Volcanic degassing, a persistent manifestation of active volcanoes, provides crucial information on the dynamics of the magmatic feeding systems, and allows identifying the phases of volcanic unrest in the runup to volcanic eruptions. While thus determining volcanic degassing rates is a central topic in modern Volcanology, direct volcanic gas flux observations by classic spectroscopic techniques are challenged by (i) the need of adequate illumination (by sunlight) and clear weather conditions (ii) difficulties in robustly estimating plume speed velocity and transport direction, and (iii) a variety of optical and radiative transfer issues. Because of these, volcanic gas flux records are often sparse and incomplete, and affected by intrinsic noise that may prevent from fully resolving the gas emission changes associated with changing volcanic activity. To overcome such limitations, measuring the infrasound produced by the expansion of over-pressurized volcanic gas in the atmosphere, using infrasonic arrays, offers as a promising alternative/complementary tool to quantify and locate degassing at active volcanoes. Here, we report on 2-year long (April 2017—March 2019) period of combined measurements of the SO₂ flux and of volcano-acoustic emissions produced by regular mild persistent strombolian activity and passive degassing of Stromboli Volcano (Sicily, Italy). These were obtained by a permanent monitoring SO₂ camera and a five-element short-aperture (~300 m) infrasonic array. Our results highlight substantial temporal changes in degassing activity, that reflect the recurrent episodes of activations/inactivation of multiple distinct degassing sources within the crater area, as coherently tracked by SO₂ and infrasound together. A simple waveform modeling of the infrasonic record, assuming a monopole acoustical source, suggests that infrasonic degassing, comprising of explosive events and continuous puffing activity, dominates the total persistent degassing budget as tracked by the SO₂ camera.

How to cite: Delle Donne, D., Lacanna, G., Bitetto, M., Ulivieri, G., Ripepe, M., and Aiuppa, A.: Quantifying volcanic gas emission rates from infrasound and SO2 cameras: potentials, limitations, and volcanological implications., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9143, https://doi.org/10.5194/egusphere-egu23-9143, 2023.

During the 14^th IAVCEI Field Workshop held in Peru from 6 to 14 November 2022, SO₂ plume measurements were carried out remotely in the volcanic plume of Sabancaya volcano. Sabancaya is an active stratovolcano located in southern Peru (15.787°S, 71.857°W), Sabancaya’s first historical record of an eruption dates to 1750 and the most recent eruption began in November 2016. Volcanic activity consist of rhythm vulcanian explosions, which produce a gas-ash rich plumes which rose few km above the summit terrace. On 10 and 11 November 2022, side-by-side observation by UV and TIR ground-based cameras were remotely carried out with the object to observe the passive and active SO₂ burden from the volcanic plume of Sambacaya. Two UV cameras systems were employed observing the volcanic plume at 2- and 5-seconds time steps and calibrating SO₂ amounts by coupling SO₂ DOAS inverted column densities ad and SO₂-quartz cell amounts. The TIR camera (named VIRSO2) is a novel system developed for the detection of volcanic plumes, the estimation of the height and the determination of columnar content and the SO₂ flux. It allows acquisition of high frequency data both during the day and at night. It is equipped with 3 cameras, two broadband TIR (7-14 micron) and a VIS, capable of acquiring data simultaneously. For the quantitative estimation of SO₂, an 8.7 μm filter is installed in front of one of the TIR camera. Retrieved cameras products were cross-compared and validated in order to determinate limit an uncertainty of both methods and results were also compared with those obtained by S5p-TROPOMI instrument.

Preliminary results show a feasible strength between the three ground and space-based techniques. Within the uncertainties of each method, differences between inverted SO₂ column densities and emission rates arise from field of view geometrical sampling set-up and radiative transfer. Results gathered in this study prove the promising application of ground-based TIR in volcanic plume SO₂ observation.

How to cite: Corradini, S., Salerno, G., Campion, R., Guerrieri, L., Merucci, L., and Stelitano, D.: Remote SO2 flux by UV and TIR ground based cameras at Sabancaya volcano (Peru), cross comparison and validation with satellite data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11832, https://doi.org/10.5194/egusphere-egu23-11832, 2023.

Volcanic sulfur dioxide (SO₂) is a gaseous precursor that is transformed into secondary sulfate aerosols (SO₄^2-) by several intricate chemical and physical atmospheric processes. It is currently unclear how quickly sulfate aerosols are produced in volcanic plumes, particularly in tropospheric plumes. We jointly analyze Aura/OMI SO₂ observations to constrain the sulfur-rich emissions and identify the volcanic plume dispersion pattern as well as multi-angle, multi-wavelength, and polarizing PARASOL/POLDER-3 observations that are particularly sensitive to fine mode particles to gain a better understanding of the lifecycle of volcanic sulfate aerosols. The GRASP/Component^[1] (Generalized retrieval of Aerosol and Surface Properties) algorithm gives us details about the soluble and insoluble aerosol components in both fine and coarse modes based on their complex refractive indices in addition to standard optical characteristics. In order to provide insight into SO₂ to particle conversion rate, we analyze the degassing of the Kilauea volcano (Hawaii, USA) between 2006 to 2012, which includes periods of passive and eruptive degassing.

We demonstrate that Kilauea SO₂-rich pixels from OMI measurements are broadly collocated with poorly-absorbing fine aerosol-rich pixels from POLDER measurements (fine AOD (440nm) ranging from 0.1 to 0.4, SSA (440nm) ranging from 0.95 to 1.0). We show that these volcanic particles also differ from long-distance transported man-made and natural fine-absorbing particles seen across the Kilauea domain from the Asian region in terms of their absorption characteristics. We, therefore attribute these fine mode particles to sulfate aerosols that result from the conversion of Kilauea SO₂ emissions.

In comparison to SO₂-rich plumes, Kilauea aerosol-rich plumes have a significantly wider spread and are characterized by an excess anomaly in fine AOD and high SSA values. Irrespective of the degassing strength, a pattern consistent with the oxidation of SO₂ to secondary sulfate aerosols is observed where the SO₂ concentration gradually drops with plume dispersion while the fine AOD gradually increases, peaking at a distance of around 800–3000 km from the Kilauea source. Depending on the intensity of volcanic activity, the season, and enduring local meteorological conditions, different time scales for oxidation of SO₂ and geographical dispersion of the Kilauea aerosol plumes are observed. We conducted additional analysis on the coarse AOD and coarse components to look for ash signals inside the plume. Furthermore, the complex refractive index of Kilauea particles, retrieved by the GRASP/Component algorithm, indicates an imaginary part (0.003-0.005) that is slightly higher than that of volcanic basaltic ash, as determined by laboratory experiments, while the real part (1.49-1.52) lies well in between pure sulfate (1.40-1.46) and basaltic ash (1.56-1.63). These refractive index values imply that Kilauea particles are not pure sulfate aerosols but instead contain some spectrally absorbing elements that may point to the existence of fine ash or sulfate-coated ash particles within the plume.

[1] Li, L., Dubovik, O., Derimian, Y., Schuster, G. L., Lapyonok, T., Litvinov, P., Ducos, F., Fuertes, D., Chen, C., Li, Z., Lopatin, A., Torres, B., and Che, H.: Retrieval of aerosol components directly from satellite and ground-based measurements, Atmos. Chem. Phys., 19, 13409–13443, https://doi.org/10.5194/acp-19- 13409-2019, 2019.

How to cite: Panda, S. R., Boichu, M., Derimian, Y., Dubovik, O., and Behera, A. K.: Insight into the conversion of SO2 to sulphate aerosols in volcanic plumes from the joint analysis of hyperspectral OMI and multi-angular polarimetric POLDER satellite observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5423, https://doi.org/10.5194/egusphere-egu23-5423, 2023.

Hyperspectral infrared sounders like IASI are used to track and quantify volcanic ash in the atmosphere. The retrieval process of physical quantities like particle radius and mass depends critically on the assumed spectrally dependent complex refractive indices that are used. Traditionally, the Pollack et al. (1973) dataset were used almost exclusively. These indices are however based on measurements of rock slabs and in recent years two datasets have become available from laboratory measurements of ash in suspension, the Reed et al. (2018) and Deguine et al. (2020) dataset. In this work, we compare for the first time the three most important datasets of CRI with respect to the three most common ash types (basaltic, andesitic and rhyolitic). The results show significant influence of the dataset used on the retrieved physical quantities. When it comes to basaltic and andesitic ash, both the Deguine and Reed samples outperform Pollack in terms of able to reconstruct the satellite observed spectra. However, all datasets overestimate the extinction near 1250 cm⁻¹, which could possibly be related to the lack of sensitivity of spectrometers (water vapour continuum) leading to a poor signal over noise ratio in this spectral region. While this is not a guarantee that the retrieved quantities are closer to the physical reality, being able to reconstruct the observed spectra is a prerequisite of constructing a consistent physical model. Finally, a case study on the 7 May 2010 plume of the Eyjafjallajokull eruption is presented. For this case study, the differences are found to be mostly related in retrieved altitudes. It is clear that while the availability of CRI based on ash suspended in air is an important milestone, a lot of further research is needed to strengthen the theoretical basis of infrared retrievals of volcanic ash. A comprehensive database of reliable in-situ measurements of volcanic clouds would in this perspective be most welcome.

A. Deguine, D. Petitprez, L. Clarisse, S. Gudmundsson, V. Outes, G. Villarosa, and H. Herbin, “Complex refractive index of volcanic ash aerosol in the infrared, visible, and ultraviolet,” Applied Optics, vol. 59, no. 4, p. 884, jan 2020.

J. B. Pollack, O. B. Toon, and B. N. Khare, “Optical properties of some terrestrial rocks and glasses,” Icarus, vol. 19, no. 3, pp. 372–389, jul 1973.

B. E. Reed, D. M. Peters, R. McPheat, and R. G. Grainger, “The complex refractive index of volcanic ash aerosol retrieved from spectral mass extinction,” Journal of Geophysical Research, vol. 123, no. 2, pp. 1339–1350, jan 2018.

How to cite: Deguine, A., Clarisse, L., Herbin, H., and Petitprez, D.: Measuring volcanic ash optical properties with high-spectral resolution infrared sounders: role of refractive indices, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2364, https://doi.org/10.5194/egusphere-egu23-2364, 2023.

Explosive volcanic eruptions emit large amounts of solid and gaseous materials into the atmosphere, thereby affect weather and climate and pose hazards to human health and aviation. To constrain those impacts it is important to understand dynamical, microphysical and chemical evolution of the eruption plumes. Especially the density of a plume and atmospheric conditions control the dynamical development of an eruption plume. To simulate those plumes correctly the flow field has to be described as a multi-constituent multiphase flow system. This is realized in eruption plume models but not in the conventional atmospheric models. The latter neglect the partial density of ash particles in relation to total air mass and cannot treat for the effect of ash particles on dynamics during simulations. To overcome this limitation, we use a modified version of ICOsahedral Nonhydrostatic model with Aerosols and Reactive Trace gases (ICON-ART) in which we extended the existing equation set. This version of ICON-ART can consider a source of total mass during the eruption as well as a mass sink due to sedimentation of ash and other constituents. The mass source is accounted by an additional source term for total density, and the mass sink is accounted by implementing the lower boundary condition of the vertical velocity at the surface. This leads to a conserved dry air mass and changing total air mass, which affects dynamics and is crucial for handling multiphase flows correctly. Additionally, a momentum forcing as well as a temperature forcing cause the strong updraft within the plume region.

We simulated the real case of the Raikoke eruption in 2019 in a LES-mode for more detailed investigations of the plume. In this experiment, in addition to ash, we also emit water vapor which might lead to an additional upward motion in the convective plume region due to latent heat release when clouds develop. The results show that the model is able to reproduce the observed plume geometry vertically and horizontally. Moreover, we simulated gravity waves that developed during the eruption around the volcano. In combination with microphysics and aerosol dynamics, the new implementations in ICON-ART enable detailed investigations of volcanic plume development across scales.

How to cite: Bierbauer, S., Hoshyaripour, G. A., Bruckert, J., Reinert, D., and Vogel, B.: Explicit simulation of volcanic eruption plumes in atmospheric models: first results and implications, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12069, https://doi.org/10.5194/egusphere-egu23-12069, 2023.

During the summer of 2019, both Mt. Etna and Stromboli volcanoes in Sicily were in the stage of no ordinary activity. Mt. Etna was featured by mild strombolian activity from the summit South East Crater producing a moderate SO₂–ash rich plume 4 km above sea level (asl). Meanwhile, at 120 km far from Etna, on 3 July and 28August, the ordinary and typical mild explosive eruptive activity of Stromboli was interrupted by two paroxysms. Both events were characterized by pyroclastic flows and consistent emission of ash–SO₂ rich plume, which spread up to height of 5–6 km asl.
In this work, we explored the spatial dispersion of the volcanic plumes released by both Mt. Etna and Stromboli on August 28 by employing the Weather Research and Forecasting Chemistry (WRF–Chem) model. The simulation was specifically configured and run by considering the time-variable Eruptive Source Parameters (ESPs) related to the SO₂ flux data for Stromboli and Mount Etna observed from ground by the FLAME DOAS scanning spectrometers network.
In order to assess the predictive performance of the WRF–Chem model, the simulated SO₂ dispersion maps were compared with data retrieved on 28 August from TROPOMI and OMI sensors onboard Sentinel–5p and Aura satellites. The results show a good agreement between WRF–Chem and satellite data. In fact, the simulated total mass of the emitted SO₂ from the two volcanoes has the same order of magnitude as the satellite data. However, for the case of Stromboli, the total SO₂ mass predicted by the WRF–Chem simulation is underestimated; this is likely due to inhibition of the real syn-eruptive SO₂ detection by FLAME due to the extreme ash–rich volcanic plume released during the paroxysm.
In conclusion, the results of these two test–cases demonstrate the feasibility of WRF–Chem model with a time-variable ESPs in reproducing different levels of volcanic SO₂ and their dispersion into the atmosphere. For these reasons, our approach could represent an effective support for the assessment of local–to-regional air quality and flight security and, in case of particularly intense events, also on a global scale.

How to cite: Castorina, G., Semprebello, A., Gattuso, A., Italiano, F., Salerno, G., Sellitto, P., and Rizza, U.: Dispersion modeling of the volcanic sulfur dioxide plumes from the simultaneous eruptive activity of Stromboli and Mt Etna on 28 August 2019, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7268, https://doi.org/10.5194/egusphere-egu23-7268, 2023.

We use a combination of seven space-borne instruments to study the unprecedented stratospheric plume after the Tonga eruption of 15 January 2022.

The aerosol plume was initially formed of two clouds at 30 and 28 km mostly composed of submicron-sized sulfate particles, without ashes washed-out within the first day following the eruption. The large amount of injected water vapour led to a fast conversion of SO₂ to sulfate aerosols and induced a descent of the plume to 24-26 km over the first 3 weeks by radiative cooling. Whereas SO₂ has returned to background levels by the end of January, volcanic sulfates and water still persisted after 6 months, mainly confined between 35°S and 20°N until June due to the zonal symmetry of the summer stratospheric circulation at 22-26 km. Sulfate particles, undergoing hygroscopic growth and coagulation, sediment and gradually separate from the moisture anomaly entrained in the ascending branch Brewer-Dobson circulation. Sulfate aerosol optical depths derived from the IASI infrared sounder show that during the first two months the aerosol plume was not simply diluted and dispersed passively but rather organized in concentrated patches. Space-borne lidar winds suggest that those structures, generated by shear-induced instabilities, were associated with vorticity anomalies that may have enhanced the duration and impact of the plume.

Reference: ACP Highlight, DOI: 10.5194/acp-22-14957-2022

How to cite: Duchamp, C., Legras, B., Sellitto, P., Podglajen, A., Carboni, E., Siddans, R., Grooss, J.-U., Ploeger, F., and Khaykin, S.: The evolution and dynamics of the sulfate aerosol plume in the stratosphere after the exceptional Tonga eruption of 15 January 2022, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7369, https://doi.org/10.5194/egusphere-egu23-7369, 2023.

Mercury is a significant volcanic volatile species from effusive and explosive activity¹. Understanding its emission to the atmosphere from volcanic activity, aids our understanding of the global mercury cycle and its environmental impacts. Sedimentary and ice core records can be archives of these mercury enrichments^2,3.

The Laki 1783-84 AD fissure eruption in Iceland was significant due to its voluminous outpouring of basaltic lava, copious sulphur emissions and widespread environmental effects locally and across the Northern Hemisphere^4,5. Extreme weather events were recorded in Europe and North America, owing to a veil of sulphur dioxide that remained at the tropopause for over a year⁵. Due to the phreatomagmatic and thus explosive nature of Laki, a significant eruption plume was produced⁴. As such, cryptotephra shards have been located at distal locations from Iceland including ice cores in Svalbard and Greenland^6,7 and in an Irish woodland peat at Brackloon Wood, Co. Mayo⁸. There is evidence to suggest significant heavy metal emission to the atmosphere during the Laki eruption, however these records are currently restricted to Greenland ice cores⁹. Previous heavy metal findings linked to Laki do not include mercury, despite its significance as a volcanic volatile, and a potentially environmentally damaging heavy metal. Therefore, to expand our knowledge of the Laki 1783-84 AD eruption plume, its associated emissions, and environmental consequences we returned to the woodland peat site in Brackloon Wood, Co. Mayo, Ireland.

Analysis of a 50 cm peat core using an AMA 254 mercury analyser was combined with a novel technique to find tephra using BSE (back scattered electron) imaging and geochemical discrimination using SEM-EDX (scanning electron microscopy-energy dispersive x-ray). The Laki tephra is successfully located using this method and coincides with a visible enrichment in mercury relative to background concentrations and organic matter. An age-depth model developed using the tephra layer and two radiocarbon dates indicate a strong likelihood that such enrichments are a product of volcanic emission. Such a finding can expand our understanding of heavy metal deposition during Laki 1783-84 AD away from the poles and to our knowledge, demonstrates the first direct exploration of mercury enrichment in distal peat for this eruption. As a secondary test of volcanic volatile enrichment, trace element analysis of the same bulk peat will be conducted to explore enrichments in other volcanic volatiles such as sulphur, cadmium, lead, copper and zinc.

1. Pyle, D. M. & Mather, T. A. Atmos. Environ. 37, 5115–5124 (2003).

2. Schuster, P. F. et al.,. Environ. Sci. Technol. 36, 2303–2310 (2002).

3. Roos-Barraclough, F. et al.,. Earth Planet. Sci. Lett. 202, 435–451 (2002).

4. Thordarson, T. & Self, S. Bull. Volcanol. 55, 233–263 (1993).

5. Thordarson, T. & Self, S., J. Geophys. Res 108, 4011 (2003).

6. Kekonen, T. et al., Polar Res. 24, 33–40 (2005).

7. Wei, L. et al., Geophys. Res. Lett. 35, L16501 (2008).

8. Reilly, E. & Mitchell, F. J., Holocene 25, 241–252 (2015).

9. Hong, S. et al., Earth Planet. Sci. Lett. 144, 605–610 (1996).

How to cite: Blennerhassett, L. and Tomlinson, Dr. E.: Laki 1783-84 AD tephra linked mercury enrichment in peat at Brackloon Wood, Mayo, Ireland., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8559, https://doi.org/10.5194/egusphere-egu23-8559, 2023.

Large volcanic eruptions have significant impacts on climate and environmental changes. The deposition of tephra in marine sediments may serve as an eruption recorder, but it has not been extensively studied in the western Pacific. This study explored a millennial-scale tephra event-stratigraphy with multiple indicators in a sediment core collected from the eastern South China Sea (SCS) basin. The magnetic susceptibility (MS), Fe and Mn concentration determined by X-ray fluorescence (XRF), and identification of individual ash particles were used to identify tephra layers and reconstruct the history of volcanic activity. Nine visible volcaniclastic units (VVU) and two cryptotephra layers have been identified based on their distinct features, as manifested by high MS, Fe, and Mn concentrations, and single-peak grain size distribution. The VVUs and cryptotephra layers reveal elevated volcanic activities. Using the radiocarbon age model and oxygen isotope stratigraphy, these episodes could roughly correspond to the following periods: 1-11 ka, 16-17 ka, 27-31 ka, 41-42 ka, 45-46 ka, 49-50 ka, 77-80 ka, 90-91 ka, 97-99 ka, 116-126 ka, and 132-140 ka. The alkenone-derived SST has significant glacial cycles and good synchronicity with other SCS SST records, which could partially help build the preliminary age model. Despite possible age errors larger than 1 kyr, the discovery and timing of tephra layers provide a preliminary framework to further investigate the impact of historical volcanic eruptions on climate changes.

How to cite: Kong, D., Feng, W., Yang, J., Bao, C., and Chen, M.-T.: A millennial-scale tephra event-stratigraphic record of the South China Sea since the penultimate interglacial, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4626, https://doi.org/10.5194/egusphere-egu23-4626, 2023.