| 1. |
- Hidalgo, Silvana, et al.
(författare)
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SO2 degassing at Tungurahua volcano (Ecuador) between 2007 and 2013: Transition from continuous to episodic activity
- 2015
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Ingår i: Journal of Volcanology and Geothermal Research. - : Elsevier BV. - 0377-0273. ; 298, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- We present continuous SO2 measurements performed at Tungurahua volcano with a permanent network of 4 scanning DOAS instruments between 2007 and 2013. The volcano has been erupting since September 1999, but on the contrary to the first years of eruption when the activity was quasi-continuous, the activity transitioned in late 2008 towards the occurrence of distinct eruptive phases separated by periods of quiescence. During our study period we distinguish 11 phases lasting from 17 to 527days separated by quiescence periods of 26 to 184days. We propose a new routine to quantify the SO2 emissions when data from a dense DOAS monitoring network are available. This routine consists in summing all the highest validated SO2 measurements among all stations during the 10h of daily working-time to obtain a daily observed SO2 mass. Since measurement time is constant at Tungurahua the "observed" amounts can be expressed in tons per 10h and can easily be converted to a daily average flux or mass per day. Our results provide time series having an improved correlation on a long time scale with the eruptive phases and with quiescence periods. A total of 1.25Mt (1.25×109kg) of SO2 has been released by Tungurahua during the study period, with 95% of these emissions occurring during phases of activity and only 5% during quiescence. This shows a contrast with previous volcanic behaviour when passive degassing dominated the total SO2 emissions. SO2 average daily mass emission rates are of 73±56t/d during quiescent periods, 735±969t/d during long-lasting phases and 1424±1224t/d during short-lasting phases. Degassing during the different eruptive phases displays variable patterns. However, two contrasting behaviours can be distinguished for the onset of eruptive phases with both sudden and progressive onsets being observed. The first is characterised by violent opening of the conduit by high energy Vulcanian explosions; and the second by a progressive, in crescendo, development of the activity. The first case is becoming more frequent at Tungurahua making the volcano more dangerous and less predictable.
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| 2. |
- Aiuppa, Sandro, et al.
(författare)
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Tracking formation of a lava lake from ground and space: Masaya volcano (Nicaragua), 2015-2017
- 2018
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Ingår i: Geochemistry, Geophysics, Geosystems. - 1525-2027. ; 19:2, s. 496-515
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Tidskriftsartikel (refereegranskat)abstract
- A vigorously degassing lava lake appeared inside the Santiago pit crater of Masaya volcano (Nicaragua) in December 2015, after years of degassing with no (or minor) incandescence. Here, we present an unprecedented-long (3 years) and continuous volcanic gas record that instrumentally characterizes the (re)activation of the lava-lake. Our results show that, before appearance of the lake, the volcanic gas plume composition became unusually CO2-rich, as testified by high CO2/SO2 ratios (mean, 12.2±6.3) and low H2O/CO2 ratios (mean, 2.3±1.3). The volcanic CO2 flux also peaked in November 2015 (mean, 81.3±40.6 kg/s; maximum, 247 kg/s). Using results of magma degassing models and budgets, we interpret this elevated CO2 degassing as sourced by degassing of a volatile-rich fast-convecting (3.6-5.2 m3·s-1) magma, supplying CO2-rich gas bubbles from minimum equivalent depths of 0.36-1.4 km. We propose this elevated gas bubbles supply destabilized the shallow (<1 km) Masaya magma reservoir, leading to upward migration of vesicular (buoyant) resident magma, and ultimately to (re)formation of the lava lake. At onset of lava lake activity on 11 December 2015 (constrained by satellite-based (MODIS) thermal observations), the gas emissions transitioned to more SO2-rich composition, and the SO2 flux increased by a factor ~40 % (11.4±5.2 kg/s) relative to background degassing (8.0 kg/s), confirming faster than normal (4.4 vs. ~3 m3·s-1) shallow magma convection. Elevated shallow magma circulation is also supported by gradual increase in irradiated thermal energy, captured by MODIS, from which we calculate that 0.4-0.8 m3·s-1 of magma have been surface-emplaced since December 2015.
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| 3. |
- Arellano, Santiago, 1981, et al.
(författare)
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Degassing patterns of Tungurahua volcano (Ecuador) during the 1999–2006 eruptive period, inferred from remote spectroscopic measurements of SO2 emissions
- 2008
-
Ingår i: Journal of Volcanology and Geothermal Research. - 0377-0273. ; 176, s. 151-162
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of 7 years (Aug. 1999–Oct. 2006) of SO2 gas measurements during the ongoingeruption of Tungurahua volcano, Ecuador. From 2004 onwards, the operation of scanning spectrometers hasfurnished high temporal resolution measurements of SO2 flux, enabling this dataset to be correlated with otherdatasets, including seismicity. The emission rate of SO2 during this period ranges from less than 100 to35000 tonnes/day (t/d) with a mean daily emission rate of 1458 t/d and a standard deviation of ±2026 t/d.Average daily emissions during inferred explosive phases are about 1.75 times greater than during passivedegassing intervals. The total amount of sulfur emitted since 1999 is estimated as at least 1.91 Mt, mostlyinjected into the troposphere and carried westwards from the volcano. Our observations suggest that the rateof passive degassing at Tungurahua requires SO2 exsolution of an andesitic magma volume that is two orders ofmagnitude larger than expected for the amount of erupted magma. Two possible, and not mutually exclusive,mechanisms are considered here to explain this excess degassing: gas flow through a permeable stagnant magma-filled conduit and gas escape from convective magma overturning in the conduit.We have found thatreal-time gas monitoring contributes significantly to better eruption forecasting at Tungurahua, because it hasprovided improved understanding of underlying physical mechanisms of magma ascent and eruption.
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| 4. |
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| 5. |
- Arellano, Santiago, 1981, et al.
(författare)
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Long-term monitoring of SO2 quiescent degassing from Nyiragongo’s lava lake
- 2017
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Ingår i: Journal of African Earth Sciences. - : Elsevier BV. - 1879-1956 .- 1464-343X .- 0899-5362. ; 134, s. 866-873
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Tidskriftsartikel (refereegranskat)abstract
- The activity of open-vent volcanoes with an active lava-lake, such as Nyiragongo, is characterized by persistent degassing, thus continuous monitoring of the rate, volume and fate of their gas emissions is of great importance to understand their geophysical state and their potential impact. We report results of SO2 emission measurements from Nyiragongo conducted between 2004 and 2012 with a network of ground-based scanning-DOAS (Differential Optical Absorption Spectroscopy) remote sensors. The mean SO2 emission rate is found to be 13 ± 9 kg s−1, similar to that observed in 1959. Daily emission rate has a distribution close to log-normal and presents large inter-day variability, reflecting the dynamics of percolation of magma batches of heterogeneous size distribution and changes in the effective permeability of the lava lake. The degassed S content is found to be between 1000 and 2000 ppm from these measurements and the reported magma flow rates sustaining the lava lake. The inter-annual trend and plume height statistics indicate stability of a quiescently degassing lava lake during the period of study.
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| 6. |
- Arellano, Santiago, 1981, et al.
(författare)
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New developments on remote sensing studies of volcanic gas emissions by solar infrared spectroscopy
- 2011
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Ingår i: 11th IAVCEI-CCVG Gas Workshop, September 1 - 10, 2011, Kamchatka, Russia.
-
Konferensbidrag (refereegranskat)abstract
- In this contribution, we will present some recent developments made by our group on the application of solar occultation remote sensing to the measurement of volcanic gas emissions in the infrared spectral region. These include the automation of Fourier Transform Spectrometers (FTS) and novel methods for radiation collection and spectrometric analysis.Solar FTS is a proven and versatile method for measuring volcanogenic gases. However, its relatively high cost and complexity on data collection and analysis have precluded its wider use by observatories as a permanent monitoring tool. We will present some results of a field experimentperformed at Popocatépetl volcano (Mexico) within the FIEL-VOLCAN project in April 2010, to show the feasibility of automating a solar FTS on volcanic settings to measure SO2/HCl molar ratios. The system includes a compact solar tracker for automatic radiation collection from a stationary point as well as an embedded computer for data acquisition. Data is evaluated off-line by using e.g., the Chalmers-QESOF program.Further simplifications of the transfer optics and spectroscopic analysis have been investigatedby our group and their operation principles and preliminary results will be presented.
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| 7. |
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| 8. |
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| 9. |
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| 10. |
- Arellano, Santiago, 1981, et al.
(författare)
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Prospects of a global network for studies of volcanic plumes
- 2009
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Ingår i: CEV-IAVCEI Workshop on Advances in studies of volcanic plumes and pyroclastic density currents, Clermont-Ferrand, France, Oct. 2009..
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)
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| 11. |
- Arellano, Santiago, 1981, et al.
(författare)
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Report on volcanic plume measurements on volcanoes in Papua New Guinea
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report summarizes the findings of plume gas measurements conducted on volcanoes of Papua New Guinea (PNG) during September 2016, as part of the DECADE project. The total sulfur dioxide (SO2) and carbon dioxide (CO2) gas fluxes of Tavurvur, Bagana and Ulawun volcanoes were determined by combining ground- remote sensing and ground-/airborne direct sampling, depending on the particular conditions on each volcano. During the campaign Tavurvur was degassing passively, without forming a continuous plume, and it was accessible for direct sampling in the crater. Its SO2 emission was found to be 0.19 ± 0.05 kg/s from scanning-DOAS and a stationary wide-field-of-view (WFOV) DOAS monitor, and the fraction of CO2/SO2 molar ratios was 2.6, obtained with a compact multi-GAS instrument. Bagana, on the other hand, had permanent degassing, producing occasional explosions and ash emission. The plume was measured by ground-based scanning-DOAS and a compact multi-GAS instrument aboard a multi-rotor UAV, resulting in a SO2 flux of 13 ± 5 kg/s and a CO2/SO2 of 15. Ulawun presented continuous passive degassing, forming an elevated plume which flux and composition were measured by car-traverses with a mobile-DOAS, a stationary dual-beam scanning DOAS, and a multi-GAS/UAV sensor. The SO2 flux of Ulawun was 11 ± 2 kg/s and the CO2/SO2 equal to 4.8. A stationary WFOV-DOAS instrument was left with the Rabaul Volcano Observatory (RVO) for longer-term monitoring of the SO2 flux from Tavurvur.
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| 12. |
- Arellano, Santiago, 1981
(författare)
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Studies of Volcanic Plumes with Remote Spectroscopic Sensing Techniques -DOAS and FTIR measurements on volcanoes of the Network for Observation of Volcanic and Atmospheric Change-
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Volcanism is a rich geodynamical process, closely linked to the origin and ongoing evolution of the lithosphere, atmosphere, hydrosphere and biosphere. Humans have benefited from the resources provided by volcanoes but also been threatened by the dangers of volcanic eruptions, which accurate prediction remains elusive. This is partly due to the inherent complexity of volcanic systems and partly because of the difficulty of conducting key observations to characterize them. In particular, since the segregation and escape of magmatic volatiles are essential mechanisms behind volcanic eruptions, monitoring the intensity and composition of the resulting emissions in the atmosphere is essential to characterize the state of volcanic activity; however, their direct measurement is not always feasible.Remote spectroscopic sensing, whereby gas species can be quantified by their spectral signatures in electromagnetic radiation gathered at a prudent distance from the plume, offers the possibility to conduct reliable and sustainable monitoring of volcanic emissions. To expand the remote sensing capabilities of volcanological observatories the Network for Observation of Volcanic and Atmospheric Change (NOVAC) was established in 2005. The central theme of this thesis is the acquisition, analysis and interpretation of measurements of volcanic gas emissions on volcanoes of NOVAC. Measurements of the mass flow rate of SO2 and the molar ratios of SO2 against BrO and HCl were obtained by scanning-Differential Optical Absorption Spectroscopy (DOAS) of scattered solar ultraviolet radiation and by Fourier-Transform Spectroscopy (FTIR) of direct solar infrared radiation. The uncertainty of the measurements is characterized and methods for combining observations from different sensors implemented. Statistical and physical models of degassing are proposed for selected volcanoes of the network. The resulting time-series of emission on 16 volcanoes is one of the more detailed compilations of volcanic degassing in the last decade, particularly from passive emissions which are difficult to detect from satellite platforms. This work aims at advancing our knowledge of volcanic eruptions for a better mitigation of their risks.
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| 13. |
- Arellano, Santiago, 1981
(författare)
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Studies of Volcanic Plumes with Spectroscopic Remote Sensing Techniques
- 2013
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Volcanism is a widespread phenomenon on Earth and other planetary bodies. Terrestrial volcanoes are shallow manifestations of deep and complex mechanisms of heat and mass transport and play an important role in the formation and change of the atmosphere and the natural landscape. Moreover, volcanic eruptions represent one of the most important natural threats for humans, whose civilizations have for ages lived and thrived in the fertile and beautiful volcanic lands, but also have sometimes succumbed after major eruptive outbursts.Active volcanoes constitute important sources of molecular species emitted to the atmosphere, such as H2O, CO2, SO2, HCl, HF, H2S, CO, which participate in several geochemical processes. Although present at relatively small concentrations in their parental magmas, the segregation of these volatiles is crucial for controlling the dynamics of shallow magma transport and thus the style of volcanic eruptions. Quantifying the source strength and the fate of volcanic gaseous emissions is therefore a highly desirable, but unfortunately not always feasible goal, due mainly to present technological, logistical or economical limitations. In this context, the development of remote sensing techniques applied to the measurement of volcanic emissions constitutes an endeavor of high scientific and societal interest.The main focus of the work presented in this thesis is the study of active volcanism by measuring emission rates and molar ratios of volcanic gases via two passive spectroscopic remote sensing techniques: Differential Optical Absorption Spectroscopy (DOAS) of sky-scattered ultraviolet solar radiation and Fourier Transform Infra-Red (FTIR) spectroscopy of direct solar radiation and passive thermal emission. The thesis presents some developments in the techniques that have been used during field campaigns in Popocatépetl, Karymsky and Tungurahua volcanoes, principally, as well as the results of the evaluation and interpretation of long-term gas emission data from Tungurahua and Nyiragongo volcanoes.This work aims at contributing to a better understanding of volcanic activity by advancing the methods for accurate, simple, robust, and safe monitoring of volcanogenic gas emissions. Increasing this understanding is very helpful to take informed decisions for reducing the risks posed by volcanic eruptions, which despite their implied potential danger, constitute some of the most fascinating, widespread and far-reaching natural phenomena on Earth
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| 14. |
- Arellano, Santiago, 1981, et al.
(författare)
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Synoptic analysis of a decade of daily measurements of SO2 emission in the troposphere from volcanoes of the global ground-based Network for Observation of Volcanic and Atmospheric Change
- 2021
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Ingår i: Earth System Science Data. - : Copernicus GmbH. - 1866-3516 .- 1866-3508. ; 13:3, s. 1167-1188
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Tidskriftsartikel (refereegranskat)abstract
- Volcanic plumes are common and far-reaching manifestations of volcanic activity during and between eruptions. Observations of the rate of emission and composition of volcanic plumes are essential to recognize and, in some cases, predict the state of volcanic activity. Measurements of the size and location of the plumes are important to assess the impact of the emission from sporadic or localized events to persistent or widespread processes of climatic and environmental importance. These observations provide information on volatile budgets on Earth, chemical evolution of magmas, and atmospheric circulation and dynamics. Space-based observations during the last decades have given us a global view of Earth's volcanic emission, particularly of sulfur dioxide (SO2). Although none of the satellite missions were intended to be used for measurement of volcanic gas emission, specially adapted algorithms have produced time-averaged global emission budgets. These have confirmed that tropospheric plumes, produced from persistent degassing of weak sources, dominate the total emission of volcanic SO2. Although space-based observations have provided this global insight into some aspects of Earth's volcanism, it still has important limitations. The magnitude and short-term variability of lower-atmosphere emissions, historically less accessible from space, remain largely uncertain. Operational monitoring of volcanic plumes, at scales relevant for adequate surveillance, has been facilitated through the use of ground-based scanning differential optical absorption spectrometer (ScanDOAS) instruments since the beginning of this century, largely due to the coordinated effort of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). In this study, we present a compilation of results of homogenized post-analysis of measurements of SO2 flux and plume parameters obtained during the period March 2005 to January 2017 of 32 volcanoes in NOVAC. This inventory opens a window into the short-term emission patterns of a diverse set of volcanoes in terms of magma composition, geographical location, magnitude of emission, and style of eruptive activity. We find that passive volcanic degassing is by no means a stationary process in time and that large sub-daily variability is observed in the flux of volcanic gases, which has implications for emission budgets produced using short-term, sporadic observations. The use of a standard evaluation method allows for intercomparison between different volcanoes and between ground- and space-based measurements of the same volcanoes. The emission of several weakly degassing volcanoes, undetected by satellites, is presented for the first time. We also compare our results with those reported in the literature, providing ranges of variability in emission not accessible in the past. The open-access data repository introduced in this article will enable further exploitation of this unique dataset, with a focus on volcanological research, risk assessment, satellite-sensor validation, and improved quantification of the prevalent tropospheric component of global volcanic emission. Datasets for each volcano are made available at https://novac.chalmers.se (last access: 1 October 2020) under the CC-BY 4 license or through the DOI (digital object identifier) links provided in Table 1.
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| 15. |
- Barrington, Charlotte, et al.
(författare)
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Wind Speed as a Dominant Source of Periodicities in Reported Emission Rates of Volcanic SO 2
- 2022
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Ingår i: Journal of Geophysical Research: Solid Earth. - 2169-9356 .- 2169-9313. ; 127:12
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Tidskriftsartikel (refereegranskat)abstract
- Volcanoes have been found to display periodicities or cyclic trends in a wide range of phenomena. These include the eruptive activity itself, but also in the time series of geophysical and geochemical monitoring data such as volcanic degassing. Here, we test the existence of periodicities of volcanic degassing at 32 volcanoes using the time series of sulfur dioxide (SO2) emission rates from data of the Network of Volcanic and Atmospheric Change (NOVAC). We use the Lomb-Scargle periodogram to analyze the SO2 data which allows efficient computation of a Fourier-like power spectrum from unevenly sampled data. We were able to calculate False-Alarm Probabilities in 28 of the 32 volcanoes, and we identified significant periodicities in the SO2 emission rates in 17 of the 28 volcanoes. However, we find that most of these periodicities are also present in the plume speeds used to determine SO2 emission rates. Periodicities at about 30–70, ∼120, and ∼180 days were identified at volcanoes located between 16°N and 16°S and are related to intraseasonality and interseasonality in global trade winds and not volcanic in origin. Periodicities between 30 and 70 days in both plume speed and SO2 emission rates are associated to the Madden-Julian Oscillation that is responsible for intraseasonal variability in the tropical atmosphere. Our study highlights the importance of using local wind data for deriving realistic SO2 emissions and the identification of short-term periodicity in volcanic behavior.
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| 16. |
- Battaglia, Jean, et al.
(författare)
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Autopsy of an eruptive phase of Tungurahua volcano (Ecuador) through coupling of seismo-acoustic and SO 2 recordings with ash characteristics
- 2019
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 1385-013X .- 0012-821X. ; 511, s. 223-232
-
Tidskriftsartikel (refereegranskat)abstract
- Eruption style and dynamics are controlled by various parameters including magma supply rate, magma viscosity, volatile content, and the permeability of the conduit. Rapid changes of these parameters can significantly modify the hazards associated to the eruption processes and understanding their relationship with multiparametric geophysical monitoring data can greatly improve our forecasting capacities. From 2008 to 2016, volcanic activity at Tungurahua was characterized by eruptive phases separated by episodes of quiescence. These phases displayed great variability of eruptive patterns including Vulcanian and Strombolian explosions, low pyroclastic fountaining, continuous or sporadic ash emissions and passive degassing. We use the comparison between geophysical data (seismic, acoustic and SO 2 emission), recorded by permanent monitoring networks, and the characteristics of the emitted ash to track changes in eruption dynamics during an eruptive phase that lasted from late December 2009 to March 2010. We show that the correlation between the analyzed parameters allows imaging and interpretation of the conditions at the vent. At Tungurahua, these conditions can rapidly change at the time scale of a single eruptive phase, corresponding to various degrees of opening, plugging and permeability of the conduit. Two magma intrusions could be identified during a single eruptive phase showing transitions between violent Strombolian and Vulcanian activity. Changes in the componentry of the analyzed ash samples, together with the geophysical data, nicely highlight these evolutions. Studying these parameters simultaneously provides a unique insight into the physical processes controlling superficial volcanic activity and offers a potential tool for better understanding volcanoes and detecting changes in their activity. The joint interpretation of multiparametric data which we propose is potentially applicable to multiple andesitic volcanoes.
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| 17. |
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| 18. |
- Bobrowski, N., et al.
(författare)
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Gas emission measurements of the active lava lake of Nyiragongo, DR Congo
- 2011
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Ingår i: Geophysical Research Abstracts, Vol. 13, EGU2011-10804, EGU General Assembly 2011, Vienna, Austria.
-
Konferensbidrag (refereegranskat)abstract
- In June 2007 and July 2010 spectroscopic measurements and chemical in-situ studies were carried out at Nyiragongovolcano located 15 km north of the city Goma, North Kivu region (DRC), both at the crater rim and within the crater itself, next to the lava lake. Nyiragongo volcano belongs to the Virunga volcanic chain and it is associated with the Western branch of the Great Rift Valley. The volcanism at Nyiragongo is caused by the rifting of the Earth’s crust where two parts of the African plates are breaking apart. Niyragongo crater contains the biggest lava lake on Earth and it is considered one of the most active volcanoes in the world.The ground-based remote sensing technique MAX-DOAS (Multi-Axis Differential Optical Absorption Spectroscopy)using scattered sunlight has been applied during both field trips at the crater rim of the volcano tomeasure sulphur dioxide, halogen oxides and nitrogen oxide. Additionally filter pack and spectroscopic in-situ carbon dioxide measurements were carried out, as well as SO2 flux measurements by a scanning DOAS instrumentfrom the NOVAC project at the flank of the volcano.Nyiragongo is the first rift volcano where halogen oxides have been observed in the plume.Observations indicate that the gas composition of Nyiragongo might change with a changing lava lake level inshort and long-term time scales. Before and during an overflow of the lava lake the molar ratios of BrO/SO2 weredecreasing in 2007 and 2010 from about 3.10-5 to about 0 (below the detection limit). Such a decreasing trendwas also observed before and during the eruption of Mt. Etna 2006 and 2008.In a larger timescale between 2007 and 2010 the molar ratios of S/Cl and CO2/SO2 generally decreased from 6.7 -16.5 to 0.7 – 2.1, from 5 -10 to 1 - 5, respectively. The lower S/Cl and CO2/SO2 could lead to the conclusion thatthe magma reservoir below Niyragongo has had no new input from a deeper source.The chemical composition as well as its temporal variability within the volcanic plume from the lava lake will be discussed, as well as its implication on the understanding of the dynamics of the plumbing system of this volcano.
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| 19. |
- Bobrowski, N., et al.
(författare)
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Gas emission strength and evolution of the molar ratio of BrO/SO2 in the plume of Nyiragongo in comparison to Etna
- 2015
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Ingår i: Journal of Geophysical Research. - : American Geophysical Union (AGU). - 0148-0227 .- 2156-2202 .- 2169-897X. ; 120:1, s. 277-291
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Tidskriftsartikel (refereegranskat)abstract
- Airborne and ground-based differential optical absorption spectroscopy observations have been carried out at the volcano Nyiragongo (Democratic Republic of Congo) to measure SO2 and bromine monoxide (BrO) in the plume in March 2004 and June 2007, respectively. Additionally filter pack and multicomponent gas analyzer system (Multi-GAS) measurements were carried out in June 2007. Our measurements provide valuable information on the chemical composition of the volcanic plume emitted from the lava lake of Nyiragongo. The main interest of this study has been to investigate for the first time the bromine emission flux of Nyiragongo (a rift volcano) and the BrO formation in its volcanic plume. Measurement data and results from a numerical model of the evolution of BrO in Nyiragongo volcanic plume are compared with earlier studies of the volcanic plume of Etna (Italy). Even though the bromine flux from Nyiragongo (2.6t/d) is slightly greater than that from Etna (1.9t/d), the BrO/SO2 ratio (maximum 7x10(-5)) is smaller than in the plume of Etna (maximum 2.1x10(-4)). A one-dimensional photochemical model to investigate halogen chemistry in the volcanic plumes of Etna and Nyiragongo was initialized using data from Multi-GAS and filter pack measurements. Model runs showed that the differences in the composition of volcanic volatiles led to a smaller fraction of total bromine being present as BrO in the Nyiragongo plume and to a smaller BrO/SO2 ratio.
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| 20. |
- Bobrowski, Nicole, et al.
(författare)
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Multi-component gas emission measurements of the active lava lake of Nyiragongo, DR Congo
- 2017
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Ingår i: Journal of African Earth Sciences. - : Elsevier BV. - 1879-1956 .- 1464-343X. ; 134, s. 856-865
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Tidskriftsartikel (refereegranskat)abstract
- Between 2007 and 2011 four measurement campaigns (June 2007, July 2010, June 2011, and December 2011) were carried out at the crater rim of Nyiragongo volcano, DR Congo. Nyiragongo is one of the most active volcanoes in Africa. The ground-based remote sensing technique Multi-Axis Differential Optical Absorption Spectroscopy (MAX-DOAS), which uses scattered sunlight, the in-situ Multi-Component Gas Analyzer System (Multi-GAS) and alkaline impregnated filter were simultaneously applied during all field trips. The bromine monoxide to sulfur dioxide (BrO/SO2) and carbon dioxide to sulfur dioxide (CO2/SO2) molar ratios were determined, among other ratios. During the different field trips variations of the level of the lava lake up to several tens of meters were observed during intervals of the order of minutes up to days and also between the years. The measured gas ratios presented covariations with the lava lake level changes. BrO/SO2 ratios and CO2/SO2 ratios showed similar behavior. Annual CO2/SO2 and BrO/SO2 average values are generally positively correlated. In June 2011 increased BrO/SO2 as well as increased CO2/SO2 ratios have been observed before a sudden decrease of the lava lake. Overall the Cl/S ratio, determined by filter-pack sampling, shows an increasing trend with time, which is accompanied by a decreasing sulfur dioxide flux, the later measured nearly continuously by automated MAX-DOAS instruments since 2004. Mean gas emission fluxes of CO2, Cl and ‘minimum-BrO’ fluxes are calculated using their ratio to SO2. The first two show an increase with time, in contrast to the SO2 fluxes. A simple conceptual model is proposed which can explain in particular the June 2011 data, but as well our entire data set. The proposed model takes up the idea of convective magma cells inside the conduit and the possible temporary interruption of part of the cycling. We propose than two alternatives to explain the observed gas emission variation: 1. It is assumed that the diffuse and fumarolic degassing could have significant influence on measured gas composition. The measured gas composition might rather represent a gas mixture of plume, diffuse and fumarolic degassing than only representing the volcanic plume. 2. It is proposed that the interruption of the convection has taken place in the upper part of the conduit and deep degassing of CO2 and bromine initially continues while mixing already with gas emissions from an ageing source, which is characterized by an already diminishing sulfur content. These complex process but as well as the gas mixing of different sources, could explain general features of our dataset, but can unfortunately neither be confirmed nor disproven by the data available today.
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| 21. |
- Bobrowski, N., et al.
(författare)
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Plume composition and volatile flux of Nyamulagira volcano, Democratic Republic of Congo, during birth and evolution of the lava lake, 2014–2015
- 2017
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Ingår i: Bulletin of Volcanology. - : Springer Science and Business Media LLC. - 0258-8900 .- 1432-0819. ; 79:12, s. 90-
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Tidskriftsartikel (refereegranskat)abstract
- Very little is known about the volatile element makeup of the gaseous emissions of Nyamulagira volcano. This paper tries to fill this gap by reporting the first gas composition measurements of Nyamulagira’s volcanic plume since the onset of its lava lake activity at the end of 2014. Two field surveys were carried out on 1 November 2014, and 13–15 October 2015. We applied a broad toolbox of volcanic gas composition measurement techniques in order to geochemically characterize Nyamulagira’s plume. Nyamulagira is a significant emitter of SO2, and our measurements confirm this, as we recorded SO2 emissions of up to ~ 14 kt/d during the studied period. In contrast to neighbouring Nyiragongo volcano, however, Nyamulagira exhibits relatively low CO2/SO2 molar ratios ( 92% of total gas emissions). Strong variations in the volatile composition, in particular for the CO2/SO2 ratio, were measured between 2014 and 2015, which appear to reflect the simultaneous variations in volcanic activity. We also determined the molar ratios for Cl/S, F/S and Br/S in the plume gas, finding values of 0.13 and 0.17, 0.06 and 0.11, and 2.3·10?4 and 1·10?4, in 2014 and 2015, respectively. A total gas emission flux of 48 kt/d was estimated for 2014. The I/S ratio in 2015 was found to be 3.6·10?6. In addition, we were able to distinguish between hydrogen halides and non-hydrogen halides in the volcanic plume. Considerable amounts of bromine (18–35% of total bromine) and iodine (8–18% of total iodine) were found in compounds other than hydrogen halides. However, only a negligible fraction of chlorine was found as compounds other than hydrogen chloride.
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| 22. |
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| 23. |
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| 24. |
- Carn, Simon, et al.
(författare)
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Daily monitoring of Ecuadorian volcanic degassing from space
- 2008
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Ingår i: Journal of Volcanology and Geothermal Research. - 0377-0273. ; 176:1, s. 141-150
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Tidskriftsartikel (refereegranskat)abstract
- We present daily measurements of sulfur dioxide (SO2) emissions from active volcanoes in Ecuador and southern Colombia between September 2004 and September 2006, derived from the Ozone Monitoring Instrument (OMI) on NASA's EOS/Aura satellite. OMI is an ultraviolet/visible spectrometer with an unprecedented combination of spatial and spectral resolution, and global coverage, that permits daily measurements of passive volcanic degassing from space. We use non-interactive processing methods to automatically extract daily SO2 burdens and information on SO2 sources from the OMI datastream. Maps of monthly average SO2 vertical columns retrieved by OMI over Ecuador and S. Colombia are also used to illustrate variations in regional SO2 loading and to pinpoint sources. The dense concentration of active volcanoes in Ecuador provides a stringent test of OMI's ability to distinguish SO2 from multiple emitting sources. Our analysis reveals that Tungurahua, Reventador and Galeras were responsible for the bulk of the SO2 emissions in the region in the timeframe of our study, with no significant SO2 discharge detected from Sangay. At Galeras and Reventador, we conclude that OMI can detect variations in SO2 release related to cycles of conduit sealing and degassing, which are a critical factor in hazard assessment. The OMI SO2 data for Reventador are the most extensive sequence of degassing measurements available for this remote volcano, which dominated regional SO2 production in June–August 2005. At Tungurahua, the OMI measurements span the waning stage of one eruptive cycle and the beginning of another, and we observe increasing SO2 burdens in the months prior to explosive eruptions of the volcano in July and August 2006. Cumulative SO2 loadings measured by OMI yield a total of ~ 1.16 Tg SO2 emitted by volcanoes on mainland Ecuador/S. Colombia between September 2004 and September 2006; as much as 95% of this SO2 may originate from non-eruptive degassing. Approximate apportionment of the total SO2 loading indicates that ~ 40% originated from Tungurahua, with ~ 30% supplied by both Reventador and Galeras. These measurements of volcanic SO2 degassing in Ecuador confirm OMI's potential as an effective, economical and risk-free tool for daily monitoring of SO2 emissions from hazardous volcanoes.
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| 25. |
- Coppola, D., et al.
(författare)
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Shallow system rejuvenation and magma discharge trends at Piton de la Fournaise volcano (La Réunion Island)
- 2017
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Ingår i: Earth and Planetary Science Letters. - : Elsevier BV. - 1385-013X .- 0012-821X. ; 463, s. 13-24
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Tidskriftsartikel (refereegranskat)abstract
- Basaltic magma chambers are often characterized by emptying and refilling cycles that influence their evolution in space and time, and the associated eruptive activity. During April 2007, the largest historical eruption of Piton de la Fournaise (Île de La Réunion, France) drained the shallow plumbing system (>240×106 m3) and resulted in collapse of the 1-km-wide summit crater. Following these major events, Piton de la Fournaise entered a seven-year long period of near-continuous deflation interrupted, in June 2014, by a new phase of significant inflation. By integrating multiple datasets (lava discharge rates, deformation, seismicity, gas flux, gas composition, and lava chemistry), we here show that the progressive migration of magma from a deeper (below sea level) storage zone gradually rejuvenated and pressurized the above-sea-level portion of the magmatic system consisting of a vertically-zoned network of relatively small-volume magma pockets. Continuous inflation provoked four small (
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