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Ash-leachates chemistry as a tool for monitoring volcanic activity: An application to Stromboli volcano from 2019 to 2024

Emanuela Bagnato1, Daniele Andronico2, Daniele Cinti1, Elisabetta Del Bello1, Piergiorgio Scarlato1, Jacopo Taddeucci1

  • Affiliations: 1Istituto Nazionale di Geofisica e Vulcanologia (INGV), sez. Roma, Italy; 2Istituto Nazionale di Geofisica e Vulcanologia (INGV), sez. Catania, Italy;

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 249

  • Programme No: 3.17.27

  • Theme 3 > Session 17

Abstract

During volcanic eruptions, the release of ash and gases triggers physical and chemical processes that result in the capture of magmatic volatiles as water-soluble minerals on ash surfaces ('ash leachates'). Previous studies have used ash leachates to examine the composition of volcanic gases and track eruption phases. Stromboli volcano in Italy, renowned for its frequent eruptions and consistent ash emissions, provides an ideal location for such research. This study investigates the temporal variation in the chemistry of leachates (Cl, F, S) from 119 ash samples collected at Stromboli between 2019 and 2024, covering various eruption conditions, including ordinary activity, paroxysms, littoral explosions and pyroclastic flows caused by lava front collapses. We focused on exploring the relationship between the chemical composition of water-soluble components on ash and the state of volcanic activity. SEM analysis of a few selected samples revealed the presence of soluble salts, like NaCl-KCl and CaSOâ‚„, supporting the occurrence of gas-ash interactions within the plume. The S/Cl and S/F ratios in leachates closely match Stromboli's bulk gas signature, reflecting changes in eruptive style and plume composition, suggesting a common magmatic source. These ratios significantly increased during intense episodes, such as the paroxysms of July 2019 and 2024, which were marked by higher volatile emissions and finer ash texture, enhancing gas-ash interaction. Similar increases were observed during explosive end effusive events from 2021 to 2023, as well as 'littoral' explosions after the July 2024 paroxysm. Once these events ended, the ratios returned to typical values observed during ordinary activity.