected and measured for their isotopic composition. The main purpose of this study was the characterization of the acquifers and, if possible, of their recharge areas. According to the results obtained, the acquifers were divided into three main groups: (a) selenitic waters, (b) cold carbonatic waters, and (c) deep thermal waters resulting from the mixing of the other two types. Besides a mixing process between carbonatic and selenitic waters, contamination processes of thermal waters by seawater take place during their ascent. The water temperature of the acquifer feeding the thermal springs was estimated by means of various geothermometers to range between 60°C and 97°C. Isotope data on rainwater samples show a wide seasonal variation of both δ 18 O and δ D values. The fairly constant values of thermal waters through time and the lack of an apparent correlation with the isotopic values of rainwater suggest the existence of a deep circuit determining an almost complete homogenisation of the seasonal variations of the isotopic values.

Dynamic fluid recycling at Laguna Caliente (Poás, Costa Rica) before and during the 2006–ongoing phreatic eruption cycle (2005–10)

Abstract Poás Volcano (Costa Rica) resumed phreatic activity on 24 March 2006 after twelve years of quiescence. From March 2006 to June 2010, the initial phase of the ongoing eruption cycle, 110 phreatic eruptions were reported. This study presents the temporal variations in the chemical and isotopic (δD and δ18O) compositions of Laguna Caliente crater lake for the period prior to the eruption until June 2010. No systematic relationship with the phreatic eruptive activity exists. A combined mass and Cl budget analysis enables quantification of the seepage rate (7 kg s−1), the input rate of the ‘volcanic fluid’ (Qf), and the Cl concentration (Cle) in the evaporation plume (13 300 mg l−1). A modelling procedure for variable seepage rates leads to more realistic estimates of 50–100 kg s−1, which better represent the observed lake water chemistry, hence suggesting dynamic fluid recycling between the lake and the underlying magmatic–hydrothermal system. The high Cl concentration in the evaporation plume and the dynamic fluid recycling at the lake bottom characterize Laguna Caliente as an ‘open-air’ fumarole, discrediting water chemistry as an efficient monitoring tool at the classic monitoring frequency. A conceptual model of phreatic eruptions is linked to our observations.

Fluid Geochemistry of Stromboli

An accurate description of the geochemical system is presented here based on a review of scientific work performed during the past decade. The surface manifestations of the volcanic system of Stromboli have been investigated using several measuring techniques. Studying the chemical composition of the volcanic plume and of fumarolic emissions has provided information on magma degassing processes. The total fluxes of the emitted gases from both the plume and the soil were found to vary with changes in volcanic activity (from normal Strombolian activity to effusive and/or paroxysmal activity). Thermal water results from the interaction between volcanic gases, host rock, seawater, and meteoric water and temporal changes observed in the chemical and the isotopic composition of the gases dissolved into thermal waters highlighted the rising of new magma batches. Combining modeling of gas―water―rock interactions with an understanding of the volcanic system allowed identifying preferential sampling sites and parameters for the geochemical monitoring of volcanic activity at Stromboli Island.

Variations of Soil Temperature, CO2 Flux, and Meteorological Parameters

The detailed analysis carried out on the data, acquired in two continuous monitoring stations during the 2002―2003 Stromboli eruption, integrated by daily field observations of the scientific personnel working at the volcanological observatory, showed that CO 2 flux and soil temperature are strictly related to volcanic events. Furthermore, the recorded signals showed a strong correlation with wind speed and direction, revealing that during the eruption, in the summit area of Stromboli, air movements were related not only to atmospheric circulation, but were also significantly affected and, in certain cases, caused by volcanic activity. The possible volcanic origin of a peculiar type of air circulation identified in the summit area of Stromboli suggests that the separation between volcanic and atmospheric signals might not be obvious, requiring monitoring of atmospheric parameters over a wide area, rather than a single location.

CO2 flux and chemistry of El Chichón crater lake (México) in the period 2013–2015: Evidence for the enhanced volcano activity

The CO2 flux from El Chichon crater in the period from 2014 to 2015 increased by a factor of 3 (from ~260 t d−1 to ~800 t d−1) compared to the 2007–2008 data. The mechanism triggering the CO2 flux from the lake surface has changed from being dominantly diffusive to mainly advective (bubbling). The Cl concentration was steadily decreasing during the last two decades in the Na-Cl boiling springs feeding the lake. Since 2013, for both lake and SP springs, the Cl concentration has increased up to the 2005 Cl concentration levels. A large degassing spot in the middle of the lake was found in April 2015 with a CO2 flux of more than 10,000 g m−2 d−1. These observations are the evidence of the onset of a new stage of activity within the volcano-hydrothermal system of El Chichon volcano associated most probably with changes in the magmatic activity at depth.

Possible Micrometeorological Anomalies Induced by Volcanic Activity Recorded at Stromboli Island (Aeolian Archipelago, Italy)

Hourly values of atmospheric pressure and air temperature have been acquired at the top of two volcanic islands, Stromboli and Salina in the Aeolian Archipelago (Italy), very similar in height and morphology but completely different with regard to their volcanic activity state: the former is permanently active, whereas the latter is extinguished. During the last four years Stromboli experienced normal activity, volcanic unrests, and an effusive eruption (August–November 2014). The comparative analysis of the recorded data, both in the time and frequency domains, evidenced a peculiar micrometeorological regime at Stromboli, more turbulent during unrests with respect to the quieter periods, but showing an apparent paradox during eruptions, characterized by a lower atmospheric turbulence. These observations suggest that the studied volcanic-micrometeorological system is chaotic, due to contemporary opposite transients generated in the atmosphere by volcanic activity changes, and that micrometeorological conditions in volcanic areas are controlled both by exogenous processes and volcanic activity.

The 5 April 2003 paroxysm at Stromboli: a review of geochemical observations

This paper reviews the published geochemical variations observed during the 2002―2003 eruption at Stromboli volcano. At the end of 2002, a new eruption began at Stromboli with a lava flow that lasted until the end of July 2003. In 5 April 2003, an explosive paroxysm occurred with the ejection of bombs that reached the village of Ginostra, about 4 km from the craters. During the eruption, specific variations in chemical composition of groundwaters and summit fumaroles were recorded before the explosion, most of them for the first time. The water pH decreased significantly (0.5 units), and the dissolved CO 2 increased in two thermal wells (Cusolito and Zurro) located near Stromboli harbor from March until 5 April. Peaks in the dissolved He were also observed at all the sampling sites. All of these changes in the thermal aquifer suggested a pressurization of the system due to the degassing of a volatile-rich magma at depth. In the summit area, the SO 2 /HCl and SO 2 /HF ratios in the plume increased suddenly between 1 and 3 April due to the degassing of an S-rich magma that was approaching the shallow levels of the plumbing system, and this was involved in the explosion that occurred a few days later. This eruption was the first at Stromboli to be analyzed using geochemical models. The variations observed in the basal aquifer and in the summit area occurred on very different timescales: a few weeks and a few days, respectively.