Rapporto sulle misure di Mercurio effettuate sull’Etna nel periodo Novembre 2005 – Marzo 2006 e loro raffronto con altri parametri geochimici

traccia nella troposfera, tende ad accumularsi nei processi biologici che seguono la sua deposizione. Il suo lungo tempo di residenza in atmosfera (circa 1 anno) combinato con la sua elevata tossicità, rendono tale elemento di primaria importanza per l’impatto ambientale, soprattutto nelle aree di maggiore emissione. Le emissioni di mercurio da aree vulcaniche attive sono considerate una delle principali sorgenti di mercurio verso l’atmosfera terrestre, insieme con le emissioni antropogeniche legate all’attività mineraria per l’estrazione del cinabro. L’entità del contributo vulcanico a scala regionale e globale rimane tuttavia altamente incerto. Le emissioni vulcaniche possono essere ricche in mercurio elementare gassoso (Hg0), mercurio gassoso reattivo (HgII) presente soprattutto come solfuro ed altre forme di mercurio che devono essere ancora determinate (Symonds et al., 1992; Nicholson, 1993; Barnes & Seward, 1997). L’Etna rappresenta una delle maggiori sorgenti potenzialmente in grado di fornire grandi quantità di Hg in atmosfera, grazie alle sue notevoli emissioni gassose dal plume craterico e dai fianchi (e.g., Ferrara et al., 2000). A partire dalla metà di Novembre 2005 si è reso disponibile un analizzatore portatile della concentrazione di mercurio in fase gassosa Lumex RA-915+ (Figura 1), in visione temporanea grazie all’accordo tra il distributore per l’Italia (Loccioni srl, Ancona) e la sezione di Catania dell’INGV ottenuto su interessamento personale di M. Burton. L’analizzatore si basa sul principio della spettrometria differenziale Zeeman di assorbimento atomico, ed utilizza la modulazione ad alta frequenza della polarizzazione della luce. Lo strumento è in grado di misurare concentrazioni di Hg in aria o in fase gassosa da 0 a 20.000 ng m-3 nella modalità a cella multi-percorso (limite di rilevabilità = 2 ng m-3), oppure da 500 a 200.000 ng m-3 nella modalità a cella singolo-percorso (limite di rilevabilità = 500 ng m-3). La misura viene effettuata mediante aspirazione del campione di aria o di gas all’interno dello strumento attraverso un tubo che, nel caso di gas del suolo o gorgogliante in acqua, viene opportunamente collegato, rispettivamente, ad una sonda inserita nel suolo o ad un imbuto posto sul punto di campionamento. Nel corso degli ultimi due mesi lo strumento è stato utilizzato sull’Etna per misure di Hg nell’aria in varie zone del vulcano, in gas del suolo emessi in due siti ubicati presso Santa Venerina e presso Paternò, in gas fumarolici presso la Torre del Filosofo e in gas gorgoglianti emessi dalle polle d’acqua delle Salinelle dello Stadio di Paternò. Purtroppo, le spesso avverse condizioni meteorologiche che hanno caratterizzato questo periodo, hanno impedito un più esteso utilizzo dell’analizzatore, così come era stato inizialmente preventivat

SO2 flux from Stromboli during the 2007 eruption: Results from the FLAME network and traverse measurements

SO2 fluxes emitted by Stromboli during the 27th February – 2nd April 2007 effusive eruption were regularly measured both by an automatic network of scanning ultraviolet spectrometers and by traverse easurements conducted by boat and helicopter. The results from both methodologies agree reasonably well, providing a validation for the automatic flux calculations produced by the network. Approximately 22,000 tonnes of SO2 were degassed during the course of the 35 day eruption at an average rate of 620 tonnes per day. Such a degassing rate is much higher than that normally observed (150-200 t/d), because the cross-sectional area occupied by ascending degassed magma is much greater than normal during the effusion, as descending, degassed magma that would normally occupy a large volume of the conduit is absent. We propose that the hydrostatically controlled magma level within Stromboli’s conduit is the main control on eruptive activity, and that a high effusion rate led to the depressurisation of an intermediate magma reservoir, creating a decrease in the magma level until it dropped beneath the eruptive fissure, causing the rapid end of the eruption. A significant decrease in SO2 flux was observed prior to a paroxysm on 15th March 2007, suggesting that choking of the gas flowing in the conduit may have induced a coalescence event, and consequent rapid ascent of gas and magma that produced the explosion

New insights into volcanic processes at Stromboli from Cerberus, a remote-controlled open-path FTIR scanner system

The ordinary, low intensity, activity of Stromboli volcano is sporadically interrupted by more energetic events termed, depending on their intensity, “major explosions” and “paroxysms”. These short-lived energetic episodes represent a potential risk to visitors to the highly accessible summit of Stromboli. Observations made at Stromboli over the last decade have shown that the composition of gas emitted from the summit craters may change prior to such explosions, allowing the possibility that such changes may be used to forecast these potentially dangerous events. In 2008 we installed a novel, remote-controlled, open-path FTIR scanning system called Cerberus at the summit of Stromboli, with the objective of measuring gas compositions from individual vents within the summit crater terrace of the volcano with high temporal resolution and for extended periods. In this work we report the first results from the Cerberus system, collected in August-September 2009, November 2009 and May-June 2010. We find significant, fairly consistent, intra-crater variability for CO2/SO2 and H2O/CO2 ratios, and relatively homogeneous SO2/HCl ratios. In general, the southwest crater is richest in CO2, and the northeast crater poorest, while the central crater is richest in H2O. It thus appears that during the measurement period the southwest crater had a somewhat more direct connection to a primary, deep degassing system; whilst the central and northeast craters reflect a slightly more secondary degassing nature, with a supplementary, shallow H2O source for the central crater, probably related to puffing activity. Such water-rich emissions from the central crater can account for the lower crystal content of its eruption products, and emphasise the role of continual magma supply to the shallowest levels of Stromboli's plumbing system. Our observations of heterogeneous crater gas emissions and high H2O/CO2 ratios do not agree with models of CO2-flushing, and we show that simple depressurisation during magma ascent to the surface is a more likely model for H2O loss at Stromboli. We highlight that alternative explanations other than CO2 flushing are required to explain distributions of H2O and CO2 amounts dissolved in melt inclusions. We detected fairly systematic increases in CO2/SO2 ratio some weeks prior to major explosions, and some evidence of a decrease in this ratio in the days immediately preceding the explosions, with periods of low, stable CO2/SO2 ratios between explosions otherwise. Our measurements, therefore, confirm the medium term (~ weeks) precursory increases previously observed with MultiGas instruments, and, in addition, reveal new, short-term precursory decreases in CO2/SO2 ratios. immediately prior to the major explosions. Such patterns, if shown to be systematic, may be of great utility for hazard management at Stromboli's summit. Our results suggest that intra-crater CO2/SO2 variability may produce short-term peaks and troughs in CO2/SO2 time series measured with in-situ MultiGas instruments, due simply to variations in wind direction

Three-years of SO2 flux measurements of Mt. Etna using an automated UV scanner array: comparison with conventional traverses and uncertainties in flux retrieval

Routine measurements of SO2 flux using the traverse method on Mt. Etna (Italy) were augmented in late 2004 when an array of automatic scanning ultraviolet spectrometers was installed. Each instrument allows one SO2 scan to be recorded every ~6 min. Here we report the methods that we developed to automatically and robustly transform SO2 profiles into SO2 flux data. Radian geometry and Fast Fourier Transform algorithm were used for reducing plume cross sections and for discriminating between volcanic plumes from those produced by water vapour clouds. Uncertainty in flux measurements depends on the accuracy of plume-height estimation, on assumptions concerning plume-geometry, and on the quality of the retrieved SO2 amounts. We compare 3 years of flux measurements made using both the automated network and “conventional” traverse methods beneath the plume. We found a good agreement between the datasets, both in terms of magnitude and in temporal variations. These results validate the Etna SO2 flux monitoring system. Emission rates are available to the 24-hour manned operations room via intranet, providing real-time information on degassing rates and plume location

Coupled Use of COSPEC and Satellite Measurements to define the Volumetric Balance During Effusive Eruptions at Mt. Etna, Italy

Mt. Etna is one of the most studied and extensively monitored volcanoes on earth (Bonaccorso et al., 2004). One of the most frequent hazards are due to the eruption of lava flows, more specifically those flows produced during flank eruptions. These eruptions potentially can produce extensive flows that can inundate densely populated communities of the lower slopes (Guest and Murray, 1979; Behncke et al., 2005). Satellite remote sensing can be used during effusive eruptions to help monitoring the volcano, by determining effusion rates of the flows, aiding in hazard management. The degassing that takes place when magma is rising to the surface can be regularly monitored using ultraviolet spectroscopic methods (e.g. Andres et al., 2001, Sutton et al., 2001). Sulfur Dioxide (SO2) fluxes have been derived from correlation spectrometer (COSPEC) measurements at Mt. Etna (Italy) on a regular basis since 1987 (e.g. Caltabiano et al., 1994; Allard, 1997; Andronico et al., 2005; Burton et al., 2005; Burton et al., in press). Previous studies have compared field-based effusion rates with the measured SO2 fluxes to determine how much of the degassed magma is erupted onto Etna’s flanks in the form of lava flows (Allard, 1997; Harris et al., 2000). However, most of these studies examine bulk volumes erupted over an eruption rather than examining the short-term variations during eruptions. Determining the amount of lava erupted and/or the balance between the amount supplied and the amount erupted remains an unresolved issue. The main objectives of this paper are to examine such short-term variations using satellite-based effusion rates along with regularly measured SO2 fluxes. Using these measurements we determine how and when the volume of supplied magma is balanced by the volume of erupted lava during individual effusive eruptions

Installazione di un radiometro nell'area sommitale del vulcano Etna

Le tecniche di telerilevamento satellitare e da terra per la stima della temperatura di anomalie termiche delle superfici vulcaniche, della loro variazione nel tempo e per individuare attività parossistiche o l’inizio di una fase di colate di lava, sono ormai entrate a far parte della sorveglianza e del monitoraggio vulcanologico [es. Francis, 1979; Geraci et al., 1985; Lombardo et al., 2011; Spampinato et al., 2011]. I sensori in una banda spettrale dell’infrarosso quali radiometri e telecamere termiche, utilizzati in prossimità di bocche eruttive, hanno fornito cospicue quantità di dati di temperatura della superficie di corpi magmatici (colate laviche, laghi di lava, duomi lavici), plume vulcanici, fumarole, registrati a distanza di totale sicurezza [Spampinato et al., 2011]. In particolare, i radiometri, sia portatili che installati in stazioni permanenti, oltre che fornire dati da confrontare con misure geochimiche, permettono l’acquisizione di dati di temperatura ad elevata frequenza, tali da essere messi in relazione con le misure derivate da osservazioni geofisiche quali ad esempio il tremore sismico [es. Harris e Ripepe, 2007; Branan et al., 2008].In questo lavoro si descrivono i dettagli dell’installazione di una stazione radiometrica collocata nell’area sommitale dell’Etna in zona Belvedere, nel sito già utilizzato da una stazione multiparametrica (con sensori sismici e infrasonici) e denominato EBEL. Si descrivono anche la metodologia di trasmissione dati in continuo, il trattamento del dato convertito in temperatura apparente nel campo di vista del radiometro, la visualizzazione in tempo quasi reale del dato e la sua diffusione tramite WEB

First observational evidence for the CO2-driven origin of Stromboli’s major explosions

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 timeaveraged 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

Novel retrieval of volcanic SO2 abundance from ultraviolet spectra

The recent development of fixed networks of scanning ultraviolet spectrometers for automatic determination of volcanic SO2 fluxes has created tremendous opportunities for monitoring volcanoes but has brought new challenges in processing of the substantial data flow they produce. A particular difficulty in standard implantation of differential optical absorption (DOAS) methods is the requirement for a clear-sky (plume-free) background spectrum. Our experience after four years of measurements with two UV scanner networks on Etna and Stromboli shows that wide plumes are frequently observed precluding simple selection of clear-sky spectra. We have therefore developed a retrieval approach based on simulation of the background spectrum. We describe the method here and tune it empirically by collecting clear, zenith sky spectra using calibration cells containing known amounts of SO2. We then test the performance of this optimised retrieval using clear-sky spectra collected with the same calibration cells but for variable scan angles, time of day, and season (through the course of 1 year). We find in all cases acceptable results (maximum ~12% error) for SO2 column amounts. The method is therefore very suitable for automated SO2-plume monitoring

Current molecular and clinical insights into uveal melanoma (Review)

Uveal melanoma (UM) represents the most prominent primary eye cancer in adults. With an incidence of approximately 5 cases per million individuals annually in the United States, UM could be considered a relatively rare cancer. The 90.95% of UM cases arise from the choroid. Diagnosis is based mainly on a clinical examination and ancillary tests, with ocular ultrasonography being of greatest value. Differential diagnosis can prove challenging in the case of indeterminate choroidal lesions and, sometimes, monitoring for documented growth may be the proper approach. Fine needle aspiration biopsy tends to be performed with a prognostic purpose, often in combination with radiotherapy. Gene expression profiling has allowed for the grading of UMs into two classes, which feature different metastatic risks. Patients with UM require a specialized multidisciplinary management. Primary tumor treatment can be either enucleation or globe preserving. Usually, enucleation is reserved for larger tumors, while radiotherapy is preferred for small/medium melanomas. The prognosis is unfavorable due to the high mortality rate and high tendency to metastasize. Following the development of metastatic disease, the mortality rate increases to 80% within one year, due to both the absence of an effective treatment and the aggressiveness of the condition. Novel molecular studies have allowed for a better understanding of the genetic and epigenetic mechanisms involved in UM biological activity, which differs compared to skin melanomas. The most commonly mutated genes are GNAQ, GNA11 and BAP1. Research in this field could help to identify effective diagnostic and prognostic biomarkers, as well as novel therapeutic targets