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Quantification of low-temperature gas emissions reveals CO2 flux underestimates at Soufrière Hills volcano, Montserrat

Alexander Riddell 1, Mike Burton1, Benjamin Esse1, Brendan McCormick Kilbride1, Antonio Chiarugi2, Thomas Christopher3,4, Francesco D'Amato5, Graham A. Ryan3,4, Adam Stinton3,4 and Silvia Viciani5

  • Affiliations:  1University of Manchester, School of Earth and Environmental Science, Manchester, UK. 2 SENSIT Technologies EMEA Srl, Bolzano, Italy. 3Montserrat Volcano Observatory, Montserrat, West Indies. 4Seismic Research Centre, The University of the West Indies, St. Augustine, Trinidad & Tobago. 5CNR -- National Institute of Optics, Firenze, Italy. 

  • Presentation type: Poster

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

  • Poster Board Number: 245

  • Programme No: 3.17.24

  • Theme 3 > Session 17

Abstract

Volcanic degassing transports volatiles from Earth's interior to the atmosphere, playing a critical role in global geochemical cycles and influencing climate on local, regional, and global scales. Volatile species not only drive volcanic eruptions but also control magma ascent processes and the style of eruptive activity. Consequently, monitoring and quantifying magmatic gas emissions and compositions are central to volcanological research. Currently, MultiGAS instruments are widely used for in-situ measurements of key volcanic gases, typically sulfur species and CO2. However, MultiGAS instruments, which combine electrochemical and optical sensors, face challenges such as differing frequency responses and sensitivity to pressure and temperature variations. This highlights the need for improved gas-sensing technology. To address these limitations, we developed a novel optical MultiGAS (OMG) analyser capable of high-frequency, simultaneous measurements of volcanic gas species. The OMG comprises multiple optical instruments, each with an open-path multipass cell that quantifies gas concentrations at 1-4 Hz. We performed helicopter-borne OMG measurements at Soufrière Hills Volcano, Montserrat, revealing distinct spikes in SO2 and HCl concentrations within a larger CO2-rich plume. Acid-rich concentration spikes matched the distribution of high-temperature fumaroles, whereas CO2 is emitted broadly from high- and low-temperature fumaroles. We demonstrate that quantification of the cold CO2 emissions would not be possible using a standard MultiGAS instrument and that the widely used CO2/SO2 x SO2 flux quantification of CO2 flux would lead to over a threefold reduction in CO2 flux. This suggests that traditional measurements may significantly underestimate cold CO2 degassing, leading to underestimated global volcanic fluxes.