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Tsanev, V. I.
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- PublicationRestrictedGas and aerosol emissions from Villarrica volcano, Chile(2011)
; ; ; ; ; ; ; ; ; ; ;Sawyer, G. M.; Department of Geography, University of Cambridge ;Salerno, G. G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Le Blond, J. S.; Department of Geography, University of Cambridge - Department of Mineralogy, Natural History Museum ;Martin, R. S.; School of Biological and Chemical Sciences, Queen Mary, University of London - Department of Earth Sciences, University of Cambridge ;Spampinato, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Roberts, T. J; Norwegian Polar Institute, Polar Environmental Centre ;Mather, T. A.; Department of Earth Sciences, University of Oxford ;Witt, M. L. I.; Department of Earth Sciences, University of Oxford ;Tsanev, V. I.; Department of Geography, University of Cambridge ;Oppenheimer, C.; Department of Geography, University of Cambridge; ; ; ; ; ; ; ; ; Here we report results from a multidisciplinary field campaign at Villarrica volcano, Chile, in March 2009. A range of direct sampling and remote sensing techniqueswas employed to assess gas and aerosol emissions from the volcano, and extend the time series of measurements that have been made during recent years. Airborne traverses beneath the plume with an ultraviolet spectrometer yielded an average SO2 flux of 3.7 kg s−1. This value is similar to previous measurements made at Villarrica during periods of quiescent activity. The composition of the plume was measured at the crater rim using electrochemical sensors and, for the first time, open-path Fourier transforminfrared spectroscopy, yielding a composition of 90.5 mol% H2O, 5.7% CO2, 2.6%SO2, 0.9% HCl, 0.3% HF and b0.01% H2S. Comparison with previous gas measurements made between 2000 and 2004 shows a correlation between increased SO2/HCl ratios and periods of increased activity. Base-treated filter packs were also employed during our campaign, yielding molar ratios of HBr/SO2=1.1×10−4, HI/SO2=1.4×10−5 and HNO3/SO2=1.1×10−3 in the gas phase. Our data represent the most comprehensive gas inventory at Villarrica to date, and the first evaluation of HBr and HI emissions from a South American volcano. Sun photometry of the plume showed the near-source aerosol size distributions were bimodal with maxima at b0.1 and ~1 μm. These findings are consistent with results from analyses in 2003. Electron microscope analysis of particulatematter collected on filters showed an abundance of sphericalmicron-sized particles that are rich in Si, Mg and Al. Non-spherical, S-rich particles were also observed.205 28 - PublicationRestrictedInvestigation into magma degassing at Nyiragongo volcano, Democratic Republic of the Congo(2008-02-28)
; ; ; ; ; ;Sawyer, G. M.; Department of Geography, University of Cambridge, Cambridge, UK ;Carn, S. A.; Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, Maryland, USA ;Tsanev, V. I.; Department of Geography, University of Cambridge, Cambridge, UK ;Oppenheimer, C.; Department of Geography, University of Cambridge, Cambridge, UK ;Burton, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ; ;We report the first combined measurements of the composition and flux of gas emitted from Nyiragongo volcano by ground-based remote-sensing techniques. Ultraviolet spectroscopic measurements made in May/June 2005 and January 2006 indicate average SO2 emission rates of 38 kg s−1 and 23 kg s−1, respectively. Open-path Fourier transform infrared spectroscopic measurements obtained in May/June 2005, January 2006, and June 2007 indicate average molar proportions of 70, 24, 4.6, 0.87, 0.26, 0.11, and 0.0016% for H2O, CO2, SO2, CO, HCl, HF, and OCS, respectively. The composition of the plume was remarkably similar in 2005, 2006, and 2007, with little temporal variation in proportions of CO2, SO2, and CO, in particular, on the scale of seconds or days or even between the three field campaigns that span a period of 24 months. This stability persisted despite a wide range of degassing behaviors on the surface of the summit crater's lava lake (including discrete strombolian bursts and lava fountains) and variations in the SO2 emission rate. We explain these observations by a regime of steady state degassing in which bubbles nucleate and ascend in chemical equilibrium with the convecting magma. Short-term (seconds to minutes) temporal fluctuations in the SO2–HCl–HF composition were observed, and these are attributed to shallow degassing processes.179 22 - PublicationRestrictedNovel retirval of volcanic SO2 abundance form ultraviolet spectra(2009)
; ; ; ; ; ; ;Salerno, G. G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Burton, M. R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Pisa, Pisa, Italia ;Oppenheimer, C.; University of Cambridge, Department of Geography ;Caltabiano, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Tsanev, V. I.; University of Cambridge, Department of Chemistry, Department of Geography ;Bruno, N.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; ; ;; ; 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 (and interpreting) the copious 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), finding acceptable results (~12% error) for SO2 column amounts. We further illustrate the analytical approach using spectra recorded at Mt. Etna during its July 2006 eruption. We demonstrate the reliability of the method for tracking volcano dynamics on different time scales, and suggest it is widely suited to automated SO2-plume monitoring158 26